JPS61239444A - Laser light heat-sensitive recording medium - Google Patents

Abstract

PURPOSE:To obtain a reloadable optical recording medium having high contrast and capable of being recorded in high density by providing a thermochromic org. material having hysteresis and a light absorbent for rapidly changing the temp. of the thermochromic org. material on a substrate. CONSTITUTION:A layer 12 of a laser light heat-sensitive recording medium contg. a thermochromic org. material and a light absorbent 13 is formed on a substrate 11. A maximally colored state and a lowly colored state which is generated when the maximally colored state is further heated are stably present at ordinary temp. in the thermochromic org. material and both staes are reversibly changed to each other by heating with laser light and cooling. In one state of recording, the material is colored at room temp. and has specified light absorption. When the material in the colored state (maximally colored state) is heated, thermochromism by which color development in the colored region is weakened is generated by heating and the region is returned to the original colored region by ordinary decrease in temp. However, the region is fixed at a state wherein the color development in the colored region is weakened (another state of recording) by rapid cooling.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a laser beam thermosensitive recording medium, more specifically, a laser beam thermosensitive recording medium in which recording can be erased and reproduced on an optical recording medium that performs optical recording using a laser. It's about the medium.

[Background of the invention]

In recent years, light from lasers and other sources has been focused into a minute spot,
Optical recording systems that perform optical recording on recording media are being actively researched. These recording media can be broadly classified into three types.

The first is a playback-only optical video disc, the Compact Audio Disc (CD).

These media have information to be reproduced recorded in advance, and the user cannot change any of the recorded information.

The second one is the so-called Write-once.
once) or DRAM (direct-read)
It is an optical recording medium of the after-write type, and is often supplied in the form of a disc with a recording position and number written in advance, called a briformant, and has a free area where the user can freely record. This kind of DRA
A Te-based recording thin film or an organic dye thin film is usually used for -type optical recording materials. The advantage of DRAW type optical recording materials is that once recorded information is stably retained. However, once recorded information cannot be erased, and repeated recording is not possible.

The third type includes magneto-optical recording and media using phase change optical recording materials. Such media are
This was done in view of the fact that the above-mentioned first and second recording media cannot be repeatedly recorded. However, since magneto-optical recording uses a magneto-optic effect (usually the Kerr effect due to reflected light) with a variation of several degrees or more, the S/N margin in recording and reproducing information is small, and special enhancement effects are not required. It was necessary to take measures such as providing an overcoat film to increase the film thickness. Furthermore, as a recording material, there have been problems with deterioration over time such as air oxidation of the magneto-optical thin film itself and collapse of anisotropy. Phase change optical recording materials include methods using crystallization and amorphization of chalcogenide glass, Te
There is a method that uses phase transition of a thin film layer made by adding SnsGe to an oxide. The disadvantage of this type of phase transformation recording method is that
This is because the reflectance (optical change) of the recorded area (amorphous) and the non-recorded area (crystalline) is small, and the metal itself deteriorates in the air, such as oxidation. In addition, due to repeated writing and erasing, there may be unwritten notes due to phase separation of the constituent materials.
This is a big problem as it sometimes leaves some residue.

Because of the above, it is desired to develop a high contrast and rewritable optical recording material using a new principle.

[Summary of the invention]

The present invention was made in view of the above points, and it is an object of the present invention to eliminate the drawbacks of conventional optical recording materials, that is, to create an optical recording medium that has high contrast, is rewritable, and is capable of high-density recording. The purpose is to provide

Therefore, in the laser beam thermosensitive recording medium according to the present invention, a maximum colored state and a lower colored state obtained by further heating the maximum colored state stably exist at room temperature, and are reversible by irradiation with laser light. The present invention is characterized in that a thermochromic organic material having hysteresis and a light absorbing agent for rapidly changing the temperature of the thermochromic organic material is provided on the substrate.

According to the present invention, a thermochromic material is used as a coloring agent, which can reversibly change the maximum colored state and a lower colored state produced by further heating the maximum colored state by irradiating laser light. Therefore, it has the advantage of being able to perform good recording with high contrast and high density.

[Detailed description of the invention]

FIG. 1 is a cross-sectional view of an example of a laser beam thermosensitive recording medium according to the present invention, in which 11 is a substrate, 12 is a laser beam thermosensitive recording medium layer containing a thermochromic organic material, and 13 is a layer containing a thermochromic organic material. It shows a light absorbent dispersed in the laser beam thermosensitive recording medium layer.

As is clear from FIG. 1, the laser beam thermosensitive recording medium according to the present invention includes a laser beam thermosensitive recording medium layer 12 containing a thermochromic organic material and a light absorbing agent 13 formed on a substrate 11.

FIG. 2 is a sectional view of a second configuration example according to the present invention, in which 21 is a substrate, 22 is a thermochromic organic material layer,
23 is a light absorbent layer.

