JP2007057985A - Optical recording method and optical recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording method and an optical recording apparatus which are excellent in selective reflection characteristics of two or more kinds of wavelengths without being affected by side lobes even in the case of the occurrence of the side lobes in the vicinity of selection reflection band, and in which the irregular reflection from the reflective film of an optical recording medium by information light and reference light is prevented and the production of noises can be prevented. <P>SOLUTION: The following method is included: light for servo is transmitted through a quarter-wave plate and is converted to circularly polarized light of either left or right in rotation direction and the optical recording medium is irradiated with the converted light and address information is detected; the information light and the reference light are transmitted through either of the combinations of the quarter-wave plate and the quarter-wave plate arranged by intersecting the phase axis orthogonally to the above quarter-wave plate to be converted to the circularly polarized light of the direction opposite to the rotation direction described above and the optical recording medium is irradiated with the converted light described above; the interference image by the interference of the information light and the reference light is formed in the recording layer and is recorded; and only the information light and the reference light are selected and reflected in a cholesteric liquid crystal layer laminated on the optical recording medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical recording method and an optical recording apparatus using wavelength selective reflection characteristics of a filter used in a hologram type optical recording medium capable of high-density image recording.

  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 the hologram type optical recording method, in general, information light given a two-dimensional intensity distribution and reference light having a substantially constant intensity are superposed inside a photosensitive recording layer to form them. Information is recorded by generating a distribution of optical characteristics inside the recording layer using an interference pattern. On the other hand, in reading (reproducing) written information, the recording layer is irradiated with only the reference light in the same arrangement as in recording, and the reproducing light having an intensity distribution corresponding to the optical characteristic distribution formed inside the recording layer is used. This is done by emitting from the recording layer.
In this hologram type optical recording method, since the optical characteristic distribution is three-dimensionally formed in the recording layer, an area where information is written by one information light, an area where information is written by other information light, and Can be partially overlapped, that is, multiple recording is possible. When digital volume holography is used, the signal-to-noise ratio (S / N ratio) of one spot is extremely high, so that the original information can be faithfully reproduced even if the S / N ratio is somewhat lowered by overwriting. 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. One having a recording layer 4 on the reflective film 2 and a first substrate 5 on the recording layer 4 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 Patent Document 3, circularly polarized light is used as information light and reference light, a cholesteric liquid crystal layer or dichroic mirror as a filter layer is provided between the recording layer and the reflective film, and the recording layer and the servo layer are arranged in the thickness direction. It is piled up. 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, when recording on an optical recording medium using such a cholesteric liquid crystal layer, as a characteristic of the cholesteric liquid crystal, the reflectance is relatively large at wavelengths near the outside of the selective reflection band, and as shown in FIG. When a portion (side lobe) that has a reflectance of ˜50% occurs and the two wavelengths to be selectively reflected are relatively close, light of a wavelength that should not be reflected should be reflected by the side lobe. As a result, there is a problem that good separation of wavelengths cannot be obtained and selective reflection characteristics are impaired.

  Therefore, even if a side lobe occurs in the vicinity of the selective reflection band, it is excellent in two or more types of wavelength selective reflection characteristics without being affected by the side lobe, and is irregularly reflected from the reflection film of the optical recording medium by information light and reference light. A hologram type optical recording method and an optical recording apparatus capable of preventing the occurrence of noise and preventing the occurrence of noise have not been realized yet, and it is desired to provide them promptly.

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 is excellent in two or more kinds of wavelength selective reflection characteristics without being affected by the side lobe even if a side lobe occurs in the vicinity of the selective reflection band, and the reflection of the optical recording medium by the information light and the reference light. An object of the present invention is to provide an optical recording method and an optical recording apparatus capable of preventing irregular reflection from a film and preventing generation of noise.

