JPS59177539A - Thin film for optical recording and its production - Google Patents

Abstract

PURPOSE:To enable readout of an optical charge in a thin film for optical recording when irradiated with visible light and to enable simple erasure of the recording by heating by laminating of depositing by evaporation tungsten trioxide and silver on a substrate or laminating silver on an oxide film contg. tungsten trioxide. CONSTITUTION:Tungsten trioxide is vacuum-deposited by using a heating boat formed of tungsten on a quartz glass substrate and in sucession, silver is deposited by evaporation thereon to obtain a thin film for optical recording. After the resultant thin film for optical recording is heated, white light is irradiated thereto and the spectral transmission characteristic of the film after the heating and the spectral transmission characteristic of the film after the irradiation of the light are inverstigated, the spectral curve A of the film after the heating and the spectral curve B after the irradiation of light are obtd. The transmissivity of the film decreases by about 5% at about 450-650nm and by about 5% at 850-1,300nm when irradiated with light as is evident from the curve. When the film after the irradiation of light is reheated, the transmissivity is reset almost to the spectral curve before the irradiation of light and the optical recording is made possible again.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording thin film that can be recorded and erased, and a method for manufacturing the same.

[Technical background of the invention and its problems]

Photochromic glass is conventionally known as an optical recording material containing silver that can be recorded and erased. In photochromic glass, silver halide dispersed in the glass is sensitized by dissociating into cyhaloquine and silver upon irradiation with light, and returns to its original state through a reverse reaction when irradiation with light is stopped.

The photosensitive range of photochromic glass is from ultraviolet to visible. In an attempt to realize the functions of photochromic glass with a thin film, we have attempted to realize the functions of photochromic glass using
+Reversible photosensitivity has been confirmed in many cases where SnBr2 and the like are mixed and deposited. However, these photochromic glasses and thin films thereof have the disadvantage that recording is lost even at room temperature when light irradiation is stopped, and that the thin films are susceptible to dissociated halogens, resulting in deterioration of their properties.

A thin film for optical recording made of an oxide and silver is a thin film made of a rare earth oxide and silver by the same inventor (Patent Application No. 57-1).
No. 67784). The change in the film upon irradiation with light is almost the same as that of the present invention, but the sensitivity and amount of change in transmittance are inferior to the present invention.

[Purpose of the invention]

The present invention causes an optical change by irradiation with visible light,
The object of the present invention is to provide an optical recording thin film whose changes can be read out optically and whose records can be easily erased by heating, and a method for manufacturing the same.

[Embodiments of the invention]

FIG. 1(a) shows a first embodiment of the present invention, in which 1 is a quartz glass substrate, 2 is a tungsten trioxide film of about 1000X deposited on it, and 3 is a tungsten trioxide film deposited on top of it. It is a evaporated silver film of about 150X. Figure 1(b) shows this after being heat-treated at an air width of approximately 200°C for 10 minutes. In layer 4, tungsten trioxide and silver partially form a compound.
When this compound and silver are dispersed in the tungsten trioxide film, a thin film for optical recording is formed.

FIG. 2(a) shows a second embodiment of the present invention, in which 1 is a quartz glass substrate, and 5 is a film formed by simultaneously depositing tungsten trioxide and silver on a glass substrate. Silver is dispersed inside. FIG. 2(b) shows a result of heat-treating this in air at 200°C for about 10 minutes. Tungsten trioxide and silver partially form a compound, resulting in an optical recording thin film 4 equivalent to that shown in FIG. 1(b). It will be done.

FIG. 3(a) shows a third embodiment of the present invention, in which 1 is a quartz glass substrate, 6 is a simple oxide other than tungsten trioxide (TiO2, Nb2O5, Ga2O3, etc.) and tungsten trioxide are simultaneously evaporated. 3 is a deposited silver film laminated thereon. Figure 3(b) shows the result of heat treatment in air at 300°C for about 10 minutes. are dispersed to form thin films for optical recording.

4 in Figures 1(b) and 2(b) or Figure 3(
When the film in step 7 of b) is irradiated with visible light, the dispersed compounds easily decompose and become silver and tungsten trioxide, resulting in a significant change in the transmission characteristics of the film and a clear contrast with the area that is not irradiated with light. occur and form a record.

It is advantageous to use a near-infrared light source for reading out records. The change in transmittance of the film caused by light irradiation extends to near-infrared light, and this film has no sensitivity to near-infrared light. No changes are made to unrecorded areas.

To erase the record, the film may be heated in air at 200-300° C. for several minutes. By heating, tungsten trioxide and silver in the film form a compound again, and the transmittance of the film returns to the state before the light irradiation.

