JP2007102185A - Optical recording medium, method of producing same, optical recording method and optical reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a hologram type optical recording medium capable of performing high-density recording and preventing noise even when information light and reference light leaks from filter layers formed of wavelength-selective reflection films; a method of producing the medium; an optical recording method; and an optical reproducing method using the optical recording medium. <P>SOLUTION: The optical recording medium includes a first substrate, a recording layer to record information by using holography, a filter layer, a light absorbing layer and a second substrate in this order. The method of producing the optical medium, the optical recording method and the reproducing method on the optical recording medium are also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hologram type optical recording medium capable of high-density image recording, a method for manufacturing the optical recording medium, and an optical recording method and an optical reproducing method using 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 medium capable of recording information three-dimensionally has attracted attention.

In general, the hologram type optical recording medium is formed by superimposing information light given a two-dimensional intensity distribution and information light and reference light having a substantially constant intensity inside a photosensitive recording layer. Information is recorded by generating a distribution of optical characteristics such as a refractive index in the recording layer using an 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 in recording, and has an intensity distribution corresponding to the optical characteristic distribution formed in the recording layer. The light is emitted from the recording layer as diffracted light.
In this hologram type optical recording medium, 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, multiple recording can be performed. When digital volume holography synthesized by a computer is used, the signal-to-noise ratio (S / N ratio) of one spot is extremely high, so the original information is faithfully reproduced even if the S / N ratio is somewhat lowered by overwriting. it can. 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).

However, the optical recording medium 20 having the configuration shown in FIG. 1 has a problem that the servo zone and the recording zone are separated in the plane, and the recording density is halved accordingly.
Therefore, in the optical recording medium 20a shown in FIG. 2, circularly polarized light is used as the information light and the reference light, and the gap layer 8 for smoothing the second substrate 1 is interposed between the recording layer 4 and the reflective film 2. A cholesteric liquid crystal layer or dichroic mirror layer as a filter layer 6 and a quarter-wave plate 10 are provided, and the recording layer and the servo layer are stacked in the thickness direction (see Patent Document 3). This technique doubles the recording density. In addition, when a single-layer cholesteric liquid crystal layer having the same rotation direction as the circular polarization of information light in a spiral structure is used as the filter layer, it is excellent in productivity and enables mass production of an optical recording medium at a low cost. The filter effect at 0 ° is good.
However, in this proposal, when the incident angle changes and the incident light is tilted by 10 ° or more, the selective reflection wavelength shifts, and the information light and the reference light pass through the filter layer and reach the reflection film and are reflected, It may cause noise. This phenomenon has a problem that it cannot be applied to incident light of a lens optical system in an ordinary optical recording medium of ± 10 ° or more that is narrowed by a lens.
When the incident angle is within 10 °, as shown in FIG. 3, the information light and the reference light 35 are all selectively reflected by the filter layer 6 and become return light. As shown, the information light and the reference light 35 are not all reflected by the filter layer 6, but slightly leak from the filter layer and reach the reflection film 2 as shown by the dotted line. The light is reflected and becomes reflected light 35a, which is mixed into the diffracted light and may cause noise.

  Therefore, it is still possible to efficiently mass-produce a hologram type optical recording medium capable of preventing the generation of noise even when information light and reference light leak from the selective reflection layer. The current situation is that prompt provision is desired.

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 provides a hologram type optical recording medium capable of preventing noise from occurring even when information light and reference light leak from a filter layer made of a wavelength selective reflection film, and capable of high-density recording, and the optical recording It is an object of the present invention to provide an optical recording medium manufacturing method capable of manufacturing a medium efficiently and at low cost, and an optical recording method and an optical reproducing method using the optical recording medium.

Means for solving the problems are as follows. That is,
<1> An optical recording medium comprising a first substrate, a recording layer for recording information using holography, a filter layer, a light absorption layer, and a second substrate in this order. .
The optical recording medium according to <1> includes a first substrate, a recording layer for recording information using holography, a filter layer, a light absorption layer, and a second substrate in this order. Therefore, even if the incident angle changes, the selective reflection wavelength does not shift, and the information light and the reference light used during recording or reproduction, and the reproduction light do not reach the reflection film. It is possible to prevent diffused light from being generated. Therefore, the noise generated by the diffused light is not superimposed on the reproduced image and detected on the CMOS sensor or CCD, but can be detected to the extent that the reproduced image can be corrected at least. The noise component due to the diffused light becomes a serious problem as the multiplicity of the hologram 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 the presence of diffusion noise makes it very difficult to detect a reproduced image. According to the present invention, such difficulty can be eliminated, and unprecedented high-density image recording can be realized. Further, since the light absorption layer is formed between the filter layer and the second substrate, the recording light leaking from the filter layer is absorbed, and a reproduced image without distortion is reproduced.
<2> The light according to <1>, wherein the light absorption layer absorbs the first light having any wavelength of 350 nm or more and less than 600 nm and transmits the second light having any wavelength of 600 to 900 nm. It is a recording medium.
<3> The composition of the light absorption layer, the composition of the light absorption layer includes any one of a dye and a pigment, and the dye and the pigment include at least one of a cyanine dye, a phthalocyanine dye, and an azo dye. The optical recording medium according to any one of <1> to <2>.
<4> The optical recording medium according to any one of <1> to <3>, wherein the light absorption layer has a thickness of 0.1 to 200 μm.
<5> The light absorption layer has a light transmittance of 0.001 to 50% with respect to the first light and a light transmittance of 50 to 100% with respect to the second light. 4>. The optical recording medium according to any one of 4).
<6> The optical recording medium according to any one of <1> to <5>, wherein a gap layer is provided between the light absorption layer and the second substrate.
<7> The optical recording medium according to any one of <1> to <6>, wherein the total thickness of the light absorption layer and the gap layer is 1 to 200 μm.
<8> The optical recording medium according to any one of <1> to <7>, wherein the filter layer includes at least one of a colorant-containing layer, a dielectric vapor deposition layer, and a cholesteric liquid crystal layer.
<9> The optical recording medium according to any one of <1> to <8>, wherein the filter layer includes a cholesteric liquid crystal layer, and the cholesteric liquid crystal layer contains at least a nematic liquid crystal compound and a photoreactive chiral compound. It is.
<10> The <9>, wherein the photoreactive chiral compound has a chiral moiety and a photoreactive group, and the chiral moiety is at least one selected from an isosorbide compound, an isomannide compound, and a binaphthol compound. This is an optical recording medium.
<11> The optical recording medium according to <10>, wherein the photoreactive group is a group that causes isomerization of a carbon-carbon double bond from trans to cis by light irradiation.
<12> The optical recording medium according to any one of <8> to <11>, wherein two or more cholesteric liquid crystal layers are laminated.
In the optical recording medium according to <12>, by laminating two or more cholesteric liquid crystal layers, the angle dependency of reflected light is reduced without causing a shift in the selective reflection wavelength even when the incident angle is changed. Can be resolved.
<13> The optical recording medium according to <8> to <12>, wherein the cholesteric liquid crystal layer has circularly polarized light separation characteristics.
<14> The optical recording medium according to any one of <8> to <13>, wherein the rotation directions of the spirals in the cholesteric liquid crystal layer are the same.
<15> The optical recording medium according to any one of <8> to <14>, wherein the selective reflection center wavelengths in the cholesteric liquid crystal layer are different from each other.
<16> The optical recording medium according to any one of <8> to <15>, wherein the selective reflection wavelength band in the cholesteric liquid crystal layer is continuous.
In the optical recording medium according to any one of <13> to <16>, the cholesteric liquid crystal layer has a circularly polarized light separation property, the rotational directions of the spirals are the same, and the selective reflection center wavelengths are different from each other. Since the selective reflection wavelength band is continuous, the angle dependency of irradiation light reflection can be eliminated without causing a shift in the selective reflection wavelength even when the incident angle changes, and it can be suitably used as a wavelength selective reflection film. .
<17> The optical recording medium according to any one of <1> to <16>, wherein the filter layer reflects the first light and transmits a second light different from the first light.
_{<18> λ 0 ~λ 0 /} cos20 ° 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 <17> This is an optical recording medium.
_{<19> 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 <18> This is an optical recording medium.
<20> The optical recording medium according to any one of <1> to <19>, wherein the first substrate has a servo pit pattern.
<21> The optical recording medium according to <20>, wherein the servo pit pattern has a reflective film on the surface.
<22> The optical recording medium according to <21>, wherein the reflective film is a metal reflective film.
<23> The optical recording medium according to any one of <1> to <22>, wherein a second gap layer is provided between the recording layer and the filter layer.
In the optical recording medium described in <23>, the second gap layer may be provided to have a point where information light and reproduction light are focused. If this area is filled with a photopolymer, excessive consumption of monomers due to overexposure occurs, resulting in a decrease in multiple recording capability. Therefore, it is effective to provide a non-reactive and transparent second gap layer.
<24> The optical recording medium according to any one of <1> to <23>, wherein the filter layer is used as a selective reflection film of an optical recording medium that records information using holography.

