KR20030068323A - Reflection and penetration type liquid crystal display - Google Patents

Abstract

PURPOSE: A transflective liquid crystal display is provided to reflect incident light leaked through a transmissive window again, thereby improving the reflectivity without affecting the transmissivity. CONSTITUTION: A transflective liquid crystal display includes a first polarizing plate(110), a first phase plate(120), a color filter substrate(130), a liquid crystal layer(140), a reflective plate(152), a transmissive window(154), a TFT array substrate(160), a non-absorbing reflective film(190), a second phase plate(170), and a second polarizing plate(180). The reflective plate inverts a path of light having passed through the liquid crystal layer for making the light enter the liquid crystal layer again. The transmissive window provides incident light to the non-absorbing reflective film via the TFT array substrate. In operating a reflective mode, according as the incident light passes through the transmissive window, the non-absorbing reflective film reflects the light via the transmissive window for improving the reflectivity.

Description

Reflective-transmissive liquid crystal display {REFLECTION AND PENETRATION TYPE LIQUID CRYSTAL DISPLAY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection-transmissive liquid crystal display, and more particularly, to a reflection-transmission liquid crystal display for preventing a decrease in reflectance while increasing transmittance while maintaining an existing reflection-transmission mode.

In general, a liquid crystal display (LCD) includes a reflective liquid crystal display (REFLECTION TYPE LCD) using external light and a transparent liquid crystal display (PENETRATION TYPE LCD) using internal light according to the type of light source for displaying an image. ) And a reflection-transmissive liquid crystal display device using the same.

FIG. 1 is a view for explaining a driving principle of a general reflective liquid crystal display device. In particular, FIG. 1 illustrates an example in which a liquid crystal in a normally white mode is provided. In general, in a normally white mode, a white color is displayed when there is no voltage applied to the liquid crystal, and a black color is shown when there is a voltage applied to the liquid crystal.

As shown in FIG. 1, first, in a reflection type liquid crystal display device, when no voltage is applied to the liquid crystal layer, external incident light passes through the polarizer 30 and then becomes linearly polarized light, and again the λ / 4 phase plate. It passes through (40) and becomes circularly polarized light. At this time, the circularly polarized light may be right circularly polarized light or may be left circularly polarized light.

The circularly polarized light passes through the liquid crystal layer 50. Since the liquid crystal layer maintains a twisted state because there is no voltage applied to the liquid crystal, the circularly polarized light is changed by λ / 4 by the twisted liquid crystal layer to become linearly polarized light. In addition, the linearly polarized light is reflected by the reflecting plate (AlNd) 60 and passes through the liquid crystal layer 50 again to change the phase by λ / 4 to become circularly polarized light. When the circularly polarized light passes through the λ / 4 phase plate 40, the circularly polarized light is converted into the same linearly polarized light as first incident light, and then light is transmitted through the upper polarizing plate 30 to display a white color.

On the other hand, when there is a voltage applied to the liquid crystal layer 50, the external incident light passes through the upper polarizing plate 30 and then becomes linearly polarized light, and again passes through the λ / 4 phase plate 40 to become circularly polarized light.

The circularly polarized light passes through the liquid crystal layer 50. At this time, since the liquid crystal layer is vertically arranged by the voltage applied to the liquid crystal, the circularly polarized light is passed through as it is, and the circularly polarized light that has passed through the liquid crystal layer is reflected by the reflecting plate 60 to form the liquid crystal layer. Again, the phase is changed by [lambda] / 4 by the [lambda] / 4 phase plate 40 to become linear polarized light with a [lambda] / 4 delay. The light is lost while the linearly polarized light passes through the upper polarizing plate 30 to display a black color. In order to provide a high reflectance in the reflective liquid crystal display, a profile or a reflective region of the reflector 60 having the greatest influence on the reflectance should be large.

However, since the reflective liquid crystal display uses light incident from the outside, the display becomes dark due to a decrease in the amount of light in a dark place, so that the displayed image cannot be properly viewed.

FIG. 2 is a view for explaining a driving principle of a general transmissive liquid crystal display device. In particular, FIG. 2 illustrates an example in which a liquid crystal in a normally white mode is provided.

