JPH0990350A - Color liquid crystal display device of reflection type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reflection type color liquid crystal display device with which colorless display is possible and the bright color display of good color purity is embodied by providing the device with liquid crystal cell, one sheet of polarizing plate and one sheet of reflection plate, providing the device with a phase difference plate between a liquid crystal layer and this polarizing plate and specifying the range of a twist angle, etc. SOLUTION: The twist angle of the liquid crystals from the first orientation direction 10 of the liquid crystal cell to the second orientation direction 11 of the liquid crystal cell is defined as θ1 in the clockwise direction and the angle from the first orientation direction 10 of the liquid crystal cell to the delay phase axis direction 12 of the phase difference plate as θ2 in the clockwise direction. The angle from the first orientation direction 10 of the liquid crystal cell to the polarization axis 13 of the polarizing plate is defined as θ3 in the clockwise direction. The Δn1 .d1 of the liquid crystal layer is specified to 0.3 to 2.00μm by adjusting refractive index anisotropy Δn1 of the liquid crystal cell and the thickness d1 of the liquid crystal layer. The >=n2 .d2 of the phase difference plate is specified to 0.3 to 2.00μm. The angles described above are set within ranges of θ1 =-160 to -300 deg., θ2 =+70 to +120 deg., θ3 =+30 to +70 deg. or +120 to 160 deg.. The displays from bright white to red, blue and green are obtd. with an increase in the effective voltage impressed on the liquid crystal cell.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective color liquid crystal display device capable of displaying achromatic colors and displaying red, blue and green colors.

[0002]

2. Description of the Related Art A reflection type color liquid crystal display device generally uses two polarizing plates on both sides of a liquid crystal cell. However, there was a problem that the brightness of white was not enough. There is also a problem that it is not possible to obtain a color with good color purity.
In addition, there is a problem that the display peculiar to the reflection type is seen twice.

JP-A-6-308479 (conventional example 1) has a two-layer structure of a liquid crystal cell and a retardation plate, one polarizing plate is arranged on one side, and one reflecting plate is arranged on the other side. Although the above configuration is shown and it can be used as a color liquid crystal display device by this, it is not described how to set the configuration conditions in order to obtain a color with high purity. The configuration has a large variation factor such as the size and angle of Δn · d, and the color development purity greatly varies depending on the configuration.

Prior art example 1 shows that when no voltage is applied, the color is blue, and then as the voltage is increased, the color changes from blue to yellow to blue to white. If the display is blue when no voltage is applied, the spaces between the lines will be blue and the display will be dark when the matrix display is performed. Further, when a voltage is applied, the color development becomes turbid, and the color development with high purity cannot be obtained.

Further, in the conventional example 1, red coloring is not obtained. Further, since 90 ° twist is used, it is not suitable for multiplex drive.

[0006]

SUMMARY OF THE INVENTION In consideration of the above problems, an object of the present invention is to enable multiplex driving without using a color filter, to display bright white in a non-selected waveform, and to select a selected waveform. Alternatively, when an intermediate voltage between the selected waveform and the non-selected waveform is applied, it is possible to develop blue, green and red with good color purity.

In other words, when no voltage is applied,
Another object of the present invention is to provide a bright reflection type color liquid crystal display device which can display a very bright and almost achromatic color when the voltage is low and can realize a bright color display with good color purity by applying a voltage.

[0008]

In order to achieve the above-mentioned object, in the present invention, a liquid crystal cell in which a nematic liquid crystal having a twist orientation is sandwiched between two substrates having electrodes,
It has one polarizing plate and one reflecting layer, and has a retardation plate between the liquid crystal layer and the polarizing plate, and the liquid crystal cell has a first alignment direction in which liquid crystal molecules are aligned on the surface on the polarizing plate side. A twist angle θ ₁ of −160 to −300 ° in a predetermined direction from the first alignment direction to the second alignment direction depending on the second alignment direction in which the liquid crystal molecules are aligned on the surface of the reflector plate. , The refractive index anisotropy Δn ₁ of the liquid crystal of the liquid crystal cell and the thickness d _{1 of the} liquid crystal cell
The product Δn ₁ · d ₁ is 0.3 to 2.00 μm, the retardation plate has uniaxial anisotropy, and the refractive index anisotropy of the in-plane slow axis and fast axis is The product Δn ₂ · d _{2 of the} difference Δn ₂ and the thickness d ₂ of the retardation plate is set to 0.3 to 2.00 μm, and the angle from the first alignment direction of the liquid crystal cell to the slow axis direction of the retardation plate is set. Θ ₂ in the predetermined direction, θ _{3 in the} predetermined direction from the slow axis direction of the retardation plate to the polarization axis direction of the polarizing plate, and θ ₂ is in the range of +70 to + 120 °, and θ
₃ is in the range of +30 to + 70 ° or +120 to 160 °, a voltage value of three or more values is selected, a drive voltage is applied to the liquid crystal cell, light is incident from the polarizing plate side, and reflected by the reflective layer, Provided is a reflective color liquid crystal display device which is characterized by being emitted from a polarizing plate.

