JPH0323353B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides laser radiation to a thin film layer formed on a substrate.
The present invention relates to a laser recording medium material that records and reproduces optical signals by irradiating a beam and changing its reflectance or transmittance.

The heat mode recording method, which utilizes the thermal effect of a laser beam for recording, has the following advantages: (1) good storage performance with no aging, (2) ability to perform additional recording and playback in real time, and (3) recording density. Because of its characteristic of higher density than magnetic recording, its application to video disks and the like is attracting attention.

Conventionally, heat mode recording media include:
Laser recording media materials are known in which a recording layer is formed on a substrate using a dye and a binder (US Pat. No. 1,117,419), and in which a metal thin film, a metal oxide, or a chalcogenite glass layer is used as the recording layer. (e.g. MLVevene
“ElectronIonandLaserBeamTechnology” No. 11
(1969), Electronics magazine (1968) 3.18.P.50, Japanese Patent Application Laid-Open No. 50-46317) However, since the recording threshold energy of the above-mentioned laser recording medium materials is high, Ar laser, He-Ne
A high-output laser light source such as a laser is required, and a large modulation polarizer must be used. The sensitivity was also designed to be maximized by the laser used. In recent years, semiconductor lasers have been used for laser recording in response to miniaturization of light sources and faster modulation, but the laser output (power) is small and
Since the oscillation wavelength is in the near-infrared region (≈800 nm), conventional recording media have low sensitivity and are difficult to use.

On the other hand, in order to record a large amount of information as a recording medium, the recording surface area is becoming larger, and laser recording media materials, which are desired to be uniform, can be manufactured by omitting processes such as binder coating and by simplifying the manufacturing method. It has become required.

The present invention relates to a laser recording medium material that utilizes a change in the state of a substance using light energy in the near-infrared region that matches the oscillation wavelength of a semiconductor laser, in which a specific metal is dispersed as fine particles in a specific organic substance. The objective is to provide a laser recording medium material that is more sensitive and easier to manufacture than conventional materials.

That is, the present invention provides metals in a transparent organic film by simultaneously vacuum-depositing an organic material selected from fluorescein, Dispose Yellow 51, squarylium dye, and polyparaxylylene and a metal selected from Te, Bi, and Ag. This is a laser recording medium material characterized by being composed of a thin film exhibiting metallic luster in which fine particles are dispersed.

It is desirable to use the metal fine particles with a particle size of 100 Å or less.

Note that it is desirable that the amount of metal fine particles dispersed in the organic substance be 80 Vol% or more. The amount of metal fine particles dispersed needs to take into consideration the thickness of the thin film to be formed, and when the thin film is to be made thin, it is preferable to set the amount of metal fine particles dispersed on the larger side within the above range.

Next, examples of the present invention will be described.

FIG. 1 shows an apparatus for manufacturing laser recording medium materials used in Examples 1 to 7 below. In the figure, 11 is a vacuum container, and a substrate holder 12 is suspended from the upper inner wall of this vacuum container 11. This board holder 1
A shutter 13 is provided below the shutter 2. In the lower part of the vacuum container 11, there is a metal 2 made of high melting point metal.
Two vapor deposition boats 14 ₁ , 14 ₂ are provided, and these boats 14 ₁ , 14 ₂ are provided with heating power sources 15 ₁ , 1
5 ₂ are connected respectively. Further, a vacuum pump 16 is connected to the vacuum container 11 for exhausting gas within the container 11.

To produce a laser recording medium material using the above-mentioned manufacturing apparatus, first, a desired substrate 17 is held in the substrate holder 12, the vacuum pump 16 is activated to evacuate the vacuum container 11, and then organic matter is removed from one side. It is housed in a vapor deposition boat 14 ₁ , and the boat 14 ₁ is heated by being supplied with electricity from a heating power source 15 ₁ , and the vacuum container 11 is filled with organic vapor and maintained at a constant pressure. Subsequently, metal is placed in the other vapor deposition boat 14 ₂ and similarly heated to evaporate the metal. The metal evaporated from the deposition board 14 ₂ collides with the organic vapor in the vacuum container 11 to form fine particles. In this state, shutter 1
By opening 3, a thin film 18 in which fine metal particles are dispersed in an organic layer is formed on the substrate 17. When forming such a thin film 18, the diameter of the metal fine particles and the content of the metal fine particles in the thin film can be controlled by adjusting the pressure of the organic vapor.

Examples of laser recording media produced using this apparatus are shown below.

