JP2010091861A - Protective layer for hologram recording medium and hologram recording medium therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protective layer for a hologram recording medium, the protective layer formed of a high-branched polycarbonate resin having both of transparency and solvent resistance, and to provide a hologram recording medium. <P>SOLUTION: The hologram recording medium has a recording layer in which information is recorded by use of holography by superposing information light imparted with information as a two-dimensional image and reference light coherent with the information light, and the medium comprises a second substrate as a support, a reflection layer, a gap layer, a filter layer, a protective layer, the recording layer and a light-transmitting first substrate. The protective layer is a film formed of a high-branched polycarbonate resin having a content of a branching agent of 2.0 to 6.0 mol% obtained by<SP>1</SP>H-NMR analysis, and a viscosity average molecular weight of 1.6×10<SP>4</SP>to 3.2×10<SP>4</SP>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hologram recording medium protective layer excellent in transparency and solvent resistance and a hologram recording medium excellent in recording performance composed of the hologram recording medium protective layer.

A hologram recording medium capable of three-dimensional information recording is one of optical recording technologies capable of realizing a large capacity and high-speed transfer as compared with a magneto-optical recording medium and a phase change optical recording medium.
The hologram recording / reproducing method irradiates and interferes with the information light given information as a two-dimensional image and the reference light, and generates an optical characteristic distribution such as refractive index in the recording layer by using the formed interference pattern. Record information with. During reproduction, only the reference light is irradiated so that the reproduction light having an optical characteristic distribution corresponding to the recorded interference pattern is emitted from the recording layer.

  As a recording layer of a hologram recording medium, a structure having a three-dimensional crosslinked polymer matrix in addition to a radical polymerizable compound and a photo radical polymerization initiator is generally known (for example, Patent Document 1). The three-dimensional cross-linked polymer matrix has a function of suppressing excessive movement of the radical polymerizable compound and suppressing volume change of a portion corresponding to the bright portion and a portion corresponding to the dark portion in the recording layer. Examples of the material of the three-dimensional crosslinked polymer matrix include a reaction cured product derived from an epoxy compound and a cationic polymerizable monomer (for example, Patent Document 2).

  Various studies have been made on the configuration of the hologram recording medium, but the hologram recording medium shown in FIG. 1 has been proposed (for example, Patent Documents 3 to 5). A servo pit pattern 8 is provided on the surface of the second substrate 1 serving as a support, and a reflective layer 2 made of a metal reflective film is laminated on the surface of the servo pit pattern 8. Further, a gap layer 3 is provided between the reflective layer 2 and the filter layer 4 for the purpose of flattening the second substrate 1. Then, the protective layer 5, the recording layer 6, and the light-transmitting first substrate 7 are sequentially laminated on the filter layer 4.

  As a substrate used for the protective layer 5 constituting the hologram recording medium, an optical film formed from a polycarbonate resin obtained from bisphenol A (hereinafter PC-A) has been proposed. Since the film is excellent in transparency, dimensional stability and hydrolysis resistance, it is widely used as an optical substrate such as a retardation film and an optical disc cover film.

However, when an optical film made of PC-A is used for the protective layer 5, the PC-A becomes cloudy due to the effects of the composition, solvent, etc. in the recording layer 6, and the transparency of the laser wavelength used for recording and reproduction deteriorates. It was found that the hologram recording / reproducing characteristics deteriorate. Therefore, when an inorganic protective layer such as SiO ₂ is laminated on the PC-A film of the protective layer to prevent white turbidity of the protective layer, the white turbidity of the protective layer is improved, but the adhesion with the recording layer is improved. This causes a problem that the adhesion between the protective layer 5 and the recording layer 6 is lowered. Moreover, the recording layer shrinks due to the reaction and heat at the time of hologram recording, stress is generated in the protective layer 5 and the inorganic protective film, and defects such as cracks are generated in the inorganic protective film. Furthermore, when an ultraviolet curable resin is applied on a PC-A film, photocured, and provided as an organic protective film, the white turbidity of the protective layer is improved, but a small amount of unreacted molecules in the ultraviolet curable resin are recorded on the recording layer. There is a fatal problem in that the photoreaction is hindered and the recording / reproducing characteristics are deteriorated.
Thus, a material having transparency and solvent resistance is required as a light transmission layer used for a volume hologram recording medium.

JP-A-11-161137 Japanese Patent Laid-Open No. 2005-107312 JP 2007-102185 A JP 2007-093799 A JP 2007-079164 A

  An object of the present invention is to provide a protective layer for a hologram recording medium and a hologram recording medium formed from a highly branched polycarbonate resin having both transparency and solvent resistance.

  In order to achieve the above-mentioned object, the present inventor has conducted earnest studies on a hologram recording medium protective layer and a hologram recording medium. As a result, it was found that the white turbidity of the optical film made of PC-A when in contact with the recording layer was caused by crystallization by the composition and solvent in the recording layer.

  PC-A has a low crystallinity of 0.3 to 0.7 under normal use. In order to achieve high crystallization, there is a method of treating for a long time at a temperature higher than the glass transition temperature or dissolving in a solvent and gradually evaporating the solvent. Is possible. Factors affecting crystallization with a solvent include the type of solvent, the evaporation rate, and the molecular structure of the solute. If the molecular structure of the solute has a symmetry in the central carbon position of bisphenol, which is a structural unit of the polycarbonate resin, as a factor affecting the crystallization, crystallization is relatively easy. Therefore, PC-A having bisphenol A having symmetry as a structural unit is relatively easily crystallized. In addition, introduction of a bulky substituent at the central carbon position is an obstacle to crystallization, but the use of a special monomer is not preferable because it greatly increases the raw material cost.

  Therefore, in order to suppress crystallization of PC-A, the crystallization mechanism with a solvent was considered. PC-A is non-crystalline (amorphous) at room temperature and normal humidity, so it does not take a regular arrangement, but the polymer molecular chains swell by contact with the solvent, and the entanglement between the molecular chains relaxes, and the solvent evaporates. At the same time, the polymer molecular chains take a regular arrangement and crystallize. Therefore, in order to suppress crystallization, it is necessary to suppress entanglement relaxation due to swelling between molecular chains and to inhibit regular arrangement (molecular chain movement) during solvent evaporation.

  As a technique for solving these problems, it has been found that a branched polycarbonate resin having highly branched polymer molecular chains and a specific viscosity average molecular weight is used. That is, it is possible to increase the density of the entanglement points between the molecular chains by highly branching the polymer molecular chains and to inhibit the regular arrangement by the branched structure. However, even in the case of a branched polycarbonate resin, if the polymer molecular chain is short, the effect of suppressing the entanglement point density and the regular arrangement cannot be obtained, and therefore a specific viscosity average molecular weight is required. As a result, it was possible to obtain a protective layer made of a film resistant to the hologram recording layer using PC-A having an inexpensive bisphenol A as a structural unit. That is, a film formed from PC-A having a certain degree of viscosity average molecular weight and highly branched has excellent solvent resistance, has transparency, and a hologram recording medium using the protective layer is The present inventors have found that the recording / reproducing performance is excellent and completed the present invention.