In a preferred embodiment, the predetermined direction is a clockwise direction or a counterclockwise direction. In another preferred embodiment, the retardation plate is biaxially anisotropic, the in-plane refractive indices are n _x and n _y (n _x > _ny ), and _nz is the thickness of the retardation plate. When the refractive index in the direction is 0.7 ≧ N _z = (n _x −n _z ) / (n _x −
n _y ) ≧ 0.2 is satisfied.

In still another preferred embodiment, the liquid crystal cell has Δn ₁ · d ₁ of 1.00 to 1.50 μm. In still another preferred embodiment, Δn ₂ · d _{2 of the} retardation plate is 0.90 to 1.
It is characterized by being 50 μm. In yet another preferred embodiment, the absolute value of θ ₁ of the liquid crystal cell is 1
It is characterized in that it is 70 to 190 °.

In still another preferred embodiment, the θ ₂ is in the range of 85 to 105 ° and the θ ₃ is in the range of 45 to 65 ° or 135 to 155 °. In still another preferred embodiment, the θ ₂ is in the range of 105 to 115 °, and the θ _{3 is}
Is in the range of 35 to 45 ° or 125 to 135 °.

In still another preferred embodiment, the duty ratio of the multiplex drive is 1/32 to 1/3.
It is characterized by being 00. In yet another preferred embodiment, the electrodes are arranged in a matrix of rows and columns, and a plurality of row electrodes are selected and driven at the same time.

A further preferred embodiment is characterized in that a reflector is provided on the liquid crystal side of the substrate forming the liquid crystal cell. In still another preferred embodiment, a temperature compensating circuit in which a driving voltage applied to the liquid crystal cell changes according to temperature is installed. In still another preferred embodiment, the adjusting means (for example, a knob of a variable resistor or a semi-fixed switch) for adjusting the drive voltage applied to the liquid crystal cell of the reflective color liquid crystal display device is a reflective color. It is characterized by constituting a portable electronic device installed outside the liquid crystal display device.

In the structure shown in the conventional example 1, there are problems that blue is displayed and no red is produced when no voltage is applied. In addition, the cell configuration conditions used in Conventional Example 1 have not been optimized, and thus are not suitable for multiplex drive.

The liquid crystal cell has a first alignment direction 10 (FIG. 2) in which liquid crystal molecules are aligned on the polarizing plate side and a second alignment direction 11 in which liquid crystal molecules are aligned on the reflecting plate side. The twist angle θ ₁ is set clockwise from the first orientation direction 10 to the second orientation direction 11. The angle from the first alignment direction 10 of the liquid crystal cell to the slow axis direction 12 of the retardation plate is θ ₂ clockwise, and the angle from the slow axis direction 12 of the retardation plate to the polarization axis direction 13 of the polarizing plate. Is set to θ ₃ clockwise. Since the polarization axis and the slow axis have no direction, the angle is the same even when rotated by 180 °.

When the relationship of θ ₂ and θ ₃ is satisfied, bright color development with good color purity can be obtained. FIG. 3 shows the relationship.
The shaded area provides good color. Especially the area surrounded by the grid (the area where the diagonal lines overlap)
However, this is where better color development can be obtained.

In FIG. 3, two large shaded portions and one small shaded portion are shown. These are the horizontal axis (θ ₃ ),
In the coordinate system of the vertical axis (θ ₂ ), the vertical axis is approximately 70 ° and 12
The horizontal axis is about 30 to 70 ° and about 120 in the range between 0 °.
A range of a shape that fits within two rectangles of ˜160 °, and a range of a circle having a center coordinate of (80 °, 80 °) and a diameter of about 5 to 10 °. Further, particularly in the range of good color development, the center coordinates are approximately (40 °, 110 °) and (13
0 °, 110 °) and two approximately circular areas corresponding to a diameter of about 5 °, and the vertical axis is between about 85 ° and 105 °, and the horizontal axis is about 45-65 ° and about 135-135. It is a shaped portion that fits in two ranges of 155 °.

Further, when the relationship between Δn ₁ · d ₁ of the liquid crystal cell and Δn ₂ · d ₂ of the retardation plate satisfies the relationship, bright color development with good color purity can be obtained. FIG. 4 shows the relationship. The shaded area gives good color.

The range shown in FIG. 4 is the horizontal axis (Δn ₂ · d
₂ ), the coordinate system of the vertical axis (Δn ₁ · d ₁ ), the center coordinates are approximately (1.2, 1.25), the major axis is about 0.6 μm, and the minor axis is about 0.3 μm. The range is within the shape close to that.

