KR102224092B1 - Trans-flective mode liquidcrystal display device - Google Patents

Abstract

The present invention discloses a reflection-transmissive liquid crystal display device. The disclosed reflective liquid crystal display device of the present invention includes a liquid crystal layer disposed between a first substrate and a second substrate spaced apart from each other, and composed of a plurality of liquid crystal molecules, and an alignment layer disposed above and below the liquid crystal layer, respectively. Includes. In addition, a first phase delay film disposed on the second substrate and a first polarizing plate disposed on the first phase delay film, and a second phase delay film disposed under the first substrate and the second It includes a second polarizing plate disposed under the 2 phase delay film. Here, the optical axis of the first phase delay film and the optical axis of the second phase delay film are perpendicular to each other.

Description

Trans-flective mode liquidcrystal display device

The present invention relates to a reflective-transmissive liquid crystal display device, and more specifically, to a reflective-transmissive liquid crystal display device capable of simultaneously realizing front reflection and front transmission.

As the era rapidly advances into an information-oriented society, a display field that processes and displays a large amount of information is developing.

In particular, in recent years, the need for a flat panel display has emerged in order to meet the era of thinner, lighter, and low power consumption, and accordingly, thin film transistor liquid crystal display with excellent color reproducibility and thinness has emerged. Display: TFT-LCD) was developed.

Such a liquid crystal display device can be divided into a transmission type and a reflection type according to the light source used, and the transmission type liquid crystal display device is from a back-light which is a back light source attached to the back side of the liquid crystal panel. It is a form in which artificial light is incident on the liquid crystal and the amount of light is adjusted according to the arrangement of the liquid crystal to display color.

Therefore, since the transmissive liquid crystal display uses an artificial back light source, there is a large disadvantage in power consumption, whereas the reflective liquid crystal display has a structure that relies on external natural light or artificial light source for most of the light. , Power consumption is lower than that of the transmissive liquid crystal display device. However, there is a limitation in that the reflective liquid crystal display device cannot use external light in a dark place or when the weather is cloudy. For this reason, as a necessity of a device capable of appropriately selecting and using the two modes according to a necessary situation, a liquid crystal display device for both reflection and transmission has been proposed.

However, in a liquid crystal display for both reflection and transmission, a transflective liquid crystal display is implemented by dividing one pixel into a reflective portion and a transmitting portion. In such a transflective liquid crystal display, light is reflected only in the reflective portion in the reflection mode, and light is transmitted only in the transmission portion in the transmission mode. For this reason, there is a problem that the aperture ratio of the transmissive portion decreases in the reflection mode and the aperture ratio of the reflective portion decreases in the transmission mode.

To solve this problem, a front-reflective front-transmission liquid crystal display device has been proposed. Front-reflection The front-transmission liquid crystal display device further requires an additional liquid crystal layer to serve as a transmission plate or a reflection plate. Accordingly, the front-reflective front-transmission liquid crystal display device requires two liquid crystal layers, thereby complicating the process and increasing the manufacturing cost.

In the present invention, by disposing a first phase delay film and a second phase delay film whose optical axes are perpendicular to each other between a first polarizing plate and a second polarizing plate disposed on each of the upper and lower portions of the liquid crystal panel, front reflection and front transmission are possible. It is an object to provide a transmissive liquid crystal display device.

A reflective-transmissive liquid crystal display device for solving the problems of the prior art as described above, is disposed between a first substrate and a second substrate disposed to be spaced apart from each other, and a liquid crystal layer composed of a plurality of liquid crystal molecules, and an upper portion of the liquid crystal layer. It includes an alignment layer disposed on each of the lower portion. In addition, a first phase delay film disposed on the second substrate and a first polarizing plate disposed on the first phase delay film, and a second phase delay film disposed under the first substrate and the second It includes a second polarizing plate disposed under the 2 phase delay film. Here, the optical axis of the first phase delay film and the optical axis of the second phase delay film are perpendicular to each other.

The reflective-transmissive liquid crystal display device according to the present invention includes a first phase delay film and a second phase delay film having optical axes perpendicular to each other between a first polarizing plate and a second polarizing plate disposed on the upper and lower portions of the liquid crystal panel, respectively, There is an effect that reflection and front transmission are possible.

1 is a schematic diagram of a liquid crystal display device according to a first embodiment of the present invention.
2A to 2D show optical paths according to the first embodiment of the present invention.
3 is a cross-sectional view of a liquid crystal display device according to a first embodiment of the present invention.
4A and 4B are graphs showing optical characteristics of a liquid crystal display according to the first embodiment of the present invention.
5 is a schematic diagram of a liquid crystal display device according to a second embodiment of the present invention.
6A and 6B show an optical path according to a second embodiment of the present invention.
7 is a cross-sectional view of a liquid crystal display device according to a second embodiment of the present invention.
8A and 8B are graphs showing optical characteristics of a liquid crystal display according to the second embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following embodiments are provided as examples in order to sufficiently convey the spirit of the present invention to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. In addition, in the drawings, the size and thickness of the device may be exaggerated for convenience. The same reference numbers throughout the specification indicate the same elements.

1 is a schematic diagram of a liquid crystal display device according to a first embodiment of the present invention. Referring to FIG. 1, a liquid crystal display device according to a first embodiment of the present invention includes a liquid crystal panel 10, a first phase delay film 400, a second phase delay film 410, a first polarizing plate 500, and It includes a second polarizing plate 510.

In detail, the first phase delay film 400 is disposed on the liquid crystal panel 10. In addition, a first polarizing plate 500 is disposed on the first phase delay film 400. In addition, a second phase delay film 410 is disposed under the liquid crystal panel 10. In addition, a second polarizing plate 510 is disposed under the second phase delay film 410.

Although not shown in the drawings, the liquid crystal panel 10 includes a liquid crystal layer, and the liquid crystal layer includes a plurality of liquid crystal molecules. In addition, an alignment layer is disposed above and below the liquid crystal layer. Here, the liquid crystal display may be in a dark state when an angle of the long axis of the liquid crystal molecules ^{is arranged to have a value between 70 o} and 90 ^{o from the surface of the alignment layer.} That is, the liquid crystal display may be in a dark state when the liquid crystal molecules are vertically aligned.

