JPH08203121A - Optical recording medium - Google Patents

Abstract

PURPOSE: To obtain an optical recording medium which has excellent scratching resistance and hardly causes warpage or cracks by bending. CONSTITUTION: A multilayered hardened layer 9 is formed on a transparent protective layer 1 by using a radiation-curing resin in such a manner that the shrinking rate due to hardening increases from the innermost layer (first layer 6) to the outermost layer (third layer 8) and that the thickness of each layer in the hardened layer 9 is decreased from the innermost layer (first layer 6) to the outermost layer (third layer 8). Thus, the obtd. medium has little warpage as a whole and has excellent pencil scratching hardness and Taber's wear resistance is obtd. by the synergistic effect of layers.

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 and the like.

[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 medium having the above-mentioned 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 cured layer on the surface in order to improve scratch resistance. In this case, if a surface-cured layer is formed on the transparent protective layer using a normal radiation-curable resin that has a high curing shrinkage, it may shrink and warp when cured by radiation, or even cracks due to bending may occur. Therefore, it cannot be formed with a thickness of 15 μm or more. As described above, when the thickness of the surface-hardened layer is at most about 15 μm, it is affected by the underlying transparent protective layer when a pencil hardness test is performed,
There is a problem that only a hardness of F to HB can be obtained, and a surface hardened layer having a hardness of H or more, which is sufficient for scratch resistance, cannot be obtained.

Although an acrylic resin is often used for the transparent protective layer, in general, an acrylic resin is superior in pencil hardness to a polycarbonate resin, but in order to further improve scratch resistance, a radiation curable resin having a large curing shrinkage is used. If an attempt is made to form a surface-hardened layer on the surface using the same, it is still impossible to form a surface-hardened layer with a thickness of 15 μm or more for the same reason as described above.

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.

[0007]

To achieve the above object, an optical recording medium according to the present invention is an optical recording medium in which at least a transparent protective layer and an optical recording layer are laminated, and the innermost layer is formed on the transparent protective layer. From the outermost layer to the outermost layer in order to increase the curing shrinkage is provided with a multilayer curing layer formed by using a radiation curable resin, the thickness of each layer forming the cured layer from the innermost layer to the outermost layer sequentially thin It is characterized by having done.

Then, it is preferable to add a leveling agent to the outermost layer of the cured layer, or to add an internally curable leveling agent to the layers other than the outermost layer, and to add an antistatic agent to each layer of the cured layer. Is preferred.

[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 stacking radiation curable resins having a large curing shrinkage in order from the innermost layer to the outermost layer, and further providing a multilayer cured layer in which the thickness of each layer is successively decreased from the innermost layer to the outermost layer, warpage The optical recording medium is excellent in pencil hardness, Taber abrasion, etc. due to the synergistic effect of each layer.

[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 the first layer 6 on the transparent protective layer 1,
It has a configuration in which three hardened layers 9 including the second layer 7 and the third layer 8 are laminated.

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 9.
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 surface by the 2P method, "Teijin-made Panlite film", "GE-made, Lexan film" or the like obtained by extruding a polycarbonate resin can be used.

The first layer 6 of the hardened layer 9 is formed on the transparent protective layer 1 with a thickness of 20 by using a radiation curable resin containing a functional monomer and / or a functional oligomer and having a low cure shrinkage.
It is formed to a thickness of μm or more. For example, 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 of 200 × 200 mm and a thickness of 0.4 mm and placed on a desk, the warp of the PC sheet is 4.5 mm. 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, a radiation curable resin having a cure shrinkage of 11.9% is used as
When formed with a thickness of 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.
It is within 8 mm and is within specifications. Therefore, in this embodiment, a radiation curable resin having a curing shrinkage rate of 12% or less is used.

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 6 to 20 μm or more so as not to be influenced 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%. The most suitable thickness is about 25 to 30 μm.

