KR20020002401A - Holographic Recording Material - Google Patents

Abstract

The present invention relates to a novel holographic recording material for use in the area of photo addressing polymers.

Description

Holographic Recording Material

The present invention relates to a recording material for holographic volumetric storage media, to its manufacture and to use in volumetric hologram recording.

Holography is a method of creating an image of an object in a suitable storage material by using interference between two interfering lights (signal and reference wave), and re-reading this image using light rays (reading light) ( D. Gabor, Nature 151, 454 (1948), NH Farath, Advances in Holography, Vol. 3, Marcel Decker (1977), HM Smith, Holographic Recording Materials, Springer (1977). By changing the angle between the signal wave and the reference wave on the one hand and the holographic storage material on the other hand, many holograms can be written to the material at one and the same sample location, and ultimately each can be read back. The coherent light source used is generally laser light. Storage materials include a wide variety of materials, for example inorganic crystals such as LiNbO ₃ , organic polymers (eg, M. Eich, JH Wendorff, Makromol. Chem., Rapid Commun. 8, 467 (1987), JH Wendorff, M). Eich, Mol.Cyst.Liq.Cyst. 169, 133 (1989)) or photopolymers (Uh-Sock Rhee et al., Applied Optics, 34 (5), 846 (1995)). have.

However, these materials do not meet all the requirements for holographic recording media. In particular, the stability of the recorded hologram is not appropriate. Multi-recording is generally only possible in a limited range, because when recording a new hologram, the previously recorded hologram is erased because it must be written over the previously recorded hologram. Inorganic crystals are particularly so and require complex heat treatment to compensate for their stability problems. On the other hand, photopolymers exhibit shrinkage problems that adversely affect holographic image properties.

Highly stable materials of recorded holograms are also known, for example, from EP 0 704 513 (LeA 30655) and German application DE-A-19703132 (LeA 31821), which have not yet been published.

However, because these materials have high optical densities, it is not possible to produce holographic volumetric storage media required to store several holograms in the storage material.

Therefore, there is a need for a material that is suitable for the production of sufficiently thick holographic volumetric storage media and capable of storing several holograms stably in one sample position of the recording material for a long time. As far as the known materials are stored, the holographic information is gradually erased when several holograms are stored at one location. Since the later recorded holograms were located in the same molecule used to form the first recorded holograms, the information of the first recorded holograms was erased after only a few recording processes.

Accordingly, the present invention is a holographic volume type characterized by being capable of recording multiple holograms at one sample location, containing one or more dyes and optionally one or more shaped anisotropic atomic groups whose spatial arrangement changes when the hologram is recorded. A recording material for a storage medium is provided.

Preferably, the present invention changes the spatial arrangement or its absorption behavior in such a way that the one or more dyes are no longer excited by electromagnetic radiation, so that in particular the sensitivity to actinic radiation is sufficient to record the initial hologram. It is achieved by decreasing 10%-100%, More preferably, 50%-100%, and Most preferably, about 90%-100% based on a previous sensitivity.

However, the dye also moves in a direction perpendicular to the polarization direction of actinic rays such that its molecular longitudinal axis is 10 ° to 90 °, preferably 50 ° to 90 °, more preferably 75 ° to 90 ° and most Preferably it is placed at an angle of 85 ° to 90 ° to reduce the absorption behavior, in particular the sensitivity to actinic light.

In this way, multiple holograms can be successfully recorded at one sample location. In other words, the information of the first recorded hologram is not completely erased.

This change in the excitation behavior for the electromagnetic beam when the hologram is recorded can be achieved by a dye that changes its spatial arrangement in the amorphous organic polymer or oligomeric material.

This type of material can prevent the hologram already recorded on the material from being recorded when the hologram is unacceptably reduced, completely damaged or completely overlapped.

Unacceptable attenuation residual information in terms of measurement technology means that the image is no longer displayed against background noise.

The information is stored in a holographic way. For this purpose, two polarized interfering lights are allowed to interfere on the sample.

Upon exposure to actinic light, the dyes change their spatial position in the polymer or oligomer layer. A dye whose molecular longitudinal axis is oriented towards a plane (incident surface) by two recording beams upon exposure can no longer be excited by the light if its polarization is perpendicular to the incident surface. The information (hologram) recorded in this dye during the recording process is protected from changes during the recording of subsequent holograms. The dye which is not completely perpendicular to the polarization direction of the light but forms a predetermined θ angle other than 90 ° with the polarization direction is further addressed during subsequent hologram exposure. However, the likelihood of such dyes being redirected, in particular the light sensitivity of the dyes, decreases further as the angle of molecular longitudinal axis approaches 90 °.

Molecular longitudinal axis can be determined by molecular morphology, for example by molecular modeling (eg CERIUS ² ).

For example, it is possible to know whether or not the dye is redirected after exposure to actinic radiation by irradiation with polarization absorption spectroscopy. Samples previously exposed to actinic light were examined with two polarizers in a UV / VIS spectrometer (eg, CARY 4G, UV / VIS spectrometer) in the absorption spectral range of the dye. When the sample is rotated around the normal sample with polarizers at a suitable location, for example an orthogonal position, the change in the excitation intensity with the change of the sample angle implies the reorientation of the dye and as a result the dye is reliably measured. can do.

Methods of recording multiple holograms include various multiplexing methods, for example, angular multiplexing, wavelength multiplexing, phase multiplexing, shift multiplexing, and peristrophic multiplexing.

The measure of sensitivity to actinic radiation is holography sensitivity. For example, it is calculated from the holographic growth curve, i.e., the diffraction value obtained as a function of the energy accumulated by the recording beam (diffraction intensity based on the incident intensity of the reading laser). Sensitivity is defined as the increase or decrease of the square root of the diffraction rate with the accumulated energy, converted in accordance with the thickness of the storage medium.

