JPH11167339A - Hologram recording medium, recording device and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording medium which is large in the ratio D/μ of a diffusion coefft. D and mobility μ, allows recording even without impression of an electric field from the outside and makes it possible to easily obtain reproducing light from the record written by interference fringes irradiation with recording medium in the absence of the electric field by maximizing the content of a charge generating material at a photoirradiation surface. SOLUTION: This recording medium contains the charge generating material, a charge transfer material and a material having an electro-optic effect and is formed with the interference fringes by irradiation with light. The content of the charge generating material has the max. value on the surface of the recording medium to be irradiated with the light and decreases monotonously in a film pressure direction. The recording medium of such constitution includes a recording medium having a laminated structure obtd. by, for example, applying a layer having the high content of the charge generating material on a layer having the low content of the charge generating material. The content of the charge generating material of the medium obtd. at this time decreases monotonously from the front surface of the recording medium toward the other surface. The way of the decrease may be continuous or stepwise. A concn. distribution may be formed within the one layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a hologram recording medium, a recording apparatus and a reproducing apparatus.

[0002]

2. Description of the Related Art A photorefractive medium is known as one of optical recording media for performing recording at a much higher density than a conventional magneto-optical recording or photothermal phase change type medium (such as an optical disk). This photorefractive medium is a medium that can record large-capacity data such as a high-density image, and changes the refractive index of the recording layer by the following mechanism. That is, by irradiating an electromagnetic wave, the electric charges existing therein are spatially separated, and the electric field generated by the electric charges changes the refractive index of the recording material. Therefore, if the electric field generated inside the medium is increased, 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 an interference pattern of an electromagnetic wave as a refractive index grating, it is also expected to be applied to a holographic memory, an optical operation element, and the like.

In recent years, photorefractive media using an organic polymer compound have been actively developed due to ease of production (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 a photorefractive medium is irradiated with an interference pattern of electromagnetic waves, non-equilibrium carriers corresponding to the intensity of the electromagnetic waves are generated in the photorefractive medium. The external electric field E _ex is set so as to be parallel to the electromagnetic wave irradiation surface.
Is applied to the photorefractive medium, the electric field E generated is represented by the following equation (3). _{E = E 0 [(1 +} iE ex / E d) / {1 + iE ex / (E d + E q)}] (I 1 + I 0) (3) E 0 = iE d / (1 + E d / E q) (4) E _d = (2πD) / (μΛ) (5) E _q = (eNΛ) / (2πε) (6) I ₀ is a spatial average of irradiation light intensity, and I ₁ is a maximum value and a minimum value of irradiation light intensity. And the difference. Λ is the distance (spatial wavelength) between the closest local maximum values. ε is the dielectric constant of the photorefractive medium, N is the space charge concentration, D is the diffusion coefficient, and μ is the mobility. e is an elementary charge amount, i is an imaginary unit, and represents a phase (for example, Pochi Y
eh, Introduction to Photo
refractive Nonlinear Opti
cs, John Wiley & Sons, March 1993
chapter).

Physically, E _d represents the electric field due to charge diffusion, and E _q represents the spatial electric field due to ionized impurities and immobile charges. Usually, between the diffusion coefficient D and the mobility μ, Einstein's relational expression D
/ Μ = kT / e (k is Boltzmann's constant, T is absolute temperature)
Is considered to hold, so that E _d is a constant that does not depend on the substance. Therefore, to obtain a large electric field E,
Large enough to E _q compared to E _d, and it is necessary to increase the E _ex. In order to increase the E _q is compared with the E _d, in the above formula (6), it is necessary to increase the Λ and N. However, when Λ is increased, the density of interference fringes decreases, so that the recording density of a recording element decreases. On the other hand, when the concentration N of the space charge is increased, there is a disadvantage that the mobility is reduced due to scattering by the charge.

[0006] The time required to form an electric field when an external electric field is applied is determined by the drift speed of the electric charge, so that a decrease in the mobility means a decrease in the writing speed. Therefore, a decrease in mobility must be avoided as much as possible.

When an electric field E _ex is applied from the outside,
Movable charges (carriers) move in the direction of the electric field,
E substantially coincides with the direction of the external electric field. Since the refractive index modulation by the Pockels effect is performed in the direction of the electric field, in order to read out the change in the refractive index by using an electromagnetic wave, the direction of the electric field must be made closer to the direction perpendicular to the incident direction of the electromagnetic wave.
For this reason, it is necessary to devise the shape of the electrode to which an electric field is applied, and it has not been possible to manufacture it at low cost. Further, the use has been limited, for example, it cannot be used for an ordinary optical disk.

[0008] Normally the material, i.e., in the very small substances for D / mu follows the relationship of Einstein, the electric field E _d by diffusion in space wavelength lambda = 1 [mu] m at room temperature (300K) in 0.163MV / m Yes, not big enough. Therefore, in a photorefractive polymer using such a substance, an electric field of 10 MV / m or more has been externally applied (for example, WE Moe).
rner and Scott M.R. Silence,
Chem. Rev .. 94, pp 127-155 (199
4)). The same internal electric field as in this case, D / μ is 5
As described above, preferably, a substance of 10 or more can be generated without applying an electric field from outside. So, D /
The development of measures to increase μ was desired.

