JP2686984B2 - New optical recording material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical recording material comprising at least two layers having different reflectances, and in particular, writing is performed by utilizing the difference in reflectance between the two layers. The present invention relates to an optical recording material for reading. In particular, the optical recording material of the present invention can be a digital recording material suitable for writing and reading by laser light.

(Prior Art) In recent years, various new recording materials have been proposed along with remarkable progress in laser-related technologies.

A typical example of this is a high density digital recording material such as an optical disk, but apart from this, a flexible optical card material has been recently proposed as a material that can be handled more easily. As one example, an optical card developed by Drexler, which is described in JP-A-59-502139 and JP-A-58-188346, is famous. On the other hand, an optical tape has been proposed as a material which is more compact than an optical disc and can record a large amount of information.

Although several systems and materials have been proposed as described above, various characteristics required as a recording material such as writing sensitivity, storage stability of the recording material, recording density, and error rate have still been insufficient.

For example, a material having high sensitivity to a laser beam does not necessarily have good storage stability and is liable to deteriorate under high humidity conditions, or it is gradually oxidized by oxygen in the air, resulting in a decrease in sensitivity. Was pointed out, and it was a step ahead in terms of reliability.

In addition, for optical cards and optical tapes that are expected to be used under severer conditions than optical discs in terms of bending, new materials have been craved because metal thin film materials used so far may crack.

Drexler has already proposed to use a silver thin film material obtained by developing a wet silver halide photographic material under special developing conditions for an optical card. However,
This material is restricted by a silver salt photographic film, such as the use of hydrophilic gelatin as a binder, and has been pointed out to be problematic, for example, that it is weak for long-term storage under high humidity.

(Problems to be Solved by the Invention) The present invention is intended to provide a recording material having extremely excellent storage stability, which has been a problem particularly in this type of recording material.

In particular, it is an object of the present invention to provide an optical recording material layer which is not damaged by cracks or the like even under severe use conditions such as bending and is hardly deteriorated even under severe storage conditions of high temperature and high humidity.

Further, the present invention is intended to provide a low-cost recording material capable of continuous production. That is, a very common industrial production means such as continuous coating by a roll coater or continuous heating by a hot roll can be selected, and an appropriate preformat can be provided as necessary by performing pattern exposure through a mask. . This is a very important issue in reducing the cost of the recording material.

(Means for Solving the Problem) A light-sensitive material containing an organic silver salt oxidizing agent as a main material for silver image formation is known as a so-called heat-developable silver salt photographic film, but the present application is based on this basic composition. This is the finding of a new optical recording material.

In particular, the point of the invention is that the material composition is designed so that the shape of the silver metal reduced by heat development can be controlled so that at least two metallic silver layers having different reflectances can be obtained.

The two layers may be formed as separate layers, or two layers may be simultaneously formed.

For the first layer, a usual preparation method is to apply and dry a composition in which an organic silver salt oxidizing agent and a reducing agent are dispersed or dissolved in an organic binder. Further, the second layer may be coated with a composition containing metallic silver development nuclei thereon,
Alternatively, by treating the surface layer of the first layer, metallic silver development nuclei may be formed on the surface layer.

The organic silver salt oxidizing agent is a metal in which fine metallic silver having a low reflection density is dispersed in the system when heated, as in so-called thermal development of a so-called heat-developable silver salt photographic film, by adding an appropriate reducing agent to the system. Two layers, a silver dispersion layer and a metallic silver glossy layer, are provided in advance on the surface layer with silver or a noble metal development nucleus that is noble than silver, and the organic silver salt oxidizing agent is reduced around this nucleus during heating. It was made possible. As described above, it was completely novel to find out that the organic silver salt oxidizing agent inside can be diffused to the surface by heating and a metal thin film layer having a high reflectance can be formed on the surface.

Such a novel optical recording material can be defined as follows. That is, the organic silver salt oxidizing agent and the reducing agent for forming the metal silver dispersion layer, and the organic silver salt oxidizing agent and the reducing agent in the presence of silver or a metal development nucleus more noble than silver. In the optical recording material comprising at least two layers of a metallic silver gloss layer, the reflectance A of the metallic silver dispersion layer and the reflectance B of the metallic silver gloss layer are: 0.03 ≦ (BA) / (B + A ) ≦ 0.9, an optical recording material.

When B−A / B + A <0.03, since the contrast is low even when information is written, an error is likely to occur during reading. Also, the larger B-A / B + A is, the more preferable it is for recording information.
A material having an A / B + A value exceeding 0.9 and having a writable sensitivity has not been found in practice.

In the present invention, it is necessary that the metallic silver dispersion layer and the metallic silver luster layer have different reflectances so as to satisfy the above equation, but it is essential that the metallic silver forms of the respective layers are different. That is not the case.

In addition, it is not important as an optical recording material whether or not each layer has a clear boundary.

