JPH0651424B2 - Thermal recording paper - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermal recording paper for recording with a thermal head, a thermal pen, and the like. More specifically, the invention relates to a thermal head and a thermosensitive coloring layer. The present invention relates to a thermal recording paper which does not have piling on a thermal head, has good dot reproducibility even at high speed recording, and can obtain clear and high-density recording.

(Prior art) In recent years, the development of fax machines, printers, etc. has been remarkable,
In particular, the heat-sensitive recording method described in Japanese Patent Publication No. 45-14039 and the like, which uses a combination of a heat-sensitive recording paper coated with a colorless compound such as crystal violet lettactone and a phenol compound and a heat head, is widely adopted in these devices. Has been done.

This heat-sensitive recording method has many advantages such as that the recording paper has a primary color, no development is required, the recording device can be simplified, the cost of the recording paper and the recording device is low, there is no impact, and there is no noise. Yes, it has established itself as a low-speed recording system. However, a major drawback of heat-sensitive recording is that the recording speed is slower than other recording methods such as electrostatic recording, and it is the current situation that the adoption range does not reach to high-speed recording.

In thermal recording, the main reason why high-speed recording cannot be performed is that thermal conduction between the thermal head and the thermal recording paper in contact therewith is not sufficiently performed, and sufficient recording density cannot be obtained. The thermal head, which is a collection of dot-shaped electric resistance heating elements, generates heat in response to a recording signal, and the thermosensitive coloring layer in contact with the thermal head melts and develops color. In order to obtain clear and high-density recording, good dot reproducibility, that is, the thermal head and the thermosensitive coloring layer are in intimate contact with each other as efficiently as possible, the heat conduction is performed efficiently, and it is perfectly compatible with high-speed recording signals. It is necessary to form dots on the thermosensitive coloring layer, which are completely colored and correspond to the shape of the thermal heating dot heating element. But,
At present, only a few percent of the amount of heat generated by the thermal head is conducted to the thermosensitive coloring layer, and the thermal conduction efficiency is extremely low.

Several methods have been proposed for improving the smoothness of the heat-sensitive color developing layer so that the heat head and the heat-sensitive color developing layer are in close contact with each other as much as possible.

Japanese Patent Publication No. 52-20142 describes that the surface of the thermosensitive color developing layer is subjected to surface smoothing for 200 to 1000 seconds. Japanese Patent Application Laid-Open No. 54-115255 discloses that a surface smoothness of 200 to 1000 seconds can be applied only to a heat pulse of about 5 to 6 milliseconds, and for high speed recording of 1 millisecond or less, the surface of the thermosensitive coloring layer is coated. It is described that it is necessary to perform a smoothing treatment for smoothness of 1100 seconds or more.
If the flatness of the surface is set to 1100 seconds or more, color fog will occur due to the pressure.
Bek smoothness is improved to 500 seconds or more to prevent color fog. JP-A-53-156086 describes that the surface roughness Ra of the surface of the thermosensitive color developing layer is 1.2 μm or less and the glossiness is 25% or less.

All of the above-mentioned conventional techniques for improving the smoothness improve the smoothness of the heat-sensitive color developing layer only by a calendar treatment such as a super calendar, a machine calendar and a gloss calendar. The calendering is performed only on the base paper, or the base paper and the thermal paper, or only the thermal paper. Thermal paper with smoothness improved by these calender treatments has more staking and piling as the smoothness improves and the recording density improves. Therefore, the smoothness is actually suppressed to an appropriate level. Thus, the recording density, the staging, and the piling are properly balanced. The conventional technique is not practical for high-speed recording in terms of recording density or recording stability regardless of smoothness level.

With staking, the thermal head and the thermosensitive coloring layer adhere,
Peeling is a phenomenon in which peeling noise is generated or dot reproducibility is deteriorated.Piling is a phenomenon in which the thermal melt of the thermosensitive coloring layer accumulates on the thermal head, resulting in a decrease in recording density and dot reproducibility. Both are phenomena that prevent stable recording.

