JPS6137473A - Optical recording element - Google Patents

Abstract

PURPOSE:To obtain optical recording elements capable of highly reliable higher density recording by providing a layer A of color-forming compound, a layer B of assistant color-forming compound and a light-absorbing layer 3 of light- absorbing material which exists between the layer A and the layer B, and making up each layer of either a monomolecular film or an accumulated film. CONSTITUTION:The titled optical recording element is composed of a layer-A 2 of color-forming compound, a layer-B 4 of assistant color-forming compound and a light-absorbing layer 3 of light-absorbing material which exists between the layers A and B. All these layers are laminates of monomolecular film or its accumulated film and the layer-B 4 is supported on a substrate 1. The substrate, layer B, light-absorbing layer and layer A are laminated in that order. Consequently, compared to the conventional optical recording element, the titled element has higher packing density and has a higher signal/noise ratio, thus enhancing recording reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical recording element using an organic material, and particularly to an optical recording element using an organic material with highly molecular orientation. ! The present invention relates to an optical recording element that uses a thin film and is capable of highly reliable and high-density recording.

[Prior Art] Optical disks are attracting attention as a central recording device for office automation (OA). The reason for this is that a single optical disc can record (or store) a large amount of documents, literature, etc. Therefore, introducing an information storage device that uses this optical disc will revolutionize the organization and management of documents and literature in offices. It is expected that this will bring about Furthermore, as recording materials for optical disks, organic materials, which have characteristics such as low cost, ease of manufacture, and high-density recording, are attracting attention.

Among the conventional techniques using such organic recording materials.

In particular, a two-component optical recording element that utilizes a color reaction caused by contact between a color former and an auxiliary colorant has been reported (Nikkei Sangyo Shimbun
(October 18, 1982).

An example of the optical recording element will be described based on the drawings.
As shown in Figure (a), the color forming agent layer 7 and the auxiliary color agent layer 5 are separated by a light absorbing layer 6 and are laminated on a substrate l.

The coloring agent (leuco compound) and auxiliary colorant are colorless or light-colored when each exists alone.

When recording on the recording element, a laser beam 8 is irradiated onto a desired position of the light absorption layer 6 as shown in FIG. 2(b).
The portion of the light-absorbing layer that is irradiated with the laser beam absorbs the laser beam, melts, and rips, leaving a small hole.

As a result, as shown in FIG. 2(C), the color forming agent and the auxiliary color agent, which were separated by the light absorbing layer 6, mix through the small holes and develop a color. Information is recorded or stored in the form of coloring points 9, and reading is performed by scanning the recording element with another light source and detecting changes in reflectance, transmittance, etc. due to the coloring points.

[Problems to be Solved by the Invention] In the above-mentioned optical recording element, in order to achieve high recording density, it is desirable that the light absorption layer 6 be as thin as possible, flat, and without unevenness in film thickness. However, in conventional optical recording elements, the light absorption layer is coated on the substrate by, for example, a vacuum evaporation method or a spin coating method, so the thickness is reduced to 20%.
When trying to print thinly to 0 to 500 Å or less, pinholes tend to occur frequently, and the two components, the color former and the auxiliary color, come into contact at these pinholes and develop color, resulting in a drawback of lack of reliability. In addition, because the molecular distribution orientation within the n range of each layer formed by the conventional coating method described above is random, light scattering occurs within the school due to light irradiation, and when viewed microscopically, each light irradiation The degree of chemical reaction that occurs differs each time. Furthermore, the above-mentioned coating method has disadvantages in that when the substrate of an optical disk is made to have a large area, the film thickness becomes unstable and the recording quality suffers.

Therefore, as an optical recording element, it is desirable that the molecular distribution and orientation within the film be uniform, that there are no pinholes, and that the film thickness is uniform, and that the film thickness be as thin as possible to achieve high recording density and high reliability. The present invention has been made in view of these demands, and an object of the present invention is to provide an optical recording element capable of highly reliable and high-density recording. Yet another object of the present invention is to provide a large area optical recording element.

