KR100283275B1 - Liquid crystal display device - Google Patents

Abstract

The liquid crystal display device includes a first substrate; A second substrate; A liquid crystal layer interposed between the first substrate and the second substrate; A first polarizing element provided on a surface of said first substrate on the opposite side to said liquid crystal layer; A second polarizing element provided on the surface of the second substrate, on the side opposite to the liquid crystal layer; A first phase difference compensating element provided between the first polarizing element and the liquid crystal layer; And a second phase difference compensating element provided between the second polarizing element and the liquid crystal layer. A plurality of pixel areas is provided for the display. The first substrate includes at least one transmissive electrode, and the second substrate includes a reflective electrode region and a transmissive electrode region corresponding to each of the plurality of pixel regions.

Description

Liquid crystal display device {LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a reflective liquid crystal display device and a liquid crystal display device operable in both reflective and transmissive modes, which are integrated into office automation equipment such as word processors and personal computers, mobile information devices such as portable computers, and cameras. It is used for a VTR having a liquid crystal monitor. The present invention also relates to a method of manufacturing such a liquid crystal display device. In this specification, the liquid crystal display device will be called "LCD". Liquid crystal display devices operable in both reflective mode and transmission will be referred to as "transmissive and reflective LCD devices".

LCD devices, unlike CRT (cathode ray tube) and EL (electroluminescence) devices, do not emit light by themselves. Therefore, a transmissive LCD device having a backlight on the back side is used.

The backlight usually consumes more than 50% of the total power consumption of the LCD device. Some mobile information devices commonly used externally or always carried by a user include a reflective LCD device including a reflecting plate and performing display using only ambient light.

Reflective LCD devices are polarizing elements and TN (twist nematic) mode devices and STNs that are widely used today as transmissive LCD devices as well as phase-change (PC) guest-host mode devices that are currently being actively studied. (Super Twist Nematic) mode device. The PC guest-host mode device does not use a polarizing element, thus realizing a brighter display. Such a device is disclosed, for example, in Japanese Laid-Open Publication No. 4-75022 and Japanese Laid-Open Publication No. 9-133930, which correspond to US Patent No. 5,220,444.

However, the PC guest-host mode LCD device performs display using optical absorption by dye in a liquid crystal layer containing liquid crystal molecules and dye dispersed therein. Accordingly, phase shift guest-host mode LCD devices provide significantly lower quality than TN devices and STN devices using polarizing elements.

In LCD devices comprising liquid crystal molecules oriented in parallel or in a twisted manner, the liquid crystal molecules near the center and the liquid crystal layer are inclined perpendicularly to the surface of the substrate. However, the liquid crystal molecules near the alignment layer do not incline perpendicularly to the surface of the substrate. Therefore, the birefringence of the liquid crystal layer cannot be zero. Thus, when the LCD device operates in a display mode that performs black display when voltage is applied, satisfactory black display is not performed due to the remaining birefringence. Therefore, sufficient contrast ratio is not obtained.

TN mode and STN mode devices do not provide sufficiently high quality displays in terms of birefringence and contrast. Therefore, further improvement in birefringence and contrast is required.

Reflective LCD devices have the disadvantage that the intensity of the reflected light used in the display is lower than when the ambient light is dark. In contrast, the transmissive LCD device has a disadvantage that its visibility is lower than outside when the ambient light is extremely bright, for example, on a sunny day.

According to one aspect of the invention, the liquid crystal display device comprises a first substrate; A second substrate; A liquid crystal layer interposed between the first substrate and the second substrate; A first polarizing element provided on a surface of said first substrate on the opposite side to said liquid crystal layer; A second polarizing element provided on the surface of the second substrate, on the side opposite to the liquid crystal layer; A first phase difference compensating element provided between the first polarizing element and the liquid crystal layer; And a second phase difference compensating element provided between the second polarizing element and the liquid crystal layer. A plurality of pixel areas is provided for the display. The first substrate includes at least one transmissive electrode, and the second substrate includes a reflective electrode region and a transmissive electrode region corresponding to each of the plurality of pixel regions.

In one embodiment of the present invention, each of the plurality of pixel areas has a reflection area for performing display using reflected light, and a transmission area for performing display using transmitted light, and the reflective electrode area is configured to reflect the reflection area. And the transmissive electrode region defines the transmissive region.

In one embodiment of the present invention, the liquid crystal layer has a delay of zero when the molecular axis of the liquid crystal molecules in the liquid crystal layer is substantially perpendicular to the surfaces of the first and second substrates, and compensates for the first phase difference. The element and the second phase difference compensating element each have a delay satisfying the lambda / 4 condition.

In one embodiment of the present invention, the liquid crystal layer has a delay of? When the molecular axis of the liquid crystal molecules in the liquid crystal layer is substantially perpendicular to the surfaces of the first and second substrates, and the first phase difference compensating element is? /. Has a delay that satisfies the 4-α condition.

In one embodiment of the present invention, the liquid crystal layer has a delay of? When the molecular axis of the liquid crystal molecules in the liquid crystal layer is substantially perpendicular to the surfaces of the first and second substrates, and the first phase difference compensating element is? /. There is a delay satisfying the 4-α condition, and the second phase difference compensating element has a delay satisfying the λ / 4- (β-α) condition.

In one embodiment of the present invention, the first retardation compensator and the second retardation compensator are each formed of a λ / 4 wave plate, and the transmission axis of the first polarization element and the first retardation compensator form an angle of about 45 degrees. The transmission axis of the second polarizer and the second retardation compensator form an angle of about 45 degrees.

In one embodiment of the present invention, the second retardation compensator is formed of a λ / 4 wave plate, and the slower optic axis of the second retardation compensator is the long or short axis of the elliptical polarization transmitted through the liquid crystal layer. Is incident on the second retardation compensating element for converting the elliptical polarization into linear polarization, and the transmission axis of the second polarization element is perpendicular to the polarization axis of the linear polarization.

According to another feature of the invention, the liquid crystal display device comprises a first substrate comprising a transmissive electrode; A second substrate including a reflective electrode; A liquid crystal layer interposed between the first substrate and the second substrate, the liquid crystal layer comprising negative dielectric anisotropy and oriented substantially perpendicular to the surface of the first substrate and the second substrate when no voltage is applied; ; A polarizing element provided on a surface of said first substrate opposite to said liquid crystal layer; And a [lambda] / 4 wavelength plate provided between the polarizing element and the liquid crystal layer. The slow axis of the λ / 4 wave plate and the transmission axis of the polarizing element form an angle of about 45 degrees.

In one embodiment of the present invention, the liquid crystal display device further comprises a phase difference compensating element between the reflective electrode and the polarizing element.

According to another feature of the invention, the liquid crystal display device comprises a first substrate; A second substrate; A liquid crystal interposed between the first substrate and the second substrate, the liquid crystal molecules being negative dielectric anisotropy and oriented substantially perpendicular to the surface of the first substrate and the second substrate when no voltage is applied; layer; A first polarizing element provided on a surface of said first substrate on the opposite side to said liquid crystal layer; A second polarizing element provided on the surface of the second substrate, on the side opposite to the liquid crystal layer; A first λ / 4 wave plate provided between the first polarizing element and the liquid crystal layer; And a second lambda / 4 wavelength plate provided between the second polarizing element and the liquid crystal layer. A plurality of pixel areas is provided for the display. The first substrate includes at least one transmissive electrode, and the second substrate includes a reflective electrode region and a transmissive electrode region corresponding to each of the plurality of pixel regions. The slow axes of the first λ / 4 wave plate and the second λ / 4 wave plate are in the same direction and form an angle of about 45 degrees with each of the transmission axes of the first and second polarization elements.

In one embodiment of the present invention, each of the plurality of pixel areas has a reflection area for performing display using reflected light, and a transmission area for performing display using transmitted light, and the reflective electrode area is configured to reflect the reflection area. And the transmissive electrode region defines the transmissive region.

In one embodiment of the present invention, the liquid crystal display device further comprises at least one phase difference compensating element between the first polarizing element and the second polarizing element.

In one embodiment of the present invention, the liquid crystal layer further comprises chiral dopent.

In one embodiment of the invention, the liquid crystal layer has a twist orientation of about 90 degrees.

In one embodiment of the present invention, the first polarizing element and the second polarizing element have transmission axes orthogonal to each other, and the first phase difference compensating element and the second phase difference compensating element have slow axes that are orthogonal to each other.

In one embodiment of the present invention, the first retardation compensator converts linearly polarized light from the first polarization element into circularly polarized light, and the second retardation compensator converts linearly polarized light from the second polarization device into circularly polarized light, The liquid crystal display device further includes a third phase difference compensation element provided between the first polarizing element and the liquid crystal layer to compensate for wavelength dependence of refractive index anisotropy of the first phase difference compensation element.

In one embodiment of the present invention, the third retardation compensator is a λ / 2 wave plate, and when the transmission axis of the first polarization element and the slow axis of the third retardation compensator form an angle of? 1, The transmission axis and the slow axis of the first retardation compensator form an angle of 2γ1 + 45 degrees.

In one embodiment of the present invention, the liquid crystal display device further includes a fourth phase difference compensation element provided between the second polarizing element and the liquid crystal layer to compensate for wavelength dependence of refractive index anisotropy of the second phase difference compensation element.

In one embodiment of the present invention, the fourth retardation compensator is a λ / 2 wave plate, and when the transmission axis of the second polarization element and the slow axis of the fourth retardation compensator form an angle of? 2, The transmission axis and the slow axis of the second retardation compensator form an angle of 2γ2 + 45 degrees.

In one embodiment of the present invention, the transmission axis of the first polarization element is perpendicular to the transmission axis of the second polarization element, the slow axis of the first phase difference compensation element is perpendicular to the slow axis of the second phase difference compensation element, and the third The slow axis of the retardation compensator is perpendicular to the slow axis of the fourth retardation compensator.

According to another feature of the invention, the liquid crystal display device comprises a first substrate; A second substrate; And a liquid crystal layer interposed between the first substrate and the second substrate. A plurality of pixel areas are provided for display, each of the plurality of pixel areas having a reflection area for performing display using reflected light and a transmission area for performing display using transmitted light. The first substrate includes a counter electrode near the liquid crystal layer. The second substrate may include a plurality of gate lines in the vicinity of the liquid crystal layer, a plurality of source lines perpendicular to the plurality of gate lines, and a plurality of gate lines provided near an intersection point of the plurality of gate lines and the plurality of source lines. Switching elements, a first conductive layer having a high light transmission efficiency, and a second conductive layer having a high light reflection efficiency, wherein the first conductive layer and the second conductive layer are interconnected to each other. Are connected to each and provided in each of the pixel regions.

In one embodiment of the present invention, the liquid crystal display device further comprises an insulating layer between the first conductive layer and the second conductive layer.

In one embodiment of the present invention, the second substrate further comprises a third conductive layer, wherein the first conductive layer and the second conductive layer are interconnected through the third conductive layer.

In one embodiment of the present invention, one of the first conductive layer, the second conductive layer and the third conductive layer is formed of the same material as one of the materials forming the plurality of gate electrodes or the plurality of source electrodes. .

In one embodiment of the present invention, the insulating layer has a wavy surface below the second conductive layer.

According to still another feature of the present invention, it is provided in a method of manufacturing a liquid crystal display device. The liquid crystal display device includes a first substrate; A second substrate; And a liquid crystal layer interposed between the first substrate and the second substrate. A plurality of pixel areas are provided for display, each of the plurality of pixel areas having a reflection area for performing display using reflected light and a transmission area for performing display using transmitted light. The first substrate includes a counter electrode in the vicinity of the liquid crystal layer. The second substrate may include a plurality of gate lines in the vicinity of the liquid crystal layer, a plurality of source lines perpendicular to the plurality of gate lines, and a plurality of gate lines provided near an intersection point of the plurality of gate lines and the plurality of source lines. Switching elements, a first conductive layer having a high light transmission efficiency, and a second conductive layer having a high light reflection efficiency, wherein the first conductive layer and the second conductive layer are each of the switching elements interconnected. And an insulating layer are provided between each of the pixel regions, the insulating layer being provided between the first conductive layer and the second conductive layer. The method includes forming a first conductive layer on a plate; Forming an insulating layer over at least the first conductive layer; Forming a second conductive layer on the insulating layer; And partially removing the second conductive layer formed on the first conductive layer.

In one embodiment of the invention, the method comprises at least a portion of the first conductive layer and the first conductive layer on the connection region on the first conductive layer such that the first conductive layer and the second conductive layer are interconnected through a third conductive layer. Forming a third conductive layer for connecting the second conductive layer; Forming an insulating layer; And partially removing at least the insulating layer on the connection region to connect the first conductive layer and the second conductive layer.

In one embodiment of the present invention, partially removing the insulating layer includes removing the insulating layer on the region of the first conductive layer.

The present invention thus described enables the advantages of providing a reflective LCD device and a transmissive and reflective LCD device and a method of manufacturing the same that provide a satisfactory display with sufficiently high contrast.

These and other advantages of the present invention will be apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying drawings.

1 is a schematic diagram of a reflective LCD device in an example according to the present invention;

2 is a schematic diagram of a transmissive and reflective LCD device in an example according to the invention;

3 is a schematic diagram of a transmissive and reflective LCD device in an example according to the invention;

Fig. 4 is a graph showing the spectral reflection characteristics of the reflective LCD device according to the present invention with a gap of d = 3.56 mu m obtained when light is incident and received vertically.

Fig. 5 is a graph showing the spectral reflection characteristics of the reflective LCD device according to the present invention with a gap of d = 4.5 mu m obtained when light is incident and received vertically.

Fig. 6 is a graph showing the relationship between the cell gap and the contrast ratio of the reflective LCD device according to the present invention obtained when light is incident and received vertically at a wavelength of 550 nm.

7A is a plan view of an active matrix substrate in a first example according to the present invention;

FIG. 7B is a cross-sectional view of the active matrix substrate taken along line 7b-7b 'of FIG. 7A.

8A is a plan view of an active matrix substrate in a second example according to the present invention;

FIG. 8B is a cross-sectional view of the active matrix substrate taken along line 8b-8b 'of FIG. 8A.

8C is a plan view of an active matrix substrate used in a semi-transmissive and semi-reflective LCD device according to the present invention;

FIG. 8D is a cross-sectional view of the active matrix substrate taken along the line 8d-8d 'of FIG. 8C. FIG.

FIG. 8E is a cross-sectional view of the active matrix substrate taken along line 8e-8e 'of FIG. 8C.

Fig. 9 is a graph showing the spectral reflection characteristics of the transmissive and reflective LCD device according to the present invention with a gap of d = 3.56 mu m obtained when light is incident and received vertically.

Fig. 10 is a graph showing the spectral reflection characteristics of the transmissive and reflective LCD device according to the present invention having a gap of d = 4.5 mu m obtained when light is incident and received vertically.

Fig. 11 is a graph showing the relationship between the cell gap and the contrast ratio of the transmissive and reflective LCD device according to the present invention obtained when light is incident and received vertically at a wavelength of 550 nm.

FIG. 12 is a graph showing the relationship between the angle and the contrast ratio of the slower optic axis of the λ / 4 wave plate in the first example. FIG.

Fig. 13A is a schematic diagram showing light transmission and reflection during black display in the LCD device according to the present invention.

Fig. 13B is a schematic diagram showing light transmission and reflection during white display in the LCD device in the second example according to the present invention.

Fig. 14A is a schematic diagram showing light transmission and reflection in the black display of the reflection mode in the LCD device in the fourth example according to the present invention;

Fig. 14B is a schematic diagram showing light transmission and reflection in white display in reflection mode in the LCD device in the fourth example according to the present invention;

Fig. 15A is a schematic diagram showing light transmission and reflection in the black display of the reflection mode in the LCD device in the fourth example according to the present invention;

Fig. 15B is a schematic diagram showing light transmission and reflection in white display in reflection mode in the LCD device in the fourth example according to the present invention;

16 is a graph showing a relationship between wavelength and transmittance in black display in a fourth example.

17 is a schematic diagram of a reflective LCD device in a fifth example according to the present invention;

18A is a schematic diagram showing light transmission and reflection in the black display of the reflection mode in the LCD device in the fifth example according to the present invention;

18B is a schematic diagram showing light transmission and reflection in white display in reflection mode in the LCD device in the fifth example according to the present invention;

18C is a schematic diagram showing light transmission and reflection in a black display of transmission mode in the LCD device in a fifth example according to the present invention;

18D is a schematic diagram showing light transmission and reflection in white display in transmission mode in the LCD device in a fifth example according to the present invention;

19 is a graph showing a relationship between wavelength and transmittance in black display in a fifth example.

20 is a graph showing a relationship between wavelength and transmittance in black display in a fifth example.

21 is a plan view of an active matrix substrate of an LCD device in a sixth example according to the present invention;

FIG. 22 is a sectional view of the active matrix substrate shown in FIG. 21;

23A-23E are cross-sectional views illustrating a method for forming the active matrix substrate shown in FIGS. 21 and 22.

24 is a plan view of an active matrix substrate of an LCD device in a seventh example according to the present invention;

25 is a cross-sectional view of the LCD device taken along the line 25-25 'in FIG.

26A to 26C are cross-sectional views showing a method for forming an active matrix substrate of an LCD device in an eighth example according to the present invention;

27A to 27C are cross-sectional views showing a method for forming an active matrix substrate of an LCD device in a ninth example according to the present invention;

28A to 28C are cross-sectional views showing a method for forming an active matrix substrate of an LCD device in a tenth example according to the present invention;

29A to 29C are cross-sectional views showing a method for forming an active matrix substrate of an LCD device in an eleventh example according to the present invention;

30 is a plan view of an active matrix substrate of the LCD device in Example 11;

31A to 31E and 32A to 32C are cross-sectional views showing a method for forming a display portion of an LCD device in an eleventh example.

33A to 33F are sectional views showing the method for forming the gate terminal portion of the LCD device in the eleventh example.

34A is a sectional view of the gate terminal portion of the LCD device in a variation of the eleventh example;

Fig. 34B is a sectional view of the source terminal portion of the LCD device in the modification of the eleventh embodiment.

35A to 35C are cross-sectional views of a method for manufacturing an LCD device in a twelfth example according to the present invention.

Fig. 36 is a sectional view of an LCD device manufactured by one method in Example 13 according to the present invention.

37A is a sectional view of an LCD device manufactured by another method in the thirteenth example according to the present invention;

FIG. 37B is a graph showing the voltage-brightness relationship of the LCD device shown in FIG. 37A. FIG.

38A is a sectional view of an LCD device manufactured by a comparison method.

FIG. 38B is a graph showing the voltage-brightness relationship of the LCD device shown in FIG. 38A. FIG.

<Explanation of symbols for main parts of drawing>

1, 2: substrate

3: reflective electrode

4: counter electrode

5: liquid crystal layer

6, 9: polarizing element

7, 10: phase difference compensating element (λ / 4 wavelength plate)

8: transmissive electrode

The terms "reflective electrode region", "transmissive electrode region", "reflective region" and "transmissive region" are described.

Reflective LCD devices for performing display using ambient light have reflective electrode regions on one of two substrates for reflecting ambient light transmitted through the liquid crystal layer. The reflective electrode region may be formed by a combination of a reflective electrode or a transmissive electrode and a reflective layer (eg, a reflector). In other words, the electrode for applying the voltage to the liquid crystal layer may be a transmissive electrode, in which case, the reflective electrode region for reflecting the incident light does not need to function as an electrode.

Transmissive and reflective LCD devices, like reflective LCD devices, have reflective electrode regions. The reflective electrode region may be formed by a combination of a reflective electrode or a transmissive electrode and a reflective layer (eg, a reflector). The transmission electrode region is typically formed of a transmission electrode. In the case of an LCD device having a relatively small transmissive electrode region in the reflective electrode (referred to as " semi-transmissive and semi-reflective LCD apparatus), the liquid crystal molecules are subjected to a voltage applied to the liquid crystal layer by the reflective electrode in the transmissive electrode region. Therefore, the transmissive electrode region need not function as an electrode In this type of LCD device, each transmissive electrode region is one dimension (eg, transmissive electrode) smaller than the thickness of the liquid crystal layer. Diameter when the region is circular .. When the reflective electrode region is formed of a combination of a transmissive electrode and a reflective layer (used in a semi-transmissive and semi-reflective LCD device), the transmissive formed in the entirety of each pixel region Reflective layers with electrodes and a plurality of openings can be used.

In the transmissive and reflective LCD device (except the semi-transmissive and semi-reflective LCD device) according to the present invention, the area for performing the display in the transmissive mode is referred to as the "transmissive area", and performs the display in the reflective mode The area to be referred to as "reflection area". The transmission region and the reflection region include a transmission electrode region, a reflection electrode region, and a liquid crystal layer defined by the transmission electrode region and the reflection electrode region, respectively. Semi-transmissive and semi-reflective LCD devices also include reflective electrode regions and transmissive electrode regions, but light reflected by the reflective electrode regions and light transmitted through the transmissive electrode regions are mixed and superimposed. Therefore, the transmission area and the reflection area are not limited independently. In other words, among LCD devices having a transmissive electrode area and a reflective electrode area for each pixel area, an LCD device in which the transmissive area and the reflective area cannot be independently defined (i.e., the areas substantially overlap) is semi- It is called transmissive and semi-reflective LCD device.

The term "pixel area" is defined as follows. The LCD device according to the present invention has a plurality of pixel areas for performing display. The term "pixel area" is defined as the part (element) of an LCD device which forms a pixel which is the smallest display unit. Typically in an active matrix LCD device comprising a counter electrode and a plurality of pixel electrodes arranged in a matrix and switched by respective active elements (e.g., TFTs), the pixel region is located at one of the pixel electrodes, the pixel electrode. And a region of a corresponding counter electrode, and a liquid crystal layer region interposed therebetween. In a simple matrix LCD device comprising strip electrodes (scanning electrode and signal electrode) each formed in two substrates and arranged such that a liquid crystal layer is inserted therebetween and intersects each other, the pixel area includes an intersection area where the strip electrodes cross each other, and An area of the liquid crystal layer corresponding to the intersection area. The transmissive and reflective LCD device according to the present invention has a reflective electrode region and a transmissive electrode region for each pixel region.

The "phase difference compensating element" includes a phase plate or a phase film, and the "polarizing element" includes a polarizing plate or a polarizing film.

"Retardation" refers to the delay for light incident perpendicular to the liquid crystal layer or retardation compensator unless otherwise specified.