Another disadvantage of calendering thermal paper is that the pressure causes discoloration fog, which increases the density of the background portion of the recording paper. On the other hand, there is a limit to the calendering process for the base paper because of the occurrence of so-called beckles, streaks and the like due to uneven basis weight. As described above, the smoothing of the thermosensitive coloring layer and the improvement of the recording density by the calendering process are necessarily limited, and a satisfactory one for high speed recording cannot be obtained.

Further, the heat-sensitive recording paper is often used by being wrapped around a small paper tube having a diameter of several inches, and there is a drawback that curling is likely to occur in the core portion after a long period of time. It was rare.

(Object of the Invention) An object of the present invention is to provide a thermal recording paper which has improved the above-mentioned drawbacks, that is, a thermal recording paper having a high recording density and less curling curl.

(Structure of the Invention) As a result of intensive studies to improve these drawbacks, the present inventors have found that a paper support containing an epoxidized fatty acid amide and a polymer latex having a MFT (minimum film forming temperature) of 40 ° C. or lower It has been found that by providing a thermosensitive coloring layer on the body, a thermosensitive recording paper satisfying all the above characteristics can be obtained.

The epoxidized fatty acid amide used in the present invention has 8 carbon atoms.
A condensate of an aliphatic carboxylic acid of ~ 30 and a polyvalent amine is converted to a quaternary salt by epichlorohydrin.
The aliphatic carboxylic acid having 8 to 30 carbon atoms has 8 to 3 carbon atoms.
0 aliphatic monocarboxylic acid and polyvalent carboxylic acid,
Particularly, those having 12 to 25 carbon atoms have a great effect. Particularly preferred are stearic acid, oleic acid, lauric acid, palmitic acid, behenic acid, alkylsuccinic acid, alkenylsuccinic acid and the like. As the polyvalent amine, polyalkylene polyamine is desirable, and among them, those having 2-3 methylene groups between amino groups are preferable. Examples thereof include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, dipropylenetriamine, tripropylenetetramine, aminoethylethanolamine and the like. The amounts of the aliphatic carboxylic acid and the polyvalent amine to be used in the reaction are used so that the amino group becomes excessive in the amount ratio of the carboxyl group and the amino group. In order to make the particles of these reactants finer, they may be modified by reacting them with urea, adipic acid, maleic acid, phthalic acid, formic acid, formalin, etc. after the reaction of the aliphatic carboxylic acid and the polyvalent amine. . In addition, rosin petroleum resin, α, β-unsaturated polybasic acid-added rosin, α, β-unsaturated polybasic acid-added petroleum resin may be allowed to coexist during the reaction of the aliphatic carboxylic acid and the polyvalent amine. .
In order to make these reactants water-soluble and to improve the fixability with pulp, they are subsequently reacted with epichlorohydrin to form a quaternary salt, which is used in the present invention. The amount of epoxidized fatty acid amide added to the base paper is preferably 0.1 to 3.0 weight percent. For the purpose of the present invention, that is, with respect to the color recording density and curl curl, the larger the addition amount, the greater the effect, but the paper strength is greatly reduced, and problems such as paper breakage occur when the heat-sensitive liquid is applied. When used alone, it can only be used in very limited amounts. As a countermeasure against this, a combination of various paper-strengthening agents was examined, and as a result, M
The above-mentioned drawbacks are solved by adding a polymer latex having an FT of 40 ° C. or lower at a weight ratio of 1 to 10 times with respect to the epoxidized fatty acid amide, and, surprisingly, the effect of the present invention is more remarkable. I found that I could get it. That is, epoxidized fatty acid amide and M
It has been found that a paper support in which a polymer latex having an FT of 40 ° C. or lower is used in combination produces effects that cannot be obtained when used alone. The addition to the paper support may be internal addition or surface size, but the polymer latex is preferably internal addition.

