JPH04247337A - Optical disk - Google Patents

Abstract

PURPOSE:To provide the optical disk which has an excellent antistatic property and improved flawing resistance by coating the photoirradiated surface of the optical disk with the cured and coated film of a curable resin compsn. CONSTITUTION:This optical disk is constituted by coating the photoirradiated surface of the optical disk with the cured and coated film of the curable resin compsn. contg. (A) 3 to 40wt.% mono(meth)acrylate of the oligoethylene oxide and oligopropylene oxide of formula CH2=CR<1>CO(OCH2CHR<2>)nOH (R<1>, R<2> denote a hydrogen atom or methyl group; (n) denotes integer from 4 to 6), (B) 40 to 80wt.% dipentaerithritol hexa(meth)acrylate or the caprolacton modified matter thereof, (C) 0 to 40wt.% of polymerizable diluent exclusive of the components (A), (B) at need, (D) an anionic surfactant at 0.01 to 10wt.% of the total weight of the components (A), (B) and (C), and (E) a photopolymn. initiator at 1 to 10wt.% of the total weight of the components (A), (B) and (C).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc on which information is recorded and reproduced using light such as a laser.

0002

2. Description of the Related Art Optical disks have attracted attention as high-density, large-capacity information recording media, and research and development are being carried out on various types of optical disks. Among these, erasable and rewritable magneto-optical disks have a wide range of applications and have high expectations for the future. For this reason, various materials and systems have been announced, and their practical application is expected.

[0003] These optical disks require antistatic treatment to prevent the adhesion of dust, etc., and usually an antistatic agent is applied to the surface of the substrate, or an antistatic agent is kneaded into the substrate. Methods such as inclusion are being used. However, the former treatment has problems with durability, and the latter has problems with moldability and light transmittance.

On the other hand, since polycarbonate resin or the like is generally used for the substrate of an optical disk, the surface hardness of the substrate is low. Therefore, to avoid surface damage, UV
It has been proposed to perform surface hardening treatment using a hardened resin or the like. However, with these UV-curable resin coatings, the resin is charged due to friction with the air while the disk is rotating, and the readout surface is often dirty due to dirt and dust, making the recording and readout signals unreliable. deteriorating sexuality.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk having excellent durability and antistatic properties, and also having sufficient surface hardness. More specifically, the object is to provide an optical disk in which a coating film with low surface electrical resistance and high surface hardness is provided on a substrate. Furthermore, resins made of organic polymers such as polycarbonate are generally used as substrate materials for optical disks, and are coated in clean rooms because they are extremely dust-resistant. Under such constraints, the use of solvents and high temperatures are undesirable, and the objective is to create an optical disc that does not require such use.

[0006]

[Means for Solving the Problems] From the viewpoint of coating properties, the present inventors have developed a method using low-viscosity ultraviolet light (
Focused on UV) curable resin compositions. However, coating films formed by curing UV curable resin compositions generally have high surface electrical resistance and poor antistatic properties. As a result of intensive studies to solve this problem, the present inventors found that mono(meth)acrylate of oligoethylene oxide has an OH group and an alkylene oxide unit in the monomer, resulting in a cured coating film with low surface electrical resistance. We have already proposed this method (Japanese Patent Application No. 172655/1999). Since this mono(meth)acrylate of oligoethylene oxide is monofunctional, from the viewpoint of curability, it is desirable to obtain a cured coating film having a low surface resistance with as little amount as possible. The present inventors conducted extensive studies with the aim of obtaining a curable resin composition with low surface resistance and high hardness by reducing the amount of this mono(meth)acrylate as much as possible.

As a result, by combining the mono(meth)acrylate of oligoethylene or propylene oxide with an anionic surfactant, the surface electrical resistance of the cured product can be greatly reduced while maintaining sufficient hardness. I found out that it is possible. Furthermore, by mixing dipentaerythritol hexaacrylate or its caprolactone modified product, the surface hardness can be increased without significantly increasing the surface electrical resistance, and if necessary, by adding low molecular weight acrylate, The present invention was achieved by discovering that the viscosity of the coating solution can be lowered to a range that allows coating.

