JP3226824B2 - Liquid crystal electro-optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD [0001] The invention disclosed in the present specification is:
The present invention relates to a liquid crystal electro-optical device having good electric characteristics and good contrast, and capable of obtaining a bright and uniform display over the entire screen.

[0002]

2. Description of the Related Art A liquid crystal electro-optical device generally has a structure in which a liquid crystal material, which is an organic material, is sandwiched between a pair of substrates. Then, the light traveling through the liquid crystal material is modulated by changing the intensity of the electric field generated from the electrodes formed on the pair of substrates. The result of the optical modulation is displayed.

Therefore, when a specific electric signal is applied to the electrode, the electric signal can be displayed in a visually recognizable state. Furthermore, a desired image can be formed by combining a plurality of the electrodes and applying image data.

In this conventional liquid crystal electro-optical device,
The light is modulated by applying the electric field perpendicular to the substrate and changing the electric field intensity so that the alignment direction of the liquid crystal molecules having a generally rod shape is parallel to the substrate or perpendicular to the substrate. Was realized by changing.

Generally, in this case, light is modulated by utilizing optical anisotropy, which is one of the characteristics of the liquid crystal material.
For this reason, a polarizing plate is arranged in the device so that the incident light becomes linearly polarized light.

However, in the liquid crystal electro-optical device employing such an operation method, the display becomes dark and unclear when viewed obliquely, even when the display is normal when viewed from a direction perpendicular to the display surface. In the case of color display, the phenomenon of discoloration was observed.

This phenomenon is explained as follows from the relationship between the output light from the liquid crystal electro-optical device and the orientation direction of the liquid crystal molecules.

In the case of employing a configuration in which liquid crystal molecules are arranged in a direction perpendicular to the substrate, an alignment state in which the major axes of the liquid crystal molecules are aligned in a predetermined display is realized. In this state, output light is observed from the vertical plane of the liquid crystal molecules.

In this state, when viewed from a direction slightly deviated from the direction perpendicular to the substrate, it is seen from a line of sight slightly inclined with respect to the long axis of the liquid crystal molecules. This means that the observation area of the output light differs greatly depending on the direction in which the display is viewed.

For this reason, the viewing angle characteristics for the observer are as follows:
The more it deviates from the vertical direction, the greater the deterioration.

As a method for solving the above problem, a method different from the operation mode of the conventional liquid crystal electro-optical device has been proposed. This is an operation mode in which the optical characteristics are changed by rotating the liquid crystal molecules only in a direction parallel to the substrate. The details are disclosed in Japanese Patent Publication No. 63-21907. Hereinafter, this operation mode is referred to as an IPS mode.

In the IPS mode, an electric field is generated between a pair of electrodes formed on one substrate. This electric field has its main component in a direction parallel to the substrate and the liquid crystal layer. With this electric field, the liquid crystal molecules are rotated in a plane parallel to the substrate.

Therefore, the above-mentioned problem of the viewing angle caused by the vertical alignment of the liquid crystal molecules during the operation can be solved.

However, in the IPS mode, light and dark are displayed by utilizing the birefringence due to the optical anisotropy of the liquid crystal material. Therefore, a polarizing plate is indispensable. However, the absorption of light by the polarizing plate is large, causing a decrease in light transmittance.

Various liquid crystal electro-optical devices have been proposed in which the reduction in light transmittance due to the above-mentioned polarizing plate has been improved.

Among them, the guest-host mode, which does not require a polarizing plate, is known as a method that can directly use the conventional technology for manufacturing a liquid crystal electro-optical device. Especially White and Tayl
The one devised by or is known as a representative one. Hereinafter, this operation mode is referred to as a WT type.

Generally, the guest-host mode is an operation mode in which a dichroic dye is added to a liquid crystal material. The reason why the mode is referred to as the guest-host mode is that the liquid crystal molecules are regarded as the host and the dichroic dye is regarded as the guest.

In the WT type, the cholesteric liquid crystal undergoes a phase transition to a nematic phase by switching between no voltage application and voltage application. Thereby, light absorption and transmission are selected.

