KR20040081821A - Reflective liquid crystal display device - Google Patents

Abstract

PURPOSE: A reflective LCD(Liquid Crystal Display) is provided to improve luminance and broaden a viewing angle using cholesteric liquid crystal color filters and an OCB(Opitcal Compensation Briefringence) mode liquid crystal. CONSTITUTION: The first substrate(100) and the second substrate(200) are separated in a certain interval, and red, green and blue pixels are defined in a certain sequence in the first substrate and the second substrate. A TFT(Thin Film Transistor) array part(102) is formed on one surface of the first substrate. Cholesteric liquid crystal color filters(104a-104c) are located on the TFT array part, and are formed to correspond to the red, green and blue pixels. A transparent buffer layer(202) is formed under one surface of the second substrate opposite with the first substrate. The transparent buffer layer is formed at a thickness(ER) corresponding to the red pixel, and is formed at a thickness(EG) corresponding to the green pixel. The transparent buffer layer is formed at a thickness(EB) corresponding to the blue pixel. The thickness of the transparent buffer layer is formed as the relation of ER≠EG≠EB. A common electrode(204) is formed under the transparent buffer layer. An OCB mode liquid crystal layer(106) is formed between the common electrode and the cholesteric liquid crystal color filters. The OCB mode liquid crystal layer is formed at a thickness(DR) corresponding to the red pixel, and is formed at a thickness(DG) corresponding to the green pixel. The OCB mode liquid crystal layer is formed at a thickness(DB) corresponding to the blue pixel. The thickness of the OCB mode liquid crystal layer is formed as the relation of DR≠ DG≠DB. An absorption layer(120) is formed under the first substrate.

Description

Reflective liquid crystal display device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a high brightness reflective liquid crystal display device including a CLC color filter and an optical compensation birefringence mode.

In general, a liquid crystal display device may be classified into a transmissive liquid crystal display device using a backlight and a reflective liquid crystal display device using an external light source according to a method of using a light source.

The transmissive liquid crystal display consumes 2/3 or more of the total power by using the backlight as a light source, whereas the reflective liquid crystal display does not need the backlight, thereby reducing power and battery consumption. However, since the reflective liquid crystal display does not have an external light source, the luminance is not sufficient.

Hereinafter, the configuration of the reflective liquid crystal display device will be described with reference to the drawings.

1 is an exploded perspective view schematically illustrating a configuration of a reflective liquid crystal display device according to the related art.

As shown in FIG. 1, in the liquid crystal panel, the first substrate (lower substrate) 6 and the second substrate (upper substrate) 23 are bonded to each other at a predetermined interval, and face the second substrate 23. On one surface of the first substrate 6, a data line 17 and a gate line 5 are formed to cross each other perpendicularly to define the pixel region P. A thin film transistor T is formed at an intersection point of the two lines. It is composed.

In the pixel region P, a reflective electrode (pixel electrode) 18 in contact with the thin film transistor T is formed.

In this case, as the material for forming the reflective electrode 18, aluminum (Al) having excellent conductivity and reflectance and an alloy-type conductive material including the same are mainly used.

On the other hand, one surface of the second substrate 23 facing the first substrate 6 has a black matrix 21 having a lattice shape and an open portion inside the lattice, that is, a color corresponding to the pixel area P. The filter layers 22a, 22b, and 22c are formed, and a transparent common electrode 24 is formed on the entire surface of the second substrate 23 including the color filter and the black matrix.

The liquid crystal layer 20 is formed in the spaced space between the first and second substrates 6 and 23.

Since the reflective liquid crystal display device configured as described above uses an external natural light source or an artificial light source, the luminance of the reflective liquid crystal display device is much lower than that of a transmissive liquid crystal display device having a separate back light.

In particular, the color filter is mainly formed using a dye or a pigment, the thickness of the color filter has a proportional relationship with the color purity, but inversely related to the color reproducibility, satisfying the color reproducibility and color purity at the same time Difficulties arise in the manufacturing process.

In order to solve this problem, a liquid crystal display using a cholesteric liquid crystal (Cholesteric Liquid Crystal) having a characteristic of selectively reflecting only light of the wavelength range as a color filter has been researched / developed.