[Means for Solving the Problems] and [Operation] That is, the present invention consists of a layer A consisting of a color-forming compound that is usually colorless or light-colored, and a layer B consisting of an auxochrome compound that develops a color when it comes into contact with the color-forming compound. and a light absorption layer interposed between the A layer and the B layer, and (a) the A layer is a monomolecular film of a color-forming compound or a cumulative film thereof, and (b) the Bfi is A layer consisting of a monomolecular film of an auxochromic compound or a cumulative film thereof; (c) the light-absorbing layer is a layer comprising a monomolecular film of a light-absorbing substance or a cumulative film thereof; It is a recording element.

The present invention will be explained in detail below.

The optical recording element according to the present invention has a light-absorbing layer interposed between the layer A, which is usually made of a colorless or light-colored color-forming compound, and the layer B5, which is made of an auxochrome compound that develops color when it comes into contact with the color-forming compound. Basically, the A layer and the B layer are required to use a combination of substances that develop color when brought into contact with each other and mixed together. Specific examples of the normally colorless to light-colored color-forming compound in layer A and the subchromic compound that develops color when it comes into contact with the color-forming compound in layer B, which have this relationship, are as follows: (a) Acidic substance (layer B) and a leuco form of a dye (dye precursor) that develops color when it comes into contact with the acidic substance (layer A) (b) An oxidizing agent (layer B) and a leuco form of a dye that develops a color when it comes into contact with the oxidizing agent ( A layer) (c) Reducing agent (B
layer), and the leuco form of the dye that develops color when it comes into contact with the reducing agent (layer A), (d) reducing agent (layer B), and an oxidizing agent that develops color when reduced, such as r52 iron stearate (layer A). ) (e) An oxidizing agent (layer B) and a reducing agent (layer A) that develops color when oxidized, such as gallic acid.

To give a more detailed example of the case (a) above, the acidic substance in layer B that reacts with the leuco form of the dye to develop color is an aromatic sulfonic acid compound such as benzenesulfonic acid, or an aromatic compound such as benzoic acid. Carboxylic acids, palmitic acid (
CI5H31COOH), stearic acid (C17H35
Cool), Araxic acid CCx? H,yy C00H
), phenolic compounds such as pt-butylphenol, α-naphthol, β-naphthol, phenolphthalein, bisphenol A, 4-hydroxydiphenoxide, and 4-hydroxyacetophenone.

Next, examples of the leuco dyes in the A layer that react with the acidic substance include triphenylmethane, fluoran, phenothiazine, auramine, and spiropyran. The details of the compounds are shown in Table 1.

In the present invention, since both the A layer and the B layer are formed from a monomolecular film or a layer consisting of a cumulative layer thereof, the above-mentioned color-forming compound and auxochrome compound are both placed at appropriate sites within the molecule. It is necessary to use a derivative into which a group, a hydrophobic group, or both groups are introduced.

Any commonly used hydrophobic group and parent tree group can be used, but particularly preferred hydrophobic groups include long-chain alkyl groups having 5 to 3 degrees of carbon atoms;
As the parent group, carboxyl groups and metal salts thereof (eg, cadmium salts) are desirable.

Note that the thickness of the A layer and the B layer is preferably in the range of 20OA to 10g, preferably 1. The range is from 100 people to 1 person.

Next, as the light-absorbing substance used for forming the light-absorbing layer in the present invention, a meltable light-absorbing dye that absorbs infrared rays and melts, or a sublimable light-absorbing dye that absorbs infrared rays and sublimates is suitable. .

Examples of such light-absorbing dyes include metal phthalocyanines such as copper phthalocyanine and vanadium phthalocyanine, and xanthine dyes such as fluorescein.

Since the light-absorbing layer is formed from a monomolecular film or a layer consisting of a cumulative film thereof, the above-mentioned light-absorbing substance is a derivative having a hydrophilic group, a hydrophobic group, or both groups introduced at appropriate sites within the molecule. It is necessary to use

Any commonly used hydrophobic group and parent tree group can be used, but particularly preferred hydrophobic groups include long-chain alkyl groups having 5 to 30 carbon atoms;
As the parent group, carboxyl groups and metal salts thereof (eg, cadmium salts) are desirable.