The second layer 7 is formed by using a radiation curable resin whose hardness and cure shrinkage are between those of the first layer 6 and the third layer 8 described later. Specifically, the cure shrinkage is 12
The functional monomer and the functional oligomer may be selected so as to be about 15%. 10 to 20 μm as thickness
Is the most suitable.

Since the third layer 8 needs to have hardness as a surface layer, a comparison of curing shrinkage including a main component of a trifunctional to pentafunctional functional monomer and a small amount of a functional oligomer added thereto. It is formed on the second layer 7 by using a highly radiation-curable resin. Further, it is preferable to mix 0.01 to 10 parts by weight of silicone or the like as a leveling agent with respect to 100 parts by weight of solid content. By adding the leveling agent, surface defects are reduced and the slipperiness is increased, so that the apparent hardness is increased. However, if the amount is more than 10 parts by weight, the adhesion to the second layer 7 is deteriorated, and if the amount is less than 0.01 parts by weight, there is no effect. Also, if necessary, a photoinitiator aid (amine-based, quinone-based, etc.), thermal polymerization inhibitor, filler (inorganic, organic), thixotropic agent, plasticizer, non-reactive polymer,
A colorant or the like may be added. In addition, in order to improve the bendability, the proportion of the functional oligomer may be increased, and in some cases, the resin of the second layer 7 may be mixed at about 0 to 30%. The cure shrinkage of the radiation curable resin used may be set to 15% or more. This third layer 8 is 15μ
If it is formed with a thickness larger than m, the warp as an optical card becomes large, and cracking occurs in the bending test, resulting in poor bendability. Conversely, the thickness is 2 μm
If it becomes smaller, the hardness becomes insufficient. Therefore, 2-1
5 μm is preferable, but 2 to 5 μm is most suitable for satisfying both bending and hardness.

An antistatic agent may be added to each of the first layer 6, the second layer 7 and the third layer 8 constituting the hardened layer 9 in order to prevent charging. Then, for each of the first layer 6, the second layer 7, and the third layer 8, a gravure coating method, a roll coating method, a comma coating method, a spin coating method,
It is applied by a knife coating method, a silk screen method, a T-die coating method, a slide coating method, a slit reverse method or the like. In this case, the coating may be performed by appropriately diluting with a solvent. The first layer 6 and the second layer 7 may be overprinted to form a multi-layered state.

Further, it is preferable to add a leveling agent to the first layer 6 and the second layer 7 in order to make the surfaces clean. However, if the leveling agent bleeds to the surface, the post-adhesion property deteriorates, so it is preferable to use an internally curable leveling agent.

In this embodiment, the case where the hardened layer 9 is three layers is shown, but it may be two layers, four layers, five layers or the like. Also in this case, the hardness of the surface of the card can be increased while suppressing the warp of the card by increasing the curing shrinkage rate of the radiation-curable resin forming each layer in order from the innermost layer to the outermost layer. Then, it becomes stronger against bending if the thickness of each layer is sequentially reduced from the innermost layer to the outermost layer. Further, since the warp state of the card changes depending on the curing shrinkage ratio and the thickness of each layer, the final layer constitution may be determined using these two as parameters so as to minimize the warp.

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 base material 4, polyvinyl chloride,
Polyethylene terephthalate, AS, 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
m and 0.05 mm are transparent polyvinyl chloride,
Those with 0.20 mm or more are opalescent polyvinyl chloride.
Then, in order to increase the abrasion resistance of printing, printing is performed on opal white 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, a magnetic stripe may be provided on the same surface or the opposite surface of the optical recording medium or both surfaces of the card substrate 4, or on the same surface or the opposite surface of the optical recording medium. It is advisable to provide an IC module.

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

(Specific Example 1) 200 × 2 with a thickness of 0.4 mm
Extrusion-molded polycarbonate having a size of 00 mm was used as the transparent protective layer 1, and a radiation curable resin having the following composition was applied on one side of the transparent protective layer 1 with a miya bar to a thickness of 20 μm. Method) to cure and form the first layer 6. The shrinkage factor of this radiation-curable resin during UV curing was 9.6%, and the warp when the first layer 6 was formed on the transparent protective layer 1 was 2.5 mm.

