JP2003098942A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium for hologram recording which is long in recording life and can make the density of multilayer optical recording additionally higher. SOLUTION: The optical recording medium contains a charge generating agent which generates first and second charges varying in polarities by irradiation with light and a trapping agent which holds the first charge and is changed in optical characteristics by holding of the charge. The recording medium records the difference in the intensity of the light with which the medium is irradiated as the difference in the optical characteristics of the trapping agent brought about by the holding of the first charge. The trapping agent >=2 groups having electron donative/receptive properties within the molecule and the groups having the donative/receptive properties are bonded by a conjugation system or are in the state that these groups overlap spatially each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium in which information is recorded as a change in optical characteristics caused by light irradiation, and in particular, a change in optical characteristics indicating recorded information is caused by holding charges generated by light irradiation. It relates to a directly produced optical recording medium.

[0002]

2. Description of the Related Art An optical recording medium is known as a medium capable of recording a large amount of data such as a high density image. Conventionally, as an optical recording medium, a magneto-optical recording medium, an optical phase change type medium and the like have been developed, but a demand for higher density of the amount of information recordable on the optical recording medium is increasing.

A holographic memory is known as a recording medium for realizing a high density of information recorded on such an optical recording medium. In this, page data in which light intensity and its phase are two-dimensionally distributed and reference light are interfered with each other to record information in the form of a hologram in the recording layer. In the holographic memory, the recording layer is made thick and a large number of holograms are recorded in the overlapping region by slightly changing the incident angle of the reference light and the recording position.

As a recording medium for such a holographic memory, inorganic substances have been studied so far.
In recent years, a photorefractive medium using an organic polymer compound has been actively developed for the reason that it is possible to avoid difficulties in producing a crystalline material and controlling characteristics (for example, Japanese Patent Laid-Open No. 9-22034). .

The photorefractive medium has a recording layer composed of a charge generating agent, a charge transporting agent, a trapping agent and a non-linear optical material, and the recording medium is irradiated with signal light and reference light which interfere with each other. Thus, information is recorded on the recording layer in the form of interference fringes of both lights, and by irradiating the recording layer with reference light at the time of recording, reproducing light having the same spatial characteristics as the signal light is reproduced.

Specifically, in the portion of the recording layer irradiated with light, charges are generated from the charge generating agent, the charges are separated by the charge transporting agent, and the separated charges are held by the trapping agent. An internal electric field is created in the layer. As a result of changing the refractive index of the nonlinear optical material by this internal electric field,
When the light that can interfere with each other is applied, the intensity pattern of the applied light is recorded in the recording layer as a change in the refractive index.

As conventional non-linear optical materials, those containing --CN groups and --NO ₂ groups are often used, and a large change in refractive index has been obtained by orienting these groups in the direction of the electric field. However, this means that when the oriented state changes due to energy such as thermal fluctuation, the change in the refractive index is greatly reduced, and such orientation relaxation is one of the factors that limits the recording life. .

On the other hand, a multi-layer type optical recording medium is known as another recording medium for realizing a high density of the amount of information recorded on the optical recording medium (DA Parthenopulous and PM).
Rentzepis, Science vol 245, pp.843-844 (1989)).
As disclosed in the literature, this is a method in which recording light is condensed at an arbitrary position in a uniform optical recording medium, and a change in optical characteristics is caused only in the vicinity of its focal point, and recording is performed. And non-recording layers are alternately laminated.

Inorganic substances have also been studied as such a multilayer optical recording medium (for example, Y. Kawata, H. Ishibash.
i, and S. Kawata, Opt. Lett. Vol 16, pp. 756-758,
(1998)) similarly, a photorefractive medium using an organic polymer compound has been actively developed in recent years for the reason that it is possible to avoid the difficulty of producing a crystalline material and controlling the characteristics. In the photorefractive medium, the change in the optical characteristics changes in proportion to the light intensity, but in the recording medium in which the change changes in proportion to the light intensity, the information recording area is recorded in the depth direction. Therefore, it is necessary to sufficiently separate the adjacent recording areas in the depth direction, which is an obstacle to high density. As a method of narrowing the space in the depth direction, a method of generating carriers by two-photon absorption has been studied (D. Day, M. Gu, and A. Smallridge, Op.
t. Lett. Vol. 24, pp. 288-290 (1999)). However, this method requires a very strong light source to generate carriers by two-photon absorption, and therefore cannot be recorded by a general semiconductor laser.

[0010]

As described above, in the conventional photorefractive medium, the state of the oriented molecules is relaxed by thermal fluctuation and the change in the refractive index is greatly reduced.
There was a problem of limiting the recording life. In addition, there is a problem that it is difficult to perform high density multi-layer recording using a general recording means.

An object of the present invention is to provide an optical recording medium in which information is recorded as a hologram and which has a long recording life.

Further, the present invention provides a multilayer optical recording medium capable of recording information at an arbitrary position within a uniform recording area,
An object of the present invention is to provide an optical recording medium capable of recording information in a sufficiently narrow area in the depth direction even when using a low power light source.

[0013]

In order to solve the above-mentioned problems, according to one aspect of the present invention, an optical recording medium has a charge generation that generates first and second charges having different polarities by irradiation with light. A recording layer containing an agent and a trapping agent that retains the first electric charge and whose optical characteristics are changed by retaining the first electric charge. It is a gist to record as a difference in the optical characteristics of the trapping agent caused by holding the electric charge of 1.

The trapping agent has two or more groups having electron accepting properties in the molecule, and the groups having electron accepting properties are bonded to each other by a conjugated system.

Alternatively, the trapping agent has two or more groups having electron accepting properties in the molecule, and the groups having electron accepting properties are spatially overlapped.

The content of the trapping agent is 20% by weight or more and 70% by weight or less of the recording layer.

The recording layer may contain a charge transporting agent that transports the first charge generated by the charge generating agent to the trapping agent.

The content of the charge transfer agent is 50% by weight or less of the recording layer.

The groups having electron accepting property in the above trapping agents are allylalkanes, allylamines, aniline and its derivatives, triphenylamine and its derivatives, enamines, hydrazones and their derivatives; julolidine, indole, carbazole, oxazole. ,
Nitrogen-containing cyclic compounds such as isoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, thiathiazole, and triazole; oxygen-containing compounds such as fluorenone and its derivatives, diphenoquinone and its derivatives, anthraquinone and its derivatives; and sulfur-containing compounds It has at least one structure selected from the group consisting of derivatives. The conjugated system in the trapping agent is vinylene, ethynylene, paraphenylene,-
C = N-, pyrrolylene, oxazolylene, thiazolylene, imidazolylene, 1,3,4-oxadiazolylene, 1,3,4-thiadiazolylene, 1H-1,2,4
It is composed of at least one divalent group selected from the group consisting of -triazolylene and -C = NN-C-.

The trapping agent is represented by the general formula (1) described below.
Alternatively, the compound represented by (2) is included.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have made intensive studies on a recording layer of an optical recording medium in which information is recorded in the form of a hologram by light irradiation, and charge transfer is performed by a structural change of a molecule having a charge-transporting group. As a result of repeated studies focusing on the fact that the speed of the magnetic field is affected and that the structural change of the molecule is accompanied by the change of the optical constant, it was found that optical recording by a trapping agent is possible, and the present invention has been accomplished. . That is, in the present invention, a change in optical characteristics (a property represented by an optical constant such as a refractive index, an absorbance, a reflectance, and a luminous efficiency) accompanying a change in a molecular structure due to the electron retention of a trapping agent is directly applied to optical recording. To use. Therefore, when the charge generating agent generates an electric charge by light irradiation, the electric charge is transported and retained in the trapping agent, and information is recorded in the recording layer by a change in the optical property of the trapping agent due to a change in the molecular structure of the trapping agent. Therefore, the present invention does not require the conventional non-linear optical material whose optical characteristics change depending on the electric field.

An example of the optical recording medium of the present invention is shown in FIG.
Recording / reproduction of information will be described with reference to FIG.

First, in the optical recording medium 7 having the recording layer 2,
Information is recorded by irradiating laser light. At this time, the transparent electrodes 1 and 3 may be provided on two opposing surfaces of the recording layer 2 to perform recording while applying a voltage between the electrodes. The laser light is divided into a signal light 4 containing information in the form of its spatial intensity distribution or phase distribution and a reference light 5, and the two lights interfere with each other in the recording layer. In this way, information is recorded in the recording layer 2 in the form of interference fringes. After blocking the two lights, the reference light 5 is applied to the recording layer 2 under the same conditions as when recording, whereby the reproduction light 6 having the same spatial characteristics as the signal light is reproduced. Information can be reproduced by detecting the intensity distribution and phase distribution of the reproduction light 6.

Generally, when the horizontal axis represents the molecular variables such as the bond length and the bond angle of the molecule and the vertical axis represents the energy level of the charge, the graph is shown in FIG. In FIG. 2, the curve a shows the energy level of the molecule in the neutral state, and the curve b
Indicates the energy level of the ionized state. When the molecular structure changes significantly when the molecule is ionized, energy is lost in the form of lattice vibration when the structure changes, and the charge is stably captured due to energy loss of the charge. One preferable form of such a structural change is a structure in which a conjugated bond is formed so that the whole molecule becomes a conjugated system. In the present invention, such a molecule is used as a trapping agent. Therefore, the trapping agent of this form in the present invention has an electron accepting property (a property of donating or receiving electrons).
Considering the easiness of charge transfer in a group having a group, the molecule contains two or more groups having an electron accepting property, and the group between them is a conjugated system (continuous without being disrupted by a non-conjugated bond). It is necessary to be connected by a series of conjugated bonds). In particular, when the group having an electron-accepting property has an electron-donating property, a structural change is likely to occur, so that the conjugated system connecting them preferably has an electron-donating property. In particular,
It is desirable that the conjugated system contains a nitrogen atom.

