KR100940612B1 - Reinscribable Optical Recording Material Exhibiting Good Solubility - Google Patents

Abstract

The invention relates to an optical recording material for storing binary and/or multibit and/or multivolume data. The invention also relates to the production of said recording material and to the use of the same as storage material.

Description

Rescribable Optical Recording Material Exhibiting Good Solubility

The present invention relates to optical recording materials for binary and / or multi-bit and / or volume data storage, and to their use as manufacturing and storage materials.

It has long been widely known that azobenzene undergoes isomerization by the action of light (see Hartley, GC Hartley, Nature 140, 281 (1937)). The nature of the isomerization and transition reactions between cis and trans states has been studied for a variety of polymers, which include azobenzenes in dispersed form, as side chains or in the backbone (CS Paik, p. H. Morawetz, Macromolecules 5 , 171 (1972)).

It is also known that azobenzene incorporated into the polymer, when exposed to polarized light at the appropriate wavelength, exhibits a defined orientation in the actinic field. For example, exposure to linearly polarized light increases the proportion of azobenzene oriented perpendicular to the polarization direction. It can also be used to generate photoinduced birefringence in polymers. The orientation mechanism of azobenzene is described in Ike et al. Eich; JH Wendorff; B. Reck; H. Ringsdorf; Makromol. Chem. Rapid Commun. 8 , 59 (1987) and by YY Shen; H. Rau, Macromol. Chem. 192 , 945 (1991), and the like.

The possibility of using these polymers for reversible optical data storage (digital or holography) is described in Todorov's [T. Todorov; L. Nikolova; N. Tomova, Appl. Opt. 23 , 4309 (1984). Prior art for storage of binary and / or multibit and / or volume data comprising azobenzene as an antenna for incident light [EP-A 1 171 877, EP-A 1 166 187, DE-A 10 027 153, EP -A 1 166 188, DE-A 100 271 529. JJ Couture; RA Lessard, Appl. Opt. 27 , 3368 (1988)], Ike et al. Eich; J. Wendorff, J. Opt. Soc. Am. B, 7 , 1428 (1990), by Nathan Tanson [A. Natansohn; P. Rochon; J. Gosselin; S. Xie; Macromolecules 25 , 2268 (1992), etc., several amorphous and liquid crystal polymers, oligomers have been synthesized, and photoexposure experiments have been conducted.

Three factors contribute to the high light-induced birefringence of these polymers.

High structural anisotropy of molecular side groups

The structural anisotropic element is called mesogen. Mesogens are generally rod-shaped because they contain a portion of a long, rigid molecule. The length-width ratio measured by van der Waals radius should be at least 4, preferably 4-6. Structural anisotropy leads to anisotropy of molecular polarization. Molecular forms of this kind are described by Kelker, H. Kelker, R. Hatz, "Handbook of Liquid Crystals", Verlag Chemie (1980), Bergman, L. Bergmann; C. Schaefer, "Lehrbuch der Experimentalphysik", Verlag de Gruyter, Vol. 5, "Vielteilchensysteme" (1992).

Azo dyes in the isomeric trans state satisfy the above conditions suitable for structural anisotropy, and also function in mesogen molecular units.

2. High water density of structural isotropic molecules in polymers, ie high azobenzene content or high mesogen content.

3. Strong anisotropic molecular orientation distribution. This is the premise for macromolecular anisotropy (see point 1).

Anisotropy can be derived from standardized linear absorption dichroism (A ₂ ). Where A ₂ can be represented by A = (2A _⊥ + A _∥ ) / (3A ₀ ), where A _∥ and A _⊥ are the absorbances of the polymer in the direction parallel to and perpendicular to the polarization direction of the actinic line, respectively. ₀ represents the absorbance before irradiation. Absorbance can be measured using a spectrometer (eg Varian CARY 4G, UV- / VIS spectrometer).

Molecular orientation may be more generally expressed by the order maeteum variable _{(order parameter, P 2),} P 2 = - is marked with _{(A ∥ A ⊥) / (} A ∥ + 2A ⊥), where P ₂ is and +1 when it indicates a case where the molecular transition dipole moment completely parallel to the polarization direction of the light, P ₂ is one when the light polarization direction and completely perpendicular -0.5, P is zero when the _two represents the isotropic state.

Particularly, in the case of the side chain polymer in which the structural anisotropic element is used as the side chain in addition to the azobenzene, the above three preconditions can be satisfied, which is characterized by high light-induced birefringence.

