JPH0489278A - Optical recording medium using laser beam - Google Patents

Abstract

PURPOSE:To obtain adequate density on a white background using the light intensity of a semiconductor laser by providing a layer which contains a basic colorless dye and an organic developer forming a near-infrared absorbing coloring element on a base. CONSTITUTION:A near-infrared absorbing basic colorless dye contains a leuco colorless dye and does not show near infrared absorptive properties in a pre- coloring state. In addition, the dye is compatible with an organic developer with the assistance of thermal energy or a solvent. Subsequently, a lactone ring breaks open to become colored and at the same time, a near infrared absorbing coloring element is generated. Organic developers are such as a bisphenol A and 4-hydroxy benzoic ester. To provide an optical recording layer on a base such as paper, plastic sheet and metal sheet, these colorless dye and organic developer are dissolved by dispersing it in an organic solvent or an organic solvent containing water. After that, both are mixed and this mixture is applied to a base. The optical recording medium obtained maintains a white background until its chemical reaction with an organic developer following its pre-development colorless state. After its color development, the medium shows a sharp contrast.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording medium that performs recording by irradiation with near-infrared light, particularly focused laser light.

The heat sensitive recording method is a direct recording method that does not require development or fixing.
It is widely used in facsimiles and printers due to its excellent operability and maintainability.

However, because the thermal head and heat-generating IC pen are brought into direct contact with the thermal recording paper to perform heating recording, colored melt adheres to the thermal head and heat-generating IC pen, causing problems such as adhesion of scum and sticking, resulting in recording failure. There were also problems with recording quality.

Particularly in the case of continuous line drawing in the recording flow direction, such as with a plotter printer, it has been impossible to perform continuous printing without causing problems such as adhesion of residue.

Further, the image resolution by the thermal head is mainly 8 lines/anus, and it is said that it is difficult to increase the resolution beyond this.

Therefore, a non-contact recording method using light has been proposed as a method to eliminate problems such as residue adhesion and stinking and further improve resolution.

For example, Japanese Patent Application Laid-Open No. 54-4142 discloses that a heat-sensitive recording material in which a support is coated with a recording layer mainly composed of a leuco dye and a metal compound having lattice defects is capable of thermal recording by absorption of light. It has been disclosed that this is possible.

Moreover, in Japanese Patent Application No. 58-209594, 0.8 to 2
JP-A-58-94494 discloses an optical recording medium in which at least one set of a near-infrared absorber having an absorption wavelength in the μ-near infrared region and a thermosensitive coloring material are laminated on a substrate. A base material is coated with one or more heat-sensitive materials and one or more near-infrared absorbers consisting of a compound having a maximum absorption wavelength in the near-infrared region of 0.7 to 3 μM. A recording medium is disclosed.

In addition, in these publications, the method of coating the near-infrared absorber and the heat-sensitive coloring material on the substrate or base material is to mix the near-infrared absorber and the heat-sensitive coloring material and coat it, or to coat the near-infrared absorber and the heat-sensitive coloring material on the substrate or base material. This is a method in which a color-forming material layer is first coated on a substrate or base material, and a near-infrared absorber is applied onto this heat-sensitive color-forming material layer to laminate or cover the layer.

Examples of near-infrared absorbers having an absorption wavelength in the near-infrared region of 0.8 to 2 μm include dyes such as cyanine dyes, thiol nickel complexes, and squarylium. Furthermore, other near-infrared absorbers include nitroso compounds and their metal complexes, polymethine-based dyes (cyanine-based dyes), as seen in "Near-infrared Absorbing Dyes" (Kagaku Kogyo 43, May 1986). , complexes of thiol and cobalt or palladium, phthalocyanine dyes, triallylmethane dyes, immonium or diimmonium dyes, naphthoquinone dyes, and the like are known.

