JPH09311309A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the number of display colors capable being recognized by a human being as different colors in a double refraction interference color type liquid crystal display device by making reflectivities of a subpixel group performing an achromatic color display to be a geometric series while changing them. SOLUTION: In a liquid crystal display device provided with pixels constituted of (n) pieces of subpixels and performing a hue display by utilizing a double refraction interference color by a reflected light, (n) pieces of subpixels are classified into two groups respectively constituted of (m) pieces (0<=m<=n) and n-m pieces of subpixels every pixel and respective groups are made to be operated by respectively being impressed with voltages being in a voltage range C becoming a chromatic display and voltage being in a voltage range G becoming an achromatic display. When Q kinds of voltage values selected among the voltage range G are defined as voltage values VG1 -VGQ in the order of higher flactivities RG of the subpixels by Q kinds of the voltage values VVG1 -VGQ and the reflectivities of pixels at the time the voltage values VG1 -VGQ are impressed on the pixels are respectively defined as RG1 -RGQ. Then, the pixel is constituted so that an x (1<=x<=Q)-th reflectivity RGX is expressed in an equation, RGX=RGI×a<(x-1)> under a constant (a) (a<1).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device which can obtain a color display by utilizing a birefringence interference color of reflected light.

[0002]

2. Description of the Related Art Since a reflection type liquid crystal display device can obtain a display by utilizing incident light from the outside, it is particularly thin, lightweight and low in power consumption among various liquid crystal display devices, and therefore, it is rapidly spread in the future. It can be said that the display device is optimal for the morphological information terminal that is expected to progress.

By the way, as a reflection type liquid crystal display device capable of color display as described above, in addition to the method of using a color filter as known in the prior art, for example, JP-A-6-95151. As described in Japanese Patent Laid-Open Publication No. JP-A-2003-264, there is known a so-called birefringence interference color type liquid crystal display device in which color display is performed by utilizing birefringence interference color due to reflected light, and a color liquid crystal display of this system is known. The device has an advantage that a color filter can be eliminated.

In this birefringence interference color type liquid crystal display device, each pixel is further divided into a plurality of pixels, that is, sub-pixels for display. At this time, the chromaticity and reflection of each sub-pixel are reflected. The applied voltage dependences of the rates are the same.

FIG. 2 shows an example of the applied voltage dependence (chromaticity locus) of the chromaticity of the sub-pixel at this time. When birefringence interference color is used, the chromaticity changes in the applied voltage. Along with,
It changes to rotate around the C light source (standard light source of daylight color). That is, one subpixel can display achromatic colors such as white and black and chromatic colors such as red, blue, green, cyan, yellow, and magenta.

On the other hand, when a color filter is used, each sub-pixel is dedicated to red display, blue display, or green display, so that the reflectance is lowered to a level where it cannot be practically used. However, the birefringence interference color liquid crystal display device has an advantage that sufficient reflectance can be obtained because one subpixel is not dedicated to a specific color display.

On the other hand, in the birefringence interference color type liquid crystal display device, the reflectance of each chromaticity can obtain only a certain value. For example, in the example of FIGS. 2 and 3, the reflectance of red is 7.6%.
It is before and after, and other red reflectance cannot be obtained. Further, the reflectance of blue is around 7.4%, and other reflectances of blue cannot be obtained. As a result, the birefringence interference color liquid crystal display device has a drawback that it is difficult to increase the number of display colors.

Therefore, in the invention of the above publication, the n sub-pixels are divided into at least two groups, one of them is displayed in achromatic color and the other is displayed in colored, and the combination of these is changed to change the display color. We are trying to get an increase in the number.

In other words, if the individual subpixels are made fine enough, a person does not recognize the display color of the individual subpixels, but the average thereof. For example, if red is displayed on one side of the subpixel group and white is displayed on the other side, humans recognize pink, which is the average of red and white. In this way,
Even if individual subpixels cannot display pink, by combining the display colors of the subpixel groups, it is possible to display pink in one pixel as a whole. Similarly,
The number of display colors can be increased by combining various colored and achromatic colors.

The above conventional technique will be described in more detail below. First, the voltages applied to the sub-pixels are classified into the following two areas. Voltage region C: A voltage region in which the color purity of the display color is high. Voltage region G: A voltage region in which the reflectance of the display color is high on one side and the color purity is low, and the reflectance is low on the other side, and the reflectance continuously changes between the two states.

The voltage regions C and G are determined from the applied voltage dependence of the chromaticity and reflectance of each subpixel. The voltage region C is an applied voltage region corresponding to a color display (red, blue, green, etc.), and the voltage region G is an achromatic display (white, gray,
It is an applied voltage region corresponding to (black). In the example of FIG. 3 described above, the applied voltage range 0.0V to 1.9V is the voltage region C, and 1.95V to 3.1V is the voltage region G.