<Example 1>

In the first embodiment of the present invention, a reflective LCD device having a higher display image quality than the conventional LCD device is provided as specifically described in the first embodiment. As shown in Fig. 1, the reflective LCD device in the first embodiment includes a first substrate 1 including a transmissive electrode 4, a second substrate 2 including a reflective electrode region 3, A liquid crystal layer 5 interposed between the first substrate 1 and the second substrate 2, a polarizing element 6 provided on the surface of the first substrate 1 opposite the liquid crystal layer 5, and polarization A λ / 4 wavelength plate 7 provided between the element 6 and the liquid crystal layer 5. 1 schematically shows one pixel area of a reflective LCD device according to the present invention.

The liquid crystal layer 5 comprises liquid crystal molecules (not shown) exhibiting negative dielectric anistropy. The liquid crystal molecules of the liquid crystal layer 5 are substantially treated to be oriented perpendicular to the surfaces of the first and second substrates 1 and 2 when no voltage is applied. (The liquid crystal layer treated to align perpendicular to the surface of the substrate when no internal liquid crystal molecules are applied will be referred to as a "vertically oriented liquid crystal layer." When the liquid crystal molecules inside are not applied any voltage, the substrate The liquid crystal layer treated to be oriented horizontally to the surface of the surface will be referred to as a "horizontal alignment liquid crystal layer".) The slower optic axis of the λ / 4 wave plate 7 and the transmission axis of the polarizing element 6 are about It is set to form an angle of 45 degrees. The linearly polarized light incident through the polarizing element 6 is converted into circularly polarized light, and the circularly polarized light reflected by the reflective electrode region 3 and transmitted through the liquid crystal layer 5 is converted into linearly polarized light. Therefore, the delay caused by the liquid crystal layer 5 is substantially zero when no voltage is applied, so that a satisfactory black display is obtained.

As shown in Fig. 2, the transmissive and reflective LCD device in the first embodiment is a liquid crystal inserted between the first substrate 1, the second substrate 2, the first and second substrates 1 and 2; On the surface of the layer 5, the first polarizing element 6 provided on the surface of the first substrate 1 opposite the liquid crystal layer 5, and the second substrate 2 facing the liquid crystal layer 5. And a second polarizing element 9 provided therein. The transmissive and reflective LCD device comprises a first retardation compensator 7 (typically? / 4 wavelength plate) provided between the first polarizing element 6 and the liquid crystal layer 5, and the second polarizing element 9; And a second phase difference compensating element 10 (typically? / 4 wavelength plate) provided between the liquid crystal layers 5. The second substrate 2 includes reflective electrode regions 3 (R) and transmission electrode regions 8 (T) for each of the plurality of pixel regions. 2 schematically shows one pixel area of a transmissive and reflective LCD device. In Fig. 2, the reflective electrode regions 3 (R) and the transmissive electrode regions 8 (T) are each shown as one region for the sake of simplicity. The transmissive and reflective LCD device according to the present invention may have a plurality of transmissive electrode areas 8 in the reflective electrode area 3, such as but not limited to a semi-transmissive and semi-reflective LCD device.

The transmissive and reflective LCD device shown in Fig. 2 operates in the following manner.

In the reflection mode, the delay (birefringence) of the liquid crystal layer in the viewing direction (thickness direction of the liquid crystal layer) is substantially zero (i.e., the saturation voltage described in the initial alignment state in the vertical alignment mode and in the horizontal alignment state). Supplied), a black (dark) display is performed for the following reasons. The linearly polarized light transmitted through the first polarization element is transmitted through the first retardation compensator and the liquid crystal layer and then reflected, and is then transmitted through the liquid crystal layer and the first retardation compensator and enters the first polarization element. At this time, the light has a sufficient polarization component perpendicular to the transmission axis of the first polarization element to perform a black display.

If there is a delay in the perspective direction, a white (bright) display is performed for the following reason. The linearly polarized light transmitted through the first polarization element is transmitted through the first retardation compensator and the liquid crystal layer and then reflected, and is then transmitted through the liquid crystal layer and the first retardation compensator and enters the first polarization element. At this time, the light has a sufficient polarization component parallel to the transmission axis of the first polarization element to perform a white display. Gray scale display corresponding to various delays by the liquid crystal layer is realized by applying voltage across the liquid crystal layer.

In the transmission mode, if the delay in the perspective direction is substantially zero, the black display is performed for the following reason. The linearly polarized light transmitted through the second polarizer is transmitted through the second retardation compensator, the liquid crystal layer, and the first retardation compensator to enter the first polarizer. At this time, the light has a sufficient polarization component perpendicular to the transmission axis of the first polarization element to perform a black display.

If there is a delay in the perspective direction, the white display is performed for the following reason. The linearly polarized light transmitted through the second polarizer is transmitted through the second phase difference compensator, the liquid crystal layer, and the first phase difference compensator to enter the first polarizer. At this time, the light has a sufficient polarization component parallel to the transmission axis of the first polarization element to perform a white display. Gray scale display corresponding to various delays is realized.

Therefore, when the reflection mode and the transmission mode are used together, the black display is performed in both modes, to realize a high contrast display. Gray scale display is performed by varying the delay by controlling the voltage.

When the reflection area for performing the display in the reflection mode and the transmission area for performing the display in the transmission mode are formed for each pixel area, the light illumination rate of the reflected light is improved. Moreover, in this structure, the thickness (delay) of the liquid crystal layer in the reflection area and the transmission area is adjusted independently. Therefore, each display mode is optimized.

The delay caused by the liquid crystal layer is substantially zero when the molecular axis of the liquid crystal molecules is substantially perpendicular to the surfaces of the first and second substrates. If the delay caused by each of the first retardation compensator and the second retardation compensator satisfies the lambda / 4 condition, the liquid crystal layer in the perspective direction is used in the reflection mode using the light reflected by the reflective function region such as the reflection layer or the reflection plate. There is almost no birefringence by. Thus, circularly polarized light is incident and reflected by the reflective electrode region to become circularly polarized light having an opposite direction of rotation. The light is transmitted through the first retardation compensator and becomes linearly polarized light perpendicular to the transmission axis of the first polarization element. Since the reflective area acts as an optical isolator, a black display with little optical leakage is provided.

If there is a delay (birefringence) by the liquid crystal layer in the perspective direction in the reflection mode, the delay can be changed by controlling the voltage so that the light incident on the first polarizing element, reflected and incident on the first polarizing element again is the first It has a component parallel to the transmission axis of a polarizing element. Thus, a bright display with gray scale is provided.

In the transmission mode, if there is almost no delay by the liquid crystal layer in the perspective direction, circularly polarized light incident on the liquid crystal layer is maintained as circularly polarized light when transmitted through the liquid crystal layer. The light is transmitted through the first retardation compensator and becomes linearly polarized light perpendicular to the transmission axis of the first polarization element. Therefore, a black display with little optical leakage is provided.

If there is a delay by the liquid crystal layer in the perspective direction in the transmission mode, the delay can be changed by controlling the voltage. Therefore, light incident on the second polarizing element is incident on the first polarizing element parallel to the transmission axis of the first polarizing element. Thus, a white display having a gray scale is provided.

As described above, if both reflective and transmissive modes are used, the state of the liquid crystal molecules for the black display is the same in both display modes, providing a black display that is substantially free of any optical leakage. Regardless of the ambient light intensity, transmissive and reflective LCD devices provide high contrast displays.

In such an LCD device, even when the delay? Caused by liquid crystal layer molecules remaining almost perpendicular to the first and second substrates cannot be ignored, for example, a horizontally oriented liquid crystal layer is used or an inclination angle When too large in this vertically aligned liquid crystal layer, a high contrast display is provided in the reflection mode by setting the residual delay caused by the liquid crystal layer and the delay caused by the phase difference compensating element to a wide wavelength range with a combination satisfying the λ / 4 condition.

In the reflective mode, the light that has passed through the liquid crystal layer twice and then exits the liquid crystal layer is an elliptically polarized light offset from the circularly polarized light due to the residual delay α. Elliptical polarization is phase-offset 90 degrees from the incident light. Thus, when transmitted through the first retardation compensator with a λ / 4-α delay, the light becomes linearly polarized light perpendicular to the transmission axis of the first polarization element. Since the reflective area acts as an optical insulator, a black display with little optical leakage is provided.

As can be seen, a high contrast display is obtained in reflection mode even if the residual delay cannot be ignored. In the case where mainly the reflection mode display is performed, for example, when the reflective pixel electrode is larger than the transmissive pixel electrode, the second phase difference compensation element 10 shown in FIG. 3 may be a λ / 4 wavelength plate.

Even if the residual delay is not negligible, for example, if a horizontally oriented liquid crystal layer is used or if the inclination angle is too large in the vertically oriented liquid crystal layer, a high contrast display is formed by the reflective LCD device, the transmissive LCD device and Provided is a transmissive and reflective LCD device. Where α is a delay caused by the liquid crystal layer in the reflection region when the liquid crystal molecules are almost perpendicularly aligned with the substrate, and β is a delay caused by the liquid crystal layer in the transmission region, the delay of the first retardation compensator is λ / 4 satisfies -α and the delay of the second phase difference compensating element satisfies λ / 4- (β-α).

As described above, in the reflective mode, the light that has passed through the liquid crystal layer twice and then exits the liquid crystal layer is an elliptically polarized light offset from the circularly polarized light by the residual retardation α. When the light is transmitted through the first retardation compensator having a delay of? / 4-α, the light becomes linearly polarized light perpendicular to the transmission axis of the first polarization element.

In the transmissive mode, if the delay? Due to the liquid crystal molecules in the visible angle is not negligible, the light exiting the liquid crystal layer is set in such a way that the second retardation compensator is set to have λ / 4- (β-α). As is elliptical polarization. The elliptical polarization becomes linear polarization perpendicular to the transmission axis of the first polarization element when transmitted through the phase difference compensating element. Therefore, a black display with little optical leakage is obtained.

Even if the residual delay is not negligible, the following structure provides a high contrast display for the reflective LCD device, the transmissive LCD device, and the transmissive and reflective LCD device.

If the residual delay is negligible, circularly polarized light is incident on the liquid crystal layer and a high contrast display is obtained with a simple structure due to the following setting. The first and second phase difference compensating elements are each formed of a λ / 4 wave plate. The transmission axis of the first polarization element and the slow axis of the first retardation compensator are set to form an angle of about 45 degrees. The transmission axis of the second polarization element and the slow axis of the second retardation compensator are set to form an angle of about 45 degrees.

In transmissive and reflective LCD devices, a liquid crystal layer in which liquid crystal molecules are oriented substantially perpendicular to the surface of the substrate when no voltage is applied may be used. In such a case, the LCD device can serve as a transmissive LCD device for performing a display using light transmitted through a transmissive electrode region formed of a material having a relatively high light transmittance from the backlight when the ambient light is dark. When the ambient light is bright, the LCD device can be used as a reflective LCD device for performing a display using ambient light reflected by a reflective electrode region formed of a material having a relatively high light reflectance. When the transmission mode and the reflection mode are used together, a substantially complete black display is performed in both modes. Therefore, high contrast display is realized. This will be explained below.

Transmissive and reflective LCD devices are generally operable in both normal black (hereinafter referred to as "NB") mode and normal white (hereinafter referred to as "NW") mode using birefringence.

In the NW mode, the voltage to be applied to obtain the black display changes as the cell gap changes. In the NB mode, the voltage to be applied to obtain the white display changes as the cell gap changes. Therefore, in the NW mode, the contrast ratio varies greatly with the cell gap, requiring accurate cell gap control. In NB mode, the contrast does not change substantially with the cell gap, thus providing a larger margin for cell gap control. Moreover, in the NB mode, when the switching element (e.g., TFT) malfunctions to interfere with voltage application to the pixel electrode, inconspicuous black spots are generated.

Transmissive and reflective LCD devices operable in the NB mode have high production efficiency, and high contrast displays are easily realized in spite of the ambient light intensity according to the present invention.

The retardation compensating element may be provided to compensate for the influence of the refractive index anisotropy of the liquid crystal molecules caused in the light incident direction and the perspective direction on the liquid crystal layer. In such a structure, the reduction of contrast along the light incidence direction and the perspective direction is prevented.

When a chiral dopant is added to a vertically oriented liquid crystal layer formed of a liquid crystal material exhibiting negative dielectric anisotropy of the LCD device, the liquid crystal molecules are rotated when a voltage is applied. Therefore, the rotation of the liquid crystal molecules upon voltage application is stabilized by the chiral dopant.

If the alignment layers near the two substrates are rubbed in different directions, the traces of the alignment treatment are less pronounced because they are not in the same direction. When the liquid crystal layer has a 90 degree twist orientation, a black display with little optical leakage is obtained for the following reason. Since the inclination direction of the liquid crystal molecules forms an angle of 90 degrees in the vicinity of the two substrates, the delays generated in the inclination direction are canceled by each other.

The refractive index of the birefringent material forming the retardation compensating element for the normal light beam and the special light beam depends greatly on the wavelength. Therefore, the phase delay accumulated in the retardation compensator at a certain thickness also depends on the wavelength. In other words, the phase retardation (eg, [lambda] / 4) can be fully provided for linear polarization of incidence only when the incident light has any single wavelength. Thus, in a region where the phase retardation of λ / 4 is not obtained due to the wavelength dependence of the refractive index anisotropy of the birefringent material forming the λ / 4 waveplate, a part of the light is not absorbed by the polarizing element but through the polarizing element on the traveling side. Is transmitted. As a result, the darkness of the black display changes. According to the present invention, the slow axes of the first and second retardation compensating elements are set perpendicular to each other. Due to this structure, the wavelength dependency of the refractive index anisotropy of the first retardation compensating element is canceled by the wavelength dependency of the refractive index anisotropy of the second retardation compensating element. Therefore, any phase difference is satisfied over the entire wavelength range. Therefore, the darkness of the black display is improved.

As shown in FIG. 17, a third retardation compensator 11 may be provided between the first polarization element 6 and the liquid crystal layer 5. Due to this structure, the wavelength dependence of refractive index anisotropy caused when linearly polarized light is converted into circularly polarized light by the first retardation compensating element cancels to some extent. Thus, in the reflection mode, the conversion to circular polarization is performed in a state where the dispersion of polarization states is reduced over a wide wavelength range. Therefore, the darkness of the black display is improved.

The third compensation element is formed of a λ / 2 wave plate, and the transmission axis of the first polarization element and the slow axis of the first phase difference compensation element have an angle of 2γ1 + 45 degrees, where γ1 is the transmission axis and the third compensation of the first polarization element. Angle of the slow axis of the device), the polarization direction of the linearly polarized light from the first retardation compensator is converted into circularly polarized light by the first retardation compensator after the orientation is changed by the third retardation compensator. . Therefore, the wavelength dependence of the refractive index anisotropy of the first retardation compensating element is optimally compensated. Therefore, since the dispersion of the polarization state is reduced over a wide wavelength range in the reflection mode, circularly polarized light is satisfactorily obtained. As such, the blackness of the black display in the reflective mode is improved. Substantially the same effect is obtained even when the first and third retardation compensating elements are placed oppositely.

In particular, if a vertically oriented liquid crystal layer is used or the residual delay caused by the liquid crystal layer is negligible in the dark state, the first retardation compensating element can be formed of a λ / 4 wave plate.

If the delay of? remains in the reflection mode liquid crystal layer in a dark state, the delay of the first retardation compensator is? / 4-? so that light offset from circularly polarized light enters the liquid crystal layer. When light is transmitted through the liquid crystal layer and reaches the reflective electrode, the light becomes circularly polarized light as a result of dispersion of the polarization state that is removed over a wide wavelength range. As such, a satisfactory black display is realized in the reflection mode.

The fourth retardation compensator 12 may be provided between the second polarization element 9 and the liquid crystal layer 5. Due to this structure, the wavelength dependence of the refractive anisotropy caused when the linearly polarized light is converted to the circular wavelength is offset to some extent. Thus, in the transmission mode, the change to circular polarization is performed in a state where the dispersion of polarization states is reduced over a wide wavelength range. As such, the blackness of the black display is improved. Even if the reflection mode and the transmission mode are used together, a satisfactory black display is realized.

The fourth compensation element is formed of a λ / 2 wave plate, and the transmission axis of the second polarization element and the slow axis of the second phase difference compensation element have an angle of 2γ2 + 45 degrees, where γ2 is the transmission axis of the second polarization element and the fourth Linear polarization from the second retardation compensating element, after the orientation is changed by the fourth retardation compensating element, is converted into circular polarization by the second retardation compensating element. Therefore, the wavelength dependence of the refractive index anisotropy of the first retardation compensating element is optimally compensated. As such, dispersion in the polarization state is reduced over a wide wavelength range in the transmission mode, so that circularly polarized light is satisfactorily obtained.

In particular, when the vertically oriented liquid crystal layer is used or when the remaining delay by the liquid crystal layer is negligible in the dark state, the second retardation compensating element may be formed of a λ / 4 wave plate.

When the liquid crystal layer in the dark state has a delay of α in the reflection mode and a delay of β in the transmission mode, the delay of the later used element is such that the light offset from the circularly polarized light is incident on the liquid crystal layer. (β-α). When light is transmitted through the liquid crystal layer, the light is in the same polarization state as in the reflection mode. Therefore, when transmitted through the third retardation compensating element, the light becomes linearly polarized light perpendicular to the transmission axis of the first polarizing element. Thus, the blackness of the black display is improved. Even when the transmission mode and the reflection mode are used together, a satisfactory black display is realized.

When the slow axes of the first and second retardation compensators are orthogonal to each other and the slow axes of the third and fourth retardation compensators are orthogonal to each other, the wavelength dependence of the refractive index anisotropy of the first and third retardation compensating elements is determined by the second and The wavelength dependence of the refractive index anisotropy of the fourth retardation compensating element is respectively canceled. As such, the blackness of the black display is improved.

(Example 1)

The LCD device in the first example according to the present invention will be described with reference to FIG.

The substrate 2 comprises a reflecting electrode 3 (shown as a reflecting electrode region in FIG. 1) formed of a material having a high reflectance such as, for example, Al or Ta. The substrate 1 comprises an opposing electrode 4 (shown as transmissive electrode in FIG. 1). A liquid crystal layer 5 formed of a liquid crystal material exhibiting negative dielectric anisotropy is inserted between the reflective electrode 3 and the counter electrode 4.

An alignment layer (not shown) is provided on the surfaces of the reflective electrode 3 and the counter electrode 4 in contact with the liquid crystal layer 5. The alignment layer is used to orient liquid crystal molecules (not shown) of the liquid crystal layer 5 so as to be perpendicular to the surfaces of the substrates 1 and 2. After the alignment layer is provided, at least one of the alignment layers is subjected to an alignment treatment such as, for example, rubbing.

Due to the alignment treatment, the liquid crystal molecules of the liquid crystal layer 5 have an inclination angle of about 0.1 ° to 5 ° with respect to the direction perpendicular to the surfaces of the substrates 1 and 2.

Since the liquid crystal layer 5 is formed of a material showing negative dielectric anisotropy, when a voltage is applied between the reflective electrode 3 and the counter electrode 4, the liquid crystal molecules are horizontal with respect to the surfaces of the substrates 1 and 2. Incline

The reflective electrode 3 is used to apply a voltage to the liquid crystal layer 5, but the reflective electrode 3 can be used only as a reflecting plate, and cannot be used as an electrode for applying a voltage. In this case, for example, the transmissive electrode 8 extends onto the reflective electrode 3 to serve as an electrode for applying a voltage to the liquid crystal layer 5 in the reflective region.

The liquid crystal material used here has refractive index anisotropy of Ne (refractive index with respect to special light) = 1.5546, No (refractive index with respect to normal light) = 1.4773, and (DELTA) N (Ne-No) = 0.0773.

A λ / 4 wave plate 7 is provided on the surface of the substrate 1 opposite the counter electrode 4. The slow axis of the λ / 4 wave plate 7 is set to be inclined at 45 ° with respect to the longitudinal axis (ie, the molecular axis) of the liquid crystal molecules when a voltage is applied to the liquid crystal layer 5.

The λ / 4 wave plate 7 is used to convert linearly polarized light into circularly polarized light and to convert circularly polarized light into linearly polarized light.

In this embodiment, the λ / 4 wave plate 7 is provided on the surface of the substrate 1 opposite to the counter electrode 4, but may be provided between the reflective electrode 3 and the liquid crystal layer 5.

The λ / 4 wave plate 7 may be installed on the surface of the substrate 1 or integrated with the polarizing element 6 to reduce the production cost.

The polarizing element 6 is provided on the surface of the λ / 4 wave plate 7 opposite to the substrate 1. The transmission axis of the polarizing element 6 is set to be inclined at 45 ° with respect to the slow axis of the λ / 4 wave plate 7.

FIG. 7A is a plan view of an active matrix substrate (substrate 2) in the first embodiment, and FIG. 7B is a cross-sectional view of the active matrix substrate cut along the line 7B-7B 'of FIG. 7A.

As shown in FIGS. 7A and 7B, the active matrix substrate may include a gate line 21, a data line 22, a driving element 23, a drain electrode 24, a storage capacitance electrode 25, and a gate insulating layer ( 26, an insulating substrate 27, a contact hole 28, an interlayer insulating layer 29, and a reflective electrode 30 (corresponding to the reflective electrode 3 in FIG. 1).

The accumulation capacitance electrode 25 is electrically connected to the drain electrode 24 and overlaps the accumulation capacitance line 32 with the gate insulating layer 26 interposed therebetween. Thus, the storage capacitance electrode 25, the insulating layer 26, and the storage capacitance line 32 form the storage capacitance.

The contact hole 28 is formed in the interlayer insulating layer 29 to connect the reflective electrode 30 and the accumulation capacitance electrode 25.

13A and 13B, light transmission and reflection of the LCD device in the reflection mode in the first embodiment will be described.

FIG. 13A shows a black display performed when no voltage is applied to the liquid crystal layer 5, and FIG. 13B shows a white display performed when a voltage is applied to the liquid crystal layer 5. In these figures, the reflective electrode 3 (reflective electrode region 3) is formed on the left side.

Referring to FIG. 13A, a black display will be described.

Light incident on the upper surface of the polarizing element 6 is transmitted through the polarizing element 6 so as to be linearly polarized light parallel to the transmission axis of the polarizing element 6, and then enters the λ / 4 wavelength plate 7.

The λ / 4 wave plate 7 is arranged such that the transmission axis of the polarizing element 6 and the slow axis of the λ / 4 wave plate 7 are at an angle of 45 °. Thus, the light transmitted through the λ / 4 wave plate 7 becomes circularly polarized light.