Examples of the polymer latex having MFT of 40 ° C. or lower used in the present invention include SBR latex and carboxyl-modified SB.
R latex, MBR latex, carboxyl modified M
BR latex, NBR latex, acrylic ester emulsion, acrylic ester acetate vinyl emulsion, styrene acrylic ester emulsion, copolymer emulsion of methyl methacrylate and acrylic ester, methyl methacrylate and styrene and acrylic ester Tertiary copolymers and the like, of which MFT of 40 ° C. or less, more preferably 30 ° C. or less are desirable. It should be noted that anion-modified polyacrylamide, cation-modified polyacrylamide, starch, melamine formaldehyde resin, polyamide polyamine epichlorohydrin, which are water-soluble paper-strengthening agents generally used in place of the polymer latex of MFT of 40 ° C. or less of the present invention, are used. Although the resin and the like are effective in improving the paper strength, they are not preferable because they deteriorate the color recording density and the curling curl which are the objects of the present invention.

The paper support used in the present invention is mainly made of natural pulp, but it is also possible to partially mix synthetic fibers or synthetic pulp, or inorganic fibers. As the natural pulp, any of softwood pulp, hardwood pulp, straw pulp, esparto pulp, bagasse pulp and the like can be used, but hardwood pulp, which is short fiber and easily smooth, is more preferable. The beating of pulp is performed with a beater, a disc cliff eyer, a conical riff eyer, a Jordan riff eyer, etc., but the water level is 500 to 200 cc.
(C.S.F) is preferable, and 400 to 3 is particularly preferable.
00 (C.S.F).

Further, the following chemicals can be added as raw materials other than pulp. That is, as a sizing agent, rosin, paraffin wax, higher fatty acid salt, alkenyl succinate,
Fatty acid anhydride, styrene maleic anhydride copolymer, alkylketene dimer epoxidized fatty acid amide, reaction product of maleic anhydride copolymer and polyalkylene polyamine as softening agent, quaternary ammonium salt of higher fatty acid, talc as pigment , Clay, kaolin, calcium carbonate,
If necessary, aluminum sulfate, aluminum chloride salt, polyamide polyamine epichlorohydrin, and other dyes, fluorescent dyes, antistatic agents, defoaming agents and the like can be added as a fixing agent such as barium sulfate and titanium oxide. The amount of the sizing agent added is such that the sizing degree of the paper support after papermaking is 30 g / m ² or less as the Cobb sizing degree, preferably 2
It is desirable to control the addition amount so as to be 0 to 10 g / m ² .

The paper support used in the present invention, after mixing these raw materials,
The paper is made by a Fourdrinier paper machine or a cylinder paper machine and has a basis weight of 30 to 200 g / m ² . The density is 0.80 to 0.98 g / cm ³ by the on-machine calender or off-machine super calender treatment.
The one finished is used.

Further, if necessary, an undercoat layer containing a pigment as a main component may be provided on these paper supports to prepare a support for thermal recording paper.

Next, the heat-sensitive coating liquid used in the present invention will be described.

In the heat-sensitive coating liquid, a color-developing agent and a color-developing agent are generally separately dispersed in a water-soluble polymer solution using a means such as a ball mill. In order to obtain a finely divided product of the color former or the developer, for example, a ball mill is used, which is achieved by using balls having different particle diameters at an appropriate mixing ratio and dispersing them for a sufficient time. It is also effective to use a model sand mill (trade name: Dyno Mill).

The resulting dispersion of the color-developing agent and the color-developing agent is mixed, and an inorganic pigment, waxes, higher fatty acid amide, metal soap, and if necessary, an ultraviolet absorber, an antioxidant, a latex binder, etc. are added to obtain a coating liquid. And These additives may be added at the time of dispersion.

The coating liquid generally has a coating amount of 0.2 g / m ² as a color former.
To 1.0 g / m ² on the support.