That is, in the present invention, at least the light irradiation surface (reading surface) of an optical disc is formed by (A) general formula (I) CH2 = CR1 CO(OCH2 CHR2 )n
OH...(I)(
In the formula, R1 and R2 represent a hydrogen atom or a methyl group, and n
represents an integer from 4 to 6. ) mono(meth) of oligoethylene oxide and oligopropylene oxide
3 to 40% by weight of one or more acrylates;
(B) 40 to 80% by weight of one or more of dipentaerythritol hexa(meth)acrylate or its modified caprolactone, (C) polymerizable diluent other than components (A) and (B) as necessary. 0 to 40% by weight, (D
) anionic surfactant as components (A), (B) and (
C) 0.001 to 10% by weight based on the total weight of components (A), (B) and (C), and (E) a photoinitiator.
An optical disc characterized in that it is coated with a coating film cured with a curable resin composition containing 1 to 10% by weight based on the total weight of the disc.

The optical disk of the present invention includes a pit-type optical disk consisting of a recording medium in which pits are formed on a substrate made of glass or resin, a recording medium in which a thermal recording layer is formed on a substrate, a recording medium that uses laser light, etc. These include bubble-type optical disks that form bubbles by irradiation and detect level fluctuations based on changes in reflected light, and magneto-optical disks that are made of recording media in which a magneto-optical recording layer is formed on a substrate.

In addition to glass substrates, resin substrates such as polycarbonate, polymethyl methacrylate, and amorphous polyolefin can be used as the substrates used in the present invention, and the present invention is particularly preferably applied to resin substrates.

[0011] The recording surface of an optical disc refers to the surface on which a recording layer is formed on a substrate such as resin. The surface opposite to the recording surface, ie, the light irradiation surface (reading surface), is a flat surface with no grooves formed in, for example, a magneto-optical disk.

Mono(meth)acrylate of oligoethylene oxide as component (A) used in the present invention [In the present invention, (meth)acrylate represents acrylate and methacrylate. ] is represented by the following formula. CH2=CR1CO(OCH2CHR2)n
In the OH formula, R1 and R2 are hydrogen atoms or methyl groups, and are selected in consideration of their UV curability, compatibility with the resin used together, and the surface electrical resistance and surface hardness of the cured product. Generally, from the viewpoint of UV curability, it is preferable for R1 to be a hydrogen atom, ie, acrylate, than a methyl group, ie, methacrylate. Moreover, when R2 is a hydrogen atom,
It is preferable because the surface electrical resistance is lower than that of a methyl group. n is an integer from 4 to 6, and the (meth)acrylate in this range lowers the surface resistance of the cured product, has sufficient compatibility with the curable resin, and impairs the adhesiveness of the cured product to the base material. do not have. Coating films obtained from (meth)acrylates in which n is 7 or more are not preferred because the adhesiveness of the cured product decreases and the compatibility is low. Furthermore, (meth)acrylates in which n is 3 or less are not preferred because the surface electrical resistance value does not decrease. Specifically, tetraethylene glycol monomethacrylate, pentaethylene glycol monomethacrylate, hexaethylene glycol monomethacrylate, tetraethylene glycol monoacrylate, pentaethylene glycol monoacrylate, hexaethylene glycol monoacrylate, tetrapropylene glycol monomethacrylate, and tetrapropylene. Glycol monoacrylate and the like are preferably used.

Mono(meth) oligoethylene oxide or oligopropylene oxide represented by the above formula (I)
The acrylic ester is contained in the composition in an amount of 5 to 40% by weight. If it is less than 5% by weight, the antistatic effect will be insufficient, while if it exceeds 40% by weight, the surface hardness of the optical disk coated with the composition and cured will be insufficient, which is not preferable.

In the present invention, component B is dipentaerythritol hexaacrylate or its caprolactone modified product. The caprolactone modified product is represented by the following formula.