Means for solving the problems are as follows. That is,
<1> Information detection for detecting address information by irradiating servo light through a quarter-wave plate and converting it into circularly polarized light whose rotation direction is either right or left. And a step of arranging the information light and the reference light with respect to the optical recording medium, the 1/4 wavelength plate, and the 1/4 wavelength plate and the 1/4 wavelength plate arranged with their phase axes orthogonal to each other. By passing through one of the four-wavelength plate combinations and converting to circularly polarized light in the rotation direction opposite to the rotation direction, an interference image due to interference between the information light and the reference light is formed on the recording layer. An interference image recording step for recording, and the information of circularly polarized light that is laminated on the optical recording medium and contains nematic liquid crystal molecules, and is converted into the same rotational direction as the helical rotational direction of the nematic liquid crystal molecules. A light reflecting only the light and the reference light. And a selective reflection step of selecting and reflecting on the steric liquid crystal layer.
In the optical recording method according to <1>, the servo light is irradiated to the optical recording medium after being transmitted through the quarter-wave plate and converted into circularly polarized light whose rotation direction is either right or left. An information detecting step for detecting address information, and information light and reference light for the optical recording medium, the quarter wavelength plate, the quarter wavelength plate, and the quarter wavelength plate, The information light and the reference light are transmitted by passing through any combination of quarter-wave plates arranged with the phase axes orthogonal to each other and irradiating the light after converting it into circularly polarized light having a rotational direction opposite to the rotational direction. An interference image recording step for forming and recording an interference image by interference on the recording layer; and a layer that is laminated on the optical recording medium and contains nematic liquid crystal molecules, the same rotation direction as the rotation direction of the spiral of the nematic liquid crystal molecules The circularly polarized information light converted to And a selective reflection step of selectively reflecting the cholesteric liquid crystal layer that reflects only the reference light, and the rotation direction of the servo light, and the information light and the reference light are circularly polarized light having opposite rotation directions. Thus, only the information light and the reference light are selected and reflected by the cholesteric liquid crystal layer, and the circularly polarized servo light in the reverse rotation direction is transmitted through the cholesteric liquid crystal layer. Therefore, a side lobe is generated in the vicinity of the wavelength selective reflection band, and even if the wavelength of the servo light and the wavelength of the side lobe coincide with each other, the rotation direction of the circularly polarized light is different. The light is transmitted without being reflected, and the distortion of the reproduced image and the harmful effects of noise due to the reflection of the servo light with respect to the side lobe are eliminated.
<2> The optical recording method according to <1>, wherein the quarter wavelength plate is disposed on a light incident surface side of the cholesteric liquid crystal layer.
In the optical recording method according to <2>, when the quarter-wave plate is disposed on the light incident surface side of the cholesteric liquid crystal layer, the servo light, the information light, and the reference light are circularly polarized. After the conversion, the light enters the cholesteric liquid crystal layer, and selective reflection is effectively caused by the cholesteric liquid crystal layer.
<3> The servo light is transmitted through a polarizing element that converts linearly polarized light with a fixed polarization direction, and the information light and the reference light are converted into linearly polarized light with a polarization direction different from the polarization direction by 90 °. The optical recording method according to any one of <1> to <2>, wherein the optical element is transmitted through a polarizing element.
In the optical recording method according to <3>, the servo light, the information light, and the reference light incident on the quarter-wave plate are linearly polarized light, the polarization direction of the servo light, the information light, and the information light If the polarization direction of the reference light is different by 90 °, the rotation direction of the servo light is different from the rotation direction of the information light and the reference light by using one quarter wavelength plate. The circularly polarized light in the rotating direction can be obtained.
<4> The optical recording method according to any one of <1> to <3>, wherein the quarter wave plate is an achromatic wave plate.
In the optical recording method according to <4>, when the quarter wave plate is an achromatic wave plate, the wavelength band to be converted into circularly polarized light is widened, and the wavelength range to be used is widened.
<5> The optical recording method according to any one of <1> to <4>, wherein the cholesteric liquid crystal layer transmits the first light and reflects a second light different from the first light.
<6> The optical recording method according to <5>, wherein the wavelength of the first light is 350 to 600 nm and the wavelength of the second light is 600 to 900 nm.
_{<7> λ 0 ~λ 0 /} cos20 ° ( However, lambda ₀ represents a wavelength of the irradiated light) optical recording method according to any one of the light reflectance is 40% or more in the <1> to <6> It is.
_{<8> λ 0 ~λ 0 /} cos40 ° ( However, lambda ₀ represents a wavelength of the irradiated light) optical recording method according to any one the light reflectance is 40% or more of <1> to <7> in It is.
<9> The optical recording method according to any one of <1> to <8>, wherein the cholesteric liquid crystal layer has a thickness of 1 to 30 μm.
<10> The optical recording method according to any one of <1> to <9>, wherein the substrate of the optical recording medium has a servo pit pattern.
<11> The optical recording method according to <10>, wherein the servo pit pattern has a reflective film on the surface.
<12> The optical recording method according to <11>, wherein the reflective film is a metal reflective film.
<13> The optical recording method according to any one of <1> to <12>, further including a first gap layer for smoothing a second substrate surface between the filter layer and the reflective film.
In the optical recording medium according to <13>, by providing the first gap layer between the filter layer and the reflective film, the reflective film is protected and the size of the hologram generated in the recording layer is adjusted. can do.
<14> The optical recording method according to any one of <1> to <13>, wherein a second gap layer is provided between the recording layer and the filter layer.
In the optical recording medium according to <14>, 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.
<15> An interference image formed by irradiating the optical recording medium with the information light and the reference light so that the optical axis of the information light and the optical axis of the reference light are coaxial, and interference between the information light and the reference light Is an optical recording method according to any one of <1> to <14>.

<16> Information detection for detecting address information by irradiating servo light through a quarter-wave plate and converting it into circularly polarized light whose rotation direction is either right or left. And the 1/4 wavelength plate, and the 1/4 wavelength plate and the 1/4 wavelength plate are arranged with the phase axis orthogonal to the optical recording medium. By passing through one of the four-wavelength plate combinations and converting to circularly polarized light in the rotation direction opposite to the rotation direction, an interference image due to interference between the information light and the reference light is formed on the recording layer. Interference information recording means for recording, and the information of circularly polarized light that is laminated on the optical recording medium and contains nematic liquid crystal molecules, and is converted into the same rotational direction as the helical rotational direction of the nematic liquid crystal molecules. Cholesteres that reflect only light and the reference light An optical recording apparatus comprising: selective reflection means for selecting and reflecting by a lick liquid crystal layer.
<17> The optical recording device according to <16>, wherein the quarter wavelength plate is disposed on a light incident surface side of the cholesteric liquid crystal layer.
<18> The servo light is transmitted through a polarizing element that converts linearly polarized light with a certain polarization direction, and the information light and the reference light are converted into linearly polarized light with a polarization direction different from the polarization direction by 90 °. The optical recording device according to any one of <16> to <17>, wherein the optical recording device transmits the light through a polarizing element.
<19> The optical recording device according to any one of <16> to <18>, wherein the quarter wave plate is an achromatic wave plate.
<20> An optical recording medium includes a first substrate, a second substrate, a recording layer that records information on the second substrate using holography, the second substrate, and the recording layer. The optical recording device according to any one of <16> to <19>, wherein the filter layer is a laminate in which two or more cholesteric liquid crystal layers are laminated.
<21> The optical recording device according to any one of <16> to <20>, wherein each cholesteric liquid crystal layer has circularly polarized light separation characteristics.
<22> The optical recording device according to any one of <16> to <26>, wherein the cholesteric liquid crystal layers have the same spiral rotation direction.
<23> The optical recording device according to any one of <16> to <22>, wherein the selective reflection center wavelengths in the cholesteric liquid crystal layers are different from each other.
<24> The optical recording device according to any one of <16> to <23>, wherein the selective reflection wavelength band in the cholesteric liquid crystal layer is continuous.
<25> The optical recording device according to any one of <16> to <24>, wherein the cholesteric liquid crystal layer transmits the first light and reflects a second light different from the first light.
<26> The optical recording apparatus according to <25>, wherein the wavelength of the first light is 350 to 600 nm and the wavelength of the second light is 600 to 900 nm.
_{<27> λ 0 ~λ 0 /} cos20 ° ( However, lambda ₀ represents a wavelength of the irradiated light) optical recording apparatus according to any one of the light reflectance is 40% or more in the <16> to <26> It is.
_{<28> λ 0 ~λ 0 /} cos40 ° ( However, lambda ₀ represents a wavelength of the irradiated light) optical recording apparatus according to any one of the light reflectance is 40% or more in the <16> to <27> It is.
<29> The optical recording device according to any one of <16> to <28>, wherein the cholesteric liquid crystal layer has a thickness of 1 to 30 μm.
<30> The optical recording apparatus according to any one of <16> to <29>, wherein the substrate has a servo pit pattern.
<31> The optical recording apparatus according to <30>, wherein the servo pit pattern has a reflective film on the surface.
<32> The optical recording apparatus according to <31>, wherein the reflective film is a metal reflective film.
<33> The optical recording device according to any one of <16> to <32>, further including a first gap layer for smoothing a second substrate surface between the filter layer and the reflective film.
In the optical recording medium according to <33>, the first gap layer is provided between the filter layer and the reflective film to protect the reflective film and adjust the size of the hologram generated in the recording layer. can do.
<34> The optical recording device according to any one of <16> to <33>, wherein a second gap layer is provided between the recording layer and the filter layer.
In the optical recording medium described in <34>, 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.
<35> An interference image due to interference between the information light and the reference light by irradiating the optical recording medium with the information light and the reference light so that the optical axis of the information light and the optical axis of the reference light are coaxial. Is an optical recording apparatus according to any one of <16> to <34>.

