JPH08235639A - Optical recording medium and its formation method - Google Patents

Abstract

PURPOSE: To obtain an optical recording medium which has an excellent abrasion resistance and prevents a warp or a crack due to a bend. CONSTITUTION: In an optical recording medium which is overlaid with a hardened layer 6 by a hardening resin on a transparent protective layer 1, the hardness of the hardened layer 6 is made continuously high from the interface toward the surface of the transparent protective layer 1. When the hardened layer 6 is to be formed, a plurality of hardening resins whose coefficients of hardening contraction are different are supplied simultaneously so as to be overlapped in a state that their coefficient of hardening contraction becomes large from the interface toward the surface of the transparent protective layer 1, and the resins are then hardened collectively. A layer whose hardness is high (whose coefficient of hardening contraction is large) exists at the outside, and a layer whose hardness is low (whose coefficient of hardening contraction is small) exists at the inside, no interface exists between the layers, and the layers are in a continued state. As a result, it is possible to obtain the optical recording medium in which a warp does not exist as a whole, whose bending fitness is excellent and whose abrasion resistance is excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium used for optical cards, flexible disks, etc., and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a thin film of a low melting point metal or an organic dye is provided as a recording layer on a substrate, and recording is performed by irradiating a laser beam or the like to cause a change in a part of the thin film and recording. Optical recording media that optically reproduce data are known.
The recording method of this optical recording medium is read-only (ROM)
Type, write-once (DRAW) type, erase write (E-DRAW)
There are types, and recording media and configurations are being examined for each.

A so-called optical card having such an optical recording medium as a card basically has a layer structure as shown in FIG. In the figure, 1 is a transparent protective layer as a support, which has a high transmittance in the wavelength range of the light source used for recording and reproduction, and does not cause deformation or deterioration in the subsequent steps, and has a mechanical strength and an optical characteristic. There is no particular limitation as long as it satisfies the requirements, and generally, a polycarbonate resin, an acrylic resin, a urethane resin, an epoxy resin, a polyvinyl chloride resin, a polyolefin resin, a styrene polycarbonate blend resin or the like is used. Reference numeral 2 is a pattern layer provided on the lower surface of the transparent protective layer 1 by the 2P method, and is provided with concave and convex grooves to be tracks. When the pattern is formed by the injection method or the casting method instead of the 2P method, the boundary between the transparent protective layer 1 and the pattern layer disappears. Reference numeral 3 is an optical recording layer provided so as to cover the concave and convex grooves of the pattern layer 2. For example, in the DRAW type, tellurium,
Inorganic materials made of low melting point metals such as bismuth and aluminum and alloys thereof, or anthraquinone series, naphthoquinone series, triphenylmethane series, carbocyanine series, merocyanine series, xanthene series, azo series, azine series, thiazine series, oxazine series, It is generally formed of an organic dye including an organic dye such as a phthalocyanine type. In the case of the ROM type, it is formed in a form in which information is recorded in advance by a highly reflective metal such as aluminum. Reference numeral 4 denotes a card base material, which supports the optical recording member having the above structure via the adhesive layer 5. Thus, the optical card has a structure in which the optical recording layer 3 is sandwiched between the transparent protective layer 1 on the front side and the card base material 4 on the back side. In addition, in order to prevent the surface from being scratched when carrying or using the card, and to improve the durability of the card and the reliability of writing and reading accuracy, the transparent protective layer 1 may be used as necessary. The surface hardened layer is provided on the front side. The surface-cured layer is usually formed of a radiation-curable resin in most cases.

[0004]

By the way, in the optical card as described in the prior art, it is desired to use a polycarbonate resin for the transparent protective layer which is the support of the optical recording layer. That is, the polycarbonate resin has a low price,
This is because it has advantages such as no water absorption and excellent bending suitability without warping or cracking. However, polycarbonate resin has a hardness against scratches (pencil hardness)
Therefore, when this is used for the transparent protective layer, it is necessary to provide a surface-hardened layer in order to improve scratch resistance. In this case, when the surface-cured layer is formed on the transparent protective layer by using a normal radiation-curable resin, the surface-cured layer contracts and is warped when cured by radiation. If the hardened layer is thickened to increase the surface hardness, cracks will occur when the card is bent. Therefore, it cannot be formed with a thickness of 15 μm or more. Thus, the thickness of the surface-hardened layer is at most 15μ.
When the hardness is about m, it is affected by the underlying transparent protective layer when a pencil hardness test is performed, and only a hardness of F to HB is obtained, and a surface-hardened layer having a hardness of H or more, which is sufficient for scratch resistance, is obtained. There is a problem that it cannot be done.

