JPH09113868A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make many color displays with a small number of pixels by generating the hue of plural subordinate pixels, pixel by pixel, as desired, displaying the remaining subordinate pixels colorlessly or with the complementary hue, and adjusting the chroma. SOLUTION: A color signal, a pure-color signal, and an achromatic signal are separated by a signal separation part 40. A comparator 41 detects data having a minimum value among respective components of the primary colors Er, Eg, and Eb and a subtracter 42 calculates the differences from the respective components. Then a voltage source 42 generates gradation voltages corresponding to the separated pure-color signal and achromatic signal and the respective gradation voltages are applied by allotting the subordinate pixels to the pure- color signal and achromatic signal by a switch part 48. Then a comparator 49 detects the intensity of the pure-color signal, switches 51 and 52 are switched with the output of a decoder 50, and a switch part 53 is controlled to connect the subordinate pixels to a terminal Vh of the voltage source so that the maximum value is proportional to the area of subordinate pixels selected as pure- color subordinate pixels. The remaining subordinate pixels are applied with the gradation voltage Vc corresponding to the achromatic signal.

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 capable of bright color display, and more particularly to a reflective type color liquid crystal display device and its driving circuit.

[0002]

2. Description of the Related Art Liquid crystal display devices are thin and light, and are therefore widely used as displays for portable information terminals. The liquid crystal is a light-receiving element that does not emit light by itself, and can be driven with a low voltage of several volts. Therefore, a reflection-type liquid crystal element, which is provided with a reflector on the back surface and is illuminated by external light to view a display, has extremely low power consumption.

However, a reflection type liquid crystal display device is usually a monochrome display, and a color display is a transmission type with a backlight placed behind it. That is, for color display, a method is used in which three pixels are covered with fine color filters of three primary colors of red, blue, and green, and white incident light is absorbed by the color filters so that each transmitted light becomes three primary colors. There is.
When all three pixels of red, blue, and green are in a transmissive state, white display is performed, and the brightest state is obtained.

Therefore, the incident light is absorbed by the color filter and the transmittance becomes 1/3 or less. Moreover, since a polarizing plate is usually used in the liquid crystal display element, one polarized light is absorbed, and the transmittance becomes half or less. Therefore, a liquid crystal display element using a color filter requires a backlight that consumes a large amount of power, which increases the thickness and weight, and also impairs the feature of low power consumption. In addition, since the color filter has a complicated manufacturing process, the cost is high, and the manufacturing cost of the liquid crystal display device is high.

On the other hand, in order to perform color display, a liquid crystal display element which utilizes color development due to a birefringence effect without using a color filter has been reported (for example, Shoichi Matsumoto and Ichio Kakuda, "Latest Liquid Crystal Technology"). , Pp. 130-132).

In this system, for example, a nematic liquid crystal having a positive dielectric anisotropy is horizontally aligned, and an angle of 45 ° is formed in the alignment direction.
A polarizing plate having a polarization axis of degrees direction and sandwich the liquid crystal layer on a polarizing plate which is orthogonal thereto, I = I ₀ sin ² for the transmitted light intensity I due to birefringence incident light intensity I ₀ (πΔnd / λ) ... (Expression 1) Where λ is the wavelength of the incident light, d is the thickness, and Δn
Is the birefringence anisotropy of the liquid crystal.

From this equation, the intensity of transmitted light depends on the wavelength and exhibits a color corresponding to the birefringence amount (product of refractive index anisotropy Δn and thickness d) of the liquid crystal layer. Since Δnd becomes smaller as the liquid crystal molecules rise due to the voltage application, the wavelength with high transmittance changes according to the applied voltage, and the display color can be controlled. In the case of the reflection type, since the incident light travels back and forth through the liquid crystal panel and has an intensity distribution obtained by squaring (Equation 1), the wavelength dependence becomes more remarkable and the color purity is improved.

A conventional example of displaying about four colors by simple matrix drive using a super twisted nematic (STN) liquid crystal with the same birefringence effect has also been reported (for example, Japanese Patent Laid-Open No. 6-301006). ).

