JPH0416382A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material which is excellent in coloring property by a method wherein a coloring layer containing aniline fluoran leuco dye, highly viscous bis(4-hydroxy-3-methylphenyl) sulfide of a specific melting point, etc., is provided onto a base material. CONSTITUTION:Anilino fluoren leuco dye being an electron donative coloring substance together with a sensitizer of p-benzil biphenyl or the like is mixed in water to prepare dispersion liquid of a coloring substance. Separately, highly pure bis(4-hydroxy-3-methylphenyl) sulfide and carboxyl denatured polyvinyl alcohol are mixed in water to prepare dispersion liquid of a developer. The dispersion liquid of the coloring substance and the dispersion liquid of the developer are mixed. A thermal coloring layer is formed by applying the mixed liquid onto a base material to be dried, and the present thermal recording material is obtained.

Description

[Detailed Description of the Invention] Skin Presentation Retired Imperial Family ■ Min! The present invention relates to a heat-sensitive recording material that has high background whiteness and excellent color development properties.

Conventionally, pressure-sensitive recording paper, heat-sensitive recording paper, heat-sensitive copying paper, etc. have been widely used as recording materials that utilize the coloring phenomenon caused by contact between a slightly strained electron-donating color-forming substance and an electron-accepting color developer. .

Among these, for example, so-called dye-colored thermal recording paper, which uses leuco bases such as triphenylmethane dyes and fluoran dyes as a color-forming substance, is used for high-speed facsimiles and POS labels, whose demand has been rapidly increasing in recent years. In such applications, it is required to improve the thermal responsiveness of the -layer.

In general, in order to improve the thermal responsiveness of dye-colored thermal recording paper, the following methods are used: the use of low-melting point color developers and sensitizers, the use of fine particles of color-forming substances and color developers, and the improvement of the smoothness of the surface of the recording paper. method has been adopted. However, according to such a method, while the recording sensitivity is improved, on the other hand, a problem of so-called background fogging occurs in which the background whiteness decreases.In order to prevent this, for example, by blending an additive, the background whiteness is Methods have been adopted to improve this. However, even with this method, due to the influence of additives,
On the contrary, it may result in a decrease in color development sensitivity, maximum color density, or background coloration, and is not necessarily suitable for achieving the original purpose.

In view of this situation, the present inventors have already developed a high-purity bismuth with a melting point in the range of 123.9 to 124.9°C as a heat-sensitive recording material that has excellent low-temperature color development and does not cause background fog. It has been proposed to use (4-hydroxy-3methylphenyl) sulfide as a color developer (Japanese Patent Application Laid-Open No. 2071/1999).

High purity bis(4-hydroxy-3-
When used in combination with certain specified dyes, methylphenyl) sulfide exhibits excellent performance that has not been previously available, but on the other hand, when used in combination with other highly versatile dyes, The problem of fogging remains and it provides a heat-sensitive recording material with low whiteness.

In addition to the above-mentioned method, there are also methods using a sulfuric acid ester salt or sulfonate surfactant as a dispersant for leuco dye (Japanese Patent Application Laid-Open No. 166096/1983), and an appropriate amount of carboxyl group-modified polyvinyl alcohol as an additive. A method of adding (Japanese Unexamined Patent Publication No. 59-207278) is known. However, even if these methods are applied to methods that use high-purity bis(4-hydroxy-3-methylphenyl) sulfide as a color developer, the effect is small in all cases, and the problem of background fogging cannot be solved. However, it is difficult to obtain a heat-sensitive recording material with excellent whiteness.

Therefore, as a result of further research, the present inventors found that in a heat-sensitive recording material equipped with a heat-sensitive coloring layer containing the color-forming substance and a color developer, sulfosuccinates were added to the heat-sensitive coloring layer, and It has been discovered that when carboxyl group-modified polyvinyl alcohol is used as a binder, it is possible to obtain a heat-sensitive recording material with high background whiteness (as well as high coloring density and coloring sensitivity (Japanese Patent Application No. 63-2)
No. 86214). However, with regard to background whiteness, so-called pressure fogging is observed due to heat generated by pressure and friction during calendering, and further improvements are required to solve this problem.