That is, according to the present invention,
1. A second substrate serving as a support, which has a recording layer for recording information using holography, by superimposing information light provided with information as a two-dimensional image and reference light capable of interfering with information light, and reflecting Hologram recording medium comprising a layer, a gap layer, a filter layer, a protective layer, a recording layer, and a light-transmitting first substrate, wherein the protective layer contains a branching agent required by ¹ H-NMR analysis A hologram characterized by being a film formed from a highly branched polycarbonate resin having an amount of 2.0 to 6.0 mol% and a viscosity average molecular weight of 1.6 × 10 ^{4 to} 3.2 × 10 ⁴ recoding media,
2. The hologram recording according to item 1 above, wherein the highly branched polycarbonate resin has a branching agent content of 2.5 to 5.0 mol% and a viscosity average molecular weight of 1.8 × 10 ^{4 to} 3.0 × 10 ⁴ .
3. The branching agent is phloroglysin, 1,1,1-tris (4-hydroxyphenyl) ethane, 1,3,5-tri (4-hydroxyphenyl) benzene, 3,3-bis (4-hydroxyphenyl) oxy 2. The hologram recording medium according to item 1, which is at least one branching agent selected from the group consisting of indole (= isatin bisphenol) and isatin bis (o-cresol);
4). The hologram recording medium according to item 1 above, wherein the highly branched polycarbonate resin has an interentangle molecular weight of 2.6 × 10 ^{3 to} 3.2 × 10 ³ g / mol.
5). The hologram recording medium according to item 1, wherein the highly branched polycarbonate resin has a crystallization rate of 3 × 10 ⁻³ % / sec or less in acetone immersion.
6). A second substrate serving as a support, which has a recording layer for recording information using holography, by superimposing information light provided with information as a two-dimensional image and reference light capable of interfering with information light, and reflecting Layer, gap layer, filter layer, protective layer, recording layer, protective layer in a hologram recording medium composed of a light-transmitting first substrate, the protective layer being branched by ¹ H-NMR analysis It is a film formed from a highly branched polycarbonate resin having an agent content of 2.0 to 6.0 mol% and a viscosity average molecular weight of 1.6 × 10 ^{4 to} 3.2 × 10 ^4. A protective layer for a hologram recording medium,
Is provided.

Hereinafter, the present invention will be described in detail.
<Hologram recording medium>
As shown in FIG. 1, the hologram recording medium of the present invention includes a second substrate 1 as a supporting substrate, a reflective layer 2, a gap layer 3, a filter layer 4, a protective layer 5, a recording layer 6, and a first substrate. The optical recording medium is composed of the substrate 7 and has an antireflection layer or the like on the first substrate as necessary. Further, the optical recording medium is used in a coaxial interference system (collinear system) in which the information light and the reference light are irradiated so that the optical axes of both lights are coaxial.

<Second substrate>
The second substrate 1 is located on the outermost layer, and is formed with information on the irradiation position of the information light and the reference light for recording on the hologram recording medium, and as a support substrate that holds the mechanical strength of the hologram recording medium It has the function of. The second substrate 1 can be appropriately selected as necessary for its shape, structure, size, and the like. For example, a disk shape, a card shape, etc. are mentioned. Further, it is preferable that the outer shape of the first substrate 7 is the same. As the material constituting the second substrate 1, glass, ceramics, plastics and the like are usually used, but plastics are particularly preferably used from the viewpoint of workability and cost.

  Examples of the plastic include polycarbonate resin, acrylic resin, epoxy resin, polyphenylene ether resin, polyphenylene resin, polyarylene resin, polystyrene resin, acrylonitrile-styrene copolymer, polylactic acid resin, polyethylene resin, polypropylene resin, fluorine resin, ABS. Resin, urethane resin, etc. are mentioned. Among these, polycarbonate resin is particularly preferably used in terms of moldability, heat resistance, optical characteristics, and cost.

  The information regarding the irradiation position of the information light or the reference light on the second substrate 1 is not particularly limited and can be appropriately selected as necessary. For example, tracking information, focus information, address information, disc condition information, and the like can be given. Examples of the tracking information include wobble pits, wobble grooves, and tracking pits. Examples of the focus information include a reflective film formed on the surface of the second substrate 1, a focus mirror portion, a focus pit, and the like. Examples of the address information include irregularities formed on the wobble pits, encoded pit strings, and wobble modulation signals.

  The information may be formed in a composite manner. For example, address-servo areas as a plurality of positioning regions extending linearly in the radial direction may be provided at predetermined angular intervals, and a sector-shaped section between adjacent address-servo areas may be used as the data area. In the address-servo area, information for performing focus servo and tracking servo by the sampled servo method and address information are formed by previously recording the servo pit pattern 8 by embossed pits (servo pits) or the like. Also good.

  As thickness of the 2nd board | substrate 1, 0.1-5 mm is preferable and 0.3-2 mm is more preferable. If the thickness of the second substrate 1 is less than 0.1 mm, it is difficult to maintain the mechanical strength of the hologram recording medium. If the thickness exceeds 5 mm, the weight of the hologram recording medium becomes too large for the spindle motor. Undesirably because a heavy load is applied.

<Reflective layer>
A reflective film is formed as the reflective layer 2 on the surface of the servo pit pattern 8 on the second substrate 1. As the material of the reflective film 2, it is preferable to use a material having a high reflectance with respect to information light and reference light. For example, Al, Al alloy, Ag, Ag alloy, Au, Cu alloy and the like are preferable. There is no restriction | limiting in particular as a formation method of the said reflecting film 2, Various PVD methods, such as a vacuum evaporation method and sputtering method, or various thin film formation methods, such as CVD method, are applicable. However, it is preferable that the hologram recording medium is manufactured under conditions where adhesion to the second substrate 1 is particularly high in order not to cause peeling that occurs in a high-temperature and high-humidity environmental resistance test. For this purpose, a sputtering method is preferably used.
The film thickness range of the reflective layer 2 is preferably 10 to 500 nm, but is more preferably 30 to 200 nm, and particularly preferably 40 to 100 nm in order to suppress a decrease in signal characteristics due to a decrease in reflectance.

<Gap layer>
The gap layer 3 is formed for the purpose of planarizing the surface of the second substrate 1. As a material used for the gap layer 3, even if the filter layer 4 is laminated on the gap layer 3, the gap layer 3 is not deformed by heat at the time of lamination, and the recording material is laminated and cured on the filter layer 4. It is preferable that the material is excellent in heat resistance so that the gap layer 3 is deformed by the heat and shrinkage stress caused by the deformation and the filter layer 4 does not have defects such as cracks. The material constituting the gap layer 3 is preferably an ultraviolet curable resin or a plastic film. In particular, a film using polycarbonate is preferable.

<Filter layer>
The filter layer 4 has a function of preventing the occurrence of noise by preventing irregular reflection from the reflection film of the hologram recording medium by the information light and the reference light without causing a shift in the selective reflection wavelength even when the incident angle changes. . By laminating the filter layer 4 on a hologram recording medium, hologram recording with high resolution and excellent diffraction efficiency can be obtained.
The function of the filter layer 4 is preferably to transmit light of the first wavelength and reflect light of the second wavelength different from the light of the first wavelength, and the light of the first wavelength is 350 to 600 nm. It is preferable that the light of the second wavelength is 600 to 900 nm.
The filter layer 4 is not particularly limited, and may be formed of, for example, a dielectric vapor deposition layer, a single layer or two or more cholesteric layers, and a laminate of other layers as necessary. Moreover, you may have a color material content layer.

<Protective layer>
The protective layer 5 is formed between the filter layer 4 and the recording layer 6. The protective layer 5 is used for the purpose of preventing deterioration in recording performance of the hologram recording medium. Although the condensing position of the information light and the reference light exists in the recording layer, when the protective layer 5 is not provided, an excessive photoreaction occurs due to overexposure and the recording performance is deteriorated. That is, by using the protective layer 5, it is possible to suppress an excessive photoreaction near the condensing position and maintain recording performance. Although there is no restriction | limiting in particular as thickness of the protective layer 5, 1-200 micrometers is preferable and 3-100 micrometers is more preferable. If it is less than 1 μm, monomer consumption in the recording layer 6 at the time of hologram recording is too large, which may cause a decrease in sensitivity and a decrease in multiplicity. On the other hand, if it exceeds 200 μm, the focal position becomes farther from the recording layer 6, which leads to a decrease in recording performance.
In the hologram recording medium of the present invention, the protective layer 5 is made of a highly branched polycarbonate resin, and may contain a phosphorus-based heat stabilizer or the like as necessary.

