JPH08262435A - Color liquid crystal display device - Google Patents

Abstract

PURPOSE: To make it possible to display plural colors and black and white which are colorless with the same pixels by obtaining a bright color display by coloring light without using color filters. CONSTITUTION: A phase difference plate 21 is arranged on the front surface side of a liquid crystal cell 10 which is formed by twist orienting liquid crystal molecules 90 deg. and providing the rear surface side with a reflection film 19. A polarizing plate 20 is arranged on the front surface side of this phase difference plate 21 and the delay axis of the phase difference plate 21 is intersected nearly orthogonally with the liquid crystal molecule orientation direction on the front surface side substrate 11 of the liquid crystal cell 10. The transmission axis 10 of the polarizing plate 20 is intersected diagonally at an angle of nearly 45 deg. with the delay phase axis of the phase difference plate 21. The Δnd of the liquid crystal cell 10 is set at 830±50nm and the retardation of the phase difference plate 21 is set at 610±40mn.

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 for obtaining a colored display without using a color filter.

[0002]

2. Description of the Related Art As a color liquid crystal display device capable of providing a colored display, one that colors light using a color filter is generally used. However, since this color liquid crystal display device uses a color filter to color light, it has a problem that the light transmittance is low and the display is dark.

This is due to the absorption of light by the color filter, and the color filter absorbs not only the wavelength light outside the wavelength band corresponding to the color but also the light in the wavelength band at a considerably high absorption rate. Therefore, the colored light that has passed through the color filter becomes light in which the light intensity is significantly reduced compared to the light in the wavelength band before entering the color filter, and the display becomes dark.

The liquid crystal display device has a transmissive type which uses the light from the backlight for display, and an external light (natural light, indoor illumination light, etc.) which is arranged on the back side. There is a reflection type that reflects on a reflection film to display, but when the color liquid crystal display device is a reflection type, light that enters from the front surface side, is reflected by the reflection film on the back surface side, and goes out to the front surface side is displayed. Since the light intensity is doubly reduced by passing through the color filter twice, the display becomes extremely dark and almost unusable as a display device.

Moreover, in the above color liquid crystal display device, since the display color of each pixel is determined by the color of the color filter corresponding to that pixel, in order to display many colors,
For example, it is necessary to obtain a desired display color by controlling the light transmission of each pixel by forming a set of three pixels corresponding to the color filters of the three primary colors of red, green and blue. The intensity of light is significantly weakened and the display color is dark.

On the other hand, as a conventional color liquid crystal display device for obtaining a colored display without using a color filter, an EC
A B-type (birefringence effect type) liquid crystal display device is known.
In this ECB type liquid crystal display device, a liquid crystal cell sandwiching a liquid crystal between a pair of substrates is sandwiched, and a polarizing plate is arranged on each of the front surface side and the back surface side of the liquid crystal cell. , The linearly polarized light that has passed through one of the polarizing plates and becomes incident light becomes elliptically polarized light with different polarization states due to the birefringence effect of the liquid crystal layer in the process of passing through the liquid crystal cell, and the other light The light incident on the polarizing plate of 1 and transmitted through the other polarizing plate becomes colored light having a color corresponding to the ratio of the light intensities of the respective wavelength lights forming the light.

That is, the ECB type liquid crystal display device is
Light is colored by utilizing the birefringence effect of the liquid crystal layer of the liquid crystal cell and the polarization effect of the pair of polarizing plates without using a color filter. Therefore, there is no absorption of light by the color filter. It is possible to obtain a bright color display by increasing the transmittance.

Moreover, in the above ECB type liquid crystal display device, the birefringence of the liquid crystal layer changes depending on the alignment state of the liquid crystal molecules according to the voltage applied between the electrodes of the two substrates of the liquid crystal cell, and accordingly the other birefringence is Since the polarization state of each wavelength light entering the polarizing plate changes, the color of the colored light can be changed by controlling the voltage applied to the liquid crystal cell, and therefore, the same pixel displays multiple colors. be able to.

[0009]

However, the conventional ECB type liquid crystal display device has a problem that it is not possible to display achromatic white and black. The present invention provides a color liquid crystal display device capable of coloring light without using a color filter to obtain a bright color display and displaying a plurality of colors and achromatic white and black in the same pixel. This is the purpose.

[0010]

In the color liquid crystal display device of the present invention, liquid crystal molecules are twist-aligned at a twist angle of about 90 ° and a liquid crystal cell provided with a reflective film on the back side, and a surface of the liquid crystal cell. A retardation plate arranged on the side,
It consists of a polarizing plate arranged on the surface side of this retardation plate,
And, the slow axis of the retardation plate is substantially orthogonal to the alignment direction of the liquid crystal molecules on the surface side substrate of the liquid crystal cell, the transmission axis of the polarizing plate with respect to the slow axis of the retardation plate Of the liquid crystal cell and the liquid crystal layer thickness d has a value Δnd of 830 ± 50 nm, and the retardation of the retardation plate is The value is 610 ± 40 nm.

