JP6932104B2 - Liquid crystal display element - Google Patents

Description

The present invention relates to a liquid crystal display element.

Ferroelectric liquid crystals are generally used because they have a strong interaction with the electric field applied between the substrates due to the strength of spontaneous polarization of the ferroelectric liquid crystal molecules (hereinafter, simply referred to as liquid crystal molecules). It has an extremely faster response than the nematic liquid crystal display, and shows high improvement ability in moving image flicker and image processing speed, which is a problem in today's liquid crystal display elements using the nematic liquid crystal display.

Further, by controlling the substrate spacing (cell gap) to 1 μm or less, the spiral structure characteristic of the ferroelectric liquid crystal disappears, and the liquid crystal molecules are left and right in the substantially vertical direction in the direction of the ferroelectric liquid crystal layer, respectively. It stabilizes at a certain angle. By switching between the two directions on the left and right, the polarization state of the incident light is changed, and whether or not the light is transmitted to the polarizer is determined. In the above-mentioned state, the liquid crystal molecule can control the polarization state of light by a very simple driving principle that only turns the driving voltage on and off.

By the way, in SSFLCD (surface-stabilized ferroelectric liquid crystal display element) with a small cell gap, a strong orientation regulating force for orienting the liquid crystal layer in a predetermined direction is required due to the strong interaction between molecules due to spontaneous polarization. Yes, the interaction from the alignment film is important.

Further, in the orientation of the SSFLCD, a twisted structure of the liquid crystal is generated and the space between the liquid crystal layers is widened. appear. This shepron structure causes a change in either of two directions with respect to the long axis direction of the liquid crystal molecule.

As an orientation method for aligning the liquid crystal display, it is necessary to create an alignment film on the substrate and give the alignment film anisotropy. Generally, a rubbing treatment method using an organic alignment film, a photoalignment film method using a photosensitive organic film, and a vapor deposition method in which an organic or inorganic material is vapor-deposited to form a film are known. There is.

However, the ferroelectric liquid crystal having spontaneous polarization and strong interaction between liquid crystal molecules has problems in each of the above orientation methods, and the display quality is deteriorated in the application to be used, for example, an image display element. There are concerns about reliability issues. Specifically, in the rubbing processing method, the generation of particles due to physical contact and the generation of scratches and streaks can be mentioned. Further, in the vapor deposition alignment film having a column structure and becoming a relatively thin film, the so-called anchoring energy for orienting the ferroelectric liquid crystal is insufficient, and the liquid crystal molecules enter the column structure and the predetermined orientation direction is set. There is a concern that it will not be obtained. Further, in the photo-alignment film having no pre-tilt angle, the occurrence of zigzag defects due to the mixture of C1 and C2 orientation due to the insufficient pre-tilt angle and the like can be mentioned.

In particular, in a surface-stabilized ferroelectric liquid crystal display element, a vapor-deposited alignment film having a conspicuous roughness on the film has a poor alignment force. As a method for improving this, for example, in the method described in Japanese Patent Application Laid-Open No. 1-234824, it has been proposed to flatten the vapor-deposited alignment film by forming a horizontal alignment film on the vapor-deposited alignment film. .. Further, in the method described in Japanese Patent No. 2724838, it is proposed to form an organic alignment film on the vapor deposition alignment film and perform a rubbing treatment.

Japanese Patent Application Laid-Open No. 1-234824 Patent No. 2724838

The methods described in Patent Documents 1 and 2 can give a constant pretilt angle to the liquid crystal display, but have the following problems. In the method described in Patent Document 1, there is a concern that the alignment force itself may be lowered by the horizontal alignment film, and a sufficient alignment force can be obtained in a ferroelectric liquid crystal display or the like that requires a strong interaction with the alignment film. No. In the method described in Patent Document 2, in addition to the concern that particles and streaks are generated in the physical contact treatment of the rubbing treatment on the organic alignment film, on the vapor-deposited alignment film having a column structure, Due to the surface roughness, an effective rubbing treatment effect may not be obtained, and a sufficient orientation force may not be obtained. These problems are remarkable in the surface-stabilized ferroelectric liquid crystal display element, but can occur in other liquid crystal display elements as well.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal display element capable of imparting a constant pretilt angle and high orientation to a liquid crystal display.

