JP3532743B2 - Optical recording method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to recording on an optical recording medium .
Regarding the method .

[0002]

2. Description of the Related Art A photorefractive medium is known as one of optical recording media for recording at a much higher density than conventional magneto-optical recording and photothermal phase change type media (optical disks, etc.). This photorefractive medium is a medium capable of recording a large amount of data such as a high-density image and changing the refractive index of the recording layer by the following mechanism. That is, by irradiating with an electromagnetic wave, the electric charges existing therein are spatially separated, and the electric field generated by this electric charge distribution changes the refractive index of the recording material. Therefore, by increasing the electric field generated inside the medium, it is possible to obtain a larger change in the refractive index due to the electro-optic effect. Since such a photorefractive medium can directly record the interference pattern of electromagnetic waves as a refractive index grating, it is expected to be applied to a holographic memory, an optical operation element, and the like.

In recent years, a photorefractive medium using an organic polymer compound has been actively developed because of its ease of preparation (for example, Japanese Patent Publication No. 6-55901).
However, when using these media, it was necessary to provide electrodes and apply an electric field from the outside (for example, JP-A-6-175167). This is due to the following circumstances.

When the photorefractive medium is irradiated with the interference pattern of electromagnetic waves, optical carriers corresponding to the intensity of the electromagnetic waves are generated in the photorefractive medium. The electric field E generated when the external electric field E _ex is applied to the photorefractive medium so as to be parallel to the irradiation surface of the electromagnetic wave is
It is expressed by the following equation (1). E = E ₀ [(1 + iE _ex / E _d ) / {1 + iE _ex / (E _d + E _q )}] (I ₁ + I ₀ ) (1) E ₀ = iE _d / (1 + E _d / E _q ) (2) E _d = (2πD) / (μΛ) (3) E _q = (eNΛ) / (2πε) (4) I ₀ is the spatial average of the irradiation light intensity, and I ₁ is the maximum and minimum values of the irradiation light intensity. Is the difference. Further, Λ is a distance (spatial wavelength) between the closest local maxima. ε is the dielectric constant of the photorefractive medium, N is the space charge density, D is the diffusion coefficient, and μ is the mobility. e is the elementary charge amount, i is the imaginary unit, and represents the phase (for example, Pochi Y
eh, Introduction to Photo
reflexive Nonlinear Opti
cs, John Wiley & Sons, March 1993.
chapter). Physically, E _d represents an electric field due to diffusion of charges, and E _q mainly represents a space electric field due to immovable charges. It is generally considered that the Einstein relational expression D / μ = kT / e (k is Boltzmann's constant, T is absolute temperature) is established between the diffusion coefficient D and the mobility μ, and thus E _d is a substance It is a constant that does not depend on. For this reason,
In order to obtain a large electric field E, it was necessary to make E _q sufficiently larger and E _ex larger than E _d . In order to make E _q larger than E _d , in the above equation (4), Λ
And N need to be increased. However, when Λ is increased, the density of the interference fringes is reduced, so that the recording density of the recording element is reduced. On the other hand,
When the space charge density N is increased, there is a drawback that mobility is lowered due to scattering by the charges. The time required to form the electric field when an external electric field is applied is determined by the drift velocity of the charges, and thus the decrease in mobility means the decrease in writing speed. Therefore, the decrease in mobility must be avoided as much as possible.
The above is the reason why it was necessary to apply an electric field when writing to a conventional medium.

When an electric field E _ex is applied from the outside,
The movable charge (carrier) moves in the direction of the electric field,
E almost coincides with the direction of the external electric field. Since the refractive index modulation by the Pockels effect of the electro-optical effect is performed in the electric field direction, in order to read this change in the refractive index by the electromagnetic wave, the direction of the electric field must be close to the incident direction of the electromagnetic wave. For this reason, it was necessary to devise the shape of the electrode for applying the electric field, and it was not possible to manufacture it at low cost. In addition, it can not be used for ordinary optical disks, etc.
The use was limited.

[0006]

The present invention is based on the diffusion coefficient D
To record information on an optical recording medium that can be recorded without applying an electric field from the outside, because the ratio (D / μ) to the mobility μ is large.
The purpose is to provide a recording method of.

[0007]

In order to solve the above problems SUMMARY OF THE INVENTION The present invention provides materials permanent dipole moment increases by application of external energy, a charge generating material, and the optical recording medium containing the charge transporting material , The first light source to the first power source
A step of irradiating a magnetic wave to form interference fringes;
On the surface of the body irradiated with the first electromagnetic wave, the first electric current is applied.
A second electromagnetic wave, which has a different wavelength from the magnetic wave, is emitted from the second light source.
Irradiating to increase the permanent dipole moment
And the second electromagnetic wave is the same as the first electromagnetic wave.
The feature is that irradiation is finished at the same time or in advance.
Optical recording method .

[0008]

The present invention will be described in detail below. As a result of earnest studies, the present inventors have found that a large internal electric field can be formed by using a substance having a large ratio (D / μ) of the diffusion coefficient D and the mobility μ, which is its charge transport property, as a medium. Based on this, the present invention has been completed. This will be described in detail below.

The present inventors have analyzed the transient photocurrent to find that
We have obtained a method that enables simultaneous measurement of mobility and diffusion coefficient (Hirao, Nishizawa, Sugiuchi, Physical Review).
wLetters. Vol. 75, No. 9, pp17
87-1790 (1995)). This method is performed as follows. That is, first, a film-shaped sample is sandwiched by two electrodes, and specific pulsed light is irradiated from one electrode side. Here, the specific pulsed light is pulsed light that is absorbed only near the interface to generate optical carriers, and is, for example, a pulsed laser having a wavelength of 337 nm and a pulse width of about 1 nanosecond. The diffusion coefficient D and the mobility μ can be obtained by fitting the theoretically obtained formula to the experimental waveform of the transient current flowing at that time.