Already in Japanese Patent Application No. 7-140896,
A basic configuration related to the present invention was proposed. Furthermore, the present invention seeks to obtain each condition region in more detail as described above. Specifically, a computer simulation was performed to search for the relationship between the optical characteristics and the configuration requirements (Δn ₁ , d ₁ , parameters such as angle conditions) of the reflective color liquid crystal display device. That is, it was possible to substantially obtain a configuration requirement for obtaining a desired color display.

The twist angle θ ₁ of the liquid crystal cell is 160 to 30.
Although it may be up to 0 °, it is particularly preferably set to 170 to 190 ° in order to obtain a good color development. Particularly, it is preferable that the angle is around 180 °.

The definition of good color development in the present invention will be described below. White display (W) means x = 0.3 in chromaticity coordinates
1, close to y = 0.316, the reflectance is 40% or more, the red display (R) is close to the color coordinates of x = 0.5, y = 0.3, and the reflectance is 20% or more. That is, the blue display (B) is close to the color coordinates of x = 0.15 and y = 0.1, the reflectance is 20% or less, and the green display is x = 0.
2, it is considered to be close to the color coordinate of y = 0.4.

As the retardation plate, Δn · d depends on the temperature.
It is more preferable to use a temperature compensating retardation plate in which is changed. It is possible to provide a good reflective color liquid crystal display device in which color development does not decrease even when the ambient temperature changes. In this case, it is desirable to provide Δn · d that changes with temperature so that the liquid crystal changes substantially with Δn · d that changes with temperature.

It is also preferable to use a retardation plate in which the dispersion of the optical anisotropy depending on the wavelength is changed. This makes it possible to provide a reflective color liquid crystal display device with further improved color purity.

The liquid crystal cell is formed by depositing ITO (In ₂ O ₃ —SnO ₂ ) or S on a substrate such as plastic or glass.
A transparent electrode such as nO ₂ is provided.

The transparent electrode is patterned into a desired pattern. For example, one substrate may be provided with 320 stripe-shaped patterns and the other substrate may be provided with 240 stripe-shaped patterns orthogonal thereto.
A striped pattern of books is formed. This enables a matrix display of 320 × 240 dots. The size of one pixel forming a dot is, for example, 270
μm × 270 μm, and the gap between pixels is 30 μm
It is a degree.

A film of polyimide, polyamide, or the like is provided on the surface of the transparent electrode, and the surface is rubbed or SiO or the like is obliquely deposited to form an orientation control film. In order to prevent a short circuit between the substrates, TiO between the electrode and the orientation control film.
An insulating film such as ₂ , SiO ₂ or Al ₂ O ₃ may be provided, or a transparent electrode may be provided with a low resistance lead electrode such as Al, Cr, Ti or Ag.

A liquid crystal layer is formed by stacking the substrates, filling the liquid crystal therein, and fixing the edges with a sealing material.

The polarizing plate itself is generally placed outside the substrate that constitutes the liquid crystal cell. In addition, within the range of desired optical performance, in order to simplify the structure and improve productivity, the substrate itself may be made of a polarizing plate, or a polarizing layer may be provided between the substrate and the electrode.

As the reflecting plate, one having Al deposited on the uneven surface is used. In addition to Al, Ag, Cr, N
Metals such as i, Au and W may be used. Further, the surface of a thin film of Al, Ag, Cr, Ni, Au, W or the like may be roughened to be used.

The wavelength dependence of reflection differs depending on the metal. For example, silver reflection has a low reflectance in the blue wavelength range,
The reflected light becomes yellowish. By making the display of the liquid crystal cell closer to the blue side, the display characteristics when a silver reflector was used were improved and a bright display with good color purity was obtained.

The reflective color liquid crystal display device of the present invention comprises:
Since light passes through the liquid crystal cell twice to generate color, a shorter distance from the liquid crystal cell to the reflection plate provides a display with better color purity.

As a method of shortening the distance from the liquid crystal cell to the reflector, for example, the thickness of the reflector-side substrate is reduced. The thickness of the glass substrate normally used as a substrate is 1.
It is 1 mm or 0.7 mm. 0.4m of this glass substrate
It may be changed to a glass substrate having a thickness of m. Thinner 0.3m
It is even more preferable to use a glass substrate having m or 0.1 mm or less.

When a large size reflection type color liquid crystal display device is made of glass having a thickness of 0.4 mm or less, the glass substrate is easily broken, which causes problems in use or production. As a countermeasure, if the thickness of the substrate on the reflection plate side is 0.4 mm or less and the thickness of the substrate on the polarizing plate side is 0.4 mm or more, cracking is less likely to occur, which is useful in use or manufacturing.

When a plastic such as polycarbonate or acrylic resin is used in place of the glass substrate, a thin reflective thin liquid crystal display can be obtained.

