JPS643678B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention is a novel optical recording medium, particularly an AlGaAs
The present invention relates to an optical recording medium used in a solid-state injection laser. BACKGROUND OF THE INVENTION US Pat. No. 4,097,895 describes a recording medium comprising a light reflective material such as aluminum or gold coated with a light absorbing layer such as fluorescein and operated by an argon laser light source. The thickness of this absorbing layer is chosen to minimize the reflectance of the structure. Because the input light beam ablates, evaporates, or melts this light-absorbing layer, leaving an opening and exposing the light-reflecting layer,
After recording, the maximum contrast occurs between the minimum reflectance of the light-absorbing layer and the reflectance of the reflective layer at the wavelength of the recording light. Furthermore, when the light-reflecting material itself is a thin film on a non-conducting substrate, almost no energy is lost either by reflection from the light-absorbing thin film or by transmission through the reflective layer. Because the energy absorbed from the light beam is thus concentrated in an extremely thin film, recording sensitivity is surprisingly high. Optical recording systems use solid-state injection lasers, especially AlGaAs lasers operating in the wavelength range of approximately 750-850 nanometers (nm), as light sources because of their low input requirements, small size, and direct modulation of the optical output by modulation of the drive current. preferable. Therefore, materials that absorb light energy in this wavelength range and ablate, evaporate, or melt at low temperatures are most useful in optical recording systems. In order to be useful as a light-absorbing layer for the above-mentioned recording media, the material must be able to be deposited on the substrate in the form of a smooth thin film of high optical quality of a given thickness, and exhibit light-absorbing properties at the frequency of the light source used. , it is necessary to form uniform pores by ablation, evaporation, or melting. U.S. patent application Ser. AlGaAs laser-operated ablative optical recording media are described which are coated with selected light-absorbing layers. However, these materials have a melting temperature of 300 to 400
It has the disadvantage of being at ℃. Materials with lower ablation temperatures require less energy to reach that temperature and are therefore more sensitive. It is a significant advance in the art to obtain a material that absorbs light in the wavelength range of 750 to 850 nm, forms a mirror-like amorphous thin film, and has a low melting point. <Summary of the Invention> The optical recording medium according to the present invention includes a light-reflecting layer and a layer that absorbs light with a wavelength of about 750 to 850 nm, and the light-absorbing layer is composed of a bis-based material in which the substituent of the ethylene group is a phenyl group or a substituted phenyl group. (dithio α-diketone)
It consists of a platinum complex salt. <Function> The light-reflecting layer must reflect the light used for recording. Suitable light reflective materials include aluminum, rhodium, gold, and the like. The light reflective layer material has a thickness such that substantially all of the recording light is reflected. Generally, this light-reflecting layer is applied to a substrate, and the surface of this substrate must be optically smooth and have good adhesion to the later-formed light-reflecting layer. Glass plates, glass disks or plastic disks are suitable for this. If this light-reflecting layer can be formed as an optically smooth self-supporting layer, the substrate becomes unnecessary. The material discovered to be useful as the light-absorbing layer of this recording medium is bis(dithio α
diketone). However, each R is a phenyl group or a phenyl group substituted with an alkyl group or an alkoxy group such as P-isopropylphenyl or P-methoxyphenyl. The method for producing this compound was described in a 1965 issue of the Journal of American Chemical Society.
Schranzer and Mayveg, Vol. 87, pp. 1483-1489.
It is described by. These materials absorb solid-state injection laser light with a wavelength of 750-850 nm and can be deposited onto the light-reflecting layer to form a smooth, optical-quality light-absorbing layer that can record information with a high signal-to-noise ratio. . The materials of this invention can be applied to the light reflective layer by conventional vacuum deposition. This material is placed in a vacuum chamber in a suitable container fitted with a resistance heater, and the heater is connected to a current source. The substrate is placed above the light absorbing layer material (dye) on a rotating support and rotated at a speed of about 50 revolutions/minute. The vacuum chamber is evacuated to approximately 10 ^-6 mmHg and a current is applied to the heater to raise the temperature of the material to its evaporation temperature.
Vapor deposition is continued until a required thickness of light-absorbing layer is deposited on the light-reflecting layer, and when this thickness is obtained, the current is cut off and air is admitted into the vacuum chamber. The thickness of the deposited layer is monitored using an optical system that measures the reflectance of a reflective surface coated with the material, and the deposition is stopped when the reflectance reaches a minimum value. <Example> Next, the present invention will be described in further detail with reference to the accompanying drawings. FIG. 1 shows a recording medium of the invention prior to exposure to a recording light beam, including a glass substrate 110, a light reflective layer 112 made of about 600 Å of metal or other metal layer of suitable thickness, and a layer of one of the materials described above. A light absorbing layer 114 is provided. FIG. 2 shows the recording medium of the present invention after exposure to a recording light beam, with the light-absorbing layer 114 being ablated to form an aperture 116 and exposing the light-reflecting layer 112. Although only one hole is shown in FIG. 2, it can be seen that there are a plurality of holes or pits 116 in the recording medium after recording. The use of the recording medium of this invention can be explained in more detail with reference to FIG. When recording