In the descriptions of patent documents related to recording by conventional laser light irradiation, especially semiconductor laser light irradiation, practically necessary knowledge, such as the relationship between the background color and absorption of the recording medium, and examples are described. Laser irradiation conditions such as laser output are ambiguous or unclear.

Furthermore, in the optical recording media disclosed in these patents, the color (ground color) of the optical recording before recording was quite dark, which was far from the feel of plain paper. If measures such as reducing the amount of near-infrared absorbing material used or providing a concealing layer with a high degree of whiteness are taken to whiten the background color, there is a problem in that the coloring sensitivity becomes low.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical recording medium that has a white background and can obtain a sufficient recording density with a light intensity comparable to the output of a semiconductor laser.

In the case of a heat mode optical recording medium, recording becomes easier in proportion to the near-infrared absorption.Materials with high near-infrared absorption absorb visible light and are colored. Therefore, from the perspective of recording, it is desirable that the absorption at the main wavelength of the vanguard laser be as high as possible, that is, the reflectance should be small, but from the perspective of ground color contrast, it is preferable that the reflectance be large. However, with conventional optical recording media, those with a white background color that has a reflectance of 80% or more,
With the output of a semiconductor laser on the order of several thousand 1, it is not possible to record even at low recording speeds.

That is, a good recording density or recording speed and a white background color are contradictory, and no technique has hitherto been found that satisfies both at the same time. Under these circumstances, the present inventor selected various colorless dyed materials as described above and conducted intensive studies to achieve the purpose of the invention. When an optical recording medium is formed with a layer containing this specific basic colorless dye and an organic color developer, this optical recording medium has a wavelength of 780 to 780.
The reflectance of the surface of the optical recording medium is 95 for light of 900r+m.
% or more, and even when it is considered that laser light is not substantially absorbed in this wavelength region, the inventors have discovered the revolutionary phenomenon that a recorded image can be obtained, and have completed the present invention.

That is, the present invention uses a basic colorless dye and an organic developer, which normally do not exhibit near-infrared absorption, but which form a near-infrared-absorbing coloring material by being compatible with an organic color developer, on a substrate. The present invention relates to optical recording using a laser beam provided with a layer containing a coloring agent. In the following description, a basic colorless dye having such properties will be referred to as a near-infrared absorbing basic colorless dye.

Furthermore, by adding an aromatic monocarboxylic acid metal salt as a photosensitizer in addition to a near-infrared absorbing basic colorless dye and an organic color developer, we have created an optical recording paper with high reflectance and excellent sensitivity. It becomes possible to obtain. Furthermore, in the present invention, a light-absorbing material containing at least one of a water-soluble organic near-infrared absorbing material or a near-infrared absorbing material ultrafinely divided into particles of 3 microns or less on the optical recording layer is provided. By providing a protective layer or providing near-infrared absorbing minute dots on the above layer, an optical recording medium with high sensitivity can be obtained.

In the present invention, near-infrared absorbing basic colorless dyes that normally do not exhibit near-infrared absorbing properties but form a near-infrared absorbing coloring material by being compatible with an organic color developer are exemplified below. It contains a leuco-based colorless dye that shows no near-infrared absorption in the state before color development, and when heat energy is applied in the presence of an organic color developer or the organic color developer is mixed with a solvent. When they are compatible, the lactone ring is cleaved, forming a coloring body that develops color and exhibits near-infrared absorption.

Classification (Structural Formula) Color Tone Abbreviation Divinylsulfonylmene Example N(CHi)z Divinylph I Dou2 Among these, especially G-118,3,6,6'-)lis(dimethylamino)spiro Fluorene dyes such as (fluorene-9,3-phthalide) are the most suitable near-infrared absorbing leuco dyes in the present invention.

Furthermore, when such a near-infrared absorbing basic colorless dye is mixed with the following leuco dye, which has been conventionally known in the field of thermal recording, optical recording with more layers and excellent color tone can be achieved. You can get a body.

