JPH04166882A - Hologram recording medium - Google Patents

Abstract

PURPOSE:To improve the reduction in exposure efficiency, facilitate an exposure process for decreasing the angle of incidence at the time of recording, and improve durability by using a photopolymetric composite containing monomers in each of which the refraction factor of hardened substance is less than 1.45, as a medium. CONSTITUTION:A photopolymetric composite in use contains polymer binder, monomer having unsaturated double bond, photopolymetric initiator, etc. As polymer binder, for example, vinyl resins such as polyvinyl acetate, polyvinyl butyral, etc. are listed. As monomer in which the refraction factor of hardened substance is less than 1.45, and having unsaturated double bond, for example, groups of styrene, vinyl, and styryl including styrene, methyl styrene, etc. and group of trivalent acrylic, etc. are listed. As photopolymetric initiator, compounds having absorption sensitivity in the visible light region are used. Thus, the reduction in exposure efficiency is improved, the exposure process for decreasing the angle of incidence at the time of recording is facilitated, and a durable hologram can be obtained.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a hologram recording medium made of a photopolymerizable composition, and more specifically, the present invention relates to a hologram recording medium made of a photopolymerizable composition, and more specifically, a hologram recording medium that facilitates the exposure process during hologram creation and that has a highly durable volume. The present invention relates to a hologram recording medium provided with a phase type hologram.

(Prior art) Holography is a method in which a light wave with good coherence, such as a laser, is irradiated onto an object, the amplitude and phase of which are modulated according to the shape of the object, and the reflected or transmitted light waves are recorded (= hologram). This technology reproduces the optical image of the original object by irradiating the hologram with a laser again.

With the progress of research on such holography technology,
Nowadays, the requirements for recording media have become quite clear, and many materials have been proposed, including bleached silver salts, photoresists, thermoplastics, dichromate gelatin, inorganic glass materials, and ferroelectric materials, and their characteristics. Research is progressing.

Further, dichromate gelatin sensitized with bleached silver salt or methylene blue is widely known as a hologram recording medium sensitive to the red wavelength region. Furthermore, from Polaroid, D is made of lithium acrylate, branched polyethyleneimine, and poly-N-vinylpyrrolidone.
MP-128 was reported, and for polyvinylcarbazole type, sensitization with triphenylmethane (JP-A-62-21
5284) has been reported.

Recently, the use of photopolymerizable compositions as a method for creating holograms with high resolution and simple processing steps (Japanese Patent Laid-Open No. 2-3081
No. and No. 2-3082) have been reported.

(Problems to be Solved by the Invention) By the way, the characteristics that a hologram recording medium should have are: (1) recording sensitivity, especially sensitivity to laser light in the visible wavelength range and high sensitivity; (2) high sensitivity; (3) the hologram has high diffraction efficiency; (4) the hologram has little noise; (5) the hologram is stable; (6) recording and reproducing operations are easy. etc., are quite strict requirements.

Among known hologram recording media, there are extremely few materials that satisfy all of these characteristics, and even partially, that have properties that can be put to practical use.

Among these, bleached silver salt and dichromate gelatin-based recording media have reached a certain level of practical use, but the former still requires a bleaching operation in addition to normal processing, and There is a disadvantage that the light resistance of the hologram is poor. Moreover, in the latter case, the obtained hologram has poor moisture resistance, and a major defect in terms of storage stability has been pointed out.

Although DMP-128 has reached a practical level compared to the above three, it is thought to be significantly affected by humidity in the production conditions, and is inferior to polyvinylcarbazole-based products from the viewpoint of heat resistance.

Furthermore, in systems sensitized with triphenylmethane dyes, there is a problem in that it is difficult to completely remove the dye after the reaction.

A polyvinylcarbazole recording medium sensitized with carbon iodide is known as a recording medium that has almost solved the problems of the conventional technology.This recording medium has excellent sensitivity, resolution, diffraction efficiency, and environmental resistance. Although it is a hologram recording medium that is superior to dichromate gelatin and silver salt film in terms of properties, etc.
There were practical limitations because the treatment process involved multiple steps.

By the way, media using the photopolymerizable composition are advantageous in terms of processing steps because the production process is simple, and they are also improved in terms of resolution, reflection efficiency, and the like. However, the refractive index of the polymer of the compound used in the photopolymerizable composition exceeds 1.45, and there is a problem in that the exposure efficiency decreases due to reflection of the irradiated light on the surface of the medium during exposure.