The present invention provides a recording material for a holographic volumetric storage medium having an optical density of 2 or less, preferably 1 or less, more preferably 0.3 or less, at a wavelength of a recording laser. In this way, actinic light causes uniform transillumination of the entire storage medium and can produce thick holograms. Optical density can be determined using commercially available UV / VIS spectrometers (eg, CARY, 4G, UV / VIS spectrometers).

The recording material according to the present invention is preferably a material having an irradiation thickness of at least 0.1 mm, more preferably at least 0.5 mm, more preferably at least 1 mm and most preferably at most 5 cm.

Atomic groups that interact with electromagnetic radiation are dyes. Thus, the material according to the invention contains at least one dye. The electromagnetic radiation is preferably laser light having a wavelength in the range from 390 to 800 nm, more preferably in the range from 400 to 650 nm, most preferably in the range from 510 to 570 nm.

For reading, the recording material is not exposed to two interfering beams as in the case of recording, but only to one beam, i.e. the reading beam.

The wavelength of the readout beam is preferably longer than the wavelengths of the signal and reference waves, for example 70 to 500 nm longer. However, it can also be read at the wavelength of the recording laser, in particular this method can be used for commercial use of holographic volumetric storage media. However, for this purpose, the energy of the readout beam is reduced by reducing the light intensity or exposure time during the readout process.

The optical density of the recording material according to the present invention is determined in the following two parameters, polymer or oligomeric organic material.

a) molar extinction coefficient of one or more dyes present and / or

b) controlled by the concentration of at least one dye present.

Dyes with low extinction coefficients are for example dyes having a nonpolar and / or very slightly polarizing structure. Such dyes can be obtained, for example, from anthraquinones, stilbenes, azastilbenes, azo or methine dyes. Azo dyes are preferred. Especially preferred are azo dyes having a maximum absorption of ππ ^* bands of 400 nm or less, more preferably less than 400 nm.

For example, the structure of the azo dye is represented by the following formula (I).

Where

R ¹ and R ² each independently represent a hydrogen or nonionic substituent,

R ¹ may further represent -X ^{1 '} -R ³ ,

m and n each independently represent an integer of 0 to 4, preferably 0 to 2,

X ¹ and X ² each represent —X ^{1 ′} —R ³ and X ^{2 ′} —R ⁴ ,

X ^{1 '} and X ^2' are a direct bond, -O-, -S-,-(NR ⁵ )-, -C (R ⁶ R ⁷ )-,-(C = O)-,-(CO-O) -,-(CO-NR ⁵ )-,-(SO ₂ )-,-(SO ₂ -O)-,-(SO ₂ -NR ⁵ )-,-(C = NR ⁸ )-or-(CNR ⁸ -NR ⁵ )-,

R ³ , R ⁴ , R ⁵ and R ⁸ are each independently of each other hydrogen, C ₁ -C ₂₀ -alkyl, C ₃ -C ₁₀ -cycloalkyl, C ₂ -C ₂₀ -alkenyl, C ₆ -C _10- Aryl, C ₁ -C ₂₀ -alkyl- (C═O)-, C ₃ -C ₁₀ -cycloalkyl- (C═O)-, C ₂ -C ₂₀ -alkenyl- (C═O)-, C _6- C ₁₀ -aryl- (C═O)-, C ₁ -C ₂₀ -alkyl- (SO ₂ )-, C ₃ -C ₁₀ -cycloalkyl- (SO ₂ )-, C ₂ -C ₂₀ -al alkenyl - (SO ₂₎ - or C ₆ -C ₁₀ - aryl - (SO ₂₎ -, or represent, or

-X ^{1 '} -R ³ and X ^2' -R ⁴ can represent hydrogen, halogen, cyano, nitro, CF ₃ or CCl ₃ ,

R ⁶ and R ⁷ are each independently hydrogen, halogen, C ₁ -C ₂₀ -alkyl, C ₁ -C ₂₀ -alkoxy, C ₃ -C ₁₀ -cycloalkyl, C ₂ -C ₂₀ -alkenyl or C _6- C ₁₀ -aryl.

Nonionic substituents include halogen, cyano, nitro, C ₁ -C ₂₀ -alkyl, C ₁ -C ₂₀ -alkoxy, phenoxy, C ₃ -C ₁₀ -cycloalkyl, C ₂ -C ₂₀ -alkenyl or C ₆ -C ₁₀ -aryl, C ₁ -C ₂₀ -alkyl- (C═O)-, C ₆ -C ₁₀ -aryl- (C═O)-, C ₁ -C ₂₀ -alkyl- (SO ₂ )-, C ₁ -C ₂₀ -alkyl- (C═O) —O—, C ₁ -C ₂₀ -alkyl- (C═O) -NH-, C ₆ -C ₂₀ -aryl- (C═O) -NH- , C ₁ -C ₂₀ -alkyl-O- (C═O)-, C ₁ -C ₂₀ -alkyl-NH- (C═O)-or C ₆ -C ₁₀ -aryl-NH- (C = O) -There is.

Alkyl, cycloalkyl, alkenyl and aryl radicals are halogen, cyano, nitro, C ₁ -C ₂₀ -alkyl, C ₁ -C ₂₀ -alkoxy, C ₃ -C ₁₀ -cycloalkyl, C ₂ -C ₂₀ -al alkenyl or C ₆ -C ₁₀ - and can be substituted by up to three radicals from the group of aryl, wherein the alkyl and alkenyl radicals may be of straight-chain or branched.

Halogens include fluorine, chlorine, bromine and iodine, in particular fluorine and chlorine.

The recording material according to the invention is preferably a polymer or oligomeric amorphous organic material, particularly preferably a branched polymer, and particularly preferably a block copolymer and / or a graft copolymer.

The main chain of the branched polymer is from a basic structure such as polyacrylate, polymethacrylate, polysiloxane, polyurea, polyurethane, polyester or cellulose. Polyacrylates and polymethacrylates are preferred.