In the case of a transflective liquid crystal display that is implemented by dividing a transmitting part and a reflecting part, a transflective liquid crystal display is implemented by dividing the reflecting part and the transmissive part in one pixel. At this time, in the transmission mode, light is transmitted only through the transmitting portion, and in the reflection mode, light is transmitted only through the reflective portion, so that the aperture ratio is lowered.

In addition, unlike a semi-transmissive liquid crystal display device, a liquid crystal display device capable of implementing front reflection and front transmission without dividing the reflective part and the transmitting part has been proposed. There is a problem that it becomes complicated and the manufacturing cost increases.

To solve this problem, the liquid crystal display device of the present invention includes first and second phase delay films 400 and 410 disposed above and below the liquid crystal panel 10 so as to implement front reflection and front transmission. Here, the liquid crystal display that implements front reflection and front transmission is a liquid crystal display capable of realizing a bright state when the transmission mode is dark, the reflection mode is also dark, and when the transmission mode is bright, the reflection mode is also bright. .

The liquid crystal, the first phase delay film 400 and the second phase delay film 410 may be appropriately optically designed so that the liquid crystal display device can reflect and transmit the front surface. This is shown in Table 1 below.

First polarizer 1st phase delay film Liquid crystal layer
(Liquid crystal molecule) 2nd phase delay film 2nd polarizer Transmission axis
/optic axis
Angle α (0 ^o ~180 ^o ) β±90 ^o
(20 ^o ~30 ^o ) α or ±90 ^o β±90 ^o α±90 ^o Phase delay value
(nm) - a=200~250 a*2 a -

Referring to Table 1, the transmission axis angle of the first polarizing plate 500 may have an angle of 90 ^o with the difference between the transmission axis of the second polarizing plate 510. In addition, the angle of the optical axis of the first phase delay film 400 may have a difference between the angle of ^{the transmission axis of the first polarizing plate 500 and an angle between 20 o} and 30 ^o.

Here, when the angle of the optical axis of the first phase delay film 400 has a difference of less than ^{20 o from the angle of the transmission axis of the first polarizing plate 500 or has an angle exceeding 30 o} , the liquid crystal display device When the transmission mode of is in a dark state, the reflection mode is also in a dark state, or when the transmission mode is in a bright state, it is difficult to implement a bright state.

In addition, the angle of the long axis of the liquid crystal molecules may be the same as the angle of the transmission axis of the first polarizing plate 500 or may have a difference of ^90°. That is, the angle of the long axis of the liquid crystal molecules may be the same as the angle of the transmission axis of the first polarizing plate 500 or the second polarizing plate 510. In this case, when the angle of the long axis of the liquid crystal molecules is not the same as the angle of the transmission axis of the first polarizing plate 500 ^{or has a difference of less than or greater than 90 o} , the front reflection and front transmission of the liquid crystal display are difficult. There is.

In a liquid crystal display device in which an angle of a long axis of a liquid crystal molecule ^{is arranged to have a value between 70 o} and 90 ^o from the surface of an alignment layer to implement black, an optical axis between the first and second polarizing plates 500 and 510 ^{By arranging the first and second phase delay films 400 and 410 having a difference of 90 o in} the angle of, there is an effect of implementing front reflection and front transmission at the same time.

In detail, in a liquid crystal display device in which the angle of the long axis of the liquid crystal molecules ^{is arranged to have a value between 70 o} and 90 ^o from the surface of the alignment layer to implement black, the first phase delay film 400 Since the angle of the optical axis is made perpendicular to the angle of the optical axis of the second phase delay film 410, the phase delay effect of the first phase delay film 400 and the second phase delay film 410 may be canceled. Accordingly, both the reflection mode and the transmission mode may be in a black state.

In addition, when the angle of the long axis of the liquid crystal molecules ^{is arranged to have a value between 0 o} and 20 ^o from the surface of the alignment layer and is in a white state, the angle of the optical axis of the first phase delay film 400 is second By being made perpendicular to the angle of the optical axis of the phase delay film 410, the phase delay effect of the first phase delay film 400 and the second phase delay film 410 may be canceled out. Accordingly, both the reflection mode and the transmission mode may be in a white state.

In addition, the first phase delay film 400 and the second phase delay film 410 may have the same phase delay value. In detail, the phase delay values of the first phase delay film 400 and the second phase delay film 410 may be 200 nm to 250 nm. In addition, the phase delay value of the liquid crystal layer may be twice the phase delay value of the first phase delay film 400 and the second phase delay film 410. Here, when the phase delay values of the first phase delay film 400, the second phase delay film 410, and the liquid crystal layer are different, it is difficult to implement front reflection and front transmission of the liquid crystal display.

The liquid crystal display according to the present invention has an effect of improving an aperture ratio compared to a semi-transmissive liquid crystal display by implementing front reflection and front transmission. In addition, since an additional liquid crystal layer is not required to serve as a four layer in order to implement front reflection and front transmission, there is an effect of simplifying the process and reducing manufacturing cost.

Next, referring to FIGS. 2A to 2D, an optical path of the liquid crystal display according to the first exemplary embodiment of the present invention will be described. 2A to 2D show optical paths according to the first embodiment of the present invention.

2A and 2B illustrate light paths in a transmission mode and a reflection mode when the liquid crystal display according to the first embodiment of the present invention is in a black state. 2C and 2D show light paths in a transmission mode and a reflection mode when the liquid crystal display according to the first embodiment of the present invention is in a white state.

2A and 2B, a first phase delay film 400 and a first polarizing plate 500 are disposed on a liquid crystal panel. In addition, a second phase delay film 410 and a second polarizing plate 510 are disposed on the rear surface of the liquid crystal panel. In addition, the liquid crystal panel includes a plurality of liquid crystal molecules 301 included in the liquid crystal layer. An alignment layer 210 is further included above and below the liquid crystal layer. In addition, a backlight unit 1000 is disposed on a rear surface of the second polarizing plate 510 to be spaced apart from the second polarizing plate 510.

