JPH04261418A - Hard coat resin composition for light information recording medium - Google Patents

Abstract

PURPOSE:To obtain a hard coat resin composition for light information recording medium, having excellent scratch resistance, adhesivity and durability. CONSTITUTION:A hard coat resin composition containing a polyfunctional urethane acrylate, a polyfunctional acrylate and a photopolymerization initiator. The hard coat layer obtained by applying and curing the hard coat resin composition has excellent scratch resistance, adhesivity and durability.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard coat resin composition that is applied to the information reading surface of an optical information recording medium, such as a magneto-optical disk, on which information can be recorded and reproduced using light.

0002

[Prior Art] Optical information recording media, such as optical discs, on which information can be recorded and reproduced using light, are capable of high-density recording.
Since information is recorded and reproduced without contact, there is almost no deterioration of the information signal, so it is a recording medium that has been attracting attention in recent years for use in large-capacity files.

[0003] In such an optical information recording medium, a recording film such as a magneto-optical recording film is formed on a substrate onto which information pits, pregrooves, and preformats have been transferred, and then a protective coating film is applied to the recording film. Used as a single plate or laminated together.

[0004] An optical pickup is used to record and reproduce information on an optical information recording medium, and information is recorded and erased by irradiation with a focused laser beam from the information reading surface of the recording medium. In addition, reflected light from the recording film is used for reproduction. At this time, if there is dust or scratches on the information reading surface,
This obstructs the optical path, making accurate recording and reproduction of information impossible.

[0005] Plastic substrates such as polycarbonate, PMMA, amorphous polyolefin, etc. or glass substrates are used as substrates for optical disks and the like. Glass substrates are a material with excellent scratch resistance, but are used for limited purposes because they are expensive. On the other hand, plastic substrates have traditionally been mainly used because they are lightweight and can be mass-produced at low cost by injection molding.

However, plastic substrates have insufficient scratch resistance, and in order to overcome this drawback, Japanese Patent Laid-Open No. 57-113432 discloses that information recording media can be manufactured by using a transparent material with high hardness. It has been proposed to provide a hard coat film on the surface. As a means of hard coating, spin coating method (Japanese Patent Application Laid-Open No. 57-164
454), a method has been proposed in which an organic polymer such as an ultraviolet curable resin is applied and cured by a 2P method or the like. It has also been proposed to provide a ceramic hard coat film of silicon dioxide or the like by a precipitation method (Japanese Unexamined Patent Publication No. 62-20876) or a sputtering method.

[0007]

[Problems to be Solved by the Invention] However, ceramic hard coats have poor productivity and are therefore inconvenient for mass production. For this reason, hard coating using ultraviolet curable resin has traditionally been used as a simple and highly productive method. It was hard to say that it was a sufficient characteristic in terms of gender. That is, resin compositions used for hard coats generally include reactive monomers, a polymerization initiator, and adhesion agents, leveling agents,
It is made by adding various additives such as diluents, and gives hardness by increasing the crosslinking density.However, due to the high curing shrinkage rate, the stress associated with shrinkage causes the substrate to warp greatly, making it difficult to harden. This had the disadvantage that the adhesion of the coat was reduced. In addition, although it was hard, it had brittle properties, and its scratch resistance was insufficient.

The problem to be solved by the present invention is to provide a hard coat resin composition for optical information recording media that has high scratch resistance.

[0009]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a hard coat resin composition characterized by containing a polyfunctional urethane acrylate, a polyfunctional acrylate, and a photopolymerization initiator. .

The present invention will be explained in detail below.

[0011] Urethane acrylate resin has flexibility,
It has characteristics such as high toughness and excellent adhesion to plastics such as polycarbonate. When an epoxy acrylate resin is used instead of a urethane acrylate resin, high hardness can be obtained, but stress due to curing shrinkage is large and adhesion is insufficient. On the other hand, polyfunctional acrylates have the function of accelerating the curing speed of the resin composition and imparting hardness to the hard coat by improving crosslinking density, as well as reducing residual monomers in the ultraviolet curable resin composition.