Examples of such a trapping agent used in the present invention include compounds represented by the following general formulas (1) and (2).

[0026]

[Chemical 3] (In the above formula (1), R1, R2, R3 and R4 may be the same or different and are a hydrogen atom, a methyl group, an ethyl group or a phenyl group.)

[Chemical 4] (In the above formula (2), R1, R2, R3 and R4 may be the same or different and are a hydrogen atom, a methyl group, an ethyl group or a phenyl group.) A molecule of the compound represented by the general formula (1) Calculating the energy levels of the structure for the neutral and ionized states gives the following results. That is, in the neutral state, this compound is a trans type as shown by the above-mentioned general formula (1), and is present on substantially the same plane except the substituents R1 to R4. When the structure in the ionized state is calculated by using the structure in the neutral state as an initial condition and the bond lengths in the neutral state and the ionized state are compared, the general formula (1)
It can be seen that the compound represented by the formula (1) is rather close to the structure represented by the following chemical formula (1 ′) in the ionized state.

[0027]

[Chemical 5] (In the above chemical formula, R1, R2, R3 and R4 may be the same or different and are a hydrogen atom, a methyl group, an ethyl group or a phenyl group.) Two groups having electron accepting properties in the molecule The trapping agent including the above can hold one charge and then hold another charge before the structure is changed. In such a case, the structure change is larger than that when one electric charge is retained. Specifically, the change in bond length is larger than that in the comparison between general formula (1) and general formula (1 ′).

When the absorption peak wavelength in the state represented by the general formula (1) and the state in which two charges are held is examined, the absorption peak exists in the vicinity of 318 nm in the state represented by the general formula (1). On the other hand, in the state where the electric charge is retained, 3
New absorption occurred around 53 nm. Since such a change in absorption accompanies a change in the refractive index due to the Kramers-Kronig relationship, it can be seen that the optical constants such as the absorption coefficient and the refractive index change as the trapping agent retains the charge and changes the structure. .

As described above, in the optical recording medium of the present invention, electric charges are generated by irradiation of light, and the electric charges are transported by an appropriate distance and held in the trapping agent. The trap agent is
Since it contains a group having an electron accepting property, the charge can be taken from the charge generating agent. The trapping agent changes its molecular structure when it receives an electric charge. The change in structure means a change in the bond length in the molecule as shown in the general formulas (1) and (1 ′), or a twist between groups having a planar structure such as a phenyl group, an oxadiazole group and a pyrrole group. Refers to changes. When the molecular structure of the trapping agent changes, the
As shown in Fig. 3, the change in the structure causes the charge to largely lose its kinetic energy, so that the charge is stably retained in the trapping agent.

However, when the trapping agent is dispersed in the matrix polymer in the optical recording medium of the present invention, this structural change does not always occur every time the trapping agent receives an electric charge. When the structure changes, the energy is lost and the charge is stably retained in the trapping agent,
It may be transported to another electrophilic group sooner than the structural change occurs, or it may be transported on multiple trapping agents. Therefore, the charge separation generated by the charge generating agent may occur even with only the trapping agent. Of course, in order to cause charge separation more efficiently, it is preferable to contain a charge transporting agent in addition to the trapping agent. When the trapping agent retains the electric charge and changes the structure, not only the energy level of the electric charge but also the optical constant changes.
According to the spatial distribution of the trapping agent, which retains the charge and has its structure changed, the spatial distribution of the portion where the optical constant is changed occurs.

In the above description, the trapping agent has an electric charge of 1
This holds true not only when two charges are held, but also when two or more charges are held. In particular, in the state where two charges are held, it is possible to realize the ideal situation in which the life of the held charges is long and the change in the optical constant is large.

When the recording layer containing such a trapping agent is irradiated with two coherent lights, if the average distance for transporting charges is sufficiently shorter than the interval of the interference fringes, the same as the interference fringes. A change in the optical constant with a period occurs. Therefore, when one of the lights forming the interference fringes is blocked, diffracted light is observed.

With reference to FIG. 3, the principle that the optical characteristics of the optical recording medium change according to the distribution of the intensity of the irradiated light will be described below.

In the conventional photorefractive medium, when the medium is irradiated with light having an intensity distribution as shown in FIG. 3A, a charge distribution as shown in FIG. 3B is generated. Of these, only the holes are transported and the mean free process is shown in Fig. 3.
If (a) is about the same as or larger than Λ, FIG.
The distribution of holes is spatially uniform, as shown by the dotted line in the middle. As a result, the total charge distribution is as shown in FIG. In general, an external electric field is applied to the photorefractive medium, so that the electric field distribution is as shown in FIG. Furthermore, when the nonlinear optical material is oriented, the refractive index changes according to the electric field intensity in FIG. 3D, and as a result, the refractive index changes according to the irradiated light intensity distribution. However, if the mean free path of the transported holes is sufficiently smaller than Λ, the distribution of the holes is almost unchanged, and the charge distribution as shown in FIG. 3C does not occur. Therefore, the electric field distribution as shown in FIG. 3D does not occur regardless of the presence or absence of the external electric field, and thus the optical characteristic does not change according to the distribution of the light intensity even when the medium contains the nonlinear optical material. .

On the other hand, in the optical recording medium of the present invention, when the medium is irradiated with light having an intensity distribution as shown in FIG. 3A, it is similar to the conventional photorefractive medium.
A charge distribution as shown in (b) occurs and only holes are transported. At this time, if a trapping agent capable of holding holes as shown in chemical formula (1) is dispersed, the light intensity is high and the charge is high. In the region where a large amount of charges are generated, a large amount of the trapping agent that retains the electric charge is present, so that the retention of the electric charge causes a change in the optical characteristics of the molecule. That is, a change in optical characteristics occurs according to the distribution of light intensity. At this time, if the mean free path of the charges is about the same as Λ, the distribution of the trapping agent holding the charges becomes uniform as in FIG.
No local change in optical properties occurs.

As described above, in the conventional photorefractive medium and the optical recording medium of the present invention, the conventional -CN is used.
The difference is not only in the presence or absence of a non-linear optical material containing a group or a —NO ₂ group but also in the mean free path of photogenerated charges.

Further, when recording light is focused on the recording layer containing the trapping agent of the present invention, a large amount of charges are generated near the focal point, so that the average moving distance of charges is equal to or less than the minimum beam diameter. At times, more trapping agent retains charge near the focal point. Therefore, the optical constant changes greatly near the focal point. In particular, in the case of such a recording method, the charges are simultaneously generated in a narrower area near the focal point, so that the probability that two charges are held by one trapping agent becomes high. The probability that two charges are held in one trap is most simply proportional to the square of the charge density. On the other hand, since the number of charges generated by light irradiation is proportional to the light intensity, the probability that two charges are held in the trapping agent is proportional to the square of the light intensity. As a result, the optical constant can be changed only in a narrower area.

Hereinafter, each material constituting the optical recording medium according to the present invention will be described in more detail.

The charge generating agent used in the present invention is
When irradiated with light, they generate carriers, that is, electric charges (electrons and holes) to be transported. For example, selenium and selenium alloys, CdS, CdSe, CsSS
e, AsSe, ZnO, ZnS, and inorganic photoconductors such as amorphous silicon; titanyl phthalocyanine,
Various crystal forms such as vanadyl phthalocyanine (α, β,
γ, δ, ε, ζ, η, θ, ι, κ, λ, μ, ν, ξ,
ο, π, ρ, σ, τ, υ, φ, χ, ψ, ω, A, B,
C, X and Y type) metal phthalocyanine pigments and various liquid crystal type metal-free phthalocyanine pigments; azo dyes and pigments such as monoazo dyes, bisazo dyes, trisazo dyes and tetrakisazo dyes; perylene anhydride and perylene imide Perylene dyes and pigments; perinone pigments; indigo dyes and pigments; quinacridone pigments; polycyclic quinone pigments such as anthraquinone, anthanthrone and dibromoanthrone; cyanine dyes; electron-capturing substances and electrons such as TTF-TCNQ eutectic complexes consisting of a pyrylium dye or thiapyrylium dye and polycarbonate resin; charge-transfer complex consisting of a donor material azulenium; C _60, fullerene and derivatives thereof such as C _70; dimethyl terephthalate, diethyl terephthalate Terephthalic acid derivatives having a carbonyl group such as, xanthene dyes and pigments, and azulenium dyes and squarylium dyes.

These charge generating agents may be used alone or in combination of two or more kinds. As described above, it is also possible to disperse two types of charge generating agents having different polarities of generated charges and different wavelengths of excited light.
At this time, one charge generating agent is used for erasing.

The charge generating agent is 0.0 with respect to the entire recording layer.
It is preferably used in a proportion of about 01 to 40% by weight. When the amount is less than 0.001% by weight, the electric charge per unit volume generated by light irradiation is small, and sufficient change in optical characteristics does not occur. On the other hand, if it exceeds 40% by weight, the light absorption by the charge generating agent becomes large, and the light cannot pass through the recording layer, so that it becomes difficult to manufacture an optical recording medium having a large film thickness.

As described above, one form of the trapping agent in the present invention is a compound containing two or more groups having an electron accepting property in one molecule and having a conjugated system between them. The conjugated system means vinylene, ethynylene, paraphenylene, -C = N-, pyrrolylene, oxazolylene,
Thiazolylene, imidazolylene, 1,3,4-oxadiazolylene, 1,3,4-thiadiazolylene, 1H-
1,2,4-triazolylene and -C = NN-N = C-
A divalent group such as or a combination of a plurality of these groups. Specific examples of conjugated bonds are shown below by structural formulas.