Here, the transmission axes of the first polarizing plate 500 and the second polarizing plate 510 have a difference of ^{90° from each other.} In addition, the optical axes of the first phase delay film 400 and the second phase delay film 410 have a difference of ^{90° from each other.}

In the transmission mode of the liquid crystal display according to the present invention, the light 20 generated from the backlight unit 1000 is linearly polarized in the horizontal direction while passing through the second polarizing plate 510. In this case, the light linearly polarized in the horizontal direction is elliptically polarized in the right direction while passing through the second phase delay film 410.

The light elliptically polarized to the right reaches the liquid crystal layer. In this case, the angle of the long axis of the liquid crystal molecules 301 included in the liquid crystal layer is arranged to have a value between ^{70 o} and 90 ^{o from the surface of the alignment layer 210.} Preferably, the angle of the long axis of the liquid crystal molecules 301 may be arranged to be ^{90 o from the surface of the alignment layer 210.} Here, the angle of the long axis of the liquid crystal molecules 301 may be the same as or perpendicular to the transmission axis of the first polarizing plate 500.

The elliptically polarized light in the right direction passes through the liquid crystal molecules 301 as it is to reach the first phase delay film 400. The elliptically polarized light to the right direction passes through the optical axis 90 ^o the first phase retardation film 400, having a difference of the second phase retardation film 410. The light passing through the first phase delay film 400 is polarized in a horizontal direction. That is, the light passing through the first phase delay film 400 is polarized in the same direction as the polarization direction of the horizontally polarized light passing through the second polarizing plate 510.

In this case, the light passing through the first phase delay film 400 is polarized in a horizontal direction, so that it is perpendicular to the transmission axis of the first polarizing plate 500. Accordingly, light that has passed through the first phase delay film 400 cannot pass through the first polarizing plate 500. Therefore, when the liquid crystal display device is arranged so that the angle of the long axis of the liquid crystal molecules 301 has ^{a value between 70 o} and 90 ^o with the surface of the alignment layer 210, the liquid crystal display is in a dark state, that is, a black state in the transmission mode. I can.

In addition, in the reflection mode of the liquid crystal display, light 30 incident from the outside passes through the first polarizing plate 500 and is linearly polarized in a vertical direction. Then, the light linearly polarized in the vertical direction is elliptically polarized in the left direction while passing through the first phase delay film 400. The elliptically polarized light in the left direction passes through the liquid crystal molecules 301 as it is and reaches the second phase delay film 410.

The elliptically polarized light in the left direction passes through the liquid crystal molecules 301 as it is to reach the second phase delay film 410. The light elliptically polarized in the left direction passes through the second phase delay film 410 having an optical axis perpendicular to the optical axis of the first phase delay film 400. The light passing through the second phase delay film 410 is linearly polarized in the horizontal direction.

In addition, the light linearly polarized in the horizontal direction may be reflected by the second polarizing plate 510, and a light path may be converted back toward the second phase delay film 410. In this case, the reflected light passes through the second phase delay film 410 and is elliptically polarized in the right direction. The elliptically polarized light in the right direction passes through the liquid crystal molecules 301 as it is and reaches the first phase delay film 400.

The light elliptically polarized in the right direction passes through the first phase delay film 400. In addition, the light passing through the first phase delay film 400 is polarized in a horizontal direction. In this case, the light passing through the first phase delay film 400 is polarized in a horizontal direction, so that it is perpendicular to the transmission axis of the first polarizing plate 500. Accordingly, light that has passed through the first phase delay film 400 cannot pass through the first polarizing plate 500. Accordingly, when the liquid crystal display device is arranged so that the angle of the long axis of the liquid crystal molecules 301 has ^{a value between 70 o} and 90 ^o with the surface of the alignment layer 210, the liquid crystal display is in a dark state, that is, a black state even in the reflection mode. Can be

In this way, the light path can be set in the transmission mode and the reflection mode of the liquid crystal display according to the present invention. However, the polarization directions of the first polarizing plate 500, the second polarizing plate 510, the first phase delay film 400, and the second phase delay film 410 are not limited thereto, and the liquid crystal molecules 301 When the angle of the long axis of is ^{arranged to have a value between 70 o} and 90 ^o with the surface of the alignment layer 210, it is sufficient if both the transmission mode and the reflection mode of the liquid crystal display are in a black state.

2C and 2D, light 20 generated from the backlight unit 1000 is linearly polarized in a horizontal direction while passing through the second polarizing plate 510. In this case, the light linearly polarized in the horizontal direction is elliptically polarized in the right direction while passing through the second phase delay film 410.

The light elliptically polarized to the right reaches the liquid crystal layer. In this case, the angle of the long axis of the liquid crystal molecules 301 included in the liquid crystal layer is arranged to have a value between ^{0 o} and 20 ^{o from the surface of the alignment layer 210.} Preferably, the angle of the long axis of the liquid crystal molecules 301 may be arranged to be ^{0 o from the surface of the alignment layer 210.} Here, the angle of the long axis of the liquid crystal molecules 301 may have a difference of ^{90 o from the transmission axis of the first polarizing plate 500.}

When the right elliptically polarized light passes through the liquid crystal layer including the liquid crystal molecules 301, the elliptically polarized light to the right is elliptically polarized to the left. The light passing through the liquid crystal layer reaches the first phase delay film 400. Said leftward elliptically polarized light passes through the optical axis 90 ^o the first phase retardation film 400, having a difference of the second phase retardation film 410. Light passing through the first phase delay film 400 is polarized in a vertical direction. That is, the light passing through the first phase delay film 400 is polarized in the same direction as the transmission axis of the first polarizing plate 500, and thus passes through the first polarizing plate 500 and is emitted to the outside.

Accordingly, when the liquid crystal display is arranged so that the angle of the long axis of the liquid crystal molecules 301 has ^{a value between 0 o} and 20 ^o with the surface of the alignment layer 210, the liquid crystal display is in a bright state, that is, a white state. Can be

In addition, in the reflection mode of the liquid crystal display, light 30 incident from the outside passes through the first polarizing plate 500 and is linearly polarized in a vertical direction. Further, the light linearly polarized in the vertical direction is elliptically polarized in the left direction while passing through the first phase delay film 400. The light elliptically polarized in the left direction reaches the liquid crystal layer including the liquid crystal molecules 301.