Triphenylmethane type such as crystal violet lactone, fluoran type such as 3-diethylamino-6-methyl-7-ayurinofluorane, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl 2- azaphthalide dyes such as methylindol-3-yl)-4-azaphthalide;

The organic color developer used in the present invention includes bisfluoro)L,
A 11.4-hydroxybenzoic acid esters, 4-hydroxyphthalic acid diesters, phthalic acid monoesters, bis-(hydroxyphenyl)phenyl sulfides, 4-hydroxyphenylaryl sulfones, 4-hydroxyphenylaryl sulfonates , 1,3-di[2-(hydroxyphenyl)-2-propyl 1-henzenes, 4-hydroxyhendiyloxobenzoic acid esters, bisphenol sulfones, and the like. Details of these materials are disclosed in, for example, Japanese Unexamined Patent Publication No. 187082/1982.

In the present invention, the aromatic monocarboxylic acid metal salt used as the photosensitizer itself exhibits almost no near-infrared absorption; specific examples include 4-chlorobenzoic acid, 3- Chlorbenzoic acid, 3,4-dichlorobenzoic acid, 4
-bromobenzoic acid, 3-bromobenzoic acid, 3,4-dibromobenzoic acid, 4-fluorobenzoic acid, 3-fluorobenzoic acid, 3,4-difluorobenzoic acid, 4-iodobenzoic acid, 3-iodobenzoic acid , 3.4 syotobenzoic acid,
0-benzoylbenzoic acid, 0-phthalic acid monohensyl ester, 4-nitrobenzoic acid, 3-nitrobenzoic acid, 3
, 4-dinitrobenzoic acid, 4-nitro-3-methylbenzoic acid, 4-nitro-5-methylbenzoic acid, 3,5-dinitrobenzoic acid, 2-hencyyl-4-nitrobenzoic acid,
2-hencyyl-3-nitrobenzoic acid, 4-t-butyl-3-nitrobenzoic acid, 4-t-butyl-3,5-dinitrobenzoic acid, 3-nitro-4-methylbenzoic acid, 3-
Nitro-5-methylbenzoic acid, 3-nitro-2-methylbenzoic acid, 4-nitro-5-chlorobenzoic acid, 4-nitro-2-chlorobenzoic acid, 4-nitro-5-chlorobenzoic acid, 3-nitro -4-lychorobenzoic acid, 3-nitro-5
- Metals such as chlorobenzoic acid, and as metal salts, C
a, Zn, Ni, Ti, Ba, Pb, Co
Polyvalent metals such as FeCu are preferred, especially Ca, Z
n is particularly excellent in that there is little deterioration in background color even in high-temperature environments.

Moreover, paper, synthetic paper, nonwoven fabric, woven fabric, plastic sheet, metal plate, etc. are used as the base material. These materials are not particularly limited in terms of transparency, opacity, coloring, thickness, etc., and are appropriately selected depending on the purpose.

Then, in order to provide an optical recording layer containing the above-mentioned near-infrared absorbing basic colorless dye, an organic color developer, and a photosensitizer on the base material, as in the case of conventional thermal recording paper, These colorless dyes, organic color developers, and photosensitizers can be dispersed or melted in an organic solvent or a water-containing organic solvent using a sandcliner or the like, and the two can be mixed to make a paint, or the two can be mixed together to form a paint. It is preferable to prepare a separate paint and apply this onto the substrate.

Of course, when preparing the paint, binders, white pigments, aggravating agents, color image stabilizers, quality control agents for adjusting the slipperiness and other qualities of the recording layer, etc. may be added as appropriate.

Specific examples of the binder, white pigment, aggravating agent, color image stabilizer, or quality control agent include those described in Japanese Patent Application Laid-open No. 187082/1982 and many other known documents regarding heat-sensitive recording paper.