Example 1 Using fluorescein as an organic substance and as a metal
Using Te, the deposition rate was 2 by volume on a glass substrate.
When the shutter 13 is opened after controlling the current to each vapor deposition boat 14 ₁ , 14 ₂ so that it becomes a pair, the substrate 1
A fluorescein film in which Te metal fine particles are dispersed is formed on 7. Fluorescein vapor pressure is 1×
At about 10 ^-5 Torr, the Te particles have a size of about 100 Å. Vapor deposition is finished when the total film thickness is 0.3 μm. The resulting film is a transparent orange fluorescein film mixed with dispersed Te, resulting in a gray-orange film with a metallic luster on the surface.

The obtained laser recording medium material is dispersed
Due to the absorption of Te fine particles, it has an absorption coefficient of 10 ⁵ cm ^-1 or more in the semiconductor laser oscillation region (800 nm). Writing was performed on this medium using a semiconductor laser pulse (830 nm) with a light beam diameter of 1.5 x 1.8 μm and a power of 6.0 mW on the medium surface. As shown in FIG. absorbed into
The Te fine particles and fluorescein were evaporated and sublimated by the heat, and recording pits 23 were formed in the thin film 22. At this time, the threshold pulse width required for pit formation was 100 nsec, which corresponded to a sensitivity of approximately 30 mJ/cm ² . The pit formation reduces the thin film surface reflectance,
By scanning with a laser beam of weakened power, the reflectance on the thin film surface changed as shown in FIG. 3, and it was possible to determine whether a signal was recorded. Note that 31 in FIG. 3 is the reflectance of the unrecorded area, and 32 is the reflectance of the recorded pits, which are lower than 31.

Example 2 In the same manner as in Example 1, a thin film was prepared on a glass substrate in which Bi particles were dispersed in a fluorescein layer at a volume ratio of 2:1. When writing was performed on the obtained thin film using a semiconductor laser pulse under the same conditions as in Example 1, the incident laser light was absorbed by the thin film 42 on the substrate 41 as shown in FIG. The remaining Bi particles were evaporated and sublimated to form recording pits 43 in the thin film 42, and the remaining Bi particles were melted to form fringe parts 44 around the pits 43. At this time, the pulse width required for pit formation was 120 nsec, which corresponded to a sensitivity of approximately 35 mJ/cm ² . The reflectance of the thin film surface decreased due to pit formation, and by scanning with a laser beam of weakened power, the reflectance of the thin film surface changed as shown in FIG. 5, and it was possible to determine whether a signal was recorded. In FIG. 5, numeral 51 indicates the reflectance of the unrecorded portion, 52 the reflectance of the fringe portion, and 53 the reflectance of the recorded pit.

Example 3 First, a 0.20 μm fluorescein film was formed on a glass substrate, and a 200 Å thick thin film containing Te fine particles and fluorescein at a volume ratio of 9:1 was further formed on the fluorescein film. The resulting two-layer structure film has a reflectance of 40% or more. When this two-layer structure film was written with a semiconductor laser pulse under the same conditions as in Example 1, most of the incident laser light was absorbed by the thin film 63 on the fluorescein film 62 of the substrate 61, as shown in FIG. The laser incident portion of this thin film 63 was evaporated and sublimated to form recording pits 64. At this time, the recording threshold was 80 nsec, which corresponded to a sensitivity of about 25 mJ/cm ² . Also,
By scanning with a laser beam in the same manner as in Example 1, the reflectance on the thin film surface changed as shown in FIG. 7, and it was possible to determine whether a signal was recorded. In addition,
In FIG. 7, 71 indicates the reflectance of the unrecorded area, 72 indicates the reflectance of the fluorescein film on the substrate, and 73 indicates the reflectance of the recording pit.

Example 4 Ag fine particles and Disperse Yellow 51 were placed on a glass substrate in a volume ratio of 2:1 in the same manner as in Example 1.
A thin film with a thickness of 200 Å was formed. When writing was performed on the obtained thin film using a semiconductor laser pulse with a pulse width of 500 nsec or less, as shown in FIG. Recording pits 84 were formed. At this time, the recording threshold was 80 nsec, which corresponded to a sensitivity of about 25 mJ/cm ² . By scanning such a thin film with a laser beam, the reflectance on the surface of the thin film changes as shown in FIG. 9, making it possible to determine the presence or absence of signal recording. In FIG. 9, 91 indicates the reflectance of the unrecorded area, 92 indicates the reflectance of the recorded pits due to crystallization, and 93 indicates the reflectance of the recorded pits due to sublimation.

Furthermore, when writing was performed using a semiconductor laser with a pulse width of 500 nsec or more, recording pits with reduced reflectance were formed due to melting of the Ag particles and sublimation of the dye. This recording threshold is approximately 500nsec.
A value corresponding to a sensitivity of 300 mJ/cm ² was shown.

