JPH11161137A - Method for producing transparent hologram - Google Patents

Abstract

(57) [Problem] To provide a method for producing a volume phase type transparent hologram which is excellent in weather resistance, heat resistance and storage stability, and has good hologram characteristics such as resolution, diffraction efficiency and transparency. I do. Kind Code: A1 One or more components of a thermosetting epoxy oligomer, an aliphatic monomer, a photoinitiator and a dye sensitizer of a hologram recording material are appropriately selected and mixed at an arbitrary ratio to form a film on a substrate. After holographic exposure of the hologram layer obtained by coating and drying by holographic exposure, visible light (wavelength 200 to 800 nm) absorbed by the dye sensitizer used for spectral sensitization is applied to an atmosphere at 40 to 150 ° C. By irradiating the entire surface of the hologram layer below,
It is possible to produce a transparent hologram in which the coloring of the dye sensitizer does not matter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is sensitive to visible light such as argon laser light with high sensitivity, and is excellent in weather resistance, heat resistance and storage stability, as well as in resolution, diffraction efficiency and transparency. The present invention relates to a method of manufacturing a volume phase type transparent hologram having good hologram characteristics.

[0002]

2. Description of the Related Art A hologram is obtained by recording an interference wavefront of coherent light such as a laser in a recording medium such as a photopolymer as a refractive index distribution or an absorbance distribution. This hologram is capable of reproducing a three-dimensional stereoscopic image. Because of its excellent design and decorative effects, it is used for covers of books and magazines, displays such as POPs, and gifts. In particular, volume phase holograms have a refractive index rather than optical absorption in the hologram recording medium. By forming different spatial interference fringes, it is possible to modulate the phase without absorbing the light beam passing through the image, and in recent years, a hologram optical element (hereinafter, referred to as HOE),
For example, a head-up display (HU)
Application to a combiner for D) is expected.

[0003] The general principle of hologram fabrication is described in several documents and specialized books, for example, Chapter 2 of "Holographic Display" (Junhei Tsujiuchi, Sangyo Tosho). According to these, a recording object is irradiated with one of two bundles of coherent light, generally laser light, on a recording object, and a photosensitive recording medium, for example, a photographic dry plate, is placed at a position where it can receive total reflected light from the object. The coherent light in addition to the reflected light from the object is directly applied to the recording medium without being applied to the object. The light reflected from the target is referred to as target light, and the light directly illuminating the recording medium is referred to as reference light, and interference fringes between the reference light and the target light are recorded as holograms (image information).

[0004] When the recording medium thus treated is exposed to light from an irradiation light source and observed at an appropriate eye position, the light from the irradiation light source emits light from the object during recording to the recording medium. Since the light is diffracted by the hologram that reproduces the wavefront of the reflected light that has arrived first, a three-dimensional object image similar to the real image of the target object is observed. The hologram formed by allowing the reference light and the target light to enter the recording medium from the same direction is a transmission hologram, and the hologram formed by allowing the reference light and the target light to enter from opposite sides of the recording medium is reflected. It is a type hologram. Transmission holograms are disclosed, for example, in US Pat. No. 3,506,327 and US Pat.
787, etc., and the reflection type hologram can be obtained, for example, in US Pat.
It can be obtained by a known method disclosed in US Pat.

[0005] The volume phase hologram recording material constituting such a volume phase hologram is sensitive to laser light having a visible oscillation wavelength with high sensitivity and exhibits high resolution. In use, hologram diffraction efficiency, reproduction light wavelength reproducibility, bandwidth (half width of reproduction light peak) and other characteristics are suitable for the purpose, and the hologram recording material itself is often a commercial product. Chemical stability, e.g. heat resistance, light resistance,
It is required that they have excellent environmental resistance such as moisture resistance and also have excellent transparency.

Heretofore, as a recording material for such a volume phase hologram, a photosensitive material based on bleached silver salt and gelatin based dichromate has been generally used. This dichromated gelatin based photosensitive material is most widely used for recording volume phase holograms due to its high diffraction efficiency and low noise characteristics, but this photosensitive material has a short shelf life,
Problems that must be adjusted each time a hologram is produced, and problems that hologram reproducibility is poor due to deformation of the hologram in the process of swelling and shrinking of gelatin required for hologram production by performing wet development. This method requires complicated processing after recording, and is not a photosensitive material satisfactory from the viewpoint of stability and workability. Furthermore, all of the above photosensitive materials have a problem that they are inferior in environmental resistance properties, for example, moisture resistance and weather resistance.

