JPH1172784A - Color liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive reflection type color liquid crystal display device making a background color black and a deep color and capable of a bright and high chroma negative type color display. SOLUTION: A pair of polarizing plates 8, 9 are arranged on both sides of a liquid crystal element 22 constituted so as to hold a nematic liquid crystal 7 between a pair of substrates 1, 4 respectively having electrodes, and a twisted phase difference plate 10 is arranged between its one side polarizing plate 9 and the liquid crystal element 22. Then, an angle between absorption axes of a pair of polarizing plates 8, 9 is made within the range of 60 deg.-120 deg., and the Δnd value of the liquid crystal element 22 shown by a product between the difference Δn of the birefringence of the nematic liquid crystal 7 and a gap (d) between a pair of substrates 1, 4 is made within the range of 1500 nm-1800 nm, and the Δnd value of the twisted phase difference plate 10 shown by the product between the difference Δn of the birefringence of the twisted phase difference plate 10 and the thickness (d) is made within the range nearly equal to the Δnd value of the liquid crystal element 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color liquid crystal display device, and more particularly to a color liquid crystal display device which performs color display by utilizing the birefringence of a liquid crystal element without using a color filter.

[0002]

2. Description of the Related Art There are two types of color liquid crystal display devices: a liquid crystal display device having a built-in color filter, and a liquid crystal display device that performs color display by using the birefringence of liquid crystal without using a color filter. In a liquid crystal display device having a built-in color filter, since one pixel is composed of three dots of R, G, and B, the amount of transmitted light is reduced to about 1/3, and a small fluorescent lamp is usually required as a backlight. It is not suitable for reflective color liquid crystal display devices.

On the other hand, a liquid crystal display device that performs color display utilizing the birefringence of liquid crystal can perform color display with only one pixel by changing the voltage applied to the liquid crystal element. Suitable for liquid crystal display devices.

The following are known as color display devices utilizing the birefringence of liquid crystal. (1) a color liquid crystal display device composed of only a liquid crystal element and a pair of polarizing plates; (2) a color liquid crystal display device composed of a liquid crystal element, a retardation plate and a pair of polarizing plates; Color liquid crystal display device composed of a plate and a pair of polarizing plates,

As a liquid crystal element used in a color liquid crystal display device, a homogeneous liquid crystal element having a twist angle of 0 degree, a TN (twisted nematic) liquid crystal element having a twist angle of about 90 degrees, and a liquid crystal element having a twist angle of 180 degrees to 270 degrees are used. STN (super twisted nematic) liquid crystal elements and the like have been developed.

[0006] A twisted phase difference plate is used, and S is used as a liquid crystal element.
A conventional example of a color liquid crystal display device using a TN liquid crystal element will be described with reference to FIGS. FIG. 18 is a schematic cross-sectional view of the color liquid crystal display device. FIG. 16 is a plan view showing the relationship between the absorption axis of the lower polarizer and the liquid crystal molecule alignment direction of the liquid crystal element when FIG. 18 is viewed from the upper polarizer 9 side. FIG. 17 is a plan view showing the relationship between the absorption axis of the upper polarizing plate and the molecular orientation direction of the torsional retardation plate. Such a color liquid crystal display device is disclosed in, for example, JP-A-7-5457.

As shown in FIG. 18, this color liquid crystal display device has a first electrode 2 made of ITO (indium tin oxide), a first substrate 1 on which an alignment film 3 is formed, and a second electrode made of ITO. A liquid crystal element 20 is formed by sandwiching a twist-aligned nematic liquid crystal 7 between a pair of substrates including a substrate 5 and a second substrate 4 on which an alignment film 6 is formed. Further, a pair of polarizing plates composed of a lower polarizing plate 8 and an upper polarizing plate 9 are arranged with the liquid crystal element 20 interposed therebetween, and a twisted phase difference plate 10 is arranged between the liquid crystal element 20 and the upper polarizing plate 9. The reflection plate 11 is arranged outside the lower polarizing plate 8.

The absorption axes (or transmission axes) of the pair of polarizing plates 8 and 9 are arranged in parallel. Here, the liquid crystal element 20
Is 250 °, and the absorption axis 8a of the lower polarizer 8 shown by a broken line with an arrow in FIG. 16 is aligned with the lower liquid crystal molecule orientation direction 7a, which is the orientation direction of the liquid crystal of the first substrate 1, by 45 °. The upper polarizer 9 forms an angle and is indicated by a solid line with an arrow in FIG.
Is arranged so as to form an angle of 45 ° with the orientation direction 10b of the upper molecule of the torsional retardation plate 10.

Note that 7b in FIG. 16 indicates the orientation direction of the upper liquid crystal molecules, which is the orientation direction of the liquid crystal of the second substrate 4,
In FIG. 17, 10a indicates the orientation direction of the lower molecule of the torsional retardation plate 10.

The difference Δ in birefringence of the nematic liquid crystal 7 is
Δnd value of the liquid crystal element 20 represented by a product of n and a cell gap d which is an interval between the first substrate 1 and the second substrate 2 is 843.
nm. The twist angle of the torsional retardation plate 10 is 250 °, which is opposite to the twist angle of the liquid crystal element 20.
The Δnd value of the torsional retardation plate expressed by the product of the birefringence difference Δn of the torsional retardation plate 10 and the thickness d is also 843 nm.

As shown in FIG. 17, the absorption axis 9a of the upper polarizer 9 and the upper molecular orientation direction 10b of the torsion retarder 10 are 4
Since they are arranged at 5 °, the linearly polarized light incident from the upper polarizing plate 9 becomes elliptically polarized when passing through the torsional retardation plate 10. However, since the upper liquid crystal molecular orientation direction 7b of the liquid crystal element 20 and the lower molecular orientation direction 10a of the twisted phase difference plate are shifted by 90 °, the elliptically polarized light generated by the liquid crystal element 20 and the twisted phase difference plate 10 is completely used. It returns to linearly polarized light and reaches the lower polarizing plate 8. Then, the absorption axis 8 of the lower polarizing plate 8
Since a is parallel to the absorption axis 9a of the upper polarizing plate 9, white display is obtained.

When a voltage is applied between the first electrode 2 and the second electrode 5, the liquid crystal molecules 7 rise and the apparent Δnd value of the liquid crystal element 20 decreases. Therefore, the elliptically polarized light state generated by the twisted phase difference plate 10 cannot be completely canceled by the liquid crystal element 20, and the lower polarizing plate 8 remains in the elliptically polarized light state.
To reach. Therefore, light of a specific wavelength is transmitted, and a plurality of colors are generated.

The light transmitted through the lower polarizing plate 8 is reflected by the reflecting plate 11, passes through the lower polarizing plate 8, the liquid crystal element 20, the twisted phase difference plate 10, and the upper polarizing plate 9 again and exits upward. .
Therefore, a reflection type color display is obtained. In other words, the display is white when no voltage is applied, but as the applied voltage is increased, it becomes possible to display yellow, purple, red and the like.

Next, a phase difference plate is used, and S is used as a liquid crystal element.
A conventional example of a color liquid crystal display device employing a TN liquid crystal element will be described with reference to FIGS. FIG. 21 is a schematic cross-sectional view of the color liquid crystal display device, and FIG. 19 is a plan view showing the relationship between the absorption axis of the lower polarizer and the liquid crystal molecule alignment direction of the liquid crystal element when FIG. 21 is viewed from the upper polarizer 9 side. FIG. 20 is a plan view showing the relationship between the absorption axis of the upper polarizing plate and the slow axis of each retardation plate. Such a color liquid crystal display device is disclosed in, for example, JP-A-8-15691.

In this color liquid crystal display device, as shown in FIG. 21, a liquid crystal element 21 (having the same twist angle as that of the liquid crystal element 20 in FIG. 18 but a different cell gap) and a lower polarizing plate 8 interposed therebetween are provided. A pair of polarizers comprising: a first retarder 15 and a second retarder 16 disposed between the liquid crystal element 21 and the upper polarizer 9;
A reflection plate 11 arranged outside the lower polarizing plate 8.

