WO2017138277A1

WO2017138277A1 - Rewritable hologram recording material, method for recording/erasing hologram, and hologram recording device

Info

Publication number: WO2017138277A1
Application number: PCT/JP2016/089023
Authority: WO
Inventors: 堤　直人; 憲司木梨; 侑樹藪原; さつき元石
Original assignee: 国立大学法人京都工芸繊維大学
Priority date: 2016-02-12
Filing date: 2016-12-28
Publication date: 2017-08-17
Also published as: JPWO2017138277A1; JP6855069B2

Abstract

A rewritable hologram recording material having characteristics in which fast responsiveness and long-term memory are both achieved, wherein the rewritable hologram recording material is characterized by containing: a copolymer obtained by introducing a carbazole azobenzene in a portion of the side chain of an acrylic polymer; and a carbazole azobenzene molecule that is the same type or a different type as the above-noted carbazole azobenzene.

Description

Rewritable hologram recording material, hologram recording / erasing method, and hologram recording apparatus

The present invention relates to a rewritable hologram recording material and a recording medium. The present invention also relates to a hologram recording / erasing method and a hologram recording apparatus for use in the method.

Certain substances are known to have good charge transporting ability, and there is a photorefractive effect as an application example. The photorefractive effect is a change in the refractive index of a substance due to the Pockels effect when irradiated with laser light or the like. Specifically, there is a case where two coherent laser beams are crossed and irradiated onto the medium. The crossed beams interfere with each other, and periodic interference fringes are formed in the medium. In this interference fringe, a bright place and a dark place appear alternately. In the bright place, the medium is photoexcited to generate charge carriers, and the generated charge carriers drift from the bright place by an external electric field applied to the medium. And trapped in the dark. This causes a periodic charge density distribution in the medium. This periodic charge density distribution induces a periodic change in refractive index in the medium via the Pockels effect.

Materials having such a photorefractive effect can be used for imaging of a distorted object, real-time holography, super-multiplex hologram recording, 3D display, 3D printer, optical amplification, and optical neural network using the photorefractive effect. It is used in many fields such as nonlinear optical information processing, pattern recognition, optical limiting, and storage of high-density optical data.

However, in a device using the conventional photorefractive effect, a high electric field of several tens of V / μm (equivalent to a voltage of several kV for an element having a thickness of several MV / cm, for example, 100 μm) is applied to the photorefractive element. Is necessary, and there is a disadvantage that there is a high risk of causing breakdown in a high electric field.

As a material to overcome the above drawbacks, photoisomerization (a phenomenon in which a certain molecule changes to an isomer by absorbing light) can induce a periodic change in refractive index in the absence of an electric field. (Some substances are colored or changed in color by irradiation with light, and then restored by heat or light having a wavelength different from that of the light that caused the coloration or color change. Development of materials composed of substances comprising Here, the substance having the photochromic property usually has a defect that there is a problem in stability and information recorded in a short time is lost.

Therefore, rewritable hologram materials made of a polymer having a polymer azobenzene liquid crystal or a liquid crystal component and a photochromic component are disclosed as materials that overcome the above-mentioned drawbacks (Patent Documents 1 and 2).

Further, as a low molecular hologram material different from the polymer hologram materials disclosed in

Patent Documents

1 and 2, a carbazole azobenzene moiety is present in the skeleton, and a substituent such as a nitro group or a cyano group is present at the para position of benzene. A material composed of an introduced low-molecular compound is disclosed (Patent Document 3). In addition, carbazole azobenzene (3-[(4-nitrophenyl) azo] -9H-carbazole-9-ethanol (NACzE)), in which the substituent at the para-position of benzene is a nitro group, is used as a material for rewritable hologram displays. It is disclosed that hologram recording is performed using a material dispersed and dissolved in methyl methacrylate (PMMA) as a photorefractive material (

Patent Documents

4 and 5,

Non-Patent Documents

1, 2, and 3). However, the above-described material in which carbazole azobenzene is dispersed and dissolved has a defect that the recorded hologram information disappears over time and lacks memory.

Therefore, as a means for solving the above-mentioned drawbacks, development of a rewritable hologram material having improved memory characteristics, including a copolymer having carbazole azobenzene in the side chain and an acrylic polymer such as PMMA as the main chain, has been developed. ing.

Japanese Patent Publication “JP 2001-265199 A (published on September 28, 2001)” Japanese Patent Publication “Japanese Unexamined Patent Application Publication No. 2004-252327 (published on September 9, 2004)” Japanese Patent Publication “Japanese Unexamined Patent Application Publication No. 2014-142393 (published on August 7, 2014)” International Publication Gazette “WO2013 / 080883 (released on June 6, 2013)” Japanese Patent Gazette “Japanese Unexamined Patent Application Publication No. 2014-240861 (December 25, 2014)”

However, although the material containing the above-mentioned copolymer has improved memory performance, it has a problem of low photoresponsiveness and a long light irradiation time required for start-up.

In addition, there is a problem that it takes time to erase the recorded hologram information in the case of a material having a good memory property such as the above-mentioned copolymer material. In other words, there has been no report that the problem of achieving both responsiveness during recording and memory performance and solving the problem of erasing recorded data quickly can be solved. For example, the erasure is usually performed by irradiation with linearly polarized light. However, in the erasure described above, the hologram information is recorded again after erasure, and the erasure is repeated again. There is a problem that it takes time to erase the hologram information, and the time required for re-recording and the response speed at the time of re-recording are lowered.

In order to solve the above problems, the present inventors have conducted intensive research and introduced a copolymer having carbazole azobenzene introduced into a part of the side chain of the acrylic polymer, and the copolymer. The inventors have found that by containing a carbazole azobenzene molecule that is the same or different from carbazole azobenzene, the photoresponsiveness can be improved while maintaining the memory property, and the present invention has been conceived. In addition, the present inventors use circularly polarized light for erasing recorded hologram information, so that diffraction efficiency is reduced even when hologram information is recorded again after erasure and erased again. Thus, the inventors have found that the time required for erasing can be shortened and the time until recording can be performed again can be shortened, and the present invention has been achieved.

The present invention includes a rewritable hologram recording material, a recording medium, a method for recording / erasing a hologram, and a hologram recording apparatus described in [1] to [14] below.
[1] A copolymer obtained by introducing carbazole azobenzene into a part of a side chain of an acrylic polymer, and a carbazole azobenzene molecule that is the same or different from the carbazole azobenzene introduced into the copolymer. A rewritable hologram recording material.
(Here, carbazole azobenzene is represented by the following formula (1).)