<25> A filter for optical recording media, wherein a filter layer is laminated on a substrate.
<26> The optical recording medium filter according to <25>, wherein the filter layer includes at least one of a colorant-containing layer, a dielectric vapor deposition layer, and a cholesteric liquid crystal layer.
<27> The optical recording medium according to any one of <25> to <26>, wherein the filter layer includes a cholesteric liquid crystal layer, and the cholesteric liquid crystal layer contains at least a nematic liquid crystal compound and a photoreactive chiral compound. It is a filter for.
<28> The <27>, wherein the photoreactive chiral compound has a chiral moiety and a photoreactive group, and the chiral moiety is at least one selected from an isosorbide compound, an isomannide compound, and a binaphthol compound. This is a filter for optical recording media.
<29> The optical recording medium filter according to <28>, wherein the photoreactive group is a group that causes isomerization of a carbon-carbon double bond from trans to cis by light irradiation.
<30> The filter for optical recording media according to any one of <27> to <29>, wherein two or more cholesteric liquid crystal layers are laminated.
<31> The filter for optical recording media according to <27> to <30>, wherein the cholesteric liquid crystal layer has circularly polarized light separation characteristics.
<32> The filter for optical recording media according to any one of <27> to <31>, wherein the rotation directions of the spirals in the cholesteric liquid crystal layer are the same.
<33> The optical recording medium filter according to any one of <27> to <32>, wherein the selective reflection center wavelengths in the cholesteric liquid crystal layer are different from each other.
<34> The optical recording medium filter according to any one of <27> to <33>, wherein the selective reflection wavelength band in the cholesteric liquid crystal layer is continuous.
<35> The filter for optical recording media according to any one of <25> to <34>, wherein the filter layer reflects the first light and transmits the second light different from the first light. .
_{<36> λ 0 ~λ 0 /} cos20 ° filter layer (where, lambda ₀ represents a wavelength of the irradiated light) light reflectance at the, wherein the 40% or more from the <25> to any one of <35> This is a filter for optical recording media.
_{<37> 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 from the <25> to any one of <35> This is a filter for optical recording media.
<38> The optical recording medium filter according to any one of <25> to <37>, which is used as a selective reflection film of an optical recording medium that records information using holography.
<39> Irradiation of the information light and the reference light to the optical recording medium is performed such that the optical axis of the information light and the optical axis of the reference light are coaxial, and interference between the information light and the reference light The filter for optical recording media according to any one of <25> to <38>, wherein information is recorded on the recording layer by the interference pattern generated by the method.

<40> A method for producing the optical recording medium according to any one of <1> to <24>, wherein a light absorption layer is laminated on a second substrate, and the light A method for producing an optical recording medium comprising at least a filter layer forming step of forming a filter layer on an absorption layer.
In the method for producing an optical recording medium according to <40>, a filter layer formed of a laminate in which a cholesteric liquid crystal layer is laminated on a second substrate is formed by the filter layer forming step. As a result, an optical recording medium can be efficiently mass-produced at a low cost by a simple method such as coating.
<41> The method for producing an optical recording medium according to <40>, including a filter layer forming step of forming a filter layer including two or more cholesteric liquid crystal layers.

<42> When the optical recording medium according to any one of <1> to <24> is irradiated with information light and reference light, the optical axis of the information light and the optical axis of the reference light are coaxial. And recording information on a recording layer by an interference pattern due to interference between the information light and the reference light.
In the optical recording method according to <42>, the optical axis of the information light and the optical axis of the reference light are coaxially irradiated with the information light and the reference light using the optical recording medium of the present invention. In this way, by recording information on the recording layer with an interference pattern due to interference between the information light and the reference light, unprecedented high-density recording can be realized.

<43> An optical reproduction method, wherein information is reproduced by irradiating the interference pattern recorded on the recording layer by the optical recording method according to <42> with the same reproduction light as the reference light.
In the optical reproduction method according to <43>, the interference pattern recorded on the recording layer by the optical recording method of the present invention can be efficiently and accurately read to reproduce high-density recorded information.
<44> The light according to <43>, wherein the reproduction information is reproduced at the same angle as the reference light used for recording on the optical recording medium, and the reproduction information is irradiated to the interference pattern to reproduce the recorded information. It is a playback method.

  According to the present invention, various problems in the prior art can be solved, and even if information light and reference light leak from a filter layer made of a wavelength selective reflection film, the generation of noise can be prevented and high-density recording is possible. It is possible to provide an optical recording medium, an optical recording medium manufacturing method capable of manufacturing the optical recording medium efficiently and at low cost, and an optical recording method and an optical reproducing method using the optical recording medium.

(Optical recording medium)
The optical recording medium of the present invention has a first substrate, a recording layer for recording information using holography, a filter layer, a light absorption layer, and a second substrate in this order, and if necessary The optical recording medium has other layers appropriately selected.

<Light absorption layer>
The light absorption layer absorbs light (indicated by an arrow in FIG. 5) that has not been sufficiently reflected by the wavelength selective reflection at the filter layer, and prevents light leaking from the filter layer from being mixed into the diffracted light. There is a function to increase the signal-to-noise ratio (SN ratio). Therefore, it is preferable to form the light absorption layer between the filter layer and the second substrate.

There is no restriction | limiting in particular as a wavelength of the light (henceforth a 1st light) which the said light absorption layer absorbs, According to the objective, it can select suitably, For example, a wavelength is 350 nm or more and 600 nm Is preferably less than 400, more preferably 400 to 550 nm. When the wavelength is less than 350 nm, it is difficult to maintain stable absorption, and when it is 600 nm or more, it is difficult to maintain stable absorption.
The light absorption layer also has a property of transmitting light having a wavelength of 600 to 900 nm (hereinafter sometimes referred to as second light). The wavelength of the transmitted light is more preferably 650 to 850 nm.
There is no restriction | limiting in particular as the light transmittance of the said light absorption layer, According to the objective, it can select suitably, For example, the average transmittance is 0.001-50% with respect to the said wavelength to absorb. Preferably, 0.01 to 20% is more preferable. When the average light transmittance is less than 0.001%, the amount of the color material increases and the long-term stability may be lacking. When the average light transmittance exceeds 50%, the light absorption function of the object of the present invention cannot be sufficiently exhibited. Sometimes.
For the wavelength of the tracking servo light other than the wavelength to be absorbed, the average transmittance is preferably 50 to 100%, and more preferably 60 to 95%. If the light transmittance is less than 50%, the amount of tracking servo light may decrease. These numerical limit ranges are not limited to the entire preferable wavelength range but only for the wavelength of recording / reproducing and tracking servo light.
There is no restriction | limiting in particular as the measuring method of the said light transmittance, According to the objective, it can select suitably, For example, it measures with a spectrophotometer using a test piece of size 2cm x 2cm and thickness 10micrometer. Can do.
The light transmittance measuring device is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a visible light transmittance measuring device and a spectrophotometer.

There is no restriction | limiting in particular as a composition of the said light absorption layer, According to the objective, it can select suitably, For example, coloring materials, such as a pigment | dye and a pigment, Furthermore, other components, such as a binder, are mentioned as needed. It is done.
Examples of the coloring material include phthalocyanine dyes, cyanine dyes, azo dyes, quinophthalone dyes, flavantron dyes, anthraquinone dyes, isoindoline dyes, perylene dyes, manganese dyes, and the like. Of these, phthalocyanine dyes, cyanine dyes, azo dyes and the like are preferable. These may be used alone or in combination of two or more. In addition, commercially available screen printing inks that are already colored are also preferred. The commercially available screen printing ink is not particularly limited and may be appropriately selected from known ones. Examples thereof include UV printing ink ("DAICURE SSD TF106 PINK"; manufactured by Dainippon Ink Co., Ltd.). .
Examples of the binder include natural organic polymer materials such as gelatin, cellulose derivatives, dextran, rosin, and rubber; hydrocarbon resins such as polyethylene, polypropylene, polystyrene, and polyisobutylene, polyvinyl chloride, polyvinylidene chloride, and polychlorinated chloride. Vinyl resins such as vinyl / polyvinyl acetate copolymers; acrylic resins such as polymethyl acrylate and polymethyl methacrylate; polyvinyl alcohol, chlorinated polyethylene, epoxy resins, butyral resins, rubber derivatives, phenol / formaldehyde resins, etc. Examples thereof include synthetic organic polymers such as an initial condensate of a thermosetting resin. These may be used alone or in combination of two or more.
When the binder is added to the light-absorbing layer, the amount added is generally 20 parts by mass or less, preferably 10 parts by mass or less, and preferably 5 parts by mass or less with respect to 100 parts by mass of the coloring material. More preferred.
Further, as the other components, the light absorbing layer forming coating solution may be added with an anti-fading agent and a binder, if necessary, and, depending on the purpose, an antioxidant, Various additives such as a UV absorber, a plasticizer, and a lubricant may be added.
Examples of the anti-fading agent include nitroso compounds, metal complexes, diimmonium salts, and aminium salts. Examples of these are described in, for example, JP-A-2-300288, JP-A-3-224793, and JP-A-4-146189.