The guest-host mode without the need for a polarizing plate is described in "Liquid Crystal Display", edited by The Institute of Television Engineers of Japan, supervised by Takataka Ohkoshi, pp. 84-94.
It is also described in "Basics of Liquid Crystal and Display Applications", Corona Publishing, Masami Yoshino, Masanori Ozaki, pp. 143-147.

However, in the conventional guest-host type liquid crystal electro-optical device, the optical axes of the liquid crystal molecules are aligned in a direction perpendicular to the substrate surface during light transmission. As a result, the above-described problem of the viewing angle also occurs in the guest-host type liquid crystal electro-optical device.

For example, even when an electric field is applied to make a non-colored state, depending on the viewing angle, a state in which the image is colored appears.

[0022]

SUMMARY OF THE INVENTION As described above, I
The liquid crystal electro-optical device that operates in the PS mode has a feature that the viewing angle is wide. However, the use of a polarizing plate has a disadvantage that the screen becomes dark.

On the other hand, the guest-host mode, which does not require a polarizing plate, has a feature that the incident light can be output as it is without using a polarizing plate, and the light can be effectively used. However, it has a disadvantage that the viewing angle dependence is large as seen in the conventional liquid crystal electro-optical device.

The invention disclosed in the present specification eliminates the above-mentioned disadvantages and has the above-mentioned significance, that is, two features of the high viewing angle characteristics of the IPS mode and the effective use of the light of the guest-host mode. An object of the present invention is to provide a liquid crystal electro-optical device having the same function.

[0025]

The invention disclosed in the present specification is characterized in that in a liquid crystal electro-optical device driven by a lateral electric field, light is transmitted and absorbed by a dimming layer formed by liquid crystal. In particular, display is possible without using a polarizing plate.

That is, one of the inventions disclosed in this specification is that at least one of the pair of substrates has a light-transmitting property, a dimming layer sandwiched between the substrates, Means for applying an electric field, wherein the light control layer comprises at least a liquid crystal, an optically active substance, and a dichroic dye.

Another aspect of the present invention is a liquid crystal display device comprising: a pair of substrates, at least one of which has a light-transmitting property; a light control layer made of a liquid crystal material containing a dichroic dye sandwiched between the substrates; Means for orienting a light layer, and means for applying an electric field in a direction parallel to the substrate, wherein the light modulating layer is at least a liquid crystal,
It is characterized by being composed of an optically active substance and a dichroic dye.

FIG. 2 shows a specific example of a liquid crystal electro-optical device utilizing the invention disclosed in this specification.

In FIG. 2, the first and second substrates (1
01) and (201) are made of a material having a light-transmitting property and having a certain strength against external force. As a material constituting these first and second substrates (101, 201), for example, an inorganic material such as glass or quartz can be used.

A liquid crystal material is provided between the substrates by a light control layer (20).
4). The liquid crystal material is a liquid crystal in which a dichroic dye and an optically active substance are added.

As a means for applying an electric field, a metal material such as copper, aluminum, tantalum, titanium or chromium, or a silicide material is used. Alternatively, a light-transmitting conductive material such as ITO (indium tin oxide), tin oxide, or indium oxide can be used.

Further, the pair of substrates (101, 201)
Is formed in a desired pattern with a sealant (202) as an adhesive.

Further, the pair of substrates (101, 20)
A spacer (203) is arranged to keep the interval of 1) constant throughout the cell.

In the liquid crystal electro-optical device disclosed in this specification, in order to obtain a good display, the cell parameters are set as follows.

(1) The wavelength λ of the incident light (generally 380 nm
780 nm), refractive index anisotropy Δn, and helical pitch p
Is λ ≧ Δn · p. (2) The helical pitch p is in a range of 1 ≦ p ≦ 15 (unit: μm). (3) The cell thickness d is in the range of 1 ≦ d ≦ 10 (unit: μm). (4) The alignment twist angle θ of the liquid crystal molecules on the upper and lower substrates is defined as θ ≦
The range is 300 °. (5) The distance L between the electrodes is in the range of L <25 μm.
(The lower limit is about 1 μm)

As a driving method, an active matrix system, a multiplex system, or the like can be used.