Block copolymers consist of a number of blocks, one or more of which contain a copolymer system as described above. The remaining blocks consist of a nonfunctionalized polymer structure that serves to dilute the functional block to adjust to the required optical density. The range of functional blocks is less than the wavelength of light, preferably less than 200 nm, more preferably less than 100 nm.

The polymerization of the block copolymers is carried out, for example, by free radical or anionic polymerization, or by other suitable polymerization processes, optionally by polymerization-like reactions, or by a combination of these methods. The homogeneity of the system is in the range of less than 2.0, preferably less than 1.5. The molecular weight of the block copolymer obtained by free radical polymerization reaches a value in the range of 50,000, and a value above 100,000 can be controlled by anionic polymerization.

Dyes, in particular azo dyes of formula I, are generally covalently bonded to this polymer structure by spacers. For example, X ¹ (or X ² or R ¹ ) is such a spacer, in particular X ^{1 ′} -(Q ¹ ) _i -T ¹ -S ^1- (where X ^{1 ′} is as defined above; Q ¹ Is -O-, -S-,-(NR ⁵ )-, -C (R ⁶ R ⁷ )-,-(C = O)-,-(CO-O)-,-(CO-NR ⁵ )- ,-(SO ₂ )-,-(SO ₂ -O)-,-(SO ₂ -NR ⁵ )-,-(C = NR ⁸ )-,-(CNR ⁸ -NR ⁵ )-,-(CH ₂ ) _p- , p- or mC ₆ H _4- , or or Represents a divalent radical of; i represents an integer of 0 to 4, where each radical Q ¹ has a different meaning when i>1; T ¹ represents — (CH ₂ ) _p —, wherein the chain may be interrupted by —O—, —NR ⁹ — or —OSiR ¹⁰ ₂ O—; S ¹ represents a direct bond, -O-, -S- or -NR ^9- ; p represents an integer of 2 to 12, preferably 2 to 8, more preferably 2 to 4; R ⁹ represents hydrogen, methyl, ethyl or propyl; R ¹⁰ represents methyl or ethyl; R ⁵ to R ⁸ are as defined above).

Preferred dye monomers of polyacrylate or polymethacrylate are represented by the following general formula (II).

Where

R represents hydrogen or methyl,

The other radicals are as defined above.

Particularly suitable are dye monomers of the formula (IIa).

Where

X ³ represents hydrogen, halogen or C ₁ -C ₄ -alkyl, preferably hydrogen,

The radicals R, S ¹ , T ¹ , Q ¹ , X ^{1 ′} , R ¹ and R ² , and i, m and n are as defined above.

Particularly preferred monomers of formula (IIa) include, for example, the following.

Also suitable are dye monomers of the general formula (IIb) when they are contained in the polymer in an amount of up to 10 mol%, preferably up to 5 mol%, more preferably up to 1 mol%.

Where

X ⁴ represents cyano or nitro,

The radicals R, S ¹ , T ¹ , Q ¹ , X ^{1 ′} , R ¹ and R ² , and i, m and n are as defined above.

Particularly preferred monomers of formula (IIb) include, for example, the following.

Polymeric or oligomeric amorphous organic materials according to the invention may contain, in addition to dyes, for example, shape-anisotrophic groupings of the formula (I). These atomic groups are also generally covalently bonded to the polymer structure through spacers.

The shape-anisotropic atom group has a structure such as, for example, the formula III, wherein Z represents a radical of formula IIIa or IIIb.

Where

A represents O, S or NC ₁ -C ₄ -alkyl,

X ³ represents -X ^{3 '} -(Q ² ) _j -T ² -S ^2- ,

X ⁴ represents X ^{4 ′} -R ¹³ ,

X ^{3 '} and X ^4' are each independently a direct bond, -O-, -S-,-(NR ⁵ )-, -C (R ⁶ R ⁷ )-,-(C = O)-,-( CO-O)-,-(CO-NR ⁵ )-,-(SO ₂ )-,-(SO ₂ -O)-,-(SO ₂ -NR ⁵ )-,-(C = NR ⁸ )-or -(CNR ⁸ -NR ⁵ )-;

R ⁵ , R ⁸ and R ¹³ are each independently of each other hydrogen, C ₁ -C ₂₀ -alkyl, C ₃ -C ₁₀ -cycloalkyl, C ₂ -C ₂₀ -alkenyl, C ₆ -C ₁₀ -aryl, C _1- C ₂₀ -alkyl- (C═O)-, C ₃ -C ₁₀ -cycloalkyl- (C═O)-, C ₂ -C ₂₀ -alkenyl- (C═O)-, C ₆ -C ₁₀ -aryl- (C = O)-, C ₁ -C ₂₀ -alkyl- (SO ₂ )-, C ₃ -C ₁₀ -cycloalkyl- (SO ₂ )-, C ₂ -C ₂₀ -alkenyl- ( SO ₂ )-or C ₆ -C ₁₀ -aryl- (SO ₂ )-, or

X ^{4 ′} -R ¹³ may represent hydrogen, halogen, cyano, nitro, CF ₃ or CCl ₃ ,

R ⁶ and R ⁷ are each independently of each other hydrogen, halogen, C ₁ -C ₂₀ -alkyl, C ₁ -C ₂₀ -alkoxy, C ₃ -C ₁₀ -cycloalkyl, C ₂ -C ₂₀ -alkenyl or C ₆ -C ₁₀ -aryl;

Y is a single bond, -COO-, -OCO-, -CONH-, -NHCO-, -CON (CH ₃ )-, -N (CH ₃ ) CO-, -O-, -NH- or -N (CH ₃ )-

