JPS6085448A - Optical recordidng medium - Google Patents

Abstract

PURPOSE:To obtain a high density optical recording medium which permits erasing of recorded information and reiterative use by forming the cumulative film of the monomolecular layers of specific photopolymerizable monomers on a base plate and using said film as a recording layer. CONSTITUTION:The cumulative film of the monomolecular layers of >=2 kinds of photopolymerizable monomers having a hydrophilic group, hydrophobic group and unsatd. bond in a molecule is formed on a base plate and is used as a recording layer. An olefin monomer having a long chain alkyl group of 10-30 carbon atoms is preferably used as the above-mentioned photopolymerizable monomer. The cumulative film of the above-mentioned monomolecular layers is formed in the following way for example: The photopolymerizable monomer is dissolved in a solvent to develop the monomer in an aq. phase and to deposit the monomer like a film. A partition plate is then provided to limit the developing area and to control the aggregating condition of the film material. The surface pressure proportional to the aggregating condition is obtd. The partition plate is moved to decrease the developing area and to control the aggregating condition of the film material, thereby increasing gradually the surface pressure. The surface pressure suitable for production of the cumulative film is thus set. While the surface pressure is maintained, the clean base plate is gently perpendicularly moved up and down, by which the monomolecular film is transferred onto the base plate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording medium having a monomolecular layer cumulative film of a photopolymerizable monomer as a recording layer.

Optical recording media that use a thin film of an organic compound as a recording layer have been known for some time.
It is also disclosed in Japanese Patent Application Laid-open No. 16948 and Japanese Patent Application Laid-Open No. 125246/1983. All of them relate to laser recording media in which recording layers are made of organic dyes and recording and reproduction are performed using laser beams. In particular, the medium disclosed in JP-A-58-125246 uses a thin film of a cyanine dye represented by the general formula (I) as a recording layer. A cyanine dye solution represented by formula (I) is coated onto a plastic substrate to a thickness of 1000X or less, for example about 300X, using a spin coater or the like to form a thin film. If the molecular distribution and orientation within the film are random, light scattering will occur within the film upon light irradiation, and when viewed microscopically, the degree of chemical reaction that occurs will differ each time the film is irradiated with light. Therefore, it is desirable for the recording medium to have a uniform molecular distribution and orientation within the film, and it is also required that the film thickness be as thin as possible in order to achieve high recording density. However, when using the coating method, the film thickness is limited to approximately AOOX, and it is difficult to solve the problem that the molecular distribution and orientation within the film are random.

A diacetylene compound cumulative film, which has been proposed as a resist material with high photon efficiency and excellent resolution, has been used not only as a resist material but also as a thin film electrical
JP-A-56-42229, JP-A-56-43220, etc. show that the present invention is also applied to optical devices, electro-acoustic devices, pressure/pyroelectric devices, etc.

Recently, Japanese Patent Application Laid-Open No. 111029/1983 discloses an improvement in the method for producing a diacetylene compound cumulative film. The diacetylene compound cumulative film on the substrate produced according to the invention can be polymerized by irradiation with ultraviolet rays to form a diacetylene compound polymer film, or masked and irradiated with ultraviolet rays to partially polymerize and remove the unused material. The overlapping portions are removed to create shapes, which are used as thin film optical devices and integrated circuit elements.

However, all of these are limited to diacetylenization and substance C, and when used as a thin film optical device,
There is no mention of the possibility of erasing what has been recorded.

An object of the present invention is to provide a reusable high-density optical recording medium from which recorded information can be erased.

The object of the present invention is achieved by the following optical recording medium.

In other words, the object of the present invention is to create a hydrophilic group within the molecule.

This is achieved by an optical recording medium characterized in that a recording layer is formed by forming a monomolecular layer cumulative film of two or more types of photopolymerizable monomers having a hydrophobic group and at least one unsaturated bond on a substrate.

