TW202338797A - Optical disc composed of a plurality of recording layers for recording data and a resin layer between the recording layers - Google Patents

Abstract

The present invention provides an optical disc whose recording layer can be reliably recognized. An optical disc is composed of a plurality of recording layers for recording data and a resin layer between the recording layers, the resin layer containing fluorine and being cured by ultraviolet rays using a polymerization initiator. The polymerization initiator is a radical polymerizable acetophenone type and contains a carbonyl group. The carbon at the [alpha] position of the carbonyl group is bonded to one oxygen or nitrogen atom, and two alkyl groups that are not cycloalkanes, and the phenyl group containing carbon at the other [alpha] position is unsubstituted or bonded to a -NC4H8O functional group.

Description

disc

This disclosure is about a type of optical disc.

Due to the popularization of the Internet and the digitization of broadcasting, the use of digital data is increasing year by year. In this environment, the optical information recording medium, that is, the optical disc, is composed of a plurality of recording layers that record data and a resin layer that exists between the recording layers as an intermediate layer. By irradiating laser light, data can be recorded and reproduced. , as a highly reliable information recording medium suitable for long-term storage of data, it has continued to evolve to increase its capacity along with the increase in the amount of information.

In order to realize a further large-capacity optical disc, it is indispensable to increase the number of recording layers. However, the recording layer of an optical disc is mainly composed of inorganic compounds. The transmittance of inorganic compounds is low and requires too much work. Therefore, it is difficult to multi-layer the recording layer composed of inorganic compounds. Therefore, there are also studies on the technology of multi-layering the recording layer composed of organic compounds. However, there is a problem that the recording layer cannot be identified without the difference in refractive index between the recording layer and the resin layer. Prior technical literature

patent documents Patent Document 1: Japanese Patent Application Publication No. 2008-137190

The problem to be solved by the invention In Patent Document 1, a fluorine-containing curable resin is used for the purpose of water and oil repellency (fouling resistance) for a material layer in which low refractive index is technically important. However, although Teflon is rich in fluorine and has a low refractive index, it has high crystallinity and low transparency, making it difficult to transmit laser light.

As a low refractive index resin, the inventors of the present invention focused on a chemical structure rich in fluorine and low in crystallinity. Among them, they also focused on an ultraviolet curable resin that can be layered by general steps such as spin coating. However, even if 3 parts of a polymerization initiator were added to 100 parts of 2,2,2-trifluoroethyl acrylate, a UV-curable resin rich in fluorine, and UV-cured, a low refractive index layer could not be produced, but it was found that Fluorine was desorbed (decreased) from a layer that could not produce a low refractive index layer. The main reason for the desorption of fluorine was presumed, and a polymerization initiator that could produce a low refractive index layer was discovered. In addition, since the identification of the recording layer is to detect the interface reflection on the incident side of the laser light, the interface reflection on the opposite side will become crosstalk. In order to reduce this crosstalk, it was found that the recording layer should be thinned to an extent that the difference between the interface reflection of the recording layer and the interface reflection on the opposite side becomes small, and the resin layer should be thickened.

Means for Solving the Problems The optical disc of the present disclosure is characterized in that it is composed of a plurality of recording layers for recording data and a resin layer located between the recording layers. The resin layer contains fluorine and is exposed to ultraviolet rays through a polymerization initiator. For hardening, the polymerization initiator is a free radical polymerization acetophenone type and contains a carbonyl group. The carbon at the α position of the carbonyl group is bonded to an oxygen atom or a nitrogen atom and two alkyl groups of a non-cycloalkane, and The phenyl group containing another carbon in the alpha position is unsubstituted or bonded to the -NC ₄ H ₈ O functional group.

Invention effect The disclosed optical disc can reliably identify the recording layer.