R ¹¹ , R ¹² , R ¹⁵ are each independently of the other hydrogen, halogen, cyano, nitro, C ₁ -C ₂₀ -alkyl, C ₁ -C ₂₀ -alkoxy, phenoxy, C ₃ -C ₁₀ -cycloalkyl, C ₂ -C ₂₀ -alkenyl or C ₆ -C ₁₀ -aryl, C ₁ -C ₂₀ -alkyl- (C═O)-, C ₆ -C ₁₀ -aryl- (C═O)-, C _1- C ₂₀ -alkyl- (SO ₂ )-, C ₁ -C ₂₀ -alkyl- (C═O) -O—, C ₁ -C ₂₀ -alkyl- (C═O) -NH-, C ₆ -C ₁₀ -Aryl- (C = 0) -NH-, C ₁ -C ₂₀ -alkyl-O- (C═O)-, C ₁ -C ₂₀ -alkyl-NH- (C═O)-or C ₆ -C ₁₀ -aryl-NH- (C = 0)-;

q, r and s each independently represent an integer of 0 to 4, preferably 0 to 2,

Q ² is -O-, -S-,-(NR ⁵ )-, -C (R ⁶ R ⁷ )-,-(C = O)-,-(CO-O)-,-(CO-NR ⁵ )-,-(SO ₂ )-,-(SO ₂ -O)-,-(SO ₂ -NR ⁵ )-,-(C = NR ⁸ )-,-(CNR ⁸ -NR ⁵ )-,-( CH ₂ ) _p- , p- or mC ₆ H ₄ -or formula or Represents a divalent radical,

j represents an integer of 0 to 4, where j> 1, each radical Q ¹ may have a different meaning,

T ² represents-(CH ₂ ) _p- , wherein the chain may be interrupted by -O-, -NR ⁹ -or -OSiR ¹⁰ ₂ O-,

S ² represents a direct bond, -O-, -S- or -NR ^9- ,

p represents an integer of 2 to 12, preferably 2 to 8, more preferably 2 to 4,

R ⁹ represents hydrogen, methyl, ethyl or propyl,

R ¹⁰ represents methyl or ethyl.

Preferred monomers for polyacrylates or polymethacrylates having such shape anisotropic atomic groups have the general formula (IV) below.

Where

R represents hydrogen or methyl,

The other radicals are as defined above.

Particularly preferred shape anisotropic monomers of the general formula (IV) include, for example:

Alkyl, cycloalkyl, alkenyl and aryl radicals are halogen, cyano, nitro, C ₁ -C ₂₀ -alkyl, C ₁ -C ₂₀ -alkoxy, C ₃ -C ₁₀ -cycloalkyl, C ₂ -C ₂₀ -al It may be substituted by up to 3 radicals from the group of kenyl or C ₆ -C ₁₀ -aryl and the alkyl and alkenyl radicals may be straight or branched.

Halogens include fluorine, chlorine, bromine and iodine, in particular fluorine and chlorine.

In addition to these functional units, the oligomers or polymers according to the invention may also contain units which serve primarily to lower the percentage content of functional units, in particular dye units. In addition to these actions, they may also provide other properties of the oligomer or polymer, such as glass transition temperature, liquid crystallinity, film forming properties, and the like.

In polyacrylates or polymethacrylates, these monomers are acrylic or methacrylic acid esters of the general formula (V).

Where

R represents hydrogen or methyl,

R ¹⁴ represents a radical containing an alkyl and alkenyl radical C ₁ -C ₂₀ -alkyl or one or more other acrylic units, which may be branched.

The polyacrylates and polymethacrylates according to the invention are preferably represented as repeating units instead of compounds of the formula (VI), preferably of the formulas (VI) and (VII) or of the formulas (VI) and (VIII) or of the compounds of the formulas (VI), (VII) and (VIII), or (VI) It contains a repeating unit of formula VIa or VIb.

Radicals in the above formula are as defined above. There may also be several in repeat units of formula VI (VIa or VIb) and / or in repeat units of formulas VII and / or VIII.

The relative proportions of VI (VIa, VIb), VII and VIII are determined as desired. The concentration of VI (VIa, VIb) is preferably 0.1 to 100% based on the mixture in question, depending on the absorption coefficient of VI (VIa, VIb). The ratio of VI (VIa, VIb) to VII is 100: 0 to 1:99, preferably 100: 0 to 30:70, more preferably 100: 0 to 50:50.

The dyes of formula (I) and dye monomers of formula (II) exhibit major absorption bands (π-π ^* bands) in the short wavelength range and secondary absorption bands (n-π ^* bands) in the long wavelength range. The molar extinction coefficient ε of the n-π ^* band is in the range of 400 to 5000 x 10 ³ cm ² / mol. In dyes assuming a molar mass of 400 g / mol, their optical density at an irradiation thickness of 0.1 mm when the oligomers or polymers contain such dyes at 1.6% or less (ε = 5000) to 20% or less (ε = 400) Is 2 or less.

The glass transition temperature T _g of the polymer and oligomer according to the invention is preferably at least 40 ° C. Glass transition temperatures are described, for example, in B. Vollmer, Grundriss der Markromolekularen Chemie, p. 406-410, Springer-Verlag, Heidelberg 1962].

The molecular weight calculated from the weight average of the polymers and oligomers according to the invention is 5000 to 2,000,000, preferably 8000 to 1,500,000 (polystyrene equivalent), calculated by gel permeation chromatography.

Graft polymers are prepared by free radical bonding to oligomeric or polymeric based systems of dye monomers of formula II or IIa or IIb, optionally additionally the shape anisotropic monomers of formula IV and / or optionally additionally monomers of formula V. Such substrate systems can be very different kinds of polymers, for example polystyrene poly (meth) acrylates, starches, celluloses, peptides. Free radical bonding can be carried out by irradiation of light or by using radical generating reagents such as tert-butyl hydroperoxide, dibenzoyl peroxide, azodiisobutyronitrile, hydrogen peroxide / iron (II) salt.

Due to the structure of this polymer and oligomer, intramolecular interactions between the components of formulas VI (VIa, VIb), or intramolecular interactions between the components of formulas VI (VIa, VIb) and VII, form a liquid crystal order state. And optically isotropic transparent non-scattering films, foils, plates or cubes are adjusted. Nevertheless, intramolecular interactions, nonetheless, are photochemically induced and interact with photochromic and non-photochromic side chains and are strong enough to result in a directional reorientation process.