In the optical recording medium of the present invention, recording is carried out by irradiating the photopolymerizable seven polymers of the recording layer with light to cause a polymerization reaction in the irradiated area, thereby creating a difference between the non-irradiated area and the irradiated area based on the presence or absence of polymerization. Do it by making it come to life. Regeneration is then carried out by measuring the difference caused by this polymerization in various ways.

Further, the recorded information is removed by depolymerization by heating.

As the compound forming the recording layer of the present invention, a wide range of photopolymerizable heptamers having a hydrophilic group, a hydrophobic group, and at least one unsaturated bond in the molecule can be used.

Such a photopolymerizable monomer has the general formula (IIa).

(IIb) and (flr).

R,=CH=CH-R,(TIa)R,-CH=C
H-R, -CH=CH-R1 (■b) R, -CmiC-C
-R, (III) In the above formulas (Ua) and (m), either a hydrophilic site and a hydrophobic site are present in the R part or in the R8 and R1 parts, or R, is R1
is hydrophobic in relation to R8, and R, is hydrophilic in relation to R8. In the above formula (TIb), R,,
Both a hydrophilic site and a hydrophobic site are present in either the R, or R8 portion, or one of the R, R2, and R8 portions is hydrophobic in relation to the other portion, and the remaining portion is hydrophobic. Either is hydrophilic. Especially 10 carbon atoms
A photopolymerizable heptamer having ~30 long-chain alkyl groups in at least one of the R1 part, the RI and electric parts, or the R, R, or R8 parts is desirable.

Specific examples of the photopolymerizable monomer of the present invention include the following compounds.

cH8-(CT(2)x-c=c-cmiC(CHt)
yC00HR=-(C)(,)nOH.

Xe= C1-, Br-I I-I CIO; #-
080,-@-C)I, .

-oso, -@-cg tx tl] jj The method for creating a monomolecular layer cumulative film is as follows:
For example, the Langmuir-Prodgett method (LB method) developed by Langmu%r et al. The Langmuir-Prodgett method uses a molecule with a structure that has a hydrophilic group and a hydrophobic group (=), and when the balance between the two (balance of amphiphilicity) is maintained appropriately, the molecule will float on the water surface. This is a method of creating a cumulative film of monomolecular layers by making use of the fact that the hydrophilic groups face downward and become monomolecular layers.The monomolecular layer on the water surface has the characteristics of a two-dimensional system.The molecules are sparsely formed. When they are dispersed, the two-dimensional ideal gas equation HA=kT holds true between the area per molecule A and the surface pressure H, resulting in a "gas film." Here, k is Boltzmann's constant. , T is the absolute temperature.If A is made sufficiently small, the intermolecular interaction becomes strong and a two-dimensional solid "condensed film (or solid film)" is formed.The condensed film is transferred layer by layer to the surface of a substrate such as glass. Using this method, the monomolecular layer cumulative film of the present invention can be produced, for example, as follows.

First, a photopolymerizable monomer is dissolved in a solvent, and this is spread in an aqueous phase to precipitate the photopolymerizable monomer in the form of a film. Next, to prevent this precipitate from freely diffusing on the aqueous phase and spreading too much, a partition plate (or float) is installed to limit the area of development and control the state of aggregation of the film substance, and the The surface pressure can be increased. By moving this partition plate, the developed area can be reduced to control the state of aggregation of the film material, and the surface pressure can be gradually increased to set the surface pressure H suitable for producing a cumulative film.

The monomolecular film is transferred onto the substrate by gently vertically moving the clean substrate up and down while maintaining this surface pressure.

By repeating the above operations, a monomolecular layer cumulative film having a certain degree of cumulativeness is formed.

Each monolayer has one type of photopolymerizable monomer on the same layer 14
- Must be created in The cumulative film may be a combination of two or more photopolymerizable monomers. Preferably, a combination of two to three types is used.

A method of combining is one, for example, two kinds of photopolymerizable monomers a.

b from the board side (ab)nt ("mbt)n*
(b)n (n+m,) is a positive integer of 1 or more), or may be accumulated in a completely random order, and various silk combinations are possible.Depending on the characteristics of the photopolymerizable monomer used, etc. , the combination method is determined.