Recently, the diffusion coefficient D, which is a charge transport characteristic,
A recording medium that does not require an electrode for applying an external electric field by increasing the ratio (D / μ) between the mobility and the mobility μ has been attempted. Such a recording medium utilizes the Pockels effect, which is an electro-optic effect, which is first-order proportional to an electric field, and the Kerr effect, which is second-order proportional to an electric field, to modulate the refractive index. When the recording medium is irradiated with light to form interference fringes as shown in FIG. 4A, the states of light intensity and charge density are shown in FIGS. 4B and 4C, respectively. At this time, the spatial electric field causes a phase difference Φ as shown in FIG. Further, the refractive index modulation by the Pockels effect is represented by FIG. 4E, and the refractive index modulation by the Kerr effect is represented by FIG.

That is, when the material having the electro-optical effect in the medium is random, the electro-optical effect is expressed by the Kerr effect proportional to the second order of the electric field, and does not depend on the direction. Therefore, the wave number of the refractive index grating to be written is two times the wave number of the irradiated interference fringe as shown in FIG.
The reproduction light cannot be obtained in the recording light transmission direction. Therefore, the ratio of the diffusion coefficient D to the mobility μ (D /
In addition to increasing μ), a medium and means for obtaining a reproduction light have been desired.

[0011]

SUMMARY OF THE INVENTION The present invention provides a diffusion coefficient D
And the mobility μ are large (D / μ), so that recording can be performed without applying an external electric field, and reproduction light can be easily obtained from recording written by irradiating interference fringes without an electric field. It is an object to provide a hologram recording medium. Another object of the present invention is to provide a recording apparatus and a reproducing apparatus which can easily obtain a reproducing light from a recording written by irradiating interference fringes in an electric field-free state.

[0012]

According to the present invention, there is provided a hologram comprising a charge generating material, a charge transporting material and a material having an electro-optical effect, wherein interference fringes are formed by light irradiation. A hologram recording medium, which is a recording medium, wherein the content of the charge generation material has a maximum value on a surface of the recording medium irradiated with the light, and monotonically decreases in a film thickness direction. I will provide a.

The present invention also provides a charge generation material, a charge transport material,
A hologram recording medium containing a material having an electro-optical effect and forming interference fringes by light irradiation,
The charge generation material has at least two different absorption wavelength regions.
And at least one of these components comprises:
The writing light for forming the interference fringes is absorbed within its absorption wavelength range, and at least one of the remaining components does not absorb the writing light for forming the interference fringes within its absorption wavelength range, and Provided is a hologram recording medium, which absorbs light having a different wavelength from writing light for forming fringes, and the penetration length of the light is shorter than the penetration length of writing light for forming the interference fringes. .

Further, the present invention relates to a recording apparatus for recording an interference fringe of an electromagnetic wave on a hologram recording medium containing a charge generating material, a charge transporting material, and a material having an electro-optical effect. A hologram having a first light source for irradiating a first light having a first wavelength for forming fringes, and a second wavelength different from the first wavelength for forming the interference fringes; A second light source for irradiating a second light having a shorter penetration length into the recording medium than the first light to an irradiation surface of the hologram recording medium with the first light. A recording device is provided.

Still further, the present invention comprises a charge generating material, a charge transporting material, and a material having an electro-optical effect.
A reproducing apparatus for reproducing an interference fringe of a hologram recording medium on which an interference fringe has been formed by irradiating a first light having a wavelength of: a reference light source for irradiating the hologram recording medium with a reference light; A second light having a second wavelength different from the first wavelength for forming the interference fringes, and having a shorter penetration length into the hologram recording medium than the first light; A second light source for irradiating the surface irradiated with the first light, and a photodetector that reads a component diffracted by the hologram recording medium among the reference light emitted from the reference light source. And a reproducing apparatus comprising:

Hereinafter, the present invention will be described in detail. The hologram recording medium of the first invention makes it possible to easily obtain reproduction light from a refractive index grating written under no electric field by maximizing the content of a charge generation material on a light irradiation surface. is there.

The hologram recording medium of the first invention will be described. As a recording medium having such a configuration, for example, a recording medium having a laminated structure in which a layer having a high charge generation material content is applied on a layer having a low charge generation material content is exemplified. In the medium obtained at this time, the content of the charge generating material monotonously decreases from the light irradiation surface, that is, the surface of the recording medium to the other surface. The decrease may be continuous or stepwise. Further, a layer in which a plurality of layers (two or more layers) are stacked or a layer in which a concentration distribution is formed in one layer may be used.

Referring to FIG. 1, the state of the electric field when the hologram recording medium of the first invention is irradiated with light will be described. In FIG. 1, the upper diagram schematically shows an electric field generated in the film thickness direction (Z) and the film surface direction (Y) of the medium. When the medium is irradiated with interference fringes of light absorbed by the charge generating material, an electric field is generated in the direction of the film surface in accordance with the light intensity as shown in FIG. An electric field is generated in the thickness direction of the film due to the electric charge (such an electric field in the film thickness direction is also called a Denver electric field). For this reason, the spatial electric field in the medium is a composite of two electric fields, an electric field in the film direction and an electric field in the film thickness direction. As shown in FIG. 1B, the spatial electric field depends on the magnitude of the electric field in the film direction. They come in different directions. In consideration of the direction of the electric field of the light irradiated for reproducing the recording, the period of the obtained refractive index grating is equal to that of the irradiated interference fringe, and the reproduction light can be obtained.

