JPH0116679B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermal recording medium, and particularly to a thermal recording medium having excellent recording sensitivity as a thermal recording medium for infrared laser. Conventionally, heat-sensitive recording materials have been well known, which utilize a coloring reaction between a coloring agent and a coloring agent that develops color when they come into contact with the coloring agent, and bring both substances into contact with heat to obtain a colored image. It is being Further, as a recording method for such a heat-sensitive recording material, a method is generally used in which a recording head (thermal head) having a heating element is closely scanned over the recording layer to record. However, in such a system, wear of the head, adhesion of residue to the head surface, and so-called staking trouble in which the head and recording layer stick together tend to occur.
Furthermore, since the recording speed depends on the heat dissipation time of the thermal head, high-speed recording is difficult, and there is also a limit to the resolution of colored images due to thermal diffusion. Therefore, in place of such thermal head contact scanning methods, various techniques have been proposed for non-contact recording by scanning with high energy density light such as a laser beam. In the method of obtaining thermal recording by scanning such a laser beam, the laser beam is absorbed by a light/heat exchange material provided on the recording medium or the device side, and the energy of the laser beam is exchanged into thermal energy. There is a need. However, in the method of exchanging heat energy with a light/heat exchange material on the device side and then supplying it to the recording medium, thermal energy diffuses and accumulates on the light/heat exchange material, making it difficult to obtain a practically preferable record. . On the other hand, in the case of a method in which the recording medium directly absorbs laser light, since general heat-sensitive recording materials hardly absorb visible and near-infrared light with a wavelength of 400 to 2000 nm, for example, colored dyes, carbon black, metal powder, etc. It is necessary to take measures such as incorporating a light-absorbing substance into the recording layer or providing it as a layer between the recording layer and the support, or providing a vapor-deposited film of a metal that absorbs laser light on the surface of the recording layer. However, in either case, the recording layer is colored and the manufacturing process is complicated, so they are not practical. Focusing on the fact that general heat-sensitive recording materials absorb infrared light, a method using an infrared laser has been proposed, but this method has not yet achieved practical recording sensitivity. In view of the current situation, the inventors of the present invention have conducted intensive research on a recording medium that uses an infrared laser as a recording light source in order to obtain a thermal recording medium for lasers that does not have a colored recording layer and has practical recording sensitivity. , completed the invention. The present invention provides at least one compound selected from zinc oxide or a zinc compound that produces zinc oxide upon heating, and at least one clay mineral.
This is a heat-sensitive recording material characterized by containing a fired product obtained by firing at a temperature of .degree. C. or higher. The present invention has an important feature in that a specific fired product is used as described above, and the compounds that are fired together with clay minerals to obtain the fired product include zinc oxide and heating (calcination).
At least one type of compound that burns zinc oxide is used. Various compounds are known as compounds that produce zinc oxide upon heating, but zinc hydroxide and zinc carbonate are more preferably used because of ease of firing treatment and easy availability of materials. Various clay minerals are known to be fired together with such zinc compounds, and specific examples include pyrophyllite, talc, minnesotaite, montmorillonite, saponite, vermiculite, sericite, illite, celadonite, amesite, Pennine, lyhydrite, thuringiaite, aprosiderite, kaolinite, daykite, nacrite, metahalosite, hallosite, serpentine, sepiolite, palygorskite,
Examples include attapulgite. Among these clay minerals, talc, montmorillonite, sericite, kaolinite and the like are particularly preferably used because they not only provide the desired effects of the present invention but also have particularly excellent whiteness. The firing treatment conditions for zinc compounds and clay minerals are adjusted appropriately depending on the materials used, but in general, about 10 to 400 parts by weight of zinc compounds are mixed with 100 parts by weight of clay minerals. This is treated by firing it in the presence of air at a temperature of 500°C or higher, preferably 800°C to 1100°C, for 1 to 3 hours. The calcined product of zinc compounds and clay minerals thus obtained is generally used in the form of powder, so it is pulverized using a suitable pulverizer such as a roll pulverizer or an impact pulverizer, and further finely pulverized using a sand glider or the like if necessary. will be applied. Note that the smaller the particle size of the powder, the better the sensitivity improvement effect, so it is generally desirable to use the powder by pulverizing it to 10 μm or less, more preferably 5 μm or less. Although the amount of these fired products to be used cannot be determined unconditionally because it varies depending on the intensity of the infrared laser beam used, etc., it is generally used in an amount of 3% by weight or more based on the total solid content of the recording layer. However, if too large an amount is used, there is a risk of a decrease in color density, so the amount is preferably adjusted within the range of 3 to 90% by weight, most preferably 10 to 80% by weight. The heat-sensitive recording material of the present invention is generally produced by a method in which a heat-sensitive coating liquid in which one or more color formers, color formers, and fine particles of the above-mentioned specific fired product are dispersed is applied to a support. 2 or 3 types in which the agent, coloring agent, and fired product are separately dispersed.