A liquid crystal display device in which the STN liquid crystal cell is driven by using a TFT has also been disclosed (Japanese Patent Laid-Open No. 7-18753).
-159752). By driving the TFT, it becomes possible to easily and accurately apply the voltage value of the color to be displayed. In the above-mentioned Japanese Patent Laid-Open No. 7-159752, when displaying some birefringent colors such as red, green, and blue that can be displayed by one pixel, drive voltage values are prepared for the number of birefringent colors to be displayed. , A method of switching a drive voltage to be applied according to a color signal, and a drive circuit are disclosed.

[0010]

Color display using a color filter is expensive, and the reflection type display is very dark.

On the other hand, in the system in which the color is variable by using the birefringence effect without using the color filter, the color that changes according to the voltage is determined by the structure of the liquid crystal panel, and the specific color on the chromaticity diagram is determined. Only can be displayed.

Further, although the color changes depending on the voltage, gradation display, that is, brightness adjustment cannot be performed.

Due to these restrictions, the method based on the birefringence effect has a problem that the number of display colors is extremely small as compared with a transmissive liquid crystal panel using a color filter, and it can be used only for a limited purpose. .

Further, the driving circuit of the color liquid crystal display device using the birefringence effect is also presented only as a means for displaying a limited birefringence color.

[0015]

In order to solve the above problems, in a liquid crystal display device of the present invention, one pixel is composed of a plurality of sub-pixels, and a nematic liquid crystal is sandwiched between opposed electrodes forming the sub-pixels. A liquid crystal layer, a polarizer in front of the liquid crystal layer, a retardation plate between the polarizer and the liquid crystal layer, and a reflector behind the liquid crystal layer are provided, and a voltage is applied between the counter electrodes. By controlling the amount of birefringence of the nematic liquid crystal, thereby changing the color of each of the plurality of subpixels by a birefringence effect, in a subpixel of the plurality of subpixels, The same color as the hue displayed on the one pixel, the remaining sub-pixels are achromatic colors or complementary colors of the hue, and the sum of the areas of the remaining sub-pixels is controlled according to the saturation of the one pixel. To maximize the number of display colors It can be increased.

That is, when a plurality of fine pixels (sub-pixels) of different colors are arranged adjacent to each other, the color of the unit pixel, which is a set of these sub-pixels, appears as an intermediate color of the colors of the sub-pixels. Is the principle of.

Therefore, if different colors are displayed on a plurality of adjacent fine sub-pixels due to the birefringence effect, an intermediate color other than the color due to the birefringence effect can be expressed in the unit pixel which is a set of these sub-pixels. Of course.

The problem is, unlike the case where a color filter is used, how efficiently a large number of gradations can be displayed due to the birefringence effect in which the brightness cannot be controlled. For example, even when white is represented by an additive color mixture, since the pixel colors are variable, complementary colors such as red and cyan or green and magenta can be used, or red, blue, green and cyan, magenta, and yellow can be used. You can say that there are countless combinations because you can mix colors.

In the color development due to the birefringence effect, considering the simple structure without using the retardation plate, the substantial Δnd of the liquid crystal is 0.
.About.0.3 .mu.m, it is possible to adjust the brightness of colors from black to gray, white and achromatic colors, and as .DELTA.nd increases,
It changes from yellow, red, purple, blue, and green.

In the liquid crystal display device of the present invention, a desired hue to be displayed in the unit pixel is developed in a part of the plurality of sub-pixels, and an achromatic color or a complementary color is displayed in the remaining sub-pixels. Adjust the degree. In the achromatic region, gradation display is possible even with the birefringence effect, so that the degree of freedom in saturation adjustment is greatly increased by finely adjusting the brightness. When the hue of the complementary color is displayed on the remaining sub-pixels, it is an area where gradation cannot be displayed, so it is not possible to adjust the saturation very much, but it is possible to display a very low saturation that cannot be produced by mixing with an achromatic color. Therefore, it is preferable to use them properly according to the saturation of the unit pixel.

The lightness of the color can be changed by controlling the number of sub-pixels displaying a desired hue and the lightness and number of achromatic sub-pixels. Desirably, the areas of the sub-pixels are made different from each other, and it is preferable to select the sub-pixels having an achromatic color according to the saturation of the unit pixel.