There is no restriction | limiting in particular as thickness of the said light absorption layer, According to the objective, it can select suitably, For example, 0.1-200 micrometers is preferable, 1-100 micrometers is more preferable, and 2-40 micrometers is especially preferable.
When the gap layer (first gap layer described later) is formed between the light absorption layer and the second substrate, the total thickness of the light absorption layer and the gap layer is 1 to 200 μm. Preferably, 5-150 μm is more preferable, and 10-100 μm is particularly preferable.

<Filter layer>
The filter layer has a wavelength selective reflection function of reflecting only light of a specific wavelength from among a plurality of types of light rays. In particular, the selective reflection wavelength does not shift even when the incident angle changes, and the function of preventing irregular reflection from the reflection film of the optical recording medium by the information light and the reference light, and also preventing the occurrence of noise. By laminating the filter layer on the recording medium, optical recording with high resolution and excellent diffraction efficiency can be obtained.
The filter layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the filter layer has a dichroic mirror layer, a color material-containing layer, a dielectric vapor deposition layer, a single layer, or two or more cholesteric layers. And it forms with the laminated body which laminated | stacked at least any one of the other layer suitably selected as needed. The filter layer is preferably composed of at least one of a colorant-containing layer, a dielectric vapor deposition layer, and a cholesteric liquid crystal layer.
The filter layer may be laminated together with a direct recording layer or the like on a substrate by coating or the like, and is laminated on a substrate such as a film to produce an optical recording medium filter. It may be laminated on a substrate.

-Dichroic mirror layer-
The dichroic mirror layer is preferably laminated in a plurality of layers to be a wavelength selective reflection film. The number of stacked layers is preferably 1 to 50 layers, more preferably 2 to 40 layers, and particularly preferably 2 to 30 layers. When the number of stacked layers exceeds 50 layers, production efficiency decreases due to multi-layer deposition, the change in spectral transmittance characteristics decreases, and the effect of increasing the number of layers decreases.

There is no restriction | limiting in particular as a lamination | stacking method of the said dichroic mirror layer, According to the objective, it can select suitably, For example, physical vapor deposition methods (Vapor deposition methods, such as ion plating and an ion beam, sputtering) ( 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 thickness of the dichroic mirror layer is preferably λ / 16 to λ, more preferably λ / 8 to 3λ / 4, and more preferably λ / 6 to 3λ / 8 in the optical wavelength order.

-Color material-containing layer-
The color material-containing layer is formed of a color material, a binder resin, a solvent, and other components as necessary.

  As the coloring material, at least one of a pigment and a dye is preferably exemplified, and among these, a red dye and a red pigment are preferable from the viewpoint of absorbing light at 532 nm and transmitting servo light at 655 nm or 780 nm, Red pigments are particularly preferred.

  There is no restriction | limiting in particular as said red dye, According to the objective, it can select suitably from well-known things, for example, C.I. I. Acid Red 1, C.I. I. Acid Red 8, C.I. I. Acid Red 13, C.I. I. Acid Red 14, C.I. I. Acid Red 18, C.I. I. Acid Red 26, C.I. I. Acid Red 27, C.I. I. Acid Red 35, C.I. I. Acid Red 37, C.I. I. Acid Red 42, C.I. I. Acid Red 52, C.I. I. Acid Red 82, C.I. I. Acid Red 87, C.I. I. Acid Red 89, C.I. I. Acid Red 92, C.I. I. Acid Red 97, C.I. I. Acid Red 106, C.I. I. Acid Red 111, C.I. I. Acid Red 114, C.I. I. Acid Red 115, C.I. I. Acid Red 134, C.I. I. Acid Red 186, C.I. I. Acid Red 249, C.I. I. Acid Red 254, C.I. I. Acid dyes such as Acid Red 289; C.I. I. Basic Red 2, C.I. I. Basic Red 12, C.I. I. Basic Red 13, C.I. I. Basic Red 14, C.I. I. Basic Red 15, C.I. I. Basic Red 18, C.I. I. Basic Red 22, C.I. I. Basic Red 23, C.I. I. Basic Red 24, C.I. I. Basic Red 27, C.I. I. Basic Red 29, C.I. I. Basic Red 35, C.I. I. Basic Red 36, C.I. I. Basic Red 38, C.I. I. Basic Red 39, C.I. I. Basic Red 46, C.I. I. Basic Red 49, C.I. I. Basic Red 51, C.I. I. Basic Red 52, C.I. I. Basic Red 54, C.I. I. Basic Red 59, C.I. I. Basic Red 68, C.I. I. Basic Red 69, C.I. I. Basic Red 70, C.I. I. Basic Red 73, C.I. I. Basic Red 78, C.I. I. Basic Red 82, C.I. I. Basic Red 102, C.I. I. Basic Red 104, C.I. I. Basic Red 109, C.I. I. Basic dyes such as Basic Red 112; I. Reactive Red 1, Reactive Red 14, Reactive Red 17, Reactive Red 25, Reactive Red 26, Reactive Red 32, Reactive Red 37, Reactive Red 44, Reactive Red 46, Reactive Red 55, And reactive dyes such as reactive red 60, reactive red 66, reactive red 74, reactive red 79, reactive red 96, reactive red 97, and the like. These may be used individually by 1 type and may use 2 or more types together.

  There is no restriction | limiting in particular as said red pigment, According to the objective, it can select suitably from well-known things, for example, C.I. I. Pigment red 9, C.I. I. Pigment red 97, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 149, C.I. I. Pigment red 168, C.I. I. Pigment red 177, C.I. I. Pigment red 180, C.I. I. Pigment red 192, C.I. I. Pigment red 209, C.I. I. Pigment red 215, C.I. I. Pigment red 216, C.I. I. Pigment red 217, C.I. I. Pigment red 220, C.I. I. Pigment red 223, C.I. I. Pigment red 224, C.I. I. Pigment red 226, C.I. I. Pigment red 227, C.I. I. Pigment red 228, C.I. I. Pigment red 240, C.I. I. Pigment Red 48: 1, Permanent Carmine FBB (CI Pigment Red 146), Permanent Ruby FBH (CI Pigment Red 11), Fastel Pink B Splash (CI Pigment Red 81), etc. Is mentioned. These may be used individually by 1 type and may use 2 or more types together.

  Among these, a red pigment exhibiting a transmission spectrum in which the transmittance for 532 nm light is 10% or less and the transmittance for 655 nm light is 90% or more is particularly preferably used.

  As content of the said color material, 0.05-90 mass% is preferable with respect to the total solid mass of the said color material content layer, and 0.1-70 mass% is more preferable. When the content is less than 0.05% by mass, the thickness of the color material-containing layer may be required to be 500 μm or more, and when it exceeds 90% by mass, the self-supporting property of the color material-containing layer is lost. The film may collapse during the color material-containing layer manufacturing process.

-Binder resin-
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 resin, a vinyl chloride / vinyl acetate copolymer; Vinyl chloride, vinyl acetate, and vinyl alcohol Copolymer with at least one of styrene, maleic acid and acrylic acid; vinyl chloride / vinylidene chloride copolymer; vinyl chloride / acrylonylyl copolymer; ethylene / vinyl acetate copolymer; cellulose derivative such as nitrocellulose resin; Examples thereof include resins, polyvinyl acetal resins, polyvinyl butyral resins, epoxy resins, phenoxy resins, polyurethane resins, and polycarbonate resins. These may be used alone or in combination of two or more.
Further, in order to further improve dispersibility and durability, the binder resin molecules listed above include polar groups (epoxy groups, CO ₂ H, OH, NH ₂ , SO ₃ M, OSO ₃ M, PO ₃ M ₂ , Those having introduced OPO ₃ M ₂ (wherein M is a hydrogen atom, an alkali metal, or ammonium and may be different from each other when a plurality of M are present in one group) are preferred. The content of is preferably 10 ⁻⁶ to 10 ⁻⁴ equivalent per gram of binder resin.
The binder resins listed above are preferably cured by adding an isocyanate-based known crosslinking agent.

  As content of the said binder resin, 10-99.95 mass% is preferable with respect to the total solid mass of the said color material content layer, and 30-99.9 mass% is more preferable.