In general, it is true that polymers have a lower solubility, and the above requirements 1 and 2 are better satisfied. In other words, there is a high possibility of large birefringence values. Dipole forces, geometric forces, and entropy forces are what cause this on the microscopic scale.

Many solvents, such as alcohols, are nontoxic or only slightly toxic, but are therefore not suitable as solvents. However, good solvents for such polymers are often toxic, carcinogenic or harmful to fruits. In many cases the volatility is also too high due to the low boiling points of the solvents. One example is tetrahydrofuran (THF). In the following, it is described why such solvents are particularly undesirable for the production of data storage materials which must meet stringent environmental requirements in the production process.

In order to be able to use the polymers as functional layers in the data storage material, the polymers must be made into a uniform thin film. Several casting, droplet or coating processes may be used for the production of thin films. The standard process used in mass production, such as in recordable compact discs (CD-R) and its alternative formats, is spin coating. In this process the pigments are dissolved and the solution drips on a rotating substrate (eg polycarbonate disc) in an automated manner. After evaporation of the solvent, a thin film of recording material remains. In order to trap evaporated solvents that are toxicologically problematic for environmental protection, production lines for data storage materials had to be sealed by complex processes, which is economically disadvantageous.

In addition, it should be noted that THF dissolves polycarbonate. Thus the printed groove structure of the polycarbonate substrate will break when in contact with THF. In order to protect the groove structure, a THF resistant cover layer had to be applied to the polycarbonate.

Recording and erasing reversible birefringence values is a fundamental premise for the use of optically recordable polymers as functional layers of rewritable data storage materials. The polymers described so far have disadvantages, which do not guarantee sufficient reversibility.

Accordingly, there is a need for recording materials that exhibit photoinduced birefringence and are soluble in one or more simple or denatured alcohols that are nontoxic or at least minimally toxic. In addition, the recording medium should show good reversibility in the exposure kinetics.

It has surprisingly been found that the recording materials described in this application satisfy the above requirements.

The present invention thus provides an optical recording material that can be used for binary and / or multibit and / or volume data storage. The recording material is characterized by the following points.                 

● It contains one or more azobenzene pigments "azo pigments".

It comprises one or more structural anisotropic grouping "mesogens". If the azo pigment has the properties of mesogens, it is not necessary to include additional mesogens.

It contains one or more molecular groups, in order to improve the solubility in one or more simple or modified alcohols in comparison to the same material without its molecular groups, and contains monomers or hydroxyethyl groups of formula (VI) or formula (VIa). Monomers included are preferred for this purpose.

It optionally comprises monomer units incorporated in the polymer, preferably monomer units of the formula (V), in order to constantly reduce the pigment content and / or mesogen content.

The recording material according to the invention is preferably a polymer or oligomer organic, amorphous material, particularly preferably a side chain containing polymer.

The main chain of the side chain containing polymer can be derived from the following basic structures: polyacrylates, polymethacrylates, polyacrylamides, polymethacrylamides, polysiloxanes, polyureas, polyurethanes, polyesters, polystyrenes or celluloses. Preference is given to polyacrylates, polymethacrylates and polyacrylamides.

The backbone may comprise monomeric units different from these basic structures. These are monomeric units according to the invention of formula (VI).

The polymers according to the invention are generally present in an amorphous state below the Clarification temperature.                 

The polymers and oligomers in the present invention preferably have a glass transition temperature of 40 ° C or higher. Glass transition temperatures are described, for example, in Volmer's [B. Vollmer, Grundriss der Makromolekularen Chemie, pp 406-410, Springer-Verlag, Heidelberg 1962.

The polymers and oligomers according to the invention have a weight average molecular weight of 5,000 to 2,000,000 g / mol, preferably 8,000 to 1,500,000 g / mole, which is the result measured using gel permeation chromatography titrated with polystyrene.

In the polymers preferably used in the present invention, azo dyes separated by flexible spacers are generally covalently bonded to the polymer backbone as side chains. The azo pigments interact with electromagnetic radiation, whereby their spatial orientation changes, so that birefringence can be induced in the polymer under the action of light, and can also be extinguished again.

Mesogens are generally bound in the same way as in azo pigments. Because they act as passive molecular groups, they do not necessarily need to absorb actinic radiation. Thus, in view of the above, they are not photoactive. Their task is to enhance the photoinduced birefringence and to stabilize it after the action of light.

Molecular groups incorporated to increase the solubility of the polymer can be incorporated in three different ways.

1. It is incorporated as a monomer unit irregularly contained in the main chain. These monomer units are not functionalized with azobenzene or mesogen.                 

