JPS6375701A - Reflection preventive film - Google Patents

Abstract

PURPOSE:To form an irregular surface which has sufficient strength and to prevent surface reflection by rotating a substrate around its perpendicular as an axis and performing slanting vapor deposition at many specific angles, and forming a film within a specific thickness range. CONSTITUTION:The film which prevents surface reflection on a cathode-ray tube, optical product, etc., is prevented from being easily peeled off. When the surface of the substrate is made rugged by vapor deposition so as to prevent the surface reflection, the angle theta of slanting vapor deposition is set to 50-70 deg., the substrate 1 is rotated around its perpendicular as an axis, and the vapor deposition is carried out in two or four directions. The vapor deposition may be carried while the substrate is rotated continuously, and the rotation and vapor deposition may be performed alternately to form a laminate in a specific direction. The overall film thickness should be 1,000-5,000Angstrom .

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to antireflection coatings.

[Conventional technology]

In cathode ray tubes, optical products, etc., it is necessary to prevent surface reflection, and this objective has conventionally been achieved by coating with multilayer films. However, as mentioned in the preface, in order to reduce the reflectance over a wide wavelength range, it is necessary to perform a multilayer coating of three or more layers, and the thickness of each layer must be formed with an accuracy of about ±20^. There must be. Therefore, the multilayer film coating method results in high costs and low throughput.

As a solution to these problems, US Patent No. 249066
As described in Publication No. 2, there is an etching method that utilizes a supersaturated aqueous solution of silica of hydrofluorosilicic acid. In this method, a glass substrate is immersed in the above aqueous solution to remove alkali metal oxides and the like from the glass surface, thereby forming a porous uneven surface on the glass surface. By forming the uneven surface in this way, the reflectance is reduced and the process is simple, resulting in low cost and high throughput.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not give consideration to film strength, and there is a problem in that the unevenness easily peels off.

An object of the present invention is to provide a method for forming an uneven surface having sufficient strength.

[Means for solving problems]

There is an oblique deposition method as a method for forming unevenness.

The oblique evaporation method is a method in which a normal vacuum evaporation method is performed by setting the substrate obliquely, and is known as a technique for forming irregularities for controlling the alignment of liquid crystal. However, there is no example of forming an antireflection film using this method.

In the present invention, first, the oblique evaporation method is carried out under conventionally known conditions (the angle between the perpendicular to the substrate and the direction of the evaporation source, hereinafter referred to as the oblique evaporation angle, is at least as high as possible). I tried, but
Although a reduction in reflectance was observed, the unevenness easily peeled off by rubbing with gauze, making it clear that it could not be put to practical use.

Therefore, we conducted studies under various conditions that are not commonly considered in conventional oblique evaporation methods, and found that the following method can reduce the reflectance and provide sufficient strength of the unevenness.

(1) Oblique evaporation angle angle: 75 degrees or more, evaporation film thickness: 1000
Oblique evaporation is performed at a temperature of ^ or more and 5000^ or less. In particular, the angle of oblique evaporation is greater than or equal to 75 degrees, and the thickness of the evaporated film is greater than or equal to 1000λ and less than 25 degrees.
00λ or less is suitable.

(2) The substrate is rotated about the perpendicular line of the substrate to perform oblique deposition from multiple directions. In this case, the vapor deposition may be performed while the substrate is continuously rotated, or the rotation and vapor deposition may be repeated alternately to stack vapor deposition from a specific direction. however,
The total film thickness should be within the range described in (1) above.

Although the method (1) described above alone can reduce the reflectance and provide sufficient strength of the unevenness, the combined use of (2) further improves the strength characteristics.

〔Example〕

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

Example 1 8L was placed on the glass substrate l in Fig. 1 at an angle of θ shown in the figure.
O@ is formed by a vacuum evaporation method. (However, the substrate temperature was about 250° C.) Table 1 shows the relationship between the oblique deposition angle θ, the deposited film thickness, the reflectance, and the film strength.

Reflectance was measured using an integrating sphere, and all scattered light was also measured. The film strength is measured by rubbing the uneven surface with an eraser to observe changes in the uneven surface, and the number of times the uneven surface peels off. As is clear from Table 1, the oblique deposition angle is 50 to 7.
Good values for both reflectance and film strength were obtained at a temperature of 5 degrees and a deposited film thickness of 1000-5000^. Especially oblique deposition angle 60~75
The effect is remarkable at a deposition film thickness of 100N500^.

Example 2 As shown in FIG. 2, the substrate is rotated about the perpendicular to the glass substrate 1, and vapor deposition is performed from two or four directions shown in FIG. The relationship between the oblique deposition angle θ, the deposited film thickness, the reflectance, and the film strength was investigated by comparing the cases of vapor deposition from two directions and four directions with the case of vapor deposition from one direction, and the obtained results are shown in Table 2. .

Better values for both reflectance and film strength were obtained by vapor deposition from two and four directions than from one direction.

In this example, data for only 2 and 4 directions were shown, but
The load is not limited to this example as long as it is deposited from multiple directions.

〔Effect of the invention〕

According to the present invention, an antireflection film with high film strength can be obtained at low cost and with high throughput, so that a cathode ray tube or the like with reduced surface reflection can be obtained at low cost.

Table 1 Oblique deposition conditions, reflectance, film strength 2) Number of eraser peels 3) Glass substrate only Note) N116, F, 8, 11, 12, 13 are the same conditions as Table 1 1) Average reflection at 450-650 nm Rate (from one side) 2) Number of times the eraser is removed

[Brief explanation of the drawing]

FIGS. 1 and 2 are configuration diagrams showing one embodiment of the present invention.

Claims (1)

[Claims] 1. The angle between the perpendicular to the substrate and the direction of the evaporation source is 50 degrees or more7.
An antireflection film characterized by having an uneven surface obtained by an oblique evaporation method, having a vapor deposition thickness of 1000 Å or more and 5000 Å or less.