The cholesteric liquid crystal forms a helical structure, and since the selective reflection wavelength band of the cholesteric liquid crystal is determined by adjusting the helical pitch, the wavelength band reflected by the distribution of pitch in one pixel can be adjusted.

The wavelength range of visible light visible to the human eye is 400 to 700 nm, and the center wavelength bands of R, G, and B correspond to 630 nm, 550 nm, and 480 nm.

That is, if the above cholesteric liquid crystal is adjusted so that left and right pitch deviations occur for each center wavelength for each of R, G, and B color pixel regions, left circle polarization or right circle in the wavelength region corresponding to the pitch deviation is achieved. By selectively reflecting polarized light, a cholesteric liquid crystal color filter can be formed.

Since the cholesteric liquid crystal color filter selectively reflects only light of a corresponding wavelength range, color purity and contrast ratio are improved as compared with the existing color filter.

2 is a cross-sectional view schematically showing the configuration of a conventional reflective liquid crystal display device using a cholesteric liquid crystal color filter.

As illustrated, the first substrate 30 and the second substrate 40 on which the plurality of pixels P _R , P _G , and P _B are defined are spaced apart from each other, and face one surface of the first substrate 30 to face each other. The thin film transistor array unit 32 including the pixel electrode is configured, and the red, green, and blue color filters 34a and 34b are disposed on the pixels P _R , P _G , and P _B on the array unit 32. And 34c) in order.

The color filters 34a, 34b, and 34c are cholesteric liquid crystal color filters described above.

A liquid crystal layer (OCB cell) 36 is formed on the color filters 34a, 34b, and 34c.

The liquid crystal layer has an optical compensation birefringence mode (OCB mode liquid crystal), and has an advantage in that a response speed is fast and a wide viewing angle is realized.

A transparent common electrode 42 is formed on one surface of the second substrate 40 facing the liquid crystal layer.

An absorbing layer 38 is formed under the first substrate 30 to absorb light that is not reflected by the color filters 34a, 34b, and 34c.

The conventional reflective liquid crystal display device configured as described above uses a CLC color filter and an optically compensated birefringent liquid crystal (OCB) to achieve high luminance characteristics and a wide viewing angle compared with the case of an absorption type color filter. There is an advantage.

3 is a graph showing reflectance of light (red, green, blue) in each wavelength band according to voltage in a conventional reflective liquid crystal display using a cholesteric liquid crystal color filter.

As shown in FIG. 3, the red, green, and blue light have different voltage values indicating maximum reflectance, and at this time, the driving voltage range of the OCB mode reflective liquid crystal display device can obtain the maximum white luminance. The value between (a) and (b) may be determined based on the green color having the maximum luminance at the highest voltage among red, green and blue.

However, in the case of point (A), the brightness inversion occurs in green, and in case of point (B), the brightness of red and green is too low.

The problem is that the phase delay values sensed by the light passing through the pixels are different.

That is, since the wavelength of light passing through each pixel is different from each other, the phase value felt by the light passing through the liquid crystal cell of the same thickness is also different for each pixel.

Therefore, the luminance of the light passing through the liquid crystal panel and the compensation film thereon is different for each pixel, which has a problem that acts as a limit to improve the luminance of the liquid crystal panel to some extent.

Accordingly, the present invention has been proposed to solve the above-described problem, and the liquid crystal panel according to the present invention has the maximum reflectance by equalizing the phase value felt by the light of each wavelength band reflected and incident on each pixel of red, green, and blue. It characterized in that to be.

The first feature of the present invention is to configure the thickness of the liquid crystal cell corresponding to each of the red, green, and blue pixels differently, and the second feature is different from that of the liquid crystal cell corresponding to each of the red, green, and blue pixels. This is to apply a gamma value.

Such a method has an advantage in that it is possible to manufacture a reflective liquid crystal panel that realizes high luminance by making the phase delay value of the light passing through each pixel the same.

1 is an exploded perspective view schematically illustrating a configuration of a general reflective liquid crystal display device;

2 is a cross-sectional view schematically showing the configuration of a conventional reflective liquid crystal display device using a cholesteric liquid crystal color filter;

3 is a graph showing the reflectance of each wavelength (red, green, blue) vs. light according to voltage in a conventional reflective liquid crystal display using a cholesteric liquid crystal color filter.

