JP3103223B2 - Color liquid crystal display - Google Patents

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 for performing color display by a birefringence effect using a double cell.

2. Description of the Related Art In recent years, expectations for a light-weight, thin, and low-power liquid crystal display have been increasing. In particular, a color-compatible and reflective display is desired as a display mounted on a portable personal computer or the like. ing.

[0003]

2. Description of the Related Art Conventionally, as a method of color development in a color liquid crystal display device, there are roughly a method using a color filter and a method using an interference color due to a birefringence effect.

[0004] In the color development by the color filter, R (red), G (green), and B (blue) are applied to each pixel to display one color with three pixels.

[0005] In addition, the coloring method by the birefringence effect includes S
BE (Super-twisted Birefringence Effect) and EC
B (Electrically Controlled Birefringence).

The ECB controls the birefringence of a liquid crystal cell by applying an electric field to cause interference between ordinary light and extraordinary light to obtain an interference color. The ECB develops each color depending on the strength of the electric field. SB
E is based on birefringence of a liquid crystal cell having a super-twisted nematic liquid crystal molecular arrangement having a twist angle of 180 ° to 360 °, and sets the linear polarization axis of incident light to the long axis direction of liquid crystal molecules on the electrode substrate surface on the incident light side. By displacing them from each other, an optical interference phenomenon due to the birefringence of the liquid crystal appears, and an interference color is obtained.

In general, a reflection type liquid crystal display device has been developed to reduce the weight and size of the color liquid crystal display device. For example, in a color display by a reflection type liquid crystal display device using SBE type birefringence, R, It is easy to obtain each color of G and B, but it is difficult to obtain black and white.

FIG. 4 is a diagram for explaining chromaticity and luminance of a conventional color liquid crystal display device utilizing birefringence. FIG. 4A is a graph of chromaticity, and FIG. 4B is a graph of luminance. These graphs are obtained by applying a voltage to a 180 μm twisted 20 μm cell.
As shown in (A) and (B), a voltage of 5 V or more is required to obtain white and black with relatively high luminance. In addition,
The chromaticity change takes a fixed locus irrespective of the liquid crystal, cell thickness and the like.

On the other hand, in the transmission type, the DSTN (Do
Double-layered Super Twisted Nematic) has been proposed. FIG. 5 shows a conventional DSTN.
FIG. 1 is a configuration diagram of a color liquid crystal display device.

The color liquid crystal display device 11 shown in FIG.
Stack two liquid crystal panels (liquid crystal cells) 12, 13
These are sandwiched between polarizing plates 14 and 15.
The liquid crystal cell 12 has a liquid crystal layer between glass substrates 12a and 12b.
12c, and the liquid crystal cell 13 is also made of glass.
Having a liquid crystal layer 13c between the substrates 13a and 13b.
is there. In this case, the liquid crystal 13 is a driving panel,
Transparent electrode 13a on substrate 13a₁Formed on a glass substrate
13b, a color filter 16 and a transparent electrode 13b ₁Is shaped
Is done.

Further, the polarizing plates 14 and 15 are shown in FIG.
As shown in (C), the transmission axes are provided substantially orthogonal to each other. FIGS. 5B and 5C are schematic diagrams of driving in the liquid crystal cell 13. In a state where no voltage is applied between the electrodes 13a ₁ and 13b ₁ , as shown in FIG. the liquid crystal molecules 13c ₁ becomes the state twist. Also,
When a voltage is applied between the electrodes 13a ₁ and 13b ₁ ,
As shown in FIG. 5 (C) a state in which the liquid crystal molecules 13c ₁ are aligned in the thickness direction.

In such a DSTN type color liquid crystal display device 11, since perfect black and white can be obtained by the compensation action, a desired color can be obtained through a color filter.

[0013]

However, in the DSTN type color liquid crystal display device 11 as described above, although the black display is improved when the voltage is not applied, it is difficult to obtain a bright white color. The reflective type has a problem that it is dark because there is no backlight. On the other hand, a transmissive type can obtain bright white, but has a problem that it is difficult to reduce power consumption and reduce the weight and size of the device.

The use of a color filter as a color developing method has a problem that it is difficult to improve the resolution because three pixels are used for color display.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a color liquid crystal display device which displays achromatic white with high brightness and improves resolution.

[0016]

The object of the present invention is to provide a first liquid crystal panel having first liquid crystal molecules having a predetermined twist angle,
A second liquid crystal panel which is arranged in tandem with the first liquid crystal panel and has a second liquid crystal molecule twisted in a direction opposite to the first liquid crystal molecule; and one of the first and second liquid crystal panels. A driving source to be driven, two polarizing parts sandwiching the first and second liquid crystal panels, the directions of transmission axes of which are the same or similar, and a reflection provided outside one of the two polarizing parts. Part, the interference due to the birefringence effect of the liquid crystal panel
With a color liquid crystal display device that performs color display using colors
There, if the cell gap is d with the refractive index anisotropy of the first and second liquid crystal panels and [Delta] n, [Delta] nd
Is set to be 1.0 to 3.0 μm.

