JPH01285384A - Thermal recoding medium - Google Patents

Abstract

PURPOSE:To prevent a dust application to a thermal head to obtain an image having a superior dot reproducibility and a high sharpness, by incorporating specific polynorbornene particles in a thermal recording layer. CONSTITUTION:A thermal recording medium has a thermal recording layer containing a colorless or light-colored color forming substance and a color developer coloring the color forming substance under heat. In the thermal recording layer, polynorbornene particles shown by a formula I are incorporated. The polynorbornene particles in particle form are obtained by a method in which a norbornene is synthesized by the Diels-Alder reaction of ethylene and cyclopentadiene and this norbornene monomer is ring-opening polymerized. The remarkably porous structure and rapid hot melt substance absorptivity of the polynorbornene particles produce remarkable effects on the improvement of image sharpness, dot reproducibility, and head running properties in a thermal recording.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention relates to a thermal recording medium, and particularly to a thermal recording device using a thermal head in which heating resistive elements (dots) are fixed in a horizontal row. This invention relates to a heat-sensitive recording medium for recording.

[Prior Art] It has been known for a long time that a colorless or light-colored color-forming substance such as crystal violet lactone reacts with a phenolic compound to form a color. 3.539 for U.S. Patent.
No. 37!1.

Generally, in order to obtain heat-sensitive recording paper by uniformly dispersing a heat-sensitive recording composition containing a two-component color former as described above in water and coating it on a support, it is necessary to disperse the heat-sensitive recording composition containing the two-component color former in water. The particles are separately dispersed in a medium using a ball mill or the like to form fine particles of several micrometers or smaller, and then the respective dispersions are mixed, coated on a support, and dried.

A phenomenon in which the recording medium and the thermal head adhere to each other during recording, that is, a sticking phenomenon, occurs in a thermal recording medium, which may cause paper feeding of the recording medium or impair recording performance, or if some of the recording layer components are exposed to heat. There is a problem that the recording material may get stuck on the head or the recording medium may be contaminated by the deposits.

Conventionally, as a countermeasure for such head troubles, a lubricant such as a fatty acid metal salt is added to the recording layer, a non-adhesive wax layer is placed on the recording layer, or a polymer composition II! Although methods such as providing a J layer have been proposed, there are problems such as insufficient effects and an increase in manufacturing steps.

There have also been proposals to solve the above-mentioned head troubles by incorporating various fillers into the heat-sensitive recording layer.

For example, since ancient times, nocolsium carbonate, silica, kaolin2. It is known that talc, various clays, alumina, titanium dioxide, etc. are blended, and even recently, hydrated aluminum silicate minerals (JP-A-416-72992), non-grade synthetic aluminum silicate (unspecified Kosho 57-1
9035), wollastonite or calcium silicate (
It has been proposed to incorporate JP-A-57-41995), alkaline earth metal salts (JP-A-57-80095), aluminum hydroxide (JP-A-57-4093), and the like.

The conventional way of thinking about these fillers is to avoid substances with large oil absorption in the heat-sensitive layer so that the thermal melt generated during recording is absorbed into the recording layer, and the idea is to focus on the absorption capacity of the filler. there were. Therefore, it has not been able to exhibit a sufficient effect on head troubles.

[Problems to be Solved by the Invention] Therefore, the name of the present invention is based on the idea that not only absorption capacity but also absorption speed is an important factor for head troubles, and the relationship between the melt viscosity characteristics of a hot melt substance and the absorption speed. As a result of various studies on the above, the present invention was completed in 1999 after discovering that polynorbornene particles have good properties in both absorption capacity and absorption rate.

The purpose of the present invention is to prevent adhesion between the thermal head and thermal recording paper that occurs when recording with a thermal recording device using a thermal head in which heating resistive elements (dots) are fixed in a horizontal row.
That is, it is an object of the present invention to provide a heat-sensitive recording material which can improve head troubles such as sticking troubles and adhesion of dust to the heat head, has excellent dot reproducibility, and can obtain images with high resolution.

[Means for Solving the Problems J] That is, the present invention provides a heat-sensitive recording material having a heat-sensitive recording layer containing a color-forming substance that is usually colorless or light-colored and a color developer that develops color by heating the color-forming substance. The present invention relates to a heat-sensitive recording material characterized by containing polynorbornene particles in the layer. Polynorbornene particles are particles having a structure represented by the following general formula, obtained by synthesizing norbornene from ethylene and cyclopentadiene through a Diels-Alder reaction, and ring-opening polymerization of this norbornene monomer.