Next, n subpixels in one pixel are classified into the following two groups. Sub-pixel group C: A sub-pixel group to which a voltage in the voltage region C is applied for color display. Sub-pixel group G: A sub-pixel group to which a voltage in the voltage region G is applied and which performs achromatic display.

FIG. 4 shows one of such sub-pixel configurations.
This is an example. In this example, one pixel is 6 (n = 6)
Sub-pixels 1 to 6. Then, first, in FIG. 4A, the sub-pixels 2, which are shaded,
3 and 5 show a state in which a sub-pixel group C is formed, and white sub-pixels 1, 4, and 6 form a sub-pixel group G. Next, FIG. ,
2, 3 form a sub-pixel group C, sub-pixels 4,
Reference numerals 5 and 6 show a state in which the sub-pixel group G is formed.

Further, FIG. 4 (c) shows a state in which the sub-pixels 1 to 6 form a sub-pixel group C, and one pixel as a whole becomes the sub-pixel group C. FIG. 4 (d) shows The sub-pixels 1 to 6 form a sub-pixel group G, and one pixel as a whole is in the sub-pixel group G.

1 composed of such sub-pixels
The reflectance R _P and chromaticity (u _P , v _P ) of the pixel are as follows.
As shown in equations (1) and (2), it is represented by a weighted average of chromaticity and reflectance of the sub-pixel groups C and G. R _P = A _C R _C + A _G R _G (1) (u _P , v _P ) = {A _C R _C (u _C , v _C ) + A _G R _G (u _G , v _G )} / R _P ............... (2) where, a _C, a _G: sub-pixel groups C, the area ratio of _G R _C, R G: subpixel group C, the reflectivity of G (u _C, v _C ), (U _G , v _G ): Chromaticity of sub-pixel groups C, G Ideally, (u _G , v _G ) should be the chromaticity of the C light source.

Thereafter, A _C , A _G , R _C , R _G , (u _C , v
_C ) and (u _G , v _G ) are called display color parameters.
As described above, the reflectance of each display color takes only a certain constant value, so that among the display color parameters, R
_C and (u _C , v _C ), R _G and (u _G , v _G ) cannot be changed independently.

The values of R _C and (u _C , v _C ) are adjusted by changing the voltage applied to the subpixel group C. Similarly, the values of R _G and (u _G , v _G ) are adjusted by changing the voltage applied to the subpixel group G. Also, A
The adjustment of the values of _C and A _G is as shown in FIG.
This is performed by changing the distribution of the subpixel groups C and G.
As described above, the chromaticity of the display color of the birefringence interference color type liquid crystal display device can be changed by changing the combination of the display color parameters.

[0018]

However, the number of display colors of the birefringence interference color type liquid crystal display device is not the number of combinations of display color parameters. In other words, even if the number of display color parameter combinations is unnecessarily increased, the number of display colors is not increased.

This will be described below. When observing two colors having different chromaticities, if the chromaticities of the two colors are significantly different, a person can easily recognize them as two different colors. However, if the difference in chromaticity between the two colors becomes small, it becomes difficult to recognize them as two different colors. If the difference in chromaticity between the two colors becomes smaller, humans cannot recognize them as two different colors.

The chromaticity coordinates that quantify chromaticity include, for example, the UCS color system, but the difference in chromaticity between two colors is the difference between two points on the chromaticity coordinates corresponding to two colors. It is represented by the distance. If the distance between the two colors on the chromaticity coordinate is large,
It can be easily recognized as two different colors, but cannot be recognized as two different colors when the distance is small.

When color display is performed, the chromaticity of each color is naturally different from each other. That is, they occupy different points on the chromaticity coordinates. For example, when displaying five colors, each display color corresponds to five points on the chromaticity coordinates.

However, for example, when three of the five points are extremely close to each other, a human cannot recognize the three display colors corresponding to the three points as different display colors. Therefore, in this case, even if five colors are displayed, humans recognize only three colors.

The same applies to the birefringence interference color liquid crystal display device. For example, when the display colors obtained by the combination of display color parameters are concentrated and distributed in a narrow area on the chromaticity coordinate, it is not possible to recognize all the display colors of these combinations as different colors. Can not.

The problem to be solved by the present invention is to increase the number of display colors of a birefringence interference color type liquid crystal display device, that is, to increase the number of display colors that can be recognized as different colors by humans. .

