JPH08286589A - Multilayered hologram recording material - Google Patents

Abstract

PURPOSE: To obtain a multilayered hologram recording body having such a layer structure that the interference fringes do not change even when the recording body is heated. CONSTITUTION: In the multilayered hologram recording body having a hologram recording layer in the layers, the outermost layers A, B on both sides of the hologram recording layer 2 have almost the same coeffts. of linear expansion. When the hologram body is heated to process the hologram recording layer 2 or even when thermal variation is given due to thermal changes in the environment during the hologram recording body is used, both sides of the recording body produce deformation by almost the same rate on the hologram recording layer 2 so that the inclination of the holographic interference fringes in the hologram recording layer 2 does not change. Thus, a multilayered hologram recording body having good optical characteristics and heat resistance can be obtd., and the obtd. recording body can be used for various kinds of hologram optical elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer hologram recording body, and more particularly to a multilayer hologram recording body having a hologram recording layer such as a photopolymer whose interference fringes easily change due to stress from other layers.

[0002]

2. Description of the Related Art Conventionally, various hologram optical elements (HOE) using a volume phase hologram are shown in FIG.
As shown in the cross-sectional layer in FIG. 1, a hologram recording layer 2 made of photopolymer, dichromated gelatin or the like is provided on a substrate 1 made of glass or the like, and inexpensive PET having good optical characteristics and durability.
A fringe pattern of a hologram is recorded by exposure on a hologram recording body formed by laminating a cover film including the film 3 and the like, and then heat treatment is performed to create the hologram.

[0003]

By the way, in the case of using, for example, a photopolymer as the hologram recording layer 2 of such an HOE, the stretched PET (which is used as the cover film when heating for the amplification of the refractive index difference after exposure is used). Polyethylene terephthalate) film 3 and glass substrate 1
As shown in FIG. 3 (b), the recording material composed of 1 shrinks when the heating temperature is equal to or lower than the glass transition temperature Tg of the PET film 3, and expands when the heating temperature is equal to or higher than Tg. Therefore, the fringe pattern of the hologram in the hologram recording layer 2 is P
It is distorted by receiving stress at the interface with the ET film 3 and the interface with the substrate 1. In particular, there is a problem that the distortion concentrates on the peripheral portion and the optical characteristics of the HOE deteriorate.

Even when the cover film 2 is integrally used as a final product, if heat is applied due to a change in environmental temperature during use of the HOE, the fringe pattern of the hologram is distorted for the same reason as above. , The optical characteristics of the HOE change, and the heat resistance becomes poor.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to obtain a multilayer hologram recording body having a layer structure in which interference fringes do not change even when heated.

[0006]

A multi-layer hologram recording body of the present invention which achieves the above object is a multi-layer hologram recording body having a hologram recording layer in the layer, wherein the linear expansion coefficient is the outermost layers on both sides of the hologram recording layer. It is characterized in that substantially the same layers are provided respectively.

More specifically, for example, a substrate, an adhesive layer,
In a multilayer hologram recording body including a hologram recording layer, a barrier layer, a cover layer, etc., layers having the same linear expansion coefficient are provided on the outermost layers on both sides. For example, the outermost layers on both sides may be a combination of glass and glass or a PET film and PET film. Desirably, the outermost layers on both sides are made of the same material and have the same product name and processing method (because they are stretched, the coefficient of linear expansion may differ slightly depending on the degree). Note that different materials having substantially equal linear expansion coefficients may be used.

As the hologram recording layer, for example, photopolymer, dichromated gelatin or the like is used.
A barrier layer or the like that prevents migration of low-molecular components such as an adhesive may be provided between the layers.

That is, in the multilayer hologram recording body of the present invention, in the multilayer hologram recording body having the hologram recording layer in the layer, layers having substantially the same linear expansion coefficient are provided as the outermost layers on both sides of the hologram recording layer. It is a feature.