Referring to FIG. 2, when no voltage is applied to the liquid crystal layer 50, the light provided from the backlight assembly (not shown) is converted into linearly polarized light while passing through the polarizing plate 90, and is applied to the λ / 4 phase plate 80. It is converted into circularly polarized light and applied to the liquid crystal layer 50 via the transparent electrode 70. At this time, since the voltage is not applied to the liquid crystal layer to be applied, the twisted state is maintained and converted into linearly polarized light by the twisted liquid crystal layer, and then the phase is λ / 4 converted by the λ / 4 phase plate 40 to become circularly polarized light. At this time, the converted circularly polarized light passes through the polarizer 30 to display a white color.

On the other hand, when there is a voltage applied to the liquid crystal layer, the light provided from the backlight assembly is converted into linearly polarized light while passing through the polarizing plate 90, and is converted into circularly polarized light by the λ / 4 phase plate 80, and then the transparent electrode ( It is applied to the liquid crystal layer 50 via 70. In this case, since a voltage is applied to the liquid crystal layer to be applied, the liquid crystals are vertically aligned, and are applied to the λ / 4 phase plate 40 while maintaining the circularly polarized light by the vertically aligned liquid crystal layers.

The circularly polarized light applied to the λ / 4 phase plate 40 is converted into linearly polarized light and then applied to the polarizing plate, and the linearly polarized light applied to the polarizing plate displays black color because light is lost.

However, the above-described transmissive liquid crystal display uses an internal light source such as a backlight, so that the image to be displayed can be recognized regardless of a bright or dark place, but the power consumption is increased by the amount of the light source. There is a disadvantage that it is not suitable for a portable display device to operate.

In view of this, recently, a reflection-transmissive liquid crystal display device capable of a reflection type and a transmission type has been developed.

3 shows a profile of a typical reflection-transmissive liquid crystal display.

Referring to FIG. 3, a thin film transistor 7 is performed on a top surface of the first substrate 1 by a thin film transistor manufacturing process. Reference numeral 3 denotes a gate electrode, 6b a source electrode, 6a a drain electrode, and 4 and 5 an active pattern.

Subsequently, a transparent and thin acrylic organic insulating film 15 is coated on the upper surface of the thin film transistor 7 to a predetermined thickness. At this time, an irregular concave-convex pattern is formed on the upper surface of the acrylic organic insulating film 15 to scatter light and improve brightness, and a portion of the acrylic organic insulating film 15 corresponding to the drain electrode 6a is opened.

Thereafter, reflection / transmission electrodes 8 and 10 necessary for controlling the liquid crystal are formed on the upper surface of the acrylic organic insulating layer 15. In this case, the reflective / transmissive electrodes 8 and 10 are composed of a transmissive electrode 8 for transmitting light and a reflective electrode 10 for reflecting light, and a part of the reflective electrode 10 is opened 11 so that this part is formed. Allow light to pass through. In this case, the transmissive electrode 8 of the reflective / transmissive electrodes 8 and 10 is made of ITO or IZO material, and the reflective electrode 10 is mainly made of aluminum, aluminum-neodymium alloy, or the like having excellent reflectance.

Thereafter, the second substrate 14 on which the common electrode 13 is formed is positioned on the upper surface of the first substrate 1, and the liquid crystal 12 is injected therebetween, whereby the reflective / transmissive liquid crystal display 20 is manufactured. .

That is, while mainly reflecting the external light incident from the display screen in a bright place with a semi-transmissive reflective film provided therein, the amount of light emitted from the display screen using optical elements such as a liquid crystal layer and a polarizing plate disposed on the optical path is pixel-by-pixel. By controlling, reflective display is performed.

On the other hand, mainly in a dark place, transmissive display is performed by controlling the amount of light emitted from the display screen using the above-described optical element while irradiating light with a built-in light source such as a backlight from behind the transflective film.

However, such a reflection-transmissive liquid crystal display device has an advantage of operating in a reflection mode in an outdoor environment with a lot of external light and in a transmissive mode in an interior where the external light is relatively less than an outdoor light. Has a disadvantage in that the transmittance is significantly lower than that of the transmissive LCD.

