JPH0724121B2 - Pyroelectric recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a pyroelectric recording medium in which a recording layer is made of a pyroelectric material, and particularly, a sensitizing dye is used to improve recording / reproducing characteristics. It is a thing.

B. SUMMARY OF THE INVENTION The present invention relates to a pyroelectric recording medium in which a pyroelectric layer for recording an information signal is sandwiched between opposed electrodes, and the pyroelectric recording medium according to the wavelength of light for heating the pyroelectric layer. By dispersing a dye for absorbing the light in the pyroelectric layer, high-speed writing, high-speed reading, high-density recording, etc. are realized.

C. Conventional technology As one of the recording / reproducing systems for recording / reproducing information signals,
There is a pyroelectric recording / reproducing system in which recording / reproduction is performed by using a pyroelectric recording medium in which a pyroelectric layer is arranged between opposing electrodes. This pyroelectric recording / reproducing system will be briefly described. First, at the time of recording, a pyroelectric recording medium in which a pyroelectric layer such as a polymer material is arranged between opposing electrodes is used, and a voltage is applied between the electrodes. At the same time, a predetermined region of the pyroelectric layer is heated. Then, the heating and the voltage control the dielectric polarization of the pyroelectric layer to record a predetermined information signal. On the other hand, at the time of reproduction, by heating a predetermined area of the pyroelectric layer and detecting and amplifying the presence or absence of the residual pole of the pyroelectric layer and the pyroelectric current according to the direction, the information signal can be reproduced. It will be possible. Further, as information recording / reproducing methods using such a technique, those disclosed in JP-A-59-215096 and JP-A-59-215097 are known.

D. Problems to be Solved by the Invention As described above, when recording or reproducing, the pyroelectric layer is heated, but this heating is usually performed by irradiating light such as a laser beam from a semiconductor laser. Is done by.

However, the heating of the pyroelectric layer is performed via the counter electrode that sandwiches the pyroelectric layer, the photoconductor layer formed on the surface of the counter electrode, and the like. The heat not only conducts to the pyroelectric layer but also disperses in the electrode, and the utilization efficiency of the light such as the laser beam becomes very low.

Recording and reproduction are performed by locally heating the pyroelectric layer, but the speed of recording and reproduction slows down and the recording density also decreases depending on the dispersion of heat.

Therefore, in view of the above problems, it is an object of the present invention to provide a pyroelectric recording medium that prevents heat dispersion in the pyroelectric layer and realizes high-speed recording / reproducing and high recording density.

E. Means for Solving the Problems The present invention is a pyroelectric recording medium in which a pyroelectric layer for recording an information signal is sandwiched by opposed electrodes, and the pyroelectric layer is heated. The above-mentioned problems are solved by a pyroelectric recording medium in which a dye for absorbing the light is dispersed in the pyroelectric layer according to the wavelength of the light.

F. Action The dye is used to efficiently raise the temperature of the pyroelectric layer by absorbing the light irradiated for heating according to its wavelength. Therefore, by dispersing such a dye in the pyroelectric layer, the light absorption efficiency is increased, and the temperature is raised at a high speed. By increasing the temperature rising speed in this way, high-speed writing and reading can be performed. It will be possible. Further, such a dye can prevent heat from being dissipated, can locally raise the temperature, and can improve the recording density.

G. Embodiment A preferred embodiment of the present invention will be described with reference to the drawings.

In the pyroelectric recording medium of the present embodiment, the dye is dispersed in the pyroelectric layer as the recording layer, and the sensitizing action of this dye realizes high-speed recording / reproduction and high-density recording. .

First, the pyroelectric recording medium of this example has a structure as shown in FIG. As shown in FIG. 1, glass,
A lower electrode 3 is formed on a substrate 2 formed of a material such as plastic, and a dye for absorbing the light is dispersed on the lower electrode 3 according to the wavelength of the light to be irradiated. The pyroelectric layer 1 is formed. An upper electrode 4 is formed on the pyroelectric layer 1 in which the dye is dispersed so as to face the lower electrode 3, and a voltage V _S is applied between the lower electrode 3 and the upper electrode 4. Is applied.

A predetermined lens 5 faces such a pyroelectric recording medium, and a laser beam 6 for heating the pyroelectric layer 1 is irradiated through the lens 5.

The pyroelectric layer 1 is a recording layer for recording an information signal according to the presence or absence of dielectric polarization or the direction of polarization. In the pyroelectric recording medium of the present embodiment, dyes for sensitization are dispersed. Therefore, depending on the irradiation of the laser beam 6, the temperature thereof rapidly rises. Here, for the pyroelectric layer 1, for example, a polymer pyroelectric material such as a polyvinylidene fluoride (PVDF) -trifluoroethylene (PTrFE) copolymer or the like can be used. It can be performed by a coating method or the like. As the dye to be dispersed in the pyroelectric layer 1, it is possible to select and disperse a dye having high absorption efficiency according to the wavelength of light used for heating. When a semiconductor laser (having a wavelength of 830 nm) or the like is used as the light source of, a benzenedithiol complex salt-based dye, a squarylium-based dye, a cyanine-based dye, a naphthoquinone-based dye, a charge-bonded substance of carbazole and a quinone-based compound, or the like can be used.