As a result, not only the number of gradations of lightness increases, but also the variable range of saturation expands. For example, considering the case where there are two sub-pixels, if each sub-pixel has the same area, when displaying red, there are three gradations of red + red, red + black, and black + black, and the saturation is red and white. Colors with lower saturation than the 1: 1 mixture of are out of the adjustment range. However, if the area of the sub-pixel is 1: 2, the number of gradations is 4, and the saturation can be finely adjusted to a low saturation range in which red and white are 1: 2.

Thus, in the liquid crystal display device of the present invention,
In a color display without a color filter using the birefringence effect, a very large number of colors can be expressed, and since hue, saturation, and lightness are separately controlled, signal processing can be easily performed.

Further, in the drive circuit of the liquid crystal display element of the present invention, each of the three components of the three primary colors of the color signal input to the liquid crystal display device in which the pixel changes its color depending on the applied voltage To obtain a pure color signal by subtracting the minimum value from among the three values, to obtain an achromatic color signal in which each component of the three primary colors has the minimum value, and to separate into a pure color signal and an achromatic color signal; And a voltage generation source that generates a plurality of gradation voltages corresponding to each of the achromatic signals, and a switch unit that switches connection between each of the plurality of sub-pixels and the plurality of gradation voltages of the voltage generation source. As a result, an extremely large number of color displays can be realized.

That is, in the drive circuit for realizing the above liquid crystal display element, the color signal is separated into the pure color signal and the achromatic color signal by the signal separation section, and the voltage generation source and the switch section
It realizes the function of applying the voltage corresponding to the pure color signal to the pure color sub-pixel that adjusts the hue of the pixel to be displayed and applying the voltage corresponding to the achromatic color signal to the achromatic color sub-pixel that adjusts the saturation. is there.

Desirably, the connection of the switch section is set so that the sum of the areas of the sub-pixels connected to the gradation voltage corresponding to the pure color signal is proportional to the maximum value of the respective components of the three primary colors of the pure color signal. And a gray scale voltage corresponding to the achromatic color signal is determined so that the quotient obtained by dividing the component of the achromatic color signal by the sum of the areas of the achromatic color subpixels other than the subpixel is proportional to the brightness of the achromatic color subpixel. As a result, a desired color can be displayed.

That is, the connection of the switch section is set so that the sum of the areas of the sub-pixels connected to the grayscale voltage corresponding to the pure color signal is proportional to the maximum value of the respective components of the three primary colors of the pure color signal, And determining a gradation voltage corresponding to the achromatic color signal such that the quotient obtained by dividing the component of the achromatic color signal by the sum of the areas of the achromatic color subpixels other than the subpixel is proportional to the brightness of the achromatic color subpixel. With this, the selection of the pure color subpixels and the achromatic color subpixels can be flexibly and optimally performed according to the color signal, so that more and more accurate color expression can be performed with a small number of pixels.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Specific examples will be described in detail below.

FIG. 1 is a plan view of a liquid crystal display device of the present invention, and FIG. 2 is a cross-sectional view taken along the alternate long and short dash line in FIG. In FIG. 2, TFT elements 3 and 4 are formed on the lower substrate 1 made of glass, and the sub-pixel electrodes 10 and 11 made of transparent indium tin oxide (ITO) are connected to the drains of the respective TFT elements. There is.

A common electrode 12 made of ITO is formed on the upper substrate 2 so as to cover the entire display screen. The polyimide alignment film 5 is printed on the upper and lower substrates, and the gate lines 6 and 45 of FIG.
The upper and lower substrates were subjected to rubbing treatment in a direction of forming an angle of 0 °. These substrates were laminated by applying a sealing resin on the periphery with a spherical spacer of 5.5 μm interposed therebetween.

