JPH09101736A - Production of hologram - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain the optical characteristics of a hologram after development and dehydration and to enhance the stability with water by exposing and developing photosensitive gelatin film consisting of a photosensitive agent and gelatin, then heating this gelatin in a gaseous acetic acid atmosphere. SOLUTION: The photosensitive gelatin consisting of the photosensitive agent and the gelatin is exposed and developed and is then heated in the gaseous acetic acid atmosphere. Namely, the photosensitive gelatin film is heated in the gaseous acetic acid atmosphere after development, by which the optical characteristics of the hologram after the development and dehydration are maintained and the stability of the hologram with the water is enhanced. The atomic valency electrons of polar amino acid are bonded to each other by maintaining the photosensitive gelatin film in the gaseous acetic acid atmosphere on the acidic side of the isoelectric point of the gelatin, by which the moisture resistance of the hologram after the development and dehydration is improved. The optical characteristics of the hologram are presumed to be consequently maintained and the stability of the hologram with the water to be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method of manufacturing a hologram using gelatin, and more particularly to a method of manufacturing a hologram capable of preventing deterioration of the hologram due to moisture.

[0002]

2. Description of the Related Art When a hologram is irradiated with reproduction light, a three-dimensional image appears. This hologram is applied to vehicle head-up displays, bar code readers, etc., and is also used for viewing holograms, credit cards, etc. As a method for producing a hologram, for example, a photosensitive gelatin film composed of a photosensitizer and gelatin is formed on the surface of a glass substrate, and object light and reference light are irradiated to cause interference in the photosensitive gelatin film. Then, interference fringes generated by the object light and the reference light are recorded on the photosensitive gelatin film. A hologram is obtained by developing the photosensitive gelatin film thus photographed.

When such a hologram is used in the presence of water, there is a problem that optical characteristics such as diffraction efficiency and reproduction wavelength of the hologram change. As a method for preventing such water deterioration, there is a conventional method in which a barrier layer is provided on the surface of a photosensitive gelatin film (JP-A-7-40764). Also, after development and dehydration, a method of treating a photosensitive gelatin film with aldehyde vapor to cross-link gelatin molecules through formaldehyde to densify gelatin and suppress adsorption of water (Japanese Patent Publication No. 7-34
143).

[0004]

However, the above conventional hologram manufacturing method has the following problems. In the former method, the barrier layer can reduce the intrusion of water, but the hologram becomes thicker by the thickness of the barrier layer. Moreover, it is very difficult to form a thin film without pinholes. For example, it is difficult to use in places where the film thickness is restricted, such as enclosing in windshield glass of automobiles. Further, in the step of applying the barrier layer to the surface of the photosensitive gelatin film, moisture adheres to the hologram due to its environmental humidity, so that sufficient humidity control is required.

Further, in the latter method, formaldehyde is an unstable substance itself, and there is a problem that process control is difficult.

In view of the above conventional problems, the present invention aims to provide a hologram manufacturing method capable of maintaining the optical characteristics of the hologram after development and dehydration and increasing the stability of the hologram against moisture. Is.

[0007]

The present invention is a method for producing a hologram, which comprises exposing a photosensitive gelatin film composed of a photosensitizer and gelatin to light, developing the film, and then heating the film in an acetic acid gas atmosphere.

The first point to be noted here is that the photosensitive gelatin film after development is subjected to heat treatment in an acetic acid gas atmosphere. The reason is that when the photosensitive gelatin film before development and before film formation is exposed to the above-mentioned acetic acid gas atmosphere, the well-known hologram manufacturing method of film formation, exposure and development, which is the subsequent process, is used. Because it will not be possible.

The second point to be noted is that the heat treatment after development is performed in an acetic acid gas atmosphere in which acetic acid is vaporized. The reason is that, as described above, when the hologram absorbs water, the interference fringes recorded by exposure disappear. Therefore, the wet method of immersing the photosensitive gelatin film in the acetic acid aqueous solution cannot be used.