Here, consider the refractive index of the medium with respect to the light beam shown in FIG. The projection of the spatial electric field onto the light electric field contributes to the refractive index modulation. Therefore, FIG.
In the spatial electric field of the left group in the medium shown in (c), since the Denver electric field in the depth direction is superimposed, the direction almost coincides with the traveling direction of light. Therefore, the projection vector of the spatial electric field onto the electric field of light is small, and the contribution to the refractive index modulation is small. On the other hand, the spatial electric field of the group on the right side of the medium shown in FIG. 1C has an angle of about π / 2 with the light traveling direction due to the superposition of the Denver electric field. Thus, the magnitude of the projection vector of the spatial electric field in the direction of the electric field of light becomes very large, and as a result, it greatly contributes to the refractive index modulation. Finally, a refractive index grating having the same wave number as that of the irradiated interference fringes is written on the hologram recording medium of the first invention.

As the charge generating material in the hologram recording medium of the first invention, any material that absorbs writing light and generates charges can be used. Such materials include, for example, selenium and selenium alloys, CdS, Cd
Inorganic photoconductors such as Se, AsSe, ZnO, α-Si, phthalocyanine dyes / pigments such as metal phthalocyanine, non-metal phthalocyanine, and derivatives thereof, naphthalocyanine dyes / pigments, and azo dyes such as monoazo, disazo, and trisazo / Pigments, perylene dyes, indigo dyes, quinacridone dyes, anthraquinone,
Polycyclic quinone-based dyes and pigments such as anthantrone, cyanine-based dyes and pigments, for example, a charge transfer complex composed of an electron-accepting substance and an electron-donating substance as represented by TTF-TCNQ, azulhenium salts, C ₆₀ , C _And fullerene represented by ₇₀ and derivatives thereof.

These charge generating materials may be used alone or in combination of two or more compounds. Since the charge generation material must absorb the writing light and generate charges, if a charge generation material having an extremely high optical density with respect to the writing light is used, even the charge generation material inside the element is used. The writing light may not reach. In order to avoid such inconveniences, the optical density of the element must be 1
It is preferred from 0 ^-6 is in the range of 10.

Also, when the additive concentration of the charge generating material is too high, the writing light does not reach the inside, so that it is difficult to write to the inside. On the other hand, when the addition concentration is excessively low, the generated charge density is low, and a desired internal electric field cannot be obtained. Therefore, it is preferable to adjust the addition concentration of the charge generating material so that the optical density of the device is in the range of 10 ^-6 to 10.

More specifically, it is desired that the amount of the charge generating material be about 0.001 to 15% by weight based on the entire recording medium. When the content is less than 0.001% by weight, the charge per unit volume generated by light irradiation is small,
If the internal charge exceeds 15% by weight, the probability of association between the charge generating materials increases, and the conductivity of the medium may increase, so that a high internal electric field may not be generated.

In the first invention, the content of the charge generating material as described above is not made uniform in the film thickness direction of the medium, but is maximized on the light-irradiated surface. To decrease monotonically. The content of the charge generating material on the irradiated surface of the medium can be determined according to the absorption coefficient of the charge generating material with respect to light used, for example, 15% by weight.
On the other hand, the content of the charge generating material on the side facing the irradiation surface can be about 0.001% by weight.
It is desirable that the content of the charge generating material is reduced by at least about 10% by weight from the irradiation surface side of the medium to the opposite side. It is more preferable that the amount is reduced by about 50% by weight, and most preferable that the amount is about 80% by weight or more. If the amount of change in the content of the charge generating material is less than the above range, it is difficult to achieve the object of the present invention.

The charge transporting material used for the hologram recording medium of the first invention transports holes or electrons. For example, any material having a function of transporting charges by hopping conduction can be used. it can. The charge transporting material may be a molecule alone, a polymer, or a copolymer with another polymer. For example, the following are listed. That is, nitrogen-containing cyclic compounds such as indole, carbazole, oxazole, isoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, thithiazole, 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 their derivatives. Furthermore,
Π-conjugated polymers and oligomers such as polyacetylene, polypyrrole, polythiophene, and polyaniline; or σ-conjugated polymers and oligomers such as polysilane and polygermane; and polycyclic aromatic compounds such as anthracene, pyrene, phenanthrene, and coronene. Can be

The amount of the charge transporting material to be added is 5 to 9 in the recording medium.
Desirably, it is about 0% by weight. When the amount is less than 5% by weight, it is difficult to obtain a sufficient function. On the other hand, when the amount is more than 90% by weight, space charge is not easily held and may not function as an optical recording medium.

The carriers generated from the above-described charge generating material 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 used charge transporting material have the following relationship with other molecules. That is, when the carrier is a hole, 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) At this time, since electrons are required not to move from the charge generating material, the electron affinity of the charge generating material χ (CGM)
And the electron affinity と (CTM) of the charge transport material preferably satisfy the following relationship.

