JPH09185054A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To orient liquid crystal molecules in a liquid crystal display element with good controilability by impressing electric fields on the liquid crystal molecules from the directions orthogonal with each other, thereby controlling the orientation state of the liquid crystal molecules and controlling the transmittance of light. SOLUTION: Side wall electrodes 20 are disposed perpendicularly via insulating film 14, 15 between opposite transparent electrodes 13, 16 made of ITO disposed on upper and lower glass substrates 12, 17. These glass substrates 12, 17 are provided with polarizing filters 11, 18 having the planes of polarization orthogonal with each other. Liquid crystals are injected into the spacing 19 between the transparent electrodes 13 and 16. The directions of the directors of the internal liquid crystals are controlled by regulating the voltages to be impressed on the respective electrodes 13, 16, 20, by which the polarization state of the light transmitted through the liquid crystal layer is controlled and the quantity of the light transmitted through the polarizer having the planes of polarization which are disposed before and behind the liquid crystal layer and are intersected orthogonally with each other is controlled. Then, the response of the liquid crystal molecules with the electric fields is capable of adjusting the directions of the liquid crystals with good controllability by the impressed magnetic fields.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a liquid crystal display device which is a display device using a liquid crystal.

[0002]

2. Description of the Related Art In a conventional liquid crystal display element, a rubbed polyimide film is usually provided on the inner wall of a cell to give uniform alignment to liquid crystal molecules and to realize a uniform display state on the entire screen. .

In the rubbing treatment of the polyimide film, the surface of the polyimide film is rubbed by rotating a roller made of a rayon cloth called a buff cloth roller in a cylindrical shape. By this rubbing treatment, the polyimide molecules on the surface are oriented,
It is said that the liquid crystal molecules are aligned by the interaction between the polyimide molecules and the liquid crystal molecules. For details, see the literature (Ishihara et al., Liquid Crystals (Liquid Crysta
ls), Vol. 4, No. 6, p. 669, 1989, referred to as "Document 1").

In order to obtain good liquid crystal alignment, along with the selection of liquid crystal material and alignment film material (type of polyimide),
Optimization of the rubbing treatment such as the number of rotations of the roller, the feeding speed of the substrate coated with the polyimide, the pressure of pressing the roller against the substrate, and the number of times of rubbing are important factors.

[0005]

It is said that the rubbing treatment causes the polyimide molecules on the surface to be oriented, and the liquid crystal molecules to be oriented by the interaction between the polyimide molecules and the liquid crystal molecules (see Ishihara et al., Supra). Some attempts have been made to observe the molecular orientation of the polyimide film. For example, Japanese Patent Laid-Open No. 6-102512 (Kurai et al., Name: “Alignment evaluation device for liquid crystal display device and method for manufacturing liquid crystal display device”) describes that the birefringence of the alignment film before rubbing with measuring light having a large spot diameter. A method has been proposed in which the phase difference is measured, the birefringence phase difference on the surface of the alignment film is measured with measuring light having a small spot diameter after rubbing, and the uniformity or strength of the rubbing treatment is evaluated by the difference between the two. In addition,
Japanese Patent Application Publication No. 4-95845 (Ishihara, name: "Method for Evaluating Liquid Crystal Alignment Ability of Alignment Film") describes a method for measuring the amount of reflected light on the surface of an alignment film and measuring the amount of reflected light on the surface of the alignment film. A method has been proposed in which the orientation state can be evaluated in the state.
The literature (Sawa et al., Japanese Journal of
Applied Physics (Japanese Journal of Applie
d Physics), Vol. 33, p. 6273, 1994, which is referred to as “Reference 2”). However, any of the above methods has problems in terms of quantitativeness and reliability. However, this method is not always effective in practical use.

Furthermore, since the interaction between liquid crystal molecules and polyimide molecules has not been clarified and the alignment mechanism of liquid crystal molecules has not been clarified, the proper molecular alignment state of the polyimide film is still unknown. It is impossible to optimize the rubbing condition for realizing the above.

At present, since the material of the alignment film and the rubbing conditions are generally set on the basis of accumulated experience so far, defective products due to poor alignment of the liquid crystal of unknown cause may occur. However, it is difficult to take effective measures against this kind of failure occurrence.

Further, in the rubbing treatment, it is difficult to remove dust, so that defects due to contamination are likely to occur.

Accordingly, the present invention has been made in view of the above-mentioned problems of the prior art, and solves the above-mentioned problems relating to the rubbed polyimide alignment film, thereby controlling the liquid crystal molecules in the liquid crystal display element. It is an object of the present invention to provide a structure of a liquid crystal display element which is well aligned.

[0010]

In order to achieve the above object, the present invention provides a method for controlling the transmittance of light by applying an electric field to liquid crystal molecules from two directions perpendicular to each other to control the alignment state of the liquid crystal molecules. The present invention provides a liquid crystal display device characterized in that:

The principle and operation of the present invention will be described below.