Another color liquid crystal display device of the present invention is a liquid crystal cell in which liquid crystal molecules are twist-aligned at a twist angle of approximately 90 °, a polarizing plate disposed on the surface side of the liquid crystal cell, and the liquid crystal cell. A retardation plate arranged on the back side of
Consisting of a reflective film arranged on the back side of the retardation plate,
And, the slow axis of the retardation plate is substantially orthogonal to the alignment direction of the liquid crystal molecules on the back side substrate of the liquid crystal cell, the transmission axis of the polarizing plate on the front side substrate of the liquid crystal cell The liquid crystal molecules intersect obliquely with the alignment direction of the liquid crystal molecules at an angle of about 45 °, and the product Δnd of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the liquid crystal layer thickness d has a value of 8
The retardation value of the retardation plate is 30 ± 50 nm, and the retardation value is 610 ± 40 nm.

[0012]

The color liquid crystal display device of the present invention utilizes external light and reflects light incident from the front surface side on the back surface side for display. In the former liquid crystal display device, the light is incident from the front surface side. Light is sequentially transmitted through the polarizing plate, the retardation plate and the liquid crystal layer of the liquid crystal cell and is reflected by the reflection film, and again transmitted through the liquid crystal layer and the retardation plate in sequence and is incident on the polarizing plate, Of the light, light of a polarization component that passes through the polarizing plate is emitted, and in the latter liquid crystal display device, incident light from the surface side thereof causes the polarizing plate, the liquid crystal layer of the liquid crystal cell, and the retardation plate. The light is transmitted through the retardation film and the liquid crystal layer in order and is then incident on the polarizing plate, and the light of the polarized component that passes through the polarizing plate is emitted. To do.

In any of the color liquid crystal display devices, in a non-selected state (a state in which the liquid crystal molecules are in the initial twist alignment state) in which a voltage for rising and aligning the liquid crystal molecules is not applied between the electrodes of the liquid crystal cell, The linearly polarized light that has entered through the polarizing plate passes through the phase difference plate and the liquid crystal layer of the liquid crystal cell, the polarization state of which is changed by the birefringence action of the phase difference plate and the liquid crystal layer. The polarization state is further changed in the process of passing through the retardation plate, and each wavelength light becomes elliptically polarized light with a different polarization state, and the light enters the polarizing plate and is transmitted through this polarizing plate. However, the colored light has a color corresponding to the ratio of the light intensities of the respective wavelengths of light.

Further, when a voltage is applied between the electrodes of the liquid crystal cell, the liquid crystal molecules are vertically aligned while maintaining the twist alignment state, and the retardation of the liquid crystal layer is changed by the change of the alignment state of the liquid crystal molecules. The light transmitted back and forth between the phase difference plate and the liquid crystal layer becomes a light in a polarization state different from the above-mentioned non-selected state and enters the polarizing plate, and when the liquid crystal molecules rise vertically and are aligned, the liquid crystal layer The birefringence effect due to is almost eliminated, and the light transmitted back and forth between the retardation plate and the liquid crystal layer is incident on the polarizing plate as light in a polarized state which is only subjected to the birefringence effect of the retardation plate.

In this case, in the former liquid crystal display device, the retardation plate is adjacent to the polarizing plate, but since the transmission axis of the polarizing plate and the slow axis of the retardation plate are slanted, The linearly polarized light that has passed through the plate and is incident first has its polarization state changed by the birefringence effect of the retardation plate, and that light enters the liquid crystal cell and changes its polarization state according to the liquid crystal molecule alignment state of the liquid crystal layer. be changed.

In the latter liquid crystal display device, the liquid crystal cell is adjacent to the polarizing plate, but the transmission axis of the polarizing plate and the alignment direction of the liquid crystal molecules on the substrate on the surface side of the liquid crystal cell are obliquely displaced. Therefore, the linearly polarized light that passes through the polarizing plate and is incident is first subjected to the birefringence effect according to the alignment state of the liquid crystal molecules by the liquid crystal layer of the liquid crystal cell to change the polarization state, and the light is transmitted to the retardation plate. Upon entering, the polarization state can be changed by this retardation plate.

Further, in the latter liquid crystal display device, the slow axis of the retardation plate is substantially orthogonal to the alignment direction of the liquid crystal molecules on the substrate on the back side of the liquid crystal cell.
The slow axis of the retardation plate and the transmission axis of the polarizing plate are obliquely displaced from each other, so that the liquid crystal molecules of the liquid crystal cell rise vertically and are aligned, and the linearly polarized light that has passed through the polarizing plate and enters is the polarized light. Even when the light passes through the liquid crystal layer of the liquid crystal cell and enters the retardation plate in that state, the polarization state of the light can be changed by the birefringence effect of the retardation plate.