The elliptically polarized light in the left direction passes through the liquid crystal molecules 301 as it is and reaches the second phase delay film 410 in a state in which the polarization direction is unchanged. Said leftward elliptically polarized light passes through the optical axis 90 ^o the second phase retardation film 410, having a difference between the first phase retardation film 400. The light passing through the second phase delay film 410 is linearly polarized in the horizontal direction.

In addition, the light linearly polarized in the horizontal direction may be reflected by the second polarizing plate 510, and a light path may be converted back toward the second phase delay film 410. In this case, the reflected light passes through the second phase delay film 410 and is elliptically polarized in the right direction. The light that is elliptically polarized in the right direction passes through the liquid crystal layer including the liquid crystal molecules 301. In this case, the light elliptically polarized in the right direction is elliptically polarized in the left direction to reach the first phase delay film 400.

The light elliptically polarized in the left direction passes through the first phase delay film 400. In addition, the light passing through the first phase delay film 400 is polarized in a vertical direction. In this case, the light that has passed through the first phase delay film 400 is polarized in a vertical direction, so that it is in a state horizontal to the transmission axis of the first polarizing plate 500. Accordingly, light that has passed through the first phase delay film 400 passes through the first polarizing plate 500 and is emitted to the outside.

Accordingly, when the liquid crystal display device is arranged so that the angle of the long axis of the liquid crystal molecules 301 has ^{a value between 0 o} and 20 ^o with the surface of the alignment layer 210, the liquid crystal display is in a bright state, that is, a white state. Can be

In this way, the light path can be set in the transmission mode and the reflection mode of the liquid crystal display according to the present invention. However, the polarization directions of the first polarizing plate 500, the second polarizing plate 510, the first phase delay film 400, and the second phase delay film 410 are not limited thereto, and the liquid crystal molecules 301 When the angle of the long axis of is ^{arranged to have a value between 0 o} and 20 ^o with the surface of the alignment layer 210, it is sufficient if both the transmission mode and the reflection mode of the liquid crystal display are white.

Next, a liquid crystal display device according to a first embodiment of the present invention will be described with reference to FIG. 3. 3 is a cross-sectional view of a liquid crystal display device according to a first embodiment of the present invention. Referring to FIG. 3, the liquid crystal display device according to the first embodiment of the present invention includes a first substrate 100, a second substrate 200 disposed to face the first substrate 100, and the first substrate ( 100) and a liquid crystal layer 300 disposed between the second substrate 200. Here, the first substrate 100 may be a thin film transistor array substrate, and the second substrate 200 may be a color filter array substrate.

A thin film transistor Tr, a pixel electrode 102 and a common electrode 108 are disposed on the first substrate 100. However, this is not limited to the drawings and may be arranged in various ways. The thin film transistor Tr includes a gate electrode 101, a gate insulating layer 103, an active layer 104, ohmic contact layers 105a and 105b, a source electrode 106, and a drain electrode 107.

Further, the pixel electrodes 102 may be alternately disposed with the common electrode 106 on the first substrate 100. In addition, the pixel electrode 102 may be made of the same material on the same layer as the gate electrode 101, and the common electrode 108 is the same as the source electrode 106 and the drain electrode 107 on the same layer. It may be made of a material, but is not limited thereto. Although shown in the drawings, 109, which is not described, is a planarization film.

The second substrate 200 covers a non-display element such as a thin film transistor Tr of the first substrate 100 on a surface facing the first substrate 100 and covers the pixel electrode 102 and the common electrode ( A black matrix 201 surrounding the pixel area P is configured to expose 108. In addition, a color filter layer 201 including R(red), G(green), and B(blue) color filter patterns is disposed as an example that is sequentially and repeatedly arranged to correspond to each pixel area P.

The liquid crystal layer 300 disposed between the first substrate 100 and the second substrate 200 includes a plurality of liquid crystal molecules 301. An alignment layer 210 is further disposed above and below the liquid crystal layer 300.

In addition, a second phase delay film 410 is disposed on the rear surface of the first substrate 100, and a second polarizing plate 510 is disposed on the rear surface of the second phase delay film 410. A first phase delay film 400 is disposed on the second substrate 200, and a first polarizing plate 500 is disposed on the first phase delay film 400. Here, the optical axes of the first phase delay film 400 and the second phase delay film 410 may be configured to be perpendicular to each other.

In order to implement black in the liquid crystal display, the angle of the long axis of the liquid crystal molecules 301 may be arranged to have a value between ^{70 o} and 90 ^{o with the surface of the alignment layer 210.} In this case, the liquid crystal display may implement black in both the transmission mode and the reflection mode.

That is, when no voltage is applied in the vertical alignment (VA) mode in which the liquid crystal molecules 301 are arranged so that the initial liquid crystal alignment direction has ^{a value between 70 o} and 90 ^{o with the surface of the alignment layer 210, the transmission mode and reflection} You can implement dark states in all modes. In addition, TN (Twisted Nematic), OCB (Optically Compensated Birefringence), or ECB (Electrically Controlled Birefringence ^{) in which the liquid crystal molecules 301 are arranged to have a value between 70 o} and 90 ^o with the surface of the alignment layer 210 by applying a voltage ), a dark state can be implemented in both the transmissive mode and the reflective mode.

In addition, in order to implement white in the liquid crystal display, the angle of the long axis of the liquid crystal molecules 301 may be arranged to have a value between ^{0 o} and 20 ^{o with the surface of the alignment layer 210.} In this case, the liquid crystal display may implement white in both the transmission mode and the reflection mode.

^{That is, in VA (Vertical Align) mode in which the liquid crystal molecules 301 are arranged to have a value between 0 o} and 20 ^o with the surface of the alignment layer 210 by applying a voltage, a bright state can be achieved in both the transmission mode and the reflection mode. I can. In addition, transmission mode and reflection in TN (Twisted Nematic), OCB (Optically Compensated Birefringence) or ECB (Electrically Controlled Birefringence), which are arranged so that the ^{initial liquid crystal alignment direction has a value between 0 o} and 20 ^o with the surface of the alignment layer 210 All bright states can be achieved in the mode.