It is possible to add a conventionally known near-infrared absorber to the optical recording layer. Many of the conventionally known near-infrared absorbing materials cannot be used in large quantities at the same time because they have a desensitizing effect when coloring with basic colorless dyes and organic color developers.
In the present invention, since it is sufficient to serve as a light-absorbing base for the initial heat conversion, a small amount is sufficient.
It can be used without worrying about deterioration of background color due to 2 effects or near-infrared absorbers.

Furthermore, several methods can be considered to provide light absorption sites to improve the recording speed. One method is to provide a light-absorbing protective layer over the entire surface of the optical recording layer.

The light-absorbing protective layer only needs to have a reflectance of the same level as the base of light absorption, and from that point of view, the surface of the optical recording medium should have a reflectance of 50% or more at the maximum wavelength of the laser beam.
Even a high reflectance of 0% is effective. As a result,
The amount of near-infrared absorbing material used up to now can be significantly reduced, and at the same time the optical recording layer described above can be protected, and the initial light-to-heat conversion efficiency can be increased without further worrying about desensitization effects. . The light-absorbing protective layer is made of at least one of a water-soluble organic near-infrared absorbing material or a near-infrared absorbing material ground into ultrafine particles of 3 microns or less by a wet or dry method. It can be dispersed in a protective film-forming binder and created in the same manner as the layer containing the near-infrared absorbing basic dye and organic color developer described above.

Furthermore, it is an extremely preferable method to prepare near-infrared absorptive microdots, which serve as bases of light absorption, on the optical recording layer by printing or the like. In that case, the dot area is preferably 0.1 to 50%, particularly preferably 1 to 30%. Also, the number of lines per inch is preferably 10 to 500, but especially 50 to 200.
is preferable. By doing so, the amount of near-infrared absorbing material used can be further significantly reduced, so that an optical recording medium capable of high-speed recording without desensitizing effect and coloring of the background can be obtained.

The water-soluble organic near-infrared absorbing material in the present invention is preferably dissolved in a solvent such as water, alcohol, or toluene by 5% or more, and near-infrared absorbing material S 101756 manufactured by IC1,
S 116510, S 116510/2, S 109
186, S 109564, S 109564/2, etc. can also be used. Among them, S 1165 is soluble in water.
10, S 109564 and alcohol-soluble S
116510/2 is preferred.

Further, near-infrared absorbing materials that are ultrafine particles of 3 microns or less include most near-infrared absorbers.

This near-infrared absorber may be one that has absorption in the near-infrared range of 0.7 to 3 Ilμ, and is known from the conventionally known methods such as JP-A-54-4142, JP-A-58-209594, and JP-A-58-209594. In addition to cyanine dyes, thiol nickel complexes, and squarylium dyes disclosed in Japanese Patent Publication No. 5894494, nitroso compounds and their metal complexes in "Near-infrared absorption dyes" (Kagaku Kogyo 43, May 1986 issue), Polymethine dyes (cyanine dyes), complexes of thiol and cobalt or palladium, phthalocyanine dyes, triallylmethane dyes, immonium or diimmonium dyes, naphthoquinone dyes, or the like discovered by the present inventors and filed for patent application. 1-27186, thiourea derivatives such as 1,3-diphenylthiourea and L3-dibenzylthiourea and organic acid salts of metals with an atomic weight of 40 or more excluding groups IA and IIA of the periodic table;
Unexamined Patent Publication No. 2003-11002 filed by the present inventors regarding an optical recording medium using a treatment product obtained by mixing and heat-treating Alcolade or hydroxide, or a dispersible near-infrared absorber.
Examples include dispersible near-infrared absorbers such as copper sulfide and graphite described in Japanese Patent No. 80486.

It is preferable that the maximum absorption wavelength of the light absorbent coincides with or is close to the king wavelength of the recording light in terms of heat conversion efficiency and the amount of heat generated. In order to obtain a record that can be read with the naked eye, it is preferable that the maximum absorption wavelength of the light absorbent and the dominant wavelength of the recording light source are outside the visible range.