Using this method, a system in which molecules having a charge-transporting ability are dispersed in a polymer, and a molecule having a small dipole moment having a charge-transporting ability and a molecule having a large dipole moment not having a charge-transporting ability are used. The diffusion coefficient D and the mobility μ of the system in which was dispersed were measured. As a result, it was found that the ratio (D / μ) between the diffusion coefficient D and the mobility μ increases as the dipole moment increases. As D / μ increases, the electric field E _d due to diffusion increases from the above formula (3), and as a result, it is unnecessary to apply an electric field from the outside.

Normally, Einstein's relational expression D / μ
= KT / e (k is Boltzmann's constant and T is absolute temperature), D / μ is a constant independent of the material.
However, in the present invention, the charge transport molecules are used in an amorphous state rather than a crystalline state, and the wave function overlap between the charge transport molecules is small. Therefore, in the present invention, there are fluctuations that do not result in a "thermal equilibrium state" that is a condition for establishing the Einstein relational expression and that spread the energy distribution of the hopping site more than thermal fluctuations. (For example, R. Richert,
L. Pautmeier, and H.M. Bassle
r, Phys. Rev. Lett. 63, 547 (19
89)). As a result, D / μ depends not only on temperature but also on material.

The possibility that D / μ does not fit the Einstein's relational expression was only suggested by simulation (PM Borsenberg).
r, E. H. Magin, M .; van der Auw
eraer, and F.F. C. de Schryve
r, Phys. Status Solidi (a), 1
40, 9 (1993)). The inventors were able to actually measure and confirm it. The reason why D / μ increases as the dipole moment of the medium-constituting molecule increases is considered to be that the larger the dipole moment, the wider the density of states and the relatively lower mobility. The dipole moment can be increased by increasing the dipole moment of a molecule having a charge-transporting ability or by mixing molecules having a dipole moment (eg, Sugiuchi, Nishizawa, Journal of Imaging Scie).
nce Technology, Vol. 37,
No. 3, pp 245-250 (1993), H .; Va
lerian, E .; Brynda, S .; Nespure
k, and W. Schnabel, J .; Appl. P
hys. 78, 6071 (1995)). Mobility can be reduced by increasing the dipole moment by either method.

That is, in the present invention, in order to increase the dipole moment, the dipole moment of a molecule having a charge transporting ability may be increased or the dipole moment of another molecule may be increased.

Further, the reason why the mobility becomes smaller as the dipole moment becomes larger is as follows. That is, since the electrostatic potential on each charge transfer molecule has a different value under the influence of the electric field created by the dipole moment, the energy distribution of the charge transport molecule spreads to a distribution width of about 0.1 eV (for example, A. Dieckm
Ann, H.A. Bassler, and P.M. M. Bor
semberger, J .; Chem. Phys. 99,
8136 (1993)). On the other hand, the potential gain when electric charges move in the direction of the external electric field is extremely small, and for example, the potential gain when hopping at 1 nm with an electric field of 1 MV / m is only 1 meV. As described above, since the gain of the electrostatic potential is larger than the gain of the potential when moving in the direction of the external electric field, it is not necessarily energetically advantageous to move the charges in the direction of the electric field. That is, since the electric charges move in a direction other than the electric field, the mobility becomes small.

As described above, the fluctuation of the electric field causes an energy distribution, and when the electric charge moves in the energy distribution, the electric charge does not always move in the direction of the electric field from the outside, so that the mobility is lowered. Happens.
However, it is a remarkable fact that the micro-movement (hopping) speed of holes (electrons) is not slowed down. That is, since charges move in all directions, the movement appears relatively slow when only the movement in the direction of the external electric field is observed (for example, H. Ba.
ssler, Phys. Status Solidi
(B) 175, 15 (1993)). As a result of this,
The diffusion coefficient D, which reflects the spread of the charge in all directions, is less affected by the dipole moment, while the mobility μ is
As the dipole moment increases, it decreases, so D /
μ increases.

As is clear from the equation (1), the larger the D / μ is, the larger the internal electric field becomes, and hence the external electric field becomes unnecessary, and therefore the electrode for applying the external electric field becomes unnecessary. The electric field E _d due to the diffusion of a normal substance is 0. 0 at room temperature (300 K) and the spatial wavelength Λ = 1 μm.
163 MV / m. On the other hand, in the photorefractive polymer that has been studied so far, the applied electric field from the outside is 10 MV / m or more (for example, WE Moe.
rner and Scott M.D. Silence,
Chem. Rev. 94, pp127-155 (199
4)). Therefore, from the above formula (1), when D / μ is 5 or more, preferably 10 or more, it is possible to generate an internal electric field due to diffusion to the same extent as the external electric field.

In brief, in ordinary substances, the Einstein relational expression holds between the mobility and the diffusion coefficient when the following two conditions are satisfied. That is, the carrier is in an equilibrium state caused by thermal transition between the energy gaps, and
Diffusion is caused by heat fluctuations.
On the other hand, in the system of the present invention, carriers are generated by light and are in a non-equilibrium state. Moreover, diffusion is caused by fluctuations in the electric field due to the dipole moment, so it is not a condition that satisfies the Einstein relation. As a result, D / μ can be increased if molecules or places having a large dipole moment are randomly present.

In the photorefractive medium, carriers generated by light irradiation are transported by hopping between charge transport materials. This transport consists of drift movement and diffusion in the direction of the electric field, and can be described by the diffusion coefficient (D) and drift mobility (μ), respectively. And this D / μ
The larger is the internal electric field can be formed without applying the external electric field.

The present inventors have obtained the following findings as a result of the examination. That is, when writing information to a recording medium by irradiating recording light, molecules having a large dipole moment only need to be present in the system, and a material that increases the permanent dipole moment due to external energy application is included. That is what makes it possible. Furthermore, when recording on such a recording medium, electromagnetic waves other than the electromagnetic waves forming the interference fringes that are the recording light, the wavelength of which is different from the electromagnetic waves forming the interference fringes, particularly preferably, It was found that the recording can be efficiently performed by irradiating a material having a long wavelength even before the irradiation of the recording light is completed.

