JPS6213604B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to provide a scale or reticle on a glass plate that has little surface reflection of light, is hard and durable, and is formed with high precision.

Graduation lines, dots, symbols formed on glass plates,
It is desirable for letters, numbers, and reticles to have high light-shielding properties and to minimize reflection on their surfaces. No matter how much the light shielding property is improved, if the surface reflection is large, the visibility effect as a scale will be reduced. In order to improve light shielding properties, it is generally necessary to increase the thickness of the film that forms the scale lines, dots, symbols, letters, numbers, etc., but the fine width scale elements formed by such means cannot be It becomes extremely vulnerable to force, such as wiping, and problems arise in processing, so in order to exhibit high light-shielding properties while maintaining strong durability against external forces, it is necessary to make the material's light-shielding properties less dependent on the film thickness. However, unless the material selected here has extremely low reflectance on the surface of the scale element, the visibility will deteriorate, especially in relatively dark areas. There may even be cases where the desired function as a scale or reticle cannot be fully demonstrated in the manner in which it is used in some places. For such a scale or reticle on a glass substrate, it is desirable to have a thin film layer that has a high light-shielding property, a low light reflectance on the surface, high hardness, and excellent durability. The ideal is to use a material that is easy to process, but it is difficult to satisfy all of these conditions with a single material, so in the past, multiple materials were used to achieve the objective. .

From a processing point of view, when forming scales or reticles on the glass surface, industrially, vacuum-deposited metal thin films are usually used, taking into consideration accuracy, durability, workability, cost, etc. has been widely used. The metal materials used here are:
Since durable strength is required as a top priority when used as a product, chromium or chromium alloys have been used unless other special requirements must be met. However, the use of chrome or an alloy containing chrome as its main component has excellent light-shielding properties and is extremely superior in terms of accuracy and durability, as well as productivity, including workability and cost. The drawback is that the reflection on the front and back surfaces is extremely high, and it is not possible to satisfy all of the above requirements by itself. As a means to reduce the surface reflection of scales, reticles, etc. formed for this purpose, for example, as disclosed in the Utility Model Application Publication Publication No. 1982-1990, a single layer coating of a transparent dielectric material is applied thereon. A method was taken. In this method, two steps are required as long as the chemical etching process that is generally used is disadvantageous in terms of productivity.

The problem of surface reflection in scales or reticles is not only the simple problem of poor visibility, but also the fact that the high reflectance poses a major obstacle to forming fine patterns with high precision. Therefore, keeping the surface reflectance low is an extremely important problem to be solved when forming these types of scales and reticles on glass plates. Focusing on the problem of surface reflectance, instead of using metallic chromium or a metal alloy mainly composed of chromium as mentioned above, there is a method of forming a coating with metal oxide, which can significantly reduce surface reflection. However, when metal oxides are used as scales or reticles, a certain film thickness is required to obtain sufficient optical density, that is, high light-shielding properties in the visible range. For example, if chromic oxide (Cr ₂ O ₃ ) is used, at least
A film thickness of 10,000 Å or more is required, which not only significantly reduces workability but also impairs processing accuracy itself. There are other printing methods such as silk screen printing, but they have inherent functional limitations that limit their scope of use to a very narrow range and lack wide-ranging applicability, so this has not been a problem.

Focusing on the above points, the present invention provides an optical product in which scales or reticles with extremely low light transmittance and surface reflectance are formed on a glass plate due to a multilayer structure. (1) The formation of multiple layers can be performed using the same technology in the same vacuum chamber, and (2) the case where the layers are deposited on a glass plate by vacuum evaporation and then chemically etched is considered. (3) Each film layer formed in multiple layers is made as thin as possible, and the etching process (4) In addition, the process was designed to be efficient and short-term, and also to reveal a fine pattern. In addition, consideration was given to optically solving the problem of refractive index.

In order to comprehensively achieve each of these objectives, the light-shielding thin film formed on the glass substrate is made of vapor-deposited metallic chromium or a chromium alloy mainly composed of chromium, and the anti-reflection coating of the light-shielding thin film is For example, chromic oxide was used. As a chromium alloy containing chromium as a main component, an alloy consisting of chromium and nickel gives preferable results, and in this case, it is desirable that the ratio thereof be up to about 4:1.

Metallic chromium and alloys based on it, such as chrome-nickel alloys, have a high light-shielding property even though they are thin layers. Figure 1A is a characteristic diagram showing the light transmittance of a metallic chromium thin film. The targets are light with a wavelength of λ = 700 nm (normally seen as red light), which is considered to be the limit of the long wavelength of visible light, and each of them passes through a metallic chrome film from the air and passes through the glass. The vertical axis represents the transmittance toward the substrate, and the horizontal axis represents the thickness of the chrome metal film. As is clear from this figure, the chrome metal film has a thickness of 200 Å or more.
The transmittance is less than 10%, and in practical terms it is 400Å to 600Å.
It has been recognized that a film thickness of about 1.5 Å exhibits almost sufficient light-shielding function, and the light-shielding property of the dichromium oxide thin film of the anti-reflection film that is covered on top of this film (its own light-shielding function is extremely low) If it is of similar thickness and exhibits the required low surface reflection function (as described above), almost complete blocking of visible light is achieved.

