JPH041749A - Digital recording material and its production - Google Patents

Abstract

PURPOSE:To carry out high-density recording especially with the error rate reduced by interposing an adhesive resin layer between a recording layer and a transparent polymer protective layer in a specified manner. CONSTITUTION:A layer of the transparent adhesive resin having -90 to +60 deg.C glass transition point is interposed between a recording layer and a transparent polymer protective layer in 0.1-50 mum thickness. The adhesive resin layer is previously provided on one between the recording layer and transparent polymer protective layer, and both layers are placed in <=50 mmHg vacuum and then firmly attached to each other. When the glass transition point exceeds +60 deg.C, the sensitivity of the recording layer is adversely affected, and the recording layer is peeled when bent or dropped at <-90 deg.C. Consequently, high-sensitivity and high-density recording is carried out.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical recording material that utilizes the change in reflectance caused by laser light, and has particularly high sensitivity, and the recording layer is suitably protected. This provides a highly versatile recording material that does not require special care in handling.

[Conventional technology]

In recent years, various digital recording materials have been proposed, mainly recording materials for optical discs. Apart from this, a light power system was proposed that was easy to handle; for example, in JP-A-59
No. 502139 and Japanese Unexamined Patent Publication No. 58-188346 have been proposed. The present inventors have also proposed a new recording material in which a reflective metal silver fine particle layer is formed in a hydrophobic binder through a reaction between an organic silver salt and a reducing side.

However, if the recording material is exposed, it is easily scratched, and some materials are oxidized by oxygen or degraded by moisture, so an appropriate protective layer is required. For this protective layer, it was necessary to select the most suitable material for the specific recording material, and to devise the optimal composition, including the adhesive, to create a high-performance, well-balanced recording material.

[Problem to be solved by the invention]

In order to make a reflective recording material made of fine metal silver particles dispersed in a hydrophobic binder unaffected by scratches and to be chemically stable, it is necessary to form an optimal protective layer. At the same time, it is necessary that the provision of this protective layer does not impair the sensitivity and high-density recording properties of the recording material. Moreover, it was necessary that the protective layer and the recording material have good adhesion over a long period of time under various environments, and at the same time, the recording material as a whole should not warp or deform under various environments.

Furthermore, as a method for producing a recording material that requires high-density recording, uniformity of the surface of the recording material is particularly required.

That is, when laminating the protective layer on top of the recording material layer,
Usually, an adhesive layer is interposed, but a manufacturing method is required that does not involve minute air bubbles at the interface between the recording layer and the adhesive layer.

[Means to solve the problem]

In order to solve the above problems, it is insufficient to consider only the recording layer in which fine metal silver particles are dispersed in a hydrophobic binder, and it is necessary to add a transparent polymer protective layer to protect the recording layer and a combination of both of these layers. It was necessary to interpose a suitable adhesive resin layer in between.

That is, the present invention provides a digital recording material comprising a recording layer provided on a base film, in which fine metal silver particles are dispersed in a hydrophobic binder, and a transparent polymeric protective layer for protecting the recording layer. The above problem was solved by interposing a transparent adhesive resin layer with a glass transition temperature of -90°C to +60°C between the layer and the transparent polymer protective layer with a thickness of 0.1 to 50 μm. be.

Furthermore, when this laminated digital recording material was produced in the next manufacturing process, it was possible to perform high-density recording, especially with a reduced error rate.

In this production method, when interposing a transparent adhesive resin layer, the adhesive resin layer is provided in advance on at least one of the recording layer or the transparent polymer protective layer, and then the adhesive resin layer is placed on at least one of the recording layer or the transparent polymer protective layer. This is a method for producing a digital recording material in which both layers are placed in a vacuum state of at least 50 mmHg or less before being brought into close contact with each other, and then the two layers are laminated by being brought into close contact with each other.

The digital recording material of the present invention is characterized in that a transparent adhesive resin layer is interposed between the recording layer and the transparent polymeric protective layer. In particular, the adhesive resin layer has a glass transition temperature of 190°C to It must be a transparent resin layer at +60℃,
If the glass transition point exceeds +60°C, it is undesirable as it will adversely affect the sensitivity of the recording material layer;
The adhesive resin layer with a glass transition temperature of less than
Harsh handling of the falling ring causes problems such as peeling of the recording layer. Moreover, the thickness of the adhesive resin layer greatly affects sensitivity, error rate, and durability performance against harsh handling, and the highest performance is obtained when the adhesive resin layer is provided with a thickness of 0.1 to 50 μ-. It becomes digital recording material.