In addition, in the case of a reflection hologram, the following equation is required based on the Bragg condition.

d=λrec / 2 n cosθ recλrec
= recording wavelength θ rec - recording incident angle n = refractive index From this formula, if n is small, the incident angle of recording light θ r
Since ec can be made small, the burden on the recording optical system can be reduced.

Therefore, an object of the present invention is to provide a hologram recording medium that can improve the reduction in exposure efficiency, reduce the incident angle during recording, facilitate the exposure process, and is highly durable.

(Means for solving problems) The above object is achieved by the present invention as described below.

That is, the present invention is a hologram recording medium comprising a photopolymerizable composition containing a monomer whose cured product has a refractive index of 1.45 or less.

(Function) By constructing a hologram recording medium from a photopolymerizable composition containing a monomer whose cured product has a refractive index of 145 or less, the exposure process improves the decrease in exposure efficiency and reduces the incident angle during recording. Provided is a hologram recording medium that can be easily used and is highly durable.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The photopolymerizable composition used in the present invention is, for example,
It contains a polymer binder, a monomer (CI) having an unsaturated double bond, a photopolymerization initiator, etc. as shown below.

Examples of the polymer binder include vinyl resins such as polyvinyl acetate, polyvinyl butyral, polyvinyl acecool, and polyvinyl carbazole. More specifically, examples include polymethyl methacrylate, polymethyl acrylate, polybutyl acrylate, and Acrylic resins such as acrylic acid, polymethacrylic acid, polyacrylamide, and polyacrylonitrile; for example, poly(4,4-isopropylidene, diphenylene-2-1,4-cyclohexylene dimethylene carbonate), poly(ethylenedioxy-3 , 3'-phenylene thiocarbonate), poly(4,4'-isopropylidene diphenylene carbonate coate terephthalate), poly(4,4'-isopropylidene diphenylene carbonate), poly(4,4
'-5ec-butylidene diphenylene carbonate),
Polyarylate resins such as poly(4,4'-isopropylidene diphenylene carbonate-block-oxyethylene) are preferably used, and acrylic resins and polyarylate resins are particularly preferred.

Examples of the monomer (I) having an unsaturated double bond include styrene, methylstyrene, chlorostyrene, bromostyrene, methoxystyrene, dimethylaminostyrene, cyanostyrene, nitrostyrene, hydroxystyrene, aminostyrene, carboxystyrene, etc. Styrenes; acrylic acid, methyl acrylate, ethyl acrylate, cyclohexyl acrylate, acrylamide, methacrylic acid, methyl methacrylate, ethyl methacrylate,
Acrylics such as propyl methacrylate, butyl methacrylate, phenyl methacrylate, and cyclohexyl methacrylate.

Vinylpyridine, N-vinylpyrrolidone, N-vinylimidazole, 2-vinylimidazole, N-methyl-2
- Vinyls such as vinyl imidazole; Vinyl ethers such as propyl vinyl ether, butyl vinyl ether, inbutyl vinyl ether, β-chloroethyl vinyl ether, phenyl vinyl ether, p-methylphenyl vinyl ether, and p-chlorophenyl vinyl ether.

For example, divinylbenzene, distyryl oxalate, distyryl malonate, distyryl succinate, distyryl glutarate, distyryl adipate, distyryl maleate, distyryl fumarate, distyryl β,β'-dimethylglutarate, distyryl 2-promoglutarate, α7
Styryls such as distyryl α'-dichloroglucurate and distyryl terephthalate.

Oxalic acid di(ethyl acrylate), oxalic acid di(methyl ethyl acrylate), malonic acid di(ethyl acrylate), malonic acid di(methyl ethyl acrylate), succinic acid di(ethyl acrylate), glutaric acid di(ethyl acrylate), Adipic acid di(ethyl acrylate), maleic acid di(ethyl acrylate), fumaric acid di(ethyl acrylate), β,β'-dimethylglutaric acid di(ethyl acrylate), ethylene diacrylamide, propylene diacrylamide, 1,4- Phenylene diacrylamide, 1,4-phenylene bis(oxyedyl acrylate), 1,4-phenylene bis(oxymethylethyl acrylate), 1,4-bis(acryloyloxyethoxy)cyclohexane, 1,4-bis(
acryloyloxymethylethoxy)cyclohexane,
1゜4-bis(acryloyloxyethoxycarbamoyl)benzene, 1.4-bis(acryloyloxymethylethoxycarbamoyl)benzene, 1.4-bis(acryloyloxyethoxycarbamoyl)cyclohexane, bis(acryloyloxyethoxycarbamoylcyclohexyl)methane, Dioxalate (ethyl methacrylate), dioxalate (methyl ethyl methacrylate),
Malonic acid di(ethyl methacrylate), malonic acid di(methyl ethyl methacrylate), succinic acid di(ethyl methacrylate), succinic acid di(methyl ethyl methacrylate), glutaric acid di(ethyl methacrylate), adipic acid di(ethyl methacrylate) , maleic acid di(ethyl methacrylate), fumaric acid di(ethyl methacrylate), fumaric acid di(methyl ethyl methacrylate), β
.