It can also be produced by a method in which heat-sensitive coating liquids are coated on a support in layers. Furthermore, it can also be produced by impregnating a support with part or all of the coloring agent, the coloring agent, and the fired product, or by rolling it into the support. There are no particular limitations on the combination of the coloring agent and the coloring agent used in the present invention, and any combination that causes a coloring reaction when the two come into contact with each other due to heat can be used. For example, colorless Examples include a combination of a basic dye or a light-colored basic dye and an inorganic or organic acidic substance, and a combination of a higher fatty acid metal salt such as ferric stearate and a phenol such as gallic acid. Furthermore, it is also possible to apply the present invention to various heat-sensitive recording materials that obtain a developed color image (recorded image) by heat, such as a heat-sensitive recording material that combines a diazonium compound, a coupler, and a basic substance. These recording bodies are also included. However, when the specific fired product used in the present invention is applied to a combination of a basic dye and an acidic substance among various combinations, it not only has the effect of improving recording sensitivity but also eliminates the need for a recording layer before use. Such a combination is particularly preferably used because it exhibits excellent properties in improving the so-called fogging phenomenon that causes color development. Various types of colorless to light-colored basic dyes are known, and examples include the following. 3,3-bis(p-dimethylaminophenyl)
-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-
(p-dimethylaminophenyl)-3-(1,2-
dimethylindol-3-yl)phthalide, 3-
(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3,3-bis(1,2-dimethylindol-3-yl)-
5-dimethylaminophthalide, 3,3-bis(1,2-dimethylindol-3-yl)-6-
Dimethylaminophthalide, 3,3-bis(9-ethylcarbazol-3-yl)-6-dimethylaminophthalide, 3,3-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide 3-p-dimethylaminophenyl-3-(1
triallylmethane dyes such as -methylpyrrol-3-yl)-6-dimethylaminophthalide, 4,
Diphenylmethane dyes such as 4'-bis-dimethylaminobenzhydryl benzyl ether, N-halophenyl-leucoauramine, N-2,4,5-trichlorophenylleucoauramine, benzoylleucomethylene blue, p-nitrobenzoylleuco Thiazine dyes such as methylene blue, 3
-Methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo)spiropyran, 3-propyl-spiro - Spiro dyes such as dibenzopyran, lactam dyes such as rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluoran, 3 -diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7 -dimethylfluorane, 3-(N-ethyl-p-toluidino)-7
-Methylfluorane, 3-diethylamino-7-
N-acetyl-N-methylaminofluorane, 3
-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-N-methyl-N-benzylaminofluorane, 3-diethylamino-7-N-chloroethyl -N-methylaminofluorane, 3-diethylamino-7-N
-diethylaminofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-(p- toluidino)fluoran, 3-diethylamino-6-methyl-7
-phenylaminofluorane, 3-diethylamino-7-(2-carbomethoxy-phenylamino)
Fluoran, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-phenylaminofluoran, 3-pyrrolidino-6-methyl-7-
Phenylaminofluorane, 3-piperidino-6
-Methyl-7-phenylaminofluorane, 3-
Diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluoran, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3-pyrrolidino-6- Fluoran dyes such as methyl-7-p-butylphenylaminofluorane, etc. Various types of inorganic or organic acidic substances that develop color upon contact with basic colorless dyes are also known, and examples thereof include the following. Inorganic acidic substances such as activated clay, acid clay, attapulgite, bentonite, colloidal silica, aluminum silicate, 4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4 -tert-octylcatechol, 2,
