JPH07333598A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device which colors light without using color filters and is capable of lessening light quantity loss by light absorption at polarizing plates and the substrates of a liquid crystal cell at the time of reflection type display as a liquid crystal display device which has a reflection type display function utilizing external light and a transmission type display function utilizing the light from a light source and is formed by using the liquid crystal cell having MIMs as active elements for the liquid crystal cell. CONSTITUTION:The polarizing plates 31, 32 are arranged on the front surface side and rear surface side, respectively, of the liquid crystal cell 10 having the MIMs 14 as the active elements. A phase difference plate 40 is arranged between the front surface side polarizing plate 31 and the liquid crystal cell 10. The light is colored by utilizing the double refractive effect of this phase difference plate 40 and the liquid crystal layer of the liquid crystal cell 10 and the polarization and analysis effect of the front surface side polarizing plate 31 at the time of the reflection type display. The light is colored by utilizing the double refractive effect, the polarization effect of the rear surface side polarizing plate 31 and the analysis effect of the front surface side polarizing plate 31 at the time of transmission type display. Further, the pixel electrodes 13 formed on the inside surface of the rear surface side polarizing plate 11 of the liquid crystal cell 10 are commonly used as translucent reflection films M.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal which has a reflective display function and a transmissive display function and which uses an active matrix type liquid crystal cell having a two-terminal nonlinear resistance element as an active element. The present invention relates to a display device.

[0002]

2. Description of the Related Art As a liquid crystal display device, there is provided a reflective display function of displaying the light incident from the front surface side by utilizing the external light such as natural light or indoor illumination light, and the light from the light source incident from the rear surface side. Some have a transmissive display function for displaying the same.

A conventional liquid crystal display device having the reflection type display function and the transmission type display function has a structure as shown in FIG. In this liquid crystal display device, polarizing plates 5 and 6 are arranged on the front surface side and the back surface side of the liquid crystal cell 1, respectively, and a polarizing plate 6 provided on the back surface side of the liquid crystal cell 1.
A half mirror 7 for reflecting and transmitting incident light with a certain reflectance and a certain transmittance is arranged on the back surface side of the light source 8, and the light source 8 is provided behind the half mirror 7.

The liquid crystal cell 1 has a pair of transparent substrates 2 and 3 each having a transparent electrode and an alignment film formed thereon.
Liquid crystal is sandwiched between the two substrates 2 and 3 with their electrode forming surfaces facing each other through a frame-shaped sealing material 4, and the molecules of the liquid crystal have the respective substrates 2 and 3. The orientation direction on 3 is regulated by the orientation film and oriented in a predetermined orientation state.

The light source 8 is generally composed of a light guide plate 9 facing almost the entire back surface of the half mirror 7, and a light source lamp 10 arranged toward one end surface of the light guide plate 9. The light guide plate 9 is formed by forming a reflective film 9a made of a vapor deposition film of Al (aluminum) or the like on the entire back surface of a transparent plate made of acrylic resin or the like.
The illumination light from is incident on the light guide plate 9 from one end face thereof, guided inside the light guide plate 9, and emitted from the entire surface of the light guide plate 9 toward the liquid crystal cell 1.

This liquid crystal display device is generally of the TN (twisted nematic) type, and the liquid crystal cell 1
The liquid crystal molecules are twist-aligned between the substrates 2 and 3 at a twist angle of 90 °, and the front surface side polarizing plate 5 has the transmission axis of the liquid crystal molecules on the front surface side substrate 3 (inner surface of the substrate) of the liquid crystal cell 1. The polarizing plate 6 on the rear surface side is arranged substantially parallel or substantially orthogonal to the alignment direction, and its transmission axis is arranged substantially parallel or substantially orthogonal to the alignment direction of the liquid crystal molecules on the rear surface side substrate 2 of the liquid crystal cell 1. There is.

The above-mentioned liquid crystal display device performs a reflection type display utilizing outside light in a bright place where the amount of outside light is sufficient. At this time, as shown by a solid arrow in FIG. External light that enters the device from its front surface side becomes linearly polarized light by the polarization action of the front surface side polarizing plate 5 and enters the liquid crystal cell 10.

On the other hand, the liquid crystal molecules of the liquid crystal cell 1 are in the initial twist alignment state when a voltage is not applied between the electrodes of the substrates 2 and 3, and the application of the voltage between the electrodes causes the substrates 2 and 3 to have the same orientation. Since the light is vertically oriented almost vertically to the plane, the linearly polarized light that is incident on the liquid crystal cell 1 is incident on a region to which the on-voltage is not applied, and is linearly rotated by 90 ° due to the birefringence effect of the liquid crystal layer. Light that has become polarized light and exits the liquid crystal cell 1 and that is incident on the voltage application region is substantially unaffected by the birefringence effect of the liquid crystal layer, and exits the liquid crystal cell 1 with the same linearly polarized light as at the time of incidence.

Then, the light emitted from the liquid crystal cell 1 is incident on the rear surface side polarizing plate 6 and becomes an image light by the detecting function of the polarizing plate 6, and then is incident on the half mirror 7. Of the light,
The light reflected by the half mirror 7 is applied to the back side polarizing plate 6
Then, the light is emitted to the front surface side of the liquid crystal display device through the liquid crystal cell 1 and the front surface side polarizing plate 5.

Further, the liquid crystal display device can display even in a dark place where the amount of external light is small by turning on the light source lamp 10. In that case, FIG.
As indicated by the broken line arrow, the illumination light from the light source 8 first enters the half mirror 7, and the light transmitted through this half mirror 7 becomes linearly polarized light by the polarization action of the back-side polarizing plate 6 and enters the liquid crystal cell 10. When incident, the light passing through the liquid crystal cell 10 becomes image light due to the light-analyzing function of the front-side polarizing plate 5, and is emitted to the front side of the liquid crystal display device.

By the way, the liquid crystal cell 1 of the above liquid crystal display device.
In general, among a pair of transparent substrates 2 and 3 facing each other across a liquid crystal layer, a plurality of pixel electrodes are provided on the inner surface of one substrate (a surface facing the liquid crystal layer) and the pixel electrodes respectively correspond to these pixel electrodes. An active matrix type liquid crystal cell is used in which a plurality of active elements are arranged and a counter electrode facing the pixel electrodes is provided on the inner surface of the other substrate.

As the active matrix type liquid crystal cell, one using a TFT (thin film transistor) as an active element is mainly used. Recently, however, the manufacturing cost of the liquid crystal cell is reduced and the price of the liquid crystal display device is reduced. For this reason, it has been considered to use an active matrix type liquid crystal cell having a two-terminal nonlinear resistance element such as an MIM or a thin film diode as an active element, which has a simpler structure than a TFT.

That is, the MIM is a laminate of the first electrode, the insulating film and the second electrode, and the thin film diode is the first electrode, the n-type semiconductor film, the p-type semiconductor film and the second electrode. And the electrodes of
Since the structure is simpler and easier to manufacture, the manufacturing process of the active element can be simplified and the manufacturing cost of the liquid crystal cell can be reduced.

[0014]

However, the above-mentioned conventional liquid crystal display device has a problem that a large amount of light is lost in the reflection type display utilizing external light, and therefore the display in the reflection type display is dark. . This is because light incident on the liquid crystal display device from its front surface side passes through the front surface side polarizing plate 5, the liquid crystal cell 1 and the rear surface side polarizing plate 6 and enters the half mirror 7, which is reflected by the half mirror 7. This is because light is emitted to the front surface side of the liquid crystal display device through the rear surface side substrate 6, the liquid crystal cell 1 and the front surface side polarizing plate 5, and therefore the light incident from the front surface side is emitted to the front surface side again. In the meantime, since the polarizing plates 5 and 6 on the front and back sides respectively pass through two times for a total of four times and both substrates 2 and 3 of the liquid crystal cell 1 pass through a total of four times for each two times, the polarizing plates 5, 6 Also, the light amount loss due to the light absorption by the substrates 2 and 3 of the liquid crystal cell 1 is large, and the display becomes dark.

When a color image is displayed on a liquid crystal display device using an active matrix type liquid crystal cell,
Conventionally, on one substrate of the liquid crystal cell, color filters of a plurality of colors, for example, three colors of red, green, and blue are provided corresponding to each pixel electrode. However, the reflective display function shown in FIG. In a liquid crystal display device having a transmission type display function and a color filter provided in the liquid crystal cell, the display is further darkened, so that it is almost impossible to display a color image.

This is due to the absorption of light by the color filter. The color filter not only absorbs light other than the wavelength band corresponding to the color, but also absorbs light in the wavelength band at a considerably high absorption rate. Since the light is absorbed, the light colored by the color filter becomes light in which the amount of light is significantly reduced as compared with the light in the wavelength band before entering the color filter.