[2] The rewritable hologram recording material according to [1], wherein the carbazole azobenzene is carbazole azobenzene in which X in the formula (1) is a cyano group, a nitro group or a methoxy group.
[3] The rewritable hologram recording material according to [1] or [2], wherein the carbazole azobenzene introduced into the side chain of the copolymer is the same as the carbazole azobenzene molecule.
[4] The rewritable hologram recording according to any one of [1] to [3], wherein the acrylic polymer is at least one selected from the group consisting of polymethyl methacrylate, polyethyl methacrylate, and polymethyl acrylate. material.
[5] The sum of the group derived from the carbazole azobenzene and the carbazole azobenzene molecule contained in the copolymer with respect to the total weight of the copolymer and the carbazole azobenzene molecule contained in the rewritable hologram recording material molar concentration, 5 × ¹⁰ -4 mol / g or more, 2.0 × is ¹⁰ -3 mol / g or less, (1) a rewritable hologram recording material according to any one of to [4].
[6] Any one of [1] to [5], wherein a molar ratio of the carbazole azobenzene molecule to a group derived from carbazole azobenzene contained in the copolymer is 0.5 or more and 2.0 or less. 2. The rewritable hologram recording material described in 1.
[7] The rewritable hologram recording material according to any one of [1] to [6], wherein the copolymer has a weight average molecular weight of 10,000 or more and 200,000 or less.
[8] A recording medium having a hologram recording element,
The hologram recording element contains a rewritable hologram recording material according to any one of [1] to [7].
[9] In a hologram recording element containing a rewritable hologram recording material, a striped pattern on a spatial light modulator (SLM) is formed using a single beam of laser light, or coherent object light and reference light. Are caused to form interference fringes in the hologram recording element, and a hologram is recorded on the hologram recording element by irradiating polarized light to the hologram recording element. A method for recording and erasing a hologram including a erasing step,
The rewritable hologram recording material is a copolymer obtained by introducing carbazole azobenzene into a part of the side chain of an acrylic polymer, and
For a hologram recording element made of a material further containing a carbazole azobenzene molecule of the same kind or different from the carbazole azobenzene introduced into the copolymer,
A method of recording and erasing a hologram, wherein at least the step of erasing the hologram is performed by irradiation with circularly polarized light.
[10] The hologram recording / erasing method according to [9], wherein the object light and the reference light in the recording step are circularly polarized light.
[11] The method according to [9] or [10], further including a step of reproducing the recorded hologram by irradiating the hologram recording element on which the hologram is recorded with polarized light having the same phase as the reference light. Hologram recording / erasing method.
[12] The hologram recording / erasing method according to [11], wherein in the step of reproducing the recorded hologram, the polarized light applied to the recording element on which the hologram is recorded is circularly polarized light.
[13] A hologram recording apparatus for using a hologram recording / erasing method by two-beam interference in order to perform the hologram recording / erasing method according to any one of [9] to [12]. ,
A hologram recording apparatus comprising: a mechanism for irradiating circularly polarized light to the hologram recording element through the circularly polarizing element at least in the erasing step.
[14] The hologram recording device according to [13], wherein the mechanism for irradiating the circularly polarized light is a λ / 4 plate.

The rewritable hologram recording material of the present invention has excellent photoresponsiveness while maintaining excellent memory properties capable of holding recorded data for a long time or improving memory properties, and is capable of recording holograms. There is an effect that the rise time can be shortened.

In addition, the hologram recording / erasing method of the present invention can reduce the time required for erasing the hologram, and prevent a decrease in response speed and diffraction efficiency in re-recording after the erasure, which usually decreases. There is an effect that can be.

In Examples 1 to 3 and Comparative Examples 1 and 2, writing light: 300 mW / 532 nm, reading light (probe light): 1 mW / 640 nm, a striped pattern on the spatial light modulator (SLM) Shows the relationship between diffraction efficiency and time from the start of light irradiation in the short-time rise from the start of light irradiation, which is the result of measuring the rise of the diffracted light when irradiating a rewritable hologram recording material with laser light. FIG. In Examples 1 to 3 and Comparative Examples 1 and 2, writing light: 300 mW / 532 nm, reading light (probe light): 1 mW / 640 nm, a striped pattern on the spatial light modulator (SLM) Relationship between diffraction efficiency and time from the start of light irradiation when a long time has elapsed from the start of light irradiation, which is the result of measuring the rise of diffracted light when irradiated to a rewritable hologram recording material using laser light FIG. In Examples 1 to 3 and Comparative Examples 1 and 2, since the lattice spacing is wide with respect to the lattice thickness, Raman-Nath diffraction is obtained, and the theoretical maximum diffraction efficiency is 16%. In Example 4, a writing grating (object light and reference light): 25 mW / 532 nm, reading light (probe light): <1 mW / 632.8 nm, using a two-beam interference, a diffraction grating was produced, and its diffraction It is a figure which shows the relationship between the time from the first light irradiation and the diffraction efficiency which are the results of measuring the time profile of the diffraction intensity from the grating. In Example 4, since the grating interval is narrower than the grating thickness, Bragg diffraction occurs, and the theoretical maximum diffraction efficiency is 100%. In Example 5, writing light (object light and reference light): 25 mW / 532 nm, reading light (probe light): <1 mW / 632.8 nm, a two-beam interference was used to produce a diffraction grating, and its diffraction It is a figure which shows the relationship between the time from the first light irradiation and the diffraction efficiency which are the results of measuring the time profile of the diffraction intensity from the grating. In Example 5, since the grating interval is narrower than the grating thickness, Bragg diffraction occurs, and the theoretical maximum diffraction efficiency is 100%. In Comparative Example 3, writing light (object light and reference light): 25 mW / 532 nm, reading light (probe light): <1 mW / 632.8 nm, a diffraction grating is produced using two-beam interference, and its diffraction It is a figure which shows the relationship between the time from the first light irradiation and the diffraction efficiency which are the results of measuring the time profile of the diffraction intensity from the grating. In Comparative Example 3, since the grating interval is narrower than the grating thickness, Bragg diffraction occurs, and the theoretical maximum diffraction efficiency is 100%. In Comparative Example 4, a writing grating (object light and reference light): 25 mW / 532 nm, reading light (probe light): <1 mW / 632.8 nm, a two-beam interference was used to produce a diffraction grating, and its diffraction It is a figure which shows the relationship between the time from the first light irradiation and the diffraction efficiency which are the results of measuring the time profile of the diffraction intensity from the grating. In Comparative Example 4, since the grating interval is narrower than the grating thickness, Bragg diffraction occurs, and the theoretical maximum diffraction efficiency is 100%. It is a figure which shows the schematic structure of the hologram recording apparatus of this invention.

[Embodiment 1: Rewriteable hologram recording material]
The rewritable hologram recording material according to Embodiment 1 of the present invention is introduced into a copolymer obtained by introducing carbazole azobenzene (NACzE) into a part of the side chain of an acrylic polymer, and the copolymer. It contains the same or different carbazole azobenzene molecule as the carbazole azobenzene.