Preferably, the change in the side chain arrangement of formula VI (VIa, VIb) by light is sufficient to force one-sided (so-cooperative) reorientation of the other side chains (VI (VIa, VIb) and / or VII). This preferably occurs between the side chain groups of the repeating units of formulas VI (VIa, VIb) or between the repeating units of formulas VI (VIa, VIb) and VII.

Very high values of optical anisotropy can be induced in optically isotropic amorphous photochromic polymers (Δn to 0.4).

Under the influence of actinic rays, optical properties are controlled because order states in the polymer or oligomer are generated and modified.

The light used is polarized light whose wavelength is in the absorption band range of the repeating unit of formula VI, preferably in the range of the long wavelength n-π ^* band.

Polymers and oligomers are described in, for example, DD 276 297, DE-A 3 808 430, Makromolekulare Chemie 187, 1327-1334 (1984), SU 887 574, Europ. Polym. 18, 561 (1982) and Liq. Cryst. 2, 195 (1987).

Production of films, foils, plates and cubes is possible without the need to use complex orientation methods using external field and / or surface effects. They may be applied to the substrate by technically controllable spin coating, dipping, pouring or other coating methods, sandwiched between two transparent plates by compression or flow, or simply by spinning or extrusion. Can be made of a freestanding material. Such films, foils, plates and cubes can also be prepared from liquid crystal polymers or oligomers containing structural components in the meanings described by quenching, ie cooling rates> 100 K / min, or by rapid removal of the solvent.

Preferred methods for the production of holographic volumetric storage media comprise the steps according to conventional injection molding methods in the range up to 300 ° C., preferably in the range up to 220 ° C. and more preferably in the range up to 180 ° C.

The layer thickness is at least 0.1 mm, preferably at least 0.5 mm, more preferably at least 1 mm. Particularly preferred layer production methods in the millimeter range are injection molding methods. In this method, the polymer melt can be sent through a nozzle to a forming vessel which can be taken out of the forming vessel after cooling.

Preferred methods for preparing the recording material or polymer according to the invention include processes in which at least one monomer is polymerized without further solvent, wherein the polymerization reaction is preferably a free radical polymerization reaction, more preferably a free radical initiator and / or ) Is a reaction initiated by UV light and heat.

This process is carried out at a temperature of 20 ° C. to 200 ° C., preferably 40 ° C. to 150 ° C., more preferably 50 ° C. to 100 ° C., and most preferably about 60 ° C.

In certain embodiments, AIBN is used as the free radical initiator.

It is often known that it is advantageous to use another liquid monomer at the same time. These monomers are monomers which are liquid at the reaction temperature, such monomers are preferably olefinically unsaturated monomers, more preferably based on acrylic acid and methacrylic acid, most preferably methyl methacrylate.

The monomer content of formula (II) in the copolymer is preferably from 0.1 to 99.9% by weight, more preferably from 0.1 to 50% by weight, more preferably from 0.1 to 5% by weight and most preferably from 0.5 to 2% by weight.

Holographic data storage methods are described, for example, in LASER FOCUS WORLD, NOVEMBER 1996, p. 81.

When recording the hologram, two coherent laser beams of wavelength are irradiated causing the light-induced redirection necessary for the polymer film described above. One beam (object beam) contains the optical information to be stored, for example a change in intensity obtained by the passage of light through a two-dimensional check pixel structure (data page). In principle, however, any two-dimensional or three-dimensional object can use as diffracted, scattered or reflected light as the object light. In a storage medium, object light interferes with a second laser beam (a reference beam, which is generally a flat or circular wavelength). The resulting interference pattern is imprinted on the storage medium with a modulation of the optical constants (reflection index and / or absorption coefficient). This modulation spreads throughout the entire irradiated area, in particular in the thickness direction of the storage medium. When the object light is blocked and the medium is exposed alone to the reference light, the modulated storage medium acts as a kind of diffraction grating for the reference light. Since the intensity distribution due to diffraction corresponds to the intensity distribution originating from the object to be stored, it can no longer be distinguished whether the light originates from the object itself or by diffraction of the reference light.

In order to store different holograms at one sample location, various multiplexing processes are used, namely wavelength multiplexing, shift multiplexing, phase multiplexing, ferristographic multiplexing and / or angular multiplexing and / or the like. . In the angular multiplexing method, the angle between the reference medium and the storage medium in which the hologram is stored at the corresponding angle is changed. Due to some angle change, the original hologram disappears (Bragg mismatch). The incident reference light is no longer deflected by the storage medium to reconstruct the object. The angle resulting therefrom is determined by the thickness of the storage medium (and the modulation of the optical constants produced in the medium). The thicker the medium, the smaller the angle at which the reference light changes.

Another hologram can be recorded in its new angular shape. The hologram is also read accurately according to the angle formation between the storage medium on which the hologram is recorded and the reference light.

By gradually changing the angle between the medium and the recording beam, multiple holograms can be recorded in the same place on the storage medium.

The polymer system described in this patent has a great advantage, when the subsequent hologram is recorded, more than three, preferably more than 50, more preferably more than 100 information is stored in the storage medium in relation to the previous hologram without being erased. More preferably, more than 500 holograms, more preferably more than 1000 holograms, can be recorded in one place on the storage medium. The storage object is a data page generated by the transmission of the liquid crystal display. This data page has 256 x 256 pixels, preferably 512 x 512 pixels, preferably 1024 x 1024 data pixels.