2. It is incorporated as a side chain at the bonding position between azobenzene and the spacer.

3. The free end of the azo dye is incorporated as a terminal group.

The polymers according to the present invention may comprise modified azobenzenes as described at the same time.

The polymers according to the invention may also comprise monomer units according to description 1, apart from azobenzene modified according to descriptions 2 and / or 3.

The azo dye preferably has a structure of formula (I).

In the above formula,

R ¹ and R ² independently of each other represent a hydrogen or nonionic substituent, m and n each independently represent an integer of 0 to 4, preferably an integer of 0 to 2,

X ¹ and X ² represent -X ^{1 '} -R ³ or -X ^2' -R ⁴ ,

here,

X ^{1 '} and X ^2' is 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 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 )-

-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 independently of one another are 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 group.

Nonionic substituents are 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 group, 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 = 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 Is interpreted as including.

It said alkyl, cycloalkyl, alkenyl and aryl groups, 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 again by up to 3 groups selected from the group consisting of kenyl or C ₆ -C ₁₀ -aryl groups, and the alkyl and alkenyl groups may be straight or branched.

Halogen is interpreted to represent fluorine, chlorine, bromine and iodine, in particular fluorine and chlorine.

Azo dyes having solubility enhancing properties within the meaning in the present invention include the above meanings, but R ⁵ is C ₂ -C ₁₀ -alkyl-OH, preferably C ₂ -C ₄ -alkyl-OH or CH ₂ Similarly covered by formula (I) which represents — (CH—OH) —CH ₂ —OH.

X ¹ (or X ² ) represents a spacer group, specifically X ^{1 ′} -(Q ¹ ) _i -T ¹ -S ^1- ,

here

X ^{1 '} has the above meaning,

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 a divalent group of the formula:

i represents an integer from 0 to 4, where each Q ¹ can have many meanings when i is greater than ¹ ,

T ¹ represents-(CH ₂ ) _p- , wherein the chain can 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 from 2 to 12, preferably from 2 to 8, particularly preferably from 2 to 4,

R ⁹ represents hydrogen, methyl, ethyl or a propyl group,

R ¹⁰ represents methyl or ethyl group,

In R ⁵ R ⁸ have the meanings as described above.

Covalent linkage of the azo dye of formula (I) with the monomer of the above-mentioned main chain base structure via a spacer leads to a dye monomer. Preferred pigment monomers of polyacrylate or polymethacrylate have a structure such as the following general formula (II).

In the above formula,

R is hydrogen or methyl,

Other groups have the same meanings as described above.

The pigment monomer of the formula (II) is particularly suitable in the following cases,

X ² represents CN, nitro and all other known electron withdrawing substituents, R ¹ is preferably CN,

This is the case where R, S ¹ , T ¹ , Q ¹ , X ^{1 ′} , R ² , i, m and n have the above meaning.

Also suitable are pigment monomers of the following formula (IIa).

In the above formula,

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

R, S ¹ , T ¹ , Q ¹ , X ^{1 ′} , R ¹ , R ² , i, m and n have the meanings described above.

Also suitable are dye monomers of the following general formula (IIb).                 

In the above formula,

X ⁴ represents a cyano or nitro group, and the groups R, S ¹ , T ¹ , Q ¹ , X ^{1 ′} , R ¹ , R ² , i, m and n have the meanings described above.

Preferred monomer units having an azo dye comprising a solubility enhancing element at the binding position to the spacer and / or at the free position have the following structure.

Mesogenic groups preferably have a structure of formula (III)

In the above formula, Z represents a group corresponding to the following formula.

또는

or

In the above formula,

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

X ³ represents a spacer group represented by the formula -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 independently of one another are 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 = 0)-, 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 independently of one another are 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- A C ₁₀ -aryl group,

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 independently of each 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 group, 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 independently of each other 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 a divalent group of the formula:

j represents an integer of 0 to 4, where each Q ¹ may have various meanings when j exceeds ¹ ,

T ² means-(CH ₂ ) _p- , wherein the chain can be blocked 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, particularly 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 structural isotropic groups have the structure of formula (IV).

In the above formula,

R represents hydrogen or methyl,

The other group has the same meaning as described above.

The alkyl, cycloalkyl, alkenyl and aryl groups 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 again with up to three groups selected from the group consisting of kenyl or C ₆ -C ₁₀ -aryl groups, and the alkyl and alkenyl groups may be straight or branched.

Halogen is interpreted to represent fluorine, chlorine, bromine and iodine, in particular fluorine and chlorine.

