JPH06118414A - Formation of oriented film for liquid crystal cell - Google Patents

Abstract

PURPOSE:To produce a liquid crystal cell having an oriented film of uniform thickness. CONSTITUTION:The relief 7 mounted on a blanket 3 is composed of a photosensitive resin, and columnar projecting parts are arranged on the relief 7, and the arrangement are arrayed in plural lines so that the center of gravity of each projecting part does not become orthogonal arrangement along a printing direction A like the projecting parts 8. The projecting parts8 are nearly hexagonal columns and arranged in turtleback-like. Or the ellipsoidal projecting part 8 is arranged alternately deviated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an alignment film for a liquid crystal cell.

[0002]

2. Description of the Related Art Recently, TN type liquid crystal cells and STN type liquid crystal cells have been widely used. However, in these liquid crystal cells, a large number of transparent conductive films are arranged on a glass substrate. Further, the transparent conductive film is coated with an alignment film such as a polyimide resin, and the surface of the alignment film is subjected to rubbing treatment, so that liquid crystal molecules can be aligned in a fixed direction.

This alignment film is generally formed by using an offset printing machine or a flexographic printing machine, and this printing machine is as shown in FIG.

In the figure, 1 is a flat base, 2 is a substrate (for example, a transparent substrate made of glass, etc.) arranged on the base, 3 is a blanket, and the blanket 3 should be printed on the peripheral surface thereof. A relief plate 5 having protrusions 4 corresponding to the pattern shape of the alignment film resin is arranged. The ink material for the orientation film having a viscosity of 10 to 1000 cps is held between the convex portions 4 of the relief plate 5, and the relief plate 5 is elastically deformed by the printing pressure with the substrate 2 as the blanket 3 rotates. The ink material for the alignment film is printed on the substrate 2 while forming a constant contact area, and the printing layer 6 is formed. Then, the printed layer 6 is heated to form an alignment film.

[0005]

However, the alignment film formed by the above-mentioned forming method has a uniform film thickness which can meet the recent demands for larger size, higher definition and higher quality of liquid crystal display devices. However, the improvement was desired.

[0006]

A method of forming an alignment film for a liquid crystal cell according to the present invention is a method of forming a substrate by using an offset printing machine or a flexographic printing machine in which a relief plate having a plurality of convex portions arranged on a blanket is arranged. In forming the alignment film on the upper surface, the plurality of convex portions are arranged in a plurality of rows along the printing direction of the printing machine so that the centers of gravity of the convex portions are not orthogonal.

[0007]

FIG. 4 is a schematic view showing an offset printing machine or a flexographic printing machine in the method of forming an alignment film for a liquid crystal cell of the present invention, and the same parts as those in FIG. 8 are designated by the same reference numerals.

As shown in FIG. 1, the relief plate 7 mounted on the blanket 3 is made of a photosensitive resin, and the relief plate 7 has columnar protrusions arranged therein. The arrangement is the black portion in FIG. 1 or FIG. Like the convex portion 8 indicated by, the plurality of columns are arranged along the printing direction A so that the centers of gravity of the respective convex portions are not in the orthogonal arrangement. In FIG. 1, the convex portions 8 having a substantially hexagonal prism shape are arranged in a hexagonal shape, and in FIG. 2, the convex portions 8 having an elliptic cylinder shape are arranged while being alternately displaced. The thickness is 10 to 100 μm. On the other hand, FIG. 3 shows a conventional relief plate 5, in which cylindrical protrusions 4 shown by black portions are arranged in a grid pattern, and the halftone dot pattern is 20.
0-400 mesh, its depth is 10-100 microns.

Next, the pressure distribution in the contact area between the relief plates 5 and 7 and the substrate 2 will be described with reference to FIG. According to the figure, a contact area B having a constant area is formed between the letterpress plates 5 and 7 and the substrate 2, and the pressure distribution of the contact area B is shown on the lower side of the figure. As shown in this pressure distribution diagram, the maximum pressure is located at the center, and such pressure causes the relief plates 5 and 7 to deform by 0.1 to 0.3 mm, and the blanket 3 rotates and moves with this deformation. A force that pushes the ink held in the grooves of the convex portions 4 and 8 along the moving direction of the blanket 3, that is, the printing direction A is applied.

As a result, according to the conventional offset printing machine, as shown in FIG. 6, the ink held in the groove portion of the convex portion 4 is extruded along the printing direction A, and the ink is printed as compared with the printing start portion. Although the amount of ink increases over the end portion, which makes the thickness of the printing layer 6 uneven, according to the offset printing of the present invention, as shown in FIG. 7, the ink is retained in the groove portion of the convex portion 8. Even if the ejected ink is about to be pushed out in the printing direction, the convex portions 8 are arranged in a plurality of rows along the printing direction so that the centers of gravity of the respective convex portions are not arranged in an orthogonal arrangement, so that the flow is prevented. As a result, the printed layer 6 has a uniform thickness. The arrow C in FIG. 6 and the arrow D in FIG. 7 indicate the ink flowing directions, respectively.

According to an experiment conducted by the present inventors, a relief plate 7 made of a photosensitive resin having hexagonal prismatic protrusions 8 shown in FIG. 1 arranged in a hexagonal pattern at intervals of 300 per inch is manufactured. Printing pressure so that the maximum deformation amount of 7 is 0.1-0.3 mm,
When the blanket 3 was printed at a rotating peripheral speed of 180 mm / sec, the film thickness accuracy was remarkably improved. Regarding this film thickness accuracy, when the range of in-plane film thickness variation was obtained when the printed film thickness was 1000Å, the accuracy was 5%. Further, also in the case of the convex portion 8 in FIG. 2, similarly excellent film thickness accuracy was obtained. On the other hand, conventionally, the film thickness is non-uniform in about 10%.

[0012]

As described above, according to the method for forming an alignment film for a liquid crystal cell of the present invention, when the alignment film is formed on the substrate by offset printing or flexographic printing, the relief plate has a plurality of protrusions in the printing direction. Since the center of gravity of each protrusion is arranged in multiple rows along the line, even if the ink held in the groove of the protrusion is pushed out in the printing direction, the flow is blocked. As a result, a printed layer having a uniform thickness can be formed. As a result, according to the liquid crystal cell including the alignment film obtained by heating the printed layer, the response uniformity to the applied voltage is remarkable. I was able to improve.

[Brief description of drawings]

FIG. 1 is a schematic view showing an array of convex portions according to the present invention.

FIG. 2 is a schematic view showing an array of convex portions according to the present invention.

FIG. 3 is a schematic diagram showing an arrangement of conventional convex portions.

FIG. 4 is a schematic diagram showing offset printing or flexographic printing in the present invention.

FIG. 5 is a pressure distribution diagram in a contact region between a relief printing plate and a substrate.

FIG. 6 is a schematic view showing the flow of ink held in the relief groove portion of the present invention.

FIG. 7 is a schematic diagram showing a flow of ink held in a conventional relief groove portion.

FIG. 8 is a schematic view of an offset printing machine.

[Explanation of symbols]

 2 ... Substrate 3 ... Blanket 5, 7 ... Relief plate 4, 8 ... Convex portion 6 ... Printing layer

Claims (1)

[Claims] 1. A method for forming an alignment film for a liquid crystal cell, which comprises forming an alignment film on a substrate by an offset printing machine or a flexographic printing machine in which a relief printing plate having a plurality of projections arranged on a blanket is arranged. A method for forming an alignment film for a liquid crystal cell, wherein the plurality of convex portions are arranged in a plurality of rows along the printing direction of the printing machine so that the centers of gravity of the convex portions are not orthogonally arranged.