To solve such problems, a hologram recording material composed of a cationically polymerizable thermosetting epoxy oligomer and a radically polymerizable ethylenic monomer (JP-A-8-1680, JP-A-8-44277) ). This hologram recording material can produce a hologram by a simple production method by dry processing, and the obtained hologram has excellent characteristics, and is excellent in environmental resistance such as light resistance and moisture resistance, high resolution, Has high diffraction efficiency.

[0008]

However, when the hologram recording material described above is used to produce a hologram by dry development, the dye sensitizer used remains in the system as it is, resulting in a colored hologram. When used in a head-up display (HUD) or the like that requires a high transmittance, a very serious problem occurs. For this reason, there is an increasing need for a hologram recording material capable of obtaining a transparent hologram and a hologram manufacturing method. For example, with respect to decolorization of dyes, there is a method using heat and / or light, and US Pat. No. 3,658,5.
No. 21 discloses decolorization of a dye used as a component of a photoconductive material for electrophotography by using light and heat at the same time, which is performed to enhance the contrast by bleaching the dye. However, there is no disclosure of a method for producing a transparent hologram by a dry processing method as in the present invention. Similarly, US Pat. No. 3,788,849
No. 4,548,896 and No. 4,594,31.
No. 2, No. 4,632,895, etc. also describe the use of heat and / or light for decolorizing dyes. However, these methods also disclose a method of producing a transparent hologram by a dry processing method as in the present invention. Nothing is disclosed.

Accordingly, the present invention provides a method for producing a volume phase type transparent hologram which is excellent in weather resistance, heat resistance and storage stability, and has good hologram characteristics such as resolution, diffraction efficiency and transparency. The purpose is to:

[0010]

Means for Solving the Problems The present invention has been made to solve the above problems, and the invention according to claim 1 has the following features.
(A) a solvent-soluble, thermosetting epoxy oligomer capable of cationic polymerization having at least one glycidyl group in a unit structure, and (B) a liquid at normal temperature and pressure and a boiling point of 100 ° C. or higher at normal pressure. An aliphatic monomer having at least one radically polymerizable ethylenically unsaturated bond, (C) a radical species that activates radical polymerization when exposed to actinic radiation, and a Bronsted acid that activates cationic polymerization or A hologram recording material comprising a photoinitiator that generates a Lewis acid and (D) a dye sensitizer capable of sensitizing the photoinitiator in the visible light region is formed on a substrate, and holographic exposure and development are performed. And (D) irradiating the entire surface with visible light having a wavelength of 200 to 800 nm absorbed by the dye of the dye sensitizer in an atmosphere of 40 to 150 ° C. It is a method of manufacture.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIG. 2 is a schematic cross-sectional view illustrating a configuration of a hologram recording medium used in the method for manufacturing a transparent hologram of the present invention in FIG. 1, and FIG. 2 is a schematic explanatory view illustrating an optical system for hologram photographing.

The component (A) constituting the hologram recording layer of the hologram recording medium of the present invention is a solvent-soluble, thermopolymerizable epoxy oligomer having at least one glycidyl group in a unit structure and capable of being cationically polymerized as bisphenol. A, bisphenol AD, bisphenol B, bisphenol AF, bisphenol S, brominated bisphenol A, hydrogenated bisphenol A, hydrogenated bisphenol AD, hydrogenated bisphenol B, hydrogenated bisphenol S, hydrogenated bisphenol AF, hydrogenated brominated bisphenol A Can be mentioned. The present invention is not limited thereto, and any epoxy compound produced by a condensation reaction between various phenol compounds and epichlorohydrin can be used. These may be used in combination of two or more.

The molecular weight of the thermosetting resin of the component (A) is preferably in the range of 900 to 6000. If the molecular weight is smaller than this range, the film-forming property is deteriorated, and uniform coating is difficult. When the molecular weight is larger than the range, synthesis is generally difficult. Further, the epoxy equivalent of the thermosetting resin is preferably from 400 to 6700, and if the epoxy equivalent is out of this range, there is a problem that favorable cationic polymerization does not proceed.

The aliphatic monomer which is liquid at normal temperature and pressure and has a boiling point of 100 ° C. or higher at normal pressure and has at least one ethylenically unsaturated bond capable of being radically polymerized has the following structure: The unit contains at least one ethylenically unsaturated bond, contains a polyfunctional vinyl monomer in addition to a monofunctional vinyl monomer, and may be a mixture thereof. In practice, it is desirable that the difference in the refractive index between the component (A) and the component (B) is 0.03 or more according to the theory of H. Kogelnik described above.