β′-dimethylglucurate di(ethyl methacrylate)
, divalent acrylics such as 1.4-phenylenebis(oxyethyl methacrylate), divalent monomers such as 1゜4-bis(methacryloyloxyethoxy)cyclohexane, acryloyloxyethoxyethyl vinyl ether:
For example, pentaerythritol triacrylate pentaerythritol trimethacrylate, pentaerythritol tri(hydroxystyrene), cyanuric acid triacrylate, cyanuric acid trimethacrylate, 1,1.1
-) Limethylolpropane triacrylate, 1,1.
1-Trimethylolpropane trimethacrylate, tri(acryloyl ethyl) cyanurate, 1,1.1-trimethylolpropane tri(acryloylethyl), tri(ethyl vinyl ether) cyanurate, tri(acryloyl ethyl) cyanurate, tri(ethyl vinyl ether), 1,1,1-trimethylolpropane tri( 3, such as a condensate of toluene diisocyanate) and hydroxyethyl acrylate.
Examples of acrylics include tetravalent acrylics such as ethylenetetraacrylamide and propylenetetraacrylamide.

Among these, styrenes, vinyls, styryls, and trivalent acrylics are preferred. More preferred monomers include isobornyl methacrylate, isobornyl acrylate, adamantyl acrylate, methacrylate, CR-39, dicyclopentadiene acrylate or methacrylate represented by the following structural formula (I), C) 12=C-C -0-(CH2-CH2-0),,)
I (X=H, CH3, C1), fenthyl methacrylate, dimenthyl methacrylate, dimethyl adamantyl methacrylate, (wherein A is etc.) As a photopolymerization initiator, it is a photopolymerization initiator that has absorption sensitivity in the visible light region. For example, peroxy acid esters such as 1,3-di(butyldioxycarbonyl)benzene and 3°3',4,4'-tetrakis(t-butyldioxycarbonyl)benzophenone are combined with Michler's ketone, etc. Systems sensitized with aromatic amines, xanthine dyes, thiopyrylium salts, merocyanine, quinoline dyes, coumarin, ketocoumarin dyes, diaryliodonium salts such as diphenyliodonium salts, acridine orange, benzoflavin, merocyanine, cyanine, xanthine. A system sensitized by a dye such as or a third component such as N-phenylglycine, the following general formula (I) (R', R2, R3, R4 each independently represents an alkyl group, an aryl group, an aralkyl group, an aryloxy group, cycloalkyl group, alkenyl group, alkynyl group, heterocyclic group, which may have a substituent, or may combine with each other to form a ring compound). , for example, tetrabutylborate, tetraethylborate, tetrabutylborate, triisobutylborate,
Di-t-butyl-dibutylborate, trifluoromethyltrifluoroborate, tetraphenylborate triphenylmethylborate, triphenylethylborate, triphenylpropylborate, triphenyl-N
-butylborate, triphenylhexylborate, trimeditylbutylborate, trianisbutylborate, tritolylisopropylborate, triphenylbenzylborate, tri-p-fluorophenylbutylborate, tri-p-chlorophenylbutylborate, tetrabenzylborate, triphenyl Phenethylborate, triphenyl-p-chlorobenzylborate, trimethallylphenylborate, tricyclohexylbutylborate, tri(phenylelanyl)butylborate, di(α-naphthyl)dipropylborate, diisopinocamphenyldiamylborate cyanine, rhodamine, etc.
Systems sensitized with dyes such as safranin, malachite green, and methylene blue, systems sensitized with iron-arene complexes with donor-type dyes, bisimidazole and hydrogen donors sensitized with (thio)xanthine dyes, ketocoumarin dyes, etc. Examples include mercaptobenzothiazole and systems with mercaptobenzothiazole.