However, in order to improve the recording density as an optical recording material, metallic silver is present in a uniformly dispersed state as a dispersion much smaller than at least 2 to 3 μm, or 2 to 3 μm.
On the order of 3 μ, a metallic silver layer that can be handled as a uniform continuous layer is preferable.

The reflectance value is represented by the intensity ratio of light reflected at a regular reflection angle (-75 °) with respect to light incident on the optical recording material at an angle of 75 °.

For the measurement of the reflectance, a light source in the vicinity of 750 to 850 nm is used.

The thickness of the recording layer itself of this optical recording material is preferably as thin as possible so that the recording density is improved as long as a difference in reflectance can be obtained, but usually the total thickness of the two layers is 1
It is set to about 20μ.

Also, the larger the difference in reflectance, the easier the system construction. However, even if the difference is small, it is possible to construct the system by improving the accuracy on the reader side, for example. Is. Therefore, the allowance of reflectance is extremely large as in the above equation. However, from the viewpoint of easily constructing a system, it is preferable that the difference in reflectance is within the range of 0.2 ≦ (BA) / (B + A) ≦ 0.8.

In the present invention, the metallic silver dispersion layer is obtained by uniformly dispersing or dissolving an organic silver salt oxidizing agent and a reducing agent therefor, uniformly coating and drying on a suitable substrate, and then uniformly heating. A silver metal dispersion layer can be deposited on.

As the organic silver salt oxidizing agent for this purpose, silver salts of various carboxylic acids such as long-chain fatty acids, silver saccharinate, and silver benzotriazole can be used. Among these, silver behenate, silver stearate and the like are particularly useful.

As a reducing agent for this organic silver salt oxidizing agent, a sterically bulky group is bonded to the carbon adjacent to the carbon to which the phenolic hydroxyl group used in ordinary dry silver salt photographic films is bonded, and the hydroxyl group is sterically converted. You can choose from hindered phenols that are impaired. For example, 2,6-di-t-
Butyl-4-methylphenol, 2,2'-methylenebis- (4-methyl-6-t-butylphenol), 2,2 '
-Methylenebis- (4-ethyl-6-t-butylphenol), 2,2,4-trimethylpentylbis- (2-hydroxy-3,5-dimethylphenyl) methane, 2,5-di-t-
Butyl-4-methoxyphenol and the like can be mentioned. Further, reducing agents for silver salts such as hydroquinone, 2,5-dimethylhydroquinone, chlorohydroquinone, p-aminophenol, methylhydronaphthalene, phenidone and methyl gallate, bisphenol A, 2,4-dihydroxybenzoic acid, P- Methoxyphenol can also be used. The amount of the reducing agent varies depending on the type of the reducing agent, etc., but is generally about 1 mol per mol of the organic silver salt oxidizing agent.
It is 0.01 to about 10 mol, preferably about 0.1 to about 3 mol.

Organic silver salt oxidizing agents and reducing agents are alcohol-based solvents such as methanol and ethanol; ketone-based solvents such as 2-butanone and acetone; ester-based solvents such as ethyl acetate; and aromatic hydrocarbon-based solvents such as toluene and xylene. An organic solvent such as a solvent and an organic synthetic polymer compound or an organic natural polymer compound are mixed and dispersed to prepare a uniform coating solution.

Here, the selection of the polymer compound as the binder is as follows.
It is extremely important not only for preparing a coating solution having good stability, but also for significantly affecting the storage stability of the optical recording material obtained after coating, drying and heat development. Hydrophilic binders such as gelatin and polyvinyl alcohol should be avoided in order to provide more favorable stability, especially under storage conditions of high humidity. The preferred binder in the present invention may be appropriately selected from a wide range of hydrophobic organic polymer compounds such as polymethylmethacrylate, polyvinylformal, polyvinylbutyral, vinyl chloride-vinyl acetate copolymer, cellulose acetate and polystyrene. it can. The hydrophobic binder is from about 10: 1 to about 1:10 by weight to the organic silver salt oxidizing agent.

In the present invention, the silver metallic luster layer having high reflectance is manufactured as follows. That is, it can be obtained by providing a layer of a metal development nucleus which is more noble than silver on the previously coated organic silver salt layer. This representative manufacturing method can be carried out by the same method as the method of applying metal nuclei by electroless plating. For example, a metal nucleus of palladium is applied to the surface layer by sequentially immersing in an aqueous solution of stannous chloride and an aqueous solution of palladium chloride. No change in appearance occurs before and after this processing.

When the organic silver salt oxidizing agent layer having such a surface layer is heated under appropriate heating conditions, for example, at least 70 ° C. or higher for several seconds to several minutes, a recording material layer having metallic silver luster can be formed on the surface layer. Suitable heating conditions are 90-16
It is about 2 to 60 seconds at 0 ° C.

