TWI621119B - Light-induced birefringent material, optical recording medium using the same, and optical recording method - Google Patents

Abstract

Forming an optical recording medium from a light-inducing birefringent material for performing polarized holographic multi-recording on the optical recording medium; the light-inducing birefringent material is a light-induced birefringent material that generates birefringence in response to a polarized state of the irradiated light, It is characterized in that it contains a polarizing inductive component and a polymer matrix, and the polarizing inductive component is bonded to the polymer matrix via a covalent bond, and the reaction of the polarizing inductive component generated by light irradiation is irreversible.

Description

Light-induced birefringent material, optical recording medium using the same, and optical recording method

The present invention relates to a light-induced birefringent material which can be applied to a high-density optical recording, a three-dimensional display, a holographic optical element, or the like, an optical recording medium using the same, and an optical recording method, in particular, a write-once type which cannot be rewritten intrinsically Light-induced birefringent material, optical recording medium using the same, and optical recording method.

The recording of the holographic recording medium is generally performed by using a light intensity distribution (interference fringe) generated by simultaneously illuminating (drying) the signal light having the image information together with the reference light having the same polarization as the signal light, as a diffraction grating. Recorded on the recording medium and proceeded. The reproduction of the hologram recording medium is performed by illuminating the reference light on the recording medium on which the image information is recorded, and reading the image information as the reproduced signal light from the diffraction grating.

The holographic recording system treats the above-mentioned image information as one page, can be recorded and reproduced in batches in units of pages, and since the pages can be multiplexed at the same position in the media, the CD, DVD, Blu-ray disc, etc. are used instead of the conventional ones. The bit-by-bit recording method is expected as a high-speed and large-capacity optical recording party. Technology.

In recent years, in a polarized recording medium using an anisotropic (birefringent) light-induced birefringent material which generates a refractive index in response to a polarized state of light to be irradiated, it has been proposed to use image information as a birefringence phase difference (hysteresis). A new polarized recording method (retardagraphy) is recorded (see Patent Document 1).

Further, Patent Document 2 also proposes a polarization distribution which simultaneously emits a signal light having image information together with reference light of a polarization state different from the signal light, and records the polarization record recorded on the polarized recording medium as a distribution of birefringence. the way. This recording method is called so-called polarized hologram recording in combination with the above-described hologram recording, and is expected to have a higher recording density, that is, a larger capacity.

The recording materials used in such recording media require that the recorded information does not deteriorate over time and can remain stable for a long period of time. Moreover, in order to avoid the erroneous elimination or tampering of the recorded information, it is desirable that the recording material be a write-once type that cannot be rewritten in essence.

As a polarizing inductive component used for a light-induced birefringent material, it is widely known that 9,10-phenanthrenequinone or the like is present in the write-once type, and azobenzene or the like is present in the overwrite type (rewritable type).

However, in the conventional light-induced birefringent material using the above-mentioned polarization-inducing component, there is a problem that the recorded information deteriorates over time.

Non-Patent Document 1 discloses that a photodegradable aromatic ketone derivative is used as a polarizing inductive component, and a maleimide resin or an epoxy resin having a high glass transition temperature (Tg) is used as a polymer matrix material. Induction double The material is refracted while the preservation stability of birefringence is increased. However, even with the aforementioned polymer matrix material, a decrease in birefringence was observed in the elapsed time range of more than 1000 hours (Fig. 3 of the same literature).

Moreover, the composition ratio of the polarization-sensitive component in the light-induced birefringent material shown in Non-Patent Document 1 is a comparatively small value of 1% by weight. When the composition ratio of the polarizing-inductive component is small, the storage stability tends to increase, but the amount of birefringence becomes small, which causes a problem that the recording signal intensity is lowered.

Patent Document 3 reports a polarizing recording material using a photoisomerization compound bonded to a liquid crystalline polymer matrix. When the photoisomerization compound is aligned by polarized light irradiation, the recording material is heated to a temperature near the glass transition temperature (Tg), and since the liquid crystal component is aligned along the alignment direction of the photoisomerization compound, it can be induced to be large. Birefringence.

However, in this mode, although large birefringence is finally induced, in order to align the liquid crystal, it is necessary to heat at the time of light irradiation. Further, in order to prevent light scattering, the liquid crystal molecules before the light irradiation must have a single-domain structure. Generally, the liquid crystal molecules tend to adopt a complex domain structure due to an increase in thickness, and the thickness required for the hologram recording layer (about 200 μm~ 2mm) is difficult to make a recording medium.

In addition, when the hologram is multiplexed using the write-once type recording material, the recording component changes by a photoreaction at a certain ratio due to the recording on the first page, and the remaining unreacted recording component is recorded by the second page. The photoreaction was changed at a certain ratio, and the remaining unreacted recording components were changed by photoreaction at a certain ratio due to the recording on page 3, and ‧ ‧ was repeated in order to perform multiplex recording.

Therefore, as the multiple records are repeated, the remaining recorded components are reduced, and the recording sensitivity is lowered. In other words, when each page is recorded with the same irradiation energy, the page reaches the second half, and the reproduced signal intensity decreases, and a problem occurs in the recording and reproducing system.

On the other hand, when multiplex recording is performed using the rewritable recording material, the recording component is changed by photoreaction at a certain ratio due to the recording on the first page, and the recorded consumption of the first page is recorded due to the recording of the second page. The components and the remaining unreacted recording components are each changed in a certain ratio by photoreaction. Due to the recording on page 3, the recorded and consumed components of pages 1 and 2 and the remaining unreacted recording components are Each of the light reactions was changed at a certain ratio, and ‧ ‧ ‧ was repeated in order to perform multiple recordings.

Therefore, as the multiple records are repeated, the recorded components of the recorded pages are reduced. If the pages are recorded with the same irradiation energy, the reproduced signal strength of the first half of the pages is reduced as compared with the write-once type. A bad condition occurred on the recording and reproducing system.

In order to eliminate such undesirable conditions, a technique called scheduling is used. In this case, it is expected that the change in the intensity of the reproduced signal caused by the multiple, that is, the change in the sensitivity of the recording, is performed by changing the irradiation energy on each page (diffraction grating), thereby making the reproduced signal from each page. The intensity becomes uniform (refer to Patent Document 4).