Example 5 When polyparaxylylene (parylene) is used as an organic substance, the following method is used. The paraxylylene dimer evaporated in the evaporation furnace passes through a decomposition furnace heated to around 650℃ and is decomposed into monomers.
It is introduced into the deposition chamber as a low-temperature gas at 25℃. The deposition chamber has deposition boats 14 ₁ and 14 ₂ shown in FIG. 1, and Te is deposited from them. In this way, the substrate 17
A Te-dispersed polyparaxylylene thin film was prepared by dispersing Te fine particles at a volume ratio of 2:1. When a semiconductor laser pulse was written on this thin film, the dispersed Te fine particles crystallized, and recording pits 103 with increased reflectance were formed in the thin film 102 on the substrate 101 as shown in FIG. .
This recording threshold corresponded to a sensitivity of about 60 mJ/cm ² at 200 nsec. By scanning such a thin film with a laser beam, the reflectance on the surface of the thin film changes as shown in FIG. 11, making it possible to determine whether a signal has been recorded.
Note that 111 in FIG. 11 is the reflectance of the unrecorded area;
112 indicates the reflectance of the recording pit.

Example 6 A metal that creates a mirror surface, such as A, is vapor-deposited on the substrate to form a reflective layer. A fluorescein film with a thickness of 0.25 μm is further vapor-deposited on the reflective layer, and then Te fine particles are added to the fluorescein layer at a volume ratio of 9:1. dispersed thickness
A thin film of 200 Å was laminated. With such a laminated structure, the writing laser beam causes interference between the reflective layer and the thin film, and the reflectance decreases to 5% or less. Although it can be used as a laser recording medium as it is, a 0.5 μm thick polyparaxylylene layer was further laminated on the surface to form a protective layer.

When writing was performed on the obtained laminated film using a semiconductor laser pulse, the laser light was absorbed by the thin film 124 on the reflective film 122 and fluorescein film 123 laminated on the substrate 121, sublimated and melted, as shown in FIG. Recording pits 125 were formed in the exposed thin film 124, and recording pits 126 were also formed in the thin film 124 under the protective layer 127. The recording threshold at this time is
At 20 nsec, and at 30 nsec at the location where the protective layer was present, values corresponding to sensitivities of approximately 6 mJ/cm ² and approximately 10 mJ/cm ² were shown, respectively. Furthermore, by scanning such a laminated film with a laser beam, the reflectance on the surface of the laminated film changed as shown in FIG. 13, and it was possible to determine the presence or absence of signal recording. In addition, 131 in FIG. 13 is the reflectance of the unrecorded area where there is no protective layer, 132 is the reflectance of the unrecorded area where the protective layer is present, and 133 is the recorded area where there is no protective layer. The reflectance of the pit, 134 is the reflectance of the recording pit at the location where the protective layer is present.
shows.

Reference Example As in Example 1, a thin film was prepared on an acrylic substrate in which Bi particles were dispersed in a copper phthalocyanine film at a volume ratio of 1:2. When writing was performed on this thin film using semiconductor laser pulses, the first
As shown in FIG. 4, part of the copper phthalocyanine and Bi fine particles in the thin film 142 on the substrate 141 evaporate and sublimate to form recording pits 143, and the remaining part evaporates and sublimates.
The Bi particles were melted and a fringe 144 was formed near the periphery of the pit 143. The laser pulse width required to form this recording pit is 140 nsec and approximately 40 mJ/cm ²
This corresponded to a recording sensitivity of Furthermore, by scanning such a thin film with a laser beam, the reflectance on the surface of the thin film changed as shown in FIG. 15, and it was possible to determine whether a signal was recorded. Note that 151 in FIG. 15 indicates the reflectance of the unrecorded portion, and 152 indicates the reflectance of the recorded pit.

Example 7 As in Example 1, Te fine particles were placed on a glass substrate at a volume ratio of 1 in a dimethylaminosquarylium film.
A thin film was prepared in which the mixture was dispersed at a ratio of 3:3. When writing was performed on the obtained thin film using semiconductor laser pulses, dimethylaminosquarylium and
A portion of the Te fine particles evaporated and sublimated, forming recording pits 163 in the thin film 162. The laser pulse width required for pit formation is 100nsec and approximately 30mJ/cm ²
Compatible with recording sensitivity. Furthermore, by scanning such a thin film with a laser beam, the reflectance on the surface of the thin film changed as shown in FIG. 17, and it was possible to determine whether or not a signal was recorded. Note that 17 in Figure 17
1 indicates the reflectance of the unrecorded area, and 172 indicates the reflectance of the recorded pit.