Form used to implement the invention Hereinafter, embodiments will be described in detail with reference to appropriate drawings. However, more detailed explanations than necessary may be omitted. For example, detailed descriptions of matters that are already well understood may be omitted or repeated descriptions of substantially the same components may be omitted. This is because the following description is to be avoided from becoming unnecessarily lengthy so that it can be easily understood by those with ordinary knowledge in the technical field to which the present invention belongs. In addition, the additional drawings and the following description are provided to allow those with ordinary knowledge in the technical field to which the present invention belongs to fully understand the present disclosure, and are not intended to limit the subject matter described in the scope of the patent application.

One aspect of the present invention relates to an optical disc, which is characterized in that it is composed of a plurality of recording layers for recording data and a resin layer located between the recording layers. The resin layer contains fluorine and is treated with a polymerization initiator. For ultraviolet curing, the aforementioned polymerization initiator is a free radical polymerization acetophenone type and contains a carbonyl group. The carbon at the α position of the carbonyl group is bonded to an oxygen atom or a nitrogen atom and two alkyl groups of a non-cycloalkane. , and the phenyl group containing another α-position carbon is unsubstituted, or is bonded with the functional group of -NC ₄ H ₈ O.

In one aspect of the present invention, the difference between the refractive index of the recording layer and the refractive index of the resin layer may be 0.15 or more.

In one aspect of the present invention, the light transmittance of the resin layer may be 80% or more.

In one aspect of the present invention, the film thickness of the recording layer may be 0.01~0.5µm, and the film thickness of the resin layer may be 1~15µm.

In one aspect of the present invention, the ratio of the film thickness of the recording layer to the film thickness of the resin layer may be 1:3~1:50.

In one aspect of the present invention, the recording layer may include 1 to 20 wt% of a two-photon absorption compound relative to the entire recording layer. (implementation form) Figure 1 shows an optical disc 100 according to this embodiment. An embodiment of the optical disc 100 will be described below.

The optical disc 100 has an adhesive 101, which is an example of a recording layer, and an adhesive 102, which is an example of a resin layer. Several layers are alternately laminated. The total number of layers of the adhesive 101 and the adhesive 102 is, for example, 4 to 30 layers, preferably 6 to 30 layers. 12 layers, preferably about 10 layers. The adhesive 101 includes a recording material that can record information by irradiation with recording laser light. The adhesive 102 does not contain a recording material, but functions as an intermediate layer. The recording material is a two-photon absorption compound and contains 1 to 20 wt% relative to the entire recording layer. The recording material is not particularly limited as long as it changes to an excited state or a ground state by irradiation with recording laser light, thereby performing optical changes. However, it can be exemplified by the material having absorption in the aforementioned laser light wavelength region. of fluorescent compounds. Examples include aniline compounds, cyclopentane derivatives, azulene derivatives, and porphyrin compounds. The recording laser light includes, for example, near-ultraviolet light with a wavelength of 405 nm.

The cover layer 104 is provided on the outermost surface of the optical disc 100 for the purpose of scratch resistance. The servo layer 106 is arbitrarily provided on the surface of the base material 105 for tracking. Tracking can be performed by only forming a groove shape in the servo layer 106. In addition to recording laser light, a pattern of laser light that can track the groove shape of the servo layer 106 is also used. Grooves can also be provided in the adhesive 101 so that Recording laser light can be tracked.

The base material 105 is a member that serves as a support for the optical disc 100. As long as it is thick enough to function as a support, it may be a relatively thick member of about several hundred µm to several mm, or a thin film of several hundred µm or less.

Binder 101 and binder 102 are usually used for the purpose of improving the film formation stability, film thickness, film density uniformity and storage stability of the composition. Therefore, they should have excellent compatibility with the composition. It can form a uniform film and produce a film with high storage stability. Thermoplastic resin, curable resin, etc. can be used alone or in combination, and additives such as release agents or dispersants can be used according to needs.