As described above, the polarization state of the light that is linearly polarized by the polarizing plate and is incident on the polarizing plate and transmitted through the retardation plate and the liquid crystal layer and incident on the polarizing plate is the alignment of the liquid crystal molecules of the liquid crystal cell. Therefore, when the voltage applied between the electrodes of the liquid crystal cell is changed, the ratio of the light intensities of the light beams of the respective wavelengths that pass through the polarizing plate and are emitted changes, and the emitted light is emitted in other colors. Becomes the colored light.

Then, as in the former liquid crystal display device, the slow axis of the retardation plate is made substantially orthogonal to the alignment direction of liquid crystal molecules on the substrate on the surface side of the liquid crystal cell, and the transmission axis of the polarizing plate is set to the above-mentioned position. The slow axis of the retardation plate is obliquely crossed at an angle of about 45 °, or the slow axis of the retardation plate is formed on the substrate on the back side of the liquid crystal cell as in the latter liquid crystal display device. The liquid crystal cell is substantially orthogonal to the alignment direction, the transmission axis of the polarizing plate is obliquely intersected with the alignment direction of the liquid crystal molecules on the substrate on the surface side of the liquid crystal cell at an angle of about 45 °, and the Δnd of the liquid crystal cell is Value 830 ± 50
nm, the retardation value of the retardation plate is 610 ± 4
By setting it to 0 nm, when the liquid crystal molecules of the liquid crystal cell are in a certain alignment state, the light passes through the retardation plate and the liquid crystal layer back and forth along the transmission axis of the polarizing plate of each wavelength light in the visible light band. The magnitudes of the components in the directions become substantially equal, and most of the light passes through the polarizing plate with a high transmittance and exits,
The display becomes white, which is an achromatic bright display. Further, when the liquid crystal molecules of the liquid crystal cell are in some other alignment state, most of the light in the visible light wavelength band is absorbed by the polarizing plate as the light transmitted back and forth between the retardation plate and the liquid crystal layer. , The display is black, which is an achromatic dark display.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to. FIG. 1 is a cross-sectional view of a color liquid crystal display device of this embodiment. This liquid crystal display device includes a liquid crystal cell 10 having a reflective film 19 on the back surface side, and this liquid crystal cell 10
Of the retardation film 21 arranged on the surface side (upper side in the figure) of the
And one polarizing plate 20 arranged on the front surface side of the retardation plate 21.

The liquid crystal cell 10 has transparent electrodes 13 and 14 formed of an ITO film or the like, on which alignment films 15 and 16 are formed.
A pair of transparent substrates (for example, glass substrates) 11 on which
A nematic liquid crystal 18 is sandwiched between 12 and molecules of the nematic liquid crystal are twisted between the substrates 11 and 12, and the substrates 11 and 12 are bonded to each other via a frame-shaped sealing material 17. Is sealed in a region surrounded by the sealing material 17 between the two substrates 11 and 12.

The liquid crystal cell 10 is of an active matrix type in which, for example, a TFT (thin film transistor) is used as an active element, and a plurality of electrodes 13 formed on a substrate 11 on the surface side thereof are arranged in rows and columns. The pixel electrode and the electrode 14 formed on the substrate 12 on the back surface side are a single film-like counter electrode facing all of the pixel electrodes 13.

Although not shown in FIG. 1, on the substrate 11 on which the pixel electrodes 13 are formed, a plurality of TFTs respectively connected to the pixel electrodes 13 and a gate wiring for supplying a gate signal to the TFTs in each row are provided. And data wiring for supplying a data signal to the TFTs in each column.

The alignment films 15 and 16 provided on both the substrates 11 and 12 are horizontal alignment films made of polyimide or the like, and the alignment films 15 and 16 are subjected to an alignment treatment (rubbing treatment) in directions substantially orthogonal to each other. The molecules of the liquid crystal 18 are regulated by the alignment films 15 and 16 in the alignment direction on both the substrates 11 and 12 (on the alignment films 15 and 16), and a slight pretilt with respect to the surfaces of the alignment films 15 and 16. In a state of being inclined at an angle, the two substrates 11 and 12 are twist-aligned at a twist angle of approximately 90 °.

The reflection film 19 is an omnidirectional reflection film obtained by vapor-depositing a metal film such as silver or aluminum on the surface of a base sheet made of a resin film or the like. The reflection film 19 is the back surface of the liquid crystal cell 10. It is attached to the outer surface of the side substrate 12.

Then, the polarizing plate 20 and the phase difference plate 21 are provided.
Is provided with its optical axis (transmission axis in polarizing plate, slow axis in retardation plate) oriented as follows. Figure 2
The orientation of liquid crystal molecules on both substrates 11 and 12 of the liquid crystal cell 10, the transmission axis of the polarizing plate 20, and the slow axis of the retardation plate 21 are shown.