[0043]

[Chemical 6]

[Chemical 7] (In the above formula, R1, R2, R3 and R4 may be the same or different and each is a hydrogen atom, a methyl group, an ethyl group or a phenyl group.) In the conjugated system as described above, the cyclic group is In the case of containing one, the position at which the electrophilic group is bonded is limited. Specifically, the position at which the electron-accepting group is bonded to the conjugated system containing the cyclic group is determined by the structures shown in the general formula (1) and the general formula (1 ′) as described above. It must be in a position where it can change.

Regarding this, the following chemical formulas (3a) and (3
This will be described in detail with reference to b), (3c) and (3d).

[0045]

[Chemical 8] The compound represented by the chemical formula (3a) is a molecule in which two groups having electron accepting ability are bonded by a conjugate bond, and therefore, when ionized, the molecule represented by the chemical formula (3b) is obtained. Structural changes throughout are possible.
On the other hand, in the chemical formulas (3c) and (3d), the position to bond to the group having electron accepting property is different from the chemical formula (3a), and the conjugated bond is broken between these groups. Therefore, since the electron-accepting group is not bound in a conjugated system, structural change does not occur throughout the molecule.

Therefore, it is an important factor for the effectiveness of the present invention that two groups having an electron accepting property, such as the chemical formula (3a), are connected by a conjugated bond.

Further, in order for the molecule to effectively cause the structural change, it is desirable that the conjugated system in the trapping agent satisfies the following. That is, when the group having an electron-accepting property transports a hole, the conjugated system preferably has an electron-donating property, and for this purpose, it preferably contains a nitrogen atom. On the contrary, when the electron-accepting group transfers an electron, the conjugated bond preferably has an electron-accepting property. Further, the trapping agent preferably has symmetry as a whole molecule, and when it contains a phenyl group and its derivative, it is preferable that the phenyl group is rotatable. In particular, in the case of containing two groups having a child-accepting property,
A line-symmetrical structure is preferable.

The hydrogen atom in such a conjugated bond system is
It can be replaced by any group. However, in order not to prevent the structural change from occurring in the entire molecule, it is desired that the introduced substituent is small. Examples thereof include an alkyl group having 2 or less carbon atoms such as an ethyl group and a methyl group, and a phenyl group. Alternatively, as shown in chemical formula (4), the polymer in which the trapping agent in the present invention is bound as a side chain can also function as an effective trapping agent. However, in the molecule represented by the chemical formula (4), the number of units of a carbazole group having a large charge-transporting property (x) and the number of units of a site having a large charge-holding ability (y) are set to an appropriate size for the mean free path of charges. Need to be adjusted. By thus binding the trapping agent as the side chain of the polymer, it is possible to prevent the deposition of the site having the trapping function. Therefore, a site having a trap function can be introduced at a high concentration. Further, since a large free space is obtained by bonding as a side chain of a polymer, there is an advantage that a structure change easily occurs when an electric charge is retained.

[0049]

[Chemical 9] On the other hand, the groups having electron accepting property in the trapping agent include allylalkanes, allylamines, aniline and its derivatives, triphenylamine and its derivatives,
Enamines, hydrazones and their derivatives; julolidine, indole, carbazole, oxazole, isoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, thiathiazole,
Nitrogen-containing cyclic compounds such as triazole; oxygen-containing compounds such as fluorenone and its derivatives, diphenoquinone and its derivatives, anthraquinone and its derivatives, and sulfur-containing derivatives such as thiopyran and its derivatives. In such a group, a hydrogen atom bonded to a site having a small effect on charge transport can be appropriately substituted with an ethyl group, a methyl group, a hydroxyl group or the like. When multiple such substituents are introduced,
They do not have to be identical.

Another form of the trapping agent in the present invention is a compound having a planar structure and having a structure in which two or more groups having electron accepting properties are spatially overlapped. When the group having an electron accepting property has a planar structure, the charge retention ability can be improved by the structural change even if the two groups having an electron accepting property are not bonded in a conjugated system. This is explained as follows. In the neutral state, it is assumed that the axis of symmetry of the electrophilic group is slightly displaced. In this molecule, when a charge is injected into one of the two groups, stability in a neutral state is lost, so that a structural change in which the symmetry axes of the two groups coincide with each other can occur. When the axes of symmetry of the two groups coincide, the energy level of the two groups changes significantly compared to when the two groups are present independently, due to the abrupt increase in the interaction between the two groups. For this reason, the ability to retain charges is improved. Examples of such a group having a planar structure and having an electron accepting property include indole, carbazole, oxazole, isoxazole, thiazole, imidazole, pyrazole,
Nitrogen-containing cyclic compounds such as oxadiazole, pyrazoline, thiathiazole and triazole; oxygen-containing compounds such as fluorenone and its derivatives, diphenoquinone and its derivatives, anthraquinone and its derivatives; and groups having a structure such as sulfur-containing derivatives. To be

The above trapping agents can be used alone or as a mixture of two or more kinds. Also,
Its content is 20% by weight or more with respect to the entire recording layer, and 7
It is desirable to set it to 0% by weight or less. When the content of the trapping agent is less than 20% by weight, the amount of dispersion is too small and the mean free path of the charge increases, so that the optical characteristics do not change according to the light intensity distribution. On the other hand, if it exceeds 70% by weight, the trapping agents may aggregate and crystallize, and it may not be possible to form a recording layer in which molecules are uniformly dispersed. The content of the trapping agent is 30 in the recording layer.
It is more preferable that the content is 50% by weight or more and 50% by weight or less.

The optical recording medium of the present invention includes, for example,
Any function that has the function of transporting electric charge by the conduction
Materials may be included as charge transport agents. Charge transfer agent
The addition also has the effect of improving the charge generation efficiency. charge
As a transport agent, for example, an amorphous semiconductor is known.
Si, Ge, Se, S, Te, B, As, Sb
Which structure is irregular semiconductor, SiC, InSb, GaA
s, GaSb, Cd_{1- x}Ge_xAs_Two, Cd_1-xS
i_xP_Two, Cd_1-xSn_xAs_Two, As_TwoSe _Three, A
s_TwoS_Three, Ge-Sb-Se, Si-Ge-As-T
e, Ge-As-Se, As_TwoSe_Three-As_TwoTe_Three,
As-Se-Te, Tl_TwoSe-As_TwoTe _Three, Cu
_1-xAu_xTe_Two, V_TwoO₅-P_TwoO5, MnO-A
l_TwoO_Three-SiO_Two, V_TwoO₅-P_TwoO₅-BaO, C
oO-Al_TwoO_Three-SiO_Two, V_TwoO₅-GeO_Two-B
aO, FeO-Al_TwoO_Three-SiO_Two, V_TwoO₅-Pb
O_Two-Fe_TwoO_Three, TiO_Two-B_TwoO_Three-BaO, Si
O_x, Al_TwoO_Three, ZrO_Two, Ta_TwoO_Three, Si
_ThreeN_Four, And semiconductors with irregular composition such as BN.
To be In addition, polyacetylene, polypyrrole, poly
Π-conjugated polymers such as thiophene and polyaniline
Oligomer; polysilane, and σ such as polygermane
Conjugated polymers and oligomers; anthracene, pyrene, fluorine
Polycyclic aromatic compounds such as enanthrene and coronene;
Indole, carbazole, oxazole, isoxa
Sol, thiazole, imidazole, pyrazole, oki
Sadiazole, pyrazoline, thiathiazole and tri
A compound having a nitrogen-containing cyclic compound such as an azole, or
Is a compound having these in the main chain or side chain; hydrazone
Compounds, aniline and its derivatives, triphenylami
Amines, triphenylmethanes, butadienes, stilbes
, TCNQ, anthraquinone, diphenoquinone, etc.
Derivative, C₆₀, C₇₀Fullerenes and their invitations
Examples include conductors.

More specifically, for example, diphenylaniline, dimethylaniline, diethylaniline, chloroanil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,4. 5,7-tetranitro-9-tetrafluorenone, 2,4,7-trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone, 2,4,9-trinitrothioxanthone, N, N -Bis (3,5-dimethylphenyl) -3,
Examples include low-molecular compounds such as 4,9,10-perylenetetracarboximide, diphenone, and stilbenzoquinone, and polymer compounds in which these compounds are introduced into the main chain or side chain of the polymer compound. In addition, it is preferable that the charge-transporting agent contains the same group as the electron-accepting group of the trapping agent or a group derived therefrom, from the viewpoint of charge-transporting ability.

The charge transfer agent is preferably used in a proportion of about 50% by weight or less with respect to the entire recording layer. The photogenerated charges are hopped from the charge generating agent to the charge transporting agent, hop between the charge transporting agents, and finally captured by the trapping agent. If the content of the charge transport agent exceeds 50% by weight, the mean free path of the charge increases,
As described above, it is not possible to change the optical characteristics according to the light intensity distribution.

It is also possible to use a charge-transporting agent for transporting each of the two types of charges having two different polarities generated in the optical recording medium. in this case,
One of the charge transfer agents can function as an erase charge transfer agent.

The above-mentioned charge generating agent, trapping agent and charge transporting agent can be used in appropriate combination so that the optical characteristics can be modulated by irradiation light.