The absorption axes (or transmission axes) of the pair of polarizing plates 8 and 9 are arranged substantially orthogonally. Here, the twist angle of the liquid crystal element 21 is 250 °,
The absorption axis 8a of the lower polarizing plate 8 shown by a broken line with an arrow in FIG.
Forms an angle of 45 ° with the lower liquid crystal molecule alignment direction 7a which is the alignment direction of the liquid crystal of the first substrate 1, and the slow axis 16a of the second retardation plate 16 shown by a broken line in FIG. 21 is arranged at an angle of 95 ° with respect to the upper liquid crystal molecule orientation direction 7b.
The absorption axis 9a of the upper polarizing plate 9 shown by a solid line with an arrow in FIG.
Of the phase difference plate 15 at an angle of 15 °.

The above-mentioned Δnd value of the liquid crystal element 21 is 1530 nm to 1730 nm. The retardation value of the first retardation plate 15 is 160
At 0 nm, the retardation value of the second retardation plate 16 is 1
550 nm.

Since the absorption axis 9a of the upper polarizing plate 9 and the slow axis 15a of the first retardation plate 15 are arranged at an angle of 15 °, the linearly polarized light incident from the upper polarizing plate 9 ,
When the light passes through the first retardation plate 15 and the second retardation plate 16, the light enters an elliptically polarized state. However, since the upper liquid crystal molecule alignment direction 7b of the liquid crystal element 21 is displaced from the slow axis 16a of the second retardation plate 16 by about 90 °, the first retardation plate 15 and the second retardation plate
The elliptically polarized light generated by the retardation plate 16 is almost returned to the original state, and returns to linearly polarized light to reach the lower polarizing plate 8. Since the absorption axis 8a of the lower polarizing plate 8 is substantially orthogonal to the absorption axis 9a of the upper polarizing plate 9, black display is performed.

Here, when a voltage is applied between the first electrode 2 and the second electrode 5, the molecules of the nematic liquid crystal 7 rise, and the apparent Δnd value of the liquid crystal element decreases. Therefore, the elliptically polarized state generated by the first retardation plate 16 and the second retardation plate 15 cannot be completely canceled by the liquid crystal element 21 and reaches the lower polarizing plate 8 in the elliptically polarized state. Therefore, light of a specific wavelength is transmitted, and a plurality of colors are generated.

The light transmitted through the lower polarizing plate 8 is reflected by the reflecting plate 11, and again the lower polarizing plate 8, the liquid crystal element 21, the second retardation plate 16, the first retardation plate 15, and the upper polarizing plate 9 And the light is emitted upward, so that a reflective color display is obtained. That is, although black is displayed when no voltage is applied, white, red, blue, green, and the like can be displayed as the applied voltage is increased.

[0021]

However, in an actual color liquid crystal display device, the change of the birefringence difference Δn of the liquid crystal material for each wavelength of light is caused by the birefringence difference Δn of the retardation plate or the twisted retardation plate. Therefore, with the arrangement of the conventional polarizing plate as described above, a favorable background color or color could not be obtained.

For a negative display in which the background color is changed to black and the color of the character is changed, the absorption axis 9a of the upper polarizing plate 9 is used.
It is disclosed in the above-mentioned document that this can be achieved by disposing the absorption axis 8a (or transmission axis) of the lower polarizing plate 8 substantially orthogonal to the transmission axis (or transmission axis). No conditions are disclosed, and a reflective color liquid crystal display device capable of displaying a negative color displaying a bright and highly saturated color has not yet been put to practical use.

The present invention has been made in view of such circumstances, and optimizes the arrangement angle of a liquid crystal element and a single retardation plate or a twisted retardation plate and a polarizing plate to change the background color to black or black. It is an object of the present invention to provide a reflective color liquid crystal display device capable of performing negative display in which dark characters are used to display brightly colored characters and graphics with high saturation.

[0024]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method of forming a twist between a pair of substrates comprising a first substrate having a first electrode and a second substrate having a second electrode. A liquid crystal element sandwiching the aligned nematic liquid crystal, and a pair of polarizing plates sandwiching the liquid crystal element,
A color liquid crystal display device including a liquid crystal element and a twisted phase difference plate disposed between one of a pair of polarizing plates is characterized as follows.

That is, the angle between the absorption axes of the pair of polarizing plates is in the range of 60 ° to 120 °, the Δnd value of the liquid crystal element is in the range of 1500 nm to 1800 nm, and the Δnd value of the twisted phase difference plate is the same. The range was almost equal to the Δnd value of the liquid crystal element. Note that, as described above, the Δnd value of the liquid crystal element is equal to the birefringence difference Δn of the nematic liquid crystal 7,
It is expressed by the product of the cell gap d, which is the distance between the first substrate 1 and the second substrate 2, and the Δnd value of the torsional retarder is the difference between the birefringence difference Δn of the torsional retarder and the thickness d. Expressed by the product.

Instead of, or in addition to, setting both the Δnd value of the liquid crystal element and the Δnd value of the twisted phase difference plate in the range of 1500 nm to 1800 nm, the twist direction of the twisted phase difference plate with respect to the twist direction of the liquid crystal element The liquid crystal element may be reversed and the absolute value of the twist angle of the twisted phase difference plate may be larger than the absolute value of the twist angle of the liquid crystal element by 5 to 30 degrees.

It is preferable to provide a reflection plate outside the polarizing plate disposed on the opposite side of the liquid crystal element of such a color liquid crystal display device from the twisted phase difference plate. Further, one or both of the pair of polarizing plates may be a color polarizing plate manufactured by dyeing a dye. Further, the torsional retardation plate may be a temperature-compensated torsional retardation plate in which the Δnd value of the torsional retardation plate varies with temperature.

The present invention also provides a first electrode having a first electrode.
A liquid crystal element having a twisted nematic liquid crystal interposed therebetween, and a pair of liquid crystal elements arranged to sandwich the liquid crystal element between a pair of substrates including a substrate having a second electrode and a second substrate having a second electrode. A color liquid crystal display device comprising a polarizing plate and a phase difference plate disposed between the liquid crystal element and one of the pair of polarizing plates is characterized as follows.

The angle formed between the absorption axis of the polarizing plate disposed on the side opposite to the retardation plate with respect to the liquid crystal element and the orientation of the lower liquid crystal molecules in the liquid crystal element is in the range of 35 ° ± 10 °. The Δnd value of the liquid crystal element is 1500 nm to 1800
nm, and the retardation value of the retardation plate is
The value is increased by 50 to 200 nm from the Δnd value of the liquid crystal element.

Alternatively, the Δnd value of the liquid crystal element is set to 13
The retardation value of the retardation plate is set to be 300 nm from the Δnd value of the liquid crystal element.
It may be up to 500 nm. In such a color liquid crystal display device, as the retardation plate, the refractive index nx of the slow axis of the retardation plate, the refractive index ny in the y-axis direction, and z
It is preferable to use a biaxial retardation plate in which the refractive index nz in the axial direction has a relationship of nx>nz> ny.

Further, it is preferable to provide a reflection plate outside the polarizing plate disposed on the side opposite to the retardation plate with respect to the liquid crystal element. Alternatively, one or both of the pair of polarizing plates,
A color polarizing plate manufactured by dyeing a dye may be used. Further, the phase difference plate may be a temperature compensation type phase difference plate whose retardation value varies with temperature.

(Operation) In the color liquid crystal display device according to the present invention, the linearly polarized light incident from the upper polarizing plate 9 enters the torsional retardation plate and becomes elliptically polarized light. When no voltage is applied, the Δnd value of the liquid crystal element is substantially equal to the Δnd value of the twisted phase difference plate, so that the elliptically polarized light returns to linearly polarized light by the liquid crystal element. The angle formed by the absorption axes of the pair of polarizing plates composed of the lower polarizing plate and the upper polarizing plate is in the range of 60 ° to 120 °, and the linearly polarized light emitted from the liquid crystal element is blocked by the lower polarizing plate to display black.

In another color liquid crystal display device according to the present invention, linearly polarized light incident from the upper polarizing plate enters the retardation plate,
Since the absorption axis of the upper polarizing plate and the slow axis of the retardation plate are arranged at 45 °, the light becomes elliptically polarized light. Since the liquid crystal element is arranged substantially orthogonal to the upper molecular orientation direction of the liquid crystal element and the slow axis of the phase difference plate is 85 °, the liquid crystal element acts to cancel out the elliptically polarized light generated by the phase difference plate.

However, since the liquid crystal element is twisted, in order to completely cancel the elliptically polarized light state generated in the phase difference plate, a difference is provided between the Δnd value of the liquid crystal element and the retardation value of the phase difference plate. Further, when the crossing angle between the absorption axis of the lower polarizing plate and the orientation direction of the lower liquid crystal molecules is set to 35 °, when no voltage is applied, the light completely returns to linearly polarized light and black display is performed.