At heat treatment temperatures lower than 200°C, the rate of compound formation is extremely slow, and at temperatures higher than 300°C, the film deteriorates and loses photosensitivity.

Next, the optical recording thin film, its manufacturing method, and the photosensitivity characteristics of the resulting optical recording thin film will be specifically explained using examples.

(Example 1) Tungsten trioxide was heated at approximately 1000X on a quartz glass substrate using a tungsten heating boat.
A thin film for optical recording was obtained by vacuum evaporation and subsequent evaporation of about 150 layers of silver. The obtained thin film for optical recording was heated at 200°C for 10
After heating for 1 minute, white light of approximately 250 mw/crn'' was irradiated for 10 minutes, and the transmission spectral characteristics of the film after heating and the transmission spectral characteristics of the film after light irradiation were examined. The results are shown in Figure 4. .

In addition, A in FIG. 4 shows the spectral curve of the film after heating, and B shows the spectral curve of the film after light irradiation. As is clear from FIG. 4, the transmittance of the film decreases by about 5% in the vicinity of 450 to 650 nm and by about 5% in the vicinity of 850 to 1300 nm by light irradiation.

Furthermore, when the film after light irradiation was heated again at 200° C. for 10 minutes, the transmittance almost returned to the spectral curve before light irradiation, making optical recording possible again.

(Example 2) Tungsten trioxide and silver were placed on a glass substrate from two heating boats at a ratio of 10:1 to 5.
The thin film for optical recording with a thickness of about 10,001 mm was obtained by simultaneously depositing at a rate of 1:1. After heating the obtained optical recording thin film at 200°C for 10 minutes, the power of about 250 mW/cr
When irradiated with n2 white light for 10 minutes and examined the transmission spectral characteristics of the film after heating and the transmission spectral characteristics of the film after light irradiation, the fourth
Almost the same results as shown in the figure were obtained. When the irradiated film was heated again at 200° C. for 10 minutes, the transmittance almost returned to the spectral curve before the irradiation, making optical recording possible again.

(Example 3) A tungsten boat for heating was filled with niobium oxide, and the niobium oxide was heated and evaporated in a vacuum to obtain a deposited film of niobium oxide about 1000× thick on a glass substrate.

The niobium oxide melted on the boat during heating partially melts tungsten tate, and the deposited film contains a large amount of tungsten in the form of tungsten trioxide. Silver was deposited on this film in a layer of about 150× to produce a thin film for optical recording. The obtained thin film for optical recording was heated at 300°C for 10 minutes, and then irradiated with tungsten Lang light of approximately 5 mw/crn2 through an interference filter with a center wavelength of 45'Onm for 10 minutes, and the transmission spectroscopy of the film after heating was performed. The characteristics and transmission spectroscopic characteristics of the film after light irradiation were investigated. The results are shown in FIG. Note that A in FIG. 5 shows the spectral curve of the film after heating, and B shows the spectral curve of the film after light irradiation. In addition, the film after light irradiation was reapplied 3 times.
When heated at 00°C for 5 minutes, the transmittance almost returned to the spectral curve before the light irradiation, making optical recording possible again.

(Example 4) Titanium oxide and tungsten trioxide were mixed at a weight ratio of 5:1 and press-molded to produce pellets. Using this pellet as an evaporation source, a titanium oxide film containing tungsten trioxide was deposited on a glass substrate by electron beam evaporation, and silver was deposited thereon to produce a thin film for optical recording. After heating the obtained optical recording thin film at 300°C for 10 minutes, tungsten lamp light of about 5 mw/crn2 was passed through an interference filter with a center wavelength of 450 nm.
After irradiation for 20 minutes, the transmission spectral characteristics of the film after heating and the transmission spectral characteristics of the film after light irradiation were examined. The results are shown in FIG. In addition, A in FIG. 6 shows the spectral curve of the film after heating, and B shows the spectral curve of the film after light irradiation.

Furthermore, when the film after the light irradiation was heated again at 300° C. for 5 minutes, the transmittance almost returned to the spectral curve before the light irradiation, and optical recording was possible again.

(Example 5) Irradiation light wavelength was 450 nm, 5
50°C m, 650°C m'f: M, and the same light
The amount of change in transmittance when 2;Hg p;
Measured at 0n. The results are shown in FIG. The horizontal axis is the irradiation light wavelength, and the vertical axis is the amount of change in transmittance. As is clear from FIG. 7, this optical recording thin film has a high sensitivity to light with a wavelength longer than 650 nm.