In the liquid crystal display according to the present invention, when the liquid crystal alignment direction is ^{arranged to have a value between 70 o} and 90 ^o with the surface of the alignment layer 210, front reflection and front transmission can be implemented in a liquid crystal display that implements a black state. There is an effect.

Next, referring to FIGS. 4A and 4B, optical characteristics of the liquid crystal display according to the first exemplary embodiment of the present invention will be described as follows. 4A and 4B are graphs showing optical characteristics of a liquid crystal display according to the first embodiment of the present invention.

4A and 4B, when the liquid crystal display device is in a dark state in the transmission mode, the transmittance is almost 0% in the visible light wavelength band. Further, when the liquid crystal display device is in a dark state in the reflection mode, the reflectance is almost 0% in the visible light wavelength band. Accordingly, it can be seen that both the transmission mode and the reflection mode are dark when the liquid crystal display is in a dark state.

In addition, when the liquid crystal display is in a bright state in the transmission mode, the transmittance in the visible wavelength band is about 35%. And, when the liquid crystal display device is in a bright state in the reflection mode, the reflectance in the visible light wavelength range is about 15% to 25%. Accordingly, it can be seen that when the liquid crystal display device is in a bright state, both the transmission mode and the reflection mode are in a bright state.

In the liquid crystal display according to the present invention, when the transmission mode is in a dark state, the reflection mode is also in a dark state, and when the transmission mode is in a bright state, the reflection mode may also be in a bright state. Through this, the visibility of the liquid crystal display can be improved, and the visibility can be improved indoors and outdoors.

Next, referring to FIG. 5, a review of a liquid crystal display device according to a second exemplary embodiment of the present invention is as follows. 5 is a schematic diagram of a liquid crystal display device according to a second embodiment of the present invention. The liquid crystal display according to the second embodiment may include the same components as those of the above-described embodiment. A description redundantly with the above-described embodiment may be omitted. In addition, the same configurations have the same reference numerals.

Referring to FIG. 5, a liquid crystal display device according to a second embodiment of the present invention includes a liquid crystal panel 20, a first phase delay film 650, a second phase delay film 660, and a third phase delay film 600. ), a fourth phase delay film 610, a first polarizing plate 500, and a second polarizing plate 510.

In detail, a third phase delay film 600 is disposed on the liquid crystal panel 20, and a first phase delay film 650 is disposed on the third phase delay film 600. In addition, a first polarizing plate 500 is disposed on the first phase delay film 650. In addition, a fourth phase delay film 610 is disposed under the liquid crystal panel 20, and a second phase delay film 660 is disposed under the fourth phase delay film 610. In addition, a second polarizing plate 510 is disposed under the second phase delay film 650.

Although not shown in the drawings, the liquid crystal panel 20 includes a liquid crystal layer, and the liquid crystal layer includes a plurality of liquid crystal molecules. In addition, an alignment layer is disposed above and below the liquid crystal layer. Here, the liquid crystal display may be in a dark state when the angle of the long axis of the liquid crystal molecules ^{is arranged to have a value between 0 o} and 20 ^{o from the surface of the alignment layer.} That is, the liquid crystal display may be in a dark state when the liquid crystal molecules are horizontally aligned.

The liquid crystal and the first to fourth phase delay films 650, 660, 600 and 610 may be appropriately optically designed so that the liquid crystal display can be front-reflected and front-transmitted. This is shown in Table 2 below.

First polarizer 1st phase delay film 2nd phase delay film Liquid crystal layer
(Liquid crystal molecule) 3rd phase delay film 4th phase delay film 2nd polarizer Transmission axis
/optic axis
Angle α (0 ^o ~180 ^o ) β = α ± (10 ^o ~20 ^o ) β±90 ^o α or ±90 ^o γ = α ± (70 ^o ~80 ^o ) γ = α ± (70 ^o ~80 ^o ) α ± 90 ^o Phase delay value
(nm) - a=300~400 a=300~400 b*2 b=150~200 b=150~200 -

Referring to Table 2, the angle of the transmission axis of the first polarizing plate 500 may have a difference of ^{90° from the angle of the transmission axis of the second polarizing plate 510.} In addition, the angle of the optical axis of the first phase delay film 650 may have a difference between the angle of ^{the transmission axis of the first polarizing plate 500 and an angle between 10 o} and 20 ^o.

Here, when the angle of the optical axis of the first phase delay film 650 has a difference of less than ^{10 o from the angle of the transmission axis of the first polarizing plate 500 or has an angle exceeding 20 o} , the liquid crystal display device When the transmission mode of is in a dark state, the reflection mode is also in a dark state, or when the transmission mode is in a bright state, it is difficult to implement a bright state. The angle of the optical axis of the first phase delay film 650 may have a difference of ^{90° from the angle of the optical axis of the second phase delay film 660.}

In addition, the angle of the long axis of the liquid crystal molecules may be the same as the angle of the transmission axis of the first polarizing plate 500 or may have a difference of ^90°. That is, the angle of the long axis of the liquid crystal molecules may be the same as the angle of the transmission axis of the first polarizing plate 500 or the second polarizing plate 510.

The angle of the optical axis of the third phase delay film 600 may have a value between ^{70 o} and 80 ^{o with the angle of the transmission axis of the first polarizing plate 500.} In addition, the angle of the optical axis of the fourth phase delay film 610 may also have a value between ^{70 o} and 80 ^{o with the angle of the transmission axis of the first polarizing plate 500.} That is, the angle of the optical axis of the third phase delay film 600 and the angle of the optical axis of the fourth phase delay film 610 may be designed to be the same. When the angles of the optical axes of the third phase delay film 600 and the fourth phase delay film 610 are not the same, it may be difficult to implement a front reflection front transmission in a liquid crystal display to which the third phase delay film 600 and the fourth phase delay film 610 are applied. Also. Liquid crystal display even when the angle of the optical axis of the third phase delay film 600 and the fourth phase delay film 610 does not have a value between ^{70 o} and 80 ^{o from the angle of the transmission axis of the first polarizing plate 500} Front reflection of the device Front transmission can be difficult.