(Highly branched polycarbonate resin)
The highly branched polycarbonate resin used in the present invention can be obtained by the reaction of dihydric phenol, branching agent, monohydric phenols, and phosgene, and the branching agent content determined by ¹ H-NMR analysis is 2. a .0～6.0 mol%, viscosity-average molecular weight of ^{1.6 × 10 4 ~3.2 × 10 4} .

(Viscosity average molecular weight)
The viscosity average molecular weight of the highly branched polycarbonate resin used in the present invention is 1.6 × 10 ^{4 to} 3.2 × 10 ⁴ , preferably 1.8 × 10 ^{4 to} 3.0 × 10 ^4. .9 × 10 ^{4 to} 2.8 × 10 ⁴ is more preferable. When the viscosity average molecular weight is less than 1.6 × 10 ⁴ , the effect of suppressing crystallization with respect to the solvent is lowered, which is not preferable. Moreover, when the viscosity average molecular weight is larger than 3.2 × 10 ⁴ , the melt viscosity at the time of molding becomes high and the moldability is inferior.
The viscosity average molecular weight in the present invention is calculated from the following formula by measuring the specific viscosity at 20 ° C. of a solution in which 0.7 g of the resin composition is dissolved in 100 ml of methylene chloride.
η _sp /c=[η]+0.45×[η] ² c
[Η] = 1.23 × 10 ⁻⁴ M ^0.83
η _sp : specific viscosity η: intrinsic viscosity c: constant (= 0.7)
M: Viscosity average molecular weight

(Glass-transition temperature)
The glass transition temperature of the hyperbranched polycarbonate resin used in the present invention is preferably in the range of 120 to 180 ° C, more preferably in the range of 130 to 170 ° C. If the glass transition temperature is less than 120 ° C., the substrate is likely to be thermally deformed, and the position of the interference fringes at the time of hologram recording is shifted, making it impossible to reproduce information. However, if the glass transition temperature exceeds 180 ° C., the flowability is poor in the molding process such as injection molding, and the moldability is inferior. The glass transition temperature in the present invention can be measured by using a differential scanning calorimeter (DSC) at a heating rate of 20 ° C./min in accordance with JIS K7121.

(Branching agent content)
The branching agent content determined by ¹ H-NMR analysis of the highly branched polycarbonate resin used in the present invention is 2.0 to 6.0 mol%, preferably 2.5 to 5.0 mol%. 0.0 to 4.5 mol% is more preferable. When the content of the branching agent is less than 2.0 mol%, the density of the entanglement points between the molecular chains is not different from that of the straight chain, which is not preferable because there is almost no effect in suppressing the crystallization rate. When the content of the branching agent is more than 6.0 mol%, methylene chloride insoluble matter (gel) is generated during injection molding, which is not preferable.

The branching agent content determined by ¹ H-NMR analysis in the present invention is, for example, when bisphenol A is used as the polycarbonate resin constituent unit and 1,1,1-tris (4-hydroxyphenyl) ethane is used as the branching agent. Branching agent for the sum of integral intensity ratios per proton of 1.679 ppm (6H, singlet) derived from bisphenol A and 1.464 ppm (3H, singlet) and 1.889 ppm (3H, singlet) as satellite peaks It is calculated | required by the integrated intensity ratio per proton of the chemical shift 2.180ppm (3H, singlet) of origin.

(Molecular weight between entanglement points)
The molecular weight between the entanglement points, which is an index of the entanglement point density of the highly branched polycarbonate resin used in the present invention, is preferably 2.6 × 10 ^{3 to} 3.2 × 10 ³ . The case of less than 2.6 × 10 ³ is not preferable because there is almost no effect of suppressing crystallization with respect to the solvent. If it is larger than 3.2 × 10 ³ , the polymer chain is crosslinked, and a large amount of heat-insoluble matter (gel) branched widely is not preferable. The molecular weight between the entanglement points in the present invention is determined from the rubber-like flat elastic modulus (G _N ) of the rubber-like flat region in the dynamic viscoelasticity measurement using a rotary rheometer. In the case of polycarbonate resin, there is actually no cross-linking point like rubber, but assuming that temporary entanglement bond occurs between molecular chains due to thermal motion, the molecular weight between entanglement points was calculated by the following formula from rubber elasticity theory. .
M _e = ρRT / _{G N}
G _N : rubbery flat elastic modulus ρ: density R: gas constant T: temperature M _e : molecular weight between entanglement points

(Crystallization speed)
The crystallization rate of the highly branched polycarbonate resin used in the present invention by immersion in acetone is preferably 3.0 × 10 ⁻³ % / sec or less. When it is larger than 3.0 × 10 ⁻³ % / sec, there is almost no effect of suppressing crystallization with respect to the solvent, which is not preferable. The crystallization rate in the present invention was calculated by the following method.

(I) A polycarbonate film having a length of 40 mm, a width of 10 mm, and a thickness of 100 μm was immersed in acetone at room temperature for 1 week in a sealed container, then the film was taken out, and the solvent was completely evaporated as a 100% crystallized film. The heat of crystal fusion (integrated value) at 220 to 230 ° C. is measured at a temperature increase rate of 20 ° C./min with a differential thermal analyzer (DSC).
(Ii) The same measurement is performed while changing the immersion time in acetone, and the crystallinity is calculated from the amount of heat of crystal melting (integral value) in each immersion time.
(Iii) Approximate K and n from the Avrami equation in crystallization theory.
X = 1−exp (−Kt ⁿ )
X: Crystallinity (%)
K, n: constant t: time (sec)
(Iv) The crystallinity is plotted against time t, and the slope in linear approximation from t = 0 to 10 sec is calculated as the crystallization speed.

(Manufacturing method of highly branched polycarbonate resin)
The highly branched polycarbonate resin used in the present invention can be obtained by an interfacial polymerization reaction of a dihydric phenol, a branching agent, a monohydric phenol, and phosgene.

  Typical examples of the dihydric phenol used in the present invention are 2,2-bis (4-hydroxyphenyl) propane (commonly known as bisphenol A), hydroquinone, resorcinol, 4,4′-biphenol, 1,1-bis. (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl)- 1-phenylethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 2,2-bis (4-hydroxyphenyl) Pentane, 4,4 '-(p-phenylenediisopropylidene) diphenol, 4,4'-(m-phenylenediisopropylidene Den) diphenol, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, bis (4-hydroxyphenyl) oxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfoxide, etc. Can be mentioned. These may be used alone or in combination of two or more. Of these, 2,2-bis (4-hydroxyphenyl) propane is preferable.

  Representative examples of the trihydric phenol used as a branching agent used in the present invention include 1,1,1-tris (4-hydroxyphenyl) ethane, 4,6-dimethyl-2,4,6-tri ( 4-hydroxyphenyl) heptene-2,4,6-dimethyl-2,4,6-tri (4-hydroxyphenyl) heptane, 1,3,5-tri (4-hydroxyphenyl) benzene, 2,6-bis (2-hydroxy-5-methylbenzyl) -4-methylphenol, tetra (4-hydroxyphenyl) methane, trisphenol, bis (2,4-dihydroxylphenyl) ketone, phloroglysin, phloroglucid, 3,3- Bis (4-hydroxyphenyl) oxindole (= isatin bisphenol), isatin bis (o-cresol), 1,4-bis (4,4-di Mud carboxymethyl triphenylmethyl) benzene, trimellitic acid, pyromellitic acid, benzophenonetetracarboxylic acid, and the like of these acid chlorides and the like. These may be used alone or in combination of two or more. Among them, from the group consisting of phloroglysin, 1,1,1-tris (4-hydroxyphenyl) ethane, 1,3,5-tri (4-hydroxyphenyl) benzene, isatin bisphenol and isatin bis (o-cresol). At least one branching agent selected is preferred, and 1,1,1-tris (4-hydroxyphenyl) ethane is particularly preferred.