In the case of a liquid crystal display device which performs only a transmissive display, the display can be brightened by using a light source with a large amount of light in anticipation of light absorption by the color filter, as shown in FIG. Further, in the liquid crystal display device, if a color filter is provided in the liquid crystal cell, the display becomes considerably dark even in the transmissive display, and further, in the reflective display, the display becomes so dark that it is hardly visible.

That is, in the liquid crystal display device shown in FIG. 17, even in the case of the transmissive display, only the light that has passed through the half mirror 7 of the illumination light from the light source 8 can be used, so that a color filter is provided in the liquid crystal cell 1. If it is provided, the display will be quite dark.

Further, in the case of the reflection type display, since external light such as natural light or indoor illumination light is used, not only the amount of incident light is limited, but also only the amount of reflected light corresponding to the reflectance of the half mirror 7 is obtained. Further, since the light colored by the color filter passes through the color filter again in the process of being reflected by the half mirror 7 and emitted to the surface side of the liquid crystal display device, the absorption of the light by the color filter is further increased. It becomes so large that the display becomes so dark that it is almost invisible.

The present invention has a reflective display function using external light and a transmissive display function using light from a light source, and an active liquid crystal cell having a two-terminal nonlinear resistance element as an active element. As a liquid crystal display device using a matrix type liquid crystal cell, light can be colored without using a color filter to display a bright color image, and a polarizing plate and a liquid crystal for reflection type display utilizing external light. An object of the present invention is to provide a device capable of sufficiently brightening a display in a reflective display by reducing a light amount loss due to light absorption in a cell substrate.

[0021]

A liquid crystal display device of the present invention includes an active matrix type liquid crystal cell having a two-terminal non-linear resistance element as an active element, and a first polarizing plate disposed on the surface side of the liquid crystal cell. And a second polarizing plate disposed on the back surface side of the liquid crystal cell, and semi-transmissive for reflecting and transmitting incident light at a certain reflectance and transmittance on the inner surface of the back surface side substrate of the liquid crystal cell. A reflection film is provided, and the transmission axis of the first polarizing plate is slanted with respect to the alignment direction of liquid crystal molecules on the substrate on the front surface side of the liquid crystal cell, and the transmission axis of the second polarizing plate. Is obliquely displaced from the alignment direction of the liquid crystal molecules on the substrate on the back surface side of the liquid crystal cell.

In the liquid crystal display device of the present invention, the semi-transmissive reflective film also serves as an electrode provided on the inner surface of the back side substrate among electrodes provided on the inner surfaces of both substrates of the liquid crystal cell. You may let me.

Further, in the liquid crystal display device of the present invention,
A retardation plate may be disposed between the liquid crystal cell and the first polarizing plate disposed on the surface side thereof, and in this case, the retardation plate is provided with the slow axis of the first polarizing plate. And the second polarizing plate may be obliquely displaced with respect to the transmission axis.

In the liquid crystal display device of the present invention,
It is desirable that the reflective surface of the semi-transmissive reflective film provided on the inner surface of the back surface side substrate of the liquid crystal cell is substantially a mirror surface, and one surface, preferably the surface, of the first polarizing plate is a light scattering surface. .

[0025]

The liquid crystal display device of the present invention performs reflection type display utilizing external light in a bright place where the amount of external light is sufficient. At this time, the liquid crystal display device receives the external light incident from the front side thereof. The first light is arranged on the front side of the liquid crystal cell.
The polarizing action of the polarizing plate makes it linearly polarized and enters the liquid crystal cell, and the light passing through the liquid crystal layer also enters the semi-transmissive reflective film provided on the inner surface of the back side substrate of the liquid crystal cell. The light reflected by the transflective film again enters the first polarizing plate through the liquid crystal layer, and the light transmitted through this polarizing plate becomes image light and is emitted to the front surface side of the liquid crystal display device.

Further, this liquid crystal display device can display by utilizing the light from the light source even in a dark place where the amount of external light is small, and in that case, the light from the light source is emitted from the liquid crystal cell. By the polarization action of the second polarizing plate disposed on the back side, linearly polarized light is made incident on the liquid crystal cell from the back side thereof, and the light transmitted through the semi-transmissive reflection film passes through the liquid crystal layer to pass the first polarized light. Light incident on the plate and transmitted through the polarizing plate becomes image light and is emitted to the front surface side of the liquid crystal display device.

In this liquid crystal display device, the transmission axis of the first polarizing plate is slanted with respect to the alignment direction of liquid crystal molecules on the substrate on the front surface side of the liquid crystal cell, and the transmission axis of the second polarizing plate is changed. Since the transmission axis is deviated obliquely with respect to the alignment direction of the liquid crystal molecules on the substrate on the back surface side of the liquid crystal cell, the incident light passes through the first polarizing plate in the case of reflective display utilizing external light. The linearly polarized light becomes elliptically polarized light having a different polarization state for each wavelength due to its birefringence effect in the process of passing through the liquid crystal layer of the liquid crystal cell, and among the light, the light reflected by the semi-transmissive reflection film is In the process of passing through the liquid crystal layer, the polarization state is further changed and the light enters the first polarizing plate,
The light of the polarization component that passes through the first polarizing plate becomes the colored light.

In the case of a transmissive display using light from a light source, of the linearly polarized light that has entered through the second polarizing plate, the light that has passed through the semi-transmissive reflective film passes through the liquid crystal cell. In the process, due to the birefringence effect of the liquid crystal layer, it becomes elliptically polarized light having a different polarization state for each wavelength and enters the first polarizing plate,
The light of the polarization component that passes through the first polarizing plate becomes the colored light.

That is, in the liquid crystal display device, at the time of reflection type display, light is colored by utilizing the birefringence effect of the liquid crystal layer of the liquid crystal cell and the polarization and analysis function of the first polarizing plate. In the transmissive display, light is colored by utilizing the birefringence effect of the liquid crystal layer of the liquid crystal cell, the polarization effect of the second polarizing plate and the light analyzing function of the first polarizing plate.

Since this liquid crystal display device colors light without using a color filter, the loss of the amount of transmitted light is greatly reduced as compared with the case of transmitting light through the color filter to obtain colored light of high brightness. Therefore, a bright color image can be displayed.

Moreover, in this liquid crystal display device, the alignment state of the liquid crystal molecules changes according to the magnitude of the voltage applied to the liquid crystal layer of the liquid crystal cell, and the birefringence effect of the liquid crystal layer changes accordingly. The color of the colored light can be changed by controlling the voltage applied to the liquid crystal cell, and one pixel can display a plurality of colors.

In addition, in this liquid crystal display device, a semi-transmissive reflective film is provided on the inner surface of the substrate on the back surface side of the liquid crystal cell, so that it is arranged on the front surface side of the liquid crystal cell in the case of reflective display utilizing external light. The first polarizing plate is provided on the back surface side of the liquid crystal cell so as to have both the polarizing function of making the incident light linearly polarized light and the analyzing function of making the light passing through the liquid crystal layer of the liquid crystal cell the image light. Since the display is performed without using the second polarizing plate,
Reflective display can be performed by the second polarizing plate disposed on the back surface side of the liquid crystal cell and the back surface side substrate of the liquid crystal cell without loss of the emitted light amount. At this time, it is possible to reduce the loss of light amount due to the absorption of light in the polarizing plate and the substrate of the liquid crystal cell, and to make the display in the reflective display sufficiently bright.

In the liquid crystal display device of the present invention, among the electrodes provided on the inner surfaces of both substrates of the liquid crystal cell, the electrode provided on the inner surface of the back side substrate also serves as the semi-transmissive reflective film. By doing so, since this electrode and the semi-transmissive reflective film can be formed at the same time, the structure of the liquid crystal cell can be simplified and its manufacture can be facilitated.

Furthermore, in the liquid crystal display device of the present invention,
A retardation plate is disposed between the liquid crystal cell and the first polarizing plate disposed on the surface side of the liquid crystal cell, and the slow axis of this retardation plate is used as the transmission axes of the first polarizing plate and the second polarizing plate. If they are slanted, the incident light receives the birefringence effect of the retardation plate and the birefringence effect of the liquid crystal layer of the liquid crystal cell in both the reflective display and the transmissive display. In order to significantly change the wavelength, elliptically polarized light whose polarization states are greatly different for each wavelength can be made incident on the first polarizing plate to obtain a colored light of a clear color, and liquid crystal molecules can be attached to the substrate surface in the liquid crystal cell. On the other hand, when a voltage that rises and aligns almost vertically is applied, that is, even when the birefringence effect of the liquid crystal layer is virtually eliminated, the birefringence effect of the retardation plate makes the incident light elliptically polarized light. Obtaining colored light by making it enter the first polarizing plate It can be.

Further, in the liquid crystal display device of the present invention, since the semi-transmissive reflective film is provided on the inner surface of the back side substrate of the liquid crystal cell, it is difficult to use this semi-transmissive reflective film as a diffuse reflective film, but the liquid crystal If one surface of the first polarizing plate arranged on the front surface side of the cell is a light scattering surface, even if the reflecting surface of the semi-transmissive reflecting film is almost a mirror surface, the face of the display observer or the background thereof, etc. The external image never appears on the reflecting surface.