Specifically, high-boiling vinyl monomers such as (meth) acrylic acid, itaconic acid, maleic acid, (meth) acrylamide, diacetone acrylamide, 2-hydroxyethyl (meth) acrylate, and aliphatic Hydroxy compounds, such as ethylene glycol,
Diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, neopentyl glycol, 1,
3-propanediol, 1,4-butanediol, 1,
5-pentanediol, 1,6-hexanediol,
1,10-decanediol, trimethylolpropane,
Di- or poly (meta) such as pentaerythritol, dipentaerythritol, sorbitol, mannitol
Acrylic esters or alicyclic polyhydroxy compounds such as dimethylol tricyclodecane monoacrylate and dimethylol tricyclodecane diacrylate, and aromatic polyhydroxy compounds such as hydroquinone, resorcin, catechol, pyrogallol, and bisphenol A Or poly (meth) acrylate,
In addition to ethylene oxide-modified (meth) acrylate of isocyanuric acid and the like, 2-phenoxyethyl methacrylate, phenol ethoxylate monoacrylate,
p-chlorophenyl acrylate, KAYARAD-R
551 (trade name, manufactured by Nippon Kayaku Co., Ltd.).

Component (C) of the present invention includes a photoinitiator system which activates radical polymerization upon exposure to actinic radiation.
Macromolecules, 10 , 1307 (19
77). And diphenyliodonium, ditolyliodonium, phenyl (p-anisyl)
Iodonium, bis (m-nitrophenyl) iodonium, bis (p-tert-butylphenyl) iodonium,
Chloride, bromide or borofluoride of iodonium such as bis (p-chlorophenyl) iodonium,
In addition to iodonium salts such as hexafluorophosphate salts and hexafluoroarsenate salts, triarylsulfonium salts, triarylphosphonium salts, and iron arene complexes, triazine compounds and the like can be mentioned. However, the present invention is not limited to these.

Further, the component (D) dye sensitizer capable of sensitizing the photoinitiator (C) of the present invention in the visible light region includes:
Specifically, rhodamine B, crystal violet, malachite green, auramine O, phosphine R, acridine orange, acridine yellow, setoflavin T, brilliant claysle blue, neutral red, thionine, methylene blue, indigo, pinacyanol, tetraphenylporphyrin, 3, 3′-carbonylbis (7-diethylaminocoumarin), 3- (2 ′
-Benzothiazole) -7-diethylaminocoumarin,
3- (2'-benzimidazole) -7-diethylaminocoumarin, 3,3'-carbonylbis (7-dimethylaminocoumarin), 7-diethylamino-5 ', 7'-
Dimethoxy-3,3'-carbonylbiscoumarin, 3-
Benzoyl-7-dimethylaminocoumarin, 3-benzoyl-7-diethylaminocoumarin, 3-acetyl-7
-Diethylaminocoumarin, 7-dimethylamino-3-
(4-iodobenzoyl) coumarin, 7-diethylamino-3- (4-diethylaminobenzoyl) coumarin,
2-benzoyl-3- (p-dimethylaminophenyl)
-2-propenenitrile, 2,5-bis {[4- (diethylamino) -phenyl] methylene} -cyclopentanone, 2,5-bis {[4- (dimethylamino) -phenyl] methylene} -cyclopentanone , 2,6-bis {[4- (diethylamino) -phenyl] methylene}-
Cyclohexanone, 2,6-bis {[4- (dimethylamino) -phenyl] methylene} -cyclohexanone,
-Ethyl-2-[(3-ethyl-2-benzothiazolinylidene) methyl] -3H-benzothiazolinium iodide, 3-ethyl-2-[(1-ethyl-2 (1H) -quinolylidene) Methyl] benzothiazolinium iodide,
3-ethyl-2- [3- (3-ethyl-2-benzoxazolinylidene) -1-propenyl] benzoxazolinium iodide. 3-ethyl-5- [2- (3-ethyl-2-benzorialinidene) ethylidene] rhodanine,
2- (p-dimethylaminostyryl) -1-ethylpyridiniiodide, 2- (p-dimethylaminostyryl)-
Examples thereof include 1-ethylpyridinium iodide and 2- (p-dimethylaminostyryl) -3-ethylbenzothiazolinium iodide. In addition, many dye compounds described in "Dye Handbook" (Shin Okawara, Teijiro Kitao, Tsuneaki Hirashima, Ken Ken Matsuoka, Kodansha 1986) can be used in the present invention. Also, these dye sensitizers can be selected to suit different wavelengths of actinic radiation depending on the intended use of the hologram,
Depending on the application, two or more types can be used in combination.