The adhesive 101 is a layer that can change the recording material into an excited state or a ground state by irradiation of recording laser light, thereby performing optical changes and recording information. As long as information can be recorded, the film thickness is not particularly limited. That is, when the adhesive 101 contains a recording material, the film thickness needs to be thicker than when the recording material is used alone, but it is sufficient as long as it is a film thickness capable of recording information. In the case of a thin film, problems with thickness accuracy during processing are likely to occur, whereas in the case of a thick film, the overall thickness of the layer becomes thicker. For example, the film thickness of the adhesive 101 can be set to 0.01~0.5µm, and it is preferable to set it to 0.1~0.3µm.

As long as the adhesive 101 can be identified, the film thickness of the adhesive 102 is not limited. However, when it is a thin film, the thickness accuracy during processing is likely to be problematic, and when it is a thick film, the entire thickness becomes thicker. For example, bonding The film thickness of the agent 102 can be set to 1~15µm, and preferably can be set to 1~5µm. When considering the intensity of reflected light used for layer identification and, for example, the access to the layer farthest from the irradiation surface of the laser light in an optical disc in which a total of about 30 layers of adhesive 101 and adhesive 102 are laminated, the adhesive 101 The refractive index difference with the adhesive 102 is preferably 0.15 or more and 0.25 or less, preferably about 0.2.

The ratio of the film thickness of the adhesive 101 to the film thickness of the adhesive 102 is preferably the film thickness of the adhesive 101: adhesive The film thickness of 102 = 1:3~1:50, for example, it can also be set to 1:3~1:10 or 1:10~1:50.

The optical disc 100 has an adhesive 101 that is transparent in the wavelength range of the recording laser light and has different refractive indexes per unit as shown in FIG. 1 for the purpose of making it easier to identify the depth direction with the recording laser light. Binder 102.

The adhesive 101 uses a resin that is transparent and has a high refractive index in the wavelength range of recording laser light. The adhesive 101 is not particularly limited as long as the difference in refractive index between the adhesive 101 and the adhesive 102 , which is a resin that is transparent and has a low refractive index in the wavelength range of the recording laser light, is 0.15 or more. As the resin used for the adhesive 101, thermoplastic resin, curable resin, etc. can be used alone or in combination. As the thermoplastic resin, styrene-based polymers or copolymers, ester-based polymers or copolymers, vinyl-based polymers or copolymers, polycarbonate-based polymers or copolymers, and polyethylene naphthalate can be used. Polymers or copolymers, acrylate polymers or copolymers, methacrylate polymers or copolymers, urethane polymers or copolymers, amide polymers or copolymers, etc., as the As the curable resin, a resin that undergoes a curing reaction by irradiation with active energy rays such as ultraviolet rays, or a thermosetting phenolic resin, epoxy resin, ester resin, urethane resin, or imide can be used. System resin, etc.

The adhesive 102 is a resin that is transparent and has a low refractive index in the wavelength range of recording laser light. The adhesive 102 is not particularly limited as long as the difference in refractive index from the adhesive 101 which is transparent in the wavelength range of the recording laser light and has a high refractive index is 0.15 or more. As the resin of the adhesive 102, thermoplastic resin, curable resin, etc. can be used alone or in combination. As the thermoplastic resin, in addition to the above, cellulose polymers or copolymers, vinyl alcohol polymers or copolymers, polylactic acid polymers or copolymers, polyolefin polymers or copolymers, and polysiloxane polymers can be used. or copolymers, etc. As the curable resin, in addition to the above, acrylate resin, methacrylate resin, olefin resin, etc. can also be used. The adhesive 102 is preferably a resin containing fluorine in its structure in order to be transparent in the wavelength range of the recording laser light and to ensure a difference in refractive index.

The material of the cover layer 104 is not particularly limited, but it is preferably transparent to recording laser light and readout laser light.

The servo layer 106 is provided to control the tracking of laser light irradiated during recording and reading.