In the following paragraphs, the expression "functional unit" is used. The functional structural unit is a monomer structural unit containing an azo group or a mesogenic unit. Therefore, both specified molecules are involved in the photoalignment process of the corresponding polymer. This means that they are functional groups. A distinction must be made between these functional groups or structural units and "dilution structural units". A "dilution structural unit" is a monomer structural unit which cannot form an oriented side chain. They are simply part of the polymer backbone and reduce the proportion of functional units in the polymer.

In addition to these functional structural units, the polymers according to the invention can also in principle comprise structural units which serve to reduce the percentage content of functional structural units, in particular pigment structural units. In addition to these actions, they may be responsible for other properties of the polymer, such as glass transition temperature, liquid crystal, and thin film formation.

In the case of polyacrylates or polymethacrylates, such monomers are acrylic or methacrylic esters of formula (V).

In the above formula,

R represents hydrogen or methyl,

R ¹⁴ represents a group comprising optionally branched C ₁ -C ₂₀ -alkyl or one or more additional acrylic units.

However, other copolymers may also be included.

Monomer units for increasing solubility have structures of the following formulas (VI) and (VIa).

In the above formula,

R 'and R "are independently of each other C _n H _{2n + 1} or C _n H _2n -OH (n is 1 to 10, preferably n is 1 to 3), or together are -C _n H _2n -bridge (n Is 2 to 6, preferably 4 or 5),-(C ₂ H ₄ -O) _n -C ₂ H ₄ -bridge (n is 1 to 5, preferably 1 to 3) or -C ₂ H ₄ -N (C _n H _{2n + 1} ) -C ₂ H ₄ -bridge (n represents 1 to 6, preferably 1 to 3),

Where R is hydrogen or methyl.

In the above formula,

R ″ 'is C _n H _2n -OH (n is 1 to 10, preferably n is 2 to 3),-(C ₂ H ₄ -O) _n -H (n is 2 to 4, preferably n Is 2), or -C _n H _2n -C (= 0) NR "" R ""'(n is 2 to 10, preferably 2 to 5, particularly preferably n is 2),

here,

R ″ ″ and R ″ ″ ′ are independently of each other C _n H _{2n + 1} or C _n H _2n —OH (n is 1 to 10, preferably 1 to 3), or together —C _n H _2n − a bridge ( n is 2 to 6, preferably 4 or 5),-(C ₂ H ₄ -O) _n -C ₂ H ₄ -bridge (n is 1 to 5, preferably 1 to 3), or -C ₂ H ₄ -N (C _n H _{2n + 1} ) -C ₂ H ₄ -bridge (n represents 1 to 6, preferably 1 to 3),

Where R is hydrogen or methyl.

The polyacrylates, polymethacrylates and poly (meth) acrylates / poly (meth) acrylamides according to the invention are then those of formula (VIII), preferably formulas (VIII) and (VIII) as repeating units. Or preferably those of formulas (iii) and (iii) or those of formulas (iii), (iii) and (iii), or

및

And

및

And

Or a repeating unit of formula (VIIa) or (VIIb) instead of formula (VII).

또는

or

Wherein the group has the same meanings as described above.

Some of the "repeating" units of formula (i) and / or repeating units of formula (iii) and / or repeating units of formula (iii) may also be present. Monomer units of formula (V) may also additionally be present. Likewise monomeric units of formula (VI) may additionally also be present.

The quantitative ratio between V, VI, V, V and V is arbitrary. Preferably the concentration of VII is 1 to 99% for each mixture. The ratio between VII and VII is 1:99 to 99: 1, preferably 10:90 to 90:10, particularly preferably 60:40 to 40:60. The proportion of V is 0 to 90%, preferably 20 to 80%, particularly preferably 30 to 70%, for each mixture. The proportion of VI is from 0 to 90% for each mixture, preferably from 20 to 80%, particularly preferably from 30 to 70%.

Due to the structure of the polymer and the oligomer, the intermolecular interactions between the structural units of formula (VII) or between the formulas (VII) and (VII) are controlled to suppress the formation of a liquid crystal order state, and optionally optically Isotropic transparent non-scattering thin films, sheets, panels or blocks, in particular thin films or coatings, can be produced. On the other hand, intermolecular interactions are still sufficiently strong, resulting in photochemically induced, cooperative, alignment, rearrangement of photoactive and non-photoactive side groups under light irradiation and / or electrostatic field action.