The light sources necessary for optical recording in the present invention include lasers such as semiconductor lasers and diode bombing YAG lasers, quartz flash lamps, and halogen lamps.
Any light source containing light in the near-infrared region wavelength of 00 to 2500 nm can be used, and any one of them can be selected depending on the purpose of use.

The light intensity needs to be high enough to generate enough heat to color the substance that develops color due to heat, but this kind of light intensity can be obtained with a small and simple device, and the light can be easily focused. It is preferable that the light is safe. From this point of view, semiconductor laser light having a dominant wavelength in the near-infrared region is currently the most preferred.

Moreover, it is most desirable to use the laser beam by condensing it with a condensing lens.

In the present invention, a laser beam recording material in which a layer containing a near-infrared absorbing basic colorless dye and an organic color developer as main components is provided on a base material has a reflectance for the maximum wavelength of the laser beam. 85
% or more, the mechanism by which the heat mode recording layer develops vivid color when the recording surface is irradiated with laser light is not necessarily clear, but even if the reflectance is high and there is a lot of reflected light, the near-infrared absorbing basic dye Because it has a photoaccumulative property, the light energy of the laser, especially the light energy focused by the condensing lens, is accumulated and then converted into heat, and the heat generated at this time is used to absorb near-infrared absorbing basic colorless dyes and It is thought that it effectively melts the color developer and produces a near-infrared absorbing color former. Once a near-infrared-absorbing color former is generated, the near-infrared absorbance of its surroundings increases to an extreme level, making it easier to undergo thermal conversion, resulting in the formation of near-infrared absorbing basic colorless dyes and organic color developers. It is thought that the near-infrared absorbing color forming material is produced at an accelerated pace as the near-infrared absorbing coloring material is sequentially melted, resulting in vivid color development. Near-infrared absorbing basic colorless dyes are virtually colorless before color development, so even if they are present together with an organic color developer, the background color remains white until they become compatible and react, and after color development, the background color remains white. An optical recording medium with excellent contrast can be obtained.

By incorporating at least one of a water-soluble organic near-infrared absorbing material or a near-infrared absorbing material ultrafinely divided into particles of 3 microns or less into the light-absorbing protective layer,
Since the light from the light source can be absorbed over a wide range and efficiently converted into heat, recording start and recording speed can be improved.

Furthermore, if near-infrared absorptive microdots are provided on the optical recording layer,
First, near-infrared light is converted into heat at a microscopic point, and the area around the microscopic point develops color due to the thermal energy. Since the coloring product absorbs near-infrared light, coloring and absorption are effectively linked, allowing continuous high-speed optical printing.

According to the present invention, the optical recording material is substantially colorless before color development, but since the produced coloring material has near-infrared absorbing property, the near-infrared light used for the light-absorbing protector or the light-absorbing minute dots The absorbing material only needs to improve the efficiency of the initial light-to-heat conversion. This makes it possible to significantly limit the amount used, which not only makes it possible to use light absorbers that have previously been abandoned due to their excellent stability but too strong coloring, but also enables the use of light absorbers that have never been seen before. An optical recording medium with excellent appearance can be obtained.

For example, in the case of a colored material that shows a density of 1.21 when coated or printed on the entire surface, the dot area is 1.
When printing at 0% and 100 lines, the density is 0.16, the amount of coloring material used is 1/10, and the whiteness is 7.5 times whiter.

Therefore, if a near-infrared absorbing material that exhibits a density of about 0.3 when coated and printed on the entire surface is printed as light-absorbing minute dots with a dot area of about 30%, a piece of paper that is almost indistinguishable from white paper with the naked eye will be obtained. Therefore, by printing a near-infrared absorbing material as a light absorber to a dot area ratio of about 30% and then forming a recorded image, an optical recording medium with excellent image contrast can be obtained.

EXAMPLE 1 Examples of the present invention will be described below. Parts in the examples are parts by weight.