In this embodiment, the refractive index difference between the adhesive 101 and the adhesive 102 in the wavelength range of the recording laser light is 0.15 or more and 0.25 or less. That is, when the refractive index of the resin used for the adhesive 101 with a high refractive index is 1.7, the refractive index of the adhesive 102 with a low refractive index is 1.55 or less. As a resin with a low refractive index, especially a resin containing fluorine in its structure, it also has excellent transparency.

As the adhesive 101, in order to obtain the adhesive 101 with a high refractive index, a resin that can be easily processed into a disc shape by spin coating or the like can be used, such as optical polyester resin (OKP) manufactured by Osaka Gas Chemical Co., Ltd. Resins such as acrylate (OGSOL) or poly(1-naphthyl methacrylate), high refractive index coating material (8DK) manufactured by Dacheng Fine Chemicals. Thermoplastic resins such as OKP can be spin-coated by being dissolved in a volatile solvent in consideration of the viscosity adjustment of the coating liquid. For UV-curable OGSOL, etc., a polymerization initiator such as IRGACURE 1843 can be added to 100 parts of the UV-curable resin. A high refractive index adhesive 101 can be produced by spin-coating a coating solution with approximately 100% of a volatile solvent added as needed, and then irradiating the coating film with ultraviolet rays. The volatile solvent used has good compatibility with the resin material, can adjust the viscosity, does not corrode the coating surface, and will evaporate after spin coating. The high refractive index binder 101 disperses the recording material in the high refractive index resin. The recording material and the resin may be dispersed in a coating liquid and formed by coating. General methods such as stirring and ultrasonic waves can be used for dispersion.

As the adhesive 102, in order to obtain the adhesive 102 with a low refractive index, a resin with a low refractive index is used. When using an ultraviolet curable resin, in addition to using an optimal polymerization initiator, the adhesive can also be produced. 101 construction methods. For low refractive index thermoplastic resin, DYNEON THV powder type manufactured by 3M can be used. As ultraviolet curable resin with low refractive index, 2,2,2-trifluoroethyl acrylate, etc. can be used.

The chemical structure of the optimal polymerization initiator for producing the ultraviolet curable adhesive 102 with a low refractive index will be described. The polymerization initiator is selected according to the monomer. As described in this embodiment, as a monomer that is required to be colorless and transparent in addition to the refractive index, an acrylic monomer or a methacrylic monomer can be used. As a polymerization initiator that can be used for such a monomer, a radical polymerization initiator can be used, and among these, an acetophenone-based polymerization initiator or a benzophenone-based polymerization initiator is often used. When acetophenone polymerization initiator is irradiated with ultraviolet rays, the carbonyl group and the α carbon of the carbonyl group will be excited to generate free radicals. In this embodiment, the α-position carbon bonded to one oxygen atom or nitrogen atom is expressed as the α-position carbon, and the other α-position carbon is expressed as the α'-position carbon. [Chemical formula 1] (1)

It is generally believed that the ease of generation of free radicals is determined by the electron resonance between the carbonyl carbon of the carbonyl group and the α carbon in the formula (1), and between the carbon of the carbonyl and the α' carbon (benzene ring), and is mainly It is the functional groups bonded to the α-carbon and α'-carbon (benzene ring), the number of functional groups, and the three-dimensional structure that have a great influence.

In Figure 2, it is generally believed that the α-position carbon will be bonded to electron-donating heteroatoms, benzene rings, etc. (for example, the hydroxyl or 1-hydroxyl ring of 2-hydroxy-2-methyl-1-phenyl acetone. The hydroxyl group of hexyl-phenyl ketone) makes the electron resonance stronger and ensures the free radical activity as a free radical polymerization initiator. In addition, it is generally believed that if the functional group is located between the carbonyl carbon and the α-position carbon, the electronic resonance will become stronger (for example, 2-hydroxy-2-methyl-1-phenyl in Figure 2 The positional relationship between the hydroxyl group and the α-carbon of acetone is often the same, but the positional relationship between the hydroxyl group and the α-carbon of 1-hydroxycyclohexyl-phenylketone is particularly affected by the increase in potential energy in the boat conformation (Figure 3 ) and becomes closer to 2-hydroxy-2-methyl-1-phenylpropanone).