When no voltage is applied to the liquid crystal layer 5, the liquid crystal molecules exhibiting negative dielectric anisotropy used for the liquid crystal layer 5 are substantially perpendicular to the surfaces of the substrates 1 and 2. Therefore, the refractive index anisotropy of the liquid crystal layer 5 with respect to incident light is very small. That is, the phase difference caused by the light transmission through the liquid crystal layer 5 is substantially zero.

Thus, the circularly polarized light from the λ / 4 wave plate 7 is transmitted through the liquid crystal layer 5 while maintaining the circularly polarized light and reflected by the reflective electrode 3 of the substrate 2.

The circularly polarized light reflected by the reflective electrode 3 is transmitted through the liquid crystal layer 5 toward the substrate 1 and enters the λ / 4 wavelength plate 7 while maintaining the circularly polarized light.

Then, the circularly polarized light is transmitted through the λ / 4 wave plate 7 so as to be linearly polarized perpendicular to the transmission axis of the polarizing element 6 and then enters the polarizing element 6.

Now, since the polarization direction of the light is orthogonal to the transmission axis of the polarizing element 6, the light is not transmitted but is absorbed by the polarizing element 6.

In this way, a black display is performed.

With reference to FIG. 13B, a white display will be described.

The process until the light is transmitted through the λ / 4 wave plate 7 so as to be circularly polarized light is the same as above and will not be described.

When a voltage is applied to the liquid crystal layer 5, the liquid crystal molecules are inclined horizontally with respect to the surfaces of the substrates 1 and 2. Therefore, circularly polarized light incident on the liquid crystal layer 5 becomes elliptically polarized light by birefringence of liquid crystal molecules. Then, the light is reflected by the reflective electrode 3, and the light is transmitted through the liquid crystal layer 5, and then the polarization is changed. After being transmitted through the [lambda] / 4 wave plate 7, the light does not become linearly polarized orthogonal to the transmission axis of the polarizing element 6. Thus, light is transmitted through the polarizing element 6.

By controlling the voltage applied to the liquid crystal layer 5, the amount of light reflected by the reflective electrode 3 and then transmitted through the polarizing element 6 can be adjusted. Thus, a gray scale display is provided.

In order to change the orientation of the liquid crystal molecules so that the phase difference by the liquid crystal layer 5 satisfies the 1/4 wavelength (λ / 4) condition, the voltage is applied to the liquid crystal layer 5 by the reflective electrode 3 and the counter electrode 4. When applied to, the circularly polarized light from the λ / 4 wave plate 7 is linear, which is orthogonal to the transmission axis of the polarizing element 6 when it reaches the reflective electrode 3 after being transmitted through the liquid crystal layer 5. It becomes polarized light. Light is transmitted again through the liquid crystal layer 5 and the λ / 4 wave plate 7 so as to be linearly polarized parallel to the transmission axis of the polarizing element 6. In this case, the amount of light transmitted through the polarizing element 6 is maximum.

As described above, when no voltage is applied across the liquid crystal layer 5, a black display is obtained because the liquid crystal layer 5 has substantially no birefringence, and a voltage is applied across the liquid crystal layer 5. The gray scale display is obtained by changing the light transmittance with respect to the voltage.

4 is a reflection type in the first embodiment obtained when the cell gap of the liquid crystal layer is d = 3.56 탆 and the delay (phase difference) caused by the liquid crystal layer is dΔN = 0.2752 when light is incident and received vertically. The spectral reflectance characteristics of the LCD device are shown.

In Fig. 4, the spectral reflectance of the single reflector when light is incident and received vertically is 100.

As shown in Fig. 4, a sufficient contrast ratio of 50 or more is obtained over the entire wavelength range of 400 nm to 700 nm between the black display when no voltage is applied and the white display when a voltage of 3.25 V is applied.

When a voltage of 3.25 V is applied, a reflectance of about 40% is obtained which is substantially equal to the transmittance of the polarizing element 6. This high light illumination rate is suitable for reflective LCD devices.

5 is a reflection type in the first embodiment obtained when the cell gap of the liquid crystal layer is d = 4.5 μm and the delay (phase difference) caused by the liquid crystal layer is dΔN = 0.3479 when light is incident and received vertically. The spectral reflectance characteristics of the LCD device are shown.

As shown in Fig. 5, a sufficient contrast ratio of 50 or more is obtained over the entire wavelength range of 400 nm to 700 nm between the black display when no voltage is applied and the white display when a voltage of 3 V is applied.

When a voltage of 3V is applied, a reflectance of about 40% is obtained as in the case of cell gap d = 3.56 mu m.

Fig. 6 shows the relationship between the cell gap and the contrast ratio of the reflective LCD device in the first embodiment when light is incident at a wavelength of 550 nm and received vertically.

The contrast ratio is measured by applying a voltage such that the delay (phase difference) dΔN due to the liquid crystal layer satisfies the 1/4 wavelength condition.

As shown in Fig. 6, the reflective LCD device in the first embodiment maintains a contrast ratio of 500 or more regardless of the cell gap of the liquid crystal layer.

Thus, when a voltage is applied across the liquid crystal layer, the display is provided without any reduction in the contrast ratio as long as the phase difference dΔN satisfies the 1/4 wavelength condition. The cell gap d may be set arbitrarily.

12 shows the relationship between the angle and the contrast ratio of the slow axis of the λ / 4 wave plate. The angle of the slow axis of the λ / 4 wave plate is set to 0 ° when the slow axis is inclined at 45 ° with respect to the transmission axis of the polarizing element.

If the angular difference of the slow axis is within 3 °, a contrast ratio of 500 or more is obtained, so that a reflective LCD device having satisfactory display characteristics is provided.

That is, high contrast is obtained even when the λ / 4 wave plate and the polarizing element are combined with the angles of the slow axis of the λ / 4 wave plate slightly offset from the set value and the transmission axis of the polarizing element.

6 shows the value after the influence of reflection by the surface of the panel is removed. In practical use, reflection by the surface of the panel cannot be ignored. The contrast ratio considering the reflection by the panel is about 20, which is still satisfactory for the reflective LCD device.

The LCD device in the first embodiment using the vertically aligned liquid crystal layer causes the delay caused by the liquid crystal layer to be substantially zero when no voltage is applied. In the case of a normal black display, the darkness of the dark state is improved, increasing the contrast.

(Example 2)

The LCD device in the second embodiment according to the present invention will be described with reference to FIG. The same elements as in the first embodiment have the same reference numerals.

The substrate 2 has a reflective electrode 3 (shown as a reflective electrode region in FIG. 2) formed of a material having a high reflectance such as, for example, Al or Ta, and a high transmittance such as, for example, ITO. A transmissive electrode 8 formed of material (shown as the transmissive electrode region in FIG. 2). Substrate 1 comprises a counter electrode 4 (shown as transmissive electrode in FIG. 2). A liquid crystal layer 5 formed of a liquid crystal material exhibiting negative dielectric anisotropy is inserted between the reflective electrode 3 / the transmissive electrode 8 and the counter electrode 4.

An alignment layer (not shown) is provided on the surfaces of the reflective electrode 3 / transmissive electrode 8 and the counter electrode 4 in contact with the liquid crystal layer 5. The alignment layer is used to arrange liquid crystal molecules (not shown) of the liquid crystal layer 8 orthogonally to the surfaces of the substrates 1 and 2. After the array layer is provided, at least one of the array layers is subjected to an alignment process such as rubbing, for example.

Due to the alignment treatment, the liquid crystal molecules of the liquid crystal layer 5 have an inclination angle of about 0.1 ° to 5 ° with respect to the direction perpendicular to the surfaces of the substrates 1 and 2.

The reflective electrode 3 is used to apply a voltage to the liquid crystal layer 5, but the reflective electrode 3 can be used only as a reflecting plate, and cannot be used as an electrode for applying a voltage. In this case, for example, the transmissive electrode 8 extends onto the reflective electrode 3 and acts as an electrode for applying a voltage to the liquid crystal layer 5 in the reflective region.

The liquid crystal material used here has refractive index anisotropy of Ne (refractive index for special light) = 1.5546 and No (refractive index for normal light) = 1.4773.

The λ / 4 wave plate 7 is provided on the surface of the substrate 1 opposite the counter electrode 4. The slow axis of the λ / 4 wave plate 7 is set to be inclined at 45 ° with respect to the longitudinal axis of the liquid crystal molecules when a voltage is applied across the liquid crystal layer 5.

The λ / 4 wave plate 10 is provided on the surface of the substrate 2 opposite the reflective electrode 3 and the transmissive electrode 8. The slow axis of the λ / 4 wave plate 10 is parallel to the slow axis of the λ / 4 wave plate 7.

The polarizing element 6 is provided on the surface of the λ / 4 wave plate 7 opposite the substrate 1. The polarizing element 9 is provided on the surface of the λ / 4 wave plate 10 opposite the substrate 2. The transmission axis of the polarizing element 6 is set to be inclined 45 degrees with respect to the slow axis of the λ / 4 wave plate 7. The transmission axis of the polarizing element 9 is set to be inclined 45 degrees with respect to the slow axis of the λ / 4 wave plate 10.

FIG. 8A is a plan view of the active matrix substrate (substrate 2) in the second embodiment, and FIG. 8B is a cross-sectional view of the active matrix substrate cut along the line 8B-8B 'of FIG. 8A.

As shown in FIGS. 8A and 8B, the active matrix substrate includes a gate line 21, a data line 22, a driving element 23, a drain electrode 24, a storage capacitance electrode 35, and a gate insulating layer 26. ), An insulating substrate 27, a contact hole 28, an interlayer insulating layer 29, a reflective pixel electrode (reflective electrode region) 30 (corresponding to the reflective electrode 3 in FIG. 2), and a transparent pixel electrode (transmissive electrode Region 31 (corresponding to transmissive electrode 8 in FIG. 2).

The accumulation capacitance electrode 35 is electrically connected to the drain electrode 24 and overlaps the gate line 21 with the gate insulating layer 26 interposed therebetween. Therefore, the storage capacitance electrode 35, the insulating layer 26 and the gate line 21 form the storage capacitance.

The contact hole 28 is formed in the interlayer insulating layer 29 to connect the transmissive pixel electrode 31 and the storage capacitance electrode 35.

The reflective pixel electrode 30 and the transparent pixel electrode 31 form a reflective region and a transparent region in each of the plurality of pixel regions in the LCD device. The reflective region substantially performs reflective mode display by reflecting external light, and the transmissive region permits light from the backlight to be transmitted to perform substantially transmissive mode display. Needless to say, the boundary between the two areas is not so clear because there is a light component that is obliquely incident on the LCD device in the actual display.

As shown in FIG. 8A, it is preferable to provide the reflective electrode region 30 in the peripheral region of the pixel region, and the transparent electrode region 31 in the center region of the pixel region. By partially overlapping the reflective electrode region 30 with the gate line 21 and the data line 22, an accumulation capacitance is formed and the display region is expanded.

In the second embodiment, a semi-transmissive and semi-reflective LCD device is provided. 8C is a plan view of an active matrix substrate used in semi-transmissive and semi-reflective LCD devices. 8D is a cross-sectional view of the active matrix substrate cut along the line 8D-8D 'of FIG. 8C, and FIG. 8E is a cross-sectional view of the active matrix substrate cut along the line 8E-8E' of FIG. 8C.

The active matrix substrate shown in FIG. 8C includes a small transmissive electrode region 30T in the reflective electrode region 30. The reflection electrode region 30 and the transmission electrode region 30T do not independently define the reflection region and the transmission region, and the display in the reflection mode and the display in the transmission mode are mixed and overlapped in the entire pixel region.

The active matrix substrate shown in FIG. 8C is manufactured by forming a reflective electrode 30 having a plurality of openings 30T, for example, as shown in FIG. 8D. Since the voltage (a gradient electric field formed between the reflective electrode 30 and the counter electrode) is applied across the liquid crystal molecules disposed on the opening 30T in the reflective electrode 30 by the reflective electrode 30, the transmissive electrode ( 31) may be omitted. That is, the reflective electrode 30 may be formed of semi-transmissive and semi-reflective layers. Optionally, when the reflective electrode 30 is patterned by photolithography, openings of a predetermined shape may be formed to a predetermined density. One dimension of these openings should not be greater than the thickness of the liquid crystal layer so that a sufficient voltage can be applied across the liquid crystal layer by an oblique electric field. Electrodes formed of semi-transmissive and semi-reflective layers are disclosed in Japanese Laid-Open Patent Publication No. 7-333598. The semi-transmissive and semi-reflective layers are formed by depositing metal particles in a very small thickness in the pixel region, or by forming fine holes or recesses in the pixel region.

Optionally, the active matrix substrate shown in FIG. 8C is fabricated by forming the transmissive electrode 44 on the reflective electrode region 30 having openings in the entire pixel region, for example, as shown in FIG. 8E. In such a configuration, the liquid crystal molecules on the transmission electrode region 30T are applied with a voltage at the same level as the voltage applied across the liquid crystal molecules on the reflective electrode region 30. During the etching process to form the transmissive electrode 44 (eg, when the reflective electrode region 30 is formed of Al and the transmissive electrode 44 is formed of ITO), the transmissive electrode region 30 and the transmissive electrode 44 are transmissive. Electrocorrosion may occur between the electrode regions 44. As shown in FIG. 8E, an interlayer insulating layer 42 (for example, formed of silicon oxide or a resin polymer) is formed on the reflective electrode region 30, and a transmissive electrode (eg, formed on the interlayer insulating layer 42). By forming 44), electrocorrosion can be avoided.

13A and 13B, light transmission and reflection in the LCD device in the transmission mode in the second embodiment are described.

FIG. 13A illustrates a black display performed when no voltage is applied across the liquid crystal layer 5, and FIG. 13B illustrates a white display performed when a voltage is applied across the liquid crystal layer 5. In these figures, the transmission electrode 8 (transmission electrode region) is formed on the right side. In FIGS. 13A and 13B, the reflective electrode region 3 has the same configuration as in the first embodiment, and thus description thereof will be omitted. When the LCD device is used as the reflective LCD device, the LCD device operates in the same manner as in the first embodiment. In the following description, the LCD device in the transmissive mode is described, and the LCD device in the reflective mode will not be described again.

A black display will be described with reference to FIG. 13A.

Light emitted by a light source (not shown) is incident on the polarizing element 9 so as to be linearly polarized light parallel to the transmission axis of the polarizing element 9.

The λ / 4 wave plate 10 is arranged such that the slow axis is inclined 45 degrees with respect to the transmission axis of the polarizing element 9. Thus, light transmitted through the λ / 4 wave plate 10 becomes circularly polarized light.

When no voltage is applied across the liquid crystal layer 5, the liquid crystal molecules exhibiting negative dielectric anisotropy used for the liquid crystal layer 5 are substantially perpendicular to the surfaces of the substrates 1 and 2. Therefore, the refractive index anisotropy of the liquid crystal layer 5 with respect to incident light is very small. In other words, the phase difference generated by the transmission of light through the liquid crystal layer 5 is substantially zero.

Therefore, the circularly polarized light from the λ / 4 wave plate 10 is transmitted through the liquid crystal layer 5 while maintaining the circularly polarized light and is incident on the λ / 4 wave plate 7.

The slow axis of the λ / 4 wave plate 10 and the slow axis of the λ / 4 wave plate 7 are parallel to each other. Therefore, the circularly polarized light incident on the λ / 4 wave plate 7 becomes linearly polarized light perpendicular to the transmission axis of the polarizing element 9 and is incident on the polarizing element 6.

The linearly polarized light from the λ / 4 wave plate 7 is absorbed by the polarizing element 6 without being transmitted perpendicular to the transmission axis of the polarizing element 6.

In this way, a black display is performed.

With reference to FIG. 13B, a white display will be described.

The process until the light is transmitted through the λ / 4 wave plate 10 is the same as the above processes and the description thereof will be omitted.

When voltage is applied across the liquid crystal layer 5, the liquid crystal molecules are inclined horizontally with respect to the surfaces of the substrates 1 and 2. Therefore, the circularly polarized light incident on the liquid crystal layer 5 becomes elliptically polarized light by the birefringence of the liquid crystal molecules. Light is transmitted through the polarizing element 6 without being linearly polarized perpendicular to the transmission axis of the polarizing element 6 even after being transmitted through the λ / 4 wave plate 7.

By controlling the voltage applied across the liquid crystal layer 5, the amount of light incident on the polarizing element 6 can be adjusted. Thus, a gray scale display is provided.

When a voltage is applied across the liquid crystal layer 5 so that the phase difference by the liquid crystal layer 5 satisfies the 1/2 wavelength condition, the circularly polarized light from the λ / 4 wave plate 10 is applied to the liquid crystal layer 5. After the linear polarization perpendicular to the transmission axis of the polarizing element 6 at 1/2 of the thickness, circular polarization is obtained when the light is completely transmitted through the liquid crystal layer 5.

Since the circularly polarized light from the liquid crystal layer 5 becomes linearly polarized light parallel to the transmission axis of the polarizing element 6 when transmitted through the λ / 4 wave plate 7, most of the incident incident on the polarizing element 6 Light is transmitted through it. In this case, the amount of light transmitted through the polarizing element 6 is maximum.

As described above, when no voltage is applied across the liquid crystal layer 5, a black display is obtained in both the reflective electrode region 3 and the transmissive electrode region 8 because there is no birefringence of the liquid crystal layer 5. Lose. When a voltage is applied across the liquid crystal layer 5 while controlling the level of the voltage, the amount of light transmitted through the LCD device is adjusted, so that a gray scale display is obtained.

Fig. 9 shows a transmissive and reflective LCD device of the second embodiment obtained when the cell gap of the liquid crystal layer is d = 3.56 mu m and the phase difference by the liquid crystal layer is dΔN = 0.2752 when light is incident and received vertically. The spectral reflectance characteristics are shown.

In FIG. 9, the spectral reflectance in the reflective electrode region is the same as in FIG.

In Fig. 9, the spectral reflectance with respect to air when light is incident and received vertically is 100.

As shown in Fig. 9, sufficient contrast is obtained over the entire wavelength range of 400 nm to 900 nm between the black display when no voltage is applied and the white display when a voltage of 5 V is applied.

When a voltage of 5 V is applied, a reflectance of about 30% is obtained, which is about 80% of the transmittance of the polarizing element 8. Such high light illumination rates are suitable for transmissive silver and reflective LCD devices.

FIG. 10 shows the transmission type and reflection of the second example when the cell gap of the liquid crystal layer is d = 4.5 μm when the light is incident and received vertically, and the phase difference by the liquid crystal layer is dΔn = 0.3749 when the light is incident vertically. The spectral reflectance characteristics of the type LCD device are shown.

As shown in Fig. 10, a sufficient contrast ratio is obtained over the entire wavelength range of 400 nm to 700 nm between the black display when no voltage is applied and the white display when a voltage of 5 V is applied.

A reflectance of about 40% is obtained when a voltage of 5V is applied.

FIG. 11 shows the relationship between the cell gap and the contrast ratio of the transmission and reflection LCD device of the second example when light having a wavelength of 550 nm is incident vertically.

Contrast ratio is measured by applying the voltage which makes the phase difference d (DELTA) N by a liquid crystal layer satisfy | fill a 1/2 wavelength condition.

As shown in Fig. 11, the transmissive and reflective LCD device of the second example maintains a contrast ratio of 800 or more in the transmissive electrode region (used as the transmissive LCD device), regardless of the cell gap of the liquid crystal layer, and (reflection In the reflective electrode region (used as a type LCD device), a contrast ratio of 500 or more is maintained.

Thus, when a voltage is applied across the liquid crystal layer, a display without any reduction in the contrast ratio is provided as long as the phase difference dΔn satisfies the 1/2 wavelength condition. The cell gap d may be set arbitrarily.

12 shows the relationship between the angle of the slow axis of the λ / 4 wave plate and the contrast ratio. The angle of the slow axis of the λ / 4 wave plate is set to zero when the slow axis is inclined 45 ° with respect to the transmission axis of the polarizing element.

The angular difference in the slow axis is within 3 °, and a contrast ratio of 50 or more is obtained in both the transmissive electrode area (when the LCD device is used as a reflective LCD device) and the reflective electrode area (when the LCD device is used as a reflective LCD device), and thus A transmissive and reflective LCD device having satisfactory display characteristics is provided.

Thus, one LCD device has a transmissive LCD device for performing a display using light from the backlight transmitted through the transmissive electrode 8 when the ambient light is dark, and a relatively high light reflectance when the ambient light is bright. It may be used as both a reflective LCD device for performing a display using the ambient light reflected by the reflective electrode 3 formed of the material.

The backlight need not be used when the ambient light is bright. Therefore, power consumption is reduced as compared with the transmissive LCD device of the prior art. When the ambient light is dark, a backlight can be used. Thus, the problem of the reflective LCD of the prior art in which a sufficient display is not obtained is overcome.

The LCD device in the second example using the vertically oriented liquid crystal layer causes the delay caused by the liquid crystal layer to be substantially zero when no voltage is applied. In the case of black displays in general, darkness in the dark state is improved in both the transmission mode and the reflection mode to improve the contrast.

(Example 3)

The LCD device in the third example according to the present invention will be described with reference to FIG. The same elements as in the first and second examples are given the same reference numerals, and detailed description will be omitted.

The LCD device in the third example includes a λ / 4 wavelength plate 10 and a phase difference compensating element 12 between the substrate 2 and the polarizing element 9, and between the substrate 1 and the polarizing element 6. Includes a λ / 4 wavelength plate 7 and a phase difference compensating element 11.

The positions of the λ / 4 wave plate 10 and the phase difference compensating element 12 and the positions of the λ / 4 wave plate 7 and the phase difference compensating element 11 are interchangeable.

When no voltage is applied across the liquid crystal layer 5, the liquid crystal molecules of the liquid crystal material showing negative dielectric anisotropy in the liquid crystal layer 5 are oriented substantially perpendicular to the surfaces of the substrates 1 and 2. Therefore, the refractive index anisotropy of the liquid crystal layer 5 with respect to light incident on the LCD device is substantially zero.

However, when the LCD device is used as a reflective LCD device, it is used for a luminosity display incident in a different direction besides the light incident vertically. When used for a luminosity display that obliquely enters the liquid crystal layer 5 including ambient light, the display is affected by refractive index anisotropy.

