JPH0477674B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat mode recording method. In heat mode, a laser beam that is intensity modulated and scanned or deflected is focused on a high power density spot and irradiated onto the recording medium to selectively melt, evaporate, remove, or deform a portion of the recording medium to perform recording. Laser beam recording is known as a new recording method with many advantages. In other words, it is a real-time recording that does not require post-processing such as heat development and fixing, and does not require processing liquids, can form images with extremely high resolution and high contrast, and the recording medium is not exposed to room light and does not require darkroom operation. One thing is that it is suitable for recording electrical signals such as computer output and transmitted time series signals, and it is possible to add information later.
It has the following advantages and can be applied to micro images, ultra-micro images, COM, micro facsimile, phototypesetting original plates, etc., and has the potential to contribute to miniaturization of devices, advancement of functions, and improvement of image quality. It is considered that there is enough. However, at present, heat mode laser beam recording is technically incomplete and has not yet achieved sufficient practicality. For example, with regard to recording media, it cannot be said that they have reached a level that satisfies all aspects such as sensitivity, resolution, and strength. Furthermore, regarding lasers, which are closely related to recording media, especially the sensitivity of recording media, there are almost no lasers that can completely cover the performance of recording media in terms of output, stability, device size, etc. Specifically, for example, a recording medium using a metal rhodium sputter film is known, but while this is extremely strong and durable, it has low sensitivity and requires a large, water-cooled laser with high output. There is a disadvantage. Recording media using dispersed coatings of non-metallic powders such as carbon powder are also known, but these have insufficient sensitivity and particularly poor resolution, making them unsuitable for micro-image applications. Films using a semimetal bismuth evaporated film are currently the most sensitive films known, but their film strength is extremely weak and they are not practical as they are. Some non-metal evaporated films have higher sensitivity and higher resolution than bismuth, but even in recording media using these, the laser wavelength that can be used in relation to the absorption spectrum is relatively short. things, e.g.
It is limited to He-Cd, Ar ion lasers, etc., and depending on the purpose, it may be unsuitable for practical use due to the stability of the laser, the size of the device, the price, etc., and at the same time, it has the drawback that it is difficult to obtain high contrast. Typical of these are a series of inorganic substances called chalcogenides. As for lasers, He--Ne lasers are stable and have a long lifespan, but generally have low output, while He-Cd lasers have unstable outputs that are greatly affected by temperature and have a short lifespan. Ar ion laser,
Although Nd:YAG lasers have high output, the overall size of the device including the cooling device, power supply, etc. is large and expensive, and sufficient consideration must be given to safety when handling these high output lasers. There are many points that are not practical. Considering the various problems related to the current lasers and the recording media used for them as described above, especially in this recording field, it is necessary to use lasers with high sensitivity, high resolution, high contrast, high intensity, and long wavelengths. It is understood that there is a strong desire to develop an improved recording medium that can sufficiently absorb laser beams of
The present invention provides a highly practical heat mode recording method that satisfies the above requirements. That is, in more detail, the recording layer is formed so that the reflectance of the entire recording layer to light of a specific wavelength is at least 1/2 or less as compared to the reflectance of the thin metallic layer alone to light of the specific wavelength,
and irradiating a recording medium with a specific wavelength light on a support, the recording layer comprising a laminated metal thin layer having a heat of vaporization that is the same or smaller than that of the metal thin layer, A heat mode recording method is provided, characterized in that the recording layer at the irradiated area is melted and removed. In the heat mode recording medium having the above structure, the contrast is mainly determined by the metallic thin layer in the recording layer, while the sensitivity, resolution and strength performance are affected by the metallic thin layer and the non-metallic thin layer. It depends on the combination of layers. According to the findings of the present inventors, especially regarding sensitivity, compared to the case where each of the above two layers, i.e., the metallic thin layer and the non-metallic thin layer, is used alone as a recording layer, a layer in which the two layers are laminated appropriately It has been found that a recording method in which a large increase in sensitivity can be expected can be achieved by using a recording layer as a recording layer and irradiating this with light of a specific wavelength. In addition, the heat of vaporization of the thin non-metal layer of the recording medium used in the present invention is approximately the same or lower than that of the thin metal layer, and as a result, the thin non-metal layer itself is easily removed thermally. Therefore, the non-metallic thin layer does not excessively impede the melting and removal of the metallic thin layer by absorbing the optical energy of the light irradiation, making it possible to realize highly sensitive recording. The thin metallic layer of the recording medium used in the present invention is preferably formed of a material with a low heat of vaporization, and furthermore, can form a stable thin film and exhibits metallic luster (i.e., has a large light absorption coefficient). metal, metalloid,
Moreover, the heat of vaporization per unit volume is 10Kcal/cm ³
Below, preferably 5Kcal/cm ³ or less, optimally
It is best to choose from materials with 3Kcal/cm3 or ^less . Specifically, it is selected from the elements listed in the table below. An alloy consisting of two or more of these elements, or an alloy to which other elements are added within a range that does not deteriorate the stability, heat of vaporization, toxicity, etc. of the elements may also be used.