Example 1 [Color forming layer] (A) liquid (colorless dye dispersion) (B) liquid (color developer dispersion) (A) liquid and (B) liquid were separately prepared in a test sandcline according to the above formulation. It was obtained by wet grinding for 1 hour in a grinder.

(A) liquid (colorless dye dispersion) 6.67 parts, (B) liquid (
An optical recording N coating liquid was obtained by mixing 25 parts of a silica (Mizukasil P-527, manufactured by Mizusawa Chemical Co., Ltd.) dispersion with a concentration of 25% with 25 parts of a color developer dispersion.

The above coating liquid was applied onto a high-quality paper with a basis weight of 60 g/nf using a Mayer bar so that the coating amount was 5 g/rrf and dried to obtain an optical recording sheet. Also, this sheet is 830n
There was almost no near-infrared light absorption in i+, and the reflectance was 95%.

A semiconductor laser device (laser diode collimator head LDC-8330-CINC) is attached to the above optical recording paper.
, manufactured by Applied Optec, center wavelength 830rv+
, output 30 mW) as shown in FIG. 1 for optical printing.

That is, the laser diode collimator head (1)
The laser beam generated from the shutter (2) was passed through the shutter (2) and condensed by the condensing lens group (3), and the optical recording paper was irradiated with the condensed laser beam. Note that (5) in the figure indicates a power source.

The condenser lens is MD P LAN5 manufactured by Olympus Optical Co., Ltd.
, (numerical aperture 0.1), and the recording movement speed during irradiation was 1.5 mn/sec. The color development line was measured using a densitometer (PDM-5 manufactured by Konishiroku Photo Industry Co., Ltd.), and the measured value was converted into Macbeth density. As a result, a green image with an excellent contrast of a color density of 1.35 and a background color of 0.04 was obtained.

Example 2 Liquid (C) (Photosensitizer Dispersion) Liquid (C) was obtained by wet grinding for 1 hour using a test sand grinder according to the above formulation.

Same as Example 1, liquid (A) (colorless dye dispersion) 6.67
25 parts of liquid (B) (developer dispersion), 25 parts of silica (Mizukashiru P-527) dispersion with a concentration of 25% are mixed, and 15 parts of liquid (C) above is further added and mixed for optical recording. A layer coating solution was obtained.

The above coating liquid was coated and dried on high-quality paper in the same manner as in Example 1 to obtain an optical recording sheet.

Using a test machine incorporating the semiconductor laser device used in Example 1 on the above optical recording paper, 1.511IIl/
The recording line width and ground color were measured by optical printing at a recording speed of seconds. The results are shown in Table 1, and test Nos. 1 to 11 using aromatic carboxylic acid metal salts had a lower recording line than the optical recording medium of Example 1 in which aromatic carboxylic acid metal salts were not added. The width is several times thicker, indicating that the heat exchange efficiency is significantly higher.

As is clear from a comparison with Comparative Example 4, which will be described later, the effect of the aromatic monocarboxylic acid metal salt is effectively exhibited for the first time in combination with a near-infrared absorbing basic colorless dye.

Example 3 G-11 of Example 1 as near-infrared absorbing basic colorless dye
Example 1 except that PSI)-802 was used instead of 8.
An optical recording sheet was prepared in the same manner as above.

The reflectance of this sheet at 830 nm was 90%. Under the same laser irradiation conditions as in Example 1, the color density was 1.
34, a black image with an excellent contrast of background color 0.05 was obtained.

Example 4 G-11 of Example 1 as near-infrared absorbing basic colorless dye
An optical recording sheet was prepared in the same manner as in Example 1 except that NIR-78 was used instead of NIR-78.

The reflectance of this sheet at 830 nm was 92%. Under the same laser irradiation conditions as in Example 1, the color density was 1.
34, a black image with an excellent contrast of background color 0.05 was obtained.