In addition, in this specification, carbazole azobenzene which is not introduced into the copolymer other than carbazole azobenzene introduced into the copolymer and is contained in the rewritable hologram recording material of the present invention in the form of a molecule. Is also referred to as a “carbazole azobenzene molecule”.

The copolymer and the carbazole azobenzene molecule contained in the rewritable hologram recording material of the present invention have photochromic properties. When the copolymer and the carbazole azobenzene molecule have photochromic properties, the entire rewritable hologram recording material of the present invention also has photochromic properties.

In the copolymer, the constituent element derived from the carbazole azobenzene constitutes a part of the side chain of the copolymer. The carbazole azobenzene may be one type or two or more types.

A copolymer obtained by introducing carbazole azobenzene into a part of the side chain of the acrylic polymer in the rewritable hologram recording material of the present invention (hereinafter also referred to as “copolymer A in the present invention”) has the following formula ( As shown in 2), it has a structure in which carbazole azobenzene is introduced into part of the side chain of the acrylic polymer.

The acrylic polymer constituting the copolymer A in the present invention is a polymer obtained by polymerizing an acrylic ester or methacrylic ester as a monomer (hereinafter also referred to as “acrylic molecule”). It is. Although the said monomer is not specifically limited, For example, methyl acrylate (MA), methyl methacrylate (MMA), ethyl methacrylate (EMA) etc. can be mentioned. That is, examples of the acrylic polymer constituting the copolymer in the present invention include polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), and polyethyl methacrylate (PEMA). The acrylic polymer constituting the copolymer in the present invention may be a polymer obtained by polymerizing one kind of monomer or a copolymer obtained by polymerizing two or more kinds of monomers.

The carbazole azobenzene introduced into the side chain of the copolymer A in the present invention or contained in the form of a molecule in the rewritable hologram recording material of the present invention (hereinafter also referred to as “carbazole azobenzene molecule”) And a skeleton structure represented by the following formula (1).

The carbazole azobenzene is not particularly limited as long as it has a skeleton structure represented by the above formula (1). For example, X in the above formula (1) is a nitro group (—NO ₂ ), a cyano group ( -CN), a methoxy group (-OCH ₃ ), an amino group (-NH ₂ ), a hydroxy group (-OH), and carbazole azobenzene, wherein X is a nitro group, a cyano group or Carbazole azobenzene having a structure that is a methoxy group is preferable, and carbazole azobenzene having a structure in which X is a cyano group or a methoxy group is more preferable. The carbazole azobenzene may be one type or two or more types.

Further, the carbazole azobenzene introduced into the side chain of the copolymer in the present invention and the carbazole azobenzene (carbazole azobenzene molecule) contained in the form of molecules in the rewritable hologram recording material of the present invention are of the same type. Although they may be different or different, they are preferably the same from the viewpoint of the compatibility between the copolymer and the carbazole azobenzene molecule in the rewritable hologram recording material of the present invention. Therefore, in the rewritable hologram recording material of the present invention, the carbazole azobenzene and the carbazole azobenzene molecule introduced into the side chain of the copolymer of the present invention are particularly preferably one kind of carbazole azobenzene.

In the rewritable hologram recording material of the present invention, a group derived from carbazole azobenzene contained in the copolymer with respect to the total weight of the copolymer and the carbazole azobenzene molecule contained in the rewritable hologram recording material, The total molar concentration with the carbazole azobenzene molecule is 5 × 10 ⁻⁴ mol / g or more and 2.0 × 10 ⁻³ mol / g or less, more preferably 7 × 10 ⁻⁴ mol / g or more, It is 1.5 × 10 ⁻³ mol / g or less, more preferably 1 × 10 ⁻³ mol / g or more and 1.3 × 10 ⁻³ mol / g or less.

In the rewritable hologram recording material of the present invention, the molar ratio of the carbazole azobenzene molecule to the group derived from carbazole azobenzene contained in the copolymer is 0.5 or more and 2.0 or less, preferably 0.8. It is 7 or more and 1.6 or less, More preferably, it is 0.9 or more and 1.2 or less.

The weight average molecular weight (Mw) of the copolymer in the present invention is preferably 10,000 to 100,000, and more preferably 20,000 to 100,000. When the weight average molecular weight of the copolymer in the present invention is in the above range, the rewritable hologram recording material of the present invention is suitable as a rewritable hologram recording material, which is a film having a preferable thickness described later. Is preferable.

Further, the dispersion degree (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the molecular weight distribution of the copolymer in the present invention is smaller in terms of uniformity of the rewritable hologram recording material of the present invention. Specifically, the value of Mw / Mn is preferably 1 to 3.

The rewritable hologram recording material of the present invention is preferably in the form of a film (thin film). The film thickness is more preferably 10 μm to 200 μm, and further preferably 20 μm to 100 μm.

The rewritable hologram recording material of the present invention may contain various additives in addition to the copolymer and the carbazole azobenzene molecule. The additive may be any additive that can be generally used in a hologram recording material, and is not particularly limited. Examples of the additive include (photo) sensitizers, nonlinear optical dyes, plasticizers, and photosensitive dyes.

The reason why the rewritable hologram recording material containing the copolymer is excellent in memory property is that the orientation of the carbazole azobenzene introduced into the side chain of the copolymer is more limited than the free carbazole azobenzene molecule. Therefore, it is considered that the photo-aligned carbazole azobenzene is difficult to return to the alignment before the light irradiation even after a lapse of time. However, as for details, we have to wait for more detailed elucidation of the operation in the future.

Since the rewritable hologram recording material of the present invention contains the copolymer and carbazole azobenzene molecule of the present invention, the memory performance is further improved, and in addition, the photoresponsiveness is improved, and the start of hologram recording Time is shortened.

The reason why the above-mentioned memory property is further improved is that the photo-oriented carbazole azobenzene molecule forms a mesophase in which the carbazole azobenzene molecule introduced into the side chain of the copolymer and the free carbazole azobenzene molecule interact with each other. It is conceivable that the carbazole azobenzene that has been photo-aligned is prevented from returning to the alignment prior to light irradiation over time by becoming stable in terms of energy (pinning effect).

In addition, the degree of freedom of orientation of the carbazole azobenzene molecule is greater than that of the carbazole azobenzene introduced into the side chain of the copolymer, and the photo orientation of the carbazole azobenzene molecule is introduced into the side chain of the copolymer upon light irradiation. It occurs in preference to carbazole azobenzene. From the above-mentioned matters, it is considered that the start of hologram recording of the rewritable hologram recording material of the present invention is accelerated by photoalignment of the carbazole azobenzene molecules even with short-time light irradiation. However, as for details, we have to wait for more detailed elucidation of the operation in the future.