  According to the present invention, various problems in the prior art can be solved, and even if a side lobe occurs in the vicinity of the selective reflection band, it is excellent in two or more types of wavelength selective reflection characteristics without being affected by the side lobe. It is possible to provide an optical recording method and an optical recording apparatus capable of preventing irregular reflection by light from the reflection film of the optical recording medium and preventing the generation of noise.

(Optical recording method)
In the optical recording method of the present invention, address information is obtained by irradiating the optical recording medium with servo light that is transmitted through a quarter-wave plate and converted into circularly polarized light whose rotation direction is either right or left. And an information detecting step for detecting the information light and the reference light with respect to the optical recording medium, the 1/4 wavelength plate, and the 1/4 wavelength plate and the 1/4 wavelength plate being orthogonal to the phase axis. The interference image by interference between the information light and the reference light is transmitted through one of the combinations of the quarter wavelength plates arranged and converted into circularly polarized light having a rotation direction opposite to the rotation direction. An interference image recording step of forming a recording layer on the recording layer and laminating the optical recording medium and containing nematic liquid crystal molecules, wherein the nematic liquid crystal molecules are converted into the same rotational direction as that of the spiral of the nematic liquid crystal molecules. Circularly polarized information light and reference light A selective reflection step of reflecting selected in the cholesteric liquid crystal layer reflecting only, an optical recording method comprising the other steps suitably selected as necessary.

The optical recording method of the present invention can be carried out by the optical recording apparatus of the present invention, and details thereof will be clarified through the description of the recording apparatus.
Addressing information is obtained by irradiating the optical recording medium in the optical recording method of the present invention with servo light transmitted through a quarter-wave plate and converted into circularly polarized light whose rotation direction is either right or left. The information detecting step to detect can be suitably performed by the information detecting means in the optical recording apparatus of the present invention,
In the optical recording method of the present invention, the information light and the reference light are transmitted to the ¼ wavelength plate, the ¼ wavelength plate, and the ¼ wavelength plate so that their phase axes are orthogonal to each other. By transmitting through one of the combination of the arranged quarter wave plates and converting it to circularly polarized light having a rotation direction opposite to the rotation direction, an interference image due to interference between the information light and the reference light is generated. The interference image recording step for forming and recording on the recording layer can be suitably performed by the interference image recording means in the optical recording apparatus of the present invention,
In the optical recording method of the present invention, the circularly polarized information light that is laminated on the optical recording medium and contains nematic liquid crystal molecules, and is converted into the same rotational direction as the helical rotational direction of the nematic liquid crystal molecules, and The selective reflection step of selectively reflecting the cholesteric liquid crystal layer that reflects only the reference light can be suitably performed by the selective reflection means in the optical recording apparatus of the present invention,
The other steps in the hologram recording method of the present invention can be suitably performed by the other means in the hologram recording apparatus of the present invention.

<Information detection means>
The information detection means transmits the servo light through a quarter-wave plate, converts the light into circularly polarized light whose rotation direction is either right or left, and irradiates the optical recording medium, thereby the optical recording This is means for detecting address information of the medium. Before the servo light is emitted from a light source and incident on the quarter-wave plate, a polarizing element that converts linearly polarized light having a certain polarization direction may be transmitted.
The information formed in the address-servo area can be detected by irradiating the servo light with the address-servo area of the substrate of the optical recording medium and reading the reflected light. The information includes information for performing focus servo and tracking servo by a sampled servo system and address information, and is 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.

  As the servo light, coherent laser light emitted from a light source is used. The laser beam is generally linearly polarized light and has a certain polarization direction. When the laser beam is circularly polarized light, it is used after being converted into constant linearly polarized light by a polarizing element or the like. Further, even if the laser light is linearly polarized light, it may be converted to linearly polarized light having a uniform polarization direction through the polarizing element. The reason for converting to the linearly polarized light is to effectively convert the laser light into circularly polarized light by the quarter wavelength plate.

  There is no restriction | limiting in particular as said light source, According to the objective, it can select suitably, For example, a solid laser light oscillator, a semiconductor laser light oscillator, a liquid laser light oscillator, a gas laser light oscillator etc. are mentioned. Among these, a gas laser light oscillator, a semiconductor laser light oscillator, and the like are preferable.

There is no restriction | limiting in particular as said laser beam, According to the objective, it can select suitably, For example, the laser beam which consists of 1 or more types of wavelengths from which a wavelength is selected from 360-850 nm is used. The wavelength is preferably 380 to 800 nm, more preferably 400 to 750, and most preferably 500 to 600 nm where the center of the visible region is most visible.
If the wavelength is less than 360 nm, a clear interference image may not be obtained, and if it exceeds 850 nm, the interference fringes may become fine and a corresponding photosensitive material may not be obtained.

The polarizing element is not particularly limited as long as it can convert light such as laser light into linearly polarized light, and can be appropriately selected according to the purpose. For example, a polarizer, a wavelength plate, a phase plate, a polarizer And a polarizing filter.
The polarization direction of the linearly polarized light varies depending on the polarization element, and the polarization element that can be converted into the polarization direction according to the purpose is used.