As shown in FIG. 2, the liquid crystal molecule orientation direction 11a on the front surface side substrate 11 of the liquid crystal cell 10 is substantially counterclockwise with respect to the horizontal axis O of the liquid crystal display device (as viewed from the front surface side). The liquid crystal molecule alignment direction 12a on the back surface side substrate 12 is substantially orthogonal to the liquid crystal molecule alignment direction 11a on the front surface side substrate 11, and the liquid crystal molecule shows its twist direction by a broken line arrow. As described above, the twist alignment is performed in the clockwise direction in the figure from the rear substrate 12 to the front substrate 11 at a twist angle of approximately 90 °.

Further, as shown in FIG. 2, the transmission axis 20a of the polarizing plate 20 is oriented substantially parallel or substantially orthogonal to the horizontal axis O (parallel in the figure), and the slow axis 21a of the retardation plate 21.
Is shifted counterclockwise by approximately 135 ° with respect to the horizontal axis O.

That is, the retardation plate 21 arranged on the front surface side of the liquid crystal cell 10 has the slow axis 21a thereof.
The polarizing plate 20 provided on the front surface side substrate 11 substantially orthogonal to the liquid crystal molecule orientation direction 11a and arranged on the front surface side of the retardation plate 21 has its transmission axis 20a in the retardation plate 21. It is provided obliquely intersecting the slow axis 21a at an angle of about 45 °.

In the liquid crystal cell 10, the product Δnd of the refractive index anisotropy Δn of the liquid crystal 18 and the liquid crystal layer thickness d has a value of 830.
The retardation film 21 is designed to have a thickness of ± 50 nm, and the retardation plate 21 has a retardation value of 610 ± 40 nm.

This color liquid crystal display device uses external light and reflects light incident from the front surface side by the reflection film 19 on the rear surface side of the liquid crystal cell 10 for display. This liquid crystal display device is a liquid crystal display device. Electrodes 1 on both substrates 11 and 12 of the cell 10
A display is driven by applying a voltage between 3 and 14.

In this color liquid crystal display device, incident light from the surface side thereof is sequentially transmitted through the polarizing plate 20, the retardation plate 21 and the liquid crystal layer of the liquid crystal cell 10, and is reflected by the reflection film 19. Again, the liquid crystal layer and the retardation film 21 are sequentially transmitted to enter the polarizing plate 20, and out of the light, the light of the polarization component that transmits the polarizing plate 20 is emitted.

Then, in a non-selected state (a state in which the liquid crystal molecules are in the initial twist alignment state) in which a voltage for rising and aligning the liquid crystal molecules is not applied between the electrodes 13 and 14 of the liquid crystal cell 10, the light is transmitted through the polarizing plate 20. The linearly polarized light that has entered is changed in polarization state by the birefringence action of the linearly polarized light in the process of passing through the retardation plate 21 and the liquid crystal layer of the liquid crystal cell 10, and is reflected by the reflection film 19 to be aligned with the liquid crystal layer again. The polarization state is further changed in the process of passing through the phase difference plate 21, and each wavelength light becomes elliptically polarized light having a different polarization state, and the light is incident on the polarizing plate 20 and the polarizing plate 2
The light transmitted through 0 becomes colored light having a color corresponding to the ratio of the light intensities of the light components of the wavelengths.

When a voltage is applied between the electrodes 13 and 14 of the liquid crystal cell 10, the liquid crystal molecules are vertically aligned while maintaining the twist alignment state, and the retardation of the liquid crystal layer is changed by the change of the alignment state of the liquid crystal molecules. The light transmitted back and forth between the retardation plate 21 and the liquid crystal layer enters the polarizing plate 20 as light having a polarization state different from the non-selected state.

Further, when the liquid crystal molecules of the liquid crystal cell 10 stand up substantially vertically, the birefringence effect of the liquid crystal layer of the liquid crystal cell 10 is almost eliminated, and the light transmitted back and forth between the retardation plate 21 and the liquid crystal layer is transmitted. , And becomes a light in a polarization state that is affected only by the birefringence effect of the retardation plate 21 and enters the polarizing plate 20.

In this case, in the liquid crystal display device of this embodiment, the retardation plate 21 is adjacent to the polarizing plate 20, but the transmission axis 20a of the polarizing plate 20 and the slow axis 21 of the retardation plate 21 are adjacent to each other.
Since a is obliquely displaced, linearly polarized light that has passed through the polarizing plate 20 and is incident is first changed in polarization state by the birefringence effect of the retardation plate 21, and the light is incident on the liquid crystal cell 10, The polarization state can be changed according to the liquid crystal molecule alignment state of the liquid crystal layer.