[0015]

[Formula 1] (wherein A is CH2 = CHCO-, p, q, r
, s, t and u are integers from 0 to 10, and p+
q+r+s+t+u≦14. ) The above-mentioned modified caprolactone is generally obtained as a mixture of dipentaerythritol, caprolactone, and acrylic acid by directly or sequentially esterifying these compounds. Further, the degree of caprolactone modification is determined by the amount of caprolactone used relative to dipentaerythritol. When p+q+r+s+t+u>15, the density of photocrosslinkable acrylate groups decreases, resulting in a decrease in crosslinking density and the desired hardness is not achieved, which is not preferable. Specifically, Nippon Kayaku's product name DPCA20, DP
Examples include CA30, DPCA60, and DPCA120. These each contain an average of 2 dipentaerythritol,
It is a monomer modified with 3, 6, or 12 molecules of caprolactone, which is less irritating to the skin and has less odor.The curing speed is extremely fast, and the cured product shows flexibility despite its high hardness. Provides a cured product with excellent weather resistance. Furthermore, since the viscosity is low, when a composition is formed, the coating properties are also good. The amount of component B used is 40 to 8 in the composition.
0% by weight, preferably 50-80% by weight. If it exceeds 80% by weight, the surface electrical resistance of the coating film becomes high, which is not preferable. Moreover, if it is less than 40% by weight, it is not preferable because the surface hardness of the coating film cannot be increased.

[0016] Component C is not essential and may be used as needed for the purpose of lowering the viscosity of the coating liquid. Therefore, mono- to trifunctional (meth)acrylates which themselves have low viscosity are used. Although it depends on the types and compositions of components (A) and (B) used together, (meth)acrylates with a viscosity of 10 poise or less, more preferably 5 poise or less are preferably used. Suitably used (meth)acrylates include hexamethylene glycol diacrylate, tetrahydrofurfuryl acrylate, hexamethylene glycol dimethacrylate, tetrahydrofurfuryl methacrylate, trimethylolpropane triacrylate, hydroxypivalate neopentyl glycol diacrylate, and glycerol diacrylate. methacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate,
Examples include pentaerythritol tetraacrylate. Among these, hexamethylene glycol diacrylate and tetrahydrofurfuryl acrylate are particularly preferably used to improve the adhesion of the cured product to the polycarbonate substrate and to adjust the viscosity of the composition. The amount of component (C) used is 40% by weight or less of the total composition, including 0% not used, i.e. 0 to 40% by weight, preferably 0 to 30% by weight.
Weight percentages are used. If it exceeds 40% by weight, the surface hardness increases depending on the type, but the surface electrical resistance does not decrease and the adhesiveness with the substrate decreases, which is not preferable.

[0017] The anionic surfactant as component (D) is 0.0 based on the total weight of components (A), (B) and (C).
It is preferable to contain 01 to 10% by weight. Ingredient (D)
If it is less than 0.001% by weight, curing is insufficient and 10% by weight
Exceeding this is unfavorable from the viewpoint of solubility. The amounts of component (A) and component (D) are appropriately selected within this range depending on the compound used. Component (A) and component (D) work together to impart excellent antistatic properties to the cured product. Although the reason is not clear, component (A) acts as a solid electrolyte, and component (D)
It is presumed that there is a special interaction with

When the component (A) is less than 3% by weight, the component (D) is less than 3% by weight.
) is insufficient and the antistatic effect is insufficient. On the other hand, if the content of component (A) exceeds 40% by weight, the surface film hardness of the optical disc coated and cured with the composition is insufficient, which is preferable. do not have.

The anionic surfactant of component (D) includes saturated or unsaturated alkali metal salts of fatty acids, saturated or unsaturated aliphatic sulfonates, and aromatic sulfonates that may contain substituents. , sulfonate salts containing ethylene oxide units, and sodium salts of sulfates containing various substituents. Specifically, sodium todecylbenzene sulfonate, sodium acyl (beef tallow) methyl taurate, sodium lauroyl methyl taurate, sodium cocoyl isetinate, α-sulfo fatty acid ester sodium salt, acid ether sodium sulfate, alkyl ether sulfonic acid. Examples include fatty acid soaps such as sodium, alkyl sulfate sodium salts, alkyl ether sulfate sodium salts, potassium oleate, and potassium coconut fatty acids. Among these, sulfonic acid salt compounds and sulfuric acid ester salt compounds are particularly preferred from the viewpoint of the above-mentioned interaction.