4 is a cross-sectional view schematically showing the configuration of a reflective liquid crystal display device according to the present invention;

5 is a graph showing reflectance of light of each wavelength (red, green, blue) according to the thickness of a liquid crystal cell in the reflective liquid crystal display device according to the present invention;

6 is a graph showing reflectance of light in each wavelength band according to voltage in the reflective LCD according to the present invention;

7 is a cross-sectional view schematically showing the configuration of a reflective liquid crystal display device according to a second embodiment of the present invention.

<Brief description of symbols for the main parts of the drawings>

100: first substrate 102: thin film transistor array unit

104a, b, c: cholesteric liquid crystal color filter

106: optical compensation birefringence mode liquid crystal layer (OCB mode liquid crystal)

120: absorber layer 200: second substrate

202: buffer layer 204: common electrode

206: linear polarizer

A first substrate and a second substrate configured to be spaced apart at a predetermined interval of the present invention, wherein red, green, and blue pixels are defined in a predetermined order; A thin film transistor array unit formed on one surface of the first substrate; A cholesteric liquid crystal color filter positioned above the thin film transistor array unit and configured to correspond to the red, green, and blue pixels; It is formed on one surface of the second substrate facing the first substrate, a thickness of E _R corresponding to the red pixel, a thickness of E _G corresponding to the green pixel, and corresponding to the blue pixel A transparent buffer layer having a thickness of E _B , wherein the thickness of the transparent buffer layer corresponding to each pixel comprises: a transparent buffer layer having a relationship of E _R ≠ E _G ≠ E _B ; A common electrode formed under the transparent buffer layer; And a thickness of D _R corresponding to the red pixel, a thickness of D _G corresponding to the green pixel, and corresponding to the blue pixel, between the common electrode and the cholesteric liquid crystal color filter. An optically compensated birefringent mode liquid crystal layer having a thickness of D _B , wherein the thickness of the liquid crystal layer corresponding to each pixel includes: an optically compensated birefringent mode liquid crystal layer configured in a relationship of D _R ≠ D _G ≠ D _B ; An absorbing layer is formed below the first substrate.

The thickness of the transparent buffer layer corresponding to each pixel may be configured in a relationship of E _R <E _G <E _B.

The thickness of the liquid crystal layer corresponding to each pixel may be configured in a relationship of D _R > D _G > D _B. In this case, the transparent buffer layer is composed of one selected from the group of transparent organic insulating materials including benzocyclobutene (BCB) and acrylic resin (resin).

The thickness D _R = 8.4 μm of the liquid crystal layer corresponding to the red pixel, the thickness D _G = 7.7 μm of the liquid crystal layer corresponding to the green pixel, and the thickness of the liquid crystal layer corresponding to the blue pixel is D _B = 7.1 μm. We do with characteristic.

According to another aspect of the present invention, there is provided a reflective liquid crystal display device comprising: a first substrate and a second substrate, each of which is spaced apart from each other by a predetermined interval and in which red, green, and blue pixels are defined in a predetermined order; A thin film transistor array unit formed on one surface of the first substrate; Located at the upper portion of the thin film transistor array unit, and configured to have a thickness of E _R corresponding to the red pixel, to have a thickness of E _G corresponding to the green pixel, and to have a thickness of E _B corresponding to the blue pixel. A protective film, wherein the thickness of the protective film corresponding to each pixel includes: a protective film having a relationship of E _R ≠ E _G ≠ E _B ; A cholesteric liquid crystal color filter formed on the passivation layer and configured to correspond to the red, green, and blue pixels; A transparent common electrode formed on one surface of the second substrate facing the first substrate; Comprising between the common electrode and the cholesteric liquid crystal color filter, a thickness of D _R corresponding to the red pixel, a thickness of D _G corresponding to the green pixel, corresponding to the blue pixel and the optical compensation birefringence mode liquid crystal layer consisting of a thickness D of _B, the thickness of the liquid crystal layer has birefringence optical compensation mode is configured in relation to D ≠ _R ≠ D D _{G B} liquid crystal layer corresponding to each pixel and; An absorbing layer is formed below the first substrate.

The thickness of the passivation layer corresponding to each pixel may be formed in a relationship of E _R <E _G <E _B.

The thickness of the liquid crystal layer corresponding to each pixel may be formed in a relationship of D _R > D _G > D _B.