However, the recording medium shown in Patent Document 4 is a holographic recording medium in which the conventional light intensity distribution is recorded, and since different information cannot be described in response to the polarization state of light, a large recording density improvement cannot be expected. Further, the recording medium shown in Patent Document 4 is arranged in a positive manner. For the purpose, the scheduling itself is still necessary.

During the scheduling, the reduced sensitivity is recorded on the predicted page (diffraction grating) with high illumination energy. The irradiation energy is the product of the irradiation power and the irradiation time. However, if the change in the irradiation power is required to be complicated in the recording system on each page, the irradiation energy is generally changed by adjusting the irradiation time.

That is, in order to perform recording with high irradiation energy, the irradiation time becomes long, which involves a problem of causing a decrease in the transfer rate on the recording system.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] JP-A-2010-020883

[Patent Document 2] Japanese Patent Publication No. Hei 10-340479

[Patent Document 3] Special Table 2006-259315

[Patent Document 4] Japanese Patent Publication No. 2008-532091

[Non-patent literature]

[Non-Patent Document 1]

Proceedings of 1st International Conference on Advanced Photonic Polymers (ICAPP 2011), pp.83-84

SUMMARY OF THE INVENTION An object of the present invention is to provide a light-inducing birefringent material which can be recorded for a long period of time without deterioration over time, which can be stably stabilized for a long period of time, and which cannot be rewritten in essence, and an optical recording medium and an optical recording method using the same. Further, there is no need to schedule, and there is no optical recording medium which causes a decrease in the transfer rate on the recording system.

In order to achieve the above object, the present invention relates to a light-induced birefringent material which is a light-induced birefringent material which generates birefringence in response to a polarized state of light to be irradiated, and is characterized in that it contains a polarization-inducing component and a polymer matrix, The polarizing inductive component is bonded to the polymer matrix via a covalent bond, and the reaction of the polarizing inductive component generated by light irradiation is irreversible.

In the conventional light-induced birefringent materials using polarized inductive components, the problem of deterioration of information recorded over time is considered to be due to the recorded birefringence due to the movement or rotation of the polarized inductive component. The distribution is disordered, or the amount of induced birefringence becomes small (the refractive index is close to isotropic). Therefore, in order to prevent the information described in the light-induced birefringent material from deteriorating over time, the stability can be maintained for a long period of time, and the polarization-inducing component in the light-induced birefringent material is not changed in position ‧ in the axial direction before and after recording The way is fixed.

According to the light-inducing birefringent material of the present invention, since the polarization-inducing component is bonded to the polymer matrix via a covalent bond, the polarization-inducing component in the light-induced birefringent material is changed in such a manner that the position ‧ the axial direction does not change fixed. Moreover, the reaction of the polarization sensitive component which occurs by light irradiation is irreversible. Therefore, it is possible to provide a light-induced birefringence in which the recording information does not deteriorate over time, and can be stabilized for a long period of time, which cannot be rewritten in nature. material.

In one embodiment of the present invention, the covalent bond of the polarizing inductive component to the polymer matrix can be formed by the same reaction as the reaction for forming the polymer matrix. That is, by including a specific functional group in at least one portion of the polarizing inductive component, it is not necessary to additionally provide a special reaction process, and in the formation of the polymer matrix, a polarizing inductive component and a polymer matrix can be formed. Covalent bond. Therefore, the above covalent bond can be easily formed.

Further, in an example of the present invention, the polarization-inducing component contained in the light-induced birefringent material can be used as a component of an intramolecular cleavage type photoradical generator, and functions as an intramolecular cleavage type photoradical generator. The component may be an α-aminoacetophenone derivative or an oxime ester derivative.

These derivatives are irreversible by light irradiation and are easy to obtain, and can be preferably used as a polarizing inductive component in the above-mentioned light-induced birefringent material. Further, as described below, when the irradiation energy of the recording signal light and the recording reference light is fixed and the polarization total image multiplexing recording is performed, the diffraction efficiency of the reproduced signal light from each of the recorded diffraction gratings can be reduced. The difference between the value ηmax and the minimum value ηmin provides a light-inducing birefringent material that does not require scheduling.

Further, the present invention is an optical recording medium characterized by having an information recording layer composed of the above-described light-induced birefringent material.

Specifically, an optical recording medium characterized by having an information recording layer composed of the light-inducing birefringent material and having the irradiation energy of the recording signal light and the recording reference light fixed, and performing polarized holographic multi-recording , from the recorded refraction signal of each diffraction grating The maximum value ηmax and the minimum value ηmin of the ejection efficiency satisfy ηmin/ηmax≧0.1.

At this time, since the information recording layer of the optical recording medium is constituted by the light-induced birefringent material, the polarization-inducing component in the light-induced birefringent material is fixed so that the position ‧ is not changed in the axial direction. Moreover, the reaction of the polarization sensitive component which occurs by light irradiation is irreversible. Therefore, it is possible to provide a write-once optical recording medium which can be degraded over time and which can be stabilized for a long period of time while being substantially incapable of being rewritten.

Further, when the irradiation energy of the recording signal light and the recording reference light is fixed and the polarization hologram multiple recording is performed, the maximum value ηmax and the minimum value ηmin of the diffraction efficiency of the reproduced signal light from each of the recorded diffraction gratings are satisfied. Ηmin/ηmax≧0.1. Therefore, even if the irradiation energy of the recording signal light and the recording reference light is fixed, especially when the scheduling is not performed, the diffraction efficiency of the reproduced signal light, that is, the reproduction signal light, is not greatly reduced in the multiplex full image multiplexing recording. strength.

As a result, since the recording operation with high irradiation energy is not required for the page (diffraction grating) whose expected sensitivity is lowered, it is not necessary to lengthen the irradiation time, and the reduction of the transfer rate on the recording system can be suppressed.

Further, such a condition is as described above, and the polarizing inductive component contained in the photoinduced birefringent material may contain an α-aminoacetophenone derivative which acts as an intramolecular cleavage type photoradical generator or The oxime ester derivative is obtained by optimizing the various materials described below.

Further, η is defined as the optical system of the reproducing light intensity signal I ₁ from the respective phase diffraction grating for the incident light i.e., the reproduction reference light intensity I ₀ is = I ₁ / I ₀ ratio η.