In the optical recording medium of the present invention, the material whose permanent dipole moment increases by the energy applied from the outside is a material whose dipole moment changes by 0.1 debye or more by absorbing light. It is also called isomerized material. The optimum content of the photoisomerizable material in the recording medium varies depending on the bulkiness of the material and the functions (charge transport function, charge generating function, function of non-linear optical material, etc.) that combine, but in the recording medium, the weight ratio is 3%. It is preferably 70% or less. When the content is less than 3% by weight, it is difficult to obtain a sufficient effect, while when it exceeds 70% by weight, the recording life may be shortened.

Examples of such a photoisomerizable material include a photochromic material and a thermochromic material. More specifically, leuco compounds of triallylmethane such as leuco cyanide, stilbenes, fulgides, bianthrone, spiropyrans, allyl disulfides, azo compounds, spirooxazines, diarylethene, cyclophanes, and chalcone derivatives. Is mentioned.

The energy applied from the outside increases the dipole moment of the above-mentioned materials contained in the system, which increases D / μ. As a result, the internal electric field can be formed without applying the external electric field. Therefore, it is desirable that the photoisomerization material is randomly present in the system containing the charge transport material. Writing may be performed by applying an electric field from the outside, but the optical recording medium of the present invention is effective when writing without applying.

At this time, the energy applied from the outside in order to increase the dipole moment includes heat, electromagnetic waves, and the like. When the external energy used to increase the dipole moment of the molecule during writing is light, the wavelength of the irradiation light is preferably longer than the wavelength of the writing light. Therefore, the molecule used at this time is preferably one that is excited by light having a wavelength longer than that of the writing light to increase the dipole moment.

On the other hand, when the external energy used to increase the dipole moment of the molecule at the time of writing is heat, the sample is heated by the interference fringes of the electromagnetic waves used as the recording light, and the heat causes the dipole moment of the molecule. It may change or may be heated when writing. At this time, heating may be performed by irradiating infrared rays or bringing a heated one into contact, and the heating method is not particularly limited.

As the charge generating material in the optical recording medium of the present invention, any material that absorbs writing light and generates charges can be used. Examples of such materials include selenium and selenium alloys, CdS, CdSe, As.
Inorganic photoconductors such as Se, ZnO and α-Si, phthalocyanine dyes / pigments such as metal phthalocyanines, metal-free phthalocyanines and their derivatives, naphthalocyanine dyes / pigments, azo dyes / pigments such as monoazo, disazo and trisazo. , Perylene dyes and pigments, indigo dyes and pigments,
Quinacridone dyes and pigments, polycyclic quinone dyes and pigments such as anthraquinone and anthanthrone, cyanine dyes and pigments, for example, electron-accepting substances and electron-donating substances represented by TTF-TCNQ and PVK-TNF Examples thereof include charge transfer complexes, azurenium salts, fullerenes represented by C ₆₀ and C ₇₀ , and their derivatives.

These charge generating materials may be used alone or in combination of two or more kinds. Since the charge generation material needs to absorb the writing light and generate charges, when using a charge generation material having an extremely high optical density with respect to the writing light, even the charge generation material inside the element can be used. Writing light may not reach. In order to avoid such inconvenience, the optical density of the device is 1
It is preferably in the range of 0 ⁻⁶ to 10.

Further, even if the concentration of the charge generating material added is too high, the writing light does not reach the inside, which makes it difficult to write to the inside. On the other hand, when the added concentration is excessively low, the generated charge density is low and the desired internal electric field cannot be obtained. Therefore, the concentration of the charge generating material added is preferably adjusted so that the optical density of the device is within the range of 10 ⁻⁶ to 10.

Specifically, it is desirable that the amount of the charge generating material added be approximately 0.01 to 20.0% by weight based on the entire recording medium. If it is less than 0.01% by weight, the charge generated per unit volume by light irradiation is small,
It becomes difficult to generate sufficient internal charges. On the other hand, when it exceeds 20.0% by weight, the probability of association between charge generating materials increases,
There is a risk that the conductivity of the medium will increase and it will not be possible to generate a high internal electric field.

The charge transport material used in the optical recording medium of the present invention transports holes or electrons, and for example, any material having a function of transporting charges by hopping conduction can be used. The charge transport material may be a molecule alone, a polymer, or a copolymer with another polymer. For example, those listed below are listed. That is, nitrogen-containing cyclic compounds such as indole, carbazole, oxazole, isoxazole, thiazole, imidazole, pyrazole, oxaadiazole, pyrazoline, thiathiazole, and triazole, or derivatives thereof, or compounds having these in the main chain or side chain. , Hydrazone compounds, triphenylamines, triphenylmethanes, butadienes, stilbenes, quinone compounds such as anthraquinone diphenoquinone or derivatives thereof, or compounds having these in the main chain or side chain, C ₆₀ , C ₇₀ And fullerene and its derivatives. Further, π-conjugated polymers and oligomers such as polyacetylene, polypyrrole, polythiophene, and polyaniline; or σ-conjugated polymers and oligomers such as polysilane and polygermane; polycyclic aromatic compounds such as anthracene, pyrene, phenanthrene, and coronene. Etc.

The charge transport material is added in an amount of 10 to 10 in the recording medium.
It is desired to be about 70% by weight. When it is less than 10% by weight, it becomes difficult to obtain a sufficient function.
If it exceeds 0% by weight, it becomes difficult to maintain the written internal electric field, and the recording life may be extremely shortened.

The carriers generated from the charge generating material as described above are injected into the charge transporting material and then move between the charge transporting materials to form an electric field. Therefore, it is desirable that the ionization potential and the electron affinity of the charge transport material used have the following relationships with other molecules. That is, when the carriers are holes, it is preferable that the ionization potential I _P (CGM) of the charge generation material and the ionization potential I _P (CTM) of the charge transport material satisfy the following relationship.