In this case, an angle of an optical axis of the third and fourth phase delay films 600 and 610 may have a difference of ^{90° from an angle of a long axis of the liquid crystal molecules.} Since the angles of the optical axes of the third and fourth phase delay films 600 and 610 ^{have a difference of 90° from} the angles of the long axes of the liquid crystal molecules, the liquid crystal display may implement black.

Specifically, when the angle of the long axis of the liquid crystal molecules is 0 ^o to 20 ^o from the surface of the alignment layer, and the angle of the long axis of the liquid crystal molecules and the angle of the transmission axis of the first polarizing plate 500 are the same , The liquid crystal display can implement a dark state in both the transmission mode and the reflection mode.

In addition, the angle of the long axis of the liquid crystal molecules ^{is arranged in a state that is 70 o} to 90 ^o from the surface of the alignment layer, and the angle of the long axis of the liquid crystal molecules and the angle of the transmission axis of the first polarizing plate 500 are 90 ^o difference. If so, the liquid crystal display can implement a bright state in both the transmission mode and the reflection mode.

In a liquid crystal display device in which an angle of a long axis of a liquid crystal molecule ^{is arranged to have a value between 0 o} and 20 ^o from a surface of an alignment layer to implement black, the first and second polarizing plates 500 and 510 are disposed between the first and second polarizing plates 500 and 510 It is configured such that the angle of the optical axis of the phase delay film 650 and the angle of the optical axis of the second phase delay film 660 are perpendicular. In addition, the angle of the optical axis of the third phase delay film 600 and the angle of the optical axis of the fourth phase delay film 610 are configured to be the same.

In addition, the phase delay value of the first phase delay film 650 and the phase delay value of the second phase delay film 660 may be the same. In addition, the third phase delay film 600 and the fourth phase delay film 610 may have the same phase delay value.

In detail, the first phase delay film 650 and the second phase delay film 660 may have a phase delay value of 300 nm to 400 nm. In addition, the phase delay values of the third phase delay film 600 and the fourth phase delay film 610 may be 150 nm to 200 nm. In addition, the phase delay value of the liquid crystal layer may be twice the phase delay value of the third phase delay film 600 and the fourth phase delay film 610. Here, when the phase delay values of the first to fourth phase delay films 650, 660, 600, and 610 and the liquid crystal layer are different, it is difficult to implement front reflection and front transmission of the liquid crystal display.

Through this, the liquid crystal display according to the present invention implements front reflection and front transmission at the same time, thereby improving an aperture ratio compared to a semi-transmissive liquid crystal display device. In addition, since a liquid crystal layer that is additionally disposed to serve as a reflective layer is not required to implement front reflection and front transmission, there is an effect of simplifying the process and reducing manufacturing cost.

Next, referring to FIGS. 6A and 6B, an optical path of a liquid crystal display device according to a second exemplary embodiment of the present invention will be described as follows. 6A and 6B show an optical path according to a second embodiment of the present invention. The liquid crystal display according to the second embodiment may include the same components as those of the above-described embodiment. A description redundantly with the above-described embodiment may be omitted. In addition, the same configurations have the same reference numerals.

6A illustrates light paths in a transmission mode and a reflection mode when the liquid crystal display according to the second embodiment of the present invention is in a black state. 6B shows light paths in a transmission mode and a reflection mode when the liquid crystal display according to the second embodiment of the present invention is in a white state.

Referring to FIG. 6A, a third phase delay film 600, a first phase delay film 650, and a first polarizing plate 500 are disposed on the liquid crystal panel. In addition, a fourth phase delay film 610, a second phase delay film 660, and a second polarizing plate 510 are disposed on the rear surface of the liquid crystal panel. In addition, the liquid crystal panel includes a plurality of liquid crystal molecules 301 included in the liquid crystal layer. An alignment layer 210 is further included above and below the liquid crystal layer. In addition, a backlight unit 1000 is disposed on a rear surface of the second polarizing plate 510 to be spaced apart from the second polarizing plate 510.

Here, the transmission axes of the first polarizing plate 500 and the second polarizing plate 510 have a difference of ^{90° from each other.} In addition, the optical axes of the first phase delay film 650 and the second phase delay film 660 have a difference of ^{90° from each other.} In addition, the optical axes of the third phase delay film 600 and the fourth phase delay film 610 are made the same.

In the transmission mode of the liquid crystal display according to the present invention, the light 20 generated from the backlight unit 1000 is linearly polarized while passing through the second polarizing plate 510. In this case, the linearly polarized light is phase delayed while passing through the second phase delay film 660, the fourth phase delay film 610, and the liquid crystal layer.

Here, the angle of the long axis of the liquid crystal molecules 301 included in the liquid crystal layer is arranged to have a value between ^{0 o} and 20 ^{o from the surface of the alignment layer 210.} Preferably, the angle of the long axis of the liquid crystal molecules 301 may be arranged to be ^{0 o from the surface of the alignment layer 210.}

Light passing through the liquid crystal layer passes through the third phase delay film 600 and the first phase delay film 650. Light passing through the third phase delay film 600 and the first phase delay film 650 is polarized perpendicularly to the transmission axis of the first polarizing plate 500. Accordingly, light passing through the first phase delay film 650 does not pass through the first polarizing plate 500.

Accordingly, when the liquid crystal display device is arranged so that the angle of the long axis of the liquid crystal molecules 301 has ^{a value between 0 o} and 20 ^o with the surface of the alignment layer 210, the liquid crystal display is in a dark state, that is, a black state in the transmission mode. I can.

In addition, in the reflection mode of the liquid crystal display, light 30 incident from the outside passes through the first polarizing plate 500 and is linearly polarized. In addition, the linearly polarized light is phase delayed while passing through the first phase delay film 650, the third phase delay film 600, and the liquid crystal layer. The light passing through the liquid crystal layer passes through the fourth phase delay film 610 and the second phase delay film 660 and is linearly polarized. At this time, the light passing through the second phase delay film 660 is reflected from the second polarizing plate 500 and passes through the second phase delay film 660, the fourth phase delay film 610, and the liquid crystal layer again. It is done.