In the multiplex system, the first substrate (1
01) Only two kinds of electrodes, a display electrode and a reference electrode, need to be formed on the substrate. In the case of the active matrix system, a non-linear element such as a thin film transistor (TFT) or a diode is formed for each pixel as a switching element. I do.

As the TFT, a TFT using a-Si (amorphous silicon) or P-Si (polycrystalline) silicon for the active layer can be used. In the case of the active matrix system, a known configuration such as a staggered type or an inverted staggered type can be used as the configuration of the driving element.

The electrode cross section is not only rectangular and trapezoidal, but also
It may be a gentle curved surface. If the electrode cross section is gentle, it is possible to form a continuous horizontal electric field with a gentle change in intensity.

On the other hand, for the opposite substrate (201), TF
It is possible to use the same type of material as the substrate on which T is formed. In addition, although it is not necessary to form an electrode on the opposing substrate, an electrode may be formed on part or the entire surface of the substrate in some cases. As the electrode material at this time, in addition to the above metals, a material having a light transmitting property, for example, ITO or the like can be used.

Further, on the counter substrate (201) or in the TF
It is effective to arrange a means (black matrix) on the T-substrate (101) or both of the substrates to shield portions not related to display for improving contrast. This light shielding means can be made of a metal such as Cr or a polymer material in which a black pigment is dispersed.

As the liquid crystal, a nematic liquid crystal or the like can be used. Further, an optically active substance is added to the liquid crystal material so as to exhibit a cholesteric phase. Further, the concentration of the dichroic dye in the liquid crystal is preferably around 1% by weight. Note that the liquid crystal is not limited to a nematic type, and any liquid crystal that exhibits a cholesteric phase in a used state may be used.

Here, a combination of a nematic liquid crystal to which an optically active substance is added and a dichroic dye (positive type) is used.

As a display mode, there are a reflection type and a transmission type. In the reflection type, a reflection plate made of metal or the like is formed on one of the pair of substrates. Further, the metallic reflector can also serve as a pixel electrode.

The switching principle of the liquid crystal electro-optical device according to the invention disclosed in this specification will be described.

In the light control layer when no electric field is applied, the alignment state of the liquid crystal / dichroic dye molecules is in a spiral state as shown in FIG.

In this state, the molecular long axis of the dichroic dye contained in the liquid crystal is parallel to the substrate and oriented in any direction with the direction perpendicular to the substrate as the axis. . Therefore, the incident natural light absorbs any polarization components. As a result, a dark state is realized.

On the other hand, when an electric field is applied, the molecular long axis of the liquid crystal / dichroic dye is oriented in the direction of the electric field. Here, since the electric field is applied in a direction parallel to the substrate, the liquid crystal molecules and the dichroic dye contained in the liquid crystal material have their molecular major axes parallel to the substrate and aligned in a predetermined direction. I do.

At this time, if a positive dye is used, light in the major axis direction of the dichroic dye is absorbed. However, light absorption in a direction shifted from the long axis direction is not so large.
Therefore, the incident light passes through the light control layer.

Although the light transmission amount is slightly absorbed by the dichroic dye, it is much larger than the liquid crystal electro-optical device driven by the IPS mode using a conventional polarizing plate. Thereby, a bright display is realized.

In driving the liquid crystal, by switching the liquid crystal molecules by an electric field parallel to the substrate,
The viewing angle dependency seen in the conventional liquid crystal display can be reduced.

Further, since the step of forming the polarizing plate is eliminated, the liquid crystal electro-optical device can be manufactured with fewer steps than in the conventional IPS mode.

Next, the reasons for limiting various parameters will be described. The characteristics of the liquid crystal electro-optical device disclosed in the present specification depend on cell parameters such as (1) cell thickness d (2) distance between electrodes L (3) refractive index anisotropy Δn of liquid crystal (4) helical pitch p I do.

In order for natural light to be absorbed by the light control layer, the relationship between the refractive index anisotropy Δn and the helical pitch p must be λ ≧
Set to satisfy Δn · p.

Note that the pitch p is such that the helical structure of the liquid crystal molecules is 3
Defined as the distance to turn 60 °.