I _P (CTM) <I _P (CGM) Further, at this time, since it is required that the electrons do not move from the charge generating material, the electron affinity χ (CGM) of the charge generating material is required.
And the electron affinity χ (CTM) of the charge transport material preferably satisfy the following relationship.

Χ (CTM) <χ (CGM) On the other hand, when the carriers are electrons, the ionization potential and electron affinity of the charge generation material and the charge transport material are desired to have the following relationships.

I _P (CGM) <I _P (CTM) χ (CGM) <χ (CTM) Furthermore, it is desirable that there is no interaction with other molecules such as a nonlinear optical material or the host matrix.

The optical recording medium of the present invention is prepared, for example, by mixing a material whose dipole moment increases due to external energy, a charge generating material and a charge transporting material to obtain a solution and evaporating the solvent. You can Examples of the solvent that can be used here include trichloroethane, toluene and the like. Alternatively, the optical recording medium of the present invention may be produced without using a solvent, for example, by mixing the fine particles in a state where the molecular mixture is heated and quenching.

When the optical recording medium of the present invention is prepared from a solution, the non-linear optical molecule may be dissolved in the solution, and when the component such as the charge generating material is not a polymer,
Further, the polymer may be dissolved as a matrix. As the polymer that can be used, for example, polyethylene resin, nylon resin, polyester resin, polycarbonate resin, polyarylate resin, butyral resin,
Examples thereof include polystyrene resins and styrene-butadiene copolymer resins. These may be used alone or in combination of two or more.

As the nonlinear optical material, for example, C
Fullerenes such as ₆₀ and C ₇₀ can be used, but as described above, the charge generation material, charge transport material, matrix,
Alternatively, the photoisomerizable material may also have a function as a nonlinear optical material.

In recording information on the optical recording medium of the present invention, first, the external energy as described above is applied simultaneously with the writing light or prior to the irradiation of the writing light. Thus, the energy applied from the outside increases the dipole moment of the material in the system, which increases D / μ, so that the internal electric field can be formed without applying the external electric field.

In the optical recording medium of the present invention, since information is recorded by forming interference fringes by two lights, coherent light can be used as a light source. In order to obtain interference fringes, it is preferable to divide and use the light from the same light source, but two light sources with the same output wavelength are mutually fed back (the output light is input to the other party), and different light sources are used. It is also possible to use.

When recording information, information is added to one of the two lights, and interference fringes generated between this and the other light are recorded on the medium. Therefore, an optical path difference is generated between the two lights, so that interference fringes do not occur if the light has a short coherence length. For this reason, a laser having a coherence longer than the optical path difference is preferable as the light source. Usually, considering the application to computer terminals, video editing, database memory, etc., the optical path difference inside the device is considered to be about 1 cm or more, so gas lasers or semiconductor lasers, especially feedback, to improve coherence length. A lengthened semiconductor laser is preferably used as a light source.

The information recorded as described above can be erased as follows. The first method is to uniformly redistribute the trapped charges by irradiating the medium with light or to apply heat to make the charge distribution uniform, and the second method is to trap the trapped charges. Is to be recombined with a charge of opposite polarity.

The first method of making the charge distribution uniform is a method suitable for erasing information recorded in a wide area of the medium, while the second method of erasing the charge is written. It is suitable for locally erasing recorded records. In this case, it is necessary to provide the medium with a mechanism for generating charges having opposite polarities. For example, when the generated charges are carriers, it is necessary to include an electron generating material and its transport material.

Since the optical recording medium of the present invention contains a material whose dipole moment increases by the application of external energy, D / μ is large and an internal electric field can be formed without applying an external electric field. Is possible. Therefore, an optical recording medium having high diffraction efficiency and excellent storage stability of recording can be obtained.

The optical recording medium of the present invention as described above can record information with the recording apparatus of the present invention. The recording apparatus of the present invention will be described in detail below. The recording apparatus of the present invention has a function of irradiating an electromagnetic wave (hereinafter, referred to as a second electromagnetic wave) having a wavelength different from that of an electromagnetic wave which is a recording light when recording information on the optical recording medium of the present invention (second A device equipped with a light source). It is preferable that the second electromagnetic wave is applied to the medium before recording is finished and after the recording is held, but the second electromagnetic wave is not limited to this. That is, the second electromagnetic wave may be emitted until after the irradiation of the recording light is completed, as long as the recorded state is maintained to the extent of being reproducible. The second electromagnetic wave is light containing a wavelength that is absorbed by a material (photoisomerization material) contained in the medium, the dipole moment of which increases by light, and has a wavelength different from that of the recording light and the reference light. Further, the second electromagnetic wave does not necessarily have to be coherent light, because it is sufficient to irradiate the place where the interference fringe is irradiated with the first electromagnetic wave at the same time as or before the first electromagnetic wave. Further, the part that irradiates the second electromagnetic wave is the part that irradiates the interference fringes.
As long as the irradiation area of the electromagnetic wave and the irradiation area of the interference fringe are not extremely different, either one may be larger. However, the second
The penetration depth of the electromagnetic wave into the medium is preferably at least 0.1 μm or more. This is because writing in the refractive index grating by irradiating the interference fringes increases the diffraction efficiency, and therefore writing is performed in a region of 0.1 μm or more in the film thickness direction.

The angle of irradiating the medium with such a second electromagnetic wave is not particularly limited, and the medium may be irradiated with an angle different from that of the recording light or the reference light. The irradiation start time is more preferably before the irradiation of the interference fringes, but may be after the irradiation of the interference fringes as long as it is before the irradiation of the interference fringes is completed.

Information can be recorded on the optical recording medium of the present invention by the recording apparatus having the second light source for irradiating the medium with the specific second electromagnetic wave as described above. Furthermore, the recording apparatus of the present invention has a function capable of moving the light source or the medium, such as a driving motor in the x, y, and z directions in order to change the recording location on the medium, or a mirror such as a micro. It is preferable to have a function of changing the optical path by combining with a mirror and the like.

[0048]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in more detail below by showing Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples. (Example 1) Each component was dispersed and dissolved in toluene according to the following formulation to prepare a toluene solution.

