JP2007072164A - Optical recording medium, and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium of high quality in which the thickness of a recording layer is fixed without narrowing the recording region of a hologram as possible, and to provide a method for efficiently producing the optical recording medium. <P>SOLUTION: The optical recording medium at least contains: a recording layer of recording information utilizing holography; a first substrate; a second substrate; a first gap layer; a second gap layer; a filter layer; and a spacer of holding the thickness of the recording layer. The width of the spacer in the layer face direction of the recording layer is at least 0.5 mm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical recording medium on which information is recorded using holography, a manufacturing method thereof, a recording method of the optical recording medium, and a reproducing method of the optical recording medium.

An optical recording medium is one of recording media capable of writing a large amount of information such as high-density image data. As this optical recording medium, for example, a rewritable optical recording medium such as a magneto-optical disk and a phase change optical disk and a write-once optical recording medium such as a CD-R have already been put into practical use. The demand for larger capacity is increasing.
However, all conventionally proposed optical recording media are two-dimensional recording, and there is a limit to increasing the recording capacity. Therefore, recently, a hologram type optical recording method capable of recording information three-dimensionally has attracted attention.
In the hologram type optical recording method, in general, information light given a two-dimensional intensity distribution and reference light having a substantially constant intensity are superposed inside a photosensitive recording layer to form them. Information is recorded by generating a distribution of optical characteristics inside the recording layer using the interference image. On the other hand, in reading (reproducing) written information, the recording layer is irradiated with only the reference light in the same arrangement as in recording, and the reproducing light having an intensity distribution corresponding to the optical characteristic distribution formed inside the recording layer is used. This is done by emitting from the recording layer.
In this hologram type optical recording method, since the optical characteristic distribution is three-dimensionally formed in the recording layer, an area where information is written by one information light, an area where information is written by other information light, and Can be partially overlapped, that is, multiplex recording is possible, which matches the demand for larger capacity. When digital volume holography is used for such multiplex recording, the signal-to-noise ratio (S / N ratio) of one spot becomes extremely high, so that the original information is faithfully maintained even if the S / N ratio is somewhat lowered by overwriting. A reproducible hologram type optical recording medium is obtained. As a result, the number of times of multiple recording reaches several hundreds, and the recording capacity of the optical recording medium can be remarkably increased (see Patent Document 1).

As such a hologram type optical recording medium, for example, as shown in FIG. 1, a servo pit pattern 3 is provided on the surface of the second substrate 1, and a reflective film 2 made of aluminum or the like is provided on the surface of the servo pit pattern. An optical recording medium 20 having a recording layer 4 on the reflective film and a first substrate 5 on the recording layer has been proposed (see Patent Document 2).
Further, as in the optical recording medium 20a shown in FIG. 2, the surface of the second substrate 1 is smoothed between the second substrate 1 and the recording layer 4, and the size of the hologram generated in the recording layer is increased. The first gap layer 8 for adjusting the wavelength, the filter layer 6 for selecting and reflecting only the wavelengths of the information light and the reference light, and the quarter-wave plate 9 are formed, and efficient recording by the information light and the reference light is performed. Improvements have been made (see Patent Document 3). Since such an optical recording medium is used in different recording / reproducing apparatuses, the thickness needs to be constant and highly accurate.
However, in the case of such an optical recording medium, the first gap layer 8, the filter layer 6, the quarter wavelength plate 9 and the recording layer 4 are laminated between the first substrate 5 and the second substrate 1. Therefore, in order to make the thickness of the optical recording medium constant, the thickness of each layer is made constant, or in the manufacturing process, the thickness of the entire laminate of the optical recording medium is set. There are productivity issues such as the need to adjust. In particular, in the case of a recording layer for recording information using holography, the thickness is 100 to 1,000 μm, which is extremely large compared to other layers, for volume recording, and the recording layer is required to have a constant thickness. It is done. As a means for keeping the thickness constant, since the hologram recording is performed on the recording layer, it is desirable to devise not to narrow the recording area as much as possible.

JP 2002-123949 A Japanese Patent Laid-Open No. 11-311936 JP 2004-265472 A

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, the present invention relates to an optical recording medium having a high recording quality with a constant thickness of the recording layer and an optical recording medium capable of efficiently producing the optical recording medium without narrowing the recording area of the hologram as much as possible. It aims at providing the manufacturing method of.

Means for solving the problems are as follows. That is,
<1> Recording layer for recording information using holography, first substrate, second substrate, first gap layer, second gap layer, filter layer, and thickness of the recording layer The optical recording medium is characterized in that it has at least a holding spacer, and the width of the recording layer in the layer surface direction of the spacer is at least 0.5 mm.
<2> The optical recording medium according to <1>, wherein the width of the recording layer of the spacer in the layer surface direction is 0.5 to 5 mm.
<3> From the above <1> used in an optical recording method in which irradiation of information light and reference light to an optical recording medium is performed such that the optical axis of the information light and the optical axis of the reference light are coaxial. <2> The optical recording medium according to any one of <2>.
<4> The optical recording medium according to any one of <1> to <3>, wherein the filter layer has a color material-containing layer containing a color material of at least one of a pigment and a dye.
<5> Any one of the items <1> to <4>, wherein the filter layer includes a color material-containing layer containing at least one colorant of a pigment and a dye, and a cholesteric liquid crystal layer on the color material-containing layer. The optical recording medium described in 1.
<6> The optical recording medium according to any one of <4> to <5>, wherein the color material is a red pigment.
<7> The optical recording medium according to <6>, wherein the red pigment has a transmittance with respect to 532 nm light of 33% or less and a transmittance with respect to 655 nm light of 66% or more.
<8> The optical recording medium according to any one of <4> to <7>, wherein the filter layer has a dielectric vapor deposition layer on the color material-containing layer.
<9> The optical recording medium according to any one of <4> to <8>, wherein the color material-containing layer contains a binder resin, and the binder resin is a polyvinyl alcohol resin.
<10> The optical recording medium according to any one of <4> to <9>, wherein the color material-containing layer surface is rubbed.
<11> The optical recording medium according to any one of <1> to <10>, wherein the filter layer includes a dielectric vapor deposition layer in which a plurality of dielectric thin films having different refractive indexes are stacked.
<12> The optical recording medium according to <11>, wherein the dielectric vapor deposition layer is formed by alternately laminating a plurality of high refractive index dielectric thin films and low refractive index dielectric thin films.
<13> The optical recording medium according to any one of <11> to <12>, wherein the dielectric vapor deposition layer is formed by laminating 2 to 20 dielectric thin films.
<14> The optical recording medium according to any one of <1> to <13, wherein the filter layer includes a single cholesteric liquid crystal layer.
<15> The optical recording medium according to any one of <1> to <14>, wherein the filter layer is a laminate in which two or more cholesteric liquid crystal layers are laminated.
In the optical recording medium described in <15>, two or more cholesteric liquid crystal layers are laminated, and information light used at the time of recording or reproducing does not cause a shift in the selective reflection wavelength even when the incident angle changes. In addition, since the reference light and the reproduction light do not reach the reflection film, it is possible to prevent the generation of diffused light due to irregular reflection on the reflection surface. Therefore, the noise generated by the diffused light is not superimposed on the reproduced image and detected on the CMOS sensor or CCD, but the reproduced image can be detected at least to the extent that error correction is possible. The noise component due to diffused light becomes a serious problem as the multiplicity of holograms increases. That is, as the multiplicity increases, for example, when the multiplicity is 10 or more, the diffraction efficiency from one hologram becomes extremely small, and detection of a reproduced image becomes very difficult if there is diffusion noise. According to this configuration, such difficulty can be eliminated, and high density image recording that has never been achieved can be realized.
<16> The optical recording medium according to any one of <14> to <15>, wherein the selective reflection wavelength band in the cholesteric liquid crystal layer is continuous.
<17> The filter layer according to any one of <1> to <16>, wherein the filter layer has a single cholesteric liquid crystal layer, and the cholesteric liquid crystal layer contains at least a nematic liquid crystal compound and a photoreactive chiral compound. This is an optical recording medium.
<18> The optical recording medium according to any one of <14> to <17>, wherein the cholesteric liquid crystal layer has circularly polarized light separation characteristics.
<19> The optical recording medium according to any one of <14> to <18>, wherein the rotation directions of the spirals in the cholesteric liquid crystal layer are the same.
<20> The optical recording medium according to any one of <14> to <19>, wherein the selective reflection center wavelengths in the cholesteric liquid crystal layer are different from each other.
<21> The optical recording medium according to any one of <14> to <20>, wherein the selective reflection wavelength bandwidth in the cholesteric liquid crystal layer is 100 nm or more.
<22> The light according to any one of <1> to <21>, wherein the filter layer transmits light having a first wavelength and reflects light having a second wavelength different from the light having the first wavelength. It is a recording medium.
<23> The optical recording medium according to <22>, wherein light having a first wavelength is 350 to 600 nm and light having a second wavelength is 600 to 900 nm.
<24> The light transmittance at 655 nm of light within ± 40 ° in the filter layer is 50% or more, and the light reflectance at 532 nm is 30% or more. An optical recording medium according to any one of the above.
<25> Any one of the items <1> to <24>, wherein the filter layer has a light transmittance at 655 nm at an incident angle of ± 40 ° of 50% or more and a light reflectance at 532 nm of 30% or more. The optical recording medium described in 1.
_{<26> λ 0 ~λ 0 /} cos20 ° filter layer (where, lambda ₀ represents a wavelength of the irradiated light) the light reflectance is 40% or more in the <1> according to any one of <25> It is an optical recording medium.
_{<27> λ 0 ~λ 0 /} cos40 ° filter layer (where, lambda ₀ represents a wavelength of the irradiated light) light reflectance at the, wherein the 40% or more to any one of <1> to <26> This is an optical recording medium.
<28> The optical recording medium according to any one of <1> to <27>, wherein the filter layer is used as a selective reflection film of an optical recording medium that records information using holography.
<29> The filter layer has a photoreactive chiral compound, the photoreactive chiral compound has a chiral site and a photoreactive group, and the chiral site is formed from an isosorbide compound, an isomannide compound, and a binaphthol compound. The optical recording medium according to any one of <1> to <28>, which is at least one selected.
<30> The optical recording medium according to <29>, wherein the photoreactive group is a group that causes isomerization from trans to cis of a carbon-carbon double bond by light irradiation.
<31> The optical recording medium according to any one of <1> to <30>, wherein the substrate has a servo pit pattern.
<32> The optical recording medium according to <31>, wherein the servo pit pattern has a reflective film on the surface.
<33> The optical recording medium according to <32>, wherein the reflective film is a metal reflective film.
<34> The optical recording medium according to any one of <1> to <33>, further including a first gap layer for smoothing a second substrate surface between the filter layer and the reflective film.
<35> The optical recording medium according to any one of <1> to <34>, wherein a second gap layer is provided between the recording layer and the filter layer.

<36> The optical recording medium according to any one of <1> to <35> is irradiated with information light and reference light so that the optical axis of the information light and the optical axis of the reference light are coaxial. The optical recording method is performed as follows.
<37> The optical recording method according to <36>, wherein the optical recording medium is a reflection hologram.

<38> The method for producing an optical recording medium according to any one of <1> to <35>, comprising a recording layer forming step.
<39> An optical recording medium filter comprising the filter layer in the optical recording medium according to any one of <1> to <35> is processed into an optical recording medium shape, and the processed filter is used as the second substrate. The method for producing an optical recording medium according to <38>, including a filter layer forming step of forming a filter layer by bonding.
<40> The optical recording according to any one of <38> to <39>, including a filter layer forming step of forming a filter layer comprising a laminate in which two or more cholesteric liquid crystal layers are stacked on the second substrate. It is a manufacturing method of a medium.