Fluorine-based positive type (positive dielectric anisotropy) nematic liquid crystal (Δn is 0.183) was injected into this cell,
The liquid crystal molecules 7 in FIG. 1 were homogeneously aligned. A polarizing plate 14 in which the polarization axes of the cell are orthogonal to each other as shown in FIG.
A uniaxially stretched retardation plate 14 of polyarylate was placed between the polarizing plate 14b and the cell, and a reflection plate 15 was placed behind the polarizing plate 14a. The polarization axis of the polarizing plate 14b is set to a direction 16 which forms 45 ° with the alignment direction of the liquid crystal,
a is the direction orthogonal to this, and the phase difference (Δnd) of the polyarylate is 980 nm, and these polarizing plate phase plates are placed on the upper substrate with the slow axis thereof oriented in the direction 17 orthogonal to the liquid crystal alignment direction. Pasted together

FIG. 3 is a chromaticity diagram showing a color change when a voltage is applied to one subpixel of this liquid crystal display element.
With no electric field, it is black and the liquid crystal starts to move from the voltage of 1.1V.
The brightness gradually becomes bright until it becomes white at 1.7 V, but in the chromaticity diagram, it is almost achromatic by only slightly moving from the black circle 31 to the white circle 32.

When, for example, polycarbonate having a smaller wavelength dispersion of Δn than polyarylate is used as the retardation plate,
Since black becomes more bluish, it is preferable to use a retardation plate such as polyarylate or polysulfur whose wavelength dependence of Δn is close to that of liquid crystal.

When the voltage is further increased from 1.7V,
From yellow (point 33) to red (point 34), purple, blue (point 3)
5), the color changes to green (point 36). Correspondence between the voltage applied to the liquid crystal and the color of one subpixel (birefringence color) (Table 1)
Shown in

[0035]

[Table 1]

The sub-pixels which develop color as described above according to the applied voltage are driven by the TFT elements with the area of 1: 2 as shown in FIG. In the case of a personal computer, data of a color image to be displayed is created from four bitmaps of red, green, blue, and intensity, and a luminance signal and two color difference signals are sent as a television video signal.

However, in any case, the signals finally sent to the display are light intensity signals of three colors of red, blue and green. If red, green, and blue intensities are treated as 2-bit data as Er, Eg, and Eb, the color signal of an arbitrary pixel is represented by a vector (Er, Eg, Eb). However, each component is assumed to have a value of 0 to 3.

FIG. 4 shows a block diagram of a driving circuit of the present invention which processes the color signals to generate a driving voltage for driving each sub-pixel.

First, the signal separation unit 40 separates a color signal into a pure color signal and an achromatic color signal. Er, Eg, Eb 3
Of the respective components of the primary colors, the minimum value data is detected by the comparator 41, and the difference from the respective components is calculated by the subtractor 42. For example, Eg
Is the minimum, (Er, Eg, Eb)-(Eg, Eg, Eg) = (Er-Eg, 0, Eb-Eg) (Equation 2) The signal represents the same pure color (color with the highest saturation) and hue as the signal, while
All three components have the minimum value Eg (Eg, Eg, Eg)
Is an achromatic signal obtained by extracting the achromatic component of the color signal.
The comparator 41 outputs a flag signal 47 indicating which color has the minimum value. If there are two minimum values,
Either signal will do.

Next, a grayscale voltage corresponding to each of the separated pure color signal and achromatic color signal is generated by the voltage source 43, and the respective grayscale voltages are supplied to the sub-pixels by the switch section 48 as pure color pixels and achromatic color pixels. And then apply.

When the pure color signal of (Equation 2) is the 0 vector, the pixel is achromatic, but in other cases, the hue is between red and blue. The color mixture ratio of how much blue is mixed based on red is expressed by the following equation (3): Kb = (Eb-Eg) / {(Er-Eg) + (Eb-Eg)} (Equation 3) The blue component of the pure color signal is divided by the total sum of each component (sum of red and blue) to detect the bluishness Kb. That is, when the blue component is 0, that is, when it is completely red, the bluishness is 0.
In the case of perfect blue, the red component becomes 0, so the bluishness becomes 1.

Assuming that the voltage indicating red in the sub-pixel is Vr and the voltage indicating blue is Vb, the gradation voltage Vh corresponding to a pure color signal is approximately the following Vh = Vr + Kb (Vr-Vb). It becomes like Formula 4). To be exact, nonlinear conversion should be performed, but in this embodiment, since the number of gradations is small, linear conversion is used.