The viewing angle does not necessarily have to be perpendicular to the surface of the substrate. As the viewing angle is offset in the direction perpendicular to the surface of the substrate, the display is further affected by the refractive index anisotropy of the liquid crystal molecules of the liquid crystal layer 5. Thus, the contrast ratio is reduced.

In this embodiment, in order to prevent the contrast from being reduced in accordance with the angle of incidence and the perspective direction of the light, phase difference compensating elements 11 and 12 are provided for compensating the influence of such refractive anisotropy of the liquid crystal molecules.

The pretilt angle of the liquid crystal molecules is slightly inclined with respect to the direction perpendicular to the substrate surface, so that when the liquid crystal molecules are inclined in one direction when a voltage is applied across the vertically aligned liquid crystal layer 5, even when no voltage is applied Some refractive index anisotropy is induced in the direction perpendicular to the substrate. The retardation compensating element is used to compensate for refractive anisotropy and further improve contrast in the direction perpendicular to the substrate.

In this example, the lambda / 4 wavelength plate and the phase difference compensating element are described separately, but the same effect is obtained even when the lambda / 4 wavelength plate and the phase difference compensating element are used in the same layer.

In this example, two phase difference compensation elements 11 and 12 are provided, but satisfactory results are obtained even if only one phase difference compensation element 11 is used.

In a third example, transmissive and reflective LCD devices are used. Even in the case of the reflective LCD device in the first example (of FIG. 1), a phase difference compensating element may be provided between the polarizing element 6 and the reflective electrode 3 to compensate for the refractive index anisotropy of the liquid crystal layer 5. have. Therefore, reduction of contrast is prevented.

In the first to third examples, black displays and white displays are described. Color display can be realized by providing a color filter on the appropriate area of the reflective electrode area and the transmissive electrode area.

When a chiral dopant is added to a vertically oriented liquid crystal layer formed of a liquid crystal material exhibiting negative dielectric anisotropy of the LCD devices in the first to third embodiments, the liquid crystal molecules are rotated when a voltage is applied. Thus, the liquid crystal molecules are stabilized upon voltage application.

When the liquid crystal layer is oriented to have a 90 ° twist, a black display with little optical leakage is obtained for the following reasons. When the voltage is applied, the liquid crystal molecules are oriented at a few degrees with respect to the normal direction to prevent the tilt when the liquid crystal molecules are oriented, causing a delay in the tilt direction of the liquid crystal molecules. However, since the liquid crystal molecules in the region near the upper and lower substrates form a 90 ° angle, the delay is offset. Thus, the resulting black display has little optical leakage.

The LCD device in the first to third examples uses a vertically oriented liquid crystal layer formed of a material having negative dielectric anisotropy. The same effect is obtained when the liquid crystal layer is processed so that the liquid crystal molecules are oriented horizontally on the substrate surface.

In such a case, when no voltage is applied, the liquid crystal molecules are oriented horizontally to the substrate, and when voltage is applied, the liquid crystal molecules are inclined toward the direction perpendicular to the substrate. Thus, a white display is performed when no voltage is applied and a black display is performed when a voltage is applied.

In the case of the black display by the horizontally oriented liquid crystal layer, the residual delay is larger than in the case of the vertically oriented liquid crystal layer due to the liquid crystal molecules near the substrate. In order to perform a more complete black display, a phase difference compensation element may be used.

In the case where the liquid crystal molecules are oriented almost perpendicular to the substrate and the delay of α remains in the reflection mode, the delay of λ / 4-α is substituted instead of the λ / 4 wavelength plate 7 (Figs. 1, 2, and 3). A phase difference compensating element may be used.

In the reflection mode, elliptical polarization that is offset from circular polarization by the residual delay of the liquid crystal layer is incident on the liquid crystal layer. Elliptical polarization becomes circular polarization when it reaches the reflective electrode region after being transmitted through the liquid crystal layer. As a result of the reflection, the light becomes circularly polarized light having a direction of half rotation. The light becomes elliptical polarization that is offset from the circularly polarized light when it passes through the liquid crystal layer. The elliptical polarization at this time is offset by 90 ° from the incident light. When transmitted through the retardation compensating element, the elliptical polarization becomes linear polarization perpendicular to the transmission axis of the polarization element 6.

As is well known, even when the delay remaining in the vertically oriented liquid crystal layer is not negligible, a high contrast display is obtained in the reflection mode by providing the phase difference compensation element in consideration of the delay.

The LCD device shown in FIG. 2 including the horizontally oriented liquid crystal layer 5 will be described.

The liquid crystal layer 5 is formed of a material available from Merck & Co., Inc., Ne = 1.5328, No = 1.4722, and Δn = 0.0606. The thickness of the liquid crystal layer 5 in the transmission region is about 5.2 탆.

The alignment layers provided on the substrates 1 and 2 are processed by rubbing in a direction perpendicular to the gate line (source line). The substrates 1 and 2 are joined so that the alignment layers on the substrates 1 and 2 face each other. When no voltage is applied across the liquid crystal layer 5, the molecular axes of the liquid crystal molecules in the liquid crystal layer 5 are oriented parallel to the surfaces of the substrates 1 and 2 and perpendicular to the gate lines. When a voltage is applied, the molecular axis of the liquid crystal molecules is inclined in the normal direction to the surface of the substrates 1 and 2 while being substantially perpendicular to the gate line. In this example, the axes of the polarizing elements 6 and 9 and the axes of the phase difference compensating elements 7 and 10 have a voltage of about 1.8 V to be applied across the liquid crystal layer 5 for the white display and the liquid crystal layer for the black display. (5) The voltage to be applied at both ends is set under the condition of about 5.3V.

The transmission axis of the polarizing element 6 is set to be about 45 ° clockwise with respect to the molecular axis of the liquid crystal molecules, and the slow axis of the phase difference compensating element 7 is 45 ° with respect to the transmission axis of the polarizing element 6. Is set. That is, the slow axis of the phase difference compensating element 7 is set to be about 90 degrees clockwise with respect to the molecular axis of the liquid crystal molecules.

In consideration of the delay caused by the liquid crystal layer 5 in the reflective region of the black display, two types of phase difference compensation elements having a delay of about 105 nm and a delay of about 95 nm are used. This delay is offset from the λ / 4 condition (about 137.5 nm). By using a phase difference compensating element having a delay of? / 4- ?, satisfactory contrast can be realized in the reflection region.

The slow axis of the retardation compensator 10 and the transmission axis of the polarization element 9 are set in consideration of the delay caused by the liquid crystal layer 5 in the transmission region of the black display. In the transmissive and reflective LCD device, first, the orientation of the polarizing element 6 and the delay and slow axis of the phase difference compensating element 7 are determined in consideration of the reflection area. Next, the delay and slow orientation of the polarizing element 6, the delay and slow axis of the phase difference compensating element 10, and the orientation of the polarizing element 9 are determined in consideration of the transmission region. The change in the polarization state of the light transmitted through each layer of the transmission area is the same when the light is incident on the display surface and when the light is incident from the backlight. In order to facilitate understanding, the light incident on the display surface will be described below.

The linearly polarized light incident on the liquid crystal layer 5 in a dark state through the polarizing element 6 is emitted from the liquid crystal layer 6 as elliptical polarized light whose major axis or minor axis is 45 degrees clockwise with respect to the molecular axis of the liquid crystal molecules. The elliptical polarized light is provided in the same direction as the long axis of the elliptical polarized light which provides the phase difference compensating element 10 formed of the lambda / 4 wavelength plate having a delay of about 140 nm and emits the slow axis from the liquid crystal layer 5, that is, It can be converted to linear polarized light by positioning it at an angle of 45 degrees clockwise relative to the molecular axis. Next, the polarizing element 9 is positioned so that its transmission axis is perpendicular to the polarization axis of the linearly polarized light emitted from the phase difference compensating element 10.

The angle of the polarization axis of the linearly polarized light emitted from the phase difference compensation element 10 depends on the polarization state of the elliptical polarization incident on the phase difference compensation element 10. In this example, when the retardation of the retardation compensator 7 is about 105 nm, the polarization axis of the linearly polarized light emitted from the retardation compensator 10 is about 10 degrees clockwise with respect to the molecular axis of the liquid crystal molecules. Therefore, by setting the transmission axis of the polarizing element 9 about 10 degrees clockwise with respect to the molecular axis of the liquid crystal molecules, a satisfactory black display in the transmission region can be achieved. When the retardation of the retardation compensator 7 is about 95 nm, the polarization axis of the linearly polarized light emitted from the retardation compensator 10 is about 97 degrees clockwise with respect to the molecular axis of the liquid crystal molecules. Therefore, by setting the transmission axis of the polarizing element 9 about 7 degrees clockwise with respect to the molecular axis of the liquid crystal molecules, a satisfactory black display in the transmission region can be achieved.

The LCD device of FIG. 3 including the horizontally oriented liquid crystal layer 5 is described below.

The liquid crystal layer 5 is formed of a material commercially available from Merck & Co. and has Ne = 1.5328, No = 1.4722 and ΔN = 0.0606. The thickness of the liquid crystal layer 5 is about 5.2 micrometers. The alignment layer is positioned in the antiparallel state. The axes of the polarizing elements 6 and 9 and the phase difference compensating elements 7, 10, 11, and 12 have a voltage to be applied to both ends of the liquid crystal layer 5 for white display, and the liquid crystal layer 5 for black display. The voltage to be applied at both ends is set under the condition of about 5.3V.

The transmission axis of the polarizing element 6 is set to be about 15 degrees clockwise with respect to the molecular axis of the liquid crystal molecules. The phase difference compensating element 11 is formed of a? / 2 wave plate having a delay of about 270 nm. The phase difference compensating element 11 is positioned so that its slow axis is about 30 degrees clockwise with respect to the molecular axis of the liquid crystal molecules. Further, the phase difference compensating element 7 is positioned so that its slow axis is about 90 degrees clockwise with respect to the molecular axis of the liquid crystal molecules. This positioning is performed in the order of the polarizing element 6, the phase difference compensating element 11, and the phase difference compensating element 7. As shown in FIG. In the black display, in consideration of the delay caused by the liquid crystal layer 5 in the reflection region, two types of phase difference compensation elements having a delay of about 105 nm and a delay of about 95 nm are used. This delay is offset from the λ / 4 condition (about 137.5 nm). By using a phase difference compensating element having a delay of? / 4- ?, satisfactory contrast can be realized in the reflection region.

The slow axis of the retardation compensator 10 and 12 and the transmission axis of the polarization element 9 are set in consideration of the delay caused by the liquid crystal layer 5 in the transmission region of the black display. This positioning is performed in order of the retardation compensator 10, the retardation compensator 12, and the polarization element 9.

The linearly polarized light incident on the liquid crystal layer 5 in the black state through the polarizing element 6 is emitted from the liquid crystal layer 6 as elliptical polarized light whose long axis or short axis is 45 degrees clockwise with respect to the molecular axis of the liquid crystal molecules. The elliptical polarized light is provided in the same direction as the long axis of the elliptical polarized light which provides the phase difference compensating element 10 formed of the lambda / 4 wavelength plate having a delay of about 140 nm and emits the slow axis from the liquid crystal layer 5, that is, It can be converted to linear polarized light by positioning it at an angle of 45 degrees clockwise relative to the molecular axis. Next, the phase difference compensating element 12 formed of the λ / 2 wave plate having a delay of about 270 nm is positioned so that its slow axis is 114 degrees clockwise with respect to the molecular axis of the liquid crystal molecules. Next, the polarizing element 9 is positioned so that its transmission axis is perpendicular to the polarization axis of the linearly polarized light emitted from the phase difference compensating element 12.

The angle of the polarization axis of the linearly polarized light emitted from the phase difference compensation element 12 depends on the polarization state of the elliptical polarization incident on the phase difference compensation element 10. In this example, when the retardation of the retardation compensator 7 is about 105 nm, the polarization axis of the linearly polarized light emitted from the retardation compensator 10 is about 10 degrees clockwise with respect to the molecular axis of the liquid crystal molecules. The polarization axis of the linearly polarized light emitted from the phase difference compensating element 12 is about 128 degrees clockwise with respect to the molecular axis of the liquid crystal molecules. Thus, by setting the transmission axis of the polarizing element 9 clockwise to about 38 degrees with respect to the molecular axis of the liquid crystal molecules, a satisfactory black display in the transmission region can be achieved. When the retardation of the retardation compensator 7 is about 95 nm, the polarization axis of the linearly polarized light emitted from the retardation compensator 10 is about 97 degrees clockwise with respect to the molecular axis of the liquid crystal molecules. The polarization axis of linearly polarized light emitted from the phase difference compensating element 12 is located at about 125 degrees clockwise with respect to the molecular axis of the liquid crystal molecules. Therefore, when the transmission axis of the polarizing element 9 is set to about 35 degrees clockwise with respect to the molecular axis of the liquid crystal molecules, a satisfactory black display in the transmission region can be achieved.

When the liquid crystal layer has a residual delay α in the reflection mode and a residual delay β in the transmission mode, a phase difference compensating element having a delay of λ / 4-α is provided instead of the λ / 4 wave plate 7, and λ / 4- A phase difference compensating element having a delay of (?-?) is provided instead of the λ / 4 wave plate 10.

In the transmissive mode using light transmitted through a region having a transmissive function such as a transmissive electrode region, a phase difference compensation element having a delay of? / 4- (β-α) when the liquid crystal molecules are arranged perpendicular to the substrate Is set so that the light emitted from the liquid crystal layer becomes elliptical polarization in the same state as the reflection mode. Elliptical polarized light having such a phase difference is incident on the phase difference compensating element having a delay of? / 4- ?. Thus, when transmitted through the phase difference compensating element having a delay of? / 4-α, the light becomes linearly polarized light perpendicular to the transmission axis of the polarizing element 6. Thus, it is possible to achieve a black display with little light leakage.

As can be appreciated, even if the residual delay in the vertically oriented liquid crystal layer is not negligible, a high contrast display can be achieved in the reflection mode by providing a phase difference compensation element in consideration of the delay.

(Example 4)

An LCD device of a fourth example according to the present invention will be described below with reference to FIG. The same reference numerals are given to the same elements as in the first example.

The substrate 2 is a reflective electrode 3 (represented by the reflective electrode region in FIG. 2) formed of a material having a high reflectance such as, for example, Al or Ta, and a material having a high transmittance such as, for example, ITO. A transmissive electrode 8 (indicated by the transmissive electrode region in FIG. 2), which is formed as follows. The substrate 1 includes an opposite electrode 4 (indicated by the transmissive electrode of FIG. 2). The liquid crystal layer 5 formed of a liquid crystal material exhibiting negative dielectric anisotropy is interposed between the reflective electrode 3 / the transmissive electrode 8 and the counter electrode.

An alignment layer (not shown) is provided on the surfaces of the reflective electrode 3 / transmissive electrode 8 and the counter electrode 4 in contact with the liquid crystal layer 5. The alignment layer is used to orient the liquid crystal molecules (not shown) of the liquid crystal layer 5 perpendicular to the surfaces of the substrates 1 and 2. After providing the alignment layer, at least one of the alignment layers is subjected to an alignment treatment such as, for example, rubbing. The orientation direction may be defined as light orientation or electrode shape instead of rubbing.

Due to the alignment treatment, the liquid crystal molecules of the liquid crystal layer 5 have an inclination angle of about 0.1 to 5 degrees with respect to the direction perpendicular to the surfaces of the substrates 1 and 2.

The reflective electrode 3 is used for applying a voltage to the liquid crystal layer 5, but the reflective electrode 3 can be used only as a reflecting plate, not as an electrode for applying a voltage. In this case, for example, the transmissive electrode 8 may extend over the reflective electrode 3 to serve as an electrode for applying a voltage to the liquid crystal layer 5 in the reflective region.

The liquid crystal material used herein has refractive index anisotropy of Ne (refractive index for abnormal light) = 1.5546 and No (refractive index for normal light) = 1.4773.

The λ / 4 wave plate 7 is located on the surface of the substrate 1 opposite the counter electrode 4. The λ / 4 wave plate 10 is located on the surface of the substrate 2 opposite the reflective electrode 3 and the transmissive electrode 8. The slow axis of the λ / 4 wave plate 10 is set perpendicular to the slow axis of the λ / 4 wave plate 7.

The polarizing element 6 is located on the surface of the λ / 4 wave plate 7 opposite the substrate 10. The polarizing element 9 is located on the surface of the λ / 4 wave plate 10 opposite the substrate 2. The transmission axis of the polarizing element 6 is set to be inclined 45 degrees with respect to the slow axis of the λ / 4 wave plate 7. The transmission axis of the polarizing element 9 is set to be inclined 45 degrees with respect to the slow axis of the λ / 4 wave plate 10. The slow axes of the λ / 4 wave plates 7 and 10 are perpendicular to each other and the transmission axes of the polarizing elements 6 and 9 are perpendicular to each other. Therefore, when the angle of the slow axis of the phase difference compensating element 7 with respect to the transmission axis of the polarizing element 6 is +45 degrees, the angle of the slow axis of the phase difference compensating element 10 with respect to the transmission axis of the polarizing element 9 is also +45 degrees. When the angle of the slow axis of the phase difference compensating element 7 with respect to the transmission axis of the polarizing element 6 is -45 degrees, the angle of the slow axis of the phase difference compensating irradiation 10 with respect to the transmission axis of the polarizing element 9 is also -45 degrees. It becomes degrees.

8A is a plan view of the active matrix substrate (substrate 2) in the fourth example, and FIG. 8B is a cross-sectional view of the active matrix substrate along the line 8B-8B 'in FIG. 8A.

As shown in FIGS. 8A and 8B, the active matrix substrate includes a gate line 21, a data line 22, a driving element 23, a drain electrode 24, a storage capacitor electrode 25, and a gate insulating layer 26. ), An insulating substrate 27, a contact hole 28, an interlayer insulating layer 29, a reflective pixel electrode (reflective electrode region) 30 (corresponding to the reflective electrode 3 in FIG. 2), and a transparent pixel electrode ( Transmission electrode region) 31 (corresponding to transmission electrode 8 of FIG. 2).

The storage capacitor electrode 25 is electrically connected to the drain electrode 24, and the gate insulating layer 26 is interposed therebetween to overlap the gate line 21. Therefore, the storage capacitor electrode 25, the insulating layer 26, and the gate line 21 form the storage capacitor.

The contact hole 28 is formed in the interlayer insulating layer 29 to connect the transmissive pixel electrode 31 and the storage capacitor electrode 25.

The active matrix substrate includes a reflective pixel electrode 30 for reflecting external light and a transparent pixel electrode 31 for allowing light from the backlight to be transmitted in one pixel region.

In FIG. 8B, the reflective electrode 30 has a flat surface, but may have a wavy surface to improve the reflectance. One pixel electrode includes the reflective pixel electrode 30 and the transparent pixel electrode 31 in this embodiment. Alternatively, semi-transmissive and semi-reflective electrodes can be used.

14A, 14B, 15A, and 15B, light transmission and reflection in the transmission mode and reflection mode of the LCD device of the fourth example will be described below.

14A and 14B show a reflection mode using a reflective electrode. 14A shows a black display when no voltage is applied across the vertically oriented liquid crystal layer, and FIG. 14B shows a white display when voltage is applied across both the vertically aligned liquid crystal layer. 15A and 15B show the transmission mode using the transmission electrode. 15A shows a black display when no voltage is applied across the vertically oriented liquid crystal layer, and FIG. 15B shows a white display when voltage is applied across both the vertically aligned liquid crystal layer.

Referring to Fig. 14A, the black display in the reflection mode will be described.

Light incident on the polarizing element 6 is transmitted through the polarizing element 6 to become linearly polarized light parallel to the transmission axis of the polarizing element 6 and then enters the λ / 4 wavelength plate 7.

The λ / 4 wave plate 7 is arranged such that the transmission axis of the polarizing element 6 and the slow axis of the λ / 4 wave plate 7 are at an angle of 45 degrees. Thus, the light transmitted through the λ / 4 wave plate 7 becomes circularly polarized light.

When no voltage is applied across the liquid crystal layer 5, the liquid crystal molecules exhibiting negative dielectric anisotropy used for the liquid crystal layer 5 are substantially perpendicular to the surfaces of the substrates 1 and 2. Therefore, the refractive index anisotropy of the liquid crystal layer 5 with respect to incident light is very small. In other words, the phase difference caused by the transmission of light passing through the liquid crystal layer 5 is substantially zero.

Thus, the circularly polarized light from the λ / 4 wave plate 7 is transmitted through the liquid crystal layer 5 while being almost circularly polarized and reflected by the reflective electrode 3 of the substrate 2.

The circularly polarized light reflected by the reflective electrode 3 becomes circularly polarized light having an opposite rotational direction, is transmitted through the λ / 4 wavelength plate 7 and is incident on the λ / 4 wavelength plate 7 from the polarizing element 6. It becomes linear polarization perpendicular to the light.

The linearly polarized light from the λ / 4 wavelength plate 7 is perpendicular to the transmission axis of the polarizing element 6. This light is not transmitted but is absorbed by the polarizing element 6.

In this way, a black display can be implemented.

Referring to Fig. 14B, the white display in the reflection mode will be described below.

The process until the light is transmitted through the λ / 4 wave plate 7 and becomes circularly polarized light is the same as above and will not be described.

When voltage is applied across the liquid crystal layer 5, the liquid crystal molecules are slightly inclined toward the horizontal direction with respect to the surfaces of the substrates 1 and 2. Therefore, the circularly polarized light incident on the liquid crystal layer 5 from the λ / 4 wavelength plate 7 becomes elliptical polarized light by the birefringence of the liquid crystal molecules. Light is then reflected by the reflective electrode 3 and further affected by the birefringence of the liquid crystal molecules of the liquid crystal layer 5. This light does not become linearly polarized light perpendicular to the transmission axis of the polarizing element 6 after passing through the λ / 4 wavelength plate 7. Thus, light is transmitted through the polarizer 6.

By controlling the voltage applied across the liquid crystal layer 5, the amount of light transmitted by the polarizing element 6 after being reflected by the reflective electrode 3 can be adjusted. Thus, a gray scale display can be provided.

When the phase difference by the liquid crystal layer 5 satisfies the 1/4 wavelength condition by applying a voltage across the liquid crystal layer 5 by the reflective electrode 3 and the counter electrode 4 to change the orientation of the liquid crystal molecules, Circularly polarized light from the λ / 4 wavelength plate 7 becomes linearly polarized light perpendicular to the transmission axis of the polarizing element 6 when it reaches the reflective electrode 3 after being transmitted through the liquid crystal layer 5. This light is again transmitted through the liquid crystal layer 5 to become circularly polarized light and then transmitted through the λ / 4 wavelength plate 7 to become linearly polarized light parallel to the transmission axis of the polarizing element 6. In this case, the amount of light transmitted through the polarizing element 6 is maximum.

