JP2742266B2 - Organic reversible optical recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat mode organic reversible optical recording medium useful for optical cards, optical disks, and the like.

[Prior Art] A polymer optical memory using a vinylidene polymer (hereinafter, referred to as a PVD polymer) as a recording medium is already known.

This is a revolutionary light memory utilizing ferroelectricity of PVD polymer, its recording principle JP 59-215096 and ibid 59-215097, JP-polymer processing 35, 418 (1986) or As disclosed in IEEE Trans. Electr. Ins., EI-21 , 359 (1986), a high electric field is applied in one direction by applying a high electric field by utilizing the property that a ferroelectric polymer material is polarized by an electric field. Irradiating and heating a given portion of the polarized ferroelectric polymer material with a light beam while applying a weak reverse electric field equal to or lower than the coercive electric field to selectively invert the polarization of only the light irradiated portion. Enables writing, and can be read using the pyroelectric effect of light or heat.

[Problems to be Solved by the Invention] When a heat mode organic reversible optical recording medium is used as an optical memory, it is necessary to adjust the temperature distribution inside the recording layer by irradiating light at a high speed for reading / writing or recording a large amount of information. Is extremely important to

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

Means for Solving the Problems The inventor of the present invention has been studying in order to solve the above-mentioned problems. However, the light absorption in the recording layer is increased so that the absorbance increases from the light incident side to the light emitting side. It has been found that dispersing the agent is effective, and the present invention has been achieved.

That is, the present invention relates to a heat mode organic reversible optical recording medium, wherein the recording layer of the optical recording medium contains a light absorber composed of a vinylidene polymer and one or more dyes and pigments, and the absorbance of the light absorber is A heat mode organic reversible optical recording medium characterized by increasing from the light incident side to the emission side of the recording layer.

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, but the present invention uses a ferroelectric polymer material. It is not limited to the case where there is.

In FIG. 1, 1 is a recording layer, 2 is a lower electrode, 3 is an upper electrode, 4 is a substrate, and light 5 from a laser is incident on the recording layer perpendicularly to each boundary surface. A pyroelectric PVD-based polymer is generally transparent, and laser light is absorbed by dyes and pigments dispersed in the recording layer. The change in light intensity I in this recording layer is: Given by Here, X is the distance measured from the light incident side to the emission side with the origin on the laser incident side end of the recording layer Z, and α is the absorbance of the dye / pigment.

The amount of heat generated per unit length Q is Given by If the amount of generated heat is made constant in the recording layer, the recording layer is uniformly heated. That is, when the condition of α for Q = constant is obtained, Becomes Here, α ₀ = α (0).

FIG. 2 shows changes in light intensity I, generated heat Q and α at this time. As shown in this figure, when the absorbance on the light exit side is higher than that on the light entrance side, Q tends to be uniform. In particular, the concentration of the dye / pigment is controlled so as to satisfy the condition (*), and the thickness of the recording layer is reduced. It can be seen that when 1 / α ₀ , the generated heat Q is constant. The above is the basic concept of the present invention.

For this reason, the optical recording medium of the present invention has a thickness of 80% or more of the thickness of the recording layer measured in the light direction so that local temperature distribution does not occur in the optical recording. It is preferable to satisfy the following.

 Hereinafter, the configuration of the present invention will be described based on the drawings.

FIGS. 3 and 4 are structural model diagrams of the ferroelectric polymer recording medium of the present invention when a light absorbing agent is dispersed in the recording layer. Reference numeral 1 in this figure denotes a portion where a PVD-based polymer film as a recording layer of the recording medium is formed. 2 is a lower electrode,
3 is an upper electrode. Reference numeral 6 denotes a dye / pigment dispersed in the recording layer. Although various compounds have been reported for the PVD-based polymer constituting the recording layer in the present invention, it is preferable that the recording medium has ferroelectricity and has a rectangular shape as measured by dielectric hysteresis, For example, a homopolymer of vinylidene fluoride and a vinylidene fluoride copolymer containing 50% by weight or more of vinylidene fluoride. Examples of the copolymer include a copolymer of vinylidene fluoride and ethylene trifluoride, propylene hexafluoride, ethylene trifluoride chloride and the like. Also, poly (vinylidene cyanide),
Examples include vinylidene cyanide and vinyl acetate copolymer, and among these, vinylidene fluoride and ethylene trifluoride copolymer (hereinafter abbreviated as P (VDF-TrFE)) are most preferable.