Nonlinear optical material: Carbon cluster C ₆₀ 0.3% by weight Charge generation material: (G-1) 0.1% by weight Charge transport material: (M-1) 45% by weight (M-2) 5% by weight Matrix: polystyrene 39.6% by weight Photoisomerization material (dipole change material): (D-1) 10.0% by weight Each component used here is shown in the following chemical formula.

[0050]

[Chemical 1]

[0051]

[Chemical 2]

[0052]

[Chemical 3]

[0053]

[Chemical 4]

[0054]

[Chemical 5]

In the equation, n is a positive number. The solvent was removed by heating and depressurizing the obtained mixed solution to obtain a dry substance. On the other hand, the quartz substrate was heated to 120 ° C. in advance, and the spacer for adjusting the film thickness and the above-mentioned dry substance were placed on the quartz substrate and dissolved. Further, another quartz substrate was pressed against it to prepare a sample having a film thickness of 150 μm.

When the absorption spectrum of this sample was measured, it was in the form of the sum of the absorption spectra of the individual materials. As a result of measuring the emission spectrum, no new emission peak was observed, and it was confirmed that no charge transfer complex was formed between C ₆₀ and another molecule.

Next, in order to evaluate the performance as an optical recording medium, the diffraction efficiency of the diffraction grating was measured due to the change in the optical characteristics due to the electric field formed in the film formed by the light irradiation.

An outline of the apparatus used is shown in FIG. As shown in FIG. 1, an argon laser 8 which is a coherent light source.
The light emitted from the first beam splitter 9 first emits a first beam (object beam) 2 and a second beam (reference beam) 3
Can be divided into The object light 2 is a micromirror array 11
Then, after the reference light 3 is reflected by the mirror 10, the two reflected lights are crossed by the lens 12 and are further transmitted through the sample 1 arranged at the crossing position. The intensity of the transmitted beam is measured by the photodetector 7 arranged in the transmission direction 6 of the object light.

In the figure, reference numeral 4 indicates external energy for increasing the dipole moment of the photoisomerizable material contained in the optical recording medium. As shown in the drawing, the object light 2 and the reference light 3 were irradiated so as to intersect with each other on the sample 1, thereby forming interference fringes by the laser light on the sample. When used as an optical recording medium, the sample is irradiated with reflected light from an object that records object light or light that has passed through a transmissive image display element (pager) composed of a liquid crystal display element, The reference light is irradiated so as to intersect with this and cover the irradiation surface. In addition, light with a wavelength of 780 nm 4
Was irradiated on the sample 1 so as to cover the interference fringes, and the sample 1 was left as it was for 5 minutes for writing.

After that, the object light 2 and the light 4 having a wavelength of 780 nm 4
Was reproduced by irradiating only the reference light 3 similar to that at the time of writing. The reference light 3 is diffracted by the medium, and is divided into a component of the reference light 3, a component 5 in the opposite direction of the object light 2, and a transmitted light component 6 of the object light 2.

As shown in FIG. 1, in the direction 6 through which the object light is transmitted, an optical power beam for measuring the intensity of the reproduction beam and a photodetector 7 such as a CCD for taking in the reproduction image are installed. The object light that should not be irradiated, that is, the reproduced image, is observed by this photodetector, and functions as an optical memory.

Here, the ratio (I _obj. / I _ref. ) Between the intensity of the object light reproduced as the reference light (I _obj. ) And the intensity of the irradiated reference light (I _ref. ) _Is obtained as the diffraction efficiency _. It was The diffraction efficiency of the film of this example measured according to the above procedure is
It was 30.0%. The records were readable for about 8 months.

(Comparative Example 1) A mixed solution was prepared in the same manner as in Example 1 except that polystyrene was added instead of the photoisomerizable material (D-1), and the mixed solution was used in the same manner as described above. A sample having a film thickness of 150 μm was prepared.

The characteristics of the obtained sample were evaluated in the same manner as in Example 1. As a result, the photorefractive effect was exhibited, but the diffraction efficiency was 3.1%, which was smaller than that in Example 1. . The record became unreadable in about 3 days.

(Example 2) Each component was dispersed and dissolved in toluene according to the following formulation to prepare a toluene solution.

Nonlinear Optical Material and Charge Generating Material: Carbon Cluster C ₇₀ 0.3 wt% Charge Transport Material: (M-1) 45 wt% (M-2) 5 wt% Matrix: Polystyrene 40.0 wt% Photoisomerism Material (dipole change material): (D-2) 9.7% by weight The components used here are shown in the following chemical formulas.

[0067]

[Chemical 6]

The solvent was removed by heating and depressurizing the obtained mixed solution to obtain a dry substance, and a sample having a film thickness of 150 μm was prepared in the same manner as in Example 1 described above. Next, in order to evaluate the performance as an optical recording medium, the diffraction efficiency of the diffraction grating due to the change in the optical characteristics due to the electric field formed in the film formed by light irradiation was measured in the same manner as in Example 1. . However, a helium-neon laser was used as a light source of the object light and the reference light, and infrared light was irradiated so as to overlap the interference fringes during writing, and writing was performed for 30 minutes.

The diffraction efficiency of the film of this example measured according to the above-mentioned procedure was 21.5%. The record was readable for about 8 months as in the case of Example 1.

(Comparative Example 2) A mixed solution was prepared in the same manner as in Example 2 except that polystyrene was added instead of the photoisomerizable material (D-2), and this was used to carry out the same procedure as described above. A sample having a film thickness of 150 μm was prepared.

The characteristics of the obtained sample were evaluated in the same manner as in Example 1. As a result, a photorefractive effect was exhibited, but its diffraction efficiency was 3.2%, which was smaller than that in Example 2.

(Example 3) Each component was dispersed and dissolved in toluene according to the following formulation to prepare a toluene solution.