According to this configuration example, a thermochromic material layer (coloring agent layer) 22 is laminated on the substrate 21, and this coloring agent 1i
22, a light absorbent layer 23 is further laminated to constitute an optical recording medium.

FIG. 3 is a cross-sectional view of a third configuration example according to the present invention, in which 31 is a substrate, 32 is a thermochromic organic material layer (
33 is a light absorber layer.

As is clear from this figure, in this configuration example, a light absorber W133 is provided on a substrate 31, and a thermochromic organic material layer 32 is further laminated on this light absorber layer 33.

FIG. 4 is a sectional view of a fourth configuration example according to the present invention, in which 41 is a substrate, 42 is a thermochromic organic material N (
Color forming agent m), 32 is a light absorbing agent layer.

As is clear from this figure, in this configuration example, a thermochromic organic material m42 is provided on the substrate 41, and a light absorbing agent WI43 is provided on this thermochromic organic material layer 42.
In addition, a thermochromic organic material Fii 42 is further laminated on this light absorbent layer 43.

As described above, in the laser light thermosensitive recording medium according to the present invention, the method of providing the thermochromic organic material and the light absorbing agent on the substrate is basically not limited. As described above, a light absorber may be mixed in the thermochromic organic material layer, or the thermochromic organic material layer and the light absorber layer may be provided separately on the substrate. When the thermochromic organic material layer and the light absorber layer are separately laminated, the product Ff! The i order is not limited either,
Stacking can be done in various orders.

The aforementioned substrate 11.21.31.41 depends on the medium readout method, but for example, in the case of a normal transmitted light readout method, an acrylic resin plate (DMMA), a polycarbonate resin plate (PC), a glass plate, or a quartz plate is used. A transparent substrate such as can be used. Further, when reading using reflected light, any material with a smooth and uniform surface, such as a metal plate, paper, or ceramic, can be used.

Thermochromic organic material M21.31.41 or laser light thermosensitive recording medium layer 1! The thermochromic organic material constituting the material stably exists at room temperature in a maximum colored state and a state with a lower colored state that changes when the maximum colored state is further heated, and when heated and cooled by laser light, It is a thermochromic organic material that has a hysteresis that reversibly changes to both colored states, and in one recording state, it develops color at room temperature, has a specified light absorption,
However, when this laser beam thermosensitive recording medium is heated, thermochromism occurs in which the color development in the colored areas is weakened.

This thermochromism returns to the original coloring region when the temperature is normally lowered (slow cooling). However, as will be described later, the color development in the colored areas was weakened by rapid cooling after heating f! (another state of record) was found to be fixed.

FIG. 5 is a schematic diagram for explaining such a colored state.

In FIG. 5, the vertical axis shows the coloring density of the thermochromic organic material, and the horizontal axis shows the temperature. Starting point A of the curve in Figure 5
is a state in which the heat-sensitive organic material (color forming material: a thermochromic organic material in which a color former and a color developer described below are separated) is completely separated, and the color density is almost 0. When this is gradually heated, the coloring material melts, mixes, develops color, and reaches state B. At this point, if the temperature increase due to heating is stopped and the temperature is lowered, the color density remains unchanged, only the temperature decreases and state C is reached, and the color development is fixed.

In other words, color develops through the A-B-C state (maximum colored state). This is the recording method used for conventional thermal recording paper. In the present invention, this maximum colored state (C state) is defined as one recording state. In this case, if a colored light absorber is mixed in the laser beam thermosensitive recording medium layer, a color difference will be created in which the light absorber and the thermochromic organic material are mixed, but since the amount of the light absorber is not so large, The color spacing is mainly due to the color development of thermochromic organic materials.

However, if the temperature continues to rise even after state B has passed, the color density of the thermochromic organic material decreases. In other words, along the route of the ^-n-D state, a weakly colored state ft (state !3D) is reached. If heating is stopped in this state and it is gradually cooled, it will return to the C state along the D - B - C state path, and the coloring density will eventually be fixed at the C state, but if it is rapidly cooled when it reaches the D state, It has been found that state E is reached in which the temperature drops to room temperature while maintaining the color density of state. In the present invention, this E state is one of the recording states. In this case, if a colored light absorber is mixed in the thermochromic organic material, the laser beam thermosensitive recording medium layer will change color to a color with a strong tone of the light absorber.

When the laser beam thermosensitive recording medium in the E state is heated up to a temperature that reaches the B state) and then slowly cooled, it returns from the E state to the B state and then back to the C state. That is, a laser beam thermosensitive recording medium in the C state can be brought to the E state by heating it by irradiating it with a laser beam to a temperature at which it becomes the D state, and rapidly cooling it. By heating the thermosensitive recording medium to a temperature at which it becomes the B state and gradually cooling it, it can be brought into the C state.In other words, the laser beam thermosensitive recording medium can reversibly change between the C state and the E state. be.