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, and curtain coating. Among them, those obtained by dip coating or spinner coating are preferable in that the PVD-based polymer film is formed to have a uniform thickness and an ultrathin film can be obtained.

Since the PVD-based polymer in the recording layer is a portion exhibiting ferroelectricity, which can also be referred to as the basis of the present recording medium, the light absorbing agent does not impair the ferroelectricity of the PVD-based polymer. Characteristics are required as appropriate.

1) Irradiation, especially absorption and possession in the vicinity of the wavelength of the semiconductor laser light 2) Low conductivity 3) Thermal stability It is particularly desirable that the first condition is satisfied. As such a light absorber, first of all, organic substances such as cyanines, pyridinium films, biliriums, quinoliniums,
Polymethine compounds such as rhodans, porphines such as phthalocyanines and naphthalocyanines, metal complex compounds such as chlorophylls, crown ethers, squalyliums, thiafulvalenes, dithiols, azo compounds, spiro compounds, fluorenone compounds , Fulgide compounds, imidazole compounds, perylene compounds,
Phthaloperinone compounds, ferrocene compounds, phenazine compounds, phenothiazine compounds, phenoxazine compounds, polyene compounds, indigo compounds, quinone compounds, quinacridone compounds, quinophthalone compounds, diphenylamine compounds, triphenylamine compounds And diphenylmethane compounds, triphenylmethane compounds, acridine compounds, acridinone compounds, carbostyril compounds, coumarin compounds and the like. More specifically, among the dyes and pigments, porphines, cyanines, and dithiol-based complexes are preferable.

To add the light absorber to the PVD polymer and control its content, dip coating using a solution with a different light absorber content or spinner several times by changing the light absorber content Coatings may be used, but the invention is not particularly limited thereto. Absorbance alpha ₀ of the light incident side can be determined from the film thickness from consideration of the opening.
When the thickness of the recording layer is 2 μm, α ₀ α1 / 2 μm = 5
× 10 ⁵ m ^-1 may be used. At this time, if the absorbance is changed so as to approximate (*) toward the light emission side, almost 100% of the light is absorbed by the end of the recording layer on the light emission side. In practice in order to prevent the spread of heat to the upper and lower electrodes, the light incident side near the recording layer without dispersing the dye or pigment, also the alpha ₀
It is good to make it about 10% larger than the theoretical value.

In order for the present ferroelectric polymer recording medium to function as an optical memory, it is desirable that at least one of the electrodes sandwiching the recording layer is as transparent as possible to the irradiation light. It is preferable to employ an electrode or a translucent electrode. Of course, both the lower electrode 2 and the upper electrode 3 may be transparent, or only the upper electrode 3 may be transparent. As the transparent electrode employed in the present invention, tin-doped indium oxide (ITO), tin oxide,
Deposition of undoped indium oxide and zinc oxide, CV
D, a sputtering film, etc., for the translucent electrode, gold, platinum, silver, copper, lead, zinc, aluminum, nickel, tantalum, titanium, cobalt, niobium, palladium, deposition of various metals such as tin, CVD, Although a sputtering film etc. are mentioned, this invention is not specifically limited to these.

Further, as a support material for these electrodes, polyethylene, polyethylene terephthalate, polypropylene, polystyrene, polyvinyl chloride, polycarbonate, polyvinyl alcohol, polyvinyl acetate, polyamide, polyimide, polyolefin, acrylic resin, phenol resin, epoxy resin and the above derivatives Although various plastics such as glass, quartz plate, ceramics and the like are preferable, it is preferable that the electrode is transparent to irradiation light like the electrode, and it is also preferable that the electrode also serves as an electrode. Similarly, the present invention is not particularly limited to these.