FIG. 14B shows a case where the liquid crystal layer retardation condition of transmitting the maximum amount of light reflected by the reflective electrode 3 through the polarizing element 6 is shown. In other words, the light of the reflective electrode 3 becomes linearly polarized light perpendicular to the transmission axis of the polarizing element 6.

As described above, when no voltage is applied across the liquid crystal layer 5, a black display can be achieved because the liquid crystal layer 5 has substantially no birefringence, and the voltage is the liquid crystal layer 5 When applied at both ends, the gray scale display can be achieved by changing the light transmittance according to the voltage.

A black display in the transmissive mode is described below with reference to FIG. 15A.

Light emitted by a light source (not shown) is incident on the polarizing element 9 to become linearly polarized light parallel to the transmission axis of the polarizing element 9.

In the λ / 4 wave plate 10, the slow axis of the λ / 4 wave plate 10 is inclined at 45 ° with respect to the transmission axis of the polarizing element 9. Thus, the light transmitted through the λ / 4 wave plate 10 is circularly polarized light.

When no voltage is applied across the liquid crystal layer 5, the liquid crystal molecules exhibiting negative dielectric anisotropy used for the liquid crystal layer 5 are substantially perpendicular to the surfaces of the substrates 1, 2. Therefore, the refractive index anisotropy of the liquid crystal layer 5 with respect to incident light is very small. In other words, the phase difference resulting from the transmission of light passing through the liquid crystal layer 5 is substantially zero.

Therefore, the circularly polarized light from the λ / 4 wave plate 10 is transmitted through the liquid crystal layer 5 while maintaining the circularly polarized light and is incident on the λ / 4 wave plate 7.

The slow axis of the λ / 4 wave plate 10 and the slow axis of the λ / 4 wave plate 7 are set to be perpendicular to each other. Thus, the circularly polarized light incident on the λ / 4 wave plate 7 is linearly polarized perpendicular to the transmission axis of the polarizing element 9 and is incident on the polarizing element 6.

The linearly polarized light from the λ / 4 wave plate 7 is perpendicular to the transmission axis of the polarizing element 6 and is absorbed by the polarizing element 6 without being transmitted.

In this way a black display is performed.

Referring to Fig. 15B, a white display in the transmissive mode is described.

The process until the light is transmitted through the λ / 4 wave plate 10 is the same as in FIG. 15A and description is omitted.

When a voltage is applied across the liquid crystal layer 5, the liquid crystal molecules are slightly inclined in the horizontal direction with respect to the surfaces of the substrates 1, 2. Therefore, the circularly polarized light incident on the liquid crystal layer 5 from the λ / 4 wave plate 10 becomes elliptical polarized light due to the birefringence of the liquid crystal molecules. The light does not become linearly polarized perpendicular to the transmission axis of the polarizing element 6 even after transmitting the λ / 4 wave plate 7, and thus is transmitted through the polarizing element 6.

The amount of light transmitted through the polarizer 6 may be controlled by controlling the voltage applied across the liquid crystal layer 5. Thus, a gray scale display is provided.

When a voltage is applied across the liquid crystal layer 5 so that the phase difference by the liquid crystal layer 5 satisfies the 1/2 wavelength condition, the circularly polarized light from the λ / 4 wave plate 10 is applied to the liquid crystal layer 5. At half thickness, linear polarization perpendicular to the transmission axis of the polarizing element 6 is obtained, and then circularly polarized when completely transmitted through the liquid crystal layer 5.

When the circularly polarized light from the liquid crystal layer 5 is transmitted through the λ / 4 wave plate 7, it becomes linearly polarized light parallel to the transmission axis of the polarizing element 6, so most of the light incident on the polarizing element 6 It is transmitted through the polarizing element 6. In this case, the amount of light transmitted through the polarizing element 6 is maximum.

FIG. 15B illustrates a case where the liquid crystal retardation condition is set such that the maximum amount of light transmitted through the polarizing element 9 is transmitted through the polarizing element 6.

As described above, when no voltage is applied across the liquid crystal layer 5, a black display is obtained. When a voltage is applied across the liquid crystal layer 5, the gray scale display is changed by changing the light transmittance according to the voltage. Get

FIG. 16 shows wavelengths for comparison when the slow axes of the λ / 4 wave plates 7 and 10 are perpendicular to each other as in the fourth example and when the slow axes of the λ / 4 wave plates 7 and 10 are parallel to each other. And the relation between the light transmittance and the light transmittance.

In the fourth example, since the slow axes of the λ / 4 wave plates 7 and 10 are perpendicular to each other, the wavelength dependency of the refractive index anisotropy of one phase difference compensating element is canceled by the wavelength dependency of the refractive index anisotropy of the other phase difference compensating element. do. Thus, the prescribed phase difference is satisfied over the entire wavelength range of 400 nm to 700 nm (visible light). Thus, the blackness of the black display is improved.

The phase difference by the liquid crystal layer 5 with the largest reflectance in the bright display in the reflection mode is lambda / 4, and the phase difference by the liquid crystal layer 5 with the maximum reflectance in the bright display in the transmissive mode is lambda / 2. As can be seen from this, when the thickness of the liquid crystal layer in the reflection region and the thickness of the liquid crystal layer in the transmission region are equal to each other, the phase difference of λ / 4 for the reflection mode and λ / 4 for the transmission mode is simultaneously satisfied. Can't.

When the display is performed while the phase difference of the liquid crystal layer is changed from 0 to λ / 4 in the reflection region, the phase difference of the liquid crystal layer in the transmissive region is changed only from 0 to λ / 4 so that satisfactory illumination rate can be obtained in the transmission mode. none.

A satisfactory illumination rate in both the reflection mode and the transmission mode is obtained by changing the thickness of the liquid crystal layer of the reflection region from the thickness of the transmission region or applying different voltages to the liquid crystal layer of the reflection region and the liquid crystal layer of the transmission region. When the thickness of the liquid crystal layer in the transmissive region is twice the thickness of the liquid crystal layer in the reflective region, the phase difference of the liquid crystal layer having lambda / 4 for the reflection mode and lambda / 2 for the transmission mode is simultaneously satisfied. It is not necessary to make the thickness for the transmission mode twice the thickness for the reflection mode. The illumination rate is improved by making the thickness for the transmission mode larger than the thickness for the reflection mode.

The refractive index of the birefringent material forming the lambda / 4 wave plates 7 and 10 for ordinary light and abnormal light depends greatly on the wavelength. Thus, the phase delay that accumulates at a wavelength with a certain thickness also depends on the wavelength. Only when the incident light has one specified wavelength can a phase delay of λ / 4 be perfectly provided in the linear polarization plane of the incident light. Therefore, in the region where the phase retardation of [lambda] / 4 is not achieved due to the wavelength dependency of the refractive index anisotropy of the birefringent material forming the [lambda] / 4 wave plate 7, 10, some light is not absorbed by the polarizing element 6 Without passing through the polarizing tube 6. As a result, the blackness of the black display changes. In the fourth example, the slow axes of the λ / 4 wave plates 7 and 10 are set perpendicular to each other, and the transmission axes of the polarizing elements 6 and 9 are set perpendicular to each other. Due to such a structure, in the transmission mode, the wavelength dependency of the refractive index anisotropy of the λ / 4 wave plate 10 is neutralized by the wavelength dependency of the refractive index anisotropy of the λ / 4 wave plate 7. Thus, the λ / 4 condition is satisfied over the entire range of 400 nm to 700 nm. Thus, the blackness of the black display is improved.

Satisfactory display when another retardation compensator is provided between at least one of the polarizing element 6 and the liquid crystal layer 5 and between the polarizing element 9 and the liquid crystal layer 5 to improve the viewing angle. Is realized at a wide viewing angle.

In the fourth example the liquid crystal layer 5 is oriented vertically. When the liquid crystal molecules around the substrate have a specific tilt angle with respect to the vertical direction of the substrate, the delay is not completely zero even when no voltage is applied. A better black display is obtained by providing a phase difference compensating element instead of the λ / 4 wave plate 7 to compensate for the delay.

In the case where the liquid crystal layer has a residual delay of? In the reflection mode, it is possible to provide a phase difference compensating element having a delay of? / 4-? Instead of the? / 4 wavelength plate 7.

In the reflection mode, elliptical polarization that is offset from circular polarization due to the residual delay of the liquid crystal layer is incident on the liquid crystal layer. The elliptical polarized light becomes circularly polarized light when it passes through the liquid crystal layer and reaches the reflective electrode. As a result of reflection, the light becomes circularly polarized light with opposite directions of rotation. The light becomes elliptical polarization offset from the circular polarization when it exits through the liquid crystal layer. The elliptical polarization at this time is offset by 90 ° and has a phase at the time of incidence. When the elliptical polarization is transmitted through the retardation compensating element, the elliptical polarization becomes linear polarization perpendicular to the transmission axis of the polarization element 6.

When the reflection mode display is mainly performed, for example, when the reflection pixel electrode is larger than the transmission pixel electrode, the λ / 4 wave plate 10 for display in the transmission mode is kept as it is.

As can be seen, even when the delay remaining in the vertically aligned liquid crystal layer cannot be ignored, a high contrast display is obtained in the reflection mode by providing a phase difference compensation element in consideration of the delay.

In the case where the liquid crystal layer has a residual delay of? In the reflection mode and a residual delay of? In the transmission mode, a phase difference compensating element having a delay of? / 4-α can be provided instead of the? / 4 wave plate 7. And a phase difference compensating element having a delay of [lambda] / 4-([beta]-[alpha]) can be provided instead of the [lambda] / 4 wavelength plate 10.

In the transmission mode using light transmitted through an area having a transmission function such as the transmission electrode area, when the liquid crystal molecules are oriented perpendicular to the substrate, the phase difference compensation element having a delay of? / 4- (β-α) The light escaping from the liquid crystal layer is set to be elliptical polarized light in the same state as in the reflection mode. The elliptical polarized light having such a phase difference is incident on the phase difference compensating element having a delay of? / 4-α. Thus, when light is transmitted through a phase difference compensating element having a delay of? / 4-α, the light becomes linearly polarized light perpendicular to the transmission axis of the polarizing element 6. Thus, a black display with little optical leakage is obtained.

As can be seen, even when the delay remaining in the vertically aligned liquid crystal layer cannot be ignored, a high contrast display can be obtained in the reflection mode by providing a phase difference compensation element in consideration of the delay.

The LCD device of the fourth example uses a vertically aligned liquid crystal layer, but the display is realized by the same principle of using a horizontally aligned liquid crystal layer. In such a case, the delay caused by the liquid crystal layer is reduced when a higher voltage is applied. However, when most of the liquid crystal molecules except the liquid crystal molecules around the substrate are perpendicular to the substrate when a voltage is applied, the liquid crystal molecules around the substrate hardly move due to the electric field. Thus, residual delay occurs due to liquid crystal molecules around the substrate. As can be seen, when the horizontally oriented liquid crystal layer is used, light leakage occurs during the black display, and the contrast is reduced by the influence of the residual delay as compared with when the vertically oriented liquid crystal layer is used. In order to provide a black display of the same quality as that provided by the vertically oriented liquid crystal layer to the horizontally oriented liquid crystal, the liquid crystal molecules around the substrate need to be oriented so as to cancel out the residual delay by the liquid crystal molecules, or a phase difference compensation element is additionally added. It needs to be provided.

(Example 5)

An LCD device of a fifth example according to the present invention is described with reference to FIG.

The substrate 2 is formed of a reflective electrode 3 (shown as the reflective electrode region in FIG. 17) formed of a material having a high reflectance, for example Al or Ta, and a material having a high transmittance, for example ITO. Transmissive electrode 8 (shown as transmissive electrode region in FIG. 17). The substrate 1 comprises an opposing electrode 4 (shown as transmissive electrode in FIG. 17). A liquid crystal layer 5 formed of a liquid crystal material exhibiting negative dielectric anisotropy is disposed between the reflective electrode 3 / the transmissive electrode 8 and the counter electrode 4.

An alignment layer (not shown) is provided on the surfaces of the reflective electrode 3 / transmissive electrode 8 and the counter electrode 4 in contact with the liquid crystal layer 5. The alignment layer is used to orient the liquid crystal molecules (not shown) in the liquid crystal layer 5 perpendicular to the surfaces of the substrates 1 and 2. After the alignment layer is provided, at least one of the alignment layers is subjected to an alignment treatment such as, for example, rubbing. The orientation direction can be determined by optical orientation or electrode shape instead of rubbing.

Due to the alignment treatment, the liquid crystal molecules in the liquid crystal layer 5 have an inclination angle of about 0.1 to 5 ° with respect to the direction perpendicular to the surfaces of the substrates 1 and 2.

The reflective electrode 3 is used to apply a voltage to the liquid crystal layer 5, but the reflective electrode 3 is not used as an electrode for applying a voltage but can be used only as a reflecting plate. In such a case, for example, the transmissive electrode 8 can be extended onto the reflective electrode 3 to serve as an electrode for applying a voltage to the liquid crystal layer 5 in the reflective region.

The liquid crystal material used here has refractive index anisotropy with Ne (refractive index for abnormal light) = 1.5546 and No (refractive index for normal light) = 1.4773.

A λ / 4 wave plate 7 is provided on the surface of the substrate 1 opposite the counter electrode 4. The λ / 4 wave plate 10 is provided on the surface of the substrate 2 opposite the reflective electrode 3 and the transmissive electrode 8. The slow axis of the λ / 4 wave plate 10 is set to be perpendicular to the slow axis of the λ / 4 wave plate 7.

[lambda] / 2 wave plate 11 is provided on the surface of the [lambda] / 4 wave plate 7 opposite to the substrate 1. The lambda / 2 wave plate 12 is provided on the surface of the lambda / 4 wave plate 10 opposite the substrate 2. The slow axis of the λ / 2 wave plate 11 is set to be inclined at 60 degrees with respect to the λ / 4 wave plate 7. The slow axis of the λ / 2 wave plate 12 is set to be perpendicular to the slow axis of the λ / 2 wave plate 11.

The polarizing element 6 is provided on the surface of the λ / 2 wave plate 11 opposite to the substrate 1. The polarizing element 9 is provided on the surface of the λ / 2 wave plate 12 opposite the substrate 2. The transmission axis of the polarizing element 6 is set so that 75 ° is inclined with respect to the slow axis of the λ / 4 wave plate 7 in the direction sandwiching the slow axis of the λ / 2 wave plate 11, and the λ / 2 wave plate 15 degrees are set to incline with respect to the slow axis of (11). The transmission axis of the polarizing element 9 is set so that 75 ° is inclined with respect to the slow axis of the λ / 4 wave plate 10 in the direction sandwiching the slow axis of the λ / 2 wave plate 12, and the λ / 2 wave plate It is set so that 15 degrees may incline with respect to the slow axis of (12). The transmission axis of the polarizing element 6 is set to be perpendicular to the transmission axis of the polarizing element 9.

8A is a plan view of the active matrix substrate (substrate 2) in the second example, and FIG. 8B is a cross-sectional view of the active matrix substrate taken along the line 8B-8B 'of FIG. 8A.

As shown in FIGS. 8A and 8B, the active matrix substrate includes a gate line 21, a data line 22, a driving element 23, a drain electrode 24, a storage capacitance electrode 25, and a gate insulating layer 26. ), Insulating substrate 27, contact hole 28, interlayer insulating layer 29, reflective pixel electrode 30 (reflective electrode region) (corresponding to reflective electrode 3 in FIG. 17), and transmissive pixel display electrode (31) (transmissive electrode region) (corresponding to the transmissive electrode 8 in FIG. 17).

The accumulation capacitance electrode 25 is electrically connected to the drain electrode 24 and overlaps the gate line 21 with the gate insulating layer 26 interposed therebetween. Thus, the storage capacitance electrode 25, the insulating layer 26, and the gate line 21 form the storage capacitance.

The contact hole 28 is formed in the interlayer insulating layer 29 to connect the transmissive pixel electrode 31 and the storage capacitance electrode 25.

The active matrix substrate includes a reflective pixel electrode 30 for reflecting external light and a transparent pixel electrode 31 for allowing light from the backlight to be transmitted in one pixel area.

In FIG. 8B, the reflective electrode 30 has a plane, but may have a wavy surface to improve reflectivity. In the present embodiment, one pixel electrode includes a reflective pixel electrode 30 and a transparent pixel electrode 31. In addition, semi-transmissive and semi-reflective electrodes can be used.

18A, 18B, 18C, and 18D, the light transmittance and the reflectance in the reflection mode and the transmission mode in the LCD device of the fifth example are described.

18A and 18B illustrate a reflection mode using reflective electrodes. 18A shows a black display when no voltage is applied to the vertically aligned liquid crystal layer, and FIG. 18B shows a white display when a voltage is applied to the vertically aligned liquid crystal layer. 18C and 18D show the transmission mode using the transmission electrode. 18C shows a black display when no voltage is applied to the vertically aligned liquid crystal layer, and FIG. 18D shows a white display when a voltage is applied to the vertically aligned liquid crystal layer.

Referring to FIG. 18A, a black display in reflective mode is described.

Light incident on the polarizing element 6 is transmitted through the polarizing element 6 to become linearly polarized light parallel to the transmission axis of the polarizing element 6, and then is incident on the λ / 2 wavelength plate 11.

The λ / 2 wave plate 11 is arranged such that the transmission axis of the polarizing element 6 and the slow axis of the λ / 2 wave plate 11 form an angle of 15 °. Thus, the light transmitted through the λ / 2 wave plate 11 is linearly polarized in which 30 ° is inclined with respect to the transmission axis of the polarizing element 6 in the direction sandwiching the slow axis of the λ / 2 wave plate 11. do. Then, light is incident on the λ / 4 wave plate 7.

The lambda / 4 wavelength plate 7 is 75 ° with respect to the transmission axis of the polarizing element 6 in the direction in which the slow axis of the lambda / 4 wave plate 7 sandwiches the slow axis of the lambda / 2 wave plate 11. It is arranged to be inclined. In other words, the slow axis of the λ / 4 wave plate 7 is set to be 45 ° from the λ / 2 wave plate 11 with respect to the polarization direction of the linearly polarized light, and thus transmitted through the λ / 4 wave plate 7. Light becomes circularly polarized light.

When no voltage is applied to the liquid crystal layer 5, the liquid crystal molecules exhibiting negative dielectric anisotropy used for the liquid crystal layer 5 are substantially perpendicular to the surfaces of the substrates 1, 2. Therefore, the refractive index anisotropy of the liquid crystal layer 5 with respect to incident light is very small. In other words, the phase difference resulting from the transmission of light through the liquid crystal layer 5 is substantially zero.

Therefore, the circularly polarized light from the λ / 4 wave plate 7 is transmitted through the liquid crystal layer 5 with almost circularly polarized light, and is reflected by the reflective electrode 3 on the substrate 2.

The circularly polarized light reflected by the reflective electrode 3 becomes circularly polarized light having an opposite rotational direction, is transmitted through the λ / 4 wave plate 7, and is transmitted from the polarizing element 6 to the λ / 4 wave plate 7. Linear polarization perpendicular to the incident light. Next, light is incident on the λ / 2 wavelength plate 11.

The linearly polarized light from the λ / 2 wave plate 11 is perpendicular to the transmission axis of the polarizing element 6. Such light is not transmitted but is absorbed by the polarizing element 6.

In this way, a black display is performed.

Referring to Fig. 18B, a white display in reflection mode is described.

The process until the light is transmitted through the λ / 4 wave plate 7 and becomes circularly polarized light is the same as above, and thus will not be described.

When voltage is applied to the liquid crystal layer 5, the liquid crystal molecules are slightly inclined in the horizontal direction with respect to the surfaces of the substrates 1, 2. Therefore, the circularly polarized light incident on the liquid crystal layer 5 from the λ / 4 wave plate 7 becomes elliptical polarized light by birefringence of the liquid crystal molecules. The light is then reflected by the reflective electrode 3 and further affected by the birefringence of the liquid crystal molecules in the liquid crystal layer 5. The light does not become linearly polarized perpendicular to the transmission axis of the polarizing element 6 after being transmitted through the λ / 4 wave plate 7 and the λ / 2 wave plate 11. Thus, light is transmitted through the polarizing element 6.

By controlling the voltage applied to the liquid crystal layer 5, the amount of light transmitted through the polarizing element 6 after being reflected by the reflective electrode 3 can be adjusted. Thus, a gray scale display is provided.

When a voltage is applied to the liquid crystal layer 5 by the reflective electrode 3 and the counter electrode 4 so as to change the orientation of the liquid crystal molecules so that the phase difference by the liquid crystal layer 5 satisfies the 1/4 wavelength condition, Circularly polarized light from the λ / 4 wave plate 7 is transmitted through the liquid crystal layer 5 and then reaches the reflective electrode 3 to become linearly polarized light perpendicular to the transmission axis of the polarizing element 6. The light is again transmitted through the liquid crystal layer 5 to become circularly polarized light, and then transmitted through the λ / 4 wave plate 7 and the λ / 2 wave plate 11 to be parallel to the transmission axis of the polarizing element 6. There is one linear polarization. In this case, the amount of light transmitted through the polarizing element 6 is maximum.

FIG. 18B shows a case where the liquid crystal layer retardation condition for transmitting the maximum amount of light reflected by the reflective electrode 3 through the polarizing element 6 is shown. In other words, the light on the reflective electrode 3 becomes linearly polarized light perpendicular to the transmission axis of the polarizing element 6.

As described above, when no voltage is applied to the liquid crystal layer 5, since the liquid crystal layer 5 has substantially no birefringence, a black display is obtained and when a voltage is applied to the liquid crystal layer 5 The gray scale display is obtained by changing the light transmittance according to the voltage.

A black display in transmissive mode is described with reference to FIG. 18C.

Light emitted by a light source (not shown) is incident on the polarizing element 9 to become linearly polarized light parallel to the transmission axis of the polarizing element 9. Then, light is incident on the λ / 2 wave plate 12.

The λ / 2 wave plate 12 has a slow axis of the λ / 2 wave plate 12 inclined at 15 ° with respect to the transmission axis of the polarizing element 9 and is perpendicular to the slow axis of the λ / 2 wave plate 11. Is arranged to be. Thus, light transmitted through the λ / 2 wave plate 12 becomes linearly polarized light inclined 30 ° with respect to the transmission axis of the polarizing element 9 in the direction sandwiching the slow axis of the λ / 2 wave plate 12. . Next, light is incident on the λ / 4 wave plate 10.