As described above, the polarization state of the light which is linearly polarized by the polarizing plate 20 and enters the polarizing plate 20 after being transmitted back and forth through the retardation plate 21 and the liquid crystal layer of the liquid crystal cell 10 is as follows. The intensity varies depending on the alignment state of the liquid crystal molecules of the liquid crystal cell 10. Therefore, when the voltage applied between the electrodes 13 and 14 of the liquid crystal cell 10 is changed, the light intensity of each wavelength light emitted through the polarizing plate 20 is emitted. The ratio of the two changes and the emitted light becomes colored light of another color.

Therefore, according to this liquid crystal display device,
Light can be colored to obtain a bright color display without using a color filter, and a plurality of colors can be displayed in the same pixel.

In this case, in the conventional ECB type liquid crystal display device, in order to change the display color, the voltage applied between the electrodes of the liquid crystal cell has to be largely changed. The display color can be changed without changing the applied voltage so much, and therefore, a plurality of colors can be displayed with a relatively low applied voltage.

Moreover, in this liquid crystal display device, the slow axis 21a of the retardation plate 21 is made substantially orthogonal to the liquid crystal molecule alignment direction 11a on the front surface side substrate 11 of the liquid crystal cell 10, and the transmission axis of the polarizing plate 20 is set. 20a is the phase difference plate 21
And the value of Δnd of the liquid crystal cell 10 is 830 ±.
50 nm, the retardation value of the retardation plate 21 is set to 610
Since it is set to ± 40 nm, not only a plurality of colors but also achromatic white and black can be displayed in the same pixel.

That is, in this liquid crystal display device,
When the liquid crystal molecules of the liquid crystal cell 10 are in an aligned state, the light transmitted back and forth between the retardation plate 21 and the liquid crystal layer is
The transmitted light component in the direction along the transmission axis 20a of the polarizing plate 20 becomes large and substantially equal for almost all wavelength light in the visible light band, and most of the light passes through the polarizing plate 20 with a high transmittance and is emitted. Then, the display becomes white, which is an achromatic bright display.

Further, when the liquid crystal molecules of the liquid crystal cell 10 are in another alignment state, most of the light transmitted back and forth between the retardation plate 21 and the liquid crystal layer is absorbed by the polarizing plate 20, and a display is made. Becomes black, which is an achromatic dark display.

In FIG. 3, the transmission axis 20a of the polarizing plate 20 and the slow axis 21a of the retardation plate 21 are oriented as shown in FIG. 2, the Δnd value of the liquid crystal cell 10 is 830 nm, and the retardation value of the retardation plate is It is a CIE chromaticity diagram which shows the color change of the emitted light of the liquid crystal display device set to 610 nm, and the point W has shown the center of the achromatic region in the figure.

As shown in this chromaticity diagram, the emitted light of the liquid crystal display device is in the yellow-green region in the non-selected state in which the voltage for rising and aligning the liquid crystal molecules is not applied between the electrodes 13 and 14 of the liquid crystal cell 10. It is light, and when a voltage is applied between the electrodes 13 and 14, the color of the emitted light changes as shown in the figure as the voltage is increased.

FIG. 4 shows the light emission rate and the color change of the emitted light with respect to the voltage applied to the liquid crystal cell 10 in the liquid crystal display device. The display color of this liquid crystal display device is applied to the liquid crystal cell 10. As the voltage increases,
From yellow green in the non-selected state, blue → black (dark display of achromatic color) →
Change from white (achromatic bright display) to magenta.

Thus, according to the above liquid crystal display device,
The same pixel can display yellow-green, blue, black, white, and red-purple colors, and all of these display colors range from 0 to about 4v.
Can be obtained at a relatively low voltage (see FIG. 4).

3 and 4, the liquid crystal cell 10 is shown.
The change of the display color when the value of Δnd of 830 nm and the value of retardation of the retardation plate 21 is 610 nm is shown. The value of Δnd of the liquid crystal cell 10 is 830 ± 50 nm, and the retardation value of the retardation plate 21 is A similar display color can be obtained within a range of 610 ± 40 nm.

In the above liquid crystal display device, the liquid crystal cell 1
Since the retardation plate 21 is arranged on the front surface side of 0, the viewing angle dependence of the light emission rate can be reduced by the retardation plate 21, so that the displayed image can be viewed brightly and with good contrast. It is possible to widen the viewing angle.

Although the reflection film 19 is provided on the outer surface of the back side substrate 12 of the liquid crystal cell 10 in the above embodiment, the reflection film 19 may be provided on the inner surface of the back side substrate 12 of the liquid crystal cell 10. In that case, the electrode (counter electrode in the above embodiment) 14 provided on the rear substrate 12 may be formed of a metal film such as an aluminum film, and the electrode 14 may also serve as a reflective film.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a cross-sectional view of the color liquid crystal display device of this embodiment. This liquid crystal display device has a liquid crystal cell 10 in which liquid crystal molecules are twist-aligned at a twist angle of approximately 90 °, and a surface side of the liquid crystal cell 10. One polarizing plate 20 arranged on the upper side in the figure, a retardation plate 21 arranged on the back side of the liquid crystal cell 10, and a reflection film 19 arranged on the back side of the retardation plate 21. It consists of

The liquid crystal cell 10 is the same as the first liquid crystal cell described above.
The reflective film 19 is separated from the liquid crystal cell 10 in the above embodiment, and the liquid crystal cell itself is the same as that in the first embodiment. . The reflection film 19 is an omnidirectional reflection film in which a metal film such as silver or aluminum is deposited on the surface of a base sheet made of a resin film or the like.