[0017]

As described above, the color liquid crystal display of the present invention is a conventional DSTN type device, in which the first and second liquid crystal panels having liquid crystal molecules whose twist directions are opposite to each other are connected to the respective transmission axes of the respective axes. It is sandwiched between two polarization parts having the same or similar directions, and a reflection part is provided outside one of the polarization parts.

That is, the first and second liquid crystal panels are:
When no voltage is applied to either one, the optical rotation dispersion and phase dispersion of light are completely compensated. Therefore, by sandwiching this state between two polarizing portions having the same or similar transmission axis directions, it is possible to obtain a completely bright achromatic white. The display of each color is performed by driving one of the liquid crystal panels by a driving source. Since the color is generated by the birefringence effect in one pixel, the resolution is improved more than the color generated by the color filter. It becomes possible.

[0019]

FIG. 1 is a block diagram showing an embodiment of the present invention.
The color liquid crystal display device 21 shown in FIG. 1 is a reflection type of the SBE system, and a compensating panel 22 as a first liquid crystal panel and a driving panel 23 as a second liquid crystal panel are provided by two polarizing plates 24 and 25. It is provided with a reflection plate (may be a reflection film) 26 outside the polarizing plate 25.

The compensation panel 22 includes glass substrates 22a, 22
2b sandwiches the liquid crystal layer 22c.
Right 18 having a right 180 ° (180 ° ~360 ° good either) the first liquid crystal molecules 22c ₁ of the twist to 2c
This is a 0 ° twist cell.

The driving panel 23 includes a glass substrate 23
a, in which the liquid crystal layer 23c is sandwiched by 23b, (may be any of 180 ° to 360 °) left 180 ° to twist in the opposite direction to the liquid crystal molecules 22c ₁ first the liquid crystal layer 23c twist (STN ) is a second left 180 ° twist cell having a liquid crystal molecule 23c ₁ of the. Note that transparent electrodes (not shown) corresponding to the respective pixels are formed on the glass substrates 23a and 23b, and are driven by the driving source 27.

Then, the compensation panel 22 and the driving panel 23
And are installed in tandem.

Here, the compensation panel 22 and the driving panel 2
In No. 3, Δnd is set to 1.0 to 3.0 μm. In this case, Δn is the refractive index anisotropy (the refractive index is 0.05 to 0.2 when the medium is anisotropic), and d is the cell gap. This is because, while the cell gap d of the conventional liquid crystal panel is 6 μm, the thickness can be increased to 10 μm to 30 μm in the present invention, which is easy in manufacturing.

On the other hand, the polarizing plates 24 and 25 are provided so that the directions of their transmission axes are the same or approximate. The same or similar means that the angle between the transmission axis of the polarizing plate 24 and the transmission axis of the polarizing plate 25 is 10 ° or less.

Here, FIG. 2 is a diagram for explaining the angle of the transmission axis in the polarizing plate of FIG. FIG. 2 (A)
The rubbing (orientation) directions of the glass substrate 23a (upper substrate) and the glass substrate 23b (lower substrate) of the drive panel 23 are shown, and the directions of the transmission axes of the polarizing plates 24 and 25 (polarizer directions) 2
The angle between 4a, 25a and each rubbing direction is 45 °
(± 5 °). Note that it is the angle between the rubbing direction of the rubbing direction and the lower substrate of the upper substrate second twist angle of the liquid crystal molecules 23c ₁ of the (TW angle).

On the other hand, as shown in FIG. 2B, when the angle between the rubbing direction of the upper and lower substrates is θ, the polarizing plate 2
The angle between the rubbing direction and the transmission axis directions (polarizer directions) 24a and 25a of the light-emitting elements 4 and 25 may be set to θ / 2 (± 5 °).

As shown in FIG. 2C, when the rubbing directions of the upper and lower substrates are the same, the angles of the polarizer (analyzer) directions 24a and 25a with respect to this direction are 45 °.
(± 5).

Next, returning to FIG.
1 will be described. In FIG. 1, first, when no voltage is applied to the drive panel 23 (0 V), incident light (polarized light) from the polarizing plate 24 is applied to the first cell in the compensation cell 22.
Of 180 ° by the liquid crystal molecules 22c ₁ of FIG.