In the current reflection-transmissive liquid crystal display device, in order to implement the display device in the reflection and transmission modes, respectively, a reflection area that reflects external light and a transmission area that transmits internal backlight light are necessary.

In order to make such a region, a reflective region is created, and a transmissive region is made by using a separate mask. The transmittance can be increased by appropriately adjusting the reflective and transmissive regions. In the present design, the area for maximizing the transmission area is about 65% depending on the structure. However, if the transmission window is maximized in this way, the transmittance can be increased, but the reflectance is relatively low.

However, there is a region that is transmitted due to the property of reflection transmission, and in addition to the light reflected by the reflection plate as shown in FIG. 3, there is light leaking through the transmission window toward the backlight. At this time, the light leaking through the transmission window toward the backlight has no effect on the reflectance and acts as a loss of light.

Accordingly, the present invention has been made in view of the foregoing, and an object of the present invention is to increase the transmittance while maintaining the reflection mode and the transmission mode in the reflection-transmissive liquid crystal display device. The present invention provides a reflection-transmissive liquid crystal display device for preventing a decrease in reflectance.

1 is a view for explaining a driving principle of a general reflective liquid crystal display.

2 is a view for explaining a driving principle of a general transmissive liquid crystal display.

3 shows a profile of a typical reflection-transmissive liquid crystal display device.

4 is a diagram for describing a reflection-transmissive liquid crystal display device according to a first embodiment of the present invention.

5 is a diagram for describing a reflection-transmissive liquid crystal display device according to a second embodiment of the present invention.

6 is a diagram for describing a reflection-transmissive liquid crystal display device according to a third embodiment of the present invention.

7 is a diagram for describing a reflection-transmissive liquid crystal display device according to a fourth embodiment of the present invention.

8 is a diagram for describing a reflection-transmissive liquid crystal display device according to a fifth embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

110, 180: polarizer 120, 170: phase plate

130: color filter substrate 140: liquid crystal layer

152: reflector plate 154: transmission window

160 TFT array substrate 190 Non-absorbing reflective film

192: Micro Lens

According to one aspect of the present invention, a reflection-transmissive liquid crystal display device includes a color filter, a first phase plate, and a first polarizing plate sequentially adjacent to a liquid crystal layer, respectively, In a reflection-transmissive liquid crystal display device comprising a TFT array substrate, a second phase plate, and a second polarizing plate sequentially adjacent to the liquid crystal layer at a lower portion thereof,

And a reflection plate including a transmission window opened between the liquid crystal layer and the TFT array substrate, and in the reflection mode operation, light passing through the transmission window as light incident from the outside passes through the transmission window. It includes a non-absorbing reflecting portion for reflecting through the transmission window to improve the reflectance.

Here, the non-absorption reflecting portion is provided between the TFT array substrate and the second phase plate, a non-absorptive reflective film using a difference in refractive index by stacking a plurality of layers of materials having different refractive indices one It is characterized by. Here, the non-absorption reflecting portion preferably further includes a micro lens pattern on a surface proximate the TFT array substrate.

In addition, the non-absorption reflecting unit is integrally formed on the surface of the second phase plate adjacent to the TFT array substrate, and the material having a different refractive index by stacking a plurality of layers to use the difference by the refractive index do.

In addition, the non-absorbing reflecting portion is formed on the lower surface of the second polarizing plate whose upper surface is facing the second phase plate, the non-absorption by using a difference by the refractive index by stacking a plurality of layers of materials having different refractive indices Another feature is that it is a reflective film.

In addition, the non-absorption reflecting portion is another feature that the surface of the second polarizing plate is a gloss layer surface-treated on the surface close to the second phase plate.

According to such a reflection-transmissive liquid crystal display device, the reflectance can be improved without affecting the transmittance by re-reflecting the light leaking into the transmission window using a transparent non-absorbing reflective film.

Hereinafter, with reference to the accompanying drawings, it will be described in detail the present invention.

4 is a diagram for describing a reflection-transmissive liquid crystal display device according to a first embodiment of the present invention.

Referring to FIG. 4, the reflection-transmissive liquid crystal display device according to the first embodiment of the present invention may include a first polarizer 110, a first phase plate 120, a color filter substrate 130, a liquid crystal layer 140, The reflective plate 152, the transmission window 154, the TFT array substrate 160, the non-absorbing reflective film 190, the second phase plate 170, and the second polarizing plate 180 are included.