Then, the polarizing plate 20 and the retardation plate 21 are used.
Is provided with its optical axis (transmission axis in polarizing plate, slow axis in retardation plate) oriented as follows. FIG.
The orientation of liquid crystal molecules on both substrates 11 and 12 of the liquid crystal cell 10, the transmission axis of the polarizing plate 20, and the slow axis of the retardation plate 21 are shown.

As shown in FIG. 6, the liquid crystal molecule orientation direction 11a on the front surface side substrate 11 of the liquid crystal cell 10 is substantially counterclockwise with respect to the horizontal axis O of the liquid crystal display device (as viewed from the front surface side). The liquid crystal molecule alignment direction 12a on the back surface side substrate 12 is substantially orthogonal to the liquid crystal molecule alignment direction 11a on the front surface side substrate 11, and the liquid crystal molecule shows its twist direction by a broken line arrow. As described above, the twist alignment is performed in the clockwise direction in the figure from the rear substrate 12 to the front substrate 11 at a twist angle of approximately 90 °.

Further, as shown in FIG. 6, the transmission axis 20a of the polarizing plate 20 is oriented substantially parallel or substantially orthogonal to the horizontal axis O (parallel in the figure), and the slow axis 21a of the retardation plate 21.
Is shifted counterclockwise by 45 ° with respect to the horizontal axis O.

That is, the polarizing plate 20 arranged on the front surface side of the liquid crystal cell 10 has its transmission axis 20a inclined at an angle of about 45 ° with respect to the liquid crystal molecule alignment direction 11a on the front surface side substrate 11 of the liquid crystal cell 10. And the phase difference plate 21 disposed on the back surface side of the liquid crystal cell 10.
Is the slow axis 21a of the backside substrate 12 of the liquid crystal cell 10.
It is provided so as to be substantially orthogonal to the liquid crystal molecule alignment direction 12a above.

In the liquid crystal cell 10, the product Δnd of the refractive index anisotropy Δn of the liquid crystal 18 and the liquid crystal layer thickness d has a value of 830.
The retardation film 21 is designed to have a thickness of ± 50 nm, and the retardation plate 21 has a retardation value of 610 ± 40 nm.

Similarly to the liquid crystal display device of the first embodiment described above, the color liquid crystal display device of this embodiment also utilizes external light to allow light incident from the front surface side to be reflected by the reflection film on the rear surface side of the liquid crystal cell 10. This liquid crystal display device reflects the light at 19 to display. The liquid crystal display device has electrodes 1 on both substrates 11 and 12 of a liquid crystal cell 10.
A display is driven by applying a voltage between 3 and 14.

In this color liquid crystal display device, incident light from the surface side thereof is sequentially transmitted through the polarizing plate 20, the liquid crystal layer of the liquid crystal cell 10 and the retardation plate 21, and is reflected by the reflection film 19. Again, the retardation plate 21 and the liquid crystal layer are sequentially transmitted to enter the polarizing plate 20, and out of the light, the light of the polarization component that transmits the polarizing plate 20 is emitted.

Then, in a non-selected state (a state in which the liquid crystal molecules are in the initial twist alignment state) in which a voltage for rising and aligning the liquid crystal molecules is not applied between the electrodes 13 and 14 of the liquid crystal cell 10, the light is transmitted through the polarizing plate 20. The linearly-polarized light that has entered is changed in its polarization state by the birefringence of the liquid crystal layer of the liquid crystal cell 10 and the retardation plate 21, and is reflected by the reflection film 19 to be reflected again.
In the process of passing through the liquid crystal layer, the polarization state is further changed, and each wavelength light becomes an elliptically polarized light having a different polarization state.
The light transmitted through 0 becomes colored light having a color corresponding to the ratio of the light intensities of the light components of the wavelengths.

Further, when a voltage is applied between the electrodes 13 and 14 of the liquid crystal cell 10, the liquid crystal molecules are vertically aligned while maintaining the twist alignment state, and the retardation of the liquid crystal layer is changed by the change of the alignment state of the liquid crystal molecules. The light transmitted back and forth between the liquid crystal layer and the retardation plate 21 enters the polarizing plate 20 as light having a polarization state different from the non-selected state.

