JPS5935989A - Information recording medium - Google Patents

Abstract

PURPOSE:To obtain an information recording medium especially excellent in the recording property such as the againg stability, sensitivity and N/S ratio by providing a conductive film on a recording layer as transmitting a high- density energy light irradiated more than a specified quantity. CONSTITUTION:This invension relates to an information recording medium in which an recording layer thermally varying with the irradiation of a high- density energy light by nature and the recording layer contains at least one of a high molecular liquid crystal and a mixture of a low molecular liquid crystal and a high molecular compound as main component. Said recording layer is laminated with a conductive thin film such as a metal thin film layer transmitting more than 5% of a high-density energy light irradiated. This utilizes thermal changes such as phase transfer caused in the high molecular liquid crystal thereby enabling the realization of a greater recording property such as aging stability, sensitivity and S/N ratio, harmlessness and easy mass production of the information recording medium.

Description

[Detailed description of the invention] The present invention relates to an information recording medium.

Conventionally, information recording involves irradiating a recording medium with high-density energy light such as a laser beam to cause a thermal state change (melting, evaporation, etc.), and then recording information using the resulting change in optical properties. medium is known.

As such information recording media, those using inorganic materials such as metal or semimetal thin films, chalcogen glass thin films, and organic materials such as squarylium dyes are known.
However, most of these materials are manufactured using methods such as vacuum evaporation or sputtering, so
It had several serious drawbacks, such as poor productivity (and the thin films produced had poor stability over time and many were toxic).

Furthermore, since the recording principle of the information recording medium is based on sublimation or evaporation of the material, it also has the drawback of causing contamination of the optical system and contamination of the recording medium. In order to improve this drawback, a method has been proposed in which a transparent protective layer made of acrylic resin or the like is provided on the recording layer. However, this method cannot be said to be sufficient because the sensitivity decreases due to inhibition of sublimation and evaporation due to the protective layer pressure.

In order to eliminate the drawbacks of such technology, Japanese Patent Application Laid-Open No. 57-
Japanese Patent No. 94943 discloses a laser beam recording medium characterized by forming an amorphous layer that is crystallized by heat and a light absorption layer.

Since such recording media utilize crystallization of an amorphous layer by heat buttoning, foreign substances (light-absorbing substances, etc.) in the amorphous layer interfere with crystallization, so the light-absorbing substance is removed from the amorphous layer. In order to overcome the drawbacks of the prior art, the present inventors have conducted intensive research to develop a material that can be thermally changed by irradiation with high-density energy light. A recording layer is provided on a support, and the recording layer contains as a main component at least one of a polymeric liquid crystal and a mixture of a low-molecular liquid crystal and a polymeric compound. 5% of high-density energy light
A conductive thin film such as a metal thin film layer that allows transmission
The information d■4 recording medium, which is characterized by a laminated structure with a control recording layer, is stable over time in terms of recording characteristics such as 41L1 sensitivity and SN ratio! He discovered that the samurai were superior and completed the present invention.

In addition, the information recording medium according to the present invention is harmless;
It also has the advantage of being easy to mass produce. Here, the above-mentioned "containing" means not only occupying a part of the layer but also occupying substantially 100%.

That is, according to the present invention, polymer liquid, W or less, and polymer liquid crystal include cases in which the polymer itself is a liquid crystal, as well as cases in which it is a mixture of a low molecular liquid crystal and a non-liquid crystal polymer compound. It is also described using the term polymer liquid crystal. ) causes changes such as thermal phase transition, which improves recording characteristics such as stability over time, sensitivity, and signal-to-noise ratio of information recording media, makes them harmless, and facilitates mass production. It can be achieved.

The invention will now be illustrated in detail with reference to the drawings.

According to the example shown in FIG. 1, a reflective layer 2 is provided on a substrate (support) 1, a layer 3 containing polymer liquid crystal is provided, and furthermore, 5% or more of the high-density energy light to be irradiated is transmitted. The information recording medium 13 is provided with a metal thin film layer 4 that is made of metal.