The λ / 4 wave plate 10 is 75 ° with respect to the transmission axis of the polarizing element 9 in the direction in which the slow axis of the λ / 4 wave plate 10 sandwiches the slow axis of the λ / 2 wave plate 12. It is arranged to be inclined. In other words, the slow axis of the λ / 4 wave plate 10 is set to be 45 ° with respect to the polarization direction of the linearly polarized light from the λ / 2 wave plate 12, so that the λ / 4 wave plate 10 is The light transmitted through becomes circularly polarized light.

When no voltage is applied to the liquid crystal layer 5, the liquid crystal molecules exhibiting negative dielectric anisotropy used for the liquid crystal layer 5 are substantially perpendicular to the surfaces of the substrates 1, 2. Therefore, the refractive index anisotropy of the liquid crystal layer 5 with respect to incident light is very small. In other words, the phase difference resulting from the transmission of light through the liquid crystal layer 5 is substantially zero.

Therefore, the circularly polarized light from the λ / 4 wave plate 10 is transmitted through the liquid crystal layer 5 polarized almost circularly and is incident on the λ / 4 wave plate 7.

The slow axes of the λ / 4 wave plates 10 and 7 are set to be perpendicular to each other. Therefore, the circularly polarized light from the λ / 4 wave plate 7 becomes linearly polarized light perpendicular to the transmission axis of the polarizing element 8 and then enters the λ / 2 wave plate 11.

The linearly polarized light transmitted through the λ / 2 wave plate 11 is perpendicular to the transmission axis of the polarizing element 6. Such light is not transmitted but is absorbed by the polarizing element 6.

In this way, a black display is performed.

Referring to FIG. 18D, the white display in the transmissive mode will be described.

Since the process until light passes through the λ / 4 wave plate 10 and becomes circularly polarized light is the same as described above, it will not be described.

When a voltage is applied to the liquid crystal layer 5, the liquid crystal molecules are slightly inclined toward the horizontal direction with respect to the surfaces of the substrates 1 and 2. Therefore, the circularly polarized light incident on the liquid crystal layer 5 from the λ / 4 wave plate 10 becomes elliptical polarized light by the birefringence of the liquid crystal molecules. This light does not become linearly polarized light perpendicular to the transmission axis of the polarization element 6 even after passing through the λ / 4 wave plate 7 and the λ / 2 wave plate 11 and a part of the light is directed to the polarization element 6. Permeate.

By controlling the voltage applied to the liquid crystal layer 5, the amount of light passing through the polarizing element 6 can be adjusted. Thus, a gray scale display is provided.

When a voltage is applied to the liquid crystal layer such that the phase difference by the liquid crystal layer 5 satisfies the 1/2 wavelength condition, the circularly polarized light from the λ / 4 wave plate 10 is at half the thickness of the liquid crystal layer 5. After the linearly polarized light perpendicular to the transmission axis of the polarizing element 6, the light is completely transmitted through the liquid crystal layer 5, thereby forming circularly polarized light.

Since the circularly polarized light from the liquid crystal layer 5 is linearly polarized parallel to the transmission axis of the polarizing element 6 when transmitted through the lambda / 4 wavelength plate 7 and the lambda / 2 wavelength plate 11, the polarization element ( Most of the light incident on 6) is transmitted. In this case, the amount of light transmitted through the polarizing element 6 is maximum.

FIG. 18D shows a case in which the maximum amount of light transmitted through the polarizing element 9 has a liquid crystal layer retardation condition allowing the polarizing element 6 to pass therethrough.

As described above, when no voltage is applied to the liquid crystal layer 5, since the liquid crystal layer 5 has substantially no birefringence, a black display is obtained, and when a voltage is applied to the liquid crystal layer 5, By changing the light transmittance in accordance with the voltage, a gray scale display is obtained.

The phase difference by the liquid crystal layer is λ / 4 when the reflectance is maximum in the bright display in the reflection mode, and the phase difference by the liquid crystal layer when the reflectance is maximum in the bright display in the transmissive mode. As can be seen from this, when the thickness of the liquid crystal layer in the reflection region and the thickness of the liquid crystal layer in the transmission region are the same, the phase difference of λ / 4 in the reflection mode and the phase difference of λ / 4 in the transmission mode are simultaneously satisfied. Can't.

When the display is performed by changing the phase difference of the liquid crystal layer in the reflection region from 0 to λ / 4, satisfactory light illumination rate cannot be obtained in the transmission mode, which means that the phase difference of the liquid crystal layer in the transmission region is 0 to λ / Because only changes up to four.

The satisfactory light illumination rate in both the reflection mode and the transmission mode is determined by varying the thickness of the liquid crystal layer in the reflection region from the thickness in the transmission region, or between the liquid crystal layer in the reflection region and the liquid crystal layer in the transmission region. This is accomplished by applying a different voltage. In the case where the thickness of the liquid crystal layer in the transmission region is twice the thickness of the liquid crystal layer in the reflection region, the phase difference of the liquid crystal layer of λ / 4 in the reflection mode and the phase difference of λ / 2 in the transmission mode are simultaneously satisfied. It is not necessary to make the thickness for the transmission mode twice the thickness for the reflection mode. The light illumination rate is increased by making the thickness for the transmission mode larger than the thickness for the reflection mode but not more than twice.

In the fifth example, the slow axis of the λ / 4 wave plate 10 is set to be perpendicular to the slow axis of the λ / 4 wave plate 7, and the slow axis of the λ / 2 wave plate 12 is λ / 2. It is set to be perpendicular to the slow axis of the wave plate 11, and is set so that the transmission axis of the polarizing element 6 is perpendicular to the transmission axis of the polarizing element 9. The present invention is not limited to such a setting. The black display is realized when the linearly polarized light transmitted through the polarizing element 9 without delay by the liquid crystal layer 5 is incident on the polarizing element 6 while being perpendicular to the transmission axis of the polarizing element 6 in the transmission mode.

More specifically, as long as the following conditions are satisfied, the black display is realized without any birefringence in the liquid crystal layer 5, and the gray scale display is realized by changing the light transmittance according to the voltage without the above setting. The conditions are as follows. When the angle formed between the transmission axis of the polarizing element 6 and the slow axis of the λ / 2 wave plate 11 is γ 1, the transmission axis of the polarization element 6 and the slow axis of the λ / 4 wave plate 7 are formed. The angle is 2γ1 + 45 degrees; When the angle formed between the transmission axis of the polarizing element 9 and the slow axis of the λ / 2 wave plate 12 is γ 2, the transmission axis of the polarization element 9 and the slow axis of the λ / 4 wave plate 10 are formed. The angle is 2γ2 + 45 degrees; Linearly polarized light transmitted through the polarizing element 9 without any delay of the liquid crystal layer 5 is incident on the polarizing element 6 while being perpendicular to the transmission axis of the polarizing element 6 in the transmission mode.

The refractive indices for the normal light beam and the abnormal light beam of the birefringent material forming the lambda / 4 wave plates 7 and 10 and the lambda / 2 wave plates 11 and 12 are highly dependent on the wavelength. Therefore, the phase delay accumulated at the wavelength with a certain thickness also depends on the wavelength. Only when the incident light has a single specific wavelength can a phase delay of λ / 4 be fully provided in the linear polarization plane of the incident light. Therefore, in the region where the phase retardation of [lambda] / 4 is not achieved due to the wavelength dependence of the refractive index anisotropy of the birefringent material forming the [lambda] / 4 wave plates 7 and 10 and the [lambda] / 2 wave plates 11 and 12, A part is not absorbed by the polarizing element 6 and passes through the polarizing element 6. As a result, the blackness of the black display changes. In the fifth example, the λ / 4 wave plate 7 is coupled with the λ / 2 wave plate 11 and the λ / 4 wave plate 10 is coupled with the λ / 2 wave plate 12. Because of such a structure, the wavelength dependency of the refractive index anisotropy of the λ / 4 wavelength plate 10 is offset to some extent by the wavelength dependency of the refractive index anisotropy of the λ / 4 wavelength plate 7. Thus, the λ / 4 condition is achieved over a relatively wide wavelength range. Thus, the darkness of the black display is improved.

Needless to say, the slow axis of the lambda / 4 wave plate 10 is not set to be perpendicular to the slow axis of the lambda / 4 wave plate 7, and the slow axis of the lambda / 2 wave plate 12 is set to the lambda / 2 wavelength. The darkness of the black display can be improved without being set to be perpendicular to the slow axis of the plate 11.

In this example, γ 1 = γ 2 = 15 degrees, but the values of γ 1 and γ 2 may vary depending on the desired degree of darkness. Even if the blackness of the black display is degraded in the transmission mode, the lambda / 2 wavelength plate 12 can be removed to improve the cost performance. In this case, however, the linearly polarized light transmitted through the polarizing element 9 without any delay in the liquid crystal layer 5 is incident on the polarizing element 6 while being perpendicular to the transmission axis of the polarizing element 6 in the transmission mode. It is necessary to set the angle of the slow axis of the λ / 4 wave plate 10 and the transmission axis of the polarizing element 9.

The slow axis of the λ / 4 wave plate 10 is set to be perpendicular to the slow axis of the λ / 4 wave plate 7, and the slow axis of the λ / 2 wave plate 12 is the λ / 2 wave plate 11. When set to be perpendicular to the slow axis of, and the transmission axis of the polarizing element 6 is set to be perpendicular to the transmission axis of the polarizing element 9, the following effects are obtained in the transmission mode. The wavelength dependency of the refractive index anisotropy of the λ / 4 wave plate 10 is offset by the wavelength dependency of the refractive index anisotropy of the λ / 4 wave plate 7, and the wavelength dependency of the refractive index anisotropy of the λ / 2 wave plate 12 is The wavelength dependence of the refractive index anisotropy of the / 2 wavelength plate 11 is canceled out. Thus, the darkness of the black display is further improved.

If another phase difference compensating element is provided at at least one position between the polarizing element 6 and the liquid crystal layer 5 and between the polarizing element 9 and the liquid crystal layer 5 to improve the viewing angle, A satisfactory display is realized.

In the fifth example, the liquid crystal layer 5 is vertically aligned. When the liquid crystal molecules near the substrate have a predetermined inclination angle with respect to the vertical direction of the substrate, the delay is not completely zero even when no voltage is applied. In the reflection mode, when the delay of? Remains, between the polarizing element 6 and the liquid crystal layer 5 and between the polarizing element 9 and the liquid crystal layer 5 to compensate for the delay and bring the delay close to zero. The phase difference compensating element may be provided at at least one position. Thus, a better black display is realized.

When the vertically oriented liquid crystal layer has a residual delay of? In the reflection mode, a phase difference compensating element having a delay of? / 4-? Can be provided instead of the? / 4 wave plate 7.

In the reflection mode, the elliptical polarization offset from the circular polarization by the residual delay of the liquid crystal layer is incident on the liquid crystal layer. The elliptical polarized light becomes circularly polarized light when it reaches the reflective electrode after passing through the liquid crystal layer. When this light is reflected, the light becomes circularly polarized light with opposite directions of rotation. When this light passes through the liquid crystal layer, the light becomes elliptical polarization offset from the circular polarization. The elliptical polarization at this time has a phase offset by 90 degrees at the time of incidence. When this elliptical polarized light passes through the phase difference compensating element, it becomes linear polarized light perpendicular to the transmission axis of the polarizing element 6.

In the case where the reflection mode display is mainly performed, for example, when the reflective pixel electrodes are larger than the transmission pixel electrodes, the λ / 4 wavelength plate 10 used for displaying in the transmission mode is kept as it is.

Even when the delay remaining in the vertically oriented liquid crystal layer is not negligible, it can be seen that the display of high contrast is obtained in the reflection mode by providing the phase difference compensation element in consideration of the delay.

When the liquid crystal layer has a residual delay of α in the reflection mode and a residual delay of β in the transmission mode, a phase difference compensation element having a delay of λ / 4-α instead of the λ / 4 wave plate 7 can be provided. And a phase difference compensating element having a delay of? / 4-(?-?) Instead of the? / 4 wave plate 10.

In a transmission mode using light transmitted through a region having a transmissive function, such as a transmission electrode region, when the liquid crystal molecules are oriented perpendicular to the substrate, the light exiting the liquid crystal layer becomes elliptical polarized light in the same state as in the reflection mode. A phase difference compensating element having a delay of? / 4-(?-?) is set. Elliptical polarized light having such a phase difference is incident on the phase difference compensating element having a delay of? / 4- ?. Therefore, when light passes through the phase difference compensating element having a delay of? / 4- ?, it becomes linearly polarized light perpendicular to the transmission axis of the polarizing element 6. Thus, a black display with almost no optical leakage is obtained.

Even when the delay remaining in the vertically oriented liquid crystal layer is not negligible, it can be seen that a display of high contrast is obtained in the reflection mode by providing the phase difference compensation element in consideration of the delay.

The LCD device in the fifth example uses a vertically aligned liquid crystal layer, but the display is realized by the same principle as using a horizontally aligned liquid crystal layer. In such a case, the higher the voltage is applied, the smaller the delay caused by the liquid crystal layer. However, when most of the liquid crystal molecules except the liquid crystal molecules near the substrate are perpendicular to the substrate when a voltage is applied, the liquid crystal molecules near the substrate hardly move due to the electric field. Accordingly, residual delay occurs due to these liquid crystal molecules near the substrate. As can be seen, when the horizontally oriented liquid crystal layer is used, optical leakage occurs and the contrast is reduced during the black display due to the influence of the residual delay as compared with the case where the vertically oriented liquid crystal layer is used. In order for the horizontally oriented liquid crystal layer to realize a black display of the same quality as that provided by the vertically oriented liquid crystal layer, the liquid crystal molecules near the substrate need to be oriented so as to cancel out the residual delays by the liquid crystal molecules, or It is necessary to additionally provide a phase difference compensating element.

FIG. 19 shows the case where the slow axes of the λ / 4 wave plates 7 and 10 are parallel to each other and the slow axes of the λ / 2 wave plates 11 and 12 are parallel to each other, and for comparison therewith, (7, 10) shows the relationship between the wavelength of light and the transmittance in the black display in the transmission mode in the case where the slow axes are parallel to each other and no λ / 2 wavelength plate is provided.

As shown in Fig. 19, by providing the lambda / 2 wave plates 11 and 12, a black display substantially free of any optical leakage is realized.

20 shows a comparison with the case where the slow axes of the λ / 4 wave plates 7 and 10 are parallel to each other and the slow axes of the λ / 2 wave plates 11 and 12 are parallel to each other as in the fifth example. Wavelength of light in the black display in the transmission mode when the slow axes of the λ / 4 wave plates 7 and 10 are perpendicular to each other and the slow axes of the λ / 2 wave plates 11 and 12 are perpendicular to each other. The relationship between and transmittance is shown.

As shown in Fig. 20, by setting the slow axes of the λ / 4 wave plates 7 and 10 to be perpendicular to each other and the slow axes of the λ / 2 wave plates 11 and 12 to be perpendicular to each other. As a result, a black display without any optical leakage is realized.

<Example 2>

As described above, according to the first embodiment of the present invention, a transmissive and reflective LCD device that provides satisfactory display quality is realized. Among the LCD devices operable in both the transmission mode and the reflection mode, the LCD device (Fig. 8C) using the semi-transmissive and semi-reflective layers is a reflection area for performing the display in the reflection mode and a transmission for performing the display in the transmission mode. It is not excellent in the following points compared with an LCD device having an area.

If semi-transmissive and semi-reflective layers formed of metal particles deposited to very small thicknesses are used, the metal particles need to have a relatively large absorption rate. Accordingly, the internal absorption of the incident light is large, and a large proportion of the incident light is absorbed or scattered and is not used for the display. Thus, the light illumination rate is relatively small (for example, in one model, 55% of the incident light is not used for the display).

When semi-transmissive and semi-reflective layers with minute holes and recesses (collectively referred to as "openings") are used, the structure of the layers becomes complicated and requires accurate production design. Therefore, it is difficult to control the thickness of the layer constantly. In other words, the reproduction of electrical and optical properties is not satisfactory. Therefore, it is difficult to control the image quality of the LCD device.

In the second embodiment, an LCD device having a transmissive area for displaying in transmissive mode and a reflective area for displaying in reflective mode and characterized by the structure of the electrode will be described. When the electrode structure of the second embodiment and the phase difference compensating element of the first embodiment are combined, the image quality is further improved.

An LCD device having a transmission area and a reflection area utilizes ambient light or irradiated light with almost no loss and has a significantly higher light illumination rate as compared to an LCD device using a half mirror. The first conductive layer is formed of a transparent conductive material such as, for example, ITO or SnO ₂ . The second conductive layer is made of Al, W, Cr or an alloy thereof. Since both the first and second conductive layers can be formed from the materials used in common reflective LCD devices and transmissive LCD devices, the LCD devices provide very stable display characteristics and reliability and are relatively easily manufactured.

Furthermore, the LCD device of the second embodiment has the problems of the conventional transmissive LCD which has low transparency due to surface reflection when the ambient light is bright, as well as the conventional reflection which cannot obtain satisfactory display due to the low brightness when the ambient light is dark. It also solves the problem of the type LCD device. Under circumstances where sufficient power is provided, backlights are utilized in conventional transmissive LCD devices. Thus, a sufficient display is realized regardless of the ambient light intensity without the dispersion of the light illumination rate of the ambient light need to be controlled exactly as in conventional reflective LCD devices. When an LCD device is used, a region comprising a first conductive layer having a relatively high transmittance and a region containing a second conductive layer having a relatively high reflectance, which are provided in one pixel region, complementarily contribute to the display. . Thus, a clear image is displayed regardless of the ambient light intensity.

When applied to the viewfinder (monitoring screen) of a battery-powered digital camera or video camera, the LCD device of the second embodiment provides an appropriately bright image that facilitates observation by adjusting the brightness of the backlight regardless of the ambient light intensity. do.

Especially when used outdoors on a sunny day, images provided by conventional transmissive LCD devices have lower contrast even when the brightness of the backlight is increased. By turning off the backlight and using the LCD device according to the invention in reflection mode, or by lowering the brightness of the backlight and using both the transmission mode and the reflection mode of the LCD device according to the invention, such image quality is improved while reducing power consumption. Can be. When the LCD device is used in a room with bright sunlight, the reflection mode and the transmission mode can be switched according to the direction of the object, or both modes can be used together to provide an easy-to-view display. If the monitoring screen receives sunlight, the LCD device can be used in the same way as it is used outdoors on a sunny day. If an object is displayed from a dark corner of the room, the backlight can be turned on to enable the LCD device in the transmissive mode.

When adopted for the monitoring of an automobile-mounted vehicle navigation apparatus, the LCD apparatus of the second embodiment provides appropriately bright images that are easy to observe. Conventional vehicle-mounted monitoring screens use backlights with brightness that is brighter than those used in personal computers and the like to handle external light incident on the screen. However, conventional automotive mounted monitoring screen steels have a problem of lower contrast. In contrast, such high brightness backlights are not suitable for display at night or in tunnels. The LCD device of the second embodiment provides a sufficient display when the ambient light is bright by using the reflection mode with the transmitted light without setting the brightness of the backlight high. Even in the dark, a display that is easy to see with a brightness of about 50 to 100 cd / m ³ is provided.

In the LCD device of the second embodiment, the pixel electrode includes a first conductive layer having a relatively high light transmittance and a second conductive layer having a relatively high light reflectance, which are electrically connected to each other. Therefore, both the transmissive region for displaying in the transmissive mode and the reflective region for displaying in the reflective mode are included in one pixel region.

The first conductive layer and the second conductive layer are provided in the separation layer with an insulating layer interposed therebetween. The thickness of the liquid crystal layer can be adjusted by changing the thickness of the insulating layer between the transmission region (for the first conductive layer) and the reflection region (for the second conductive layer). In this way, the optical properties in the two regions can be matched with each other. During the manufacturing process, two layers with different levels of dislocation have an insulating layer interposed between them. Thus, no electrical corrosion is caused by the resist stripper acting as the developer or electrolyte used to pattern and form the electrode. Thus, an extremely reliable LCD device is obtained.

When two layers of the pixel electrode (for example, the lower layer of ITO and the upper layer of Al) are formed sequentially without any insulating layer interposed therebetween, the potential levels of the ITO layer and the Al layer differ greatly. Moreover, the thin film has many fine openings. Therefore, the developer or resist release agent used for patterning acts as an electrolyte that causes electrical corrosion. As a result, the ITO layer elutes, causing pixel defects, line breaks, and contamination of the liquid crystal layer. Since an insulating layer is provided between the two layers according to the invention, the insulating layer functions as a protective layer which prevents the penetration of the liquid which causes electric corrosion.

Even when the two layers forming the pixel electrode have a relationship that causes electrical corrosion, the two layers are connected to each other through the third conductive layer to mitigate the characteristics of these two layers. Thus, insufficient connection due to electrical corrosion and other problems that lower the reliability of the LCD device are prevented.

If one of the first, second and third conductive layers is formed from a part of the material of the gate line or the source line, the production process is simplified.

The surface of the insulating layer on which the second conductive layer is to be formed may be formed in a wave shape. In this case, incident light is reflected and scattered, and the viewing angle is widened. Thus, paper white display is realized without the use of additional scattering plates.

According to the method for producing the LCD device of the present invention, complicated production conditions necessary for the conventional LCD device using the half-mirror are not necessary. Typical electrode materials and line materials and general production conditions used in conventional transmissive LCD devices and reflective devices can be used. As a result, production is relatively easy and reproducibility is satisfactory. Although the two layers forming the pixel electrode have a relationship causing electrical corrosion, the two layers may be connected to each other through an insulating layer, or a third conductive layer may be provided between them. As a result, two layers can be formed without contact or direct contact with the liquid acting as the electrolyte. Therefore, the LCD device has high reliability and is produced with high efficiency since electric corrosion is prevented.

If the step of removing the insulating layer of the contact area with the first and second conductive layers and the step of removing the insulating layer on a part of the first conductive layer are performed in the same step, the step of maintaining the reliability of the LCD device The number is reduced.

(Example 6)

A sixth example LCD device according to the present invention will be described.

21 is a plan view of an active matrix substrate of the sixth example LCD device corresponding to one pixel region. FIG. 22 is a cross-sectional view of the LCD device taken along the line 22-22 'of FIG. 21.