In this case, light passing through the second phase delay film 660, the fourth phase delay film 610, and the liquid crystal layer is phase delayed. The phase delayed light passes through the third phase delay film 600 and the first phase delay film 650 and is linearly polarized perpendicular to the transmission axis of the first polarizing plate 500.

Accordingly, when the liquid crystal display device is arranged so that the angle of the long axis of the liquid crystal molecules 301 of the liquid crystal layer has ^{a value between 0 o} and 20 ^o with the surface of the alignment layer 210, it is in a dark state in the reflection mode, that is, It may be black.

Referring to FIG. 6B, in the transmission mode of the liquid crystal display according to the present invention, light 20 generated from the backlight unit 1000 is linearly polarized while passing through the second polarizing plate 510. In this case, the linearly polarized light is phase delayed while passing through the second phase delay film 660 and the fourth phase delay film 610. The phase delayed light passes through the liquid crystal layer.

Here, the liquid crystal molecules 301 included in the liquid crystal layer are twisted. Specifically, when a voltage is applied to the liquid crystal display to generate an electric field, the liquid crystal molecules 301 rotate and the liquid crystal molecules 301 are twisted as shown in FIG. 6(b). In this case, the light passing through the second phase delay film 660 and the fourth phase delay film 610 passes through the liquid crystal layer without a phase change.

Light passing through the liquid crystal layer passes through the third phase delay film 600 and the first phase delay film 650. Light passing through the third phase delay film 600 and the first phase delay film 650 is horizontally polarized with a transmission axis of the first polarizing plate 500. Accordingly, the light passing through the first phase delay film 650 passes through the first polarizing plate 500. Accordingly, when the liquid crystal molecules 301 are twisted and arranged, they may be in a bright state, that is, a white state in the transmission mode.

In addition, in the reflection mode of the liquid crystal display, light 30 incident from the outside passes through the first polarizing plate 500 and is linearly polarized. In addition, the linearly polarized light is phase delayed while passing through the first phase delay film 650 and the third phase delay film 600.

Light passing through the first phase delay film 650 and the third phase delay film 600 passes through the light passing through the liquid crystal layer. In this case, light that has passed through the first and third phase delay films 650 and 600 passes through the liquid crystal layer without a phase change.

The light passing through the liquid crystal layer passes through the fourth phase delay film 610 and the second phase delay film 660 and is linearly polarized. At this time, the light that has passed through the second phase delay film 660 is reflected from the second polarizing plate 500 and passes through the second phase delay film 660 and the fourth phase delay film 610 again to delay the phase. do.

In addition, light passing through the second phase delay film 660 and the fourth phase delay film 610 passes through the liquid crystal layer as it is without phase delay. The light passing through the liquid crystal layer passes through the third phase delay film 600 and the first phase delay film 650 and is linearly polarized horizontally with the transmission axis of the first polarizing plate 500. Accordingly, when the liquid crystal molecules 301 of the liquid crystal layer are twisted and arranged, they may be in a bright state, that is, a white state in the reflection mode.

As described above, in the liquid crystal display according to the present invention, when the transmission mode is in a dark state, the reflection mode is also in a dark state, and when the transmission mode is in a bright state, the reflection mode may also be in a bright state.

Next, a liquid crystal display device according to a second exemplary embodiment of the present invention will be described with reference to FIG. 7. 7 is a cross-sectional view of a liquid crystal display device according to a second embodiment of the present invention. The liquid crystal display according to the second embodiment may include the same components as those of the above-described embodiment. A description redundantly with the previously described embodiment may be omitted. In addition, the same configurations have the same reference numerals.

Referring to FIG. 7, a second phase delay film 410 is disposed on the rear surface of the first substrate 100, and a second polarizing plate 510 is disposed on the rear surface of the second phase delay film 410. A first phase delay film 400 is disposed on the second substrate 200, and a first polarizing plate 500 is disposed on the first phase delay film. Here, the optical axes of the first phase delay film 400 and the second phase delay film 410 may be configured to be perpendicular to each other.

In order to implement black in the liquid crystal display, the angle of the long axis of the liquid crystal molecules 301 may be arranged to have a value between ^{0 o} and 20 ^{o with the surface of the alignment layer 210.} In this case, the liquid crystal display may implement black in both the transmission mode and the reflection mode.

That is, IPS (In-Plane Switching), AH-IPS (Advanced High-In Plane) in which the liquid crystal molecules 301 are arranged so that the initial liquid crystal alignment direction has ^{a value between 0 o} and 20 ^{o with the surface of the alignment layer 210} Switching), FFS (Fringe Field Switching), or BCSN (Bistable Chiral Splay Nematic) mode, when no voltage is applied, a dark state can be implemented in both the transmissive mode and the reflective mode.

In addition, in order to implement white in the liquid crystal display, the liquid crystal molecules 301 may be twisted and arranged. In this case, the liquid crystal display may implement white in both the transmission mode and the reflection mode.

That is, IPS (In-Plane Switching), AH-IPS (Advanced High-In Plane Switching), FFS (Fringe Field Switching), or BCSN (Bistable Chiral Splay Nematic) in which the liquid crystal molecules 301 are twisted and arranged by applying a voltage. In the) mode, a bright state can be implemented in both the transmission mode and the reflection mode.

As described above, when the liquid crystal display according to the present invention is arranged such that the liquid crystal alignment direction is 0 ^o to 20 ^o with the surface of the alignment layer 210, front reflection and front transmission can be implemented in a liquid crystal display that implements a black state. It works.

Next, referring to FIGS. 8A and 8B, optical characteristics of a liquid crystal display according to a second exemplary embodiment of the present invention will be described as follows. 8A and 8B are graphs showing optical characteristics of a liquid crystal display according to the second embodiment of the present invention.