As mentioned above, the present inventors used high-purity bis(4) as a color developer.
-When using hydroxy-3-methylphenyl) sulfide, there is no reduction in background whiteness, color development density, or color development sensitivity that occurs when combined with highly versatile leuco dyes, and heat sensitivity that does not cause pressure fog. We conducted extensive research to obtain recording materials.

As a result, the present inventors used anilinofluorane leuco dye as a color-forming substance and the above-mentioned high-purity bis(
Specified additives such as acenaphthene, fluoranthene, higher fatty acid amide, rosin, etc. are added to the heat-sensitive coloring layer containing 4-bitroxy-3-methylphenyl) sulfide, carboxyl i-modified polyvinyl alcohol and/or etherified starch as a binder. By,
The present invention was developed based on the discovery that the background whiteness is high, the coloring density and coloring sensitivity are sufficient, and the problem of pressure fogging can be solved.

Although the above-mentioned additives are already known in the production of heat-sensitive recording materials, their use in combination with the electron-donating color-forming substance and color developer in the present invention has not been known so far. According to the present invention, unexpectedly, due to the combination described above, it is possible to obtain a heat-sensitive recording material that not only has excellent color development properties but also has significantly improved background fog and pressure fog. .

The heat-sensitive recording material according to the present invention for increasing the amount of water contains an anilinofluorane leuco dye as an electron-donating color-forming substance and a high-temperature material having a melting point in the range of 123.9 to 124.9°C as an electron-accepting color developer. In a heat-sensitive recording material comprising a heat-sensitive coloring layer containing pure bis(4-hydroxy-3-methylphenyl) sulfide and carboxyl group-modified polyvinyl alcohol and/or etherified starch as a binder, as an additive (a) acenaphthene or Fluoranthene, (
b) higher fatty acid amide having 4 to 40 carbon atoms; and (c)
It is characterized by containing at least one member selected from the group consisting of rosin.

In the heat-sensitive recording material according to the present invention, the heat-sensitive color-forming layer includes an anilinofluorane leuco dye as an electron-donating color-forming substance and a melting point of 123.9 to 124 as an electron-accepting color developer.
．． High purity bis(4-hydroxy-3-
methylphenyl) sulfide and carboxyl group-modified polyvinyl alcohol and/or etherified starch as a binder.

Examples of the anilinofluorane-based leuco dye include 3-ethylisoamyl-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, and 3-methylcyclohexylamino- 6
-Methyl-7-anilinofluorane, 3-pyrrolidino-
6-Methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyl-
p-Tolylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-(p t
Examples include ert-butylamino-7-(0-chloroanilino)fluoran, 3-dibutylamino-7-(0-chloroanilino)fluoran, and 3-diethylamino-7-(0-chloroanilino)fluoran.

In the heat-sensitive recording material of the present invention, the carboxyl group-modified polyvinyl alcohol used as a binder for forming the heat-sensitive coloring layer includes fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, and itaconic anhydride. and saponified polymers of 6M vinyl and unsaturated carboxylic acids such as maleic acid, fumaric acid, and itaconic acid. Examples of the etherified starch include carboxyl starch, cyanoethyl starch, allyl starch, benzyl starch, vinyl starch, carbamylethyl starch, dialkylaminoalkyl starch, and the like.

These binders include commonly used binders such as polyvinyl alcohol, carboxyl methyl cellulose, methyl cellulose, hydroxyethyl cellulose, styrene-maleic acid copolymers, polyacrylic acid, polyacrylamide, styrene-butadiene rubber latex, synthetic polymers, and natural Alternatively, it can be used in combination with modified natural polymers and the like.

In the present invention, the carboxyl group-modified polyvinyl alcohol or etherified starch is used in an amount of 0.2 to 3 parts by weight (in terms of solid content) per 1 part by weight of the electron-donating color-forming substance. When the amount of the binder used is less than 0.2 parts by weight per 1 part by weight of the electron-donating color-forming substance, it is impossible to obtain a heat-sensitive recording material having the desired high whiteness. However, even if more than 3 parts by weight is used, no commensurate effect can be obtained.

There are no particular restrictions on the method of adding the binder, as long as it is included in at least one of the dispersions shown in Examples below.