In the present invention, when the constituents such as the trapping agent are not polymers, these constituents may be mixed with a polymer as a matrix. The polymer that can be used is not particularly limited, but a polymer that is optically inactive and has a small variation in molecular weight is preferable. For example, polyethylene resin, nylon resin, polyester resin, polycarbonate resin, polyarylate resin, butyral resin, polystyrene resin, styrene-butadiene copolymer resin, polyvinyl acetal resin, diallyl phthalate resin, silicone resin, polysulfone resin, acrylic resin, acetic acid. Vinyl, polyolefin oxide resin, alkyd resin, styrene-maleic anhydride copolymer resin, phenol resin, vinyl chloride-vinyl acetate copolymer, polyester carbonate, polyvinyl chloride, polyvinyl acetal, polyarylate and paraffin wax and the like. . These may be used alone or in combination of two or more.

Further, in order to lower the glass transition point of the recording layer, molecules having a small molecular weight called a plasticizer may be dispersed. By lowering the glass transition point,
The structure of the trapping agent can be changed more easily.

Furthermore, compounds generally known as polymeric antioxidants and ultraviolet absorbers can be used in addition to the above-mentioned components. Examples of such compounds include hindered phenols, aromatic amines, organic sulfur compounds, phosphites, chelating agents, benzophenones, benzotriazoles, and nickel complexes. The blending amount of these components is, for example, preferably 0.0001 to 5% by weight with respect to the entire recording layer.

The recording layer of the optical recording medium of the present invention can be formed by dissolving the above components in a solvent and then removing the solvent to form a film. . As the solvent, various organic solvents can be used, and examples thereof include alcohols, ketones, amides, sulfoxides, ethers, esters, aromatic halogenated hydrocarbons and aromatic hydrocarbons. To be

The recording layer is formed by, for example, spin coating method, dip coating method, roller coating method, spray coating method,
Various coating methods such as a wire bar coating method, a blade coating method and a roller coating method, a casting method, a vacuum deposition method, a sputtering method and the like are possible. Alternatively, it may be formed by a method using glow discharge such as plasma CVD. When the casting method is adopted, not only can the solution be cast, but the solvent can also be vaporized from the solution, and then the powdery mixed material can be heated and melted to form the recording layer.

The film thickness of the recording layer thus formed is usually about 0.05 to 10 mm, and 0.5 to 1 mm.
Is preferred. The film thickness of the recording layer can be appropriately selected according to the characteristics and composition required for the optical recording medium, such as recording capacity and optical transparency.

In forming the recording layer, a solution containing a composition containing the above-mentioned components is applied onto a suitable support. As the support, any material having appropriate thickness and hardness and having sufficient strength for handling may be used. When the composition constituting the recording layer has an appropriate strength at room temperature, the support may be removed and the composition alone may be used.

This support is not only used for film formation,
It can also be used as a substrate of an optical recording medium. That is, the recording layer formed on this substrate may be used to form the optical recording medium of the present invention. The substrate in this case is desired to be transparent to some extent in the wavelength range of light used for recording. The wavelength of light is, for example, 780 nm, 650 nm, and 405 nm in the case of a semiconductor laser. Ordinary resins are transparent to light with a wavelength in the visible range of 400 to 600 nm, and many of them maintain transparency up to around 800 nm, which is a long wavelength range. Therefore,
Polyvinyl chloride, polyvinylidene chloride, polyethylene,
Polycarbonate, polyester, polyamide, acrylic resin and polyimide are preferred.

These substrate materials can be used in the form of a flat plate or, if necessary, a cylindrical sheet. When used as a cylindrical sheet, the substrate is required to have appropriate flexibility.

On the recording layer side of the above-mentioned substrate, a layer serving as an electrode may be formed if necessary. Like the substrate, the material forming the electrode layer is desired to be transparent to some extent in the wavelength range of the light used. Therefore, indium tin oxide, aluminum or the like is preferably used. Further, the sheet resistance of the electrode is desired to be 50 Ωcm ⁻² or less.

In the present invention, a protective layer may be provided on the recording layer if necessary. Any material can be used as the material for forming the protective layer.
For example, acrylic resin, fluororesin, silicone resin,
Examples include thermosetting resins such as melamine resins, photocurable resins, EB curable resins, X-ray curable resins, and UV curable resins.

In such a protective layer, a small amount of additives such as an antioxidant, an ultraviolet absorber and an anti-aging agent may be added. Examples of additives that can be used include hindered phenols, aromatic amines, organic sulfur compounds, phosphite esters, chelating agents, benzophenones, benzotriazoles, and nickel complexes.

Next, a case where the optical recording medium of the present invention is used as a hologram memory, that is, a method of recording information on the medium and reproducing the recorded information will be described.

FIG. 4 shows an example of a recording apparatus for recording information on the optical recording medium of the present invention having the recording layer as described above.

As shown in FIG. 4, a rectangular parallelepiped optical recording medium 7 is manufactured. The image display element 15 is arranged on one side of the optical recording medium 7, and the reading device 19 is arranged on the opposite side with the optical recording medium 7 interposed therebetween. Reader 19
Is preferably arranged along the optical axis so that the light emitted from the image display element 15 to the optical recording medium 7 enters perpendicularly to the reading surface. As the image display element 15, for example, a liquid crystal element, a digital mirror array, Pockels Read
out Optical Modulator, Multi-channnel SpatialModul
It is possible to use an ator, a Si-PLZT element, a modified surface type element, an AO or EO modulation element, a magneto-optical effect element, or the like. Further, as the reading device 19, any photoelectric conversion element can be used. For example, CC
D, CMOS sensors, photodiodes, photoreceptors and photomultiplier tubes.

Although it is assumed in FIG. 4 that light passes through the image display element 15, the image display element 15 may be of a type that reflects light.

The light source used for recording must be coherent, that is, coherent light represented by a laser. Here, a specific example of a procedure for recording information on an optical recording medium will be described below by using a laser as an example.

The wavelength of the laser is selected according to the components of the optical recording medium used. Specifically, it is selected according to the charge generating agent and the trapping agent. For the laser 10,
Any existing gas laser, liquid laser, solid-state laser, or semiconductor laser can be used.

The output from the laser 10 is split into two using a beam splitter 12, for example. One is used as the reference light 5, and the other is used as the signal light 4 that is transmitted through the image display element 15. The signal light 4 and the reference light 5 enter the optical recording medium 7 so as to intersect with each other in the recording layer. Specifically, this is performed by the following method. The light from the laser 10 is spread into parallel light by a beam expander 11, for example, and then split into two by a beam splitter 12, for example. The information to be recorded is digitized in advance, and an image pattern corresponding to it is input to the image display element 15. One of the two light beams split by the beam splitter 12 is applied to the image display element 15 via the mirror 13, and spatially modulated according to the data for recording the light intensity distribution to obtain the signal light 4. . Further, the signal light 4 is condensed by the lens 16 and applied to the optical recording medium 7. At that time, the reference light 5 is applied to the optical recording medium 7 so that the reference light 5 intersects the recording layer at the same time. The reference light 5 is collimated and expanded by the mirror 14 and the lens 17 to be irradiated.

The interference fringes generated by the superposition of the signal light 4 and the reference light 5 generate a spatial distribution of the trapping agent holding the charges, and the optical characteristics are modulated to form a diffraction grating. At this time, a plurality of interference fringes can be formed in the overlapping region by changing the incident angle of the reference light, the incident angle of the signal light, or both. Alternatively, the incident angles of the reference light and the signal light can be changed by rotating the optical recording medium 7 with respect to the direction of the incident light. Furthermore, 1/2 to 1/10 of the area where the signal light and the reference light overlap each other.
By shifting the irradiation position of the laser light by about 00, a plurality of interference fringes can be similarly recorded in the area where the two lights overlap.

When reading the recorded information,
First, the signal light 4 is blocked, and only the reference light 5 is supplied to the optical recording medium
To irradiate. That is, the reference light 5 can also be used as the reading light. At this time, since the reproduced light having the same spatial intensity distribution as the signal light 4 is reproduced by the recorded interference fringes, the reading device 1 is transmitted after passing through the lens 18.
It can be read at 9. The recorded information can be reproduced by the intensity distribution of the read light. Lens 18
The distance from to reading device 19 is preferably equal to the focal length of lens 18. The distance between the lens 16 and the lens 18 is the focal length of the lens 16 and the lens 1
It is desirable to be equal to the sum of 8 focal lengths.

Here, a light source having the same wavelength is used for recording and reading, but the present invention is not limited to this. When the thickness of the recording layer is about 0.5 mm or less, the recorded information can be read even by using a light source having a wavelength slightly different from that at the time of recording. In such cases,
The reference light may be incident at an angle slightly different from that at the time of recording so that the intensity of the diffracted light becomes large at the time of reproduction. Also at this time, it is desirable that the reading surface of the reading device 19 is arranged so as to be perpendicular to the optical axis of the light used for reading.

Further, in this example, the reference light 5 also receives the lens 17
However, the reference light does not necessarily have to be collected. By disposing the beam expander 11 at any position on the path from the laser 10 to the image display element 15, the lens 17 can be omitted.

In reading the recorded information, phase conjugate reproduction is also possible. This will be described with reference to FIG. In FIG. 5, coherent light having the same wavelength as that used for recording is emitted in the opposite direction to that during recording.

More specifically, the reference light 5 is emitted from the laser 20 which oscillates the light having the same wavelength as the light used for recording after expanding the diameter of the light with, for example, the beam expander 21 and using the lens 22. The optical recording medium 7 is irradiated in the opposite direction to the irradiation. Due to the diffraction grating recorded on the optical recording medium 7, the virtual image 4'is reproduced in the opposite direction to the direction in which the signal light 4 travels. After the virtual image 4 ′ passes through the lens 16, it is reflected by the beam splitter 23 and read by the reading device 19, for example. In this case as well as when recording, the lens 1
The distance from 6 to the reader 19 is preferably equal to the focal length of the lens 16. Also in the phase conjugate reproduction, coherent light having a wavelength slightly different from that at the time of recording can be used as the reading light.