Since the first polarizing plate 110 generally has the same probability that the incident light has the same vibration direction in all directions, only the light that vibrates in the same direction as the polarization axis is transmitted, and the light vibrating in the other directions is constant. It absorbs or reflects using a medium to produce light that vibrates only in one specific direction. That is, the polarizing plate only passes a predetermined linearly polarized light component in the incident light.

The first phase plate 120 is made of polycarbonide, arton (ARTON), S-sina, etc. as a material, and is provided between the polarizer 110 and the color filler substrate 130. Here, the above-mentioned phase plate may be a λ / 4 phase plate or may be a λ / 2 phase plate. In general, the phase plate is formed by laminating a first layer made of a resin having a positive intrinsic birefringence value and a second layer made of a resin having a negative intrinsic birefringence value. The first layer and the second layer are birefringent, and the phase delay axes are perpendicular to each other. It is stacked.

Since the retardation of the phase plate is the sum of the respective retardations of the first layer and the second layer, the retardation on the short wavelength side of the phase plate is small by laminating orthogonally stacking the phase delay axes of the first layer and the second layer. In addition, the long-wave length side can be increased. As a result, the ratio Re ([lambda]) / [lambda] between the retardation Re ([lambda]) and the wavelength at the wavelength [lambda] of the phase plate can be maintained almost constant in the visible light region.

The color filter substrate 130 is a substrate in which each pixel of RGB, which is a color pixel in which a predetermined color is expressed while light passes, is formed by a thin film process, and a color filter pattern that implements color, and division and light blocking between the RGB cells. It is composed of a black matrix that performs a role and a common electrode made of ITO for applying a voltage to the liquid crystal cell.

The arrangement angle of the liquid crystal layer 140 is changed by an electric field, and the light transmittance is changed according to the arrangement angle to obtain a desired image. In particular, the liquid crystal layer 140 converts circularly polarized light into incident linearly polarized light, and converts the linearly polarized light into circularly polarized light when incident.

The reflective plate 152 inverts the path of the light incident through the liquid crystal layer and reenters the liquid crystal layer. On the other hand, a transmission window 154 is formed in a part of the plane on which the reflection plate is formed, and the light incident through the liquid crystal layer through the transmission window is transmitted to the non-absorbing reflection film via the TFT array substrate 160 provided below. to provide.

The TFT array substrate 160 is generally a transparent glass substrate on which a matrix thin film transistor (not shown) is formed. Here, a data line (not shown) is connected to a source terminal of the thin film transistors, and a gate line (not shown) is connected to a gate terminal. In addition, a pixel electrode made of indium tin oxide (ITO), which is a transparent conductive material, is formed in the drain terminal.

When an electrical signal is input to the data line and the gate line, an electrical signal is input to a source terminal and a gate terminal of each thin film transistor, and the thin film transistor is turned on according to the input of the electrical signal. Alternatively, the signal is turned off and the electrical signal necessary for pixel formation is output to the drain terminal.

When power is applied to the gate terminal and the source terminal of the transistor of the TFT array substrate 160 described above and the thin film transistor is turned on, an electric field is formed between the pixel electrode and the common electrode of the color filter substrate. The arrangement angle of the liquid crystal injected between the array substrate 160 and the color filter substrate 130 is changed, and the light transmittance is changed according to the changed arrangement angle to obtain a desired image. Of course, a driving signal and a timing signal are applied to the gate line and the data line of the thin film transistor in order to control the arrangement angle of the liquid crystal and the timing of the liquid crystal.

The non-absorptive reflective film 190 inverts the path of light incident through the TFT array substrate 160 through the transmission window 154 and reenters the liquid crystal layer. In particular, if the incident light is linearly polarized light, This is reincident to the liquid crystal layer 140 via the TFT array substrate 160 and the transmission window 154, and if it is circularly polarized, the liquid crystal layer 140 via the TFT array substrate 160 and the transmission window 154. Reenter to

In particular, the non-absorptive reflective film 190 is formed by stacking a plurality of layers of materials having different refractive indices, and in the present invention, the light does not absorb or pass incident light by using the difference of the refractive indices between the layers. Play a role of Of course, the incident light is preferably incident light from the outside, it is preferable to pass the light incident from the lower, that is, the backlight assembly.

