JPH0334138A - Optical recording medium and production thereof - Google Patents

Abstract

PURPOSE:To improve the solvent resistance of a high-polymer resin substrate and to stabilize the reflectivity of the coating type recording medium by subjecting the high-polymer resin substrate to a pretreatment in such a manner that the moisture content of the non-frozen water of the high-polymer resin substrate attains a specific value, then forming a solvent coating type recording medium on the high-polymer resin substrate. CONSTITUTION:A high polymer is shrunk by removing the non-frozen water of the resin substrate, by which the intermolecular force is increased and the solvent resistance of the substrate surface is improved. Vacuum drying, drying by heating, drying by a dehydrating agent, and the combined drying method thereof are used as the method for removing the non-frozen water from the transparent high-polymer resin substrate. Although the drying time varies with the drying methods, the drying is executed until the weight or shrinkage rate of the substrate attains a specified weight or rate and the moisture content of the non-frozen water of the resin substrate attains <=0.05%. The resin substrate is dried in such a manner and is subjected to the pretreatment and thereafter, the solvent coating type recording medium is formed on the resin substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium in which a solvent-coated recording medium is formed on a substrate, and a method for manufacturing the same.

[Prior Art] Conventionally, an optical recording medium using a solvent-coated recording medium made of a dye or the like is produced by coating a plastic substrate with a solution in which a dye is dissolved in a solvent by spin cording, spray coating, gravure coating, etc. It is manufactured by a method in which a dye recording layer is formed by removing the solvent.

[Problems to be Solved by the Invention] However, when a solvent-coated recording medium is formed on a plastic substrate, a problem arises in that the plastic substrate has low solvent resistance to the coating solvent. When the substrate surface is dissolved by the coating solvent, a reduction in the reflectance of the coated dye recording layer formed on the substrate surface is observed as a phenomenon in which a film forms. This phenomenon occurs because during the coating and drying process of the dye solution on the substrate, the substrate surface is dissolved by the dye solvent, and a part of the dye layer changes due to reaction or interaction between the eluted substrate constituents and dye molecules. It is thought that this occurs in

Such a decrease in reflectance during the manufacturing process promotes a decrease in the light resistance of the optical recording medium and a decrease in performance in an environmental resistance test under high temperature and high humidity.

Therefore, it is necessary to improve the solvent resistance of the substrate, and the means for achieving this are: 1. Hardening and modification of the substrate surface using electron beams.

(2) A known method is to provide an undercoat layer between the substrate and the dye layer.

However, in the electron beam processing (2), the static electricity generated during the electron beam processing causes problems in manufacturing due to the adsorption of dust and foreign matter, and extensive static elimination measures are required.

In addition, in the method (2) of providing one undercoat layer, the undercoat layer reduces recording sensitivity and increases noise in reflected light.
Alternatively, preformatted signals for an optical head provided on a substrate by an injection method or the like may become difficult to read due to the undercoat layer.

2. Description of the Related Art Conventionally, it is known as a substrate processing method to heat a substrate at a temperature near the Tg (glass transition point) of the substrate in order to remove optical distortion of the substrate, such as birefringence of the substrate. (Japanese Unexamined Patent Publication No. 184943/1983) In addition, JP 63/607:19 discloses a substrate heat treatment apparatus, which also prevents optical distortion or deformation of the substrate. This is a device to prevent this.

None of the above two conventional examples discloses the effect or function of improving the reflectance of a coated recording medium formed on a plastic substrate.

Further, if heat-treated at around 7 g, the substrate tends to be thermally deformed, and it is necessary to heat-treat the substrate on a flat heater such as a hot plate during manufacturing. If the substrate is held vertically during processing, the substrate will easily deform. Therefore, 7g
Nearby heat treatment is not suitable for mass production of optical recording media.

The present invention was made to solve the problems of the prior art, and improves the solvent resistance of polymer resin substrates and stabilizes the reflectance of coated recording media using polymer resin substrates. It is an object of the present invention to provide an optical recording medium that can be converted into an optical recording medium and a method for manufacturing the same.