[Method for producing rewritable hologram recording material]
The method for producing the rewritable hologram recording material of the present invention is not particularly limited, and methods known to those skilled in the art can be used. The rewritable hologram recording material of the present invention can be produced, for example, by a method including the following steps (1) and (2). In addition, operation in each process shown below can be implemented by a method known to those skilled in the art.

<Step (1) Preparation of Copolymer>
The method for preparing a copolymer obtained by introducing carbazole azobenzene into a part of the side chain of the acrylic polymer contained in the rewritable hologram recording material of the present invention is not particularly limited, but includes, for example, the following steps: A method can be mentioned.

Step (i): Dissolving carbazole azobenzene in tetrahydrofuran (THF), stirring in a state cooled to 0 ° C., and adding N, N-dimethyl-4-aminopyridine (DMAP) and triethylamine;
Step (ii): 1 mL each of acrylate or methacrylate is added dropwise to the solution obtained in step (i) at a temperature of 0 ° C. or less, for example, four times every 15 minutes, and the reaction mixture is added. Returning to room temperature with stirring and stirring overnight;
Step (iii): A step of removing the solvent from the solution obtained in Step (ii) by drying under reduced pressure, and dissolving the resulting crude product in chloroform;
Step (iv): The chloroform solution obtained in step (iii) is washed several times with a saturated aqueous sodium hydrogen carbonate solution and distilled water, dried over anhydrous magnesium sulfate, and a carbazole azobenzene- (meth) acrylic acid compound is obtained. Obtaining step;
Step (v): The carbazole azobenzene- (meth) acrylic acid compound obtained in step (iv) is dissolved in dry dimethylfuran (DMF), and then acrylic acid or methacrylic acid, and azoisobutylnitrile as a polymerization initiator. (AIBN) is added, the copolymerization reaction is started, freeze deaeration is performed, the mixture is stirred at 60 ° C. for 15 hours, and the liquid temperature is returned to room temperature to stop the copolymerization reaction;
Step (vi): Reprecipitation of the copolymer obtained from the solution obtained by dissolving the copolymer obtained by introducing carbazole azobenzene into a part of the side chain of the acrylic polymer obtained in the step (v). Recovering the copolymer by filtering, filtering and drying.

<Step (2): Preparation of rewritable hologram recording material>
The rewritable hologram recording material of the present invention can be prepared using the copolymer prepared in the step (1) and carbazole azobenzene molecules. Although the preparation method is not specifically limited, For example, the following method can be used.

Step (vii): Each component of the rewritable hologram recording material of the present invention containing the copolymer and carbazole azobenzene molecules obtained in step (vi) is dissolved in a solvent having a boiling point of 100 ° C. or more and applied. Obtaining a solution;
Step (viii): A step of preparing a thin-film rewritable hologram recording material by applying the coating solution obtained in the step (vii) onto a substrate and removing the solvent. Here, the method for removing the solvent is not particularly limited, but for example, a method for obtaining a cast film on a plate, specifically, casting a solution in which each component is dissolved on a glass plate, Thereafter, the solvent is evaporated at room temperature, followed by natural drying overnight, followed by vacuum drying at a high temperature using a vacuum dryer or the like to further evaporate the solvent.

In addition, after the solvent is distilled off, spacers (for example, polyimide, thickness: 50 μm) are arranged at the four corners, for example, and another glass substrate is placed thereon, and vacuum is applied while applying appropriate heat (temperature). A sandwich-type rewritable hologram recording material can also be prepared by pressure bonding with a press.

[Embodiment 2: Recording medium]
A recording medium according to Embodiment 2 of the present invention is a recording medium having a hologram recording element, and the hologram recording element includes the rewritable hologram recording material according to Embodiment 1 of the present invention. . Specifically, the recording medium according to Embodiment 2 of the present invention is a hologram formed by forming the rewritable hologram recording material according to Embodiment 1 of the present invention into a sheet-like film sandwiched between transparent plates such as glass. Contains a recording element. Therefore, the recording medium of the present invention contains a rewritable hologram recording material excellent in both photoresponsiveness and memory performance as a hologram recording element, has a short rise time when recording a hologram, and Long-term storage is possible. As a method for producing the recording medium of the present invention, a method common to those skilled in the art, for example, a die, a doctor, etc., except that the rewritable hologram recording material according to Embodiment 1 of the present invention is used as the hologram recording element. It can be manufactured by a sheet forming method using a blade or the like.

[Embodiment 3: Hologram Recording / Erasing Method]
In the hologram recording / erasing method according to Embodiment 3 of the present invention, a stripe pattern on a spatial light modulator (SLM) is converted into a single beam of laser light in a hologram recording element containing a rewritable hologram recording material. Or by causing a coherent object beam and reference beam to interfere (two-beam interference) to form interference fringes in the hologram recording element, and recording the hologram on the hologram recording element, and by applying polarized light. A hologram recording / erasing method including a step of erasing the hologram, wherein the rewritable hologram recording material is a copolymer obtained by introducing carbazole azobenzene into a part of a side chain of an acrylic polymer, and the above The same or different carbazole azobenzene as the above carbazole azobenzene introduced into the copolymer The hologram recording element made of a material that further contains molecules, characterized in that at least a step of erasing the hologram by irradiation of circularly polarized light.

The acrylic polymer may be one type or two or more types.

The carbazole azobenzene may be one kind or two or more kinds. Further, the carbazole azobenzene molecule may also be one kind or two or more kinds.

In the hologram recording and erasing method of the present invention, the spatial light modulator (SLM) is a two-dimensional array of microelements called “light modulation elements”, and a space such as the amplitude, phase, and polarization of light from the light source. It is a device that modulates light by electrically controlling the general distribution. Examples of the spatial light modulator (SLM) include products of Holoeye and Hamatsu Photonics.

In the hologram recording and erasing method of the present invention, the recorded hologram is erased by recording circularly polarized light having the same phase as either the object light or the reference light used for recording the hologram. This is done by irradiating the element.

In the hologram recording / erasing method of the present invention, the rewritable hologram recording material is introduced into a copolymer formed by introducing carbazole azobenzene into a part of the side chain of the acrylic polymer, and into the side chain of the copolymer. The hologram recording element is made of a material further containing the same kind or different kind of carbazole azobenzene molecule as the carbazole azobenzene, that is, the rewritable hologram recording material according to Embodiment 1 of the present invention.

The copolymer and carbazole azobenzene molecule obtained by introducing carbazole azobenzene into a part of the side chain of the acrylic polymer described above are the copolymer and carbazole in the rewritable hologram recording material according to Embodiment 1 of the present invention. Copolymers and molecules similar to azobenzene molecules can be used.