【table】

[Table] The thin metal layer can be easily formed into a thin film by vacuum evaporation or sputtering, and in the present invention, the film thickness is 50 to 5000 Å, preferably 100 to 1000 Å, and most preferably 300 to 800 Å. range. Within the above film thickness range, it is easy to achieve high contrast with an optical density of 1 or higher, or even 2 or higher, with the metallic thin layer alone. Note that if the film thickness is too thin, it will be difficult to obtain contrast, and if the film thickness is too thick, a large amount of recording energy will be required. However, the disadvantages of using only a metallic layer as a recording layer are as follows. That is, some types have weak film strength, and all types have high reflectance, so that less than half, usually less than 1/3, of the incident energy can be used. In extreme cases, less than 1/10 of the energy can be used and 9/10
The reflection loss shall be as follows. Therefore, most materials are
It loses absorbed energy, which makes it an apparently low-sensitivity material. In other words, the sensitivity of a heat mode recording material depends on the energy effectively absorbed by the recording layer, the heat of vaporization per unit volume, the thickness of the thin film,
The energy lost through thermal conduction, which is thought to be mostly determined by four factors: heat diffusion to the support due to thermal conduction, has a large reciprocity law failure because it depends on time. , the higher the incident power density, the higher the apparent sensitivity will be. Therefore, it can be explained from the above theoretical basis that the increase in absorbed energy is not only an effect on its own, but also has a synergistic effect with the increase in sensitivity due to reciprocity law failure, resulting in a significant increase in sensitivity. can. The material used for the non-metallic thin layer must satisfy the following conditions. (1) It can be easily formed as a stable, strong thin film with a thickness of 1 μm or less, (2) It does not react with the thin metal layer and cause the recording layer to change in quality, and (3) It does not react with the thin metal layer. (4) When laminated with a thin metal layer, the surface reflectance of the recording medium for a specific wavelength can be lowered by setting the film thickness appropriately. It can be reduced to 1/2 or less, preferably 1/3 or less, and even more preferably 1/10 or less. ) Depending on the method of use, materials should be non-polluting or low-polluting. Materials that satisfy the above conditions are mainly metal oxides, metal fluorides, or so-called chalcogenide substances. Other organic materials can also be used, but the criterion for selection is whether they can be stably formed into a film with a uniform thickness of 1μ or less. For example, polyparasilylene thin films deposited by low vacuum evaporation, thin films of epoxy resins or fluorine resins deposited by vacuum evaporation, and various polymer thin films that can be coated with a spinner using a solvent can be used because they satisfy this condition. The limitation on film thickness is also related to condition (3), and is an essential condition for increasing the sensitivity of recording media. In other words, at the stage where the metallic thin layer absorbs the energy of the laser beam, heats up to its boiling point, and obtains the heat of vaporization and evaporates, the non-metallic thin layer must not strongly impede the evaporation. For this purpose, it is necessary to melt or vaporize with energy at least equal to, and preferably much smaller than, the heat of vaporization of the thin metal layer. That is, the melting point is 1000℃ or less, preferably
The temperature should be below 800℃. When melted, it becomes liquid and can be easily dispersed with the explosive evaporation of the thin metal layer, so melting is sufficient, and generally speaking, the heating energy and heat of fusion are smaller than the heat of vaporization. It is small and can be ignored. However, for this purpose, it is desirable that the film thickness be as thin as possible, preferably 1μ or less, preferably 0.5μ or less. The film thickness must be controlled with an accuracy of two orders of magnitude or more, preferably three orders of magnitude or more, depending on condition (4), and must be formed to a desired thickness. The reason for this is probably that the reflectance is reduced due to the interference effect of the thin film. This was also clarified based on the Examples described later or experimental data related thereto. A reflectance of 1/2 or less in condition (4) is necessary in order to substantially produce the effect of increasing sensitivity. Many thin metallic layers have a surface reflectance of over 90%,
Bi, which is a metalloid, has a reflectance of 70% or more, although it is somewhat low. Reducing the surface reflectance to 1/2 or less has the effect of increasing the absorbed energy by at least 1.5 times, and due to the synergistic effect with reciprocity failure, the effective sensitivity can be increased by at least twice as much. . Specific examples of metal oxides and chalcogenide substances cannot be listed individually because there are many types and many physical property constants are unknown, but for metal oxides and fluorides, the following conditions are mainly used: is the selection criterion, and the other conditions are almost satisfied. For example, the heat of vaporization of PbO, WO ₃ , etc.
2.18, 1.32 (Kcal/cm ³ ) and can be used. Others TiO ₂ , SiO, SiO ₂ , ZrO ₂ , MgF ₂ ,
CaF ₂ and the like are also used. Chalcogenide substances are known as materials with low melting points, and since conditions (3) and (4) are fully satisfied, (2) and (5) are the selection criteria. Chalcogenide substances are known to react with metals such as Ag and Cu due to the action of light or heat. Therefore, when using chalcogenide substances, the material of the metallic thin layer must be a material other than Ag or Cu. Must. Some other materials also react to a lesser extent with chalcogenide materials. At this time, it is necessary to appropriately select a combination of the two in order to minimize the reaction and keep the recording layer stable. A chalcogenide substance is a compound containing chalcogen elements, that is, S, Se, and Te, and in a broad sense, S,
It refers to a wide variety of materials including Se and Te alone. In particular, since the composition can be continuously changed, an infinite number of types exist. In addition to chalcogen elements, typical examples include As, Sb, P, Ge, Si,
Contains one or more materials selected from Tl, other metals, and halogen elements. However, when condition (5) is considered, the chalcogen element is S, and the materials that should form compounds with it are Ge, In, Sn, Cu, Ag, Fe, Bi, Al, Si,
Metals, semimetals, or semiconductors such as Zn, V, etc. are particularly preferred as thin films, and Ge, In,
A chalcogenide substance containing one or more of Sn, Cu, and Ag. Hereinafter, the configuration of the recording medium used in the present invention and the recording process will be explained in further detail with reference to the accompanying drawings. 1a to 5a illustrate various embodiments of the heat mode recording medium used in the present invention. In the figure, numeral 1 represents a support, which may be made of glass, film, paper, metal, or the like. In particular, organic polymer films such as polyester, acetate, vinyl, and polyethylene are used as the film. When irradiating light for recording from the support side, the support is limited to a transparent support. In the case where the support is light-diffusive, recording light is irradiated from the side opposite to the support, and reading is performed by illumination from the support side, the support may be light-diffusive. 2 is a metallic thin layer, 3 is a non-metallic thin layer, and 4 is light irradiated for recording, usually a laser beam. The table shows typical lasers used and their wavelengths.

