JPH05100291A - Focusing screen and production of matrix thereof - Google Patents

Abstract

PURPOSE:To obtain the focusing screen which has adequate lightness and can provide good out-of-focus when a finder image is formed and the process for production the matrix thereof. CONSTITUTION:A lower layer 3 having a latent rugged relief to be developed by heating is previously provided on a substrate 2, then a photosensitive layer 5 is formed thereon and is exposed via a mask 6 having fine patterns 1 of the pitch and diameter different from the pitch and diameter of the latent rugged relief patterns and is subjected to development processing to form the rugged relief; thereafter, the latent rugged relief of the lower layer is developed by heat development to form the double relief patterns on the substrate. A mold is produced by using such patterns as the matrix and further, the focusing screen is molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focusing screen provided on a focusing plate of a single-lens reflex camera or the like and a method for producing a focusing screen mother die used for manufacturing the focusing screen.

[0002]

2. Description of the Related Art Conventionally, as a focusing screen, a screen having an optical material such as an acrylic plate on which a diffusing relief having sharp irregularities having an irregular cross section is formed is widely used. As a method of manufacturing this focusing screen, a method of transferring a surface of a metal plate sanded onto a plate-shaped optical material is used as a mold.

However, most of the irregularities of the mold obtained by sanding are formed to have a pointed shape. Therefore, the focusing screen manufactured by transferring the uneven portion has a defect that incident light is bent at a steep angle, an image obtained through a finder has low brightness, and graininess is conspicuous.

In order to overcome this drawback, a method for recording a laser speckle pattern on a photosensitive material or a method for recording a regular fine pattern on a photosensitive material by projection exposure using a mask and then developing the mother pattern for a focusing screen is used. A method has been proposed in which a molding die is manufactured by transferring the fine pattern of the mother die by electroforming, and various plastic optical materials including acrylic resin are molded using the molding die.

However, in this method, since the light diffusion surface has a regular fine structure arrangement, a diffraction phenomenon occurs and an interference color appears. Further, since the diffused light shows a regular spectrum, a blurred image becomes unnatural, and there is a drawback that natural blurring such as a focusing screen of a sanding mat cannot be produced.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art and has an appropriate brightness when a finder image is formed,
An object of the present invention is to provide a focusing screen capable of achieving good blurring and a method for producing a master mold thereof.

[0007]

The present invention achieves the above object by adding irregularity to a fine structure array by forming two different relief patterns on a substrate in an overlapping manner. That is, the method for producing a master mold for a focusing screen according to the present invention is a focusing screen in which a photosensitive layer is formed on a substrate, a regular fine pattern formed on a mask is exposed, and then development processing is performed to form an uneven portion. In the method for producing a master mold, an underlayer having a latent uneven relief developed by heating is provided between the substrate and the photosensitive layer, and the photosensitive layer is provided with an uneven relief different from the latent uneven relief. After forming, the latent relief of the underlying layer is developed by heat development to form a double relief pattern on the substrate.

In the present invention, the method for providing the lower layer having a latent uneven relief developed by heating between the substrate and the photosensitive layer is not particularly limited, but for example, glass or metal may be used. First, a layer containing a polymer having a reactive group and a dopant component which is immobilized by reacting with the reactive group by irradiation of light is formed on a substrate composed of the polymer, and the layer is formed through a mask having a fine pattern. There is a method of exposing. At this time, the amount of the fixed dopant component varies depending on the intensity distribution of the transmitted light, and a latent uneven relief is formed inside the layer.

As the above-mentioned polymer having a reactive group,
Epoxy groups, non-conjugated double bond-containing groups, for example, 2-propenyl group, acrylate-based or methacrylate-based polymer having at least one of 2-butenyl group and the like, and more specifically, for example, , Glycidyl methacrylate, 2-propenyl methacrylate or 2-
Examples thereof include a homopolymer of butenyl methacrylate or a copolymer of methacrylic acid alkyl ester and / or acrylic acid alkyl ester with glycidyl methacrylate, 2-propenyl methacrylate or 2-butenyl methacrylate.