In any case, when a voltage is applied between the first electrode and the second electrode of the liquid crystal element, the apparent Δnd value of the liquid crystal element decreases and the twisted phase difference plate or the phase difference plate The generated elliptically polarized light does not completely return to linearly polarized light,
Only light of a certain wavelength is transmitted through the lower polarizing plate, and color display becomes possible.

The arrangement angle between the absorption axis of the upper polarizing plate and the upper molecular orientation direction of the torsional retardation plate is 35 ° to 40 ° or 5 °.
By arranging in the range of 0 ° to 55 °, the background color black generated by the difference between the wavelength dependence of the birefringence difference Δn of the twisted phase difference plate 10 and the wavelength dependence of the birefringence difference Δn of the liquid crystal is changed. It is possible to correct the decrease in the color and the saturation of the display color, and it is more preferable that the arrangement angle is 45 °.

Further, the arrangement angle between the absorption axis of the lower polarizing plate and the orientation of the lower liquid crystal molecules of the liquid crystal element is in the range of 35 ° to 40 ° or 50 ° to 55 °.
Similarly, a decrease in the blackness of the background color caused by the difference between the wavelength dependence of the birefringence difference Δn of the torsional retardation plate 10 and the wavelength dependence of the birefringence difference Δn of the liquid crystal element, and the saturation of the display color This can be compensated for, and it is more preferable that the arrangement angle is 45 °.

Further, in each case, the Δ
The nd value and the Δnd value of the twisted phase difference plate are set to 1500 nm or more.
By setting in the range of 1800 nm, the apparent Δnd value greatly changes with a slight difference in applied voltage, so that it is possible to change from black to green of the final color, and it is possible to display a plurality of colors even by time division driving. Will be possible.

When a twisted phase difference plate is used, the twist direction is set to be opposite to the twist direction of the liquid crystal element, and the absolute value of the twist angle of the twisted phase difference plate is set to the absolute value of the twist angle of the liquid crystal element. By making it larger, the wavelength dependence of the birefringence difference Δn of the liquid crystal element and the wavelength dependence of the birefringence difference Δn of the torsional retardation plate 10 are corrected,
The background color has been improved, the display color has also become brighter,
A better negative display is possible.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments for carrying out the present invention will be specifically described below with reference to the drawings.

(First Embodiment: FIGS. 1 to 4) First, a first embodiment of a color liquid crystal display device according to the present invention will be described with reference to FIGS. FIG. 3 is a schematic sectional view showing the structure of the color liquid crystal display device, and FIG.
Is a plan view showing the relationship between the absorption axis of the lower polarizer and the orientation of the liquid crystal molecules of the liquid crystal element when viewed from the upper polarizer 9 side. FIG. 2 also shows the absorption axis of the upper polarizer and the molecular orientation of the torsional retardation plate. FIG. 4 is a plan view showing the relationship between the directions, and FIG. 4 is a chromaticity diagram.

The structure of this color liquid crystal display device is shown in FIG.
Although they are not the same as the conventional color liquid crystal display devices shown in FIGS. 18 to 18, they have the same basic configuration, and therefore, for convenience of explanation, in FIGS. Have the same reference numerals.

As shown in FIG. 3, the color liquid crystal display device of the first embodiment comprises a first electrode 2 and an alignment film 3 formed of a 0.7 mm thick glass plate. A nematic liquid crystal twisted between a pair of substrates consisting of a substrate 1 and a second substrate 4 made of a 0.7 mm thick glass plate on which a second electrode 5 and an alignment film 6 are formed. 7, the liquid crystal element 22 is formed. The first electrode 2 and the second electrode 5 are transparent electrodes made of ITO (indium tin oxide).

The difference Δn in birefringence of the nematic liquid crystal used in the liquid crystal element 22 is 0.2, and the cell gap d, which is the gap between the first substrate 1 and the second substrate 4, is 8 μm. Therefore, the Δnd value of the liquid crystal element 22 represented by the product of the birefringence difference Δn of the nematic liquid crystal 7 and the cell gap d is 16
00 nm.

The alignment film 3 of the first substrate 1 has been rubbed in parallel with the lower liquid crystal molecule alignment direction 7a shown in FIG. 1, and the alignment film 6 of the second substrate 4 has the upper liquid crystal molecule alignment direction. 7
A rubbing process is performed in parallel with b. Viscosity 20cp
In the nematic liquid crystal of the above, a revolving substance called a chiral material is added, the twist pitch P is adjusted to 16 μm, and d /
By setting P = 0.5, a liquid crystal element having a counterclockwise twist of 240 ° is formed.

The twisted phase difference plate 10 is formed by applying a cholesteric liquid crystal polymer having a high phase transition temperature on a tri-acetyl cellulose (TAC) film, performing an orientation treatment at a high temperature, and rapidly cooling to solidify. , A film with a twist like a liquid crystal. The torsional retarder 10 is disposed between the second substrate 4 and the upper polarizer 9, and the Δnd value of the torsional retarder represented by the product of the birefringence difference Δn of the torsional retarder 10 and the thickness d is: Set to 1600 nm.

The lower molecular alignment direction 10a of the twisted phase plate 10 shown in FIG. 2 is arranged so as to be shifted from the upper liquid crystal molecule alignment direction 7b of the liquid crystal element 22 by 90 °. The upper molecular orientation direction 10b is set to a clockwise twist of 240 ° so as to be opposite to the twist angle of the liquid crystal element 22. The lower polarizing plate 8 is disposed outside the first substrate 1 of the liquid crystal element 22, and the upper polarizing plate 9 is
Place outside 0.

The absorption axis 9 of the upper polarizing plate 9 shown in FIG.
a is the upper molecular orientation directions 10b and 3 of the torsional retarder 10;
5 °, and the absorption axis 8 of the lower polarizing plate 8
“a” is arranged so as to form an angle of 55 ° with the lower liquid crystal molecule alignment direction 7a of the liquid crystal element 22, and the crossing angle of the pair of upper and lower polarizing plates 8 and 9 is 70 °. Further, the reflecting plate 11 that reflects the color light transmitted through the lower polarizing plate 8 is disposed outside the lower polarizing plate 8.

In the color liquid crystal display device configured as described above, when no voltage is applied, the linearly polarized light incident from the upper polarizer 9 becomes elliptically polarized light due to the birefringence of the torsion retardation plate 10. Since the Δnd value of the phase difference plate 10 and the Δnd value of the liquid crystal element 22 are equal, the liquid crystal element 22 returns to linearly polarized light. At this time, since the absorption axis 9a of the upper polarizing plate 9 and the absorption axis 8a of the lower polarizing plate 8 intersect at an angle of 70 °, light does not pass through the lower polarizing plate 8 and black display is performed.

Next, when a voltage is applied between the first electrode 2 and the second electrode 5, the molecules of the nematic liquid crystal 7 rise, and the apparent Δnd value of the liquid crystal element 22 decreases. Therefore, even if the elliptically polarized light generated by the twisted phase difference plate 10 passes through the liquid crystal element 22, it does not return to perfect linearly polarized light. Accordingly, the light reaches the lower polarizing plate 8 in an elliptically polarized state, and light of a specific wavelength passes through the lower polarizing plate 8 to become color light. The color light that has passed through the lower polarizing plate 8 is reflected by the reflecting plate 11, again passes through the liquid crystal element 22, the twisted phase difference plate 10, and the upper polarizing plate 9, and is emitted upward to perform a negative color display. .

FIG. 4 is a chromaticity diagram showing a curve 30 indicated by a solid line.
Represents a color change when the applied voltage is gradually increased from the non-application state in the color liquid crystal display device of the first embodiment. When no voltage is applied, the color is almost achromatic black. However, when a voltage is applied, the color changes to white, then yellow, red, blue, and finally green.

The absorption axis 9a of the upper polarizer 9 and the upper molecular orientation direction 10b of the torsional retardation plate 10 are arranged at an angle of 35 °, and the absorption axis 8a of the lower polarizer 8 and the lower liquid crystal molecular orientation of the liquid crystal element 22 are arranged. By arranging the direction 7a at an angle of 55 °, the difference in the wavelength dependence of the birefringence difference Δn of the liquid crystal element 22 and the difference in the wavelength dependence of the birefringence difference Δn of the twisted phase difference plate 10 is corrected. A good black background can be obtained, and good and bright colors can be obtained. In particular, in a negative display on a black background,
Since light incident from the periphery of the pixel is also blocked, the display becomes dark. Therefore, it is preferable that the display color is bright.