On the other hand, according to Figure 4, it is generally believed that the α' carbon (benzene ring) will change the chemical activity between the carbonyl carbon and the α' carbon (benzene ring) due to the functional group bonded to the benzene ring ( For example, the chemical activity of the functional group increases in the order of halogen < alkyl group < hydroxyl group, and the chemical activity of the benzene ring increases in the order of benzene < toluene), which will also change the electronic resonance at the same position.

Here, the main cause of the problem that the refractive index of the adhesive layer changes due to the difference in the polymerization initiator is presumed to be the difference in the fluorine content of the polymer film (adhesive) depending on the polymerization initiator, that is, the generation of free radicals If the degree of ease is too high, the fluorine of the monomer will be easily desorbed during polymerization, and elemental analysis and refractive index measurement of the polymer film were performed to change the chemical structure of the polymerization initiator.

(Example) The monomer was set to 100 parts of 2,2,2-trifluoroethyl acrylate, the added amount of the polymerization initiator was set to 3 parts, and all other mixing conditions and light irradiation conditions were set to the same conditions. Elemental analysis uses SEM (JSM-6700F) and EDS (JED-2300F) manufactured by JEOL to measure the mass % of F (fluorine) and C (carbon) of the polymer film, and divide F [mass %]/C [mass %] A polymer film with a large value serves as a polymerization initiator that can maintain a large amount of fluorine, and a polymer film with a small value serves as a polymerization initiator that can desorb a large amount of fluorine (Table 1).

The refractive index at the recording and reproduction wavelength, etc. was measured in the direct measurement mode using a fine shape measuring machine ET4000A manufactured by Kosaka Laboratory Co., Ltd., and the film thickness was measured in the standard mode using alpha-SE and CompleteEASE6 manufactured by JAWoollam Co. ), Sample Alignment-Robust, and Angle: 65° and 70° were measured (Table 1). [Table 1]

As can be seen from Table 1, the amount of fluorine contained in the polymer film will vary depending on the chemical structure of the polymerization initiator.

2-hydroxy-2-methyl-1-phenylpropanone (2-hydroxy-2-methyl-1-phenylpropanone) is bonded with -OH containing an oxygen atom at αC, and as an alkyl group of a non-cycloalkane, it is bonded with 2 -CH3, the phenyl group containing α'C is unsubstituted. 2-Benzyl-2-(dimethylamine)-4'- Phylinobutyrophenone (2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone) has -N(CH ₃ ) ₂ containing nitrogen bonded to αC, and as a non-cycloalkane, the alkyl group has -C bonded ₂ H ₅ , -CH ₂ -C ₆ H ₅ , the phenyl group containing α'C is bonded to -NC ₄ H ₈ O.

The adhesive 102 is not particularly limited as long as it can sufficiently transmit recording and reproducing light and contains fluorine. For example, a radical polymerization acrylic compound, a methacrylic compound, etc. can be used. The adhesive 102 is formed through the steps of blending, film formation and ultraviolet irradiation. Each step is described in detail below. Here, "sufficiently transmitting recording and reproducing light" means that the light transmittance measured by a spectrometer such as an ellipsometer (ellipsometer) is 80% or more. ＜Blending＞

The binder 102 may be a mixture, but is not particularly limited as long as at least one monomer contains fluorine in the chemical structure. In order to confirm the difference in the polymerization initiator, the monomer was set to acrylic acid 2,2,2-trifluoroethyl, and only the chemical structure of the compound as the polymerization initiator was changed, and acrylic acid 2,2,2 -Add 3 parts of polymerization initiator to 100 parts of trifluoroethyl, and go through the following steps to prepare each binder. ＜Film formation＞

The manufacturing method of the optical disc 100 is not particularly limited, but spin coating, which is a simple and low-cost coating, is used. As the spin coating device, an Opticoat spin coater (MS-B200) manufactured by MIKASA Co., Ltd. was used. ＜Ultraviolet irradiation＞

When using a radically polymerizable monomer as the adhesive 102, the adhesive 102 is produced by irradiating ultraviolet rays. For ultraviolet irradiation, a lamp (ANUF82001T) manufactured by Panasonic Co., Ltd. was used as a light source.