Thermochromic organic materials having such hysteresis are not fundamentally limited in the present invention. Any thermochromic organic material that maintains a glassy state can be used. For example, crystal violet lactone, malachite green lactone, red colored leuco dyes (e.g. RED-D
CF: Oudugaya Chemical ■, trade name), green leuco dye (e.g. QZ-1012, QZ-1010: Oudugaya Chemical ■, trade name), black leuco dye (e.g. Tl-107: Oudugaya Chemical ■, product) It can be a thermochromic organic material that is a combination of one or more leuco dye color formers such as (name) and one or more solid organic acid color developers such as phenolphthalene, thymolphthalene, fluorescein, and bisphenol A. . Of course, the thermochromic organic material is not limited to a combination of a color former and a color developer, but as long as the color former alone exhibits hysteresis as described above, it can be used alone as a thermochromic organic material. it is obvious.

The light absorber used in the present invention is provided to cause a rapid change in temperature of the thermochromic organic material, and therefore may absorb laser light and cause a sudden change in the temperature of the thermochromic organic material. It can be anything.

When a thermochromic organic material in the C state is irradiated with short pulses of high-power light such as a laser beam focused into a minute spot of about 1 μm mist, the irradiation spot portion is due to the light absorber and the high-power laser beam. rises rapidly. When the laser beam irradiation is stopped, most of the area near the spot is close to room temperature, so heat is rapidly lost and the spot is rapidly cooled, and the spot shifts to the E state.

It is clear that the light absorbing agent as described above differs depending on the type of laser light used for recording.

For example, when using a semiconductor laser beam, it is preferable to absorb the light (1.5 to 600 μ(1)) of the semiconductor laser beam. For example, Te5HisIn,
, Sns Ge etc., vanadium phthalocyanine, aluminum phthalocyanine, bis-[cis-1.2-tolyl]ethylene-1,2-dithiolate ninkel, bis-(
One or more types of nickel (1chloro-3,4 dithiophenolate), dimethylaminophenol squarylium, diethylaminophenol aquarium, etc. can be used.

The method of manufacturing such an optical recording medium is not particularly limited. For example, it can be manufactured by a spin cord method, a casting method, a vacuum deposition method, a codeposition method, or the like.

For example, a leuco dye, a solid acid, and a light absorber are dissolved in a solvent. In this case, the light absorber is preferably the above-mentioned organic dye that can be dissolved in a solvent. Such a solution initially exhibits coloration due to the leuco dye and solid acid, and as a solvent is added, the color disappears, and finally it exhibits the color tone of only the light absorber. Next, the solvent is removed from this solution by casting, spin coding, etc., to form a thin film. As the solvent is removed and dried, an absorption spectrum in which the coloring caused by the leuco dye and organic acid overlaps with the light absorbing agent begins to appear (maximum colored state M4).
. This is used as a laser light-sensitive thermochromic medium layer.

Furthermore, when manufacturing the optical recording medium layer by vacuum deposition, the leuco dye and solid acid are deposited onto the substrate from an evaporation boat. The two sources can be deposited from separate boats or from the same boat. At the same time, a light absorbing agent is simultaneously vapor-deposited from a vapor deposition boat different from these boats to produce a laser light heat-sensitive medium layer. In this case, the light absorbent may be an organic substance, an inorganic substance, or a metal, as long as it can be vapor-deposited. When a laser light heat-sensitive medium is produced by this method, the coloring of the leuco dye and solid acid disappears from the laser light heat-sensitive medium layer, and the layer exhibits an absorption spectrum of only the light absorbent (state E). When this is heated to a predetermined temperature, it changes to the maximum colored state (state C) as in the case from a solution.

When recording on an optical recording medium that is in the C state before recording, for example, using such a laser beam thermosensitive recording medium,
For example, a recording focus (E state) can be formed by irradiating with a semiconductor laser or the like. In this case, the coloring density of the thermochromic organic material decreases, so if the light absorber is colored, the coloring is mainly caused by the color of the light absorber. When the light absorber is colorless, the color of the thermochromic organic material is low.

Below is the fruit! ? J will be explained.

Example 1 Crystal violet lactone (C
VL ), phenolphthalene (PP) as solid acid
, methylene chloride/vanadium phthalocyanine as a light absorbing agent in the ratio of 47.5 parts, 47.5 parts, and 5 parts, respectively.
A thin film (laser light thermosensitive recording medium layer: state C) was prepared by dissolving it in a mixed solvent of ethanol (1:1) and spin-coding it on a glass substrate.

This laser beam thermosensitive recording medium layer was a thin film with a deep ultramarine blue color and a good surface condition.