Χ (CTM) <χ (CGM) On the other hand, when the carrier is an electron, it is desired that the ionization potential and the electron affinity of the charge generating material and the charge transporting material have the following relationship.

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 a host matrix.

The material having an electro-optical effect contained in the hologram recording medium of the first invention may also serve as the above-described charge generation material and charge transport material. The hologram recording medium of the first invention can be manufactured, for example, by laminating a plurality of layers having different charge generating material contents. In this case, first, a charge generating material, a charge transport material and a material having an electro-optical effect are mixed to obtain a solution,
A predetermined recording medium is produced by evaporating the solvent. Examples of the solvent that can be used here include trichloroethane, toluene and the like. Alternatively, the hologram recording medium of the first invention may be manufactured by mixing fine particles in a state where a molecular mixture is heated without using a solvent, for example, and rapidly cooling to form each layer, and then laminating the layers. .

When the hologram recording medium of the first invention is prepared from a solution, the nonlinear optical molecules may be dissolved in the solution. May be dissolved as a matrix. Examples of the polymer that can be used include polyethylene resin, nylon resin, polyester resin, polycarbonate resin, polyarylate resin, butyral resin, polystyrene resin, and styrene-butadiene copolymer resin. These may be used alone or as a mixture of two or more.

As the nonlinear optical material, for example, C
_{Although 60} or the like can be used, it may also function as a charge generating material, a charge transporting material, or a matrix as described above.

Further, the hologram recording medium of the first invention can be manufactured by the following method in addition to laminating a plurality of layers. That is, a layer containing no charge generating material may be formed in advance, and the charge generating material may be implanted and doped toward the light irradiation surface of this layer.

Next, the optical recording medium of the second invention will be described in detail. In the hologram recording medium of the second invention, at least two types of charge generating materials having different absorption wavelength ranges are blended together with a charge transporting material and a material having an electro-optical effect, so that the Denver electric field in the film direction is superimposed. Thus, it is possible to obtain reproduction light by In particular, at least one of the charge generation materials according to the second invention absorbs the writing light in the absorption wavelength range, and at least one of the charge generation materials does not absorb the writing light in the absorption wavelength range. Light that absorbs light having a different wavelength from the writing light for forming the fringes is used, and the penetration depth of the light is shorter than the penetration length of the writing light for forming the interference fringes. Here, the absorption wavelength range is defined as follows. That is, in the electronic spectrum measured in the wavelength range from 400 nm to 800 nm, when the maximum absorbance is A, the wavelength range showing absorption of 0.1 A or more is defined as the absorption wavelength range. The light penetration length is the depth from the incident surface at a position where the light intensity is 1 / e of the incident light intensity.

The hologram recording medium of the second invention has a first charge generating material for absorbing writing light (first light),
It can be said that at least two types of charge generation materials including a second charge generation material that absorbs light (second light) other than the writing light are contained. This second charge generating material is
To generate a photocarrier that forms a Denver electric field, so that reproduction light can be obtained in the same manner as in the first embodiment. It is necessary that the penetration length of the second light is shorter than the penetration length of the first light, but it is preferable that the penetration length of the second light is not more than half of the penetration length of the first light. , 1/10 or less.

The charge generating materials that can be used include the above-mentioned first charge generating materials.
And two or more components having different absorption wavelength ranges can be appropriately selected and used from them. Since the first charge generation material needs to absorb the write light to generate charges, the concentration of the first charge generation material should be determined so that the optical density of the device is in the range of 10 ^-6 to 10. Is preferred. on the other hand,
As described above, the second charge generating material absorbs the second light and generates photocarriers that form a Denver electric field, and thus has the second light absorption coefficient of the second charge generating material. The amount of addition can be appropriately determined according to.

Another charge generating material may be added as long as the effects of the first and second charge generating materials are not impaired. Also, as the charge transport material, the components described in the hologram recording medium of the first invention can be blended, and the blending amounts are the same. That is, 5 wt% to 9 wt.
It is preferable to set it to about 0% by weight. It is preferable that the ionization potential and the electron affinity of the charge transport material used have the above-mentioned relationship between the ionization potential and the electron affinity of the charge generation material.

The hologram recording medium of the second invention is characterized in that at least two kinds of charge generating materials are dissolved together with a charge transporting material and a material having an electro-optical effect in a predetermined solvent to obtain a solution. Can be produced by evaporating. Alternatively, the hologram recording medium of the second invention may be manufactured without using a solvent, for example, by mixing fine particles in a state where a molecular mixture is heated and rapidly cooling the mixture.

As in the case of the first hologram recording medium, when none of the components such as the charge transport material is a polymer, a polymer as a matrix may be blended. Examples of the polymer that can be used here include polyester, PMMA, and polystyrene that are amorphous and almost transparent in the visible light region.

The hologram recording medium of the present invention as described above can record and reproduce information by using the recording device and the reproducing device of the present invention. In the hologram recording medium of the present invention, information is recorded by forming interference fringes by two lights, so that coherent light can be used as a light source. In order to obtain interference fringes, it is preferable to use the light of the same light source after splitting it. Can also be used.