[0025]

In order to increase the number of display colors that humans can recognize as different colors, it is necessary to distribute the points corresponding to each display color over a wide area on the chromaticity coordinates. Good. In the case of the birefringence interference color type liquid crystal display device, the points corresponding to the respective display colors obtained by the combination of the display color parameters are distributed inside the chromaticity locus of the sub-pixel shown as an example in FIG. Therefore, the points corresponding to the respective display colors may be evenly distributed inside the chromaticity locus.

Therefore, first, a method of changing the chromaticity of the display color when the combination of the display color parameters is sequentially changed will be described. First, pay attention to the point β shown in FIG. At this point β, none of A _C , A _G , R _C , and R _G is zero. There are two ways to change the chromaticity of the display color corresponding to the point β, that is, to move the point β on the chromaticity coordinates. That is, the direction around the C light source (a, b in FIG. 5) and the direction of the straight line connecting the point β and the C light source (c, d in FIG. 5).

Chromaticity is classified into two, hue (hue) and color purity (vividness of color), where a and b are changes in hue and c and
d corresponds to the change in color purity. And the change in hue a, b
Corresponds to changing (u _C , v _C ) in the equation (2). That is, the hue of the display color of one pixel is changed by changing the hue of the sub-pixel group C that performs color display.

The changes c and d in color purity are made by the following two methods. One way is to change A _C and A _G. That is, the color purity of the display color of one pixel is changed by changing the area ratio of the sub-pixel groups C and G.

Another method is to change R _G. That is, the color purity of the display color of one pixel is changed by changing the reflectance of the sub-pixel group G that displays an achromatic color. If A _G = 0 or R _G = 0, the display color moves to the point α on the chromaticity locus. At this time, the color purity of the display color of one pixel is maximized.

As described above, when the combination of display color parameters is sequentially changed, the display color changes in two directions.
That is, the direction around the C light source (a, b in FIG. 5)
And the direction connecting the point α on the chromaticity locus and the C light source (c, d in FIG. 5).

In practice, (u _C , v _C ) cannot be changed continuously. This is because the voltage applied to the subpixel group C cannot be continuously changed within the voltage region C. Also, for the same reason, R _G cannot be changed continuously.

[0032] Therefore, in practice, selecting a P number of the applied voltage V _C1 ~V _CP from voltage region C, P number of chromaticities corresponding to these _{V C1 ~V CP (u C1,} v C1) ~ ( u _CP , v _CP )
(u _C , v _C ) is selected. Similarly, Q applied voltages V _{G1 to} V _GQ are selected from the voltage region G, and Q reflectivities R _G1 to V _{G1 to} V _GQ corresponding to V _{G1 to} V _GQ are selected. R _GQ (R _G1 ＞ R _G2 ＞ 〜 ＞ R _GQ
RG is selected from among the above).

In order to evenly distribute the points corresponding to the respective display colors inside the chromaticity locus, first, (u _C1 ,
It is sufficient to set V _{C1 to} V _CP so that v _C1 ) to (u _CP , v _CP ) are distributed at equal intervals on the chromaticity locus. Such V _C1 ~
V _CP can be easily obtained if the applied voltage corresponding to each point on the chromaticity locus is clear, and such V _{C1 to} V _CP can be obtained.
Table 1 shows one example.

[0034]

[Table 1]

Here, V _{G1 to} V _GQ are (u) in the equation (2).
_C , v _C ) and R _C are fixed, and each (u _P , v _P ) obtained by changing other display color parameters is equidistant on a straight line connecting each point on the chromaticity locus and the C light source. It may be set so as to be distributed.
A method for obtaining such V _{G1 to} V _GQ will be considered below.

If one pixel is composed of three sub-pixels having an area ratio of 1: 2: 4, as will be described later, A
The ratio of _G to A _C can be changed by 1/7 at equal intervals. A _G : A _C = 0/7: 7/7, 1/7: 6/7, 2/7:
5/7, 3/7: 4/7, 4/7: 3/7, 5/7: 2
/ 7, 6/7: 1/7, 7/7: 0/7 Next, when changing each of A _G and A _C ,
The distribution of (u _P , v _P ) is shown by white circles in FIG.

First, FIG. 14A shows the case where R _C > R _G. In this case, each (u _P , v _P ) is distributed biased to the chromaticity locus side. Next, FIG. 14B shows the case where R _C = R _G , and
(u _P , v _P ) are distributed at equal intervals. Further, FIG. 14 (c) shows
In the case of R _C <R _G , each (u _P , v _P ) is unevenly distributed on the C light source side.

