JPH0229958A - organic reversible optical recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat mode organic reversible optical recording medium useful for optical cards, optical discs, and the like.

[Prior Art] Polymer optical memories using vinylidene polymers (hereinafter referred to as PVD polymers) as recording media are already known.

This is a revolutionary optical memory that utilizes the ferroelectric properties of PVD polymers, and its recording principle is based on Japanese Patent Application Laid-Open No. 59-21509.
6 and No. 59-215097, Polymer Processing 35
．． 418 (198B) or IEEE Trans
.

EIecLr, Ins, EI-21,359 (lH&
), utilizing the property of ferroelectric polymer materials to be polarized by an electric field, a high electric field is applied to the ferroelectric polymer materials to polarize them in one direction. Writing is possible by irradiating and heating an arbitrary part with a light beam while applying a weak reverse electric field, which is less than the electric field, and selectively inverting the polarization of only the light irradiated part. Furthermore, writing is possible by suppressing the pyroelectric effect caused by light or heat. It can be used and read out.

[Problems to be Solved by the Invention] When using a heat mode organic reversible optical recording medium as an optical memory, it is necessary to optimize the temperature distribution inside the recording layer by light irradiation to achieve high-speed reading/writing or recording of large amounts of information. It is extremely important for

An object of the present invention is to provide a heat mode organic reversible optical recording medium in which the temperature distribution inside the recording layer by light irradiation is made appropriate.

[Means for Solving the Problems] The present inventor has been conducting research in order to solve the above problems. It has been discovered that dispersing the agent is effective, leading to the present invention.

That is, the present invention provides a heat mode organic reversible optical recording medium, in which the recording layer of the optical recording medium contains a light absorbing agent consisting of a vinylidene polymer and one or more dyes and pigments, and the absorbance of the light absorbing agent is This is a heat mode organic reversible optical recording medium characterized in that the recording layer increases from the light incident side to the light output side.

In order to explain the concept of the heat mode organic reversible optical recording medium of the present invention, FIG. 1 shows a case where the recording medium is a ferroelectric polymer optical memory. It is not limited to cases where

In FIG. 1, 1 is a recording layer, 2 is a lower electrode, 3 is an upper electrode, and 4 is a substrate, and light 5 from a laser is incident on the recording layer perpendicularly to each boundary surface.

PVD polymers exhibiting pyroelectricity are generally transparent, and laser light is absorbed by dyes and pigments dispersed in the recording layer. The change in the light intensity in this recording layer is given by αl x . Here, X is the distance Ml from the light incidence side to the light emission side, with the origin at the end of the recording layer Z on the laser incidence side, α
is the absorbance of the dye and pigment.

Further, the amount of heat generated per unit length Q is given by Q - lifetime ±X. By making the amount of heat generation constant within the recording layer, the recording layer can be uniformly heated. In other words, if we find the condition for α to be Q-constant, we get ao X × α. ...(*) a″″1−α, x. Here α. −α(0).

Figure 2 shows the intensity of the light at this time! 1 heat generation ff1Q and changes in α are shown. This figure shows that if the absorbance is made higher on the light output side than on the light input side, Q becomes more uniform.In particular, the concentration of the dye and pigment should be controlled to satisfy the condition (*), and the thickness of the recording layer should be adjusted. It can be seen that when 1/α0 is set, the amount of heat generated Q becomes constant. The above is the basic idea of the present invention.

For this reason, the optical recording medium of the present invention is designed to prevent local temperature distribution from occurring within the optical recording in a region of 80% or more of the thickness of the recording layer measured in the direction of light. 8≦a/ao≦1.21− α.

X It is preferable to satisfy the following.

The configuration of the present invention will be explained below based on the drawings.

Figure 3.4 is a structural model diagram of a ferroelectric polymer recording medium of the present invention in which a light absorbent is dispersed in the recording layer. 1 in this figure is the recording layer of the recording medium (PVD)
This is the part where the polymer film is made. Further, 2 is a lower electrode, and 3 is an upper electrode. 6 is a dye and pigment dispersed in the recording layer.