In this information recording medium, layer 3 is in the state of being coated, the liquid crystal is not oriented, and it is an optically uniform film. Next button: When this information recording medium 13 is irradiated with high-density energy light from the side of the metal thin film layer 4 and the temperature of the layer 3 containing polymer liquid crystal is raised to the point where the layer 3 is oriented, the area irradiated with light is In this case, the liquid crystal is aligned, optical anisotropy occurs, the reflectance and transmittance decrease, and t*@ recording becomes possible. In particular, optical anisotropy caused by alignment of liquid crystals appears as a large rotation of the polarization angle when the readout light is polarized light, and exhibits excellent recording properties such as improved optical contrast. This is advantageous in the case of information recording systems that use laser light such as high-density energy light. This is because the polarization property of laser light can be used as is.

In addition, if the layer 3 is not oriented by the thermal effect of an appropriate high-density energy light pressure alone, or if the degree of orientation is small, the orientation of the layer 3 can be achieved by using other means in combination. For example, if both the reflective layer 2 and the metal thin film layer 4 are conductive in FIG.
A voltage necessary to orient the layer 3 may be applied during recording. Even if this applied voltage is erased after recording, information recording is preserved because layer 3 is a polymer layer. Another similar method is to provide a liquid crystal alignment layer 5 made of silicon oxide, polyvinyl alcohol, polyimide resin, etc. on the reflective layer 2 as shown in FIG.
A metal thin film layer 4 that transmits high-density energy light to be irradiated with a coefficient of 5 or more is provided thereon, and an information recording medium 1 is provided.
3 should be created. In some cases, the liquid crystal alignment layer can achieve alignment of the liquid crystal only by rubbing treatment, and in that case, the information recording medium of the present invention can be obtained even without the liquid crystal alignment layer 5.

In the case of Figures 1 and 2 above, the recorded information is read using reflected light, but in the case of transmitted light, the reflective layer 2 is not necessary and it is not necessary to apply a voltage. If there is a transparent electrode, a transparent electrode is used instead of the reflective layer 20. Furthermore, in the case of an information recording medium for transmitted light reading, the recording light may be incident from either side of the medium (the substrate l side or the 'J side opposite thereof), and the reading light may also be incident from either side. It's good to restrain you.

Since the metal thin film layer 4 used in the present invention is used for the purpose of improving the optical contrast of information recording, properties such as sublimability and low melting point are not required, and almost any metal can be used. be.

The metal thin film layer may be formed by any method as long as an appropriate light transmittance is obtained, but in order to control the film thickness and transmittance, a vacuum evaporation method or a sputtering method is preferable. The thickness of the metal thin film layer 4 may be such that it can transmit five or more high-density energy beams to be irradiated for recording. On the other hand, with the transmittance of 6 inches without a drop, the record j
This is unsuitable because sufficient irradiation energy does not reach -, resulting in a significant decrease in sensitivity as shown in FIG.

The polymer liquid crystal used in the present invention is
In addition to the cholesteric polymer liquid crystal disclosed in Japanese Patent No. 5-21479 and other known cholesteric polymer liquid crystals, nematic polymer liquid crystals and smectic polymer liquid crystals are used.

These polymer liquid crystals are fundamentally different from conventional low-molecular liquid crystals in that they have a regular structure and can be easily made into large areas, making them extremely excellent for information storage. be.

Due to its nature, polymeric liquid crystals may have poor film-forming properties, but in this case, a polymeric liquid crystal film may be created by blending them with ordinary polymers (for example, methacrylate resins). Regarding this mixing ratio, there is an optimum value because increasing the amount of normal polymer improves film forming properties but decreases liquid crystallinity. The amount is preferably 0.1 to 4.0 parts by weight.

Examples of the above-mentioned polymers that can be used include methyl, propyl, isopropyl, and butyl methacrylate resins, as well as acrylic resins, volistine resins, polyester resins, and polycarbonate resins.
In addition, as a copolymer resin, stincybutadiene copolymer and vinylidene chloride-ac! JP2)! Jul copolymer and the like can be used as the polymer.

Further, a film prepared by blending a low-molecular liquid crystal with a conventional polymer as described above may exhibit the same function as the layer containing the above-mentioned polymeric liquid crystal according to the present invention. In this case, similarly to the layer containing polymer liquid crystal related to the button of the present invention,
It can be used as an information recording layer. However, it is desirable that the mixing ratio of ordinary poly-7- (high molecular compound) is 0.5 to 4.0 parts by weight per 1 part by weight of low-molecular liquid crystal.
This means that when the polymer increases beyond 4.0 parts by weight,
Liquid crystallinity decreases, and some combinations do not exhibit phase transition. On the other hand, if the polymer component is too small (less than 0.5 parts by weight), the mechanical strength will decrease and it will not be possible to obtain a good information recording medium.