When the reference beam 5 is not focused during recording, the beam expander 2 is also used during phase conjugate reproduction.
1 and the lens 22 can be omitted.

The information recorded on the optical recording medium can be erased. The record is erased, for example, by irradiating light having a uniform intensity distribution over a region wider than the recording region or by heating the optical recording medium to a temperature lower than the glass transition point.

The method of recording and reproducing information on the optical recording medium of the present invention is not limited to the above-mentioned example, but various changes can be made. For example, as shown in Figure 6,
The signal light 4 and the reference light 5 may be incident on the optical recording medium 7 from different surfaces.

When the information is recorded as digital data, a plurality of pixels of the image display element 15 may represent one data.

When the information is given by the intensity distribution of the signal light, the light intensity in the bright portion and the dark portion need not be uniform over the entire beam diameter. That is, the light transmittance of the image display element can be lowered in the central portion and increased in the portion distant from the central portion. by this,
It is possible to correct in advance that the reproduction light is weakened in the part farther from the center than the center of the reproduction signal. Alternatively, the reading device 1 uses a light intensity modulation element having a large absorption coefficient near the center and a small absorption coefficient away from the center.
It is the same even if it is arranged before 9.

Next, when the optical recording medium of the present invention is used as a multilayer optical recording medium, that is, a method of recording information on a plurality of layers on the medium and reproducing the recorded information will be described with reference to FIG.
Will be explained.

The light from the semiconductor laser 31 is collimated by the collimator lens 32 and then is condensed in the recording layer by using the objective lens 33. By increasing the injection current to the semiconductor laser 31 for an appropriate time, laser light is emitted for an appropriate time, and information is recorded as a change in the optical constant only near the focal point. By arranging the focal position at an arbitrary position in the medium, information can be recorded in the form of a region 34 where the optical constant changes and a region where the optical constant does not change.

The recorded information can be reproduced by, for example, disposing the iris 35 on the optical axis and measuring the light intensity transmitted through the iris using the photodetector 36. That is, when irradiation is performed so that the optical axis of the read light passes through a region where the optical constant is changed and the focal position is scanned in the depth direction of the recording layer, the observed transmitted light intensity I is the position Z in the depth direction. (Here, the center of the region where the optical constant has changed is Z = 0.
8) as a function. When the area where the optical constant does not change is scanned, the transmitted light intensity does not change. Therefore, it is possible to know whether the area where the optical constant has changed or not depending on whether or not the transmitted light intensity changes. Therefore, the information is recorded and read as the fluctuation of the optical characteristics in the area where the recording light is condensed.

However, the injection current is adjusted so that the light intensity of the read light is about 1/2 to 1/100 of that at the time of recording so that a new change in the optical constant does not occur during reproduction of information. Is desirable.

Alternatively, as a simpler reproducing method, it is possible to reproduce the recorded information at the recording position by detecting the transmitted light intensity near the recording position. That is, information can be reproduced by detecting the transmitted light intensity at a position distant by Z ₀ shown in FIG. 8 from the position where information is recorded in the depth direction. When the focal point of the reading light is at a position shifted by Z _{0 in the} depth direction from the area in which no information is recorded, the transmitted light intensity shows the value of I ₀ , but Z is the depth in the depth direction from the area in which the information is recorded. When the focal point is at a position deviated by ₀ , the light intensity is I ₀ + ΔI, and therefore, by detecting this light intensity, the recorded information at a position deviated by Z ₀ from the focal point of the reading light is reproduced. Therefore, the information is recorded and read as a changed optical characteristic value near the focus position where the recording light is focused.

When the film thickness is sufficiently large or when the glass substrate is provided on the objective lens side of the recording layer, the objective lens is CF IC LCD Plan CR 100 manufactured by NIKON.
It is preferable to use one having a long working distance such as double. When substrates are provided above and below the recording layer, the substrate on the objective lens side is preferably 0.5 mm or less.
Alternatively, the substrate may not be provided on the objective layer side of the recording layer. In this case, the recording layer may be housed in a diskette in order to prevent the recording layer from being scratched.

The method of recording and reproducing information on the optical recording medium of the present invention is not limited to the above-mentioned example, and various changes can be made. For example, playing information
It can be performed similarly to the confocal microscope. Alternatively, a reflection surface may be arranged at a position opposite to the objective lens of the optical recording medium, and information may be reproduced using the reflected light.

The optical recording medium of the present invention comprises a trapping agent composed of molecules having two or more groups having electron accepting properties in the molecule and having a conjugated system between them, or an electron in the molecule. It contains a trapping agent composed of a molecule having two or more groups having susceptibility and wherein the groups having electron accepting ability are spatially overlapped. Since such a trapping agent changes the optical constant when the charge is retained, the optical constant can be changed according to the spatial distribution of the trapping agent that retains the charge. Therefore, an optical recording medium having a longer recording life than that of the conventional hologram optical recording medium can be obtained. In addition, in the multi-layered optical recording, information can be recorded at any position in the recording layer, and by recording the information in a narrower area, an optical recording medium that can realize higher density can be obtained.

[0095]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples.

Example I-1 First, an optical recording medium was prepared as follows.

Fullerene (C ₇₀ ): 0.4% by weight, poly (N-vinylcarbazole) (PVK): 39.6% by weight, N-ethylcarbazole (EtCz): 10% by weight, bis-carbazolylpropane (BisCzPr
o): 10 wt% and 40 wt% of the compound represented by the following chemical formula (3) were dissolved in toluene to prepare a toluene solution. The compound represented by the chemical formula (5) acts as a trapping agent, and EtCz and BisCzPro
Acts as a plasticizer that lowers the glass transition point. As shown in chemical formula (5), this compound has two carbazole groups, which are groups having an electron accepting property, and they are bonded in a conjugated system.

[0098]

[Chemical 10] An ITO (Indium Tin Oxide) film was formed on the surface of the glass substrate to prepare the substrate. The above-mentioned toluene solution was applied onto this substrate by a casting method to form a recording layer to obtain an optical recording medium. The film thickness of the recording layer was adjusted to 50 μm using a Teflon (registered trademark) spacer.

Holograms were recorded and reproduced on this optical recording medium using the recording apparatus having the structure shown in FIG. In the illustrated apparatus, a He-Ne laser (output 30 mW) 10
The light emitted from the beam splitter was first split into two by the beam splitter 12. The light reflected by the beam splitter 12 is transmitted through a liquid crystal filter 15 as an image display element after expanding the light diameter using the beam expander 11. The liquid crystal filter 15 modulates its transmittance according to the information to be recorded in advance, and the transmitted light is the signal light 4. The transmitted light was condensed using a lens 16 (focal length 150 mm). The distance between the lens 16 and the optical recording medium 7 was 135 mm.

On the other hand, the light transmitted through the beam splitter 12 was directly applied to the optical recording medium 7 as the reference light 5. At this time, the optical path of the reference light 5 was adjusted so that the reference light covered the area where the signal light 4 was condensed on the optical recording medium.
The angles at which the signal light 4 and the reference light 5 were incident on the optical recording medium 7 were measured, and they were 40 ° and 50 °, respectively, when measured outside the optical recording medium 7.

Since the substrate of the optical recording medium 7 was connected to an external power source (not shown) of 2 kV, an external electric field of 40 V / μm was applied. By irradiating light for 1 second in this way, a hologram could be recorded on the optical recording medium 7.

Subsequently, the recorded information was reproduced. At the time of reproduction, the optical path of the signal light 4 is blocked by a shutter,
When the optical recording medium 7 was irradiated with the light transmitted through the beam splitter 12 as the reading light, diffracted light was observed. After passing the diffracted light through a lens 18 (focal length 150 mm) similar to the lens 16, C as a reader
Upon entering the CD 19, reproduction light having an intensity distribution similar to that of the signal light 4 was detected. In addition,
The lens 18 is arranged at a position 300 mm from the lens 16 and perpendicular to the optical axis so that the optical axis passes through the center of the lens 18. The CCD 19 was also arranged perpendicular to the optical axis. Also,
The distance from the lens 18 to the CCD 19 is equal to the focal length of the lens 18.

The recorded information could be reproduced even after one month.

Example I-2 First, an optical recording medium was prepared as follows.

Fullerene (C ₇₀ ): 0.4% by weight, poly-N-vinylcarbazole (PVK): 39.6% by weight,
N-ethylcarbazole (EtCz): 10% by weight, bis-carbazolylpropane (BisCzPro): 10
By weight, 40% by weight of the compound represented by the following chemical formula (6) was dissolved in toluene to prepare a toluene solution. The compound represented by the chemical formula (6) acts as a trapping agent, and EtCz and BisCzPro act as a plasticizer that lowers the glass transition point. As shown in chemical formula (6), this compound has two carbazole groups which are groups having an electron accepting property, and these are bonded in a conjugated system.

[0106]

[Chemical 11] When recording was performed on the obtained optical recording medium in the same manner as in Example I-1, sufficient recording could be performed with a recording time of 1 second. The recorded information could be reproduced even after one month had passed.

(Example I-3) First, an optical recording medium was prepared as follows.

Fullerene (C ₇₀ ): 0.4% by weight, poly-N-vinylcarbazole (PVK): 39.6% by weight,
N-ethylcarbazole (EtCz): 10% by weight, bis-carbazolylpropane (BisCzPro): 10
By weight, 40% by weight of the compound represented by the following chemical formula (7) was dissolved in toluene to prepare a toluene solution. The compound represented by the chemical formula (7) acts as a trapping agent, and EtCz and BisCzPro act as a plasticizer that lowers the glass transition point. As shown in chemical formula (7), this compound has two carbazole groups, which are groups having an electron accepting property, and they are bonded in a conjugated system.