The color forming agent used in the present invention is not particularly limited as long as it is used in general pressure sensitive recording paper, heat sensitive recording paper and the like. Specific examples include (1) triarylmethane compounds such as 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3- (p -Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3 , 3-bis- (p-ethylcarbazole-3
-Yl) -3-dimethylaminophthalide, 3,3-bis- (2-phenylindol-3-yl) -5-dimethylaminophthalide, etc .; (2) diphenylmethane compounds, for example, 4,4 -Bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine, etc .; (3) xanthene compounds such as rhodamine B-anilino Lactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-
Butylaminofluorane, 3-diethylamino-7-
(2-chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyl-tolylamino-6-methyl-7-ani Rinofluorane, 3-cyclohexyl-methylamino-6-methyl-
7-anilinofluorane, 3-diethylamino-6-chloro-7- (β-ethoxyethyl) aminofluorane,
3-Diethylamino-6-chloro-7- (γ-chloropropyl) aminofluorane, 3-diethylamino-6-
Chloro-7-anilinofluorane, 3-N-cyclohexyl-N-methylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7-phenylfluorane, etc .; (4) thiazine-based compound, For example, benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue and the like; (5) Spiro compounds such as 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3
-Methylnaphtho- (3-methoxy-benzo) -spiropyran or the like, or a mixture thereof can be mentioned. These are determined by the application and the desired properties.

The color developer used in the present invention is a phenol derivative,
Aromatic carboxylic acid derivatives are preferable, and bisphenols are particularly preferable. Specifically, as phenols, p
-Octylphenol, p-tert-butylphenol, p-phenylphenol, 2,2 bis (p-hydroxy) propane, 1,1-bis (p-hydroxyphenyl) bentane, 1,1-bis (p- Hydroxyphenyl) hexane, 2,2-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) -2-ethyl-hexane, 2,2-bis (4-hydroxy-3) , 5-dichlorophenyl) propane and the like.

As the aromatic carboxylic acid derivative, p-hydroxybenzoic acid, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate,
Examples of 3,5-di-α-methylbenzyl salicylic acid and carboxylic acid include polyvalent metal salts thereof.

These color developers are added as a eutectic with a low-melting heat-fusible substance in order to cause a color reaction by melting at a desired temperature, or the low-melting compound is added to the surface of the color developer particles. It is preferable to add it in the state of being fused to the.

Examples of waxes include paraffin wax, carnauba wax, microcrystalline wax, polyethylene wax, and higher fatty acid amides such as stearic acid amide, ethylene bis stearoamide, and higher fatty acid ester.

Examples of the metal soap include higher fatty acid polyvalent metal salts, that is, zinc stearate, aluminum stearate, calcium stearate, zinc oleate and the like.

As the inorganic pigment, carion, calion carion, talc,
Examples thereof include wax, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, titanium oxide and barium carbonate.

These inorganic pigments preferably have an oil absorption of 60 ml / 100 g or more and an average particle diameter of 5 μm or less. For the oil-absorbing inorganic pigment, the dry weight in the recording layer is 5 to 50% by weight,
It is desirable to add 10 to 40% by weight.

These are dispersed and applied in a binder. As the binder, water-soluble ones are generally used, and polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer. , Polyacrylic acid, starch derivative casein, gelatin and the like.

Further, a water-proofing agent (gelling agent, cross-linking agent) is added to these binders for the purpose of imparting water resistance, or a hydrophobic polymer emulsion, specifically, styrene-butadiene rubber latex, acrylic resin emulsion, etc. Can also be added.

The binder reacts in the recording layer at a dry weight of 10 to 30% by weight. Further, various auxiliaries such as defoaming agents, fluorescent dyes, and coloring dyes can be appropriately added to the coating liquid as needed.

The coating liquid for forming such a recording layer is a blade coating method,
Conventionally known coating methods such as an air knife coating method, a gravure coating method, a roll coating coating method, a spray coating method, a dip coating method, a bar coating method and an extrusion coating method can be used.