In both cases of the above-mentioned polymer liquid crystal-containing layer and low-molecular liquid crystal-containing polymer single layer, the lower limit of the transition temperature is determined by storage stability, and the upper limit is determined by writing energy, and the preferred transition temperature is 80. °C ~ 8[sO
It's ℃.

Method for inputting information into an information recording medium according to the present invention, (9)
8' That is, the recording method may be a method using image exposure for image information or a scanning light using a time-series signal.

The same goes for information readout, in which physical changes (transmittance, reflectance, and degree of polarization) of a layer containing polymeric liquid crystals are read out using light, but full-surface exposure or a scanning type may be used. That is, the information recording medium according to the present invention can be used as an optical memory or as a display.

Note that high-density energy light such as a xenon lamp, a mercury lamp, or a laser beam is preferably used as a light source during recording, but depending on the spectral characteristics of the light source, absorption in the layer containing the polymer liquid crystal may be low. be. In this case, a light absorber may be added to the layer containing the polymeric liquid crystal. As the light absorber, known dyes, dyes, pigments, etc. are used, and they are dissolved or dispersed in the layer containing the polymeric liquid crystal. Further, a light absorption layer may be separately provided between the layer containing the polymer liquid crystal and the substrate or between the layer containing the polymer liquid crystal and the electrode. In either case (10), it is preferable that the pigment or dye used as the light absorber is one that does not easily sublimate at the temperature at which the layer containing the polymeric liquid crystal undergoes a phase transition. Also, the substrate may be made of plastic, glass, etc. However, it is preferable that the plastic has good thermal stability and stability over time. Furthermore, when reading records using reflected light, the substrate does not need to be transparent, and a metal plate or the like can also be used.

Next, the ↑R@ recording medium according to the present invention will be described in more detail with reference to specific implementation pressures, but the present invention is not limited to this embodiment. A 7=3 copolymer of funsteryl methacrylate and stilt methacrylate was synthesized in a conventional manner.

3 g of this copolymer and 0.5.9 of Sumiplast Blue 3R (manufactured by Sumitomo Chemical Co., Ltd.) as a light absorbent were mixed with 31' of toluene.
The K-dissolved solution was coated using a 1-inch square glass Kichiro rotary coating machine that vacuum-deposited aluminum as a reflective layer so that the film thickness after drying was 3 μm. Furthermore, aluminum was vacuum-deposited on this material so that the transmittance at 632.811 m was 15 degrees, thereby obtaining the information recording medium of the present invention.

A 20 mW output He-Ne laser beam focused on a 1.4 μm diameter spot pressure (
cs 32.8 nm) at 4.7 m/s using a rotating mirror.
Recording was performed by scanning at a scanning speed of ec and applying a 500 ns pulse signal using an acoustic optical modulation element.

When this recorded portion was read by reflection with a He-No laser beam, the S/N ratio for recording and reproduction was as good as 40 dB or more.

[Brief explanation of the drawing]

The drawings illustrate the present invention, and FIGS. 1 and 2 are cross-sectional views showing two sides of the information recording medium according to the present invention, and FIG. 3 shows the photosensitivity due to the light transmittance of the metal thin film layer. This is a graph showing. In addition, in the symbols shown in the drawings, 1...
・・・・・・・・・Substrate 2・・・・・・・・・River・
...Reflection layer 3 ..... Layer containing polymer liquid crystal (12) 4 ..... Metal thin film layer 5 ...
......It is a liquid crystal alignment treatment layer. Agent Patent Attorney Hiroshi Aisaka Figure 1

Claims (1)

[Claims] 1. A recording layer having properties that can be thermally changed by irradiation with high-density energy light is provided on a support, and the recording layer is composed of a polymer liquid crystal, a mixture of a low-molecular liquid crystal, and a polymer compound. An information recording medium containing at least one of them as a main component, wherein a conductive thin film that transmits 5% or more of irradiated high-density energy light is provided on the recording layer. recoding media.