By satisfying the above relational expression, each polarization component of the incident light can be effectively absorbed in the light control layer.

When each parameter does not satisfy the above relational expression, components of the polarized light component of the light incident on the light control layer that are not absorbed by the light control layer remain. In this case, light is transmitted even in a dark state. This causes a reduction in display contrast.

In the invention disclosed in this specification, the light absorption by the light control layer can be more effectively performed by reducing the helical pitch p. Therefore, the display contrast can be further increased.

However, if the helical pitch p is too small, the threshold value becomes high, and the driving voltage becomes large. For this reason, power consumption increases, and the low power consumption characteristics of the liquid crystal display cannot be fully utilized. This is a problem common to both the multiplex type and the active matrix type liquid crystal display.

When the driving voltage is large, the load on the thin film transistor increases, and the durability of the display decreases.

As another problem, as the helical pitch p becomes smaller, there occurs a phenomenon that the sharpness of the threshold value of the liquid crystal material becomes lower. Therefore, when the spiral pitch p is small, switching cannot be performed at high speed.

In this case, when switching from the no voltage application state to the voltage application state, the light absorption state continues for a while, and the light transmission state is not quickly realized.

On the other hand, when switching from the voltage applied state to the voltage non-applied state, the light absorption state is not quickly realized, and the light passes through the light control layer for a while. For this reason, it is difficult to realize a high-speed display.

As described above, the relationship between the contrast and the threshold characteristic is in a trade-off relationship. And the relationship depends on the helical pitch.

In the invention disclosed in this specification, the helical pitch p is set to fall within the range of 1 ≦ p ≦ 15 (μm). By doing so, it is possible to satisfy both the contrast and the threshold characteristics. Then, the display state of the display can be maintained.

The display characteristics also depend on the cell thickness d.
Further, the display state is affected not only by the cell thickness but also by the viscosity of the added optically active substance and the helical pitch p of the liquid crystal.

Therefore, in order to reduce the influence thereof, a dichroic dye which is said to have a relatively small viscosity increasing effect on the liquid crystal layer by addition is used.

The results obtained by examining the effect of the cell thickness d when an azo dye is used as the dichroic dye are shown below.

Here, the helical pitch p of the liquid crystal is made constant by adjusting the addition amount of the optically active substance.

The threshold characteristics, contrast, rise time, and display uniformity in the cell thickness direction depend on the cell thickness of the entire light control layer having a specific spiral pitch p.

As the cell thickness d decreases, the threshold value increases,
The driving voltage increases. Therefore, it is difficult to achieve low power consumption. Further, a voltage exceeding the voltage setting range of the conventional driving circuit is required. For this reason, a new circuit design is required.

However, as the cell thickness d increases, the intensity of the electric field becomes non-uniform. As a result, in the rise time of the liquid crystal material when the electric field is applied (the time when the orientation of the liquid crystal material changes in a direction parallel to the substrate and in a predetermined direction),
Variations occur. For this reason, when the hue changes due to the dichroic dye, the color display fluctuates.

Further, as the cell thickness d increases, the contrast decreases. Therefore, it is desirable to reduce the cell thickness in order to improve the contrast.

In particular, in the invention disclosed in this specification,
The cell thickness d is in the range of 1 ≦ d ≦ 10 (μm). This makes it possible to obtain a relatively good display in terms of the threshold value, contrast, rise time, and display uniformity in the cell thickness direction.

It has been confirmed that the contrast increases when the orientation twist angle θ of the liquid crystal molecules is increased.

On the other hand, if the torsion angle θ is too large, the rising characteristic when the electric field is ON and the falling characteristic when the electric field is OFF do not match, which is not preferable for a display device.

It is preferable that the range in which the two characteristics, that is, the contrast and threshold characteristics, are good is θ ≦ 300 °.

The point that the distance L between the electrodes is 25 μm or less will be described below.

First, the state of alignment of dichroic dye molecules by an electric field will be described. The dichroic dye is oriented in the same direction as the liquid crystal molecules. That is, when a horizontal electric field is applied, the liquid crystal molecules are oriented in a predetermined direction with the major axis direction parallel to the substrate. Similarly, the dichroic dye molecules have their major axes parallel to the substrate and aligned in a predetermined direction.

