JPH11316379A - Optical irradiation method for liquid crystal alignment having uniform point inclination angle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning type optical irradiation method while moving a substrate by arranging a cylindrical lens on an ultraviolet lamp for linearizing light made to exit from a source of ultraviolet rays, and irradiating the substrate coated with optical alignment material at an angle of 0-60 degrees. SOLUTION: The proposed optical irradiation method makes it possible to efficiently irradiate a large substrate 3 with continuous light; to provide liquid crystal alignment with a uniform point tilt angle by irradiating the substrate coated with an optical alignment material with an inclined ultraviolet beam having a uniform energy; and to manufacture a high quality liquid crystal display.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a uniform tilt angle (p).
The present invention relates to a light irradiation method for aligning a liquid crystal having a retilt angle. More specifically, the present invention relates to a scanning-type light irradiation method capable of generating a high-quality liquid crystal display substrate having a large area using optical alignment.

[0002]

2. Description of the Related Art In general, a liquid crystal display (LCD) has been attracting attention as a most competitive display capable of replacing a cathode ray tube because of its advantages of being light and having low power consumption. A liquid crystal display cell is manufactured by injecting and curing a liquid crystal material between a pair of substrates and forming a liquid crystal layer.

As a method of aligning liquid crystal molecules in a liquid crystal display cell, a rubbing step (r) in which an alignment material is applied on a substrate and rubbed with a rubbing cloth such as nylon or rayon is used.
ubbing process). However, the above-mentioned method is not suitable for mass production because the coating speed is low and the production yield is low. Therefore, polyimide (polyimid)
A method of spin-coating or rubbing using a heat-resistant polymer as an alignment material, such as e), has been developed. However, such a method can apply the alignment material quickly and cheaply and simplifies the production process. Due to its advantages, it is currently applied to most mass production processes. However, the above-described rubbing process has a disadvantage that the production yield is rapidly lowered because defects are generated due to dust and fiber particles generated from the cloth.

Therefore, a non-rubbing process (non-rubbing) using a photopolymerizable alignment material that causes photopolymerization by light irradiation to induce the alignment of the polymer and align the liquid crystal.
process) has been developed. As a typical example of such a non-rubbing step, M.P. S
chadt et al. (Jpn. J. Appl. Phys.,
Vol. 31, 1992, 2155), Dae S. et al. K
Ang et al. (U.S. Pat. No. 5,464,669), Yu.
riy Reznikov (Jpn. J. Appl. P
hys. Vol. 34, 1995, L1000).

[0005] Photoalignment refers to a photoreaction of a photosensitive group bonded to a polymer by ultraviolet light that is linearly polarized,
In this process, the main chain of the polymer is arranged in a certain direction, and the liquid crystal is eventually aligned.
When the above-described optical alignment method is used in manufacturing a liquid crystal display, the alignment is induced by one-time inclined irradiation of linearly polarized ultraviolet rays using the optical alignment material as the liquid crystal alignment material.

[0006]

However, a part which has been a subject of controversy in the manufacturing process relates to a method of irradiating the photo-alignment material with ultraviolet rays. When the size of the substrate is small, a single ultraviolet light source can effectively irradiate the entire area of the substrate effectively, but as the size of the substrate increases, such direct irradiation is limited to include the entire area There is no choice but to select a partial irradiation method using a mask or scan the entire substrate.

When the size of the substrate is large, a method commonly used by developers is to perform masking using a photomask, as shown in FIG. 1A. This is a method in which a photo-alignment material is applied to a substrate (3), a polarizing plate (4) is adhered, and light is irradiated with an ultraviolet beam using a photomask (5). In FIG. 1b, the hatched portion indicates the portion irradiated with light. When partial irradiation is performed using a photomask, the substrate is tilted at a certain angle with respect to the light source so that the liquid crystal has a pre-tilt angle even when a collimated beam is used. Since the energy of the polarized ultraviolet light reaching each part is changed, the non-uniformity of the orientation is caused over the entire irradiation area of the substrate, and further, the inclination angle is changed. or,
This method is also unsuitable for producing a liquid crystal display substrate having a large area.