The coating amount of the coating liquid for forming the recording layer on the support is not limited, but is usually 3 to 15 g / m ² in dry weight,
It is preferably in the range of 4 to 10 g / m ² .

(Effects of the Invention) The effects obtained by the heat-sensitive recording paper according to the present invention using a paper support containing an epoxidized fatty acid amide and a polymer latex having an MFT of 40 ° C. or lower are as follows. That is, the contact area is increased to obtain high recording density and good dot reproducibility. Second, the flexibility of the support is increased, and a thermal recording paper with less curling curl can be obtained.

(Examples of the Invention) Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

Example 70 parts of LBKP and 30 parts of NBKP were beaten to 280 cc Canadian freeness with a disiffiner, and then 8.0 parts of talc, 1.0 part of rosin, and sulfuric acid band 2.
All 0 parts were added in a weight percentage relative to the bone-dry pulp. Further, the epoxidized fatty acid amide and the polymer latex were added in the addition amounts shown in Table 1, and a base paper having a basis weight of 60 g / m ² was made with a Fourdrinier paper machine. After that, the thickness was adjusted to 67 μ using a super calendar.

The epoxidized fatty acid amide used in this example is NS-715 manufactured by Hyundai Kagaku Co., Ltd., and its production is as follows.

In the above formula, R is an alkyl group having 15 or 17 carbon atoms and those having 15 and 17 carbon atoms are mixed at a ratio of about 4: 6.

(Sample Nos. 1 to 5) Similarly, base papers to which the epoxidized fatty acid amide of the present invention or the polymer latex of the present invention was not added were prepared and used as comparative examples. (Sample Nos. 6 to 10) The heat-sensitive coating liquid was applied to the base papers of Examples and Comparative Examples to obtain heat-sensitive papers. Thermal recording was performed on this thermal paper and the recording density was measured. Further, this thermal paper was wound around a 2-inch paper tube, and the state of curling curl in the core portion after 5 months at 20 ° C. and 60% RH was evaluated. The results are shown in Table 2. The method for producing the heat-sensitive coating liquid, the coating method, and the method for measuring the heat-sensitive recording density are shown below.

Method for producing heat-sensitive coating liquid 20 kg of crystal bio-leptlactone was dispersed with a 10% aqueous solution of polyvinyl alcohol (saponification degree: 98%, polymerization degree: 500) in a 300-ball mill overnight. Similarly, 2,2-bis (4-hydroxyphenyl) propane 2
0 kg together with 10% polyvinyl alcohol aqueous solution 30
It was dispersed all day and night in a 0 ball mill. Both dispersions were mixed so that the ratio of crystal violet lettactone and 2,2-bis (4-hydroxyphenyl) propane was 1: 5 by weight, and 5 kg of light calcium carbonate was added to 20 kg of the mixed solution. Was added and sufficiently dispersed to obtain a coating liquid.

Coating method of heat-sensitive coating liquid 6g / m in solid content on one side of base paper with air knife coater
^It was applied so that it would be ² , dried in a hot-air dryer at 50 ° C., and machine-calendered.

Measuring method of thermal recording density Recording speed 2 ms per dot, recording density 5 in main scanning direction
Solid color development was performed at a dot / mm, a sub-scanning direction of 6 dots / mm, and a thermal head energy of 50 mm / mm ² . The recording density was a reflection density of 610 nm.

From the results shown in Table 2, it is clear that the thermosensitive recording paper according to the present invention has excellent properties in terms of color recording density, dot reproducibility and curl curl.

Claims (2)

[Claims] 1. A thermosensitive recording paper comprising a thermosensitive coloring layer provided on a paper support, wherein the paper support contains an epoxidized fatty acid amide and a polymer latex having an MFT (minimum film forming temperature) of 40 ° C. or less. Characteristic thermal recording paper. 2. The heat-sensitive recording paper according to claim 1, wherein the absolute dry weight content ratio of the polymer latex to the epoxidized fatty acid amide is 1 to 10.