JPH04282287A - Thermal recording paper - Google Patents

Abstract

PURPOSE:To obtain a sharp image by a method wherein thermal recording paper hardly gets into a habit of curling even under a long-term storage in a small-diameter roll state and has superior properties in being contained in a tray after recording and a reduced background fog at a high density. CONSTITUTION:In thermal recording paper provided with a thermal color- forming layer on a substrate, a material having a transfer amount of 20ml/m<2> or less in a Bristol test and a transfer amount difference of 2ml/m<2> or less between the top surface and the rear surface is used as the substrate, the bulk density of the thermal recording paper is 0.98g/cm<3> or less, and the smoothness of a non-printing surface is 150 sec or more.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to thermal recording paper, and more particularly, it is capable of forming a high-density, clear image with little background fog at low energy and with little curling when finished into a small-diameter roll. This paper relates to thermal recording paper that can be used.

0002

BACKGROUND OF THE INVENTION In recent years, facsimiles and the like have made remarkable progress, and thermal recording has come to be widely adopted as a recording method. In the thermal recording method described in Japanese Patent Publication No. 45-14039, which uses a combination of a thermal head and a thermal paper coated with a colorless dye such as crystal violet lactone and a phenol compound, the recording paper develops primary color. It has many advantages such as no development is required, the recording device can be simplified, the costs of the recording paper and recording device are low, and there is no noise during recording. Sensitivity has also improved due to improvements in thermal heads and thermal paper, and it has become widespread in the field of high-speed recording, where electrostatic recording had traditionally been used.

[0003] Therefore, it is desired to develop a heat-sensitive recording paper capable of increasing the speed of recording apparatuses and to cope with the speed increase. A major factor in achieving higher speeds is the fixing ability between the thermal head and the thermal recording paper, and improving the efficiency of thermal conductivity. For this reason, Japanese Patent Publication No. 52-20142 describes a method of surface-treating the surface of the heat-sensitive coloring layer to a Bekk smoothness of 200 to 1000 seconds, but this method tends to cause background fogging due to the calender. On the contrary, unevenness in basis weight and surface irregularities are accentuated, reducing the adhesion of the head and causing a decrease in recording density.

Furthermore, most of these thermal recording papers are loaded into a recording device such as a facsimile machine as a small-diameter roll, and after recording is performed on the thermal recording paper unwound from the roll, the paper is cut into sheets with a cutter and then stored in a sheet stacking section. Accumulated. Small-diameter rolls are usually wound around 100 m with dimensions such as 210 mm in width around a core with an outer diameter of 25.4 mm, and have an outer diameter of 90 to 100 mm.
It comes in rolls. The longer a small-diameter roll is stored and the smaller its winding diameter is, the more curls are likely to form in the roll, and the more likely recording paper running defects such as jamming in the recording section and sheet stacking failure in the stacking section will occur. Further, the type of base paper and the composition of the heat-sensitive coating liquid have a large influence on curling.

Various proposals have been made to reduce this curl. For example, JP-A-60-18487
Publication No. 5 proposes using a specific cationic softener in a specific amount in the support, but this increases the cost due to the addition of the softener and the presence of the softener causes problems in the heat-sensitive coloring layer. There is a drawback that formulation design is restricted, and in Japanese Patent Application Laid-Open No. 61-268482, after applying a heat-sensitive coloring layer to the glossy surface dried with a Yankee dryer, the base paper is coated with a small diameter so that the felt surface is on the outside. Although it is mentioned that the paper is finished into a roll, it is generally assumed that the effect of the heat-sensitive coloring liquid application conditions (particularly the penetration of the coating liquid) is greater than the effect of the difference between the front and back sides of the base paper on curling. So I can't expect much.

Furthermore, JP-A No. 62-218183 proposes the use of a support containing a specific amount of a specific white pigment and a polymer latex.
However, increasing the amount of pigment is not practical because it impairs the durability of the cutter blade commonly used in facsimile machines that use small-diameter rolls of thermal recording paper.
Furthermore, JP-A No. 62-218184 describes the use of base paper containing specific amounts of a specific epoxidized fatty acid amide and polymer latex; As a paper strength enhancer added to compensate for the deterioration, ordinary ones cannot be used, and in particular, only the polymer latex described in the publication can be used, which is a drawback of lack of versatility. Furthermore, Japanese Patent Application Laid-open No. 62-25084 states that the fiber length distribution measured by the sieving method (JIS-P-8207) is such that the sum of 24 mesh remaining weight % and 42 mesh remaining weight % is 60 weight % or less. Although it has been proposed to use a base paper having a residual weight percentage of 24 mesh of 10% or less as a support, it cannot be expected that this will always reduce curling.

[0007] In addition, JP-A No. 62-32081 proposes providing a back coat layer containing colloidal silica on the back surface of the support, but this is also said to be effective against curls. I can't say that. Also, JP-A-2
Publication No. 227280 discloses that a base paper having a dynamic wettability value of -0.3 to 0.20 g after 2 seconds of water immersion in a dynamic wettability tester is used as a support, and the vapor pressure of a saturated aqueous solution is 3. .0
It has been proposed to provide a layer containing ~13.0 mmHg of salt on the back surface, but this method is not suitable for expressing the difference between the front and back because the dynamic wetting value is due to immersion. In addition, there is no clear relationship between the back layer and blocking, and we cannot expect much effect on curling.

