JPH035189A - heat sensitive recording sheet - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a heat-sensitive recording sheet.

More specifically, the present invention relates to a heat-sensitive recording sheet in which printed images have little smudge and are free or have little problem of deposits on the heat-sensitive head.

(Prior Art) Various types of heat-sensitive recording materials have so far been constructed using a heating color-forming reaction between at least one colorless or light-colored basic dye and phenols, organic acids, etc. These heat-sensitive recording materials have been widely used for recording in a wide range of fields, including measurement recorders, computers and information communication terminals, facsimile machines, and automatic ticket vending machines. These recording devices are
The device is equipped with a thermal element such as a thermometer or a thermal pen, and each time the thermal element is heated and brought into contact with a heat-sensitive recording material, a desired colored image can be formed and a record can be obtained.

Recently, applications have diversified and equipment has become more sophisticated, and along with this, the quality required for heat-sensitive recording materials has also become more advanced.For example, facsimile machines have also become faster. What used to take several minutes to record on A4 size paper can now be done in less than one minute.With this increase in recording speed, thermal recording materials are also required to have significantly higher recording sensitivity than before. Many proposals have been made to meet this requirement, but most of them involve a combination of a colorless or light-colored basic dye and a color developer, generally consisting of a phenolic acid or an organic acid. Furthermore, it was associated with the concomitant use of thermofusible substances (generally referred to as sensitizers).

[Problems to be Solved by the Invention] In order to achieve the above-mentioned high sensitivity in heat-sensitive recording materials, it is necessary to increase the total content of basic dye, color developer, and sensitizer in the heat-sensitive recording layer as much as possible. There is a tendency to These components (color-forming components) are colored by melting and reacting with the heat applied from the thermal head, but if they are mixed in a large amount, the molten matter will inevitably adhere to the thermal head, causing so-called head scum. This causes problems such as paper feeding problems (sticking, printing noise) and printing problems (streaks and kisses on the printed surface).

One way to prevent such debris from adhering to the heat-sensitive head is to add fine powders such as calcium carbonate, magnesila carbonate J1, talc, sauce, silica, calcium silicate, and aluminum silicate to the heat-sensitive coloring layer. However, this method cannot completely solve the problem of opacity and first wear in the case of high-sensitivity heat-sensitive recording materials that contain a large amount of color-forming components. As another means for solving the problem of foil impingement on the heat-sensitive head, it is also known to incorporate a low-melting point wax into the heat-sensitive coloring layer. However, when a large amount of such low-melting point wax is blended, the coloring components in the heat-sensitive coloring layer melt easily even at very low temperatures, and the residual heat from the heat-sensitive head causes the color to develop, so when printing a large number of sheets, There is a drawback that the recorded image has some stains, especially thin lines and letters with many strokes, which become unclear.
) (4) A so-called fogging phenomenon may occur, in which the residual heat from the thermal head causes the non-image areas of the recording surface to develop a faint color and become dark.

An object of the present invention is to provide a heat-sensitive recording sheet that is free from problems caused by adhesion of debris to a heat-sensitive head and is capable of forming clear recorded images with no or little wrinkles or fog in colored images. It is.

[Failure to solve the problem]

The heat-sensitive recording sheet of the present invention that solves the above problems is as follows:
A heat-sensitive coloring layer formed on at least one surface of the sheet-like support and comprising a colorless or light-colored coloring dye and a color developer that reacts with the dye under heating to develop color. and (B) a low melting point wax agent having a melting point of 65° C. or lower, and (B) 14.
and a high melting point wax agent having a melting point of 0°C or higher in a ratio of 1:3.
It is characterized by containing in a content (solid content weight) ratio of ~3:1.

The mixture of the above-mentioned low melting point wax agent and high melting point wax agent in a solid content weight ratio of 1-3 to 3-1 prevents the adhesion of residue in the heat-sensitive head and produces clear recorded images without any dullness. Effective for forming.