Each of the above components is dissolved or dispersed in an appropriate solvent, prepared as a coating solution, and this coating solution is applied onto a substrate described later by a desired coating method to form a color material-containing layer. it can.
The solvent is not particularly limited and may be appropriately selected from known solvents according to the purpose. Examples thereof include water, 3-methoxypropionic acid methyl ester, 3-methoxypropionic acid ethyl ester, and 3-methoxypropion. Alkoxypropionic acid esters such as acid propyl ester, 3-ethoxypropionic acid methyl ester, 3-ethoxypropionic acid ethyl ester, 3-ethoxypropionic acid propyl ester; 2-methoxypropyl acetate, 2-ethoxypropyl acetate, 3-methoxy Esters of alkoxy alcohols such as butyl acetate; Lactic acid esters such as methyl lactate and ethyl lactate; Ketones such as methyl ethyl ketone, cyclohexanone and methylcyclohexanone; γ-butyrolactone, N-methylpyrrolidone Dimethyl sulfoxide, chloroform, tetrahydrofuran, and the like. These may be used alone or in combination of two or more.

  The coating method is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the inkjet method, spin coating method, kneader coating method, bar coating method, blade coating method, casting method, dip method, curtain And coating method.

  The thickness of the color material-containing layer is, for example, preferably 0.5 to 200 μm, and more preferably 1.0 to 100 μm. When the thickness is less than 0.5 μm, it may not be possible to add a sufficient amount of a binder resin for wrapping the color material to form a film. When the thickness exceeds 200 μm, the thickness of the filter becomes too large. Thus, an excessively large optical system for irradiation light and servo light may be required.

-Dielectric deposition layer-
The dielectric vapor-deposited layer is formed on the colorant-containing layer, and is formed by laminating a plurality of thin dielectric layers having different refractive indexes. In order to obtain a wavelength selective reflection film, a dielectric material having a high refractive index is used. It is preferable to laminate a plurality of thin layers and low-refractive-index dielectric thin layers alternately, but the number of layers is not limited to two or more and may be more.
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 stacking order of the dielectric thin layers is not particularly limited and can be appropriately selected depending on the purpose. For example, when the refractive index of an adjacent film is high, a film having a lower refractive index is first selected. Laminate. 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 material for the high refractive index dielectric thin layer is not particularly limited and may be appropriately selected depending on the intended 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. 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 layer 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.
The material of the dielectric thin layer is not particularly limited as to the atomic ratio, and can be appropriately selected according to the purpose. The atomic ratio can be adjusted by changing the atmospheric gas concentration during film formation. it can.

There is no restriction | limiting in particular as a lamination | stacking method of the said dielectric material thin layer, According to the objective, it can select suitably, For example, the method similar to the lamination | stacking method used for lamination | stacking of the said dichroic mirror layer can be used.
The thickness of the dielectric thin layer is preferably λ / 16 to λ, more preferably λ / 8 to 3λ / 4, and more preferably λ / 6 to 3λ / 8 in the optical wavelength order.

In the dielectric vapor deposition layer, a part of the light propagating in the dielectric vapor deposition layer is multiple-reflected for each dielectric thin layer, and the reflected light interferes with each other. Only light having a wavelength determined by the product of the refractive index of the film with respect to the light is selectively transmitted. Further, the central transmission wavelength of the dielectric vapor deposition layer has an angle dependency with respect to the incident light, and the transmission wavelength can be changed by changing the incident light.
However, when the number of laminated layers of the dielectric vapor deposition layer is 20 or less, several% to several tens of% selective reflection wavelength light leaks through the filter and passes through the filter. It is absorbed by the color material-containing layer charged in. Since the color material-containing layer contains a red pigment or a red dye, it absorbs light of 350 nm or more and less than 600 nm, but transmits light of 600 to 900 nm used as servo light.
The function of the filter for an optical recording medium having the color material-containing layer and the dielectric vapor-deposited layer preferably reflects the first light and transmits the second light different from the first light. It is preferable that the wavelength of the first light is 350 nm or more and less than 600 nm, and the wavelength of the second light is 600 to 900 nm. For this purpose, it is preferable that the optical recording medium has a structure in which a recording layer, a dielectric deposition layer, a color material-containing 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.

-Cholesteric liquid crystal layer-
The cholesteric liquid crystal layer contains at least a nematic liquid crystal compound and a chiral compound, and contains a polymerizable monomer and, if necessary, other components.

  The cholesteric liquid crystal layer may be a single layer, or two or more layers may be laminated. There is no restriction | limiting in particular as the number of lamination | stacking of this 2 or more layers, According to the objective, it can select suitably, For example, 2-10 layers are preferable. On the other hand, when the number of laminated layers exceeds 10, the production efficiency by coating may decrease, and the object and effect of the present invention may not be achieved.

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 has only a circularly polarized light component in which the rotation direction (clockwise or counterclockwise) of the liquid crystal is coincident with the circular polarization direction and the wavelength is the helical pitch of the liquid crystal. Has a selective reflection characteristic of reflecting 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.
Therefore, each of the cholesteric liquid crystal layers preferably reflects the first light and transmits the second light different from the first light, and the wavelength of the first light is 350 nm or more and less than 600 nm, And it is preferable that the wavelength of said 2nd light is 600-900 nm.

The selective reflection characteristic of the cholesteric liquid crystal layer is limited to a specific wavelength band, and it is difficult to cover the visible light range. That is, the selective reflection wavelength region width Δλ of the cholesteric liquid crystal layer is expressed by the following formula 1.
<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.

  As shown in Equation 1, the selective reflection wavelength bandwidth Δλ depends on the molecular structure of the nematic liquid crystal itself. From Equation 1, if (ne−no) is increased, the selective reflection wavelength bandwidth Δλ can be expanded. However, (ne−no) is usually 0.3 or less, and when it is greater than 0.3, the liquid crystal Other functions such as alignment characteristics, liquid crystal temperature, etc. are insufficient, making it difficult to put into practical use. Therefore, in reality, the selective reflection wavelength bandwidth Δλ of the cholesteric liquid crystal layer is about 150 nm at the maximum, and usually about 30 to 100 nm is preferable.

The selective reflection center wavelength λ of the cholesteric liquid crystal layer is expressed by the following formula 2.
<Formula 2>
λ = (ne + no) P / 2
However, in the said Numerical formula 2, ne and no represent the same meaning as the said Numerical formula 1. P represents the helical pitch length required for one rotation twist of the cholesteric liquid crystal layer.

As shown in Equation 2, the selective reflection center wavelength λ depends on the average refractive index and the helical pitch length P of the cholesteric liquid crystal layer if the helical pitch of the cholesteric liquid crystal layer is constant. Therefore, in order to expand the selective reflection characteristics of the cholesteric liquid crystal layer, the selective reflection center wavelengths of the cholesteric liquid crystal layers are different from each other, and the rotational directions (clockwise or counterclockwise) of the spirals of the cholesteric liquid crystal layers are the same. Preferably there is. The selective reflection wavelength band of each cholesteric liquid crystal layer is preferably continuous. Here, the “continuous” means that there is no gap between the two selective reflection wavelength bands, and the reflectance in this range is substantially 40% or more.
Therefore, the distance between the selective reflection center wavelengths λ of each cholesteric liquid crystal layer is preferably within a range in which each selective reflection wavelength band is continuous with at least one other selective reflection wavelength band.

The filter layer is a normal incidence 0 ° and to be in the range of _{± 20 ° λ 0 ~λ 0 /} cos20 ° ( However, lambda ₀ represents a wavelength of the irradiated light) that light reflectance at not less than 40% preferably, 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) is particularly preferred light reflectance at not less than 40%.
Wherein λ ₀ ~λ ₀ / cos20 °, especially λ ₀ ~λ ₀ / cos40 ° (However, lambda ₀ represents a wavelength of the irradiated light) as long as the light reflectance of 40% or more in the range of the angle of the irradiation light reflected The dependency can be eliminated, and a lens optical system used in a normal optical recording medium can be employed.

Specifically, when three cholesteric liquid crystal layers having different selective reflection center wavelengths and the same spiral rotation directions of the cholesteric liquid crystal layers are stacked, a filter layer having reflection characteristics as shown in FIG. can get. FIG. 10 shows that the reflection characteristic with respect to vertically incident light from the front (0 °) is 40% or more. On the other hand, when it becomes the incident light from the oblique direction, it gradually shifts to the short wavelength side, and when tilted by 40 ° in the liquid crystal layer, the reflection characteristic as shown in FIG. 10 is shown.
Similarly, when two cholesteric liquid crystal layers having different selective reflection center wavelengths and the same spiral rotation directions of the cholesteric liquid crystal layers are laminated, a filter layer having reflection characteristics as shown in FIG. 12 is obtained. . FIG. 12 shows that the reflection characteristic for vertically incident light from the front (0 °) is 40% or more. On the other hand, when it becomes the incident light from the oblique direction, it gradually shifts to the short wavelength side, and when tilted by 20 ° in the liquid crystal layer, the reflection characteristic as shown in FIG. 11 is shown.