However, in the color liquid crystal display device according to the present invention, the absorption axis 9a of the upper polarizer 9 and the twisted retarder 1
The angle formed by the upper molecular orientation direction 10b with respect to 0 is not limited to 35 °, but may be 35 ° to 40 ° or 50 ° to 55 °.
By arranging in the range of ゜, the difference in the wavelength dependence of the birefringence difference Δn of the liquid crystal element and the difference in the wavelength dependence of the birefringence difference Δn of the torsional retardation plate 10 are corrected, and a good and bright color is obtained. be able to.

If the crossing angle between the upper polarizer 9 and the lower polarizer 8 is made smaller than 70 °, the display color becomes brighter, but the background color black becomes lighter.
It is preferable to arrange the intersection angle between the lower polarizing plate 8 and the lower polarizing plate 8 in the range of 60 ° to 120 °.

Further, in this embodiment, Δ Δ
Although the nd value and the Δnd value of the twisted phase difference plate are set to 1600 nm, almost the same effect can be obtained by setting the nd value in the range of 1500 nm to 1800 nm.
When the Δnd value of the liquid crystal element is smaller than 1500 nm,
The steepness of the liquid crystal is reduced, and time-division driving becomes difficult, which is not preferable. However, low-division driving or active matrix driving can be used.

If the Δnd value of the liquid crystal element and the Δnd value of the twisted phase difference plate are larger than 1800 nm, the response time of the liquid crystal element becomes slow because the cell gap d is thickened, and the twisted phase difference plate due to manufacturing problems. No. 10 is not preferable because the characteristics of No. 10 deteriorate.

In this embodiment, the Δnd value of the liquid crystal element and the Δnd value of the twisted phase difference plate are the same, but the Δnd value of the liquid crystal element can be made larger than the Δnd value of the twisted phase difference plate. When the Δnd value of the liquid crystal element is increased by about 50 nm from the Δnd value of the twisted phase difference plate, the Δnd value of the liquid crystal element decreases at a high temperature, becomes equal to the Δnd value of the twisted phase difference plate, and the high-temperature characteristics are improved.

In this embodiment, a 240 ° twisted STN (super twisted nematic) liquid crystal element is used as a liquid crystal element, but a 90 ° twisted TN liquid crystal element is used.
Similar effects can be obtained by using a (twisted nematic) liquid crystal element or an STN liquid crystal element having a twist of 180 ° or more.

Further, in this embodiment, since the retardation plate made of a liquid crystal polymer whose twisted state is fixed at room temperature is used as the torsion retardation plate, the Δnd value does not change even if the temperature changes. On the other hand, in a temperature-compensated torsional retardation plate subjected to a twist alignment process in a state in which a part of liquid crystal molecules is bonded to polymer molecules on a chain, the Δnd value varies with temperature.

When this temperature-compensated twisted phase difference plate is used, the change of the Δnd value of the twisted phase difference plate follows the change of the Δnd value of the liquid crystal element due to the temperature. As a result, the color change due to the temperature of the background color is suppressed, and the operating temperature range is expanded, which is more preferable.

(Second Embodiment: FIGS. 5 to 8) Next, a second embodiment of the color liquid crystal display device according to the present invention will be described with reference to FIGS. FIG. 7 is a schematic sectional view showing the structure of the color liquid crystal display device, and FIG.
FIG. 6 is a plan view showing the relationship between the absorption axis of the lower polarizer and the orientation of the liquid crystal molecules of the liquid crystal element when viewed from above. FIG. 6 also shows the relationship between the absorption axis of the upper polarizer and the orientation of the molecules of the twisted retardation plate. FIG. 8 is a chromaticity diagram.

In FIGS. 5 to 7, parts corresponding to those in FIGS. 1 to 3 are denoted by the same reference numerals, and description thereof will be omitted. The color liquid crystal display device according to the second embodiment has a configuration in which the twist angle of the twisted phase difference plate, the material of the upper polarizer, and the characteristics of the reflector are different from those of the first embodiment. It has lights.

The structure of the liquid crystal element 22 in this color liquid crystal display device is the same as that of the liquid crystal element 22 of the first embodiment described above, and the difference Δn in the birefringence of the nematic liquid crystal 7 is 0.1.
2, the cell gap d as a gap between the first substrate 1 and the second substrate 4 is 8 μm, and the Δnd value of the liquid crystal element 22 is 16
00 nm.

The alignment film 3 of the first substrate 1 has been subjected to a rubbing treatment in parallel with the lower liquid crystal molecule alignment direction 7a shown in FIG. 7, and the alignment film 6 of the second substrate 4 has the upper liquid crystal molecule alignment direction. 7
A rubbing process is performed in parallel with b. Viscosity 20cp
In the nematic liquid crystal of the above, a revolving substance called a chiral material is added, the twist pitch P is adjusted to 16 μm, and d / P =
The liquid crystal element 22 having a twist of 240 ° in the counterclockwise direction is formed.

The twisted phase difference plate 10 is obtained by applying a cholesteric liquid crystal polymer having a high phase transition temperature on a TAC film, and subjecting the cholesteric liquid crystal polymer to alignment treatment at a high temperature and then quenching to solidify. Film. This twisted phase difference plate 10 is arranged outside the second substrate 4 of the liquid crystal element 20, and the Δnd value of the twisted phase difference plate represented by the product of the birefringence difference Δn of the twisted phase difference plate 10 and the thickness d is defined as 1600
Set to nm.

The lower molecular alignment direction 10a of the twisted phase difference plate 10 shown in FIG. 6 is arranged at a position shifted from the upper liquid crystal molecule alignment direction 7b of the liquid crystal element 22 by 90 °.
Upper molecular orientation direction 10b of torsion retardation plate 10 shown in FIG.
Are arranged so as to have a clockwise twist of 250 ° so as to be opposite to the twist angle of the liquid crystal element 22.

The lower polarizing plate 8 is disposed outside the first substrate 1 of the liquid crystal element 22, and serves as a blue color polarizing plate 1 as an upper polarizing plate.
2 is arranged outside the twisted phase difference plate 10. The absorption axis 12a of the color polarizing plate 12 shown in FIG. 6 is arranged at an angle of 40 ° with the upper molecular orientation direction 10b of the twisted phase difference plate 10, and the absorption axis 8a of the lower polarizing plate 8 shown in FIG.
Are arranged at an angle of 55 ° with the lower liquid crystal molecule orientation direction 7a of the liquid crystal element 22, and the crossing angle between the lower polarizing plate 8 and the color polarizing plate 12 is 65 °.

The upper polarizing plate 9 and the lower polarizing plate 8 used in the first embodiment are obtained by dyeing stretched PVA with iodine,
Although it is sandwiched between films, the color polarizing plate 12 is
A polarizing plate dyed with a dichroic dye as a substitute for iodine. Usually, when two color polarizers are arranged in parallel, the color of the dye becomes lighter but almost white, and when two color polarizers are arranged orthogonally, the color of the dye is clearly shown. When two blue color polarizers 12 used in this embodiment are arranged in parallel, the color becomes pale bluish white, but when arranged perpendicularly, it becomes dark blue.

As shown in FIG. 7, a semi-transmissive reflection plate 13 is arranged outside the lower polarizing plate 8 and a backlight 14 using white light-emitting electroluminescence (EL).
Are disposed outside the transflective plate 13. With the above configuration, a reflective and transmissive color liquid crystal display device is provided. Normally, it is used as a reflection type color liquid crystal display device.
Is turned on to be used as a transmission type color liquid crystal display device.

In the color liquid crystal display device of the second embodiment, when no voltage is applied, the color liquid crystal display device shows a dark blue color, which is the orthogonal color of the color polarizer 12, but when a voltage is applied to the liquid crystal element, the color liquid crystal display device becomes slightly bluish. After passing through white, a negative color display indicating magenta, blue, and blue-green is obtained. FIG. 8 is a chromaticity diagram, and a curve 21 shown by a solid line shows a change in color due to voltage application by the color liquid crystal display device of the second embodiment.