In order to solve this problem, attempts have been made to laminate radiation curable resins having different hardnesses in multiple layers to increase the hardness toward the outermost layer (for example, Japanese Patent Laid-Open No. 2-239).
No. 438). However, in this conventional technique, since hardened layers having different hardnesses are laminated and an interface exists between the layers, cracks are likely to occur in bending, and thus it is difficult to increase the thickness of each layer. However, there is a problem that it is difficult to increase the hardness of the surface.

The present invention has been made in view of the above problems, and an object of the present invention is to provide excellent abrasion resistance, warpage and cracking due to bending. It is to provide a non-optical recording medium and a manufacturing method thereof.

[0007]

In order to achieve the above object, an optical recording medium according to the present invention comprises at least a transparent protective layer and an optical recording layer laminated, and is cured by a curable resin on the transparent protective layer. In the optical recording medium provided with a layer, the hardness of the cured layer is continuously increased from the interface with the transparent protective layer toward the surface. And
A leveling agent or an antistatic agent may be added to the cured layer.

In addition, the method for producing the optical recording medium having the above-described structure comprises at least a transparent protective layer and an optical recording layer,
In the method for producing an optical recording medium in which a curable layer made of a curable resin is provided on the transparent protective layer, a plurality of curable resins having different curing shrinkages are cured and contracted from the interface with the transparent protective layer toward the surface. In such a state that the cured layer becomes large, the layers are simultaneously supplied so as to be superposed, and then they are collectively cured to form the cured layer.

[0009]

[Function] A radiation-curable resin having a low curing shrinkage ratio can suppress the warp of the transparent protective layer to a small extent even if it is thickly coated, so that it is not affected by the underlying transparent protective layer when performing a pencil hardness test. Coating with a thickness necessary to achieve this is possible, and a pencil hardness of H to 2H can be obtained by coating with such a thickness. However, the radiation curable resin, which has a low curing shrinkage rate, is flexible but the resin itself is soft, so a thick coating improves the pencil hardness, but Taber abrasion (Taber abrasion test stipulated in ASTM D1044) and falling sand abrasion. There is a weak side to the abrasion test such as (Sandfall abrasion test defined in JIS T8147).
On the contrary, the radiation curable resin having a large curing shrinkage has a large warp at the time of shrinkage, but is excellent in Taber abrasion. Therefore, by providing a hardened layer whose hardness is continuously increased from the interface of the transparent protective layer to the surface, warpage is suppressed and pencil hardness, Taber abrasion, etc. are excellent, and moreover, Since there is no interface in the hardened layer, the bendability is also excellent.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a sectional view showing an embodiment of an optical card which is one form of the optical recording medium according to the present invention.

As shown in the figure, in this optical card, an optical recording layer 3 is provided on the lower surface of the transparent protective layer 1 so as to cover the pattern layer 2 and the concave and convex grooves of the pattern layer 2, and the optical recording layer 3 is provided. The card substrate 4 has an adhesive layer 5 so that the
And a cured layer 6 apparently composed of a first layer a, a second layer b and a third layer c is further laminated on the transparent protective layer 1. The cured layer 6 is prepared by simultaneously supplying three types of curable resins having different curing shrinkage rates onto the transparent protective layer 1 so as to be superposed on each other, and then collectively curing the resin so that the resin on the contact surface of each resin layer is When mixed, the interface between the resin layers disappears and the hardness is continuously changed.

The resin used for the transparent protective layer 1 is preferably rich in optical characteristics. Specifically, the light transmittance is 90% or more (780 nm, 830 nm), the birefringence is 100 nm or less (single pass), or the optical elastic axis. It is better to use the one with ± 5% or less. The thickness is 380 ± including the hardened layer 6.
About 20 μm is preferable. Of the commonly used resins, polycarbonate resin (PC) is particularly preferable,
An acrylic resin having the above optical characteristics may be used. For example, when the pattern layer 2 is formed on one side by the 2P method, "Teijin made Panlite film", "GE made lexan film" and the like obtained by extruding a polycarbonate resin can be used.

