JPS6251478A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance developed color density, to prevent the contamination of a thermal head and to improve a running property, in a thermal recording material wherein a thermal color forming layer consisting of a microcapsule including a diazo compound and a coupling component is provided on a paper support, by specifying the optical surface roughness and Cobb water absorbing capacity of the paper support. CONSTITUTION:The optical surface roughness (Rp value) of a paper support is set to 8mum or less and the Cobb water absorbing capacity (prescribed by JIS-P-8140) to 25g/m<2> or less. If the optical surface roughness becomes larger than 8mum, developed color density is lowered and satisfactory developed color density is not obtained. If Cobb water absorbing capacity becomes larger than 25g/m<2>, the flatness of a coating layer when a thermal layer is applied becomes inferior and developed color density is lowered. The thermal recording material using the above mentioned support shows excellent characteristics to all of developed color density, head contamination and a running property.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heat-sensitive recording material, and particularly to a fixable diazo-based heat-sensitive recording material.

(Prior Art) As a recording material used in a heat-sensitive recording method, a leuco color-forming heat-sensitive recording material is usually used. However, this heat-sensitive recording material has the disadvantage that color develops in unexpected places due to harsh handling, heating, or adhesion of solvents after recording, which stains the recorded image. In recent years, research has been actively conducted on diazo color-forming heat-sensitive recording materials as heat-sensitive recording materials that do not have these drawbacks. For example, JP-A-77-12
No. 3014, Journal of the Institute of Image Electronics Engineers, //%KotaO(/rirx
), etc., but it is thermally recorded on a recording material using a diazo compound, a coupling component, and a basic component (including substances that become basic when heated), and then irradiated with light to detect any unreacted components. It decomposes the diazo compound and stops color development.

Indeed, according to this method, it is possible to stop color development (hereinafter referred to as fixing) in areas that do not require recording.

However, this recording material may also undergo gradual pre-coupling during storage, resulting in undesirable coloration (capri). For this purpose, any of the coloring components/m1! -Presence in the form of discontinuous particles (solid dispersion) prevents contact between components and prevents sagging, but the storage stability (hereinafter referred to as storage stability) of recording materials is It is still not sufficient and has the disadvantage that thermal color development is reduced. As another measure, it is known to separate the diazo compound and the coupling component as separate layers in order to minimize contact between the components (for example,
7-/Co No. 3014). Although this method improves raw storage stability, the thermal coloring properties are greatly reduced, and it cannot respond to high-speed recording with short pulse widths, making it impractical. Furthermore, as a method to satisfy both raw storage stability and thermal coloring properties, either the coupling component or the basic substance is replaced with a non-polar waxy substance (JP-A-17-17-#$/#/, JP-A-17-7- /
4 (No. 2434) or a hydrophobic polymer substance (No. 41ij Kaishojt7-/?J5F44μ) to isolate it from other components.

However, these encapsulation methods involve dissolving wax or polymeric substances in their solvents, and dissolving or dispersing the color-forming ingredients in these solutions to form capsules. This is different from the concept of a normal capsule covered with water. For this reason, when the coloring component is dissolved and formed, the coloring component does not become the core material of the capsule, but mixes uniformly with the encapsulating material, and pre-coupling gradually progresses on the outer surface of the capsule wall during storage. Raw storage stability is not fully satisfied. In addition, when a color-forming component is dispersed and formed, the color-forming reaction does not occur unless the capsule wall is thermally melted, resulting in a decrease in thermal color-forming properties.

Furthermore, there is a manufacturing problem in which the wax or the solvent used to dissolve the polymeric substance must be removed after the capsules are formed, which is not completely satisfactory.

Therefore, in order to solve these problems, there is a method in which at least seven of the components involved in the color reaction are contained in a core material, and a wall is formed around this core material by polymerization to form a microcapsule. !r-410 Ko 3 Specification), an excellent heat-sensitive recording material was discovered.

However, even in heat-sensitive recording materials produced by this microencapsulation method, the color density during heat recording is insufficient, and higher sensitivity is required for high-speed recording.

In addition, during thermal recording, the thermal head is always in contact with the surface of the thermal recording material, so the recording material becomes sticky under heating, causing stains on the thermal head and reducing the runnability of the thermal recording material. It is known, for example, to incorporate an appropriate amount of anti-blocking agent into thermal recording materials in order to prevent staining of the thermal head and improve the feeding performance, which tends to deteriorate.However, there are problems such as a decrease in recording density, so isn't it.

(Object of the Invention) The object of the present invention is to provide a heat-sensitive recording material that improves the above-mentioned drawbacks, that is, has a high color density, and prevents the thermal head from becoming dirty.
An object of the present invention is to provide a heat-sensitive recording material with improved running properties.

(Structure of the Invention) As a result of intensive research to improve these drawbacks, the present inventors have found that the optical surface roughness (p value) of the paper support is 1.
6 m or less, preferably 4.7 μm or less, and Cobb water absorption (JI8-P-rt4c).

The object of the present invention has been achieved by setting the distance (defined by xz) to 17 m or less, preferably 7 m or less.

Q. In the present invention, the university surface roughness (Rp value) is a value optically measured on the surface unevenness of the intermediate layer when a prism is pressed onto the intermediate layer.The measurement principle is "optical". "Measuring method of printing smoothness of paper based on the contact method" by Shinpei Inamoto, Ministry of Finance Printing Bureau Research Institute Report, Volume G, Tip to T
It is described on this page (Showa! February 2nd year). As a device, the ``Dynamic Printing Smoothness Measuring Device'' manufactured by Toyo Seiki Seisakusho can be used.