In the case of this embodiment, the color polarizing plate 12
, The blue light always leaks to some extent, so that the saturation of the display color is lower than that in the case of using a normal polarizing plate. However, the absorption axis 12a of the color polarizing plate 12 and the lower liquid crystal molecule orientation direction 7a Angle between 35 ° and 40 ° or 5
By arranging in the range of 0 ° to 55 °, the wavelength dependence of the birefringence difference Δn of the liquid crystal element and the twisted phase difference plate 10
And the difference in the wavelength dependence of the birefringence difference Δn can be corrected, and a good and bright color can be obtained.

Further, the absolute value of the twist angle of the torsional phase difference plate 10 is set to be 10 times smaller than the absolute value of the twist angle of the liquid crystal element 22.
゜ By increasing the size, it is possible to suppress a decrease in saturation and further improve the brightness of display colors, thereby providing a favorable negative color display device.

In this embodiment, the crossing angle between the lower polarizer 8 and the color polarizer 12 is set to 65 °. If the crossing angle is further reduced, the display color becomes brighter, but the background color black also becomes lighter. Therefore, the range of 60 ° to 120 ° is preferable.

In this embodiment, the twist angle of the twisted phase difference plate 10 is set to 250 °. If the twist angle is further increased, the display color becomes brighter, but the background color black becomes lighter. Therefore, it is preferable that the absolute value of the twist angle of the twisted phase difference plate 10 is set larger than the absolute value of the twist angle of the liquid crystal element 22 in the range of 5 ° to 30 °.

In this embodiment, the Δn of the liquid crystal element
Although the d value and the Δnd value of the torsional retardation plate 10 are set to 1600 nm, almost the same effect can be obtained by setting the d value and the Δnd value in the range of 1500 nm to 1800 nm. If the Δnd value of the liquid crystal element is smaller than 1500 nm, the sharpness of the liquid crystal decreases, and it becomes difficult to perform time-division driving. Although not preferable, the absolute value of the twist angle of the torsional retardation plate 10 is set to The effect of improving the color by making the value larger than the above value can be similarly obtained, and can be used in the case of low-division driving or active matrix driving.

Further, when the Δnd value of the liquid crystal element and the Δnd value of the twisted phase difference plate are larger than 1800 nm, the response time of the liquid crystal element becomes slow because the cell gap d is thickened. Although the characteristics of the phase difference plate 10 are deteriorated, it is not preferable. However, the effect of color improvement by making the absolute value of the twist angle of the twisted phase difference plate 10 larger than the absolute value of the twist angle of the liquid crystal element 22 can be similarly obtained.

In this embodiment, a blue color polarizer is used. However, even when a color polarizer of another color such as red, green, or purple, or of course, a normal iodine polarizer of a normal color is used, By making the absolute value of the twist angle of the twisted phase difference plate larger than the absolute value of the twist angle of the liquid crystal, the effect of improving the color can be obtained.

(Third Embodiment: FIGS. 9 to 12)
A third embodiment of the color liquid crystal display device according to the present invention will be described with reference to FIGS. FIG. 11 is a schematic cross-sectional view showing the structure of the color liquid crystal display device. FIG. 9 is a plan view showing the relationship between the absorption axis of the lower polarizing plate and the liquid crystal molecule alignment direction of the liquid crystal element as viewed from above. 10 is a plan view showing the relationship between the absorption axis of the upper polarizing plate and the slow axis of the retardation plate. FIG. 12 is a chromaticity diagram of the color liquid crystal display device.

In these figures, parts corresponding to those in FIGS. 1 to 3 are denoted by the same reference numerals. In the third embodiment, a phase difference plate 17 is used instead of the twisted phase difference plate 10 used in the first and second embodiments.

The liquid crystal element 23 of this color liquid crystal display device has almost the same configuration as the liquid crystal element 22 of the first embodiment described with reference to FIG. However, nematic liquid crystal 7
Is 0.21 and the cell gap d which is a gap between the first substrate 1 and the second substrate 4 is 8 μm. The difference Δn in birefringence of the nematic liquid crystal 7 and the cell gap d
The Δnd value of the liquid crystal element represented by the product of the above is 1680 nm.

The alignment film 3 of the first substrate 1 has been rubbed in parallel to the lower liquid crystal molecule alignment direction 7a shown in FIG. 7, and the alignment film 6 of the second substrate 4 has the upper liquid crystal molecule alignment direction. 7
The rubbing process is performed in parallel with b. Viscosity 20cp
In the nematic liquid crystal of the above, a revolving substance called a chiral material is added, the twist pitch P is adjusted to 16 μm, and d / P =
0.5 to form a left-handed 240 ° twist liquid crystal element.

The retardation plate 17 shown in FIG. 11 is a film obtained by uniaxially stretching a polycarbonate film. Therefore, the refractive index of the retardation plate 17 in the slow axis 17a shown in FIG. 10 is nx, the refractive index in the y-axis direction orthogonal to the slow axis 17a is ny, and the refractive index in the z-axis direction is the thickness direction. Is defined as nz, then nx> ny = nz.

The retardation plate 17 is disposed outside the second substrate 4 of the liquid crystal element 23. Then, the retardation value of the phase difference plate 17 is set to 1800 nm. Therefore,
The retardation value of the phase difference plate 17 is ΔΔ of the liquid crystal element 23.
It is 120 nm larger than the nd value. Further, the retardation plate 17 is arranged such that the slow axis 17a thereof is at a position shifted from the upper direction of the liquid crystal molecules 7b by 85 ° from the liquid crystal element 23.

The lower polarizing plate 8 shown in FIG.
And the upper polarizing plate 9 is disposed outside the retardation plate 17. The absorption axis 9a of the upper polarizing plate 9 shown in FIG. 10 is arranged at 45 ° counterclockwise with respect to the slow axis 17a of the retardation plate 17, and the absorption axis 8a of the lower polarizing plate 8 shown in FIG.
Is disposed at an angle of 35 ° counterclockwise with respect to the lower liquid crystal molecule alignment direction 7a of the liquid crystal element 23, and the crossing angle between the pair of upper and lower polarizing plates 8 and 9 is 45 °. Further, the reflection plate 11 that reflects the color light transmitted through the lower polarizing plate 8 is disposed outside the lower polarizing plate 8.

In the thus configured color liquid crystal display device according to the third embodiment of the present invention, when no voltage is applied, the linearly polarized light incident from the upper polarizer 9 is applied to the retarder 1.
7 becomes elliptically polarized light due to the birefringence, but a difference is provided between the retardation value of the phase difference plate 17 and the Δnd value of the liquid crystal element 23, and the arrangement angle of the pair of polarizing plates 8 and 9 is optimized. The element 23 returns to linearly polarized light. At this time, the lower polarizing plate 8
When the arrangement relationship between the absorption axis 8a and the absorption axis 9a of the upper polarizing plate 9 is as described above, the linearly polarized light does not pass through the lower polarizing plate 8 and a black display is obtained.

Next, the first electrode 3 of the liquid crystal element 23 and the second
When a voltage is applied between the electrodes 5, the molecules of the nematic liquid crystal 7 rise, and the Δnd value of the apparent liquid crystal element decreases. Therefore, the elliptically polarized light generated by the phase difference plate 17 is
Even when the light passes through the liquid crystal element 23, it does not return to perfect linearly polarized light. Therefore, the light reaches the lower polarizing plate 8 in an elliptically polarized state, and light of a specific wavelength passes through the lower polarizing plate 8 to become color light.
The color light that has passed through the lower polarizing plate 8 is reflected by the reflecting plate 11, again passes through the liquid crystal element 23, the retardation plate 17, and the upper polarizing plate 9 and is emitted upward, thereby performing a negative color display.

In the chromaticity diagram of FIG. 12, a curve 32 shown by a solid line represents a color change when the applied voltage is gradually increased from the non-application state in the color liquid crystal display device of the third embodiment. I have. When no voltage is applied, the color is almost achromatic black. However, when a voltage is applied, the color changes to white, then yellow, red, then blue, and finally green.

As shown in FIG. 9, the absorption axis 8a of the lower polarizing plate 8 and the lower liquid crystal molecule orientation direction 7a of the liquid crystal element 23 are set at 35 degrees.
By arranging at the intersection angle of ゜, the wavelength dependence of the birefringence difference Δn of the liquid crystal element 20 and the retardation of the retardation plate 17
By correcting the difference in the wavelength dependence of the option value, a good black background can be obtained, and a good and bright color can be obtained.
In particular, in a negative display with a black background, incident light from the periphery of the pixel is also blocked, resulting in a dark display. Therefore, it is preferable that the display color is bright.