<41> The recording information corresponding to the interference image is reproduced by irradiating the interference image formed on the recording layer by the optical recording method according to any one of <36> to <37> with the same reproduction light as the reference light This is an optical recording / reproducing method.
<42> The optical recording according to <41>, wherein the reproduction information is reproduced by irradiating the interference image with the reproduction light so that the reproduction light has the same angle as the reference light used for recording on the optical recording medium. It is a playback method.

  According to the present invention, conventional problems can be solved, and the recording layer thickness is constant and the optical recording medium having high quality can be efficiently manufactured without reducing the recording area of the hologram as much as possible. It is possible to provide a method for manufacturing an optical recording medium that can be used.

(Optical recording medium)
The optical recording medium of the present invention includes a recording layer for recording information using holography, a first substrate, a second substrate, a first gap layer, a second gap layer, a filter layer, And a spacer for maintaining the thickness of the recording layer, and the width of the spacer in the layer surface direction of the recording layer is at least 0.5 mm. The optical recording medium of the present invention is an optical recording method (collinear method) in which the irradiation of the information light and the reference light is performed such that the optical axis of the information light and the optical axis of the reference light are coaxial. Used for.

<Spacer>
The spacer makes it possible to obtain an optical recording medium having a high precision thickness with a constant thickness of the recording layer, and by using the spacer, intrusion of moisture and other harmful gases from the end face of the optical recording medium. And the function of preventing the recording layer from drying.
The spacer has an outer shape that is substantially the same as the outer shape of the optical recording medium, and is provided at an outer peripheral spacer that acts to make the thickness of the outer peripheral portion of the recording layer constant, and at the center of the optical recording medium. There is an inner peripheral spacer that has an opening substantially the same as the opening and has an effect of changing the thickness of the inner peripheral portion of the recording layer together with the outer peripheral spacer.
The spacer of the present invention means at least one of the outer peripheral spacer and the inner peripheral spacer. With the outer peripheral spacer and the inner peripheral spacer, the thickness of the recording layer can be manufactured with high accuracy.

-Outer spacer-
The shape of the outer peripheral spacer is not particularly limited as long as the outer periphery is substantially the same as the outer peripheral shape of the optical recording medium, and can be appropriately selected according to the purpose. Is mentioned. Among these, a circle is preferable.
Examples of the cross-sectional shape of the outer peripheral spacer include a quadrangle, a rectangle, a trapezoid, a circle, and an ellipse. Among these, a quadrangle, a trapezoid, a rectangle, and the like are preferable from the viewpoint of the effect of making the thickness constant. The spacer shown in FIGS. 4 and 5 is an example of a square cross section.
There is no restriction | limiting in particular as thickness of the said outer periphery spacer, According to the objective, it can select suitably, For example, it is preferable that it is substantially the same thickness as the thickness of the said recording layer. Specifically, the thickness is preferably 100 to 1,000 μm, which is the same as the thickness of the recording layer.
The width of the outer peripheral spacer is not particularly limited as long as it is at least 0.5 mm, and can be appropriately selected according to the purpose. For example, 0.5 to 5 mm is preferable, and 0.5 to 3 mm is more preferable. 0.5-2 mm is particularly preferable. When the width is less than 0.5 mm, the holding function for keeping the recording layer thickness constant may be reduced in terms of mechanical strength and support area. As a result, the recording capacity may be reduced.

There is no restriction | limiting in particular as a material of the said outer periphery spacer, Although both an inorganic material and an organic material can be used suitably, the said organic material is preferable from the point of a moldability and cost.
Examples of the inorganic material include glass, ceramic, quartz, silicon, and the like.
The organic material is not particularly limited and may be appropriately selected according to the purpose. , Polyamide resin, polyimide resin, polyolefin resin, acrylic resin, polynorbornene resin, cellulose resin, polyarylate resin, polystyrene resin, polyvinyl alcohol resin, polyvinyl chloride resin, polyvinylidene chloride Examples thereof include resins and polyacrylic resins. These may be used individually by 1 type and may use 2 or more types together. Among these, polycarbonate resins and acrylic resins are preferable from the viewpoints of moldability, peelability, and cost.

  There is no restriction | limiting in particular as a manufacturing method of the said spacer, According to the objective, it can select suitably, For example, injection molding, blow molding, compression molding, a vacuum forming die extrusion process, a cutting process etc. are mentioned.

-Inner circumference spacer-
The shape of the inner peripheral spacer is not particularly limited as long as the inner periphery is substantially the same as the shape of the opening provided in the optical recording medium, and can be appropriately selected according to the purpose. A circle, an ellipse, a polygon, etc. are mentioned. Among these, a circle is preferable.
The cross-sectional shape of the inner peripheral spacer is preferably the same shape as the outer peripheral spacer, and examples thereof include a quadrangle, a rectangle, a trapezoid, a circle, and an ellipse. Among these, a quadrangle, a trapezoid, a rectangle, and the like are preferable from the viewpoint of the effect of making the thickness constant.
The thickness of the inner circumferential spacer is required to be the same as that of the outer circumferential spacer from the viewpoint of the uniformity of the thickness of the recording layer.
The width of the inner circumferential spacer may be the same as or different from that of the outer circumferential spacer from the viewpoint of maintaining the uniformity of the recording layer thickness and securing the recording area of the recording layer. The material and manufacturing method of the inner peripheral spacer may be different from or different from those of the outer peripheral spacer.

<First substrate>
As shown in FIGS. 3 and 4, the first substrate is laminated on the surface of the recording layer 4 to protect the surface of the recording layer 4 and to act as a mechanical strength member of the optical recording medium 21. But there is.

  The shape, structure, size, etc. of the first substrate are not particularly limited and can be appropriately selected according to the purpose. Examples of the shape include a disk shape, a card shape, a flat plate shape, Examples of the structure include a single-layer structure and a laminated structure, and the size is appropriately selected according to the size of the optical recording medium. be able to.

The material of the first substrate can be appropriately selected according to the purpose. For example, any of an inorganic material and an organic material can be suitably used.
Examples of the inorganic material include glass, quartz, silicon, and the like.
Examples of the organic material include acetate resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and acrylic resins. Polynorbornene resin, cellulose resin, polyarylate resin, polystyrene resin, polyvinyl alcohol resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyacrylic resin, polylactic acid resin, plastic film laminated paper And synthetic paper. These may be used individually by 1 type and may use 2 or more types together. Among these, polycarbonate resins and acrylic resins are preferable from the viewpoints of moldability, peelability, and cost.

As said 1st board | substrate, what was synthesize | combined suitably may be used and a commercial item may be used.
There is no restriction | limiting in particular as thickness of said 1st board | substrate, According to the objective, it can select suitably, 5-1,200 micrometers is preferable and 100-700 micrometers is more preferable. If the thickness of the support is less than 5 μm, the role of protecting the recording layer may be reduced. If the thickness exceeds 100 μm, the distance from the disk surface to the recording layer and the pit layer increases, and the recording / reproducing light The focal length may be too long.

<Second substrate>
The second substrate is disposed opposite to the first substrate and is positioned on the outermost layer, and information on the irradiation position of the information light and the reference light for recording on the optical recording medium is formed, and the light It has a function as a support that acts as a mechanical strength member of the recording medium.

The shape, structure, size, and the like of the second substrate can be appropriately selected according to the purpose. Examples of the shape include a disk shape and a card shape. Although it is necessary to select the shape which can ensure mechanical strength, it is preferable that an outer shape is the same shape as said 1st board | substrate. In addition, when light used for recording and reproduction enters through the substrate, it is necessary to be sufficiently transparent in the wavelength region of the light used.
As the material for the second substrate, glass, ceramics, resin, or the like is usually used, but resin is particularly preferable from the viewpoint of moldability and cost.
Examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, and urethane resin. Among these, polycarbonate resin and acrylic resin are particularly preferable from the viewpoints of moldability, optical characteristics, and cost.
As said 2nd board | substrate, what was synthesize | combined suitably similarly to said 1st board | substrate may be used, and a commercial item may be used.

There is no restriction | limiting in particular as information regarding the light irradiation position in said 2nd board | substrate, According to the objective, it can select suitably, For example, tracking information, focus information, address information, disk condition information etc. are mentioned.
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, a focus mirror portion, and a focus pit.
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 areas 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 may be formed by previously recording a servo pit pattern by embossed pits (servo pits) or the like. Good (preformat).
If the optical recording medium has a card shape, the servo pit pattern may be omitted.

  There is no restriction | limiting in particular as thickness of said 2nd board | substrate, According to the objective, it can select suitably, 0.1-5 mm is preferable and 0.3-2 mm is more preferable. If the thickness of the second substrate is less than 0.1 mm, the distortion of the shape during storage of the disk may not be suppressed. If the thickness exceeds 5 mm, the weight of the entire disk increases, which is excessive for the drive motor. There may be a load.

The reflective film may be formed on the surface of the servo pit pattern on the second substrate.
As the material of the reflective film, a material having a high reflectance with respect to recording light or reference light is preferably used. When the wavelength of light to be used is 400 to 780 nm, for example, Al, Al alloy, Ag, Ag alloy, etc. are preferably used. When the wavelength of light to be used is 650 nm or more, it is preferable to use Al, Al alloy, Ag, Ag alloy, Au, Cu alloy, TiN, or the like.
As the reflective film, an optical recording medium that reflects light and can be written or erased, such as a DVD (digital video disk), is used. It is also possible to add and rewrite directory information such as information on which part has an error and how replacement processing is performed without affecting the hologram.

There is no restriction | limiting in particular as a formation method of the said reflecting film, According to the objective, it can select suitably, Various vapor phase growth methods, for example, a vacuum evaporation method, sputtering method, plasma CVD method, photo-CVD method, ion plate method. A ting method, an electron beam evaporation method, or the like is used. Among these, the sputtering method is excellent in terms of mass productivity and film quality.
The thickness of the reflective film is preferably 50 nm or more, and more preferably 100 nm or more so that sufficient reflectance can be realized.

-Recording layer-
The recording layer can record information using holography, and a material whose optical characteristics such as an extinction coefficient and a refractive index change according to the intensity of the recording layer when irradiated with an electromagnetic wave having a predetermined wavelength is used.

  The material of the recording layer is not particularly limited and may be appropriately selected depending on the purpose. For example, (1) a photopolymer that undergoes polymerization reaction upon irradiation with light and becomes a polymer, (2) a photorefractive effect ( (3) Photochromic material in which molecular isomerization occurs due to light irradiation and the refractive index is modulated, (4) Lithium niobate, titanic acid Examples thereof include inorganic materials such as barium, and (5) chalcogen materials. Among these, the photopolymer (1) is particularly preferable.

  The photopolymer (1) is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the photopolymer contains a monomer and a photoinitiator, and further a sensitizer or oligomer as necessary. It contains other components such as.

  Examples of the photopolymer include “Photopolymer Handbook” (Industry Research Society, 1989), “Photopolymer Technology” (Nikkan Kogyo Shimbun, 1989), SPIE Proceedings Vol. 3010 p354-372 (1997), and SPIE Proceedings Vol. 3291 p89-103 (1998) can be used. Also, US Pat. Nos. 5,759,721, 4,942,112, 4,959,284, 6,221,536, International Publication No. No. 97/44714, No. 97/13183, No. 99/26112, No. 97/13183, No. 2880342, No. 2873126, No. 2849021, No. Photopolymers described in Japanese Patent Nos. 3070882, 3161230, Japanese Patent Application Laid-Open No. 2001-316416, Japanese Patent Application Laid-Open No. 2000-275859, and the like can be used.