If the reflecting surface of the semi-transmissive reflective film is almost mirror-finished, the light whose polarization state is changed by the liquid crystal layer of the liquid crystal cell in the reflective display is not scattered by the semi-transmissive reflective film. Further, also in the transmissive display, light that enters the liquid crystal cell from the back side thereof through the second polarizing plate is not scattered by the semi-transmissive reflective film.

Further, in this case, if the surface of the first polarizing plate is a light-scattering surface, the first polarized light is scattered after the light incident on the liquid crystal display device from the surface side in the reflection type display is scattered. After the light is transmitted through the liquid crystal layer of the liquid crystal cell into the image light due to the analyzing function of the first polarizing plate in both the reflective display and the transmissive display, the light becomes a linearly polarized light by the polarizing action of the plate. Since the light is scattered, the light is not scattered until the incident light passes through the first polarizing plate to become the image light, and therefore a high quality image can be displayed.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A first embodiment of the present invention will be described below with reference to FIGS.
Will be described with reference to. FIG. 10 is a basic configuration diagram of a liquid crystal display device. In this liquid crystal display device, a first polarizing plate (hereinafter referred to as a front surface side polarizing plate) 31 is arranged on the front surface side (upper side in the drawing) of a liquid crystal cell 10, A second polarizing plate (hereinafter referred to as a back surface side polarizing plate) 32 is arranged on the back surface side (lower side in the drawing) of the liquid crystal cell 10, and the liquid crystal cell 10
The retardation plate 40 is disposed between the front side polarizing plate 31 and the front side polarizing plate 31, and the light source 50 is disposed behind the back side polarizing plate 32.

The specific structure of this liquid crystal display device will be described. FIG. 1 is a sectional view of a part of the liquid crystal display device, and FIG. 2 is a plan view of a part of the liquid crystal cell 10. First, the liquid crystal cell 10 will be described. The liquid crystal cell 10 is an active matrix liquid crystal cell in which a two-terminal nonlinear resistance element is used as an active element. In this embodiment, an MIM is used as an active element. .

The liquid crystal cell 10 is one in which a liquid crystal LC is sandwiched between a pair of transparent substrates 11 and 12 made of glass or the like.
A plurality of pixel electrodes 13 and a plurality of MIMs 14 respectively corresponding to the respective pixel electrodes 13 are provided on the inner surface of 1 (that is, on the surface facing the liquid crystal layer) in the row direction (horizontal direction in FIG. 2) and the column direction (in FIG. 2). They are arranged in a matrix in the (vertical direction), and a transparent alignment film 19 is provided thereon.

The MIM 14 comprises a lower electrode 15 formed on the backside substrate 11, an insulating film 16 covering the lower electrode 15, and an upper electrode 17 formed on the insulating film 16. The lower electrode 15 of the MIM 14 in each row is connected to the drive signal supply line 18 wired on the substrate 11 for each pixel electrode row.
Each of the 14 upper electrodes 17 is connected to the pixel electrode 13 to which the MIM 14 corresponds.

In this embodiment, the lower electrode 15 of the MIM 14 and the signal supply line 18 are integrally formed,
The upper electrode 17 is formed integrally with the pixel electrode 13. Further, in this embodiment, the lower electrode 15 and the signal supply line 18 are formed of a metal film such as Al or an Al-based alloy, and the surface thereof is anodized to form the insulating film 16. The surface of the signal supply line 18 is also covered with an insulating film (anodic oxide film) 16 except for its terminal portion (not shown).

Each pixel electrode 13 also serves as a semi-transmissive reflection film M, and its reflection surface is almost a mirror surface. This semi-transmissive reflective film M reflects and transmits incident light at a certain reflectance and a certain transmittance, as in a commercially available half mirror. In this embodiment, the pixel electrode 13 has a transmittance of 5 to 20. % Of the semi-transmissive reflective film M. The reflectance may be about 14% or more.

The semi-transmissive reflective film M (pixel electrode 13) is
It is formed of a metal film such as Al or an Al-based alloy, or is a laminated film of a transparent conductive film such as an ITO film and a metal film.

3 and 4 are a sectional view and a plan view of a part of the first example of the semi-transmissive reflective film M. The semi-transmissive reflective film M is an extremely thin metal film formed by a sputtering apparatus. It is composed of a thin film 13a.

That is, the semi-transmissive reflective film M is formed by depositing metal particles on the underlying surface (here, the surface of the rear substrate 11 in this case) of a metal particle very thinly by a sputtering apparatus. The illustrated semi-transmissive reflective film M is composed of a metal thin film 13a in which minute defects k such as hole defects in which metal particles are not deposited and recessed defects in which metal particles are thinly deposited are scattered. The defective portion k has an irregular shape, and its size and distribution state change depending on the film thickness of the metal thin film 13a.

The semi-transmissive reflection film M reflects and reflects both incident light from the front side indicated by the solid arrow in FIG. 3 and incident light from the rear side indicated by the broken arrow at a certain reflectance and transmittance. A part of the light that is transmitted and is incident on the film portion of the metal thin film 13a (the portion other than the defect portion k) is reflected by the film surface of the metal thin film 13a, and a certain amount of light is emitted by the metal thin film 1a.
The remaining light passes through 3a and is absorbed by the metal thin film 13a.

On the other hand, of the defective portion k of the metal thin film 13a, the recessed defect portion where the deposition thickness of the metal particles is thin has a very thin metal film thickness, so the amount of reflection and absorption at this recessed defect portion. Therefore, most of the light incident on the recessed defect portion is transmitted. Further, all of the light incident on the hole defect portion where the metal particles are not deposited becomes the transmitted light.

However, the total area of the defective portion k per unit area of the metal thin film 13a is extremely small compared to the area of the film portion per unit area, and therefore the transmittance of the semi-transmissive reflective film M is small. Is almost dominated by the transmittance of the film portion of the metal thin film 13a.

Since the transmittance of the film portion of the metal thin film 13a is determined by the optical constant and the film thickness of the material metal, if the film thickness of the metal thin film 13a is selected,
It is possible to obtain the transflective film M having the above-mentioned transmittance of 5 to 20%.

The semi-transmissive reflective film M shown in FIGS. 3 and 4 is made of a metal thin film 13a having minute defects k such as hole defects and recessed defects scattered therein. The reflective film M may be a metal thin film having few hole defects, recessed defects, etc. Even in that case, if the thickness of the metal thin film is about 20 nm or less, this metal thin film is used as a semi-transmissive reflective film. It can be used as M.

That is, in forming a metal thin film by a sputtering apparatus, if the film thickness is about 10 nm or less, the formed metal thin film becomes a film having a hole defect or a recess defect. When the film thickness is increased to about 10 nm or more,
Along with this, the size of the hole defects and recessed defects becomes smaller and the number of distributions thereof also decreases, and when the film thickness exceeds a certain level, most of the hole defects and recessed defects are closed, and a film with a substantially flat surface is obtained. Become.

As an example, when the metal thin film is formed of Al or Al-Ti (titanium) alloy, the metal thin film formed to a thickness of 8.5 nm is shown in FIGS. 3 and 4. The film has such a minute defect portion k. The transmittance of this metal thin film is about 10 to 20%, and the sheet resistance is 53.
Ω.

Further, the Al or Al-Ti alloy is
The metal thin film formed to a thickness of 7.0 nm is a film having a substantially flat surface with almost no hole defects or pitting defects, and the metal thin film has a transmittance of about 5% or less and a sheet resistance of 14Ω.
Is.

The transmissivity of the semi-transmissive reflective film M may be in the range of 5 to 20% described above, but in order to use the light from the light source 50 more effectively, the transmissivity is set to 6%. %
The above is more preferable, and it is more preferable to be 7% or more.

However, in order to increase the transmissivity of the semi-transmissive reflective film M as described above, the film resistance of the metal thin film has to be reduced to some extent, so that the sheet resistance becomes high. If the reflective film M is a laminated film of a transparent conductive film such as an ITO film and a high-reflectance metal film, the sheet resistance can be lowered.

That is, FIGS. 5 and 6 are cross-sectional views of a part of the second and third examples of the semi-transmissive reflective film M, respectively, and the semi-transmissive reflective film M shown in FIG. The ITO film 13b is formed on the (back surface side substrate 11 surface) by a sputtering device, and the metal thin film 13a shown in FIGS. 3 and 4 is formed thereon.

The semi-transmissive reflective film M shown in FIG. 6 has the metal thin film 13a shown in FIGS. 3 and 4 formed on the underlying surface (the surface of the backside substrate 11), and the metal thin film 13a shown in FIG. ITO film 1
3b is formed by a sputtering device.

The sheet resistance of the ITO film 13b of the transflective film M shown in FIG. 5 and FIG.
When the film thickness of 3b is 50 nm, it is 40Ω. Therefore, even if the sheet resistance of the metal thin film 13a is high to some extent, the apparent sheet resistance of the semi-transmissive reflective film M can be lowered.