In Figure 1B, chromium is used as a chromium alloy.
The characteristics of light transmittance provided by a deposited film on a glass substrate using an alloy with a nickel ratio of 4:1 are shown.
In the case of a chromium-nickel alloy, the light-shielding property is somewhat inferior to that of a vapor-deposited film of chromium alone, but the light shielding property is 700Å.
It is clear that a film with a thickness of about 900 Å can provide a practically sufficient light-shielding function, and this is even more so than with a single-layer film composed of only dichromic oxide. It has more than 10 times the light-shielding properties, so even if a thin film of chromic oxide, which is necessary to exhibit the anti-reflection function, is deposited on top of this, the total thickness is only that of a single layer of chromic oxide. The thickness is still only about a fraction of the thickness of the case.

According to such a multilayer structure, first, a film thickness of 1/8 to 1/10 of that of a single layer of chromic oxide can achieve the same level of light-shielding properties and a better antireflection effect. As a result, it is possible to express minute patterns on scales or reticles, and the same type of technology can be applied continuously in the same vacuum. Optical products in which scales or reticles of the present invention are formed on a glass plate will be described in detail below using several examples.

Embodiment 1 FIG. 2a shows a front view of a glass scale plate of the present invention, and FIG. 2b shows an enlarged view of a part of the scale plate. 11 in the figure is normal BK-7 with a refractive index of 1.52.
On this substrate, a metallic chromium film is formed using a normal vacuum evaporation method, and then a chromic oxide film is formed using a similar method in the same vacuum, and then etched using a chemical etching method. This is what I did. The thickness of each film layer in this case is as follows.

Metallic chromium film 21...665 Å Second chromium oxide film 31...520 Å Figure 2c shows the spectral reflectance characteristics given by the scale surface of the scale plate in the visible light region in this example. be. The solid line in the figure shows the surface reflectance characteristics of metallic chromium whose reflection is prevented by the second chromium oxide film 31, and the dashed line shows the glass substrate 11.
The surface reflectance characteristics are shown when only the metal chromium film 21 is deposited thereon.

Embodiment 2 FIGS. 3a and 3b show another embodiment of the present invention, in which a reticle is formed on a glass substrate. Third
Figure a is a front view thereof, and Figure 3b is a partially enlarged cross-sectional view. A chromium alloy (chromium to nickel ratio 4:1) was vacuum-deposited on the glass substrate 12 by a conventional method, and chromic oxide was further deposited in the same deposition process, and the same chemical etching process as in Example 1 was applied to form a reticle. formed. In FIGS. 3a and 3b, the reference numeral 22 indicates a chromium alloy film, and the reference numeral 32 indicates a second chromium oxide film, which is an antireflection film formed to cover the surface thereof. The surface reflection characteristics of this example are shown in FIG. 3c. In this case, chrome alloy (chrome
The thicknesses of the nickel alloy film 22 and the second chromium oxide film 32 covering it are as follows.

Chromium alloy film 22...795 Å Second chromium oxide film 32...450 Å In Fig. 3c, the solid line indicates the surface reflectance characteristics of the chromium alloy whose reflection is prevented by the second chromium oxide film 32 under the visible light region. The dashed line shows the state in which the chromium alloy film 22 is deposited on the glass substrate 12.

Example 3 In the example shown in FIGS. 4a and 4b, in order to further improve the reflection on the scale surface of the scale plate formed in Example 1, a dielectric three-layer anti-reflection coating was applied by vacuum deposition. A glass scale plate formed and etched using the RF sputter etching method is shown. FIG. 4a is a front view thereof, and FIG. 4b is an enlarged view of a portion thereof. In the figure, 11 is a glass substrate, 21 is a metal chromium film, 31 is a chromic oxide film, and 41 is a magnesium fluoride film. The film 51 interposed between the magnesium fluoride films 41 is a cerium fluoride film. The thickness of each film layer in this case is as follows.

1st layer Metallic chromium film 21...665 Å 2nd layer Second chromium oxide film 31...520 Å 3rd layer Magnesium fluoride film 41...905 Å 4th layer Cerium fluoride film 51...780 Å 5th layer Magnesium fluoride Film 41...905Å The spectral reflectance of the scale surface according to this example is the fourth
The characteristics shown by a solid line in FIG.