According to the present invention, two pairs of electrodes whose electric field application directions are orthogonal to each other are provided in place of the rubbed polyimide thin film for aligning the liquid crystal molecules, and the intensity of the electric field applied to these electrodes is appropriately adjusted. The adjustment controls the orientation of the liquid crystal molecules.

That is, in the present invention, preferably, liquid crystal is injected into a container provided with electrodes on a light transmitting surface and a pair of side walls perpendicular to the light transmitting surface, and polarized light whose polarization planes are perpendicular to each other on the outside thereof. It controls the direction of the director of the internal liquid crystal by adjusting the voltage applied to each electrode to control the polarization state of the light passing through the liquid crystal layer, and the polarization provided before and after the liquid crystal layer. Controls the amount of light transmitted through polarizers whose planes are perpendicular to each other.

One of the two pairs of electrodes is a transparent electrode made of a material such as ITO, and light transmits through the electrodes. The other counter electrode is arranged perpendicular to the transparent electrode,
The side wall of the liquid crystal cell is formed.

Outside the liquid crystal cell, two polarizers are provided such that the polarization planes are orthogonal to each other and the electrodes on the side walls are both non-parallel to the direction of the applied electric field. .

In this structure, when an electric field is applied between the transparent electrodes, the axis of the liquid crystal molecules having optically uniaxial anisotropy becomes perpendicular to the transparent electrode. In this state, the liquid crystal molecules are linearly polarized by one polarizer. Incident light is not affected by the polarization state,
The light passes through the liquid crystal layer and reaches another polarizer whose polarization plane is orthogonal to the one polarization plane, so that the light is blocked there.

On the other hand, when an electric field is applied between the transparent electrode and the perpendicular electrode, incident light passing through one polarizer undergoes birefringence in the liquid crystal layer, becomes elliptically polarized light, and reaches another polarizer. Finally, part of the incident light is transmitted.

As described above, according to the present invention, by adjusting the voltage applied between the electrodes, the intensity of the transmitted light of the cell can be controlled, thereby having a function as a display element.

In the liquid crystal display device according to the present invention, the response of the liquid crystal molecules to the electric field is determined by the viscosity, elasticity, and dielectric constant of the liquid crystal. Therefore, there is no unknown factor such as a polyimide alignment film. The direction of the liquid crystal can be adjusted with good controllability by the applied electric field.

[0020]

Embodiments of the present invention will be described in detail below with reference to the drawings.

[0021]

[Embodiment 1] An embodiment of a liquid crystal display device according to the present invention will be described below with reference to FIGS. 1, 2 and 3 showing the structure of a liquid crystal display device actually manufactured.

In the present embodiment, the size of the liquid crystal display element is a square of about 2 mm × 2 mm, and is manufactured for the purpose of simulating the operation of one pixel portion of a liquid crystal display panel (LCD) for displaying an image.

Referring to FIG. 2, a liquid crystal display device according to the present embodiment is provided with opposed transparent electrode films 1 made of ITO (indium-tin-oxide) provided on upper and lower glass substrates 12 and 17.
Between side walls 3 and 16 via insulating films 14 and 15
Are provided vertically, and glass substrates 12 and 17 are provided with polarizing filters 11 and 18 whose polarizing planes are orthogonal to each other, and a liquid crystal is injected into a space 19 between the transparent electrodes 13 and 16.

The liquid crystal display device according to this embodiment was manufactured in the following procedure.

First, transparent electrode films 13 and 16 made of ITO are vapor-deposited on glass substrates 12 and 17.

Then, in FIG. 1, 500 angstroms (= 50) are formed at the positions where the side wall electrodes 1 are formed.
nm) of silicon oxide (SiO ₂ ) insulating film 14,
15 and then gold (Au) is deposited on the side wall electrode 1.
To form The portion on which the gold is deposited (sidewall electrode) is denoted by reference numeral 20 (crossed hatched portion (hatched)) in FIG.
It shows with.

After the thermosetting epoxy resin 3 for sealing is applied to the edges of the two substrates thus processed, which are orthogonal to the side wall electrodes 1, a cell having a diameter of approximately 5.4 μm is formed. Spacer (micropearl) 2 to maintain gap
(Reference numeral 21 in FIG. 2).

At this time, care must be taken so that the spacers (2, 21) do not ride on the gold-deposited portions (20).

Subsequently, the two substrates are stuck together so that their patterns match each other, and cured by heating to form cells.

The thermosetting epoxy resin 3 is not applied to the entire edge, but a hole for injecting liquid crystal into the cell is formed as shown in FIG.

After the liquid crystal is introduced into the cell, an ultraviolet-curable resin 4 (see FIG. 1) is applied to the hole into which the liquid crystal has been injected, and the cell is sealed with ultraviolet light.

Finally, a polarizing filter 1 is provided on both sides of the glass.
Paste 1, 18 (see FIG. 2).