If the crossing angle between the absorption axis 8a of the lower polarizing plate 8 and the lower liquid crystal molecule orientation direction 7a of the liquid crystal element 23 is made smaller than 35 °, the display color becomes brighter, but the background color black also becomes lighter. Therefore, it is preferable that the crossing angle between the absorption axis 8a of the lower polarizing plate 8 and the lower liquid crystal molecule alignment direction 7a is set in the range of 25 ° to 45 °.

In this embodiment, the Δn of the liquid crystal element
The d value was set at 1680 nm, but from 1500 nm to 18
Almost the same effect can be obtained by setting the range to 00 nm. Also in this case, the retardation value of the phase difference plate 17 is 50 to 200 times larger than the Δnd value of the liquid crystal element 23.
nm.

If the Δnd value of the liquid crystal element is smaller than 1500 nm, the sharpness of the liquid crystal decreases, and it becomes difficult to perform time-division driving. However, it is not preferable, but low-division driving or active matrix driving can be used. On the other hand, if the Δnd value of the liquid crystal element is larger than 1800 nm, the response time of the liquid crystal element becomes slow because the cell gap d is increased, and the characteristics of the retardation plate 17 are deteriorated due to manufacturing problems. The difference between the retardation value of the retardation plate 17 and the Δnd value of the liquid crystal element is smaller than 50 nm even if it is smaller than 50 nm.
Even if it is larger than 0 nm, the background black becomes lighter, which is not preferable.

In this embodiment, the absorption axis 9a of the upper polarizing plate 9 is arranged at 45 ° counterclockwise with respect to the slow axis 17a of the phase difference plate 17, but the absorption axis 9a of the upper polarizing plate 9 is positioned at the left. When it is disposed 45 ° clockwise with respect to the slow axis 17a of the phase difference plate 17, white display is obtained when no voltage is applied, and when a voltage is applied, a black, blue, green, red and positive display type color display device is obtained. .

Further, in this embodiment, a 240 ° twisted STN (super twisted nematic) liquid crystal element is used as the liquid crystal element, but a 90 ° twisted TN (super twisted nematic) liquid crystal element is used.
Similar effects can be obtained by using an N (twisted nematic) liquid crystal element or an STN liquid crystal element having a twist of 180 ° or more.

In this embodiment, the phase difference plate 1
Although a retardation plate made of a polycarbonate film was used as 7, the retardation value did not change even if the temperature changed, but the polycarbonate film was impregnated with liquid crystal molecules, or a part of the liquid crystal molecules was bonded to polymer molecules on the chain. The retardation value of the temperature-compensated phase difference plate varies with temperature. When this temperature compensation type phase difference plate is used, the change of the retardation value of the phase difference plate follows the change of the Δnd value of the liquid crystal cell due to the temperature. As a result, the color change due to the temperature of the background color is suppressed, and the operating temperature range is expanded, which is more preferable.

(Fourth Embodiment: FIGS. 13 to 15) Next, a fourth embodiment of the color liquid crystal display device according to the present invention will be described with reference to FIGS. FIG.
FIG. 13 is a schematic cross-sectional view showing the structure of the color liquid crystal display device, FIG. 13 is a plan view showing the relationship between the absorption axis of the upper polarizing plate and the slow axis of the retardation plate viewed from above, and FIG. It is a chromaticity diagram by this color liquid crystal display device. Note that a plan view showing the relationship between the absorption axis of the lower polarizing plate and the orientation direction of the liquid crystal molecules of the liquid crystal element is the same as FIG. FIG.
In FIG. 7, portions corresponding to those in FIG. 7 are denoted by the same reference numerals.

The color liquid crystal display of the fourth embodiment is different from the color liquid crystal display of the third embodiment in that the Δnd value of the liquid crystal element 20, the material and retardation of the retardation plate Values, the arrangement angle of the upper polarizer 9, and the characteristics of the reflector 13.
Is provided.

The liquid crystal element 24 in this color liquid crystal display device has almost the same configuration as the liquid crystal element 22 of the first embodiment described with reference to FIG. However, nematic liquid crystal 7
Is 0.21 and the cell gap d, which is the gap between the first substrate 1 and the second substrate 4, is 7 μm. The birefringence difference Δn of the nematic liquid crystal 7 and the cell gap d
The Δnd value of the liquid crystal element expressed by the product of the above is 1470 μm.

The alignment film 3 of the first substrate 1 has been rubbed in parallel to the lower liquid crystal molecule alignment direction 7a shown in FIG. 9, and the alignment film 6 of the second substrate 4 has the upper liquid crystal molecule alignment. Direction 7
The rubbing process is performed in parallel with b. Viscosity 20cp
In the nematic liquid crystal of the above, a revolving substance called a chiral material was added, the twist pitch P was adjusted to 14 μm, and d / P =
0.5 to form a left-handed 240 ° twist liquid crystal element.

The retardation plate 18 is a film obtained by biaxially stretching polycarbonate. The retardation plate 18 has a refractive index of a slow axis 18a shown in FIG. 13 of nx and a refraction in the y-axis direction orthogonal to the slow axis 18a. If the refractive index is defined as ny and the refractive index in the z-axis direction, which is the thickness direction, is defined as nz, then nx>nz> ny.

In the biaxial retardation plate 18, the amount of change in the retardation value when the retardation plate 18 is tilted about the y-axis direction is the same as that of the uniaxial stretching used in the third embodiment. Since the number is smaller than that of the phase difference plate 17, the color change due to the change of the viewing angle is reduced and the viewing angle characteristic is improved even in a color liquid crystal display device, which is preferable.

As shown in FIG. 14, this retardation plate 18 is arranged outside the second substrate 4 of the liquid crystal element 24, and its retardation value is set to 1850 nm. That is, the retardation value of the phase difference plate 18 is set 380 nm larger than the Δnd value (1470 nm) of the liquid crystal element 24. Further, the slow axis 18a of the retardation plate 18 shown in FIG.
Arrange them so that they are shifted by 5 °.

The lower polarizing plate 8 is arranged outside the first substrate 1 of the liquid crystal element 24, and the upper polarizing plate 9 is arranged outside the phase difference plate 18. The absorption axis 9a of the upper polarizing plate 9 shown in FIG. 13 is disposed 45 ° clockwise with respect to the slow axis 18a of the phase difference plate 18, and the absorption axis 8a of the lower polarizing plate 8 is oriented in the lower liquid crystal molecule alignment direction of the liquid crystal element 24. 7a and counterclockwise 35 ° (see FIG. 9), and the crossing angle of the pair of upper and lower polarizing plates 8 and 9 is 45 °.

The transflective plate 13 is arranged outside the lower polarizing plate 8, and a backlight 14 using a white light emitting EL is arranged outside the transflective plate 13. With this configuration, the color liquid crystal display device of the fourth embodiment is a reflection type and transmission type color liquid crystal display device. In other words, it is normally used as a reflective color liquid crystal display device, but it can be used as a backlight 14 in dark nights.
Is turned on to be used as a transmission type color liquid crystal display device.

In the color liquid crystal display device of this embodiment, when no voltage is applied, the linearly polarized light incident from the upper polarizer 9 becomes elliptically polarized light due to the birefringence of the retarder 18. Retardation value and liquid crystal element 24
Is provided, and the liquid crystal element 24 returns to the linearly polarized light by optimizing the arrangement angles of the polarizing plates 8 and 9.
At this time, if the arrangement relationship between the absorption axis 8a of the lower polarizing plate 8 and the absorption axis 9a of the upper polarizing plate 9 is as described above, the linearly polarized light does not pass through the lower polarizing plate 8 and a black display is obtained.

Then, when a voltage is applied to the liquid crystal element 24, a negative color display of blue, green, and red is obtained according to the voltage. Curve 3 shown by a solid line in the chromaticity diagram of FIG.
Reference numeral 3 denotes a color change when the voltage applied to the liquid crystal element 24 is gradually increased from the non-application state in the color liquid crystal display device of this embodiment. When no voltage is applied, the color is almost achromatic black, but when a voltage is applied, the color goes through blue and green, and finally, the display becomes red.

By arranging the absorption axis 8a of the lower polarizing plate 8 and the lower liquid crystal molecule orientation direction 7a of the liquid crystal element 24 at 35 °, the wavelength dependence of the birefringence difference Δn of the liquid crystal element and the phase difference plate 12 The difference in the wavelength dependence of the retardation value can be corrected to obtain a good black background and a good and bright color. In particular, in a negative display with a black background, incident light from the periphery of the pixel is also blocked, resulting in a dark display. Therefore, it is preferable that the display color is bright.