The thickness D _R = 8.4 μm of the liquid crystal layer corresponding to the red pixel, the thickness D _G = 7.7 μm of the liquid crystal layer corresponding to the green pixel, and the thickness of the liquid crystal layer corresponding to the blue pixel is D _B = 7.1 μm. It features.

According to an aspect of the present invention, there is provided a method of driving a reflective liquid crystal display device comprising: a first substrate and a second substrate, each of which is spaced apart from each other by a predetermined interval, and wherein red, green, and blue pixels are defined in a predetermined order; A thin film transistor array unit formed on one surface of the first substrate; A passivation layer on the thin film transistor array unit; A cholesteric liquid crystal color filter disposed above the passivation layer and configured to correspond to the red, green, and blue pixels; A transparent common electrode formed on one surface of the second substrate facing the first substrate; A driving method of a reflective liquid crystal display device comprising a constituent optical compensation birefringent mode liquid crystal (OCB liquid crystal) layer between the common electrode and the passivation layer.

The gamma value set corresponding to the red pixel is 1.22V to 4.98V, the gamma value set corresponding to the green pixel is 1.47V to 5.36V, and the gamma value set corresponding to the blue pixel is It is 1.71-6.10V.

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

First Embodiment

According to the first embodiment of the present invention, in order to configure the thickness of the liquid crystal cell corresponding to each of the red, green, and blue pixels differently, a separate means for changing the thickness of the liquid crystal cell is configured on the upper substrate. .

4 is a cross-sectional view schematically showing the configuration of a reflective liquid crystal display device according to a first embodiment of the present invention.

As illustrated, the liquid crystal display device 99 according to the first exemplary embodiment of the present invention is configured to be spaced apart from the first substrate 100 and the second substrate 200 in which a plurality of pixels are defined.

A thin film transistor array unit 102 including a pixel electrode (not shown) is formed on an inner surface of the first substrate 100, and red, green, and blue colors are formed on the array unit 102 to correspond to each pixel. The cholesteric liquid crystal color filters 104a, 104b, 104c are formed in a predetermined order.

On the cholesteric liquid crystal color filters 104a, 104b and 104c, different thicknesses D _R , D _G , D according to the pixels P _R , P _G , and P _B representing the red, green, and blue colors _B ) constitutes a liquid crystal layer 104 composed of (wherein the liquid crystal uses an OCB mode liquid crystal).

A buffer layer 202, which is a transparent organic film, is formed on one surface of the second substrate 200 facing the liquid crystal layer 104, and corresponds to the red, green, and blue pixels P _R , P _G , and P _B. Consists of different thicknesses.

A transparent common electrode 204 is formed below the buffer layer 202, and a linear polarizing film 206 is formed on the second substrate 200.

An absorbing layer 120 is formed under the first substrate 100.

When the thickness relationship between the buffer layer 202 and the liquid crystal layer 104 is described again, the thicknesses E _R , E _G , and E _B of the organic layer 202 may be represented by E _R <in order of red, green, and blue pixels. Configure it so that E _G <E _B. In this way, the thicknesses D _R , D _G , and D _B of the liquid crystal layer are configured in a relationship of D _R > D _G > D _B in the order of red, green, and blue pixels.

As described above, the thickness of the liquid crystal cell must be configured differently for each pixel of red, green, and blue, so that light of each wavelength band reflected corresponding to each pixel (P _R , P _G , P _B ) passes through the OCB mode liquid crystal. The phase delay value is sensed (ie, the polarization characteristic of the light passing through the OCB mode liquid crystal is the same).

This will be described in detail below.

In general, the light passing through the OCB mode liquid crystal may exhibit the maximum luminance value when it has a phase delay value of (λ / 4 to 3λ / 4).

Therefore, at 1.474V, the initial voltage value for driving the OCB mode liquid crystal, i.e., the voltage at which the green reflectance is maximum (see FIG. 3), the phase delay of light in each pixel to maximize the red and blue reflectances The value Δnd should have the same phase value (i.e. 3 / 4λ relative to green).

Accordingly, a liquid crystal cell gap capable of exhibiting a maximum reflectance at the initial driving voltage through a relationship between the initial driving voltage value (1.474 V), the respective peak wavelength bands of red / green / blue, and the phase value (3λ / 4). The results of the simulation of Fig. 5 were obtained below.