The thickness of the light absorption layer is preferably in the range of 30A to 1,000A. The preferred range is 50 to 200 people.

In addition, the materials used for the substrate in the present invention include:
Semiconductor materials such as silicon, metal materials such as aluminum, preferably tempered glass, more preferably acrylic (PMMA),
Plastic materials such as polycarbonate (PC), polypropylene, polyvinyl chloride (PVC), polystyrene, and ceramic materials are preferred.

In the optical recording element according to the present invention, the A layer is a layer consisting of a monomolecular film of a color-forming compound or a cumulative film thereof, BP:! : is 1 model of a single molecule of an auxochrome compound or 11 of its cumulative number! One feature is that the layer made of J and the light absorption layer are composed of a monomolecular film of a light absorption substance or a layer made of a cumulative film thereof.

As a method for producing a monomolecular film or a cumulative film thereof having such high orderliness and orientation of molecules, for example, 1. La
The Langmuir-Prodgett method (LB method) developed by Ngmuir et al. is used. The Langmuir-Prodgett method is based on the Langmuir-Prodgett method. For example, when a molecule has a parent tree group and a hydrophobic group in its molecule, and the balance between the two (balance of amphiphilicity) is maintained appropriately, the molecule will react to the parent tree on the water surface. This is a method of creating a monomolecular film or a monomolecular cumulative film by using the fact that the monomolecular layer is formed with the group facing downward. When the monomolecular layer on the water surface has the characteristics of a two-dimensional system and zero molecules are sparsely dispersed, the two-dimensional ideal gas equation, nA = kT, is expressed between the surface per molecule vIA and the surface pressure n. holds, and becomes ° “gas v ”, where k is Portzmann's constant and T is the absolute temperature. If A is made sufficiently small, the intermolecular interaction will be strengthened, resulting in a two-dimensional solid “°condensed film (or solid film)°”.The condensed film is formed on a plastic substrate,
It can be transferred layer by layer onto the surface of carriers having various materials and shapes, such as glass substrates.

Next, the method for forming a monomolecule/film of an organic molecule having both a hydrophilic group and a hydrophobic group, or a cumulative film thereof, which is a color-forming compound, an auxochrome compound, or a light-absorbing substance used in the present invention, will be explained in detail. Describe.

First, the organic molecule is dissolved in a volatile solvent such as benzene, chloroform, etc., and spread on the aqueous phase 11 in water+e10 of the monomolecular cumulative film forming apparatus schematically shown in FIG. 3 using a cylinder or the like.

As the solvent evaporates, the organic molecules develop on the water phase 11 with the parent tree groups 12 facing the water phase and the hydrophobic groups 13 facing the gas phase.

Next, to prevent the precipitates (organic molecules) from freely diffusing and spreading over the aqueous phase 11, a partition plate (or float) 14 is provided to limit the spread area and control the aggregation state of the substances. , obtain a surface pressure n proportional to its collective state. By moving the partition plate 14, the developed area can be reduced to control the aggregation state of the film material, and the surface pressure can be gradually increased to set the surface pressure (2) suitable for producing a cumulative film. By gently vertically moving the clean substrate 14 up and down while maintaining this surface pressure, the monomolecular film 16 is transferred onto the substrate. The monomolecular layer 16 is manufactured as described above, and the monomolecular layer cumulative film 17 is formed by repeating the above-mentioned operations to form a desired cumulative number of monomolecular layer cumulative films.

For example, when a substrate 15 with a hydrophilic surface is pulled out of water in a direction transverse to the water surface, parent wood groups of the organic molecules are removed from the substrate 15.
A side facing monolayer 1B is formed on the substrate 15. When the substrate 15 is moved up and down as described above, the monomolecular layer 1B is stacked one by one in each step. Since the direction of the film-forming molecules is reversed in the pulling step and the dipping step, according to this method, there is a gap between each layer. In this case, a so-called Y-type film is formed in which the parent wood groups of the organic molecules and the parent wood groups and the hydrophobic groups of the organic molecules face each other (Figure 4(a)).