Further, a copolymer obtained by introducing carbazole azobenzene into a part of the side chain of the acrylic polymer is prepared in the step described in step (1) in the above [Method for producing rewritable hologram recording material]. Can be done. Furthermore, a rewritable hologram recording material containing a copolymer obtained by introducing carbazole azobenzene into a part of the side chain of the above-mentioned acrylic polymer and a carbazole azobenzene molecule is the above [Method for producing rewritable hologram recording material]. Can be produced according to the method described in 1).

The hologram recording / erasing method of the present invention reduces the time required for erasing the hologram by performing at least the hologram erasing step by irradiation with circularly polarized light, and the response speed and diffraction in the re-recording after the erasing. A decrease in efficiency can be prevented.

When erasing a recorded hologram by irradiation with linearly polarized light, the alignment of the molecules or groups having photochromic properties in the hologram recording material is fixed by irradiation with linearly polarized light for erasure, and the erasure and recording are performed again. By repeating, it is considered that the diffraction efficiency is gradually lowered, the response speed is lowered, and it is necessary to apply light irradiation and heat for a long time in order to obtain a re-recordable state.

On the other hand, when the recorded hologram is erased by irradiation with circularly polarized light, the orientation of molecules or groups having photochromic properties in the hologram recording material is randomized and the orientation is not fixed. It is considered that it is possible to prevent a decrease in efficiency and a decrease in response speed and to shorten a time until a re-recording is possible. However, as for details, we have to wait for more detailed elucidation of the operation in the future.

In the hologram recording / erasing method of the present invention, it is preferable to perform not only hologram erasing but also hologram recording by irradiation with circularly polarized light. Performing hologram recording by applying circularly polarized light can improve diffraction efficiency by about 2 to 5 times compared to recording hologram by linearly polarized light at the same time, making it brighter and clearer. It is preferable in terms of recording a simple hologram.

Further, the hologram recording / erasing method of the present invention may include a step of reproducing the recorded hologram. The step of reproducing the recorded hologram is performed by irradiating the recording element on which the hologram is recorded with reading light (polarized light) having the same phase as the reference light. The reading light is preferably circularly polarized light. The number of diffraction points of the diffracted light representing the hologram image generated in the reproducing step is confirmed when using linearly polarized light, whereas only one is confirmed when using circularly polarized light, The intensity of the diffracted light is also greater when circularly polarized light is used. Therefore, it is preferable that the reading light is circularly polarized in terms of a brighter and clearer reproduced hologram.

[Embodiment 4: Hologram recording apparatus]
A hologram recording apparatus according to Embodiment 4 of the present invention uses a hologram recording / erasing method based on two-beam interference to perform the hologram recording / erasing method according to Embodiment 3 of the present invention. Then, at least in the erasing step, a mechanism for irradiating circularly polarized light to the hologram recording element through the circularly polarizing element is provided.

The hologram recording apparatus of the present invention is normally used in the field to which the present invention belongs, except that it includes a mechanism for irradiating the hologram recording element with circularly polarized light through the circularly polarizing element at least in the process of erasing the recorded hologram. The hologram recording apparatus can be the same as the hologram recording apparatus to be used.

That is, the hologram recording apparatus of the present invention includes a hologram recording element made of a rewritable hologram recording material, irradiating the hologram recording element with coherent object light and reference light, and interference fringes in the hologram recording element. And a mechanism for recording the hologram, and a mechanism for erasing the hologram by irradiating the recording element on which the hologram is recorded with circularly polarized light. In addition, the hologram recording apparatus of the present invention may further include a mechanism for reproducing the recorded hologram by irradiating the recording element on which the hologram is recorded with reading light.

The mechanism for erasing the recorded hologram includes a member for obtaining linearly polarized light by converting a linearly polarized laser light source or the like into circularly polarized light. The member for obtaining the circularly polarized light is not particularly limited, and examples thereof include a λ / 4 plate (¼ wavelength plate), a phase difference plate, and the like. From the viewpoint of easy installation, the λ / 4 plate is used. preferable.

Also, the hologram recording apparatus of the present invention can include a member for obtaining circularly polarized light with respect to the hologram recording element even in the mechanism for recording the hologram. In addition, the member for obtaining the circularly polarized light in the mechanism for recording the hologram can be the same member as the member for obtaining the circularly polarized light in the mechanism for erasing the recorded hologram.

Furthermore, the hologram recording apparatus of the present invention may include a mechanism for reproducing the recorded hologram by irradiating the recording element on which the hologram is recorded with reading light (polarized light). In addition, the mechanism for reproducing the recorded hologram preferably includes a member for obtaining circularly polarized light as the reading light. The member for obtaining circularly polarized light in the mechanism for reproducing the recorded hologram can be the same member as the member for obtaining circularly polarized light in the mechanism for erasing the recorded hologram.

In addition, each member such as a member that irradiates light in each of the above-described mechanisms can be a member that is common in the field to which the present invention belongs.

The mechanism for recording a hologram in the hologram recording apparatus of the present invention includes, for example, a mechanism that performs two-beam interference using linearly polarized light or circularly polarized light.

The mechanism for erasing the recorded hologram in the hologram recording apparatus of the present invention includes, for example, a mechanism for irradiating one beam of circularly polarized light.

The mechanism for reproducing the recorded hologram in the hologram recording apparatus of the present invention includes, for example, a mechanism for irradiating linearly polarized light or circularly polarized light with one light beam.

Here, the configuration of the hologram recording apparatus of the present invention will be specifically described with reference to FIG. FIG. 7 is a diagram showing a schematic configuration of the hologram recording apparatus of the present invention.

A hologram recording / reproducing / erasing apparatus, which is an example of a hologram recording apparatus of the present invention, irradiates a holographic display device (Sample) for recording and displaying a hologram image, and object light and reference light to the holographic display device. The recording means (erasing means) for recording the hologram image by the above and the reproducing means for reproducing the hologram image recorded by the recording means by irradiating the holographic display device with the probe light. In this specification, “means” is intended to be “apparatus” or “mechanism”.

