JPH05204287A - Hologram recording material - Google Patents

Abstract

PURPOSE:To obtain the hologram which has a high modulation rate of a refractive index, is simple in developing process and is short in exposing time by dispersing microballs into a base polymer and incorporating a material which generate gas by a chemical reaction into these microballs. CONSTITUTION:Polyvinyl alcohol (about 500 degrees of polymn.) is used for the base polymer and a polyester resin is used for the microballs as more specific examples. The microballs are incorporated at 30 pts.wt. into 70 pts.wt. base polymer. An adize compd.; 2, 6-bis(p-azide benzylidene) cyclohexanone is used as a gas generating agent and ketocumarine is used as a sensitizer. This gas generating agent is cracked by a laser beam and the generated gas forms extremely small voids in the microballs. The refractive index of the voids is nearly 1 and is extremely different from the refractive index of the base polymer. The hologram having a large change in the refractive index is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram widely used in display devices, display fields, etc., and more particularly to a volume phase hologram recording material.

[0002]

2. Description of the Related Art Various conventional volume phase hologram recording materials have been proposed. The typical ones are as shown below. a) Dichromated gelatin, which is obtained by adding ammon dichromate and a sensitizing dye to gelatin to make it sensitive to laser light. It has been confirmed that this material has minute voids in the non-crosslinked portion during the development processing, and it is considered that a large refractive index modulation is obtained by this. In addition, although dichromated gelatin has sensitivity only to red, it is possible to give sensitivity to green and blue by sensitizing it with a dye, and trial production of a color hologram image has been made. .

B) Photopolymerizable material, which is a base polymer to which a monomer photoinitiator, a sensitizing dye, a plasticizer and the like are added. This is because a difference in refractive index occurs between a polymerized portion and a non-polymerized portion due to polymerization of a monomer dispersed in a base polymer, and a diffraction image can be recorded. In addition, the monomer dispersed in the base polymer is polymerized in the bright part of the interference fringes, and the density of the monomer decreases, so the monomer is supplied from the dark part in the surrounding area, and there is a case where a higher refractive index distribution is obtained. . With these materials, as in the case of dichromated gelatin, the light-sensitive area can be selected by selecting a sensitizing dye.

C) A photocrosslinkable material, which crosslinks a photosensitive polymer. As for this, those that crosslink the base polymer, those that crosslink the crosslinking agent dispersed in the polymer, and the like have been devised. Similar to the above-described two methods, this method also records a diffraction image by examining the refractive index of a crosslinked portion and a non-crosslinked portion. Further, even in the case of the material of this system, there is a material in which minute voids are generated in the film due to the development processing and a larger refractive index modulation is obtained. Furthermore, some of the generated minute voids are larger than the wavelength, which scatters the light and changes the diffraction efficiency,
In some cases, the generated minute voids are impregnated with a monomer, and the impregnated monomer is polymerized to obtain a difference in refractive index. Although the above is a typical example of the hologram recording material, many hologram recording materials by other methods have been devised.

[0005]

The above hologram material has the following problems. a) Since dichromated gelatin has a good resolution and a large degree of refractive index modulation, it is possible to obtain a very high diffraction efficiency and the image characteristics are very good. However, gelatin has poor moisture resistance, and the image gradually disappears when the plate is left as it is. Therefore, it is necessary to perform processing such as laminating with a glass plate. In addition, the material requires an extremely large number of wet processes and is laborious to manufacture. Further, the dry plate made of the same material has the drawback that it has poor stability and cannot be stored for a long time.

As the photopolymerizable material b), a material having better moisture resistance can be selected as compared with the dichromated gelatin, so that the same characteristics can be improved. Further, some photopolymerizable materials do not require a wet process at all, and their handling properties are improved as compared with dichromated gelatin. In addition, the stability of the dry plate is good and long-term storage is possible. However, this material has a poor resolution and a small degree of refractive index modulation as compared with dichromated gelatin. further,
For the type in which the monomer in the photopolymerizable material moves, it is difficult to shorten the exposure time because the time for the monomer to move is rate-determining.

As for the photopolymerizable material c, like the photopolymerizable material, it is possible to select a material having better moisture resistance than dichromated gelatin, so that the same characteristics can be improved. The resolving power and the degree of refractive index modulation are almost the same as those of dichromated gelatin and show extremely good characteristics. However, this material has a drawback that it includes a wet process in the developing step and has very poor operability.

[0008]

SUMMARY OF THE INVENTION The present invention provides a hologram recording material having a large degree of refractive index modulation, a simple developing process, a short exposure time, and moisture resistance and weather resistance. That is, the present invention is a hologram recording material characterized by having a recording layer composed of a base polymer and microspheres containing a substance capable of generating a gas upon exposure.

According to the present invention, the gas generating agent contained in the microspheres is decomposed by laser light to generate gas, and the generated gas forms extremely small voids in the microspheres. The refractive index of this void is almost 1, which is a large difference from the refractive index of the base polymer, and a hologram having a large change in refractive index can be realized.