In the invention disclosed in this specification, a positive type dichroic dye is switched by a lateral electric field. Therefore, even when an electric field is applied, light is absorbed in the major axis direction of the dichroic dye, so that some light absorption occurs.

At the time of the conventional vertical electric field driving, the dichroic dye is vertically oriented. Therefore, light absorption by the positive type dichroic dye does not occur. That is, in the method using the horizontal electric field driving, a decrease in contrast is theoretically inevitable as compared with the vertical electric field driving method.

Therefore, the formed horizontal electric field affects the light transmission state of the light control layer. As described above, the dichroic dye has the major axis direction parallel to the substrate surface. However, the electric field near the electrodes is in a direction perpendicular to the substrate. That is, the major axis of the dichroic dye molecule near the electrode is oriented perpendicular to the substrate.

The positive type dichroic dye has a large absorption coefficient in the major axis direction. Further, there is almost no light absorption in the molecular short axis direction of the dye. That is, the vertically oriented dichroic dye near the electrode hardly absorbs light.

Therefore, as the distance L between the electrodes is relatively short, the overall light absorption by the dichroic dye becomes smaller. This is because the shorter the distance between the electrodes, the sharper the rise of the formed electric field near the electrodes.

In the invention disclosed in this specification, a light transmitting state is realized when a lateral electric field is applied. Therefore, the overall contrast can be increased by increasing the amount of light transmission when an electric field is applied. That is, it is desirable that the distance L between the electrodes is small in terms of contrast.

In the threshold characteristics, the distance L between the electrodes
Influences. When the distance L between the electrodes is increased, the threshold value increases, and the driving voltage increases. For this reason, low-voltage driving is hardly realized.

According to the experiment of the present inventor, when the change in contrast was measured by changing the distance L between the electrodes, it was found that L <
It has been found that a relatively good contrast can be obtained when the thickness is 25 μm (the adjustment is about 1 μm).

[0088]

An embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram when the light control layer is in a state where incident light is not transmitted, that is, when it is in a dark state.

In this case, as shown in FIG. 3, the alignment state of the light control layer is such that the alignment vector of the liquid crystal molecule (301) is oriented around the short axis direction of the liquid crystal molecule (301).
Each time the layer formed in 1) changes, the angle is gradually changed.

In the state shown in FIG. 3, the long axes of the liquid crystal molecules (301) and the dichroic dye (302) are aligned with the substrate (101).
This is an example of a case where the substrate has an alignment state rotated by 180 ° from the direction perpendicular to the substrate to the substrate (201).

When no electric field is applied in the direction parallel to the substrate, the dichroic dye added to the liquid crystal is oriented in all directions with the direction perpendicular to the substrate as an axis, as shown in FIG.

Accordingly, no matter what component of the natural light is incident, the dichroic dye molecule has a component in the major axis direction. In this case, since most of the incident light is absorbed by the dichroic dye molecules, a state where the incident light does not pass through the light control layer is realized. That is, a dark state is obtained.

On the other hand, when an electric field is applied, as shown in FIG. 4, the molecules constituting the light control layer (204) are in a state where their major axes are oriented in the direction of the electric field parallel to the substrate.

Therefore, of the incident natural light, the polarized light component parallel to the molecular long axis direction is absorbed, but the other components are not absorbed and pass through the light control layer. Therefore, a transmission state can be obtained visually. That is, a bright state is obtained.

The black and transparent states can be displayed by switching between the above-mentioned electric field non-application state and electric field application state.

[0096]

EXAMPLE In this example, a manufacturing process of the liquid crystal electro-optical device shown in FIG. 2 will be described. FIG. 2 is a schematic sectional view of the liquid crystal electro-optical device according to the present embodiment. The liquid crystal electro-optical device in FIG. 2 uses a substrate on which TFTs, wirings, and the like are formed as shown in FIG. 1 as one substrate.

FIG. 1A is a schematic top view of the pixel portion. FIG. 1B is a line A in FIG.
It is the schematic of the cross section in -A '.