The Y-type film is strong because the hydrophilic groups and hydrophobic groups of the organic molecules face each other.

In contrast, only when lowering the substrate 15 into the water,
There is also a method of transferring the organic molecules onto the substrate surface.

In this method, there is no change in the direction of the film-forming molecules even if they are accumulated, and in all layers the hydrophobic groups are directed to the substrate 15 side.
A type film is formed (FIG. 4(b)). On the other hand, a cumulative film in which parent wood groups in all layers face the substrate 15 side is called an X-type film (FIG. 4(C)).

The X-type film is obtained by transferring organic molecules to the substrate surface only when the substrate 15 is lifted out of the water.

The monomolecular film and monomolecular layer cumulative film formed on the substrate by the above method have high density and a high degree of order and orientation, and by configuring the recording layer with these films, photothermal Accordingly, it is possible to obtain a recording element having a high-density and high-resolution recording function capable of performing digital recording. Further, as can be seen from the principles thereof, these film forming methods are very simple methods, and a recording element having the above-mentioned excellent recording function can be provided at low cost.

The substrate on which the monomolecular film or monomolecular cumulative film in the present invention is formed as described above is not particularly limited, but if a surfactant is attached to the surface of the substrate, when the monomolecular layer is transferred from the water surface, the monomolecular Since the film is disturbed and a good monomolecular film or monomolecular layer stack cannot be formed, it is necessary to use a substrate with a clean surface.

The monomolecular film or monomolecular layer stack on the substrate is sufficiently strongly fixed and hardly peels off from the substrate or makes a peeling sound. An adhesive layer can also be provided between the layer stacks. Furthermore, the adhesion force can be strengthened by selecting the monomolecular layer formation conditions, such as the hydrogen ion concentration of the aqueous phase, the ion species, the water temperature, the rate of raising and lowering the carrier, or the surface pressure.

An example of the structure of an optical recording element according to the present invention manufactured by the method described above is shown in FIG. 1, as shown in FIG. It consists of 8 layers 4 and a light absorbing layer 3 made of a light absorbing substance interposed between layers A and B, and all of these layers are a laminate consisting of a monomolecular film or a cumulative film thereof, and the 8 layers 4 is supported on a substrate 1 and laminated in the order of substrate/B layer/light absorption layer/A layer.

Furthermore, as another example, the A layer of the laminate may be used as a substrate.

The B layer may be supported in the order of the substrate/A layer/light absorption layer/B layer, or the laminate may be stacked on top of each other to form the bottom layer A.
The layer or B layer may be supported on the substrate.

Since the optical recording element according to the present invention is constructed by separating the A layer and the B layer by a light absorption layer, by melting or sublimating the light absorption layer by infrared irradiation and making holes at desired positions, The color-forming compound of layer A and the auxochrome compound of layer B come into contact and a color-forming reaction proceeds, forming a color-forming point at the position and recording information.

Therefore, the optical recording element according to the present invention can be mainly used as an optical disc. FIG. 5 shows an example of an information storage device having an optical pickup optical system for writing or reading information from the optical disc.

The information record tI! The apparatus is composed of a writing means consisting of a control circuit 27 and an optical pickup optical system, an optical recording element according to the present invention, and a reading means consisting of an output circuit 28 and an optical pickup optical system.

Writing is performed as follows. The control circuit 27 controls the oscillation of the semiconductor laser 26. Therefore, the input information is converted into an optical signal by the control circuit 27 and the semiconductor laser 26. The optical signal 28 passes through the optical pickup optical system shown in FIG. 5, forms an image on the recording layer of the optical disc 18 which is rotating synchronously, and is recorded in color by the coloring mechanism described above.

Reading is performed as follows. Low-output continuous wave light emitted from the semiconductor laser 26 is used as the reading light. Since the output is low, color recording is not performed during reading. Alternatively, another visible light source may be used as the reading light source.