In the present invention, since the gas generating agent is added to the microspheres dispersed in the base polymer, the gas generated by the laser light can be confined in the microspheres and formed by the generated gas. The size of the void to be formed can be controlled by controlling the size of the microsphere. The size of the microspheres in the present invention may be any size as long as it is equal to or smaller than the wavelength of the light used, but the diameter is preferably 0.1 μm or less, more preferably the diameter is 0.1 μm or less. It is at most 05 μm.

The base polymer used in the present invention is not particularly limited as long as it can disperse the microsphere colloid in a solvent, but a resin having a good gas barrier property is preferable. The polymer forming the microspheres used in the present invention is not particularly limited, but a polyester resin is preferable. Furthermore, the gas generating mechanism in the present invention is not particularly limited, and it is one that decomposes to generate gas when irradiated with laser light, or a second material that generates gas by a substance decomposed by laser light irradiation. However, the gas to be generated is not limited, but oxygen or nitrogen is preferable in view of the gas barrier property of the resin.

In the present invention, the hologram recording material of the present invention can be used as a base polymer by applying not only the plastic deformation of the base polymer due to gas generation at room temperature but also the laser irradiation as a process for producing the minute voids. ,
In addition to the gas generating agent, a sensitizing dye for adjusting the sensitivity of the laser wavelength, a gas generating catalyst, and plasticity of the base polymer may be added.

The present invention is also capable of reproducing by using incoherent light or coherent light by contact exposure or a method similar thereto, according to the light and shade of interference fringes. A hologram recording material characterized in that the interference fringes are recorded by generating gas due to a chemical reaction therein and generating bubbles having a diameter of not more than a visible light wavelength.

[0014]

Example 1 Polyvinyl alcohol (polymerization degree: about 500) was used as a base polymer (70 parts by weight), and a polyester resin (30 parts by weight) (E1515NH, manufactured by Toyobo Co., Ltd.) was used as microspheres. In addition, an azide compound; 2,6-bis (p-azidobenzylidene) cyclohexanone was used as a gas generating agent (5 parts by weight), and ketocoumarin was used as a sensitizer (1 part by weight). The polyester resin to be microspheres is dissolved in butanol, which is a good solvent, and then the agit compound, which is a gas generating agent, and ketocoumarin are added and dissolved in a dark room. Then, water is added to the solution to prepare an emulsion. At this time, the gas generating agent added previously is taken into the emulsion. Further, this was heated to evaporate the solvent used first to obtain an aqueous dispersion emulsion, which is referred to as stock solution A. At this time, the size of the emulsion was about 0.1 μm in diameter. This emulsion was used as microspheres.

Next, a base polymer, polyvinyl alcohol, was dissolved in water to prepare a stock solution B. Stock solution A and stock solution B were mixed in a dark room to prepare a photosensitive solution. The photosensitive solution was coated on a PET film having a thickness of 100 μm using an applicator with a gap of 100 μm,
It was dried at ℃ open. The thickness of the recording layer (photosensitive layer) after drying was about 7 μm.

The thus produced film was used as a photosensitive film (dry plate). Next, the manufactured photosensitive film was exposed using an optical system as shown in FIG. In the exposed film, the azide compound in the microspheres decomposes and nitrogen gas is generated in the bright part of the interference fringes, but in this state, there is no change in the microspheres. Immediately the film was heated to about 70 ° C. At this time,
The resin is plastically deformed and voids are generated in the microspheres. A diffraction grating could be manufactured by the micro voids formed by the voids. The diffraction efficiency of the diffraction grating formed by exposure and the angle dependence of incident light were measured and evaluated. The laser used was A
The oscillation wavelength of the r laser is 457.9 nm.

FIG. 2 shows the angle dependence of the incident light of the diffraction grating manufactured using the photosensitive material (recording material) according to the present invention. As shown in the drawing, the maximum diffraction efficiency is 90% or more, and A holographic photosensitive material having a large angle dependency was completed.

[0018]

Example 2 The hologram produced as in Example 1 was used as a master hologram, and a hologram duplicate was produced using the hologram photosensitive material according to the present invention. As the hologram photosensitive material, the same material as that manufactured in Example 1 was used. The master hologram was brought into close contact with the hologram photosensitive material according to the present invention, and contact exposure was performed with a low pressure mercury lamp for about 3 seconds. Immediately thereafter, it was heated to about 70 ° C. and developed. The replica of the hologram produced in this way provided characteristics similar to those of the master hologram.

[0019]

According to the present invention, it is possible to obtain a hologram having a large degree of refractive index modulation with a short time for using a laser for producing a hologram and an extremely simple manufacturing process.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an optical system for hologram production used in Example 1 for evaluating a hologram recording material of the present invention.

FIG. 2 shows the results of measuring the angle dependence of incident light of the diffraction grating according to the present invention manufactured in Example 1.

[Simple explanation of symbols]

 In FIG. 1, 1: Ar laser generation source 2: Beam expander 3: Half mirror 4: Mirror 5: Dry plate according to the present invention

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G03F 7/032 502 7/033

Claims (1)

[Claims] 1. A hologram recording material having a recording layer mainly composed of a base polymer and microspheres containing a substance capable of generating a gas upon exposure.