For the first layer a of the cured layer 6, a radiation curable resin containing a functional monomer and / or a functional oligomer and having a low curing shrinkage is used. For example, the thickness is 0.4m
When a radiation curable resin having a curing shrinkage ratio of 12.3% is formed in a thickness of 20 μm on a PC sheet having a size of 200 × 200 mm and a thickness of 20 μm and placed on a desk, the warp of the PC sheet is 4.5.
However, in the case where a single-wafer process is performed, a warp of 4 mm or more as described above is not preferable because it interferes with a subsequent process. Further, when the card is formed into a card form, the warp of the card inherits the warp of the PC sheet and becomes 2.2 mm, which is out of the specification as a card, and further the optical characteristics are deteriorated. Similarly, when a radiation curable resin having a cure shrinkage of 11.9% is formed to a thickness of 20 μm and placed on a desk, the warp of the PC sheet becomes 4.0 mm, and the warp when formed into a card is 1.8 mm. And is within specifications.
Therefore, here, a radiation curable resin having a curing shrinkage ratio of 12% or less is used for the first layer a.

As the functional monomer, monofunctional acrylates (2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, etc.), bifunctional acrylates (1,3-butanediol diacrylate, 1,4-butane) are used. Diol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, etc., trifunctional acrylate (pentaerythritol triacrylate, trimethylolpropane triacrylate, etc.), tetrafunctional acrylate (pentaerythritol tetraacrylate) Etc.) 5-functional acrylates (dipentaerythritol pentaacrylate, etc.), 6-functional acrylates (dipentaerythritol hexaacryl) Etc.), 5 as such multifunctional acrylates or more functional acrylate (dipentaerythritol penta and hexaacrylate, etc.) can be used.

As the functional oligomer, epoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, silicone acrylate, unsaturated polyester, polyene / thiol and the like can be used.

When a polycarbonate resin is used for the transparent protective layer 1, N-vinylpyrrolidone as an adhesiveness-imparting agent and a reaction diluent, an initiator (benzoin-based, acetophenone-based, A radiation curable resin is produced by combining Irgacure 651, 184 (which is a thioxanthone type, a peroxide type, etc.) and the like so that the curing shrinkage rate is 12% or less. Depending on the case, a photoinitiator aid (amine-based, quinone-based, etc.), a thermal polymerization inhibitor, a filler (inorganic or organic), a thixotropic agent, a plasticizer, a non-reactive polymer, a colorant and the like may be added. Generally, when a polyfunctional acrylate is used, the hardness tends to increase and the curing shrinkage rate tends to increase. In order to reduce the thickness of the first layer a to 20 μm or more so as not to be affected by the base, the curing shrinkage ratio is 1 in order to reduce the warp and maintain the hardness.
The allowable range is up to 2%. Pencil hardness is 2H on glass
Use something of a degree. The most suitable thickness is about 25 to 30 μm.

For the second layer b, a radiation curable resin whose hardness and cure shrinkage ratio are between those of the first layer a and the third layer c described later is used. Specifically, the curing shrinkage is 12 to 15
The functional monomer and the functional oligomer may be selected so as to be about%. Use a pencil hardness of about 4H on glass. The most suitable thickness is 10 to 20 μm.

A leveling agent may be added to the radiation-curable resin used for the first layer a and the second layer b in order to obtain a clean surface.

The third layer c has 3 functionalities to 5 in order to obtain hardness.
It is formed on the second layer b using a radiation curable resin having a relatively high curing shrinkage ratio, which contains a functional functional monomer as a main component and a small amount of a functional oligomer added thereto. When a polycarbonate resin is used for the transparent protective layer 1, N-vinylpyrrolidone as an adhesion promoter and a reaction diluent and an initiator are added, and silicone as a leveling agent is added in an amount of 0.01 to 100 parts by weight based on the solid content. It is preferable to mix 10 parts by weight. By adding the leveling agent, surface defects are reduced and the slipperiness is increased, so that the apparent hardness is increased. The proportion of the functional oligomer may be increased in order to improve bendability. In some cases,
Photoinitiating aid (amine, quinone, etc.), thermal polymerization inhibitor,
Fillers (inorganic or organic), thixotropic agents, plasticizers, non-reactive polymers, colorants and the like may be added. If the thickness is 15 μm or more, the warp as an optical card becomes large and the bending property becomes poor. Specifically, cracking will occur in the bending test. Thickness is 2 μm
If it becomes less than the following, hardness becomes insufficient. Therefore, 2 ~ 15μ
m is good, but 2 to satisfy both bending and hardness
10 μm is preferable. In addition, in order to increase the bendability, the resin of the second layer b may be mixed in an amount of 0 to 30% in some cases. The pencil hardness is about 6 to 7H on glass. The curing shrinkage rate is preferably set to 15% or more.