Furthermore, the present invention relates to an optical recording method characterized in that a multiplexed omni-directional multiple recording is provided, and a recording signal light of the same or mutually orthogonal polarization state is irradiated to a recording area of the optical recording medium, and recording reference light is recorded. a step of recording the first hologram; and recording the recording signal light of the same or mutually orthogonal polarization state and recording the reference light in a state in which the recording area is different from the first hologram recording in the Bragg condition The step of the second hologram recording.

As described above, according to the present invention, it is possible to provide a write-once type light-inducing birefringent material, an optical recording medium using the same, and an optical recording method which can be degraded over time and can be stabilized for a long period of time while being substantially unrewriteable. . Further, according to the present invention, it is possible to provide an optical recording medium which does not require scheduling and which does not cause a decrease in the transfer rate on the recording system.

10‧‧‧ optical recording media

11‧‧‧Transparent substrate

12‧‧‧Information Recording Layer

21‧‧‧record signal light

22‧‧ Recording reference light

23‧‧‧Renewed reference light

Fig. 1 is a perspective view showing a schematic configuration of an optical recording medium in an embodiment.

Fig. 2 is a schematic block diagram showing an example of a recording optical system for multiplexed omnidirectional recording.

Fig. 3 is a schematic block diagram showing an example of a reproducing optical system for multiplexed omnidirectional recording.

Figure 4 is a graph showing the M# deterioration rate in the embodiment versus the recorded Over time curve.

Fig. 5 is a view showing the outline of the relative diffraction intensity η/ηmax from each diffraction grating when the polarization total multiplex recording is performed in the embodiment.

Fig. 6 is a view showing the outline of the relative diffraction intensity η/ηmax from each diffraction grating when the polarization total multiplex recording is performed in the embodiment.

Fig. 7 is a view showing the contours of the relative diffraction intensities η/ηmax from the respective diffraction gratings when the polarization total multiplex recording is performed in the comparative example.

Fig. 8 is a view showing the outline of the relative diffraction intensity η/ηmax from each diffraction grating when the polarization total multiplex recording is performed in the comparative example.

Fig. 9 is a schematic configuration diagram showing an example of an optical system for measuring light-induced birefringence in the examples.

Fig. 10 is a graph showing the rate of change of birefringence in the examples.

[Formation of the Invention]

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(optical recording medium)

First, an example of the optical recording medium of the present invention will be described. Fig. 1 is a perspective view showing a schematic configuration of an optical recording medium in the embodiment. As shown in Fig. 1, the optical recording medium 10 of the present embodiment is formed by forming an information recording layer 12 composed of a light-induced birefringent material on a substrate 11.

For the substrate 11, for example, glass, resin, or the like is used, but from the viewpoint of moldability, cost, and the like, a resin is preferable. As the resin, for example, polycarbonate is exemplified. Ester resin, acrylic resin, cycloolefin resin, polystyrene resin, AS resin (acrylonitrile-styrene copolymer), ABS resin (acrylonitrile-butadiene-styrene copolymer), MS resin (methacrylic acid) Methyl ester-styrene copolymer), maleic imine-styrene copolymer, lanthanide resin, polyamide resin, polyimide resin, polyester resin, polypropylene resin, phenoxy resin, phenol resin, An epoxy resin, a urethane resin, a polyoxymethylene resin, a fluorine resin, an organic/inorganic hybrid resin, or the like. Among these, a polycarbonate resin, an acrylic resin, and a cycloolefin resin are particularly preferable from the viewpoints of moldability, optical properties, cost, and the like.

Moreover, in order to correspond to the recording and reproduction by the reflected light, a reflective layer can be provided on the surface of the substrate 11, and it becomes a reflective recording medium.

Further, on the surface of the substrate 11, fine processing may be carried out as needed, and hard coating treatment may be performed using a UV curable resin or the like. Furthermore, anti-reflection treatment can also be performed.

Further, the substrate 11 may be made of ceramic or the like as long as it does not affect recording and reproduction as described below.

The thickness of the substrate 11 is suitably set to a thickness that does not affect the recording and reproduction of the optical recording medium 10, that is, the information recording layer 12.

The information recording layer 12 is a light-induced birefringent material that generates birefringence in response to the polarized state of the light to be irradiated. The light-induced birefringent material contains a polarizing inductive component and a polymer matrix, and the polarized inductive component is via a covalent bond. The reaction with the aforementioned polymer matrix is such that the reaction of the aforementioned polarizing sensitive component caused by light irradiation is irreversible.

The type of the polymer matrix is not particularly limited, and for example, poly Carbonate resin, acrylic resin, cycloolefin resin, polystyrene resin, AS resin (acrylonitrile-styrene copolymer), ABS resin (acrylonitrile-butadiene-styrene copolymer), MS resin (methacrylic acid) Methyl ester-styrene copolymer), maleic imine-styrene copolymer, lanthanide resin, polyamide resin, polyimide resin, polyester resin, polypropylene resin, phenoxy resin, phenol resin An epoxy resin, a urethane resin, a polyoxymethylene resin, a fluorine resin, an organic/inorganic hybrid resin, various elastomers, and the like. These may be used singly or in combination of two or more kinds, or a copolymer may also be used. As the polymer matrix, it is preferably optically transparent, and particularly preferably is a small birefringence.

The polarizing-inductive component contained in the light-induced birefringent material is an anisotropic refractive index due to a polarized state of the irradiated light, and is bonded to the polymer matrix via a covalent bond, and is irradiated by light. The reaction that occurs is irreversible, and is not particularly limited, but is preferably a component that acts as an intramolecular cleavage type photoradical generator.

Examples of the component which acts as an intramolecular cleavage type photoradical generator include an α-aminoacetophenone structure, an α-hydroxyacetophenone structure, an oxime ester structure, a mercaptophosphine oxide structure, and a benzyl group. Ketone structure, ferrocene structure, etc. Among these, it is preferred to have an α-aminoacetophenone structure or an oxime ester structure, that is, an α-aminoacetophenone derivative or an oxime ester derivative.

The method for forming the information recording layer 12 can be specifically formed by dissolving a polymer matrix in which a polarization-sensitive component has been bonded in a solvent, drying and drying the transparent substrate 11, or by using a polarization-sensitive portion. The polymer matrix in which the components have been bonded is formed by melt-kneading, and may also be constructed. The monomer of the polymer matrix to which the polarization-inducing component has been bonded is polymerized.