[0020] As the photopolymerization initiator, benzophenone,
Benzophenone initiators such as Michler's ketone, diketone initiators such as benzyl and phenylmethoxy diketone, acetophenone initiators such as acetophenone, benzoin initiators such as benzoin ethyl ether and benzyl dimethyl ketal, and 2,4-diethylthioxanthone. Thioxanthone-based initiators, quinone-based initiators such as 2-methylanthraquinone, camphorquinone, and the like are preferably used. If necessary, it is also possible to use a promoter such as an amine promoter. The upper limit of the amount of initiator used is limited from practical aspects such as cost, and the amount of initiator used is
, B, and C in an amount of 1 to 10% by weight, preferably 2 to 5% by weight, based on the total amount of B and C.

The curable resin composition of the present invention can be coated on the surface of an optical disk by a known method such as spin coating, dip coating, coating with a doctor knife, or coating with a bar coater. In particular, the spin coating method is the most preferred in practical terms because the film thickness can be easily controlled. When coating an optical disk, the antistatic effect can be improved by also coating the side surfaces of the optical disk. In any case, in order to enable coating without using a solvent, the viscosity of the curable resin composition is 20 poise or less, preferably 10 poise or less, more preferably 5 poise or less. If it exceeds 20 poise, it is not preferable because the coating film cannot be controlled smoothly.

[0022] The thickness of the coating film after curing of the present invention is 1 to 30 μm.
m, preferably 5 to 25 μm. 1μm
If the hardness is less than 30μ, sufficient performance will not be exhibited in terms of hardness.
If it exceeds m, not only will it be difficult to control the film thickness, but also the internal hardening properties will decrease, which is not preferable.

The optical disc coated with the composition is cured by known methods and conditions using ultraviolet lamps such as low-pressure mercury lamps, medium-pressure mercury lamps, and high-pressure mercury lamps, halogen lamps, and actinic light such as electron beams.

The surface resistance of the optical disc obtained by the present invention is less than 1015 Ω/□, preferably 1014 Ω/□ or less. Those having a resistance higher than this are ineffective from the viewpoint of antistatic properties. Further, the surface hardness is such that the pencil hardness is HB or more, preferably F or more from the viewpoint of handling.

[0025]

Effects of the Invention The present invention can provide an optical disc that is solvent-free, has highly durable antistatic properties, and has sufficient surface hardness.

[0026]

EXAMPLES The present invention will be explained in more detail with reference to Examples below. The invention is not limited to such embodiments.

In the example, the surface resistance (Ω/□) is J
According to IS K6911. Moreover, the pencil hardness was measured using Uni manufactured by Mitsubishi Pencil.

[0028]

[Example 1] 10% by weight of tetraethylene glycol monoacrylate represented by CH2 = CH-CO(OCH2 CH2 )4OH, DPCA60 manufactured by Nippon Kayaku, which is caprolactone-modified dipentaerythritol hexaacrylate
To 100 parts by weight of a composition consisting of 30% by weight each of DPCA30 and 30% by weight of dipentaerythritol hexaacrylate, and 10% by weight of hexamethylene glycol diacrylate, 0.5 parts by weight of sodium dodecylbenzenesulfonate was added to initiate photopolymerization. A curable resin composition containing 3 parts by weight of the agent Irgacure 907 (manufactured by Ciba Geigy) was prepared. The viscosity of this composition was determined by a B-type viscometer at 25°C.
The measurement result was 1.9 poise. This composition was applied to a thickness of 1.
1 on the flat side of a 2mm polycarbonate disc.
It was applied by spin coating to a thickness of 0 μm. Subsequently, the coating film was cured by irradiating it with ultraviolet rays for 1 minute from a height of 20 cm using a high-pressure mercury lamp with a length of about 27 cm and a power output of 2 KW.

Surface resistance and pencil hardness of the cured surface of the polycarbonate disk after curing were measured.

As a result, the surface pencil hardness was H and the surface resistance was 2.6×10 13 Ω/□.

[0031] Also, the substrate with this cured coating film was heated to 80°C.
A weather resistance test was conducted for 2,000 hours in a heat and humidity tester at 85% humidity, but no change was observed in the cured coating before and after the test.