[0109]

[Chemical 12] When recording was performed on the obtained optical recording medium in the same manner as in Example I-1, sufficient recording could be performed with a recording time of 1 second. The recorded information could be reproduced even after one month had passed.

(Example I-4) First, an optical recording medium was prepared as follows.

Fullerene (C ₇₀ ): 0.4% by weight, poly-N-vinylcarbazole (PVK): 39.6% by weight,
N-ethylcarbazole (EtCz): 10% by weight, bis-carbazolylpropane (BisCzPro): 10
By weight, 40% by weight of a compound represented by the following chemical formula (8) was dissolved in toluene to prepare a toluene solution. The compound represented by the chemical formula (8) acts as a trapping agent, and EtCz and BisCzPro act as a plasticizer that lowers the glass transition point. As shown in chemical formula (8), this compound has two carbazole groups, which are groups having an electron accepting property, and these are bonded in a conjugated system.

[0112]

[Chemical 13] When recording was performed on the obtained optical recording medium in the same manner as in Example I-1, sufficient recording could be performed with a recording time of 1 second. The recorded information could be reproduced even after one month had passed.

(Example I-5) First, an optical recording medium was prepared as follows.

Fullerene (C ₇₀ ): 0.4% by weight, poly-N-vinylcarbazole (PVK): 39.6% by weight,
N-ethylcarbazole (EtCz): 10% by weight, bis-carbazolylpropane (BisCzPro): 10
By weight, 40% by weight of the compound represented by the following chemical formula (9) was dissolved in toluene to prepare a toluene solution. The compound represented by the chemical formula (9) acts as a trapping agent, and EtCz and BisCzPro act as a plasticizer for lowering the glass transition point. As shown in chemical formula (9), this compound has two carbazole groups, which are groups having an electron accepting property, and these are bonded in a conjugated system.

[0115]

[Chemical 14] When recording was performed on the obtained optical recording medium in the same manner as in Example I-1, sufficient recording could be performed with a recording time of 1 second. The recorded information could be reproduced even after one month had passed.

(Example I-6) First, an optical recording medium was prepared as follows.

Fullerene (C ₇₀ ): 0.4% by weight, poly-N-vinylcarbazole (PVK): 39.6% by weight,
N-ethylcarbazole (EtCz): 10% by weight, bis-carbazolylpropane (BisCzPro): 10
By weight, 40% by weight of the compound represented by the following chemical formula (10) was dissolved in toluene to prepare a toluene solution. The compound represented by the chemical formula (10) acts as a trapping agent, and EtCz and BisCzPro act as a plasticizer that lowers the glass transition point. Chemical formula (1
As shown in 0), this compound has two carbazole groups which are groups having an electron accepting property, and these are bonded in a conjugated system.

[0118]

[Chemical 15] When recording was performed on the obtained optical recording medium in the same manner as in Example I-1, sufficient recording could be performed with a recording time of 1 second. The recorded information could be reproduced even after one month had passed.

(Comparative Example I-1) C ₇₀ : 0.4% by weight,
PVK: 39.6 wt%, EtCz: 10 wt%, Bi
sCzPro: 10% by weight, and 4- (dimethylamino) benzaldehyde-diphenylhydrazone (DE
H): 40 wt% was dissolved in toluene to prepare a toluene solution. In this comparative example, DEH acts as a trapping agent.

Using the resulting toluene solution, Example I
A recording layer having a film thickness of 50 μm was formed by the same method as described above.

When recording was carried out under the same conditions as in Example I, recording was not possible. It is considered that this is because the DEH does not cause a large change in the optical constant when the charge is held.

(Comparative Example I-2) C ₇₀ : 0.4% by weight,
PVK: 39.6 wt%, EtCz: 10 wt%, Bi
sCzPro: 10% by weight and the following chemical formula (1
40% by weight of the compound represented by 1) was dissolved in toluene to prepare a toluene solution. In this comparative example, the compound represented by the chemical formula (11) acts as a trapping agent.

[0123]

[Chemical 16] Using the obtained toluene solution, a recording layer having a film thickness of 50 μm was formed in the same manner as in Example I, and recording was attempted under the same conditions as in Example I.

As a result, the diffracted light could not be observed. This is the chemical formula (1
This is because, in the compound represented by 1), the connection between the carbazole groups has a non-conjugated bond, so that the optical constant does not significantly change even if the molecule retains the charge.

(Example II) First, an optical recording medium was prepared as follows.

Fullerene (C ₇₀ ): 0.4% by weight, poly-N-vinylcarbazole (PVK): 39.6% by weight,
N-ethylcarbazole (EtCz): 10% by weight, bis-carbazolylpropane (BisCzPro): 10
A toluene solution was prepared by dissolving 40% by weight of a compound represented by the following chemical formula (12) in toluene. The compound represented by the chemical formula (12) acts as a trapping agent, and EtCz and BisCzPro act as a plasticizer that lowers the glass transition point. Chemical formula (1
As shown in 2), this compound contains two or more carbazole groups, which are groups having electron accepting properties, in one molecule, but they are not bound by a conjugated system. But,
From the absorption spectrum of the substance represented by the chemical formula (12),
It has been confirmed that this molecule exists in a state where carbazole groups are spatially overlapped with each other. That is,
When holes are injected into one of the carbazole groups, the overlap of the electron cloud with the other carbazole group, which exists spatially overlapping with each other, becomes large. This increase in the overlap of electron clouds not only prolongs the retention life of charges, but also involves a change in optical characteristics.

[0127]

[Chemical 17] Information was recorded on this optical recording medium under the same conditions as in Example I-1. As a result, it took 3 seconds to record, but it was possible to reproduce the information for 1 month or more.

(Comparative Example II) First, an optical recording medium was prepared as follows.

Fullerene (C ₇₀ ): 0.4% by weight, poly (N-vinylcarbazole) (PVK): 39.6% by weight, N-ethylcarbazole (EtCz): 10% by weight, bis-carbazolylpropane (BisCzPr
o): 10% by weight and 40% by weight of a compound represented by the following chemical formula (13) were dissolved in toluene to prepare a toluene solution. The compound represented by the chemical formula (13) acts as a trapping agent, and EtCz and BisCzP
ro acts as a plasticizer that lowers the glass transition point. The molecule represented by the chemical formula (13) used as the trapping agent has a structure similar to that of the molecule represented by the chemical formula (12), but its absorption spectrum indicates that the carbazole groups do not exist spatially overlapping with each other. Has been confirmed. That is, even if holes are injected into one of the carbazole groups, the electron clouds do not overlap. Therefore, the optical constant does not change due to the structure change.

[0130]

[Chemical 18] Using the obtained toluene solution, a recording layer having a film thickness of 50 μm was formed in the same manner as in Example I, and recording was attempted under the same conditions as in Example I.

As a result, the diffracted light could not be observed. This is the chemical formula (1
This is because, in the compound represented by 3), since the carbazole groups do not spatially overlap with each other, the optical constant does not significantly change even if the molecule retains the electric charge.

(Example III) C ₇₀ : 0.3% by weight, P
S (polystyrene): 49.7% by weight, the following chemical formula (1
A toluene solution was prepared by dissolving 20% by weight of the compound represented by 4) and 30% by weight of the compound represented by the chemical formula (5) in toluene. In this example, the compound represented by the chemical formula (14) acts as a charge transport agent, and the compound represented by the chemical formula (5) acts as a trapping agent.

[0133]

[Chemical 19] As a substrate, a glass substrate not coated with ITO was prepared, and the above-mentioned toluene solution was applied onto the substrate by a casting method to form a recording layer to obtain an optical recording medium. The thickness of the recording layer was adjusted to 50 μm using a Teflon spacer.

Information was recorded on this optical recording medium in the same manner as in Example I except that no external electric field was applied.
As a result, it was possible to sufficiently perform recording by irradiation for 30 seconds. The recorded information could be reproduced even after one month.

(Comparative Example III) C ₇₀ : 0.3% by weight, P
S (polystyrene): 49.7% by weight, the chemical formula (1
20% by weight of the compound represented by 4) and 30% by weight of the compound represented by the chemical formula (11) were dissolved in toluene to prepare a toluene solution. In this comparative example, the compound represented by the chemical formula (11) acts as a trapping agent.

Using the resulting toluene solution, Example I
An optical recording medium was obtained by producing a recording layer by the same method as described above.

When information was recorded on this optical recording medium without applying an external electric field as in Example III, no information could be recorded. This is the chemical formula (1
This is because even if the molecule represented by 1) retains an electric charge, its molecular structure does not change significantly and the optical constant does not change.

(Example IV) (Example IV-1) C ₇₀ : 0.3% by weight, polystyrene: 69.7% by weight, and 30% by weight of a compound represented by the following chemical formula (15) were dissolved in toluene. Then, a toluene solution was prepared. In this example, the chemical formula (1
The compound represented by 5) acts as a charge transport agent and a trap agent.

[0139]

[Chemical 20] A recording layer having a film thickness of 50 μm was formed using the obtained toluene solution by the same method as in Example I-1.

Information was recorded on the obtained optical recording medium under the same conditions as in Example I. As a result, sufficient recording could be performed with a recording time of 0.5 seconds. The recorded information could be reproduced even after one month had passed.