The metal thin film 13a of the semi-transmissive reflective film M shown in FIGS. 5 and 6 is a metal thin film having minute defects k such as hole defects and recessed defects scattered therein. May be a thin metal film having a substantially flat surface with almost no defect portion k.

7 and 8 are a sectional view and a plan view of a part of the semi-transmissive reflective film M, showing a fourth example thereof. The semi-transmissive reflective film M is dotted with minute openings m. It is composed of a light-impervious metal film 13c provided by being provided.

That is, the thickness of the semi-transmissive reflective film M is such that the metal film 13c made of Al or an Al-based alloy or the like does not transmit light on the underlying surface (the surface of the rear surface side substrate 11) by the sputtering device ( A film having a thickness of about 300 nm is formed, and a large number of minute openings m are provided in the metal film 13c by a photolithography method.

The semi-transmissive reflective film M is the metal film 13c.
The light incident on the film portion (portion other than the opening m) is reflected by the metal surface and the light incident on the opening m portion is transmitted, and the incident light from the surface side indicated by the solid arrow in FIG. ,
Further, the incident light from the back surface side indicated by the dashed arrow is also reflected and transmitted with a certain reflectance and transmittance.

Since the semi-transmissive reflective film M is composed of a relatively thick metal film 13c formed to a thickness that does not transmit light, it has an advantage of low sheet resistance. The transmissivity of the semi-transmissive reflective film M is the same as that of the metal film 13c.
Is determined by the total area of the openings m distributed within the unit area of.

However, in this semi-transmissive reflective film M,
When the area of each opening m is large, when the light is made incident from the front surface side and the reflected light is observed, the opening m portion appears as a black spot, and the light is made incident from the back surface side to transmit the transmitted light. When observed, the opening m portion appears as a bright spot. Therefore, in order to make such black spots and bright spots inconspicuous, the width of each opening m is set to about 3 μm or less, and the desired number is set according to the number. It is desirable to obtain transmittance.

The pixel electrode 13 is formed by forming the semi-transmissive reflective film M according to any one of the above-mentioned first to fourth examples on the back side substrate 11, and the semi-transmissive reflective film M is formed by the photolithography method. Is formed by patterning. When the pixel electrode is formed of the semi-transmissive reflective film M shown in FIGS. 6 and 7, formation of the opening m in the metal film 13c and patterning of the pixel electrode 13 can be performed at the same time.

Further, as shown in FIGS. 1 and 2, on the inner surface of the front surface side substrate 12 of the liquid crystal cell 10, that is, the surface facing the liquid crystal layer, the pixel electrodes of each column disposed on the back surface side substrate 11 are arranged. A plurality of transparent counter electrodes 20 facing each other
Is provided, and the transparent alignment film 21 is provided thereon. The counter electrode 20 is formed of a transparent conductive film such as ITO.

Furthermore, on the inner surface of the front surface side substrate 12,
A black mask 22 corresponding to the gap between the pixel electrodes 13 arranged on the back substrate 11 is provided, and the black mask 22 is also covered with the alignment film 21.

As shown in FIG. 2, the black mask 22 is formed in a grid-like pattern corresponding to the rows and columns of the pixel electrodes 13 arranged on the back surface side substrate 11, and each of the vertical and horizontal directions. The side portions are formed such that both side edges thereof face the edge portions of the adjacent pixel electrodes 13 with a slight overlapping width.

The MIM 1 provided on the rear substrate 11
4 is in a portion between the pixel electrodes 13 as shown in FIG.
It also faces the IM 14 so as to cover the entire IM14.

The black mask 22 is an insulating mask made of a black resin, and the vertical side portions (side portions corresponding to the columns of the pixel electrodes 13) of the black mask 22 are provided between the counter electrodes 20. It is formed on a portion (inner surface of the substrate 12) by overlapping both side edges thereof with the edge portions of the opposing electrodes 20 adjacent to each other with a slight overlapping width, and the horizontal side portions (side portions corresponding to the rows of the pixel electrodes 13) are , Is formed on the counter electrode 20 so as to cross the electrode 20.

The black mask 22 is, for example, coated with a black photosensitive resin on the surface of the front surface side substrate 12 on which the counter electrode 20 is formed, is exposed using an exposure mask having a predetermined pattern, and then is exposed to light. It is formed by a method of developing a photosensitive resin and baking it.

The back-side substrate 11 and the front-side substrate 12 have a frame-shaped sealing material 25 at their outer peripheral edges.
(See FIG. 10) and the liquid crystal LC is filled in a region surrounded by the sealing material 25 between the substrates 11 and 12.

This liquid crystal LC is a nematic liquid crystal having a positive dielectric anisotropy, and the molecules of this liquid crystal LC have
Alignment directions on the substrates 11 and 12 are regulated by the alignment films 19 and 21 provided on the substrates 1 and 12, respectively.
A twist angle of approximately 90 ° is provided between 1 and 12. The alignment films 19 and 21 are horizontal alignment films made of polyimide or the like, and the film surfaces thereof are subjected to an alignment treatment by rubbing.

On the other hand, of the front and back polarizing plates 31 and 32, the back side polarizing plate 32 is an ordinary polarizing plate and the front side polarizing plate 3
Reference numeral 1 denotes a polarizing plate whose one surface, for example, the surface is a light scattering surface A, and the light scattering surface A of the surface side polarizing plate 31 is
As shown in an enlarged view of a cross section of a part thereof in FIG. 9, a transparent film 33 having minute irregularities is formed on the surface of the polarizing plate 31.

The transparent film 33 is made of a resin having a high light transmittance such as an acrylic resin, and the transparent film 33 is transferred and printed on the surface of the polarizing plate 31 by using a printing plate having a minute unevenness made of a resin material. Curing, a method of applying the resin material on the surface of the polarizing plate 31 to a uniform thickness and making unevenness by embossing, and then curing, or mixing transparent fine particles such as silica into the resin material. It is formed by any of the methods of applying a material to the surface of the polarizing plate 31 and curing it.

The average height (height difference between the concave surface and the convex surface) of the unevenness of the transparent film 33 is 1 to 5 μm, the average pitch p of the unevenness is 5 to 40 μm, and the haze value of the light scattering surface A is Is 9 to 14%.

The haze value is based on JIS K 67.
It is a value measured by an integrating sphere type light transmittance measuring device (haze meter) according to 14. This haze value is calculated by the following formula.

Total light transmittance; Tt (%) = T2 / T1 parallel light transmittance; Tp (%) = Tt-Td diffuse transmittance; Td (%) = [T4-T3 * (T2 / T1)]
/ T1 haze value; H (%) = (Td / Tt) x 100 T1; Incident light amount T2; Total light transmitted light amount T3; Measuring device diffused light amount T4; Test piece (transparent film 31) and diffused light amount by measuring device Further, the retardation plate 40 is made of a uniaxially stretched film such as polycarbonate, and the retardation plate 40 is disposed on the front surface side of the liquid crystal cell 10 and is a front surface side polarizing plate 31.
Between the liquid crystal cell 10 and the liquid crystal cell 10, the slow axis (stretching axis) of the retardation plate 40 and the transmission axis of the front-side polarizing plate 31 are obliquely displaced by a predetermined angle.

The retardation plate 40 is adhered to the surface of the liquid crystal cell 10 (the outer surface of the front surface side substrate 12), and the front surface side polarizing plate 31 is adhered to the surface of the retardation plate 40. The polarizing plate 32 is adhered to the back surface of the liquid crystal cell 10 (the outer surface of the back surface side substrate 11).

The light source 50 is the same as the light source used in the conventional liquid crystal display device, and as shown in FIG. 10, the light guide plate 51 facing almost the entire back surface of the back side polarizing plate 32. And a light source lamp 52 that emits white light and is arranged toward one end surface of the light guide plate 51.

The light guide plate 51, as shown in FIG.
A transparent plate made of acrylic resin or the like is formed with a reflective film 51a made of a vapor deposition film of Al or the like on the entire back surface. Illumination light from the light source lamp 52 enters the light guide plate 51 from one end surface thereof and enters the light guide plate 51. The light is guided through the inside and emitted toward the liquid crystal cell 10 from the entire surface of the light guide plate 51.

In the liquid crystal display device of this embodiment,
The front-side polarizing plate 31 is arranged such that its transmission axis is slanted at a predetermined angle with respect to the alignment direction of the liquid crystal molecules on the front-side substrate 12 of the liquid crystal cell 10 (the rubbing direction of the alignment film 21), and The retardation plate 40 is arranged such that its slow axis (stretching axis) is slanted by a predetermined angle with respect to the transmission axis of the front surface side polarizing plate 31, and the back surface side polarizing plate 32 is further arranged.
The transmission axis is arranged so as to be slanted at a predetermined angle with respect to the alignment direction of the liquid crystal molecules (the rubbing direction of the alignment film 19) on the rear substrate 11 of the liquid crystal cell 10.