As a method of shortening the distance between the liquid crystal cell and the reflector, if the reflector is formed on the liquid crystal side of the substrate of the liquid crystal cell, the distance between the liquid crystal and the reflector is further shortened, and the color purity is improved. It

For example, the surface of the glass substrate is made uneven by etching it with hydrofluoric acid or the like. Alternatively, there is a method of forming irregularities on the surface by arranging particles having a diameter of several tens of μm to several μm on the glass surface. As for the unevenness of the reflection plate, the unevenness from the peak to the peak is about 1 to 2 μm at a pitch of 10 to 20 μm, and the reflection brightness is high and the appearance is good. Al on the uneven surface by vapor deposition or sputtering
A thin film of is formed as a reflective layer. In addition to Al, Ag, C
You may use r, Ni, Au, W etc.

A flattening film or an insulating film for flattening unevenness is formed on Al. Furthermore, a transparent electrode is formed on it,
Pattern into a desired pattern.

Further, the electrodes may have a function as a reflector. Al, Ag, Cr, Ni,
By forming a thin film of a material having a high reflectance such as Au or W and patterning the thin film, the thin film serves as a reflection plate and an electrode.

When the electrode is used as a reflective layer, for example, when it is patterned in a stripe shape, the lines are not reflected. Light entering between the lines is not used for reflection, which causes a dark state. Therefore, a reflection layer may be further arranged outside the substrate (on the side opposite to the liquid crystal cell).

Various methods such as frame gradation, amplitude gradation, and pulse width gradation are known as methods for driving the gradation of voltage. Any method can be used as long as it can change the magnitude of the effective voltage applied to the liquid crystal. Although the frame gray scale is generally used at present, good display is obtained even by using this method. Further, a pseudo gradation may be used.

Driving method for simultaneously selecting a plurality of row electrodes (a driving technique for simultaneously selecting a plurality of row electrodes and preventing selection of liquid crystals by dispersing selection pulses to obtain a high contrast display. Multi-line selection) The driving method disclosed in US Pat. No. 5,262,881) may be employed. As a result, a display with good color purity can be obtained. Further, it is possible to provide a reflective color liquid crystal display device capable of supporting a bright moving image without deteriorating the color purity even at high speed display.

Since the drive voltage changes depending on the temperature, it is an easy-to-use device that the temperature compensation circuit is installed so that the drive voltage changes according to the temperature change. When the drive voltage changes substantially linearly with temperature, the drive voltage may be set to change linearly with temperature.

In the reflection type color liquid crystal display device, the driving voltage width for color development is narrow. Therefore, if the adjustment knob is provided so that the user of the electronic device using the reflective color liquid crystal display device can adjust the drive voltage by himself, the electronic device is easy to use.

According to the present invention, multiplex driving can be performed without using a color filter, bright white display can be performed in the case of a non-selected waveform, and a voltage between the selected waveform or the selected and non-selected waveforms is applied. Sometimes it is possible to develop blue or green or red.

In other words, when no voltage is applied,
Alternatively, it is possible to obtain a reflective color liquid crystal display device that can display an almost achromatic color when the voltage is low and can realize a color display by applying a voltage.

Since this color liquid crystal display device uses only one polarizing plate, bright display can be performed. Therefore, it can be used as a very bright reflective color liquid crystal display device without a backlight. Since it is not necessary to provide a backlight, the power consumption can be reduced and it is particularly suitable for carrying.
Further, the thickness of the liquid crystal display device can be made relatively thin.

In particular, when the electrode is used as the reflecting layer, a display with extremely high visibility can be realized without generating a shadow or clouding the color.

[0049]

EXAMPLES The present invention will be described below with reference to Examples (Examples 1 to 6) and Comparative Examples (Example 7).

Example 1 FIG. 1 is a sectional view schematically showing this example. In FIG. 1, a polarizing plate 1, a retardation plate 2, a liquid crystal cell 3, and a reflective layer 9 are sequentially provided. The liquid crystal cell includes a liquid crystal layer 8, a first substrate 4A, a second substrate 4B, a first electrode 5A of the liquid crystal cell, a first alignment control film 7A of the liquid crystal cell, and a second alignment control film 7B of the liquid crystal cell. , Having a second electrode 5B of the liquid crystal cell. A drive voltage (not shown) applies a drive voltage to the upper and lower electrodes (first electrode 5A, second electrode 5B) of the liquid crystal cell.

In the liquid crystal cell, the peripheral seal of the liquid crystal layer, the insulating film 6 disposed between the electrode and the alignment control film, the light shielding film, the lead electrode terminal, the base film, the protective film, and other ordinary liquid crystals. The components used in the cell are provided. Next, the formation of the liquid crystal cell will be described.