Furthermore, the long-term stability of digital recording materials, reliability under harsh handling, and chemical stability of the recording material layer against direct sunlight, etc. are especially important when using a hydrophobic binder with silver metal fine particles dispersed in a high concentration on the surface. It largely depends on the affinity of the adhesive resin layer with the hydrophobic binder, and in particular, a hydrophobic adhesive resin layer that has a high affinity with the hydrophobic binder is selected.

Typical resins that make up this adhesive resin layer include polyurethane resins, aliphatic linear polyester resins, polyvinyl chloride, vinyl chloride/vinyl acetate copolymers, and various acrylic ester/methacrylic ester-containing acrylic resins. Generally selected from resins soluble in organic solvents. Among these, urethane resins in particular can be easily designed to have a suitable glass transition point, and can be expected to have strong adhesive properties by being three-dimensionally crosslinked at room temperature or by heat treatment.
The resin itself has good affinity with the hydrophobic binder containing fine silver particles, and is particularly effective in keeping the chemical stability of the silver metal fine particles constant.

Furthermore, although urethane resin has a high affinity with hydrophobic binders, it does not have any effect on the properties of the hydrophobic binder or metal silver particles that determine sensitivity, and digital recording materials with urethane resin binders interposed was particularly sensitive.

The reflective recording layer in which fine silver particles of the present invention are dispersed in a hydrophobic binder can be produced by providing a layer containing an organic silver salt, a reducing agent, and a hydrophobic binder on a base film, and then heat-treating the layer.

Prior to this heat treatment, the digital recording material of the present invention has a base film on which a very small amount of silver or a metal more harmful than silver is deposited on the surface of the base film, and a layer containing an organic silver salt, a reducing agent, and a hydrophobic binder is placed on top of this. A reflective silver fine particle dispersed layer may be formed by heat-treating the reflective layer.

First, as a method for depositing silver or a metal heavier than silver on the base film, vapor deposition, sputtering, or electroless plating pretreatment methods can be applied. This small amount of metal attached acts as a catalytic nucleus when heating reduces the silver salt to form metallic silver, forming a reflective recording material when viewed from the base film side. On the other hand, instead of forming reduction catalyst nuclei on the base film, the surface of a recording layer forming precursor layer containing a silver salt compound, a reducing agent, and a hydrophobic binder is coated and dried to coat silver or a metal more sensitive than silver. It is also possible to attach a nucleus and heat it. Examples of organic silver salt compounds include long-chain aliphatic silver carboxylates such as silver behenate and silver stearate, nitrogen-containing organic silver compounds such as silver phthalazinone and silver benzotriazole, and various silver-aurate complexes. A wide variety of compounds can be used, such as. In particular, silver compounds that are soluble in organic binders are useful in the present invention;
For example, fluorine-containing organic silver compounds such as silver trifluoroacetate can be used as suitable compounds. The reducing agent used in the present invention is a so-called hindered phenol as a slow reducing agent for organic silver salts. The hydrophobic binder used in the present invention can be arbitrarily selected from a wide range of organic polymer compounds. For example, polystyrene,
It can be selected from polymethyl methacrylate, polyvinyl butyral, linear polyester resin, linear polyurethane resin, etc. The base film can be selected from a wide range of chemically and physically stable materials such as polyester films typified by polyethylene terephthalate, various polyimide films, polycarbonate resins, polymethyl methacrylate resins, and glass substrates.

As the transparent polymer protective layer for protecting the recording layer of the present invention, a transparent and tough polymer sheet, such as a sheet of polycarbonate, polymethyl methacrylate, polyester, etc., is used. The thickness of this transparent sheet is determined by the optical design of the system applied to the digital recording material, and a thickness of about 0.2 to 2 mm is usually used.

The digital recording material of the present invention records data such as music recording information, video recording information, or document information converted into digital signals by a semiconductor laser of about 2 to 20 mW focused to about 1 to 2 μm. be. Therefore, it is practically required to keep the error rate of recorded bits low. Therefore, when laminating a transparent polymer protective layer via an adhesive resin layer for a given purpose, it is necessary to manufacture the layer as smoothly as possible and without trapping air bubbles. As a result of various studies, we found that the error rate of data strings consisting of bits of about 1 to 2 μm can be significantly improved by placing the laminate in a vacuum system and then applying pressure before the adhesive layer is completely adhered. I understand.