Preferably, the interaction force is between the side groups of the repeating unit of formula (VII) and between the side groups of the repeating unit of formula (VII), the side groups having different structural changes in the side groups of formula (VII). ) And / or (i)) the same oriented-so-called cooperative-reorientation takes place sufficiently.

The production of polymers and oligomers is described in DD-A 276 297, DE-A 3 808 430, Makromolekulare Chemie 187 , 1327-1334 (1984), SU-A 887 574, Europ. Polym. 18 , 561 (1982) and Liq. Cryst. 2 , 195 (1987), and the like.

Another method of preparing the recording material or polymer according to the invention is that one or more monomers are polymerized without further solvent, preferably free group polymerized, particularly preferably the polymer is free radical initiator and / or UV light and / or ) Thermally initiated process.

The polymerization is carried out at temperatures between 20 ° C. and 200 ° C., preferably between 40 ° C. and 150 ° C., particularly preferably between 50 ° C. and 100 ° C. and very particularly preferably around 60 ° C.

In a preferred embodiment AIBN (Azoisobutyronitrile) is used as the free group initiator.

It is often found to be convenient to use additional, preferably liquid monomers together. Such monomers are understood to include monomers which are liquid at the reaction temperature, preferably olefinically unsaturated monomers, particularly preferably monomers based on acrylic acid and methacrylic acid, very particularly preferably methyl methacrylate.

Example 1 Synthesis of Monomer

200 g 2-anilinoethanol, 580 ml methacrylic acid and 115.6 g hydroquinone and 880 ml chloroform were refluxed with stirring. 148 ml of concentrated sulfuric acid was slowly added dropwise. The reaction water was removed azeotropically. After cooling, water was added to the reaction mixture, which was then adjusted to a concentrated aqueous soda solution to pH 6. After separation of the organic layer, the solvent was removed by rotary evaporator. The product was purified by chromatography (silica gel; methylene chloride). The yield of N- [2- (methacryloyloxy) ethyl] aniline was 112 g (34% of theory yield).

30 g of 2-bromoethanol was added to the reaction vessel at 70 ° C. under argon atmosphere. 30 g of N- [2- (methacryloyloxy) ethyl] aniline was added slowly. The reaction mixture was then stirred for 24 h at 100 ° C., then after cooling chloroform was added and washed with water. After the reaction product was dried over magnesium sulfate, chloroform was removed and the product was purified by chromatography (aluminum oxide, dioxane). The yield of N- (hydroxyethyl) -N- [2- (methacryloyloxy) ethyl] aniline was 10.2 g (28%).                 

Elemental Analysis: C ₁₄ H ₁₉ NO ₃ (249.31)

Calc .: C67.45; H7.68; N5.62;

Found: C67.30; H7.40; N5.60.

5.7 g of 4-amino-3-methyl-4'-cyanoazobenzene was added to 40 ml of acetic acid and 13 ml of hydrochloric acid at 5 ° C., and 8.6 g of 30% sodium nitrite solution was added slowly to diazotize. The reaction was allowed to couple at 15 ° C. with 6 g of N- (hydroxyethyl) -N- [2- (methacryloyloxy) ethyl] aniline in 200 ml of methanol. Sodium acetate was added to maintain the pH value between 2.0 and 2.5. The precipitate obtained was stirred for 1 h, then filtered, washed with water and methanol, dried and filtered through dioxane through a layer of aluminum oxide. Yield of 1.1 : 6.2 g, Melting point: 148 캜.

Elemental Analysis: C ₂₈ H ₂₈ N ₆ O ₃ (496.57)

Calc .: C67.73; H5.68; N16.92;

Found: C67.80; H5.70; N16.70.

N- (2,3-dihydroxypropyl) -N- [2- (methacryloyloxy) ethyl] aniline was treated with 3-bromo-1,2-propanediol and N- [in a similar manner as in 1.1. From 2- (methacryloyloxy) ethyl] aniline. The product was purified by chromatography (aluminum oxide, first toluene / dioxane = 1: 1, then dioxane). Yield 28%.

Similar to 1.1 in monomer 1.2, diazotization of 4-amino-3-methyl-4'-cyanoazobenzene and N- (2,3-dihydroxypropyl) -N- [2- (methacrylo) Produced via coupling with yloxy) ethyl] aniline. Chromatographic purification was carried out on silica gel (toluene / dioxane = 1: 1). Yield: 30%, Melting Point: 148 ° C.