First, a glass substrate provided with a transparent electrode (ITO) is patterned into a stripe shape of ITO to form a first electrode 5A which is one electrode, and TiO ₂ is formed on the first electrode 5A.
By the to produce a thin film of SiO _2, an insulating film is formed, to form a thin film of polyimide, rubbed with cloth,
The first alignment control film 7A was formed. This substrate and another substrate formed in the same manner are superposed on each other so that the striped electrodes intersect, and the liquid crystal 8 is put therein.
A first liquid crystal cell was formed by fixing the edges with a sealing material.

In FIG. 2, the first alignment direction of the liquid crystal cell is 10, the second alignment direction of the liquid crystal cell is 11, the first slow axis direction of the retardation plate is 12, and the polarization axis of the polarizing plate is 13. And Further, in FIG. 2, the direction of the arrow indicating the alignment direction of the liquid crystal molecules indicates the direction in which the liquid crystal molecules are inclined with respect to the substrate surface (alignment control film).

Further, the liquid crystal twist angle from the first alignment direction 10 of the liquid crystal cell to the second alignment direction 11 of the liquid crystal cell is θ _{1 in} the clockwise direction, and from the first alignment direction 10 of the liquid crystal cell to the phase difference plate. The angle up to the slow axis direction 12 is set to θ ₂ in the clockwise direction. From the slow axis direction 12 of the retardation plate to the polarization axis 13 of the polarizing plate
Set the angle up to θ ₃ clockwise.

In this example, the liquid crystal cell is a left spiral, but even if the spiral is reversed, the relationship between the orientation direction of the liquid crystal cell and the polarization axis direction of the polarizing plate is rotated by θ ₁ , θ ₂ , and θ ₃ . By reversing the direction, color display can be easily obtained as in the above example.

The refractive index anisotropy Δn ₁ of the liquid crystal cell and the thickness d ₁ of the liquid crystal layer were adjusted so that Δn ₁ · d ₁ of the liquid crystal layer was approximately 1.24 μm. Δn ₂ · d ₂ of the retardation plate was set to approximately 1.15 μm. Then, θ ₁ = −180 °, θ ₂
= 100 ° and θ ₃ = 50 °.

Chromaticity diagram (CIE 1
As shown in a partially enlarged view of the 931 chromaticity diagram), display of bright white, red, blue, and green was obtained as the effective voltage applied increased. It was possible to achieve a color liquid crystal display having good color purity that was sufficiently visible.

By driving this liquid crystal display element with 8 gradations at 1/32 duty, white display at 0/7 level,
Red display at 3/7 level, blue display at 5/7 level, 7/7
A green display was obtained at the level. Of course, static driving is also possible.

As the size of the display screen, 128 × 64 dots were displayed. Graphs were displayed using the reflective color liquid crystal display device of this example. The background color was white and the bar graph was displayed in three colors, red, blue and green. As a result, the visibility was significantly improved.

Further, when displaying the schedule management, important meetings can be displayed in red to call attention. Further, when displaying the calendar, Saturday and Sunday are displayed in red, weekdays are displayed in blue, and today's day of the week is displayed in green. In this case also, the background color was white.

Further, sentences were displayed. Similarly, the background color is white, the characters are displayed in blue, and a certain block in the sentence is displayed in red for marking. The title is shown in green and the underline is shown in green or red.

The graphic display uses white, red, blue, and green, and by using a large amount of intermediate voltage, whitish red, purple, and blue-green are used to express a human face or color the scenery. Could be displayed.

As described above, in this example, the conventional polarizing plate is
It was brighter than the one used, the visibility was improved in the display, and an environment with good workability was provided.

A biaxial retardation plate was used instead of the uniaxial retardation plate. N _z was set to 0.5. A display with a wide viewing angle with little color change even when viewed from an angle was obtained. In the vertical direction, the same color was obtained in both uniaxial and biaxial directions.

Further, instead of the reflective layer attached to the lower side of the liquid crystal cell, the electrode 5B also serves as the reflective layer. Specifically, a glass substrate used as a substrate is exposed on one side only and is exposed to hydrofluoric acid to make the glass surface uneven, and Al is vapor-deposited thereon. After that, patterning is performed to produce a striped electrode.

Further, an insulating film of SiO ₂ and TiO ₂ was formed thereon, and a polyimide orientation control film was formed thereon. This substrate and an ITO transparent electrode patterned in a stripe pattern were overlapped with each other with a spacer interposed therebetween, and the periphery was fixed with a sealant, and liquid crystal was injected to form a liquid crystal cell.

When the electrode and the reflective layer are used in this way,
Since there is almost no shadow, it is easy to see and it is possible to display with good color purity. Even when silver was vapor-deposited instead of Al, a brighter display was obtained.

Further, even if a spherical glass having a radius of several μm is adhered on a glass substrate used as a substrate to make the glass surface uneven, and Al is vapor-deposited thereon, almost no shadow is generated and the color is A good display of purity was made.