Note that the reflection range of λ _{0 to} 1.3λ ₀ shown in FIG. 10 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 an optical recording medium filter. However, when actually using such a large oblique light, the incident angle is within ± 20 °. If servo light is masked and used, servo control can be performed without any problem. If the average refractive index of each cholesteric liquid crystal layer in the filter to be used is sufficiently large, it is easy to design all the incident angles within ± 20 ° in the optical recording medium filter, in which case FIG. It is sufficient to stack two cholesteric liquid crystal layers of λ _{0 to} 1.1λ ₀ shown in FIG.
Accordingly, from the results shown in FIGS. 10 to 13, in the filter for optical recording media of the present invention, even when the incident wavelength is inclined by 0 ° to 20 ° (preferably 0 ° to 40 °), the reflectance is 40% or more. Therefore, it is possible to obtain a filter layer that does not interfere with signal reading.

  Each 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 compound-
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 the 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 subjected to alignment treatment such as rubbing, and then cooling and fixing as it is.

  There is no restriction | limiting in particular as said nematic liquid crystal compound, According to the objective, it can select suitably, For example, the following compound etc. can be mentioned.

  In the above formula, n represents an integer of 1 to 1,000. In addition, in each of the exemplified compounds, those in which the side chain linking group is changed to the following structure can also be cited as suitable.

  Among the above exemplified compounds, the nematic liquid crystal compound is preferably a nematic liquid crystal compound having a polymerizable group in the molecule from the viewpoint of ensuring sufficient curability, and among these, an ultraviolet (UV) polymerizable liquid crystal is preferable. Is 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 compound--
The chiral compound is not particularly limited 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, for example, an isomalide compound, a catechin compound, an isosorbide compound, In addition to the Fencon compound, the carboxylic compound, etc., the following compounds can be exemplified. These may be used alone or in combination of two or more.

  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, etc. are mentioned, for example.

  As content of the said chiral compound, 30 mass% or less is preferable with respect to the total solid content mass of each said cholesteric liquid crystal layer, and 20 mass% or less is more preferable. 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. Examples thereof include polyfunctional monomers such as tetraacrylate and dipentaerythritol hexaacrylate.
Specific examples of the monomer having an ethylenically unsaturated bond include the following compounds. These may be used alone or in combination of two or more.

  As addition amount of the said polymerizable monomer, 50 mass% or less is preferable with respect to the total solid content mass of each 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 thereof include dimethyl ketal and thioxanthone / amine. These may be used alone or in combination of two or more.
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; And Lucylin TPO.

  As addition amount of the said photoinitiator, 0.1-20 mass% is preferable with respect to the total solid content mass of each said cholesteric liquid crystal layer, and 0.5-5 mass% is more preferable. 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% by mass with respect to the total solid mass of each 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 methacrylate, and other polymers having a hydroxyl group. These may be used alone or in combination of two or more.
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. Cyclohexyl group, 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. Polymer, and the like.

  As addition amount of the said binder resin, 80 mass% or less is preferable with respect to the total solid mass of each said cholesteric liquid crystal layer, and 50 mass% or less 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, 10 mass% or less 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.

<Filter for optical recording media>
The filter for optical recording media is a laminate in which the filter layer and other layers appropriately selected as necessary are laminated on a base material.

-Base material-
The shape, structure, size and the like of the substrate are not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape include a flat plate shape and a sheet shape. The structure may be a single layer structure or a laminated structure, and the size can be appropriately selected according to the size of the filter for optical recording media.

There is no restriction | limiting in particular as a material of the said base material, Both an inorganic material and an organic material can be used suitably.
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 resins, cellulose resins, polyarylate resins, polystyrene resins, polyvinyl alcohol resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyacrylic resins, and the like. These may be used alone or in combination of two or more.

The base material may be appropriately synthesized, or a commercially available product 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 base material 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 largely shifted, and the optical system size may be increased.

As a method for forming the filter for an optical recording medium, it can be suitably manufactured by the method for manufacturing an optical recording medium of the present invention, which will be described later. For example, each cholesteric liquid crystal layer coating solution prepared using the solvent described above Each cholesteric liquid crystal layer can be formed by coating on a substrate by a desired coating method.
The most suitable method for mass production is to prepare the base material in the form of a roll, and apply each cholesteric liquid crystal layer coating solution onto the base material, such as bar coating, die coating, blade coating, curtain coating, etc. A type in which coating is performed with a long continuous coater is preferable.

The thickness of each cholesteric liquid crystal layer is, for example, preferably 1 to 10 μm, and more preferably 2 to 7 μm. When the thickness is less than 1 μm, the selective reflectance may not be sufficient, and when it exceeds 10 μm, the uniform alignment of the liquid crystal layer may be disturbed.
In addition, the thickness of the optical recording medium filter (total thickness of each cholesteric liquid crystal layer excluding the base material) is preferably 1 to 30 μm, and more preferably 3 to 10 μm, for example.

  Each cholesteric liquid crystal layer is not particularly limited and can be appropriately selected depending on the purpose. The cholesteric liquid crystal layer coating liquid is applied on the base material, aligned, solidified, and disk-shaped with the base material. And is preferably placed on the second substrate. In addition, 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.

  The optical recording medium filter of the present invention can be used in various fields, and can be suitably used for forming or manufacturing a hologram type optical recording medium. The following hologram type optical recording medium of the present invention and It can be particularly suitably used for the production method, optical recording method and optical reproduction method.

<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.

  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 JP-A-3057082, JP-A-3161230, JP-A-2001-316416, JP-A-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, what utilized the photocrosslinking reaction may be used.

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 roxypropyltriethoxysilane 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 alone or in combination of two or more. 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. If the obtained photopolymer has a sufficiently low viscosity, a recording layer can be formed by casting. On the other hand, in the case of a high-viscosity photopolymer that cannot be cast, the photopolymer is placed on the second substrate using a dispenser, and the photopolymer is pressed to cover the first substrate and spread over the entire surface. A recording layer can be formed.

  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 alone or in combination of two or more.

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; C ₆₀ and C _70, etc. Fullerenes and derivatives thereof; π-conjugated polymers or oligomers such as polyacetylene, polypyrrole, polythiophene, and polyaniline; σ-conjugated polymers or oligomers such as polysilane and polygermane; anthracene, pyrene, phenanthrene, Polycyclic aromatic compounds such Ronen, and the like. These may be used alone or in combination of two or more.

  As a method for forming a recording layer using the photorefractive material, for example, a coating film is formed using a coating solution obtained by dissolving or dispersing the photorefractive material in a solvent, and the solvent is removed from the coating film. By doing so, a recording layer can be formed. Alternatively, the recording layer can be formed by forming a coating film using the photorefractive material that has been heated and fluidized and rapidly cooling the coating film.

  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, a vapor deposition method, a wet film formation method, an MBE (molecular beam epitaxy) method, a cluster ion beam method, a molecular lamination method, an LB method, It can be suitably formed by a printing method, a transfer method, or the like. Among these, a vapor deposition method and a wet film-forming method are preferable.

  There is no restriction | limiting in particular as said vapor deposition method, Although it can select suitably from well-known things according to the objective, For example, a vacuum evaporation method, resistance heating vapor deposition, chemical vapor deposition method, physical vapor deposition method etc. are mentioned. . Examples of the chemical vapor deposition method include a plasma CVD method, a laser CVD method, a thermal CVD method, and a gas source CVD method.

  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 substrate and second substrate>
There is no restriction | limiting in particular as said 1st board | substrate and 2nd board | substrate, According to the objective, it can select suitably, For example, the same board | substrate may be sufficient and a different board | substrate may be sufficient, but at least the shape and magnitude | size are the same It is preferable that Further, the shape, structure, size and the like of the substrate are not particularly limited and can be appropriately selected according to the purpose. Examples of the shape include a disk shape and a card shape. It is necessary to select a material that can ensure the mechanical strength of the medium. 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 first substrate and the second substrate, glass, ceramics, resin, and the like are usually used. 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.
Both the first substrate and the second substrate may be appropriately synthesized, or commercially available products may be used.

  In the second substrate, address-servo areas as a plurality of positioning areas extending linearly in the radial direction are provided at predetermined angular intervals, and a sector-shaped section between adjacent address-servo areas becomes a data area. ing. In the address-servo area, information for performing focus servo and tracking servo by the sampled servo method and address information are recorded in advance by embossed pits (servo pits) (preformat). Note that the focus servo can be performed using the reflective surface of the reflective film. As information for performing the tracking servo, for example, a wobble pit can be used. 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 1st board | substrate and a 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 substrate is less than 0.1 mm, 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 and an excessive load is applied to the drive motor. Sometimes.

-Reflective film-
The reflective film is formed on the servo pit pattern surface of 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.