-1/4 wave plate
The quarter-wave plate has a function of converting linearly polarized light into circularly polarized light or converting circularly polarized light into linearly polarized light.
There is no restriction | limiting in particular as said quarter wave plate, According to the objective, it can select suitably, For example, an achromatic wave plate, a wave plate, a retardation plate, a phase shifter etc. are mentioned. Among these, an achromatic wave plate that is made of quartz and magnesium fluoride, has little change in retardation due to a change in wavelength, and can be used for a wide wavelength range is preferable.
In order to convert the linearly polarized light into circularly polarized light, as shown in FIG. 4, the linearly polarized light is polarized so that the polarization direction of the linearly polarized light is 45 ° with respect to the fast axis or the slow axis of the quarter-wave plate. Can be converted into circularly polarized light. If the polarization direction of the linearly polarized light is adjusted so that the rotation direction of the circularly polarized light is 45 ° from the fast axis of the quarter wave plate as shown in the upper diagram of FIG. can get. As shown in the lower diagram of FIG. 4, when the polarization direction of the linearly polarized light is adjusted so as to be at a position of 45 ° from the high-speed axis of the quarter-wave plate, right-handed circularly polarized light is obtained. That is, circularly polarized light can be obtained by combining the linearly polarized incident light and the ¼ wavelength plate so that the polarization direction of the linearly polarized light and the fast axis of the ¼ wavelength plate are 45 °. It is done.

The arrangement of the quarter-wave plate can be appropriately selected according to the purpose. For example, the quarter-wave plate is preferably arranged on the light incident surface side of the cholesteric liquid crystal layer. When the incident light is collected by the objective lens, as shown in FIG. 2, the objective lens 12 is disposed on the light incident surface side of the cholesteric liquid crystal layer 6 on the optical path of the light 34. It is preferable to arrange the quarter wavelength plate 35 on the light incident surface side so as to be parallel to the plane of the objective lens.
With such an arrangement, linearly polarized incident light incident on the quarter-wave plate can be converted into circularly polarized light. For example, if the linearly polarized light can be converted into either right circularly polarized light or left circularly polarized light along the polarization direction of the linearly polarized light, and the linearly polarized light is two types and the polarization directions are different by 90 °, By making it incident on the quarter-wave plate, one light can be converted into right circularly polarized light and the other light can be converted into left circularly polarized light.

<Interference image recording means>
The interference image recording means transmits the information light and the reference light to a circularly polarized light having a rotation direction of either right or left through a quarter-wave plate, and irradiates the recording layer with the recording light. Means for forming an interference image in a layer and recording the interference image on the recording layer simultaneously with the formation.
When the information light and the reference light overlap in the recording layer, light interference occurs and interference fringes are generated. The interference fringes contain information such as an image and various data possessed by the information light, and are simultaneously recorded on the recording layer as interference images.
The information light and the reference light are not particularly limited as long as they are coherent laser light, and can be appropriately selected according to the purpose. For example, the wavelength is selected from 360 to 850 nm. Laser light having the above wavelengths is used. The wavelength is preferably 380 to 800 nm, more preferably 400 to 750, and most preferably 500 to 600 nm where the center of the visible region is most visible.
If the wavelength is less than 360 nm, a clear interference image may not be obtained, and if it exceeds 850 nm, the interference fringes may become fine and a corresponding photosensitive material may not be obtained.
The laser beam is generally linearly polarized light and has a certain polarization direction. When the laser light is circularly polarized light, it is used after being converted into linearly polarized light by a polarizing element or the like. Further, even if the laser light is linearly polarized light, it may be converted to linearly polarized light having a uniform polarization direction through the polarizing element. The reason for converting to the linearly polarized light is to effectively convert the laser light into circularly polarized light by the quarter wavelength plate. It is preferable that the polarization direction of the linearly polarized light used for the servo light and the polarization direction of the linearly polarized light used for the information light and the reference light are different from each other by 90 °. If the polarization directions are different from each other by 90 °, the servo light, the information light, and the reference light can be incident on the same quarter-wave plate to obtain circularly polarized lights having different rotation directions. .
Even if the polarization direction of the servo light and the polarization direction of the information light and the reference light are the same, it is possible to obtain circularly polarized light with different rotation directions by using different quarter wavelength plates. it can. Even if the polarization direction is the same, by using a half-wave plate for either the servo light, the information light, or the reference light, the polarization direction is converted to light that differs by 90 °. In this case, the servo light, the information light, and the reference light can be incident on the same quarter-wave plate to obtain circularly polarized light in different rotation directions. Further, even when the servo light, the information light, and the reference light are circularly polarized light in the same rotation direction when transmitted through the quarter-wave plate, any one of the half-wave plates is used. It is possible to reverse the direction of rotation by allowing the light to pass through.

<Selective reflection means>
The selective reflection means reflects light of a specific wavelength by utilizing wavelength selective reflection characteristics of the cholesteric liquid crystal layer that reflect only incident light having a specific wavelength and a circularly polarized light rotation direction, and other than that It is a means for transmitting light of a wavelength.
Specifically, for the light of a specific wavelength, utilizing the optical characteristics of reflecting circularly polarized light in the same rotational direction as the helical rotational direction of the nematic liquid crystal molecules contained in the cholesteric liquid crystal layer, the nematic liquid crystal molecules In the case of right-handed spiral, right circularly polarized light is totally reflected and left circularly polarized light is transmitted. In the case of left-handed spiral, left circularly polarized light is totally reflected and right circularly polarized light is transmitted. Further, there is an optical characteristic that right-circularly polarized reflected light is right-circularly polarized light, and left-circularly polarized reflected light is left-circularly polarized light.

  Due to the optical characteristics, even when the wavelengths of the two kinds of light are close to each other, selective reflection can be accurately performed. For example, when the cholesteric liquid crystal layer is a right-handed spiral, only right circularly polarized light is reflected, and left circularly polarized light is not reflected among the two types of incident light. Specifically, as shown in FIG. 3, as a characteristic of the cholesteric liquid crystal, a portion having a relatively large reflectance at a wavelength near the outside of the reflection band and a reflectance of 10 to 50% (side lobe) When the wavelength of selective reflection is a relatively close wavelength, light of a wavelength that should not be reflected will be reflected by the side lobe, even if good wavelength separation cannot be obtained, If the cholesteric liquid crystal layer is formed in a right-handed spiral so that only right-circularly polarized incident light is reflected in the reflection band and in the side lobe, and incident light having a wavelength in the side lobe portion is left-circularly polarized, In this case, the incident light is not reflected but is transmitted, so that a good separation of wavelengths can be obtained. For example, when the wavelength of one light to be selectively reflected is 532 nm and the wavelength of the other light is 650 nm, the wavelength of the one light is right circularly polarized light, and the wavelength of the other light is left circularly polarized light. Then, only the wavelength of the one light is reflected, and the wavelength of the other light is not reflected by the side lobe portion.