The polyfunctional urethane acrylate used in the hard coat resin composition used in the present invention is synthesized from polyvalent isocyanate, polyhydric alcohol and hydroxyacrylate by a general synthesis method.

Examples of polyvalent isocyanates include aliphatic isocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate and methylene bis(4-cyclohexyl isocyanate). In addition, tolylene diisocyanate, 4
Aromatic isocyanates such as , 4-diphenylmethane diisocyanate cause yellowing and are not preferred as hard coat resin compositions.

Examples of polyhydric alcohols include polyester polyols produced by the esterification reaction between organic polybasic acids such as adipic acid and sebacic acid and polyhydric alcohols such as 1,6-hexanediol and neopentyl glycol; Examples include polyether polyols such as poly(propylene oxide) diol and poly(tetramethylene oxide) diol.

Examples of the hydroxyacrylate include 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate.

[0016] When synthesizing urethane acrylate,
It is important to adjust the average molecular weight to 3,000 to 10,000. If the average molecular weight is less than 3,000, hardness can be obtained upon curing, but flexibility tends to be lost, making it brittle and easily damaged, which is not preferable. On the other hand, if the average molecular weight is greater than 10,000, the required hardness cannot be obtained and the curing rate tends to be slow, which is not preferable.

Examples of the polyfunctional acrylate include neopentyl glycol diacrylate and pentaerythritol triacrylate.

Examples of the photopolymerization initiator include "Irgacure-184" (manufactured by Ciba Geigy), "Darocure-1169" (manufactured by Merck Japan), and "Darocur-1" (manufactured by Merck Japan).
173" (same), "Lucirin TPO" (manufactured by BASF), etc. are suitable.

[0019] The content of polyfunctional urethane acrylate is
A range of 40 to 80% by weight is preferred, and 50 to 60% by weight.
A range of is particularly preferred. The content of polyfunctional acrylate is preferably in the range of 20 to 60% by weight. The content of the photopolymerization initiator is preferably in the range of 0.5 to 5% by weight. When the proportion of polyfunctional urethane acrylate used is more than 80% by weight, or when the proportion of polyfunctional acrylate used is less than 20% by weight, the hard coat has good flexibility, but the required hardness cannot be obtained. This is not desirable because there is a tendency that there is no such thing. The usage ratio of polyfunctional urethane acrylate is 4
If it is less than 0% by weight, or if the proportion of polyfunctional acrylate used is more than 60% by weight, sufficient hardness can be obtained, but adhesion and durability tend to be insufficient, which is not preferable.

Furthermore, leveling agents, antistatic agents, other reactive diluents, solvents, etc. may be added to this hard coat resin composition to the extent that its performance is not impaired. Particularly when applying this hard coat resin composition to an optical disk substrate by spin coating, dilution with a solvent such as toluene is effective.

[0021]

[Examples] The present invention will be explained in more detail with reference to Examples below. In the examples, "parts" and "%" represent "parts by weight" and "% by weight," respectively.

(Examples 1 to 5) Commercially available polyfunctional urethane acrylates listed in Table 1 below, neopentyl glycol diacrylate (manufactured by Nippon Kayaku, trade name "Kayarad NPGDA") as a polyfunctional acrylate, and light A hard coat resin composition was prepared by blending "Irgacure-184" as a polymerization initiator.

[0023]

[Table 1]

[0024] In Table 1, "urethane acrylate" is
It stands for “polyfunctional urethane acrylate resin” and “NP
"GDA" stands for "Kayarad NPGDA",
"UV-7550B" and "UV-7000B" are manufactured by Nippon Gosei Kagaku Kogyo, "UN-9000PEP" is manufactured by Negami Kogyo, "SR-9600" and "SR-9630"
” is a polyfunctional urethane acrylate manufactured by Sartomer.