The formation of the reflective film is not particularly limited and can be appropriately selected according to the purpose. Various vapor deposition methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating 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.

<Other layers>
There is no restriction | limiting in particular as said other layer, According to the objective, it can select suitably, For example, a gap layer is mentioned. Examples of the gap layer include a first gap layer and a second gap layer.

-First gap layer-
The first gap layer is provided between the light absorption layer and the second substrate as necessary, and is formed for the purpose of smoothing the surface of the second substrate. It is also effective for adjusting the size of the hologram generated in the recording layer. 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.
There is no restriction | limiting in particular as thickness of said 1st gap layer, According to the objective, it can select suitably, 1-100 micrometers is preferable.

-Second gap layer-
The second gap layer is provided between the recording layer and the filter layer as necessary. In the second gap layer, if the portion of the point where the information light and the reference light are focused is filled with a photopolymer, excessive exposure of the monomer occurs when the overexposure is performed, and the multiple recording capability may be reduced. There is a function to prevent this harmful effect.
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.

Here, the optical recording medium of the present invention will be described in more detail with reference to the drawings.
<First embodiment>
FIG. 7 is a schematic cross-sectional view showing the configuration of the optical recording medium in the first embodiment of the present invention. In the optical recording medium 21 according to the first embodiment, the servo pit pattern 3 is formed on the second substrate 1 made of polycarbonate resin or glass material, and the servo pit pattern 3 is coated with aluminum, gold, platinum, or the like. Thus, the reflective film 2 is provided. In FIG. 7, the servo pit pattern 3 is formed on the entire surface of the second substrate 1. However, it may be formed periodically as shown in FIG. The maximum height of the servo pit is 1,750 mm (175 nm), which is sufficiently smaller than the thickness of the other layers including the second substrate.

The light absorbing layer 9 is formed by applying a material such as screen printing ink on the reflective film 2 of the second substrate 1 by screen printing or spin coating.
A filter layer 6 is provided on the light absorption layer 9, a recording layer 4 is provided on the filter layer 6, and the first substrate 5 and the second substrate 1 (polycarbonate resin substrate or glass substrate) An optical recording medium 21 is configured by sandwiching the light absorption layer 9, the filter layer 6, and the recording layer 4.

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 three cholesteric liquid crystal layers 6a, 6b, and 6c are laminated. The filter layer 6 which is a laminate of the cholesteric liquid crystal layers may be directly formed on the light absorbing layer 9 by coating, or a film in which four cholesteric liquid crystal layers are laminated on a substrate is formed into an optical recording medium shape. It may be arranged by punching into By three-layer cholesteric liquid crystal _{layer, λ 0 ~λ 0 / cos20 °} , especially λ ₀ ~λ ₀ / cos40 ° (However, lambda ₀ represents a wavelength of the irradiated light) light reflectance is 40% or more in Even if the incident angle changes, the selective reflection wavelength does not shift.
In this embodiment in which the light absorption layer 9 is formed in three layers like the cholesteric liquid crystal layers 6a, 6b and 6c, it is formed between the second substrate 1 and the cholesteric liquid crystal layer 6c and leaks from the cholesteric liquid crystal layer 6c. Since the information light and the reference light are absorbed, the reproduced image is not distorted.

The optical recording medium 21 in the first embodiment may be disk-shaped or card-shaped. In the case of a card shape, there is no need for the servo pit pattern. Further, in this optical recording medium 21, the second substrate 1 is 0.6 mm, the light absorption layer 9 is 100 μm, the filter layer 6 is 2 to 3 μm, the recording layer 4 is 0.6 mm, and the first substrate 5 is 0.2 mm. The thickness is 6 mm, and the total thickness is about 1.93 mm.
The first embodiment also includes an optical recording medium 22 in which a second gap layer 7 is formed between the filter layer 6 and the recording layer 4 as shown in FIGS. The second gap layer 7 is a layer provided to prevent the multiple recording ability from being reduced due to excessive consumption of monomer due to overexposure when the focusing area of the information light and the reference light is filled with a photopolymer. is there.

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 filter layer 6, and the light absorption layer 9, is reflected by the reflective film 2, and again The light absorption layer 9, the filter layer 6, the recording layer 4, and the first substrate 5 are transmitted through the incident / exit surface A. 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 reflection film 2 is reflected almost 100% by the dichroic mirror 13, the servo light is not detected by the CMOS sensor or the CCD 14 for detecting the reproduced image. There is no noise with respect to the diffracted light.
Note that the reflection range of λ _{0 to} 1.3λ ₀ shown in FIG. 10 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 average refractive index of each 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. Since two cholesteric liquid crystal layers of λ _{0 to} 1.1λ ₀ shown in FIG.

  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 enter the recording layer 4 and 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 has three cholesteric liquid crystal layers stacked and has a property of transmitting only red light. Even if there is light that leaks through the filter layer 6, it is absorbed by the light absorption layer 9, so that it is not mixed with the diffracted light, and high-quality diffracted light is obtained. In the first embodiment, it is also effective to provide the second gap layer 7 between the recording layer 4 and the filter layer 6 as shown in FIG. The provision of the second gap layer has the adverse effect of reducing the multiplex recording capability due to excessive consumption of monomers when overexposure is performed when the portion where information light and reference light are focused is filled with a photopolymer. Can be prevented.

<Second Embodiment>
FIG. 9 is a schematic cross-sectional view showing the configuration of the optical recording medium in the second embodiment of the present invention. In the optical recording medium 23 according to the second embodiment, the servo pit pattern 3 is formed on the second substrate 1 from a polycarbonate resin or a glass material, and the surface of the servo pit pattern 3 is coated with aluminum, gold, platinum, or the like. A reflective film 2 is provided. The servo pit pattern 3 has the same height as that of the first embodiment in that the height is usually 1,750 mm (175 nm).

  The difference in structure between the second embodiment and the first embodiment is that, in the optical recording medium 23 according to the second embodiment, the first gap layer 8 is provided between the second substrate 1 and the filter layer 6. And a light absorption layer 9 is formed between the first gap layer 8 and the filter layer 6. That is, the second embodiment is different from the first embodiment in that a part of the first gap layer 8 is the light absorption layer 9.

  The filter layer 6, which is a three-layer laminate of cholesteric liquid crystal layers, is formed on the light absorption layer 9 by forming the light absorption layer 9 on the first gap layer 8 after forming the first gap layer 8. It can form using the thing similar to said 1st embodiment.

  As described above, the second gap layer 7 has a point where the information light and the reference light are focused. If this area is filled with a photopolymer, excessive consumption of monomers due to overexposure occurs, resulting in a decrease in multiple recording capability. Therefore, it is effective to provide a non-reactive and transparent second gap layer.

  In the optical recording medium 23, the second substrate 1 is 1.0 mm, the first gap layer 8 is 90 μm, the light absorption layer 9 is 10 μm, the filter layer 6 is 3 to 5 μm, the second gap layer 7 is 100 μm, The recording layer 4 has a thickness of 0.6 mm, the first substrate 5 has a thickness of 0.4 mm, and the total thickness is about 2.22 mm.

When recording or reproducing information, the optical recording medium 23 having such a structure is irradiated with red servo light, green information light, and recording and reproduction reference light. The servo light enters from the incident / exit surface A, passes through the recording layer 4, the second gap layer 7, the filter layer 6, the light absorption layer 9, and the first gap layer 8, and is reflected by the reflective film 2 to return light. It becomes. The return light again passes through the first gap layer 8, the light absorption layer 9, the filter layer 6, the second gap layer 7, the recording layer 4, and the first substrate 5 in this order, and from the incident / exit surface A. Exit. The emitted return light is used for focus servo, tracking 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. Green information light or the like enters from the incident / exit surface A, passes through the recording layer 4 and the second gap layer 7, is reflected by the filter layer 6, and becomes return light. The return light again passes through the second gap layer 7, the recording layer 4, and the first substrate 5 in this order, and is emitted from the incident / exit surface A. Also during reproduction, not only the reproduction reference light but also the diffracted light generated by irradiating the recording reference light with the reproduction reference light is emitted from the incident / exit surface A without reaching the reflection film 2. The optical operation in the vicinity of the optical recording medium 23 (the objective lens 12, the filter layer 6, the CMOS sensor or the CCD 14 as a detector in FIG. 14) is the same as in the first embodiment (FIG. 7), and the description thereof is omitted. .

(Method for producing optical recording medium)
The method for producing an optical recording medium of the present invention is a method for producing the optical recording medium of the present invention, comprising at least a light absorption layer laminating step and a filter layer forming step. A process, a 1st gap layer formation process, a 2nd gap layer formation process, and also the other process as needed.