FIG. 3 is a diagram schematically showing the relationship between the polarization directions of the two polarizing filters and the directions of the side wall electrodes. FIG.
In, the hatched portion 25 indicates the polarizing filter on the front side,
The direction of the arrow is the polarization direction. Although the polarizing filter 25 is drawn only on a part of the cell for the convenience of drawing, it is actually attached on the entire surface. Further, the glass substrate, the spacer pattern, and the epoxy resin used in the actual structure are not shown.

Referring to FIG. 3, regarding the relationship between the polarization direction of the polarizing filter and the side wall electrode, the transmission direction of the upper polarizing plate 25 shown by oblique lines is from the upper right to the lower left as indicated by the solid line arrow. The vibration direction of the polarizing plate 22 on the side is from the upper left to the lower right, as shown by the dashed arrow, and is perpendicular to the direction of the polarizing plate 25 on the upper side.

The side wall electrodes 23 and 24 are composed of two polarizing plates 2
It is manufactured along a direction forming an angle of 45 ° with respect to the polarization directions of 2, 25.

The thickness of the side wall electrode 20 and the thickness of the insulating films 14 and 15 (see FIG. 2) are both 2.77 μm, that is, the He− of the cell manufactured so that the cell gap is 5.54 μm.
The transmittance of the Ne laser at 633 nm was measured.

The injected liquid crystal was measured at 5 CB in an environment of a temperature of 30 ° C. so as to obtain a stable operation.

A voltage of 100 V was applied to the side wall, and the voltage V applied to the transparent electrode was changed in the range of 0 to 3 V.

FIG. 4 shows the relationship between the transparent electrode voltage and the transmittance obtained by the above measurement. That is, FIG.
The graph shows the results of measuring the change in transmittance with respect to the applied voltage when light of a 633 nm Ne laser is substantially perpendicularly incident on the cell surface. The horizontal axis represents voltage, and the vertical axis represents transmittance.

FIG. 4 shows that when the transparent electrode voltage is 0.6 V or less, about 25% of the light is transmitted, and when the transparent electrode voltage is 1.8 V or more, almost no light is transmitted.

Ideally, the transmittance is expected to be 50% when the transparent electrode voltage is 0 V. However, the actual cell gap is deviated from the design value, and the reflection at the cell surface or interface is caused. Is considered to be the cause of the maximum transmittance actually measured being about 25%.

[0042]

As described above, the liquid crystal display device according to the present invention enables the alignment of liquid crystal to be controlled only by the electric field applied to the device without using a rubbed polyimide film. is there. Thus, according to the present invention,
Since a rubbing process that causes contamination is not performed, occurrence of defects due to contamination can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a liquid crystal display element according to an embodiment of the present invention, which is a cross-sectional view when a center of the liquid crystal display element is cut parallel to a screen.

FIG. 2 is a diagram showing a configuration of a liquid crystal display element according to an embodiment of the present invention, which is a cross-sectional view of the liquid crystal display element taken along a plane perpendicular to a screen and sidewall electrodes.

FIG. 3 is a diagram schematically illustrating a liquid crystal display device according to an embodiment of the present invention, and is a diagram illustrating a relationship between the polarization direction of two polarizing filters and the direction of a side wall electrode.

FIG. 4 is a view showing measured data of light transmittance of a liquid crystal display element according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Side wall electrode 2 Spacer for holding a cell gap 3 Thermosetting epoxy resin for sealing 4 UV curable epoxy resin for sealing a liquid crystal injection part 5 ITO transparent electrode film is vapor-deposited on the surface and a polarizing filter is formed on the back Glass substrate 11, 18 Polarization filter (each polarization plane is orthogonal to each other) 12, 17 Glass substrate 13, 16 ITO transparent electrode film 14, 15 Insulating film SiO ₂ 19 Liquid crystal injection gap Reference Signs List 20 side wall electrode 21 spacer 22 back side polarizing filter 23, 24 side wall electrode 25 front side polarizing filter

Claims (5)

[Claims] 1. A liquid crystal display device wherein a light transmittance is controlled by applying an electric field to liquid crystal molecules in two directions perpendicular to each other to control an alignment state of the liquid crystal molecules. 2. An apparatus according to claim 1, further comprising two pairs of electrodes arranged so that directions of electric fields to be applied are orthogonal to each other, and controlling an intensity of the electric field applied to said two pairs of electrodes to control an alignment state of liquid crystal molecules. A liquid crystal display element configured to perform. 3. One of the two pairs of electrodes comprises a transparent electrode disposed on a light transmitting surface, and the other counter electrode comprises:
3. The liquid crystal display device according to claim 2, comprising a side wall electrode arranged perpendicular to the transparent electrode to form a side wall of the liquid crystal cell. 4. The apparatus according to claim 3, further comprising two polarizers whose polarization planes are orthogonal to each other and which are both non-parallel to the direction of the electric field applied by said side wall electrode. The liquid crystal display element as described in the above. 5. The liquid crystal display device according to claim 3, wherein said side wall electrode is inserted between said pair of transparent electrodes via an insulating member.