The result of FIG. 14 is explained as follows. First, when R _C = R _G , each (u _P , v _P ) is A _G and A _C
However, since the ratio of A _G and A _C changes to be evenly spaced as described above, the distribution of each (u _P , v _P ) can also be equally spaced. However, in the case of R _C > R _G , the weighting of (u _C , v _C ) becomes stronger and the distribution is biased toward the chromaticity locus side.

When R _C <R _G , the weighting of (u _G , v _G ) is increased, and each (u _P , v _P ) is unevenly distributed on the C light source side. From the above, in order to distribute each (u _P , v _P ) on the straight line connecting each point on the chromaticity locus and the C light source at equal intervals, R
It was required that _C = _RG .

Of these, R _C is the above-mentioned (u _C1 , v _C1 )-(u
_CP , v _CP ) is determined by a request to distribute them at equal intervals on the chromaticity locus, and is, for example, (P = 18) in Table 1 above. That is, as is clear from Table 1,
R _{C1 to} R _CP corresponding to (u _C1 , v _C1 ) to (u _CP , v _CP ) are
It takes various values depending on the display color.

For example, the maximum green is 31.8%, whereas the minimum purple is 3.3%, and there is a difference of nearly 10 times between the two. Green has a high reflectance because it has a maximum reflectance in the vicinity of a wavelength of 555 nm at which human visibility is maximized. In addition, purple has a low reflectance because it has a wavelength of 5
This is because it has a minimum reflectance in the vicinity of 55 nm.

As described above, the variation in R _{C1 to} R _CP is caused by the shape of the reflection spectrum peculiar to each color, and is a problem always associated with R _{C1 to} R _CP that gives high color purity. Further, if R _{C1 to} R _CP are averaged, the color purity of each color decreases, which is not preferable.

In order to substantially satisfy R _C = R _G for any of R _{C1 to} R _{CP with} a large variation, R _{G1 to} R _G
Similarly, _GQ may be set to include a large value to a small value. An example of such a method of setting R _{G1 to} R _GQ is shown below. First, R _{C1 to} R _CP have a nearly 10-fold difference between the maximum green and the minimum purple. Therefore, the difference between R _{G1 and} R _GQ may be at least about 10 times. As described above, if R _{G1 to} R _GQ are R _G1 > R _G2 >to> R _GQ , then R _G1 having the highest reflectance and R _GQ having the lowest reflectance are:
It may be set as in equation (3).

0.1 × R _G1 > R _GQ ……………… (3) Here, R _G1 has the same reflectance as that of green, which has the lowest reflectance among R _{C1 to} R _CP . The reflectance may be set such that R _GQ has a reflectance comparable to that of purple, which has the lowest reflectance among RC _{1 to} R _CP .

Alternatively, R _GQ is displayed in black and the voltage range G
_Is set to the lowest reflectance obtained in the above, R _GQ is displayed in white, and the highest reflectance obtained in the voltage region G is set, and then R _G2 and R _GQ having the highest reflectance next to R _G1 are reflected. R _{G (Q-1)} having a low rate may be set as in the following expression (4).

0.1 × R _G2 > R _{G (Q-1)} (4) Here, R _GQ is the lowest reflectance obtained in the voltage region G, and R _G1 is the voltage. In addition to having the highest reflectance obtained in the region G, R _G2 has a reflectance similar to that of green, which has the lowest reflectance among R _{C1 to} R _CP , and R _{G (Q-1)} is R
The reflectance may be the same as that of purple, which has the lowest reflectance among _{C1 to} R _CP .

Alternatively, R _{G1 to} R _GQ may be geometric series as in the following equation (5).

R _Gx = R _G1 × _â (x−1) (5) Here, 1 ≦ x ≦ Q. From this equation (5), R _G1 ~
R _GQ can be set to include large to small values. In order to set R _{G1 to} R _GQ mainly at a particularly low reflectance, a in the formula (5) may be set to 0.5 or less. Strictly speaking, R _{C1 to} R _CP and R _{G1 to} R _GQ may be perfectly matched with P = Q.

On the other hand, even if R _{G1 to} R _GQ are not strictly set in this way, they may be set by the following simpler method. That is, first, R _{C1 to} R _CP are classified into Q groups having reflectance values close to each other. Next, a representative value of the reflectance values of each group is obtained, and R _{G1 to} R _GQ are set to the representative values of the reflectance values of each group.

The representative value of the reflectance values of each group may be, for example, the average value of the reflectance values of each group. Alternatively, for example, it may be a value included in the distribution range of reflectance values of each group, or a value sufficiently close to the distribution range of reflectance values of each group.