A semiconductor laser (wavelength 83
0 nm) (laser power (8 mW, on the medium) 1°5 μ-φ) and irradiated with a 200 n5ec pulse.

As a result, the irradiated area formed a recording focus with a thin edge (the color of the light absorbing agent) with an erased ultramarine blue color. Next, this bit was irradiated for 10 μsec with a semiconductor laser (830 ns+, laser power 1 mW, 1.5 μm diameter on the medium). Then the recording pit returned to its original ultramarine state.

This erasure and reproduction of recorded pits could be repeated many times.

Example 2 Red coloring leuco dye RED-DCF as 0 ico dye,
Thymol phthalene (TP) as a solid acid, nickel bis-[cis-1,2-tolyl]ethylene-1゜2 dithiolate as a light absorber, (Ni dithiolate-based near-infrared absorber PA-1006: Mitsui Toatsu Chemical Co., Ltd.: Product 45 parts, 45 parts, and 10 parts, respectively, were dissolved in acetone and spin-coated to produce a thin film (laser light thermosensitive recording medium layer) on an acrylic substrate.

This laser beam thermosensitive recording medium layer exhibited a bright red color (state C).

When the same laser pulse as in Example 1 was irradiated to form recording pits, recording pits with transparent thin edges were formed. When the recorded pits were repeatedly erased and reproduced, good recording and erasure were achieved.

Example 3 Green coloring leuco dye QZ-1012 as Oico dye,
Phenolphthalene as a solid acid was taken from a Ta boat.
1 xio-5Torr or less, set 81 to 50 in advance
Vacuum deposition was performed to a film thickness of 3000 on a glass substrate on which 0 was deposited (E state).

This laser beam thermosensitive recording medium is heated using a semiconductor laser beam (wavelength 83
0 nm, power 0.5 mW, spot diameter 1.5 μm
The DC light of φ) was scanned in a rectangular XY manner using a galvanometer mirror. As a result, the medium became colored green.

Next, when this colored part was irradiated with a semiconductor laser having a power of 8 mW and a width of 1.5 .mu.m with a pulse width of 200 nsec, recording pits with a transparent thin edge color were formed which lost their green coloring. Further, when DC scanning was repeated under the above conditions, recording and erasing of pits could be performed with good reproducibility.

〔Effect of the invention〕

As explained above, the laser beam thermosensitive recording medium according to the present invention can be manufactured using a simple method and apparatus such as spin cord and vacuum evaporation. Another advantage is that recording and erasing can be performed using a semiconductor laser, which is easy to modulate and control intensity.

Furthermore, since the recording and erasing principle of the recording pits is based on thermochromism, it has the property of being able to withstand repeated recording and erasing with little flammability compared to photochromism, which involves the breaking of chemical bonds.

In addition, the recording contrast has a clear color tone in the visible area,
Since this method involves decoloring, it has a high contrast S/N ratio. In addition, the recording resolution is on the μ network order and it has a high-density recording capacity, like ordinary optical disk materials.

As described above, the laser beam thermosensitive recording medium according to the present invention is a completely new laser beam thermosensitive recording medium that enables fine recording and recording rewriting using semiconductor laser light.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example of a laser beam thermosensitive recording medium according to the present invention, FIG. 2 is a sectional view of another structural example of a laser beam thermosensitive recording medium according to the present invention, and FIG. 3 is a sectional view of a laser beam thermosensitive recording medium according to the present invention. FIG. 4 is a cross-sectional view of a third configuration example of the medium, and FIG.
The figure shows the thermochromism of the laser beam thermosensitive recording medium.
It is a figure showing a hysteresis curve. 11... Substrate, 12... Laser light thermosensitive recording medium layer,
13... Light absorber, 21.31.41... Substrate, 22.32.42...
Thermochromic organic material layer, 23.33.43...
Light absorber layer.

Claims (3)

[Claims] (1) A maximum colored state and a less colored state that occurs when the maximum colored state is further heated stably exist at room temperature, and reversibly change to both colored states by irradiation with laser light. 1. A laser beam thermosensitive recording medium, characterized in that a thermochromic organic material having hysteresis and a light absorber for rapidly changing the temperature of the thermochromic organic material are provided on a substrate. (2) The laser light thermosensitive recording medium according to claim 1, wherein the thermochromic organic material is a mixture of a leuco dye and an organic solid acid. (3) The light absorbent is Te, Bi, In, Sn, Ge.
, vanadium phthalocyanine, aluminum phthalocyanine, bis-[cis-1,2-tolyl]ethylene-1,2
Claim No. 1 characterized in that it is one or more selected from the group consisting of nickel dithiolate, nickel bis-(1chloro-3,4 dithiophenolate), dimethylaminophenol squarylium, and diethylaminophenol aquarium. The laser beam thermosensitive recording medium according to item 1 or 2.