<Other means>
The other means is not particularly limited and can be appropriately selected according to the purpose. For example, as shown in FIG. 8, the optical recording medium 22 is rotated by a spindle servo circuit or the like, and the pickup 31 is interposed. For example, a means for detecting focus, tracking, etc. and continuously recording can be mentioned.

<Cholesteric liquid crystal layer>
The cholesteric liquid crystal layer contains at least a cholesterol derivative, or a nematic liquid crystal compound and a chiral compound, and further contains a polymerizable monomer and, if necessary, other components.

  The cholesteric liquid crystal layer 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. By utilizing 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 or laser light in a certain wavelength band, and the remainder is reflected.

The optical recording medium filter may have a light reflectance of 40% or more at λ0 to λ0 / cos20 ° (where λ0 represents the wavelength of irradiated light) where normal incidence is 0 ° and ± 20 °. It is particularly preferable that the light reflectance is 40% or more at λ0 to λ0 / cos 40 ° (provided that λ0 represents the irradiation light wavelength) in which the normal incidence is 0 ° and is in a range of ± 40 °. If the light reflectance at λ0 to λ0 / cos 20 °, particularly λ0 to λ0 / cos 40 ° (where λ0 represents the irradiation light wavelength) is 40% or more, the angle dependency of the irradiation light reflection can be eliminated. The lens optical system used in the optical recording medium can be employed. For this purpose, it is preferable that the selective reflection wavelength width of the cholesteric liquid crystal layer is large.
Specifically, in the case of a cholesteric liquid crystal layer, the selective reflection wavelength region width Δλ of the cholesteric liquid crystal layer is expressed by the following formula 1, and therefore, a liquid crystal having a large Δn, that is, (ne−no) is used. preferable.
<Formula 1>
Δλ = p · (ne−no) · cos θ
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. θ represents the incident angle of light rays in the cholesteric liquid crystal layer.
In addition, as described in Japanese Patent Application No. 2004-352081, a photoreactive chiral compound having photosensitivity as a chiral compound and capable of greatly changing the helical pitch of liquid crystal by light is used. It is preferable to use a filter for an optical recording medium in which the helical pitch is continuously changed in the thickness direction of the liquid crystal layer by adjusting the compound content and the UV irradiation time.

-Nematic liquid crystal compounds-
The nematic liquid crystal compound is characterized in that the liquid crystal phase is fixed below the liquid crystal transition temperature, the liquid crystal compound having a refractive index anisotropy Δn of 0.10 to 0.40, a polymer liquid crystal compound, and polymerization The liquid crystal compound can be appropriately selected according to the purpose. While it is in 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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  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.

(Optical recording medium)
The optical recording medium of the present invention has a first substrate, a second substrate, a recording layer on the second substrate, and a filter layer between the second substrate and the recording layer. A reflection film, a first gap layer, a second gap layer, and other layers as necessary. As the filter layer, the filter for optical recording media is used.

-Board-
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 substrate material, glass, ceramics, resin, and the like are usually used, but resin is particularly preferable from the viewpoint of moldability and cost.
Examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, and urethane resin. Among these, polycarbonate resin and acrylic resin are particularly preferable from the viewpoints of moldability, optical characteristics, and cost.
The substrate may be appropriately synthesized or a commercially available product may be used.

  The substrate is provided with a plurality of address-servo areas serving as positioning areas extending linearly in the radial direction at predetermined angular intervals, and a sector-shaped section between adjacent address-servo areas is a data area. 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 the said 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.

-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 Japanese Patent Nos. 3070882, 3161230, Japanese Patent Application Laid-Open No. 2001-316416, Japanese Patent Application Laid-Open No. 2000-275859, and the like can be used.

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

  The monomer is not particularly limited and may be appropriately selected depending on the purpose. For example, a radical polymerization type monomer having an unsaturated bond such as an acryl group or a methacryl group, an epoxy ring or an oxetane ring. Examples thereof include a cationic polymerization type monomer having an ether structure. These monomers may be monofunctional or polyfunctional. Moreover, 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 loxypropyltriethoxysilane and compounds represented by the following structural formulas (A) to (E).
These monomers may be used alone or in combination of two or more.

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

  The photopolymer can be obtained by stirring and mixing the monomer, the photoinitiator, and, if necessary, other components and reacting them. 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 so as to cover the second substrate A and spread over the entire surface. Thus, 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 individually by 1 type and may use 2 or more types together.

The charge transport material is a material that transports holes or electrons, and may be a low molecular compound or a high molecular compound.
The charge transport material is not particularly limited and may be appropriately selected depending on the intended purpose. For example, indole, carbazole, oxazole, inoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, thiathiazole, triazole Nitrogen-containing cyclic compounds such as, or derivatives thereof; hydrazone compounds; triphenylamines; triphenylmethanes; butadienes; stilbenes; quinone compounds such as anthraquinone diphenoquinone, or derivatives thereof; 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 individually by 1 type and may use 2 or more types together.

  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 2.0% by volume, more preferably 0.1 to 1.0% by volume based on the total volume of the recording layer. When 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 be deteriorated. In some cases, it is difficult to sufficiently generate light dope due to a decrease in the light transmittance of the light.

  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.

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

-First gap layer-
The first gap layer is provided between the filter layer and the reflective film as necessary, and is formed for the purpose of smoothing the second substrate surface. 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. Moreover, when using what apply | coated and formed on the transparent base material as a filter layer, this transparent base material will work | function also as a 1st gap layer.
There is no restriction | limiting in particular as thickness of the said 1st gap layer, According to the objective, it can select suitably, 1-200 micrometers is preferable.