As shown in the examples above, a photosensitive film can be obtained by producing a film containing tungsten trioxide and laminating it with silver. Silver deposited on an oxide film easily diffuses into the oxide film by heating in the air, and when this oxide film is made of or contains tungsten trioxide, it creates a unique compound. Form. This compound is
Because it easily decomposes and precipitates silver when irradiated with light, when a film containing this compound is irradiated with light, silver is precipitated in the irradiated area, causing a significant change in transmittance and forming a record. This is the photosensitive principle of this thin film for optical recording. Photosensitivity does not depend on the method for producing the tungsten trioxide film or the oxide film containing tungsten dioxide.

When producing a tungsten trioxide film or an oxide film containing tungsten trioxide by a vacuum evaporation method, the raw material to be filled in the shade does not need to be limited to tungsten dioxide; It becomes a tungsten trioxide film. Furthermore, as shown in Example 3, even when tungsten tate is used as a heating source for another oxide, the resulting oxide film contains only tungsten trioxide. The amount of change in transmittance upon irradiation with light varies depending on the type of oxide.

〔Effect of the invention〕

As detailed above, according to the present invention, tungsten trioxide and silver may be laminated or simultaneously deposited on a substrate.
Alternatively, by layering silver on an oxide film containing tungsten trioxide, it is possible to record a remarkable change in transmittance in a wide wavelength range that is sensitive to visible light and extends to near infrared, and to record the corresponding wavelength. The light source can be used as readout light,
Furthermore, it is possible to provide a thin film for optical recording that can be erased by heating the whole or a part of the film, and can be repeatedly recorded and erased. In addition, such optical recording thin films use oxides and silver as raw materials.
Since it does not contain silver chloride, it is easy to control the deposition process and has good reproducibility, there is no need for halogen to be lost due to repeated recording and playback and the recording characteristics deteriorate, and it is stable over a long period of time. It has various effects such as.

In addition, in the above example, the case where titanium oxide or niobium oxide is used as a simple oxide other than tungsten trioxide to produce a thin film for optical recording is explained, but the invention is not limited to this, and oxides such as gallium oxide (Ga205) can also be used. It can be carried out in the same way even if it is used.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are block diagrams of the optical recording thin film of the present invention, in which (a) shows the state after vapor deposition, and (b) shows the state after heat treatment in air. FIG. 4 is a diagram showing the transmission spectral characteristics of the optical recording thin film made of tungsten trioxide and silver in (Example 1) and (Example 2) of the present invention,
FIG. 5 is a diagram showing the transmission spectral characteristics of an optical recording thin film made of niobium oxide and silver containing tungsten trioxide in (Example 3) of the present invention, and FIG. FIG. 2 is a diagram showing the transmission spectral characteristics of an optical recording thin film made of silver and titanium oxide containing tungsten trioxide. Figure 7 is a spectral sensitivity curve of the optical recording thin film made of titanium oxide and silver containing tungsten trioxide in (Example 5), where the horizontal axis is the wavelength of the light irradiated to the optical recording thin film, and the vertical axis is the wavelength of the light irradiated to the optical recording thin film. is the wavelength of 1000 when irradiated with 5J/Crn2
This is the amount of change in transmittance in nm. 1...Glass substrate, 2...Tungsten trioxide film,
3... Silver film, 4... Film in which silver and a compound of silver and tungsten trioxide are dispersed in tungsten trioxide, 5...
・・Film in which silver is dispersed in tungsten trioxide, 6・・r
A film in which tungsten trioxide is dispersed in an oxide other than tungsten trioxide, 7... A film in which silver and tungsten trioxide and a compound of silver and tungsten trioxide are dispersed in an oxide other than tungsten trioxide, A. ... Spectral curve of the film after heating, B... Spectral curve of the film after light irradiation. Applicant's agent Patent attorney Takehiko Suzue 30 Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A thin film for optical recording made of tungsten trioxide and silver. 2. A thin film for optical recording consisting of tungsten trioxide, silver, and a simple oxide other than tungsten trioxide 3. A thin film for optical recording consisting of titanium oxide or niobium oxide as a simple oxide other than tungsten trioxide Thin film for optical recording. 4. A method for producing a thin film for optical recording, which comprises sequentially depositing tungsten trioxide and silver on a substrate, or depositing them simultaneously, and then heat-treating them in air. 5. Sequentially stack and deposit silver and simple oxides other than tungsten trioxide, including tungsten trioxide, on the substrate, or
Alternatively, a method for producing a thin film for optical recording, characterized in that the film is simultaneously vapor-deposited and then heat-treated in air.