As shown in Figs. 21 and 22, the plurality of gate lines 53 and the plurality of source lines 59a are provided to be perpendicular to each other on a transparent insulating plate (not shown) formed of a glass or plastic material. The TFT 57 is provided near each of the intersections of the gate lines 53 and the source lines 59a. The drain electrode 59c of the TFT 57 is connected to the reflection electrode 61 and the transmission electrode 58a which function together as a pixel electrode. Some LCD devices having a pixel electrode as an upper electrode have an area T (transmission area) having a relatively high light transmittance and an area R (reflection area) having a relatively high light reflectance when viewed in the above-described LCD device.

Although not shown, an alignment layer for orienting liquid crystal molecules is provided on the active matrix substrate shown in FIG. 21.

The LCD device of the sixth and following examples includes the active matrix substrate described above and an opposing substrate comprising a transmissive electrode and an alignment layer. If necessary, a color filter, retardation compensating element or polarizing element may be provided.

Region T is rectangular and lies in the center of the pixel electrode. In the cross section, the region T includes a plurality of layers formed of a material having a high light reflectance, and includes a transmission electrode 58a as an upper layer connected to the drain electrode 59c of the TFT 57. The region R surrounds the region T and includes the reflective electrode 61 as an upper layer. The reflective electrode 61 is formed of Al or an alloy containing Al having a high light reflectance and is connected to the drain electrode 59c of the TFT 57. Due to such a structure, the region R can reflect incident light. Reflective electrode 61 with a corrugated surface scatters incident light in a suitable range of directions.

The liquid crystal material used for the LCD device in the sixth example is a guest-host liquid crystal material ZLI2327 (manufactured by Merck) which contains a black pigment and contains the photoactive material S-811 in a proportion of 0.5%.

As shown in FIG. 22, the TFT 57 includes a gate insulating layer 54, a semiconductor layer 55, semiconductor contact layers 56a and 56b, a source electrode 59b, a drain electrode 59c, and the device. These include a gate electrode 52 which is provided sequentially. Gate electrode 52 branches from each of gate lines 53 (FIG. 21).

The drain electrode 59c is connected to the transmission electrode 58a which is a part of the pixel electrode of the region T. In the region R, the interlayer insulating layer 60 and the reflective electrode 61 are sequentially provided on the transmissive electrode 58a. The reflective electrode 61 is electrically connected to the transmission electrode 58a through the contact hole 63 formed in the interlayer insulating layer 60. The reflective electrode 61 and the transmissive electrode 58a form a pixel electrode to apply a voltage to the liquid crystal material. The transmissive electrode 58a and the reflective electrode 61 are not directly connected to each other, but are connected via the conductive metal layer 62 made of Ti.

When the reflective electrode 61 is formed by patterning, the transmissive electrode 58a may be covered with the interlayer insulating layer 60 (the method for producing the LCD device will be described in detail below). Thus, ITO and Al cause electrical corrosion and effectively prevent disadvantages such as line breaks. When the interlayer insulating layer 60 is formed on the transmissive electrode 58a with a relatively thin thickness to completely cover the transmissive electrode 58a, electrical corrosion occurring between ITO and Al after the LCD device is produced is prevented.

In this example, the metal layer 62 is formed of Ti, but the same effect can be obtained as long as the metal layer 62 is formed of a conductive metal other than Al, for example, Cr, Mo, Ta, or W. In general, the reflective electrode 61 is formed of an Al-containing alloy containing a metal material having a higher potential than Al, such as W, Ni, Pd, V, or Zr, instead of forming the metal layer 62. . Even in this case, electrical corrosion between ITO and Al is prevented after producing the LCD device. For example, by adding about 5.0 wt.% Of W to Al, electrocorrosion is more effectively prevented.

The LCD device manufacturing method in this example will be described with reference to Figs. 23A to 23E.

As shown in FIG. 23A, the conductive thin film is formed on the insulating plate 51 and patterned into a shape selected by photolithography, thereby forming a gate electrode 52 and a gate line (not shown). In this embodiment, the insulating plate 51 is formed of glass, and the gate electrode 52 and the gate line are formed of Ta. The insulating plate 51 may be formed of plastic or the like instead of glass, and the gate electrode 52 and the gate line may be formed of other conductive materials such as Al, Cr, Mo, W, Cu, or Ti.

Next, as shown in FIG. 23B, the gate insulating layer 54 of SiN _X , the semiconductor layer 55 of a-Si, and the P-doped n ⁺ -a-Si layer for the semiconductor contact layers 56a and 56b. It is formed sequentially by this CVD and then patterned by photolithography.

Next, the conductive layer is formed and patterned into a shape selected by photolithography, thereby forming the source line 59a, the source electrode 59b, and the drain electrode 59c. The conductive layer is formed of Cr-containing material in this embodiment, but may be formed of other conductive materials, such as Al, Mo, Ta, W, Cu or Ti.

Next, as shown in Fig. 23C, the transparent conductive layer is formed and patterned by photolithography, whereby the transmission electrode 58a is formed. The transmissive electrode 58a is formed of ITO in this embodiment.

Next, the metal layer is formed and patterned by photolithography, whereby the metal layer 62 is formed. This metal layer 62 is used to connect the transmissive electrode 58a and the reflective electrode 61 to be formed later. The metal layer 62 is formed of Ti in this embodiment, but may be formed of other conductive materials other than Ti, for example, Cr, Mo, Ta or W.

Next, the P-doped n ⁺ -a-Si layer is etched using the source electrode 59b and the drain electrode 59c as a mask, thereby forming the semiconductor contact layers 56a and 56b. In this way, the TFT 57 is completed.

The source electrode 59b and the drain electrode 59c may overlap the transmissive electrode 58a.

Next, as shown in FIG. 23D, an interlayer insulating layer 60 is formed. This interlayer insulating layer 60 is patterned by photolithography to form a contact hole 63 and remove a portion of the interlayer insulating layer 60 in the region T. As shown in FIG. At the same time, the surface of the interlayer insulating layer 60 in the region R (the surface on which the reflective electrode 61 is to be formed) is formed in a wave-like manner.

By removing a part of the interlayer insulating layer 60 in the region T, the transmittance of the region T can be improved. However, the interlayer insulating layer 60 is not completely removed but remains at a predetermined thickness. This prevents electrical corrosion when the reflective electrode 61 is formed by patterning. In other words, the alignment states of the liquid crystal molecules may be substantially the same in each pixel region.

The surface of the interlayer insulating layer 60 in the region R appears to have a plurality of rounded projections 64 when viewed from above. In cross section, the surface area of the interlayer insulating layer 60 oscillates slowly. When the reflective electrode 61 is formed on such a wavy surface, the incident light is effectively reflected by the wavy surface of the reflective electrode 61 and scattered in the appropriate range of directions. The shape of the wavy surface can be optimally determined according to the desired display characteristics. If there is no need to scatter light, the surface need not be wave-like.

The interlayer insulating layer 60 is formed of a single layer of organic resin (thickness: 2.5 mu m) in this embodiment, but may be formed of a plurality of laminated layers made of different materials. A single layer of a relatively thick organic resin as in this embodiment has the advantage that the occurrence of parasitic capacitance can be prevented even when the reflective electrode 61 partially overlaps the TFT 57. As a result, the image quality is improved and the numerical aperture is improved. In addition, the relatively thick organic resin layer facilitates the formation of the corrugated surface.

Alternatively, interlayer insulating layer 60 may be formed of a common inorganic layer, for example SiN _X. Such layers are advantageous for achieving high insulation even though they are relatively thin, but have the disadvantage that the formation of corrugated surfaces is difficult. Such a layer is preferred if it is not necessary to form a corrugated surface due to the desired display characteristics.

As shown in Fig. 23E, the Al layer is formed and patterned, so that the reflective electrode 61 is formed in the region R. The reflective electrode 61 is electrically connected to the transmissive electrode 58a and the drain electrode 59c of the TFT 57 via the contact hole 63 and the metal layer 62. The reflective electrode 61 is formed of Al in this embodiment, but may be formed of another Al-containing alloy or a conductive material having high light reflectance.

Thus, the active matrix substrate shown in Figs. 21 and 22 is completed.

Although not shown, an alignment layer is formed on top of the active matrix substrate. The active matrix substrate provided with the alignment layer includes a transmissive electrode and is bonded to the opposite substrate provided with the alignment layer. Liquid crystal material is injected into the gap between the two substrates. Thus, the LCD device of the sixth example is completed. If necessary, a color filter or retardation compensator may be added.

As described above, the liquid crystal material used in the LCD device of this embodiment contains a black pigment and a guest-host liquid crystal material ZLI2327 (manufactured by Merck Co., Ltd.) containing a photoactive material S-811 in a proportion of 0.5%. )to be.

In this example, sufficient display characteristics are obtained by setting the area ratio to area T: area R = 40: 60. This area ratio is not limited to this and can be appropriately changed depending on the transmittance and reflectance of the regions T and R and the use of the LCD device. In this embodiment, only one region T is provided in the center of the pixel region. A plurality of regions T may be provided, and the region T may be any other shape.

In the LCD device of the second embodiment, the pixel electrode includes a region T having a relatively high transmittance located at the center and a region R having a relatively high light reflectance disposed around the region T. FIG. Due to such a structure, the LCD device uses ambient light and illumination light with less loss compared to the conventional LCD device using a half-mirror. Moreover, the LCD device of the second embodiment has the problems of the conventional transmissive LCD device in which the perspective is degraded due to the surface reflection when the ambient light is bright, and the conventional reflection in which sufficient display cannot be obtained due to the lower sharpness when the ambient light is dark. Solve the problem of the type LCD device. In other words, the LCD device of the second embodiment provides a sufficient display irrespective of the ambient light intensity without the need to accurately control the dispersion of the light illumination rate due to the dispersion of the characteristics of the reflection as in the case of the conventional reflective LCD device. do.

The LCD device of this example can be manufactured with common electrodes and wiring materials and conditions used in conventional transmissive LCD devices and reflective LCD devices. The complicated conditions required for conventional LCD devices using half-mirrors are not necessary. Thus, the LCD device of this example is relatively easily manufactured with satisfactory reproducibility. In addition, in the conventional LCD device using the half-mirror, difficult display characteristics can be performed relatively easily.

(Example 7)

An LCD apparatus according to the seventh example of the present invention will be described.

24 is a plan view of an active matrix substrate of the seventh example LCD device corresponding to one pixel region. FIG. 25 is a cross-sectional view of the LCD device taken along the line 25-25 ′ of FIG. 24.

The LCD device of the seventh example differs from the LCD device of the sixth example in the structure of the electrical connection between the reflective electrode 61 as a part of the pixel electrode and the TFT 57 and the manufacturing method of the structure.

As shown in Figs. 24 and 25, the drain electrode 59c of the TFT 57 is connected to the transmission electrode 58a. The transmissive electrode 58a functions as part of the pixel electrode for applying a voltage to the liquid crystal material in the region T. In the region R, the interlayer insulating layer 60 and the reflective electrode 61 are provided on the transmission electrode 58a. The reflective electrode 61 is directly connected to the drain electrode 59c through the contact hole 63. The reflective electrode 61 also functions as part of the pixel electrode. As in the sixth example, the transmissive electrode 58a formed of ITO is not directly connected to the reflective electrode 61 formed of Al. Because of this structure, the TFT 57 is reliably electrically connected to these materials without the possibility of unwanted electrical corrosion or the like, while utilizing the high reflectance of the ambient light in the region R and the high light transmittance from the backlight in the region T.

In this example, electrical corrosion of ITO and Al is prevented. The present invention is effectively applicable to any combination of several other materials that are susceptible to electrical corrosion.

Hereinafter, the active matrix substrate shown in FIGS. 24 and 25 will be described.

The process until the layer to be the semiconductor layer 55 and the semiconductor contact layers 56a and 56b is formed is performed in the same manner as in the sixth example.

Then, the conductive layer is formed and patterned by photolithography to form the source line 59a, the source electrode 59b, the drain electrode 59c, and the connecting metal layer 59d. The conductive layer is formed of a material containing Cr in this embodiment, but may be formed of another conductive material such as, for example, Al, Mo, Ta, W, Cu, or Ti.

Then, the transmissive electrode 58a is formed so as to partially overlap the connecting metal layer 59d. In general, the connection metal layer 59d may partially overlap the transmission electrode 58a. Also in this embodiment, the transmissive electrode 58a is formed of ITO.

The source line 59a, the source electrode 59b, the drain electrode 59c, and the connecting metal layer 59d are formed on the transmission electrode 58a.

Then, the interlayer insulating layer 60 is formed in the same manner as in the sixth example and patterned by photolithography to form the contact hole 63 and to remove the interlayer insulating layer 60 in the region T. Then, the reflective electrode 61 is formed. Also in this embodiment, the reflective electrode 61 is made of Al.

As can be understood in this example, the transmissive electrode 58a formed of ITO is not directly connected to the reflective electrode 61 formed of Al. This structure prevents the occurrence of malfunctions at the contact portions due to the electrical corrosion between ITO and Al, thereby improving the reliability. The metal layer 62 formed of the same material as the source electrode 59b can be formed relatively easily.

(Example 8)

In an eighth example, another method of manufacturing the LCD device described in the seventh example will be described with reference to Figs. 26A to 26C.

26A to 26C corresponding to FIG. 25 are cross-sectional views illustrating a method of manufacturing the LCD device described in the seventh example.

The process until the interlayer insulating layer 60 is formed is as described in the seventh example.

Then, as shown in FIG. 26A, a portion of the interlayer insulating layer 60 is removed by photolithography, whereby a contact hole 63 is formed. In the same step, the surface of the interlayer insulating layer in the region R is formed in a wave form, so that incident light is scattered by the surface. Unlike the seventh example, a part of the interlayer insulating layer 60 in the region T is not removed.

On the surface of the interlayer insulating layer 60, an Al layer or an Al containing alloy layer is formed. In this example, the interlayer insulating layer 60 is formed of a single organic resin layer, but may be formed of a plurality of layers made of different materials. The surface of the interlayer insulating layer 60 need not be wavy.

Then, as shown in FIG. 26B, the Al layer is patterned by photolithography to form the reflective electrode 61.

Next, as shown in FIG. 26C, the interlayer insulating layer 60 is removed in all or part of the region T. As shown in FIG.

In this way, the active matrix substrate shown in FIGS. 24 and 25 is completed.

An LCD device having such an active matrix substrate can be operated simultaneously in both transmission mode and reflection mode. The reflective electrode 61 formed of Al and the transmissive electrode 58a formed of ITO are not directly connected to each other after the LCD device is completed and thus do not cause electrical corrosion. Therefore, malfunction due to electrical corrosion is prevented, thereby improving the reliability of the LCD device. Even during the manufacturing process, electrical corrosion is prevented because the reflective electrode 61 is formed by patterning but the transmissive electrode 58a is not exposed to the etchant.

(Example 9)

An LCD device according to a ninth example of the present invention will be described.

The LCD device of the ninth example differs from the LCD device of the seventh and eighth examples in the order of forming the transmissive electrode 58a and the drain electrode 59c and in the step of forming the contact hole 63.

27A to 27C corresponding to FIG. 25 are cross-sectional views illustrating a method of manufacturing the LCD device in the ninth example.

The process until the layer to be the semiconductor layers 56a and 56b is formed is performed as described in the sixth and seventh examples.

As shown in Fig. 27A, the light-transmissive conductive layer is formed and patterned by photolithography to form the transmissive electrode 58a. In this example, the transmission electrode 58a is formed of ITO.

Thereafter, a conductive layer is formed and patterned by photolithography to form a source line 59a, a source electrode 59b, a drain electrode 59c, a connection metal layer 59d, and a metal layer 59e for the region T. Is formed. Source electrode 59b branches off from source line 59a. The drain electrode 59c, the connecting metal layer 59d, and the metal layer 59e for the region T are electrically interconnected. The connection layer is formed of a Ta-containing material in this example, but may also be formed of another conductive material such as, for example, Al, Cr, Mo, W, Cu or Ti.

Thereafter, etching is performed using the source electrode 59b and the drain electrode 59c as a mask, so that the semiconductor conductive layers 56a and 56b are formed. Thus, the TFT 57 is completed.

Next, the interlayer insulating layer 60 is formed. A contact hole 63 is formed and a part of the interlayer insulating layer 60 in the region T is removed by photolithography. In the same step, the surface of the interlayer insulating layer 60 in the region R is formed in a wave form so as to scatter incident light. On the surface, an Al layer or an Al containing alloy layer is formed. The interlayer insulating layer 60 is formed of a single organic resin layer in this example, but may be formed of a plurality of different materials. The surface of the interlayer insulating layer 60 need not be wavy.

As shown in Fig. 27B, an Al or Al-containing alloy layer is formed by photolithography, so that the reflective electrode 61 is formed.

Then, as shown in FIG. 27C, part or all of the layer 59e in the region T is removed by photolithography or by etching using the reflective electrode 61 as a mask. Alternatively, the layer 59e may be etched while the reflective electrode 61 is formed by patterning by etching.

As described above, in this example, the reflective electrode 61 formed of Al is not directly connected to the transmissive electrode 58a formed of ITO. Thus, after the LCD device is completed, electrical corrosion between Al and ITO is prevented, thereby preventing malfunction due to electrical corrosion, thereby improving reliability. In addition, during the manufacturing process, electrical corrosion is prevented because the transmissive electrode 58a is not exposed to the etchant while the reflective electrode 61 is formed by patterning.

(Example 10)

The LCD device in the tenth example according to the present invention will be described.

The LCD device in the tenth example is different from the LCD device in the seventh and eighth examples in the structure of the TFT 57 and the transmission electrode 58a and in forming the contact hole 63.

28A to 28C corresponding to FIG. 25 are cross-sectional views illustrating a method of manufacturing the LCD device in the tenth example.

As described in the sixth and seventh examples, the process up to the formation of the layer to be the semiconductor contact layers 56a and 56b is performed.

As shown in FIG. 28A, the light transmitting conductive layer and the metal layer are sequentially formed. The metal layer is patterned by photolithography so that the upper half of the source line 59a, the upper half of the source electrode 59b, the upper half of the drain electrode 59c, the connecting metal layer 59d and the metal layer 59e for the region T are removed. Form. Next, the light transmissive conductive layer is patterned in the same pattern as that of the source line 59a, the upper half of the source electrode 59b, the upper half of the drain electrode 59c, the connecting metal layer 59d and the metal layer 59e. Thus, the lower half of the source line, the lower half of the source electrode 58b, the lower half of the drain electrode 58c, and the transmissive electrode 58a are formed.

As can be seen from the above, the source line, the source electrode and the drain electrode have a two-layer structure. Even if a disconnection or any other malfunction occurs in one of the two layers, a normal display is implemented because a normal signal is sent through the other layers.

In this example, the light transmissive conductive layer is formed of ITO and the metal layer is formed of Ta-containing material. The light transmissive conductive layer may be continuously etched from the metal layer or may be etched using a separate mask after the mask for the metal layer is removed.

Next, by performing etching using the source electrodes 59b / 58b and the drain electrodes 59c / 58c as masks, the semiconductor contact layers 56a and 56b are formed. Thus, the TFT 57 is completed.

Next, the interlayer insulating layer 60 is formed. A contact hole 63 is formed and a part of the interlayer insulating layer 60 in the region T is removed by photolithography. In the same step, the surface of the interlayer insulating layer 60 in the region R is formed into a wave to scatter incident light. On the surface, an Al layer or an Al containing alloy layer is formed. Although the interlayer insulating layer 60 is formed of a single organic resin layer in this example, it may be formed of a plurality of layers of different materials. The surface of the interlayer insulating layer 60 need not be corrugated.

As shown in Fig. 28B, an Al layer or an Al-containing alloy layer is formed by photolithography, whereby a reflective electrode 61 is formed.

Next, as shown in FIG. 28C, the layer 59e in the region T is partially or wholly removed by photolithography or by etching using the reflective electrode 61 as a mask. Alternatively, layer 59e may be etched while reflective electrode 61 is patterned and formed by etching.

As described above, in this example, the reflective electrode 61 formed of Al is not directly connected to the transmissive electrode 58a formed of ITO. Therefore, since electrical corrosion between Al and ITO is prevented after the LCD device is completed, malfunction due to electrical corrosion is prevented and reliability is improved. Even during the manufacturing process, electrical corrosion is prevented because the transmissive electrode 58a is not exposed to the etchant while the reflective electrode 61 is formed by patterning. Moreover, since the pixel electrode (transmission electrode 58a) is formed at the same stage as the other lines and electrodes, the manufacturing method is simplified.

The pixel electrode (transmission electrode 58a) is formed in the same step as the source line, the source electrode and the drain electrode in this example, but may be formed in the same step as the gate line and the gate electrode. Instead of the transmissive electrode 58a, a reflective electrode can be formed in the same step as the other lines and electrodes.

(Example 11)

An LCD device of an eleventh example according to the present invention will be described. In addition, the structure of the terminal portion and a method of forming the same will be described.

The LCD device of the eleventh example is different from the LCD devices of the sixth to tenth examples in that the transmissive electrode 58a is provided on the same layer as the gate electrode and the gate line.

29A to 29C are cross sectional views showing a method for producing an active matrix substrate and a terminal portion of an LCD device of an eleventh example, more specifically, an LCD device. FIG. 29A corresponding to FIG. 25 illustrates a structure of a display unit of the LCD device. 30 is a plan view of the LCD device of Example 11; Fig. 29B, which is a sectional view of the LCD device taken along the lines 29B-29B 'in Fig. 30, shows the terminal structure of the gate terminal portion. Fig. 29C, which is a sectional view of the LCD device cut along the lines 29C-29C 'in Fig. 30, shows the terminal structure of the source terminal portion.

As shown in FIG. 29A, the TFT 57 is provided on the insulating plate 51. The transmissive electrode 58a is provided on the same layer as the TFT 57 and the gate electrode 52 of the gate line (not shown). The drain electrode 59c is connected to the reflective electrode 61 through the contact hole 63 in the interlayer insulating layer 60, and is also transmitted through the contact hole 63 formed in the gate insulating layer 54. Is also connected.

According to this structure, after the transmissive electrode 58a is formed, but before the reflective electrode 61 is completely formed in the same pixel region as the transmissive electrode 58a, the minimum transmissive electrode 58a is formed by the gate insulating layer 54. Covered with) Therefore, occurrence of electrical corrosion due to a potential difference between the electrodes 58a and 61 is prevented.