-Second gap layer-
The second gap layer is provided between the recording layer and the filter layer as necessary.
The material of the second gap layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, triacetyl cellulose (TAC), polycarbonate (PC), polyethylene terephthalate (PET), polystyrene (PS) ), Transparent resin films such as polysulfone (PSF), polyvinyl alcohol (PVA), polymethyl methacrylate = polymethyl methacrylate (PMMA), etc. 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 the 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. 5 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, a servo pit pattern 3 is formed on a polycarbonate resin substrate or a glass substrate 1, and the servo pit pattern 3 is coated with aluminum, gold, platinum or the like to be a reflective film 2 is provided. In FIG. 5, 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 height of this servo pit is 1750 mm (175 nm) at the maximum, which is sufficiently smaller than the thickness of the substrate and other layers.

The first gap layer 8 is formed by applying a material such as an ultraviolet curable resin on the reflective film 2 of the second substrate 1 by spin coating or the like. The first gap layer 8 is effective for protecting the reflective film 2 and adjusting the size of the hologram generated in the recording layer 4. That is, since it is necessary to form an interference area between the recording reference light and the information light in a certain size in the recording layer 4, it is effective to provide a gap between the recording layer 4 and the servo pit pattern 3.
A filter layer 6 is provided on the first gap layer 8, and an optical recording medium 21 is configured by sandwiching the recording layer 4 between the filter layer 6 and a first substrate 5 (a polycarbonate resin substrate or a glass substrate).

In FIG. 5, 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 made of the cholesteric liquid crystal layer may be directly formed on the first gap layer 8 by coating, or a film in which four cholesteric liquid crystal layers are laminated on a substrate is punched into an optical recording medium shape. May be arranged.

  The optical recording medium 21 in the present embodiment may be disk-shaped or card-shaped. In the case of a card shape, there is no need for the servo pit pattern. In this optical recording medium 21, the second substrate 1 is 0.6 mm, the first gap layer 8 is 100 μm, the filter layer 6 is 2 to 3 μm, the recording layer 4 is 0.6 mm, and the first substrate 5 is 0 mm. The total thickness is about 1.9 mm.

  Next, the optical operation around the optical recording medium 22 will be described with reference to FIG. First, the light (red light) emitted from the servo laser is reflected almost 100% by the dichroic mirror 13, converted to linearly polarized light by the polarizing element 9, and incident on the quarter-wave plate 10 to become left circularly polarized light. It is converted and passes through the objective lens 12. Servo light is applied to the optical recording medium 22 by the objective lens 12 so as to be focused on the reflective film 2. That is, the dichroic mirror 13 transmits light having a wavelength of green or blue, and reflects light having a wavelength of red almost 100%. The servo light incident from the light incident / exit surface A of the optical recording medium 22 passes through the first substrate 5, the recording layer 4, the filter layer 6, and the first gap layer 8, and is reflected by the reflective film 2. Again, the light passes through the first gap layer 8, the filter layer 6, the recording layer 4, and the first substrate 5 and is emitted from the incident / exit surface A. The emitted return light passes through the objective lens 12, the polarizing element 9, and the quarter wavelength plate 10, is reflected almost 100% by the dichroic mirror 13, and servo information is detected by a servo information detector (not shown). . The detected servo information is used for focus servo, tracking servo, slide servo, and the like. Since the hologram material constituting the recording layer 4 is not sensitive to red light, even if the servo light passes through the recording layer 4 or the servo light is irregularly reflected by the reflective film 2, the recording layer 4 is not affected. In addition, since the return light of the servo light reflected by the reflective film 2 is reflected almost 100% by the dichroic mirror 13, the servo light is detected by the CMOS sensor or the CCD 14 for detecting the reproduced image. In addition, there is no noise with respect to the reproduction light.

  Further, the information light and the recording reference light generated from the recording / reproducing laser pass through the polarizing element 16 to become linearly polarized light, pass through the half mirror 17 and pass through the quarter-wave plate 15 to the right. It becomes circularly polarized light. The optical recording medium 22 is irradiated with information light and recording reference light through the dichroic mirror 13 so as to generate an interference pattern in the recording layer 4 by the objective lens 12. The information light and the recording reference light are incident from the incident / exit surface A and interfere with each other in the recording layer 4 to generate an interference pattern there. Thereafter, the information light and the recording reference light pass through the recording layer 4 and enter the filter layer 6, but are reflected between the bottom of the filter layer 6 and become return light. That is, the information light and the recording reference light do not reach the reflective film 2. This is because the filter layer 6 includes four cholesteric liquid crystal layers and has a property of transmitting only red light. Alternatively, if the light passing through the filter layer leaks to 20% or less of the incident light intensity, even if the leaked light reaches the bottom surface and becomes return light, it is reflected again by the filter layer and reproduced. The intensity of light mixed into the light is 20% × 20% = 4% or less, which is not substantially a problem. Even if a side lobe occurs in the vicinity of the selective reflection band, the servo light is converted to left circularly polarized light, and is not reflected by the filter layer 6 that reflects only right circularly polarized light. There will be no negative effects of the robe.

<Second Embodiment>
FIG. 6 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 22 according to the second embodiment, a servo pit pattern 3 is formed on a polycarbonate resin or glass substrate 1, and the surface of the servo pit pattern 3 is coated with aluminum, gold, platinum or the like to form a reflective film 2. Is provided. The height of the servo pit pattern 3 is the same as that of the first embodiment in that it is normally 1750 mm (175 nm).

  The difference in structure between the second embodiment and the first embodiment is that the second gap layer 7 is provided between the filter layer 6 and the recording layer 4 in the optical recording medium 22 according to the second embodiment. It is that you are.

  The filter layer 6 made of a cholesteric liquid crystal layer is formed on the first gap layer 8 after the first gap layer 8 is formed, and the same layer as in the first embodiment can be used.

  The second gap layer 7 has 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.

  In the optical recording medium 22, the second substrate 1 is 1.0 mm, the first gap layer 8 is 100 μm, the filter layer 6 is 3 to 5 μm, the second gap layer 7 is 70 μm, the recording layer 4 is 0.6 mm, The first substrate 5 has a thickness of 0.4 mm, and the total thickness is about 2.2 mm.