The above-mentioned optical surface roughness (Rp value) is a value measured when the prism pressure applied to the intermediate layer is j kg/cII.

When the optical surface roughness of the paper support is greater than 28 m, the color density decreases and a satisfactory color density cannot be obtained. Therefore, the optical surface roughness is preferably t μm or less, particularly preferably 4.7 μm or less.

It should be noted that when the Cobb water absorption becomes larger than If/m2, the flatness of the coated layer deteriorates when the heat-sensitive layer is coated with gold, and the color density decreases. Therefore; the water absorption is koj f / m
"The following is preferable, particularly preferably koOf/m2
It is as follows.

Surprisingly, the combination of the two also reduces head contamination and improves the runnability of the heat-sensitive recording material.

A specific method for obtaining the optical surface roughness and Cobb water absorption of the paper support specified in the present invention is to apply a super calender to a paper support made of the formulation described below, or to press a wet paper. Alternatively, a method is preferred in which paper moistened with water is pressed into a dryer in a smooth line and dried.

Also, in order to enhance the effect of the super calender, it is desirable to heat it to ≠o'C-λoo'c, and the water content of the paper support can also be reduced! Preferably it is from 1 to 6, particularly preferably from 6 to 2. In addition, the raw material surface f is short fiber and easily smooth hardwood/(It is preferable to use Luzo Tub 04 or above. Also, vinylon, polyester,
It is also effective to mix t-70 to 1fiO% of synthetic fibers such as nylon or synthetic pulps such as polyethylene and polypropylene.

The freeness of Norzo at this time is 300 to 100 cc (C
, S, F) are desirable. In addition, size properties are determined by adding and/or surface sizing of rosin, nografine wax, higher fatty acid salts, alkenyl, succinate, fatty acid anhydride, alkyl ketene dimer, etc., and determining the Cobb water absorbency (JIS-P
et) is preferably 21 f/m2 or less.

In addition, the addition of a softening agent consisting of a reaction product of maleic anhydride copolymer and polyalkylene polyamine, fillers such as clay, talc, calcium carbonate, urea-formalin resin fine powder, sulfate band, polyamide polyamine epichlorohydrin, etc. A fixing agent may be added if necessary.

Further, an anti-curl layer made of latex such as 88% MBR; starch, water-soluble polymeric material such as PVA, etc. may be provided on the back side of the base paper.

(Examples of the Invention) Examples are shown below, but the present invention is not limited thereto.

As shown in Table 1, the pulp, freeness, sizing agent, drying method after paper making, and super calendering were determined by selecting the conditions.

A paper support with optical surface roughness (Rp value) and Cobb water absorption was obtained. All paper is made using a fourdrinier paper machine and the basis weight! O
f/m2. Apply a heat-sensitive coating liquid to these supports,
I got thermal paper.

Next, thermal recording was carried out on these thermal papers and the recording density was measured, and the results are shown in the following pages.

In addition, the manufacturing method of the heat-sensitive coating liquid, the coating method, and the measuring method of coloring density, head staining, and feeding performance are shown.

(Manufacturing and coating method of heat-sensitive coating liquid) The following diano compound φ part and (j: / ) adduct i of quicrylene diincyanate and trimethylolcropane
A solution of the diazo compound obtained by adding and dissolving 1 part of the diazo compound in a mixed solvent of 3 parts of tricresyl phosphate and 73 parts of dichloromethane was mixed with 3 parts of polyvinyl alcohol, 1 part of gelatin. F part,
l, di(-monohydroxyethoxy)ben 4 ph 2,4
Mix in an aqueous solution in which 4 parts are dissolved in 11 parts of water.
'C emulsified the valve.

Add 100 parts of water to the obtained emulsion and mix with stirring.
After 2 hours of cVc heating, capsules containing the diazo compound and having an average particle size of 3 μm were obtained.

(Diazo compound) OC4) 1゜Next, it was added to 100 parts of co-hydroxy-3-naphthoic acid anilide coO part't-rs polyvinyl alcohol aqueous solution, and dispersed in a sand mill for about 1 hour to obtain a dispersion with an average particle size of 3μ. Ta.

Next, triphenylguanidine was added to 1 DO part of an aqueous polyvinyl alcohol solution and dispersed in a sand mill for about 2 hours to obtain a dispersion with an average particle size of 3 μm.

Diazo compound capsule liquid 1 obtained as above
15 parts of a coupling component dispersion and 73 parts of a triphenylguanidine dispersion were added to 0 parts to prepare a heat-sensitive coating liquid.

(Method for measuring color density, head dirt, and runnability) Heat recording was performed on the obtained heat-sensitive recording material using a Gel mode thermal printer (HIFATSU GISF 003 manufactured by Hitachi, Ltd.), and then Recopy Super Dry/00 (IJ Co., Ltd.) was used. The entire surface was exposed to light and fixed using a commercially available commercially available commercially available product. The sol concentration of the obtained recorded image was measured using a Macbeth reflection densitometer.

In addition, relative comparisons were made regarding head dirt and runnability.

(Effects of the Invention) From the results in Table 2, it is clear that the heat-sensitive recording material according to the present invention has excellent properties in terms of color density, head staining, and runnability.

Claims (2)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive coloring layer consisting of microcapsules encapsulating a diazo compound and a coupling component is provided on a paper support, the optical surface roughness (Rp value) of the paper support is 8 μm or less. Dekatsu Cobb water absorption (JIS-P
-8140) is 25 g/m^2 or less. (2) The thermosensitive recording paper according to claim 1, wherein the paper support is a base paper that has been subjected to a supercalender treatment with a moisture content in the range of 6 to 9%.