  Examples of a method for changing the optical characteristics by irradiating the photopolymer with recording light include a method using diffusion of a low molecular component. Moreover, in order to relieve the volume change at the time of superposition | polymerization, the component which diffuses in the reverse direction to a superposition | polymerization component may be added, or the compound which has an acid cleavage structure may be added separately besides a polymer. In the case where the recording layer is formed using the photopolymer containing the low molecular component, a structure capable of holding the liquid in the recording layer may be required. Moreover, when adding the compound which has the said acid cleavage structure, you may suppress a volume change by compensating the expansion | swelling which arises by the cleavage, and the shrinkage which arises by superposition | polymerization of a monomer.

  The monomer is not particularly limited and may be appropriately selected depending on the purpose. For example, a radical polymerization type monomer having an unsaturated bond such as an acryl group or a methacryl group, an epoxy ring or an oxetane ring. Examples thereof include a cationic polymerization type monomer having an ether structure. These monomers may be monofunctional or polyfunctional. Moreover, you may utilize a photocrosslinking reaction.

Examples of the radical polymerization type monomer include acryloylmorpholine, phenoxyethyl acrylate, isobornyl acrylate, 2-hydroxypropyl acrylate, 2-ethylhexyl acrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, neo Pentyl glycol PO-modified diacrylate, 1,9-nonanediol diacrylate, hydroxypivalate neopentyl glycol diacrylate, EO-modified bisphenol A diacrylate, polyethylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol hexa Acrylate, EO-modified glycerol triacrylate, trimethylol pro Triacrylate, EO-modified trimethylolpropane triacrylate, 2-naphth-1-oxyethyl acrylate, 2-carbazoyl-9-ylethyl acrylate, (trimethylsilyloxy) dimethylsilylpropyl acrylate, vinyl-1-naphthoate, N-vinylcarbazole , Etc.
Examples of the cationic polymerization type monomer include bisphenol A epoxy resin, phenol novolac epoxy resin, glycerol triglycidyl ether, 1,6-hexane glycidyl ether, vinyltrimethoxysilane, 4-vinylphenyltrimethoxysilane, and γ-methacrylic acid. Examples include loxypropyltriethoxysilane and compounds represented by the following structural formulas (A) to (E).
These monomers may be used alone or in combination of two or more.

The photoinitiator is not particularly limited as long as it has sensitivity to recording light, and examples thereof include materials that cause radical polymerization, cationic polymerization, crosslinking reaction, and the like by light irradiation.
Examples of the photoinitiator include 2,2′-bis (o-chlorophenyl) -4,4 ′, 5,5′-tetraphenyl-1,1′-biimidazole, 2,4,6-tris ( Trichloromethyl) -1,3,5-triazine, 2,4-bis (trichloromethyl) -6- (p-methoxyphenylvinyl) -1,3,5-triazine, diphenyliodonium tetrafluoroborate, diphenyliodonium hexafluoro Phosphate, 4,4'-di-t-butyldiphenyliodonium tetrafluoroborate, 4-diethylaminophenylbenzenediazonium hexafluorophosphate, benzoin, 2-hydroxy-2-methyl-1-phenylpropan-2-one, benzophenone, thioxanthone 2,4,6-trimethylbenzoyldiphenyla Examples thereof include silphosphine oxide, triphenylbutyl borate tetraethylammonium, and a titanocene compound represented by the following structural formula. These may be used individually by 1 type and may use 2 or more types together. Moreover, you may use a sensitizing dye together according to the wavelength of the light to irradiate.

  The photopolymer can be obtained by stirring and mixing the monomer, the photoinitiator, and, if necessary, other components and reacting them.

  The photorefractive material (2) is not particularly limited as long as it exhibits a photorefractive effect, and can be appropriately selected according to the purpose. For example, it contains a charge generation material and a charge transport material. And further contains other components as necessary.

The charge generation material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include phthalocyanine dyes / pigments such as metal phthalocyanine, metal-free phthalocyanine, or derivatives thereof; naphthalocyanine dye / pigment; monoazo Azo dyes / pigments such as diazo and trisazo; perylene dyes / pigments; indigo dyes / pigments; quinacridone dyes / pigments; polycyclic quinone dyes / pigments such as anthraquinone and anthanthrone; cyanine dyes / pigments; Examples include a charge transfer complex composed of an electron accepting substance and an electron donating substance represented by TTF-TCNQ; an azurenium salt; a fullerene represented by C ₆₀ and C ₇₀ and a methanofullerene which is a derivative thereof. . These may be used individually by 1 type and may use 2 or more types together.

The charge transport material is a material that transports holes or electrons, and may be a low molecular compound or a high molecular compound.
The charge transport material is not particularly limited and may be appropriately selected depending on the intended purpose. For example, indole, carbazole, oxazole, inoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, thiathiazole, triazole Nitrogen-containing cyclic compounds such as, or derivatives thereof; hydrazone compounds; triphenylamines; triphenylmethanes; butadienes; stilbenes; quinone compounds such as anthraquinone diphenoquinone, or derivatives thereof; And π-conjugated polymers or oligomers such as polyacetylene, polypyrrole, polythiophene, and polyaniline; σ-conjugated polymers or oligomers such as polysilane and polygerman; anthracene, pyrene, phenanthrene, co And polycyclic aromatic compounds such as Ronene. These may be used individually by 1 type and may use 2 or more types together.

  The photochromic material (3) is not particularly limited as long as it is a material that causes a photochromic reaction, and can be appropriately selected according to the purpose. For example, an azobenzene compound, a stilbene compound, an indigo compound, a thioindigo compound, a spiropyran compound, Examples include spirooxazine compounds, fluoride compounds, anthracene compounds, hydrazone compounds, and cinnamic acid compounds. Among these, azobenzene derivatives and stilbene derivatives that cause a structural change by cis-trans isomerization by light irradiation, spiropyran derivatives and spirooxazine derivatives that cause a ring-opening and ring-closing structural change by light irradiation are particularly preferable.

Examples of the chalcogen material of (5) include, for example, a material containing a chalcogenide glass containing a chalcogen element and metal particles made of a metal that is dispersed in the chalcogenide glass and can be diffused in the chalcogenide glass by light irradiation, Etc.
The chalcogenide glass is composed of a non-oxide type amorphous material containing a chalcogen element of S, Te, or Se, and is not particularly limited as long as it can dope metal particles.
Examples of the amorphous material containing the chalcogen element include Ge—S glass, As—S glass, As—Se glass, As—Se—Ce glass, and the like. S-based glass is preferred. When Ge-S glass is used as the chalcogenide glass, the composition ratio of Ge and S constituting the glass can be arbitrarily changed according to the wavelength of light to be irradiated, but is mainly represented by GeS _2. A chalcogenide glass having a chemical composition is preferred.
The metal particles are not particularly limited as long as they have the property of being light-doped into chalcogenide glass by light irradiation, and can be appropriately selected according to the purpose. For example, Al, Au, Cu, Cr, Ni, Pt, Sn, In, Pd, Ti, Fe, Ta, W, Zn, Ag, etc. are mentioned. Among these, Ag, Au, or Cu has a characteristic that it is more likely to cause light doping, and Ag is particularly preferable because it significantly causes light doping.
The content of the metal particles dispersed in the chalcogenide glass is preferably 0.1 to 2% by volume, more preferably 0.1 to 1.0% by volume based on the total volume of the recording layer. If the content of the metal particles is less than 0.1% by volume, the change in transmittance due to light doping may be insufficient, and the recording accuracy may decrease. The transmittance may be lowered, and it may be difficult to sufficiently generate light dope.

  The recording layer can be formed according to a known method depending on the material. For example, an injection method, a vapor deposition method, a wet film formation method, an MBE (molecular beam epitaxy) method, a cluster ion beam method, a molecular lamination method, LB It can be suitably formed by a method, a printing method, a transfer method, or the like. Among these, an injection method and a wet film formation method are preferable. The injection method will be described in the method for manufacturing an optical recording medium of the present invention described later.

  Formation of the recording layer by the wet film formation method can be suitably performed by using (coating and drying) a solution (coating liquid) in which the recording layer material is dissolved or dispersed in a solvent. The wet film forming method is not particularly limited and can be appropriately selected from known ones according to the purpose. For example, an ink jet method, a spin coating method, a kneader coating method, a bar coating method, a blade coating method, Examples thereof include a casting method, a dip method, and a curtain coating method.

There is no restriction | limiting in particular as thickness of the said recording layer, According to the objective, it can select suitably, 1-1000 micrometers is preferable and 100-700 micrometers is more preferable.
When the thickness of the recording layer is within the preferable numerical range, a sufficient S / N ratio can be obtained even when 10 to 300 multiple shift multiplexing is performed, and when the thickness is within the more preferable numerical range, this is remarkable. It is advantageous in some respects.

<First gap layer>
The first gap layer is provided between the filter layer and the reflective film as necessary, and is formed for the purpose of smoothing the surface of the second substrate. It is also effective to adjust the size of the hologram generated in the recording layer by the mechanism of increasing the S / N ratio of the hologram signal light by shifting the focus of the hologram signal light. That is, since it is necessary for the recording layer to form an interference region for recording reference light and information light to a certain size, it is effective to provide a gap between the recording layer and the servo pit pattern.
The first gap layer can be formed, for example, by applying a material such as an ultraviolet curable resin on the servo pit pattern by spin coating or the like and curing it. Moreover, when using what apply | coated and formed on the transparent base material as a filter layer, this transparent base material will work | function also as a 1st gap layer.
There is no restriction | limiting in particular as thickness of said 1st gap layer, According to the objective, it can select suitably, 1-200 micrometers is preferable.

<Second gap layer>
The second gap layer is provided between the recording layer and the filter layer. The second gap layer has a function of preventing a decrease in the multiplex recording capability of the optical recording medium. That is, a point where the information light and the reproduction light are focused exists in the recording layer. However, if this focusing area is filled with a photopolymer, excessive consumption of the monomer due to overexposure occurs, and multiple recording capability is achieved. It will go down. Therefore, by providing a non-reactive and transparent second gap layer, a non-reactive region is formed, the excessive consumption can be suppressed, and high multiplex recording capability can be maintained.
There is no restriction | limiting in particular as a material of said 2nd gap layer, According to the objective, it can select suitably, For example, a triacetyl cellulose (TAC), a polycarbonate (PC), a polyethylene terephthalate (PET), polystyrene (PS) ), Transparent resin films such as polysulfone (PSF), polyvinyl alcohol (PVA), polymethyl methacrylate = polymethyl methacrylate (PMMA), etc., or JSR brand name ARTON film or Nippon Zeon brand name ZEONOR And norbornene-based resin films. Among these, those having high isotropic properties are preferred, and TAC, PC, trade name ARTON, and trade name ZEONOR are particularly preferred.
There is no restriction | limiting in particular as thickness of said 2nd gap layer, According to the objective, it can select suitably, 1-200 micrometers is preferable.

<Filter layer>
The filter layer has a function of preventing the occurrence of noise by preventing irregular reflection from the reflection film of the optical recording medium by information light and reference light without causing a shift in the selective reflection wavelength even when the incident angle changes. . By laminating the filter layer on the optical recording medium, optical recording with high resolution and excellent diffraction efficiency can be obtained.
The function of the optical recording medium filter is preferably to transmit light having a first wavelength and reflect light having a second wavelength different from the light having the first wavelength. It is preferable that it is 350-600 nm and the light of the 2nd wavelength is 600-900 nm. For that purpose, it is preferable that the optical recording medium has a structure in which a recording layer, a filter layer, and a servo bit pattern are laminated in this order as viewed from the optical system side.
The filter layer has a light transmittance at 655 nm of 50% or more, preferably 80% or more, and a light reflectance at 532 nm of 30% or more and 40% or more at an incident angle of ± 40 °. Is preferred.
There is no restriction | limiting in particular as said filter layer, According to the objective, it can select suitably, For example, a laminated body of a dielectric vapor deposition layer, a single layer or two or more cholesteric layers, and also other layers as needed It is formed by. Moreover, you may have a color material content layer.
The filter layer may be laminated together with a direct recording layer or the like on the support by coating or the like, and is laminated on a substrate such as a film to produce an optical recording medium filter, and the optical recording medium filter May be laminated on a support.