[0032]

[Comparative Example 1] Nippon Kayaku DPCA60 and DP containing 10% by weight of tetraethylene glycol monoacrylate represented by CH2 = CH-CO(OCH2 CH2 )4OH and caprolactone-modified dipentaerythritol hexaacrylate
Composition 100 consisting of 30% by weight each of CA30, 20% by weight of dipentaerythritol hexaacrylate, and 10% by weight of hexamethylene glycol diacrylate.
A curable resin composition containing 3 parts by weight of a photopolymerization initiator Irgacure 907 (manufactured by Ciba Geigy) was prepared.

This composition was applied to the flat surface of a 1.2 mm thick polycarbonate disk by spin coating to a thickness of 10 μm. Subsequently, the coating film was cured by irradiating it with ultraviolet rays for 1 minute from a height of 20 cm using a high-pressure mercury lamp with a length of about 27 cm and a power output of 2 KW.

Surface resistance and pencil hardness of the cured surface of the polycarbonate disk after curing were measured.

As a result, the surface pencil hardness was H and the surface resistance was 1.1×10 15 Ω/□.

[0036]

[Example 2] 10% by weight of hexaethylene glycol monoacrylate represented by CH2 = CH-CO(OCH2 CH2 )6OH, 30% by weight of each of caprolactone-modified dipentaerythritol hexaacrylate DPCA120 and DPCA20 manufactured by Nippon Kayaku. , Composition 10 consisting of 20% by weight of dipentaerythritol hexaacrylate and 10% by weight of hexamethylene glycol diacrylate.
0 parts by weight, 1 part of sodium dodecylbenzenesulfonate
A curable resin composition containing 5 parts by weight of a photopolymerization initiator Irgacure 907 (manufactured by Ciba Geigy) was prepared. The viscosity of this composition was 1.7 poise as measured at 25°C using a B-type viscometer. This composition was made to a thickness of 1.2 mm.
10 μm on the flat surface of the polycarbonate disk.
The coating was applied by spin coating to a thickness of . Next, using a 2KW high-pressure mercury lamp with a length of about 27cm,
The coating film was cured by irradiating ultraviolet rays from a height of 20 cm for 1 minute.

Surface resistance and pencil hardness of the cured surface of the polycarbonate disk after curing were measured.

The surface hardness of the obtained disk is H,
The surface resistance was 1.5×10 13 Ω/□.

[0039]

[Comparative Example 2] 10% by weight of hexaethylene glycol monoacrylate represented by CH2 = CH-CO(OCH2 CH2 )6OH, caprolactone-modified dipentaerythritol hexaacrylate and DPCA120 manufactured by Nippon Kayaku Co., Ltd.
To 100 parts by weight of a composition consisting of 30% by weight of DPCA20 and 30% by weight of dipentaerythritol hexaacrylate, and 10% by weight of hexamethylene glycol diacrylate, 5% by weight of the photopolymerization initiator Irgacure 907 (manufactured by Ciba Geigy) was added. A curable resin composition containing 50% of the curable resin composition was prepared. The viscosity of this composition was determined by a B-type viscometer at 25°C.
The measured value was 1.7 poise. This composition was applied to a thickness of 1.
1 on the flat side of a 2mm polycarbonate disc.
It was applied by spin coating to a thickness of 0 μm. Subsequently, the coating film was cured by irradiating it with ultraviolet rays for 1 minute from a height of 20 cm using a high-pressure mercury lamp with a length of about 27 cm and a power output of 2 KW.

Surface resistance and pencil hardness of the cured surface of the polycarbonate disk after curing were measured.

The surface hardness of the obtained disk is H,
The surface resistance was 1.5×10 15 Ω/□.