2'-Dihydroxydiphenol, 2,2'-methylenebis(4-methyl-6-tert-isobutylphenol), 4,4'-isopropylidenebis(2-
tert-butylphenol), 4,4'-sec-butylidene diphenol, 4-phenylphenol,
4,4'-isopropylidenediphenol, 2,
Phenolic compounds such as 2'-methylenebis(4-chlorophenol), hydroquinone, 4,4'-cyclohexylidene diphenol, novolac type phenolic resin, phenolic polymer, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid Acid, terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert- Butylsalicylic acid, 3-
Benzylsalicylic acid, 3-(α-methylbenzyl)
Salicylic acid, 3-chloro-5-(α-methylbenzyl)salicylic acid, 3,5-di-tert-butylsalicylic acid, 3-phenyl-5-(α,α-dimethylbenzyl)salicylic acid, 3,5-di-α - aromatic carboxylic acids such as methylbenzylsalicylic acid,
and organic acidic substances such as these phenolic compounds, salts of aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel. In the heat-sensitive recording material of the present invention, the ratio of the color former and color former in the recording layer is appropriately selected depending on the type of color former and color former used, and is not particularly limited. For example, when using a basic colorless dye and an acidic substance, generally 1 to 50 parts by weight, preferably 4 parts by weight, per 1 part by weight of the basic colorless dye.
~10 parts by weight of acidic substance are used. To prepare coating solutions containing these substances, water is generally used as a dispersion medium and a ball mill, attritor,
A coating liquid is prepared by dispersing the coloring agent and the coloring agent together or separately using a sand grinder or other stirring or pulverizing machine, but the powder of the specific fired product in the present invention is prepared by dispersing the coloring agent and the coloring agent together or separately using a sand grinder or the like. It may be dispersed or added to the coating liquid after being dispersed. In addition, such coating liquids usually contain starches, hydroxyethyl cellulose,
Methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene/maleic anhydride copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion, etc. with a total solid content of 2 to 40% % by weight, preferably from 5 to 25% by weight. Furthermore, various auxiliary agents can be added to the coating liquid. For example, dispersants such as sodium dioctylsulfosuccinate, sodium dotecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, ultraviolet absorbers such as benzophenones and triadoles, and other antifoaming agents, Examples include fluorescent dyes and colored dyes. In order to further whiten the heat-sensitive recording layer, inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, and activated clay may be added. In addition, fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, matcha oleic acid amide, coconut fatty acid amide, stearic acid, polyethylene, carnauba wax, paraffin wax, calcium stearate, ester wax, etc. Waxes such as dispersions or emulsions may also be added as sensitizers. In the heat-sensitive recording material of the present invention, the method of forming the recording layer is not particularly limited as described above, and can be formed according to conventionally well-known and commonly used techniques. For example, in a method of applying a heat-sensitive coating liquid to a support, an appropriate coating device such as an air knife coater or a blade coater is used. There is also no particular limitation on the amount of coating liquid applied.