At this time, the polarizing inductive component advantageously has one or more functional groups which are capable of reacting with the polymer matrix to form a bond in a stage prior to bonding with the polymer matrix. Thereby, a polymer matrix in which a polarizing-sensitive component is bonded via a covalent bond can be easily formed.

Examples of the functional group include a hydroxyl group, an amine group, a thiol group, a carboxyl group, a sulfo group, a vinyl group, a propylene group, a methacryl group, an isocyanate group, an epoxy group, a halogen group, and the like.

The polarizing inductive component may be present in the polymer matrix alone or in combination of two or more.

The polarizing-sensitive component having the functional group as described above, for example, is exemplified below, and examples thereof include readily available compounds No. 1 to No. 17 containing a hydroxyl group, an amine group, and a thiol group.

The reaction of forming a covalent bond with a polymer matrix as a polarizing-sensitive component may, for example, be a radical addition reaction, an epoxy-anhydride addition reaction, an epoxy-amine addition reaction, or an epoxy-thiol addition reaction. , isocyanate-hydroxy addition reaction (formation of urethane), isocyanate-amine addition reaction (formation of urea), hydroquinonelation reaction, and the like.

Furthermore, the above reaction can take place in the same step as the reaction to form the polymer matrix.

Therefore, examples of the reaction for forming the polymer matrix include the above-described radical addition reaction, epoxy-anhydride addition reaction, epoxy-amine addition reaction, epoxy-thiol addition reaction, and isocyanate-hydroxy addition. A reaction (formation of a urethane), an isocyanate-amine addition reaction (formation of urea), a hydroquinone reaction, and the like.

The polarization-inducing component thus formed is preferably a 3-dimensional crosslinked body via a covalently bonded polymer matrix. Further, when the polymer matrix to which the polarizing-inductive component is bonded via the covalent bond is a linear polymer, the molecular weight is preferably 3,000 or more, more preferably 5,000 or more, and still more preferably 10,000 or more.

Further, a sensitizing dye may be used in combination as a sensitizer in combination with the wavelength of the light to be irradiated.

Further, in the present embodiment, the substrate 11 is provided on one side of the recording medium, but the substrate may be provided on the other side of the recording medium to sandwich the recording layer.

For example, when a polymer matrix is composed of a thermosetting resin such as a phenol resin or an epoxy resin or an engineering plastic such as polycarbonate, and the substrate itself has sufficient strength, the substrate 11 can be omitted.

The thickness of the information recording layer 12 is preferably in the range of 1 μm to 3,000 μm. At this time, the transmittance in the recording wavelength range of 350 nm to 800 nm is high, and even if the recording signal light of relatively low energy and the reference light are recorded, recording can be sufficiently performed, and energy efficiency can be increased.

The surface of the information recording layer 12 may be subjected to microfabrication as needed, or may be subjected to a hard coat treatment using a UV curable resin or the like. Furthermore, you can enter Anti-reflection processing.

In the present invention, when the information recording layer 12 is subjected to the polarization total multiplex recording, when the irradiation energy of the recording signal light and the recording reference light is fixed, the diffraction efficiency of the reproduced signal light from each of the recorded diffraction gratings is obtained. The ratio (ηmin/ηmax) of the minimum value ηmin to the maximum value ηmax is preferably 0.1 or more, preferably 0.5 or more, and particularly preferably 0.75 or more.

Therefore, when the illuminating omni-directional multiplex recording is performed, when the irradiation energy of the recording signal light and the recording reference light is fixed, particularly in the case where the scheduling is not performed, the reproduction signal light is not greatly increased or decreased. Diffraction efficiency, and thus the intensity of the signal light. That is, since the operation of recording with high irradiation energy for the page whose prediction sensitivity is lowered is not required, it is not necessary to lengthen the irradiation time for recording with high irradiation energy, and it is possible to suppress a decrease in the transfer rate on the recording system.

Further, the ratio (ηmin/ηmax) of the minimum value ηmin of the diffraction efficiency of the reproduced signal light to the maximum value ηmax can be achieved by forming the information recording layer 12 by the above-described material. In particular, it can be easily realized by using a structure having an α-aminoacetophenone structure and an oxime ester structure as a polarizing inductive component.

It is preferable that ηmin/ηmax is closer to the upper limit value of 1, and a high value of 0.75 or more can be achieved by using the above material.

(Polarized hologram multiple recording and its reproduction)

Next, referring to Figure 1, the multiplexed omni-directional multiple recording and its reproduction will be described. The outline of the principle.

As shown in FIG. 1, when recording is performed on the optical recording medium 10, the coherent recording signal light 21 and the recording reference light 22 are simultaneously irradiated onto a recording area of the information recording layer 12.

For example, if the recording signal light 21 is regarded as p-polarized light and the recording reference light 22 is regarded as s-polarized light, the polarization direction is spatially ‧ periodically modulated in a recording area of the information recording layer 12, ±45 The linearly polarized portion 12A and the circularly polarized portion 12B alternately appear periodically.

At this time, the light intensity distribution in the information recording layer 12 is the same, but for example, the light-induced birefringent material is given birefringence corresponding to the modulated polarization direction. As a result, in the linearly polarized portion 12A, a linearly polarized light of ±45 degrees, an absorptivity or a refractive index having a different spatial directivity, and a birefringent grating distributed at ±45 degrees are formed as a hologram.

Then, the Bragg condition (for example, the angle of the optical recording medium 10) is changed in the information recording layer 12 of the optical recording medium 10, and the irradiation energy of the irradiation of the recording signal light 21 and the recording reference light 22 is fixed, and the same applies to the above. A recording area of the information recording layer 12 is irradiated with them. Thereby, the polarization direction of the information recording layer 12 is spatially modulated periodically, and the linearly polarized portion 12A' of ±45 degrees and the circularly polarized portion 12B' alternately appear periodically.

At this time, the light intensity distribution in the information recording layer 12 is the same, but among the polarization inductive components contained in the light-induced birefringent material, one of the directions in the same direction as the modulated polarization direction is compared. Those who are facing other directions are more strongly excited by light. As a result, in the linearly polarized portion In the 12A', in order to compensate for linear polarization of ±45 degrees, the absorptivity or refractive index which is different in spatial directivity, and the birefringence grating which is distributed at ±45 degrees are formed as a hologram.