Furthermore, R _{G1 to} R 1 can be obtained by the method shown in FIG.
You may set _GQ . First, with Q = 5, the highest reflectance in the voltage region G is set to R _G1 and the lowest reflectance is set to R _GQ . Next, R _{C1 to} R _CP corresponding to the color display of green, cyan, yellow, red, blue, purple, and magenta are classified into the following three groups. Of these, the group with the highest reflectance consists of green, cyan, and yellow, and the next highest group is red,
It is composed of blue, and the group with the lowest reflectance is composed of purple and magenta. Then, R _G2 , R _G3 , and R _G4 are determined by using the values included in the distribution range of the reflectance value of each group as a representative value.

In the voltage region G, if the dependency of the reflectance on the applied voltage is clear, V _{G1 to} V _GQ that give any of the above R _{G1 to} R _GQ can be easily obtained.

As described above, R _{C1 to} R _CQ and R _{G1 to} R _GQ
By determining, the distribution of the points corresponding to each display color can be made more uniform inside the chromaticity locus, and a birefringence interference color liquid crystal with many display colors that can be recognized by humans as different colors. A display device can be realized.

In order to change the ratio of A _C and A _G at equal intervals, the area of n sub-pixels forming one pixel is
It can be determined by equation (6).

X _y = 2 ^ (y−1) (6) Here, y (1 ≦ y ≦ n) is a number given to the sub-pixels in ascending order of the area, and X y _y is the area of the y-th subpixel. The X _y is always greater by X ₁ than the sum of the X _y-1 to X _1, as a result, the area ratio sequence of A _C and A _G where the X ₁ and unit area is obtained.

[0056]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the liquid crystal display device according to the present invention will be described more specifically by way of examples. Embodiment 1 FIG. 6 is a plan view showing one pixel portion in one embodiment of the liquid crystal display device according to the present invention, and FIGS. 7 and 8 are sectional views taken along line 1-1 ′ and line 2-2 ′ of FIG. 6, respectively. It is sectional drawing in a line.

First, in this embodiment, one pixel is made up of two sub-pixels, which are represented by sub-pixels SP1 and SP2, as is apparent from FIG. The area ratio of the sub-pixels SP1 and SP2 is set to 1: 2 based on the equation (3), and as shown in FIG.
By switching to the subpixel group G, the areas A _C and A _{G of the} subpixel groups C and G can be changed.

Next, in these figures, the lower substrate 10
Is made of alkali-free borosilicate glass and has silicon oxide layers on the top and bottom. The gate electrode 20 is made of an aluminum film formed by sputtering, and has an anodized aluminum film on the upper side. The insulating film 25 has a film thickness of 2000Å
Is a silicon nitride film, and is formed by the plasma CVD method.

A TFT which constitutes an active element is composed of a gate electrode 20, an insulating film 25, an i-type semiconductor layer 30, a source electrode 40 and a drain electrode 45.
The i-type semiconductor layer 30 is made of amorphous silicon and has a layer thickness of 200.
It is 0Å. Then, phosphorus is doped above the portion overlapping the source electrode 40 and the drain electrode 45 to form an N (+) type amorphous silicon semiconductor layer.

The source electrode 40 and the drain electrode 45 are composed of two layers, and the upper layer is a layer thickness 300 formed by the sputtering method.
It is 0 Å aluminum, and the lower layer is chrome with a layer thickness of 600 Å also formed by the sputtering method. This TFT
Operates so that a positive bias is applied to the gate electrode 20 to reduce the channel resistance and a zero bias increases the channel resistance.

A flattening film 50 is provided on the TFT, which is a silicon nitride film having a film thickness of 1 μm formed by a plasma CVD apparatus. The pixel electrode 57 on the flattening film 50 is made of aluminum and is connected to the source electrode 20 through the through hole 55.

The organic alignment film 60 is made of a polyimide organic polymer material, and the liquid crystal layer 70 is traded under the trade name HA-5073XX.
The one provided in the market was used. Pixel electrode 5
The maximum value of the thickness of the liquid crystal layer 70 in the portion where 7 is present is 6.
2 μm, and on the premise of this, the retardation of the liquid crystal layer 70 when no voltage is applied is 0.85 μm.

The organic alignment film 60 on the upper substrate 80 is also the same material as that on the flattening film 50 described above. And
The upper and lower two organic alignment films 60 have their alignment treatment directions orthogonal to each other and are given a pretilt angle of 5 degrees.

The common transparent pixel electrode 75 on the lower surface of the upper substrate 80 is made of ITO (Indium-Ti) formed by sputtering.
n-Oxide) film, and the film thickness is 1400Å. Like the lower substrate 10, the upper substrate 80 is made of non-alkali borosilicate glass and has silicon oxide layers on the top and bottom.