Example 5 G-1 of Example '1 as near-infrared absorbing basic colorless dye
An optical recording sheet was obtained in the same manner as in Example 1 except that divinylsulfonylmethane-based leuco dye R-1 was used in place of No. 18. The reflectance of this sheet at 830 nm was 90%. Under the same laser irradiation conditions as in Example 1, a green image with an excellent contrast of a developed color density of 1.33 and a ground color of 0.05 was obtained.

Example 6 On the optical recording layer of the optical recording sheet obtained in Example 1, 4 g/day of a wet-milled light-absorbing protective layer coating solution containing a near-infrared absorber having the following composition was applied and dried. An optical recording sheet having a light-absorbing protective layer with a reflectance of 75% was obtained.

(D) Liquid (light-absorbing protective layer liquid) A second optical recording sheet was irradiated with a laser in the same manner as in Example 1,
A green image with a color density of 1.32 and a background color of 0.08 was obtained.

Example 7 An optical recording sheet having a light-absorbing protective layer was obtained in the same manner as in Example 5, except that liquid (E) having the following composition was used instead of liquid (D) in Example 6.

Liquid (E): Light-absorbing protective layer coating liquid When the optical recording sheet of coating liquid 2 was irradiated with a laser under the same conditions as in Example 1, a green image with a color density of 1.36 and a background color of 0.09 was obtained.

Example 8 A protective layer coating liquid containing no near-infrared absorbing material having the following composition was coated at 4 g/nr on the optical recording sheet obtained in Example 1 and dried.

(F) Liquid: Protective layer coating liquid Next, on the recording sheet having the above-mentioned protective layer, printing was performed using a gravure ink having the following composition at an area ratio of 15% and 188 lines/inch. When an optical recording sheet with dots printed thereon was prepared, the reflectance at 830 nm was 85%.

When the thus obtained optical recording medium having a large number of near-infrared absorbing minute dots was irradiated with a laser under the same conditions as in Example 1, prompt recording was observed starting from the printed light-absorbing minute dots. A green image with an excellent contrast of density 1.36 and ground color 0.08 was obtained.

Example 9 Near-infrared absorber 5109 manufactured by IC1 used in Example 8
Instead of 564, a water-soluble printing ink with the following composition was prepared using naphthol green B, and light-absorbing minute dots were gravure printed in the same manner as in Example 7.
An optical recording sheet with a reflectance of 87% was obtained.

When laser irradiation was performed under the same conditions as in Example 1,
A green image with an excellent contrast of a density of 1.36 and a ground color of 0.11 was obtained, with the printed light-absorbing minute dots being the starting point for rapid color development.

Comparative Example 1 Near-infrared absorbing basic colorless dye G-11 in Example 1
In place of 8, the usual leuco dye diethylamino-6-methyl-7-anilinofluorane (
The ground color is 0 using the same method as in Example 1 using
．． An optical recording sheet No. 07 was obtained.

Under the same laser irradiation conditions as in Example 1, no color developed and no black image was obtained.

Comparative Example 2 Near-infrared absorbing basic colorless dye G-1 used in Example 1
An optical recording sheet with a ground color of 0.07 was obtained in the same manner as in Example 1 except that crystal violet lactone (CVL), a normal leuco dye with no near-infrared absorption, was used in place of No. 18.

Under the same laser irradiation conditions as in Example 1, no color developed and no image was obtained.

The recording media provided with the protective layer of Examples 6 to 9 had almost the same image density and background color as those without the protective layer, and even when the surface of the optical recording paper was rubbed with a wet finger, the recording layer did not change. It did not peel off and had excellent water resistance and abrasion resistance.

Comparative Example 3 On the optical recording layer of the optical recording sheet obtained in Comparative Example 1, 4 g of a light-absorbing protective layer coating liquid having the following composition was applied and dried to prepare an optical recording medium of Comparative Example 3.

The reflectance of this recording sheet at 830 nm was 32%, but the background color was quite dark at 0.45.
It was a far cry from the feel of regular paper.