Accordingly, the present inventors have developed a light irradiation method having a uniform tilt angle of liquid crystal alignment by obliquely irradiating the entire alignment film surface with an ultraviolet beam having a certain energy linearized by a scanning method. It leads to.

Accordingly, it is a primary object of the present invention to provide a method for irradiating a liquid crystal having a uniform tilt angle, and a secondary object is to continuously irradiate a large area substrate with light. And a light irradiation method capable of obtaining a high-quality liquid crystal display.

[0010]

According to the present invention, there is provided a light irradiation method for generating a liquid crystal alignment having a uniform tilt angle, wherein the focus of an ultraviolet beam from a light source is linearized and a substrate coated with a photo alignment material is provided. Or linearly irradiating the substrate with a linearized ultraviolet beam while moving the light source.

In the light irradiation method for generating a liquid crystal alignment having a uniform tilt angle according to the present invention, in addition to the above-described structure, the linearized ultraviolet beam is generated by installing a cylindrical lens in a light source. Is preferred.

In the light irradiation method for generating a liquid crystal alignment having a uniform tilt angle according to the present invention, in addition to the above-described structure, it is preferable that the cylindrical lens has a disk shape or a rectangular shape.

In addition to the above structure, the light irradiation method for generating a liquid crystal alignment having a uniform tilt angle according to the present invention is arranged so that the linearized ultraviolet beam is at an angle of 0 to 60 ° with respect to the substrate. It is preferable that the irradiation is performed at an angle.

In the light irradiation method for producing a liquid crystal alignment having a uniform tilt angle according to the present invention in addition to the above configuration, it is preferable that the light source is a fusion lamp, a mercury lamp or a xenon lamp.

[0015]

The above and other objects of the present invention can all be achieved by the present invention described below. Hereinafter, the contents of the present invention will be described in detail below.

According to the light irradiation method of the present invention, a cylindrical lens is provided on an ultraviolet lamp to linearize light from an ultraviolet light source and obliquely irradiate the substrate coated with a photo-alignment material at an angle of 0 to 60 °. The scanning method is to move.

The light source may be a UV light source, for example, a fusion lamp (Fusion lamp, Mikuni Fusion Sys.).
lamps that emit ultraviolet light such as a mercury lamp or a xenon lamp.

A liquid crystal display cell is manufactured by injecting a liquid crystal material between a pair of substrates manufactured by light irradiation and hardening to form a liquid crystal layer. In order for the liquid crystal display cell to be driven, that is, for the liquid crystal to be used as an optical switch, the liquid crystal of the display cell must basically be oriented in a certain direction. The degree of alignment of the liquid crystal is the most important factor for determining the image quality of the liquid crystal display. The degree of alignment of the liquid crystal is evaluated and determined by the uniformity of light energy. That is,
As the light energy becomes more uniform, a liquid crystal display with higher image quality can be manufactured. Further, according to the present invention, a photomask is not required, productivity is improved, and a continuous process can be performed.

The present invention is characterized in that a linearized ultraviolet beam having a constant energy is obliquely irradiated so that the liquid crystal alignment has a uniform forward tilt angle. This will be described in more detail with reference to the accompanying drawings.

As shown in FIG. 2A, a photo-alignment material is applied on the substrate (3), and a polarizing plate (4) is attached thereto. Then, an ultraviolet beam having a linearized focus is irradiated by a scanning method. FIG. 2B shows a front view of the state in which the substrate is irradiated with the ultraviolet beam. In FIG. 2C, a portion indicated by oblique lines indicates a portion irradiated with instantaneous light during scanning. The arrows in FIGS. 2a and 2c indicate the direction of movement of the substrate (3). In order to irradiate light by a scanning method, a lens (2) for linearizing light emitted through an ultraviolet light source (1) is required. The linearized beam is more effective when the beam focuses on the panel or the focused beam is closer to the panel without also focusing on the panel. This is because a linearized beam can be applied regardless of the length of the beam because the amount of energy received by the panel is constant. A cylindrical lens (2) is used to produce such a linearized beam.