A liquid crystal display element in which a liquid crystal display element is formed by bonding a first electrode substrate having an electrode for applying a voltage to the liquid crystal and a second electrode substrate, and the liquid crystal is sealed in a gap between the two substrates. A first alignment film and a second alignment film for aligning the liquid crystal are formed on at least one of the electrode substrate and the second electrode substrate, and the first alignment film is an alignment film having a column structure. The second alignment film is a liquid crystal display element which is a photo-alignment film and is formed on the first alignment film.

The liquid crystal may be a liquid crystal display element which is a ferroelectric liquid crystal.

The first alignment film may be a liquid crystal display element formed by an oblique vapor deposition method.

The second alignment film may be a liquid crystal display element having a thickness equal to or less than that of the first alignment film.

According to the present invention, it is possible to provide a liquid crystal display element capable of imparting a constant pretilt angle and high orientation to a liquid crystal display.

Vertical sectional view of the liquid crystal display element according to the embodiment of the present invention. Vertical sectional view of the liquid crystal display element according to the embodiment of the present invention.

The liquid crystal display element according to the embodiment of the present invention is, for example, a surface-stabilized ferroelectric liquid crystal display element that requires a strong orientation regulating force and a constant pretilt angle for controlling the shepron structure, and generates particles and sizzles. It has a structure of an alignment film that suppresses and makes it possible to give a high alignment force and a constant pretilt angle to the liquid crystal display. Specifically, it has a structure of an alignment film in which a photo-alignment film made of a photosensitizing organic film is laminated on a thin-film alignment film made of a SiO2 vapor-deposited film having a column structure. As a result, it is possible to give a high orientation force and a constant pretilt angle to the liquid crystal without generating particles or sizzle, and it is possible to suppress the occurrence of zigzag defects in the ferroelectric liquid crystal.

In the liquid crystal display element according to the present embodiment, in order to obtain a constant pretilt angle from the vapor deposition alignment film of the first layer, the column structure of the vapor deposition alignment film of the first layer has a predetermined angle. Further, in order to effectively obtain the pretilt angle from the vapor deposition alignment film of the first layer, the photoalignment film of the second layer formed on the vapor deposition alignment film of the first layer is equivalent to the vapor deposition alignment film of the first layer. It has the following film thickness. Further, in order to obtain a high alignment force from the photoalignment film of the second layer, the photoalignment film of the second layer is imparted with anisotropy in a predetermined direction by, for example, polarized UV.

Hereinafter, a more specific configuration of the liquid crystal display element according to the present embodiment will be described. FIG. 1 is a vertical cross-sectional view of the liquid crystal display element according to the embodiment of the present invention, and shows a state before the liquid crystal is sealed inside the liquid crystal display element. As shown in FIG. 1, SiO2 is deposited by an oblique vapor deposition method on electrode substrates 101 and 102 (for example, a silicon substrate and a glass substrate, respectively) on which electrodes (not shown) for applying a voltage to a liquid crystal are formed. The thin-film deposition alignment film 103 of the first layer formed is formed, and the photoalignment film 104 of the second layer made of an organic film having photosensitivity is formed on the vapor deposition alignment film 103. Several manufacturing methods can be considered for forming the photoalignment film 104, and examples thereof include a spin coating method.