[0025] The obtained hard coat resin composition was heated to 13
After spin coating on a 0 mmφ polycarbonate optical disk substrate, it was cured by irradiation with ultraviolet rays to a film thickness of 10 mm.
A hard coat layer with a thickness of μm was formed.

[0026] For the obtained sample, JIS K
A cross-cut peeling test was conducted using "cellotape" (cellophane adhesive tape manufactured by Nichiban Co., Ltd.) based on No. 5400. Evaluation was performed based on the residual rate on the disk substrate, and the results are shown in Table 2.

[0027]

[Table 2]

From the results shown in Table 2, it can be seen that the hard coat layers obtained in each example exhibited good adhesion.

[0029] Also, for the obtained sample, JIS
The Taber abrasion test specified in K 7204 was carried out using abrasion wheel "CS-10", load 500g x 2, rotation speed 70
The cloudiness was measured using a haze meter under the conditions of rpm and 100 wear cycles, and the results are shown in Table 3.

[0030]

[Table 3]

From the results shown in Table 3, it can be seen that the hard coat layers obtained in each example exhibited good scratch resistance with a haze of 30 or less.

(Comparative Example 1) In Example 1, “UV-
A hard coat layer was formed on a polycarbonate optical disk substrate in the same manner as in Example 1, except that 60 parts by weight of "Viscoat 540" (epoxy acrylate resin manufactured by Osaka Organic Co., Ltd.) was used instead of "7550B".

The obtained samples were tested in the same manner as in the examples, and the results are shown in Table 4. From the results shown in Table 4, it is clear that the hard coat layer obtained in Comparative Example 1 had good scratch resistance but insufficient adhesion.

(Comparative Example 2) A polycarbonate resin composition was prepared in the same manner as in Example except that a hard coat resin composition containing 95 parts by weight of "UV-7000B" and 5 parts by weight of "Irgacure-184" was used. A hard coat layer was formed on the optical disc substrate.

The obtained samples were tested in the same manner as in the examples, and the results are shown in Table 4. From the results shown in Table 4, it is clear that the hard coat layer obtained in Comparative Example 2 had good adhesion but insufficient scratch resistance.

(Comparative Example 3) “Kayalad NPGDA
A hard coat layer was formed on a polycarbonate optical disk substrate in the same manner as in the example except that a hard coat resin composition containing 98 parts by weight of "Irgacure-184" and 2 parts by weight of "Irgacure-184" was used.

The obtained samples were tested in the same manner as in the examples, and the results are shown in Table 4. From the results shown in Table 4, it is clear that the hard coat layer obtained in Comparative Example 3 had insufficient adhesion, and in terms of scratch resistance, although it was hard, it was brittle and had a high degree of haze. It is.

[0038]

[Table 4]

[0039]

Effects of the Invention The hard coat resin composition of the present invention can form a hard coat with excellent scratch resistance, adhesion, and durability, so it can be used as a material for forming a hard coat layer of an optical information recording medium. Extremely useful.

Claims (4)

[Claims] 1. A hard coat resin composition to be applied to the information reading surface of an optical information recording medium having a recording film on which information can be recorded and reproduced by light, the composition comprising a polyfunctional urethane acrylate, a polyfunctional acrylate, and a photopolymerization initiator. 1. A hard coat resin composition for an optical information recording medium, comprising a hard coating agent. 2. The hard coat resin composition for an optical information recording medium according to claim 1, wherein the polyfunctional urethane acrylate has an average molecular weight in the range of 3,000 to 10,000. 3. The hard coat resin composition for optical information recording media according to claim 1, wherein the content of polyfunctional urethane acrylate is in the range of 40 to 80% by weight. [Claim 4] The content of polyfunctional acrylate is 20 to 20%.
The hard coat resin composition for optical information recording media according to claim 1 or 2, wherein the content is in the range of 60% by weight.