If the content ratio of the low melting point wax agent to the high melting point wax agent is less than 1:3, the effect of preventing scum from adhering to the thermal head will be insufficient, and the scum itself will become hard, resulting in paper feeding problems and printing problems. If it is larger than 3:1, the obtained thermosensitive coloring layer will easily develop color even at a considerably low temperature, causing problems such as blurring of recorded images and coloring of non-image areas. This causes an inconvenience in that it is more likely to cause distortion.

The low melting point and high melting point wax agents used in the present invention are:
Each wax may be a natural product or a synthetic product, and an appropriate one can be selected from paraffin, amide wax, bisimide wax, metal salts of higher fatty acids, etc., depending on its melting point. Generally, the melting point of wax varies depending on various factors such as its composition, degree of purification, degree of crystallinity, and molecular weight, but waxes useful in the present invention are exemplified below.

Paraffin wax with a melting point of around 45°C to around 90°C is usually sold.

Temperature: 140℃" 2-9 Temperature: Ethylene bisstearamide: Melting point: 144℃ Ethylene bislauric acid amide: Melting point: 153℃ Distearyl adipate: Melting point: 144℃ Hexamide bishehenic acid amide: Melting point: 143℃ These are merely examples, and the wax agent used in the present invention is not limited to these.

The total content of these wax agents in the heat-sensitive coloring layer is preferably 2 to 30 parts, more preferably 5 to 20 parts per 100 parts dry weight of all components of the heat-sensitive layer.
Used within the scope of the section.

In the heat-sensitive recording sheet of the present invention, a heat-sensitive coloring layer is formed on at least one surface of the support directly or via an intermediate layer. The material forming the support and the dye, developer, sensitizer, binder, etc. forming the thermosensitive coloring layer can be selected from conventionally used materials.

For example, as a support, generally -1-quality paper, medium quality paper,
Newsprint, pure white roll paper, pigment-coated high-quality paper, synthetic valve paper, synthetic paper or plastic film are used.

A heat-sensitive coloring layer forming coating solution is applied onto such a support, and if necessary, a smoothing treatment is performed using a supercalender or the like to form a heat-sensitive recording sheet.

The color-forming dye contained in the heat-sensitive color-forming layer is an organic compound (dye) that is colorless or light-colored before heat-sensitive treatment, and that develops color by reacting with a color developer consisting of an organic acid or phenolic compound upon heat treatment. It is. Such color-forming dyes include various leuco dyes such as triphenylmethane, triphenylmethane-phthalide, fluoran, diphenylmethane, leucoolamine, spiropyran, indoline, and indigo dyes. You can choose from.

Such dyes are generally contained in the thermosensitive coloring layer in a content of 5 to 20% by weight.

Phenol compounds are often used as color developers, including monophenols such as P-hydroxybenzoic acid derivatives, phthalic acid derivatives, and naphthoic acid derivatives;
Any of -bis(4-hydroxyphenyl)propane (hisphenol A) and similar compounds thereof, diphenols such as bisphenol sulfone and bisphenol sulfide, gallic acid derivatives and other triphenols, etc. can be used.

The various component chemicals in the thermosensitive coloring layer are bound together by a binder.

As the binder used in the present invention, there are generally known water-soluble resins. Specifically, polyvinyl alcohol, methylcellulose, hydroxyethylcellulose,
Carboxymethyl cellulose, gum arabic, gelatin, casein, starch, starch derivatives (e.g. phosphorylated starch, hydroxyalkylated starch and hinyl acetate grafted starch) polyhinylpyrrolidone, styrene-maleic anhydride copolymer, polyacrylic Examples include acid salts, polyacrylic acid copolymers, and the like. It is also possible to use an aqueous resin emulsion such as styrene-citadiene copolymer latex.

Generally, the color developer is contained in the heat-sensitive coloring layer at a content of 10 to 40% by weight.

When preparing a coating solution for forming a heat-sensitive coloring layer, a surfactant such as a dispersant for dispersing various component chemicals and an antifoaming agent may be added as necessary.