The above-mentioned cylindrical lenses are circular and rectangular.
r). Linearizing the ultraviolet beam using a cylindrical lens (linear fo)
The principle of this is shown in FIG.
(A) and (b). It can be seen that the circular beam emitted from the UV light source is linearized after passing through the lens.

According to the light irradiation method of the present invention, in order to obtain a desired inclination angle, the substrate (3) moving at a constant speed in the horizontal direction is irradiated with a linearized beam while guiding the orientation to the irradiated portion. The method comprises tilting and irradiating the substrate (3) while moving the substrate (3) at a constant speed at which a high energy can be supplied. The linearized UV beam is applied to the substrate (3)
Irradiation is performed at an angle of 0 to 60 ° (θ) with respect to the vertical direction.

The linearized beam is formed by a light source (1) and a cylindrical lens (2), which are used by being connected to a support. This light source (1) and lens (2)
Can be changed by changing the position, the tilt angle can be uniformly obtained by adjusting the scanning time and the irradiation angle of the substrate (3). A substrate (3) is coated with a photo-alignment material, and a polarizing plate (4)
And then scanning with a linearized UV beam. In order to move the substrate (3), a conveyor system provided with a stepping motor can be used. Substrate (3)
Are aligned with the conveyor system and the system is moved at a speed of 1 to 20 cm / min.

The present invention is further embodied by the following examples, which are for illustrative purposes of the present invention and are not intended to limit the protection scope of the present invention.

[0025]

(Embodiment) A description will be given of the measurement of the tilt angle of a photo-aligned liquid crystal cell using scanning of a linearized ultraviolet light source.

A 40 × 50 mm glass substrate (3) is prepared by dissolving the applied cinamate-based photo-alignment material in a solvent in which N-methylpyrrolidine, γ-butyrolactone and butyl cellosolve are appropriately mixed at a concentration of 1 wt% and then 3,000 r.
After spin coating at pm and drying at 200 ° C. for 30 minutes or more, the solvent was removed. After the 1 KW mercury lamp (1) was turned into a collimated UV light source (1) as shown in FIG. 2a and fixed at an angle of 30 ° (θ = 30 °) with respect to the vertical of the glass substrate (3). A rectangular cylindrical lens (2) with a focal length of 50 mm was fixed in front of the UV light source (1) to linearize the circular beam. After attaching a film having a thickness of 1 mm to the outer edge of the glass substrate (3) coated with the photo-alignment material, the polarizing plate (4) is placed on the glass substrate (3) at intervals of 1 mm in consideration of the orientation direction. Fixed. In order to scan the glass substrate (3) with the polarizing plate (4) attached thereto with linearized ultraviolet light, a conveyor system capable of moving at a constant speed in a horizontal direction using a stepping motor was manufactured. The glass substrate (3) to which the polarizing plate (4) was attached was aligned on the conveyor system, and irradiation was performed while moving the system at a speed of 1 to 20 cm / min. As shown in FIG. 4, in order to confirm the pretilt angle and the orientation state of the two glass substrates (3 and 3 ') after the irradiation process, a cell gap was used.
7 is 50 to 60 μm.
ll) A liquid crystal cell was manufactured. Arrows shown in FIG. 4 indicate liquid crystal alignment directions. The tilt angles at three places (a, b, and c) of the liquid crystal cell were measured by a crystal rotation method and are shown in Table 1.

(Comparative Example) The measurement of the tilt angle of the photo-aligned liquid crystal cell using parallel ultraviolet light will be described.