When irradiated with laser light under the same conditions as in Example 1,
The recording density was 1.15, and only a slightly faint color was obtained.

Comparative Example 4 A photosensitizer dispersion having the following composition was added to the optical recording layer coating liquid of Comparative Example 1, and the coating was applied and dried in the same manner as in Comparative Example 1 to obtain an optical recording medium of Comparative Example 4.

The reflectance of the sheet of 5.0 copies at 830 nm was 95% and the ground color was 0.08, and when it was irradiated with laser light under the same conditions as in Example 1, no records were obtained.

As explained above, the optical recording medium of the present invention can emit near-infrared light,
In particular, images can be directly obtained by irradiating near-infrared light from a semiconductor laser.

In particular, in the present invention, a near-infrared-absorbing basic colorless dye that normally does not exhibit near-infrared absorption but forms a near-infrared-absorbing color forming material by being compatible with an organic color developer, and an organic color developer. Since the optical recording layer containing the agent is provided on the base material, there is no need to use special dyes or near-infrared absorbers for light absorption, and even low-output laser light of about 30 mW can produce clear images. It is possible to obtain an optical recording medium that develops color and has a significantly superior background color. Furthermore, by containing an aromatic carboxylic acid metal salt having substantially no near-infrared absorption in this optical recording layer, an optical recording medium with extremely high heat exchange efficiency can be obtained. Further, on the layer, a water-soluble organic near-infrared absorbing material or 3
By providing a light-absorbing protective layer containing at least one of near-infrared absorbing materials made into ultrafine particles of less than a micron, the recording layer is protected and the light-absorbing property is increased.
Clear images can be obtained even with high-speed recording of 20 a/sec or higher or with even lower output laser light.

Furthermore, by providing near-infrared absorbing minute dots on the layer, clear images can be obtained even with low-output laser light, and the amount of near-infrared absorbent used can be greatly reduced. This makes it possible to obtain an optical recording medium with even better ground color.

The present invention basically discovered an optical recording medium that can be recorded without adding a near-infrared absorber, and it has become possible to effectively utilize a semiconductor laser that is compact and has a stable output, and has a heat mode. This has brought good results in promoting the practical application of optical recording media.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of an embodiment of a recording apparatus that performs optical recording using the laser beam recording medium of the present invention. 1 is a laser diode collimator head, 2 is a shutter, 3 is a condensing lens group, 4 is an optical recording paper, and 5 is a power source.

Claims (4)

[Claims] (1) A basic colorless dye and an organic color developer, which normally do not exhibit near-infrared absorption, but which form a near-infrared-absorbing coloring material by being compatible with the organic color developer, are placed on the substrate. 1. An optical recording medium produced by a laser beam, characterized in that it is provided with a layer containing. (2) On the substrate, a basic colorless dye that normally does not exhibit near-infrared absorption but forms a near-infrared-absorbing coloring material by being compatible with an organic color developer, and an organic color developer. and an aromatic monocarboxylic acid metal salt compound as a photosensitizer. (3) A basic colorless dye and an organic color developer, which normally do not exhibit near-infrared absorption, but which form a near-infrared-absorbing coloring material by being compatible with the organic color developer, are placed on the substrate. A light absorbing layer containing at least one of a water-soluble organic near-infrared absorbing material or a near-infrared absorbing material ultrafinely divided into particles of 3 microns or less on the layer. An optical recording medium produced by laser light, characterized in that it has a three-layer structure with a protective layer. (4) A basic colorless dye and an organic color developer that normally do not exhibit near-infrared absorption, but which form a near-infrared-absorbing coloring material by being compatible with the organic color developer, are placed on the substrate. 1. An optical recording medium using laser light, characterized in that a layer containing: (5) The optical recording medium using a laser beam according to claim (1), wherein the reflectance of the surface of the optical recording medium at the maximum wavelength of the recording laser beam is 75% or more.