【table】

[Table] 5 is a layer to protect the metal surface, and is basically selected from the same materials as layer 3, but the film thickness is
If the thickness is 1μ or less, there is no need to particularly control the thickness. When the thickness is controlled to provide an antireflection effect, a structure as shown in FIG. 5a is obtained, and a medium capable of recording with high sensitivity from either side can be obtained. Reference numeral 6 denotes an intermediate layer provided to increase the adhesion force of the thin metal layer to the support when the adhesion force is insufficient, thereby increasing the film strength and the durability of the recording medium. When the support is glass or an organic film, it is preferable to apply a thin layer of various resins to form an intermediate layer. Epoxy resin, silicone resin, vinyl resin,
Gelatin etc. are used. Chalcogen substances can also be suitably used as the intermediate layer. Functionally, the intermediate layer can be either part of the support or part of the recording layer. 1b to 5b show the recorded state as a result of irradiating light (laser) onto the corresponding recording medium (shown in each figure a). The irradiated light is mainly absorbed by the metallic thin layer, but a portion is also absorbed by the non-metallic thin layer. The absorbed light energy turns into thermal energy and raises the temperature of the recording layer, and when the energy is low, internal stress remaining in the recording layer causes a tortoise formation in the heated portion. When the energy further increases, the recording layer becomes molten and the liquid surface deforms due to surface tension. Boiling occurs at the part where the temperature rises the most and reaches the boiling point, but because the phenomenon is short-lived, explosive boiling occurs. becomes. This explosion displaces and flings the molten material, forming a hole and a bulge around it. Depending on the amount of energy and the thickness of the recording layer, the depth of the hole may or may not reach the support. The surface area of the support may also be influenced and changed. From the viewpoint of image contrast, it is most desirable for the depth of the hole to reach the support. Various cases are illustrated in Figures 1b to 5b. For example, Figure 4b
In the illustration, the depth of the hole may sometimes stop at the surface of the intermediate layer. Figures 6a, b, c, d, and e show the positional relationship between the illumination light 7 and the photoreceptor 8 when reading records. Although the recording medium of FIG. 1b is shown as an example, the same applies to other cases. FIGS. 6a and 6b show readout in transparent mode. c, d, and e are reading in reflection mode. In c and d, the recording layer originally has a low reflectance for a specific wavelength, but it has a high reflectance for other wavelengths, so reading with sufficiently high contrast is possible even with surface reflection. It shows something. Particularly in the case of d, the support is a light absorption layer.
e is an example of reflection mode readout from the back surface. The present invention will be further explained with reference to specific examples below. Example 1