As described above, in the present invention, the photosensitive gelatin film is developed and then heated in an acetic acid gas atmosphere. Therefore, the optical characteristics of the hologram after development and dehydration can be maintained and the stability of the hologram against moisture can be increased.

The reason why the above effects are obtained will be described below together with the points of interest of the present invention. That is, it is considered that most of the photosensitizer (for example, chromium when the photosensitive gelatin film is dichromated gelatin) is washed away by the development processing, and the hologram after heating is almost only gelatin. From this, it is considered that the humidity resistance of the gelatin itself should be improved in order to improve the humidity resistance of the hologram.

Therefore, first, the reason why gelatin absorbs water was considered. A gelatin molecule consists of a polypeptide chain in which amino acids are linked by peptide bonds.
It is considered that water molecules in the atmosphere or the like are attached to the polar amino acids constituting the polypeptide chain or the polar amino acids bound to the polypeptide chain as a side chain.

As a measure for preventing the adhesion of water molecules,
As shown in FIG. 1, it is considered that the attachment of water molecules can be suppressed by binding the valence electrons of polar amino acids.

From this point of view, it was decided to bond the valence electrons of polar amino acids by making the photosensitive gelatin film on the acidic side of the isoelectric point of gelatin in an acetic acid gas atmosphere. Thereby, as described above, the humidity resistance of the hologram after development and dehydration is improved. Therefore, it is considered that the optical characteristics of the hologram can be maintained and the stability of the hologram against moisture can be increased.

Further, according to the present invention, since it is not necessary to cover the photosensitive gelatin film with the barrier layer, it can be used only as a hologram. Therefore, it can be used in a place where the film thickness is limited, for example, by enclosing it in the windshield glass of an automobile.

The acetic acid gas comprises acetic acid vapor and carrier gas. The carrier gas is N ₂ gas, Ar ₂
Gas, He ₂ gas, Ne ₂ gas, Kr ₂ gas, Xe ₂ gas, Rn ₂ gas and the like are preferable. As a result, it is possible to prevent alteration of the hologram during heating.

The acetic acid gas atmosphere preferably has an acetic acid vapor concentration of 0.0264 to 100%. 0.0
If it is less than 264%, the stability of the hologram against moisture may not be improved. The acetic acid vapor concentration means the percentage of the volume occupied by acetic acid vapor in the total volume of carrier gas and acetic acid vapor.

The acetic acid gas atmosphere preferably has a humidity of 0 to 10% RH. If it exceeds 10% RH, the removal of water from the photosensitive gelatin film may be insufficient.

The acetic acid gas atmosphere is preferably 20 to 150 ° C. If the temperature is lower than 20 ° C, the removal of water from the photosensitive gelatin film may be insufficient.
On the other hand, if the temperature exceeds 150 ° C., the photosensitive gelatin film may be deteriorated and desired hologram characteristics may not be obtained.

The above-mentioned photosensitive gelatin film is a photosensitive film using gelatin. The photosensitizer used for the photosensitive gelatin film includes, for example, dichromate, dye-sensitized dichromate, silver salt, etc., but is not particularly limited as long as it is a photosensitive material.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

First Exemplary Embodiment A hologram manufacturing method according to an exemplary embodiment of the present invention will be described with reference to FIGS. First, a photosensitive gelatin film consisting of a photosensitizer and gelatin is formed on the surface of a substrate such as glass or polymer film to obtain a hologram dry plate. Dichromate is used as the photosensitizer. Next, the photosensitive gelatin film is irradiated with object light and reference light to record interference fringes.

Next, the photosensitive gelatin film is developed. The development consists of a series of steps including washing of chromium in the photosensitive gelatin film, hardening treatment, chemical dehydration, and drying.
The cleaning of chromium was performed by immersing the hologram dry plate in running water. In performing the above hardening treatment, a hardening gelatin solution is added to a hardening gelatin solution (for example, potassium alum) to start a hardening reaction to harden the whole photosensitive gelatin film, and then a hologram is formed. The dry plate was dipped in running water to remove the hardening agent, and the hardening reaction was terminated. The above chemical dehydration is
The hologram dry plate was immersed in isopropyl alcohol. The above-mentioned drying was performed by removing isopropyl alcohol from the photosensitive gelatin film by heating.

