Hologram recording material, hologram recording method and optical recording medium

1. A hologram recording material comprising:

a sensitizing dye capable of absorbing light having a hologram recording wavelength to generate an excited state thereof; and

an interference fringe-recording component capable of recording interference fringes providing a refractive index modulation by an electron or energy transfer from the excited state,

the hologram recording material has a thickness of 500 μm or larger,

wherein the sensitizing dye in the hologram recording material comprises at least one of a cyanine dye and a merocyanine dye, and has a molar absorption coefficient within a range of 1 to 10,000 at the hologram recording wavelength; and

the interference fringe-recording component is a component capable of recording the interference fringes providing a refractive index modulation by a latent image-sensitized polymerization reaction sensitized by a latent image of a residual of a color-erasable dye, and

the component records the interference fringes by a method comprising:

a first step in which:

the sensitizing dye absorbs light upon holographic exposure to generate the excited state thereof,

a color of a color-erasable dye is erased by at least one of: an energy or electron transfer from the excited state of the sensitizing dye directly to the color-erasable dye; and a color-erasing agent formed by an energy or electron transfer from the excited state of the sensitizing dye to a color-erasing agent precursor, the color-erasing agent precursor comprising at least one of a radical generator, an acid generator, a base generator, a nucleophilic agent generator, an electrophilic agent generator or a triplet oxygen, and

a residual of the color-erasable dye forms a latent image; and

a second step of irradiating the latent image of the residual of the color-erasable dye with light of a wavelength region, which is different from that of the holographic exposure, to cause a polymerization reaction by activating a polymerization initiator as a result of an energy or electron transfer from the residual of the color-erasable dye.

2. The hologram recording material according to claim 1 , wherein the sensitizing dye in the hologram recording material has a molar absorption coefficient within a range of 5 to 2,500 at the hologram recording wavelength.

3. The hologram recording material according to claim 1 , wherein the sensitizing dye in the hologram recording material has an absorption maximum within a region shorter in wavelength than the hologram recording wavelength by 20 to 100 nm.

4. The hologram recording material according to claim 1 , wherein the sensitizing dye in the hologram recording material has a molar absorption coefficient equal to or less than 1/10 of the molar absorption coefficient at an absorption maximum thereof.

5. The hologram recording material according to claim 1 , wherein the sensitizing dye in the hologram recording material has a molar absorption coefficient equal to or less than 1/20 of the molar absorption coefficient at the absorption maximum thereof.

6. The hologram recording material according to claim 1 , wherein the sensitizing dye is a cyanine dye represented by formula (1):

wherein R 1 and R 2 each independently represents an alkyl group, an alkenyl group, an alkynyl group or a cycloalkyl group; R 3 and R 4 each independently represents a substituent; and a3 and a4 each independently represents an integer of 0 to 4, and in a case a3 or a4 is 2 or larger, plural R 3 s or R 4 s are mutually same or different and may be mutually bonded to form a ring; R 5 , R 6 and R 7 each independently represents a hydrogen atom or a substituent, and may be mutually bonded to form a ring; n1 represents an integer of 0 to 2; CI represents a charge neutralizing ion; and y represents a number required for neutralizing the charge.

7. The hologram recording material according to claim 6 , wherein a3 and a4 are both zero, n1 is 1, and the hologram recording wavelength is 532 nm.

8. The hologram recording material according to claim 1 , wherein the sensitizing dye is a merocyanine dye represented by formula (2):

wherein X 1 represents O or S; X 2 represents —O—, —S—, —NR 17 —, or —CR 18 R 19 —; R 11 and R 12 each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group or a heterocyclic group; R 17 , R 18 and R 19 each independently represents an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group or a heterocyclic group; R 13 represents an alkyl group, an alkenyl group, an alkynyl group, or a cycloalkyl group; R 14 represents a substituent; a14 represents an integer of 0 to 4, and in case a14 is 2 or larger, plural R 14 s are mutually same or different or may be mutually bonded to form a ring; R 15 and R 16 each independently represents a hydrogen atom or a substituent, and may be mutually bonded to form a ring; and n2 represents an integer of 0 to 2.

9. The hologram recording material according to claim 8 , wherein n2 is 1, and the hologram recording wavelength is 532 nm.

10. The hologram recording material according to claim 1 , which has the sensitizing dye in such an amount as to have an optical transmittance of 30 to 90% when the hologram recording material is irradiated with the light having the hologram recording wavelength.

11. The hologram recording material according to claim 1 , wherein

the sensitizing dye absorbs the light upon holographic exposure in the first step to generate the excited state thereof, and

the hologram recording material further comprises:

a color-erasable dye capable of erasing a color thereof in the first step as a result of at least one of: an energy or electron transfer directly from the excited state of the sensitizing dye; and an generation of the color-erasing agent by an energy or electron transfer from the excited state of the sensitizing dye to the color-erasing agent precursor, the color-erasable dye having a molar absorption coefficient of 1,000 or less at a wavelength of a hologram reproducing light;

a polymerizable compound;

a polymerization initiator capable of initiating a polymerization of the polymerizable compound by an electron or energy transfer from the excited state of the residual of the color-erasable dye in the second step; and

a binder.

12. The hologram recording material according to claim 1 , wherein the interference fringes are unrewritable.

13. An optical recording medium comprising a hologram recording material according to claim 1 .

14. The optical recording medium according to claim 13 , wherein the hologram recording material is stored in a light-shielding cartridge.

15. A hologram recording method comprising recording interference fringes providing a refractive index modulation in a hologram recording material by at least one of 1) a polymerization reaction, 2) a color developing reaction, 3) a color developing reaction amplified by a self-sensitization with a color developed substance of a latent image, 4) a polymerization reaction sensitized with a color developed substance of a latent image, 5) an alignment change in a compound having a specific birefringence, and 6) a color erasing reaction of a dye, and a latent image-sensitized polymerization reaction sensitized by a latent image of a residual of a color-erasable dye, and

the recording of the interference fringes comprising:

a first step in which:

the sensitizing dye absorbs light upon holographic exposure to generate the excited state thereof,

a color of a color-erasable dye is erased by at least one of: an energy or electron transfer from the excited state of the sensitizing dye directly to the color-erasable dye; and a color-erasing agent formed by an energy or electron transfer from the excited state of the sensitizing dye to a color-erasing agent precursor, the color-erasing agent precursor comprising at least one of a radical generator, an acid generator, a base generator, a nucleophilic agent generator, an electrophilic agent generator or a triplet oxygen, and

a residual of the color-erasable dye forms a latent image; and

a second step of irradiating the latent image of the residual of the color-erasable dye with light of a wavelength region, which is different from that of the holographic exposure, to cause a polymerization reaction by activating a polymerization initiator as a result of an energy or electron transfer from the residual of the color-erasable dye,

wherein the hologram recording material comprising:

a sensitizing dye capable of absorbing light having a hologram recording wavelength to generate an excited state thereof; and

an interference fringe-recording component capable of recording interference fringes providing a refractive index modulation by an electron or energy transfer from the excited state,

the hologram recording material has a thickness of 500 μm or larger,

wherein the sensitizing dye in the hologram recording material comprises at least one of a cyanine dye and a merocyanine dye, and has a molar absorption coefficient within a range of 1 to 10,000 at the hologram recording wavelength.

16. The hologram recording method according to claims 15 , wherein a multiplex hologram recording is performed by effecting the holographic exposure 10 times or more.

17. The hologram recording method according to claim 16 , wherein the multiplex hologram recording is performed under a common exposure amount in each holographic exposure.