If the crossing angle between the absorption axis 8a of the lower polarizing plate 8 and the lower liquid crystal molecule alignment direction 7a is made smaller than 35 °, the display color becomes brighter, but the background color black becomes lighter. The intersection angle between the absorption axis 8a of the plate and the lower liquid crystal molecule alignment direction 7a is preferably set in the range of 25 ° to 45 °.

In this embodiment, the Δnd value of the liquid crystal element 24 is set to 1470 nm.
By setting the wavelength to the range of 1600 nm, substantially the same effect can be obtained. Also in this case, the retardation value of the retardation plate 18 is 300 to 300 times smaller than the Δnd value of the liquid crystal element 20.
It needs to be increased by 500 nm.

If the Δnd value of the liquid crystal element 24 is smaller than 1300 nm, the sharpness of the liquid crystal is reduced, and it becomes difficult to perform time-division driving. . Further, when the Δnd value of the liquid crystal element 24 is larger than 1600 nm, the final display color changes from red to white.
The retardation value of the retardation plate 18 becomes 1900 nm or more, and the characteristics of the retardation plate 18 are deteriorated due to manufacturing problems, which is not preferable.

If the difference between the retardation value of the retardation plate 18 and the Δnd value of the liquid crystal element 24 is smaller than 300 nm or larger than 500 nm, the background black becomes undesirably thin.

In this embodiment, the absorption axis 9a of the upper polarizing plate 9 is arranged clockwise 45 ° with respect to the slow axis 18a of the phase difference plate 18. When arranged at 45 ° counterclockwise with respect to the slow axis 18 a of the phase difference plate 18, a white display is obtained when no voltage is applied, and a positive display type color display device that displays green through yellow and blue when a voltage is applied is applied. Becomes

The types of liquid crystal that can be used in the liquid crystal element are the same as in the above-described embodiments. Upper polarizing plate 9
The lower polarizer 8 is obtained by dyeing stretched polyvinyl alcohol (PVA) with iodine and sandwiching it with a TAC film. Instead of iodine, a color polarizer dyed with a dichroic dye is used as an upper and lower polarizer. The display color can be changed by adopting either one or both of them.

Usually, when two color polarizing plates are arranged in parallel, the color of the dye becomes lighter but almost white, and when two color polarizing plates are arranged orthogonally, the color of the dye is clearly shown. For example, when two blue color polarizers are arranged in parallel, the color becomes pale bluish white, but when arranged perpendicularly, the color becomes dark blue.

When the upper polarizer 9 of the color liquid crystal display device of the fourth embodiment is changed to a blue color polarizer, a dark blue color, which is an orthogonal color of the color polarizer, is shown when no voltage is applied. When a voltage is applied to the liquid crystal element, a negative color display of red through blue, blue-green is obtained.

[0115]

As described above, according to the present invention, there is provided a reflective color liquid crystal display device capable of displaying a black or dark background color and capable of displaying a bright and highly saturated negative color display.
It can be provided with a simple configuration including only a liquid crystal element, a polarizing plate, and one retardation plate. Also, by applying this color liquid crystal display device, a colorful digital wristwatch display can be realized.

[Brief description of the drawings]

FIG. 1 is a plan view showing a relationship between an absorption axis of a lower polarizing plate and a liquid crystal molecule alignment direction of a liquid crystal element when FIG. 3 is viewed from above.

FIG. 2 is a plan view showing the relationship between the absorption axis of the upper polarizing plate and the molecular orientation direction of the twisted phase difference plate.

FIG. 3 is a schematic sectional view showing the structure of the first embodiment of the color liquid crystal display device according to the present invention.

FIG. 4 is a chromaticity diagram for explaining a change in display color when a voltage applied to a liquid crystal element is changed in the first embodiment of the present invention.

5 is a plan view showing the relationship between the absorption axis of the lower polarizing plate and the liquid crystal molecule alignment direction of the liquid crystal element when FIG. 7 is viewed from above.

FIG. 6 is a plan view showing the relationship between the absorption axis of the upper polarizing plate and the molecular orientation direction of the twisted phase difference plate.

FIG. 7 is a schematic sectional view showing the structure of a second embodiment of the color liquid crystal display device according to the present invention.

FIG. 8 is a chromaticity diagram for explaining a change in display color when a voltage applied to a liquid crystal element is changed in the second embodiment of the present invention.

9 is a plan view showing the relationship between the absorption axis of the lower polarizer and the liquid crystal molecule alignment direction of the liquid crystal element when FIG. 11 is viewed from above.

FIG. 10 is a plan view showing the relationship between the absorption axis of the upper polarizing plate and the slow axis of the retardation plate.

FIG. 11 is a schematic sectional view showing the structure of a third embodiment of the color liquid crystal display device according to the present invention.

FIG. 12 is a chromaticity diagram for explaining a change in display color when a voltage applied to a liquid crystal element is changed in a third embodiment of the present invention.

13 is a plan view showing the relationship between the absorption axis of the upper polarizer and the slow axis of the retardation plate when FIG. 14 is viewed from above.

FIG. 14 is a schematic sectional view showing the structure of a fourth embodiment of the color liquid crystal display device according to the present invention.

FIG. 15 is a chromaticity diagram for explaining a change in display color when a voltage applied to a liquid crystal element is changed in a fourth embodiment of the present invention.

FIG. 16 is a plan view showing the relationship between the absorption axis of the lower polarizing plate and the liquid crystal molecule alignment direction of the liquid crystal element when FIG. 18 is viewed from above.

FIG. 17 is a plan view showing the relationship between the absorption axis of the upper polarizing plate and the molecular orientation direction of the twisted phase difference plate.

FIG. 18 is a schematic sectional view showing the structure of a conventional color liquid crystal display device using a twisted phase difference plate.

19 is a plan view showing the relationship between the absorption axis of the lower polarizer and the liquid crystal molecule alignment direction of the liquid crystal element when FIG. 21 is viewed from above.

FIG. 20 is a plan view showing the relationship between the absorption axis of the upper polarizing plate and the slow axis of the retardation plate.

FIG. 21 is a schematic sectional view showing the structure of a conventional color liquid crystal display device using a phase difference plate.

[Explanation of symbols]

 1: First substrate 2: First electrode 3, 6: Alignment film 4: Second substrate 5: Second electrode 7: Nematic liquid crystal 7a: Lower liquid crystal molecule alignment direction 7b: Upper liquid crystal molecule alignment direction 8: Lower polarizing plate 8a: Absorption axis of lower polarizing plate 9: Upper polarizing plate 9a: Absorption axis of upper polarizing plate 10: Twisted phase difference plate 10a: Lower molecular orientation direction of twisted phase difference plate 10b: Upper molecule of twisted phase difference plate Orientation direction 11: Reflector 12: Color polarizer 12a: Absorption axis of color polarizer 13: Semi-transmissive reflector 14: Backlight 17: 1-axis retardation plate 17a: Slow axis 18: Biaxial position Phase difference plate 18a: Slow axis 20, 21, 22, 23, 24: Liquid crystal element

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] September 30, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0025

[Correction method] Change

[Correction contents]

That is, the angle between the absorption axes of the pair of polarizing plates is in the range of 60 ° to 120 °, the Δnd value of the liquid crystal element is in the range of 1500 nm to 1800 nm, and the Δnd value of the twisted phase difference plate is the same. The range was almost equal to the Δnd value of the liquid crystal element. As described above, the Δnd value of the liquid crystal element is equal to the birefringence difference Δn of the nematic liquid crystal and the Δnd value .
Is represented by the first substrate and the product of cell gap d is the distance of the second substrate, [Delta] nd value of the twisted retardation film, the table by the product of the difference Δn and the thickness d of the birefringence of the twisted retardation film Is done.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0059

[Correction method] Change

[Correction contents]

Further, in this embodiment, since the retardation plate made of a liquid crystal polymer whose twisted state is fixed at room temperature is used as the torsion retardation plate, the Δnd value does not change even if the temperature changes. In a temperature-compensated torsional retardation plate subjected to a twist alignment treatment in a state where a part of liquid crystal molecules is bonded to a chain-like polymer molecule, the Δnd value varies with temperature.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0064

[Correction method] Change

[Correction contents]