Urethane acrylate oligomer (Nippon Synthetic Chemical Industry, Gocerac UV7500B) 100 parts by weight Hexamethylene diacrylate (Nippon Kayaku, Kayarad HDDA) 3 parts by weight Pentaerythritol triacrylate (Toagosei Kagaku, 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 (Ciba Geigy, Irgacure) 184) 10 parts by weight

A radiation curable resin having the following composition was coated on the first layer 6 with a miya bar so as to have a thickness of 10 μm, and then this was irradiated with a UV lamp (made by Fusion, microwave system). The second layer 7 was formed by curing. The shrinkage factor of this radiation-curable resin during UV curing was 13.0%, and the warp when the second layer 7 was formed was 3.0 mm.

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, Aronix M- 450) 10 parts by weight dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku, Kayarad DPHA) 3 parts by weight N-vinylpyrrolidone (manufactured by Toagosei Kagaku, Aronix M-150) 50 parts by weight 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba Geigy, Irgacure 184) 10 parts by weight

On this second layer 7, a silicone (X-22-5, manufactured by Shin-Etsu Silicon, manufactured by Shin-Etsu Silicon Co., Ltd.) which is reactive with 100 parts by weight of a radiation curable resin (UV-3700, manufactured by Toagosei Kagaku).
002) A composition in which 0.5 parts by weight was dispersed was applied with a miya bar so as to have a thickness of 5 μm, and was then cured by irradiation with a UV lamp (made by Fusion, microwave system) to form the third layer 8. . The cure shrinkage of this radiation curable resin was 14.5%. At this point, Taber abrasion was CS-10, 1 kg load, 100 rotations, haze value was 9.8%, and pencil hardness was H.

Next, on the opposite surface of the transparent protective layer 1 having the hardened layer 9 composed of the first layer 6, the second layer 7 and the third layer 8,
The guide track pattern layer 2 was formed by the 2P method, and TeOx was sputtered on the guide track pattern layer 2 to form the optical recording layer 3. On the other hand, double-sided silk offset printing was performed on a core sheet of 0.20 mm opalescent vinyl chloride, sandwiched between two sheets of 0.05 mm oversheet, and heat-fused to form a three-layer card base material 4. 650 on one side of the overseat
The Oersted magnetic tape was formed. And
An adhesive (made by Toray, T
U-4210) was used for adhesion. After the adhesive was cured, it was punched out into a card size (85.5 × 54 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) In Specific Example 1, the hardened layer 9
The third layer 8 of was formed as follows. 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 intermediate layer 7 was applied by a bar to a thickness of 5 μm, and then UV lamp (fusion) Manufactured by a microwave method) and cured to form the third layer 8. The curing shrinkage is 1
It was 4.0%. At this point, Taber wear is CS-1
The haze value was 10.5% at 0, 1 kg load and 100 rotations, and 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 the transparent protective layer 1, and a radiation curable resin having the following composition was applied to one side of the transparent protective layer with a miya bar so as to have a thickness of 20 μm. This was irradiated with a UV lamp (made by Fusion, microwave system) and cured to form the first layer 6. The shrinkage factor of this radiation-curable resin during UV curing was 11.9%, and the warp when the first layer 6 was formed on the transparent protective layer 1 was 4.0 mm.

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, Aronix M- 450) 10 parts by weight dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku, Kayarad DPHA) 3 parts by weight N-vinylpyrrolidone (manufactured by Toagosei Kagaku, Aronix M-150) 50 parts by weight 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba Geigy, Irgacure 184) 10 parts by weight Reactive silicone (Shin-Etsu Silicon, X-22-5002) 1 part by weight

A radiation curable resin having the following composition was coated on the first layer 6 with a miya bar so as to have a thickness of 10 μm, and then this was irradiated with a UV lamp (made by Fusion, microwave system). The second layer 7 was formed by curing. The shrinkage ratio of this radiation-curable resin during UV curing was 13.5%, and the warp when the second layer 7 was formed was 3.2 mm.