[0008]

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned state of the prior art, and it is an object of the present invention to reduce curling when finished with a small diameter roll of 100 m, and to produce a high-density, clear roll with low energy consumption. An object of the present invention is to provide a heat-sensitive recording paper capable of forming an image with less background fog.

[0009]

[Means for Solving the Problems] In order to solve the above problems, the present inventors have made extensive studies and have found a method using a support having specific physical properties, a specific tension, and a smoothness of the non-printing surface. The inventors have discovered that the above-mentioned problems can be solved by a thermosensitive recording paper having the above-described method, and have completed the present invention.

That is, according to the present invention, in a heat-sensitive recording paper in which a heat-sensitive color forming layer containing a leuco dye and a color developer as main components is provided on a support, the J.I. TAPPI
No. Transfer volume of Bristow test according to 51 is 20ml
/m2 or less, and the difference in the amount of transfer between the front and back surfaces is 2ml/m
2 or less, and the tension of the thermal recording paper is 0.9 g/c
m3 or less and J. TAPPI No.
．． There is provided a thermal recording paper characterized by a smoothness of 150 seconds or more according to 5B.

According to the research carried out by the present inventors, the reason why the curl of a small diameter roll increases over time is that the rearrangement of the bonds between fibers due to moisture absorption on the non-printing surface of the thermal recording paper greatly contributes. It was also found that this moisture absorption occurs more easily when the smoothness of the non-printed surface is lower.

For general heat-sensitive recording paper, it is important to improve the smoothness of the printed surface using a calender to improve the adhesion with the head, but this method tends to cause background fog, and the non-printed surface Regarding the smoothness, the smoothness targeted by the present invention cannot be obtained. In addition, when manufacturing thermal recording paper, coating only one side increases curling on the non-coated side, which is unfavorable for running during coating. A binder or emulsion may be applied. If this method is carried out, the smoothness that is the goal of the present invention can be obtained, and the barrier effect will suppress water absorption and desorption. This is undesirable because the surfaces are in close contact and chemical reactions tend to cause problems such as blocking and background discoloration.

In addition to the method using chemicals as described above, as a method for achieving smoothness of the non-printing surface of 150 sec or more, the present inventors used a support with a transfer amount of 20 ml/m2 by Bristow test on both sides. It has been found that the following can be achieved by using a support in which the difference in the amount of transfer on both sides of the support is 2 ml/m2 or less.

[0014] The Bristow test is described by J. TAPPI
No. 51, and the measurement conditions were that the amount of transfer when the contact time between the test liquid and the support was 2 seconds was estimated to be closest to the immersion time to relax the bond between fibers. , the amount of transfer during this contact time is defined in the present invention.

In general, the base paper used as a support for thermosensitive recording paper has problems such as poor sizing agent yield, fewer fine fibers, and wire marks on the non-thermal liquid coated side (back side), resulting in poor smoothness and size. In terms of properties, it is inferior to the heat-sensitive liquid applied surface (surface), and the permeability of liquid is greater.
Effects like those of the present invention cannot be obtained. However, the support specified in the present invention has a small difference between the front and back sides, and the difference in Bristow transfer amount is within 2 ml/m2, and the coating liquid for coating on a non-thermal surface in order to improve the runnability in coating. Even if water is applied instead of using an aqueous binder emulsion solution with high barrier properties, water permeability is low and swelling of the surface fibers is suppressed, so the deterioration of surface properties is minimized and a highly smooth surface is achieved. A non-printing surface of 100% is obtained. There are other methods to measure the permeability of water into the support, such as the Cobb water absorption test and the sizing test, but none of these methods simulate immersion in actual coating, and the measurement results may differ from those of other methods. No relationship was found with the smoothness of the printed surface.

[0016] Also, the amount of transfer in the Bristow test on both sides was 2.
Since it is 0 ml/m2 or less, penetration of the heat-sensitive coloring liquid is also suppressed to a minimum, and the coloring uniformity of the image is also improved. In addition, it is particularly preferable that the amount of bristow transfer on both sides is 15 ml/m2 or less in terms of both curling and image formation.

In the present invention, it is not necessary to obtain high smoothness by forcibly increasing the density using a calender, etc., and thermal recording paper with high smoothness and no background fog can be obtained even with a tightness of 0.9 g/cm3 or less. It will be done.

[0018] The method for manufacturing the support used in the present invention requires adjusting the type and amount of internally added and externally added chemicals, the ratio of internally and externally added chemicals, and the press in the wet part.
There are no restrictions on the type and adjustment of pulp.