The arithmetic operation of the equations (3) and (4) is performed by the arithmetic unit 44.
Do with. Even when the hue of the pixel color signal is between blue and green, the same calculation as above may be performed. Therefore, depending on the flag signal of the comparator 41, the hue may be between red and blue or between blue and green. Or select.

However, when the hue is between green and red,
Since the voltages for coloring green and red are discontinuous, the setting of the applied voltage Vh to the pure color sub-pixel is different from the above. The hue vector and the redness degree Kr are respectively (Er, Eg, Eb)-(Eb, Eb, Eb) = (Er) as in (Equation 2) and (Equation 3).
-Eb, Eg-Eb, 0) Calculated as Kr = (Er-Eb) / (Er + Eg-2Eb), but when Kr is 0.5, Vh is set to the voltage Vy at which yellow is displayed in a birefringent color. To do.

In this example, it was about 2.1V. K
When r is between 0.5 and 1.0, it is a color between yellow and red, so Vh = 2 × (Kr−0.5) (Vr−Vy) + Vy (Formula 5) is set. To do.

On the other hand, when Kr is less than 0.5, it is an intermediate color between green and yellow, but as shown in FIG. 3, when the voltage is raised from the voltage Vg for making it green, yellow green can be displayed. At this time, if a voltage is set as Vh = Vg + Kr (Equation 6), it is possible to display a color between approximately yellow and green. The arithmetic unit 45 performs the operations according to (Equation 5) and (Equation 6). The results of the arithmetic units 44 and 45 are selected by the switch 53 by the flag 47 to obtain the final Vh.

By the way, since only the hue of the pure color sub-pixel changes depending on the voltage, its brightness must be controlled by the area of the sub-pixel. Therefore, by detecting the intensity of the pure color signal, that is, the maximum value of the component of (Equation 2) with the comparator 49, and switching the switches 51 and 52 with the output of the decoder 50,
When the maximum value is 3, both the sub-pixels 10 and 11 are arranged so that the maximum value and the area of the sub-pixel selected as the pure color sub-pixel are proportional to each other.
When it is 2, only the sub-pixel 10 is connected, and when it is 1, only the sub-pixel 11 is connected to the Vh terminal of the voltage source.

Then, the gradation voltage Vc corresponding to the achromatic signal is applied to the remaining sub-pixels. Since the lightness of the achromatic subpixel is Eg, a value obtained by dividing Eg by the sum S of the areas of the achromatic subpixels is the lightness of each achromatic subpixel. The sum S of areas is equal to the maximum value of the comparator 49.

As described above, since the brightness of the achromatic sub-pixel can be controlled by the voltage, the voltage Vc corresponding to the brightness Eg / S is calculated by the calculator 46 based on (Equation 5) and output. That is, Vc = (Vw-Vth) * Eg / S + Vth (Equation 7), where Vth is the threshold voltage at which the response of the liquid crystal starts from the initial black display and Vw is the voltage at which the liquid crystal becomes white. However, when the number of colors is increased by a method such as increasing the number of pixels as compared with the present embodiment and strict color reproduction is performed, the correction coefficient a is expressed by the following equation: Vc = a (Vw−Vth) × Eg / S. Need to multiply. Here, the correction coefficient a is for correcting the difference in color saturation between the color due to the birefringence effect and the color mixture of the three primary colors.

As shown in the chromaticity diagram of FIG. 3, in the color display by the birefringence effect, the color locus 32 draws an arc, and in the intermediate hues of red, blue, and green, the two primary colors are linearly mixed. It passes outside the locus 37 of different colors. Therefore, the blueness Kb is 0.5
The closer to, the higher the brightness of the achromatic subpixel needs to be.
For example, a = (0.5− | Kb−0.5 |) × 1.05 may be set.

The gradation voltages of the switches 51 and 52 are transferred to a conventional source side driving LSI via a sample hold circuit and applied to the TFT in synchronization with a gate signal to drive each subpixel.

The above voltages Vr, Vg and Vb are as shown in (Table 1) in this embodiment. However, these voltages slightly change depending on the temperature, and the voltage in Table 1 is a value at 25 ° C.