The suitable thickness of the recording layer is 30X to 3 cotton, especially 100
X to 3000X is suitable. The selection of the type of photopolymerizable monomer, the degree of accumulation, etc. are determined in consideration of this.

In order to transfer the monomolecular layer onto the substrate, in addition to the vertical dipping method described above, methods such as horizontal deposition method and double rotation cylinder method are used. The horizontal deposition method is a method in which substrates are brought into horizontal contact and transferred, and the rotating cylinder method is a method in which a cylindrical substrate is rotated on the water surface to transfer a monomolecular layer onto the surface of the substrate. In the vertical immersion method described above, when the substrate is lowered in a direction across the water surface, a monomolecular layer with the hydrophilic groups facing the substrate is formed on the substrate as the first layer. When the substrate is moved up and down as described above, one monolayer is overlapped with each step. Since the direction of the film-forming molecules is reversed between the pulling process and the dipping process, according to this method, a Y-shaped film is formed in which hydrophilic groups and hydrophilic groups and hydrophobic groups face each other between each layer. On the other hand, the horizontal deposition method is a method in which the substrate is brought into horizontal contact with the water surface and transferred, and a monomolecular layer with hydrophobic groups facing the substrate is formed on the substrate. In this method, there is no change in the orientation of the film-forming molecules even when the films are accumulated, and in all cases an X-shaped film is formed in which the hydrophobic groups face the substrate side.

On the other hand, a cumulative film in which all the layers have hydrophilic groups facing the substrate side is called a type 2 film. The rotating cylinder method is a method in which a cylindrical substrate is rotated on the water surface to transfer a monomolecular layer onto the surface of the substrate. The method of transferring the monomolecular layer onto the substrate is not limited to these methods, and when using a large-area substrate, a method of extruding the substrate from a substrate roll into an aqueous phase may also be used. Furthermore, the directions of the hydrophilic groups and hydrophobic groups described above toward the substrate are in principle, and can be changed by surface treatment of the substrate, etc.

When the prepared optical recording medium is irradiated with light such as gamma rays, X-rays, and ultraviolet rays that supply the energy necessary for polymerization according to a certain pattern, polymerization occurs at the irradiated area as shown in equation (2).

Further, regarding the diacetylene compound represented by the general formula (m), polymerization occurs as shown in the formula (V) by light irradiation.

/\R2 These reactions occur when the distance between adjacent unsaturated bonds is 4X
This can occur in the following cases, and in a monomolecular film or a monomolecular stacked film created by the method described above, it can occur between adjacent molecules in the same layer or between adjacent molecules in the cumulative layer. It is. In addition, after polymerization, depolymerization does not occur even in the dark, and the non-irradiated parts remain monomers.
As shown in FIG. 1, recording is performed according to the pattern.

The recorded information is read, for example, by irradiation with visible light. That is, the conjugated system of monomers is destroyed by polymerization, which causes a change in the absorption wavelength of visible light. Since the maximum absorption wavelength shifts to the lower wavelength side, information can be reproduced by reading changes in the attractive spectrum (Figure 2). Therefore, in this case, information reproduction is easier when the conjugated system is longer because the change in the maximum absorption wavelength of the monomer and polymer is greater.

For regeneration, in addition to reading changes in absorption spectrum using visible light, it is also possible to read changes in volume during monomerization and after polymerization using the Schlieren method.

This method is particularly suitable for a monomolecular layer cumulative film of a compound having a structure that exhibits a large volume change between monomer and post-polymerization. In addition, instead of forming a monomolecular J-cumulative film directly on the substrate, by forming a photoconductor layer of S, ZnO, CdS, etc. on the substrate and forming a monomolecular layer cumulative film on it, It is also possible to electrically read the difference in absorbance between the monomer and the electrolyte.

Information is removed by depolymerization by heating, for example at 300-450° C. (FIG. 3).

The optical recording medium of the present invention can be used up to about 100 times, although deterioration occurs due to heating to remove information.