In this manner, by making the irradiation energy of the irradiation of the recording signal light 21 and the recording reference light 22 constant, the Bragg conditions are changed in the information recording layer 12, and they are sequentially irradiated, and each of the diffraction gratings is recorded as information. By functioning, it is possible to perform multi-recording of the polarized hologram of the information recording layer 12.

Then, the information recording layer 12 which has been subjected to the multiplex multiplex recording as described above is irradiated with the reference light 22 and the reproduced light 23 of the same polarization from the front side or the back side so as to satisfy the Bragg condition. In this way, the diffracted light from each of the recorded diffraction gratings is obtained as the reproduction signal light. At this time, the diffracted light system is p-polarized light which is different from the incident light by 90 degrees. In this manner, the reproduction reference light 23 is irradiated to each of the diffraction gratings of the information recording layer 12 which has been subjected to the polarization total multiplex recording, whereby reproduction (reading) from the information recording layer 12, that is, the optical recording medium can be performed.

Furthermore, in the above description, for the different diffraction gratings of the information recording layer 12, the polarization states of the recording signal light 21 and the recording reference light 22 are fixed in the p-polarized light and the S-polarized light, respectively, but the recording signal light 21 and The polarization state in which the reference light 22 is recorded may be any combination of the same or mutually orthogonal polarization states.

Further, in the above, the optical recording medium 10 shown in Fig. 1 is of a transmissive type, and the principle of recording and reproducing relating to the transmissive optical recording medium will be described. However, the recording and reproduction relating to the reflective optical recording medium is described. , only The point at which the reproduction reference light 23 is incident from the irradiation side of the recording signal light 21 and the recording reference light 22 of the information recording layer 12 is different, and the other operation is the same as the principle of recording and reproduction relating to the transmissive optical recording medium.

(Specific examples of polarized hologram multiple recording and its reproduction)

2 is a schematic configuration diagram showing an example of a recording optical system used for the multiplexed omni-directional multiple recording of the present invention, and FIG. 3 is a view showing a reproducing optical system used for reading the recorded information after performing the multiplex full-image multiplex recording. A schematic diagram of an example.

In order to perform the above-described polarization omnidirectional multiple recording, for example, an optical system as shown in Fig. 2 is used. In this optical system, after the laser light passes through the shutter 1, HWP (1/2 wavelength plate) 1, it is divided into 2 by PBS (polarizing beam splitter), and one of them is used as a recording signal light to pass through the shutter 2, and is then SLM. (Spatial light modulator) reflects, penetrates the PBS, and is irradiated to the optical recording medium. At this time, the light reflected by the SLM is mixed with the s-polarized light, but since only the p-polarized component penetrates the PBS, the p-polarized component passes through the lens as signal light, and is irradiated onto the optical recording medium.

Further, the other one divided by the PBS is reflected by the SPLM (Spatial Polarizing Transducer) as the recording reference light, and is irradiated to the optical recording medium by the lens. At this time, the SPLM is used to control the polarization state of the recording reference light to be s-polarized orthogonal to the polarization state of the recording signal light. Thereby, as described above, in the information recording layer of the optical recording medium, the polarization direction is spatially modulated ‧ periodically, and the linearly polarized portion of ±45 degrees and the circularly polarized portion alternately appear periodically. Then, in the linearly polarized portion, it is ±45 The linear polarization of the degree, the absorptivity or refractive index of different spatial directivity, and the diffraction grating of birefringence distributed at ±45 degrees are formed as a hologram.

Next, in the optical system shown in FIG. 2, the angle of the optical recording medium is changed by using a control system (not shown), and the above-described operation is performed on the information recording layer which is the optical recording medium, and the information recording layer, that is, the optical recording is performed. The polarizedness of the media is like multiple records.

Further, when the signal is read (reproduced) by the information recording layer which is an optical recording medium which has been subjected to the multiplex full image multiplexing recording, for example, an optical system as shown in FIG. 3 is used. This optical system is based on the optical system shown in Fig. 2, and an imaging optical system, a polarizing plate, and an imager for imaging the regenerated light (diffracted light) after penetrating (diffusing) the recording medium.

Using the reproducing operation of the optical system shown in FIG. 3, the shutter 2 is closed, and the laser light that has passed through the shutter 1, HWP, and PBS is reflected by the SPLM, and is irradiated to the optical recording medium as the regenerated reference light of the s-polarized light.

In the optical recording medium on which the polarized hologram has been recorded, if the reference light and the reproduced light of the same polarization are irradiated as described above to satisfy the Bragg condition, the diffracted light from the recorded diffraction grating is used as the reproduction signal light. obtain. At this time, the diffracted light is p-polarized light which is different from the incident light (s-polarized light) by 90 degrees. Next, the angle of the optical recording medium is changed by a control system (not shown), and the refraction reference light of the s-polarized light is irradiated to each of the diffraction gratings that have been subjected to the multiplex full-image recording, and the polarized light can be performed. The optical recording medium like multiple recording is the reproduction (reading) of the information recording layer.

Furthermore, the diffracted light is imaged by the imaging lens, and only the p-polarized light is transmitted through the polarizing plate, and is incident on the imager to perform analysis of the recorded information.

[Examples] <Example 1>

Synthesis of (A) 1-(4-fluorophenyl)-2-bromobutan-1-one

9.61 g (100 mmol) of fluorobenzene was dissolved in 50 ml of dichloromethane, and after cooling to 0 ° C under a nitrogen atmosphere, 26.7 g (200 mmol) of anhydrous aluminum chloride was slowly added, and the mixture was stirred for 15 minutes. 23 g (100 mmol) of 2-bromobutylphosphonium bromide was dissolved in 50 ml of dichloromethane at 0 ° C, and the mixture was stirred for 30 minutes, and then the mixture was warmed to room temperature and stirred overnight. After completion of the reaction, the mixture was poured into ice water (150 ml). The organic layer was washed with water (100 ml) and brine The desiccant was separated by filtration, and the solvent was evaporated under reduced pressure. The obtained crude product was purified by column chromatography (n-hexane: ethyl acetate = 9:1) to give the desired benzene.