Due to its extremely porous structure and rapid absorption of heat-melting substances, it has a remarkable effect on improving image clarity, dot reproducibility, and head running in thermal recording.

The number of polynorbornene particles contained in the heat-sensitive composition is 10.
The amount is preferably 60% by weight. If it is less than 10%, the effect on head troubles will be insufficient, and if it exceeds 60%, the color development will deteriorate. Further, the particle diameter of the polynorbornene particles is preferably 8 μm or less.

Further, the polynorbornene particles of the present invention may be contained not only in the heat-sensitive recording layer but also in the undercoat layer or one overcoat layer.

Further, polynorbornene particles can also be used in combination with other fillers.

Next, the heat-sensitive recording material used in the present invention will be explained.

(1) Leuco compound A colorless or light-colored substance that develops color by reacting with a color developer, including triphenylmethane, triphenylmethanephthalide, fluoran, leucoolamine, diphenylmethane, phenothiazine, and phenylmethane. Various derivatives such as sazin, spiropyran, indoline, and indigo derivatives may be mentioned, and the following may be exemplified, although the derivatives are not particularly limited.

For example, crystal violet lactone (blue), 3
-diethylamino-6-methyl-7-anilinofluorane (black), 3-(N-ethyl-P-toluidino)-6
-Methyl-7-anilinofluorane (black), 3-diethylamino-6-methyl-7-(ortho, para-dimethylanilino)fluorane (black), 3-pyrrolidino-6
-Methyl-7-anilinofluorane (black), 3-piperidino-6-medy-7-anilinofluorane (black>
, 3-(N-cyclohexyl-N-methylamino)-6
-Methyl-7-anilinofluoran (black), 3-diethylamino-7-(ortho-chloroanilino)fluoran (black), 3-diethylamino-7-(meta-1-lifluoromethylanilino)fluoran (black) , 3-diethylamino-6-medyru9 3-diethylamino-6-methyl-fluoran (red)
, 3-cyclohexylamino-6-chlorofluorane (
[Color), 3-(N-isoamyl-N-■thylamino)-
6-methyl-7-anilinofluorane (black).

+21 color developer A substance that is solid at room temperature, softens or melts in the heat, and develops color when it comes into contact with the above leuco compound, for example 4
- Tertiary butisif 1-nol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol,
β-naphthol, methyl-4-hydroxybenzoate, 4'-hydroxyacetophenone, 4-tertiaryoctylcabucol, 2,2'-dihydroxydiphenyl, 2,2'-methylenebis(4-chlorophenol)
, 4.4'-Secondarybutylidene diphenol, 4.
4'-isopropylidene bis(2-methylphenol)
, 4.4°-isopropylidene bis(2,6 dimethylphenol), benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, dibenzyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, benzyl-4-hydroxyphenylacetate or resorcin monobenzoate.

(3) Color development accelerator In order to further improve the recording properties of the heat-sensitive recording medium of the present invention, conventionally known color development accelerators such as fatty acid amides such as stearamide, terephthalic acid esters, terphenyl, and parabens may be used. Dilbisphenyl, octahydroanthracene, benzylmandelic acid, various naphthalene derivatives, etc. are used.

(4) Adhesive A water-soluble adhesive is used to isolate and fix coloring agents dispersed in fine particles from each other, and includes polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroquinone, 1-methyl cellulose latin, starch, and Examples include derivatives of these.

(5) Other additives The heat-sensitive recording material of the present invention may contain other additives in the heat-sensitive layer as necessary, such as inorganic or organic additives such as clay, calcium carbonate, aluminum hydroxide, talc, titanium oxide, zinc oxide, etc. m pigments, waxes, antioxidants for storage stability, ultraviolet absorbers, various fatty acid metal salts to prevent stickiness, water resistant agents to improve water resistance, phenolic resins,
It is also possible to add a surfactant.

+61 Substrate The present invention is made by coating a substrate with a heat-sensitive paint containing the above-mentioned substances. Papers such as wood-free paper, medium-quality paper, and coated paper are generally used as the substrate, but glass IIIfi sheets, plastic sheets, film-laminated papers, and the like can also be used as the substrate.

[Example] The present invention will be specifically put to practical use in the following examples.