In addition, the present invention has an optical density of 2 or less, preferably 1 or less, more preferably 0.3 or less, consisting of a polymer or oligomeric amorphous organic material containing one or more atomic groups and optionally one or more shaped anisotropic atomic groups that interact with electromagnetic radiation. A recording material for a holographic volumetric storage medium is provided. The recording material can be used for data storage in the form of a freestanding film, which is preferably a multilayer structure. The multilayer structure is, for example, a sandwich in which the actual recording medium is surrounded by one or more substrates. The substrate may be an optical high quality transparent medium, for example a glass plate, a quartz plate or a polycarbonate plate. Optical high quality means scattering efficiency, ie the ratio between the scattered light and the incident light in its sandwich structure, which is at least 10 ⁻⁴ , preferably at least 10 ⁻⁵ , more preferably at least 10 ⁻⁶ . To determine this ratio, the sample can be exposed to a HeNe laser beam. It is detected by a CCD camera.

<Example 1>

Preparation of Monomers:

a) 4- (2-hydroxyethyloxy) benzoic acid

138 g of p-hydroxybenzoic acid and 0.5 g of KI were added to 350 ml of ethanol with stirring. A solution of 150 g KOH in 150 ml water was added dropwise. 88.6 g of ethylenechlorohydrin were added dropwise at 30 to 60 ° C. over 30 minutes. The reaction mixture was stirred at reflux for 15 h. The solvent was then completely distilled off first under constant pressure and under vacuum. The residue was dissolved in 1 l of water and acidified with HCl. The precipitate was suction filtered and recrystallized from 1.8 l of water. The product was dried and recrystallized twice from ethanol. The yield was 46 g (25% of theoretical yield). M. p. 179.5 ° C.

b) 4- (2-methacryloyloxyethyloxy) benzoic acid

45 g of 4- (2-hydroxyethyloxy) benzoic acid, 180 ml of methacrylic acid, 10 g of p-toluenesulfonic acid and 10 g of hydroquinone in 150 ml of chloroform were heated with stirring under reflux. Water formed during the reaction was separated off with a water separator. The reaction mixture was diluted with 150 ml of chloroform, washed several times with 100 ml of water each time and dried over Na ₂ S0 ₄ . The desiccant was filtered off and the chloroform was distilled off to 2/3 in a rotary evaporator. The precipitated product was suction filtered and recrystallized twice from isopropanol. The yield was 28 g (45% of theoretical yield). M. p. 146 ° C.

c) 4- (2-methacryloyloxyethyloxy) benzoic acid chloride

25 g of 4- (2-methacryloyloxyethyloxy) benzoic acid, 80 ml thionyl chloride and 0.5 ml DMF were stirred at room temperature for 30 minutes. Excess thionyl chloride was then distilled off under mild vacuum followed by high vacuum. The acid chloride formed in virtually quantitative yield was then slowly crystallized at room temperature.

Elemental Analysis: C ₁₃ H ₁₃ ClO ₄ (268.7)

Theoretical: C 58.11; H 4.88; Cl 13.19;

Measured value: C 58.00; H 4.90; Cl 13.20

d) 4-pivalinoylamino-4'-aminoazobenzene

36 g of 4,4'-diaminoazobenzene and 62 g of triethylamine were added to 400 ml THF. A solution of 23.2 g pivalic chloride in 100 ml THF was slowly added dropwise. After stirring for 2 hours at room temperature, water was added to the reaction mixture. The precipitate was filtered off and dried. 42 g of the product were obtained. Further purification by chromatography (silica gel; toluene / ethyl acetate 1: 1). Yield was 8 g. M. p. 230 ° C.

e) 4-pivalinoylamino-4 '-[p- (2-methacryloyloxy-ethyloxy) benzoylamino] azobenzene

1 g of 4-pivalinoylamino-4′-aminoazobenzene is placed in 10 ml of N-methyl-2-pyrrolidone (NMP) at 50 ° C. and 1 g of 4-g in 1 ml of NMP at 50 ° To a solution of (2-methacryloyloxyethyloxy) benzoic acid. The reaction mixture was stirred at this temperature for 1 hour and cooled before 200 ml of water was added. The precipitate was filtered off and stirred in 30 ml of methanol at room temperature. The mother liquor was filtered and dried under vacuum. Yield was 1.2 g. M. p. 194 ° C. λ _max = 378 nm (DMF); ε = 37000 l / (mol * cm).

<Example 2>

a) 32 g of N-benzoyl-p-phenylenediamine was added to a mixture of 210 ml glacial acetic acid, 75 ml propionic acid and 31 ml concentrated hydrochloric acid at 3 ° C to 5 ° C. 50 g nitrosulfuric acid (about 40%) was added dropwise at this temperature over 1 hour.

b) 16 g of m-toluidine was dissolved in 130 ml of glacial acetic acid. The diazoside from a) was added dropwise over 2 hours at 0 ° C to 5 ° C. The mixture was stirred overnight at room temperature. The dye obtained was suction filtered and suspended in 550 ml of water. The pH was adjusted to 8.4 using soda. The dye was again suction filtered and washed with isopropanol to dry. 27 g (54.5% of theory yield) of the following formula were obtained. UV / VIS in dimethylformamide: λ _max = 416 nm

c) 5 g of the dye from b) were dissolved in 20 ml of N-methylpyrrolidone at 50 ° C. 3.5 g of chemical formula Acid chloride was added. The mixture was stirred at 50 ° C for 1.5 h. Finally, the dye obtained by adding 20 ml of water was suction filtered. It was stirred with 50 ml of isopropanol, filtered off by suction and dried. 6.2 g (73.4% of theoretical yield) of the dye monomer of the following formula were obtained. UV / VIS in dimethylformamide: λ _max = 386 nm

The dye monomers in the following table were similarly prepared.