An antistatic agent may be added to the first layer a, the second layer b and the third layer c in order to prevent charging.
Then, the first layer a, the second layer b and the third layer c are simultaneously coated on the transparent protective layer 1 by a slide coating method. That is, it is applied by being extruded from the slide head so as to be superposed in a wet state. Applied first layer a, second
The layer b and the third layer c are delicately mixed during air-drying or heat-drying, and apparently have no interface before radiation curing. Then, it is cured by irradiation with radiation. As a result, the interface is eliminated, and the bendability is improved. in this case,
The coating may be performed by appropriately diluting with a solvent. Alternatively, it may be applied by a curtain coating method, a slot coating method, or the like. Specific coating methods include JP-B-33-8977, JP-B-45-12390, JP-A-52-115214, and JP-B-63-
22192 and Japanese Patent Publication No. 2-18143.

Although the hardened layer 6 is composed of three layers in this embodiment, it may be composed of two layers, four layers, five layers or the like. Also in this case, the hardness of the card surface can be increased while suppressing the warp of the card by increasing the curing shrinkage of the radiation curable resin forming each layer from the interface with the transparent protective layer 1 toward the surface. It should be noted that it becomes stronger against bending if the thickness of each layer is successively reduced toward the outermost layer. Also,
The warp state of the card changes depending on the curing shrinkage rate and thickness of each layer, so that the final layer constitution may be determined using these two as parameters so as to minimize the warp.
In addition to the pencil hardness, any of drop wear, steel wool, Taber wear, etc. may be used as the criterion for determining the hardness.

Further, although the case where the cured layer 6 is formed by using the radiation curable resin has been described in this embodiment, it is also possible to use other reaction curable resins such as silicon type and melamine type.

The pattern layer 2 formed on the lower surface of the transparent protective layer 1 is formed as a pattern layer by the generally known 2P method, injection method, casting method or the like.
At this time, when the pattern layer 2 is formed by the 2P method, a UV-curable resin is used, and by the injection method or the casting method, the same transparent protective layer 1 is used.

As the optical recording layer 3, in addition to the commonly used metallic optical recording materials such as tellurium and bismuth,
Phthalocyanine-based and naphthoquinone-based dye recording materials can be used. Further, not only the write-once type but also the ROM type may be used.

As the card substrate 4, polyvinyl chloride,
Polyethylene terephthalate, ABS, polycarbonate, polypropylene and the like can be used. When polyvinyl chloride is used, the composition is 0.05 / 0.
20 / 0.05mm, 0.05 / 0.24 / 0.05m
m, 0.05 / 0.26 / 0.05 mm, 0.05 /
3 layers of 0.30 / 0.05mm, 0.20 / 0.10
mm, 0.24 / 0.10 mm, 0.26 / 0.10 m
m, two layers of 0.30 / 0.10 mm, 0.30 mm,
Any layer structure is possible, such as one layer of 0.34 mm, 0.36 mm, and 0.40 mm. In addition, 0.10m
Those with m and 0.05 mm are transparent, and those with 0.20 mm or more are milky white. Then, in order to increase the abrasion resistance of printing, when polyvinyl chloride is used, printing is performed on milky polyvinyl chloride and heat fusion is performed with transparent polyvinyl chloride. 2
Layers or three layers are preferred.

As the adhesive used for the adhesive layer 5, conventionally known adhesives such as urethane type, epoxy type, acrylic type, vinyl type and amide type can be used. The adhesive is the optical recording layer 3
Since it is in direct contact with, it is preferable to have good recording sensitivity and excellent temperature and humidity suitability. A film thickness of about 10 to 100 μm is desirable, and a gravure coating method, a spin coating method, a knife coating method, a silk screen method,
It is applied by the Miyabar coating method, the T-die coating method or the like, and is heat pressed and adhered by the flat pressing method, the roll pressing method or the like.