On the glass substrate, mirror-like Al electrodes are formed and patterned to form stripe electrodes. An insulating film of SiO ₂ and TiO ₂ was formed thereon, and a polyimide alignment film was formed thereon. This substrate and a transparent insulating film of ITO patterned in a stripe pattern were overlapped with a spacer interposed therebetween, fixed around the periphery with a sealing material, and injected with liquid crystal to produce a first liquid crystal cell.

When the reflection layer acts as a mirror surface in this way, only light incident at a specific angle is used. When viewed from a specific direction, a good display is obtained, but when the angle slightly changes, the display sharply deteriorates. Therefore, by placing a diffuser on the observer side, a prism array, or a lenticular lens,
A display with a wide viewing angle was obtained.

Example 2 Δn ₁ · d ₁ of the liquid crystal cell was set to approximately 1.24 μm. Similarly, the phase difference plate Δn ₂ · d ₂
Was about 1.20 μm. θ ₁ = −180 °, θ ₂ =
It was set to 110 ° and θ ₃ = 40 °. Display was performed by multiplex driving with 1/32 duty and 8 gradations. 0
/ 7 for white display, 3/7 for blue display, 5/7 for green display, 7 /
It was possible to display red in 7.

Example 3 Δn ₁ · d ₁ of the liquid crystal cell was set to about 1.11 μm. Similarly, the phase difference plate Δn ₂ · d ₂
Was about 1.20 μm. θ ₁ = −180 °, θ ₂ =
It was set to 110 ° and θ ₃ = 130 °. Display was performed by multiplex driving with 1/32 duty and 8 gradations.
0/7 for white display, 3/7 for blue display, 5/7 for green display, 7
It was possible to display red at / 7.

(Example 4) Δn of liquid crystal cell₁ ・ D₁ Almost
It was set to 1.11 μm. Similarly, the phase difference plate Δn ₂ ・ D₂ 
Was about 1.20 μm. θ₁ = -180 °, θ₂ =
110 °, θ_Three= 40 ° was set. 1/32 Deute
Display was performed by multiplex driving with 8 gradations. 0
/ 7 for white display, 3/7 for blue display, 5/7 for green display, 7 /
It was possible to display red in 7.

(Example 5) Δn ₁ · d ₁ of the liquid crystal cell was set to approximately 1.24 μm. Similarly, the phase difference plate Δn ₂ · d ₂
Was about 1.20 μm. θ ₁ = −180 °, θ ₂ =
It was set to 100 ° and θ ₃ = 50 °. Display was performed by multiplex driving with 1/32 duty and 8 gradations. 0
/ 7 for white display, 3/7 for red display, 5/7 for blue display, 7 /
It was possible to display green in 7.

Example 6 The Δn ₁ · d ₁ of the liquid crystal cell was set to approximately 1.24 μm. Similarly, the phase difference plate Δn ₂ · d ₂
Was approximately 1.15 μm. θ ₁ = −180 °, θ ₂ =
90 ° and θ ₃ = 45 ° were set. Display was performed by multiplex driving with 1/32 duty and 8 gradations. 0
/ 7 for white display, 3/7 for red display, 5/7 for blue display, 7 /
It was possible to display green in 7. The range between θ ₂ and θ ₃ is the shaded area, and the color is worse than the grid area. It is dark when no voltage is applied, and the display is dark as a whole.

(Example 7) Δn ₁ · d ₁ is 0.98 μm, Δ
Same as Example 6 except that n ₂ · d ₂ was set to 0.90 μm. The color purity was lower than that in Example 6.

In the present invention described above, the size of the pixel formed by the matrix is 400 × 400 μ.
m. The thickness of the transparent substrate on the reflective layer side is 0.4 m.
m.

Next, the pixel size and the thickness of the transparent substrate in the present invention for obtaining a color display by utilizing reflection will be described. FIG. 19 shows a sectional view and an optical path of a reflective color liquid crystal display device. In the drawing, Φ indicates the range of the open angle where substantially good color development can be visually recognized. This Φ is preferably as wide as possible within a practical range. In the present invention, an angle range of at least 20 ° is obtained.

FIG. 20 shows the relationship between the thickness of the transparent substrate (a glass substrate or the like arranged behind the light traveling direction is used), the line width of the pixel, and the opening angle Φ. This opening angle Φ
Good color display can be seen within the range. In a range larger than the opening angle, the color purity tends to decrease.
Approximately, (the thickness T of the transparent substrate on the reflective layer side) ≦ 1.4.
If the relationship of (pixel size) is satisfied, good color development can be obtained. More preferably, T ≦ 1.2 · (pixel size). Further, a display with high color purity can be obtained under the condition that the thickness of the substrate is thin and T ≦ 1.0 · (pixel size).

Table 1 shows the parameters of these Examples 1 to 7. Further, the color change and reflectance with respect to the voltage of Examples 1 to 6 are shown in FIGS. 5 to 16, and the color change and reflectance of Example 7 are shown in FIGS. 17 and 18.