Various compounds have been reported as the PVD polymer constituting the recording layer in the present invention, but in the present recording medium, it is desirable to use one that has ferroelectricity and exhibits a rectangular shape when measured with dielectric hysteresis. For example, vinylidene fluoride homopolymers and vinylidene fluoride copolymers containing 50% by weight or more of vinylidene fluoride are used. Examples of the copolymer include copolymers of vinylidene fluoride and ethylene trifluoride, propylene hexafluoride, ethylene chloride trifluoride, and the like. Also included are polyvinylidene cyanide, vinylidene cyanide, and vinyl acetate copolymers, but among these, vinylidene fluoride and ethylene trifluoride copolymers [hereinafter abbreviated as P (VDF-TrFE)] are most preferred.

The PVD polymer film of the recording layer can be formed by a solution coating method such as dip coating, spray coating, spinner coating, blade coating, roller coating, curtain coating, or the like. Among these methods, dip coating or spinner coating is preferable because the PVD polymer film can be formed to a uniform thickness and an ultra-thin film can be obtained.

In the recording layer, the PVD polymer is a part that exhibits ferroelectricity, which can be called the basis of this recording medium. characteristics are required accordingly.

In particular, it is desirable that the material satisfies the following conditions: 1) It should have absorption near the wavelength of irradiated light, especially semiconductor laser light. 2) It should have low conductivity. 3) It should be thermally stable. As such light absorbers, organic substances such as cyanines,
Polymethine compounds such as pyridiniums, birylliums, quinoliniums, rhodanines, phthalocyanines,
Porphines such as naphthalocyanine, chlorophylls, crown ethers, squalirium, thiafulvalenes, metal complex compounds such as dithiols, azo compounds, spiro compounds, fluorenone compounds, fulgide compounds, imidazole compounds, perylene compounds Compounds, phthaloperinone compounds, ferrocene compounds, phenazine compounds, phenothiazine compounds, phenoxazine compounds, polyene compounds, indigo compounds, quinone compounds, quinacridone compounds, quinophthalone compounds, diphenylamine compounds, triphenylamine Examples thereof include diphenylmethane-based compounds, triphenylmethane-based compounds, acridine-based compounds, acridinone-based compounds, carbostyryl-based compounds, coumarin-based compounds, and the like. More specifically, among the dyes and pigments, porphines, cyanines, and dithiol complexes are preferred.

To add the light absorber into the PVD polymer and control its content, dip coating with solutions with different light absorber contents or spinner coating several times with varying light absorber contents can be used. Coatings may be used, but the invention is not particularly limited thereto. Absorbance α on the light incident side. can be determined from the film thickness from the discussion above.

When the thickness of the recording layer is 2 μl, α. ~l/2μm-
m-5XIO5' may be used.

At this time, if the absorbance is changed toward the light-emitting side so as to approximate (E), almost 100% of the light will be absorbed by the end of the light-emitting side of the recording layer.

In practice, in order to prevent heat from diffusing to the upper and lower electrodes, dyes and pigments should not be dispersed near the light incident side of the recording layer, and α should be maintained. lO
It is preferable to make it larger than the theoretical value by about %.

In order for a zero ferroelectric polymer recording medium to function as an optical memory, it is desirable that at least one of the electrodes sandwiching the recording layer be as transparent as possible to the irradiated light. It is preferable to employ electrodes or semi-transparent electrodes. Of course, both the lower electrode 2 and the upper electrode 3 may be transparent, or only the upper electrode 3 may be transparent. Transparent electrodes used in the present invention include tin-doped indium oxide (ITO), tin oxide,
Vapor deposition of undoped indium oxide, zinc oxide, etc., CV
D, sputtering film, etc., and semitransparent electrodes include gold, platinum, silver, copper, lead, zinc, aluminum, nickel,
Examples include vapor deposition of various metals such as tantalum, titanium, cobalt, niobium, palladium, and tin, and CVD1 sputtering films, but the present invention is not particularly limited to these.

Support materials for these electrodes include polyethylene, polyethylene terephthalate, polypropylene, polystyrene, polyvinyl chloride, polycarbonate, polyvinyl alcohol, polyvinyl acetate, polyamide,
Various plastics such as polyimide, polyolefin, acrylic resin, phenol resin, epoxy resin, and the above derivatives, glass, quartz plate, ceramic, etc. are suitable, but like the electrode, it is desirable that they are transparent to irradiated light, and the electrode Although it is preferable that the material also serves as insulation from the electrode, the present invention is not particularly limited thereto, as is the case with the electrode.