The reading light beam forms an image on the substrate surface of the optical disk 18 and is reflected, but since the reflectance differs between the coloring point and the non-coloring point, this reflected light is applied to the light receiving surface of the photodiode 25 through the optical pickup optical system. This converts the signal into an electrical signal and reproduces and reads it.

In order to increase the contrast of the reproduced signal and improve the image quality, it is preferable to provide a reflective layer of metal such as aluminum on the substrate of the optical recording element.

The thickness of the metal reflective layer is preferably 1.000 A to 2,000 A. Other dielectric mirrors can be used as needed.
;1゜Furthermore, a protective layer may be provided on the surface of the outermost layer to protect the Ai, B layer, light absorption layer, etc. Materials for such a protective layer include dielectrics such as 5i02, plastic resins, Other polymerizable LB films and the like are suitable.

[Example] Hereinafter, the present invention will be briefly and concretely explained with reference to Examples. In the following, unless otherwise specified, "1 part" means "part by weight" and "1%" means "% by weight."

Synthesis Example 1 (Synthesis Example of Light-Absorbing Substance) After mixing and dissolving 10 parts of -'-urea of vanadium phlocyanine 7-n and 1 part of a 10-15% phosphoric acid aqueous solution, 2 parts of phthalic anhydride and 2 parts of VOCJI were mixed and dissolved. (vanadyl salt)
10 parts and 8 parts of anhydrous phthalcyanine derivative represented by formula (I) C-0-C2H5,
It was heated at 100°C for 5 hours. After cooling.

After adding 100 parts of a 2% dilute NaOH aqueous solution and hydrolyzing, the product was separated by chromatography, and the product was expressed by the formula (IF) [in the formula (■), R represents 11" C-0-02Hs CH(CH2)/9 ClO3]. 0.1 part of the desired substance (vanadium phthalocyanine derivative) was obtained.

Synthesis Example 2 (Synthesis Example of Color-Forming Compound) Lysulviolate chlorine; - 1 part of the doaminobenzoic acid derivative represented by formula (III) and 1 part of Michler's hydrol represented by formula (IV) H 1 part of acid) was added and the mixture was refluxed for 8 hours to produce triphenylmethane conductors represented by the formula (V) (CH2), CH3.

Next, the triphenylmethane derivative of the product was converted into lead dioxide (
1 part)) After heating in sulfur for 3 hours in the presence of the formula (V(CH2), 70H).

A crystal violet lactone derivative represented by was obtained.

Next, by adding an aqueous solution of caustic soda to this and cyclizing it.

Crystal violet lactone derivative represented by formula (■) (OH2), CH3 0.
Got 2 copies.

Example 1 (1) Method for Forming Layer B A sufficiently cleaned glass (disc) substrate on a disk with a thickness of 10+ am and a diameter of 18 h+* was prepared with an auxochrome compound using the monomolecular accumulator described above. A monomolecular cumulative film of araxic acid was formed.

The method for forming the monomolecular film of alaxic acid tallQ was performed as follows.

After submerging the substrate in the water so that it is perpendicular to the water surface, a chloroform solution of araxic acid with a concentration of 2 x 10'mal/jL is dropped onto the water surface to spread a monomolecular film on the water surface. Set the surface pressure to 30 dyne/c,
A monomolecular cumulative film (Y-type film) having 27 layers was created by moving the substrate up and down at a speed of 2 cm/win.

By the same method, samples of monomolecular cumulative films of 1 layer, 50 layers, 200 layers, and 400 layers were obtained.

(2) Method for forming a light-absorbing layer Next, layer B formed on the glass substrate of each sample obtained in (1) above is coated with a light-absorbing substance using the single-molecule accumulator described in Ih. A monomolecular cumulative film of vanadium phthalocyanine derivatives was formed.

The method for forming a monomolecular cumulative film of /henacium phthalocyanine derivative was performed as follows.