When recording information, information is added to one of the two lights, and interference fringes generated between the two lights are recorded on a medium. For this reason, an optical path difference is generated between the two lights, so that interference fringes do not occur if the light has a short coherent length. For this reason, a laser or etalon 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 and semiconductor lasers, especially feedback, reduce the coherence length. An elongated semiconductor laser is preferably used as a light source.

Although writing may be performed by applying an electric field from the outside, the present invention is particularly effective when writing is performed without applying an electric field. According to the recording apparatus of the present invention, in addition to a first light source for irradiating light (first light) for forming an interference fringe used for recording information, the wavelength of the first light is different from that of the first light.
This is an apparatus further provided with a function of irradiating light (second light) having a shorter penetration length into a medium (hereinafter, referred to as a second light source). It should be noted that if the above-described second light source is provided in a reproducing apparatus having a photodetector, the reproducing apparatus of the present invention can be obtained. Further, the recording device and the reproducing device of the present invention may have two functions.

By using such an apparatus, it is possible to easily obtain a reproduction light. Since the Denver electric field may be formed by the time of reading the information recorded on the medium, the above-described irradiation of the second light may be performed at the time of writing or at the time of reading.

In the recording apparatus of the present invention, it is desirable that the second light be irradiated before the irradiation of the recording light is completed. In the reproducing apparatus of the present invention, the second light is irradiated before the reading is completed. Is preferred. This is because the Denver electric field generated by the second light irradiation contributes to the electric field during recording or reproduction.

In order to make the generated Denver electric field sufficiently high, the optical density of the hologram recording medium of the present invention for such a second light source needs to be higher than that of the writing light.

The second light emitted from the second light source is light having a wavelength that is absorbed by the charge generating material contained in the medium near the surface of the medium, and has a different wavelength from the recording light and the reference light. Light. The second light does not necessarily have to be coherent light, since the irradiation of the interference fringes may be performed simultaneously with or before the first light. Further, the portion to be irradiated with the second light is the portion to be irradiated with the interference fringes, and either may be larger as long as the irradiation area of the second light and the irradiation area of the interference fringes are not extremely different.

The angle at which the medium is irradiated with the second light is not particularly limited, and the medium may be irradiated at an angle different from that of the recording light or the reference light. In the recording apparatus, the irradiation start time is preferably before the irradiation of the interference fringes. However, the irradiation start time may be after the start of the irradiation of the interference fringes as long as the irradiation of the interference fringes is completed. In the reproducing apparatus, the irradiation start time of the second light is more preferably before the irradiation of the readout light, but may be after the start of the irradiation of the readout light before the end of the irradiation of the readout light.

Furthermore, in order to change the recording location on the medium, the recording apparatus of the present invention also has a function capable of moving the light source or the medium with a drive motor in the x, y, and z directions, or a mirror. For example, it is preferable to have a function of changing an optical path, such as a micromirror.

The recording apparatus and the reproducing apparatus of the present invention as described above can be applied to other than the hologram recording medium of the present invention. Specifically, a desired effect can be obtained by appropriately changing the wavelength of the first light source for recording information and the wavelength of the second light source according to the absorption wavelength of the charge generating material. It is possible.

The information recorded on the hologram recording medium of the present invention can be erased by the following two methods. The first method is to uniformly redistribute the trapped charges by irradiating the medium with light or applying heat to make the charge distribution uniform, and the second method is to trap the trapped charges. Is recombined with a charge of the opposite polarity.

A first method for making the charge distribution uniform is a method suitable for erasing information recorded in a wide area of the medium, while a second method for erasing the charge is local. It is suitable for erasing a record written in the. In this case, it is necessary to provide a mechanism for generating a charge having the opposite polarity to the medium. For example, when the generated charge is a carrier, it is necessary to include an electron generating material and a transport material thereof.

The hologram recording medium of the present invention has a D / D ratio by providing a gradient in the content of the charge generating material or by blending two specific types of charge generating materials.
As well as increasing μ, it was possible to superimpose the Denver electric field in the film direction. For this reason, an internal electric field can be formed without applying an electric field from the outside, and a hologram recording medium having high diffraction efficiency, excellent storage stability of recording, and easily obtaining reproduction light has been realized.

In the recording apparatus and the reproducing apparatus according to the present invention, the second light source for irradiating the second light having a different wavelength from the recording light for forming the interference fringes and having a shorter penetration length is used. With such an arrangement, it has become possible to easily obtain reproduction light from a medium on which information is recorded.

[0055]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples of the present invention, but the present invention is not limited to these examples. (Example 1) First, each component was dispersed and dissolved in toluene according to the following formulation to prepare a first toluene solution.

Nonlinear optical material and charge generating material: carbon cluster C ₇₀ 0.3% by weight Charge transporting material: (M-1) 40% by weight Matrix: polystyrene 59.7% by weight A second toluene solution was prepared by dispersing and dissolving in toluene.

Nonlinear optical material and charge generating material: 3.0% by weight of carbon cluster C ₇₀ Charge transporting material: (M-1) 40% by weight Matrix: polystyrene 57.0% by weight The components used here were as follows: Shown in the chemical formula.