5 is a graph showing reflectance characteristics of light in each wavelength band according to the liquid crystal cell gap in the reflective liquid crystal display device according to the present invention.

(At this time, the graph of FIG. 5 shows that the liquid crystal cell having the highest reflectance at the initial voltage value of 1,474V when the intrinsic refraction value Δn of the liquid crystal is 0.1723 and the phase value Δnd is (3/4) λ. It shows the result of simulating thickness.)

As shown, the thickness of the liquid crystal cell becomes thicker in correspondence with the blue, green, and red pixels. In detail, the liquid crystal cell gap corresponding to the blue pixel is about 7.1 μm, and the liquid crystal cell gap corresponding to the green pixel is about 7.7 μm. The liquid crystal cell gap corresponding to the red pixel was able to obtain a value of 8.4 µm.

In this way, the phase retardation values of the light passing through the red, green, and auditory pixels become the same, and therefore, the maximum luminance value can be obtained.

Hereinafter, FIG. 6 is a graph showing reflectance of light in each wavelength band according to voltage in a reflective liquid crystal display device having a liquid crystal cell gap as described above.

As shown, when the thickness of the liquid crystal cell positioned corresponding to each pixel is adjusted to the value of FIG. 5, the reflectance of red, green and blue light is maximized at 1.474V, which is the starting voltage of the OCB liquid crystal. Can be.

As described above, according to the first exemplary embodiment of the present invention, a transparent buffer layer having different thicknesses is formed on the upper substrate, and the thicknesses of the liquid crystal layers corresponding to the red, green, and blue pixels are different.

As another method of varying the thickness of the liquid crystal layer for each calcination, the thickness of the protective layer constituting the lower substrate may be varied to configure the thickness of the liquid crystal cell corresponding to each pixel.

This will be described below with reference to the second embodiment.

Second Embodiment

The second embodiment of the present invention is characterized in that the liquid crystal cell gap ratios corresponding to the red, green, and blue pixels are configured differently by differently configuring the thickness of the passivation layer formed on the lower substrate.

7 is a cross-sectional view schematically showing the configuration of a liquid crystal display according to the present invention.

As illustrated, the reflective liquid crystal display device 199 according to the second exemplary embodiment of the present invention may have a first substrate 300 and a second substrate 400 with an OBC cell 320 interposed therebetween. Configure it apart.

The first substrate 300 and the second substrate 400 are defined by a plurality of pixels P _R , P _G , and P _B , and each pixel on the opposite surface of the first substrate 300 has a gate electrode ( 302 and a thin film transistor T including an active layer 306 and a source electrode 308 and a drain electrode 310 positioned on the gate electrode 302 with the gate insulating layer 304 interposed therebetween. do.

One side of the pixels P _R , P _G , and P _B configures a gate wiring (not shown) connected to the gate electrode 302 in one direction, and one side of the pixels P _R , P _G , P _B. The data line 312 connected to the source electrode 310 is formed in one direction on the other side perpendicular to the side.

The thin film transistor T includes a thin film transistor T formed on the upper surface of the thin film transistor T by depositing and patterning one selected from a group of transparent organic insulating materials including benzocyclobutene (BCB) and an acrylic resin. The protective film 314 is formed on the entire surface of the substrate 300.

Subsequently, a transparent pixel electrode 316 is formed on the passivation layer 314 to contact the drain electrode 310 for each pixel P _R , P _G , and P _B.

A cholesteric liquid crystal reflecting red, green, and blue wavelengths, respectively, on the substrate 300 on which the pixel electrode 316 is formed, corresponding to the red, green, and blue pixels P _R , P _G , and P _B. Color filters 318a, 318b and 318c are formed.

A transparent common electrode 402 is formed on one surface of the second substrate 400 facing the first substrate 300.

An absorbing layer 320 is formed below the first substrate 300.

In the above-described configuration, the thickness of the passivation layer 314 is configured differently corresponding to the red, green, and blue pixels P _R , P _G , and P _B , so that the thickness ratios of the liquid crystal cells corresponding to the red, green, and blue pixels are different. Let (D _R , D _G , D _B ) be the same as D _R > D _G > D _B.

To this end, the thicknesses E _R , E _G , E _B of the passivation layer 314 corresponding to the red, green, and blue pixels P _R , P _G , and P _B have a relationship of E _R <E _G <E _B. Form to be.