The recording means for recording the hologram image includes a laser oscillator 1 that oscillates a laser, a first fixed mirror 2 that reflects a laser beam oscillated from the laser oscillator 1, and a laser that is reflected by the first fixed mirror 2. A first half-wave plate 3 disposed on the optical axis of the beam, and a first and second polarization of p-polarized light and s-polarized light by dividing the laser beam that has passed through the first half-wave plate 3 A beam splitter 4 as a laser beam, a second half-wave plate 5 arranged on the optical axis of the first polarized laser beam, a quarter-wave plate 6, the second half-wave plate and the first In the recording means for recording the hologram image, the second fixed mirror includes a second fixed mirror 7 that reflects the circularly polarized first polarized laser beam that passes through the quarter wavelength plate 6 Reflected by 7 Was first polarized laser beam circularly polarized is irradiated to the holographic display device (Sample) as object light. The recording means for recording the hologram image includes a second quarter-wave plate 8 on the optical axis of the second polarized laser beam, and circularly polarized light passing through the second quarter-wave plate 8. In the recording means for recording the hologram image, the second circularly polarized light reflected by the third fixed mirror 9 is included in the recording means for recording the hologram image. A polarized laser beam is applied to a holographic display device (Sample) as reference light. That is, the laser beam oscillated from the laser oscillator 1 is divided into a circularly polarized first polarized laser beam (object light) and a circularly polarized second polarized laser beam (reference light).

Then, the object light is irradiated onto the holographic display device together with the reference light, and the spatial information of the object light is recorded in the holographic display device using the spatial intensity distribution and phase distribution included in the object light as interference fringes.

The reproducing means for reproducing the recorded hologram image includes a laser oscillator 10 that oscillates a laser, a half-wave plate 11 for probe light arranged on the optical axis of the laser beam oscillated from the laser oscillation device 10, and probe light. The fourth fixed mirror 12 reflects the laser beam that has passed through the half-wave plate 11 for use. The laser beam oscillated from the laser oscillator 10 is converted into p-polarized light by the probe light half-wave plate 11 and reflected by the fourth fixed mirror 12. Then, the spatial information written (recorded) by the recording means is read out as a hologram image with p-polarized probe light and reproduced.

When erasing the hologram, the object light is blocked by closing the mechanical shutter, and the circularly polarized reference light is used as the erasing light. Further, the object beam and the reference beam of the overwritten hologram image to be written next may be used as the erasing beam.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

[A: Rewriteable hologram recording material]
[Production Example 1]
In accordance with the following scheme, a carbazole azobenzene (CACzE) in which a cyano group is coordinated to the para-position of the benzene ring (see the left figure of the following scheme) is introduced into a part of the side chain of polymethyl methacrylate (PMMA). A union (Poly (CACzE-MMA)) (see the right figure of the scheme below) was prepared.

The specific method is as follows.

Synthesis of acrylic acid-2- [3- (4-cyano-phenylazo) -carbazol-9-yl] -ethyl ester (CACzE-MMA) (see central diagram in the above scheme) CACzE 1.97 g (5.79 mmol) Was dissolved in 80 mL of THF and stirred while being cooled to 0 ° C., and 0.042 g (0.34 mmol) of DMAP and 1.26 g (12.45 mmol) of triethylamine were added. Thereto, 1 mL (12.36 mmol) of acryloyl chloride was added dropwise every 15 minutes while keeping the temperature below 0 ° C. The reaction mixture was returned to room temperature (around 20-25 ° C.) with stirring and stirred overnight. After completion of the stirring, the solvent was removed from the reaction mixture under reduced pressure, and the resulting crude product was dissolved in chloroform. This was washed several times with a saturated aqueous sodium bicarbonate solution and distilled water, and dried over anhydrous magnesium sulfate. Thereafter, suction filtration was performed, and the solvent was distilled off from the filtrate under reduced pressure to obtain an orange powder (yield 87.6%).

The obtained orange powder was subjected to NMR measurement (using a nuclear magnetic resonance apparatus AV-300) to identify the molecular structure. As a result, it was confirmed that CACzE-MMA was synthesized.
NMR measurement: solvent CDCl ₃ used, magnetic field 300 MHz
Measurement results: 8.73 (bs, 1H, carbazole ring), 8.16 (m, 2H, carbazole ring), 8.02 (m, 2H, PhCN ring), 7.82 (m, 2H, PhCN ring), 7.55 (m, 3H, carbazole ring), 7.32 (m, 1H, carbazole ring), 4.00-4.82 (m, 4H, CH ₂ CH ₂ O), 3.47-3.99 (m, 3H, COOCH ₃ ), 1.71-2.00 (m, 3H, CH ₃ ) ppm].

Synthesis of Poly (CACzE-MMA) 0.5 g of CACzE-MMA was dissolved in 20 ml of dry DMF, and 1.17 g of MMA and 0.03 g of AIBN were added to this solution. In order to remove oxygen in the mixed solution, freeze deaeration was performed four times using liquid nitrogen. After freeze degassing, the mixture was stirred at 60 ° C. for 15 hours, the liquid temperature was returned to room temperature (20 to 25 ° C.), and the copolymerization reaction was stopped. The obtained DMF solution was added dropwise to 500 ml of methanol, and the copolymer was reprecipitated and recovered by filtration. This operation was repeated again (2 times in total) and dried to obtain 0.81 g of copolymer (yield 66.4%).

The glass transition temperature of the copolymer obtained by DSC measurement was 103 ° C., the weight average molecular weight was 18,660 g / mol, and the degree of dispersion was 1.58 by GPC measurement. DSC measurement was performed using DSC2920 manufactured by TA Instruments, and GPC measurement was performed using Showdex GPC KF-805 manufactured by Showa Denko.

Here, a cyano group coordinated to the para-position of the benzene ring is prepared, but as described above, as a substituent coordinated to the para-position of the benzene ring, other than the cyano group (—CN), A nitro group (—NO ₂ ), a methoxy group (—OCH ₃ ), an amino group (—NH ₂ ), a hydroxy group (—OH), or the like can be used. As the carbazole azobenzene, carbazole azobenzene having a structure in which the substituent is a nitro group, a cyano group, or a methoxy group is preferable, and carbazole azobenzene having a structure in which the substituent is a cyano group or a methoxy group is more preferable. The carbazole azobenzene may be one type or two or more types.

Here, polymethyl methacrylate (PMMA) is used as the acrylic polymer, but as described above, one or more acrylic polymers of polyethyl methacrylate (PMMA), polymethyl acrylate (PMA), and the like are used. You can also.

[Example 1]
[Preparation of rewritable hologram recording material]
Poly (CACzE-MMA) obtained in Production Example 1 and CACzE were mixed at a weight ratio of 50: 5, and the resulting mixture was dissolved in THF to obtain a cast solution. The cast solution was cast on a petri dish (product name: glass petri dish made from TOP) and then allowed to stand at room temperature (25 ° C.) for 48 hours to evaporate the solvent (THF) to obtain a uniform film. Subsequently, the uniform film was further air-dried overnight, and then dried under reduced pressure at a temperature of about 80 ° C. in a vacuum drier to further evaporate the solvent (THF). Thereafter, spacers (for example, polyimide, thickness: 50 μm) are arranged at the four corners of the obtained film, and then another glass substrate (glass plate (product name: Tempax heat-resistant glass)) is placed thereon. The sandwich-type rewritable hologram recording material 1 having a uniform film thickness was prepared by pressure bonding with a vacuum press machine while applying appropriate heat (temperature). As a result of measuring the film thickness of the rewritable hologram recording material 1 using a micrometer, the film thickness was 80 μm.