Nonlinear Optical Material and Charge Generating Material: Carbon Cluster C ₇₀ 0.3 wt% Charge Transport Material and Matrix Material: (M-3) 45 wt% (M-4) 45 wt% Photoisomerization Material (Dipole Change material): (D-3) 9.7 wt% The components used here are shown in the following chemical formulas.

[0074]

[Chemical 7]

[0075]

[Chemical 8]

[0076]

[Chemical 9]

The solvent was removed by heating and depressurizing the obtained mixed solution to obtain a dry substance, and a sample having a film thickness of 150 μm was prepared in the same manner as in Example 1 described above. Next, in order to evaluate the performance as an optical recording medium, the diffraction efficiency of the diffraction grating due to the change in the optical characteristics due to the electric field formed in the film formed by light irradiation was measured in the same manner as in Example 1. . However, a helium-neon laser was used as a light source of the object light and the reference light, and ultraviolet light containing a wavelength of 340 nm was irradiated so as to overlap the interference fringes during writing, and writing was performed for 1 minute.

The diffraction efficiency of the film of this example measured according to the above-mentioned procedure was 15.5%. The records were readable for about 6 months. (Comparative Example 3) Example 3 described above except that the matrix materials (M-3) and (M-4) were mixed in equal amounts instead of the photoisomerizable material (D-3). A mixed solution is prepared in the same manner, and using this, a film thickness of 15 is obtained by the same method as described above.
A 0 μm sample was prepared.

The characteristics of the obtained sample were evaluated in the same manner as in Example 1. As a result, a photorefractive effect was exhibited, but its diffraction efficiency was 0.08%, which was extremely small.

Example 4 Each component was dispersed and dissolved in toluene according to the following formulation to prepare a toluene solution.

[0081]     Charge generation material:             Almicol Phthalocyanine (AlClPc) 0.3% by weight     Charge transport materials and matrix materials:                       (M-5) 20% by weight     Charge transport material: (M-3) 25% by weight     Photoisomerization material (dipole change material): (D-3) 9.7% by weight     Matrix material: Polycarbonate 25% by weight The components used here are shown in the following chemical formulas.

[0082]

[Chemical 10]

[0083]

[Chemical 11]

In the equation, n is a positive number. The solvent was removed by heating and depressurizing the obtained mixed solution to obtain a dry substance, and a film thickness of 150 μm was obtained by the same method as in the case of Example 1 described above.
m samples were prepared.

Next, in order to evaluate the performance as an optical recording medium, the diffraction efficiency of the diffraction grating due to the change in the optical characteristics caused by the electric field formed in the film by the light irradiation is
The measurement was performed in the same manner as in Example 1. However, a helium-neon laser was used as a light source of the object light and the reference light, and ultraviolet light containing a wavelength of 340 nm was irradiated so as to overlap the interference fringes during writing, and writing was performed for 3 minutes.

The diffraction efficiency of the film of this example measured according to the procedure described above was 10.2%. The records were readable for about 1 month. (Comparative Example 4) A mixed solution was prepared in the same manner as in Example 4 except that an equal amount of polycarbonate, which was a matrix material, was mixed instead of the photoisomerizable material (D-3).
Using this, a sample having a film thickness of 150 μm was prepared by the same method as described above.

The characteristics of the obtained sample were evaluated in the same manner as in Example 1. As a result, a photorefractive effect was exhibited, but the diffraction efficiency was 0.15%, which was extremely small.

(Example 5) Each component was dispersed and dissolved in toluene according to the following formulation to prepare a toluene solution.

[0089]     Charge generation material: Copper phthalocyanine 0.3% by weight     Charge transport materials and matrix materials:                       (M-5) 20% by weight                       (M-3) 25% by weight                       (M-4) 25% by weight     Photoisomerization material (dipole change material): (D-4) 9.7% by weight The components used here are shown in the following chemical formulas.

[0090]

[Chemical 12]

The solvent was removed by heating and depressurizing the obtained mixed solution to obtain a dry substance, and a sample having a film thickness of 150 μm was prepared in the same manner as in Example 1 described above. Next, in order to evaluate the performance as an optical recording medium, the diffraction efficiency of the diffraction grating due to the change in the optical characteristics due to the electric field formed in the film formed by light irradiation was measured in the same manner as in Example 1. . However, a helium-neon laser was used as a light source of the object light and the reference light, and ultraviolet light containing a wavelength of 340 nm was irradiated so as to overlap the interference fringes during writing, and writing was performed for 3 minutes.

The diffraction efficiency of the film of this example measured according to the above-mentioned procedure was 13.5%. The records were readable for about 3 months. (Comparative Example 5) The same as Example 5 described above except that the matrix materials (M-3) and (M-4) were mixed in equal amounts instead of the photoisomerizable material (D-4). To prepare a mixed solution, and use this to prepare a film with a film thickness of 1
A 50 μm sample was prepared.

The characteristics of the obtained sample were evaluated in the same manner as in Example 1. As a result, a photorefractive effect was exhibited, but its diffraction efficiency was 0.09%, which was extremely small.

Example 6 Each component was dispersed and dissolved in toluene according to the formulation shown below to prepare a toluene solution.

Charge Generating Material: Carbon Cluster C ₇₀ 0.3 wt% Charge Transporting Material: (M-6) 45 wt% Nonlinear Optical Material and Matrix Material: (N-1) 45 wt% Photoisomerization Material (Dipole Change material): (D-1) 9.7 wt% The components used here are shown in the following chemical formulas.

[0096]

[Chemical 13]

[0097]

[Chemical 14]

The solvent was removed by heating and depressurizing the obtained mixed solution to obtain a dry substance, and a sample having a film thickness of 150 μm was prepared in the same manner as in Example 1 described above. Next, in order to evaluate the performance as an optical recording medium, the diffraction efficiency of the diffraction grating due to the change in the optical characteristics due to the electric field formed in the film formed by light irradiation was measured in the same manner as in Example 1. . However, a helium-neon laser was used as a light source of the object light and the reference light, and ultraviolet light containing a wavelength of 340 nm was irradiated so as to overlap the interference fringes during writing, and writing was performed for 3 minutes.