  When recording or reproducing information, the optical recording medium 22 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 first substrate 5, the recording layer 4, the second gap layer 7, the filter layer 6, and the first gap layer 8, and is reflected by the reflective film 2. Return light. The return light again passes through the first gap layer 8, the filter layer 6, the second gap layer 7, the recording layer 4, and the first substrate 5 in this order, and is emitted from the incident / exit surface A. 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 first substrate 5, 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 reproduction light generated by irradiating the reproduction reference light onto the recording layer 4 is emitted from the incident / exit surface A without reaching the reflection film 2. The optical operation in the periphery of the optical recording medium 22 (the objective lens 12, the filter layer 6, the CMOS sensor as the detector or the CCD 14 in FIG. 7) is the same as that in the first embodiment (FIG. 8), and a description thereof will be omitted. . Even if a side lobe occurs in the vicinity of the selective reflection band, the servo light is converted to left circularly polarized light, and is not reflected by the filter layer 6 that reflects only right circularly polarized light. There will be no negative effects of the robe.

(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 filter layer forming step, a reflective film forming step, a recording layer forming step, and further if necessary. And other steps.

(Light regeneration 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.
The optical reproduction method of the present invention reproduces information by irradiating the interference pattern recorded on the recording layer with the reference 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 reading (reproducing) written information, the recording layer is irradiated with only the reference light in the same arrangement as during recording, and the reproduction has an intensity distribution corresponding to the optical characteristic distribution formed inside the recording layer. Light is emitted from the recording layer as light.
Here, the optical recording method and the 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. 8 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 22 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 22 with information light and recording reference light, and irradiates the optical recording medium 22 with reproduction reference light to reproduce information. A pickup 31 for detecting light and reproducing information recorded on the optical recording medium 22 and a drive device 84 that enables the pickup 31 to move in the radial direction of the optical recording medium 22 are provided.

  The optical recording / reproducing apparatus 100 uses a detection circuit 85 for detecting a focus error signal FE, a tracking error signal TE, and a reproduction signal RF from an output signal of the pickup 31, and a focus error signal FE detected by the detection circuit 85. Based on this, the actuator in the pickup 31 is driven to move the objective lens (not shown) in the thickness direction of the optical recording medium 22 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 the actuator in the pickup 31 to move the objective lens in the radial direction of the optical recording medium 22 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 22.

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 22 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. It is possible to prevent irregular reflection from the reflection film of the optical recording medium by the information light and the reference light, to prevent the generation of noise, and to realize an unprecedented high density recording.

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

Example 1
In order to carry out the optical recording method of the present invention, an optical recording medium filter was prepared and the optical recording medium filter was laminated on a substrate to prepare an optical recording medium.

-Production of filters for optical recording media-
First, a base film was prepared by applying polyvinyl alcohol (trade name MP203, manufactured by Kuraray Co., Ltd.) to a thickness of 1 μm on a polycarbonate film (trade name: Iupil, manufactured by Mitsubishi Gas Chemical Co., Inc.) having a thickness of 100 μm. This base film was passed through a rubbing apparatus to rub the surface of the polyvinyl alcohol film to give liquid crystal alignment ability.

  Next, a cholesteric liquid crystal layer coating solution A having the composition shown in Table 1 below was prepared by a conventional method.

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

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

Next, the cholesteric liquid crystal layer coating solution A was applied onto the base film with a bar coater, dried, and then subjected to orientation aging at 110 ° C. for 20 seconds. Then, it exposed by irradiation energy 500mJ / cm < ² > with the ultrahigh pressure mercury lamp at 110 degreeC, and the cholesteric liquid crystal layer cured film A with a thickness of 3.5 micrometers was formed.
As described above, the optical recording medium of Example 1 having circularly polarized light separation characteristics, the selective reflection center wavelengths in the cholesteric liquid crystal layers are different from each other, and the rotational directions of the spirals in the cholesteric liquid crystal layers are the same in the clockwise direction. A filter was prepared.

-Production of optical recording media-
As the optical recording medium, an optical recording medium comprising a first substrate, a second substrate, a recording layer, and a filter layer was produced.
As the second substrate, a general polycarbonate resin substrate used for DVD + RW having a diameter of 120 mm and a plate thickness of 0.6 mm was used. A servo pit pattern is formed on the entire surface of the substrate, the track pitch is 0.74 μm, the groove depth is 175 nm, and the groove width is 300 nm.
First, a reflective film was formed on the servo pit pattern surface of the second substrate. Aluminum (Al) was used as the reflective film material. A 200 nm-thick Al reflective film was formed by DC magnetron sputtering. A polycarbonate film having a thickness of 100 μm was used as the first gap layer on the reflective film, and adhered with an ultraviolet curable resin.

  Next, the produced optical recording medium filter was punched into a predetermined disk size so that it could be placed on the substrate, and the base film surface was pasted with the servo pit pattern side. 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.

Next, as a recording layer material, the following composition was mixed under a nitrogen stream to prepare a photopolymer coating solution.
-Composition of photopolymer coating solution-
------------------------------------
・ Biscyclohexylmethane diisocyanate 31.5% by mass
Polypropylene oxide triol (molecular weight 1,000) 61.2% by mass
・ Tetramethylene glycol 2.5% by mass
・ 2,4,6-tribromophenyl acrylate 3.1% by mass
Photopolymerization initiator [Ciba Special Chemical Co., Irgacure 784] 0.69% by mass
・ Dibutyl dilaurate tin 1.01% by mass
------------------------------------

  The obtained photopolymer coating liquid was placed on the filter layer using a dispenser, and the first end 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 disk and the first The substrates were 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. 5 is a schematic sectional view showing a form similar to the present embodiment.

-Selective reflection characteristics of optical recording media-
About the obtained optical recording medium, the light reflection characteristic was measured using a spectroscopic reflection measuring instrument (manufactured by Hamamatsu Photonics Co., Ltd., L-5862 as a light source, and photomultichannel analyzer, produced by Hamamatsu Photonics Co., Ltd., PMA-11).
As shown in FIG. 3, in the cholesteric liquid crystal layer of Example 1, it was recognized that side lobes were generated in the vicinity of the selective reflection band. As shown in FIG. 7, the optical recording medium is converted into linearly polarized laser light by the polarizing element 16 as information light and reference light, and an achromatic wave plate is used as the quarter wave plate 15, The laser light having a wavelength of 532 nm converted into the circularly polarized light is irradiated, the laser light having a wavelength of 650 nm is passed through the polarizing element 9 as servo light, an achromatic wave plate is used as the quarter-wave plate 10, It was converted to circularly polarized light and irradiated. As a result, it was confirmed that the servo light was transmitted without being reflected by the side lobe, and was reflected by the reflecting plate 2.

(Comparative Example 1)
An optical recording medium was produced in the same manner as in Example 1.