In this embodiment, the orientation direction of the liquid crystal molecules on the back side substrate 11 of the liquid crystal cell 10 is 0 °.
Direction, and with this direction as a reference, the alignment direction of the liquid crystal molecules on the front substrate 12 of the liquid crystal cell 10 and the polarizing plate 3
The transmission axis directions of 1 and 32 and the slow axis direction of the retardation plate 40 are set.

That is, FIG. 11 shows the alignment direction of liquid crystal molecules of the liquid crystal cell 10 and the retardation plate 4 in the liquid crystal display device.
3 is a plan view showing the slow axis of 0 and the transmission axes of the polarizing plates 31 and 32, where 11a is the alignment direction of the liquid crystal molecules on the rear substrate 11 of the liquid crystal cell 10, and 12a is the surface of the liquid crystal cell 10. FIG. The alignment direction of the liquid crystal molecules on the side substrate 12 is shown.

As shown in FIG. 11, the liquid crystal molecule alignment direction 12a on the front surface side substrate 12 of the liquid crystal cell 10 is the surface with respect to the liquid crystal molecule alignment direction 11a on the back surface side substrate 11, that is, the azimuth angle of 0 °. The molecules of the liquid crystal LC are shifted by 90 ° counterclockwise when viewed from the side, and the molecules of the liquid crystal LC are
In the meantime, the twist orientation is made at a twist angle of about 90 °.

Further, in FIG. 11, 31a indicates the transmission axis of the front surface side polarizing plate 31, 40a indicates the slow axis of the retardation plate 40, and the transmission axis 31a of the front surface side polarizing plate 31 is the azimuth angle 0 °. Approximately 170 counterclockwise when viewed from the surface side with respect to
Direction, the slow axis 40a of the retardation plate 40 is in the direction of approximately 150 ° counterclockwise when viewed from the surface side with respect to the direction of the azimuth angle of 0 °. Therefore, the slow axis 40a of the retardation plate 40 is ,
With respect to the transmission axis 31a of the front surface side polarizing plate 31, it is deviated by about 20 ° in a clockwise direction when viewed from the front surface side.

Further, in FIG. 11, reference numeral 32a denotes the transmission axis of the back surface side polarizing plate 32, and the back surface side polarizing plate 3
The transmission axis 32a of No. 2 is in the direction of approximately 150 ° counterclockwise when viewed from the surface side with respect to the direction of the above azimuth angle of 0 °.

This liquid crystal display device performs reflection type display utilizing the outside light in a bright place where the amount of the outside light (natural light, indoor illumination light, etc.) is sufficient, and at this time, FIGS. As indicated by a solid arrow in FIG.
Of the semi-transmissive reflective film M provided on the inner surface of the rear substrate 11 of the liquid crystal cell 10.
The light that enters the (pixel electrode 13) and is reflected by the semi-transmissive reflective film M again passes through the liquid crystal layer and enters the front-side polarizing plate 31, and the light that passes through the polarizing plate 31 becomes the image light. Then, the light is emitted to the front surface side of the liquid crystal display device.

Further, this liquid crystal display device can perform display by utilizing the light from the light source 50 even in a dark place where the amount of external light is small, and in that case, the broken line arrow in FIGS. As shown, the light from the light source 50 is converted into linearly polarized light by the polarization effect of the back side polarizing plate 32, and the liquid crystal cell 10 is shown.
To the front side polarizing plate 31 through the liquid crystal layer and the light transmitted through the semi-transmissive reflective film M (pixel electrode 13) provided on the inner surface of the back side substrate 11 is incident on the front side polarizing plate 31. The light passing through 31 becomes image light and is emitted to the front surface side of the liquid crystal display device.

That is, in the above-mentioned liquid crystal display device, the semi-transmissive reflective film M is provided on the inner surface of the back surface side substrate 11 of the liquid crystal cell 10 so that the surface side of the liquid crystal cell 10 is used in the reflective display utilizing external light. The front-side polarizing plate 31 disposed at the position of the liquid crystal cell 10 is caused to have both a polarization action of making incident light linearly polarized light and an analysis action of making light passing through the liquid crystal layer of the liquid crystal cell 10 into image light. Back side polarizing plate 32 arranged on the back side
In the case of a transmissive display in which light from the light source 50 is used, the back surface side polarizing plate 32 serves as a polarizer and the front surface side polarizing plate 31 serves as an analyzer.

The display operation of the above liquid crystal display device will be described first with respect to the reflection type display utilizing external light. In this liquid crystal display device, the transmission axis 31 of the front side polarizing plate 31 will be described.
a is obliquely displaced with respect to the liquid crystal molecule alignment direction 12a on the front surface side substrate 12 of the liquid crystal cell 10, and the retardation plate 40
Is the slow axis 40a of the transmission axis 31a of the front side polarizing plate 31.
On the other hand, since the slow axis 40a of the retardation plate 40 is deviated obliquely, the linearly polarized light that has entered through the front-side polarizing plate 31 passes through the retardation plate 40, and due to its birefringence effect It becomes elliptically polarized light having a different polarization state, and this elliptically polarized light is further changed in polarization state by the birefringence effect in the process of passing through the liquid crystal layer of the liquid crystal cell 10, and is reflected by the semi-transmissive reflection film among the light. When the light passes through the liquid crystal layer and the retardation plate 40 again, the polarization state is further changed by the birefringence effect of the light and the front side polarizing plate 3
Incident on 1.

The reflected light incident on the front-side polarizing plate 31 is non-linearly polarized light whose polarization state is changed by the birefringence effect of the retardation plate 40 and the liquid crystal layer of the liquid crystal cell 10. Among these, only the wavelength light of the polarization component that passes through the front-side polarizing plate 31 passes through the polarizing plate 31 and is emitted, and becomes colored light corresponding to the ratio of each wavelength light in the emitted light.

Next, the display when using the light from the light source 50 will be described. At this time, the light from the light source 50 passes through the rear side polarizing plate 32 to become linearly polarized light, and this linearly polarized light is the liquid crystal cell 10. Light incident on the back surface of the liquid crystal cell 10 and transmitted through the semi-transmissive reflective film M provided on the inner surface of the back surface side substrate 11 of the liquid crystal cell 10 is incident on the liquid crystal layer. Since the transmission axis 32a of the back side polarizing plate 32 is obliquely displaced with respect to the alignment direction 11a of the liquid crystal molecules on the back side substrate 11 of the liquid crystal cell 10, the straight line incident on the back side of the liquid crystal cell 10 is While the polarized light passes through the liquid crystal layer of the liquid crystal cell 10, it becomes elliptically polarized light having a different polarization state depending on the wavelength due to its birefringence effect, and this elliptically polarized light is caused by the birefringence effect as it passes through the retardation plate 40. Furthermore incident on the surface side polarizing plate 31 is changing its polarization state.

Also at this time, the light incident on the front-side polarizing plate 31 is non-linearly polarized light whose polarization state is changed by the birefringence effect of the liquid crystal layer of the liquid crystal cell 10 and the retardation plate 40. Of the light, only the wavelength light of the polarization component that passes through the front-side polarizing plate 31 passes through the polarizing plate 31 and is emitted, and becomes colored light corresponding to the ratio of each wavelength light in the emitted light.

That is, the above-mentioned liquid crystal display device utilizes the birefringence effect of the retardation plate 40 and the liquid crystal layer of the liquid crystal cell 10 and the polarization and analysis function of the front side polarizing plate 31 in the reflection type display. In the transmission type display, the birefringence effect between the liquid crystal layer of the liquid crystal cell 10 and the retardation plate 40, the polarization effect of the back side polarizing plate 32, and the analysis of the front side polarizing plate 31 are performed. The action is used to color light.

Since this liquid crystal display device colors the light without using the color filter, the loss of the amount of transmitted light is greatly reduced as compared with the case of transmitting the color filter, and the colored light of high brightness is obtained. Therefore, a bright color image can be displayed.

That is, the color filter absorbs light having a wavelength other than the wavelength range corresponding to the color and colors the light.
Since this color filter also absorbs light in the wavelength range corresponding to that color with a considerably high absorptivity, in a liquid crystal display device that colors light with the color filter, the wavelength that becomes colored light of the light that enters the display device. The amount of colored light passing through the color filter is considerably reduced as compared with the amount of light in the band.

In this respect, since the liquid crystal display device colors light without using a color filter, there is no light absorption by the color filter, and the retardation plate 40 and the liquid crystal LC of the liquid crystal cell 10 are also transmitted. It only changes the polarization state of light and absorbs almost no light.

Therefore, the polarization state is changed by these birefringence effects, and the amount of colored light that passes through and is emitted from the front-side polarizing plate 31 is incident through the front-side polarizing plate 31 in the reflective display. Then, of the light reflected by the semi-transmissive reflective film M, the amount of light in the wavelength band that becomes the colored light, or the semi-transmissive light incident through the back-side polarizing plate 32 in the case of reflective display. The amount of light in the wavelength band, which is the colored light, of the light transmitted through the reflective film M is almost the same, and therefore, colored light with high brightness is obtained, so that a bright color image can be displayed.