When the recording sensitivity of the optical recording layer 3 is low,
A sensitizing layer is formed between the optical recording layer 3 and the adhesive layer 5, but it is not necessary if the recording sensitivity is sufficient. Further, the adhesive layer 5 is in contact with the optical recording layer 3, but if the sensitivity of the optical recording layer 3 deteriorates due to the adhesive, a transparent protective layer is provided to avoid this. When the sensitizing layer is provided, the transparent protective layer is formed between the transparent protective layer and the adhesive layer 5, but it can also serve as the sensitizing layer. However,
When a material that does not deteriorate the optical recording layer 3 is selected, it is not necessary to provide this transparent protective layer.

In order to diversify the use of the card, magnetic stripes may be provided on the same surface or opposite surfaces of the optical recording member or both surfaces of the card substrate 4, or on the same surface or opposite surface of the optical recording member. It is advisable to provide an IC module.

Next, a specific example will be described together with a comparative example.

(Specific example 1) 400 m when the thickness is 0.4 mm
Extruded polycarbonate with a width of m is used as a transparent protective layer, and three types of radiation-curable resins having the following compositions are diluted on one side with IPA to a thickness of 20 μm, 10 μm, and 5 μm, respectively, and they are overlapped by a slide coating method. As described above, they were simultaneously coated and then cured using a high pressure mercury lamp. The curing shrinkage rates of the radiation curable resins used for the first layer, the second layer, and the third layer are 9.6%, 13.0%, and 14.
5% and the pencil hardness is 2H and 4 on glass, respectively.
H and 7H. And, the pencil hardness in the final form is H, and Taber abrasion is CS-10, 1 kg load, 100
The haze value was 9.8% by rotation.

<First layer> Urethane acrylate oligomer (Nippon Gosei Kagaku Kogyo, Gocerac UV7500B) 100 parts by weight Hexamethylene diacrylate (Nippon Kayaku, Kayarad HDDA) 3 parts by weight Pentaerythritol triacrylate (Toagosei Co., Ltd., Aronix M-305) 3 parts by weight dipentaerythritol hexaacrylate (Nippon Kayaku, Kayarad DPHA) 3 parts by weight N-vinylpyrrolidone (Toagosei Kagaku, Aronix M-150) 50 parts by weight 1-hydroxycyclohexyl phenyl ketone ( Made by Ciba Geigy, Irgacure 184) 10 parts by weight

<Second layer> Urethane acrylate oligomer (Nippon Gosei Kagaku Kogyo, Gocerac UV7500B) 80 parts by weight pentaerythritol triacrylate (Toagosei Kagaku, Aronix M-305) 10 parts by weight pentaerythritol tetraacrylate (Toagosei Kagaku) Manufactured by Aronix M-450) 10 parts by weight dipentaerythritol hexaacrylate (Nippon Kayaku, Kayarad DPHA) 3 parts by weight N-vinylpyrrolidone (Toagosei Kagaku, Aronix M-150) 50 parts by weight 1-hydroxycyclohexylphenyl Ketone (Ciba Geigy, Irgacure 184) 10 parts by weight

<Third layer> Radiation curable resin (UV-3700, manufactured by Toagosei) 100 parts by weight Reactive silicone (X-22-5002, manufactured by Shin-Etsu Silicone) 0.5 parts by weight

Next, a pattern layer of the guide track is formed by the 2P method on the opposite surface of the transparent protective layer having the hardened layer consisting of the first layer, the second layer and the third layer, and TeOx is formed thereon.
Was sputtered to form an optical recording layer. On the other hand, 0.
Double-sided silk offset printing was performed on a 20 mm core sheet made of milky vinyl chloride, sandwiched between two 0.05 mm oversheets, and heat-fused to form a three-layer card base material. A magnetic tape of 650 Oersted was formed on one surface of the oversheet. Then, the card base material and the transparent protective layer were adhered to each other using an adhesive (manufactured by Toray, TU-4210). After curing the adhesive, the card size (85.5
It was punched out to (x54 mm) to produce an optical card.