Next, using the oven 1 shown in FIG. 2, the hologram dry plate 7 composed of the photosensitive gelatin film 701 and the substrate 702 was heated in an acetic acid gas atmosphere 2. A heat-resistant container 3 is installed in the oven 1. The inside of the heat-resistant container 3 is the acetic acid gas atmosphere 2. An inlet pipe 31 for introducing acetic acid gas and a discharge pipe 32 for discharging acetic acid gas are attached to the heat-resistant container 3.

The introducing pipe 31 is branched on the way, and a container 311 for storing liquid acetic acid 21 is provided on one side thereof, and an appropriate amount of nitrogen gas (carrier gas) 22 is introduced on the other side. An introduction part 312 is provided. The container 311 storing the liquid acetic acid 21 is kept warm by the warmer 310. Liquid acetic acid 21 is used as a warmer 310
The acetic acid vapor vaporized at the temperature of 1 is carried to the heat-resistant container 3 as acetic acid gas 20 together with the nitrogen gas 22 introduced from the introduction part 313. The discharge pipe 32 is also branched in the middle, and the vacuum pump 321 and the exhaust unit 31 are provided on one side of the discharge pipe 32.
4 is provided, and the other is provided with a discharge part 315 that is connected to the exhaust device. The acetic acid gas discharged from the heat-resistant container 3 is sent to an exhaust device (not shown) through the exhaust unit 314.

The introduction pipe 31 includes a check valve 318 for keeping the pressure in the heat-resistant container 3 constant, and a check valve 318.
And a discharge pipe 317 for discharging the acetic acid gas further discharged. Further, the discharge pipe 32 has an air inlet 318 for introducing the atmosphere into the heat-resistant container 3,
The heat-resistant container 3 has an opening / closing valve 303 for switching the acetic acid gas atmosphere to the atmosphere. Also, heat-resistant container 3
And in the oven 1, there are thermometers 43, 4 for temperature adjustment.
1 is attached. In FIG. 2, reference numeral 30
Reference numerals 1, 302, 304 are open / close valves for adjusting the flow rate of acetic acid gas.

After placing the hologram dry plate 7 in the heat-resistant container 3 in the oven 1, the air in the heat-resistant container 3 is
It is removed by the vacuum pump 321. This prevented the photosensitive gelatin film from deteriorating during heating.

Next, the temperature of the warmer 310 is raised to vaporize the liquid acetic acid 21 in the container 311. The concentration of vaporized acetic acid vapor is changed by nitrogen gas 22.
For example, it is adjusted to 0.02 to 1% and introduced into the heat resistant container 3. The more preferable acetic acid vapor concentration at this time is 0.2 to
1%. The reason is that at such a density, the optical characteristics of the hologram do not deteriorate and the moisture resistance also improves. The humidity inside the heat-resistant container 3 is 10% RH or less.

Thereafter, the hologram dry plate 7 was heated to 150 ° C. in the oven 1. The heating time is 2 hours.
The above temperature is the maximum temperature at which the photosensitive gelatin film can be heated, which was obtained by preliminary experiments. When heated at this temperature for 2 hours, evaporation of water disappeared and weight change disappeared.

From the above, a hologram was obtained. The hologram produced in this example and treated in an acetic acid gas atmosphere had high humidity resistance and stable optical characteristics. This is because, as shown in FIG. 1, when heating in an acetic acid gas atmosphere, the gelatin molecules of the photosensitive gelatin film formed a peptide bond 62 between adjacent polypeptide chains 61, so that the water adsorption site of the gelatin molecule. It is considered that this is because the moisture resistance of the hologram is improved by reducing the amount of water and the amount of adsorbed water.

On the other hand, the hologram which was not treated in the acetic acid gas atmosphere had low moisture resistance and its optical characteristics were unstable. The above-mentioned heating temperature and heating time are values as an example of the embodiment, and the present invention is not limited thereto. Even when the heating temperature is 150 ° C. or lower, the humidity resistance of the hologram is improved. In this case, it is necessary to lengthen the heating time.