Further, in the liquid crystal display device in which light is colored by the color filter, the display color is determined by the color of the color filter, so that one pixel cannot display a plurality of colors. According to the liquid crystal display device, the alignment state of the liquid crystal molecules changes according to the magnitude of the voltage applied to the liquid crystal layer of the liquid crystal cell 10, and the birefringence effect of the liquid crystal layer changes accordingly. It is possible to change the color of the colored light by controlling the applied voltage of, and display a plurality of colors with one pixel.

That is, in this liquid crystal display device,
The birefringence effect of the retardation plate 40 does not change, but the liquid crystal cell 1
The birefringence effect of the 0 liquid crystal layer changes as the alignment state of the liquid crystal molecules changes according to the voltage applied between the electrodes 13 and 20 of both substrates 11 and 12.

The liquid crystal cell 10 has liquid crystal molecules on the substrate 1.
When a voltage that rises and is oriented almost perpendicularly to the 1st and 12th planes is applied, the birefringence effect of the liquid crystal layer virtually disappears, but even then, the incident light is elliptically polarized due to the birefringence effect of the retardation plate 40. Becomes

Therefore, if the voltage applied to the liquid crystal cell 10 is controlled to change the polarization state of the light passing through the retardation plate 40 and the liquid crystal layer of the liquid crystal cell 10, the surface side polarizing plate 31
It is possible to change the color of the colored light that passes through and is emitted, and therefore, one pixel can display a plurality of colors.

The display drive of this liquid crystal display device is basically the same as the display drive of a generally known active matrix type liquid crystal display device (those using TFTs as active elements). A reference signal having a waveform synchronized with the synchronizing signal is supplied to the counter electrode 20, a gate signal is sequentially supplied to each gate line in synchronization with the synchronizing signal, and a potential corresponding to image data is supplied to each data line in synchronization with the reference signal. Of the data signal is controlled by controlling the potential of the data signal in accordance with the image data, the data signal of the potential corresponding to the image data is supplied to the pixel through the TFT 14 during the selection period of the pixel in each row. The voltage supplied to the electrode 13 and applied to the data signal is applied between the pixel electrode 13 and the counter electrode 20.

The display color of the liquid crystal display device will be described. For example, as described above, the liquid crystal cell 10 is one in which liquid crystal molecules are twist-aligned between the substrates 11 and 12 at a twist angle of about 90 °. Both substrates 11,
Alignment directions 11a and 12a of liquid crystal molecules on 12;
The transmission axes 31a and 32a of the polarizing plates 31 and 32 and the slow axis 40a of the retardation plate 40 are in the directions shown in FIG. 11, and Δn · d of the liquid crystal cell 10 (refractive index difference of the liquid crystal LC is different. The product of the anisotropic Δn and the liquid crystal layer thickness d) is about 980 nm.
(For example, Δn = 0.204, d = 4.8 μm), and when the retardation value of the retardation plate 40 is about 370 nm, the display color of each pixel is the liquid crystal cell 10 in the reflection type display using external light. In a transmissive display that changes to red, blue, green, black, and white according to the applied voltage to the liquid crystal display device, and the light from the light source 50 is used, the display color of each pixel depends on the applied voltage to the liquid crystal cell 10. It changes to red, green, blue, and white.

12 and 13 show changes in display color in the reflective display of the above liquid crystal display device.
2 is a CIE chromaticity diagram showing a color change of emitted light with respect to an applied voltage, and FIG. 13 is a voltage-emission rate characteristic diagram. In addition, here, the result of observing the emitted light from the normal direction of the liquid crystal display device is shown by injecting white light into the liquid crystal display device from a direction of 30 ° with respect to the normal line (the azimuth may be arbitrary). There is.

In this reflective display, the liquid crystal cell 10
As the voltage value applied between the electrodes 13 and 20 of the output light is increased, the color of the emitted light changes in the direction of the arrow as shown in FIG. As shown, red, blue, with high light intensity and good color purity
It comes in green, black and white colors. The red emitted light in this case is purple-red light.

As described above, in the liquid crystal display device, in the case of the reflection type display utilizing external light, the red, blue, and
It is possible to display green, black, and white colors, and by displaying different colors on a plurality of adjacent pixels, a mixed color of a plurality of the red, blue, green, black, and white colors is displayed. You can also let it.

14 and 15 show the change in display color in the transmissive display of the liquid crystal display device, and FIG. 14 shows the change in the color of the emitted light with respect to the applied voltage.
The IE chromaticity diagram and FIG. 15 are voltage-emission rate characteristic diagrams. 14 and 15, white light was made incident on the liquid crystal display device from the direction of 30 ° with respect to the normal line (the azimuth may be arbitrary), and the emitted light was observed from the normal line direction of the liquid crystal display device. The results are shown.

In this reflective display, the liquid crystal cell 10
As the voltage value applied between the electrodes 13 and 23 of the output light is increased, the color of the emitted light changes in the direction of the arrow as shown in FIG. As shown, red, green, with high light intensity and good color purity,
Blue and white colors.

As described above, the liquid crystal display device includes the light source 5
Even in the reflective display using light from 0, one pixel can display the red, green, blue, and white colors, and by displaying different colors in a plurality of adjacent pixels, It is also possible to display a mixed color of a plurality of colors of red, green, blue, and white.

Since the display color and the number of colors corresponding to the applied voltage in the reflective display are different from those in the transmissive display, the liquid crystal cell 10 is also used in the reflective display as in the transmissive display. Is driven, a color image of a color different from that in the transmissive display is displayed. However, if the drive condition of the liquid crystal cell 10 (potential of a data signal corresponding to image data, etc.) is controlled in the reflective display. Even in the reflective display, it is possible to display a color image having a color close to that of the transmissive display.

However, the above liquid crystal display device is used as a reflection type display device utilizing external light in most cases,
Since it is used as a reflection type display device by turning on the light source 50 when it is desired to see display information temporarily in a dark place where the amount of external light is small, the difference in the color of the display image in the reflection type display is not so problematic. Therefore, the driving condition of the liquid crystal cell 10 may be designed based on the transmissive display, and the liquid crystal cell 10 may be driven under the same driving condition as the transmissive display in the reflective display.

The liquid crystal display device of the above embodiment displays red, blue, green, black, and white colors in the reflective display and displays red, green, blue, and white colors in the transmissive display. However, the display color of this liquid crystal display device depends on the applied voltage, the alignment directions 11a and 12a of the liquid crystal molecules on both substrates 11 and 12 of the liquid crystal cell 10, the twist angle of the liquid crystal molecules, and the polarization plates 31 and 32. Since it depends on the directions of the transmission axes 31a and 32a and the direction of the slow axis 40a of the retardation plate 40, the display color can be arbitrarily selected by selecting these conditions.

The liquid crystal display device has the liquid crystal cell 1
By providing the semi-transmissive reflection film M on the inner surface of the back surface side substrate 11 of 0, the front surface side polarizing plate 31 is caused to have both a polarization effect and an analysis effect at the time of a reflective display utilizing external light. Since the display is performed without using the back side polarizing plate 32, the reflective display is used for the back side polarizing plate 32 and the liquid crystal cell 1.
With the back side substrate 11 of 0, the amount of emitted light can be performed without loss, and therefore, the loss of light amount due to light absorption in the polarizing plate and the substrate of the liquid crystal cell at the time of reflection type display utilizing external light can be reduced, The display in the reflective display can be made sufficiently bright.

In the above liquid crystal display device, light also passes through the phase difference plate 40 and the liquid crystal layer of the liquid crystal cell 10, but since the phase difference plate 40 and the liquid crystal layer absorb little light as described above, There is almost no light loss due to these.

In the liquid crystal display device, the pixel electrode 13 and the counter electrode 20 provided on the inner surfaces of the substrates 11 and 12 of the liquid crystal cell 10 are provided on the inner surface of the back side substrate 11. Since the existing pixel electrode 13 also serves as the semi-transmissive reflective film M, the pixel electrode 13 and the semi-transmissive reflective film M can be simultaneously formed.
The structure of 0 can be simplified and its manufacture can be facilitated.

Further, in the above liquid crystal display device, since the semi-transmissive reflective film M is provided on the inner surface of the back surface side substrate 11 of the liquid crystal cell 10, it is difficult to use this semi-transmissive reflective film M as a diffuse reflective film. As described above, if one surface of the front-side polarizing plate 31 arranged on the front surface side of the liquid crystal cell 10 is the light-scattering surface A, the light incident on and the light emitted from the liquid crystal display device can be detected by the light-scattering surface A. Since the light can be scattered, even if the reflective surface of the semi-transmissive reflective film M is almost a mirror surface, an external image such as the face of the display observer or its background is not visible on the reflective surface.