The heat-sensitive recording material according to the present invention includes an additive selected from the group consisting of (a) acenaphthene or fluoranthene, (b) an amide of a higher fatty acid having 4 to 40 carbon atoms, and (c) rosin in the heat-sensitive coloring layer as described above. At least one selected type is contained.

Examples of the higher fatty acid amides include valeric acid amide, caproic acid amide, capric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, melisic acid amide, pentatriacontanoic acid amide, and tetraconcnic acid amide. Among them, stearic acid amide or balmitic acid amide is particularly preferably used.

In addition, as the rosin, for example, natural resin rosin and abietic acid, which is its main component, and preferably carbon number 1 to 5
various rosin esters consisting of abietic acid and alkyl alcohol, various rosin esters consisting of abietic acid and glycol or glycerin, various metal salts of abietic acid such as sodium salt, potassium salt, magnesium salt, calcium salt, and For example, rosin oil obtained by carbonizing rosin is used.

Although such an additive may be added to the dispersion containing the electron-donating color-forming substance, a greater effect can be obtained if it is added to the dispersion containing the color developer. The reason for this is not clear, but in the latter case, the color developing ability of the color developer is suppressed by dissolving the additive into the color developer, and the equilibrium between the color former and the color developer shifts to the decoloring side. As a result, application of the coating liquid, heating during drying, or pressure during calendering.
It seems possible to prevent color development even under heating conditions.

In the present invention, the above additive is used in an amount of 0.1 to 5 parts by weight, preferably 0.5 to 1 part by weight, per 1 part by weight of the electron-donating color-forming substance.

When the amount of the additive is less than 0.1 part by weight per 1 part by weight of the color-forming substance, the desired effect cannot be obtained;
On the other hand, if it exceeds 5 parts by weight, it is not preferable because it may cause a decrease in the whiteness of the background or increase the viscosity of the dispersion.

The heat-sensitive recording material of the present invention includes, but is not limited to,
- For boat fishing, it is manufactured by the following method.

First, an electron-donating color-forming substance is thoroughly mixed or pulverized in water with a sensitizer such as p-benzylbiphenyl, ethylene glycol diphenyl ether, ethylene glycol-m-tolyl ether, etc. to prepare a dispersion of the color-forming substance. do. Separately, a color developer dispersion is prepared by thoroughly mixing or pulverizing the color developer together with the pigment, additives, and binder in water. In either case, it is desirable that the material to be dispersed be ground in advance using a ball mill or the like until it becomes fine particles, specifically fine particles of 1 μm or less.

A heat-sensitive recording sheet can be obtained by applying the thus prepared dispersion onto a suitable support such as paper and drying it. To apply a dispersion to a support, the two dispersions described above are usually mixed and this is applied onto the support. It may be applied on top.

In the production of the heat-sensitive recording sheet, if necessary, an inorganic or organic pigment such as talc, kaolin, titanium oxide, calcium carbonate, zinc oxide, diatomaceous earth, urea-formaldehyde resin, or an aqueous solution having crosslinking properties may be added to the dispersion. binders or crosslinking accelerators, protein adhesives and waterproofing agents such as gel tar aldehyde, animal waxes such as beeswax and shellac wax, vegetable waxes such as carnauba wax, petroleum wax, paraffin wax, microcrystalline wax, polyethylene Synthetic waxes such as wax, metal soaps (higher fatty acid metal salts) such as calcium stearate and zinc stearate, pressure coloring inhibitors, surfactants such as sodium sulfosuccinate, antifoaming agents, etc., as appropriate. When used in combination, the coating suitability and properties of the recording sheet can be improved.

As described above, according to the present invention, a heat sensitive method using high purity bis(4-hydroxy-3-methylphenyl) sulfide as a color developer and carboxyl group-modified polyvinyl alcohol or etherified starch as a binder. In the coloring layer, acenaphthene and fluoranthene are added as additives.
Or, if specified additives such as higher fatty acid amides such as stearic acid amide and palmitic acid amide, and rosin are added,
By using anilinofluoran dye as a color-forming substance, it is possible to obtain a heat-sensitive recording material with high background whiteness and excellent color-forming properties.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way. Parts indicate parts by weight.

The preparation of the heat-sensitive recording sheet and the measurement of its various coloring characteristics, background whiteness, etc. were carried out by the methods described below.