Although the substrate on which the photopolymerizable monomolecular layer cumulative film of the present invention is formed is not particularly limited, if a surfactant is attached to the surface of the substrate, when the monomolecular layer is transferred from the water surface, the monomolecular It is necessary to use a substrate with a clean surface because the film will be disturbed and a good monomolecular layer cumulative film cannot be obtained. Examples of substrates that can be used include glass, metals such as aluminum, plastics, ceramics, and the like.

The monomolecular layer film on the substrate is sufficiently strongly fixed and rarely peels off or peels off from the substrate.
An adhesive layer can also be provided between the substrate and the monomolecular layer stack for the purpose of strengthening the adhesive force. Furthermore, the adhesive strength can also be strengthened by selecting the monomolecular layer formation conditions, such as the hydrogen ion concentration of the aqueous phase, the ionic species, or the surface pressure.

Providing a protective film on top of the monomolecular layer stack is preferable in order to improve the chemical stability of the monolayer stack, but when selecting the film forming molecules, A monomolecular layer cumulative film was produced. 9 was dissolved in chloroform, the solution was developed in an aqueous phase, and a film was precipitated. In the same manner, the solution was dissolved in chloroform, and the solution was spread in a water tank separate from Step 9, to precipitate the solution in the form of a film. While keeping the surface pressure constant, the glass substrate whose surface was sufficiently clean and hydrophilic was gently lowered into a water tank in step 9, and the monomolecular film was transferred onto the substrate. Next, it was lowered into a water tank and the monomolecular film was transferred onto the substrate. This operation was repeated to create an optical recording medium with a recording layer having a thickness of 50 to aooo X.

Information was recorded on the created optical recording medium by irradiating it with X-rays according to the pattern. When the recorded information was reproduced using visible light with a wavelength of 420 nm, it was found that the thickness of the recording layer was 30 nm.
Reproduction was possible with a good S/N ratio on an optical recording medium of 0 to aooo X.

This optical recording medium was heated to 350° C. to remove information, and then X-ray irradiation was performed again according to the pattern to record information.

From the above, the optical recording medium of this example was capable of high-density recording on the order of molecular units, and moreover, could be used repeatedly.

Example 2 An optical recording medium was produced in the same manner as in Example 1 using the combinations of photopolymerizable monomers shown in Table 1.

Recording was performed on the manufactured optical recording medium using the light shown in Table 1, and reproduction was performed. In each case, high-density recording on the order of molecular units was possible, and by heating the medium after recording, repeated use was possible in the same manner as in Example 1.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing recording of information on the optical recording medium of the present invention, FIG. 2 is an explanatory diagram showing reading of recorded information, and FIG. 3 is an explanatory diagram showing information removal. . R1...Hydrophilic group R,...Hydrophobic group 1...Substrate 2...Light (X-rays, etc.) 6...Polymerization 4...Visible light patent applicant Canon Co., Ltd. procedural amendment 1 ) August 1, 1980 Mr. Commissioner of the Japan Patent Office ■, Indication of the case 1981 Patent Application No. 190834
No. 2, Name of the invention Optical recording medium 3, Relationship with the case of the person making the amendment Patent applicant (100) Canon Co., Ltd. 4 Agent address No. 16 Kowa Building 8, 1-9-20 Akasaka, Minato-ku, Tokyo Floor 5, Column 6 of Detailed Description of the Invention of the Specification Subject to Amendment, Contents of the Amendment In the first line from the bottom of page 15 of the specification, ``Lower the substrate'' is amended to ``Pull the substrate out of the water.''

Claims (1)

[Claims] 1. A recording layer formed by forming a monomolecular layer cumulative film of two or more types of photopolymerizable polymers having a hydrophilic group, a hydrophobic group, and at least one unsaturated bond in the molecule on a substrate. An optical recording medium characterized by the following. 2. The optical recording medium according to claim 1, wherein the photopolymerizable monomer is an olefin monomer having a long-chain alkyl group having 10 to 30 carbon atoms.