A polysulfone phase plate was used as the phase plate 90, the retardation was 0.23 μm, and the azimuth of the slow axis was parallel to the liquid crystal alignment direction in the liquid crystal layer 70. Phase plate 9
A polyvinyl alcohol phase plate was used for 1, the retardation was 0.47 μm, and the azimuth of the slow axis was orthogonal to the liquid crystal alignment direction of the liquid crystal layer. The polarizing plate 95 was arranged so that the azimuth of its absorption axis was 45 ° with respect to the liquid crystal alignment direction.

A drive device was combined with this liquid crystal display device, and the display characteristics of each sub-pixel were evaluated in the gate open state. The display obtained at this time is that the applied voltage is 0.00V.
Above, 1.90V or less, color display, 1.95V or more,
It becomes achromatic at 3.10V or less. Therefore, the applied voltage range of 0.00V or more and 1.90V or less is set to the voltage region C, 1.9.
The voltage region G is 5 V or more and 3.10 V or less. The voltage is set in this region G by setting the constant a to about 0.3 and substantially according to the equation (5).

Table 1 shows 18 kinds of voltages V _{C1 to} V _C18 selected from the voltage range C, reflectances R _{C1 to} R _C18 when these voltages V _{C1 to} V _{C18 are} applied, and display colors.

[0068]

[Table 1]

Next, Table 2 shows five kinds of voltages V _{G1 to} V _G5 selected from the voltage region G and reflectances R _{G1 to} R _G5 when these voltages V _{G1 to} V _{G5 are} applied.

[0070]

[Table 2]

Here, the reflectances R _{G1 to} R _G5 in the voltage region G
Was specifically determined as follows. That is, first, the reflectance R _G1 and the reflectance R _G5 are set to the maximum and minimum reflectances in the voltage region G. Then, the reflectivity R _G2 and the reflectance R _G3, for the reflectance R _G4 thereto, the difference between the largest R _G2 and minimum R _G4 among these was set to 10 times or more.

Next, as shown in FIG. 9, the operation of the subpixel SP1 and the subpixel SP2 as the subpixel groups C and G is changed to four ways (a) to (d), and the above-mentioned regions The voltages V _{C1 to} V _C18 and V _{G1 to} V _G5 were applied. In FIG. 9, the shaded area represents the sub-pixel group C, and the non-white area represents the sub-pixel group G.

FIG. 10 shows the display color of one pixel obtained by changing the combination of the subpixel groups shown in FIG. 9 and applying each of the voltages shown in Tables 1 and 2. FIG. 10 shows the UCS chromaticity coordinate system. When the display according to the first embodiment is represented in this coordinate system, as shown in the figure, the display can be obtained at any point in a wide range centered on the C light source. It was possible to display a large number of gradations.

As described above, according to the first embodiment, the reflectance R
_G1 and the reflectance R _G5 are respectively set to the maximum reflectance and the minimum reflectance in the voltage region G, and the difference between the reflectance R _G2 and the reflectance R _G4 is set to be 10 times or more, so that It was possible to display almost all display colors.

Example 2 In the liquid crystal display device described with reference to FIGS. 6 to 8, the reflectance R
Example 2 was changed by changing _G2 , R _G3 , and R _G4 as shown in Table 3.

[0076]

[Table 3]

That is, in the second embodiment, first, the attention is paid to the reflectances R _{C1 to} R _C18 of the respective color displays. Then, first, the reflectances R _{C1 to} R _C18 are classified into a group 1 composed of green, cyan and yellow, a group 2 composed of blue and red, and a group 3 composed of purple and magenta. Group 1 reflectance (R
_C3 , R _C4 , R _{C10 to} R _C12 ) are in the range of 31.8% to 13.7%, and the reflectance of the group 2 (R _C1 , R _C2 , R _{C13 to} R _C13
C18 ) ranged from 10.4% to 5.3%, and Group 3
Reflectance (R _{C5 to} R _C9 ) is in the range of 5.4% to 3.3%.

The representative value of the reflectance of each group is selected from the range of the respective reflectance, and the representative values of groups 1, 2 and 3 are 16.9%, 7.6% and 3.4%, respectively. did.
As shown in Table 2, R _G2 , R _G3 , R
_{It was G4} .

[0079]

[Table 2]

The combinations of the sub-pixel groups C and G were changed to the four combinations shown in FIG. 9, and the above-mentioned voltages V _{C1 to} V _C18 and voltages VG _{1 to} VG ₅ were applied to the sub-pixel groups C and G. Then, the display color of one pixel obtained by all of these combinations is shown in FIG.