Furthermore, when the liquid crystal molecules of the liquid crystal cell 10 rise and align almost vertically, the birefringence effect of the liquid crystal layer of the liquid crystal cell 10 is almost eliminated, and the liquid crystal layer and the retardation film 2 are eliminated.
The light transmitted back and forth to and from 1 enters the polarizing plate 20 as light in a polarization state that is subjected only to the birefringence effect of the retardation plate 21.

In this case, in the liquid crystal display device of this embodiment, the liquid crystal cell 10 is adjacent to the polarizing plate 20, but the transmission axis 20a of the polarizing plate 20 and the liquid crystal molecules on the front side substrate 11 of the liquid crystal cell 10 are arranged. Since the alignment direction 11a is obliquely deviated, the linearly polarized light that has passed through the polarizing plate 20 and is incident is first subjected to a birefringence action according to the alignment state of the liquid crystal molecules by the liquid crystal layer of the liquid crystal cell 10 to change the polarization state. The light is changed, and the light enters the retardation plate 21, and the polarization state is changed by the retardation plate 21.

Further, in this liquid crystal display device, the slow axis 21a of the retardation plate 21 is the rear substrate 1 of the liquid crystal cell 10.
2 is almost orthogonal to the liquid crystal molecule orientation direction 12a on the second side, the slow axis 21a of the retardation plate 21 and the polarizing plate 2
The linearly polarized light that is obliquely displaced from the transmission axis 20 of 0 (the deviation angle is approximately 45 °), and therefore the liquid crystal molecules of the liquid crystal cell 10 are almost vertically risen and aligned and transmitted through the polarizing plate 20 to enter. When the light is transmitted through the liquid crystal layer of the liquid crystal cell 10 in that polarization state and enters the retardation plate 21, the polarization state of the light can be changed by the birefringence action of the retardation plate 21.

As described above, the polarization state of the light which is linearly polarized by the polarizing plate 20 and enters the polarizing plate 20 after being transmitted back and forth between the liquid crystal layer of the liquid crystal cell 10 and the retardation plate 21 is: The intensity varies depending on the alignment state of the liquid crystal molecules of the liquid crystal cell 10. Therefore, when the voltage applied between the electrodes 13 and 14 of the liquid crystal cell 10 is changed, the light intensity of each wavelength light emitted through the polarizing plate 20 is emitted. The ratio of the two changes and the emitted light becomes colored light of another color.

Therefore, also in the liquid crystal display device of this embodiment, light can be colored to obtain a bright color display without using a color filter, as in the first embodiment described above. A plurality of colors can be displayed by the pixel, and these plurality of colors can be obtained with a relatively low applied voltage.

Moreover, in this liquid crystal display device, the slow axis 21a of the retardation plate 21 is made substantially orthogonal to the liquid crystal molecule orientation direction 12a on the rear substrate 12 of the liquid crystal cell 10, and the transmission axis of the polarizing plate 20 is set. 20a is the liquid crystal cell 10
And the liquid crystal molecule alignment direction 11a on the surface side substrate 11 is obliquely crossed at an angle of approximately 45 °,
Since the value of Δnd of the liquid crystal cell 10 is set to 830 ± 50 nm and the value of retardation of the retardation plate 21 is set to 610 ± 40 nm, not only a plurality of colors but also achromatic white and black in the same pixel. Can be displayed.

That is, in this liquid crystal display device,
When the liquid crystal molecules of the liquid crystal cell 10 are in an aligned state, the light transmitted back and forth between the retardation plate 21 and the liquid crystal layer is
The transmitted light component in the direction along the transmission axis 20a of the polarizing plate 20 becomes large and substantially equal for almost all wavelength light in the visible light band, and most of the light passes through the polarizing plate 20 with a high transmittance and is emitted. Then, the display becomes white, which is an achromatic bright display.

Further, when the liquid crystal molecules of the liquid crystal cell 10 are in another alignment state, most of the light transmitted back and forth between the retardation plate 21 and the liquid crystal layer is absorbed by the polarizing plate 20, and the display is performed. Becomes black, which is an achromatic dark display.

In FIG. 7, the transmission axis 20a of the polarizing plate 20 and the slow axis 21a of the retardation plate 21 are oriented as shown in FIG. 6, the Δnd value of the liquid crystal cell 10 is 830 nm, and the retardation value of the retardation plate is It is a CIE chromaticity diagram which shows the color change of the emitted light of the liquid crystal display device set to 610 nm, and the point W has shown the center of the achromatic region in the figure.

As shown in this chromaticity diagram, the emitted light of the liquid crystal display device is in the yellow-green region in the non-selected state in which the voltage for rising and aligning the liquid crystal molecules is not applied between the electrodes 13 and 14 of the liquid crystal cell 10. It is light, and when a voltage is applied between the electrodes 13 and 14, the color of the emitted light changes as shown in the figure as the voltage is increased.