This metallic silver luster layer incorporates an extremely small amount of noble metal development nuclei than silver, and a catalytically acting noble metal species than silver is essential for the development of this luster layer. The noble metal species than silver include palladium, platinum, gold, rhodium,
Examples thereof include ruthenium, thallium and mercury. These metal nuclei need not be a single metal species,
It may be a complex system or a sulfide.

Further, as a method of giving a metal species nobler than silver to the surface layer, a method of dispersing the minute metal development nuclei in a solvent containing an appropriate binder and coating as a second layer on the surface layer, or vapor deposition It is also possible to adopt a method of forming a trace amount of metal development nuclei on the surface under vapor phase conditions such as.

Furthermore, more simply, it is also possible to utilize the silver metal nucleus itself as a catalyst nucleus. In this case, instead of using a metal species that is more noble than silver, a stronger reducing agent such as ascorbic acid is used. It is also possible to substitute by covering the surface of the organic silver salt oxidizing agent layer.

Further, a compound which forms silver sulfide nuclei such as sodium sulfide may be arranged on the surface layer.

Alternatively, the surface may be exposed to a reducing gas such as hydrogen gas for a short period of time to provide silver metal development nuclei on the surface layer.

Some of these methods are those in which physical development, which is so-called photographic chemistry, is skillfully performed on the surface layer by a heat development method to form a metallic silver luster layer.

The optical recording material of the present invention may contain various additive components to improve the performance of the intended material. For example, a toning agent such as phthalazone in a dry silver salt photographic film, an antifoggant, and a sensitizer can be added for the purpose of controlling the silver metal to a predetermined size.

Among the by-products formed by the reaction between the organic silver salt oxidizing agent and the reducing agent, organic compounds such as fatty acids formed from silver salts of long-chain fatty acids are in the binder and play a role as plasticizers. It was confirmed that the writing sensitivity can be controlled.

Further, in the present invention, it is possible to incorporate a photosensitive silver halide into a recording material by applying the dry silver salt technique, and by such compounding, pattern exposure is performed through a mask in advance at the time of manufacturing. It was also found that the pre-formatting process can be easily performed.

Such composition changes include a method in which a halogen ion source is allowed to act on a part of the organic silver salt oxidizing agent and a part of the organic silver salt oxidizing agent is changed to photosensitive silver halide in advance, or it is prepared separately. There is a method of dispersing the prepared silver halide fine crystals in a coating solution containing an organic silver salt oxidizing agent.

The optical recording material of the present invention is provided with a transparent protective layer for the purpose of protecting the recording layer. This protective layer is selected from highly transparent organic polymer compounds such as polycarbonate, polystyrene, polymethylmethacrylate, polyvinyl chloride, polyvinylidene chloride, and polyethylene terephthalate. Further, the back surface of the optical recording material layer may be composed of only the base film to which the optical recording layer is applied, or further, a reinforcing layer for bending etc. may be present on the back surface.

The optical recording material of the present invention generally has a card shape, but is not limited thereto and may have a disk shape or a tape shape.

The optical recording material of the present invention can be recorded with various laser light sources having an appropriate power, and typical ones thereof are He-Ne laser and semiconductor laser. For example, a semiconductor laser of about 10 mW can be used to write with a beam diameter of 2 to 3 μ at a speed of several tens of cm / sec.

The optical recording material of the present invention can be utilized as a so-called write-once recording material that can be written by a user as needed, and can also be used as a read-only ROM card or the like in which information is previously written.

It should be noted that the following examples are given to describe the present invention in more detail, but this does not limit the present invention.

Example 1 A suspension containing the following components was prepared.

Silver behenate 20g Polyvinyl butyral 18g Phthalazone 4g 2,2-Methylenebis (4-ethyl-6-t-butylphenol) 9g 2-Butanone 200g Toluene 60g This suspension was homogenized by a ball mill for about 12 hours and then averaged. Undispersed substances and the like were removed through a filter having a pore size of 1.5μ.

This suspension is dried by a small applicator,
A slit having a thickness of 6 μm was selected, uniformly coated on a 125 μm-thick polyester film, and dried at room temperature. (The obtained sample is referred to as Sample No. 1.) Next, the sheet of Sample No. 1 was sequentially dipped in the following aqueous solutions for 10 seconds, washed with water, and then air-dried. (Sample No.
2) (Aqueous solution 1) Stannous chloride 7 g Distilled water 200 ml Concentrated sulfuric acid 4 ml (Aqueous solution 2) Palladium chloride 0.1 g Distilled water 200 ml Concentrated hydrochloric acid 5 ml The obtained samples were respectively heated at 130 ° C. for 10 seconds.

Sample No.1 was completely blackened, whereas sample No.2
The coating surface layer had a metallic luster layer, and the polyester film (base film) side was black.