The lower electrode 3 and the upper electrode 4 are arranged so as to face each other, and a voltage is applied at the time of recording, and a pyroelectric current is taken out at the time of reading through these electrodes 3 and 4. The lower electrode 3 and the upper electrode 4 can be formed by using a transparent electrode such as ITO, In ₂ O ₃ , SnO ₂ or the like, and when forming such a transparent electrode, a reactive ion is used. By the plating method, deposition is performed in two steps with different film forming rates, and in this case, it is preferable to perform the deposition while maintaining the substrate at a low temperature of, for example, 75 ° C.

Lead wires are attached to the upper electrode 4 and the lower electrode 3 respectively, and a voltage V _S is supplied from a power source during recording. The upper electrode 4 and the lower electrode 3 may be divided electrodes divided into predetermined regions, or may be formed via a photoconductor. Further, a structure may be adopted in which only the light-irradiated portion is made conductive to form a partial electrode.

Recording and reproduction on such a pyroelectric recording medium can be carried out, for example, by the following method, and a dye for sensitization is dispersed in the pyroelectric layer of the pyroelectric recording medium. Therefore, high-speed recording / reproduction and high-density recording are possible.

First, regarding the writing of the information signal, the upper electrode 4 is used.
Then, a voltage is applied to the lower electrode 3 to align the polarization state in a certain direction and initialize it. Next, apply reverse voltage,
For example, a laser beam 6 for heating is applied. At the time of irradiation with this light, the dye dispersed in the pyroelectric layer 1 absorbs the light, and the absorption of this light raises the temperature at that position, lowers the coercive electric field, and changes the direction of spontaneous polarization. It is inverted and high speed writing is performed.

The reading of the information signal is performed by irradiating a laser beam weaker than that at the time of writing and detecting the information signal according to the direction of the pyroelectric current generated. At this time, the dye is dispersed in the pyroelectric layer 1 as described above, and from the sensitizing action,
High-speed and reliable signal detection will be performed.

The information signal may be recorded depending on the presence or absence of the polarization state.

Next, the pyroelectric recording medium will be described based on an experiment conducted to clarify the effect of the pyroelectric recording medium of the present embodiment.

First, the pyroelectric recording medium used in the experiment uses a polyvinylidene fluoride (PVDF) -polytrifluoroethylene (PTrFE) copolymer as the pyroelectric layer. The ratio of ethylene is 51:49. A benzenedithiol complex salt dye was used as a dye for absorbing the light depending on the wavelength of the light to be heated. Then, the solvent is changed to methyl ethyl ketone (ME
As K), a solution was prepared by mixing MEK ... 90 wt% PVDF-PTrFE ... 9 wt% benzenedithiol complex salt-based dye ... 1 wt%.

Then, this solution was coated on a substrate having one electrode formed thereon by a spin coating method to obtain a pyroelectric layer (a film thickness of about 2 μm) containing a dye. Then, a transparent upper electrode (In ₂ O ₃ film) was formed, and the following experimental results were obtained using this pyroelectric recording medium.

As shown in FIG. 2, due to the presence or absence of the dye, a remarkable difference appears in the light absorption rate (absorbance%). In Figure 2,
Curve A shows the absorbance when the dye is dispersed in the pyroelectric layer, while curve B shows the absorbance when it contains no dye. The horizontal axis of FIG. 2 represents the wavelength λ (nm) of light.

Comparing these two curves A and B, the one in which the dye is dispersed in the pyroelectric layer as a whole (curve A) has a higher absorbance, and especially at the laser beam wavelength of 830 nm, the dye is Due to the dispersion of, the absorbance is dramatically increased from 10% to 45%. Therefore, by using the pyroelectric layer in which the dye is dispersed as the recording layer, the efficiency of temperature rise can be increased and high-speed recording / reproducing can be performed.

Further, when the performances of the above-described pyroelectric recording medium according to the present example and the conventional pyroelectric recording medium were compared, the results shown in Table 1 were obtained. The conventional pyroelectric recording medium is a black body coated with an Al film as an electrode.

As is clear from Table 1 above, the pyroelectric recording medium (invention) in which the dye is dispersed in the pyroelectric layer has faster writing and reading times, and the resolution is 1 / It can be seen that it becomes 5, which enables high-density recording.

H. Effect of the Invention The pyroelectric recording medium of the present invention is a pyroelectric layer in which a dye that absorbs light according to the wavelength of light used to heat the pyroelectric layer that is the recording layer is dispersed. Therefore, the temperature rise of the pyroelectric layer can be accelerated, which enables high-speed recording / reproduction. At the same time, it is possible to increase the recording density by improving the resolution.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the structure of the pyroelectric recording medium of the present invention, and FIG. 2 is a characteristic diagram in a comparative experiment for explaining the effect when the pyroelectric recording medium of the present invention is used. Is. 1 ... Pyroelectric layer 2 ... Substrate 3 ... Lower electrode 4 ... Upper electrode

Claims (1)

[Claims] 1. A pyroelectric recording medium in which a pyroelectric layer for recording an information signal is sandwiched between opposing electrodes, and the pyroelectric layer is heated according to the wavelength of the light for heating the pyroelectric layer. A pyroelectric recording medium in which a dye for absorption is dispersed in the pyroelectric layer.