The second phase plate 170 is provided below the non-absorption reflective film 190.

The second polarizing plate 180 may be attached to be perpendicular to each other or perpendicular to the polarization axes of the first polarizing plate 110, or may be attached to be parallel to each other. The polarization axes of the first and second polarizing plates 110 and 180 may be attached. The intensity of the transmitted light is adjusted according to the degree of rotation of the gray to enable the gray between the black color and the white color.

Then, for convenience of description, the area in which the reflection plate 152 is formed is defined as the reflection area, the area in which the transmission window 154 is defined as the transmission area, and only the reflection mode operation of the reflection-transmissive liquid crystal display device The first embodiment will be described.

First, while the electric field and the magnetic field vibrate perpendicularly to the traveling direction, the light incident on the reflective region is converted into linearly polarized light through the polarizer 110, and the light is transmitted through the first phase plate 120 and the color filter substrate 130. Polarized light, preferably left circularly polarized light. The light converted into the left circularly polarized light is converted into linearly polarized light while passing through the liquid crystal layer 140, and the converted linearly polarized light is reflected by the reflecting plate and inverted from the incident path. At this time, the light passing through the liquid crystal layer 140 is left circularly polarized light.

On the other hand, light incident on the transmission region is linearly polarized when passing through the polarizing plate 110, and converted into circularly polarized light, preferably left circularly polarized light, via the first phase plate 120 and the color filter substrate 130. The light converted into left circularly polarized light is converted into linearly polarized light while passing through the liquid crystal layer 140, and the converted linearly polarized light is reflected by the non-absorbing reflective film 190 through the transmission window 154 and the TFT array substrate 160. It is reflected by inverting the incident path. At this time, the light passing through the liquid crystal layer 140 is left circularly polarized light.

Although not shown in the drawings, when the reflection-transmissive liquid crystal display device operates in the transmission mode, the light provided from the backlight assembly (not shown) provided under the second polarizing plate 180 passes through the transmission window 154. A constant image is displayed. Since this description has been described above, the description thereof will be omitted.

As such, by stacking a plurality of materials having different refractive indices and using a non-absorptive reflective film 190 using a reflection characteristic due to a difference in refractive index, the TFT array substrate 160 and the second phase plate 170 are provided. The light leaking into the transmission window can be reflected again, thereby maintaining the transmittance and improving the reflectance.

5 is a diagram for describing a reflection-transmissive liquid crystal display device according to a second embodiment of the present invention.

Referring to FIG. 5, the reflective-transmissive liquid crystal display device according to the second exemplary embodiment of the present invention includes a polarizing plate 110, a first phase plate 120, a color filter substrate 130, a liquid crystal layer 140, and a reflecting plate ( 152, a transmission window 154, a TFT array substrate 160, a non-absorbing reflective film 190 having a micro lens 192 mounted thereon, a second phase plate 170, and a polarizing plate 180. In this case, the same reference numerals are assigned to the same components described with reference to FIG. 4, and a description thereof will be omitted.

In this case, a method of forming the microlens 192 mounted on the non-absorption reflective film 190 may include a method of patterning using a mold or a method of forming using a bread.

As such, by forming a fine pattern such as the microlens 192 on the non-absorption reflective film, the light reflected by the non-absorption reflective film 190 can be driven in the vertical direction to increase the reflectance improvement.

6 is a diagram for describing a reflection-transmissive liquid crystal display device according to a third embodiment of the present invention.

Referring to FIG. 6, the reflective-transmissive liquid crystal display according to the third exemplary embodiment of the present invention includes a polarizing plate 110, a first phase plate 120, a color filter substrate 130, a liquid crystal layer 140, and a reflecting plate ( 152, a transmission window 154, a TFT array substrate 160, a second phase plate 170 and a polarizer 180 on which a non-absorbing reflective film 172 is mounted. Here, the same reference numerals are assigned to the same components described with reference to FIG. 4, and description thereof will be omitted.