[0058]

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[0059]

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[0060]

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In the formula, n is an integer. The solvent was removed by heating and decompressing the obtained first toluene solution to obtain a dry substance. On the other hand, the quartz substrate was heated to 120 ° C. in advance, and a spacer for adjusting the film thickness and the above-mentioned dry substance were arranged and dissolved thereon. Further, another quartz substrate is pressed against the substrate to form a film having a thickness of 150 mm.
A first layer of μm was made. Thereafter, the upper quartz substrate was removed, a second toluene solution was applied on the first layer, and dried to form a second layer having a thickness of about 0.2 μm.

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

FIG. 2 is a schematic diagram for explaining the principle of writing / reading using the recording medium of the present invention. As shown in FIG.
And the reference beam 3 were irradiated so as to intersect on the sample 1, thereby forming an interference fringe by the laser beam on the sample. Due to the interference fringes thus generated, an internal electric field is generated to modulate optical characteristics, and a diffraction grating is formed on the medium. When used as an optical recording medium, the sample is irradiated with reflected light from an object for recording object light or light transmitted through a transmission type image display element (pager) composed of a liquid crystal display element or the like, The reference light is irradiated so as to intersect this and cover the irradiation surface. Further, the sample 4 was irradiated with light 4 having a wavelength of 480 nm from the second light source so as to overlap the interference fringes, and left as it was for 1 minute to perform writing.

Thereafter, the object light 2 and the light 4 having a wavelength of 480 nm
And reproduction was performed by irradiating only the same reference beam 3 as in writing. If the writing has been performed, since the diffraction grating is formed in the medium as described above, the reference light 3 is diffracted by the medium, and the reflection direction component 5 from the reference light 3 to the transmission direction of the object light 2; And a transmission direction component 6.

Therefore, in the direction 5 in which the object light is transmitted,
If an optical power beam for measuring the intensity of the reproducing beam and a photodetector 7 such as a CCD for taking in a reproduced image are previously installed, the object light which should not be irradiated by the photodetector, An image is observed and functions as an optical memory.

Here, the ratio (I _obj. / I _ref. ) Of the intensity (I _obj. ) Of the object light reproduced to the reference light and the intensity (I _ref. ) Of the irradiated reference light is obtained as the diffraction efficiency _. Was. The diffraction efficiency of the film of this example measured according to the above-described procedure is
30.0% and the record was readable for about 8 months.

(Example 2) Using the hologram recording medium used in Example 1, light from the second light source was irradiated at the time of reading, and whether or not reading was possible was examined. Specifically, the object light 2, the reference light 3 and the wavelength of 480 nm from the second light source are the same as in the first embodiment except that the light 4 from the second light source is irradiated not at the time of writing but at the time of reading.
Write to the same hologram recording medium using the light 4
Reading was performed.

On the written medium, a diffraction grating of an internal electric field corresponding to an interference fringe generated by superimposing the object light 2 and the reference light 3 is formed. When the light 4 having a wavelength of 480 nm from the second light source is irradiated thereon, the electric field due to the Denver effect is superimposed on the electric field written in advance, and a refractive index grating corresponding to the interference fringe irradiated at the time of writing is formed. Will be. Therefore, the reference light 3 irradiated at the time of reading is
Is diffracted by the medium 1 and is divided into a reflection direction component 5 and a transmission direction component 6 from the reference light 3 in the transmission direction of the object light 2.

When the diffraction efficiency was measured in the same manner as in Example 1, it was 30.3%, which was almost the same as that in Example 1. The records were readable for about 9 months.

Example 3 Using the hologram recording media used in Examples 1 and 2, it was examined whether writing and reading were possible without using the second light source. Specifically, writing / reading was performed on the same hologram recording medium using the same object light 2 and reference light 3 as in Example 1 described above, except that the light 4 from the second light source was not irradiated.

On the written medium, a diffraction grating of an internal electric field corresponding to an interference fringe generated by superposition of the object light 2 and the reference light 3 is formed. The internal electric field formed at this time has a high intensity of charge generation near the surface of the medium, so that the intensity is distributed in the depth direction of the film. Therefore, the reference light 3 irradiated at the time of reproduction is diffracted by the medium 1 and is divided into a reflection direction component 5 and a transmission direction component 6 from the reference light 3 in the transmission direction of the object light 2.

When the diffraction efficiency was measured in the same manner as in Example 1, the result was 5.8%, which was readable. The records were readable for about one month. Example 4 First, each component was dispersed in toluene according to the following formulation to prepare a toluene solution.

Charge transporting material: (M-1) 40% by weight Matrix: Polystyrene 60% by weight From this solution, cast to a thickness of 150 μm on a quartz substrate by casting.
m was prepared. Then, as the nonlinear optical material and a charge generating material, a carbon cluster C ₇₀ by milling are dispersed in toluene, it was implanted doped membrane made by casting a spray gun. This was dried to obtain a sample.

In order to evaluate the performance as an optical recording medium, the diffraction efficiency of the diffraction grating caused by the electric field formed in the film by optical recording was measured in the same manner as in Example 1. Specifically, the above-described sample is irradiated with the object light 2, the reference light 3 and the light 4 having a wavelength of 480 nm from the second light source as in the first embodiment to write, and the reference light 3 alone is irradiated and read. Was performed.