  The monohydric phenol used as a terminal terminator used in the present invention may have any structure and is not particularly limited. For example, p-tert-butylphenol, p-tert-octylphenol, p-cumylphenol, 4-hydroxybenzophenone, phenol and the like can be mentioned. These may be used alone or in combination of two or more. Of these, p-tert-butylphenol is preferable.

The hyperbranched polycarbonate resin used in the present invention is preferably produced by the following first method or second method.
In the first production method, a polycarbonate oligomer is obtained by reacting a dihydric phenol with phosgene in the presence of a solvent. This is reacted with monohydric phenols. Next, after the branching agent is reacted with the obtained polycarbonate oligomer, the polycarbonate oligomer is emulsified and polymerized under non-stirring conditions. The reaction temperature from phosgenation to before emulsification is preferably 10 to 40 ° C, more preferably 15 to 30 ° C. The reaction temperature after emulsification is preferably 20 to 50 ° C, more preferably 30 to 40 ° C. The polymerization time is preferably 1 to 6 hours, more preferably 2 to 4 hours. The obtained reaction mixture is treated by usual means such as washing and separation to obtain the desired hyperbranched polycarbonate of the present invention.

  In the second production method, a dihydric phenol, a branching agent and phosgene are first reacted in the presence of a solvent to obtain a polycarbonate oligomer. This is reacted with monohydric phenol. After emulsifying the obtained polycarbonate oligomer, 1/30 to 1/200 of the amount of dihydric phenol reacted first, preferably 1/40 to 1/100 of dihydric phenol is added and stirred. It is a method of polymerizing under conditions.

  The reaction temperature from phosgenation to before emulsification is preferably 10 to 40 ° C, more preferably 15 to 30 ° C. The reaction temperature after emulsification is preferably 20 to 50 ° C, more preferably 30 to 40 ° C. When the polymerization reaction is continuously performed, the stirring speed in each polymerization tank is 100 rpm or less, preferably 50 rpm or less, and the high-viscosity emulsified fluid in the polymerization tank is not much in residence time in the direction perpendicular to the fluid traveling direction in the piston flow. It is sufficient to mix so that there is no difference. The polymerization time is preferably 1 to 6 hours, more preferably 2 to 4 hours. The obtained reaction mixture is treated by usual means such as washing and separation to obtain the desired hyperbranched polycarbonate of the present invention.

  A tertiary amine such as triethylamine, tetra-n-butylammonium bromide, tetra-n-butylphosphonium bromide, etc. can be used as a reaction catalyst, but this catalyst reacts with the chloroformate group and is thermally inactivated. Since a stable urethane bond is formed and the catalyst remains and the total nitrogen content in the highly branched polycarbonate resin increases, the amount of tertiary amine used is 0.2 mol% or less based on the dihydric phenol used. Is preferable, 0.1 mol% or less is more preferable, and 0.05 mol% or less is more preferable.

  In order to reduce the total chlorine content in the highly branched polycarbonate resin, dichloromethane (methylene chloride), dichloroethane, trichloroethane, tetrachloroethane, pentachloroethane, hexachloroethane, dichloroethylene, chlorobenzene, dichlorobenzene used as solvents during the reaction It is necessary to remove chlorinated hydrocarbon solvents such as. For example, it is possible to sufficiently dry the powder and pellets.

(Additive)
The hyperbranched polycarbonate resin used in the present invention includes a heat stabilizer, an antioxidant, a release agent (fatty acid ester, etc.), a weathering agent (ultraviolet absorber), a core, as long as the characteristics of the present invention are not impaired. Agents, lubricants, plasticizers, antistatic agents, whitening agents, antibacterial agents, colorants (pigments, dyes, etc.), fillers, reinforcing agents, other resins and polymers such as rubber, and flame retardants, etc. Can be used as appropriate.

(Release agent)
The highly branched polycarbonate resin used in the present invention preferably contains a higher fatty acid ester of a monohydric and / or polyhydric alcohol as a release agent.
As such higher fatty acid esters of monohydric and / or polyhydric alcohols, partial esters or total esters of monohydric or polyhydric alcohols having 1 to 22 carbon atoms and saturated fatty acids having 12 to 22 carbon atoms are preferred.

  Specifically, stearic acid monoglyceride, stearic acid monosorbate, behenic acid monoglyceride, pentaerythritol monostearate, pentaerythritol tetrastearate, propylene glycol monostearate, stearyl stearate, palmityl palmitate, butyl stearate, Examples thereof include methyl laurate, isopropyl palmitate, and 2-ethylhexyl stearate.

  Among them, at least one selected from the group consisting of mono- or diesters of glycerin and stearic acid, mono- or diesters of glycerin and behenic acid, all esters of pentaerythritol and stearic acid, and all esters of pentaerythritol and behenic acid. Are preferred. In particular, stearic acid monoglyceride or pentaerythritol tetrastearate is preferably used.

  The content of the higher fatty acid ester of the monohydric and / or polyhydric alcohol is preferably 0.01 to 1% by weight, more preferably 0.015 to 0.5% by weight with respect to the polycarbonate resin, and 0.02 to 0.2 wt% is more preferable. When the content is within this range, it is preferable that the mold release property is excellent and the mold release agent does not migrate and adhere to the metal surface. Further, the content of sodium metal contained in the higher fatty acid ester of the monohydric and / or polyhydric alcohol is preferably 1 ppm or less. If the content exceeds 1 ppm, the hue of the produced light transmitting layer substrate deteriorates, and the quality deteriorates due to an increase in white defects due to hydrolysis of the light transmitting layer substrate.

(Phosphorus heat stabilizer)
The hyperbranched polycarbonate resin used in the present invention preferably contains a phosphorus heat stabilizer. Examples of the phosphorus-based heat stabilizer include phosphorous acid, phosphoric acid, phosphonous acid, phosphonic acid and esters thereof. Specifically, triphenyl phosphite, tris (nonylphenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite, tris (2,6-di-tert-butylphenyl) phosphite, tridecyl phosphite, trioctyl phosphite, trioctadecyl phosphite, didecyl monophenyl Phosphite, dioctyl monophenyl phosphite, diisopropyl monophenyl phosphite, monobutyl diphenyl phosphite, monodecyl diphenyl phosphite, monooctyl diphenyl phosphite, bis (2,6-di-tert-butyl-4-methylphenyl) Pentaellis Tall diphosphite, 2,2-methylenebis (4,6-di-tert-butylphenyl) octyl phosphite, bis (nonylphenyl) pentaerythritol diphosphite, bis (2,4-di-tert-butylphenyl) Pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, tributyl phosphate, triethyl phosphate, trimethyl phosphate, triphenyl phosphate, diphenyl monoorthoxenyl phosphate, dibutyl phosphate, dioctyl phosphate, diisopropyl phosphate, 4,4'-biphenylenediphosphine Acid tetrakis (2,4-di-tert-butylphenyl), benzenephosphonic acid dimethyl, benzenephosphonic acid diethyl, benzenephosphonic acid Propyl and the like.

  Among them, tris (nonylphenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite, tris (2,6-di-tert-butylphenyl) phosphite, and 4,4′-biphenylene Diphosphinic acid tetrakis (2,4-di-tert-butylphenyl) and the like are preferably used, and tris (2,4-di-tert-butylphenyl) phosphite is particularly preferable. These can be used individually or in mixture of 2 or more types. The blending amount of these phosphorus heat stabilizers is preferably 10 to 10000 ppm, more preferably 20 to 1000 ppm with respect to the polycarbonate resin. By blending these phosphorus heat stabilizers, the thermal stability of the highly branched polycarbonate resin is further improved.