Synthesis of (B) 1-(4-fluorophenyl)-2-dimethylaminobutan-1-one

20.0 g (81.6 mmol) of 1-(4-fluorophenyl)-2-bromobutan-1-one was dissolved in 50 ml of ethanol, and the solution was cooled to 0 ° C, and 11% by weight of dimethylamine was slowly dropped therefrom. The ethanol solution was 198 g. After the mixture was stirred at 0 ° C for 12 hours, excess dimethylamine was removed by bubbling nitrogen at room temperature, and water (100 ml) and dichloromethane (100 ml) were added for extraction. The organic layer was dried over anhydrous magnesium sulfate, and the desiccant was separated by filtration, and the solvent was evaporated under reduced pressure. The obtained crude product was purified by column chromatography (hexane: ethyl acetate = 2:1) to give the desired compound. g.

Synthesis of (C) 1-(4-fluorophenyl)-2-dimethylamino-2-(4-methylbenzyl)butan-1-one

1-(4-Fluorophenyl)-2-dimethylaminobutan-1-one 8.00 g (38.2 mmol) was dissolved in 50 ml of acetonitrile, and 4-methylbenzyl bromide was slowly dropped with stirring. 8.49 g (45.9 mmol). After the mixture was stirred at room temperature for 12 hours, the solvent was evaporated under reduced pressure to dissolve residue. The solution was heated to 60 ° C in 50 ml of water. At this temperature, 9.00 g (76.4 mmol) of a 34% NaOH solution was added dropwise, and stirring was continued for 30 minutes. After stirring, the mixture was cooled to room temperature, and dichloromethane (100 ml) and water (100 ml) were added and extracted. The organic layer was dried over anhydrous magnesium sulfate, and the dried solvent was filtered, and the solvent was evaporated. The obtained crude product was used in the following reaction without further purification.

(D) 2-Dimethylamino-2-(4-methylbenzyl)-1-{4-[4-(2-hydroxyethyl)peri Synthesis of -1-yl]phenyl}butan-1-one (Compound No.1)

While stirring 1-(4-fluorophenyl)-2-dimethylamino-2-(4-methylbenzyl)butan-1-one (crude product from C) 9.50 g (30.3 mmol), 1-piper 7.89 g (60.6 mmol) of ethanol, 8.39 g (60.6 mmol) of potassium carbonate, and 100 ml of dimethyl hydrazine were stirred at 160 ° C for 12 hours. After stirring, the reaction solution was cooled at room temperature, and extracted with water (100 ml) and dichloromethane (100 ml). The organic layer was dried over anhydrous magnesium sulfate, and the solvent was evaporated, and the solvent was evaporated. The crude product was purified by column chromatography (ethyl acetate) to give the desired compound 8.29 g.

Further, the obtained compound was identified by NMR, and as a result, the following data was obtained, and the above compound was found to be 2-dimethylamino-2-(4-methylbenzyl)-1-{4-[ 4-(2-hydroxyethyl)perazine 1-yl]phenyl}butan-1-one (Compound No. 1).

¹ H-NMR (CDCl ₃ ) δ (ppm): 8.35 (d, 2H); 7.11 (d, 2H); 7.02 (d, 2H); 6.82 (d, 2H); 3.73 (t, 2H); t, 2H); 3.15 (s, 2H); 2.76 (t, 4H); 2.69 (t, 2H); 2.36 (s, 6H); 2.30 (s, 3H); 1.79-2.09 (m, 2H); (t, 3H). FD-MS: 423.

[Production of Optical Recording Media]

Modulation of 2-dimethylamino-2-(4-methylbenzyl)-1-{4-[4-(2-hydroxyethyl)perepine as a polarizing inductive component 5.0 parts by weight of -1-yl]phenyl}butan-1-one (Compound No. 1), TEPIC-S (triglycidyl isocyanurate) as a polymer matrix forming component (precursor), Nissan Chemical Industry Co., Ltd.) 34.4 parts by weight, 4-methylcyclohexane-1,2-dicarboxylic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.), 60.3 parts by weight, tetrabutylphosphonium diethylbenzene as a hardening catalyst 0.4 parts by weight of a recording material precursor composed of bisphosphonate (manufactured by Wako Pure Chemical Industries, Ltd.). This recording material precursor was introduced into a space of two glass substrates (30 mm × 30 mm, thickness: 0.5 mm) to which antireflection treatment was applied via a tantalum film spacer (thickness: 0.3 mm), and was carried out at 100 ° C. The heat treatment was carried out for 2 hours, followed by heat treatment at 140 ° C for 10 hours. An optical recording medium in which an information recording layer composed of a light-induced birefringent material was formed between two glass substrates was obtained.

<Example 2>

In addition to the use of 2-dimethylamino-2-(4-methylbenzyl)-1-{4-[4-(2-hydroxyethyl)per 10.0 parts by weight of -1-yl]phenyl}butan-1-one (Compound No. 1) as a polarizing inductive component, using 9,9-bis(4-epoxypropoxyphenyl)fluorene (Nippon Steel) 49.6 parts by weight of 4-methylcyclohexane-1,2-dicarboxylic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.), which is a polymer matrix forming component (precursor), and In the same manner as in Example 1, an optical recording medium was obtained.

<Example 3>

Synthesis of (A) 1-(4-fluorophenyl)-2-bromo-2-methylpropan-1-one

A suspension of 40 ml of dichloromethane and 10.34 g (77.5 mmol) of anhydrous aluminum chloride was cooled to 3 ° C under a nitrogen atmosphere, and a solution of 7.45 g (77.5 mmol) of fluorobenzene in dichloromethane was added thereto, followed by stirring for 30 minutes. In the meantime, 17.83 g (77.5 mmol) of 2-bromobutylphosphonium bromide was added dropwise. After the completion of the dropwise addition, the reaction mixture was warmed to room temperature and stirred overnight. followed by The obtained reaction mixture was poured into ice water (150 ml). The organic layer was washed with brine (100 ml) and dried over anhydrous magnesium sulfate. By the NMR measurement, it was confirmed that 19.00 g of a crude product (reddish brown liquid) was used as a target, and it was used directly for the following reaction.