In comparison with the optical card obtained as described above, an optical card R / W (manufactured by OMRON, 3B3H-DJ-0
When data of 100 tracks was written and read in 1), the error rate was 1 × 10 ⁻⁴ or less, which was good. Further, there were no problems in bending strength, adhesiveness, permeability, and warpage, and the temperature and humidity storability was good, and the card was sufficiently durable to use.

(Specific Example 2) A hardened layer was formed by changing only the composition of the third layer in Specific Example 1. That is, 100 parts by weight of a radiation curable resin (UV-3700 manufactured by Toagosei) is reactive silicone (X-X manufactured by Shin-Etsu Silicon).
22-5002) 0.5 part by weight was dispersed, and a composition obtained by further mixing 20 parts by weight of the resin used in the second layer was used. The cure shrinkage of this composition is 14.0%. Taber wear in this case is CS-10, 1 kg load, 100
The haze value was 10.5% by rotation. The pencil hardness was H. When an optical card was manufactured in the same manner as in Example 1, the bending suitability was further improved.

(Specific Example 3) The same extruded polycarbonate as in Specific Example 1 was used as a transparent protective layer, and three types of radiation curable resins having the following compositions were formed on one surface of the transparent protective layer so that the thicknesses were about 25 μm, 12 μm and 4 μm, respectively. Was diluted with toluene and simultaneously coated by a slide coating method so as to overlap each other, and then cured using a high pressure mercury lamp. The first layer,
The curing shrinkage rates of the radiation curable resins used for the second layer and the third layer are 11.9%, 13.5% and 14.3%, respectively, and the pencil hardness is 2H, 4H and 7H on glass, respectively. is there. Then, the pencil hardness in the final form was H, and the Taber abrasion was CS-10, a load of 100 kg, a haze value of 9.0% at 100 rotations.

<First Layer> Urethane Acrylate Oligomer (Nippon Gosei Kagaku Kogyo, Gocerac UV7500B) 100 parts by weight pentaerythritol triacrylate (Toagosei Kagaku, Aronix M-305) 10 parts by weight pentaerythritol tetraacrylate (Toagosei Kagaku) Manufactured by Aronix M-450) 10 parts by weight dipentaerythritol hexaacrylate (Nippon Kayaku, Kayarad DPHA) 3 parts by weight N-vinylpyrrolidone (Toagosei Kagaku, Aronix M-150) 50 parts by weight 1-hydroxycyclohexylphenyl Ketone (Ciba-Geigy, Irgacure 184) 10 parts by weight Reactive silicone (Shin-Etsu Silicon, X-22-5002) 1 part by weight

<Second layer> Urethane acrylate oligomer (Nippon Gosei Kagaku Kogyo, Gocerac UV7500B) 70 parts by weight pentaerythritol triacrylate (Toagosei Kagaku, Aronix M-305) 10 parts by weight pentaerythritol tetraacrylate (Toagosei Kagaku) Manufactured by Aronix M-450) 10 parts by weight dipentaerythritol hexaacrylate (Nippon Kayaku, Kayarad DPHA) 3 parts by weight N-vinylpyrrolidone (Toagosei Kagaku, Aronix M-150) 50 parts by weight 1-hydroxycyclohexylphenyl Ketone (Ciba-Geigy, Irgacure 184) 10 parts by weight Reactive silicone (Shin-Etsu Silicon, X-22-5002) 1 part by weight

<Third Layer> Dipentaerythritol Hexaacrylate (Nippon Kayaku, Kayarad DPHA) 10 parts by weight Pentaerythritol Tetraacrylate (Toa Gosei Kagaku, Aronix M-450) 10 parts by weight Urethane Acrylate Oligomer (Nippon Synthetic Chemistry) Industrial, Gocelac UV7500B) 3 parts by weight N-vinylpyrrolidone (Toagosei Kagaku, Aronix M-150) 5 parts by weight 1-Hydroxycyclohexyl phenyl ketone (Ciba-Geigy, Irgacure 184) 0.5 parts by weight Silicon hexaacrylate ( Daicel UCB, Ebecryl-1360) 0.01 parts by weight

Thereafter, in the same manner as in Example 1, a pattern layer,
An optical recording layer was formed, bonded to a card substrate, and then punched into a card size to prepare an optical card. Then, an optical card R / W is used for the optical card thus obtained.
When data of 100 tracks was written and read by (3B3H-DJ-01 manufactured by OMRON), the error rate was 1 × 10 ⁻⁴ or less, which was good. Also, there is no problem in bending strength, adhesion, permeability, or warpage,
The temperature and humidity storability was good, and it was able to withstand card usage.