Another example using the present invention will be described. For PDA (Personal Digital Assistant),
The reflective color liquid crystal display devices of Examples 1 to 5 described above were used.
Conventionally, only TFTs and STNs using color filters have been used for color display. However, since the liquid crystal display device using the color filter has a low transmittance, it cannot be used as a reflection type and needs a backlight. The backlight consumes a large amount of power and cannot be used for a long time as a portable terminal. A liquid crystal display device using a backlight is
The power consumption is about 2W.

When this reflective color liquid crystal display device was used as the display portion of the PDA, the power consumption was about 0.5 W. Therefore, it can be used for a long time while displaying in color.

Since only one polarizing plate is used as compared with the conventional type using two polarizing plates, brighter display is possible.

[0084]

[Table 1]

[0085]

EFFECTS OF THE INVENTION According to the present invention, almost achromatic display can be performed in one pixel when a voltage is not applied or when a voltage is low, without using a color filter, and by applying a voltage, color purity is good. We have realized a reflective color liquid crystal display device that can display red, blue, and green colors. Bright display can be achieved by using only one polarizing plate without using a color filter. Therefore, a reflective color display device suitable for carrying is made possible. Further, since no color filter is used, it can be produced at low cost. Therefore, an inexpensive display device can be provided regardless of the color display.

The liquid crystal display device of the present invention includes a personal computer, a word processor, a fish finder, an in-vehicle instrument panel, a public telephone display, a public display device,
Destination status display, information terminal, and operation status display on industrial information display devices (for example, copy machine operation panel) (red is copying, number of sheets is green, lines are blue, background is white) Or, various consumer dot-matrix display devices (audio equipment, clocks, game equipment, amusement, communication equipment, etc.) such as driving display of power equipment (white background, green operating status, red danger display)
(Display of car navigation, camera, TV phone, calculator)
It can be used as a functional element responsible for the display function such as.

In particular, since the reflective color liquid crystal display device of the present invention can be used with low power consumption, portable electronic devices such as a mobile phone, an electronic notebook, an electronic book, an electronic dictionary, a PDA (portable information), among others. When used in terminals, pagers (pagers), portable personal computers, etc., it exhibits high functionality combined with its high visibility and expressiveness. Further, the present invention can be applied to various applications as long as the effect is not impaired. For example, since it has excellent visibility, it can be preferably used in a touch panel, a liquid crystal device controlled by the line of sight, and the like.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing Example 1.

FIG. 2 is a schematic diagram showing an angular relationship in a plane of a polarization axis of a polarizing plate, an alignment direction of a liquid crystal cell, and a slow axis direction of a retardation plate in Example 1.

FIG. 3 is a diagram showing the relationship between θ ₂ and θ ₃ that produce good color.

FIG. 4 is a diagram showing the relationship between Δn ₁ · d ₁ and Δn ₂ · d ₂ that produce good color.

FIG. 5 is a chromaticity diagram showing a color change with respect to voltage in Example 1.

FIG. 6 is a diagram showing the reflectance with respect to the voltage of Example 1.

FIG. 7 is a chromaticity diagram showing a color change with respect to voltage in Example 2.

FIG. 8 is a diagram showing the reflectance with respect to the voltage of Example 2;

FIG. 9 is a chromaticity diagram showing a color change with respect to voltage in Example 3.

FIG. 10 is a diagram showing the reflectance with respect to the voltage of Example 3;

FIG. 11 is a chromaticity diagram showing a color change with respect to voltage in Example 4.

FIG. 12 is a diagram showing the reflectance with respect to the voltage of Example 4;

FIG. 13 is a chromaticity diagram showing a color change with respect to voltage in Example 5.

FIG. 14 is a diagram showing the reflectance with respect to the voltage of Example 5;

FIG. 15 is a chromaticity diagram showing a color change with respect to voltage in Example 6.

FIG. 16 is a diagram showing the reflectance with respect to the voltage of Example 6;

FIG. 17 is a chromaticity diagram showing a color change with respect to voltage in Example 7.

FIG. 18 is a diagram showing the reflectance with respect to the voltage of Example 7.

FIG. 19 is a schematic view showing a cross section and an optical path of a reflective color liquid crystal display device of the present invention.

FIG. 20 is a diagram showing the relationship between the opening angle Φ, the thickness of the transparent substrate, and the color display.