-Dielectric deposition layer-
The dielectric vapor deposition layer is formed by laminating a plurality of dielectric thin films having different refractive indexes. In order to obtain a wavelength selective reflection film, a dielectric thin film having a high refractive index and a dielectric thin film having a low refractive index are used. Although it is preferable to laminate a plurality of layers alternately, it is not limited to two or more types, and may be more types. Moreover, when providing a color material content layer, it forms under a dielectric material vapor deposition layer.
The number of stacked layers is preferably 2 to 20 layers, more preferably 2 to 12 layers, still more preferably 4 to 10 layers, and particularly preferably 6 to 8 layers. If the number of stacked layers exceeds 20, the production efficiency may decrease due to multi-layer deposition, and the objects and effects of the present invention may not be achieved.

  The order of lamination of the dielectric thin films is not particularly limited and can be appropriately selected according to the purpose. For example, when the refractive index of an adjacent film is high, a film having a lower refractive index is first laminated. To do. Conversely, when the refractive index of the adjacent layer is low, a film having a higher refractive index is first laminated. The threshold value for determining whether the refractive index is high or low is preferably 1.8. Note that whether the refractive index is high or low is not absolute. Among high-refractive-index materials, there may be a material with a relatively high refractive index and a material with a relatively low refractive index, which are used alternately. May be.

The dielectric thin film of the high refractive index is not particularly limited and may be appropriately selected depending on the purpose, for _{example, Sb 2 O 3, Sb 2} S 3, Bi 2 O 3, CeO 2, CeF _{3, HfO 2, La 2 O} 3, Nd 2 O 3, Pr 6 O 11, Sc 2 O 3, SiO, Ta 2 O 5, TiO 2, TlCl, Y 2 O 3, ZnSe, ZnS, ZrO 2 , etc. Can be mentioned. Among these, Bi ₂ O ₃ , CeO ₂ , CeF ₃ , HfO ₂ , SiO, Ta ₂ O ₅ , TiO ₂ , Y ₂ O ₃ , ZnSe, ZnS, ZrO ₂ are preferable, and among these, SiO, Ta ₂ O ₅ , TiO ₂ , Y ₂ O ₃ , ZnSe, ZnS, and ZrO ₂ are more preferable.

The material for the low refractive index dielectric thin film is not particularly limited and may be appropriately selected depending on the intended purpose. For example, Al ₂ O ₃ , BiF ₃ , CaF ₂ , LaF ₃ , PbCl ₂ , PbF ₂ , LiF, MgF ₂ , MgO, NdF ₃ , SiO ₂ , Si ₂ O ₃ , NaF, ThO ₂ , ThF _{4 and the} like. Among these, Al ₂ O ₃ , BiF ₃ , CaF ₂ , MgF ₂ , MgO, SiO ₂ , Si ₂ O ₃ are preferable, and among these, Al ₂ O ₃ , CaF ₂ , MgF ₂ , MgO, SiO ₂ , Si ₂ O ₃ is more preferable.
In the dielectric thin film material, the atomic ratio is not particularly limited and can be appropriately selected according to the purpose. The atomic ratio can be adjusted by changing the atmospheric gas concentration during film formation. .

The method for forming the dielectric thin film is not particularly limited and may be appropriately selected depending on the purpose. For example, a physical vapor deposition method such as ion plating, vacuum deposition using an ion beam, sputtering, or the like. (PVD method), chemical vapor deposition method (CVD method) and the like. Among these, vacuum deposition and sputtering are preferable, and sputtering is more preferable.
As the sputtering, a DC sputtering method having a high film formation rate is preferable. In the DC sputtering method, it is preferable to use a material having high conductivity.
In addition, as a method for forming a multilayer film by sputtering, for example, (1) a one-chamber method in which a plurality of targets are alternately or sequentially formed in one chamber, and (2) continuous film formation in a plurality of chambers. There is a multi-chamber method. Among these, the multi-chamber method is particularly preferable from the viewpoint of preventing productivity and material contamination.
The film thickness of the dielectric thin film is preferably λ / 16 to λ, more preferably λ / 8 to 3λ / 4, and particularly preferably λ / 6 to 3λ / 8 in the optical wavelength order.

-Cholesteric liquid crystal layer-
The cholesteric liquid crystal layer contains at least a cholesterol derivative, or a nematic liquid crystal compound and a chiral compound, and further contains a polymerizable monomer and, if necessary, other components.
The cholesteric liquid crystal layer may be either a single-layer cholesteric liquid crystal layer or two or more cholesteric liquid crystal layers.

  The cholesteric liquid crystal layer preferably has a circularly polarized light separation function. The cholesteric liquid crystal layer having the function of separating circularly polarized light is a light having a circularly polarized component in which the direction of rotation of the spiral of the liquid crystal (clockwise or counterclockwise) coincides with the direction of circular polarization and the wavelength is the spiral pitch of the liquid crystal. It has a selective reflection characteristic that reflects only the light. Using the selective reflection characteristics of the cholesteric liquid crystal layer, only circularly polarized light having a specific wavelength is transmitted and separated from natural light in a certain wavelength band, and the rest is reflected.

In the filter for optical recording medium, the normal incidence 0 ° and to ± 20 ° range at which λ ₀ ~λ _{0 /} cos20 ° (but, lambda ₀ represents a wavelength of the irradiated light) in the light reflectance of 40% or more preferably there, lambda ₀ to [lambda] a perpendicular incidence in the range of ± 40 ° and ₀ ° 0 _/ cos40 ° (However, lambda ₀ represents a wavelength of the irradiated light) that light reflectance at not less than 40% Particularly preferred. Wherein λ ₀ ~λ ₀ / cos20 °, especially λ ₀ ~λ ₀ / cos40 ° (However, lambda ₀ represents a wavelength of the irradiated light) If the light reflectance is 40% or more at the angular dependence of the irradiation light reflected The lens optical system used for a normal optical recording medium can be employed. For this purpose, it is preferable that the selective reflection wavelength width of the cholesteric liquid crystal layer is large.
Specifically, (1) In the case of a single-layer cholesteric liquid crystal layer, the selective reflection wavelength region width Δλ of the cholesteric liquid crystal layer is expressed by the following formula 1, and therefore, a liquid crystal having a large (ne-no) is used. Is preferred.
<Formula 1>
Δλ = 2λ (ne−no) / (ne + no)
In Equation 1, no represents the refractive index of nematic liquid crystal molecules contained in the cholesteric liquid crystal layer with respect to normal light. ne represents the refractive index of the nematic liquid crystal molecules with respect to extraordinary light. λ represents the center wavelength of selective reflection.
In addition, as described in Japanese Patent Application No. 2004-352081, a photoreactive chiral compound having photosensitivity as a chiral compound and capable of greatly changing the helical pitch of liquid crystal by light is used. It is preferable to use a filter for an optical recording medium in which the helical pitch is continuously changed in the thickness direction of the liquid crystal layer by adjusting the compound content and the UV irradiation time.

In the case of (2) a plurality of cholesteric liquid crystal layers, it is preferable to stack cholesteric liquid crystal layers having different selective reflection center wavelengths and having the same rotational direction of the spirals of the cholesteric liquid crystal layers.
The cholesteric liquid crystal layer is not particularly limited as long as it satisfies the above characteristics, and can be appropriately selected according to the purpose.As described above, the cholesteric liquid crystal layer contains a nematic liquid crystal compound and a chiral compound. Further, it contains other components as required.

-Nematic liquid crystal compounds-
The nematic liquid crystal compound is characterized in that the liquid crystal phase is fixed below the liquid crystal transition temperature, the liquid crystal compound having a refractive index anisotropy Δn of 0.10 to 0.40, a polymer liquid crystal compound, and polymerization The liquid crystal compound can be appropriately selected according to the purpose. While it is in a liquid crystal state at the time of melting, it can be used as a solid phase by, for example, aligning by using an alignment substrate that has been subjected to an alignment treatment such as a rubbing treatment, and cooling and fixing as it is.

  The nematic liquid crystal compound is not particularly limited and may be appropriately selected depending on the purpose. From the viewpoint of ensuring sufficient curability, a nematic liquid crystal compound having a polymerizable group in the molecule is preferable, and among these, Ultraviolet (UV) polymerizable liquid crystals are preferred. Commercially available products can be used as the UV polymerizable liquid crystal, for example, trade name PALIOCOLOR LC242 manufactured by BASF; trade name E7 manufactured by Merck; trade name LC-Slicon-CC3767 manufactured by Wacker-Chem; Takasago Examples include trade names L35, L42, L55, L59, L63, L79, and L83 manufactured by Perfume Co., Ltd.

  As content of the said nematic liquid crystal compound, 30-99 mass% is preferable with respect to the total solid content mass of each said cholesteric liquid crystal layer, and 50-99 mass% is more preferable. When the content is less than 30% by mass, the alignment of the nematic liquid crystal compound may be insufficient.

-Chiral compounds-
The chiral compound is not particularly limited in the case of (1) a multi-layer cholesteric liquid crystal layer, and can be appropriately selected from known compounds according to the purpose. From the viewpoint of improving the hue and color purity of the liquid crystal compound. From, for example, an isomannide compound, a catechin compound, an isosorbide compound, a fencon compound, a carboxylic compound, and the like can be given. These may be used individually by 1 type and may use 2 or more types together.
Moreover, a commercial item can be used as said chiral compound, As this commercial item, the brand name S101, R811, CB15 by Merck, and the brand name PALIOCOLOR LC756 by BASF are mentioned, for example.

  The chiral compound content in each liquid crystal layer of the multi-layer cholesteric liquid crystal layer is preferably 0 to 30% by mass and more preferably 0 to 20% by mass with respect to the total solid mass of each cholesteric liquid crystal layer. When the content exceeds 30% by mass, the orientation of the cholesteric liquid crystal layer may be insufficient.

-Polymerizable monomer-
In the cholesteric liquid crystal layer, for example, a polymerizable monomer can be used in combination for the purpose of improving the degree of curing such as film strength. When the polymerizable monomer is used in combination, after changing the twisting force of the liquid crystal by light irradiation (patterning) (for example, after forming a selective reflection wavelength distribution), the helical structure (selective reflectivity) is fixed, The strength of the cholesteric liquid crystal layer after fixation can be further improved. However, when the liquid crystal compound has a polymerizable group in the same molecule, it is not necessarily added.
The polymerizable monomer is not particularly limited and may be appropriately selected from known ones according to the purpose. Examples thereof include monomers having an ethylenically unsaturated bond, and specifically, pentaerythritol. And polyfunctional monomers such as tetraacrylate and dipentaerythritol hexaacrylate. These may be used individually by 1 type and may use 2 or more types together.
As addition amount of the said polymerizable monomer, 0-50 mass% is preferable with respect to the total solid content mass of the said cholesteric liquid crystal layer, and 1-20 mass% is more preferable. When the addition amount exceeds 50% by mass, the orientation of the cholesteric liquid crystal layer may be inhibited.

-Other ingredients-
The other components are not particularly limited and may be appropriately selected depending on the purpose. For example, photopolymerization initiator, sensitizer, binder resin, polymerization inhibitor, solvent, surfactant, thickener , Dyes, pigments, ultraviolet absorbers, gelling agents and the like.