In the hologram recording material, a leveling agent, an antifoaming agent, an antioxidant, a plasticizer,
Various additives such as a polymerization inhibitor may be added. The hologram characteristics referred to here include diffraction efficiency, peak half-value width, refractive index modulation, and the like. In particular, the refractive index modulation is a value for comparing holograms formed as images. This is because when the recording medium is directly irradiated with the two light beams at the same angle to the medium and a diffraction grating is produced, the ratio of the incident light diffracted by the diffraction grating, that is, the diffraction efficiency and the recording medium It is a value specified from the thickness. Refractive index modulation is a quantitative measure of the change in refractive index that occurs in exposed and unexposed areas of a volume hologram, that is, the areas where light interferes and strengthens, and is described by H. Kogelnik. Theoretical formula [Bell. Syst. Tech. J. , 48 ,
2909, (1969). ].

In the present invention, a photosensitive composition obtained by appropriately selecting one or more of each component of a thermosetting epoxy oligomer, an aliphatic monomer, a photoinitiator and a dye sensitizer of a hologram recording material and mixing them at an arbitrary ratio. The liquid is applied to a transparent substrate 2 such as a glass plate, a polycarbonate plate, a polymethyl methacrylate plate, or a polyester film in the form of a film using a known coating means such as a spin coater, a roll coater, or a bar coater, and is dried. Thus, the hologram recording medium 1 shown in FIG. 1 is obtained. According to the schematic diagram for explaining the optical system for hologram photographing shown in FIG. 2 showing the process of performing holographic exposure on the hologram recording medium 1 to form a latent image, the laser beam 6 oscillated from the laser 5 Are mirror 7, lens 10, lens 11,
When the light enters the hologram recording medium 1 via the spatial filter 9, interference fringes are formed and a hologram image is recorded. Furthermore, in the present invention, after hologram imaging by exposure, visible light (wavelength 200 to 800 nm) absorbed by the dye sensitizer used for spectral sensitization is 40 to 150.
By irradiating the entire surface of the hologram layer 3 in an atmosphere of ° C., a transparent hologram can be obtained in which the coloring of the dye sensitizer does not matter.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on specific embodiments. <Example 1> 100 parts by weight of a bisphenol-based epoxy oligomer (trade name “Epicoat 1007”, polymerization degree n = 10.8, epoxy equivalent: 1750 to 2100, manufactured by Yuka Shell Epoxy), 50 parts by weight of triethylene glycol diacrylate, and diphenyl 5 parts by weight of iodonium hexafluorophosphate and 1 part by weight of 3- (2′-benzothiazole) -7-diethylaminocoumarin
-200 parts by weight of butanone were mixed and dissolved to prepare a hologram recording material, which was used as a photosensitive liquid. This photosensitive liquid was applied to a transparent substrate so as to have a thickness of about 15 μm, and dried to form a hologram layer, thereby producing a hologram recording medium.

The hologram recording medium is subjected to holographic exposure from both sides of the hologram recording medium using an argon laser (514.5 nm; 20 mJ / cm ² ) as a light source by a hologram recording optical system shown in FIG. After producing the hologram, the entire surface of the hologram layer was irradiated with light from a xenon lamp while heating at 60 ° C.

The characteristics (diffraction efficiency, transmittance) of the obtained transparent hologram were measured with a spectrophotometer manufactured by JASCO Corporation. This spectrophotometer uses a photomultimeter having a slit with a width of 3 mm and a radius of 20 mm around the sample.
The sample was placed on a circumference of cm, and the measurement conditions were such that monochromatic light having a width of 0.3 mm was incident on the sample at an angle of 45 °, and diffracted light from the sample was detected. The ratio of the largest value other than the specularly reflected light to the value when the incident light was directly received without placing the sample was defined as the diffraction efficiency. At this time, the diffraction efficiency was 95%, and the average transmittance in the visible light region (400 to 700 nm) was 90%.