Synthesis of (B) 1-(4-fluorophenyl)-2-methyl-2-morpholinylpropan-1-one

7.54 g (86.5 mmol) of morpholine was dissolved in 18 mL of tetrahydrofuran, and after cooling to 3 ° C, 1-(4-fluorophenyl)-2-bromo-2-methylpropan-1-one dissolved in 18 mL of tetrahydrofuran was added dropwise. 8.51 g (34.7 mmol). After the obtained mixture was refluxed at 50 ° C for 72 hours, ethyl acetate was added to the mixed solution, and the mixture was extracted three times with 1N hydrochloric acid (150 ml). An aqueous sodium hydroxide solution was added to the aqueous layer to make it alkaline, and the mixture was extracted twice with ethyl acetate (100 ml). The ethyl acetate layer was washed with distilled water (100 ml) and brine (100 ml) and dried over anhydrous magnesium sulfate. After refining by column chromatography using a 50/50 mixture of ethyl acetate/hexane, and recrystallization from methanol, pale yellow crystals (5.8 g) were obtained. By The target product was confirmed by NMR measurement.

Synthesis of (C) 1-[4-(2-hydroxyethylthio)-phenyl]-2-methyl-2-morpholinylpropan-1-one (Compound No. 4)

0.67 g (8.5 mmol) of mercaptoethanol and 0.34 g (8.5 mmol) of sodium hydroxide were dissolved in 5 ml of toluene, and refluxed at 120 ° C for 3 hours using a Dean-Stark apparatus. On the other hand, toluene ‧ water is removed by distillation. 2.5 ml of dimethylformamide was added to the solid formed, and after cooling the solution to room temperature, 1-(4-fluorophenyl)-2-methyl-2-morpholinylpropan-1- was added. Ketone 1.7 g (6.8 mmol). The mixture was heated and stirred at 50 ° C for 15 hours under a nitrogen atmosphere. Then, 30 ml of water was added, and the mixture was extracted twice with 30 ml of ethyl acetate. The organic layer was washed with 40 ml of a 2% aqueous sodium hydroxide solution and 40 ml of a saturated aqueous sodium chloride solution, and dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The column chromatography of 50 mixtures was purified to give a yellow viscous liquid (1.8 g, 5.8 mmol). The target product was confirmed by NMR measurement.

[Production of Optical Recording Media]

In addition to using 5.0 parts by weight of 1-[4-(2-hydroxyethylthio)-phenyl]-2-methyl-2-morpholinylpropan-1-one (Compound No. 4) as a polarizing inductive component, 35.4 parts by weight of TEPIC-S (triglycidyl isocyanurate, manufactured by Nissan Chemical Industries Co., Ltd.), 4-methylcyclohexane-1,2-dicarboxylic anhydride (Tokyo Chemical Industry Co., Ltd.) An optical recording medium was obtained in the same manner as in Example 1 except that 60.0 parts by weight of the polymer matrix-forming component (precursor) was used.

<Comparative Example 1>

Except that 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)butan-1-one (IRGACURE 379, manufactured by BASF Corporation) 5.0 was used. As a polarizing inductive component, 54.8 parts by weight of 9,9-bis(4-glycidoxyphenyl)fluorene (manufactured by Nippon Steel Chemical Co., Ltd.) and 4-methylcyclohexane-1 were used. An optical recording medium was obtained in the same manner as in Example 1 except that 39.9 parts by weight of a 2,-dicarboxylic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as a polymer matrix-forming compound.

<Comparative Example 2>

1.0 part by weight of 9,10-phenanthrenequinone (manufactured by Tokyo Chemical Industry Co., Ltd.) as a polarizing inductive component, and methyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.) as a thermal polymerization monomer A recording material precursor composed of 0.4 parts by weight of 2,2'-azobis(isobutyronitrile) as a thermal polymerization initiator. This recording material precursor was heated at 60 ° C for 2 hours. Thereafter, the film was introduced into a space of two glass substrates bonded to each other through a dicing spacer (thickness: 1.0 mm) which was cut into a concave shape. Then, heat treatment was carried out at 60 ° C for 6 hours to obtain an optical recording medium.

<Comparative Example 3>

10.0 parts by weight of 2,4,6-trimethylbenzhydryldiphenylphosphine oxide (DAROCUR TPO, manufactured by BASF Corporation) as a polarizing inductive component, and dicyclohexylmethane as a polymer matrix forming material were prepared. 40.9 parts by weight of 4,4'-diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) and pentaerythritol propoxide (average molecular weight 629: manufactured by Aldrich Co., Ltd.) 49.1 parts by weight, dibutyltin laurate as a hardening catalyst (Tokyo 0.07 parts by weight of a recording material precursor composed of Chemical Industry Co., Ltd.). This recording material precursor was introduced into a space of two glass substrates bonded through a tantalum film spacer (thickness: 0.3 mm). Then, heat treatment was performed at 55 ° C for 3 hours in a nitrogen atmosphere to obtain an optical recording medium.

<Comparative Example 4>

In addition to 1-[4-(phenylthio)phenyl]-1,2-octanedione, 2-(o-benzylidene fluorene) (IRGACURE OXE01, manufactured by BASF) 10.0 parts by weight as a polarizing inductive component An optical recording medium was obtained in the same manner as in Comparative Example 3 except for the above.

<Comparative Example 5>

In addition to using 2-dimethylamino-2-(4-methylbenzyl)-1-(4-? Phenyl-4-yl-phenyl)butan-1-one (IRGACURE 379, manufactured by BASF Corporation) 10.0 parts by weight as a polarizing inductive component, using 9,9-bis(4-glycidoxyphenyl)anthracene ( 51.9 parts by weight of Nippon Steel Chemical Co., Ltd., 37.8 parts by weight of 4-methylcyclohexane-1,2-dicarboxylic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) as a polymer matrix forming component (precursor) A recording medium was obtained in the same manner as in Example 1 except for the above.

[Recording method]

The recording and reproduction system was carried out in accordance with the above-described recording and reproducing procedure using the optical system shown in Figs. 2 and 3. In the recording optical system shown in FIG. 2, a semiconductor laser having a wavelength of 405 nm which oscillates in a single mode is used for the light source for recording, the SLM is a full-pixel total reflection state, and the PSLM is a full-pixel 90-degree polarization modulation. status. Further, in the reproducing optical system shown in Fig. 3, a He-Ne laser having a wavelength of 633 nm is used for the light source for reproduction.