Here, the film thickness of the adhesive 102 measured in the direct measurement mode using a fine shape measuring machine ET4000A manufactured by Kosaka Laboratory Co., Ltd. is 0.06µm~0.14µm. Due to problems with the measuring machine used, the film thickness must be set thin for refractive index measurement. However, for the adhesive 102 actually used in the present invention, for example, a film thickness in the range of 1 to 15 μm can be used. In addition, the transmittance of the adhesive 102 is in the range of 99.9%≦ at the wavelength of 405 nm.

The refractive index of the adhesive 102 at the recording and reproduction wavelength is determined by using alpha-SE and CompleteEASE6 manufactured by J.A. Woollam Co., in Standard mode, Sample Alignment-Robust, and Angle: 65 °, 70° were measured.

As described above, by forming the adhesive 102, the optical information optical disc can recognize the adhesive by the optical recording and reproducing device.

industrial availability The resin layer disclosed in the present disclosure is a colorless, transparent, low refractive index resin layer, and can be used as an adhesive for optical recording discs.

100:CD 101,102:Binder 104: Covering layer 105:Substrate 106:Servo layer

Figure 1 is a schematic cross-sectional view of an optical disc. FIG. 2 is a diagram showing the three-dimensional structure of each polymerization initiator. Figure 3 is a diagram of the energy and three-dimensional structure of cyclohexane. Figure 4 is a graph showing the relationship between the activity of the carbon at the α' position and the functional group.

Claims (10)

An optical disc, characterized in that it is composed of a plurality of recording layers for recording data and a resin layer located between the recording layers. The resin layer contains fluorine and is cured by ultraviolet rays with a polymerization initiator. The polymerization The initiator is a free radical polymerization acetophenone type and contains a carbonyl group. The carbon at the α position of the carbonyl group is bonded to an oxygen atom or a nitrogen atom and two alkyl groups of non-cycloalkanes, and contains another α The phenyl group at the carbon position is unsubstituted or bonded with the -NC ₄ H ₈ O functional group. The optical disc of claim 1, wherein the difference between the refractive index of the recording layer and the refractive index of the resin layer is 0.15 or more. Such as the optical disc of claim 1 or 2, wherein the light transmittance of the aforementioned resin layer is above 80%. For example, the optical disc of claim 1 or 2, wherein the film thickness of the aforementioned recording layer is 0.01~0.5µm, and the film thickness of the aforementioned resin layer is 1~15µm. Such as the optical disc of claim 1 or 2, wherein the ratio of the film thickness of the aforementioned recording layer to the film thickness of the aforementioned resin layer is 1:3~1:50. Such as the optical disc of claim 3, wherein the ratio of the film thickness of the aforementioned recording layer to the film thickness of the aforementioned resin layer is 1:3~1:50. Such as the optical disc of claim 4, wherein the ratio of the film thickness of the aforementioned recording layer to the film thickness of the aforementioned resin layer is 1:3~1:50. The optical disc of claim 1 or 2, wherein the recording layer contains 1 to 20 wt% of a two-photon absorption compound relative to the entire recording layer. The optical disc of claim 3, wherein the recording layer contains 1 to 20 wt% of a two-photon absorption compound relative to the entire recording layer. The optical disc of claim 4, wherein the recording layer contains 1 to 20 wt% of a two-photon absorption compound relative to the entire recording layer.

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