First, a silicon oxide film is formed as a base film (102) on a glass substrate (101) to a thickness of 2000 ° by a plasma CVD method or a thermal CVD method.

At this time, a substrate (hereinafter referred to as a TFT substrate) 10
For 1, it is desirable to use non-alkali glass such as Corning # 1737 or quartz glass.

When the purpose is to reduce the weight of the liquid crystal electro-optical device, a film having low birefringence, for example, PES
(Polyethylene sulfate) and the like can also be used.

Next, an amorphous silicon film is formed in a thickness of 300 to 2000 Å, for example, 500 に よ り by a plasma CVD method.

Next, at 600 ° C. or less, preferably at 550 ° C.
Thermal annealing was performed at the following temperature to perform crystallization. After the thermal annealing, annealing may be performed by laser light or a strong light equivalent thereto to improve crystallinity.

In particular, at the time of thermal crystallization, the crystallization is promoted by adding a trace amount of a catalyst element such as nickel to the amorphous silicon film to promote crystallization, and the amorphous silicon film has high crystallinity on an inexpensive glass substrate. A polysilicon film can be formed. Details are disclosed in JP-A-6-244103.

The silicon film thus obtained is etched to obtain an island-like silicon film (103). Next, a silicon oxide film as a gate insulating film (104) is formed to a thickness of 500 to 1200 ° by a plasma CVD method using TEOS.
For example, a film is formed to a thickness of 1000 °.

Thereafter, aluminum is formed to a thickness of 2000 to 6000 ° by a sputtering method, and is patterned to obtain a gate line (105). Gate line (10
The width of 5) is 8 μm.

The gate line (105) is subjected to anodic oxidation on its surface using a weak acid solution as a chemical solution to form an anodic oxide film (10).
6) is formed. This anodic oxide film (106) has a dense film quality. The thickness of the anodic oxide film (106) is 700 °.

This anodic oxide film (106) has a function of mechanically and electrically protecting the gate electrode.

Next, impurity ions are implanted into the island-like silicon region (103) in a self-aligned manner by using the gate line (105) as a mask by ion doping.
A conductive region (107) is formed by giving a mold type or a p-type conductivity type. One of the conductive layers (107) serves as a source region, and the other serves as a drain region.

It is effective to use a so-called monolithic type in which a thin film transistor made of polysilicon constitutes a peripheral drive circuit (not shown) around the outside of the active matrix region. In that case, p-channel type and n-channel type thin film transistor complementary types are manufactured.

A silicon nitride film having a thickness of 3000 to 6000 (for example, 4000) is formed thereon by a plasma CVD method to form a first interlayer insulating film (108). This may be a silicon oxide film or a multilayer film of a silicon oxide film and a silicon nitride film.

Next, a first interlayer insulating film (108) on the source and drain regions (107) of the thin film transistor
Next, a contact hole is formed by etching. On top of that, a thickness of 2000 to 6000 mm by sputtering or the like,
A source line (109) and a drain electrode (110) are formed, for example, by forming and patterning a multilayer film of 3000 ° of aluminum or titanium and aluminum. The width of the source line (109) is 6 μm and the drain electrode (1
The width of 10) is 8 μm.

On this, a transparent organic resin film of polyimide or acrylic is coated at 4000 to 10000 (for example, 5000).
Å to form a second interlayer insulating film (111). It is needless to say that an inorganic material such as silicon oxide, silicon nitride, or silicon oxynitride can be used for the interlayer insulating film. However, when the polyimide or acrylic organic material is used, unevenness due to electrodes, elements, and the like is reduced. It can be planarized.

Then, a conductive film of aluminum, copper, chromium, titanium, ITO or the like is formed and patterned by a known method such as sputtering to form a common line (112). The width of the common line (112) is 8 μm. Also,
As shown in FIG. 1, the common line (112) has a portion parallel to the drain electrode (110), and the distance between the common line (112) and the drain electrode (110) is 12 μm.
m.

Here, in FIG. 1B, the cross-sectional shape of the electrode is shown as a rectangle, but it may be a trapezoid having an inclined surface or a curved surface. In this case, after forming a photoresist, isotropic plasma etching or wet etching is performed.