〔The measurement results〕

With respect to the recording media obtained in the examples and the comparative examples, there was no scheduling (that is, the irradiation energy of the recording signal light and the recording reference light was fixed), and 48 multiple polarization hologram multiple recordings were performed, and the measurement was performed within one hour after recording. M# (M number), as the initial M#.

Here, M# indicates one of the indexes of the multiple recording performance, and M# in the case of m multiple recording is defined by the following formula.

Then, the recording medium was stored under the environmental conditions of a temperature of 23 ° C to 25 ° C and a humidity of 30% to 50%, and after a certain period of time, M# was again measured, and the M# deterioration rate was obtained by the following formula.

The M# deterioration rate with respect to the elapsed time after recording is shown in FIG. According to the same figure, in Comparative Examples 1 and 2, M# deteriorated with the passage of time. On the other hand, in the examples, no deterioration of M# was observed even after 2,000 hours passed, and the stability of the recording signal was good.

5 to 8 show the outlines of the relative diffraction intensities η/ηmax from the respective diffraction gratings when the recording medium obtained in the examples and the comparative examples was multiplexed as described above. Further, Table 1 shows ηmin/ηmax obtained from the data.

As is apparent from Figs. 5 to 8 and Table 1, the ηmin/ηmax of the recording medium obtained in the present embodiment shows a high value of 0.800, and in the above 48 multiple recordings, the scheduling is not essential in nature. Further, in the recording medium obtained in Comparative Example 1, since ηmin/ηmax is also 0.5 or more, the arrangement is not essential in nature, but it is understood that the embodiment having a higher ηmin/ηmax is preferable. Further, as described above, the recording medium obtained in Comparative Example 1 cannot be said to be a good recording medium because of a problem in the stability of the recorded signal. Further, in the recording medium obtained in Comparative Example 2, ηmin/ηmax was a low value of less than 0.1, and in the above-described 48 multiplex recording, it was found that scheduling was required.

[Evaluation of the stability of light-induced birefringence]

The recording medium is irradiated with a polarization distribution in the polarization hologram recording, and a birefringence distribution corresponding to the polarization distribution is generated in the recording medium. Therefore, the stability of the recorded signal recorded by the polarized hologram may be, in other words, the stability of the induced birefringence distribution, and the linearity of the recording medium may be measured to measure the stability of the induced birefringence, which can be easily determined. Record the stability of the signal.

For the recording media obtained in the examples and the comparative examples, measurement of light-induced birefringence was carried out using an optical system as shown in FIG.

Excitation light irradiation condition

Detecting light exposure conditions

The maximum value of the birefringence induced by the irradiation of the linearly polarized light is regarded as the initial birefringence, and the light irradiation is stopped at the time point when the maximum value is obtained. The recording medium in which the maximum light value was not displayed for 10 minutes was regarded as the initial birefringence when the light was irradiated for 10 minutes. Then, the recording medium is stored at an ambient temperature of 25 ° C to 120 ° C, and after a certain period of time, the birefringence is measured again, and the birefringence deterioration rate is obtained by the following formula. The results are shown in Figure 10.

According to the same figure, in the comparative example, the birefringence rapidly deteriorated with the passage of time under the storage conditions. On the other hand, in the examples, the stability of the recorded signal was good even under high temperature conditions.

The present invention will be described in detail above on the basis of the specific examples described above, but the present invention is not limited to the specific examples described above, and all modifications and changes may be made without departing from the scope of the invention.

Claims (8)

A light-induced birefringent material which is a light-induced birefringent material which generates birefringence in response to a polarized state of light to be irradiated, and is characterized in that it contains a polarizing inductive component and a polymer matrix, and the polarized inductive component is covalently The bond is bonded to the polymer matrix, and the bond between the polarizing-sensitive component and the polymer matrix is formed by the same reaction as the reaction for forming the polymer matrix, and the polarization inducing due to light irradiation The reaction of the ingredients is irreversible. The light-inducing birefringent material according to claim 1, wherein the polarizing inductive component is a component of the action of an intramolecular cleavage type photoradical generator. The light-inducing birefringent material according to claim 2, wherein the component acting as an intramolecular cleavage type photoradical generator is an α-aminoacetophenone derivative or an oxime ester derivative. The light-induced birefringent material according to claim 1, wherein the foregoing reaction is a radical addition reaction, an epoxy-anhydride addition reaction, an epoxy-amine addition reaction, an epoxy-thiol addition reaction, an isocyanate-hydroxyl group At least one selected from the group consisting of an addition reaction (formation of a urethane), an isocyanate-amine addition reaction (formation of urea), and a hydroquinonelation reaction. An optical recording medium characterized by having an information recording layer composed of the light-induced birefringent material according to any one of claims 1 to 4. The optical recording medium of claim 5, wherein the first hologram is recorded by irradiating the recording area with the recording signal light of the same or mutually orthogonal polarization state and recording the reference light, and the recording area is the first The hologram records different Bragg conditions and the illumination is the same Or the recording signal light in the polarized state and the recording reference light which are orthogonal to each other, and when the second hologram recording is performed to perform the multiplex full image multiplexing recording, the diffraction efficiency of the reproduced signal light from each of the recorded diffraction gratings is the largest. The value ηmax and the minimum value ηmin satisfy ηmin/ηmax≧0.1. An optical recording method characterized in that a polarized holographic multi-recording is provided, the polarized holographic multi-recording comprising: illuminating the same or mutually orthogonal polarization states with respect to a recording area of the optical recording medium as recited in claim 5 or a step of recording the signal light and recording the reference light to perform the first hologram recording; and illuminating the recording signal of the same or mutually orthogonal polarization state in a state in which the recording region is different from the first hologram recording in the Bragg state The step of recording the second hologram by light and recording the reference light. The optical recording method according to claim 7, wherein the diffraction efficiency of the reproduced signal light from each of the recorded diffraction gratings is performed when the irradiation energy of the recording signal light and the recording reference light is fixed and the polarization total image multiplexing is performed. The maximum value ηmax and the minimum value ηmin of the middle satisfy ηmin/ηmax≧0.1.