Embodiment 2 In this example, as shown in FIGS. 3 to 5, the humidity resistance test of the hologram was conducted. In the test, as shown in FIG. 3, the photosensitive gelatin film was formed, exposed, and developed in the same manner as in the first embodiment. Two hologram dry plates 71 and 72 after the development processing were prepared. Of these hologram dry plates, one hologram dry plate 72 for comparison was placed in the oven 1 and exposed to the atmosphere 10.

On the other hand, one hologram dry plate 7 for the present invention
1 was placed in a heat-resistant container 3 filled with an acetic acid gas atmosphere 2, and the heat-resistant container 3 was placed in an oven 1. The temperature in the oven 1 is 150 ° C. Acetic acid gas atmosphere 2
The acetic acid vapor concentration in Example 2 was set variously as shown in FIG. Under this condition, the hologram dry plates 71 and 72 for the present invention and for comparison were heated for 2 hours. The same heat treatment as the oven 1 used in the first embodiment was used (see FIG. 2).

Immediately after the above heating, the hologram dry plates 71 and 72 were weighed by an electronic balance. Next, as shown in FIG. 4, the hologram dry plates 71 and 72 are
The photosensitive gelatin film was allowed to stand for 40 minutes in a humidified atmosphere 60 in a constant temperature and constant humidity tank 6 to make the water absorption of the photosensitive gelatin film saturated. The humidified atmosphere is 20 ° C. and 50% RH. Immediately after this humidification treatment, the weight was measured by an electronic balance. Next, the percentage change in weight of the hologram dry plate before and after being left in the humidified atmosphere was determined as the water absorption of the hologram.

Water absorption rate (wt.%) = 100 × (weight immediately after being left in a humidified atmosphere-weight immediately before being left in a humidified atmosphere) / weight immediately after left in a humidified atmosphere

The water absorption of the hologram is shown in FIG.
In the figure, the number in parentheses on the horizontal scale is about 10
It has a% error. As is known from the figure, in the hologram of the present invention, the higher the acetic acid vapor concentration, the lower the water absorption rate. On the other hand, the water absorption of the comparative hologram is 17 wt.
%, Which absorbed more water than the hologram of the present invention.

From this, it is understood that the humidity resistance of the hologram is improved by heating the photosensitive gelatin film in the acetic acid gas atmosphere after the development. Further, in the hologram of the present invention, the interference fringes were hard to disappear and the optical characteristics were stable.

[0037]

According to the present invention, it is possible to provide a method of manufacturing a hologram which can maintain the optical characteristics of the hologram after development and increase the stability of the hologram against moisture.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the effect of an acetic acid gas atmosphere on a photosensitive gelatin film in Embodiment 1.

FIG. 2 is an explanatory view showing a method of heating a hologram dry plate in an acetic acid gas atmosphere in the first embodiment.

FIG. 3 is an explanatory view showing a heat treatment method for a hologram dry plate in the second embodiment.

FIG. 4 is an explanatory diagram showing a method of humidifying a hologram dry plate according to the second embodiment.

FIG. 5 is a diagram showing a water absorption rate of a hologram in the second embodiment.

[Explanation of symbols]

 1. . . Oven, 2. . . Acetic acid gas atmosphere, 3. . . Heat-resistant container, 7. . . Hologram dry plate, 701. . . A photosensitive gelatin film, 702. . . substrate,

Claims (4)

[Claims] 1. A method for producing a hologram, which comprises exposing a photosensitive gelatin film comprising a photosensitizer and gelatin to light, developing the film, and then heating the film in an acetic acid gas atmosphere. 2. The hologram manufacturing method according to claim 1, wherein the acetic acid gas atmosphere has an acetic acid vapor concentration of 0.0264 to 100%. 3. The method for manufacturing a hologram according to claim 1, wherein the acetic acid gas atmosphere has a humidity of 0 to 10% RH. 4. The method according to claim 1, wherein
The method for producing a hologram, wherein the acetic acid gas atmosphere is 20 to 150 ° C.