In particular, the second phase plate 170 may be manufactured using a material such as polycarbonide, arton (ARTON), S-sina, and the like. The non-absorbing reflective film 172 may include the second phase plate. The same material as that used at 170 is used, and the difference in refractive index is made to be one-piece.

As such, since the non-absorbing reflective film can be integrated with the λ / 4 phase plate, the light leaking through the transmission window can be reflected back to maintain the transmittance and improve the reflectance.

7 is a diagram for describing a reflection-transmissive liquid crystal display device according to a fourth embodiment of the present invention.

Referring to FIG. 7, the reflective-transmissive liquid crystal display device according to the fourth embodiment of the present invention includes a polarizer 110, a first phase plate 120, a color filter substrate 130, a liquid crystal layer 140, and a reflector plate ( 152, a transmission window 154, a TFT array substrate 160, a second phase plate 170, a polarizer 180, and a non-absorbing reflective film 190. Here, the same reference numerals are assigned to the same components described with reference to FIG. 4, and description thereof will be omitted.

In this way, by attaching the non-absorbing reflective film behind the lower plate polarizing plate, the light leaking into the transmission window can be reflected back to maintain the transmittance and improve the reflectance.

8 is a diagram for describing a reflection-transmissive liquid crystal display device according to a fifth embodiment of the present invention.

Referring to FIG. 8, the reflection-transmissive liquid crystal display according to the fifth embodiment of the present invention includes a polarizing plate 110, a first phase plate 120, a color filter substrate 130, a liquid crystal layer 140, and a reflecting plate ( 152, a transmission window 154, a TFT array substrate 160, a second phase plate 170, and a polarizing plate 180 including a glossy surface thereon. Here, the same reference numerals are assigned to the same components described with reference to FIG. 4, and description thereof will be omitted.

In particular, most polarizers have an anti-reflection (AR) or anti-glare (AG) treatment to reduce surface reflection. Therefore, by performing a surface treatment to increase the gloss component on the upper surface of the second polarizing plate 180 disposed below the transmission window, the loss of light flowing through the transmission window to the backlight in the reflection mode is reflected back onto the upper glass. The reflectance can be improved.

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

As described above, in general, when the display operation is performed through the reflection mode of the reflection-transmissive liquid crystal display device, the reflection plate performs the normal reflection mode operation. Although the leakage caused a problem in that the reflection efficiency was reduced, according to the present invention, even when external incident light leaks through the transmission window, the reflection is re-reflected using a transparent non-absorbing reflective film formed by stacking a plurality of media having different refractive indices. By doing so, the reflectance can be improved without affecting the transmittance.

Claims (6)

A color filter, a first phase plate, and a first polarizing plate are sequentially disposed adjacent to the liquid crystal layer, respectively, and a TFT array substrate, a second phase plate, and a second polarizing plate are disposed adjacent to the liquid crystal layer. In the reflection-transmissive liquid crystal display device including each in sequence, A reflection plate including a transmission window opened between the liquid crystal layer and the TFT array substrate; In a reflection mode operation, a reflection-transmissive liquid crystal display including a non-absorption reflector for reflecting light passing through the transmission window through the transmission window to improve reflectance as light incident from the outside passes through the transmission window. . The method of claim 1, wherein the non-absorption reflecting portion A reflective-transmissive liquid crystal display device, which is provided between the TFT array substrate and the second phase plate, is a non-absorbing reflective film which uses a difference in refractive index by stacking a plurality of layers of materials having different refractive indices. . The non-absorbing reflector of claim 2, wherein And a microlens pattern on a surface proximate the TFT array substrate. The method of claim 1, wherein the non-absorption reflecting portion And the second phase plate is integrally formed on a surface proximate to the TFT array substrate, and a plurality of layers of materials having different refractive indices are stacked to use a difference by refractive index. The method of claim 1, wherein the non-absorption reflecting portion An upper surface is formed on the lower surface of the second polarizing plate facing the second phase plate, the reflection is a non-absorbing reflective film using a difference in refractive index by stacking a plurality of layers of materials having different refractive index -Transmissive liquid crystal display device. The method of claim 1, wherein the non-absorption reflecting portion A reflection-transmissive liquid crystal display device, characterized in that the surface of the second polarizing plate is a gloss layer surface-treated on a surface close to the second phase plate.