[Explanation of symbols]

 1: Polarizing plate 2: Twisted phase difference plate 3: Liquid crystal cell 4: Substrate 5: Transparent conductive film 6: Insulating layer 7: Alignment control film 8: Liquid crystal layer 9: Reflector 10: First alignment direction of liquid crystal cell 11 : Second alignment direction of liquid crystal cell 12: slow axis direction of retardation plate 13: polarization axis of polarizing plate

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshihiko Suzuki 1150, Hazawa-machi, Kanagawa-ku, Yokohama-shi, Kanagawa Asahi Glass Co., Ltd. Central Research Laboratory

Claims (15)

[Claims] 1. A liquid crystal cell comprising a nematic liquid crystal having a twist orientation sandwiched between two substrates having electrodes, a polarizing plate and a reflecting layer, and a liquid crystal layer and a polarizing plate. The liquid crystal cell has a phase difference plate between the plates, and the liquid crystal cell has a first alignment direction in which liquid crystal molecules are aligned on the polarizing plate side and a second alignment direction in which liquid crystal molecules are aligned on the reflecting plate side. Second from the orientation direction of
Has a twist angle θ ₁ of −160 to −300 ° in a predetermined direction toward the orientation direction of, and has a refractive index anisotropy Δ of the liquid crystal of the liquid crystal cell.
The product Δn ₁ · d _{1 of} n ₁ and the thickness d ₁ of the liquid crystal cell is 0.3 to
2.00 μm, the retardation plate has uniaxial anisotropy, the difference Δn _{2 in} refractive index anisotropy between the in-plane slow axis and the fast axis of the retardation plate and the thickness d of the retardation plate.
₂ of the product [Delta] n ₂ · d ₂ is the 0.3～2.00Myuemu, the angle from the first alignment direction of the liquid crystal cell to the slow axis direction of the retardation plate and theta ₂ in the predetermined direction, the phase difference The angle from the slow axis direction of the plate to the polarization axis direction of the polarizing plate is θ
₃ , θ ₂ is in the range of +70 to + 120 °, and θ ₃ is in the range of +30 to + 70 ° or +120 to 160 °, a voltage value of 3 or more is selected, and the driving voltage is applied to the liquid crystal cell. A reflection type color liquid crystal display device, in which light is applied, enters from a polarizing plate side, is reflected by a reflecting layer, and is emitted from the polarizing plate. 2. The reflection type color liquid crystal display device according to claim 1, wherein the predetermined direction is a clockwise direction or a counterclockwise direction. 3. The retardation plate is biaxially anisotropic, the in-plane refractive indices are n _x and n _y (n _x > n _y ), and _nz is the refraction in the thickness direction of the retardation plate. When it is set as a ratio, the relation of 0.7 ≧ N _z = (n _x −n _z ) / (n _x −n _y ) ≧ 0.2 is satisfied, and the reflection type of claim 1 or 2 is satisfied. Color liquid crystal display device. 4. The liquid crystal cell has Δn ₁ · d ₁ of 1.00 to 1.00.
The reflective color liquid crystal display device according to claim 1, wherein the reflective color liquid crystal display device has a thickness of 1.50 μm. 5. The retardation plate has Δn ₂ · d ₂ of 0.90 or more.
The reflective color liquid crystal display device according to claim 1, wherein the reflective color liquid crystal display device has a thickness of 1.50 μm. 6. The absolute value of θ ₁ of the liquid crystal cell is 170 to
The reflective color liquid crystal display device according to claim 1, wherein the reflective color liquid crystal display device has an angle of 190 °. 7. The θ ₂ is in the range of 85 to 105 °,
7. The reflective color liquid crystal display device according to claim 1, wherein the θ ₃ is in the range of 45 to 65 ° or 135 to 155 °. 8. The θ ₂ is in the range of 105 to 115 °, and the θ ₃ is 35 to 45 ° or 125 to 135 °.
The reflective color liquid crystal display device according to any one of claims 1 to 6, wherein 9. A reflective color liquid crystal according to claim 1, wherein a voltage value of three or more values is selected by multiplex driving and a voltage is applied to the first liquid crystal cell. Display device. 10. A white display is performed during a non-selected waveform of multiplex drive, and a blue display, a green display, or a red display is displayed when a voltage between the selected waveform or the selected and non-selected waveforms is applied. 10. Color development is performed.
Reflective color liquid crystal display device. 11. A multiplex drive duty ratio is 1/32 to 1/300.
Alternatively, 10 reflective color liquid crystal display devices. 12. A reflective color liquid crystal display device according to claim 1, wherein the electrodes are provided in a matrix of rows and columns, and a plurality of row electrodes are selected and driven at the same time. . 13. A reflective type color liquid crystal display device according to claim 1, further comprising a reflecting plate provided on a liquid crystal side of a substrate forming the liquid crystal cell. 14. The reflection type color liquid crystal display device according to claim 1, further comprising a temperature compensation circuit in which a driving voltage applied to the liquid crystal cell changes with temperature. 15. A portable electronic device, wherein an adjusting means for adjusting a driving voltage applied to a liquid crystal cell of the reflective color liquid crystal display device constitutes a portable electronic device installed outside the reflective color liquid crystal display device. The reflective color liquid crystal display device according to claim 1.