As is clear from the above Examples 1 to 7, the laser recording medium material obtained by the present invention can be easily and uniformly produced by a method such as vapor deposition of two types of substances on a substrate without using substrate heating or the like. can be obtained. For this reason, materials that are deformed by heat, such as plastics, can also be used as the substrate material.

In addition, metals and metalloids such as Te, Bi, and Ag that absorb semiconductor laser light (with large absorption coefficients) become fine particles, forming a sublimable organic material matrix (with small absorption coefficients) whose thermal conductivity is much lower than that of metals. Since it is dispersed, pits are formed by laser beam irradiation through the following actions.

(1) The irradiated laser beam is absorbed by the dispersed metal particles. Because it is in the form of fine particles, the surface area is much larger than that of a continuous vapor-deposited film of the same volume, so it is effectively absorbed and converted into heat internally.

(2) The generated heat causes the fine particles of Te, Bi, and Ag to sublimate and melt themselves, but at the same time, they transfer heat to the surroundings through thermal diffusion. However, since the organic matrix has extremely low thermal conductivity, the generated heat diffuses less than in metal/semimetal films and is concentrated locally, resulting in extremely high temperatures.

(3) Since the organic matrix itself has sublimation properties at temperatures equal to or lower than those of metals, the organic matrix sublimates and evaporates, and at the same time the metal fine particles that serve as absorbers also begin to sublimate and melt. As a result, recording pits are generated in the laser recording medium due to sublimation and melting due to laser beam irradiation.

As described in detail above, the laser recording medium obtained by the present invention is a vapor-deposited film made only of metals or semimetals, or a film made only of an organic matrix (for example, a Te film,
It has a high semiconductor laser recording sensitivity due to its effective light absorption and heat concentration compared to the fluorescein film (fluorescein film), and it also has a thin film interference effect as in Example 6 by giving a concentration gradient to the metal particles to be dispersed. Using this method, the contrast during readout of the recording pits can be increased, and it has remarkable effects such as high sensitivity and high contrast readability, and large area uniform media can be easily achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of a manufacturing apparatus for obtaining the laser recording medium material of the present invention, and FIG. 2 is a schematic diagram showing the state of the laser recording medium obtained in Example 1 of the present invention after writing. 3 is a characteristic diagram showing the reflectance of the recording medium in FIG. 2, FIG. 4 is a schematic diagram showing the state of the laser recording medium obtained in Example 2 of the present invention after writing, and FIG. is a characteristic diagram showing the reflectance of the same medium shown in FIG. 4, and FIG. 6 is a characteristic diagram showing the reflectance of the same medium as shown in FIG.
7 is a characteristic diagram showing the reflectance of the same medium in FIG. 6, and FIG. 8 is a schematic diagram showing the state of the laser recording medium obtained in Example 4 of the present invention after writing. A schematic diagram showing the state of the recording medium after writing, FIG. 9 is a characteristic diagram showing the reflectance of the same medium in FIG. 8, and FIG. 10 is a diagram showing the state of the laser recording medium obtained in Example 5 of the present invention after writing. FIG. 11 is a characteristic diagram showing the reflectance of the same medium in FIG. 10, and FIG. 12 is a schematic diagram showing the state of the laser recording medium obtained in Example 6 of the present invention after writing. 13 is a characteristic diagram showing the reflectance of the same medium in FIG. 12, FIG. 14 is a schematic diagram showing the state of the laser recording medium obtained in Example 7 of the present invention after writing, and FIG. 15 is a characteristic diagram showing the reflectance of the same medium in FIG. is a characteristic diagram showing the reflectance of the same medium in FIG. 14, FIG. 16 is a schematic diagram showing the state of the laser recording medium obtained in Example 8 of the present invention after writing, and FIG. 7 is a characteristic diagram showing the reflectance of the same medium in FIG. It is a characteristic diagram showing the reflectance of the same medium. 11...vacuum container, 13...shutter, 14 ₁ ,
14 ₂ ... Adsorption boat, 15 ₁ , 15 ₂ ... Heating power supply, 16 ... Vacuum pump, 17, 21, 41, 6
1,81,101,121,141,161...
Substrate, 22, 42, 63, 82, 102, 12
4,142,162... Thin film (medium), 23,
43,64,84,103,125,126,1
43,163...Record pit.

Claims (1)

[Claims] 1. Fluorescein, Dispose Yellow 51,
By simultaneously vacuum-depositing an organic material selected from squarylium dye and polyparaxylylene and a metal selected from Te, Bi, and Ag, a thin film exhibiting metallic luster with fine metal particles dispersed in a transparent organic material film is formed. A laser recording medium material characterized by: 2. The laser recording medium material according to claim 1, wherein the upper surface of the thin film is coated with a protective film layer, and the lower surface of the thin film is coated with a reflective layer.