Examples of Graft Polymers

8.7 g of starch Perfectamyl A 4692 (86.3%) from Avebe, Foxhole, The Netherlands was dissolved in 60 ml of water at 86 ° C. To this was added a mixture of 1.5 g 1 wt% aqueous FeSO ₄ solution and 6.1 g 3 wt% aqueous H ₂ O ₂ solution. Stirring was performed at 86 ° C. for 15 minutes. The formula is then formulated in 12.5 g of methyl methacrylate and 4.1 g of 3 wt% aqueous H ₂ 0 ₂ solution at the same temperature. 1.4 g of the dye monomer of were added dropwise simultaneously over 90 minutes. After 15 minutes at the same temperature, 0.105 g tert-butyl hydroperoxide was added and stirred at 86 ° C. for 1 hour. The pure yellow dispersion was filtered through a 100 μm polyamide filter.

The dispersion was diluted 1:10 with water, applied to a glass plate and dried. The light yellow transparent film on the glass plate was irradiated for 10 minutes with polarization using a KL 500 cold light lamp (spot diameter 6 mm) from Schott. Among the orthogonal polarizers, the spot irradiated appeared bright on a dark background.

<Example 3>

Preparation of Holographic Materials by Block Copolymerization

0.314 g 4- (2-methacryloyloxyethyloxy) azobenzene (1 mol%) in 10 g methyl methacrylate ( ) And 0.052 g of 2,2 ^'- azo-isobutyric acid was rinsed and a solution of the nitrile with dry argon for 30 minutes in a glass ampoule. The ampoules were covered with rubber stoppers and annealed at 60 ° C. for 7 days. A clear polymer column was obtained. The polymer pillar could be isolated by breaking the ampoule and removing the broken glass. Store at 60 ° C. for 2 more weeks to remove methyl methacrylate residues and relieve stress in the polymer block.

The PAP column thus obtained was cut and polished into plates of diameter 17 mm and thickness 1.9 mm in a precision engineering workshop. The plate had the following optical densities at significant wavelengths: OD (514 nm) = 2.502; OD (532 nm) = 0.755; OD (568 nm) = 0.052.

In a similar manner, copolymers having an azo dye content of 10 mol% were prepared. In a similar way, the chemical formula A copolymer having a monomer content of 1 mol% and a methyl methacrylate content of 99 mol% was prepared.

<Example 4>

The polymer from Example 3 was applied to a glass substrate having a thickness of 150 μm by spin coating from a solution. The layer thickness at the measurement point located in the center of the substrate was 600 nm. The reflection index n of the polymer layer was determined for three spatial directions x, y (horizontal to the layer) and z (perpendicular to the layer) by the prism coupling method. To this end, the base of the prism was brought into close contact with the polymer layer. The angle at which the polarization of the laser couples to the polymer layer and passes through the layer in a waveguide-like manner provides information about the index of reflection at that light wavelength. Every coupling is clearly seen as a signal degradation at the detector during reflection.

When the polarization of the laser is perpendicular to the plane of incidence (s-polarization), the reflection index in the polarization direction can be determined. Depending on the orientation of the substrate, the n _x and n _y values can be determined. The index of the substrate with the low index of reflection, the index of the prism and the laser wavelength (λ = 633 nm) are included in the calculation. When polarized to the plane of incidence (p-polarized light), the value of n _z can be determined. For this purpose, one of the two spatial directions x or y must match the plane of incidence. In addition, the index of reflection (n _x or n _y ) in this selected direction is also included in the calculation.

Reflection indices n _x , n _y and n _z were determined before, during and after some exposure and cancellation processes. The exposure was performed by irradiating the polymer layer with laser light of wavelength λ = 514 nm at normal incidence. The light output was 200 mW / cm ² . The light was linearly polarized in the x direction. Erase of the orientation anisotropy induced in the xy plane occurs upon polarization in the y direction.

Sample reflection index at λ = 633 nm n _x n _y n _z Untreated 1.692 1.692 1.627 After exposure for 200 seconds 1.657 1.721 1.682 After exposure for 500 seconds 1.626 1.732 1.700 After exposure for 5000 seconds 1.596 1.746 1.716 After the first erase 1.672 1.675 1.723 After secondary exposure (5000 seconds) 1.588 1.721 1.730 After secondary erasure 1.650 1.651 1.735

The level of reflection index in each spatial direction is a measure of the average number of chromophores oriented in that direction because it is related to incident polarization and consists mainly of high molecular polarization along each molecular axis. Since n _x and n _y were originally identical, they were distributed isotropically macroscopically in the xy plane. Small n _z values indicate planar molecular orientation, which is due to the manufacturing process. Due to the first exposure, the number of chromophores lying in the x direction was gradually decreased in orientation distribution. Depletion in that direction occurred randomly in the same portion for the other two spatial directions y and z to read from increasing n _y and n _z values. In the film plane the double reflection n _y -n _x could be almost completely erased again. However, further performing the exposure process or the erase process increased the number of chromophores oriented in the z direction.

Example 5

The polymer from Example 3 was made in the form of granules. It was applied to a glass plate and heated to about 180 ° C. At this temperature, the polymer was melted. The spacer and another cover glass, for example a mylar film or glass fiber, were placed on the substrate. Layers ranging from 20 to 1000 μm were prepared using glass-polymer-glass sandwiches.

<Example 6>

The holographic structure of the 500 μm thick polymer film prepared by the method of Example 5 was studied. SHG Nd: YAG laser (532 nm) was used as the recording source. In the beam path of the object light, a spatial light modulator is provided that provides a data mask of 1024 x 1024 pixels. The intensity ratio of the reference light to the object light was 7: 1, and the total power density in the sample was 200 mW / cm ² . The hologram was recorded by foaming the reference light and the object light, which were polarized perpendicularly to the plane of incidence, respectively, projected at an angle of 40 ° to each other and exposed for 30 seconds. The hologram was then read alone by exposure to reference light (10 milliseconds of exposure time). By varying the angle of the reference light by 0.25 °, the Bragg state was broken and the original hologram was no longer visible. The new hologram was recorded under a new angle configuration. This process was repeated 100 times. After each recording process, all previously recorded holograms were read as well as the hologram just recorded by adjusting the corresponding reference angle. Even after 100 recording processes, the information of all the holograms was maintained.