In this case, preferably, the thickness d _R = 8.4 μm of the liquid crystal cell corresponding to the red pixel, the thickness d _G = 7.7 μm of the liquid crystal cell corresponding to the green pixel, and the thickness d _R = of the liquid crystal cell corresponding to the blue pixel. The thickness of the protective film 314 is adjusted to be 7.1 μm.

In the above-described configuration, the method of patterning the passivation layer 315 can be largely presented in two ways. (It is also applied to the process of manufacturing the buffer layer in the first embodiment.)

First, when the material for forming the passivation layer 314 is made of a material in which its material plays a role of PR, such as photo-acryl, it corresponds to each pixel (P _R , P _G , P _B ). By using a mask to irradiate light of different intensities, a protective film 314 having different thicknesses is formed in a single process.

Second, when the material for forming the protective film 314 is a general organic material, forming a thick organic film on the entire surface of the substrate 300, and then removing the organic film corresponding to each pixel through two photolithography processes. You can use how to proceed.

That is, after forming the first PR layer on the organic film, the pattern is removed to remove a part of the organic film of the red pixel P _R.

Next, the second PR layer is formed and then patterned to expose the organic layers of the pixels P _R and P _G corresponding to the red and green portions, and then a part of the second PR layer is removed.

In this manner, the protective films 314 having different thicknesses may be formed corresponding to the red, green, and blue pixels P _R , P _G , and P _B.

With the above configuration, the reflective liquid crystal display device according to the second embodiment of the present invention can be manufactured.

Hereinafter, another method for improving the luminance of the reflective liquid crystal display device including the CLC color filter will be described through the third embodiment.

-Third Example-

The third embodiment of the present invention is characterized by applying different voltage values (gamma values) corresponding to the red, green and blue pixels.

As mentioned in the related art, since the wavelengths of light reflected from the color filters corresponding to red, green, and blue are different, phase values that light feels while passing through liquid crystal layers having the same thickness are different.

Therefore, in order to match the phase value, there is also a method of differently configuring the thickness of the liquid crystal cell as in the first to second embodiments, but by varying the orientation of the liquid crystal cell by changing the gamma value, A method of equalizing the phase change can be used.

As mentioned above, when it is assumed that the luminance is maximum in each pixel when the phase value of (3/4) λ is sensed, the phase value of light corresponding to each pixel and the gamma value applied accordingly The range of is as follows.

Phase value of light in red pixel: Δnd = (3/4) λ = (3/4) × 630nm = 472.5

----- Signal voltage (gamma value): 1.22V ~ 4.98V

Phase value of light in green pixel: Δnd = (3/4) λ = (3/4) × 550nm = 412.5

----- Signal voltage (gamma value): 1.47V ~ 5.26V

Phase value of light in blue pixel: Δnd = (3/4) λ = (3/4) × 480nm = 360

----- Signal voltage (gamma value): 1.71V ~ 6.01V

The range of the voltage value applied corresponding to each of the red, green, and blue pixels is as described above.

That is, when the gamma value is set for each pixel to match the above conditions, it is possible to manufacture an OCB mode reflective liquid crystal display device having high brightness.

The reflection type liquid crystal display device according to the present invention has the effect of improving luminance and widening the viewing angle by using a cholesteric liquid crystal color filter and using an OCB mode liquid crystal.

In addition, using a method of varying the thickness of the liquid crystal cell corresponding to the red, green, and blue pixels, or applying a different gamma value to each pixel, the maximum luminance can be obtained.

Claims (11)