When the diffraction efficiency was measured in the same manner as in Example 1, it was 25%. The record was readable for about 7 months. (Comparative Example 1) A recording medium was produced in the same manner as in Example 1 except that the second layer was not formed and the first layer was a single-layer structure. That is, a toluene solution having the same composition as the first toluene solution in Example 1 was prepared, and the solvent was removed by heating and reducing the pressure to obtain a dry substance. On the other hand, the quartz substrate was heated to 120 ° C. in advance, and a spacer for adjusting the film thickness and the above-mentioned dry substance were arranged and dissolved thereon. Further, another quartz substrate was pressed against the sample to produce a sample having a thickness of 150 μm. Thereafter, the upper quartz substrate was removed to obtain a sample.

When the characteristics of the obtained sample were evaluated in the same manner as in Example 1, no photorefractive effect was observed. (Example 5) 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: 0.3% by weight of carbon cluster C ₇₀ 1.0% by weight of carbon cluster C ₆₀ Charge transporting material: 40.0% by weight of (M-2) Matrix: 58.7% by weight of polystyrene % The components used here are represented by the following chemical formula.

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The resulting mixed solution was heated and depressurized to remove the solvent to obtain a dried substance. Using this, a sample having a thickness of 150 μm was prepared in the same manner as in Example 1 described above.

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

FIG. 3 schematically shows the apparatus used. The device shown is a type of holographic memory device,
This is a device that simultaneously irradiates a signal light (or object light) 12 and a reference light 13 onto a recording medium 18 and records interference fringes generated at that time. In the present embodiment, the second light source 11
The medium 18 is simultaneously irradiated with light from the medium 18 during reproduction. As a method of producing signal light, 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.

As shown in FIG. 3, the light emitted from the laser light source 8 is first split into two lights by a beam splitter 9. Light is applied to a spatial light modulator, which is a micromirror array, and information of a digital signal is carried on the light. That is, information is added depending on whether the light is guided to the optical path of the signal light by the inclination of the mirror or not, and the signal light 12 is created. At this time, the micro mirror array
At the same time, it also functions to guide the signal light to a desired position on the medium 18. In addition, depending on the size of the micromirror array, the beam diameter of the light applied to the micromirror array may be expanded by a beam expander or the like.

On the other hand, the other light split by the beam splitter 9 becomes the reference light 13, and the light from the second light source 11 is mixed with the reference light 13. Recording is performed by arranging the mirror 10 at a desired position on the recording medium 18 to guide the reference light 13 and irradiating the medium simultaneously with the signal light 12.

The recording is read out by irradiating the medium with the light from the second light source 11 and the reference light 13 in the same manner as during recording. The reproduced light 14 is guided to the photodetector 17 by using a mirror or a lens 16 located on the opposite side of the mirror used for recording via a medium, and detects information as an electric signal.

Specifically, in this embodiment, the signal light 12 and the reference light 13 are irradiated so as to intersect on the optical recording medium 18 to form interference fringes on the optical recording medium. Further, writing was performed by irradiating light of a wavelength of 400 nm from the second light source 11 for 30 seconds.

Thereafter, the signal light 12 and the light having a wavelength of 400 nm from the second light source 11 were cut off, and reading was performed by irradiating only the reference light 13 similar to that at the time of writing.
The recorded information could be read. The record was readable for about 8 months.

(Example 6) Using the hologram recording medium used in Example 5, light from the second light source was irradiated at the time of reading, and it was examined whether or not reading was possible. Specifically, the signal light 12, the reference light 13, and the wavelength 4 from the second light source 11 are the same as those in the fifth embodiment except that the light from the second light source 11 is irradiated not at the time of writing but at the time of reading.
Writing and reading were performed on the same hologram recording medium using light of 00 nm.

On the written medium, a diffraction grating of the internal electric field corresponding to the interference fringe generated by the superposition of the signal light 12 and the reference light 13 is formed. There, the second light source 11
When the light having a wavelength of 400 nm is irradiated, the electric field due to the Denver effect is superimposed on the electric field written in advance, and a refractive index grating corresponding to the interference fringe irradiated at the time of writing is formed.

The photodetector 17 is operated in the same manner as in the fifth embodiment.
As a result, the recorded information could be read. The record was readable for about 8 months.

Example 7 Using the hologram recording media used in Examples 5 and 6, it was examined whether writing and reading were possible without using the second light source. Specifically, the same write / read operation is performed on the same optical recording medium 18 using the same signal light 12 and reference light 13 as in the fifth embodiment, except that the light from the second light source 11 is not irradiated. Was.

The photodetector 17 is operated in the same manner as in the fifth embodiment.
As a result, the recorded information could be read. The records were readable for about eight months.
On the medium 18, a diffraction grating of an internal electric field is formed according to an interference fringe generated by superimposing the object light 12 and the reference light 13. The internal electric field formed at this time has a distribution of the intensity in the thickness direction of the film due to high charge generation efficiency near the surface of the medium. Therefore, it is considered that the reference light was diffracted by the medium and functioned as an optical memory.

Example 8 Each component was dispersed and dissolved in toluene according to the following formulation to prepare a toluene solution.

Nonlinear optical material and charge generating agent: (G-1) 0.2% by weight (G-2) 0.1% by weight (G-3) 0.2% by weight Charge transporting material: (M-3) 35.0% by weight Matrix: polystyrene 64.4% by weight Each component used here is represented by the following chemical formula.