-Light absorption layer lamination process-
The light absorption layer laminating step is a step of laminating the light absorption layer by coating the light absorption layer material on the second substrate. When a reflective film is formed on the second substrate, a light absorption layer is laminated on the reflective film. When the first gap layer is laminated on the second substrate, a light absorption layer is laminated on the first gap layer.
There is no restriction | limiting in particular as said coating method, According to the objective, it can select suitably, For example, the coating method etc. which are used for application | coating of the said recording layer, a cholesteric liquid crystal layer, etc. are mentioned. Examples of the coating solution used in the coating method include screen printing ink (magenta manufactured by Dainippon Ink Co., Ltd.).
As the light absorbing layer material, those described in the description of the optical recording medium can be used.

-Filter layer formation process-
The filter layer forming step is a step of forming a filter layer made of a laminate in which at least one of the dichroic mirror layer, a color material-containing layer, a dielectric vapor deposition layer, a cholesteric layer, and the like is laminated on the light absorption layer. is there.

As the filter layer forming step, the optical recording medium filter of the present invention is processed into an optical recording medium shape, and the processed filter is bonded to the light absorbing layer to form a filter layer. It is preferable from the point.
There is no restriction | limiting in particular as a shape of the said optical recording medium, According to the objective, it can select suitably, A disk shape, a card | curd shape, etc. are mentioned.
There is no restriction | limiting in particular as said process, According to the objective, it can select suitably, For example, the cutting process by a press cutter, the punching process by a punch cutter, the baking process by a laser cutter, 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, 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, cellulose pressure sensitive adhesive, and the like.

  The method of laminating each cholesteric liquid crystal layer is not particularly limited and can be appropriately selected from known methods according to the purpose. For example, (1) each cholesteric liquid crystal layer produced separately is A method of laminating via an adhesive or a pressure-sensitive adhesive, (2) a method of laminating the separately prepared cholesteric liquid crystal layers by thermocompression bonding, and (3) each separately prepared cholesteric liquid crystal layer by interfacial compatibility. A method of laminating, (4) a method of laminating a cholesteric liquid crystal layer on a cholesteric liquid crystal layer formed by coating, and (5) a cholesteric liquid crystal layer deposited on a transparent substrate. On top of this, there is a method in which a poval (polyvinyl alcohol: PVA) film is applied and rubbed, and then a cholesteric liquid crystal layer is applied and an alignment aging treatment is performed. That. Among these, the coating method (5) is particularly preferable from the viewpoints of productivity and economy.

  In the laminating method (1), the adhesive and the pressure-sensitive adhesive are not particularly limited and can be appropriately selected according to the purpose. For example, a UV curable adhesive and an acrylic pressure-sensitive adhesive are suitable. It is. 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 the laminating method (2), examples of the thermocompression bonding method include a heat sealing method, an ultrasonic method, an impulse sealing method, and a high frequency bonding method.

In the layering method (3), examples of the compatibility method include a method of applying a solvent that slightly dissolves or swells the cholesteric liquid crystal layer and integrating them by compatibility at the interface.
Solvents that slightly dissolve or swell the cholesteric liquid crystal layer include, for example, aromatics such as toluene, benzene and xylene; alcohols such as methanol and ethanol; cyclic hydrocarbons such as cyclohexane and cyclopentane; acetone and methyl ethyl ketone ( Ketones such as MEK); ethers such as isopropyl ether; esters such as ethyl acetate; chlorinated solvents such as chloroform and dichloromethane; among these, toluene, cyclohexane, cyclopentane, methyl ethyl ketone (MEK) Isopropyl alcohol is particularly preferred.

In the laminating method (4), the coating method is used, and the coating method is not particularly limited and may be appropriately selected depending on the intended purpose. For example, an inkjet method, a spin coating method, a kneader coating method , Bar coating method, die coating method, blade coating method, casting method, dipping method, curtain coating method, and the like.
Formation of the cholesteric liquid crystal layer by the coating method can be suitably performed, for example, by using a solution (coating liquid) in the cholesteric liquid crystal layer material as a solvent (coating and drying).
Furthermore, there are no particular limitations on the conditions for UV curing the coating film as necessary, and it can be appropriately selected according to the purpose. For example, the irradiation ultraviolet rays are preferably 160 to 380 nm, more preferably 250 to 380 nm. preferable. For example, when the exposure illuminance is 10 mW / cm ² , the exposure time is preferably 10 to 600 seconds, and more preferably 10 to 300 seconds. Further, when the exposure illuminance is reduced to 1 mW / cm ² , since the amount of the reaction initiator is usually increased, the exposure time does not change so much, for example, 10 to 600 seconds are preferable, and 10 to 300 seconds are preferable. More preferred.

  In the lamination method (5), as the material for the transparent substrate, either an inorganic material or an organic material can be used. Examples of the inorganic material include glass, quartz, and silicon. 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 resins, cellulose resins, polyarylate resins, polystyrene resins, polyvinyl alcohol resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyacrylic resins, and the like. These may be used individually by 1 type and may use 2 or more types together.

(add to)
The reflective film forming step is a step of forming a reflective film on the second substrate, and details of materials, forming methods, and the like are as described in the description of the optical recording medium.
The recording layer forming step is a step of forming a recording layer on the filter layer, and details of materials, forming methods and the like are as described in the description of the optical recording medium.
The first gap layer forming step is a step of forming a first gap layer on the second substrate. When a reflective film is formed on the second substrate, the first gap layer is formed on the reflective film. It is formed. Details of the material and the forming method of the first gap layer are as described in the description of the optical recording medium.
The second gap layer forming step is a step of forming a second gap layer on the filter layer, and details of the material and forming method of the second gap layer are as described in the description of the optical recording medium. It is.

(Optical recording method and optical reproduction method)
In the optical recording method of the present invention, the optical recording medium of the present invention is irradiated with information light and reference light as a coaxial light beam, and information is recorded on the recording layer by an interference pattern due to interference between the information light and the reference light.
In the optical reproducing method of the present invention, information is reproduced by irradiating the interference pattern recorded on the recording layer with the reproducing light by the optical recording method of the present invention.

In the optical recording method and the optical reproduction method of the present invention, as described above, the information light provided with a two-dimensional intensity distribution and the information light and the reference light having a substantially constant intensity are transferred into the photosensitive recording layer. Information is recorded by generating an optical characteristic distribution inside the recording layer by using the interference pattern formed by the above. On the other hand, when the written information is read (reproduced), the recording layer is irradiated with only the reference light (reproduced light) in the same arrangement as during recording, so that it corresponds to the optical characteristic distribution formed inside the recording layer. The diffracted light having the intensity distribution is emitted from the recording layer, and information is reproduced from the diffracted light.
Here, the optical recording method and the optical reproducing method of the present invention are performed using the optical recording / reproducing apparatus of the present invention described below.

An optical recording / reproducing apparatus used in the optical recording method and the optical reproducing method of the present invention will be described with reference to FIG.
FIG. 15 is an overall configuration diagram of an optical recording / reproducing apparatus according to an embodiment of the present invention. The optical recording / reproducing apparatus includes an optical recording apparatus and an optical 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 also reproduces reference light (reproducing light) for the optical recording medium 21. A pickup 31 for irradiating and detecting diffracted light to reproduce information recorded on the optical recording medium 21, and a drive device 84 that enables the pickup 31 to move in the radial direction of the optical recording medium 21. I have.

  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 21 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; It 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.

  Since the optical recording and reproducing apparatus used in the optical recording method and the optical reproducing method of the present invention uses the optical recording medium of the present invention, the selective reflection wavelength does not shift even if the incident angle changes. The light absorption layer absorbs light leaking from the filter layer, thereby preventing irregular reflection from the reflection film of the optical recording medium by information light and reference light, and preventing the generation of noise. Density recording can be realized.

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

Example 1
-Production of filters for optical recording media-
A polycarbonate film (manufactured by Teijin Kasei Co., Ltd.) having a thickness of 80 μm is used as the substrate, and a plurality of dielectric thin layers having a high refractive index and thin dielectric layers having a low refractive index are alternately formed on the substrate by vacuum deposition. The layers were laminated to produce a filter for an optical recording medium comprising a dielectric vapor deposition layer.
Nine layers (TiO ₂₎ are alternately formed by DC oxygen reactive sputtering using TiO ₂ as the material for the high refractive index dielectric layer and SiO ₂ as the material for the low refractive index dielectric thin layer. / SiO ₂ / TiO ₂ / SiO ₂ / TiO ₂ / SiO ₂ / TiO ₂ / SiO ₂ / TiO ₂ ). The thickness of each layer was 532 nm / 4n, and n was 2.5 for TiO ₂ and 1.5 for SiO ₂ .

-Evaluation of light reflection characteristics-
For each of the obtained filters for optical recording media, the light reflection characteristics were measured using a spectroscopic reflection measuring device (Hamamatsu Photonics, L-5562 as a light source, and Hamamatsu Photonics, PMA-11 as a photo multichannel analyzer). It was measured.
As a result, it was confirmed that the optical recording medium filter can reflect 40% or more of 532 nm light, which is the selected wavelength, with respect to light having an incident angle within ± 20 °.