Further, silicon oxide as a protective film (not shown) is formed on the surface of the film at 5000 to 10000.degree.
Formed.

Next, as shown in FIG. 2, one substrate (2
01) sealing material (202) with epoxy resin around
Is formed, and substrates (101) and (201) are attached to each other,
Form cells.

In this embodiment, the pair of substrates sandwiched a spherical spacer (203) having a diameter of 4 μm between the substrates, so that the intervals between the substrates were uniform over the entire panel surface. In addition,
FIG. 2 does not show the TFT elements, wirings, and the like shown in FIG.

The sealing material (202) is not limited to an epoxy resin, and there is no problem if another resin, for example, a urethane acrylate resin is used. Further, the material of the spherical spacer does not matter whether it is an inorganic material or an organic material.

In this embodiment, the cell thickness is 4 μm.

Thereafter, liquid crystal or the like is injected between the pair of substrates (101) and (201) by a vacuum injection method or the like to form a light control layer (204).

As a material constituting the light control layer (204), a material obtained by mixing a dichroic dye and an optically active substance with a liquid crystal material is used.

In this embodiment, as the liquid crystal material, ZLI-3200 (manufactured by Merck) obtained by adding an azo dye to nematic liquid crystal is used. Its dielectric anisotropy is -4.8 and refractive anisotropy is +0.0437. The dye is added at 3.46%.

The nematic liquid crystal material is not limited to the above materials, and any material exhibiting nematic properties at room temperature can be used.

As the dichroic dye, a dye having high solubility in liquid crystal and being photochemically stable is desirable. Specifically, azo dyes, anthraquinone dyes, naphthoquinone dyes, perylene dyes, quinophthalone dyes,
It is possible to use a tetrazine dye, a coumarin dye or the like.

The viscosity of the liquid crystal (light control layer 204) changes due to the addition of the dichroic dye. The change in viscosity depends on the dichroic dye to be added, and the azo dye has a smaller thickening effect than anthraquinone and other dyes.

Further, S-811 (manufactured by Merck) was added as an optically active substance to the liquid crystal material. When the optically active substance is mixed with the liquid crystal material, the liquid crystal material exhibits a cholesteric phase at room temperature.

FIG. 3 is a schematic diagram when the light control layer is in a state where incident light is not transmitted, that is, when it is in a dark state.

In this case, as shown in FIG. 3, the alignment state of the dimming layer (204) is such that the alignment vector of the liquid crystal molecule (301) is oriented around the minor axis of the liquid crystal molecule (301). Each time the layer formed by the molecule (301) changes, the state is a spiral state in which the angle is gradually changed.

FIG. 3 schematically shows the liquid crystal molecules (301) and the dichroic dye molecules (302), and the scale is not the same as that of the substrates (101, 102). FIG.
3 are not shown in FIG. 3, and the TFT elements and wirings shown in FIG. Actually, the molecules exist innumerably between the substrates (101) and (201). Further, an optically active substance (not shown)
Is not limited to the above materials, and any material may be used as long as it can be dissolved in the liquid crystal material.

In the present embodiment, the amount of the optically active substance is adjusted so that the helical pitch p is 8 μm. With such a configuration, the liquid crystal molecules (30
1) and the dichroic dye (302) have a molecular major axis of the substrate (1).
From (01) to the substrate (201), the alignment state is rotated by 180 ° about the direction perpendicular to the substrate.

In the liquid crystal electro-optical device shown in this embodiment, the dichroism added to the liquid crystal material is maintained when no electric field is applied between the drain electrode (110) and the common electrode (112), the distance of which is indicated by L. The dye (302) is oriented in all directions around a direction perpendicular to the substrate.

Here, no matter what component of the natural light is incident, the dichroic dye molecule (302) has a component in the major axis direction. Therefore, the incident light is absorbed by the dye molecules, and black display is performed. That is, a state where incident light does not pass through the light control layer (204) is realized.

On the other hand, when the electric field is applied, as shown in FIG. 4, the molecules constituting the light control layer (204) are in a state where their major axes are oriented in the direction of the electric field parallel to the substrate (101).