Specifically, for some color data,
Based on (Equation 2) to (Equation 7), the voltages V10 and V11 applied to the sub-pixels 10 and 11, the color of each sub-pixel, and the color of the pixel that is a set of sub-pixels are calculated as follows. Examples are shown in Table 2).

[0054]

[Table 2]

In the first line, since the color data for Er, Eg, and Eb is 3, the hue vector is 0, which is an achromatic color, and the sub-pixels 10 and 11 are also white. In the second line, the minimum component of color data is Er = 1, so the hue vector is (0,1,2) from (Equation 2), and the hue between blue and green is Kg = 1 / Equation from (Equation 3). Since (1 + 2) = 1/3 and the greenness is 1/3 blue, Vh = Vb + Kg (Vg−Vb) = 3.2 + 1/3 × (4.0−) from (Equation 4) and (Table 1). 3.2) = 3.47 (V).

At this time, the maximum value of the hue vector is Eb =
Since it is 2, V10 = Vh for the sub-pixel 10 for hue adjustment.
Is applied, a greenish blue color is obtained. When the brightness Er of the sub-pixel 11 that is the other saturation adjustment sub-pixel is 1, the area S
Since (= 1), V11 = Vc = Vw = 1.7 (V) from (Equation 5).

In the case of the third row in (Table 2), the minimum value of the color data is Eb, which is a hue between green and red. Therefore, applying (Equation 6) and (Equation 7), Kr = 0.5 Vh = Vy = 2.1 (V). Since the maximum value of the hue vector is 1, the smaller subpixel 11 is selected for hue adjustment, and the saturation adjustment subpixel 10 is selected.
Should be white.

In the color data of the fourth row, the minimum value is Er = 0, the hue vector is (0,3,3), and Kg = 0.5 is blue-green. Therefore, Vh = 3.6 V, Since the maximum value of the hue vector is 3, both sub-pixels 10 and 11 are for hue adjustment, and therefore V11 = V10 = Vh.

With respect to the color data on the fifth line, since the hue vector is (1, 0, 0), the sub-pixel 11 is made red and the other sub-pixel 10 is used for saturation adjustment. Since the brightness of the sub-pixel 10 is 1, Vc = (1.7-1.1) × 1/2 + 1.1 = 1.4 (V) from (Equation 7). At this time, the sub-pixel 10 becomes gray (50% of the brightness of white).

Since the color data (2, 0, 0) in the final sixth row is red with a lightness of 2 and the hue vector is the same, the sub-pixel 10
The voltage may be set so that is red and the sub-pixel 11 is black.

In this embodiment, as shown in FIG.
Although 5 is placed behind the liquid crystal layer to make it a reflection type, a bright transmissive color liquid crystal without a color filter can be realized by removing the reflector and placing a light source at the back.

Further, if the number of sub-pixels having different areas is increased, the number of colors can be made extremely large, and a display close to full color is possible.

Further, in the present embodiment, all of the pure color pixels have the same color, but a plurality of sub-pixels may be made to develop different colors and the color corresponding to the pure color signal may be displayed by additive color mixture. For example, when a pure color signal corresponds to blue-green, two or more sub-pixels of blue and green may express the intermediate color blue-green. Even in this case, it is possible to change the selected sub-pixel according to the intensity of the pure color signal and adjust the saturation with the remaining sub-pixels, and the present invention can exert the effect.

Further, although the liquid crystal is driven by the TFT element in this embodiment, the number of colors can be increased by performing the same signal processing even in the case of driving by a two-terminal active element or simple matrix driving. Can be achieved and the effect can be demonstrated.

As described above, the liquid crystal display device and its driving circuit of the present invention can express a great number of colors using a bright color liquid crystal at low cost without using a color filter.

[0066]

The liquid crystal display device and its driving circuit of the present invention can display a great number of colors with a small number of pixels in a color liquid crystal device with a birefringence effect that can change the color by voltage without using a color filter. As a result, a bright color liquid crystal display device can be realized at low cost. In particular, full-color display of reflective liquid crystal, which has been difficult in the past, can be realized.

[Brief description of the drawings]

FIG. 1 is a plan view of a liquid crystal display element as an embodiment of the liquid crystal display element of the present invention.