(A) Liquid color-forming substance 5.3 parts Binder (10% by weight aqueous solution) 29.2 parts Sensitizer
l016 part water
54.9 copies total
100.0 parts [B] Liquid High purity bis(4-hydroxy-3-monomethylphenyl) sulfide 7.8 parts Binder (10% by weight aqueous solution) 28.0 parts Calcium carbonate
7.8 parts zinc stearate
0.8 parts additive
3.8 parts water
51.8 copies total 100
．． 0 parts The liquids [A] and [B] were separately dispersed in a paint shaker to prepare a dispersion.

Next, 2 parts by weight of liquid [A] and (B) liquid were mixed again in a paint shaker, and then this was applied onto high-quality paper at a dry coating amount of 5 to 6 g/rr? After coating and drying, supercalendering was performed using a manual hydraulic test calender (M-1925, manufactured by Yuri Roll Co., Ltd.) to prepare a heat-sensitive recording sheet.

(a) Background whiteness The background whiteness before applying the super calendar and the background whiteness after applying the super calendar were measured using a Macbeth reflection densitometer (Macbeth RD).
-914) to determine the degree of pressure fog.

(b) The coloring temperature characteristic recording sheet was brought into contact with a metal block having a temperature gradient of 60 to 130°C for 5 seconds at a pressure of 0.6 Kg/aJ to develop color using a Type 738 heat sealer (manufactured by Tester Sangyo). . After color development, the relationship between color density and color temperature was determined using a Macbeth reflection density needle.

(c) Maximum color density The metal block described above was heated to 200°C and the pressure was 0.
Color was developed by contacting at 6 kg/cj for 3 minutes.

After color development, the density was measured by the method described above.

Examples 1 to 8 A 10% by weight carboxyl group-modified polyvinyl alcohol aqueous solution (KL-318 manufactured by Kuraray ■) was added to the above [A] solution and C.
B) High purity bis(
4-Hydroxy-3-methylphenyl) sulfide (melting point 123.9-124°5°C) was added in a predetermined amount of the additive listed in Table 1, and combined with various color-forming substances to produce a heat-sensitive recording sheet. did.

Table 2 shows the evaluation results of the heat-sensitive recording sheets obtained.

Examples 9 to 12 [B] As the binder for the liquid, a 20% by weight etherified starch aqueous solution (Biostarch LT manufactured by Nippon Starch ■) was used instead of the 10% by weight carboxyl group-modified polyvinyl alcohol aqueous solution, and the other conditions were as follows. A swear recording sheet was prepared under the same conditions as in Examples 1 to 8.

Examples 13 and 14 A thermosensitive recording sheet was prepared under the same conditions as in Example 1, except that in 1"A)i, the sensitizer listed in Table 1 was used instead of the sensitizer p-pendylbiphenyl. Created.

Example 15 In liquid (A), 3-diethylamino-6- was used instead of 3-dibutylamino-6-methylanilinofluorane.
A thermosensitive recording sheet was produced under the same conditions as in Example 1 except that methylanilinofluorane was used.

Comparative Examples 1 and 2 Example 1 without adding additives to the CBl liquid, respectively
A thermosensitive recording sheet was produced under the same conditions as in Example 9.

Comparative Examples 3 and 4 10% by weight as a binder for liquids (A) and CB)
Thermosensitive recording sheets were produced under the same conditions as in Examples 1 and 2, respectively, except that an aqueous polyvinyl alcohol solution was used.

Claims (2)

[Claims] (1) Anilinofluorane leuco dye as an electron-donating color forming substance, melting point of 123.9 as an electron-accepting color developer
In a heat-sensitive recording material comprising a heat-sensitive coloring layer containing high-purity bis(4-hydroxy-3-methylphenyl) sulfide in the range of ~124.9°C and carboxyl group-modified polyvinyl alcohol and/or etherified starch as a binder. A heat-sensitive recording material characterized in that it contains as an additive at least one member selected from the group consisting of (a) acenaphthene or fluoranthene, (b) higher fatty acid amide having 4 to 40 carbon atoms, and (c) rosin. (2) The heat-sensitive recording material according to claim 1, wherein the additive is contained in an amount of 0.1 to 5 parts by weight per 1 part by weight of the electron-donating color-forming substance.