That is, since the liquid crystal display device has a very high light transmittance, if the reflection surface of the semi-transmissive reflective film M is a mirror surface, an external image such as the face of the display observer or its background is semi-transmissive. Although the image appears on the reflection surface of the reflection film M and overlaps with the display image, if one surface of the polarizing plate 31 on the surface of the liquid crystal display device is the light scattering surface A, the light corresponding to the external image is also the light. Since the light is scattered on the scattering surface A, the external image is not reflected.

If the reflective surface of the semi-transmissive reflective film M is almost a mirror surface, the light whose polarization state is changed by the liquid crystal layer of the liquid crystal cell 10 is used for the transmissive reflective film M in the reflective display.
The light is not scattered by the semi-transmissive reflective film M, and the light that enters the liquid crystal cell 10 from the rear surface side through the rear surface side polarizing plate 32 is not scattered by the semi-transmissive reflective film M also in the transmissive display.

In this case, if the surface of the front-side polarizing plate 31 is the light-scattering surface A, the light incident on the liquid-crystal display device from the front side is scattered after the reflection-type display and then the front-side polarization is performed. In the reflective display and the transmissive display, the light that has passed through the liquid crystal layer of the liquid crystal cell 10 becomes the image light due to the analyzing function of the front-side polarizing plate 31 in the reflective display and the transmissive display. Since the light is scattered after it is incident, the light is not scattered until the incident light passes through the front-side polarizing plate 31 to become image light, so that a high-quality image can be displayed.

The scattering effect of the light-scattering surface A is determined by the haze value described above. If the haze value is 25% or more, the light that has become image light due to the analyzing action of the front-side polarizing plate 31 is also included. If the haze value of the light scattering surface A is in the range of 9 to 14%, it is clear if the external image is reflected when the haze value is 6% or less. It is possible to obtain a clear display image and to prevent the reflection of an external image.

Further, in the above liquid crystal display device, the liquid crystal cell 1 is formed on the inner surface of the front substrate 12 of the liquid crystal cell 10.
Since the black mask 22 corresponding to the gap between the pixel electrodes 13 arranged on the back side substrate 11 of 0 is provided, the contrast between the pixels can be made clear and a high-quality image can be displayed.

In the first embodiment described above, the pixel electrode 1 is formed on the inner surface of the rear substrate 11 as the liquid crystal cell 10.
3 and MIM 14 are provided, and the counter electrode 20 is provided on the inner surface of the front substrate 12, the liquid crystal cell 10 is used.
Is the pixel electrode 13 and the MIM 14 on the inner surface of the front substrate 12.
And the counter electrode 20 may be provided on the inner surface of the back-side substrate 11.

FIG. 16 is a sectional view of a part of a liquid crystal display device showing a second embodiment of the present invention. In this embodiment, a liquid crystal cell 10 is provided on the inner surface of a front side substrate 12 thereof with a pixel electrode 1 formed thereon.
3 and the MIM 14, and the counter electrode 20 is provided on the inner surface of the back surface side substrate 11, and the back surface side substrate 1
The counter electrode 20 provided on the inner surface of 1 also serves as the semi-transmissive reflective film M.

The liquid crystal display device of this embodiment is similar to the first embodiment described above except that the rear substrate 1 of the liquid crystal cell 10 is used.
1, the pixel electrode 13, the MIM 14, and the alignment film 19
Is provided on the front side substrate 12, and the pixel electrode 13 is a transparent electrode, and the counter electrode 20, the alignment film 21, and the black mask 22 provided on the front side substrate 12 of the liquid crystal cell 10 in the first embodiment are provided on the back side substrate. 11, the counter electrode 20 also serves as the semi-transmissive reflective film M, and the other configurations are the same as those of the first embodiment, and therefore the description of the configurations is given the same reference numerals in the drawings. And omit.

Further, also in the liquid crystal display device of this embodiment, by providing the semi-transmissive reflective film M on the inner surface of the back surface side substrate 11 of the liquid crystal cell 10, in the case of the reflective display utilizing external light,
The front-side polarizing plate 31 arranged on the front surface side of the liquid crystal cell 10 is caused to have both the polarizing action and the analyzing action, and the rear-side polarizing plate 32 arranged on the rear face side of the liquid crystal cell 10 is used for display. At the same time, without using a color filter, the birefringence effect of the retardation plate 40 and the liquid crystal layer of the liquid crystal cell 10 and the polarizing plate (the front side 31 in the reflective display, the back side polarizing plate 32 and the front side polarizing plate in the transmissive display). Since the light is colored by utilizing the polarization and the analyzing action of 31) and various effects obtained are the same as those in the first embodiment, the description thereof will be omitted.

In the first and second embodiments described above, one of the substrates 11 and 12 of the liquid crystal cell 10 on which the counter electrode 20 is provided (in the first embodiment, the front-side substrate 1).
2. In the second embodiment, the backside substrate 11) is provided with the black mask 22, but the black mask 22 may be provided on the inner surface of the substrate on which the pixel electrodes 13 and the MIM 14 are provided. However, the black mask 22 is not always necessary.

Further, in the liquid crystal display devices of the first and second embodiments, the retardation plate 40 is arranged between the polarizing plate 30 and the liquid crystal cell 10, but the retardation plate 40 is not necessary. Even in that case, the front-side polarizing plate 31 is provided with its transmission axis obliquely shifted with respect to the liquid crystal molecule alignment direction 12a on the front-side substrate 12 of the liquid crystal cell 10, and the back-side polarizing plate 32 is provided. If the transmission axis is provided so as to be slanted with respect to the liquid crystal molecule alignment direction 11a on the back surface side substrate 11 of the liquid crystal cell 10, the liquid crystal layer of the liquid crystal cell 10 can be used in both reflective display and transmissive display. Light can be colored by utilizing the effect of birefringence and the polarization and analysis of the polarizing plate.

That is, in the case of the reflection type display, if the transmission axis of the front surface side polarizing plate 31 is deviated obliquely with respect to the liquid crystal molecule alignment direction 12a on the front surface side substrate 12 of the liquid crystal cell 10, the front surface side polarizing plate 31. The linearly polarized light that has entered through the liquid crystal cell 10 becomes elliptically polarized light having a different polarization state for each wavelength due to the birefringence effect of the liquid crystal layer in the process of passing through the liquid crystal cell 10, and the light reflected by the semi-transmissive reflection film M is again reflected in the liquid crystal layer. In the process of passing through, the polarization state is further changed to enter the front surface side polarizing plate 31, and the light of the polarization component transmitted through the polarizing plate 31 becomes colored light and is emitted to the surface of the liquid crystal display device.

In the case of a transmissive display, the back surface side polarizing plate 3
If the transmission axis of 2 is obliquely displaced with respect to the liquid crystal molecule alignment direction 11a on the back surface side substrate 11 of the liquid crystal cell 10,
Of the linearly polarized light that has entered the liquid crystal cell 10 through the rear surface side polarizing plate 32, the light that has transmitted through the semi-transmissive reflective film M has an elliptically polarized light that has a different polarization state for each wavelength due to its birefringence effect in the process of passing through the liquid crystal layer. Then, the light of the polarization component that enters the front surface side polarizing plate 31 and is transmitted through the polarizing plate 31 becomes colored light and is emitted to the surface of the liquid crystal display device.

Also in this liquid crystal display device, the loss of the amount of transmitted light can be greatly reduced as compared with the case where light is transmitted through the color filter, so that high-intensity colored light can be obtained, and the liquid crystal cell 10 can be obtained. The alignment state of the liquid crystal molecules changes according to the magnitude of the voltage applied to the liquid crystal layer, and the birefringence effect of the liquid crystal layer changes accordingly.
By controlling the voltage applied to 0, the color of the colored light can be changed and one pixel can display a plurality of colors.

However, if the retardation plate 40 is disposed between the liquid crystal cell 10 and the front-side polarizing plate 31 as in the above-described first and second embodiments, a transmissive display can be achieved even in the reflective display. At this time, the incident light causes the birefringence effect of the retardation plate 40 and the liquid crystal cell 1.
Since the polarization state is greatly changed in response to the birefringence effect of the liquid crystal layer of 0, elliptically polarized light having a different polarization state for each wavelength can be incident on the front-side polarizing plate 31 to obtain a colored light of a clear color. In addition, even when a voltage is applied to the liquid crystal cell 10 so that the liquid crystal molecules rise and are aligned almost perpendicularly to the substrate surface, that is, even when the birefringence effect of the liquid crystal layer is virtually eliminated, the phase difference plate 40 The incident light is made into elliptically polarized light by the birefringence effect, and this elliptically polarized light is made into the surface side polarizing plate 3
It is desirable to provide the retardation plate 40 because it is possible to obtain colored light by making it enter 1. In addition, you may provide this phase difference plate in piles of 2 or more sheets.