(Antioxidant)
The hyperbranched polycarbonate resin used in the present invention can be added with an antioxidant generally known for the purpose of preventing oxidation. Examples thereof include phenolic antioxidants, specifically, for example, triethylene glycol-bis (3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate), 1, 6-hexanediol-bis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate), pentaerythritol-tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) ) Propionate), octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert- Butyl-4-hydroxybenzyl) benzene, N, N-hexamethylenebis (3,5-di-tert-butyl-4- Droxy-hydrocinnamide), 3,5-di-tert-butyl-4-hydroxy-benzylphosphonate-diethyl ester, tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 3,9 -Bis {1,1-dimethyl-2- [β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl} -2,4,8,10-tetraoxaspiro (5 5) Undecane etc. are mentioned. The range of the preferable addition amount of these antioxidants is 0.0001-0.05 weight% with respect to polycarbonate resin.

(Pellet manufacturing process)
Considering that the purpose of use of the highly branched polycarbonate resin used in the present invention is a light-transmitting substrate of a hologram recording medium, it is produced by a conventionally known conventional method, and then subjected to a filtration treatment in a solution state so as to be unreacted. It is preferable to remove impurities such as components and foreign matters. Further, in the extrusion process (pelletizing process) for obtaining a pellet-like polycarbonate resin for use in injection molding (including injection compression molding), foreign matters are removed by passing a sintered metal filter or the like in the molten state. Is desirable. As the filter, those having a filtration accuracy of 10 μm or less are preferably used. In any case, it is necessary that the raw material resin before injection molding (including injection compression molding) has a low content of foreign matters, impurities, solvents and the like as much as possible.

  Furthermore, in order to produce such low foreign matter pellets, in addition to the above, a manufacturing device such as an extruder or pelletizer should be installed in a clean air atmosphere, and the cooling water for the cooling bath should have a small amount of foreign matter. It is preferable that the raw material supply hopper, the supply flow path, the storage tank for the obtained pellets, and the like be filled with cleaner air or the like. For example, it is appropriate to adopt a method similar to that proposed in JP-A-11-21357. Further, a method of pouring an inert gas typified by nitrogen gas into the extruder and shielding oxygen can be suitably used as a means for improving hue.

  Furthermore, in the production of such pellets, various methods already proposed for polycarbonate resins for optical molding materials are used to narrow the shape distribution of pellets, further reduce miscuts, and generate minute amounts during transportation or transportation. Further reduction of powder and reduction of bubbles (vacuum bubbles) generated in the strands and pellets can be appropriately performed. These prescriptions can further increase the molding cycle and reduce the occurrence rate of defects such as silver.

  Moreover, although the shape of a pellet can take common shapes, such as a cylinder, a prism, and a spherical shape, it is a cylinder (including an elliptical column) more preferably. The diameter of such a cylinder is preferably 1 to 5 mm, more preferably 1.5 to 4 mm, and still more preferably 2 to 3.3 mm. In the elliptic cylinder, the ratio of the minor axis to the major axis is preferably 60% or more, more preferably 65% or more. On the other hand, the length of the cylinder is preferably 1 to 30 mm, more preferably 2 to 5 mm, and still more preferably 2.5 to 3.5 mm.

(Film production method)
Next, a method for producing a highly branched polycarbonate film used in the present invention will be described. The production method of the film of the present invention is not particularly limited, and examples thereof include a melt extrusion method and a solution casting method (casting method).

(Melt extrusion method)
A specific method of the melt extrusion method is, for example, that a high-branched polycarbonate resin is quantitatively supplied to an extruder, heated and melted, and the molten resin is extruded in a sheet form on a mirror roll from the tip of a T-die, and is formed into a plurality of rolls. Then, it is taken out while being cooled, and when solidified, it is cut into an appropriate size or wound up.

(Solution casting method)
A specific method of the solution casting method is, for example, casting a solution (concentration 5% to 40%) of a highly branched polycarbonate resin in methylene chloride on a mirror-polished stainless steel plate from a T die, and gradually increasing the temperature. The film is peeled off while passing through a controlled oven, the solvent is removed, and then cooled and wound.

(Thickness and unevenness of film)
When used as the protective layer 5 of the hologram recording medium, the thickness of the film is preferably in the range of 5 to 200 μm because it has a function of preventing the deterioration of the multiple recording performance. If it is less than 5 μm, the servo signal light and the hologram signal light are mixed, and the S / N ratio of the hologram signal light is lowered and the error rate is increased. On the other hand, if it exceeds 200 μm, the total thickness of the disc increases and the disc weight increases, which is not preferable. The preferred thickness is 10 to 150 μm, more preferably 20 to 100 μm.

Moreover, it is better that the thickness unevenness is small. Although the thickness variation varies depending on the thickness of the film, the range of the thickness variation with respect to the thickness is preferably ± 5% or less, more preferably ± 3% or less, and further preferably ± 1% or less. Here, 5% means that the difference between the maximum value and the minimum value of the thickness of a film having a thickness of 100 μm is 5 μm. If the thickness unevenness is larger than ± 5%, the surface smoothness is impaired.
The measuring method of the thickness unevenness of the film full width can be performed using, for example, a continuous thickness meter (Film Thickness Tester Model KG601A manufactured by Anritsu Co., Ltd.).

(Total light transmittance of film)
The higher the total light transmittance of the film is desirable, preferably 80% or more, more preferably 85%, and further preferably 89% or more. If the total light transmittance of the film becomes too low, it becomes difficult to use it as the protective layer 5 of the hologram recording medium.

(In-plane retardation of film)
The film is also characterized by high optical isotropy, and the phase difference (Re) represented by the product of thickness and birefringence is preferably 20 nm or less at the laser wavelength used, and more preferably 10 nm or less. Preferably, it is 8 nm or less, more preferably 5 nm or less. Ideally, this value is as close to zero as possible. If the in-plane retardation exceeds 20 nm, the reproduction signal level of the servo signal becomes unstable and the S / N ratio deteriorates, which is not preferable.
The measuring method of the in-plane retardation value (Re) is measured with a retardation continuous measuring instrument (trade name KOBRA-WFD manufactured by Oji Scientific Instruments Co., Ltd.) for the entire width of the sample in the width direction. The wavelength of the measurement light source is 589 nm.

(Retardation in the thickness direction of the film)
In addition to the above properties, the highly branched polycarbonate film used in the present invention has a retardation value (R _th ) in the thickness direction of the film of preferably 60 nm or less, more preferably 50 nm or less at the laser wavelength used. Preferably it is 45 nm or less. If the retardation in the thickness direction exceeds 60 nm, the noise of the servo signal increases, which is not preferable.

As a method for measuring _Rth , for example, the entire width is sampled and divided into five equal parts in the width direction of the film. A measurement sample piece is cut out from the sample divided into five equal parts, and measured with an automatic birefringence measuring device (trade name, KOBRA-WR, manufactured by Oji Scientific Instruments). The film sample is rotated at the slow axis or fast axis by changing the incident angle measured retardation by, calculates the refractive indices n _x, n _y and n _z from these data. From these values,
R _th [nm] = {(n _x + n _y ) / 2−n _z } × d
Is obtained by calculating. Here, the symbol d represents the thickness (nm) of the measurement film.

<Recording layer>
The recording layer 6 is a layer on which information is recorded by superimposing information light provided with information as a two-dimensional image and reference light capable of interfering with the information light inside the recording medium by using holography. When an electromagnetic wave (γ ray, X-ray, ultraviolet ray, visible ray, infrared ray, radio wave, etc.) having a wavelength of is used, a material whose optical properties such as an extinction coefficient and a refractive index change depending on its intensity is used. As a material constituting the recording layer 6, generally, a structure having a three-dimensional cross-linked polymer matrix in addition to a radical polymerizable compound and a photo radical polymerization initiator is suitably used.