10.7 g of 2,2 '-[4- (4-aminophenylazo) phenylimino] diethanol is added to 60 ml of water and 20 ml of hydrochloric acid mixture at 5 ° C., and 12.8 g of 30% sodium nitrite solution Was added slowly to diazotize, and 10 g of N-methyl-N- [2- (methacryloyloxy) ethyl] aniline in 300 ml of methanol was coupled to react at 15 ° C. Sodium acetate was added to maintain the pH value at 2.7. The precipitate obtained was stirred for 1 h, then filtered, washed with water and dried and then recrystallized from xylene. Yield of 1.3: 7.2 g, Melting point: 149 ° C.

Elemental analysis: C ₂₉ H ₃₄ N ₆ O ₄ (530.63)

Calc .: C65.64; H6.46; N15.84;

Found: C65.70; H6.40; N15.70.

12.8 g of 2,2 '-[4- (4-amitophenylazo) phenylimino] diethanol is added to 60 ml of water and 20 ml of hydrochloric acid mixture at 5 ° C. and 15.2 g of 30% sodium nitrite The solution was slowly added to diazotize, and was subjected to a coupling reaction at 15 ° C. with 10.6 g of N- (hydroxyethyl) -N- [2- (methacryloyloxy) ethyl] aniline in 300 ml of methanol. Sodium acetate was added to maintain the pH value at 2.7. The resulting precipitate was stirred for 1 hour, then filtered, washed with water and dried and then recrystallized from xylene. Yield: 1.4: 15 g, Melting point: 105 ° C.

Elemental analysis: C ₃₀ H ₃₆ N ₆ O ₅ (560.66)

Calc .: C64.27; H6.47; N14.99                 

Found: C64.10; H6.40; N14.20.

Example 2a: Improvement of Solubility by Incorporation of Dimethylacrylamide

Copolymers having the following structures according to the invention are described below:

The x-monomer is functionalized with azobenzene pigment molecules. The y-monomer consists of dimethylacrylamide (DMAA).

Five other copolymers were prepared for the monomer ratio x: y (see the following table; polymers indicated by serial numbers 1 to 5). The copolymers were compared to homopolymers (x = 100%; polymer 6 label).

The molecular weights of the polymers were determined by gel permeation chromatography (GPC). GPC was performed using N, N-dimethylacetamide (DMAC) as a solvent. The evaluation of the signal was made based on a valid calibration relationship for PMMA at 60 ° C. in DMAC. The weight average molecular weight values were from 10500 to 13300 g / mol. The number average molecular weight values were 5500 to 6810 g / mol.

The glass transition temperature was measured using a heat flow calorimeter (device: DSC-2 calorimeter, manufactured by Perkin-Elmer). Two heating experiments were conducted at a heating rate of 20 K / min from room temperature to 300 ° C. Between heating experiments samples were quickly cooled to room temperature at a rate of 320 K / min and flushed with nitrogen (30 ml / min) in each case. The glass transition temperatures of the polymers 1-6 in the second heating experiment were 92 ° C to 104 ° C.

The solubility of the polymers was tested in various simple and modified alcohols. The results are shown in the following table: "+" indicates a suitable solvent, "(+)" indicates incomplete dissolution and "-" indicates an inappropriate solvent. 2% solution of the polymer was used. The following solvents were tested: methanol, ethanol, butanol, 4-hydroxy-4-methyl-2-pentanone (HMP), 2,2,3,3-tetrafluoropropanol (TFP) and tetrahydrofuran (THF ).

Surprisingly, the incorporation of DMAA resulted in a significant improvement in the solubility of TFP. Comparing Polymer 6 to Polymers 1-5, TFP is a suitable solvent for later polymers. These polymers included at least 50 mol% or at least 18 wt% DMAA.

Example 2b: Comparative example not according to the present invention

Copolymers having the following structure are described below.

Monomer unit x corresponds to Polymer 6 (Example 2a). The units are included in amounts of 20, 30, 40 and 50 mole percent. The polymers in this order are labeled polymers 2b, 3b, 4b and 5b. Monomer unit y consists of acrylamide.

The solubility of the polymers in 2,2,3,3-tetrafluoropropanol (TFP) was measured similar to that in Example 2a (20% solution). The results are summarized in the following table.

The solubility enhancing effect of the monomer unit y is slight. At least 80 mol% of monomer units y must be included in the later polymer to be completely dissolved in TFP. On the other hand, with regard to the polymer according to the invention (see Example 2a), only 50 mol% of dimethylacrylamide (DMAA) is needed to achieve the same effect.