Claims (19)

For holographic volumetric storage media characterized by the ability to record multiple holograms at one sample location, containing one or more dyes, and optionally one or more shape-isotropic atoms, whose spatial arrangement changes when the hologram is recorded Recording material. The method according to claim 1, wherein the dye present in at least one kind changes its absorption behavior, in particular, the sensitivity to actinic rays is preferably 10% to 100%, based on the sensitivity before recording the first hologram, More preferably 50% to 100%, most preferably 90% to 100%, so that its spatial arrangement changes. The method according to claim 1, wherein the dye present in at least one kind is moved in such a manner as to change its absorption behavior, in particular in a direction perpendicular to the polarization direction of actinic rays, such that the molecular longitudinal axis of the dye is 10 ° from the polarization direction of actinic rays. At an angle of from 90 ° to 90 °, preferably from 50 ° to 90 °, more preferably from 75 ° to 90 °, most preferably from 85 ° to 90 °, in a manner that reduces the sensitivity of the dye to actinic rays. A recording material, characterized in that the arrangement changes. The optical density according to any one of claims 1 to 3, wherein the optical density is 2 or less, preferably 1 or less, more preferably 0.3 or less, and the wavelength range is 390 to 800 nm, preferably 400 to 650 nm, More preferably, it is 510-570 nm, Most preferably, it is 520-570 nm. The recording material according to any one of claims 1 to 4, wherein the irradiation thickness is 0.1 mm or more, preferably more than 0.5 mm, more preferably more than 1.0 mm, most preferably 5 cm or less. The recording material according to any one of claims 1 to 5, which mainly contains a polymer organic material or an oligomeric organic material. 7. The recording material according to any one of claims 1 to 6, wherein the optical density of the recording material is adjusted via a concentration of a dye, which preferably exists at least one. 8. The recording material according to any one of claims 1 to 7, wherein the optical density is adjusted through a molar extinction coefficient of at least one dye present. The process according to any of the preceding claims, characterized in that it is a polymeric amorphous organic material or an oligomeric amorphous organic material, preferably branched polymers and / or block copolymers and / or graft polymers. Recording material. The wavelength range of the electromagnetic beam of claim 1, wherein the wavelength of the laser is preferably 390-800 nm, more preferably 400-650 nm, more preferably 510-570 nm, most preferred. Preferably 520-570 nm light. Claim 1, in the recording of at least three, preferably more than 100, more preferably more than 500 and most preferably more than 1000 volumetric holograms, in particular angle-dependent recording, in one location of the storage material Use of the recording material according to any one of claims 10 to 10. Use of a recording material according to any of the preceding claims in the reading of volumetric holograms, in particular in angle-dependent reading. A holographic volume storage medium comprising the recording material according to any one of claims 1 to 10. 14. The unsupported film of claim 13, wherein the recording material is contained in any desired form, preferably in a multilayer structure having one or more substrate layers, preferably an unsupported two-dimensional structure, more preferably in the form of an unsupported film. A holographic volumetric storage medium containing one or more objects. The holographic volume according to claim 13 or 14, characterized in that it comprises the step carried out in the range of 300 ° C. or less, preferably 220 ° C. or less, more preferably 180 ° C. or less according to a conventional injection-molding process. Method of Making Storage Media. A polymer having a chemically bound dye of formula (I) <Formula I> Where R ¹ and R ² each independently represent a hydrogen or nonionic substituent, R ¹ may further represent -X ^{1 '} -R ³ , m and n each independently represent an integer of 0 to 4, preferably 0 to 2, X ¹ and X ² each represent —X ^{1 ′} —R ³ and X ^{2 ′} —R ⁴ , X ^{1 '} and X ^2' are a direct bond, -O-, -S-,-(NR ⁵ )-, -C (R ⁶ R ⁷ )-,-(C = O)-,-(CO-O) -,-(CO-NR ⁵ )-,-(SO ₂ )-,-(SO ₂ -O)-,-(SO ₂ -NR ⁵ )-,-(C = NR ⁸ )-or-(CNR ⁸ -NR ⁵ )-, R ³ , R ⁴ , R ⁵ and R ⁸ are each independently of each other hydrogen, C ₁ -C ₂₀ -alkyl, C ₃ -C ₁₀ -cycloalkyl, C ₂ -C ₂₀ -alkenyl, C ₆ -C _10- Aryl, C ₁ -C ₂₀ -alkyl- (C═O)-, C ₃ -C ₁₀ -cycloalkyl- (C═O)-, C ₂ -C ₂₀ -alkenyl- (C═O)-, C _6- C ₁₀ -aryl- (C═O)-, C ₁ -C ₂₀ -alkyl- (SO ₂ )-, C ₃ -C ₁₀ -cycloalkyl- (SO ₂ )-, C ₂ -C ₂₀ -al alkenyl - (SO ₂₎ - or C ₆ -C ₁₀ - aryl - (SO ₂₎ -, or represent, or -X ^{1 '} -R ³ and X ^2' -R ⁴ can represent hydrogen, halogen, cyano, nitro, CF ₃ or CCl ₃ , R ⁶ and R ⁷ are each independently of each other hydrogen, halogen, C ₁ -C ₂₀ -alkyl, C ₁ -C ₂₀ -alkoxy, C ₃ -C ₁₀ -cycloalkyl, C ₂ -C ₂₀ -alkenyl or C ₆ -C ₁₀ -aryl. The polymer of claim 16 containing at least one monomer of formula (II). <Formula II> Where R represents hydrogen or methyl, The other radicals are as defined above. 18. The polymer of claim 16 or 17, which contains at least one monomer of formula (IIa) and / or (IIb). Characterized in that at least one monomer present is polymerised, preferably free radical polymerization, more preferably free radical initiator and / or free radical polymerization initiated by UV light and / or heat without further solvent. The manufacturing method of the recording material of any one of Claims 1-10, or the polymer of Claims 16-18.