  An epoxy compound is used as the compound that forms the three-dimensional crosslinked polymer forming the matrix. Specifically, as the epoxy compound, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol Diglycidyl ether, diepoxy octane, resorcinol diglycidyl ether, diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, 3,4-epoxycyclohexenylmethyl-3 ', 4'-epoxycyclohexene carboxylate, and epoxy propoxy Examples include propyl-terminated polydimethylsiloxane.

  Examples of the radical polymerizable compound include compounds having an ethylenically unsaturated double bond. Examples thereof include unsaturated carboxylic acids, unsaturated carboxylic acid esters, unsaturated carboxylic acid amides, and vinyl compounds. More specifically, acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, bicyclopentenyl Acrylate, phenyl acrylate, isobornyl acrylate, adamantyl acrylate, methacrylic acid, methyl methacrylate, propyl methacrylate, butyl methacrylate, phenyl methacrylate, phenoxyethyl acrylate, chlorophenyl acrylate, adamantyl methacrylate, isobornyl methacrylate, N-methylacrylamide, N, N-dimethylacrylamide, N, N-methylenebisacrylamide, acryloyl Ruphorin, vinyl pyridine, styrene, bromostyrene, chlorostyrene, tribromophenyl acrylate, trichlorophenyl acrylate, tribromophenyl methacrylate, trichlorophenyl methacrylate, vinyl benzoate, 3,5-dichlorovinyl benzoate, vinyl naphthalene, vinyl naphthoate, naphthyl Methacrylate, naphthyl acrylate, N-phenyl methacrylamide, N-phenyl acrylamide, N-vinyl pyrrolidinone, N-vinyl carbazole, 1-vinyl imidazole, bicyclopentenyl acrylate, 1,6-hexanediol diacrylate, pentaerythritol triacrylate, penta Erythritol tetraacrylate, dipentaerythritol hexaacrylate, di Chi glycol diacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, tripropylene glycol diacrylate, propylene glycol trimethacrylate, include N- vinylcarbazole and N- vinylpyrrolidone.

Examples of the photo radical polymerization initiator include imidazole derivatives, organic azide compounds, titanocenes, organic peroxides, and thioxanthone derivatives. Specifically, benzyl, benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, benzoin isobutyl ether, 1-hydroxycyclohexyl phenyl ketone, benzyl methyl ketal, benzyl ethyl ketal, benzyl methoxy ethyl ether, 2,2′-diethyl Acetophenone, 2,2′-dipropylacetophenone, 2-hydroxy-2-methylpropiophenone, p-tert-butyltrichloroacetophenone, thioxanthone, 2-chlorothioxanthone, 3,3′4,4′-tetra (t- Butylperoxycarbonyl) benzophenone, 2,4,6-tris (trichloromethyl) 1,3,5-triazine, 2- (p-methoxyphenyl) -4,6-bis (trichloromethyl) 1,3,5-triazine, 2-[(p-methoxyphenyl) ethylene] -4,6-bis (trichloromethyl) 1,3,5-triazine, Irgacure 149, 184, 369 manufactured by Ciba Specialty Chemicals, 651, 784, 819, 907, 1700, 1800, 1850 and the like, di-t-butyl peroxide, dicumyl peroxide, t-butyl cumyl peroxide, t-butyl peroxyacetate, t-butyl peroxide Oxyphthalate, t-butylperoxybenzoate, acetyl peroxide, isobutyryl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, methyl ethyl keto Peroxide, and cyclohexanone peroxide.
If necessary, sensitizing dyes such as cyanine, merocyanine, xanthene, coumarin, and eosin, silane coupling agents, and plasticizers may be added.

  To apply the recording layer solution containing the above three-dimensional crosslinked polymer, radical polymerizable monomer, and photopolymerization initiator on the protective layer 5, a casting or spin coating method can be employed. It is also possible to dispose the second substrate 1 including the filter layer 4 and the first substrate 7 through a resin spacer, and pour the recording layer material solution into the gap. The three-dimensional crosslinking of the matrix polymer proceeds at room temperature with aliphatic primary amines, but may be heated to about 30 ° C. to 150 ° C. depending on the reactivity of the curing agent. The film thickness of the recording layer 6 is preferably in the range of 20 μm to 2 mm. If it is less than 20 μm, it is difficult to obtain a sufficient recording capacity, and if it exceeds 2 mm, the sensitivity and diffraction efficiency of the recording layer 6 may be reduced. More preferably, the film thickness of the recording layer 6 is in the range of 50 μm to 1 mm.

<First substrate>
The first substrate 7 is preferably laminated on the recording layer 6 and is a light transmissive substrate. The shape, structure, size and the like are not particularly limited and can be appropriately selected as necessary. The same shape and material as those of the second substrate 1 can be used.
There is no restriction | limiting in particular in the thickness of the 1st board | substrate 7, 5-1200 micrometers is preferable and 100-700 micrometers is more preferable. When the thickness of the support is less than 5 μm, the function of protecting the recording layer is reduced, and when it exceeds 1200 μm, the distance from the surface of the first substrate 7 to the layer on which the recording layer 6 and the servo pit pattern 8 are formed. Is not preferable because the focal length of the recording / reproducing light is too long.

<Hologram recording and playback method>
There is no restriction | limiting in particular as a hologram recording method, According to the objective, it can select suitably. For example, the hologram recording method is a collinear hologram recording method in which information light and reference light are irradiated as a coaxial light beam on the hologram recording medium, and information is recorded on the recording layer 6 by an interference pattern due to interference between the information light and the reference light.
The reproduction method is not particularly limited and can be appropriately selected depending on the purpose. For example, the interference image formed on the recording layer by the optical recording method is irradiated with the same light as the reference light. Recording information corresponding to can be reproduced.

  In the optical recording method and the reproducing method, information light provided with information as a two-dimensional image is superimposed on the information light and reference light having a substantially constant intensity inside the recording layer, and an interference pattern formed by them is used. Then, information is recorded by generating a distribution of optical characteristics inside the recording layer. On the other hand, when reproducing the written information, only the reference light is irradiated to the recording layer 6 in the same arrangement as in recording, and the reproduction light has an intensity distribution corresponding to the optical characteristic distribution formed inside the recording layer 6. Is obtained.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. In this example, a series of operations were performed in a room where light shorter than a wavelength of 600 nm was shielded so that the recording layer 6 was not exposed.

  The protective layer for hologram recording medium of the present invention is excellent in transparency and solvent resistance, and the hologram recording medium using the protective layer is not impaired in transparency even when it comes into contact with the recording layer, and Excellent adhesion and good hologram recording / reproduction characteristics.

  Hereinafter, although an example is given and explained in detail, the present invention is not limited to this unless it exceeds the purpose. In the examples and comparative examples, “parts” is parts by weight. Evaluation was according to the following method.

(1) Glass transition temperature Using a thermal analysis system DSC-2910 manufactured by TA Instruments Inc. in accordance with JIS K7121, under a nitrogen atmosphere (nitrogen flow rate: 40 ml / min), rate of temperature increase: 20 ° C./min The measurement was performed under the following conditions.