Generally 2 to 12 g/m ² in dry weight, preferably 3
It is adjusted in the range of 10 g/m ² to 10 g/m 2 . Note that the support is not particularly limited, and paper, synthetic fiber paper, synthetic resin film, etc. may be used as appropriate, but paper is generally preferably used. Thus, the heat-sensitive recording material obtained by the present invention has no unnecessary coloring of the recording layer, and has extremely excellent recording sensitivity as a recording material using an infrared laser as a recording light source, and is superior to conventional contact-type recording. It also enables high-speed recording that cannot be achieved with conventional methods. In particular, when a carbon dioxide laser, among infrared lasers, is used as a recording light source, the improvement in recording sensitivity is remarkable, and the heat-sensitive recording material of the present invention exhibits extremely excellent characteristics as a heat-sensitive recording material for a carbon dioxide laser. It is something. EXAMPLES Examples and comparative examples are listed below in order to make the effects of the present invention even clearer, but the present invention is not limited thereto. In addition, % in an example represents weight %. Example 1 3,3-bis(p-dimethylaminophenyl)
- Dispersion liquid (A) made by adding water to 25 g of 6-dimethylaminophthalide and 5 g of 10% polyvinyl alcohol aqueous solution to make the solid content concentration 25%, and 100 g of 4,4'-isopropylidene diphenol and 10% polyvinyl alcohol aqueous solution The dispersion (B) made up to 25% concentration by adding 5 g and water was each treated in a magnetic ball mill for 8 hours. Add 125g of kaolinite and 125g of zinc oxide in advance.
A dispersion (C) obtained by mixing the fired product obtained by firing at 800° C. for 3 hours, 15 g of a 10% polyvinyl alcohol aqueous solution, and 1000 g of water was processed with a sand grinder so that the average particle size was 4 μ. After treatment, the three dispersions (A), (B), and (C) were mixed, and 100 g of styrene-butadiene-acrylic acid ester copolymer latex (solid content concentration 50%) was added to form a coating liquid for thermal recording. Obtained. 49g/of the obtained coating liquid
The mixture was coated on m ² of high-quality paper to a dry coating weight of 7 g/m ² and dried to obtain a blue-colored thermosensitive recording paper. Example 2 The procedure was carried out in the same manner as in Example 1, except that instead of the kaolinite used in the dispersion (C) of Example 1, a fired product obtained by firing talc at 1200°C for 3 hours was used. A thermosensitive recording paper was obtained. Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1, except that kaolinite and zinc oxide before firing were used instead of the specific fired product used in dispersion (C) in Example 1. . Comparative Example 2 A thermosensitive recording paper was obtained in the same manner as in Example 2, except that talc and zinc oxide before firing were used instead of the specific fired product used in Example 2. Example 3 3-(N-ethyl-p-
A black coloring thermosensitive recording paper was obtained in the same manner as in Example 1 except that (toluidino)-6-methyl-7-phenylaminofluorane was used. Example 4 The same procedure as in Example 3 was used except that the specific fired product used in the dispersion (C) was a fired product obtained in the same manner except that zinc oxide was replaced with zinc carbonate. A thermosensitive recording paper was obtained. Example 5 A fired product was treated in the same manner as in Example 3, except that 65 g of zinc hydroxide and 60 g of zinc oxide were used instead of 125 g of zinc oxide as the specific fired product used in dispersion (C). A thermosensitive recording paper was obtained in the same manner as in Example 3 except for this. Evaluation test Using the thermal paper obtained in Examples 1 to 5 and Comparative Examples 1 and 2, the linear density was measured using a carbon dioxide laser (output 1W, center oscillation wavelength 10.6μ, beam diameter 100μ).
Recording was performed at 10 lines/mm, and the color density was measured using a Macbeth densitometer. From the relationship between recording speed and color density, the recording energy density required to obtain a color density of 1.0 was determined and shown in Table 1. The Macbeth densitometer was measured using a red filter in Examples 1 and 2 and Comparative Examples 1 and 2, and a yellow filter in Examples 3, 4, and 5.

[Table] As is clear from Table 1, the thermal recording paper obtained in the present invention had excellent recording sensitivity as a thermal recording medium for laser use.

Claims (1)

[Claims] 1. Contains a fired product obtained by firing at least one type of clay mineral and at least one compound selected from zinc oxide or a zinc compound that generates zinc oxide upon heating at a temperature of 500°C or higher. A thermosensitive recording medium.