Therefore, of the incident natural light, the polarized light component parallel to the molecular long axis direction is absorbed, but other components are not absorbed and pass through the light control layer. Therefore, a transmission state can be obtained visually. That is, a bright state is obtained.

By switching between the above-mentioned electric field non-application state and electric field application state, a black state and a transparent state can be displayed.

In this embodiment, an alignment film may be provided on at least one of the substrates (101) and (201) to exert an alignment regulating force on the liquid crystal or the like. When an alignment film is formed, uniform liquid crystal alignment is realized by the alignment control force, and a display with less color unevenness is realized. Further, the occurrence of alignment defects such as disclination is reduced.

[0137]

By using the invention disclosed in the present invention, a polarizing plate becomes unnecessary, and an excellent liquid crystal electro-optical device which is bright, has a high contrast ratio, and has little viewing angle dependency can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a TFT substrate of a liquid crystal electro-optical device according to an embodiment.

FIG. 2 is a schematic cross-sectional view of a liquid crystal electro-optical device according to an example.

FIG. 3 is a diagram illustrating a light absorption state of the liquid crystal electro-optical device according to the present embodiment.

FIG. 4 is a diagram illustrating a light transmission state of the liquid crystal electro-optical device according to the embodiment.

FIG. 5 is a diagram illustrating a light transmission state of a conventional liquid crystal electro-optical device.

[Explanation of symbols]

 101, 201, 501, 502 Substrate 102 Underlayer 103 Silicon film 104 Gate insulating film 105 Gate line 106 Anodized film 107 Conductive region 108 First interlayer insulating film 109 Source line 110 Drain electrode 111 Second interlayer insulating film 112 Common line 202 Seal material 203 Spacer 204 Light control layer 301, 503 Liquid crystal molecule 302, 504 Dichroic dye

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-225388 (JP, A) JP-A-7-92504 (JP, A) JP-A-54-43048 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G02F 1/137 500 G02F 1/1343

Claims (7)

(57) [Claims] 1. A substrate comprising at least one substrate having a light-transmitting property, a dimming layer containing a liquid crystal, an optically active substance and a dichroic dye between the two substrates; On the other hand, there are two wirings formed in parallel with each other for forming an electric field in a direction parallel to the two substrates, and a distance L between the two wirings is L <25 (unit: μm In a state where no electric field is formed in a direction parallel to the two substrates, the molecular long axes of the liquid crystal and the dichroic dye are parallel to the two substrates and the two In a state where the liquid crystal and the dichroic dye are oriented in a helical manner in all directions around a direction perpendicular to the substrate and an electric field is formed in a direction parallel to the two substrates,
A liquid crystal electro-optical device, which is oriented in a direction parallel to a plurality of substrates. 2. A light-adjusting layer containing at least one substrate having a light-transmitting property, a liquid crystal, an optically active substance, and a dichroic dye between the two substrates; on the other hand, has a two line formed in parallel to each other to form an electric field to the two substrates in a direction parallel, the distance L between the two wires L <25 (unit: [mu] m In a state where no electric field is formed in a direction parallel to the two substrates, the molecular long axes of the liquid crystal and the dichroic dye are parallel to the two substrates and the two In a state where the liquid crystal and the dichroic dye are oriented in a helical manner in all directions around a direction perpendicular to the substrate and an electric field is formed in a direction parallel to the two substrates,
A liquid crystal electro-optical device which is oriented in a direction parallel to a plurality of substrates and has no polarizing plate. 3. The liquid crystal electro-optical device according to claim 1, wherein the two wirings include a drain line and a wiring formed in parallel with the drain line. 4. The liquid crystal electro-optical device according to claim 1, wherein a helical pitch p of the liquid crystal is in a range of 1 ≦ p ≦ 15 (unit: μm). . 5. The cell according to claim 1, wherein a cell thickness d indicating an interval between the light control layers is 1 ≦ d ≦ 1.
A liquid crystal electro-optical device having a range of 0 (unit: μm). 6. A any one of claims 1 to 5, the liquid crystal electro-optical device, wherein at least one alignment film is provided before Symbol two substrates. 7. A liquid crystal electro-optical device according to claim 1, wherein said dichroic dye is of a positive type.