The irradiation light source is a semiconductor laser (LD) in terms of mass production and cost.
) is considered optimal. The direction of irradiation of the LD light may be from either the upper or lower electrode side, but it is desirable that at least the electrode on the light source side is transparent to the irradiated light.

FIG. 5 shows an example in which an undercoat layer 7 is provided on the surface of the lower electrode 2. The undercoat layer 7 is formed by coating or vapor depositing a surface treatment agent on the surface of the lower electrode 2, and its purpose is as follows.

1) Improved adhesion to electrodes 2) Improved storage stability of the recording layer 3) Barrier properties against water, gas, solvents, etc. In the above, the main properties are particularly required of 1. The surface treatment agents used therein include hexamethyldisilanzane (HMDS), dimethylchlorosilane (TM01),
, dimethylchlorosilane (DMCS), dimethyldichlorosilane (DMDCS), bis(trimethylsilyl)acetamide, t-butyldimethylchlorosilane,
bis(trimethylsilyl)trifluoroacetamide,
Examples include trimethylsilyldiphenylurea, bistrimethylsilylurea, and the like. In addition to the above-mentioned silyl and other agents, titanium-based coupling agents (anchor coating agents) have also been confirmed to be effective.

Fig. 6 shows an example in which a protective layer 8 is provided on the upper electrode 3, and this protective layer is intended to protect the recording layer from scratches, dust, dirt, etc., and to improve the storage stability of the recording layer. It is formed from various polymeric materials, silane coupling agents, glass, etc.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A recording layer was formed by applying a P (VDF-TrFE) film in which cyanine dye was dispersed four times to a thickness of 0.5 μm using a spin coating method on an ITO-deposited glass having a thickness of approximately II. . At this time, the absorbance of the dye in each layer is 5.7×tos m” 8.OX tos from the light incident side.
m-' 1.3X 10G m-'4, OX
10G m''.Next, after aluminum was vapor-deposited as the upper electrode of this sample, the
FE) Membrane 1: Poling treatment was performed by applying a voltage of 100 V (7). Furthermore, while applying a reverse electric field of 25 V, a semiconductor laser (hereinafter abbreviated as LD) with an oscillation wavelength of 780 rv is applied.
P (
Information was recorded by heating several locations within the VDF-TrFE) layer. After that, the LD light intensity was weakened to 0.16 mW and 10
While chopping at kHz, P (VDF-Tr
When the FE) layer is irradiated with LD light and the pyroelectric current generated between the electrodes is measured and information is read out, the S/N ratio is 45.
It turned out that dB.

Example 2 P (VDF-Tr
F E) A film with cyanine dye dispersed in it has a thickness of 0.
A recording layer was formed by coating 6 times at a thickness of 5 μm.

At this time, the absorbance of each layer is set to 0 and Otr from the light incident side, respectively.
r −' (does not include dyes and pigments), 3.9X 105 I
I-'4.8X105+a-' 6.3X1
05m-'9.2X105m-'1.7X 10
6 m-1. Furthermore, aluminum was vapor-deposited as an upper electrode. When information was recorded and read out using the same method as in Example 1, it was found that the S/N ratio was 43 dB.

[Effect of the invention] By utilizing the above invention, the heat generated in the heat mode organic reversible optical recording medium can be uniformly applied to the recording medium, and an optimum temperature distribution can be achieved without causing local high or low temperatures. The sensitivity of the optical recording medium can be increased, and the information recording density can also be increased. As a result, it reacts extremely sensitively even to low-power irradiation light such as that of a semiconductor laser, and a series of operations such as scratching, reading, and erasing can be performed smoothly.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are diagrams for explaining the basic idea of the present invention, and FIGS. 3 to 6 are diagrams for explaining the layer structure of the optical recording medium of the present invention.

Claims (1)

[Claims] In a heat mode organic reversible optical recording medium, the recording layer of the optical recording medium contains a light absorbent consisting of a vinylidene polymer and one or more dyes and pigments, and the absorbance of the light absorbent is equal to the light absorbance of the recording layer. A heat mode organic reversible optical recording medium characterized in that the heat mode increases from the incident side to the output side.