【table】

[Table] The spectral total reflectance of the recording layer side of the recording medium obtained under the above conditions is compared with the Bi single layer above.
Shown in the figure. On the other hand, the spectral transmittance is 1 in the wavelength range shown in the figure.
% or less. As shown in the figure, for each laser wavelength, an absorption increase of more than twice that for the direct metallic layer is achieved. The results of laser recording experiments performed on each of the samples are summarized in a table. To measure the sensitivity, the recording medium 15 is mounted on a turntable 16 as shown in FIG. Spiral recording was performed by condensing the light to a spot size of approximately 3 μm, and calculations were made from the limit point where the linear velocity at the outer periphery increased and recording became impossible. The laser beam focusing optical system consisted of a laser 11, a beam expander 12, a mirror 13, and a microscope objective lens 14, and the optical loss due to the optical system was 70% for visible light and 75% for infrared light. As shown in the table, a large improvement in sensitivity has been made, which is extremely important in practical terms, and it is due to this that the heat mode recording medium has been significantly improved.
This opens the way to practical applications such as COM and microfilmers. As shown in the table, the large reciprocity law failure of heat mode recording media is manifested in the large dependence of sensitivity on laser power.

[Table] Example 2 A Bi layer was formed under the same conditions as in Example 1, and _two GeS layers were formed thereon under the following conditions.

【table】

【table】

[Table] Figure 8 shows the spectral total reflectance of the medium obtained above in comparison with the Bi layer. 3000
Approximately 80% of HeNe laser light is absorbed with a film thickness of Å, which is approximately 2.7 times more absorbed energy than directly irradiating the Bi surface with laser light. The sensitivity of this product was measured in the same manner as in Example 1, and the result was 1.5× for a 20 mW He-Ne laser.
10 ⁶ erg/cm ² , which is about 4 erg/cm 2 compared to Bi alone.
The sensitivity has increased twice as much. Incidentally, the deposited film of Bi has low surface strength and adhesive strength, and will be scratched by just lightly rubbing it with paper, and will peel off from the support if rubbed a little too forcefully. In addition, in Examples 1 and 2, the films in which chalcogenide substances were vapor-deposited on the surface had strong film strength, were resistant to scratches, and were extremely durable. Example 3 Almost the same conditions as Example 2, except that the support was 80μ
An acetate film with a thickness of about 2000 Å was first formed as an intermediate layer of GeS ₂ . This layer is substantially uniformly transparent to visible light. After forming this intermediate layer, add another 500 Å of Bi and 3000 Å of Bi.
A layer of GeS ₂ was formed under the same conditions, and almost the same results as in Example 2 were obtained in terms of sensitivity. The recording layer of this recording medium had high adhesive strength and surface strength and had sufficient durability for practical use. When this recording medium was observed in a transmission mode as shown in FIG. 6a or 6, the image contrast was 2.0 in terms of light intensity difference. Example 4 A recording medium substantially similar to that in Example 1 was produced. However, the layer thickness of Ge ₅₀ S ₅₀ was 1700 Å. Also, when depositing Ge ₅₀ S ₅₀ , a mask was partially placed on the Bi surface.
A portion was provided where the Ge ₅₀ S ₅₀ layer was not formed. Recording was performed on this recording medium using the same sensitivity measuring device as in Example 1. However, the light source has an output of 10mW.
A 40x microscope objective lens was used for the He-Cd laser and the focusing objective lens. The turntable was rotating at 341 revolutions per minute. As a result, a spiral line was recorded on the medium. In terms of sensitivity, it is possible to record up to the outer periphery where the circumferential speed is fastest, but when recording was performed with the objective lens defocused and the recording medium slightly out of focus, it was possible to record between a Bi single layer and a Ge ₅₀ S ₅₀ layer. The difference in the recording layer, which is a stack of layers, could be clearly understood through microscopic observation. In other words, when looking at the boundary between the exposed Bi part and the part with the Ge ₅₀ S ₅₀ layer at the inner circumference, lines were recorded in both parts, but the line width of the recorded lines on Bi was not constant, and The line edges were rough. on the other hand
In the area where _{50 Ge 50} S ₅₀ layers were provided, the line width was thicker and more constant than on the Bi layer, and the line edge was very sharp.
This tendency is even more remarkable at the outer periphery; at the outermost periphery, no recording was made on Bi, whereas a clear line was recorded on the area where ₅₀ Ge ₅₀ S layers were provided. . From the results obtained above, it has become clear that the recording method of the present invention is superior not only in high sensitivity but also in high resolution and good image quality. Example 5 A recording medium was formed under the following conditions.