FIG. 2 is a cross-sectional view of a liquid crystal display element of an embodiment of the liquid crystal display element of the present invention.

FIG. 3 is a chromaticity diagram of an example of the liquid crystal display device of the present invention.

FIG. 4 is a block diagram of a drive circuit for a liquid crystal display element of the present invention.

[Explanation of symbols]

 1 Lower Substrate 2 Upper Substrate 3, 4 TFT Element 5 Alignment Film 6 Gate Line 7 Liquid Crystal Molecule 8 Liquid Crystal Molecule 9 Dichroic Dye 10, 11 Sub-Pixel Electrode 12 Common Electrode 13 Phase Difference Plate 14a, 14b Polarizing Plate 15 Reflector

Claims (8)

[Claims] 1. A liquid crystal layer in which a pixel is composed of a plurality of sub-pixels, and nematic liquid crystal is sandwiched between electrodes forming the sub-pixels,
It has a polarizer adjacent to the liquid crystal layer and a retardation plate, and controls the birefringence amount of the nematic liquid crystal by applying a voltage between the electrodes, and the birefringence effect causes the birefringence of the plurality of sub-pixels to increase. In a liquid crystal display element that makes each pixel a desired color corresponding to a color signal by varying each color, the color signal is separated into an achromatic color signal and a pure color signal, and selected according to the intensity of the pure color signal. A voltage corresponding to the pure color signal is applied to some or all of the plurality of subpixels,
A liquid crystal display device characterized in that a voltage corresponding to an achromatic signal is applied to the remaining sub-pixels. 2. The area of each of the plurality of subpixels is made different from each other, and the sum of the areas of the subpixels selected according to the intensity of the pure color signal is proportional to the intensity of the pure color signal, and the area of the remaining subpixels. 2. The liquid crystal display element according to claim 1, wherein the product of the lightness and the lightness is proportional to the intensity of the achromatic signal. 3. A liquid crystal layer, a retardation plate, and a polarizer, and due to the birefringence effect, the color of each subpixel is an achromatic color having different brightness from black to white and at least three colors of red, blue, and green. The liquid crystal display element according to claim 2, which develops color in accordance with an applied voltage. 4. A reflector is provided behind the liquid crystal layer.
4. The liquid crystal display device according to any one of 3 to 3. 5. A liquid crystal layer sandwiched between two polarizers, a retardation plate between at least one of the two polarizers and the liquid crystal layer, and a light source behind the liquid crystal layer and the polarizer. The liquid crystal display element according to claim 1, which comprises: 6. A three-color signal input to a liquid crystal display device, in which a pixel is composed of a plurality of sub-pixels whose color changes according to an applied voltage.
From each component of the primary color, the minimum value of each component is subtracted to obtain a pure color signal, and an achromatic color signal in which each component of the three primary colors has the minimum value is obtained to obtain the pure color signal and the achromatic color signal. A signal separation unit for separating, a voltage generation source for generating a plurality of grayscale voltages corresponding to each of the pure color signal and the achromatic color signal, each of the plurality of subpixels, and a plurality of grayscale voltages of the voltage generation source. 2. A drive circuit for a liquid crystal display device, comprising: 7. The connection of the switch unit is set such that the sum of the areas of the sub-pixels connected to the grayscale voltage corresponding to the pure color signal is proportional to the maximum value of the respective components of the three primary colors of the pure color signal, The gradation voltage corresponding to the achromatic color signal is determined so that the quotient obtained by dividing the component of the achromatic color signal by the sum of the areas of the achromatic color subpixels other than the subpixel is proportional to the brightness of the achromatic color subpixel. The drive circuit for the liquid crystal display element according to claim 6. 8. When generating a gradation voltage corresponding to a pure color signal in a voltage generation source, at least three reference colors and gradation voltages corresponding to the reference colors are set in advance, and the pure color signal is set. A pure color corresponding to a signal is mixed with two of the reference colors to obtain a color mixture ratio, which is correlated with the color mixture ratio to interpolate a voltage between gradation voltages of the two colors to obtain the color mixture ratio. 7. The drive circuit for a liquid crystal display element according to claim 6, wherein a grayscale voltage corresponding to a pure color signal is generated.