Thus, the reflectances R _{C1 to} R _C18 are classified into three groups, three representative values are selected from the reflectance range of each group, and these are _designated as R _G2 , R _G3 , and R _G4. As a result, it was possible to display almost the entire display color in the chromaticity locus.

Example 3 In the liquid crystal display device described with reference to FIGS. 6 to 8, the reflectance R
_{G1 to} R _G5 are determined according to the equation (1), and their reflectances R _G1 to
Example 3 was carried out by setting R _G4 as shown in Table 4.

[0083]

[Table 4]

At this time, R _G1 in the equation (4) is the voltage region G
The maximum reflectance was set to the constant a = 0.35.

The operation of the sub-pixel groups C and G was changed to the four ways shown in FIG. 9, and the above-mentioned voltages V _{C1 to} V _C18 and voltages V _{G1 to} V _G5 were applied to the sub-pixel groups C and G. Then, the display color of one pixel obtained by all these combinations is shown in FIG.

As described above, by setting the maximum reflectance in the voltage region G to R _G1 and setting the constant a = 0.35, it is possible to display almost the entire display color in the chromaticity locus.

Comparative Example In the liquid crystal display device of Example 1, the reflectances R _G2 , R _G3 ,
R _G4 was changed as shown in Table 5 to give a comparative example. That is, the reflectances R _G2 , R _G3 , and R _G4 are set so that the minimum reflectance R _G1 and the maximum reflectance R _{G5 in} the voltage region G are divided into four equal parts. It was.

[0088]

[Table 5]

The operation of the sub-pixel groups C and G is changed to four ways shown in FIG. 9, and the above-mentioned voltages V _{C1 to} V _C18 and voltages V _{G1 to} V _G5 are applied to the sub-pixel groups C and G, The display color of one pixel obtained by all of these combinations is shown in FIG.

As is apparent from FIG. 13, the display colors according to this comparative example are unevenly distributed near the C light source,
In the areas corresponding to blue, purple, and magenta (the right direction, the lower right direction, and the downward direction of the C light source in FIG. 13), the display color distribution is sparse.

Therefore, as in this comparative example, the voltage region G
It is understood that if the minimum reflectance and the maximum reflectance in the inside are simply equally divided and the respective reflectances R _{G1 to} R _GQ are determined, it is impossible to display the display color over almost the entire area within the chromaticity locus.

In the above-described embodiments of the present invention, the layer structure of the liquid crystal layer has a homogeneous alignment. However, the present invention is not limited to this, and the same effect can be obtained by implementing the layer structure having a twist. . Also, the shape of the subpixel is
The same effect can be obtained not only by the shape shown in FIG. 9 but also by implementing other shapes.

[0093]

According to the present invention, since the hues of the display obtained by the combination of the color display and the achromatic color display are evenly distributed on the chromaticity coordinates, a large number of display colors can be obtained and high color purity can be obtained. In addition, a high-quality reflective color liquid crystal display device having a large number of display colors can be easily obtained.

[Brief description of drawings]

FIG. 1 is a display characteristic diagram of an embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a characteristic diagram showing an example of applied voltage dependency of hue and color purity of each sub-pixel in a conventional example of a liquid crystal display device using a birefringence interference color of reflected light.

FIG. 3 is a characteristic diagram showing an example of applied voltage dependency of reflectance of each sub-pixel in a conventional example of a liquid crystal display device using a birefringence interference color of reflected light.

FIG. 4 is an explanatory diagram showing an example of a pixel and sub-pixels constituting the pixel in a liquid crystal display device that utilizes a birefringence interference color of reflected light.

FIG. 5 is a characteristic diagram for explaining a method of controlling hue and color purity in a conventional example of a liquid crystal display device using a birefringence interference color of reflected light.

FIG. 6 is a plan view of a pixel in an embodiment of the liquid crystal display device according to the present invention.

FIG. 7 is a partial cross-sectional view of a pixel in an embodiment of the liquid crystal display device according to the present invention.

FIG. 8 is a partial cross-sectional view of a pixel in an embodiment of the liquid crystal display device according to the present invention.

FIG. 9 is an explanatory diagram of a combination of subpixel groups in an embodiment of the liquid crystal display device according to the present invention.

FIG. 10 is a characteristic diagram showing a distribution of display colors on the chromaticity diagram according to the first embodiment of the present invention.

FIG. 11 is a characteristic diagram showing a distribution of display colors on the chromaticity diagram according to the second embodiment of the present invention.

FIG. 12 is a characteristic diagram showing a distribution of display colors on a chromaticity diagram according to Example 3 of the present invention.

FIG. 13 is a characteristic diagram showing a distribution of display colors on a chromaticity diagram according to a comparative example.