The thin-film alignment film 103 has a plurality of column structures that are inclined at a constant angle with respect to the surfaces of the electrode substrates 101 and 102, and a space is formed between the column structures. The photoalignment film 104 enters the space, and the photoalignment film 104 is formed so as to cover the upper surface of the column structure. In this state, the total thickness of the vapor-deposited alignment film 103 and the photo-alignment film 104 is smaller than the total thickness of each of the vapor-deposited alignment film 103 and the photo-alignment film 104. In order to obtain the effect of pretilt of the vapor deposition alignment film 103, the vapor deposition alignment film 103 is not completely buried under the photoalignment film 104, and its column structure needs to give a certain directionality to the surface shape of the photoalignment film 104. .. Therefore, the photoalignment film 104 is a film having the same thickness as or thinner than the vapor deposition alignment film 103. Further, the photoalignment film 104 is subjected to exposure in a certain direction with, for example, polarized UV, in order to obtain sufficient alignment force with respect to the liquid crystal display and anchoring energy, and anisotropy is imparted.

FIG. 2 is a vertical sectional view of the liquid crystal display element according to the embodiment of the present invention, and shows a state after the liquid crystal is sealed inside the liquid crystal display element. A pair of electrode substrates (electrode substrates 101, 102) on which the vapor deposition alignment film 103 and the photoalignment film 104 are formed as described above are attached to each other via a substantially frame-shaped sealing material (which may include a spacer). The liquid crystal display element shown in FIG. 2 is configured by enclosing a liquid crystal 105 made of a ferroelectric liquid crystal in a gap (cell gap) created by the alignment. The liquid crystal 105 enclosed between the pair of substrates is appropriately oriented according to the anisotropy of the photoalignment films 104 formed on the electrode substrates 101 and 102. Further, the liquid crystal 105 in contact with the interface with the photoalignment film 104 is given a constant pretilt angle under the influence of the column angle from the vapor deposition alignment film 103. As a result, the shepron structure 106 of the liquid crystal 105 is restricted in a certain direction, and the occurrence of zigzag defects is suppressed. Further, in the vapor-deposited alignment film 103 and the photo-alignment film 104 that do not require the rubbing treatment, there is no concern that particles or streaks are generated.

In the above embodiment, the liquid crystal 105 may be a nematic liquid crystal or the like. However, the present invention is particularly effective when the liquid crystal 105 is a ferroelectric liquid crystal.

The vapor deposition alignment film 103 may be an alignment film formed by a method other than the thin film deposition method.

The photoalignment film 104 may be a film thicker than the vapor deposition alignment film 103. However, the photoalignment film 104 is preferably a film having the same thickness as the vapor deposition alignment film 103, and more preferably a thinner film.

The alignment film in which the vapor deposition alignment film 103 and the photoalignment film 104 are laminated is formed on only one of the electrode substrates 101 and 102, and the other alignment film is different from the alignment film (for example, a single-layer alignment film). May be formed. However, it is desirable that the alignment film in which the vapor deposition alignment film 103 and the photoalignment film 104 are laminated is formed on both the electrode substrates 101 and 102.

101, 102 Electrode substrate 103 Thin-film alignment film 104 Photo-alignment film 105 Liquid crystal 106 Shepron structure

Claims (4)

A liquid crystal display element in which a liquid crystal display element is formed by bonding a first electrode substrate having an electrode for applying a voltage to a liquid crystal and a second electrode substrate, and the liquid crystal is sealed in a gap between the two substrates.
A first alignment film and a second alignment film for aligning the liquid crystal are formed on at least one of the first electrode substrate and the second electrode substrate.
The first alignment film is an alignment film having a column structure, and is
The second alignment film is a photo-alignment film and is formed on the first alignment film.
A liquid crystal display element characterized by this. The liquid crystal display element according to claim 1, wherein the liquid crystal display is a ferroelectric liquid crystal display. The liquid crystal display element according to claim 1 or 2, wherein the first alignment film is formed by an oblique vapor deposition method. The liquid crystal display element according to any one of claims 1 to 3, wherein the second alignment film has a thickness equal to or less than that of the first alignment film.

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