[Means for Solving the Problems] That is, the present invention provides an optical recording medium formed by forming a solvent-coated recording medium on a polymer resin substrate, in which the antifreeze water content of the polymer resin substrate is 0. In an optical recording medium and a method for producing an optical recording medium in which a solvent-coated recording medium is formed on a polymer resin substrate, the water content of antifreeze water in the polymer resin substrate is .05% or less. Provided is a method for producing an optical recording medium, characterized in that a polymer resin substrate is pretreated so that the amount of 0.05% or less is obtained, and then a solvent-coated recording medium is formed on the polymer resin substrate. That's true.

The present invention will be explained in detail below.

Transparent resins such as polycarbonate, polymethyl methacrylate, and polystyrene are used as the polymer resin substrate (hereinafter referred to as resin substrate) used in the method for manufacturing an optical recording medium of the present invention. If it is manufactured at room temperature and humidity, it will always contain water. The water contained in these resin substrates is defined as polymer-containing water. Furthermore, the water contained in the polymer was measured using a differential scanning calorimeter (D, S, C: Differential Scanning Calorimeter).
nnningCalorimetry), the "unfreeze water" expressed in the present invention,
It can be broadly classified into what is commonly known as ``freezing water.'' Dividing the water contained in this polymer into two parts is reported in the cited document below.

Cited document 1, r NETSUSOKUTEIJ 7 (1
) 18-25 (1980) Thermal analysis for beginners (2) Application of DTA and DSC to polymeric liquid crystal materials, etc. 2, T., Hatakeyama, H.
, Hatakeyama and K, Nak
a-aura, r 5tudies on boun
d water of cellulose by di
fferential scanning color
imetryJ, TextRes-J,, 51
(1981) 607゜3, M, A, From
mer and D, J, Lancet, r
Freezing and nonfreezing
wa, ter in cellulose acet
a-te membranes J, J,
Appl, Polym, Sci, 1
6 (1972) 1295°4. Y, Ogawa and S, 5uzuki,
ron the nature of fre
e and bound water in
water per+5ation of ce
lulose acetate membrane
es in reverse osmosisJ
, Desalination, 42 (1982) 5
7゜5, 5IR) IAsHDEODFIAR, and
PHILIP LINER,r Measurem
Ent of Bound (Nonfreez
ing) water by Differenti
al Scanning Chromimetry,
J AIlericanChemical 5oci
ety Report, No. 127 (1980
Chapter 16.237 - 285゜The generally known "frozen water" is referred to as free water (free water) in literature.
When measuring D-3,C when the temperature is raised from a low temperature, it is observed as a peak of the heat of melting of ice around -3 to +3°C.

On the other hand, antifreeze water is called bound water and bound water, and is composed of O, S
It is defined as water that does not show a heat of fusion peak during the temperature raising process from a low temperature (-30 to -40°C) using C, or water that shows a heat of fusion peak below 110°C (cited Literature: T., Hatakeyama, H.

Hatakeyama and K, Nakamu
ra, rstudies onbound w
ater of cellulose by
differential scanning cal
orimetryJ,Text,Res,J,,5
1 (1981) 607) It is thought that antifreeze water forms hydrogen bonds with a polymer matrix, creating a (polymer)-(water)-(polymer) bond within the polymer matrix.

On the other hand, in a polymer having a dense structure, most of the polymer-containing water is considered to be antifreeze water.

(References: Water in Polymer,
AC3Report No.

127 (1980) chapter 16.27
3-285. ) Therefore, when using polycarbonate, polymethyl methacrylate, other acrylic resins such as polybutyl methacrylate, and transparent resin substrates such as polystyrene as substrates for optical recording media, the inventors have found that By removing water, the bond between (polymer) - (water) - (polymer) is changed to (polymer) -
(Polymer) bond, the polymer contracts, and as a result, the inter-polymer force increases and the solvent resistance of the substrate surface improves.

As a method for removing antifreeze water from the transparent resin substrate, vacuum drying, heating (90 to 110° C.) drying, drying using a dehydrating agent (hygroscopic material), and a combination of these drying methods can be used.

The drying time varies depending on the drying method, but depends on the weight of the substrate (g
) or the amount of contraction (mm or ILm order) is constant,
This process is continued until the water content of the antifreeze water on the resin substrate becomes 0.05% or less. If the water content of the antifreeze water exceeds 0.05%, the solvent resistance of the polymer surface will be low, causing a decrease in the reflectance of the coated dye recording layer, which is not preferable.