The dopant component is not particularly limited as long as it reacts with a polymer having a reactive group by irradiation with light and vaporizes by heating in an unreacted state, and examples thereof include cinnamic acid and aromatic compounds. Group ketones such as benzophenone, 3-benzoylbenzophenone, and the like. The dopant component is selected in consideration of the reactivity with the reactive group of the polymer. For example, the polymer is a copolymer of alkyl methacrylate and glycidyl methacrylate (having an epoxy group as a reactive group). Resin), it is preferable to use cinnamic acid as a dopant.

In the method of the present invention, the dopant component is contained in an amount of 0.5 to 1.5 equivalents based on the reactive groups contained in the polymer. If the amount of the dopant component is too small, the unevenness of the uneven relief obtained by heat development will be low, and the effect of adding this component will be insufficient. Further, when the amount of the dopant component is too large, there are disadvantages that the heat development requires a long time and the heat development does not proceed sufficiently.

If necessary, a photosensitizer and the like may be added to the lower layer provided on the substrate together with the polymer having a reactive group and the dopant component. 2-Isopropylthioxanthone or the like can be used as the photosensitizer.

The lower layer is formed by fluidizing the above-mentioned various components using a solvent, if necessary, and then coating and drying on the substrate by an arbitrary method such as a spin coating method, a spray coating method or a roll coating method. Formed by. The layer thickness can be adjusted by the component ratio and concentration of the coating liquid, the coating conditions, and the like, and can be appropriately selected depending on the properties as the final focusing screen, etc., but normally the dry thickness is 0.5 to 6 μm. , Preferably 2 to 4 μm.
If this layer thickness is less than 0.5 μm, the effect of double relief becomes insufficient, and if it exceeds 6 μm, the fixing of the dopant component by light cannot be achieved to the lower layer portion, and the shape due to heat development becomes unstable. Become.

After providing the lower layer as described above, exposure is performed through a photomask having a fine pattern. At that time, the shape of the latent uneven relief to be formed can be changed by changing the distance Δt ₁ between the layer and the mask to a predetermined value and performing the exposure. When the layer and the mask are brought into close contact with each other and exposed with the distance Δt _{1 set} to substantially 0, a latent relief pattern in which the shape of the fine pattern is accurately transferred is formed. However, in the present invention, it is preferable to appropriately select the distance Δt ₁ so that the latent uneven relief is a continuous gentle curve. The preferred distance Δt ₁ is usually
It is 10 to 50 μm.

In the method of the present invention, a lower layer having a latent relief is provided on a substrate as described above, and then a photosensitive layer made of various photosensitive materials such as photoresist is formed thereon. .. This photosensitive layer can be formed by applying a photosensitive material by a known method, for example, an arbitrary method such as a spin coating method, a spray coating method, or a roll coating method, and then drying it. The dry thickness of the photosensitive layer is 1 to 6 μm, preferably 3 to 4 μm. When the thickness is less than 1 μm, the light scattering effect of the uneven relief formed is insufficient, and the light passing through this layer affects the shape of the lower layer. On the other hand, when it exceeds 6 μm, the sublimation of the dopant component contained in the lower layer is insufficient, and the latent uneven relief is not sufficiently achieved.

Then, the photosensitive layer is exposed and developed by a conventional method through a photomask having a fine pattern. At this time, it is preferable to use a strip photomask having a pattern different from that used for the formation of the latent uneven relief. That is, in the case of a dot-shaped fine pattern, fine patterns having different pitches and diameters are used. The pitch and diameter of the fine pattern photomask can be arbitrarily selected according to the property of the final focusing screen, but it is selected in consideration of the combination with the one used when forming the potential relief. Is preferred. More specifically, it is preferable to use a photomask having a fine pattern having a smaller pitch and diameter than that used for forming the latent relief.