(2) Viscosity average molecular weight 0.7 g of polycarbonate resin composition pellets were dissolved in 100 ml of methylene chloride, the specific viscosity (η _sp ) of the solution at 20 ° C. was measured, and the viscosity average molecular weight was calculated by the following formula.
η _sp /c=[η]+0.45×[η] ² c
[Η] = 1.23 × 10 ⁻⁴ M ^0.83
η _sp : specific viscosity η: intrinsic viscosity c: constant (= 0.7)
M: Viscosity average molecular weight

(3) Molecular weight between entanglement points Using a dynamic viscoelastic device RDA-III manufactured by TA Instruments, using a parallel plate of 25 mmφ as a jig, a frequency of 0.05 to 500 rad / sec, a temperature of 180 The rotational shear strain (storage elastic modulus G ′, loss elastic modulus G ″) at 200 and 220 ° C. was measured. A master curve of rotational shear strain at a reference temperature of 200 ° C. was created from the obtained results, and a rubbery flat region was obtained. The value of the storage elastic modulus at the minimum value of the loss elastic modulus G ″ was defined as the rubber-like flat elastic modulus, and the molecular weight between the entanglement points was measured by the following formula.
M _e = ρRT / _{G N}
G _N : Rubber-like flat elastic modulus [MPa]
ρ: Density [g / cm ³ ]
R: Gas constant (= 8.20574 × 10 ⁻² [cm ³ · atm · K ⁻¹ · mol ⁻¹ ])
* 1 [atm] = 1.0132 [MPa]
T: Temperature [K]
M _e : Molecular weight between entanglement points [g / mol]

(4) Branching agent content ¹ H-NMR was measured for the branching agent content with a JOEL NMR apparatus and calculated from the peak integrated intensity ratio.

(5) Crystallization speed A polycarbonate film having a length of 40 mm, a width of 10 mm, and a thickness of 100 μm is immersed in acetone in a sealed container at room temperature for 1 week, then taken out of the film, and 100% crystallized from the completely evaporated solvent. As a film, the heat of crystal fusion (integrated value) at 220 to 230 ° C. was measured at a temperature rising rate of 20 ° C./min using a thermal analysis system DSC-2910 manufactured by TA Instruments. The amount of heat of crystal fusion of 100% crystal was used. Thereafter, the same measurement was performed by changing the immersion time, and the degree of crystallinity was calculated from the amount of heat of crystal fusion (integrated value) at each immersion time. In order to approximate K and n from the Avrami equation in the crystallization theory, the crystallinity was plotted against time t, and the slope in linear approximation from t = 0 to 10 sec was calculated as the crystallization speed.
X = 1−exp (−Kt ⁿ )
X: Crystallinity (%)
K, n: constant t: time (sec)

(6) Thickness unevenness of film The thickness unevenness of the full width of the film was performed using a continuous thickness meter (Film Sickness Tester Model KG601A manufactured by Anritsu Co., Ltd.).

(7) Total light transmittance of film Samples were collected from three places in the width direction of the film. The total light transmittance of the sample was measured using a color difference / turbidity measuring machine COH-300A manufactured by Nippon Denshoku Industries Co., Ltd. Five points were measured for each sample, and an average value of a total of 15 points for three samples in the width direction was defined as the total light transmittance. This measurement was performed according to JISK7105.

(8) Measurement of in-plane retardation value (Re) Retardation values were measured at intervals of 10 mm with a retardation continuous measuring instrument (trade name KOBRA-WFD manufactured by Oji Scientific Instruments Co., Ltd.) for the full width of the sample in the width direction. The wavelength of the measurement light source is 589 nm.

(9) Measurement of retardation value (R _th ) in the thickness direction The full width was sampled in the same manner as the measurement in the above item (8), and was divided into 5 equal parts in the width direction of the film. A measurement sample piece was cut out from the equally divided sample and measured with an automatic birefringence measuring apparatus (trade name, KOBRA-WR, manufactured by Oji Scientific Instruments). The film sample is rotated at the slow axis or fast axis by changing the incident angle is measured retardation by was calculated refractive indices n _x, n _y and n _z from these data. From these values,
R _th [nm] = {(n _x + n _y ) / 2−n _z } × d
Was calculated. Here, d represents the thickness (nm) of the measurement film.

(10) Preparation of hologram recording layer 1,6-hexanediol diglycidyl ether was used as a three-dimensional crosslinked polymer. In addition, polyethylene glycol diacrylate was used as the radical polymerizable compound. The monomer is liquid at room temperature. 3 parts by weight of Irgacure-784 (manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator was added to and mixed with 100 parts by weight of polyethylene glycol diacrylate. Further, 0.3 parts by weight of THF as a viscosity adjusting solvent was added and mixed. The hologram recording layer solution was prepared by mixing at room temperature so that the ratio of the matrix material was 67% by weight and the ratio of the photopolymerizable monomer was 33% by weight with respect to the total amount of the hologram recording layer solution.

(11) Preparation of hologram recording medium After drying polycarbonate resin pellets (Teijin Kasei Panlite (registered trademark) AD-5503) as a second substrate resin at 120 ° C. for 5 hours, an optical disk injection molding machine (Sumitomo Heavy Industries) A disc substrate containing a format signal having an outer diameter of 120 mmφ, an inner diameter of 15 mmφ, and a thickness of 1.1 mm was formed by SD-40E manufactured by Kogyo Co., Ltd.
Using the obtained disk substrate, it was supplied to a Blu-ray Disc bonding device (Mevius F-1 manufactured by Shibaura Mechatronics Co., Ltd.). In addition to this disk substrate, Mobius F-1 includes Teijin Chemicals Panlite (registered trademark) film D- as a film for gap layer film, a target for magnetron sputtering of Ag alloy manufactured by Kobelco Research Institute, Ltd. 92, EX-8410 manufactured by Dainippon Ink & Chemicals, Inc. was supplied as a resin for bonding the film and the disk substrate. In Mobius F-1, after forming a reflective film of Ag alloy on the disk substrate by sputtering, spin coating with an adhesive resin, and only the polycarbonate film is drawn out from the laminated film roll for the gap layer, and then punched into a disk shape. The punched gap layer film was bonded to the above substrate and irradiated with ultraviolet rays to form a gap layer.
Thereafter, a dichroic mirror layer was laminated as a filter layer by vacuum deposition of SiO ₂ and TiO ₂ by vacuum deposition. Next, the protective layer was laminated | stacked by the method similar to a gap layer using the highly branched polycarbonate film. Here, a glass substrate (0.6 mm thick mirror disk manufactured by Tokiwa Optical Co., Ltd.) having an outer diameter of 120 mmφ, an inner diameter of 15 mmφ, and a thickness of 0.6 mm is used as the first substrate, and the hologram recording layer solution prepared in the above (10) is spinned. It apply | coated on the protective layer by the coating, and the 1st board | substrate was bonded together on it. This was shielded from light and held at 80 ° C. for 5 hours to produce a hologram recording medium (see FIG. 1) having a recording layer having a thickness of 0.6 mm. At that time, the presence or absence of cloudiness of the protective layer was confirmed visually.

(12) Recording / reproduction evaluation of hologram recording medium The hologram recording medium was irradiated with information light and recording reference light by a semiconductor laser (532 nm) using a collinear hologram recording tester SHOT-2000 manufactured by Pulstec Industrial Co., Ltd. A series of multiple holograms 13 × 13 (49 multiples) with a recording spot diameter of 200 μm at the focal position of the recording hologram was recorded as an interference image on the recording layer of the hologram recording medium. The disk rotation speed at the time of recording is 10 rpm, the irradiation time of laser light for one information recording is 100 μs, and the light intensity is 100 mW. In addition, reproduction was performed using the same apparatus. The reproduction condition is such that the rotation speed of the hologram recording medium is 10 rpm, laser light having a wavelength of 532 nm similar to that of the reference light is used as reproduction light, and the bit error rate (hereinafter referred to as “bit error rate”) when reproducing with an irradiation time of 100 μsec and a light intensity of 100 mW. (Abbreviated as BER) and SNR. As a practical standard, the SNR is 4 or more and the BER is 10 ⁻³ or less.