Urethane acrylate oligomer (Nippon Gosei Kagaku Kogyo, Gocelac UV7500B) 70 parts by weight pentaerythritol triacrylate (Toagosei Kagaku, Aronix M-305) 10 parts by weight pentaerythritol tetraacrylate (Toagosei Kagaku, Aronix M- 450) 10 parts by weight dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku, Kayarad DPHA) 3 parts by weight N-vinylpyrrolidone (manufactured by Toagosei Kagaku, Aronix M-150) 50 parts by weight 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba Geigy, Irgacure 184) 10 parts by weight Reactive silicone (Shin-Etsu Silicon, X-22-5002) 1 part by weight

A radiation curable resin having the following composition was coated on the second layer 7 with a miya bar so as to have a thickness of 5 μm, and then irradiated with a UV lamp (made by Fusion, microwave system) to cure the resin. The third layer 8 was formed. The cure shrinkage was 14.3%. At this point, Taber abrasion was CS-10, 1 kg load, 100 rotations, haze value was 9.0%, and pencil hardness was H.

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 (Nippon Synthetic Chemical Industry, Gocerac 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, Ebecril) -1360) 0.01 parts by weight

Thereafter, the pattern layer 2 and the optical recording layer 3 were formed in the same manner as in Example 1, and after being bonded to the card base material 4, punched into a card size to manufacture an optical card. Then, with respect to the optical card thus obtained, the optical card R / W (manufactured by OMRON, 3B3H-DJ-01)
When the data of 0 track was written and read, 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.

(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 one cured layer. In addition,
The shrinkage factor of this radiation-curable resin during UV curing is 1
It was 4.1%.

Dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku, Kayarad DPHA) 10 parts by weight Pentaerythritol tetraacrylate (manufactured by Toa Gosei Kagaku, Aronix M-450) 10 parts by weight Urethane acrylate oligomer (Nippon Synthetic Chemical Industry, Gocerac 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 formed to a thickness of 10 μm in this way, Taber abrasion was CS-10, 1 kg load,
Haze value is 9.5% at 100 rotations and pencil hardness is HB
Met. 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.

[0049]

As described above, the optical recording medium of the present invention is an optical recording medium in which at least a transparent protective layer and an optical recording layer are laminated, on the transparent protective layer, from the innermost layer to the outermost layer. With the provision of a multilayer curing layer formed by using a radiation curable resin whose curing shrinkage increases in order, the thickness of each layer forming the curing layer is made thinner in order from the innermost layer to the outermost layer. There is little warpage on the whole,
It has excellent bendability and scratch resistance.

[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]

 1 Transparent Protective Layer 2 Pattern Layer 3 Optical Recording Layer 4 Card Base Material 5 Adhesive Layer 6 First Layer (Innermost Layer) 7 Intermediate Layer 8 Third Layer (Outermost Layer) 9 Cured Layer

Claims (4)

[Claims] 1. An optical recording medium in which at least a transparent protective layer and an optical recording layer are laminated, wherein a radiation curable resin having a curing shrinkage increasing in order from the innermost layer to the outermost layer is used on the transparent protective layer. An optical recording medium, characterized in that a plurality of formed hardened layers are provided, and the thickness of each layer forming the hardened layer is successively reduced from the innermost layer to the outermost layer. 2. The optical recording medium according to claim 1, wherein a leveling agent is added to the outermost layer of the cured layer. 3. The optical recording medium according to claim 1, wherein an internally curable leveling agent is added to all layers of the cured layer except the outermost layer. 4. The optical recording medium according to claim 1, wherein an antistatic agent is added to each layer of the cured layer.