8A and 8B, when the liquid crystal display device is in a dark state in the transmission mode, the transmittance is almost 0% in the visible light wavelength band. Further, when the liquid crystal display device is in a dark state in the reflection mode, the reflectance is almost 0% in the visible light wavelength band. Accordingly, it can be seen that both the transmission mode and the reflection mode are dark when the liquid crystal display is in a dark state.

In addition, when the liquid crystal display is in a bright state in the transmission mode, the transmittance in the visible wavelength band is about 35%. And, when the liquid crystal display is in a bright state in the reflection mode, the reflectance in the visible light wavelength range is about 20% to 28%. Accordingly, it can be seen that when the liquid crystal display device is in a bright state, both the transmission mode and the reflection mode are in a bright state.

In the liquid crystal display according to the present invention, when the transmission mode is in a dark state, the reflection mode is also in a dark state, and when the transmission mode is in a bright state, the reflection mode may also be in a bright state. Through this, it is possible to improve the visibility of the liquid crystal display device indoors and outdoors.

It will be appreciated by those skilled in the art through the above description that various changes and modifications can be made without departing from the technical idea of the present invention. Accordingly, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be determined by the claims.

10: liquid crystal panel 400: first phase delay film
410: second phase delay film 500: first polarizing plate
510: second polarizing plate

Claims (19)

A first substrate and a second substrate disposed to be spaced apart from each other;
A liquid crystal layer disposed between the first substrate and the second substrate and composed of a plurality of liquid crystal molecules;
An alignment layer disposed on each of the upper and lower portions of the liquid crystal layer;
A first phase delay film disposed on the second substrate;
A first polarizing plate disposed on the first phase delay film;
A second phase delay film disposed under the first substrate;
Including; a second polarizing plate disposed under the second phase delay film,
The optical axis of the first phase delay film and the optical axis of the second phase delay film are perpendicular to each other,
The angle of the transmission axis of the first polarizing plate has a difference of ^{90 o from the angle of the transmission axis of the second polarizing plate,}
The angle of the long axis of the liquid crystal molecules is the same as the angle of the transmission axis of the first polarizing plate or has a difference of ^{90 o,}
A reflective transmissive liquid crystal display device, wherein a single number of phase delay films are disposed between the alignment layer and the first polarizing plate, and between the alignment layer and the second polarizing plate.
The method of claim 1,
An angle of the optical axis of the liquid crystal molecules is arranged to have a value between ^{70 o} and 90 ^{o from the surface of the alignment layer to implement black.}
The method of claim 1,
The reflective transmissive liquid crystal display device, wherein an angle of the optical axis of the first phase delay film has a ^{difference of 20 o} to 30 ^{o from an angle of a transmission axis of the first polarizing plate.}
delete The method of claim 1,
The reflection transmission type liquid crystal display device, characterized in that the phase delay value of the first phase delay film is the same as the phase delay value of the second phase delay film.
The method of claim 5,
Each of the first phase delay film and the second phase delay film has a phase delay value of 200 nm to 250 nm.
The method of claim 1,
The phase delay value of the liquid crystal layer is twice the phase delay value of the first phase delay film and the phase delay value of the second phase delay film.
A first substrate and a second substrate disposed to be spaced apart from each other;
A liquid crystal layer disposed between the first substrate and the second substrate and composed of a plurality of liquid crystal molecules;
An alignment layer disposed on each of the upper and lower portions of the liquid crystal layer;
A first phase delay film disposed on the second substrate;
A third phase delay film disposed between the second substrate and the first phase delay film;
A first polarizing plate disposed on the first phase delay film;
A second phase delay film disposed under the first substrate;
A fourth phase delay film disposed between the first substrate and the second phase delay film; And
Including; a second polarizing plate disposed under the second phase delay film,
The optical axis of the first phase delay film and the optical axis of the second phase delay film are perpendicular to each other,
The angle of the transmission axis of the first polarizing plate has a difference of ^{90 o from the angle of the transmission axis of the second polarizing plate,}
The angle of the optical axis of the first phase delay film has a difference of ^{10 o} to 20 ^{o from the angle of the transmission axis of the first polarizing plate,}
The angle of the optical axis of the third phase delay film and the angle of the optical axis of the fourth phase delay film have an angle difference between the angle ^{of the transmission axis of the first polarizing plate and 70 o} to 80 ^o,
The angle of the optical axis of the third phase delay film is the same as the angle of the optical axis of the fourth phase delay film,
The third phase retardation film and the angle of the optical axis of the fourth phase retardation film is a reflective type liquid crystal display, characterized in that having an angle of 90 ^o with the difference between the major axis of the liquid crystal molecules.
The method of claim 8,
An angle of the optical axis of the liquid crystal molecules is arranged to have a value between ^{0 o} and 20 ^{o from the surface of the alignment layer to implement black.}
delete delete delete The method of claim 8,
The phase delay value of the first phase delay film and the phase delay value of the second phase delay film are the same,
The reflection transmission type liquid crystal display device, characterized in that the phase delay value of the third phase delay film and the phase delay value of the fourth phase delay film are the same.
The method of claim 13,
The phase delay value of each of the first phase delay film and the second phase delay film is 300 nm to 400 nm,
Each of the third phase delay film and the fourth phase delay film has a phase delay value of 150 nm to 200 nm.
The method of claim 8,
A reflective transmissive liquid crystal display device, characterized in that the phase delay value of the liquid crystal layer disposed between the third phase delay film and the fourth phase delay film is twice the phase delay value of the third phase delay film and the fourth phase delay film. .
The method according to any one of claims 2 or 9,
The liquid crystal display device is a reflective transmissive liquid crystal display device in a black state in both a reflective mode and a transmissive mode.
The method of claim 1,
An angle of the optical axis of the liquid crystal molecules is arranged to have a value between ^{0 o} and 20 ^{o from the surface of the alignment layer to implement white.}
The method of claim 8,
An angle of the optical axis of the liquid crystal molecules is arranged to have a value between ^{70 o} and 90 ^{o from the surface of the alignment layer to implement white.}
The method according to any one of claims 17 or 18,
The liquid crystal display device is a reflective-transmissive liquid crystal display device in a white state in both a reflection mode and a transmission mode.

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