Example 3: Increasing Solubility by Using Dyestuffs Containing Hydroxyethyl Groups

Polymers containing azobenzene pigments as a side chain which resulted in a solubility enhancing effect in the present invention were synthesized. The solubility enhancing hydroxyethyl groups are attached at the binding position to the spacer and / or at the free position of each azobenzene pigment.

The synthesized polymers were consecutively numbered 7-10.

Polymer 7:

(Monomer in Example 1.1)

Polymer 8:

(Monomer in Example 1.2)                 

Polymer 9:

(Monomer in Example 1.3)

Polymer 10:

(Monomer in Example 1.4)

These polymers are compared to Polymer 6 (see Example 2). The result is as follows: polymers 7 to 10 are not only soluble in THF (similar to polymer 6) but also in HMP (2% concentration). As the proportion of OH groups in the polymer increases, the interaction force with the hydroxyl group of the solvent HMP increases, and HMP can function better as a solvent. Details are as follows: polymer 7 is incompletely dissolved in HMP, polymers 8 and 9 are almost completely soluble, and polymer 10 is very well soluble in HMP.

Example 4 Magnitudes of Light Induced Birefringence Values

Several polymers according to the present invention exhibiting high light-induced birefringence values as thin films were synthesized. Polymers 1 to 5 and 7 to 10 (see Example 2) according to the present invention were studied through irradiation experiments (see Example 3). The magnitude of the photoinduced birefringence values of the original isotropic polymer thin films was measured.

Technology of Thin Film Manufacturing:

A polymer thin film was provided on a 1 mm thick glass substrate. The thin film was applied by spin coating. To this end, the polymer was dissolved in a suitable alcohol at a typical concentration of 20 to 75 g / l, and then the polymer solution was added dropwise to the rotating substrate at a rotational speed of 2000 m ⁻¹ . The formed polymer thin film typically has a thickness of 200 nm. Solvent residues were removed from the thin film by storing the coated glass support in a vacuum oven at 60 ° C. for 2 hours.

Techniques of survey experiments:

Each sample provided as described above was irradiated with a polarized laser light incident perpendicularly thereto from the polymer side (writing process). An argon ion laser (manufactured by Continuum) having a wavelength of 514 nm served as a light source. The intensity of this so-called recording laser was 100 mW / cm ² . Trans-cis-trans isomerization cycles are induced in the azobenzene side group molecules of the polymer, leading to the net orientation of the side groups away from the polarization direction of the laser. This molecular dynamics is clearly shown macroscopically in birefringence Δn in terms of the polymer thin film. The dynamics are expressed in minutes under given survey parameters.

The time behavior of the induced birefringence was measured experimentally with a helium-neon laser (typical intensity: 10 mW / cm ² ) at a wavelength of 633 nm. The light of this so-called reading laser, incident on the polymer layer, forms a solid angle of 15 degrees with respect to the perpendicular to the thin film. The read light and the record light overlap on the polymer layer. The polarization direction of the read light forms an angle of 45 degrees with respect to the polarization direction of the recording light in the polymer thin film plane. If the polymer layer is birefringent, it will rotate as it passes through the layer. This rotation entails an increase in the intensity I _s of the read light in the spectrometer, which is placed in the light path behind the sample and allows light to pass through perpendicular to the original polarization direction. The intensity I _p decreases to the same extent as the increase in I _s . I _p is defined as the transmission intensity in a similarly positioned spectrometer, but this selects the original polarization direction of the read light. Experimentally two components of the polarization direction parallel and perpendicular to the original direction are separated by a polarization beam splitter and detected with the help of two Si photodiodes. The birefringence Δn is calculated from the intensity measured by the following equation:

Where d represents the thickness of the polymer layer and λ = 633 nm represents the optical wavelength of the read laser. In this equation, it is assumed that the reading occurs perpendicular to the polymer layer.                 

The polymers have the following birefringence values:

Polymer 1: Δn = 0.06; Polymer 2: Δn = 0.11; Polymer 3: Δn = 0.17; Polymer 4: Δn = 0.20; Polymer 5: Δn = 0.21; Polymer 6: Δn = 0.44; Polymer 7: Δn = 0.39; Polymer 8: Δn = 0.10; Polymer 9: Δn = 0.23; Polymer 10: Δn = 0.12.

