Radiation imagery chemistry: process – composition – or product th – Holographic process – composition – or product
Reexamination Certificate
2002-05-28
2004-11-02
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Holographic process, composition, or product
C430S002000, C430S290000, C430S418000, C430S426000, C430S427000, C430S430000
Reexamination Certificate
active
06811930
ABSTRACT:
Priority is claimed to patent application No. 2001-30084 filed in Rep. of Korea on May 30, 2001, herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a post-exposure treatment method of a holographic recording material, and more particularly, to a post-exposure treatment method of a silver halide emulsion layer in the manufacture of a hologram, a hologram manufactured using the post-exposure treatment method, and a holographic optical element (HOE) including the hologram.
2. Description of the Related Art
Holographic optical elements (HOEs) are recorded in dichromated gelatin (DCG) known to have a high efficiency and low noise characteristics. However, DCG suffers a low sensitivity and poor color reproducibility. Therefore, it is not easy to manufacture a full-color hologram or HOE using the DCG.
For this reason, research on photopolymer or other holographic recording materials has been continuously performed. A silver salt-containing silver halide material and a treatment process thereof have become more interesting in recent years.
As a result of efforts made to attain similar or superior properties to the DCG, a new treatment technique called a “silver halide sensitive gelatin (SHSG) process” has been established.
Some research institutes reported that this SHSG process provides a 90% efficiency for transmission HOEs. The SHSG process is characterized as leading a low noise and high efficiency. Also, the residue from the SHSG process is pure gelatin, so there is no problem of print-out.
SHSG techniques developed so far have been applied for recording with holographic materials available from Agfa, Kodak, and liford, causing a problem of scattering during recording. No scattering is observed when applied to the DCG or photopolymers.
The recent development of some sorts of ultra-fine grain silver halide emulsion has increased an interest in the SHSG technique. This is because the SHSG technique is expected to provide comparable effects with the DCG when applied to an ultra-fine grain silver halide emulsion. However, there hasn't been reported yet a SHSG technique capable of effecting similar properties to the DCG or photopolymers.
Briefly, the SHSG technique involves exposing and locally tanning a silver halide emulsion layer. Then, silver salt or silver in the emulsion layer diffuses out due to fixing, so that only pure gelatin remains. In the last step, the remaining gelatin is dehydrogenated using a hydrophilic organic solvent. The dried SHSG hologram includes only gelatin and microvoids of air. Like this, since the internal component of the dried SHSG hologram varies and refractive indexes of the two components differ, that is, the gelatin has a refractive index of 1.5, and the air filling the microvoids has a refractive index of 1.0, the refractive index of the SHSG hologram with respect to incident light varies. The SHSG hologram or a HOE including the SHSG hologram (hereinafter, referred to as an “SHSG HOE”) operates using the variation of refractive index.
SHSG holograms or SHSG HOEs are categorized into a transmission type or a reflection type according to the transmittance of the hologram at recording or reproduction. It has been known that the reflection type SHSG hologram is more difficult to manufacture than the transmission type SHSG hologram.
A reflection type SHSG hologram having an efficiency of 40-70% has been reported. Also, a reflection type SHSG hologram having an efficiency of 80% was reported in Russia. However, this level of efficiency is impractical. These conventional reflection type SHSG holograms have a problem of the reliability of recording materials or processing reproducibility. This is associated with the fact that the reflection type SHSG hologram or reflection type SHSG HOE has an end structure of multiple layers including a pure gelatin layer and a microvoid layer, which is difficult to be kept intact.
Gelatin or a silver halide emulsion easily swells, collapses, or shrinks during processing. Therefore, it is difficult to keep a fringe that is an interference pattern formed during recording. Thus, a SHSG hologram with excellent quality cannot be manufactured using the gelatin or silver halide emulsion.
An SHSG process using a red sensitive BB-640 emulsion (ultra-fine grain silver halide emulsion) having a grain size of 25 nm was reported by Blendze and Neipp. The SHSG process provides an improved efficiency above 90%, compared to 40% for an Agfa's product and 85% for a simple BB640 emulsion.
Bledze reported an efficiency of 90% using a red-sensitive PFG-01 emulsion. Usanov succeeded in manufacturing a reflection type hologram through reversal solvent bleaching with an efficiency of 80% for each wavelength of the R, G, B colors. However, his disclosure was not fully described, and the efficiency is not high enough for practical use.
Holographic recording materials that have been developed or reported as having been developed so far, such as DCG or photopolymer, fail to fully meet the requirement of characteristics. The DCG has excellent efficiency, signal-to-noise ratio (S/N), and long-term reliability, but very low photosensitivity and spectral sensitivity. Therefore, the DCG has limited applications. The photopolymer is excellent in most characteristics, but is slightly unstable and difficult to handle. Up to now, no photopolymer has been produced on an industrial scale.
Common silver halide emulsions have been found to be inferior to the DCG or photopolymer in all of the characteristics. There has not been reported any SHSG process capable of providing a comparable effect to the DCG or photopolymer using ultra-fine grain silver halide emulsion.
SUMMARY OF THE INVENTION
To solve the above-described problems, it is an object of the present invention to provide a post-exposure treatment method of a silver halide emulsion layer, capable of providing excellent spectral sensitivity, energy sensitivity, efficiency, signal-to-noise ratio, and long-term reliability as well as the advantages of conventional silver halide, dichromated gelatin (DCT), and photopolymers.
It is a second object of the present invention to provide a hologram manufactured using the post-exposure treatment method and a holographic optical element (HOE) employing the hologram.
To achieve the first object of the present invention, there is provided a post-exposure treatment method of a silver halide emulsion layer in the manufacture of a hologram, the method comprising: pre-hardening the silver halide emulsion layer after exposure; developing the pre-hardened silver halide emulsion layer using a high-contrast developer solution; bleaching the developed silver halide emulsion layer; hardening the bleached silver halide emulsion layer; drying the hardened silver halide emulsion layer; surface-hardening the dried silver halide emulsion layer; fixing the hardened silver halide emulsion layer; treating the fixed silver halide emulsion layer using warm water; and drying the silver halide emulsion layer which has been treated using warm water.
In pre-hardening the silver halide emulsion layer, preferably, a mixture of an organic solvent including an aldehyde group, potassium bromide, sodium carbonate, and deionized water in a predetermined ratio is used.
In bleaching the developed silver halide emulsion layer, preferably, a hardening agent of 1-8% for cross-linking gelatin in the silver halide emulsion layer and a rehalogenate-bleaching agent containing a basic substance of 0-5% for the adjustment of pH are used.
In hardening the bleached silver halide emulsion layer, the bleached silver halide emulsion layer can be thermally treated to harden gelatin in the bleached silver halide emulsion layer. Preferably, the bleached silver halide emulsion layer is left in warm water, a high-temperature and high-humidity atmosphere, or a microwave oven for a predetermined period of time to facilitate the cross-linking of the gelatin.
Preferably, before bleaching the developed silver halide emulsion layer, the post-exp
Samsung Electronics Co,. Ltd.
Schilling Richard L.
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