Further, in the obtained rewritable hologram recording material 1, and a group derived from a carbazole azobenzene contained in the copolymer, the molar concentration of the total of the carbazole azobenzene molecule, 9.7 × 10 -4 ^{mol /} g Met. The molar ratio of the carbazole azobenzene molecule to the group derived from carbazole azobenzene contained in the copolymer was 0.38.

[Measurement of rising speed and memory]
The obtained rewritable hologram recording material is used as a hologram recording element, and a hologram recording apparatus is used to irradiate light for 20 seconds under the following conditions to record a hologram. It measured using. The relationship between the time after the start of light irradiation and the diffraction efficiency is shown in FIG. In addition, FIG. 2 shows the time course of diffraction efficiency and recording hologram retention characteristics (memory characteristics).
・ Laser used in measurement conditions: 25 mW / 532 nm
Object light, reference light: wavelength 532 nm, intensity 0.535 W / cm ² .

[Example 2]
A rewritable hologram recording material 2 was prepared in the same manner as in Example 1 except that Poly (CACzE-MMA) obtained in Production Example 1 and CACzE were mixed at a weight ratio of 50:10. The thickness was measured. In addition, diffraction efficiency was measured in the same manner as in Example 1 using the rewritable hologram recording material 2. 1 and 2 show the relationship between the time from the start of light irradiation, the diffraction efficiency, and the memory characteristics.

The film thickness of the rewritable hologram recording material 2 was 80 μm. In the obtained rewritable hologram recording material 2, and groups derived from carbazole azobenzene contained in the copolymer, the molar concentration of the total of the carbazole azobenzene molecule, met 1.1 × 10 -3 ^{mol /} g It was. The molar ratio of the carbazole azobenzene molecule to the group derived from carbazole azobenzene contained in the copolymer was 0.76.

[Example 3]
Except that Poly (CACzE-MMA) obtained in Production Example 1 was mixed with CACzE so that the component derived from MMA: the component derived from CACzE = 70: 30, the same as Example 1 Thus, a rewritable hologram recording material 3 was prepared, and its film thickness was measured. In addition, diffraction efficiency was measured in the same manner as in Example 1 using the rewritable hologram recording material 3. 1 and 2 show the relationship between the time from the start of light irradiation, the diffraction efficiency, and the memory characteristics.

The film thickness of the rewritable hologram recording material 3 was 80 μm. In the obtained rewritable hologram recording material 3, the total molar concentration of the group derived from carbazole azobenzene contained in the copolymer and the carbazole azobenzene molecule was 1.4 × 10 ⁻³ mol / g. It was. Further, the molar ratio of the carbazole azobenzene molecule to the group derived from carbazole azobenzene contained in the copolymer was 1.52.

[Comparative Example 1]
Example 1 except that Poly (CACzE-MMA) obtained in Production Example 1 was used alone instead of the mixture of Poly (CACzE-MMA) obtained in Production Example 1 and CACzE. Similarly, a rewritable hologram recording material 4 was prepared and its film thickness was measured. Further, diffraction efficiency was measured by the same method as in Example 1 using the rewritable hologram recording material 4. 1 and 2 show the relationship between the time from the start of light irradiation, the diffraction efficiency, and the memory characteristics.

The film thickness of the rewritable hologram recording material 4 was 82 μm. In the obtained rewritable hologram recording material 4, the molar concentration of the group derived from the carbazole azobenzene contained in the copolymer was 7 × 10 ⁻⁴ mol / g.

[Comparative Example 2]
The same as Example 1 except that polymethyl methacrylate (PMMA) was used instead of Poly (CACzE-MMA) obtained in Production Example 1 and the weight ratio of PMMA to CACzE was mixed at 70:30. Then, a rewritable hologram recording material 5 was prepared, and its film thickness was measured. Further, diffraction efficiency was measured by the same method as in Example 1 using the rewritable hologram recording material 5. 1 and 2 show the relationship between the time from the start of light irradiation, the diffraction efficiency, and the memory characteristics.

The film thickness of the rewritable hologram recording material 5 was 80 μm. In the rewritable hologram recording material 5 obtained, the number of moles of the above-mentioned carbazole azobenzene molecule is the molar concentration of the group derived from the acrylic molecule constituting the above acrylic polymer is 8.8 × 10 ⁻⁴ mol / g. Met.

[result]
From the description of FIG. 1, the rewritable hologram recording material comprising the CACzE / (CACzE-MMA) copolymer prepared in Examples 1 to 3 was obtained from the (CACzE-MMA) copolymer alone in the comparative example. It was found that the photoresponsiveness was higher than the hologram recording material (Comparative Example 1) and the CACzE dispersion type hologram recording material (Comparative Example 2), and the rise time in hologram recording was shorter.

In addition, from the description of FIG. 2, the hologram recording material (Comparative Example 1) and the CACzE dispersion type hologram recording material (Comparative Example 2) each consisting of a (CACzE-MMA) copolymer alone have a long time elapsed from light irradiation. Then, while the diffraction efficiency is lowered, the rewritable hologram recording material made of the CACzE / (CACzE-MMA) copolymer prepared in Examples 1 to 3 is diffracted even after a long time. It was found that the efficiency was hardly attenuated and the memory performance was superior.

[Conclusion]
From the results of Examples 1 to 3 and Comparative Examples 1 and 2 described above, a copolymer having carbazole azobenzene introduced into a part of the side chain of the acrylic polymer, and the carbazole introduced into the copolymer It has been found that a rewritable hologram recording material containing a carbazole azobenzene molecule of the same kind or different kind from azobenzene has high photoresponsiveness, a shorter rise time in hologram recording, and superior memory performance.

[B: Erase by circularly polarized light]
[Example 4]
Using the two-beam interference hologram recording apparatus, a hologram recording is performed by irradiating hologram recording material 3 as a recording element with hologram recording light (object light and reference light) for 50 seconds under the following conditions: After that, the hologram recording material 3 was irradiated with circularly polarized light for erasing the hologram for 50 seconds to erase the recorded hologram.
・ Laser using light for recording measurement conditions: 25 mW / 532 nm
Object light, reference light: wavelength 532 nm, intensity 0.535 W / cm ²
Erasing light: wavelength 532 nm, intensity 0.268 W / cm ² .

Subsequently, the process of recording the hologram and the process of erasing the hologram were set as a set, and the set was repeated a total of 5 times including the first set, and the diffraction efficiency was measured. FIG. 3 shows the relationship between the time from the first light irradiation and the diffraction efficiency obtained as a result.