[0042]

[Example 3] 5% by weight of pentaethylene glycol monoacrylate represented by CH2=CH-CO(OCH2CH2)5OH, 45% by weight of DPCA60 manufactured by Nippon Kayaku Co., Ltd. and DPCA30 as well as caprolactone-modified dipentaerythritol hexaacrylate. Sodium alkyl ether sulfonate (Avanel S70; manufactured by NOF Corporation) was added to 100 parts by weight of a composition consisting of 20% by weight of trimethylolpropane triacrylate, 20% by weight of trimethylolpropane triacrylate, and 10% by weight of hexamethylene glycol diacrylate. A curable resin composition containing 1 part by weight and 3 parts by weight of a photopolymerization initiator Irgacure 907 (manufactured by Ciba Geigy) was prepared. The viscosity of this composition was measured at 25°C using a B-type viscometer, and the viscosity was 2.
It was 1 poise. This composition was applied to a flat surface of a 1.2 mm thick polycarbonate disk to a thickness of 10 μm by spin coating. Next, using a 2KW high-pressure mercury lamp with a length of about 27cm, 20
The coating film was cured by irradiating ultraviolet rays from a height of cm for 1 minute. The surface resistance and pencil hardness of the cured surface of the polycarbonate disk after curing were measured.

The surface hardness of the obtained disk was H,
The surface resistance was 3.1×10 13 Ω/□.

[0044]

[Example 4] CH2=CH(CH3)-CO(OCH2
20% by weight of tetraethylene glycol monomethacrylate represented by CH2)4OH, 45% by weight of caprolactone-modified dipentaerythritol hexaacrylate, DPCA60 manufactured by Nippon Kayaku, and DPCA30.
R(OC
H2 CH2 O)n SO3 Na(Levenol WX
A curable resin composition containing 1 part by weight of Irgacure 907 (manufactured by Kao Corporation) and 3 parts by weight of a photopolymerization initiator Irgacure 907 (manufactured by Ciba Geigy) was prepared. The viscosity of this composition was 2.0 poise as measured at 25°C using a B-type viscometer. This composition was applied to a flat surface of a 1.2 mm thick polycarbonate disk to a thickness of 10 μm by spin coating. Continuing, length approximately 27cm, 2KW
The coating film was cured by irradiating it with ultraviolet rays for 1 minute from a height of 20 cm using a high-pressure mercury lamp.

Surface resistance and pencil hardness of the cured surface of the polycarbonate disk after curing were measured.

The surface hardness of the obtained disk is F,
The surface resistance was 6.8×10 13 Ω/□.

Claims (7)

[Claims] Claim 1: At least the light irradiation surface (reading surface) of the optical disc is formed by (A) general formula (I) CH2 = CR1 CO(OCH2 CHR2 )n
OH...(I)(
In the formula, R1 and R2 represent a hydrogen atom or a methyl group, and n
represents an integer from 4 to 6. ) mono(meth) of oligoethylene oxide and oligopropylene oxide
3 to 40% by weight of one or more acrylates;
(B) 40 to 80% by weight of one or more of dipentaerythritol hexa(meth)acrylate or its modified caprolactone, (C) polymerizable diluent other than components (A) and (B) as necessary. 0 to 40% by weight, (D)
Anionic surfactants are added to components (A), (B) and (C).
0.001 to 10% by weight based on the total weight of components (A), (B) and (C), and (E) a photoinitiator.
1. An optical disk coated with a coating formed by curing a curable resin composition containing 1 to 10% by weight based on the total weight of the optical disk. 2. The optical disc according to claim 1, wherein component (B) is caprolactone-modified dipentaerythritol hexa(meth)acrylate. 3. The optical disc according to claim 1 or 2, wherein component (D) is a sulfonic acid salt compound and/or a sulfuric acid ester salt compound. Claim 4: Component (C) is 25% as measured by a B-type viscometer.
4. The optical disc according to claim 1, 2 or 3, wherein the optical disc is a mono- to trifunctional (meth)acrylate having a viscosity of 10 poise or less as measured at °C. 5. The optical disc according to claim 1, wherein component (C) is hexamethylene glycol diacrylate and/or tetrahydrofurfuryl acrylate. 6. The optical disk according to claim 1, wherein the curable resin composition has a viscosity of 10 poise or less as measured at 25° C. with a B-type viscometer. 7. A paint film obtained by curing the curable resin composition has a pencil hardness of F or more and a surface resistance of 1014.
7. The optical disk according to claim 1, wherein the optical disc has a resistance of Ω/□ or less.