[Example 1]
A reactor equipped with a thermometer, a stirrer and a reflux condenser was charged with 3570 parts of a 48% aqueous sodium hydroxide solution and 20777 parts of ion-exchanged water, to which 3290 parts of 2,2-bis (4-hydroxyphenyl) propane, After dissolving 6.58 parts of hydrosulfite, 9812 parts of methylene chloride was added, and 2000 parts of phosgene was blown in at 15-25 ° C. over about 60 minutes with stirring. After completion of the phosgene blowing, 595 parts of 48% aqueous sodium hydroxide and 194 parts of p-tert-butylphenol were added, 142 parts of 1,1,1-tris (4-hydroxyphenyl) ethane was added and stirring was resumed, after emulsification 5 parts of triethylamine was added and the mixture was further stirred at 28 to 33 ° C. for 1 hour to complete the reaction. After completion of the reaction, the product is diluted with methylene chloride, washed with water, acidified with hydrochloric acid, washed with water, and further washed with water until the conductivity of the aqueous phase becomes substantially the same as that of ion-exchanged water. Obtained.

  Next, this solution is passed through a filter having an aperture of 0.3 μm, and further dropped into warm water in a kneader with an isolation chamber having a foreign matter outlet at the bearing, and the polycarbonate resin is flaked while distilling off methylene chloride. The liquid-containing flakes were pulverized and dried to obtain a powder. Thereafter, tris (2,4-di-tert-butylphenyl) phosphite was added to the powder so as to be 0.0025% by weight and mixed uniformly, and then the obtained powder was melted by heating to 110 ° C. It put into the heating hopper of the extruder and melt-extruded at 280 degreeC. A disk-shaped filter made of stainless steel nonwoven fabric having an average aperture of 10 μm for removing foreign matters from the molten polymer was used. The molten resin after filtration was extruded onto a cooling roll surface having a rotating diameter of 800 mm and a roll surface length of 1800 mm with a die set at 290 ° C. The lip width of the extrusion die was 1500 mm, and the lip gap was about 2 mm. In order to uniformly cool and take out the film, the entire width of the film was brought into close contact with the surface of the cooling roll by an electrostatic contact method. As the electrode for electrostatic adhesion, a stainless steel piano wire that was cleanly polished was used. A positive electrode of a DC power source was connected to this piano wire, and the cooling drum side was grounded. The applied voltage was 7 KV. Thus, a film having a thickness of 100 μm was taken up through the take-off roll at a cooling roll rotational speed of 10 m / min. The obtained polycarbonate films were evaluated in the above (1) to (9), and the results are shown in Table 1.

[Example 2]
Except for using 324 parts of p-tert-butylphenol and 238 parts of 1,1,1-tris (4-hydroxyphenyl) ethane, all operations were performed in the same manner as in Example 1 to obtain a highly branched polycarbonate film. The films (1) to (9) were evaluated and the results are shown in Table 1.

[Example 3]
The same operation as in Example 1 was carried out except that 162 parts of p-tert-butylphenol and 119 parts of 1,1,1-tris (4-hydroxyphenyl) ethane were obtained to obtain a highly branched polycarbonate film. The films (1) to (9) were evaluated and the results are shown in Table 1.

[Comparative Example 1]
Except that 97 parts of p-tert-butylphenol and 71 parts of 1,1,1-tris (4-hydroxyphenyl) ethane were used, the same operation as in Example 1 was carried out to obtain a highly branched polycarbonate film. The films (1) to (9) were evaluated and the results are shown in Table 1.

[Comparative Example 2]
Except for using 281 parts of p-tert-butylphenol and 309 parts of 1,1,1-tris (4-hydroxyphenyl) ethane, all operations were performed in the same manner as in Example 1 to obtain a highly branched polycarbonate film. The films (1) to (9) were evaluated and the results are shown in Table 1.

[Comparative Example 3]
The same operation as in Example 1 was carried out except that 205 parts of p-tert-butylphenol and 142 parts of 1,1,1-tris (4-hydroxyphenyl) ethane were obtained to obtain a highly branched polycarbonate film. The films (1) to (9) were evaluated and the results are shown in Table 1.

[Comparative Example 4]
The same operation as in Example 1 was carried out except that 32 parts of p-tert-butylphenol and 142 parts of 1,1,1-tris (4-hydroxyphenyl) ethane were obtained to obtain a highly branched polycarbonate film. The films (1) to (9) were evaluated and the results are shown in Table 1.

[Comparative Example 5]
Except for using 129 parts of p-tert-butylphenol and 71 parts of 1,1,1-tris (4-hydroxyphenyl) ethane, all operations were carried out in the same manner as in Example 1 to obtain a highly branched polycarbonate film. The films (1) to (9) were evaluated and the results are shown in Table 1.

[Comparative Example 6]
A polycarbonate film was obtained in the same manner as in Example 1 except that Panlite (registered trademark) L-1225 manufactured by Teijin Chemicals Ltd. was used as the polycarbonate resin. The films (1) to (9) were evaluated and the results are shown in Table 1.

[Comparative Example 7]
A polycarbonate film was obtained in the same manner as in Example 1 except that Panlite (registered trademark) AD-5503 manufactured by Teijin Chemicals Ltd. was used as the polycarbonate resin. The films (1) to (9) were evaluated and the results are shown in Table 1.

It is the schematic which shows the hologram recording medium used with a collinear system, its information light, and reference light.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Second substrate 2 Reflective layer 3 Gap layer 4 Filter layer 5 Protective layer 6 Recording layer 7 First substrate 8 Servo pit pattern 9 Light for servo (red laser)
10 Information light / reference light (green laser with a wavelength of 532 nm or blue laser with a wavelength of 405 nm)

Claims (6)

A second substrate serving as a support, which has a recording layer for recording information using holography, by superimposing information light provided with information as a two-dimensional image and reference light capable of interfering with information light, and reflecting Hologram recording medium comprising a layer, a gap layer, a filter layer, a protective layer, a recording layer, and a light-transmitting first substrate, wherein the protective layer contains a branching agent required by ¹ H-NMR analysis A hologram characterized by being a film formed from a highly branched polycarbonate resin having an amount of 2.0 to 6.0 mol% and a viscosity average molecular weight of 1.6 × 10 ^{4 to} 3.2 × 10 ⁴ recoding media. The hologram recording according to claim 1, wherein the highly branched polycarbonate resin has a branching agent content of 2.5 to 5.0 mol% and a viscosity average molecular weight of 1.8 × 10 ^{4 to} 3.0 × 10 ^4. Medium.   The branching agent is phloroglysin, 1,1,1-tris (4-hydroxyphenyl) ethane, 1,3,5-tri (4-hydroxyphenyl) benzene, 3,3-bis (4-hydroxyphenyl) oxy 2. The hologram recording medium according to claim 1, wherein the hologram recording medium is at least one branching agent selected from the group consisting of indole (= isatin bisphenol) and isatin bis (o-cresol). The hologram recording medium according to claim 1, wherein the highly branched polycarbonate resin has a molecular weight between entanglement points of 2.6 × 10 ^{3 to} 3.2 × 10 ³ g / mol. The hologram recording medium according to claim 1, wherein the highly branched polycarbonate resin has a crystallization rate of 3 × 10 ⁻³ % / sec or less when immersed in acetone. A second substrate serving as a support, which has a recording layer for recording information using holography, by superimposing information light provided with information as a two-dimensional image and reference light capable of interfering with information light, and reflecting Layer, gap layer, filter layer, protective layer, recording layer, protective layer in a hologram recording medium composed of a light-transmitting first substrate, the protective layer being branched by ¹ H-NMR analysis It is a film formed from a highly branched polycarbonate resin having an agent content of 2.0 to 6.0 mol% and a viscosity average molecular weight of 1.6 × 10 ^{4 to} 3.2 × 10 ^4. A protective layer for a hologram recording medium.

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