Example 1 Solution A (dye dispersion) 3-(N-isoamyl-N-ethyl) Amino-6-methyl-7-anilinofluorane 3 parts Zinc stearate 3 parts 10% polyvinyl alcohol aqueous solution 8 parts Water
3 parts Liquid B (1 color agent dispersion) Benzyl 4-hydroxybenzoate 6 parts Stearic acid 11 parts 3 parts 10% polyvinyl alcohol aqueous solution 15 parts Water
9 parts Each of the above compositions was ground to a particle size of 2 μm using a paint shaker (manufactured by Toyo Seiki).

C liquid polynorbornene particles (France Cd FChimie
(trade name: Nosolex) 5 parts 10% polyvinyl alcohol aqueous solution 30 parts water
7 Parts C Solution was mixed with polynorbornene particle size 4 μm using a vent shaker as above.
crushed to.

Next, 17 parts of liquid A, 33 parts of liquid B, and 50 parts of liquid C were mixed to prepare a thermal paint. Furthermore, this paint was applied to the surface of high-quality paper with a weight of 150 g per tsubo using a Mayer bar, and the applied amount after drying was 5 g.
/m (solid content), then super calendering is performed to reduce the Bekk smoothness of the surface of the recording layer to 6.
A thermosensitive recording material with a temperature of 0.00 seconds was obtained. The obtained heat-sensitive recording material was evaluated by the following quality characteristic test, and the results shown in the table were obtained.

Example 2 Thermosensitive material obtained in the same manner as in Example 1 except that in the composition of liquid C in Example 1, the content of polynorbornene particles (pulverized to a particle size of 4 μm) was changed to 20 parts, and the water was changed to 18 parts. The quality of the recording medium was evaluated in the same manner as in Example 1, and the results shown in the table were obtained.

As Comparative Example 1, synthetic silica (oil absorption ffi 160d/1009 average particle size 1.7μ), which is a light white fine powder of hydrated silicic acid, was used instead of the polynorbornene particles in Liquid C of Example 1.
P-527 manufactured by Mizusawa Chemical Co., Ltd. as Comparative Example 2, calcium carbonate (PC manufactured by Shiraishi Kogyo) was substituted for the polynorbornene particles in Solution C of Example 1, and Solution C of Example 2 as Comparative Example 3. The above synthetic silica (Mizusawa Chemical P-527) was used instead of the polynorbornene particles inside.
As Comparative Example 4, a thermosensitive recording material was obtained in the same manner as in Example 1 except that the above calcium carbonate (PC manufactured by Shiraishi Kogyo) was used in place of the polynorbornene particles in Liquid C of Example 2. A quality evaluation was conducted.

The results are shown in the table.

In addition, as Comparative Example 5, Example 1 was prepared except that the polynorbornene particles in the C liquid composition of Example 1 were replaced with particles of urea-formalin resin (Vargovac 82 manufactured by Ciba Geigy).
After obtaining a heat-sensitive recording material in the same manner as above, quality evaluation was performed. The results are shown in the table.

Quality characteristic test (1) Sticking test method A heat-sensitive recording material sample was subjected to an applied voltage of 21. IV, solid printing was performed in a printing atmosphere of 5° C., and the state of sticking was evaluated.

(Two-head adhering residue test method) After printing 200 sheets of heat-sensitive recording material samples using C0PIX6500 (manufactured by Toshiba) at an applied voltage of 21.IV and in a printing atmosphere of 20°C using the Institute of Image Electronics Engineers Test Chart Na 27, The degree of adhesion of glaze was visually determined.

(3) Dot reproducibility (The sample recorded in 2 was photographed using a microscope S1, and the dot reproducibility was evaluated.

The above evaluations (1) to 3) were performed according to the following criteria.

○... Good Δ... or) Bad
-514 (using a visual filter), and it was determined that the higher the print density, the better the clarity.

[Effects of the Invention] The thermal recording medium of the present invention has less head trouble such as adhesion between the thermal recording paper and the thermal head, that is, sticking trouble, and adhesion of residue to the thermal head, and has excellent dot reproducibility. It is an extremely useful thermosensitive recording medium that can produce images with high clarity.

Claims (1)

[Scope of Claims] A heat-sensitive recording material having a heat-sensitive recording layer containing a color-forming substance that is normally colorless or light-colored and a color developer that develops color by heating the color-forming substance, in which the heat-sensitive recording layer contains a compound represented by the following general formula. A heat-sensitive recording material characterized by containing polynorbornene particles. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