A first substrate and a second substrate configured to be spaced apart at a predetermined interval, wherein red, green, and blue pixels are defined in a predetermined order; A thin film transistor array unit formed on one surface of the first substrate; A cholesteric liquid crystal color filter positioned above the thin film transistor array unit and configured to correspond to the red, green, and blue pixels; It is formed on one surface of the second substrate facing the first substrate, a thickness of E _R corresponding to the red pixel, a thickness of E _G corresponding to the green pixel, and corresponding to the blue pixel In the transparent buffer layer consisting of a thickness of E _B , A thickness of the transparent buffer layer corresponding to each pixel includes a transparent buffer layer having a relationship of E _R ≠ E _G ≠ E _B ; A common electrode formed under the transparent buffer layer; And a thickness of D _R corresponding to the red pixel, a thickness of D _G corresponding to the green pixel, and corresponding to the blue pixel, between the common electrode and the cholesteric liquid crystal color filter. In the optically compensated birefringent mode liquid crystal layer composed of a thickness of D _B , The thickness of the liquid crystal layer corresponding to each pixel is the optical compensation birefringence mode liquid crystal layer having a relationship of D _R ≠ D _G ≠ D _B and; Absorption layer formed under the first substrate Reflective liquid crystal display device comprising a. The method of claim 1, The thickness of the transparent buffer layer corresponding to each pixel is a reflection type liquid crystal display device having a relationship of E _R <E _G <E _B. The method of claim 1, The thickness of the liquid crystal layer corresponding to each of the pixels is a reflection type liquid crystal display device having a relationship of D _R > D _G > D _B. The method of claim 1, The transparent buffer layer is a reflective liquid crystal display device comprising one selected from the group of transparent organic insulating materials including benzocyclobutene (BCB) and acrylic resin (resin). The method of claim 1, The reflection of the liquid crystal layer corresponding to the red pixel with a thickness D _R = 8.4 μm, the liquid crystal layer corresponding to the green pixel with a thickness D _G = 7.7 μm, and the liquid crystal layer corresponding to the blue pixel with a D _B = 7.1 μm. Type liquid crystal display device. A first substrate and a second substrate configured to be spaced apart at a predetermined interval, wherein red, green, and blue pixels are defined in a predetermined order; A thin film transistor array unit formed on one surface of the first substrate; Located at the upper portion of the thin film transistor array unit, and configured to have a thickness of E _R corresponding to the red pixel, to have a thickness of E _G corresponding to the green pixel, and to have a thickness of E _B corresponding to the blue pixel. In the protective film, A thickness of the passivation film corresponding to each of the pixels is configured to have a relationship of E _R ≠ E _G ≠ E _B ; A cholesteric liquid crystal color filter formed on the passivation layer and configured to correspond to the red, green, and blue pixels; A transparent common electrode formed on one surface of the second substrate facing the first substrate; Comprising between the common electrode and the cholesteric liquid crystal color filter, a thickness of D _R corresponding to the red pixel, a thickness of D _G corresponding to the green pixel, corresponding to the blue pixel In the optical compensation birefringence mode liquid crystal layer composed of a thickness of D _B , A thickness of the liquid crystal layer corresponding to each pixel is an optical compensation birefringence mode liquid crystal layer having a relationship of D _R ? D _G ? D _B ; Absorption layer formed under the first substrate Reflective liquid crystal display device comprising a. The method of claim 6, The thickness of the passivation layer corresponding to each pixel is formed in the relationship of E _R <E _G <E _B. The method of claim 6, The thickness of the liquid crystal layer corresponding to each pixel is formed in the relationship of D _R > D _G > D _B. The method of claim 6, The protective layer is a reflective liquid crystal display device comprising one selected from the group of transparent organic insulating materials including benzocyclobutene (BCB) and acrylic resin. The method of claim 6, The reflection of the liquid crystal layer corresponding to the red pixel with a thickness D _R = 8.4 μm, the liquid crystal layer corresponding to the green pixel with a thickness D _G = 7.7 μm, and the liquid crystal layer corresponding to the blue pixel with a D _B = 7.1 μm. Type liquid crystal display device. A first substrate and a second substrate configured to be spaced apart at a predetermined interval, wherein red, green, and blue pixels are defined in a predetermined order; A thin film transistor array unit formed on one surface of the first substrate; A passivation layer on the thin film transistor array unit; A cholesteric liquid crystal color filter disposed above the passivation layer and configured to correspond to the red, green, and blue pixels; A transparent common electrode formed on one surface of the second substrate facing the first substrate; A driving method of a reflective liquid crystal display device comprising a constituent optical compensation birefringent mode liquid crystal (OCB liquid crystal) layer between the common electrode and the passivation layer. The gamma value set corresponding to the red pixel is 1.22V to 4.98V, the gamma value set corresponding to the green pixel is 1.47V to 5.36V, and the gamma value set corresponding to the blue pixel is 1.71 to 6.10 V Method of driving a reflective liquid crystal display device.