The heat-sensitive coloring layer may also contain organic or inorganic pigments, examples of which include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, curcum, and surface pigments. Examples include treated inorganic fine powders such as calcium carbonate and silica, as well as organic fine powders such as urea-polmarine resin, (9) (10) styrene/methacrylic acid copolymer, and polystyrene resin. . The pigment has the effect of suppressing the adhesion of heat-sensitive head residue and visually brightening the surface of the heat-sensitive coloring layer, and generally has a pigment content of 5 to 50%.
It is contained in the heat-sensitive coloring layer in an amount of % by weight. Furthermore, it is also effective to add an antifoaming agent to suppress foaming during coating, or a surfactant to improve coating properties.

[Example] The present invention will be further explained below with reference to Examples. In each Example and Comparative Example, "1 part" indicates "part by weight", and unless otherwise specified, "part by weight of solid content" is indicated.

"For implementation" Solution A (dye dispersion) and Solution B (developer solution) with the following compositions:
was prepared.

10% polyvinyl alcohol 40 parts water
40 parts Kushi J,
1 Rule - Liquid - Bisphenol A 15 parts Parahensyl biphenyl 15 parts] 0% Borihynyl alcohol 406++ Water
30 parts of the above two solutions A and B were each subjected to a separate -IJ grinder and ground until the average particle size of the component drug became 1 porcelain. Next, a pigment and a low-melting point and high-melting point Nox agent were mixed with both liquids AB in the following proportions to prepare a coating liquid for forming a heat-sensitive coloring layer.

A/& Io part B liquid
15 parts calcium carbonate (50% dispersion) 8 parts 10% polyvinyl alcohol
30 parts ethylene bisstearamide 3
(melting point 144°C) (30% dispersion $j) This coating liquid was applied to double-sided paper with a weight of 50 g/rr using a Mayer coater (11) (12) - to give a coating weight of 7 g/rrf after drying. It was applied and dried. Further, the surface of the heat-sensitive coloring layer was smoothed using a supercalender so that the base smoothness of the surface was 800 seconds.

The heat-sensitive recording sheet produced as described above was heated to 257
Roll up 100 m of Surin L-L to a width of mm, and send it to a facsimile machine (trademark: HIFAX).
-27, Hitachi manufactured rupture), Image Electronics Engineers of Japan No.
Images are recorded continuously using 2 channels, approximately 320
A record sheet was obtained. The recording test results were evaluated. The results are shown in Table 1.

The same operation as in Example 1 was performed. However, in the coating solution, 3 parts of ethylene bislaurylic acid amide (melting point: 153° C., 130% dispersion) was used instead of ethylene hisstearic acid amide. Recording test I results are shown in Table 1.

Actual J Can - Example 1 The same operations as in Example 1 were performed. However, zinc stearate (melting point 120'C) (30% dispersion) is added to the coating solution.
Added 3 parts. The recording test results are shown in Table 1.

The same operations as in Example 1 were performed. However, the amount of paraffin wax (330% dispersion with a melting point of 60°C) in the coating solution is 1
The amount of ethylene bisstearamide (melting point: 145° C., 330% dispersion) was 4 parts. The recording test results are shown in Table 1.

Comparison - The same operation as in Example 1 was performed. However, the amount of paraffin wax (melting point 60°C, 130% molecular lt liquid) in the coating liquid was 4 parts, and the amount of ethylene bisstearamide (melting point 145°C, 130% dispersion) was 1 part. . Recording sheet 1 - Results are shown in Table 1. (15) It has good sharpness and uneven recording performance.

Claims (1)

[Scope of Claims] 1. A sheet-like support, a colorless or light-colored color-forming dye formed on at least one surface of the support, and a developer that reacts with the dye under heating to develop color. (A) a low melting point wax agent having a melting point of 65° C. or lower;
and (B) a high melting point wax agent having a melting point of 140° C. or higher, in a content (solid content weight) ratio of 1:3 to 3:0.