The irradiation light source is a semiconductor laser (L
D) is considered optimal. The irradiation direction of the LD light may be from either the upper or lower electrode side. At this time, it is desirable that at least the electrode on the light source side is transparent to the irradiation 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 applying or vapor-depositing a surface treating agent on the surface of the lower electrode 2, and the following are mentioned for the purpose.

1) Improvement in adhesion to electrodes 2) Improvement in storage stability of the recording layer 3) Barrier properties of water, gas, solvent, etc. In the above, particularly, the main properties are required. The surface treatment agents used there include hexamethyldisilane (HMDS), trimethylchlorosilane (TMCS), dimethylchlorosilane (DMCS), and dimethyldichlorosilane (DMCS).
DCS), bis (trimethylsilyl) acetamide, t-
Butyldimethylchlorosilane, bis (trimethylsilyl) trifluoroacetamide, trimethylsilyldiphenylurea, bistrimethylsilylurea and the like. It has also been confirmed that a titanium-based coupling agent (anchor coating agent) is effective in addition to the silylating agent.

FIG. 6 shows an example in which a protective layer 8 is provided on the upper electrode 3. This protective layer aims at protecting the recording layer from scratches, dust, dirt, etc. and improving the storage stability of the recording layer. As
It is formed from various polymer materials, silane coupling agents, glass, and the like.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A recording layer was formed by coating a P (VDF-TrFE) film having a phthalocyanine dye dispersed therein by a spin coating method four times at a thickness of 0.5 μm on an ITO vapor-deposited glass having a thickness of about 1 mm four times.
At this time, the absorbance of the dye in each layer was 5.7
× 10 ⁵ m ⁻¹ , 8.0 × 10 ⁵ m ⁻¹ , 1.3 × 10 ⁶ m ⁻¹ , and 4.0 × 10 ⁶ m ⁻¹ . Next, after vapor deposition of aluminum as an upper electrode of this sample, a poling treatment was performed by applying a voltage of 100 V to the P (VDF-TrFE) film. Further, while applying a reverse electric field of 25 V, P (V
(DF-TrFE) Information was recorded by heating several places in the layer. After that, the LD light intensity was reduced to 0.16 mW and the P (VDF-TrFE) layer was irradiated with LD light again while chopping at 10 kHz, the pyroelectric current generated between the electrodes was measured, and the information was read out. The S / N ratio was found to be 45dB.

Example 2 In the same manner as in Example 1, a P (VDF-TrFE) film in which a naphthalocyanine dye was dispersed was applied six times at a thickness of 0.5 μm by dip coating on a 1 mm-thick ITO-deposited glass to form a recording layer. Formed. At this time, the absorbance of each layer was measured from the light incident side as 0.0 m ^-1 (excluding dyes and pigments), 3.9 × 10 ⁵ m ^-1 and 4.8 × 10
⁵ m ^-1 , 6.3 × 10 ⁵ m ⁻¹ , 9.2 × 10 ⁵ m ⁻¹ , and 1.7 × 10 ⁶ m ⁻¹ . Further, aluminum was deposited as an upper electrode. When information was recorded and read out in the same manner as in Example 1, the S / N ratio was found to be 43 dB.

[Effect of the Invention] By utilizing the above-mentioned invention, heat generated in the heat mode organic reversible optical recording medium is uniformly applied to the recording medium to obtain an optimum temperature distribution without locally increasing or decreasing the temperature. This can increase the sensitivity of the optical recording medium and increase the information recording density. As a result, a series of operations such as writing and reading and erasing can be smoothly performed in response to extremely low-power irradiation light such as a semiconductor laser.

[Brief description of the drawings]

1 and 2 are diagrams for explaining the basic concept of the present invention, and FIGS. 3 to 6 are diagrams for explaining a layer configuration of an optical recording medium of the present invention.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Motomura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A 1-256047 (JP, A) JP-A Sho 64-3839 (JP, A) JP-A-63-46638 (JP, A)

Claims (1)

(57) [Claims] In a heat mode organic reversible optical recording medium, the recording layer of the optical recording medium contains a light absorber composed of a vinylidene polymer and one or more dyes and pigments. A heat mode organic reversible optical recording medium characterized by increasing from a light incident side to an output side of the recording layer.