In this example, magnesium fluoride 41,
A cerium fluoride film 51 is interposed between the film layers of 41, but aluminum oxide (n≒1.6) or silicon oxide (n≒1.47) having a refractive index close to this film 51 is used instead of the cerium fluoride film 51. Almost the same antireflection effect can be expected. Also, in this example,
Although the etching process was performed using the RF sputter etching method, a transparent dielectric multilayer film may be directly formed by sequential vapor deposition on the product etched according to Example 1. In this case, the product of Example 1 that has undergone etching processing has the disadvantage that the light transmittance of the transparent part of the substrate is somewhat reduced and the number of work steps is increased by one step, but chemical etching is easy in terms of equipment and work. It has the advantage of being able to be processed using this method.

As mentioned above, the optical products such as the scale plate and reticle of the present invention have a thin layer with sufficient light shielding properties and a scale that includes scale lines, dots, letters, symbols, and numbers with low surface reflection. are mounted on a glass plate,
Therefore, these can be revealed with extremely fine pattern configurations, and not only can durability be kept high, but also from the viewpoint of productivity, metal chromium or alloys mainly composed of chromium can be used. The film used to provide a light-shielding layer and reduce surface reflection is also made of the same metal chromium oxide and is deposited continuously, so it has a high mutual affinity and can be continuously deposited using the same deposition space. This makes it possible to use a common etching solution even in subsequent processing using chemical etching.

On the other hand, it is difficult to prevent reflection by depositing the transparent dielectric film directly on a film of metallic chromium or chromium alloy due to the refractive index. Since a second chromium oxide film having excellent anti-reflection conditions is deposited on the deposited film made of the alloy, more efficient surface anti-reflection can be achieved. Furthermore, in order to further enhance the antireflection effect, it is easy to overlay a transparent dielectric film (single layer or multilayer) as an antireflection film on this dichromic oxide film, and in order to fully demonstrate its function. It will be extremely effective.

In the above examples, the products obtained by directly depositing metal chromium or its alloy on a glass substrate were described; The explanation is limited to many actual examples based on the premise that scales are visible from the sides, and the present invention is applicable to optical equipment where scales need to be visually recognized from both sides of a glass substrate. In order to deal with ghost images, flare, and other undesirable optical disturbances in the optical system due to reflection of light incident from the opposite side of the glass substrate on the metal chrome film or chrome alloy film on the glass substrate, A chromic oxide film is deposited on a glass substrate to prevent reflection on the back surface of the metal, a metallic chromium film or a chromium alloy is deposited on top of this, a chromic oxide film is formed on this, and a transparent dielectric is further formed. It should be understood that this does not preclude implementation of embodiments in which the membranes are layered.

[Brief explanation of the drawing]

Figure 1A is a characteristic diagram showing the relationship between the optical transmittance and film thickness of metallic chromium used in the present invention, and Figure 2A is a characteristic diagram showing the relationship between the optical transmittance and film thickness of the chromium alloy used in the present invention. Characteristic diagrams showing the relationship, FIGS. 2a and b, show one embodiment of the present invention,
FIG. 2a shows a front view of the scale plate, and FIG. 2b shows a partially enlarged vertical cross-sectional view. FIG. 2c is an actual measurement diagram showing the light reflection characteristics of the products shown in FIGS. 2a and 2b. 3a and 3b show another embodiment of the present invention, in which FIG. 3a shows a front view of the reticle, and FIG. 3b shows an enlarged view of a portion of the reticle. FIG. 3c is an actual measurement diagram showing the spectral reflection characteristics of this example. Figures 4a and 4b show an example in which a dielectric multilayer film is further deposited on the embodiment shown in Figures 2a and 2b. Figure 4a is a front view, and Figure 4b is a part of it. It is a longitudinally enlarged view of Figure 4c.
is an actual measurement diagram showing spectral reflection characteristics in this example. 11...Glass substrate, 21...Metal chrome film,
31...Second chromium oxide film, 12...Glass substrate, 22...Metal chromium film, 32...Second oxidation
Chrome film, 41... Magnesium fluoride film, 51
...Cerium fluoride membrane.

Claims (1)

[Scope of Claims] 1. A light-shielding thin film made of metallic chromium or a chromium alloy mainly composed of chromium metal formed by vacuum deposition on a glass substrate, and a chromic oxide thin film as the metal antireflection film. An optical product that has a scale or reticle formed on a glass substrate by etching it. 2. On a glass substrate, a light-shielding thin film made of metallic chromium or a chromium alloy mainly composed of metallic chromium formed by vacuum evaporation and a chromic oxide thin film as the metal antireflection film are provided. An optical product that uses the refractive index of a thin film to form scales or reticles on a glass substrate by layering a single or multiple layers of transparent dielectric on top of the thin film and etching it.