[Table] The spectral total reflectance of the recording layer obtained as described above is shown in FIG. 9 in comparison with the above Au layer. He
The absorption amount for the laser beam was approximately 17 times greater than the wavelength of the -Ne laser, and the sensitivity was approximately 50 times greater.
It is well known that Au vapor-deposited films are easily peeled off and scratched, but the Ge ₅₀ S ₅₀ laminated film was durable and resistant to scratches. Example 6 In, Sn, and Zn can be easily formed as a layer of about 800 Å in place of Au in Example 5, although _there are some _differences in the deposition conditions. I got good results. Example 7 Si and Rh layers were formed by electron beam evaporation.

[Table] The above materials could also be layered by sputtering. Two GeS layers were laminated on the above layer in the same manner as in Example ₂ , and an increase in sensitivity of 3 to 10 times was obtained. Example 8 As a chalcogen substance on various metallic layers
Ge ₂ S ₃ , Sn ₁₂ Ge ₂₅ S ₆₃ , Sn ₁₆ Ge ₁₇ S ₆₇ , Sn ₂₅ Ge ₇ S ₆₈ ,
Sn ₇ Ge ₁₆ S ₇₇ , In ₁₄ Ge ₂₉ S ₅₇ , In ₂₀ Ge ₂₀ S ₆₀ ,
In ₃₀ Ge ₁₀ S ₆₀ , In ₁₀ Ge ₂₀ S ₇₀ , Ag ₂₅ Ge ₂₅ S ₅₀ ,
Ag ₃₃ Ge ₁₇ S ₅₀ , Ag ₁₀ Ge ₃₅ S ₅₅ , Ag ₂₀ Ge ₁₅ S ₆₅ ,
A layer of Ag ₅ Ge ₂₃ S ₇₂ , Cu ₁₄ Ge ₂₉ S ₅₇ , Cu ₃₃ Ge ₁₇ S ₅₀ was formed to a thickness of 1000 to 5000 Å under conditions not much different from the deposition conditions of the chalcogen substance in Example 1 or 2. A recording medium suitable for use with various laser wavelengths was obtained. However, the three-dimensional compound was deposited using a flash deposition method. Example 9 Bi layer in Example 1 and Example 5
A layer of WO ₃ was formed on the Au layer under the following conditions.

[Table] The measurement results for each of the above-mentioned recording layers are summarized in the table for comparison in the case of a single layer.

【table】 [Brief explanation of drawings]

FIGS. 1a, 2a, 3a, 4a, and 5a are schematic diagrams illustrating various aspects of the heat mode recording medium used in the present invention, and FIGS. 1b and 2 b, FIG. 3b, FIG. 4b, and FIG. 5b are laser beams applied to each recording medium shown in FIG. 1a, FIG. FIG. 3 is a schematic diagram illustrating the results of recording. Figure 6 a, b, c,
d and e are explanatory diagrams showing examples of reading from a recording medium after laser recording. FIG. 7, FIG. 8, and FIG. 9 are graphs showing the spectral total reflectance of the recording medium used in the present invention. FIG. 10 is a diagram illustrating an outline of a method for measuring the sensitivity of a recording medium used in the present invention. DESCRIPTION OF SYMBOLS 1...Support, 2...Metal thin layer, 3...Nonmetal thin layer, 4...Recording light (laser), 5...Protective layer, 6...Intermediate layer.

Claims (1)

[Claims] 1 Preventing the reflectance of metallic thin layer and irradiation light,
In addition, in a recording medium having a recording layer on a support formed by laminating non-metallic thin layers having a heat of vaporization that is the same or lower than that of the metallic thin layer, the reflectance of the entire recording layer is equal to or less than that of the metallic thin layer alone. 1. A heat mode recording method, characterized in that the recording layer at the irradiated area is melted and removed by irradiating light with a wavelength that is at least 1/2 or less compared to the irradiation rate.