In the driving panel 23, the second liquid crystal molecules 23c
180 ° optical rotation dispersion in the opposite direction by ₁
In the state where the light is incident on the polarizing plate 2, the light passes through the polarizing plate 25 whose transmission axis is substantially the same as that of the polarizing plate 24, and is reflected by the reflecting plate 26. The reflected light is
Passing through the polarizing plate 25 again, the optical rotation is dispersed by the driving panel 23, and further the optical rotation is dispersed in the opposite direction by the compensating panel 22 to pass through the polarizing plate 24, thereby displaying a high brightness and completely achromatic white. Can be done.

On the other hand, when a voltage of 5 V is applied to the drive panel 23, the incident light that is optically dispersed by the compensation panel 22 is
Pass are phase dispersed in a driving panel 23 to the second liquid crystal molecules 23c ₁ of the 180 ° twisted by applying a voltage, it is reflected by the reflecting plate 26 through the polarizing plate 25. The reflected light is
After being polarized by the polarizing plate 25 and phase-dispersed by the drive panel 23, it is further optically dispersed by the compensating panel 22 and passes through the polarizing plate 24 to perform color display (red display).

Further, the drive panel 23, by applying an appropriate voltage between the 0V of 5V, phase dispersion corresponding to the second voltage applied by the liquid crystal molecules 23c ₁ of the drive panel 23 is performed, birefringence effect The color display (blue display) is performed with a desired interference color.

FIG. 3 is a diagram for explaining the reflectance of each color according to the present invention. FIG. 3 shows the reflection of each color when the transmission axis directions of the two polarizing plates in the conventional DSTN method are in a cross state (orthogonal state) and when the transmission axis directions are in a parallel state (substantially the same direction) in the present invention. It is an example of a result of a measured value (Y value) of a rate. As shown in FIG. 3, the reflectance in the case of white was significantly improved as compared with the conventional case.

Further, according to the present invention, the color can be displayed with one pixel as compared with the related art using a color filter, so that the resolution can be improved.

In the above embodiment, the compensation panel 22 is described as a 180 ° right twist cell, but the same effect can be obtained by using a twisted phase difference plate.

[0035]

As described above, according to the present invention, the first and second liquid crystal panels having liquid crystal molecules having opposite twist directions are arranged in tandem, and the directions of their transmission axes are the same or approximate. By sandwiching between two polarizing portions and providing a reflecting portion outside one of the polarizing portions, achromatic white with high brightness can be displayed and resolution can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram for explaining an angle of a transmission axis in the polarizing plate of FIG.

FIG. 3 is a diagram for explaining the reflectance of each color according to the present invention.

FIG. 4 is a diagram for explaining chromaticity and luminance of a conventional color liquid crystal display device using birefringence.

FIG. 5 is a configuration diagram of a conventional DSTN type color liquid crystal display device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 21 Color liquid crystal display device 22 Compensation panel 23 Drive panel 24, 25 Polarizer 26 Reflector 27 Drive source 22a, 22b, 23a, 23b Glass substrate 22c, 23c Liquid crystal layer 22c ₁ First liquid crystal molecule 23c ₁ Second liquid crystal molecule 24a, 25a Transmission axis direction

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-118516 (JP, A) JP-A-4-13924 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1347

Claims (3)

(57) [Claims] A first twisted liquid crystal molecule having a predetermined twist angle;
A first liquid crystal panel, and the first liquid crystal panel is arranged in tandem with the first liquid crystal panel;
Having a second liquid crystal molecule twisted in the opposite direction to
A liquid crystal panel, and a drive source for driving any of the first and second liquid crystal panels
And sandwiching the first and second liquid crystal panels, and
It includes two polarizing parts having the same or similar axis directions, and a reflecting part provided outside one of the two polarizing parts.
SeeUsing the interference color due to the birefringence effect of the liquid crystal panel,
A color liquid crystal display device for performing color display, The Let the refractive index anisotropy of the first and second liquid crystal panels be Δn.
Together withCell gapIs d, Δnd is 1.0 to
Color liquid characterized to be set to 3.0 μm
Crystal display device. 2. A transmission axis of one of the two polarizing portions is a rubbing axis on the upper side of the first liquid crystal panel, or the other polarizing portion is on a lower side of the second liquid crystal panel. 2. The color liquid crystal display device according to claim 1, wherein the angle is 45 degrees or near the rubbing axis. 3. Upper and lower substrates of the first or second liquid crystal panel.
Assuming that the angle formed by the rubbing direction of the plate is θ, at least one transmission axis of the two polarizing portions is
The angle between the rubbing directions of the upper and lower substrates is (θ / 2)
2. The color liquid crystal display device according to claim 1 , wherein the angle is set at or near the angle .