JPH03169673A - Recording medium for laser beam - Google Patents

Abstract

PURPOSE:To obtain a recording medium excellent in weather and chemical resistance by forming a recording layer containing an inorg. compound absorbing laser beam and generating discoloration on a sheet like support such as paper or a film. CONSTITUTION:A recording layer containing an inorg. compound absorbing laser beam and generating discoloration is formed on a sheet like support. As the sheet like support, paper or a synthetic resin film is used. As the inorg. compound having discoloring properties, a lead compound such as red lead, lead sulfite, lead phosphite, basic lead sulfite, basic lead phosphite sulfite or dibasic lead phosphite is pref. Since the recording image is formed on this recording medium by the high temp. thermal discoloration of the inorg. compound, this image is extremely stable and markedly excellent in weather and chemical resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording medium for laser beams that has excellent weather resistance and chemical resistance.

[Prior art and its problems]

BACKGROUND ART Conventionally, as recording materials, there have been known those that generate heat-sensitive coloring by utilizing a reaction between a leuco dye and an acidic substance, and so-called diazo thermosensitive recording materials that utilize a reaction between a diazo compound and a coupler. However, heat-sensitive recording materials produced by the reaction of leuco dyes and acidic substances generally have the disadvantage that when exposed to an environment of 70°C or higher, the entire surface develops color, making the record illegible. It has the disadvantage that its records are erased when it comes into contact with the plasticizer inside, and it also has a disadvantage of poor weather resistance. Regarding diazo thermosensitive recording materials,
It has drawbacks such as the color density of printed characters being weak and poor clarity, as well as poor weather resistance and chemical resistance.

On the other hand, in recent years, it has become known that in order to laser mark the product name or part number on the surface of resin-sealed electronic components, an inorganic compound that absorbs the laser beam and causes discoloration is mixed into the resin in advance. ing. In this case, the color-changing inorganic compound is 2PbCO, .Pb(OH)
, (Japanese Unexamined Patent Publication No. 61-69488), yellow iron oxide (
JP-A-60-155493) and the like are used. However, such laser marking technology has only been applied to resin or shapes, and has not been used as a recording medium.

[Problem of invention]

An object of the present invention is to provide a laser beam recording medium with excellent weather resistance and chemical resistance.

[Means to solve the problem]

As a result of intensive research aimed at solving the above problems, the present inventors formed a recording layer containing an inorganic compound that absorbs laser beams and causes discoloration on a sheet-like support such as paper or film. The inventors have discovered that a recording medium with excellent weather resistance and chemical resistance can be obtained by doing so, and have completed the present invention.

That is, according to the present invention, BW! contains an inorganic compound that absorbs a laser beam and causes discoloration on a sheet-like support. There is provided a recording medium for a laser beam in the form of j.

In the present invention, the recording layer formed on the sheet support contains an inorganic compound (hereinafter also simply referred to as a color-changing inorganic compound) that absorbs a laser beam and changes color due to the heat generated. Such color-changing inorganic compounds include pbco
,・Pb(OH)2. In addition to yellow iron oxide, laser beam-absorbing inorganic pigments such as lithopone, titanium yellow, chrome yellow titanium dioxide, and titanates can be used. The color-changing inorganic compounds that make up the recording layer include:
A material that exhibits a white color at room temperature and changes color to a black color upon absorption of a laser beam is advantageous in obtaining images with high contrast. As a result of intensive research to develop an inorganic compound that exhibits such discoloration, the present inventors found that
It has been found that lead compounds such as red lead, lead sulfite, lead phosphite, basic lead sulfite, basic lead sulfite phosphite, and dibasic lead zinc are suitable.

The recording medium of the present invention can be manufactured by applying and drying a coating liquid containing a color-changing inorganic compound and a polymeric binder onto a sheet 1 support. Paper or synthetic resin film is used as the sheet-like support. As the synthetic resin film, for example, films made of various polymers such as polyester, nylon, polycarbonate, polyimide, polyethylene, polypropylene, polysulfan, etc. are used. From the viewpoint of obtaining images with high contrast, the polymer film is preferably made opaque, particularly white and opaque, by mixing pigments into the film. Additionally, metal films can also be used.

Examples of polymer binders include various synthetic resins such as thermoplastic resins, thermosetting resins, and photocurable resins, resin emulsions, carboxymethyl cellulose, ethyl cellulose,
Polymer binders derived from natural products such as starch and sodium alginate are used. The coating liquid can be an aqueous solution, an organic solvent solution, an emulsion, or the like.