<Embodiment 2-5> 3- of Embodiment 1
3,3′-carbonylbis (7-diethylaminocoumarin) (Dye-2) instead of (2′-benzothiazole) -7-diethylaminocoumarin (Dye-1),
2,5-bis {[4- (diethylamino) -phenyl]
Methylene｝ -cyclopentanone (Dye-3), 2,6
-Bis {[4- (dimethylamino) -phenyl] methylene} -cyclohexanone (Dye-4), 3-ethyl-
The same procedure as in Example 1 was carried out except that 5- [2- (3-ethyl-2-benzotriazolinylidene) ethylidene] rhodanine (Dye-5) was used, and the diffraction efficiency and average transmittance of the obtained hologram were obtained. Was measured. This is shown in Table 1 together with the results of Example 1. However, T (%) in the table is
The average transmittance in the visible light range (400 to 700 nm) at the time of producing the hologram is shown. E. FIG. (%) Indicates diffraction efficiency.

[0024]

[Table 1]

Dye-1: 3- (2'-benzothiazole) -7-diethylaminocoumarin Dye-2: 3
3'-carbonylbis (7-diethylaminocoumarin) Dye-3: 2,5-bis {[4- (diethylamino)
-Phenyl] methylene} -cyclopentanone Dye-4: 2,6-bis} [4- (dimethylamino)
-Phenyl] methylene} -cyclohexanone Dye-5: 3-ethyl-5- [2- (3-ethyl-2
-Benzoliazolinylidene) ethylidene] rhodanine

Example 6-10 Diphenyliodonium tetrafluoroborate, diphenyliodonium hexafluoroarsenate, diphenyliodonium hexafluoroantimonate were used instead of the photoinitiator diphenyliodonium hexafluorophosphate of Examples 1-5. The diffraction efficiency and average transmittance of the obtained hologram were measured in the same manner as in Example 1-5, except that an iron arene complex (xafluorophosphate salt) and 1,3,5-trichloromethyltriazine were used. . Table 2 shows the results.

[0027]

[Table 2]

DPITFB; diphenyliodonium tetrafluoroborate DPIHFA; diphenyliodonium hexafluoroarsenate DPIHFS; diphenyliodonium hexafluoroantimonate IAHFP; iron arene complex (oxafluorophosphate salt) TCT; 1,3,5-trichloromethyltriazine

[0029]

As described above, according to the method for producing a transparent hologram of the present invention, the dye sensitizer used for producing a hologram colors and remains on the hologram layer even after the hologram is produced. By irradiating the entire hologram layer with visible light (wavelength: 200 to 800 nm) suitable for the sensitizer in an atmosphere of 40 to 150 ° C., the dye sensitizer is decomposed by the interaction with the remaining photoinitiator, Decolorization occurs. At this time, the decomposition reaction is promoted by heating,
The hologram layer can be decolorized with a small amount of irradiation.
At this time, since the monomer hardly exists in the system, it does not affect the formed hologram. This is a volume phase type transparent hologram that is sensitive to visible light with high sensitivity, has excellent weather resistance, heat resistance and storage stability, and has good hologram characteristics such as resolution, diffraction efficiency, and transparency. Can be obtained, and the hologram optical element (HO
E) For example, it is useful for applications such as a head-up display (HUD) mounted on a vehicle.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating the configuration of a hologram recording medium used in a method for producing a transparent hologram of the present invention.

FIG. 2 is a schematic explanatory view illustrating an optical system for hologram imaging.

[Explanation of symbols]

 Reference Signs List 1 hologram recording medium 2 transparent substrate 3 hologram layer 5 laser 6 laser beam 7 mirror 8 beam splitter 9 spatial filter 10 lens 11 lens

Claims (1)

[Claims] (A) a cationically polymerizable thermosetting epoxy oligomer having at least one glycidyl group in a unit structure, which is soluble in a solvent, and (B) a liquid at normal temperature and pressure and a boiling point at normal pressure. An aliphatic monomer having at least one radically polymerizable ethylenically unsaturated bond having a temperature of 100 ° C. or higher, (C) a radical species that activates radical polymerization when exposed to actinic radiation, and a cationic polymerization. Forming a hologram recording material comprising a photoinitiator that generates a Bronsted acid or a Lewis acid to be reacted and a dye sensitizer (D) capable of sensitizing the photoinitiator in the visible light region on a substrate, After holographic exposure and development, the wavelength (D) of the dye of the dye sensitizer (D) is 200 to 80.
A method for producing a transparent hologram, wherein the entire surface is irradiated with 0 nm visible light in an atmosphere at 40 to 150 ° C.