There is no restriction | limiting in particular as said photoinitiator, According to the objective, it can select suitably according to the objective, For example, p-methoxyphenyl-2,4-bis (trichloromethyl) -s-triazine, 2- (p-butoxystyryl) -5-trichloromethyl 1,3,4-oxadiazole, 9-phenylacridine, 9,10-dimethylbenzphenazine, benzophenone / Michler's ketone, hexaarylbiimidazole / mercaptobenzimidazole, benzyl Examples include dimethyl ketal, acylphosphine derivatives, and thioxanthone / amine. These may be used individually by 1 type and may use 2 or more types together.
As the photopolymerization initiator, commercially available products can be used. Examples of the commercially available products include trade names of Irgacure 907, Irgacure 369, Irgacure 784, and Irgacure 814 manufactured by Ciba Specialty Chemicals; Examples include lucillin TPO.

  The addition amount of the photopolymerization initiator is preferably 0.1 to 20% by mass, and more preferably 0.5 to 5% by mass with respect to the total solid mass of the cholesteric liquid crystal layer. When the addition amount is less than 0.1% by mass, it may take a long time because the curing efficiency at the time of light irradiation is low, and when it exceeds 20% by mass, the light transmittance from the ultraviolet region to the visible light region is increased. May be inferior.

The sensitizer is added as necessary to increase the degree of cure of the cholesteric liquid crystal layer.
There is no restriction | limiting in particular as said sensitizer, According to the objective, it can select suitably according to the objective, For example, diethyl thioxanthone, isopropyl thioxanthone, etc. are mentioned.
The addition amount of the sensitizer is preferably 0.001 to 1.0 mass% with respect to the total solid mass of the cholesteric liquid crystal layer.

There is no restriction | limiting in particular as said binder resin, According to the objective, it can select suitably according to the objective, For example, Polyvinyl alcohol; Polystyrene compounds, such as a polystyrene and poly-alpha-methylstyrene; Methylcellulose, ethylcellulose, acetyl Cellulose resins such as cellulose; acidic cellulose derivatives having a carboxyl group in the side chain; acetal resins such as polyvinyl formal and polyvinyl butyral; methacrylic acid copolymer, acrylic acid copolymer, itaconic acid copolymer, crotonic acid copolymer Examples thereof include a polymer, a maleic acid copolymer, a partially esterified maleic acid copolymer; a homopolymer of acrylic acid alkyl ester or a homopolymer of alkyl methacrylic acid; other polymer having a hydroxyl group. These may be used individually by 1 type and may use 2 or more types together.
Examples of the alkyl group in the homopolymer of acrylic acid alkyl ester or homopolymer of methacrylic acid alkyl ester include, for example, methyl group, ethyl group, n-propyl group, n-butyl group, iso-butyl group, and n-hexyl group. , A cyclohexyl group, a 2-ethylhexyl group, and the like.
Examples of the other polymer having a hydroxyl group include benzyl (meth) acrylate / (homopolymer of methacrylic acid) acrylic acid copolymer, benzyl (meth) acrylate / (meth) acrylic acid / multiple monomers of other monomers. A polymer etc. are mentioned.

  As addition amount of the said binder resin, 0-80 mass% is preferable with respect to the total solid mass of the said cholesteric liquid crystal layer, and 0-50 mass% is more preferable. When the addition amount exceeds 80% by mass, the orientation of the cholesteric liquid crystal layer may be insufficient.

There is no restriction | limiting in particular as said polymerization inhibitor, According to the objective, it can select suitably, For example, hydroquinone, hydroquinone monomethyl ether, phenothiazine, benzoquinone, or these derivatives etc. are mentioned.
As addition amount of the said polymerization inhibitor, 0-10 mass% is preferable with respect to solid content of the said polymerizable monomer, and 100 ppm-1 mass% is more preferable.

  The solvent is not particularly limited and may be appropriately selected from known solvents according to the purpose. For example, 3-methoxypropionic acid methyl ester, 3-methoxypropionic acid ethyl ester, 3-methoxypropionic acid propyl Esters, alkoxypropionic acid esters such as 3-ethoxypropionic acid methyl ester, 3-ethoxypropionic acid ethyl ester, 3-ethoxypropionic acid propyl ester; 2-methoxypropyl acetate, 2-ethoxypropyl acetate, 3-methoxybutyl acetate Esters of alkoxy alcohols such as: Lactic acid esters such as methyl lactate and ethyl lactate; Ketones such as methyl ethyl ketone, cyclohexanone and methylcyclohexanone; γ-butyrolactone, N-methylpyrrolidone, di Sulfoxide, chloroform, tetrahydrofuran, and the like. These may be used individually by 1 type and may use 2 or more types together.

As a method for forming the cholesteric liquid crystal layer, for example, a coating solution for a cholesteric liquid crystal layer prepared using the solvent (in the case of a plurality of layers, a coating solution for each cholesteric liquid crystal layer) is applied onto the substrate and dried. For example, a cholesteric liquid crystal layer can be formed by irradiating with ultraviolet rays.
The most suitable method for mass production is to prepare the base material in a roll form, and apply a coating solution for the cholesteric liquid crystal layer on the base material such as bar coat, die coat, blade coat, curtain coat, etc. A type in which coating is performed with a long continuous coater is preferable.

Examples of the coating method include spin coating, casting, roll coating, flow coating, printing, dip coating, casting film formation, bar coating, and gravure printing.
There is no restriction | limiting in particular as conditions for the said ultraviolet irradiation, According to the objective, it can select suitably, For example, 160-380 nm is preferable and, as for irradiation ultraviolet rays, 250-380 nm is more preferable. For example, the irradiation time is preferably 0.1 to 600 seconds, and more preferably 0.3 to 300 seconds. By adjusting the conditions of ultraviolet irradiation, the helical pitch in the optical cholesteric liquid crystal layer using the reactive chiral agent can be continuously changed along the thickness direction of the liquid crystal layer.

  In order to adjust the conditions of the ultraviolet irradiation, an ultraviolet absorber may be added to the cholesteric liquid crystal layer. There is no restriction | limiting in particular as this ultraviolet absorber, According to the objective, it can select suitably, For example, a benzophenone type ultraviolet absorber, a benzotriazole type ultraviolet absorber, a salicylic acid type ultraviolet absorber, a cyanoacrylate type ultraviolet absorber Preferable examples include oxalic acid anilide-based ultraviolet absorbers. Specific examples of these ultraviolet absorbers include JP-A Nos. 47-10537, 58-111942, 58-212844, 59-19945, 59-46646, 59. No. -109055, No. 63-53544, No. 36-10466, No. 42-26187, No. 48-30492, No. 48-31255, No. 48-41572, No. 48. -54965, 50-10726, U.S. Pat. Nos. 2,719,086, 3,707,375, 3,754,919, 4, No. 220,711 and the like.

In the case of the plural layers, the thickness of each cholesteric liquid crystal layer is preferably, for example, 1 to 10 μm, and more preferably 2 to 7 μm. When the thickness is less than 1 μm, the selective reflectance is not sufficient, and when it exceeds 10 μm, the uniform alignment of the liquid crystal layer may be disturbed.
Further, the total thickness of each cholesteric liquid crystal layer (in the case of a single layer, the thickness of the cholesteric liquid crystal layer) is, for example, preferably 1 to 30 μm, and more preferably 3 to 10 μm.

<Method for Producing Filter for Optical Recording Medium Having Cholesteric Layer>
There is no restriction | limiting in particular as a manufacturing method of the said filter for optical recording media, According to the objective, it can select suitably.
The optical recording medium filter is not particularly limited and may be appropriately selected depending on the purpose. However, the entire base material is processed into a disk shape (for example, punching processing), and is applied to the second substrate of the optical recording medium. Is preferably arranged. Moreover, when using for the filter layer of an optical recording medium, it can also provide directly on a 2nd board | substrate not via a base material.

-Base material-
There is no restriction | limiting in particular as said base material, According to the objective, it can select suitably, For example, the same material as the support body used for said 1st form can be used.

As said base material, what was synthesize | combined suitably may be used and a commercial item may be used.
There is no restriction | limiting in particular as thickness of the said base material, According to the objective, it can select suitably, 10-500 micrometers is preferable and 50-300 micrometers is more preferable. When the thickness of the substrate is less than 10 μm, the adhesion may be lowered due to the bending of the substrate. On the other hand, if it exceeds 500 μm, the focal positions of the information light and the reference light must be greatly shifted, and the optical system size becomes large. For laminating the wavelength selective films, known adhesives can be used in any combination.
There is no restriction | limiting in particular as said adhesive, According to the objective, it can select suitably, For example, a rubber adhesive, an acrylic adhesive, a silicone adhesive, a urethane adhesive, a vinyl alkyl ether adhesive , Polyvinyl alcohol pressure sensitive adhesive, polyvinyl pyrrolidone pressure sensitive adhesive, polyacrylamide pressure sensitive adhesive, and cellulose pressure sensitive adhesive.
The application thickness of the adhesive or the pressure-sensitive adhesive is not particularly limited and can be appropriately selected according to the purpose. From the viewpoint of optical properties and thinning, 0.1 to 10 μm is preferable in the case of an adhesive, 0.1-5 micrometers is more preferable. Moreover, in the case of an adhesive, 1-50 micrometers is preferable and 2-30 micrometers is more preferable.

  In some cases, the filter layer can be formed directly on the substrate.

(Method for producing optical recording medium)
The method for producing the optical recording medium of the present invention is not particularly limited and may be appropriately selected depending on the purpose. For example, the composition preparing step, the recording layer laminating step, the filter layer forming step, the first It includes a gap layer forming step and a laminate forming step, and further includes other steps as necessary.

<Composition preparation process>
The composition preparation step is a step of preparing a composition for optical recording, and includes a photopolymer composed of a monomer, a photoinitiator, a sensitizer, an oligomer and a binder, and other components appropriately selected as necessary. An optical recording composition is prepared by dissolving, dispersing, mixing, etc. with a solvent. As the conditions for the preparation, for example, the temperature is 23 ° C., the humidity is 10%, and the drying is performed in a low humidity environment.

<Recording layer lamination process>
The recording layer laminating step is a step of laminating a recording layer for recording information by holography on the second gap layer when the second gap layer is laminated on the filter layer or the filter layer. In this step, the optical recording composition prepared in the composition preparation step is laminated by an injection method or a wet film formation method.

-Injection method-
The injection method is a method of injecting the recording layer solution into the gap between the first substrate and the second substrate. The outer peripheral spacer and the inner peripheral spacer are previously sandwiched between a first substrate and a second substrate to form a disk cell, and a recording layer solution is injected using a notch in a part of the outer peripheral spacer and using the opening as an inlet.
There is no restriction | limiting in particular as said injection | pouring method, According to the objective, it can select suitably, For example, the outer periphery injection method, the inner periphery injection method, a gap injection method etc. are mentioned.
The injection conditions include a temperature of 23 ° C., a viscosity of 330 mPa · s, a pressure of 0.5 MPa, a humidity of 10%, a curing time of 80 ° C. for 40 minutes, and the like.
There is no restriction | limiting in particular as said injection | pouring apparatus, According to the objective, it can select suitably, For example, a syringe, an air pressure dispenser, etc. are mentioned.

-Wet deposition method-
The wet film forming method is a method of forming (using and drying) a solution (coating liquid) in which the recording layer material is dissolved or dispersed in a solvent, and the wet film forming method is particularly limited. Can be appropriately selected from known ones according to the purpose, for example, inkjet method, spin coating method, kneader coating method, bar coating method, blade coating method, casting method, dip method, curtain coating method, etc. Is mentioned.

There is no restriction | limiting in particular as thickness of the said recording layer, According to the objective, it can select suitably, 1-1000 micrometers is preferable and 100-700 micrometers is more preferable.
When the thickness of the recording layer is within the preferable numerical range, a sufficient S / N ratio can be obtained even when 10 to 300 multiple shift multiplexing is performed, and when the thickness is within the more preferable numerical range, this is remarkable. It is advantageous in some respects.

  By the above method, the optical recording medium of the present invention has a constant thickness, and a high-quality optical recording medium can be obtained without narrowing the area where hologram recording can be performed.