Light emitted from the AlGaAs injection laser 10 is directly modulated in response to an input electrical signal 14, and this modulated light beam is expanded by a recording optical system 16 to an objective in a plane parallel and perpendicular to the plane of the laser 10. The diameter of the intensity modulated laser beam is increased to fill the aperture of lens 18. This expanded modulated laser beam is sent to a polarizing beam splitter 2.
0, and enters the objective lens 18 through the 1/4 wavelength plate 22. Furthermore, this modulated recording beam impinges on the recording medium 24 shown in FIG. 1 to ablate or evaporate a portion of its light-absorbing layer and expose a portion of its light-reflecting layer. The recording medium 24 is a turntable 26
It rotates at approximately 1800 revolutions per minute. A focusing servo mechanism 28 maintains a constant distance between the objective lens 18 and the surface of the recording medium 24. During reproduction, an unmodulated, less intense laser beam, that is, a beam that does not cause ablation of the recording medium, follows the same path to the recording medium 24 as the recording beam. The recorded reflective/non-reflective pattern is the objective lens 1.
The reflected light returning through the 8 and 1/4 wave plate 22 is modulated. This light passes through the 1/4 wavelength plate 22 twice and the plane of polarization has been rotated by 90 degrees, but passes through the polarization beam splitter 20 and is guided to the photodetector 32 by the reproducing optical system 30. Photodetector 32 converts the reflected light beam at terminal 34 into an electrical output signal corresponding to the input signal from signal source 14 . A tracking servomechanism 36 monitors the reflected light passing through the reproduction optics 30 and radially deflects the incoming light beam so that it is always focused on the track of interest. The invention will now be described by way of example, but this does not mean that the invention is limited to the details of this description. Example 1 A metal with a thickness of about 600 Å is deposited on a vinyl disc substrate by vapor deposition, and the coated substrate is placed in a platinum bis(diphenyldithio α-diketone) complex salt in a vacuum chamber for 50 Å.
Place it on an evaporation boat that rotates at a rotational speed of 100 m/min, evacuate the vacuum chamber to about 60 ^-6 mmH, connect a current source to the boat and heat it to about 225-275°C, and open the shutter at this temperature. The material was deposited at a rate of approximately 4 Å/second. The deposition continued until an approximately 600 Å thick absorbing layer was deposited on top of the gold layer. A smooth amorphous specular continuous layer was deposited.
Platinum bis(diphenyldithio α) at 800nm
The real part n and imaginary part k of the dielectric constant of the diketone layer are 2.08 and 0.5, respectively. The completed recording medium is processed using the device shown in Figure 3.
50n with a wavelength of approximately 800nm from an AlGaAs injection laser
When exposed to a second light pulse train, the absorbing material was 10 m
was ablated from the disc by multiple exposures of W incident light. Example 2 Following the general procedure of Example 1, the gold-coated substrate of Example 1 was coated with a 1324 Å thick layer of platinum bis(di-p-isopropylphenyl dithio alpha diketone) complex.
Platinum bis(di-p-isopropylphenylthio α
The real part n and imaginary part k of the dielectric constant of the diketone layer at 800 nm are 1.75 and 0.78, respectively. A smooth amorphous specular continuous layer was deposited. Example 3 Following the general procedure of Example 1, the gold-coated substrate of Example 1 was coated with a 1900 Å thick layer of platinum bis(di-p-methoxyphenyl dithio alpha diketone) complex. Real part n of the dielectric constant at 800 nm of a layer of platinum bis(di-p-methoxyphenyldithio α-diketone)
and the imaginary part k are 1.61 and 0.76, respectively. A smooth amorphous specular continuous layer was deposited. This coating has a reflectance of approximately 95% of the gold layer before adding the light absorbing layer.
The reflectance of the recording medium was reduced to about 7%. Comparative Example Bis(dithio-alpha diketones) of Pt, Pd or Ni with the same or different allyl or alkyl substituents were prepared on gold-coated vinyl discs following the general procedure of Example 1.
Coated with complex salt. This complex belongs to the class with the following formula. However, M is Pt, Pd or Ni, and R ₁ and R ₂ are an alkyl group, a phenyl group, or an alkyl- or alkoxy-substituted phenyl group. These materials formed non-specular coatings with poor antireflection performance after deposition.
In almost all cases the coatings were cloudy from the beginning and crystallization progressed within a few days. All of these materials (dies) are unsuitable for this invention. The data are shown in Table 1. 【table】

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a recording medium according to the present invention before recording, FIG. 2 is a cross-sectional view of a recording medium after recording according to the present invention, and FIG. 3 is a record that can use the recording medium according to the present invention. 1 is a schematic diagram of a reproduction method. 110...Glass substrate, 112...Light reflective layer,
114...Light absorption layer.

Claims (1)

[Scope of Claims] 1. A light-reflecting layer covered with a light-absorbing layer, which generates light of a predetermined frequency, characterized by using a platinum bis(dithio-α-diketone) complex compound having the following formula as the light-absorbing layer. ablative optical recording media for use with recording lasers; However, R is a phenyl group or a substituted phenyl group. 2. A light-reflecting layer coated with a light-absorbing layer, having an information track formed on the light-absorbing layer, and using a platinum bis(dithio α-diketone) complex compound having the following formula as the light-absorbing layer. An information recording medium for use in a reproducing device that uses a reproducing beam of light with a predetermined frequency. However, R is a phenyl group or a substituted phenyl group.