In addition to the color-changing inorganic compound and the polymer binder, various auxiliary additives can be added to the coating liquid. Such auxiliary additives include inorganic fillers, surfactants, viscosity modifiers, and the like.

In the present invention, it is particularly advantageous to use an inorganic filler as a dispersion medium for the color-changing inorganic compound. Inorganic fillers include silica, alumina, silica alumina, magnesia, zirconia, calcium carbonate, aluminum hydroxide,
Examples include calcium hydroxide, magnesium hydroxide, clay, diatomaceous earth, and zeolite.

The content of the color-changing inorganic compound in the recording layer of the present invention is 1 to 20% by weight2, preferably 2 to 12% by weight2, based on the total solid content.

In the recording medium of the present invention, an intermediate layer containing a white inorganic filler is preferably provided between the recording layer and the support. This intermediate layer acts as a reflective layer for the laser beam, increasing the absorption efficiency of the laser beam into the color-changing inorganic compound, and also prevents heat transfer from the recording layer to the support. accelerates the temperature rise of the compound,
It also prevents thermal deterioration of the support.

〔Effect of the invention〕

In the recording medium of the present invention, a desired image can be recorded by irradiating the recording layer with a laser beam image-wise through a mask or by scanning the laser beam image-wise. In this case, a light beam with a wavelength of 190 to 1100 nm is used as the laser beam. As such a laser beam generator, various conventionally known devices such as a carbon dioxide laser beam generator, an argon laser, an excimer laser, a YAG laser, etc. can be used.

The recorded image formed on the recording medium of the present invention is an inorganic compound that has been thermally discolored at high temperatures, so it is extremely stable and has better weather resistance and chemical resistance than conventional heat-sensitive recording materials. It is extremely superior in terms of quality. The recording medium of the present invention can be used as recording paper for various information recording devices in the same way as conventional heat-sensitive recording materials, and can also be used as various labels by forming an adhesive layer on the back surface. It is also possible to use it as a magnetic ticket paper by forming a .

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Table 1 was printed on a polyester film having a thickness of 50 pII1.
A coating liquid having the composition shown in is applied to a film thickness of 9p■ using a wire bar wound with a wire of diameter 0.80, and the temperature is 13cm.
It was dried by heating at 0° C. for 1 minute.

Table 1 Next, the printing clarity and weather resistance of the recording sheets obtained as described above were evaluated as follows.

The results are shown in Table-3.

(1) Printing clarity Laser irradiation device (manufactured by Ushio Inc., product name Unimark 400 model LM-401^GV-Rl {-01} with energy density of approximately 20 J/al, printing in approximately 3 microseconds, and visually checking evaluated.

(2) Weather resistance Weather resistance measuring device (Suga Test Instruments, product name: Standard Sunshine Super Long Life Weather Meter [
The decrease in print density after 12 hours of irradiation was visually evaluated using EL-SUN-HCH-B type).

Example 2 A certain amount of coating liquid shown in Table 2 was applied onto medium-quality paper with a basis weight of 60 g/m using a blade coater at a solid content of 10 g/m.
m, heated for 20 seconds at a temperature of 140°C, and dried.
Then, a recording sheet was obtained by supercalendering.

Table 2 Next, the performance of the obtained recording sheet was evaluated in the same manner as in Example 1. The results are shown in Table-3.

Table 3 The evaluation results in Table 3 are based on a three-stage evaluation method.
○: Good, Δ: Average, ×: Bad.

Example 3 In Example 2, dibasic lead phosphite (2PbO・P
Recording sheets were produced in the same manner except that various lead compounds were used instead of bl+PO3.58,O), and their discoloration by laser beams was examined. The results are shown in Table 4.

The evaluation criteria for the quality of images shown in Table 4 are as follows.

0...Very clear Δ...Slightly unclear ×・・・Substantial image cannot be obtained

Claims (2)

[Claims] (1) Absorb the laser beam on the sheet-like support,
A laser beam recording medium comprising a recording layer containing an inorganic compound that causes discoloration. (2) The inorganic compound is lead red, lead sulfite, lead phosphite,
The recording medium according to claim 1, wherein the recording medium is at least one selected from basic lead sulfite, basic phosphite lead sulfite, and dibasic lead phosphite.