(Example IV-2) C ₇₀ : 0.3% by weight,
Polystyrene: 49.7% by weight, compound represented by the chemical formula (14): 20% by weight, and the chemical formula (1)
A toluene solution was prepared by dissolving 30% by weight of the compound represented by 5) in toluene. In this example, the compound represented by the chemical formula (14) acts as a charge transport agent, and the compound represented by the chemical formula (15) acts as a trapping agent.

Using the resulting toluene solution, Example I
A recording layer having a film thickness of 50 μm was formed by the same method as in -1.

Information was recorded on the obtained optical recording medium under the same conditions as in Example I. As a result, sufficient recording could be performed with a recording time of 0.5 seconds. The recorded information could be reproduced even after one month had passed.

(Example IV-3) C ₇₀ : 0.3% by weight,
Polystyrene: 49.7 wt%, compound represented by the chemical formula (14): 20 wt%, and the following chemical formula (1
A toluene solution was prepared by dissolving 30% by weight of the compound represented by 6) in toluene. In this example, the compound represented by the chemical formula (14) acts as a charge transport agent, and the compound represented by the chemical formula (16) acts as a trapping agent.

[0145]

[Chemical 21] A recording layer having a film thickness of 50 μm was formed using the obtained toluene solution by the same method as in Example I-1.

Information was recorded on the obtained optical recording medium under the same conditions as in Example I. As a result, sufficient recording could be performed with a recording time of 0.5 seconds. The recorded information could be reproduced even after one month had passed.

(Example IV-4) C ₇₀ : 0.3% by weight,
Polystyrene: 49.7 wt%, compound represented by the chemical formula (14): 20 wt%, and the following chemical formula (1
30% by weight of the compound represented by 7) was dissolved in toluene to prepare a toluene solution. In this example, the compound represented by the chemical formula (14) was used as a charge transport agent.
The compound represented by the chemical formula (17) acts as a trapping agent.

[0148]

[Chemical formula 22] A recording layer having a film thickness of 50 μm was formed using the obtained toluene solution by the same method as in Example I-1.

Information was recorded on the obtained optical recording medium under the same conditions as in Example I. As a result, sufficient recording could be performed with a recording time of 0.5 seconds. The recorded information could be reproduced even after one month had passed.

(Example IV-5) C ₇₀ : 0.3% by weight,
Polystyrene: 49.7 wt%, compound represented by the chemical formula (14): 20 wt%, and the following chemical formula (1
A toluene solution was prepared by dissolving 30% by weight of the compound represented by 8) in toluene. In this example, the compound represented by the chemical formula (14) acts as a charge transport agent, and the compound represented by the chemical formula (18) acts as a trapping agent.

[0151]

[Chemical formula 23] A recording layer having a film thickness of 50 μm was formed using the obtained toluene solution by the same method as in Example I-1.

Information was recorded on the obtained optical recording medium under the same conditions as in Example I. As a result, sufficient recording could be performed with a recording time of 0.5 seconds. The recorded information could be reproduced even after one month had passed.

Example IV-6 Information was recorded by applying an external electric field of 10 V / μm to the optical recording medium prepared in Example IV-5. Recording was carried out in the same manner as in Example I-1 under other recording conditions, and it was possible to sufficiently perform recording with a recording time of 0.5 seconds. The recorded information could be reproduced even after one month had passed.

(Example IV-7) C ₇₀ : 0.3% by weight,
Polystyrene: 49.7% by weight, compound represented by the following chemical formula (19): 20% by weight, and the chemical formula (1)
A toluene solution was prepared by dissolving 30% by weight of the compound represented by 8) in toluene. In this example, the compound represented by the chemical formula (19) was used as a charge transport agent.
The compound represented by the chemical formula (18) acts as a trapping agent.

[0155]

[Chemical formula 24] A recording layer having a film thickness of 50 μm was formed using the obtained toluene solution by the same method as in Example I-1.

Information was recorded on the obtained optical recording medium under the same conditions as in Example I. As a result, sufficient recording could be performed with a recording time of 0.5 seconds. The recorded information could be reproduced even after one month had passed.

(Example IV-8) C ₇₀ : 0.3% by weight,
Polystyrene: 49.7% by weight, phenylmethylpolysilane (PMPS): 20% by weight, and 30% by weight of the compound represented by the chemical formula (18) were dissolved in toluene to prepare a toluene solution. In this embodiment,
PMPS acts as a charge transport agent, and the compound represented by the chemical formula (18) acts as a trap agent.

Using the resulting toluene solution, Example I
A recording layer having a film thickness of 50 μm was formed by the same method as in -1.

Information was recorded on the obtained optical recording medium under the same conditions as in Example I. As a result, sufficient recording could be performed with a recording time of 0.5 seconds. The recorded information could be reproduced even after one month had passed.

(Comparative Example IV-1) C ₇₀ : 0.3% by weight,
Polystyrene: 49.7 wt%, compound represented by the chemical formula (14): 20 wt%, and the following chemical formula (2
30% by weight of the compound represented by 0) was dissolved in toluene to prepare a toluene solution. In this example, the compound represented by the chemical formula (14) was used as a charge transport agent.
The compound represented by the chemical formula (20) acts as a trapping agent.

[0161]

[Chemical 25] A recording layer having a film thickness of 50 μm was formed using the obtained toluene solution by the same method as in Example I-1.

When information was recorded on the obtained optical recording medium under the same conditions as in Example I, the information could not be recorded. This is the chemical formula (2
This is because the compound represented by 0) did not significantly change the structure even if the charge was retained, and did not cause a change in optical constant.

(Comparative Example IV-2) C ₇₀ : 0.3% by weight,
Polystyrene: 49.7% by weight, the compound represented by the chemical formula (14): 20% by weight, and DEH: 30% by weight were dissolved in toluene to prepare a toluene solution. In this example, the compound represented by the chemical formula (14) acts as a charge transport agent, and DEH acts as a trap agent.

Using the resulting toluene solution, Example I
A recording layer having a film thickness of 50 μm was formed by the same method as in -1.

When information was recorded on the obtained optical recording medium under the same conditions as in Example I, the information could not be recorded. This is because DEH did not significantly change the structure even if it retained charges, and did not change the optical constant.

Example V-1 ITO was formed on the surface of a glass substrate in order to prepare an optical recording medium for a multilayer optical recording medium.
A (Indium Tin Oxide) film was formed and a substrate was prepared.
On this substrate, the toluene solution prepared in Example I-1 was dropped on a glass substrate and applied by a casting method to form a recording layer, thereby obtaining an optical recording medium. The thickness of the recording layer is 250 using a Teflon spacer.
It was adjusted to μm. The glass substrate on the objective lens side was rapidly cooled and removed to obtain an optical recording medium.

Information was recorded as follows. The output light from the semiconductor laser is converted into parallel light using a collimator lens and then condensed into an optical recording medium by an objective lens. Here, the operation distance is long and NA (Numerical Aperture) is set so that the light can be condensed at an arbitrary position in the depth direction.
As a large objective lens, a lens manufactured by NIKON (trade name: CF IC LCD Plan CR, 100 times) was used as an objective lens.

First, the position at which the semiconductor laser was focused was adjusted to the surface of the recording layer while the injection current to the semiconductor laser was made small and the irradiation light intensity was sufficiently lowered. Then, the stage was moved without irradiating light, and the focus was placed at a position of 10 μm from the surface of the recording layer.

After that, the injection current was increased for a predetermined time to irradiate the recording light. Further, in order to record information at different positions in the depth direction, the focus position was moved to a position 30 μm deeper using the stage without irradiation with light. In order to record information at this position, the injection current was also modulated and the recording light was irradiated. By repeating this, four data were recorded at different depths in the recording layer. In this way
Information can be recorded at any position in the recording layer by irradiating the recording light for a predetermined time after moving the focal position to a desired position by using the stage without irradiating the light.

Subsequently, the optical recording medium is moved by using the stage so that the optical axis passes through the center of the recording area and the focal position is located 5 μm deeper than the recording area without irradiating the light. The injection current was modulated so that the light amount was about 1/100 smaller than the recording light, and the transmitted light intensity Is on the optical axis was measured at this position. The ratio of this light intensity Is to the transmitted light intensity Ir previously measured with the same light amount before recording, Is / Ir, was 1.2. On the other hand, when the focal position was sufficiently separated from the recording area, Is / Ir was 1.0.

Example V-2 Using the toluene solution prepared in Example I-3, an optical recording medium having a recording layer thickness of 250 μm was prepared in the same manner as in Example V-1. On this medium, light irradiation for 1 second was repeated in the same manner as in Example V-1, and four data were continuously recorded.

Subsequently, when information was reproduced,
The value of / Ir was 1.3.

Example V-3 Using the toluene solution prepared in Example II-1, an optical recording medium having a recording layer thickness of 250 μm was prepared in the same manner as in Example V-1. On this medium, light irradiation for 1 second was repeated in the same manner as in Example V-1, and four data were continuously recorded.

Subsequently, when the information was reproduced,
The value of / Ir was 1.1.

Example V-4 Using the toluene solution prepared in Example III-1, an optical recording medium having a recording layer thickness of 250 μm was prepared in the same manner as in Example V-1. On this medium, light irradiation for 1 second was repeated in the same manner as in Example V-1, and four data were continuously recorded.

Subsequently, when the information was reproduced,
The value of / Ir was 1.2.

Example V-5 Using the toluene solution prepared in Example IV-1, an optical recording medium having a recording layer thickness of 250 μm was prepared in the same manner as in Example V-1. Similarly to Example V-1, light irradiation for 1 second was repeated on this medium, and four data were continuously recorded.

Subsequently, when information was reproduced,
The value of / Ir was 1.3.