The diffraction efficiency of the film of this example measured according to the above-mentioned procedure was 19.5%. The records were readable for about 3 months. (Comparative Example 6) A mixed solution was prepared in the same manner as in Example 6 except that the matrix material (N-1) was mixed instead of the photoisomerizable material (D-1). A sample having a film thickness of 150 μm was prepared using the same method as described above.

The characteristics of the obtained sample were evaluated in the same manner as in Example 1. As a result, the photorefractive effect was exhibited, but the diffraction efficiency was 2.0%. (Example 7) Each component was dispersed and dissolved in toluene by the following formulation to prepare a toluene solution.

[0101]     Charge generating material: (G-1) 0.3% by weight     Charge transport material: (M-7) 30% by weight     Nonlinear optical material and photoisomerization material: (D-5) 30% by weight     Matrix material: polystyrene 30% by weight The components used here are shown in the following chemical formulas.

[0102]

[Chemical 15]

[0103]

[Chemical 16]

The solvent was removed by heating and depressurizing the obtained mixed solution to obtain a dry substance, and a sample having a film thickness of 150 μm was prepared in the same manner as in Example 1 described above. Next, in order to evaluate the performance as an optical recording medium, the diffraction efficiency of the diffraction grating due to the change in the optical characteristics due to the electric field formed in the film formed by light irradiation was measured in the same manner as in Example 1. . However, an argon ion laser was used as a light source of the object light and the reference light, and light having a wavelength of 580 nm was irradiated so as to overlap the interference fringes at the time of writing, and writing was performed for 30 seconds.

The diffraction efficiency of the film of this example measured according to the above-mentioned procedure was 14.8%. The records were readable for about 3 months. (Comparative Example 7) A mixed solution was prepared in the same manner as in Example 7 except that polystyrene as a matrix material was mixed in place of the photoisomerizable material (D-5), and the mixed solution was used as described above. A sample having a film thickness of 150 μm was prepared in the same manner as in.

The characteristics of the obtained sample were evaluated in the same manner as in Example 1. As a result, the photorefractive effect was exhibited, but the diffraction efficiency was 0.5%. (Example 8) Each component was dispersed and dissolved in toluene according to the following formulation to prepare a toluene solution.

Charge generation material: (G-1) 0.3 wt% Charge transport material: (M-7) 30 wt% Non-linear optical material and photoisomerization material: (D-5) 30 wt% Matrix material: ( M-3) 30% by weight (M-4) 30% by weight By heating and decompressing the obtained mixed solution, the solvent is removed to obtain a dry substance, and a film thickness is obtained by the same method as in the case of Example 1 described above. A 150 μm sample was prepared.

Next, in order to evaluate the performance as an optical recording medium, the diffraction efficiency of the diffraction grating was measured by the change of the optical characteristics caused by the electric field formed in the film formed by the light irradiation.

The outline of the apparatus used is shown in FIG. The device shown is a type of holographic memory device,
This is a device for irradiating the recording medium 25 with the signal light (or object light) 18 and the reference light 19 at the same time and recording or reading the interference fringes generated at that time. Particularly in this embodiment, the medium 25 is simultaneously irradiated with light from the second light source 17 for increasing the permanent dipole moment of the photoisomerizable material contained in the recording medium. As a method of creating the signal light 18, a method of passing light through a spatial modulator made of liquid crystal or the like is generally used. Here, a micromirror is used as the spatial light modulator. The specific device will be described below.

As shown in FIG. 2, the light emitted from the laser light source 13 is first reflected by the beam splitter 14.
It is divided into two. One of the divided lights is applied to the spatial light modulator 15 which is a micromirror array, and information of a digital signal is put on the light. That is, the signal light 18 is created by adding information depending on whether the light is guided to the optical path of the signal light due to the tilt of the mirror. At this time, depending on the size of the micromirror array, the beam irradiated by the micromirror array may be expanded in beam diameter by a beam expander or the like.

On the other hand, the other light split by the beam splitter 14 becomes reference light 19, and the light from the second light source 17 is mixed with this reference light. The signal light 18 is reflected by the mirror 22 of the micro mirror array 21, and the reference light 19 including the light from the second light source is also reflected by the mirror 22 in the same manner, and the reference light 19 is reflected at a desired position on the medium 25. Recording is performed by simultaneously irradiating light from different directions.

Reading of recording is performed by reflecting the reference light 19 containing no light from the second light source 17 on the micromirror array and irradiating the medium 25 in the same manner as during recording. The reproduced light 20 is guided to a photodetector 24 using a micromirror array, a lens 23, and a mirror 16, which are located on the opposite side of the micromirror array used at the time of recording, and detects information as an electric signal. To do.

Specifically, in this embodiment, the signal light 18 and the reference light 19 are irradiated so as to intersect with each other on the optical recording medium 25 to form interference fringes on the optical recording medium, and at the same time, Laser light including a wavelength of 580 nm from the light source 17 was irradiated onto the optical recording medium 25 from the same optical path as the reference light 19 so as to overlap the interference fringes, and writing was performed for 30 seconds.

After that, the signal light 18 and the light from the second light source were cut off, and only the reference light 19 similar to that at the time of writing was irradiated to read the record by the photodetector 24. I was able to read it. The record was readable for about 3 months.

(Comparative Example 8) Instead of the photoisomerizable material (D-5), matrix materials (M-3) and (M-) were used.
A mixed solution was prepared in the same manner as in Example 8 except that 4) was mixed in equal amounts, and this was used to prepare a sample having a film thickness of 150 μm by the same method as described above.

The characteristics of the obtained sample were evaluated in the same manner as in Example 1. As a result, the diffraction efficiency of light was low and reading could not be performed. (Example 9) Each component was dispersed and dissolved in toluene by the following formulation to prepare a toluene solution.