FIG. 8 shows the light emission rate and the color change of the emitted light with respect to the applied voltage to the liquid crystal cell 10 in the liquid crystal display device. The display color of this liquid crystal display device is applied to the liquid crystal cell 10. As the voltage increases,
From yellow green in the non-selected state, blue → black (dark display of achromatic color) →
Change from white (achromatic bright display) to magenta.

Thus, according to the above liquid crystal display device,
The same pixel can display yellow-green, blue, black, white, and red-purple colors, and all of these display colors range from 0 to about 4v.
Can be obtained at a relatively low voltage (see FIG. 8).

The liquid crystal cell 10 is shown in FIGS.
The change of the display color when the value of Δnd of 830 nm and the value of retardation of the retardation plate 21 is 610 nm is shown. The value of Δnd of the liquid crystal cell 10 is 830 ± 50 nm, and the retardation value of the retardation plate 21 is A similar display color can be obtained within a range of 610 ± 40 nm.

Further, in the liquid crystal display device, contrary to the first embodiment described above, since the retardation plate 21 is arranged on the back surface side of the liquid crystal cell 10, the black display becomes closer to the achromatic color. Thus, black with high purity can be displayed.

The display color in the first and second embodiments is the color of one pixel. However, in the color liquid crystal display device, in addition to the display color of each pixel, a plurality of adjacent pixels are used. It is also possible to represent the composite color by combining the display colors of.

Further, although the active matrix type is used as the liquid crystal cell 10 in the above embodiment, the liquid crystal cell 10 may be a simple matrix type or a segment type. Good.

[0077]

According to the color liquid crystal display device of the present invention, light is colored without using a color filter to obtain a bright color display, and a plurality of colors and achromatic black and white are formed in the same pixel. Can be displayed.

[Brief description of drawings]

FIG. 1 is a sectional view of a color liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a view showing the orientation of liquid crystal molecules on both substrates of the liquid crystal cell, the transmission axis of the polarizing plate, and the slow axis of the retardation plate.

FIG. 3 is a CI of the color liquid crystal display device according to the first embodiment.
E chromaticity diagram.

FIG. 4 is a diagram showing a light emission rate and a color change of the emitted light with respect to an applied voltage of the color liquid crystal display device according to the first embodiment.

FIG. 5 is a sectional view of a color liquid crystal display device according to a second embodiment of the present invention.

FIG. 6 is a view showing the orientation of liquid crystal molecules on both substrates of the liquid crystal cell, the transmission axis of the polarizing plate, and the slow axis of the retardation plate.

FIG. 7 is a CI of a color liquid crystal display device according to a second embodiment.
E chromaticity diagram.

FIG. 8 is a diagram showing a light emission rate and a color change of emitted light with respect to an applied voltage of a color liquid crystal display device according to a twenty-first embodiment.

[Explanation of symbols]

 10 ... Liquid crystal cell 11a ... Liquid crystal molecule orientation direction on front side substrate 12a ... Liquid crystal molecule orientation direction on back side substrate 19 ... Reflective film 20 ... Polarizing plate 20a ... Transmission axis 21 ... Retardation plate 21a ... Slow axis

Claims (2)

[Claims] 1. A liquid crystal cell in which liquid crystal molecules are twist-aligned at a twist angle of about 90 ° and a reflective film is provided on the back surface side, a retardation plate disposed on the front surface side of the liquid crystal cell, and the phase difference. A polarizing plate disposed on the surface side of the plate, and the slow axis of the retardation plate is substantially orthogonal to the alignment direction of liquid crystal molecules on the substrate on the surface side of the liquid crystal cell, Has a transmission axis intersecting obliquely with the slow axis of the retardation plate at an angle of approximately 45 °, and the product Δnd of the refractive index anisotropy Δn of the liquid crystal of the liquid crystal cell and the liquid crystal layer thickness d. Value is 830 ± 50 nm, and the retardation value of the retardation plate is 610 ± 40 nm. 2. A liquid crystal cell in which liquid crystal molecules are twist-aligned at a twist angle of about 90 °, a polarizing plate arranged on the front surface side of the liquid crystal cell, and a phase difference arranged on the rear surface side of the liquid crystal cell. Plate, and a reflective film disposed on the back surface side of the retardation plate, and the slow axis of the retardation plate is substantially relative to the alignment direction of liquid crystal molecules on the substrate on the back surface side of the liquid crystal cell. The transmission axes of the polarizing plates intersect each other obliquely at an angle of about 45 ° with respect to the alignment direction of the liquid crystal molecules on the substrate on the surface side of the liquid crystal cell, and the refractive index of the liquid crystal of the liquid crystal cell. A color liquid crystal display device, wherein a value of a product Δnd of anisotropy Δn and a liquid crystal layer thickness d is 830 ± 50 nm, and a retardation value of the retardation plate is 610 ± 40 nm.