-Production of optical recording media-
As the second 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. 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.

Next, a polycarbonate film having a thickness of 90 μm was adhered to the reflective film with an ultraviolet curable resin as a first gap layer. On the first gap layer, UV absorbing ink made of magenta clear (DAICURE SSD TF106 PINK) made of magenta clear is used as a light absorbing layer material, and a light absorbing layer having a thickness of 10 μm is formed using a screen printer. It laminated | stacked by apply | coating.
The recording information light and reference light, and the reproduction light (first light) for reproduction use light having a wavelength of 532 nm, and the servo light (second light) uses light of 650 nm. Table 1 shows light transmittances of the first light and the second light in the light absorption layer.
The light transmittance was measured by UV130 manufactured by Shimadzu Corporation.

  Next, the produced optical recording medium filter was punched into a predetermined disk size so that it could be placed on the substrate, and was pasted on the base material surface so as to face the light absorption layer. The bonding was performed using an ultraviolet curable resin or an adhesive so that no air bubbles would enter. The filter layer was formed as described above.

-Preparation of photopolymer coating liquid-
Next, as a recording layer material, a photopolymer coating solution having the following composition was prepared.
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・ 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 ----------------------------------

  The obtained photopolymer coating solution was placed on the filter layer using a dispenser, and a first substrate made of a polycarbonate resin having a diameter of 12 cm and a thickness of 0.6 mm was pressed onto the photopolymer while the end of the disc and the One substrate was bonded with an adhesive. Note that a flange portion is provided at the end of the disc so that the photopolymer layer has a thickness of 500 μm. The thickness of the photopolymer layer is determined by bonding the first substrate to the flange, and an extra portion is provided. The photopolymer overflows and is removed. Thus, an optical recording medium was produced. FIG. 7 is a schematic sectional view showing a form similar to the present embodiment.

<Performance evaluation>
Next, the obtained optical recording medium was mounted on an optical recording / reproducing apparatus as shown in FIG. 15, information was actually recorded and reproduced, and evaluated by the number of reproduced image errors (pieces / frame). . The results are shown in Table 1.

(Example 2)
In Example 1, except that the thickness of the light absorption layer was 5 μm and the thickness of the first gap layer was 95 μm, an optical recording medium of Example 2 was produced in the same manner as in Example 1, and Evaluation was performed in the same manner. The results are shown in Table 1.

(Example 3)
In Example 1, the optical recording medium of Example 2 was prepared in the same manner as in Example 1 except that the thickness of the light absorption layer was 20 μm and the thickness of the first gap layer was 80 μm. Evaluated. The results are shown in Table 1.

Example 4
In Example 1, the optical recording medium of Example 4 was produced in the same manner as in Example 1 except that the thickness of the light absorption layer was 3 μm and the thickness of the first gap layer was 10 μm. And evaluated in the same manner. The results are shown in Table 1.

(Comparative Example 1)
In Example 1, an optical recording medium of Comparative Example 1 was produced in the same manner as in Example 1 except that the light absorption layer was not formed and only the first gap layer having a thickness of 100 μm was formed. It was evaluated in the same manner as above. The results are shown in Table 1.

表１の結果から、実施例１〜実施例４の光記録媒体は、光吸収層を積層することで、誘電体蒸着層からなるフィルタ層で反射しきれなかった情報光及び参照光を効果的に吸収することができ、比較例１に対して、エラーが極めて少なく、ノイズの発生がなく、歪みのない高画質な再生像が得られることが判った。

From the results shown in Table 1, the optical recording media of Examples 1 to 4 effectively stack information light and reference light that could not be reflected by the filter layer composed of the dielectric deposition layer by laminating the light absorption layer. As compared with Comparative Example 1, it was found that there was very little error, no noise was generated, and a high-quality reproduced image without distortion was obtained.

The optical recording medium of the present invention is a hologram type optical recording medium capable of preventing noise from being generated and capable of high-density recording even if information light and reference light leak from a filter layer made of a wavelength selective reflection film. Widely used.
The method for producing an optical recording medium of the present invention can be suitably used as a method for producing various hologram type optical recording media capable of preventing the generation of noise and capable of recording an unprecedented high-density image.
The optical recording method of the present invention can prevent the generation of noise and can record an unprecedented high density image, and is suitably used as a recording method for various hologram type optical recording media.
The optical reproducing method of the present invention can prevent the generation of noise, can reproduce an unprecedented high density image, and is suitably used as a reproducing method for various hologram type optical recording media.

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 an optical recording medium having a conventional filter layer. FIG. 3 is a conceptual diagram illustrating irradiation of information light and servo light on the optical recording medium. FIG. 4 is a conceptual diagram illustrating light reflection of a conventional optical recording medium. FIG. 5 is a conceptual diagram illustrating the function of the light absorption layer of the optical recording medium according to the present invention. FIG. 6 is a perspective view of a part of the optical recording medium according to the present invention. FIG. 7 is a schematic sectional view showing an example of the optical recording medium according to the first embodiment of the present invention. FIG. 8 is a schematic sectional view showing an example of the optical recording medium according to the first embodiment of the present invention. FIG. 9 is a schematic sectional view showing an example of an optical recording medium according to the second embodiment of the present invention. FIG. 10 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. 11 is a graph showing reflection characteristics with respect to incident light from a 40 ° tilt direction in a filter layer in which three cholesteric liquid crystal layers are laminated. FIG. 12 is a graph showing reflection characteristics with respect to incident light from the front (0 °) of a filter in which two cholesteric liquid crystal layers are laminated. FIG. 13 is a graph showing reflection characteristics with respect to incident light from a 20 ° tilt direction in a filter layer in which two cholesteric liquid crystal layers are laminated. FIG. 14 is an explanatory diagram showing an example of an optical system around the optical recording medium according to the present invention. FIG. 15 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 2 Reflecting film 3 Servo pit pattern 4 Recording layer 5 1st board | substrate 6 Filter layer 6a, 6b, 6c Cholesteric liquid crystal layer 6d Quarter wave plate layer 7 Second gap layer 8 First gap layer 9 Light absorbing layer 10 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, 23 Optical recording medium 31 Pickup 33 Light for servo 35 Information Light and reference light 35a Reflected light 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 Outgoing surface FE Focus Error signal TE tracking error signal RF playback signal

Claims (14)

  An optical recording medium comprising a first substrate, a recording layer for recording information using holography, a filter layer, a light absorption layer, and a second substrate in this order.   The optical recording medium according to claim 1, wherein the light absorption layer absorbs first light having any wavelength of 350 nm or more and less than 600 nm and transmits second light having any wavelength of 600 to 900 nm.   The light according to any one of claims 1 to 2, wherein the composition of the light absorption layer includes any one of a dye and a pigment, and the dye and the pigment include at least one of a cyanine dye, a phthalocyanine dye, and an azo dye. recoding media.   The optical recording medium according to claim 1, wherein the light absorption layer has a thickness of 0.1 to 200 μm.   5. The light absorption layer according to claim 1, wherein the light transmittance for the first light is 0.001 to 50%, and the light transmittance for the second light is 50 to 100%. The optical recording medium described.   6. The optical recording medium according to claim 1, further comprising a gap layer between the light absorption layer and the second substrate.   The optical recording medium according to claim 1, wherein the total thickness of the light absorption layer and the gap layer is 1 to 200 μm.   The optical recording medium according to claim 1, wherein the filter layer reflects the first light and transmits a second light different from the first light.   The optical recording medium according to any one of claims 1 to 8, wherein the filter layer comprises at least one of a colorant-containing layer, a dielectric vapor deposition layer, and a cholesteric liquid crystal layer.   The optical recording medium according to claim 1, wherein the first substrate has a servo pit pattern.   11. A method for producing an optical recording medium according to claim 1, wherein a light absorbing layer laminating step of laminating a light absorbing layer on a second substrate, and a filter on the light absorbing layer. A method for producing an optical recording medium, comprising at least a filter layer forming step of forming a layer.   Irradiation of information light and reference light to the optical recording medium according to any one of claims 1 to 10 is performed so that an optical axis of the information light and an optical axis of the reference light are coaxial, An optical recording method, wherein information is recorded on a recording layer by an interference pattern generated by interference between information light and the reference light.   13. An optical reproducing method, wherein the recorded information is reproduced by irradiating the interference pattern recorded on the recording layer by the optical recording method according to claim 12 with the same reproducing light as the reference light. The optical reproduction method according to claim 13, wherein the reproduction information is reproduced by irradiating the reproduction light on the interference pattern so that the reproduction light has the same angle as the reference light used for recording on the optical recording medium.

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