In the above embodiment, the active matrix type cell having the MIM 14 as an active element is used as the liquid crystal cell 10, but this liquid crystal cell uses a two-terminal nonlinear resistance element such as a thin film diode as an active element. It may be an active matrix type cell, and the twist angle of liquid crystal molecules is not limited to 90 °, but may be, for example, 180 to 270 °.
Further, the liquid crystal cell 10 may be one in which liquid crystal molecules are aligned in an alignment state such as homogeneous alignment, homeotropic alignment, hybrid alignment or the like.

[0136]

According to the liquid crystal display device of the present invention, in reflection type display, light is colored by utilizing the birefringence effect of the liquid crystal layer of the liquid crystal cell and the polarization and analysis function of the first polarizing plate. However, in the transmissive display, light is colored by utilizing the birefringence effect of the liquid crystal layer of the liquid crystal cell, the polarization effect of the second polarizing plate and the light analyzing effect of the first polarizing plate. Since this liquid crystal display device colors light without using a color filter, it is possible to obtain a highly bright colored light by significantly reducing the loss of the amount of transmitted light as compared with the case of transmitting the color filter. Therefore, a bright color image can be displayed.

Moreover, in this liquid crystal display device, the alignment state of the liquid crystal molecules changes according to the magnitude of the voltage applied to the liquid crystal layer of the liquid crystal cell, and the birefringence effect of the liquid crystal layer changes accordingly. The color of the colored light can be changed by controlling the voltage applied to the liquid crystal cell, and one pixel can display a plurality of colors.

Further, in this liquid crystal display device, a semi-transmissive reflective film is provided on the inner surface of the substrate on the rear surface side of the liquid crystal cell, so that it is arranged on the front surface side of the liquid crystal cell in the case of reflective display utilizing external light. The first polarizing plate is provided on the back surface side of the liquid crystal cell so as to have both the polarizing effect of making the incident light linearly polarized light and the analyzing effect of making the light passing through the liquid crystal layer of the liquid crystal cell the image light. Since the display is performed without using the second polarizing plate,
Reflective display can be performed by the second polarizing plate disposed on the back surface side of the liquid crystal cell and the back surface side substrate of the liquid crystal cell without loss of the emitted light amount. At this time, it is possible to reduce the loss of light amount due to the absorption of light in the polarizing plate and the substrate of the liquid crystal cell, and to make the display in the reflective display sufficiently bright.

In the liquid crystal display device of the present invention, among the electrodes provided on the inner surfaces of both substrates of the liquid crystal cell, the electrode provided on the inner surface of the back side substrate also serves as the semi-transmissive reflective film. By doing so, since this electrode and the semi-transmissive reflective film can be formed at the same time, the structure of the liquid crystal cell can be simplified and its manufacture can be facilitated.

Furthermore, in the liquid crystal display device of the present invention,
A retardation plate is disposed between the liquid crystal cell and the first polarizing plate disposed on the surface side of the liquid crystal cell, and the slow axis of this retardation plate is used as the transmission axes of the first polarizing plate and the second polarizing plate. If they are slanted, the incident light receives the birefringence effect of the retardation plate and the birefringence effect of the liquid crystal layer of the liquid crystal cell in both the reflective display and the transmissive display. In order to significantly change the wavelength, elliptically polarized light whose polarization states are greatly different for each wavelength can be made incident on the first polarizing plate to obtain a colored light of a clear color, and liquid crystal molecules can be attached to the substrate surface in the liquid crystal cell. On the other hand, when a voltage that rises and aligns almost vertically is applied, that is, even when the birefringence effect of the liquid crystal layer is virtually eliminated, the birefringence effect of the retardation plate makes the incident light elliptically polarized light. Obtaining colored light by making it enter the first polarizing plate It can be.

Further, in the liquid crystal display device of the present invention, since the semi-transmissive reflective film is provided on the inner surface of the back side substrate of the liquid crystal cell, it is difficult to use this semi-transmissive reflective film as a diffuse reflective film, but the liquid crystal If one surface of the first polarizing plate arranged on the front surface side of the cell is a light scattering surface, even if the reflecting surface of the semi-transmissive reflecting film is almost a mirror surface, the face of the display observer or the background thereof, etc. The external image never appears on the reflecting surface.

If the reflection surface of the semi-transmissive reflection film is almost a mirror surface, the light whose polarization state is changed by the liquid crystal layer of the liquid crystal cell in the reflection type display is not scattered by the semi-transmission reflection film. Further, also in the transmissive display, light that enters the liquid crystal cell from the back side thereof through the second polarizing plate is not scattered by the semi-transmissive reflective film.

In this case, if the surface of the first polarizing plate is a light-scattering surface, the first polarized light is scattered after the light incident on the liquid crystal display device from the surface side is scattered during the reflective display. After the light is transmitted through the liquid crystal layer of the liquid crystal cell into the image light by the analyzing function of the first polarizing plate in both the reflective display and the transmissive display, the light becomes a linearly polarized light by the polarizing action of the plate. Since the light is scattered, the light is not scattered until the incident light passes through the first polarizing plate to become the image light, and therefore a high quality image can be displayed.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a liquid crystal display device showing a first embodiment of the present invention.

FIG. 2 is a plan view of a part of a liquid crystal cell.

FIG. 3 is a partial cross-sectional view showing a first example of a semi-transmissive reflective film.

FIG. 4 is a plan view of the semi-transmissive reflective film shown in FIG.

FIG. 5 is a partial sectional view showing a second example of a semi-transmissive reflective film.

FIG. 6 is a partial cross-sectional view showing a third example of a semi-transmissive reflective film.

FIG. 7 is a partial sectional view showing a fourth example of a semi-transmissive reflective film.

FIG. 8 is a plan view of the semi-transmissive reflective film shown in FIG.

FIG. 9 is an enlarged cross-sectional view of the surface of the front-side polarizing plate.

FIG. 10 is a basic configuration diagram of the liquid crystal display device of the first embodiment.

FIG. 11 is a plan view showing a liquid crystal molecule alignment direction of a liquid crystal cell, a slow axis of a retardation plate, and a transmission axis of a polarizing plate.

FIG. 12 is a CIE chromaticity diagram showing a color change of emitted light with respect to an applied voltage during reflective display.

FIG. 13 is a voltage-emissivity characteristic diagram for reflective display.

FIG. 14 is a CIE chromaticity diagram showing a color change of emitted light with respect to an applied voltage in transmissive display.

FIG. 15 is a voltage-emissivity characteristic diagram for transmissive display.

FIG. 16 is a partial cross-sectional view of a liquid crystal display device showing a second embodiment of the present invention.

FIG. 17 is a basic configuration diagram of a conventional liquid crystal display device.

[Explanation of symbols]

 10 ... Liquid crystal cell 11 ... Back side substrate 12 ... Front side substrate 13 ... Pixel electrode M ... Semi-transmissive reflective film 14 ... MIM (non-linear resistance element) 19 ... Alignment film 20 ... Counter electrode 21 ... Alignment film 22 ... Black mask LC ... Liquid crystal 31 ... Front-side polarizing plate (first polarizing plate) A ... Light-scattering surface 32 ... Back-side polarizing plate (second polarizing plate) 40 ... Phase difference plate 50 ... Light source

Claims (6)

[Claims] 1. A reflection type display function of displaying external light by making external light incident from the front side and reflecting the light, and a transmission type display function of making light from a light source incident from the back side to display. A liquid crystal display device using, as a liquid crystal cell, an active matrix liquid crystal cell having a two-terminal nonlinear resistance element as an active element, wherein the liquid crystal cell and a first polarizing plate arranged on the front surface side of the liquid crystal cell. And a second panel disposed on the back side of the liquid crystal cell.
And a semi-transmissive reflective film for reflecting and transmitting incident light with a certain reflectance and a certain transmittance on the inner surface of the substrate on the back surface side of the liquid crystal cell. The transmission axis of the polarizing plate is obliquely displaced with respect to the alignment direction of the liquid crystal molecules on the substrate on the surface side of the liquid crystal cell,
A liquid crystal display device, wherein a transmission axis of the second polarizing plate is obliquely displaced with respect to an alignment direction of liquid crystal molecules on a substrate on the back surface side of the liquid crystal cell. 2. The electrode provided on the inner surface of the back-side substrate among the electrodes provided on the inner surfaces of both substrates of the liquid crystal cell also serves as a semi-transmissive reflective film. The liquid crystal display device according to item 1. 3. A retardation plate is disposed between a liquid crystal cell and a first polarizing plate disposed on the surface side of the liquid crystal cell, and the retardation plate has the slow axis of the first polarizing plate. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is provided so as to be obliquely displaced with respect to the transmission axes of the second polarizing plate. 4. The liquid crystal display device according to claim 1, wherein the reflective surface of the semi-transmissive reflective film is substantially a mirror surface. 5. The liquid crystal display device according to claim 1, wherein one surface of the first polarizing plate arranged on the front surface side of the liquid crystal cell is a light scattering surface. 6. The liquid crystal display device according to claim 5, wherein the surface of the polarizing plate is a light scattering surface.