FIG. 14 is a characteristic diagram showing a distribution of display colors on a chromaticity diagram in the liquid crystal display device according to the present invention.

[Explanation of symbols]

 10 Lower Substrate 20 Gate Electrode 25 Insulating Film 27, 27 ′ Scan Line 30 i-Type Semiconductor Layer 35 Reference Electrode 38 Storage Capacitance 40 Source Electrode 45 Drain Electrode 50 Flattening Film 55 Through Hole 57 Pixel Electrode 60 Organic Alignment Film 70 Liquid Crystal Layer 80 Upper Substrate 75 Common Electrode 80 Upper Substrate 90, 91 Phase Plate 95 Polarizing Plate SP1 Subpixel 1 SP2 Subpixel 2

Claims (5)

[Claims] 1. A color display is provided in a voltage range C, and an achromatic display is provided in a voltage range G, each of which is provided with an independently controllable pixel composed of n (n ≧ 2) subpixels.
In a liquid crystal display device using a birefringence interference color due to reflected light to display a hue, a group of m subpixels (0≤m≤n) of each subpixel and nm The sub-pixels are divided into two groups and are configured to be operated by applying a voltage within the voltage range C and a voltage within the voltage range G to each of the sub-pixels. Select the Q type voltage value from
The voltage values V _{G1 to} V _GQ are set in order from the highest reflectance R _G of the sub-pixels according to the respective voltage values, and the reflectances when the respective voltage values V _{G1 to} V _GQ are applied are R _G1 to R _G , respectively.
_{If GQ} , then the x (1 ≦ x ≦ Q) th reflectance RG _X is configured to be expressed as R _GX = R _G1 × a ^ (x−1) under the constant a (<1). A liquid crystal display device characterized by the above. 2. The liquid crystal display device according to claim 1, wherein the constant a is 0.5 or less. 3. A color display is provided in the voltage range C, and an achromatic display is provided in the voltage range G, each of which is provided with an independently controllable pixel composed of n (n ≧ 2) sub-pixels.
In a liquid crystal display device of a type that uses a birefringence interference color due to reflected light to perform a hue display, the sub-pixel includes a group of m (0≤m≤n) sub-pixels for each pixel and nm. The sub-pixels are divided into two groups and are configured to be operated by applying a voltage within the voltage range C and a voltage within the voltage range G to each of them. Select the voltage value of Q type,
The voltage values V _{G1 to} V _GQ are set in order from the highest reflectance R _G of the sub-pixels according to the respective voltage values, and the reflectances when the respective voltage values V _{G1 to} V _GQ are applied are R _G1 to R _G , respectively.
_GQ is the reflectance R _G1 and the reflectance R _GQ are respectively the maximum reflectance and the minimum reflectance within the voltage range G, and the relationship between the reflectance R _G2 and the reflectance R _{G (Q-1)} is 0.1. A liquid crystal display device characterized in that it can be expressed as × _RG2 > _{RG (Q-1)} . 4. A color display is provided in the voltage range C, and an achromatic display is provided in the voltage range G, each of which is provided with an independently controllable pixel composed of n (n ≧ 2) sub-pixels.
In a liquid crystal display device of a type that uses a birefringence interference color due to reflected light to perform a hue display, the sub-pixel includes a group of m (0≤m≤n) sub-pixels for each pixel and nm. The sub-pixels are divided into two groups and are configured to be operated by applying a voltage within the voltage range C and a voltage within the voltage range G to each of the sub-pixels. Select the voltage value of Q type,
The voltage values V _{G1 to} V _GQ are set in order from the highest reflectance R _G of the sub-pixels according to the respective voltage values, and the reflectances when the respective voltage values V _{G1 to} V _GQ are applied are R _G1 to R _G , respectively.
_{When GQ} is set, the reflectance R _G1 and the reflectance R _GQ are respectively set to the maximum reflectance and the minimum reflectance within the voltage range G, and the voltage V _{C1 to} V _CP of the P type (P ≧ Q) within the voltage range C is applied. The reflectance of R _C1 ~
If R _CP is used, the persons having similar reflectances among the reflectances R _{C1 to} R _CP are classified into Q-2 groups, and these are grouped in descending order of reflectance into groups 2 to (Q-1). , And reflectivity R _{G2 to} R _{G (Q-1)} are group 2 to group, respectively.
A liquid crystal display device characterized in that it is included in the reflectance range of (Q-1). 5. The invention according to claim 1, wherein the sub-pixels have areas X ₁ to X _{1 in} order from a smaller area.
X _n , the area X _{y of the} y-th (1 ≦ y ≦ n) sub-pixel
Is configured so that X _y = X1 × 2 ^ (y-1).