(Comparative Example 1) 200 × 2 with a thickness of 0.4 mm
Extrusion-molded polycarbonate of 00 mm size was used as a transparent protective layer, and a radiation curable resin having the following composition was applied on one side thereof with a miya bar to a thickness of 10 μm, and a UV lamp (made by Fusion, microwave method)
Was irradiated and cured to form a cured layer. The shrinkage ratio of this radiation-curable resin during UV curing was 13.
5%.

Dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku, Kayarad DPHA) 10 parts by weight Pentaerythritol tetraacrylate (manufactured by Toagosei Kagaku, Aronix M-450) 10 parts by weight Urethane acrylate oligomer (manufactured by Nippon Synthetic Chemical Industry, Gocellac UV7500B) ) 2 parts by weight N-vinylpyrrolidone (manufactured by Toagosei Kagaku, Aronix M-150) 5 parts by weight 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba Geigy, Irgacure 184) 0.5 parts by weight

When the hardened layer was thus formed to have a thickness of 10 μm, Taber abrasion was CS-10, 1 kg load,
The haze value was 9.5% at 100 rotations, but the pencil hardness was HB. The warpage was 3.5 mm. If the thickness is insufficient as described above, sufficient pencil hardness cannot be obtained.

Comparative Example 2 In Comparative Example 1, when the hardened layer was formed to a thickness of 25 μm, the Taber abrasion had a haze value of 9.5% and the pencil hardness was H. However,
The warp at this time was 4.8 mm, and cracks were generated in the bending test. As described above, when a material having a large curing shrinkage is used, the warp becomes large when the thickness is increased, resulting in poor bending appropriateness.

[0047]

Since the present invention is constructed as described above, it has the following effects.

In the optical recording medium of the present invention, the hardened layer formed on the transparent protective layer by the curable resin is structured so that its hardness continuously increases from the interface with the transparent protective layer toward the surface. Those with high hardness, that is, those with high curing shrinkage, are on the outside, and those with low hardness, that is, those with low curing shrinkage, are inside, and there is no interface between them and they are in a continuous state. Therefore, there is little warpage as a whole, the bending property is very excellent, and the scratch resistance is excellent.

Further, a plurality of curable resins having different curing shrinkage rates are simultaneously supplied so as to be superposed, and then they are collectively cured to form a cured layer on the transparent protective layer. Optical recording with excellent bending suitability and excellent scratch resistance and warpage due to the fact that there is no apparent interface between them and the hardness increases from the interface with the transparent protective layer toward the surface. Media can be created.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a general optical card.

FIG. 2 is a sectional view showing an embodiment of an optical card according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent protective layer 2 Pattern layer 3 Optical recording layer 4 Card base material 5 Adhesive layer 6 Curing layer a 1st layer b 2nd layer c 3rd layer

Claims (6)

[Claims] 1. An optical recording medium comprising at least a transparent protective layer and an optical recording layer laminated, and a cured layer of a curable resin provided on the transparent protective layer, wherein the hardness of the cured layer is the transparent protective layer. The optical recording medium is characterized in that the height increases continuously from the interface to the surface. 2. The optical recording medium according to claim 1, wherein a leveling agent is added to the cured layer. 3. The optical recording medium according to claim 1, wherein an antistatic agent is added to the cured layer. 4. A method for producing an optical recording medium, which comprises at least a transparent protective layer and an optical recording layer laminated, and a cured layer of a curable resin is provided on the transparent protective layer. The curable resin is simultaneously supplied so as to be superposed from the interface with the transparent protective layer toward the surface so that the curing shrinkage rate increases, and then the curable resin is collectively cured to form the cured layer. Method for making optical recording medium. 5. The method for producing an optical recording medium according to claim 4, wherein a curable resin added with a leveling agent is used. 6. The method for producing an optical recording medium according to claim 4 or 5, wherein a curable resin containing an antistatic agent is used.