Also in the gate and source terminal portions shown in Figs. 29B and 29C, the gate lines 70 and 53 and the source line 71 formed on the same layer as the transmissive electrode 58a are the gate insulating layer 54 and the interlayer insulating layer ( 60). Thus, the gate lines 70 and 53 and the source line 71 are covered with insulating layers until the reflective electrode 61 is completely formed on the interlayer insulating layer 60. In this way, electrical corrosion between the gate lines 70 and 53 / source lines 71 formed of different metal materials and the reflective electrode 61 is prevented.

With reference to Figs. 31A to 31E and 32A to 32C, a method for producing an LCD device in the eleventh example is described in relation to the display portion.

As shown in FIG. 31A, a light transmissive conductive layer is formed on the insulating plate 51 and patterned by photolithography to form the transmissive electrode 58a. In this example, the insulating plate 51 is made of glass, and the transmissive electrode 58a is made of ITO.

Next, a gate electrode 52 and a gate line (not shown) are formed by forming a predetermined layer on the insulating plate 51 and patterning the layer by photolithography. The gate electrode 52 and the gate line are made of a Ta-containing material in this embodiment, but may be formed of another conductive material such as, for example, Al, Cr, Mo, W, Cu, or Ti.

The gate electrode 52 and the gate line may be formed before the transmission electrode 58a.

Next, as shown in FIG. 31B, P-doped n ⁺ − for the gate insulating layer 54 of SiN _x , the semiconductor layer 55 of a-Si, and the semiconductor contact layers 56a and 56b. The a-Si layer is formed sequentially by CVD and then patterned by photolithography.

In order to electrically interconnect the transmissive electrode 58a and the drain electrode 59c to be formed later, a contact hole 63 is formed in the gate insulating layer 54. The gate terminal (FIG. 29B) and the gate insulating layer 54 on the source terminal (FIG. 29C) in the gate and source terminal portions may be removed in the same step.

Next, as shown in FIG. 31C, a conductive layer is formed and patterned by photolithography to form a source line 59a, a source electrode 59b and a drain electrode 59c. The conductive layer is made of Cr-containing material in this embodiment, but may be formed of another conductive material such as, for example, Al, Mo, Ta, W, Cu, or Ti.

Next, etching is performed using the source electrode 59b and the drain electrode 59c to form the semiconductor contact layers 56a and 56b. In this way, the TFT 57 is completed.

As shown in FIG. 31D, an interlayer insulating layer 60 is formed, and a contact hole 63 is formed in the interlayer insulating layer 60 by photolithography. Part of the interlayer insulating layer 60 in the region T is not removed in this step, but is removed after the reflective electrode 61 is formed.

As shown in Fig. 31E, the surface of the interlayer insulating layer 60 is formed into a wave by photolithography.

The interlayer insulating layer 60 is formed of a single organic insulating material layer in this example, but may be formed of a plurality of layers of different materials. The surface of the interlayer insulating layer 60 need not be wavy.

Next, as shown in FIG. 32A, a conductive layer having a relatively high reflectance is formed on the surface of the interlayer insulating layer 60.

As shown in FIG. 32B, the conductive layer is patterned by photolithography to form the reflective electrode 61. The reflective electrode 61 is not formed at least in the region T.

Next, as shown in FIG. 32C, a part of the interlayer insulating layer 60 in the region T is removed. Part of the gate insulating layer 54 in region T is also removed. It is desirable that both insulating layers 54 and 60 be removed in region T, since the layers may undesirably cause a voltage drop to interfere with sufficient voltage to the liquid crystal material. In particular, in the case where a voltage is applied across the liquid crystal material by the transmissive electrodes 58a and the reflective electrode 61 electrically connected to each other, the presence of the insulating layers in the region T is applied across the liquid crystal material in the region T and the region R. Differences between the set voltages become undesirable.

In this manner, the liquid crystal matrix substrate shown in FIG. 29A is completed.

An alignment layer is formed on the active matrix substrate, and an alignment process is performed on the alignment layer when necessary. Next, the active matrix substrate is combined with the counter electrode. Liquid crystal material is injected into the gap between the substrates. Thus, the LCD device of the eleventh example is completed.

33A to 33F, a method for forming a gate terminal portion is described. The gate terminal portion may be formed in the same steps as that of the display portion.

As shown in FIG. 33A, a light transmissive conductive layer serving as the lower layer 70 of the gate line is formed on the insulating plate 51. In the same step, the transmissive electrode 58a (FIG. 31A) is formed in the display portion. The upper layer 53 of the gate line is formed on the lower layer 70. As such, the lower layer 70 and the upper layer 53 of the gate line are electrically interconnected (corresponding to the step shown in FIG. 31A).

As shown in Fig. 33B, a gate insulating layer 54 is formed on the gate line and the gate terminal (corresponding to the step shown in Fig. 31B). Part of the gate insulating layer 54 on the gate terminal is not removed in this step, but is removed next.

In this way, the TFT 57 is completed in the display portion (Fig. 31C).

As shown in Fig. 33C, an interlayer insulating layer 60 is formed on the gate insulating layer 54 (corresponding to the step shown in Fig. 31D).

As shown in FIG. 33D, a conductive layer used for the reflective electrode 61 is formed on the interlayer insulating layer 60 (corresponding to the step shown in FIG. 32A).

As shown in Fig. 33E, the conductive layer is patterned to form the reflective electrode 61 (Fig. 32B) in the display portion. Thus, part of the conductive layer in the gate terminal portion is removed.

As shown in FIG. 33F, a portion of the gate insulating layer 54 and a portion of the interlayer insulating layer 60 on the gate terminal are removed. In the same step, portions of the gate insulating layer 54 and the interlayer insulating layer 60 in the region T are removed from the display portion (Fig. 32C).

As described above, not only the display portion but also the gate terminal portion, the terminal and the gate line are covered with the gate insulating layer 54 and the interlayer insulating layer 60 until the formation of the reflective electrode 61 is completed. Thus, electrical corrosion between the gate terminal / gate line formed of different metal materials and the reflective electrode 61 is prevented.

The source terminal portion (Fig. 29C) is formed in the same manner in the same steps as the display portion. In this way, electrical corrosion is prevented.

In the display portion, in the case where the gate electrode 52 and the gate lines are formed before the transmission electrode 58a, electrical corrosion can be effectively prevented. 34A shows a cross-sectional view of the gate terminal portion formed in the same manner, and FIG. 34B shows a cross-sectional view of the source terminal portion formed in the same manner. Both the gate line and the source have a two layer structure formed of a gate or source material and a transmissive material.

In addition, the gate and source lines in the structure are covered with at least the gate insulating layer until the formation of the reflective electrode is completed. Thus, electrical corrosion is effectively prevented.

(Example 12)

After the steps described with reference to FIG. 31C, the steps shown in FIGS. 35A-35C may optionally be used. Electrical corrosion is effectively prevented by this method.

As shown in FIG. 35A, an interlayer insulating layer 60 is formed. Contact holes 63 are formed in the interlayer insulating layer 60 by photolithography. In the same step, part of the interlayer insulating layer 60 in the region T is removed. The surface of the interlayer insulating layer 60 is formed in a wave shape.

Next, as shown in FIG. 35B, a conductive layer is formed on the surface of the interlayer insulating layer 60.

As shown in FIG. 35C, the conductive layer is patterned to remove part of it in the region T to form the reflective electrode 61.

According to this method, the transmission electrode 58a is covered with the gate insulating layer 54 until the formation of the reflective electrode 61 is completed. Thus, electrical corrosion between the reflective electrode 61 and the transmissive electrode 58a formed of different metal materials is prevented. However, the transmissive electrode 58a is covered only by the gate insulating layer 54 in this method. Thus, the method described with reference to FIGS. 31A-31E and 32A-32C is more effective in preventing electrical corrosion.

Since part of the interlayer insulating layer 60 in the region T is removed in the same step as forming the contact hole 63, the number of steps is reduced compared to the method described above with reference to Figs. 31A to 31E and 32A to 32C.

(Example 13)

In the transmissive and reflective LCD device according to the present invention, an electrode structure for matching the optical characteristics of the reflective area and the transmissive area is described. There are two ways to match the photoelectric characteristics (voltage-brightness characteristics) of the reflective and transmissive regions. According to the first method, the thickness of the liquid crystal layer in the reflection area is changed from the thickness of the liquid crystal layer in the transmission area. According to another method, different levels of voltage are applied across the liquid crystal layer in the reflective and transmissive regions.

The first method is described with reference to FIG. 36 is a schematic sectional view of one pixel area of the LCD device according to the present invention; The LCD device includes an opposing substrate including a color filter layer and a transmission electrode (opposing electrode), another substrate including a reflection region 90R and a transmission region 90T, and a liquid crystal layer interposed between the two substrates. The transmission electrode is provided near the liquid crystal layer, and the color filter layer is provided outside the transmission electrode with respect to the liquid crystal layer. The reflective region 90R and the transmissive region 90T are provided near the liquid crystal layer. Needless to say, the color filter can be removed.

The reflective region 90R is formed of the transmissive electrode 78 (e.g. ITO), the reflective layer 79 (e.g. AL), and the transmissive interlayer insulating layer 80 (e.g., polymeric resin) provided on the reflective layer 79. ). The transmissive region 90T includes a transmissive electrode 78. The thickness dr of the liquid crystal layer in the reflective region 90R and the thickness dt of the liquid crystal layer in the transmissive region 90T can be adjusted independently by changing the thickness of the interlayer insulating layer 80 in each region.

The light used for displaying in the transmissive region is transmitted once through the liquid crystal layer having a thickness of dt, while the light used for displaying in the reflective region is transmitted twice through the liquid crystal layer having a thickness of dr. In order to match the delay caused by the liquid crystal layer in the reflective region with the delay caused by the liquid crystal layer in the transmissive region, the thicknesses dt and dr are preferably set to have a relationship of dt = 2 · dr. However, for display in the reflective area, light incident on the reflective layer 79 at the angle indicated by the dotted arrows is also used. Therefore, the relationship of dt> 2.dr is more preferable.

The second method is described with reference to FIGS. 37A, 37B, 38A and 38B. Fig. 37A is a sectional view of one pixel area of the LCD device according to the present invention. FIG. 37B is a graph showing the photoelectric characteristics of the LCD device shown in FIG. 37A.

As shown in Fig. 37A, the LCD device includes an opposing substrate including a transmission electrode (opposing electrode), another substrate including a reflection region 90R and a transmission region 90T, and a liquid crystal inserted between the two substrates. Layer. The counter electrode is provided near the liquid crystal layer, and the reflective region 90R and the transmissive region 90T are provided near the liquid crystal layer.

Reflective region 90T is transparent electrode 88 (e.g. ITO), reflective electrode 89 (e.g. AL), and transmissive interlayer insulating layer 100 (e.g., provided on transmissive layer 88). Polymerized fibers). Since the thickness of the reflective electrode 89 is thinner than that of the liquid crystal layer, the thickness of the liquid crystal layer is substantially the same in the reflective region 90R and the transmissive region 90T. Therefore, the delay caused by the liquid crystal layer is different between the reflection region 90R and the transmission region 90T. As a result, the photoelectric characteristics in the reflecting region 90R and the transmitting region 90T are different as shown in FIG. 37B.

This phenomenon is described with reference to FIGS. 38A and 38B. FIG. 38A schematically illustrates a cross-sectional view of one pixel region of an LCD device different from the LCD device shown in FIG. 37A in that it does not include an interlayer insulating layer. FIG. 38B is a graph showing the photoelectric characteristics of the LCD device shown in FIG. 38A. In the LCD device shown in Fig. 38A, the thickness of the liquid crystal layer is substantially the same in the reflection area 90R and the transmission area 90T. The same level of voltage is applied across the liquid crystal layer by the transmission electrode 88a and the reflection electrode 89a in the reflection region 90R and the transmission region 90T. Therefore, the delay caused by the liquid crystal layer is greatly different between the reflection region 90R and the transmission region 90T. Therefore, the photoelectric properties differ greatly in reflection mode and transmission mode.

In contrast, in the LCD device shown in FIG. 37A, a voltage is applied across the liquid crystal layer by the transmissive electrode 88 in the transmissive region 90T through the interlayer insulating layer 100. The interlayer insulating layer 100 separates capacitance. Although the same level of voltage is supplied from the driving circuit (not shown) to the transmission electrode 88 and the reflection electrode 89, the voltage applied in the transmission region 90T is smaller than the voltage applied in the reflection region 90R. Thus, as shown in Fig. 37B, the voltage-brightness curve in the transmission mode is shifted closer to the voltage-brightness curve in the higher voltage, i. As can be appreciated from the above, the voltage-brightness characteristics in the reflection mode and the transmission mode can be matched with each other by adjusting the thickness and / or the dielectric constant of the interlayer insulating layer 100.

The structure in which the thickness of the liquid crystal layer is controlled in the transmission region and the reflection region may be applied to the electrode structure shown in FIG. 22.

Accordingly, the present invention described has the effect of providing a reflective LCD device, a transmissive and reflective LCD device, and a method of manufacturing the same, which provide a satisfactory display with sufficiently high contrast.

It is apparent that various changes can be made easily by those skilled in the art without departing from the scope and spirit of the present invention. Accordingly, the scope of the appended claims is not to be limited by the description herein, but is to be construed broadly.

Claims (28)

In the liquid crystal display device, A first substrate; A second substrate; A liquid crystal layer interposed between the first substrate and the second substrate; A first polarizing element provided on a surface of said first substrate on the opposite side to said liquid crystal layer; A second polarizing element provided on the surface of the second substrate, on the side opposite to the liquid crystal layer; A first phase difference compensating element provided between the first polarizing element and the liquid crystal layer; And A second phase difference compensation element provided between the second polarizing element and the liquid crystal layer Including but not limited to: A plurality of pixel regions are provided for display, The first substrate includes at least one transmissive electrode, and the second substrate includes a reflective electrode region and a transmissive electrode region corresponding to each of the plurality of pixel regions. The method of claim 1, Each of the plurality of pixel areas has a reflection area for performing display using reflected light and a transmission area for performing display using transmitted light, And the reflective electrode region defines the reflective region and the transmissive electrode region defines the transmissive region. The method of claim 1, The liquid crystal layer has a zero delay when the molecular axis of liquid crystal molecules in the liquid crystal layer is substantially perpendicular to the surfaces of the first and second substrates, And the first retardation compensator and the second retardation compensator each have a delay satisfying the lambda / 4 condition. The method of claim 2, The liquid crystal layer has a delay of α when the molecular axis of the liquid crystal molecules in the liquid crystal layer is substantially perpendicular to the surfaces of the first and second substrates, And the first retardation compensating element has a delay that satisfies a λ / 4-α condition. The method of claim 2, The liquid crystal layer has a delay of α when the molecular axis of the liquid crystal molecules in the liquid crystal layer is substantially perpendicular to the surfaces of the first and second substrates, And the first retardation compensating element has a delay satisfying the lambda / 4-alpha condition, and the second retardation compensating element has a delay satisfying the lambda / 4-(β-α) condition. The method of claim 1, The first retardation compensator and the second retardation compensator are each formed of a λ / 4 wave plate. The transmission axis of the first polarization element and the first retardation compensator form an angle of about 45 degrees, And a transmission axis of the second polarizing element and the second phase difference compensating element form an angle of about 45 degrees. The method of claim 2, The second retardation compensator is formed of a λ / 4 wave plate, A slower optic axis of the second retardation compensator corresponds to one of the long axis or short axis of the elliptical polarization transmitted through the liquid crystal layer, and a second retardation compensator for converting the elliptical polarization into linear polarization. Joined, The transmission axis of the second polarizing element is perpendicular to the polarization axis of the linearly polarized light. In the liquid crystal display device, A first substrate comprising a transmissive electrode; A second substrate including a reflective electrode; A liquid crystal layer interposed between the first substrate and the second substrate, the liquid crystal layer comprising negative dielectric anisotropy and oriented substantially perpendicular to the surface of the first substrate and the second substrate when no voltage is applied; ; A polarizing element provided on a surface of said first substrate opposite to said liquid crystal layer; And Λ / 4 wavelength plate provided between the polarizing element and the liquid crystal layer Including, A slow axis of the λ / 4 wave plate and a transmission axis of the polarizing element form an angle of about 45 degrees. The liquid crystal display device of claim 8, further comprising a phase difference compensating element between the reflective electrode and the polarizing element. In the liquid crystal display device, A first substrate; A second substrate; A liquid crystal interposed between the first substrate and the second substrate, the liquid crystal molecules being negative dielectric anisotropy and oriented substantially perpendicular to the surface of the first substrate and the second substrate when no voltage is applied; layer; A first polarizing element provided on a surface of said first substrate on the opposite side to said liquid crystal layer; A second polarizing element provided on the surface of the second substrate, on the side opposite to the liquid crystal layer; A first λ / 4 wave plate provided between the first polarizing element and the liquid crystal layer; And A second λ / 4 wavelength plate provided between the second polarizing element and the liquid crystal layer Including, A plurality of pixel regions are provided for display, The first substrate includes at least one transmissive electrode, the second substrate includes a reflective electrode region and a transmissive electrode region corresponding to each of the plurality of pixel regions, The slow axes of the first λ / 4 wave plate and the second λ / 4 wave plate are in the same direction and form an angle of about 45 degrees with each of the transmission axes of the first and second polarization elements. Device. The method of claim 10, Each of the plurality of pixel areas has a reflection area for performing display using reflected light and a transmission area for performing display using transmitted light, And the reflective electrode region defines the reflective region and the transmissive electrode region defines the transmissive region. The liquid crystal display device of claim 10, further comprising at least one phase difference compensating element between the first polarizing element and the second polarizing element. The liquid crystal display device of claim 10, wherein the liquid crystal layer further comprises a chiral dopent. The liquid crystal display device of claim 13, wherein the liquid crystal layer has a twist orientation of about 90 degrees. The method of claim 1, wherein the first polarizing element and the second polarizing element has a transmission axis perpendicular to each other, And the first retardation compensator and the second retardation compensator have a slower axis orthogonal to each other. The method of claim 1, The first phase difference compensating element converts linearly polarized light from the first polarizing device into circularly polarized light, The second phase difference compensating element converts linearly polarized light from the second polarizing device into circularly polarized light, The liquid crystal display device And a third phase difference compensation element provided between the first polarizing element and the liquid crystal layer to compensate for wavelength dependence of refractive index anisotropy of the first phase difference compensation element. The method of claim 16, The third retardation compensator is a λ / 2 wavelength plate, When the transmission axis of the first polarization element and the slow axis of the third retardation compensator form an angle of γ1, the transmission axis of the first polarization element and the slow axis of the first retardation compensator have an angle of 2γ1 + 45 degrees. Liquid crystal display device. The liquid crystal display device of claim 16, further comprising a fourth phase difference compensation element provided between the second polarization element and the liquid crystal layer to compensate for wavelength dependence of refractive index anisotropy of the second phase difference compensation element. The method of claim 18, The fourth retardation compensator is a λ / 2 wavelength plate, When the transmission axis of the second polarization element and the slow axis of the fourth retardation compensator form an angle of γ 2, the transmission axis of the second polarization element and the slow axis of the second retardation compensator measure an angle of 2γ 2 +45 degrees. Liquid crystal display device. The method of claim 18, The transmission axis of the first polarization element is perpendicular to the transmission axis of the second polarization element, The slow axis of the first retardation compensator is perpendicular to the slow axis of the second retardation compensator, And a slow axis of the third retardation compensator is perpendicular to a slow axis of the fourth retardation compensator. In the liquid crystal display device, A first substrate; A second substrate; And A liquid crystal layer interposed between the first substrate and the second substrate Including, A plurality of pixel areas are provided for display, each of the plurality of pixel areas having a reflection area for performing display using reflected light and a transmission area for performing display using transmitted light, The first substrate includes a counter electrode in the vicinity of the liquid crystal layer, The second substrate may include a plurality of gate lines in the vicinity of the liquid crystal layer, a plurality of source lines perpendicular to the plurality of gate lines, and a plurality of gate lines provided near an intersection point of the plurality of gate lines and the plurality of source lines. Switching elements, a first conductive layer having a high light transmission efficiency, and a second conductive layer having a high light reflection efficiency, And the first conductive layer and the second conductive layer are connected to each of the switching elements interconnected and provided in each of the pixel regions. The liquid crystal display device of claim 21, further comprising an insulating layer between the first conductive layer and the second conductive layer. The method of claim 21, wherein the second substrate further comprises a third conductive layer, And the first conductive layer and the second conductive layer are interconnected through the third conductive layer. 24. The method of claim 23, wherein one of the first conductive layer, the second conductive layer, and the third conductive layer is the same material as one of the materials forming the plurality of gate electrodes or the plurality of source electrodes. Liquid crystal display device formed with. The liquid crystal display device of claim 22, wherein the insulating layer has a wavy surface under the second conductive layer. A first substrate; A second substrate; And A liquid crystal layer interposed between the first substrate and the second substrate, wherein a plurality of pixel regions are provided for display; Each of the plurality of pixel areas has a reflection area for performing display using reflected light and a transmission area for performing display using transmitted light, The first substrate includes a counter electrode in the vicinity of the liquid crystal layer, The second substrate may include a plurality of gate lines in the vicinity of the liquid crystal layer, a plurality of source lines perpendicular to the plurality of gate lines, and a plurality of gate lines provided near an intersection point of the plurality of gate lines and the plurality of source lines. Switching elements, a first conductive layer having a high light transmission efficiency, and a second conductive layer having a high light reflection efficiency, The first conductive layer and the second conductive layer are connected to each of the switching elements interconnected and provided in each of the pixel regions, In the manufacturing method of the liquid crystal display device provided with the insulating layer between the said 1st conductive layer and the said 2nd conductive layer, Forming the first conductive layer on a plate; Forming the insulating layer on at least the first conductive layer; Forming the second conductive layer on the insulating layer; And Partially removing the second conductive layer formed on the first conductive layer Method of manufacturing a liquid crystal display device comprising a. The method of claim 26, A first device for connecting the first conductive layer and the second conductive layer on at least a connection region on the first conductive layer such that the first conductive layer and the second conductive layer are interconnected through a third conductive layer; Forming a conductive layer; Forming the insulating layer; And Partially removing the insulating layer on the connection region at least for connecting the first conductive layer and the second conductive layer. Method of manufacturing a liquid crystal display device further comprising. 27. The method of claim 26, wherein partially removing the insulating layer comprises removing the insulating layer on a region of the first conductive layer.