Example 5 Enhancement of Reversibility of Photoinduced Molecular Dynamics through Incorporation of Dimethylacrylamide

Thin films of polymers 1-5 according to the invention, described in Example 2a, were synthesized by the protocol of Example 4, irradiated for 10 minutes, and the birefringent structure was tested with a readout laser. The birefringence Δn reached its maximum within the irradiation time and then maintained there. Δn was then extinguished by rotating the polarization direction of the recording light by 90 degrees. This erase process was completed as soon as Δn = 0. Immediately following this initial step, four additional recording / erase steps were carried out in the same manner. The result is as follows: The time curve Δn (t) remained almost unchanged for each cycle. The maximum obtainable birefringence values were the same for each cycle. (Accepted tolerance: 5%). The behavior of polymers 1 to 5 can be classified reversibly as they are quite close in these write / erase cycles.

1 shows birefringence curves for five recording / erase cycles of polymer 4 as an example.

Comparable experiments have previously been made in polymer 6 which does not contain solubility enhancing monomer units according to the invention. Since the birefringence Δn has not yet reached its maximum after 10 minutes of irradiation, the irradiation time of the five recording steps has been extended to 30 minutes. It is worth noting that the shape of the birefringence curve changes with each new cycle. In particular, the maximum attainable birefringence decreases with increasing number of cycles. After the end of the fifth recording step, birefringence is only 33% of the value obtained in the first recording step (see table below).

FIG. 2 shows the birefringence curves for five recording / erase cycles of Polymer 6. FIG.

In order to ensure that longer irradiation times compared to polymers 1 to 5 did not quantitatively distort the results, write / erase cycles were performed in polymer 6 with a recording time of only 100 seconds in each case. The birefringence curves did not reach their maximum value during this short recording time. The results are as follows. These cycles also did not behave reversibly, ie for values reached after 100 seconds, only 71% of the values reached in the first cycle after the fifth cycle.

3 shows the birefringence curves involved in this experiment.

Summary of results:

Polymer 1 Polymer 2 Polymer 3 Polymer 4 Polymer 5 Polymer 6  Fraction x [mol%]  10  20  30  45  50  100  Fraction y [mol%]  90  80  70  55  50  0 Birefringence value after 5 cycles [%] ^*  100  100  100  100  100 33/71 ^**  * Value related to the birefringence value of the first cycle ** 1800 sec / 100 sec Recording time

When the dimethylacrylamide monomer unit was incorporated in an amount of 50 mol% or more (see the fraction y in the above table), not only the solubility of the polymer in TFP but also the reversibility of the optical dynamics was remarkably improved. Recording and erasing of reversible birefringence values is a basic premise for the use of optically recordable polymers as recording layers in rewritable data storage materials.

Example 6: Suitability of the Polymers for Blue Recording Lasers

Examples of Polymer 4 show that not only green recording light is suitable (Examples 4 and 5), for example blue recording lasers are also suitable. Laser irradiation was carried out according to the principle outlined in Example 4. The recording laser had a light wavelength of 407 nm and an intensity of 100 mW / cm ² . The results are as follows: A maximum birefringence value with Δn = 0.2 could likewise be derived (measurement error about 10%).

Claims (13)

a) contains a unit derived from at least one azobenzene dye-containing monomer selected from the group consisting of formulas (X) to (XIII), or b) containing at least one unit derived from a monomer of formula (IIb) and a unit derived from a monomer of formula (VI) Polymer materials.

<Formula IIb>

(In the above formula, R is hydrogen or methyl, R ¹ and R ² are independently of each other hydrogen or C ₁ -C ₄ -alkyl, m and n are each independently an integer from 0 to 4, X ⁴ is cyano, S ¹ is -O-, T ¹ represents-(CH ₂ ) _p- , where p is an integer from 2 to 8, Q ¹ is -C ₆ H ₄ -or-(NR ⁵ )-, wherein R ⁵ is C ₁ -C ₄ -alkyl or C ₆ -aryl, i is an integer from 0 to 4, i> 1 , Each Q ¹ may have various meanings, X ^{1 '} means -N = N-) <Formula VI>

(In the above formula, R is H or methyl, R ′ and R ″ independently represent C _n H _{2n + 1} (n = 1 to 10) A polymeric material according to claim 1, comprising a) units derived from at least one azobenzene pigment-containing monomer selected from the group consisting of formulas (X) to (XIII). The polymeric material of claim 1, comprising b) at least one unit derived from a monomer of formula (IIb) and a unit derived from monomer of formula (VI). delete delete delete delete delete An optical recording medium comprising the polymeric material of claim 1 in the form of a layer or film. delete delete The polymeric material of claim 1, wherein the polymeric material further comprises one or more monomer units incorporated to uniformly reduce the content of component a) or the content of component b) in the material. The polymer material according to claim 1, which contains a unit derived from the following monomers.

In the above formula, x and y means the fraction of each monomer.

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