Further, in the present invention, a cured product has a refractive index of 1.45 or less, and a low refractive index monomer (TI) having an unsaturated double bond as shown below is used. That is, -(CF2),
-1-(CF2)y-CF, -CH(CF3)-1
Acrylic esters, meccrylic esters, acrylamides, methacrylamides, etc. having a substituent containing a fluorine atom such as -CF(CF3)-, for example, CH
2=(1; HCOOCH2CF3. CH2=CHC0
0C2H,C,R7,CH3 CH2=CHC00C2H,C5F, ,,CH2=C
C00C2H4C4F9, CH, CH.

l CH2=CC00C2H4C8F, , CH2=C
C00CH, CF...? 1. Listen CH3 CH2=CC00CH(CF3)2, CH2=CHC0
0CH2CF(CF3)2, CH3 CH2=CC00CH2CFHCF,, CH2=CHC
00CHC4F9, 硼CF.

CH3CH.

l CH2=CC0NHC, H4C4F,, CH2=CC0
NHC2H4C6F, 3, etc. can be mentioned.

In the present invention, 5 to 70 parts by weight, preferably 10 to 5 parts by weight of monomer (II) is added to 100 parts by weight of the mixture of the polymer binder, monomer (1) and photoinitiator.
It is added in a proportion of 0 parts by weight.

Photopolymerizable compositions using such monomers can lower the refractive index of the cured product than before, so they can be cured using an exposure optical system as shown in Figure 1-1. When recording a hologram, it is possible to improve the reduction in exposure efficiency due to reflection of irradiated light on the surface of the recording medium, making it easier to adjust the incident angle.

The photopolymerizable composition for forming the recording medium of the present invention can be obtained by dissolving or dispersing the above-mentioned necessary components all at once or sequentially in an appropriate solvent.

Examples of solvents used include toluene, xylene,
Examples include chlorobenzene, chloroform, dichloroethane, dichloroethylene, trichloroethylene, methyl ethyl ketone, methyl isobutyl ketone, dioxane, tetrahydrofuran, isoprobanol, n-butanol, and mixtures thereof.

In addition to the above-mentioned necessary components, thermal polymerization inhibitors, chain transfer agents, surfactants, etc. can be added.

The recording medium of the present invention can be obtained by coating the photopolymerizable composition on a support such as glass or a transparent film and drying it to form a film.

(Example) Next, the present invention will be explained in more detail by giving examples and comparative examples. Note that the text in the middle of the text is based on weight unless otherwise specified.

Example 1 A solution having the following composition was applied onto a glass substrate using a spinner and then dried to obtain a film having a thickness of 8 μm. Thereafter, a polyethylene terephthalate (PET) film was laminated on the photosensitive film side.

1) Toluene 20 parts 2) Isopropatol 20 parts 3) Polyvinyl butyral 8 parts Nyl-n-butyl borate salt 0.5 parts 5) Ethyl 4-dimethylaminobenzoate 0.5 parts 6) Pentaerythritol tetraacrylate 2 parts This The hologram recording medium is a He-Ne laser 632
．． It was exposed to light of 8 parts m at 200 mJ/crtf using the exposure system shown in Fig. 1-1.

Next, the PET film was peeled off, the entire surface was exposed from the photosensitive film side with a tungsten lamp, and then the PET film was laminated again. The obtained hologram had a diffraction efficiency of 80% and a transmittance of 80%. This recording medium is 25
Similar performance was observed after one week at °C.

Comparative Example A hologram formed in the same manner as in Example 1 except that 7) was not used had a diffraction efficiency of 25% and a transmittance of 70%.

Example 2 7) of Example 1 was changed to CTo=CI(COOC284CF
(CFs) A hologram was created in the same manner except that x was replaced.

The diffraction efficiency was 78% and the transmittance was 80%.

A hologram was created in the same manner except that the refractive index of 140) was used. The diffraction efficiency was 82% and the transmittance was 78%.

(Effects of the Invention) As explained above, the recording medium according to the present invention makes it possible to improve the decline in exposure efficiency and simplify the exposure process by reducing the incident angle during recording, and to obtain a highly durable hologram. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating an example of an exposure optical system used for hologram recording.

Claims (3)

[Claims] (1) A holographic recording medium comprising a photopolymerizable composition containing a monomer whose cured product has a refractive index of 1.45 or less. (2) The hologram recording medium according to claim 1, wherein the monomer contains a fluorine atom. (3) The hologram recording medium according to claim 1, wherein the photopolymerizable composition comprises a polymer binder, a monomer not containing a fluorine atom, a monomer containing a fluorine atom, and a photopolymerization initiator.