In this case, the materials of the outermost layers on both sides may be the same or different. When they differ, it is desirable that the difference in linear expansion coefficient is within 15%.
Within this range, the change in the inclination of the hologram interference fringes can be suppressed within about 3 °, which is practical.

As the hologram recording layer, photopolymer, gelatin dichromate, etc. are used.

[0012]

In the present invention, in the multilayer hologram recording body having the hologram recording layer in the layer, the layers having substantially the same linear expansion coefficient are provided as the outermost layers on both sides of the hologram recording layer. For heating,
Even if there are thermal fluctuations due to environmental temperature changes during use of the multilayer hologram recording body, the hologram recording layer is deformed from both sides by substantially the same proportion, so the inclination of the hologram interference fringes in the hologram recording layer does not change, A multilayer hologram recording body having excellent optical characteristics and heat resistance can be obtained and can be used as various hologram optical elements.

[0013]

EXAMPLES The basic principle of the multilayer hologram recording body of the present invention is, as schematically shown in FIG. 1, a multilayer hologram having a hologram recording layer 2 for a volume phase hologram made of photopolymer, dichromated gelatin or the like. In the recording medium, the outermost layers A and B on both sides of the recording medium are made to have substantially the same coefficient of linear expansion so that heating for processing the hologram recording layer and thermal fluctuation due to environmental temperature changes during use of the multilayer hologram recording medium. As a result, even if the outermost layers A and B on both sides expand or contract, stress is applied to the hologram recording layer 2 from both sides at substantially the same rate, and this does not lead to distortion of the hologram fringe pattern in the hologram recording layer 2. , HO
That is, the deterioration of the optical characteristics of E can be suppressed.

As an example of the layer structure of the multilayer hologram recording body of the present invention, as shown in FIG. 2A, the hologram recording layer 2 is provided on the glass substrate 4 via the adhesive layer 5, and the hologram recording layer 2 is adhered thereon. When the glass 7 made of the same material as the substrate 4 is provided via the layer 6, as shown in FIG. 2B, when the hologram recording layer 2 is provided on the PET film 8 and the same PET film 9 is provided thereon, As shown in FIG. 2C, PVA
A barrier layer made of a high-density polymer or the like for providing a hologram recording layer 2 on a (polyvinyl alcohol) film 10 via an adhesive layer 5 and preventing a low-molecular component such as an adhesive from migrating to the hologram recording layer 2 thereon. Same PV through 11
When the A film 12 is provided, as shown in FIG. 2D, polymethylmethacrylate (coefficient of linear expansion α = 80 × 10
^-6 / ° C) 13 on which a hologram recording layer 2 is formed with an adhesive layer 5 interposed therebetween.
It is conceivable that an acrylic optical adhesive (α = (80 ± 9) × 10 ⁻⁶ / ° C.) 14 is provided on top of this with a barrier layer 11 ^interposed therebetween.

When the materials of the outermost layers 13 and 14 on both sides of the hologram recording layer 2 are different as in the case of FIG. 2D, the difference in linear expansion coefficient between the two 13 and 14 is within 15%. Is desirable.

Examples of the multilayer hologram recording medium according to the present invention will be described below together with comparative examples. The diffraction angles shown below are values at the center of the sample. [Comparative Example] Thickness 20 applied to a 2 mm thick soda glass substrate
A biaxially stretched polyethylene terephthalate (PET) film was attached as a cover film to a holographic recording layer (photopolymer: Omnidex 352, manufactured by DuPont, USA) as a cover film, and holograms interference-recorded in the holographic recording layer (diffraction angle 40 °, diffraction Efficiency 35%) at 120 ° C
When heated for 2 hours, the recorded hologram interference fringes were tilted due to the distortion caused by the difference in the linear expansion coefficient between the PET film and the soda glass, and the diffraction angle became 35 °. The diffraction efficiency was 85%.