<Filter layer forming step>
The filter layer forming step is a step of processing the optical recording medium filter of the present invention into an optical recording medium shape, and bonding the processed filter to the second substrate to form a filter layer. Here, the method for manufacturing the filter for optical recording media is as described above. In some cases, the filter layer can be formed directly on the substrate. For example, a method of forming a color material-containing layer by applying a coating material for a color material-containing layer on a substrate and forming a dielectric vapor deposition film on the color material-containing layer by a sputtering method may be mentioned.
Examples of the optical recording medium shape include a disk shape and a card shape, and the processing is not particularly limited, and can be appropriately selected according to the purpose. For example, a cutting process using a press cutter, a punching cutter Punching by, etc. are mentioned. In the bonding, for example, an adhesive, a pressure-sensitive adhesive, or the like is used to attach a filter to the substrate so that bubbles do not enter.
The adhesive is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include various adhesives such as a UV curable type, an emulsion type, a one-component curable type, and a two-component curable type, Known adhesives can be used in any combination.
There is no restriction | limiting in particular as said adhesive, According to the objective, it can select suitably, For example, rubber adhesive, acrylic adhesive, silicone adhesive, urethane adhesive, vinyl alkyl ether adhesive , Polyvinyl alcohol pressure sensitive adhesive, polyvinyl pyrrolidone pressure sensitive adhesive, polyacrylamide pressure sensitive adhesive, cellulose pressure sensitive adhesive, and the like.
The application thickness of the adhesive or the pressure-sensitive adhesive is not particularly limited and can be appropriately selected according to the purpose. From the viewpoint of optical properties and thinning, 0.1 to 10 μm is preferable in the case of an adhesive, 0.1-5 micrometers is more preferable. Moreover, in the case of an adhesive, 1-50 micrometers is preferable and 2-30 micrometers is more preferable.

<First gap layer forming step>
The first gap layer forming step is a step of forming a first gap layer between the second substrate and the filter layer. The method for forming the first gap layer is not particularly limited and may be appropriately selected depending on the intended purpose. The method of sticking, the said vapor deposition, the said sputtering, etc. are mentioned.

<Laminated body formation process>
The laminated body forming step includes a second substrate on which the recording layer, the filter layer, and the first gap layer are formed by the recording layer lamination step, the filter layer forming step, and the first gap layer forming step; It is a process including the other process suitably selected as needed, bonding a said 1st board | substrate and forming a laminated body.
The bonding method is not particularly limited and can be appropriately selected depending on the purpose.For example, the first substrate, the second substrate, and other layers appropriately selected as necessary, Examples thereof include a method of bonding with an adhesive, a method of pressure bonding without using an adhesive, and a method of bonding in a vacuum.
The method of adhering with the adhesive is to match the outer periphery of the first substrate, the second substrate, and other layers appropriately selected as necessary, and apply an adhesive between each layer, It adheres at 23-100 degreeC, applying the pressure of 0.001-0.5 Mpa from the outside.
In order to make it adhere | attach and there is no bubble in the case of this adhesion | attachment, it is preferable to bond together in a vacuum.

-Adhesive-
There is no restriction | limiting in particular as said adhesive agent, According to the objective, it can select suitably, For example, an acrylic adhesive, an epoxy-type adhesive agent, a rubber-type adhesive agent etc. are mentioned.
Of these, acrylic adhesives and epoxy adhesives are more preferable because of their good transparency.

  The method of performing pressure bonding without using the adhesive can also be used to form a laminated body by using the adhesiveness of each layer for adhesion. The first substrate, the second substrate, and other layers appropriately selected as necessary are matched to each outer periphery, and a pressure of 0.001 to 0.5 MPa is applied from the outside to Adhere at 100 ° C. In order to adhere without any bubbles during the adhesion, it is preferable to bond them in a vacuum.

<Other processes>
There is no restriction | limiting in particular as said other process, According to the objective, it can select suitably, For example, the 2nd gap layer formation process etc. which form a 2nd gap layer between the said recording layer and the said filter layer, etc. Is mentioned.

(Optical recording method and optical reproduction method)
The optical recording method is not particularly limited and may be appropriately selected depending on the purpose. For example, the optical recording medium is irradiated with information light and reference light as a coaxial light beam, This is an optical recording method based on a so-called collinear method in which information is recorded on a recording layer by an interference pattern due to interference.
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, the information light provided with a two-dimensional intensity distribution and the information light and the reference light having a substantially constant intensity are superposed inside the photosensitive recording layer to form them. Information is recorded by generating an optical characteristic distribution inside the recording layer using the interference pattern. On the other hand, when reading (reproducing) written information, the recording layer is irradiated with only the reference light in the same arrangement as during recording, and the reproduction has an intensity distribution corresponding to the optical characteristic distribution formed inside the recording layer. Light is emitted from the recording layer as light.
Here, the optical recording method and the reproducing method are performed using an optical recording / reproducing apparatus described below.

An optical recording / reproducing apparatus used in the optical recording method and reproducing method will be described with reference to FIG.
FIG. 10 is an overall configuration diagram of the optical recording / reproducing apparatus. The optical recording / reproducing apparatus includes an optical recording apparatus and a reproducing apparatus. The optical recording / reproducing apparatus 100 controls a spindle 81 to which the optical recording medium 21 is attached, a spindle motor 82 for rotating the spindle 81, and the spindle motor 82 so as to keep the rotational speed of the optical recording medium 21 at a predetermined value. A spindle servo circuit 83.
The optical recording / reproducing apparatus 100 records information by irradiating the optical recording medium 21 with information light and recording reference light, and irradiates the optical recording medium 21 with reproduction reference light for reproduction. A pickup 31 for detecting light and reproducing information recorded on the optical recording medium 21, and a drive device 84 that can move the pickup 31 in the radial direction of the optical recording medium 21 are provided.

  The optical recording / reproducing apparatus 100 uses a detection circuit 85 for detecting a focus error signal FE, a tracking error signal TE, and a reproduction signal RF from an output signal of the pickup 31, and a focus error signal FE detected by the detection circuit 85. Based on this, the actuator in the pickup 31 is driven to move the objective lens (not shown) in the thickness direction of the optical recording medium 20 to perform focus servo, and the tracking error signal detected by the detection circuit 85. Based on TE, a tracking servo circuit 87 that drives an actuator in the pickup 31 to move the objective lens in the radial direction of the optical recording medium 21 to perform tracking servo, a tracking error signal TE, and a command from a controller to be described later. Drive 84 controlled by a and a slide servo circuit 88 for performing a slide servo for moving the pickup 31 in the radial direction of the optical recording medium 21.

The optical recording / reproducing apparatus 100 further decodes output data of a later-described CMOS or CCD array in the pickup 31 to reproduce data recorded in the data area of the optical recording medium 21 or reproduce from the detection circuit 85. A signal processing circuit 89 that reproduces a basic clock and discriminates an address from the signal RF, a controller 90 that controls the entire optical recording / reproducing apparatus 100, and an operation unit 91 that gives various instructions to the controller 90. And has.
The controller 90 inputs the basic clock and address information output from the signal processing circuit 89, and controls the pickup 31, spindle servo circuit 83, slide servo circuit 88, and the like. The spindle servo circuit 83 receives the basic clock output from the signal processing circuit 89. The controller 90 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and the CPU executes a program stored in the ROM using the RAM as a work area. The function of the controller 90 is realized.

  The optical recording / reproducing apparatus used in the optical recording method and reproducing method uses the optical recording medium of the present invention, and sensitizes the photothermal conversion by sensitization simultaneously with the recording of interference fringes by information light and reference light. Therefore, an optical recording medium with high resolution and high diffraction efficiency can be obtained.

  Specific examples 1 and 2 of the optical recording medium of the present invention will be described in more detail with reference to the drawings. Note that an optical recording medium may be manufactured without stacking the second gap layer.

<Specific example 1 of optical recording medium>
FIG. 6 is a schematic cross-sectional view showing the configuration of the optical recording medium in Example 1 of the present invention. In the optical recording medium 21 according to the specific example 1, the servo pit pattern 3 is formed on the second substrate 1 made of polycarbonate resin or glass, and the servo pit pattern 3 is coated with aluminum, gold, platinum, etc. 2 is provided. In FIG. 6, the servo pit pattern 3 is formed on the entire surface of the second substrate 1, but it may be formed periodically as shown in FIG. The height of the servo pit pattern 3 is normally 1,750 mm (175 nm), which is sufficiently smaller than the thicknesses of the substrate and other layers.

The first gap layer 8 is formed by applying a material such as an ultraviolet curable resin on the reflective film 2 of the second substrate 1 by spin coating or the like. The first gap layer 8 is effective for protecting the reflective film 2 and adjusting the size of the hologram generated in the recording layer 4. That is, since it is necessary to form an interference area between the recording reference light and the information light in a certain size in the recording layer 4, it is effective to provide a gap between the recording layer 4 and the servo pit pattern 3.
A filter layer 6 is provided on the first gap layer 8, and a second gap layer 7 is provided between the filter layer 6 and the recording layer 4, and the filter layer 6 and the first substrate 5 (polycarbonate resin). The optical recording medium 21 is configured by sandwiching the second gap layer and the recording layer 4 by a substrate or a glass substrate. Although there is a point where the information light and the reproduction light are focused, if the focusing area is filled with a photopolymer, the monomer is excessively consumed due to overexposure, and the multiple recording ability is lowered. Therefore, it is effective to provide the second gap layer 7 that is non-reactive and transparent.

In FIG. 6, the filter layer 6 transmits only red light and does not transmit light of other colors. Therefore, since the information light, the recording and reproduction reference light are green or blue light, the light does not pass through the filter layer 6 and does not reach the reflection film 2 but becomes return light and is emitted from the incident / exit surface A. Become.
The filter layer 6 is composed of three cholesteric liquid crystal layers 6a, 6b, and 6c whose spiral pitch continuously changes in the thickness direction of the liquid crystal layer. The filter layer 6 made of this cholesteric liquid crystal layer may be directly formed on the first gap layer 8 by coating, or a film in which a cholesteric liquid crystal layer is formed on a substrate is punched into an optical recording medium shape and arranged. Also good. Λ _{0 to} λ ₀ / cos 20 °, especially λ _{0 to} λ ₀ / cos 40 ° (in particular, λ ₀ is the wavelength of the irradiation light) by the three cholesteric liquid crystal layers whose spiral pitch continuously changes in the thickness direction of the liquid crystal layer. In this case, the light reflectance is 40% or more, and the selective reflection wavelength does not shift even if the incident angle changes.

  The optical recording medium 21 in the first specific example may be disk-shaped or card-shaped. In the case of a card shape, there is no need for the servo pit pattern. In this optical recording medium 21, the second substrate 1 is 0.6 mm, the first gap layer 8 is 100 μm, the filter layer 6 is 2 to 3 μm, the second gap layer 7 is 70 μm, and the recording layer 4 is 0.6 mm. The first substrate 5 has a thickness of 0.6 mm, and the total thickness is about 1.9 mm.