[Example 5]
Diffraction efficiency was measured in the same manner as in Example 4 except that the time for irradiating the circularly polarized light for erasing the hologram was extended to 450 seconds and the above set was repeated a total of two times. FIG. 4 shows the relationship between the time from the first light irradiation and the diffraction efficiency obtained as a result.

[Comparative Examples 3 and 4]
Diffraction efficiency was measured in the same manner as in Examples 4 and 5, except that the hologram recording light and the hologram erasing light were linearly polarized light shown below. The relationship between the time from the first light irradiation and the diffraction efficiency obtained as a result is shown in FIGS.
・ Laser using light for recording measurement conditions: 25 mW / 532 nm
Object light, reference light: wavelength 532 nm, intensity 0.535 W / cm ²
Light for erasing: wavelength 532nm, intensity of 0.268W / ^cm 2.

[result]
From comparison between FIG. 3 and FIG. 5, when linearly polarized light is used for erasing the hologram, the diffraction efficiency gradually decreases when the above recording and erasing set is repeated, while circularly polarized light is used for erasing the hologram. In this case, it was found that the above-described decrease in the diffraction efficiency did not occur even when the recording and erasing set was repeated.

4 and 6, when linearly polarized light is used for erasing the hologram, irradiating light for erasing for a long time reduces the diffraction efficiency when recording the hologram again, It has been found that when circularly polarized light is used for erasure, the diffraction efficiency when a hologram is recorded again is not lowered even when erasing light is irradiated for a long time. Therefore, when linearly polarized light is used for erasing the hologram, after irradiating the erasing light for a long time, the recording element can be left for a long time in order to re-record the hologram with the same performance as the first time, On the other hand, when circularly polarized light is used for erasing the hologram, the hologram is rerecorded with the same performance as the first time immediately after irradiating the erasing light for a long time. It turns out that can be done.

[Conclusion]
From the results of Examples 4 and 5 and Comparative Examples 3 and 4, a copolymer in which carbazole azobenzene was introduced into a part of the side chain of the acrylic polymer, and the same kind of carbazole azobenzene introduced into the copolymer, or In a hologram recording / erasing method using a hologram recording element containing a rewritable hologram recording material containing different kinds of carbazole azobenzene molecules, the time required for erasing the hologram is reduced by using circularly polarized light for erasing the hologram. It has been found that the reduction in response speed and diffraction efficiency in re-recording after the erasure, which can be shortened and normally reduced, can be prevented.

The hologram recording material and hologram recording / erasing method of the present invention can preferably improve the rising speed in hologram recording, and can improve the memory performance in hologram recording. Further, re-recording after erasing the hologram can be facilitated. Therefore, it is suitable for use in manufacturing a hologram recording apparatus that has a short rise time when recording a hologram, can store the hologram recording for a long period of time, and can repeatedly record and erase the hologram. can do.

DESCRIPTION OF SYMBOLS 1 Laser oscillator 2 1st fixed mirror 3 1st half wave plate 4 Beam splitter 5 2nd half wave plate 6 1st 1/4 wavelength plate 7 2nd fixed mirror 8 2nd 1/4 wavelength plate 9 Third fixed mirror 10 Laser oscillator 11 Half-wave plate for probe light 12 Fourth fixed mirror

Claims

A copolymer obtained by introducing carbazole azobenzene into a part of the side chain of the acrylic polymer; and
A rewritable hologram recording material comprising a carbazole azobenzene molecule of the same kind or different from the carbazole azobenzene.
(Here, carbazole azobenzene is represented by the following formula (1).)
The rewritable hologram recording material according to claim 1, wherein the carbazole azobenzene is carbazole azobenzene in which X in the formula (1) is a cyano group, a nitro group or a methoxy group.
The rewritable hologram recording material according to claim 1 or 2, wherein the carbazole azobenzene introduced into the side chain of the copolymer and the carbazole azobenzene molecule are of the same kind.
The rewritable hologram recording material according to any one of claims 1 to 3, wherein the acrylic polymer is selected from the group consisting of polymethyl methacrylate, polyethyl methacrylate, and polymethyl acrylate.
The total molar concentration of the group derived from the carbazole azobenzene and the carbazole azobenzene molecule contained in the copolymer with respect to the total weight of the copolymer and the carbazole azobenzene molecule contained in the rewritable hologram recording material 5. The rewritable hologram recording material according to claim 1, wherein the rewritable hologram recording material is 5 × 10 −4 mol / g or more and 2.0 × 10 −3 mol / g or less.
The rewriting according to any one of claims 1 to 5, wherein a molar ratio of the carbazole azobenzene molecule to a group derived from carbazole azobenzene contained in the copolymer is 0.5 or more and 2.0 or less. Hologram recording material.
The rewritable hologram recording material according to any one of claims 1 to 6, wherein the copolymer has a weight average molecular weight of 10,000 or more and 200,000 or less.
A recording medium having a hologram recording element,
8. A recording medium, wherein the hologram recording element contains the rewritable hologram recording material according to any one of claims 1 to 7.
In a hologram recording element containing a rewritable hologram recording material, a striped pattern on a spatial light modulator (SLM) is caused to interfere with a coherent object beam and reference beam using a single beam of laser beam. (Two-beam interference) to form interference fringes in the hologram recording element, record the hologram on the hologram recording element, and erase the hologram by irradiating the hologram recording element with polarized light A hologram recording / erasing method including:
The rewritable hologram recording material is a copolymer obtained by introducing carbazole azobenzene into a part of the side chain of an acrylic polymer, and
For a hologram recording element made of a material further containing a carbazole azobenzene molecule of the same kind or different from the carbazole azobenzene introduced into the copolymer,
A method of recording and erasing a hologram, wherein at least the step of erasing the hologram is performed by irradiation with circularly polarized light.
10. The hologram recording / erasing method according to claim 9, wherein the object light and the reference light in the recording step are circularly polarized light.
The hologram recording / erasing according to claim 9 or 10, further comprising a step of reproducing the recorded hologram by irradiating the hologram recording element on which the hologram is recorded with polarized light having the same phase as the reference light. Method.
12. The hologram recording / erasing method according to claim 11, wherein in the step of reproducing the recorded hologram, the polarized light applied to the hologram recording element on which the hologram is recorded is circularly polarized light.
A hologram recording apparatus for using a hologram recording / erasing method by two-beam interference to perform the hologram recording / erasing method according to any one of claims 9 to 12,
A hologram recording apparatus comprising: a mechanism for obtaining circularly polarized light with respect to the hologram recording element through the element for circular polarization at least in the erasing step.
The hologram recording apparatus according to claim 13, wherein the mechanism for obtaining the circularly polarized light is a λ / 4 plate.