[Example 1] PET having the layer structure of the above-mentioned comparative example
When soda glass was laminated on the outside of the film and the hologram recorded by interference recording in the hologram recording layer was heated at 120 ° C. for 2 hours, the diffraction angle of 40 ° was maintained and the diffraction efficiency was 87%. Also, in the heat resistance test at 120 ° C. for 8 hours, similarly, the change of the diffraction angle did not occur.

Example 2 The glass substrate of Example 1 was used as a polymethylmethacrylate plate (manufactured by Nitto Plastic Co., Ltd., 2 mm thickness:
Linear expansion coefficient of 80 × 10 ⁻⁶ / ° C.), visible light curable adhesive (manufactured by Toagosei Co., Ltd., Lux Track LCR0136: linear expansion coefficient of 89 × 10 ⁻⁶ ) instead of soda glass to be laminated.
/ ° C) and heating at 80 ° C for 10 hours and then measuring at room temperature, the diffraction angle is 38 °, and the diffraction efficiency is 85%.
Became. The coefficient of linear expansion of the outermost layers on both sides differs by about 10%,
The change in diffraction angle was within the allowable range.

[Example 3] The above-mentioned Omnidex 3 comprising a PET film / holographic recording layer / PET film
An interference fringe similar to that of the practical example 1 was recorded in 52 and heated at 120 ° C. for 2 hours, and the diffraction angle was 40 ° and the diffraction efficiency was 85.
% Hologram was obtained (). When this was attached to a soda glass via the adhesive of Example 2 (), there was no change in the diffraction characteristics.

A multilayer hologram recording body having the above-mentioned structure is used.
When the diffractive property was measured by leaving it for 3 hours in an environment of ° C, the difference as shown in the following table occurred. In the above case, the diffraction angle changes due to the difference in the linear expansion coefficient of the outermost layer.

The multi-layer hologram recording body of the present invention has been described above based on the embodiments, but the present invention is not limited to these embodiments and various modifications can be made. Further, the layer structure of the multilayer hologram recording body is not limited to that shown in FIG. 2, and various modifications can be made.

[0022]

As is apparent from the above description, according to the multilayer hologram recording body of the present invention, in the multilayer hologram recording body having the hologram recording layer in the layer, the coefficient of linear expansion is the outermost layer on both sides of the hologram recording layer. However, even if there is heat fluctuation due to heating for processing the hologram recording layer or environmental temperature change during use of the multi-layer hologram recording body, the hologram recording layer has substantially the same ratio from both sides. Since the deformation is added only, the inclination of the hologram interference fringes in the hologram recording layer does not change, and a multilayer hologram recording body having excellent optical characteristics and heat resistance can be obtained, which can be used as various hologram optical elements.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the basic principle of a multilayer hologram recording body of the present invention.

FIG. 2 is a cross-sectional view for illustrating the layer structure of the multilayer hologram recording body of the present invention.

FIG. 3 is a cross-sectional view for explaining the configuration of a conventional multilayer hologram recording body and its operation.

[Explanation of symbols]

 A, B ... Outermost layer 2 ... Hologram recording layer 4 ... Glass substrate 5 ... Adhesive layer 6 ... Adhesive layer 7 ... Glass 8 ... PET film 9 ... PET film 10 ... PVA film 11 ... Barrier layer 12 ... PVA film 13 ... Polymethacryl Methyl acid 14 ... Acrylic optical adhesive

Claims (5)

[Claims] 1. A multilayer hologram recording body having a hologram recording layer in the layer, wherein layers having substantially the same linear expansion coefficient are provided as outermost layers on both sides of the hologram recording layer. 2. The multilayer hologram recording body according to claim 1, wherein the outermost layers on both sides are made of the same material. 3. The multilayer hologram recording body according to claim 1, wherein the outermost layers on both sides are made of different materials. 4. The difference in linear expansion coefficient between the outermost layers on both sides is 1
The multilayer hologram recording body according to claim 3, wherein the content is within 5%. 5. The multilayer hologram recording body according to claim 1, wherein the hologram recording layer is made of a photopolymer or dichromated gelatin.