When the respective reflectances (A, B) were measured, the following results were obtained.

(Measurement wavelength is 830 nm.) From these results, sample No. 2 (BA) / (B +
It can be seen that A) is 0.39.

Next, a writing test was performed on the sample No. 2 by using a semiconductor laser beam having an emission wavelength of 830 nm (beam diameter 3 μ, emission output 10 mW). Scanning speed was set to 40 cm / sec and pulse was emitted.
.mu., 3.5 .mu. holes were recorded parallel to the scanning direction.

Example 2 The sample of Sample No. 1 in Example 1 was spin-coated with a solution of the following components and applied so that the coating thickness after drying would be 0.6 μm.

Polyvinyl alcohol 10 g Sodium chloroaurate (III) 100 mg Methanol 20 ml Distilled water 500 ml The sample dried at room temperature was further vacuum dried at 50 ° C. for 24 hours.

When the obtained sample was heat-treated in the same manner as in Example 1, an optical recording material having a surface reflectance of 42% and a back surface reflectance of 12% could be prepared. This could be written with the semiconductor laser light as in the first embodiment.

Example 3 A suspension containing the following components was prepared in a dark room, and an optical recording material was prepared in the same manner as in Sample 2 of Example 1 under red light.

Silver behenate 20 g Vinyl chloride-vinyl acetate copolymer 15 g Phthalazone 6 g 2,2'-Methylenebis (4-methyl-6-t-butylphenol) 10 g Calcium bromide 0.3 g Cobalt iodide 0.3 g 2-Butanone 200 g toluene 50 g The obtained optical recording material was exposed to a 300 W high-pressure mercury lamp for 3 seconds through a chromium mask having a 10 μ pitch and a 2 μ width mark, and immediately heated at 130 ° C. for 8 seconds on the entire surface.

In the obtained optical recording material, a metallic glossy layer having a 2 μ pitch non-glossy portion (which can be used as a tracking guide) in the exposed portion was obtained.

The reflectance of the gloss layer was 45%. This is a test machine for optical guards equipped with a 10mW semiconductor laser.
It has been demonstrated that it is writable and readable at a rate of cm / sec.

Example 4 The sample No. 2 of Example 1 and the samples of Examples 2 and 3 were stored for one week under the accelerated storage test conditions of 70 ° C. and 80% RH, and the deterioration degree was examined.

Almost no change in appearance such as reflectivity and pit shape was observed, indicating that the optical recording material of the present invention was a material having extremely excellent stability.

Example 5 A sample was prepared in which 100 mg each of mercuric acetate and hydroquinone were used in place of the sodium gold (III) chloride in Example 2.

Similarly, a sample using potassium diiodic potassium platinate instead of the palladium chloride of Example 1 was also prepared.
Each of these samples was found to have a metallic glossy surface after heat treatment at 130 ° C. for 10 seconds.

(Effect of the invention) In the invention, by setting the ratio of the respective reflectances of both layers in an optical recording material comprising at least two layers of a metallic silver dispersion layer and a metallic silver gloss layer within a certain range; It has the effect of providing a novel and useful optical recording material that is excellent and that does not suffer damage such as cracks even under severe usage conditions such as bending, and that enables preformat processing by pattern exposure and enables continuous production.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-60-78786 (JP, A) JP-A-58-37853 (JP, A) JP-A-58-224794 (JP, A) JP-A-57- 133099 (JP, A) JP 59-2892 (JP, A) JP 57-212633 (JP, A)

Claims (7)

(57) [Claims] 1. An organic silver salt oxidizing agent and a reducing agent therefor, a metallic silver dispersion layer, and the organic silver salt oxidizing agent and the reduction in the presence of silver or a metal development nucleus more noble than silver. In an optical recording material comprising at least two layers of a metallic silver luster layer formed of an agent, the reflectance A of the metallic silver dispersion layer and the reflectance B of the metallic silver gloss layer are: 0.03 ≦ (BA) /(B+A)≦0.9, an optical recording material. 2. The optical recording material according to claim 1, wherein the metallic silver luster layer contains a metal nobler than a trace amount of silver metal. 3. The optical recording material according to claim 1, wherein the metal silver dispersion layer contains an organic compound formed by a redox reaction of the organic silver salt oxidizing agent and the reducing agent. 4. The optical recording material according to claim 1, wherein the binder is a hydrophobic organic polymer compound. 5. The optical recording material according to claim 1, which contains photosensitive silver halide microcrystals and can be preformatted by pattern exposure. 6. The organic silver salt oxidizing agent, a reducing agent therefor, and a metal metal or a trace amount of a metal catalyst nucleus nobler than silver metal are heated to a temperature of at least 70 ° C. or higher. A method for producing the optical recording material according to item (1). 7. A recording method for recording information by irradiating a pulsed laser beam on the optical recording material according to claim 1 to cause a change in reflectance.