Example V-6 Using the toluene solution prepared in Example IV-2, an optical recording medium having a recording layer thickness of 250 μm was prepared in the same manner as in Example V-1. Similarly to Example V-1, light irradiation for 1 second was repeated on this medium, and four data were continuously recorded.

Subsequently, when information was reproduced,
The value of / Ir was 1.5.

(Example V-7) Using the toluene solution prepared in Example IV-5, the same procedure as in Example V-1 was repeated.
An optical recording medium having a recording layer thickness of 50 μm was produced. Similarly to Example V-1, light irradiation for 1 second was repeated on this medium, and four data were continuously recorded.

Subsequently, when information was reproduced,
The value of / Ir was 1.5.

(Example V-8) C ₇₀ : 0.3% by weight,
Polystyrene: 59.7% by weight and a compound represented by the following chemical formula (21): 40% by weight were dissolved in toluene to prepare a toluene solution. In this example, the compound represented by the chemical formula (21) acts as a charge transport agent and a trap agent.

[0184]

[Chemical formula 26] Using the produced toluene solution, an optical recording medium having a recording layer thickness of 250 μm was produced in the same manner as in Example V-1. Light irradiation for 1 second was repeated on this medium in the same manner as in Example V-1, and four data were continuously recorded.

Subsequently, when information was reproduced,
The value of / Ir was 1.2.

(Example V-9) C ₇₀ : 0.3% by weight,
Polystyrene: 49.7 wt%, compound represented by the chemical formula (19): 20 wt%, and the chemical formula (2
A toluene solution was prepared by dissolving 30% by weight of the compound represented by 1) in toluene. In this example, the compound represented by the chemical formula (19) acts as a charge transport agent, and the compound represented by the chemical formula (21) acts as a trapping agent.

Example V was prepared using the prepared toluene solution.
An optical recording medium having a recording layer thickness of 250 μm was prepared in the same manner as in -1. Light irradiation for 1 second was repeated on this medium in the same manner as in Example V-1, and four data were continuously recorded.

Subsequently, when information was reproduced, Is
The value of / Ir was 1.7.

(Example V-10) C ₇₀ : 0.3% by weight, polystyrene: 49.7% by weight, the chemical formula (1)
A toluene solution was prepared by dissolving 20% by weight of the compound represented by 9) and 30% by weight of the compound represented by the following chemical formula (22) in toluene. In this example, the compound represented by the chemical formula (19) acts as a charge transport agent, and the compound represented by the chemical formula (22) acts as a trapping agent.

[0190]

[Chemical 27] Using the produced toluene solution, an optical recording medium having a recording layer thickness of 250 μm was produced in the same manner as in Example V-1. Light irradiation for 1 second was repeated on this medium in the same manner as in Example V-1, and four data were continuously recorded.

Subsequently, when information was reproduced,
The value of / Ir was 1.7.

(Example V-11) C ₇₀ : 0.3% by weight, polystyrene: 49.7% by weight, the chemical formula (1)
A toluene solution was prepared by dissolving 20% by weight of the compound represented by 9) and 30% by weight of the compound represented by the chemical formula (23) in toluene. In this example, the compound represented by the chemical formula (19) acts as a charge transport agent, and the compound represented by the chemical formula (23) acts as a trapping agent.

[0193]

[Chemical 28] Using the produced toluene solution, an optical recording medium having a recording layer thickness of 250 μm was produced in the same manner as in Example V-1. Light irradiation for 1 second was repeated on this medium in the same manner as in Example V-1, and four data were continuously recorded.

Subsequently, when information was reproduced,
The value of / Ir was 1.7.

Comparative Example V-1 Using the toluene solution prepared in Comparative Example I-1, an optical recording medium having a recording layer thickness of 250 μm was prepared in the same manner as in Example V-1. Light irradiation for 1 second was repeated on this medium in the same manner as in Example V-1, and four data were continuously recorded.

Subsequently, when information was reproduced,
The value of / Ir was almost 1.

Comparative Example V-2 Using the toluene solution prepared in Comparative Example I-2, an optical recording medium having a recording layer thickness of 250 μm was prepared in the same manner as in Example V-1. Light irradiation for 1 second was repeated on this medium in the same manner as in Example V-1, and four data were continuously recorded.

Subsequently, when information was reproduced,
The value of / Ir was almost 1.

Example VI C ₇₀ : 0.3% by weight, polystyrene: 49.7% by weight, compound represented by the following chemical formula (24): 10% by weight, and the following chemical formula (25)
A compound represented by: 40 wt% was dissolved in toluene to prepare a toluene solution. In this example, the compound represented by the chemical formula (24) acts as a charge transport agent, and the compound represented by the chemical formula (25) acts as a trapping agent.

[0200]

[Chemical 29] A recording layer having a film thickness of 50 μm was formed using the obtained toluene solution by the same method as in Example I-1.

Information was recorded on the obtained optical recording medium under the same conditions as in Example I. The result was 0.5.
Sufficient recording was possible with irradiation for 2 seconds. The recorded information could be reproduced even after one month.

[0202]

As described in detail above, according to the present invention, there is provided an optical recording medium in which information is recorded as a hologram,
An optical recording medium having a long recording life is provided. Further, according to the present invention, in a multilayer optical recording medium capable of recording information at an arbitrary position within a uniform recording area, information can be recorded in a sufficiently narrow area in the depth direction even if a low power light source is used. A recordable optical recording medium is provided.

The optical recording medium of the present invention is effective for realizing high density recording and its industrial value is enormous.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating an optical recording medium.

FIG. 2 is a diagram for explaining energy changes due to the structure of a trapping agent.

FIG. 3 is an explanatory diagram showing a hologram recording principle.

FIG. 4 is a schematic diagram showing an example of a configuration of an apparatus for recording / reproducing a hologram on / from an optical recording medium according to the present invention.

FIG. 5 is a schematic diagram showing another example of the configuration of an apparatus for recording / reproducing a hologram on / from an optical recording medium according to the present invention.

FIG. 6 is a schematic diagram showing still another example of the configuration of an apparatus for recording / reproducing a hologram on / from an optical recording medium according to the present invention.

FIG. 7 is a schematic diagram showing an example of the configuration of an apparatus for recording information in multiple layers on an optical recording medium according to the present invention.

FIG. 8 is a diagram illustrating reproduction of data when information is multi-layer recorded on the optical recording medium according to the present invention.

[Explanation of symbols]

1 ... Electrode, 2 ... Recording layer, 3 ... Electrode, 4 ... Signal light,
5 ... Reference light, 6 ... Reproducing light, 7 ... Optical recording medium, 10
... laser, 11 ... beam expander, 12 ... beam splitter, 13,14 ... mirror, 15 ... image display element, 16,17,18 ... lens, 19 ... reading device, 20 ... laser, 21 ... beam expander, 22 ... lens , 23 ... Beam splitter, 31
… Semiconductor laser, 32… Collimating lens, 33…
Objective lens, 34 ... Area where optical constant is changed, 35 ...
Iris, 36 ... Detector.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2K008 AA04 DD12 EE01 FF17 HH01                       HH06 HH18 HH26                 5D029 JA04

Claims (10)

[Claims] 1. A charge generating agent that generates first and second charges having different polarities by irradiation of light, and a trap that holds the first charge and changes optical characteristics by holding the first charge. A recording layer containing an agent, and records the difference in the intensity of the irradiated light as the difference in the optical characteristics of the trapping agent caused by holding the first charge. Optical recording medium. 2. The optical recording medium according to claim 1, wherein the trapping agent changes its optical characteristics by changing its molecular structure when the first charge is retained. 3. The trapping agent has two or more groups having electron accepting properties in the molecule, and the groups having electron accepting properties are bound to each other by a conjugated system. Item 3. The optical recording medium according to Item 1 or 2. 4. The trapping agent has two or more groups having electron accepting properties in a molecule, and the groups having electron accepting properties are spatially overlapped with each other. Optical recording medium. 5. The optical recording medium according to claim 1, wherein the content of the trapping agent is 20% by weight or more and 70% by weight or less of the recording layer. 6. The optical recording medium according to claim 1, wherein the recording layer contains a charge transporting agent that transports the first charge generated by the charge generating agent to the trapping agent. 7. The optical recording medium according to claim 6, wherein the content of the charge transport material is 50% by weight or less of the recording layer. 8. The group having electron accepting property in the trapping agent includes allylalkanes, allylamines, aniline and its derivatives, triphenylamine and its derivatives, enamines, hydrazone and its derivatives; julolidine, indole and carbazole. , Nitrogen-containing cyclic compounds such as oxazole, isoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, thiathiazole and triazole; oxygen-containing compounds such as fluorenone and its derivatives, diphenoquinone and its derivatives, anthraquinone and its derivatives; And at least one structure selected from the group consisting of sulfur-containing derivatives.
7. The optical recording medium according to any one of 7. 9. The conjugated system in the trapping agent is vinylene, ethynylene, paraphenylene, -C = N-, pyrrolylene, oxazolylene, thiazolylene, imidazolylene, 1,3,4-oxadiazolylene, 1,3,4- 9. A compound having at least one divalent group selected from the group consisting of thiadiazolylene, 1H-1,2,4-triazolylene and -C = NN-C-. The optical recording medium according to any one of 1. 10. The trapping agent is represented by the following general formula (1):
Alternatively, the optical recording medium according to any one of claims 1 to 9, comprising the compound represented by (2). [Chemical 1] (In the general formula (1), R1, R2, R3 and R4
May be the same or different and are a hydrogen atom, a methyl group, an ethyl group or a phenyl group. ) [Chemical 2] (In the general formula (2), R1, R2, R3 and R4
May be the same or different and are a hydrogen atom, a methyl group, an ethyl group or a phenyl group. )