After the photo-alignment material is applied on the glass substrate (3) as in the above embodiment, the polarizing plate (4) is fixed on the glass substrate (3), and the 1 KW mercury lamp (1) is collimated. The glass substrate (3) was used as a UV light source, but without using the cylindrical lens (2) for linearization, so that the irradiation angle of the parallel ultraviolet rays with respect to the vertical plane of the glass substrate (3) was 30 °. And simply irradiated for 2 to 10 minutes. In this case, the energy of the ultraviolet light applied to the photo-alignment material was adjusted with respect to the central portion of the glass substrate (3) in the same manner as in the case of the scanning method in the above embodiment. As shown in FIG. 4, an anti-parallel liquid crystal cell having a cell gap (7) of 50 to 60 μm is manufactured using the two glass substrates (3 and 3 ′) after the irradiation process, and is tilted forward by a crystal rotation method. The angles were measured and the results are shown in Table 1.

[0029]

[Table 1]

As shown in Table 1, when the liquid crystal display cell is manufactured by the irradiation method by scanning the linearized ultraviolet beam according to the embodiment, it can be seen that there is almost no difference in the inclination angle. On the other hand, it can be seen that the liquid crystal cell of the comparative example has a large change in the front tilt angle depending on the irradiation position due to the difference in energy during the tilt irradiation.

[0031]

According to the light irradiation method of the present invention, the linearized ultraviolet light continuously passes through the substrate to which the polarizing plate is attached, so that the light energy applied to the entire substrate is constant and uniform. A large-area substrate having an appropriate inclination angle can be easily obtained, and productivity can be improved by continuously moving a plurality of substrates. According to the light irradiation method of the present invention, since the liquid crystal display cell has a uniform front tilt angle, excellent image quality and quality can be obtained. Further, by changing the position of the ultraviolet lamp and the lens to change the irradiation angle, the desired inclination angle can be made uniform.

Simple modifications and variations of the present invention can be easily implemented by those skilled in the art, and all such variations and modifications are included in the scope of the present invention.

[Brief description of the drawings]

FIG. 1a shows a conventional photo mask.
FIG. 2 is a schematic view showing a method for irradiating a photo-alignment film with UV light by a ing method.

FIG. 1b is a perspective view showing a photo-alignment film irradiated with light by a photo-masking method.

FIG. 2a is a schematic view illustrating a method for irradiating a photo-alignment film with UV light by a scanning method according to the present invention.

FIG. 2b is a front view of the UV irradiation state of the photo-alignment film according to the scanning method of the present invention, showing a method using a fusion lamp and a mercury lamp.

FIG. 2c is a perspective view showing a photo-alignment film irradiated with light by the scanning method of the present invention.

3A is a schematic diagram illustrating the principle of linear UV irradiation by a disk-shaped cylindrical lens, and FIG. 3B is a schematic diagram illustrating the principle of linear UV irradiation by a rectangular cylindrical lens.

FIG. 4 shows an antiparallel (a) manufactured using two photo-aligned substrates.
FIG. 2 is a schematic diagram of an (antiparallel) liquid crystal cell.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 fusion lamp (or mercury lamp) 2 cylindrical lens 3, 3 'substrate 4 polarizing plate 5 photomask 6 liquid crystal layer 7 cell gap

Claims (5)

[Claims] 1. The method according to claim 1, further comprising: linearizing a focus of the ultraviolet beam from the light source, continuously moving the substrate coated with the photo-alignment material, or obliquely moving the linearized ultraviolet beam while moving the light source with respect to the substrate. A light irradiation method for generating a liquid crystal alignment having a uniform front tilt angle, wherein the light irradiation is performed from above. 2. The light irradiation method according to claim 1, wherein the linearized ultraviolet beam is generated by installing a cylindrical lens in the light source. 3. The light irradiation method according to claim 2, wherein the cylindrical lens has a disk shape or a rectangular shape. 4. The light irradiation method according to claim 1, wherein the linearized ultraviolet beam is irradiated on the substrate at an angle of 0 to 60 °. 5. The light irradiation method according to claim 1, wherein the light source is a fusion lamp, a mercury lamp, or a xenon lamp.