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The solvent was removed by heating and reducing the pressure of the obtained toluene solution to obtain a dry substance. On the other hand, the quartz substrate was heated to 120 ° C. in advance, and a spacer for adjusting the film thickness and the above-mentioned dry substance were arranged and dissolved thereon. Further, another quartz substrate was pressed against the sample to produce a sample having a thickness of 150 μm.

In order to evaluate the performance as an optical recording medium, the diffraction efficiency of a refraction grating caused by an electric field formed in the film by light irradiation was measured in the same manner as in Example 1. Specifically, the sample is irradiated with the object light 2, the reference light 3 and the light 4 having a wavelength of 480 nm from the second light source as in the first embodiment, and the above-described sample is written. Done.

When the diffraction efficiency was measured in the same manner as in Example 1, it was 20%, and the recording life was one year or more. Comparative Example 2 As a nonlinear optical material and a charge generating material,
Except for not blending the C ₆₀ is A recording medium was prepared in the same manner as in Example 5 above. Specifically, first, a solution obtained by dispersing and dissolving each component in toluene according to the following formulation was prepared.

Nonlinear optical material and charge generating material: carbon cluster C ₇₀ 0.3% by weight Charge transporting material: (M-2) 40% by weight Matrix: polystyrene 59.7% by weight The thus obtained mixed solution is heated and reduced in pressure. Thereby, the solvent was removed to obtain a dry substance. On the other hand, the quartz substrate is
After heating to 20 ° C., a spacer for adjusting the film thickness and the above-mentioned dry substance were arranged and dissolved thereon. Further, another quartz substrate was pressed against the sample to produce a sample having a thickness of 150 μm. Thereafter, the upper quartz substrate was removed to obtain a sample. When evaluation was performed in the same manner as in Example 5, no photorefractive effect was observed, and reading was not possible.

[0103]

As described above, according to the present invention, the ratio (D / .mu.) Between the diffusion coefficient D and the mobility .mu. Is large, and high-density information can be obtained by light irradiation without applying an external electric field. And a hologram recording medium capable of easily obtaining reproduction light from recording written by irradiating interference fringes under no electric field. Further, according to the present invention, there is provided a recording apparatus and a reproducing apparatus capable of easily obtaining reproduction light from recording written by irradiating interference fringes in an electric field-free state.

[Brief description of the drawings]

FIG. 1 is a view for explaining an expression model of a nonlocal response under an electric field-free due to the superposition of the Denver effect.

FIG. 2 illustrates the principle of writing and reading.

FIG. 3 illustrates an example of a writing and reading device.

FIG. 4 is a photorefractive index grating generated by irradiating interference fringes.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sample 2 ... Object light from 1st light source 3 ... Reference light from 1st light source 4 ... 2nd light from 2nd light source 5 ... Transmission direction of object light 6 ... Transmission direction of reference light 7 ... Light detector 8 ... Laser light source 9 ... Beam splitter 10 ... Mirror 11 ... Second light source 12 ... Signal light (writing) 13 ... Reference light 14 ... Signal light (reading) 15 ... Micromirror array device 16 ... Lens 17 ... Photodetector 18 Optical recording medium

Claims (4)

[Claims] 1. A hologram recording medium comprising a charge generating material, a charge transporting material, and a material having an electro-optical effect, wherein interference fringes are formed by light irradiation, wherein the content of the charge generating material is A hologram recording medium, wherein the hologram recording medium has a maximum value on a surface of the recording medium irradiated with the light and monotonically decreases in a film thickness direction. 2. A hologram recording medium comprising a charge generation material, a charge transport material, and a material having an electro-optic effect, wherein interference fringes are formed by light irradiation, wherein the charge generation material has an absorption wavelength range. At least two different
At least one of these components absorbs the writing light for forming the interference fringes in the absorption wavelength range, and at least one of the remaining components forms the interference fringes. Does not absorb the writing light in the absorption wavelength range, absorbs light having a different wavelength from the writing light for forming the interference fringes, and the penetration length of the light is the length of the writing light for forming the interference fringes. A hologram recording medium characterized by being shorter than the penetration length. 3. A hologram recording medium containing a charge generation material, a charge transport material, and a material having an electro-optic effect,
What is claimed is: 1. A recording apparatus for recording interference fringes of electromagnetic waves, comprising: a first device for forming interference fringes on the hologram recording medium;
A first light source for irradiating a first light having a first wavelength, and a second light source different from a first wavelength for forming the interference fringes.
A second light for irradiating an irradiation surface of the hologram recording medium with the first light, the second light having a wavelength of less than the first light and having a penetration length shorter than the first light.
And a light source. 4. A first material having a first wavelength, comprising a charge generation material, a charge transport material, and a material having an electro-optic effect.
A reproducing apparatus for reproducing interference fringes of the hologram recording medium on which the interference fringes are formed by irradiating light, and a reference light source for irradiating the hologram recording medium with reference light; and forming the interference fringes. A second wavelength different from the first wavelength
A second light for irradiating a surface of the hologram recording medium irradiated with the first light with a second light having a wavelength of less than the first light and having a penetration length shorter than the first light. And a light detector that reads a component diffracted by the hologram recording medium among the reference light emitted from the reference light source.