Next, the optical operation around the optical recording medium 21 will be described with reference to FIG. First, light (red light) emitted from the servo laser is reflected almost 100% by the dichroic mirror 13 and passes through the objective lens 12. Servo light is applied to the optical recording medium 21 by the objective lens 12 so as to be focused on the reflective film 2. That is, the dichroic mirror 13 transmits light having a wavelength of green or blue, and reflects light having a wavelength of red by almost 100%. The servo light incident from the light incident / exit surface A of the optical recording medium 21 passes through the first substrate 5, the recording layer 4, the second gap layer 7, the filter layer 6, and the first gap layer 8, and is reflected. The light is reflected by the film 2, passes through the first gap layer 8, the filter layer 6, the second gap layer 7, the recording layer 4, and the first substrate 5 and is emitted from the incident / exit surface A again. The returned return light passes through the objective lens 12, is reflected almost 100% by the dichroic mirror 13, and servo information is detected by a servo information detector (not shown). The detected servo information is used for focus servo, tracking servo, slide servo, and the like. Since the hologram material constituting the recording layer 4 is not sensitive to red light, even if the servo light passes through the recording layer 4 or the servo light is irregularly reflected by the reflective film 2, the recording layer 4 is not affected. In addition, since the return light of the servo light reflected by the reflective film 2 is reflected almost 100% by the dichroic mirror 13, the servo light is detected by the CMOS sensor or the CCD 14 for detecting the reproduced image. In addition, there is no noise with respect to the reproduction light.
Note that the reflection range of λ _{0 to} 1.3λ ₀ shown in FIG. 8 is 1.3λ ₀ = 692 nm when λ ₀ = 532 nm, and the servo light is reflected when the servo light is 655 nm. The range of λ _{0 to} 1.3λ ₀ shown here is suitability for ± 40 ° incident light in the filter layer, but when actually using such a large oblique light, servo light with an incident angle within ± 20 ° is used. Servo control can be performed without hindrance if masked. If the spiral pitch of the cholesteric liquid crystal layer in the filter layer to be used is sufficiently large, it is easy to design all the incident angles within ± 20 ° in the filter layer, in which case λ _{0 to} 1.1λ. _{Since a zero} cholesteric liquid crystal layer is sufficient, there is no hindrance to servo light transmission.

  In addition, the information light and the recording reference light generated from the recording / reproducing laser pass through the polarizing plate 16 to become linearly polarized light, pass through the half mirror 17 and pass through the quarter-wave plate 15 at a time. Become polarized. The optical recording medium 21 is irradiated with information light and recording reference light through the dichroic mirror 13 so as to generate an interference pattern in the recording layer 4 by the objective lens 12. The information light and the recording reference light are incident from the incident / exit surface A and interfere with each other in the recording layer 4 to generate an interference pattern there. Thereafter, the information light and the recording reference light pass through the recording layer 4 and enter the filter layer 6, but are reflected between the bottom of the filter layer 6 and become return light. That is, the information light and the recording reference light do not reach the reflective film 2. This is because the filter layer 6 is formed of three cholesteric liquid crystal layers whose spiral pitch continuously changes in the thickness direction of the liquid crystal layer, and has a property of transmitting only red light. Alternatively, if light leaking through the filter layer is suppressed to 20% or less of the incident light intensity, even if the leaked light reaches the bottom surface and becomes return light, it is reflected again by the filter layer and reproduced. The light intensity mixed into the light is 20% × 20% = 4% or less, which is not substantially a problem.

<Specific example 2 of optical recording medium>
FIG. 7 is a schematic cross-sectional view showing the configuration of the optical recording medium in the second specific example. The optical recording medium 22 according to Example 2 is configured in the same manner as Example 1 except for the filter layer 6.

In FIG. 7, the filter layer 6 transmits only red light and does not transmit light of other colors. Therefore, since the information light, the recording and reproduction reference light are green or blue light, the light does not pass through the filter layer 6 and does not reach the reflection film 2 but becomes return light and is emitted from the incident / exit surface A. Become.
The filter layer 6 is a laminate in which a dielectric vapor deposition layer is formed by laminating seven dielectric thin films having different refractive indexes on a color material-containing layer. The filter layer 6 that is a combination of the color material-containing layer and the dielectric vapor-deposited film may be directly formed on the first gap layer 8 by coating and vapor deposition, or may be formed on the base material. The film on which the deposited film is formed may be punched into an optical recording medium shape and disposed. By using a combination of a colorant-containing layer and a dielectric deposited film as a filter layer, the light transmittance at 655 nm is 50% or more and the light reflectance at 532 nm is 30% at an incident angle of ± 40 °. Thus, even if the incident angle changes, the selective reflection wavelength does not shift.

  The shape of the optical recording medium 22 in the specific example 2 may be a disk shape or a card shape, and is formed in the same manner as the specific example 1.

  Next, an optical operation around the optical recording medium 22 configured in the same manner as the optical recording medium 21 will be described with reference to FIG. In the optical recording medium 22, as in the optical recording medium 21, first, light (red light) emitted from the servo laser is reflected almost 100% by the dichroic mirror 13 and passes through the objective lens 12. Servo light is applied to the optical recording medium 22 by the objective lens 12 so as to be focused on the reflective film 2. That is, the dichroic mirror 13 transmits light having a wavelength of green or blue, and reflects light having a wavelength of red almost 100%. The servo light incident from the light incident / exit surface A of the optical recording medium 22 passes through the first substrate 5, the recording layer 4, the second gap layer 7, the filter layer 6, and the first gap layer 8 and is reflected. The light is reflected by the film 2, passes through the first gap layer 8, the filter layer 6, the second gap layer 7, the recording layer 4, and the first substrate 5 and is emitted from the incident / exit surface A again. The returned return light passes through the objective lens 12, is reflected almost 100% by the dichroic mirror 13, and servo information is detected by a servo information detector (not shown). The detected servo information is used for focus servo, tracking servo, slide servo, and the like. As in the first specific example, the hologram material constituting the recording layer 4 is not sensitive to red light, so that the servo light passes through the recording layer 4 or the servo light is reflected by the reflective film 2. Even if it is irregularly reflected, the recording layer 4 is not affected. In addition, since the return light of the servo light reflected by the reflective film 2 is reflected almost 100% by the dichroic mirror 13, the servo light is detected by the CMOS sensor or the CCD 14 for detecting the reproduced image. In addition, there is no noise with respect to the reproduction light.

  In addition, the information light and the recording reference light generated from the recording / reproducing laser pass through the polarizing plate 16 to become linearly polarized light, pass through the half mirror 17 and pass through the quarter-wave plate 15 at a time. Become polarized. The optical recording medium 22 is irradiated with information light and recording reference light through the dichroic mirror 13 so as to generate an interference pattern in the recording layer 4 by the objective lens 12. The information light and the recording reference light are incident from the incident / exit surface A and interfere with each other in the recording layer 4 to generate an interference pattern there. Thereafter, the information light and the recording reference light pass through the recording layer 4 and enter the filter layer 6, but are reflected between the bottom of the filter layer 6 and become return light. That is, the information light and the recording reference light do not reach the reflective film 2. This is because the filter layer 6 is a combination of a color material-containing layer and a dielectric deposited film, and has a property of transmitting only red light. Alternatively, if light leaking through the filter layer is suppressed to 20% or less of the incident light intensity, even if the leaked light reaches the bottom surface and becomes return light, it is reflected again by the filter layer and reproduced. The light intensity mixed into the light is 20% × 20% = 4% or less, which is not substantially a problem.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
<Preparation of optical recording medium>
The optical recording medium of Example 1 is formed by laminating a first substrate, a recording layer, a second gap layer, a filter layer, a first gap layer, and a second substrate in this order. It produced as follows. The filter layer was formed as follows by preparing and laminating a film-like filter. The recording layer has a structure in which the thickness is held by an outer peripheral spacer and an inner peripheral spacer.

-Composition of composition solution for optical recording layer-
An optical recording layer composition solution having the following composition was prepared.
-----------------------------------
・ Di (urethane acrylate) oligomer (manufactured by Echo Resins, ALU-351) ・ ・ ・ ・ ・ ・ 59 parts by mass ・ Isobornyl acrylate ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・30 parts by mass-Vinyl benzoate-10 parts by mass-Polymerization initiator (Ciba Specialty Chemicals, Irgacure 784)-1 part by mass -----------------------------------

-Fabrication of filter-
First, a base film is prepared by applying polyvinyl alcohol (trade name MP203, manufactured by Kuraray Co., Ltd.) to a thickness of 1 μm on a polycarbonate film (trade name: Iupil, manufactured by Mitsubishi Gas Chemical Co., Inc.) having a thickness of 100 μm. This base film can be passed through a rubbing apparatus to rub the surface of the polyvinyl alcohol film and impart liquid crystal alignment ability.

  Next, cholesteric liquid crystal layer coating liquids A, B, and C having the compositions shown in Table 1 below can be prepared by a conventional method.

＊ＵＶ重合性液晶：ＢＡＳＦ社製、商品名ＰＡＬＩＯＣＯＬＯＲ ＬＣ２４２
＊カイラル剤：ＢＡＳＦ社製、商品名ＰＡＬＩＯＣＯＬＯＲ ＬＣ７５６
＊光重合開始剤：チバスペシャルティケミカルズ社製、商品名イルガキュア３６９
＊増感剤：ジエチルチオキサントン
＊溶剤：メチルエチルケトン（ＭＥＫ）

* UV polymerizable liquid crystal: manufactured by BASF, trade name PALIOCOLOR LC242
* Chiral agent: BASF Corporation, trade name PALIOCOLOR LC756
* Photopolymerization initiator: Product name Irgacure 369, manufactured by Ciba Specialty Chemicals
* Sensitizer: Diethylthioxanthone * Solvent: Methyl ethyl ketone (MEK)

Next, the cholesteric liquid crystal layer coating solution A was applied onto the base film with a bar coater, dried, and then subjected to orientation aging at 110 ° C. for 20 seconds. Thereafter, the film was exposed to an irradiation energy of 500 mJ / cm ² with an ultrahigh pressure mercury lamp at 110 ° C. to form a cured cholesteric liquid crystal layer A having a thickness of 2 μm.
Next, the cholesteric liquid crystal layer coating solution B was applied onto the cholesteric liquid crystal layer A with a bar coater, dried, and then subjected to alignment aging at 110 ° C. for 20 seconds. Then, it exposed by irradiation energy 500mJ / cm < ² > with the ultrahigh pressure mercury lamp under 110 degreeC, and the cholesteric liquid crystal layer cured film B with a thickness of 2 micrometers was formed.
Next, the cholesteric liquid crystal layer coating solution B was applied onto the cholesteric liquid crystal layer B with a bar coater, dried, and then subjected to alignment aging at 110 ° C. for 20 seconds. Thereafter, exposure was performed at an irradiation energy of 500 mJ / cm ² with an ultrahigh pressure mercury lamp at 110 ° C. to form a cured cholesteric liquid crystal layer C having a thickness of 2 μm.
As described above, Embodiment 1 of a three-layer structure having circularly polarized light separation characteristics, different selective reflection center wavelengths in each cholesteric liquid crystal layer, and the same rotational direction of the spiral in each cholesteric liquid crystal layer in the clockwise direction. An optical recording medium filter was prepared.

  Next, the produced optical recording medium filter was punched into a predetermined disk size so that it could be placed on the substrate.

-First substrate-
As the first substrate, a general polycarbonate resin substrate used for DVD + RW having a diameter of 120 mm and a thickness of 0.6 mm was used. The substrate surface was smooth and had no irregularities such as servo pit patterns.

-Second substrate-
As the second substrate, a general polycarbonate resin substrate used for DVD + RW having a diameter of 120 mm and a plate thickness of 0.6 mm was used. A servo pit pattern is formed on the entire surface of the substrate, the track pitch is 0.74 μm, the groove depth is 175 nm, and the groove width is 300 nm.
First, a reflective film was formed on the servo pit pattern surface of the second substrate. Aluminum (Al) was used as the reflective film material. A 200 nm thick Al reflective film was formed by DC magnetron sputtering.

-First gap layer-
--Preparation of coating solution for first gap layer--
SD-640 (manufactured by Dainippon Ink) was prepared as a coating solution for the first gap layer.

The obtained first gap layer coating solution was applied to the surface of the reflective film on the second substrate on which the Al reflective film was formed by a spin coater (model name 1H-B7, manufactured by Mikasa) at 1,500 rpm, 15 The film was spin-coated under the conditions for 2 seconds, and cured by UV irradiation at a temperature of 23 ° C. and 1,500 mJ / cm ² . The cured thickness was 25 μm. These were repeated three times, and the total film thickness was 75 μm.