After the resin substrate is dried and pretreated as described above, a solvent-coated recording medium is formed on the resin substrate. The method of forming a dye layer on a pretreated resin substrate by coating is to dissolve polymethine-based, biryllium-based, cyanine-based, naphthoquinone-based, triphenylmethane-based dyes, etc. in a solvent, and then use a spin coater, gravure coater, etc. It is formed by coating with a spray coater or the like. The solvent is not particularly limited, and commonly used organic solvents may be used, such as ethanol, diacetone alcohol, dichloroethane, methylcellosolve, or a mixture thereof.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Figure 1 shows the vacuum drying time of a resin substrate, changes in the amount of antifreeze water in the resin substrate, and shrinkage of the resin substrate when 0.4-inch thick polymethyl methacrylate (PMMA) is used as the resin substrate. Shows the relationship with quantity. System pressure 1-2 am) I
By vacuum drying at a temperature of 25°C for 2 to 10 hours, the amount of antifreeze water on the resin substrate decreased and the resin substrate shrank.The water content of the amount of antifreeze water on the resin substrate was measured by a differential scanning calorimeter. shows the value.

Next, the following structure i(r
) (C2)(-)J+NtN(C2H9)2
cI! o4e Dissolved in acetone alcohol to a concentration of 3 wt%,
It was coated using a gravure coater. Furthermore, ethylene-
Vinyl acetate adhesive (Nippon Matai, Elfan 0H)
506), polymethyl methacrylate (PM
A protective substrate made of MA) was provided, and an optical card medium as shown in FIG. 2 was produced.

The reflectance of the medium was measured for each optical card, and the relationship between the vacuum drying time and the reflectance is shown in FIG.

In the figure, the larger the width of the binary values, the more unstable the reflectance value is.

As is clear from Figure 3, the reflectance increases as the vacuum drying time increases, and when the amount of antifreeze water is less than O,OS%, the reflectance reaches a saturated value, and when a solvent-coated recording medium is used, the reflectance increases. We were also able to create an optical card medium with stable reflectance.

When vacuum drying was not performed, the reflectance varied greatly and an optical card medium with a stable reflectance value could not be obtained.

Example 2 Using PMMA with a thickness of 0.4 mm as a resin substrate, the resin substrate was heated in vacuum (pressure 1 hm) at Ig, temperature 90°C for 2 hours 2
120 minutes), an optical cart medium was obtained using the same materials as in Example 1.

FIG. 4 shows the relationship between the reflectance of these optical card detachments, the amount of antifreeze water, and the vacuum drying time. From FIG. 4, the reflectance reached a saturation value when the amount of antifreeze water was 0.05% or less, and an optical card medium with stable reflectance could be produced.

[Effects of the Invention] As explained above, according to the present invention, by reducing the water content of antifreeze water in the resin substrate to 0.05% or less, the interpolymer force of the resin substrate increases, and the strength of the resin substrate increases. Solvent resistance can be improved. As a result, the reflectance of the solvent-coated recording medium has less variation in numerical values, and compared to the case where antifreeze water is present, the reflectance is 1 to 2% in absolute value, making it a stable optical recording medium. I was able to get

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the vacuum drying time, the moisture content of the resin substrate, and the shrinkage rate of the resin substrate in Example 1, and FIG. 2 is a schematic diagram of the optical card medium manufactured in Example 1. , FIG. 3 is a graph showing the relationship between vacuum drying time and reflectance of the resin substrate in the optical card medium of FIG. 2, and FIG. 4 is a graph showing the reflectance of the optical card medium of Example 2 and the amount of antifreeze water on the resin substrate. It is a graph which shows the relationship between and vacuum drying time. l... Resin substrate 2... Solvent coated recording medium 3... Adhesive layer 4... Protective substrate

Claims (2)

[Claims] (1) An optical recording medium formed by forming a solvent-coated recording medium on a polymer resin substrate, characterized in that the antifreeze water content of the polymer resin substrate is 0.05% or less. recoding media. (2) In a method for manufacturing an optical recording medium in which a solvent-coated recording medium is formed on a polymer resin substrate, the polymer resin is A method for producing an optical recording medium, which comprises forming a solvent-coated recording medium on a polymer resin substrate after pre-treating the substrate.