[0117]     Charge generating material: (G-2) 0.3% by weight     Charge transport materials and matrix materials:                     (M-3) 30% by weight                     (M-4) 30% by weight     Nonlinear optical material: (N-2) 30% by weight     Photoisomerization material: (D-1) 30% by weight The components used here are shown in the following chemical formulas.

[0118]

[Chemical 17]

[0119]

[Chemical 18]

The solvent was removed by heating and depressurizing the obtained mixed solution to obtain a dry substance, and a sample having a film thickness of 150 μm was prepared in the same manner as in Example 1 described above. Next, in order to evaluate the performance as an optical recording medium, the diffraction efficiency of the diffraction grating due to the change in the optical characteristics due to the electric field formed in the film formed by the light irradiation was measured.

An outline of the apparatus used is shown in FIG. The device shown is a type of holographic memory device,
This is a device that irradiates the recording medium 25 with the signal light (or object light) 18 and the reference light 19 at the same time, and records the interference fringes generated at that time. In the present embodiment, the light from the second light source 17 for increasing the permanent dipole moment of the photoisomerizable material contained in the optical recording medium is supplied to the medium 2 during recording.
Irradiate 5 simultaneously. As a method of creating the signal light, a method of passing light through a spatial modulator made of liquid crystal or the like is generally used, but here, a micromirror is used as the spatial light modulator. The optical recording apparatus shown in FIG. 3 differs from that shown in FIG. 2 in that a micromirror array is not used for determining the optical path of the reference light. The specific device will be described below.

As shown in FIG. 3, the light emitted from the laser light source 13 is first reflected by the beam splitter 14.
It is divided into two lights. Light is applied to the spatial light modulator, which is a micromirror array, and information of digital signals is placed on the light. That is, information is added depending on whether the light is guided to the optical path of the signal light depending on the tilt of the mirror,
The signal light 18 is created. At this time, the micromirror array also serves to guide the signal light to a desired position on the medium 25. Further, as in the case of the optical recording device shown in FIG. 2, the light irradiated to the micromirror array may be expanded in beam diameter by a beam expander or the like depending on the size of the micromirror array.

On the other hand, the other light split by the beam splitter 14 becomes reference light 19, and the light from the second light source 17 is mixed with this reference light. The reference light 19 is guided by arranging the mirror 16 at a desired position on the recording medium 25, and the signal light 18
At the same time, recording is performed by irradiating the medium.

The reading of the recording is performed by irradiating the medium with the reference light 19 containing no light from the second light source 17, as in the recording. The reproduced light 20 is guided to a photodetector 24 using a mirror and a lens 23 located on the opposite side of the medium used for recording from the medium used for recording, and detects information as an electric signal.

Specifically, in this embodiment, the signal light 18 and the reference light 19 are irradiated so as to intersect with each other on the optical recording medium 25 to form interference fringes on the optical recording medium, and at the same time, White light including a wavelength of 780 nm from the light source 17 was irradiated onto the optical recording medium 25 from the same optical path as the reference light 19 so as to overlap the interference fringes, and writing was performed for 30 seconds.

After that, the signal light 18 and the light from the second light source were cut off, and only the reference light 19 similar to that at the time of writing was irradiated to read the record by the photodetector 24. I was able to read it. The record was readable for about 1 month.

(Comparative Example 9) Instead of the photoisomerizable material (D-1), matrix materials (M-3) and (M-) were used.
A mixed solution was prepared in the same manner as in Example 9 except that 4) was mixed in equal amounts, and this was used to prepare a sample having a film thickness of 150 μm by the same method as described above.

The characteristics of the obtained sample were evaluated in the same manner as in Example 1, and as a result, it was possible to read the recorded information within 10 minutes after writing, but after that, reading was impossible. It has become possible.

[0129]

As described above, according to the present invention,
The ratio (D / μ) of diffusion coefficient D and mobility μ is large,
Information is recorded on an optical recording medium that can be recorded without applying an electric field.
A recording method for recording is provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a recording apparatus of the present invention.

FIG. 2 is a schematic view showing another example of the recording apparatus of the present invention.

FIG. 3 is a schematic view showing another example of the recording apparatus of the present invention.

[Explanation of symbols]

1 ... Sample 2… Object light 3 ... Reference light 4 ... External energy source 5 ... Reflection direction of object light 6 ... Transmission direction of object light 7 ... Photodetector 8 ... Coherence light source 9, 14 ... Beam splitter 10, 16 ... Mirror 11 ... Micromirror array 12 ... Lens 13 ... Laser light source 15 ... Spatial light modulator 17 ... Second light source 18 ... Signal light (writing) 19 ... Reference light 20 ... Signal light (readout) 21 ... Micromirror array device 22 ... Micro mirror 23 ... Lens 24 ... Photodetector 25 ... Optical recording medium

Claims (5)

(57) [Claims] Materials permanent dipole moment increases by application of claim 1] external energy, charge generating material, and the optical recording medium containing a charge-transporting material, the first conductive from the first light source
A step of irradiating a magnetic wave to form interference fringes, and a step of irradiating the first electromagnetic wave irradiation surface of the optical recording medium with
The second electromagnetic wave having a wavelength different from that of the first electromagnetic wave
The permanent dipole moment is increased by irradiating from the light source of
And a step of causing the second electromagnetic wave to simultaneously or simultaneously with the first electromagnetic wave.
Optical recording method characterized in that irradiation is completed prior to this
Law. 2. The wavelength of the second electromagnetic wave is the same as that of the first electromagnetic wave.
The optical recording method according to claim 1, which is longer than the wavelength of the electromagnetic wave . 3. The optical recording medium of the second electromagnetic wave
The penetration length is at least 0.1 μm or more
The optical recording method according to claim 1 or 2. 4. A permanent dipole when external energy is applied.
The material of which the moment is increased is the irradiation of the second electromagnetic wave.
Is excited by, and the permanent dipole moment increases
The method according to any one of claims 1 to 3, characterized in that
Optical recording method of mounting. 5. The first electromagnetic wave is coherent light.
5. The method according to claim 1, wherein
The optical recording method according to the item.