In particular, the degree of vacuum is closely related to the error rate, and when the degree of vacuum is set to 50 mmFIg or less, a digital recording material with an extremely low error rate can be produced. The effect can be improved by further increasing the degree of vacuum, but there is no need to increase the vacuum unnecessarily, and it is usually 10-
A degree of vacuum of about 3 mmt (g) or less is not required.

Examples are described below to explain the present invention in more detail, but the present invention is not limited thereto.

Example 1 A coating liquid consisting of the following components was prepared.

Silver trifluoroacetate -225g Polymethyl methacrylate 178g2-t-butyB-6-(3-t-buty)2-human-oxy
75 g5-Methylpencil)-4-methylphenylacrylate methyl ethyl ketone 1
720g toluene 500g
This coating solution was stirred for about 2 hours to make it homogeneous, and was passed through a filter with an average pore size of 1.5 μm to remove undissolved matter and dust.

After drying this coating liquid with a small applicator, apply 6μ
The slits were selected so as to have a diameter of m, and the film was uniformly coated on a polyethylene terephthalate film and dried at a temperature of 30°C. Next, this sample was immersed in the following aqueous solutions for 30 seconds each, washed with water, and air-dried.

Aqueous solution 1> Activator Neogant 834 40d (trade name of Nippon Schering Co., Ltd.) Distilled water 956Id Sodium hydroxide 3 g Aqueous solution 2> Reducer Neogant WA 5d (trade name of Nippon Schering Co., Ltd.) Distilled water 950d Boric acid
5g, then heated to 150℃40 using a block heater.
When heated for 0 seconds, a metal silver particle dispersion layer with a reflectance of 76% (
recording layer) could be formed. Thereafter, a photomask was brought into close contact with the recording layer and xenon flash exposure was performed to form a preformat on the surface of the recording material.

Next, 1.2 m of the recording layer (reflective surface side) of the optical recording material was
A polycarbonate resin of m was laminated with an adhesive.

Various types of adhesives were selected at this time, and sensitivity and stability were examined. Here, a coating liquid was applied to the polycarbonate resin and dried so that the thickness of the adhesive layer was about 20 μm after drying, and then the surface of the recording material and the adhesive layer were passed through a pressure roll to laminate. The composition of the adhesive used is
The sensitivity and stability results using this material are shown in Table 2. Sensitivity was evaluated by expressing the rate of change in reflectance as a contrast ratio in percentage when recording was performed for about 25 microseconds using a 10 mW semiconductor laser with an optical diameter condensing light into a spot diameter of about 2 micrometers. Furthermore, stability is the result of measuring the sensitivity after the recording material was left at 70° C. and 90% for two weeks, and expressing the sensitivity retention rate (change rate of contrast ratio) as a percentage of the initial sensitivity.

(Margin below) Table Table Example 2 When laminating using the adhesive of composition 1 of Example 1, before pressing the adhesive layer and recording material layer, both materials were left in a vacuum condition and then brought into close contact. I did it like that. Materials were prepared with different degrees of vacuum at this time as shown in Table 3, and their error rates as optical memory materials were evaluated, and the results are shown in Table 3.

The error rate is determined by setting the error rate before lamination as 100 and determining the increase or decrease in the error rate after lamination relative to the error rate before lamination.

Table 3

Claims (2)

[Claims] (1) A digital recording material consisting of a recording layer formed by dispersing metal silver fine particles in a hydrophobic binder provided on a base film, and a transparent polymer protective layer for protecting the recording layer. A digital recording material characterized in that a transparent adhesive resin layer having a glass transition temperature of -90°C to +60°C is interposed between the transparent polymer protective layer and the thickness of 0.1 to 50 μm. (2) When interposing a transparent adhesive resin layer in the digital recording material according to claim (1), the adhesive resin layer is provided in advance on at least one of the recording layer or the transparent polymer protective layer; Then, when laminating this with the adhesive resin layer in between, ensure that both layers are placed in a vacuum state of at least 50 mmHg or less before being brought into close contact with each other, and then the two layers are brought into close contact with each other to be laminated. A method for producing a featured digital recording material.