After submerging the substrate in water so that the substrate on which layer B was formed is perpendicular to the water surface, a solution of the vanadium phthalocyanine derivative in chloroform with a concentration of 2 x 10' mol/fL was dropped onto the water surface to obtain 11 g of single molecules. The surface pressure developed on the water surface is set to 30 dyne/c, and the speed is set to 2 c.
A monomolecular cumulative film (Y-type film) was prepared for each sample by moving the substrate up and down at a rate of m/win to accumulate the layers shown in Table 2.

(3) Method for Forming Layer A Next, on the light absorption layer formed on the glass substrate of each sample in (2) above, a crystal violet lactone derivative, which is a color-forming compound, was deposited on the light absorption layer formed on the glass substrate of each sample using the single molecule accumulator described above. A monomolecular cumulative film was formed.

The method for forming a monomolecular cumulative film of the crystal violet lactone derivative was performed as follows.

After submerging the substrate in an acidic solution of pH 4 so that the substrate on which the 8 layers and the light absorption layer were formed is perpendicular to the water surface, the crystal violet lactone derivative was added at a concentration of 2×10'
Make a 1/41 chloroform solution and drop it onto the water surface to spread a monomolecular film on the water surface at a surface pressure of 30 dyne/am.
and move the board up and down at a speed of 2 cm/win.
A monomolecular cumulative film (Y-type M) in each layer shown in the table was prepared for each sample.

(4) Performance test The optical recording element according to the present invention manufactured by the above-mentioned method and a conventional optical disk having a similar structure (all of which are constructed without using a monomolecular film or a cumulative film thereof) were used as a comparative example.
After recording under the following recording conditions using the information storage device shown in the figure, the performance of both was compared by reading and reproducing.

(Recording conditions) Semiconductor laser wavelength: 830n layer laser output: 6 to 9 mW Recording frequency: 5 MHz Optical disk rotation speed: 1,800 rpm or higher, reading was performed at a laser output of 1 -, and the signal/noise ratio was determined. Shown in Table 2.

Notes to Table 2: Zero indicates a comparative example, and each layer was formed by a spin coating method.

From the results in the ftIJ2 table, when comparing No. 1 (when each layer is made of a monomolecular film) and No. 8, it is recognized that No. 1 is significantly superior in signal/noise ratio. No. 1 and No. 8 have almost the same film thickness, but this difference in performance appears to be because No. 1 has fewer defects such as pinholes than No. 1. Similarly, No. 2
Comparing No. 5 (when each layer is composed of a monomolecular cumulative film) and No. 7, it is recognized that No. 2 to No. 085 is superior in signal/noise ratio.

C Effect of the invention] As explained above, the optical recording element according to the present invention has a layer A, a layer B
Since all of the light absorbing layer 5 and the light absorption layer are composed of a monomolecular film or a layer formed of a cumulative film thereof, there are excellent effects as shown below.

(1) Compared to an optical recording element that does not use a conventional monomolecular film or a cumulative film thereof, the b/noise ratio is higher, and the reliability of recording can be improved. .

(2) Physical defects such as pinholes in optical recording elements can be significantly reduced.

(3) Higher density recording is possible than with conventional optical recording elements.

(4) It is possible to increase the area of the optical recording element.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the optical recording element according to the present invention, FIGS. 2(a) to 2(C) are explanatory diagrams showing the recording process of a conventional optical recording element, and FIG. The figure is a schematic cross-sectional view of the monomolecular cumulative film forming apparatus, and Fig. 4(a) to Fig. 4(
c) is a manufacturing process diagram of a monomolecular cumulative film, and FIG. 5 is a block diagram of an information storage device.

Claims (1)

[Claims] (1) A layer consisting of a normally colorless or light-colored color-forming compound, a B layer consisting of an auxochrome compound that develops color when in contact with the color-forming compound, and light absorption interposed between the A layer and the B layer. (a) the A layer is a monomolecular film of a color-forming compound or a cumulative film thereof; and (b) the B layer is a monomolecular film of an auxochrome compound or a cumulative film thereof. (c) An optical recording element characterized in that the light absorption layer is composed of a monomolecular film of a light-absorbing substance or a layer consisting of a cumulative film thereof.