-Second gap layer-
As the second gap layer, a polycarbonate film having a thickness of 100 μm was used.

-Outer spacer-
The outer peripheral spacer has a circular shape with a diameter of 120 mm, which is the same as the outer shape of the first substrate and the second substrate, the width in the surface direction is 0.5 mm ± 100 μm, and the thickness is 500 μm, which is the same as the thickness of the recording layer 4. The cross-sectional shape is a square of 0.5 mm × 500 μm.
The material of the outer periphery spacer was produced by injection molding (manufactured by Sumitomo Heavy Industries, Ltd.) using polycarbonate having excellent moldability and mechanical strength.

-Inner circumference spacer-
As shown in FIG. 4, the inner circumferential spacer is a 15 mm circle having the same outer diameter as the opening diameters of the openings 5a and 1a of the first substrate 5 and the second substrate 1, and the width in the surface direction is 0. 0.5 mm ± 100 μm, and the thickness is 500 μm, which is the same as the thickness of the recording layer 4. Therefore, the cross-sectional shape is a square of 0.5 mm × 500 μm which is the same as the outer peripheral spacer.
The material of the inner peripheral spacer was produced by injection molding (manufactured by Sumitomo Heavy Industries, Ltd.) using the same polycarbonate as the outer peripheral spacer, which was excellent in moldability and mechanical strength.

-Formation of laminate-
As shown in FIG. 4, on the second substrate 1 on which the first gap layer 8 has been spin-coated, the filter is placed on a UV adhesive (model name SD-640, Dainippon, Japan) so that air bubbles do not enter the gap. Ink Co., Ltd. is applied and then laminated to form a filter layer 6. On the filter layer 6, a laminator device (model name HAL110aa, manufactured by Sankyo Co., Ltd.) is used. The second gap layer 7 was attached under the conditions of 1 MPa and a pressure bonding speed of 1.0 m / min.
Further, the outer peripheral spacer 37 thus obtained was bonded to the surface of the second gap layer 7 so that the outer shape of the second substrate 1 and the outer shape of the outer peripheral spacer 37 were matched, and the inner peripheral spacer 38 was Adhesion was performed so that the center of the inner peripheral spacer and the center of the second substrate 1 coincided. As the adhesive, a UV adhesive (model name SD-640, manufactured by Dainippon Ink Co., Ltd.) was used and adhered by irradiating UV light.
The composition coating solution for an optical recording layer obtained by the injection method was injected into a groove having a depth of 500 μm formed by the outer peripheral spacer 37 and the inner peripheral spacer 38 with a syringe.
The injection conditions were a temperature of 23 ° C., a liquid viscosity of 300 mPas, and a humidity of 50%.
After the injection, the optical recording layer composition was cured under the conditions of a temperature of 80 ° C. for 40 minutes to form a recording layer 4. The recording layer 4 had a thickness of 500 μm.
Since the recording layer is formed by the injection method in the groove portion formed by the outer peripheral spacer 37 and the inner peripheral spacer 38 of the present invention, the thickness of the recording layer 4 is maintained at a constant thickness with high accuracy.
On the recording layer 4, an adhesive (model name GM-9002, manufactured by Brennie Giken Co., Ltd.) is applied and laminated in this order, and the outside of the first substrate and the outside of the second substrate are set to 0.08 MPa. The optical recording medium 21 shown in FIG. 3 was produced by pressurizing at 80 ° C. for 40 minutes to form a laminate and drying and curing.

-Recording and evaluation of optical recording media-
Using the collinear hologram recording / reproduction tester SHOT-1000, manufactured by Pulstec Industrial Co., Ltd., the obtained optical recording medium was written with a series of multiple holograms with a recording spot size of 200 μm in diameter at the focal position of the recording hologram. (Recording energy) and multiplex number were measured and evaluated. The results are shown in Table 2.

-Measurement of sensitivity-
The irradiation light power (mJ / cm ² ) at the time of recording was changed, and the change in the error probability (BER: Bit Error Rate) of the reproduction signal was measured. Normally, the BER of a reproduction signal tends to gradually decrease as the reproduction signal luminance increases with an increase in recording light power. Here, the recording power of the recording material is defined as the lowest recording light power at which a substantially good reproduced image (BER <10 ⁻³ ) can be obtained. As a result, BER <10 ⁻³ was obtained at a recording sensitivity recording light power of 150 mJ / cm ² . (Recording sensitivity 75 mJ / cm ² ) The results are shown in Table 2.

-Evaluation of multiple numbers-
As a multiple evaluation method for optical recording media, ISOM'04, Th-J-06, pp. 184-185, Oct. The recording spot described in 2004 was shifted by a spiral and evaluated. Here, the number of recorded holograms is 11 × 11 = 121 holograms, and the recording pitch is 28.5 μm. The multiplicity at the time of recording the final 121st hologram is 49. Since the multiplicity increases as the number of recording holograms increases, if the recording material has insufficient multiplexing characteristics, the BER increases as the number of recordings increases. Here, the number of recording holograms that gives BER> 10 ⁻³ is defined as the multi-characteristic M of the material. It was confirmed that a characteristic equivalent to 121 multiplexing was obtained as the multiplexing characteristic M by this method.

-Evaluation of reduction in recording capacity by using spacers-
By setting each width of the outer peripheral spacer and the inner peripheral spacer to 0.5, a decrease in the recording capacity was estimated and evaluated based on the volume ratio of the recording layer with respect to the recording layer not using the both spacers.
In an actual optical recording medium, since 0.5 mm from the outer periphery is not used for recording, the reduction amount is about 2%, and it has been found that there is no problem.

(Example 2)
In the optical recording medium in Example 1, the same operation as in Example 1 was performed except that the width of the outer peripheral spacer 37 was changed to 1.0 mm and the width of the inner peripheral spacer 38 was changed to 1.0 mm. The optical recording medium of Example 2 was fabricated and evaluated for recording sensitivity, multiple characteristics, and reduction in recording capacity. The results are shown in Table 2.

(Example 3)
In the optical recording medium in Example 1, the same operation as in Example 1 was performed except that the width of the outer peripheral spacer 37 was changed to 3.0 mm and the width of the inner peripheral spacer 38 was changed to 3.0 mm. The optical recording medium of Example 3 was fabricated and evaluated for recording sensitivity, multiple characteristics, and reduction in recording capacity. The results are shown in Table 2.

Example 4
In the optical recording medium in Example 1, the same operation as in Example 1 was performed except that the width of the outer peripheral spacer 37 was changed to 5.0 mm and the width of the inner peripheral spacer 38 was changed to 5.0 mm. The optical recording medium of Example 4 was produced and evaluated for reduction in recording sensitivity, multiple characteristics, and recording capacity. The results are shown in Table 2.

(Example 5)
In the optical recording medium in Example 1, the same operation as in Example 1 was performed except that the width of the outer peripheral spacer 37 was changed to 10.0 mm and the width of the inner peripheral spacer 38 was changed to 10.0 mm. The optical recording medium of Example 5 was fabricated and evaluated for recording sensitivity, multiple characteristics, and reduction in recording capacity. The results are shown in Table 2.

(Comparative Example 1)
In the optical recording medium in Example 1, the comparison was made in the same manner as in Example 1 except that the width of the outer peripheral spacer 37 was changed to 0.3 mm and the width of the inner peripheral spacer 38 was changed to 0.3 mm. The optical recording medium of Example 1 was fabricated and evaluated for recording sensitivity, multiple characteristics, and reduction in recording capacity. The results are shown in Table 2.

(Comparative Example 2)
In the optical recording medium of Example 1, the outer peripheral spacer 37 and the inner peripheral spacer 38 are not used, and the recording layer having a thickness of 500 μm similar to that of Example 1 is laminated by the substrate parallel holding gap method. Then, an optical recording medium of Comparative Example 2 was prepared and evaluated for reduction in recording sensitivity, multiple characteristics, and recording capacity. The results are shown in Table 2.

表２の結果から、本発明の光記録媒体により、実施例１〜５は、比較例１に対して、記憶容量の減少は大きいが、記録層の厚みのばらつきは小さい。比較例１では、記憶容量の減少については優れているが、記録層の厚みのばらつきが非常に大きく、多重特性も低いことがわかる。

From the results of Table 2, according to the optical recording medium of the present invention, Examples 1 to 5 have a large decrease in storage capacity but small variations in the thickness of the recording layer compared to Comparative Example 1. Comparative Example 1 is excellent in reducing the storage capacity, but it can be seen that the variation in the thickness of the recording layer is very large and the multiplex characteristics are low.

The optical recording medium of the present invention has a recording layer with a constant thickness and high quality without narrowing the hologram recording area as much as possible. It is widely used for volume holograms that record a large amount of information such as images, and reflection holograms.
The method for producing an optical recording medium of the present invention can efficiently produce a high-quality optical recording medium having a uniform recording layer thickness without narrowing the hologram recording region as much as possible. It is widely used for relatively thin planar holograms for recording information such as volume holograms for recording large amounts of information such as stereoscopic images, and reflection holograms.

FIG. 1 is a schematic sectional view showing the structure of a conventional optical recording medium. FIG. 2 is a schematic sectional view showing the structure of a conventional optical recording medium. FIG. 3 is a partial cross-sectional view of an example of the optical recording medium of the present invention. FIG. 4 is a partial sectional view showing an example of the layer structure of the optical recording medium of the present invention. FIG. 5 is a schematic cross-sectional view showing a recording layer stack using the outer peripheral spacer and the inner peripheral spacer of the optical recording medium of the present invention. FIG. 6 is a schematic cross-sectional view showing an example of an optical recording medium according to Example 1 according to the present invention. FIG. 7 is a schematic cross-sectional view showing an example of an optical recording medium according to Example 2 according to the present invention. FIG. 8 is a graph showing reflection characteristics with respect to incident light from the front (0 °) of a filter in which three cholesteric liquid crystal layers are laminated. FIG. 9 is an explanatory diagram showing an example of an optical system around the optical recording medium according to the present invention. FIG. 10 is a block diagram showing an example of the overall configuration of the optical recording / reproducing apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 2nd board | substrate 1a Opening part 2 Reflecting film 3 Servo bit pattern 4 Recording layer 5 1st board | substrate 5a Opening part 6 Filter layer 6a, 6b, 6c Cholesteric liquid crystal layer 7 2nd gap layer 8 1st gap layer 9 1 / 4 wavelength plate 12 Objective lens 13 Dichroic mirror 14 Detector 15 1/4 wavelength plate 16 Polarizing plate 17 Half mirror 20, 20a, 21, 22 Optical recording medium 31 Pickup 37 Outer spacer 38 Inner spacer 81 Spindle 82 Spindle motor 83 Spindle Servo circuit 84 Drive device 85 Detection circuit 86 Focus servo circuit 87 Tracking servo circuit 88 Slide servo circuit 89 Signal processing circuit 90 Controller 91 Operation unit 100 Optical recording / reproducing device A Input / output surface FE Focus error signal TE Tracking error -Signal RF playback signal

Claims (4)

  A recording layer for recording information using holography, a first substrate, a second substrate, a first gap layer, a second gap layer, a filter layer, and a spacer for maintaining the thickness of the recording layer And the spacer has a width in the layer surface direction of the recording layer of at least 0.5 mm.   The optical recording medium according to claim 1, wherein a width of the recording layer in the layer surface direction of the spacer is 0.5 to 5 mm.   3. The optical recording method according to claim 1, wherein the optical recording medium is irradiated with the information light and the reference light so that the optical axis of the information light and the optical axis of the reference light are coaxial. An optical recording medium according to 1. 4. A method for producing an optical recording medium according to claim 1, comprising a recording layer forming step.

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