Further, in order to obtain a natural blurred image, it is necessary to appropriately select the distance Δt ₂ between the photosensitive layer and the mask upon exposure so that the relief pattern formed by development draws a continuous continuous curve. Is. Preferred distance Δt ₂
Is usually about 10 to 30 μm.

Further, the exposure is preferably carried out with an exposure amount such that light is transmitted only to the upper photosensitive layer and not to the lower photosensitive layer. Development can be performed by a known method.

After the uneven relief is formed on the surface layer by the development as described above, in the present invention, the unreacted dopant component is vaporized and removed to the outside of the layer to reveal the latent uneven relief of the lower layer. Let The heating temperature can be appropriately determined depending on the vaporization temperature of the used dopant component, but it is preferable to perform heating under vacuum conditions in order to promote removal of the dopant component out of the layer. As a result, a master for a focusing screen is obtained, in which two types of relief patterns of the concavo-convex pattern are overlapped on the substrate.

The molding die for a focusing screen thus produced is transferred by an electroforming method to produce a forming die, which can be used to produce a focusing screen in which irregularities of the die are accurately reflected.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the drawings on the basis of an embodiment of a method for producing a focusing screen mother die according to the present invention, but the present invention is not limited to these illustrated examples. Not something.

FIG. 1 is an explanatory view schematically showing a process of producing a focusing screen mother die of the present invention.
FIG. 2 is a plan view of a main part of a photomask having a fine pattern used at that time. In addition, in (A) to (F) of FIG. 1, each component is shown in a schematic cross-sectional view.

First, the photomask used in this embodiment will be briefly described with reference to FIG. The photomask 6 used in this embodiment has a dot-shaped fine pattern 1 made of chromium on a glass plate and has a pitch P.
And two types having different diameters. One of them is 5
One having a pitch P of about 0 to 100 μm and a diameter of about 25 to 50 μm (for exposing the lower layer), the other one is 15
It had a pitch P of about 20 μm and a diameter of about 10 to 16 μm (for photoresist exposure).

FIG. 1A shows a step of forming a lower layer 3 for forming a latent relief on the substrate 2. The lower layer 3 is a 1: 1 copolymer of methyl methacrylate and glycidyl methacrylate (weight average molecular weight 800,00).
0) 2.5 g and 1.5 g of cinnamic acid dissolved in 100 ml of 1,4-dioxane (solvent) were applied and dried to have a thickness of about 3 μm.

Next, as shown in FIG. 1B, a photomask 6 is arranged above the lower layer 3 at a distance Δt ₁ , and ultraviolet rays 4 are emitted.
By irradiating with, the latent uneven relief corresponding to the ultraviolet intensity distribution was formed inside the lower layer 3. That is, in the portion irradiated with ultraviolet rays, the cinnamic acid present in the lower layer 3 reacts with the glycidyl group of the above-mentioned copolymer and is chemically bonded to be immobilized. Since the intensity of the irradiated ultraviolet rays passes through the photomask to generate an intensity distribution, the amount of cinnamic acid corresponding to the intensity distribution is fixed, and the distribution of the amount of cinnamic acid fixed corresponding to the pattern of the photomask is fixed. It is formed inside the layer.

Further, the distance Δt ₁ between the photomask 6 and the lower layer 3 affects the ultraviolet intensity distribution, and the larger Δt ₁ causes the contour of the image of the photomask to be blurred by the diffracted light.
In this embodiment, Δt _{1 is set} to about 30 μm.
The intensity distribution is such that a smoothly changing curve as shown by the broken line in (B) is drawn.

Next, as shown in FIG. 1C, a positive photoresist generally used in photolithography or the like was applied by spin coating to form a photosensitive layer 5 having a thickness of about 3 μm.

FIG. 1D shows a step of disposing a photomask 6 on the photosensitive layer 5 and performing pattern exposure. Also here, the distance Δt between the photomask 6 and the photosensitive layer 5 is
₂ affects the relief shape formed. In this example, the exposure was performed with the distance Δt _{2 set} to about 20 μm.