-Selective reflection characteristics of optical recording media-
About the obtained optical recording medium, the light reflection characteristic was measured using a spectroscopic reflection measuring instrument (manufactured by Hamamatsu Photonics Co., Ltd., L-5862 as a light source, and photomultichannel analyzer, produced by Hamamatsu Photonics Co., Ltd., PMA-11).
As shown in FIG. 3, in the cholesteric liquid crystal layer of Comparative Example 1, it was recognized that side lobes were generated in the vicinity of the selective reflection band. With respect to this optical recording medium, as shown in FIG. 7, as information light and reference light, an achromatic wave plate is used as the quarter wave plate 15 and laser light having a wavelength of 532 nm converted into clockwise circularly polarized light is used. Irradiation was performed, and laser light having a wavelength of 650 nm was irradiated as servo light with the linearly polarized light emitted from the light source without using a quarter wavelength plate. As a result, it has been found that the servo light is reflected by the side lobes, causing distortion in servo detection and causing noise.

The filter for an optical recording medium of the present invention is excellent in two or more kinds of wavelength selective reflection characteristics without being affected by the side lobe even if a side lobe occurs in the vicinity of the selective reflection band, and can prevent the occurrence of noise. It is suitably used as a wavelength selective reflection film in a hologram type optical recording medium capable of recording an unprecedented high density image.
The optical recording medium of the present invention is excellent in two or more types of wavelength selective reflection characteristics without being affected by the side lobe even when a side lobe occurs in the vicinity of the selective reflection band, and can prevent the occurrence of noise. It is widely used as various holographic optical recording media capable of high-density image recording.

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 arrangement of the quarter-wave plate of the present invention. FIG. 3 is a graph showing the reflectance characteristics of the cholesteric liquid crystal layer. FIG. 4 is an explanatory diagram for converting linearly polarized light into circularly polarized light using a quarter wavelength plate. FIG. 5 is a schematic sectional view showing an example of the optical recording medium according to the first embodiment of the present invention. FIG. 6 is a schematic sectional view showing an example of an optical recording medium according to the second embodiment of the present invention. FIG. 7 is an explanatory diagram showing an example of an optical system around the optical recording medium according to the present invention. FIG. 8 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 bit pattern 4 Recording layer 5 1st board | substrate 6 Filter layer 6a, 6b, 6c, 6d Cholesteric liquid crystal layer 7 2nd gap layer 8 1st gap layer 9 Polarizing element 10 1/4 Wavelength plate 12 Objective lens 13 Dichroic mirror 14 Detector 15 1/4 wavelength plate 16 Polarizing element 17 Half mirror 20 Optical recording medium 21 Optical recording medium 22 Optical recording medium 31 Pickup 34 Light 35 1/4 wavelength plate 81 Spindle 82 Spindle motor 83 Spindle servo circuit 84 Drive device 85 Detection circuit 86 Focal servo circuit 87 Tracking servo circuit 88 Slide servo circuit 89 Signal processing circuit 90 Controller 91 Scanning unit 100 Optical recording / reproducing device A Input / output surface FE Focus error signal TE Tracking error Signal RF playback signal

Claims (10)

An information detection step of detecting address information by irradiating the optical recording medium with servo light that is transmitted through a quarter-wave plate and converted into circularly polarized light of either the right or left rotation direction;
The quarter-wave plate in which the information light and the reference light are arranged with respect to the optical recording medium, and the quarter-wave plate and the quarter-wave plate and the quarter-wave plate are arranged with the phase axis orthogonal to each other. By passing through one of the above combinations and converting it into circularly polarized light having a rotational direction opposite to the rotational direction and irradiating it, an interference image due to interference between the information light and the reference light is formed on the recording layer and recorded. An interference image recording step;
It is laminated on the optical recording medium and contains nematic liquid crystal molecules, and reflects only the circularly polarized information light and reference light converted into the same rotational direction as the spiral direction of the nematic liquid crystal molecules. And a selective reflection step of selectively reflecting on the cholesteric liquid crystal layer.   The optical recording method according to claim 1, wherein the quarter-wave plate is disposed on the light incident surface side of the cholesteric liquid crystal layer.   A polarizing element disposed so that servo light is transmitted through a polarizing element that converts linearly polarized light with a certain polarization direction, and information light and reference light are converted into linearly polarized light with a polarization direction different from the polarization direction by 90 °. The optical recording method according to claim 1, wherein the optical recording method is allowed to pass through.   4. The optical recording method according to claim 1, wherein the quarter wave plate is an achromatic wave plate.   The optical recording method according to claim 1, wherein the cholesteric liquid crystal layer transmits the first light and reflects a second light different from the first light.   6. The optical recording method according to claim 5, wherein the wavelength of the first light is 350 to 600 nm, and the wavelength of the second light is 600 to 900 nm. λ ₀ ~λ ₀ / cos20 ° (However, lambda ₀ represents a wavelength of the irradiated light) optical recording method according to any one of claims 1 to 6 light reflectance at not less than 40%. λ ₀ ~λ ₀ / cos40 ° (However, lambda ₀ represents a wavelength of the irradiated light) optical recording method according to any one of claims 1 to 7 light reflectance at not less than 40%.   An optical recording medium is irradiated with the information light and the reference light so that the optical axis of the information light and the optical axis of the reference light are coaxial, and an interference image due to interference between the information light and the reference light is recorded on the recording layer The optical recording method according to claim 1, wherein the optical recording method is formed. Information detecting means for detecting address information by irradiating the optical recording medium with servo light that is transmitted through a quarter-wave plate and converted into circularly polarized light whose rotation direction is either right or left; and
The quarter-wave plate in which the information light and the reference light are arranged with respect to the optical recording medium, and the quarter-wave plate and the quarter-wave plate and the quarter-wave plate are arranged with the phase axis orthogonal to each other. By passing through one of the above combinations and converting it into circularly polarized light having a rotational direction opposite to the rotational direction and irradiating it, an interference image due to interference between the information light and the reference light is formed on the recording layer and recorded. Interference image recording means;
It is laminated on the optical recording medium and contains nematic liquid crystal molecules, and reflects only the circularly polarized information light and reference light converted into the same rotational direction as the spiral direction of the nematic liquid crystal molecules. An optical recording apparatus comprising: selective reflection means for selectively reflecting on a cholesteric liquid crystal layer.

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