The alignment film 3 of the first substrate 1 has been rubbed in parallel with the lower liquid crystal molecule alignment direction 7a shown in FIG. 7 , and the alignment film 6 of the second substrate 4 has the upper liquid crystal molecule alignment direction. 7
A rubbing process is performed in parallel with b. Viscosity 20cp
In the nematic liquid crystal of the above, a revolving substance called a chiral material is added, the twist pitch P is adjusted to 16 μm, and d / P =
The liquid crystal element 22 having a twist of 240 ° in the counterclockwise direction is formed.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 008

[Correction method] Change

[Correction contents]

Next, the first electrode 2 of the liquid crystal element 23 and the second electrode 2
When a voltage is applied between the electrodes 5, the molecules of the nematic liquid crystal 7 rise, and the Δnd value of the apparent liquid crystal element decreases. Therefore, the elliptically polarized light generated by the phase difference plate 17 is
Even when the light passes through the liquid crystal element 23, it does not return to perfect linearly polarized light. Therefore, the light reaches the lower polarizing plate 8 in an elliptically polarized state, and light of a specific wavelength passes through the lower polarizing plate 8 to become color light.
The color light that has passed through the lower polarizing plate 8 is reflected by the reflecting plate 11, again passes through the liquid crystal element 23, the retardation plate 17, and the upper polarizing plate 9 and is emitted upward, thereby performing a negative color display.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0088

[Correction method] Change

[Correction contents]

As shown in FIG. 9, the absorption axis 8a of the lower polarizing plate 8 and the lower liquid crystal molecule orientation direction 7a of the liquid crystal element 23 are set at 35 degrees.
By arranging at an intersection angle of ゜, the wavelength dependence of the birefringence difference Δn of the liquid crystal element 23 and the retardation of the retardation plate 17
By correcting the difference in the wavelength dependence of the option value, a good black background can be obtained, and a good and bright color can be obtained.
In particular, in a negative display with a black background, incident light from the periphery of the pixel is also blocked, resulting in a dark display. Therefore, it is preferable that the display color is bright.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

In this embodiment, the phase difference plate 1
Since using a phase difference plate made of a polycarbonate film as 7, but does not change the retardation value even if the temperature changes bond, or impregnated with the liquid crystal molecules in polycarbonate film, the chain of the polymer molecule a portion of the liquid crystal molecules The retardation value of the temperature-compensated phase difference plate varies with temperature. When this temperature compensation type phase difference plate is used, the change of the retardation value of the phase difference plate follows the change of the Δnd value of the liquid crystal cell due to the temperature. As a result, the color change due to the temperature of the background color is suppressed, and the operating temperature range is expanded, which is more preferable.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0096

[Correction method] Change

[Correction contents]

The color liquid crystal display device of the fourth embodiment is different from the color liquid crystal display device of the third embodiment in that the Δnd value of the liquid crystal element 24 , the material and retardation of the retardation plate 18 are different. Values, the arrangement angle of the upper polarizer 9, and the characteristics of the reflector 13.
Is provided.

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0108

[Correction method] Change

[Correction contents]

In this embodiment, the Δnd value of the liquid crystal element 24 is set to 1470 nm.
By setting the wavelength to the range of 1600 nm, substantially the same effect can be obtained. Also in this case, the retardation value of the retardation plate 18 is 300 to 300 times smaller than the Δnd value of the liquid crystal element 24.
It needs to be increased by 500 nm.

Claims (12)

[Claims] 1. A liquid crystal element in which a twist-aligned nematic liquid crystal is sandwiched between a pair of substrates including a first substrate having a first electrode and a second substrate having a second electrode. And a pair of polarizing plates disposed so as to sandwich the liquid crystal element, and a torsional retardation plate disposed between the liquid crystal element and one of the pair of polarizing plates, wherein an absorption axis of the pair of polarizing plates is provided. Angle between 60 ° and 120 °
And the Δnd value of the liquid crystal element represented by the product of the birefringence difference Δn of the nematic liquid crystal and the distance d between the pair of substrates is 150.
0 nm to 1800 nm, and the Δnd value of the twisted phase difference plate represented by the product of the birefringence difference Δn of the twisted phase difference plate and the thickness d is Δn of the liquid crystal element.
A color liquid crystal display device characterized by having a range substantially equal to the d value. 2. A pair of substrates including a first substrate having a first electrode and a second substrate having a second electrode,
A liquid crystal element sandwiching a twisted nematic liquid crystal; a pair of polarizing plates sandwiching the liquid crystal element; and a twist disposed between the liquid crystal element and one of the pair of polarizing plates. A phase difference plate, and the angle between the absorption axes of the pair of polarizing plates is 60 ° to 120 °.
範 囲, the twist direction of the twisted phase difference plate is opposite to the twist direction of the liquid crystal element, and the absolute value of the twist angle of the twisted phase difference plate is greater than the absolute value of the twist angle of the liquid crystal element. A color liquid crystal display device characterized by being 5 to 30 degrees larger. 3. The color liquid crystal display device according to claim 1, wherein the twist direction of the twisted phase plate is opposite to the twist direction of the liquid crystal element, and the twist angle of the twisted phase plate is A color liquid crystal display device wherein the absolute value is larger than the absolute value of the twist angle of the liquid crystal element by 5 to 30 degrees. 4. The color liquid crystal display device according to claim 1, wherein the color liquid crystal display device is provided outside a polarizing plate disposed on a side opposite to the twisted phase difference plate with respect to the liquid crystal element. A color liquid crystal display device comprising a reflection plate. 5. The color liquid crystal display device according to claim 1, wherein one or both of the pair of polarizing plates is a color polarizing plate manufactured by dyeing a dye. A color liquid crystal display device, comprising: 6. The color liquid crystal display device according to claim 1, wherein the twisted phase difference plate has a temperature-compensated type in which the Δnd value of the twisted phase difference plate varies with temperature. A color liquid crystal display device comprising a twisted phase difference plate. 7. A pair of substrates including a first substrate having a first electrode and a second substrate having a second electrode,
A liquid crystal element sandwiching a twisted nematic liquid crystal; a pair of polarizing plates sandwiching the liquid crystal element; and a position disposed between the liquid crystal element and one of the pair of polarizing plates. A retardation plate, wherein the angle between the absorption axis of the polarizing plate disposed on the opposite side of the retardation plate with respect to the liquid crystal element and the lower liquid crystal molecule alignment direction of the liquid crystal element is 35 ° ± 10 °. And the Δnd value of the liquid crystal element expressed by the product of the difference Δn in birefringence of the nematic liquid crystal and the distance d between the pair of substrates is 150.
0 nm to 1800 nm, and the retardation value of the retardation plate is Δn of the liquid crystal element.
A color liquid crystal display device having a value larger than the d value by 50 to 200 nm. 8. A pair of substrates including a first substrate having a first electrode and a second substrate having a second electrode,
A liquid crystal element sandwiching a twisted nematic liquid crystal; a pair of polarizing plates sandwiching the liquid crystal element; and a position disposed between the liquid crystal element and one of the pair of polarizing plates. A phase difference plate, wherein the angle between the absorption axis of the polarizing plate disposed on the opposite side of the phase difference plate with respect to the liquid crystal element and the lower liquid crystal molecule alignment direction of the liquid crystal element is 35 ° ± 10 °. And the Δnd value of the liquid crystal element expressed by the product of the difference Δn in birefringence of the nematic liquid crystal and the distance d between the pair of substrates is 130.
0 nm to 1600 nm, and the retardation value of the retardation plate is Δn of the liquid crystal element.
A color liquid crystal display device characterized by being 300 to 500 nm larger than d value. 9. The color liquid crystal display device according to claim 7, wherein the phase difference plate has a refractive index nx of a slow axis of the phase difference plate,
The refractive index ny in the y-axis direction and the refractive index nz in the z-axis direction are:
A color liquid crystal display device comprising a biaxial retardation plate having a relationship of nx>nz> ny. 10. The color liquid crystal display device according to claim 7, wherein a reflection plate is provided outside a polarizing plate disposed on a side opposite to the retardation plate with respect to the liquid crystal element. Characteristic liquid crystal display device. 11. The color liquid crystal display device according to claim 7, wherein one or both of the pair of polarizing plates is a color polarizing plate manufactured by dyeing a dye. Color liquid crystal display. 12. The color liquid crystal display device according to claim 7, wherein the phase difference plate is a temperature compensation type phase difference plate whose retardation value varies with temperature. Display device.