After that, development processing is carried out by a conventional method, and FIG.
An uneven portion as shown in (E) is formed. The uneven portion obtained at this time is a simple uneven relief surface, but if it is subsequently heated in vacuum (1 torr) at 100 ° C. for 2 hours, unreacted and unfixed cinnamic acid is vaporized to form a layer. Removed outside. As a result, the substance decreases in accordance with the vaporized amount of cinnamic acid, so that the uneven relief latent in the lower layer 3 is developed, and a double relief pattern as shown in FIG. 1 (F) is formed. ..

After obtaining a molding die using the mother die obtained by this method, molding of an optical material similar to the conventional one was carried out. As a result, a bright focusing screen having excellent diffusivity and no graininess was produced. I was able to.

In the above examples, the case where a copolymer of methyl methacrylate and glycidyl methacrylate is used as the lower layer polymer, cinnamic acid is used as the dopant component, and a positive resist material is used as the photosensitive material has been described. The present invention is not limited to this, and even if other homopolymers or copolymers or other dopant components are used,
Alternatively, even if a negative resist material is used, good results can be obtained as in the above embodiment.

[0032]

According to the method of the present invention, a master for a focusing screen having a double relief pattern can be easily manufactured by an optical method. This matrix has an uneven relief pattern that draws a continuous gentle curve, and since two types of patterns are formed in an overlapping manner, irregularity is added. Therefore, by using the focusing screen mother die obtained by the method of the present invention, excellent focusing which can eliminate the graininess without impairing the brightness and diffuse light efficiently with a good blur effect. The screen can be manufactured simply and easily.

[Brief description of drawings]

FIG. 1 is an explanatory view showing each step of a method for producing a focusing screen mother die of the present invention.

FIG. 2 is a plan view of a main part of a photomask used in the method of the present invention.

[Explanation of symbols] 1 dot-shaped fine pattern 2 substrate 3 lower layer 4 ultraviolet ray 5 photosensitive layer 6 photomask

Claims (8)

[Claims] 1. A method of manufacturing a master die for a focusing screen, comprising: forming a photosensitive layer on a substrate; exposing a regular fine pattern formed on a mask; A lower layer having a latent uneven relief that is developed by heating is provided between the photosensitive layer, and after forming an uneven relief different from the latent uneven relief in the photosensitive layer, the lower layer is formed by heat development. A method for producing a master die for a focusing screen, which comprises forming a latent relief pattern and forming a double relief pattern on a substrate. 2. The lower layer is obtained by exposing through a mask a photosensitive layer containing a polymer having a reactive group and a dopant component which is immobilized by reacting with the reactive group by irradiation of light. Item 2. A method for producing a focusing screen mother die according to Item 1. 3. The mother for a focusing screen according to claim 2, wherein the polymer having a reactive group is an acrylate or methacrylate polymer having at least one of an epoxy group and a non-conjugated double bond-containing group. Mold making method. 4. The polymer having a reactive group is glycidyl methacrylate, 2-propenyl methacrylate or 2-
The mother for a focusing screen according to claim 3, which is a homopolymer of butenyl methacrylate or a copolymer of alkyl methacrylate and / or alkyl acrylate and glycidyl methacrylate, 2-propenyl methacrylate or 2-butenyl methacrylate. Mold making method. 5. The mother for a focusing screen according to claim 2, wherein the dopant component reacts with a reactive group of the polymer upon irradiation with light, is unreacted in a portion not exposed to light and is vaporized by heating. Mold making method. 6. The method for producing a master die for a focusing screen according to claim 5, wherein the dopant component is cinnamic acid or an aromatic ketone. 7. The method for producing a master die for a focusing screen according to claim 1, wherein a double relief pattern is formed by using two kinds of masks having fine dot patterns having different pitches and diameters. 8. A molding die is produced by transferring the concavo-convex shape of the mother die produced by the method according to claim 1 by electroforming.
A method for producing a focusing screen, which comprises molding an optical material using this molding die.