[0019] When forming the support used in the present invention, for example, as a softening agent, a reaction product of a maleic anhydride copolymer and a polyalkylene polyamine, a higher fatty acid
grade ammonium salts, etc., polyacrylamide, starch, polyvinyl alcohol, melamine formaldehyde condensate, gelatin, etc. as paper strength enhancers, sulfuric acid bandate, polyamide polyamine epichlorohydrin, etc. as fixing agents,
In addition, pigments, dyes, fluorescent dyes, antistatic agents, etc. can be added as necessary. Among these, pigments are effective for further enhancing the effects of the present invention, and are preferably added in an amount of 10% by weight or more based on the pulp.

The heat-sensitive recording paper of the present invention is provided with a heat-sensitive color-forming layer containing a leuco dye and a color developer which causes the leuco dye to develop color when brought into contact with heat as the main components, on the above-mentioned support.

[0021] The leuco dyes used in the heat-sensitive coloring layer can be applied singly or in a mixture of two or more kinds, and as such leuco dyes, those used in this type of heat-sensitive materials can be arbitrarily applied. For example, triphenylmethane type, fluoran type, phenothiazine type, auramine type,
Leuco compounds of spiropyran and indolinophthalide dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3,3-bis(p-dimethylaminophenyl)-phthalide, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis( p-dimethylaminophenyl)-6-diethylaminophthalide, 3
, 3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3,3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-5,7- Dimethylfluorane, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluorane, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 3-
Diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-
7,8-benzfluorane, 3-diethylamino-6-
Methyl-7-chlorofluorane, 3-(N-ethyl-N
-p-tolyl)-6-methyl-7-anilinofluorane, 3-(N-p-tolyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-
Methyl-7-anilinofluorane, 2-{N-(3'-
trifluoromethylphenyl)amino}-6-diethylaminofluorane, 2-{3,6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam}, 3-diethylamino-6-methyl-7-(
m-trichloromethylanilino)fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran,
3-dibutylamino-7-(o-chloroanilino)fluoran, 3-N-methyl-N-amylamino-6-methyl-7-anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl- 7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-(
2',4'-dimethylanilino)fluorane, 3-(N
,N-diethylamino)-5-methyl-7-(N,N-
dibenzylamino)fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-3'-methoxy-benzoindolino-spiropyran, 3-(2'-hydroxy- 4'-dimethylaminophenyl)-3-(2
'-Methoxy-5'-chlorophenyl)phthalide, 3-
(2'-hydroxy-4'-dimethylaminophenyl)
-3-(2'-methoxy-5'-nitrophenyl)phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide, 3- (2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-
Chlor-5'-methylphenyl)phthalide, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro -7-(N-benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethyl amino)
Fluoran, 3-(N-ethyl-p-toluidino)-7
-(α-phenylethylamino)fluoran, 3-diethylamino-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-
7-(α-phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3-(N-methyltoluidino)-7-(p-n-butylanilino)fluorane, 3-(N -Methyl-N-isopropylamino)-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3,6-bis(dimethylamino)fluorenespiro(9, 3')-6'-dimethylaminophthalide,
3-(N-benzyl-N-cyclohexylamino)-5
, 6-benzo-7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl-N-(2-ethoxypropyl)amino- 6-methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino-4', 5'
-Benzofluorane, 3-(p-dimethylaminophenyl)-3-{1,1-bis(p-dimethylaminophenyl)ethylene-2-yl}phthalide, 3-(p-dimethylaminophenyl)-3- {1,1-bis(p-dimethylaminophenyl)ethylene-2-yl}-6-dimethylaminophthalide, 3-(p-dimethylaminophenyl)-3-(1-p-dimethylaminophenylethylene-
2-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(1-p-dimethylaminophenyl-1-p
-chlorophenylethylene-2-yl)-6-dimethylaminophthalide, 3-(4'-dimethylamino-2'-
methoxy)-3-(1''-p-dimethylaminophenyl-1''-p-chlorophenyl-1'',3''-butadien-4''-yl)benzophthalide, 3-(4'
-dimethylamino-2'-benzyloxy)-3-(1
''-p-dimethylaminophenyl-1''-phenyl-1'',3''-butadien-4''-yl)benzophthalide, 3-dimethylamino-6-dimethylaminofluorene-9-spiro-3'-(6'-dimethylamino)phthalide, 3,3-bis{2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl}
-4,5,6,7-tetrachlorophthalide, 3-bis{
1,1-bis(4-pyrrolidinophenyl)ethylene-2
-yl}-5,6-dichloro-4,7-dibromophthalide, bis(p-dimethylaminostyryl)-1-naphthalenesulfonylmethane, and the like.

The color developer used in the heat-sensitive coloring layer may include various electron-accepting compounds that cause the leuco dye to develop color upon contact, such as phenolic compounds, thiophenolic compounds, thiourea derivatives, organic acids, and their like. Metal salts and the like are preferably used, and specific examples thereof include those shown below.

4,4'-isopropylidene bisphenol, 4,4'-isopropylidene bis(o-methylphenol), 4,4'-secondary butylidene bisphenol 4,4'-isopropylidene bis(2-tert-butylphenol) ), 4,4'-cyclohexylidene diphenol, 4,4'-isopropylidene bis(2
-chlorophenol), 2,2'-methylenebis(4-
methyl-6-tert-butylphenol), 2,2
'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis(6-tert-butyl-2-methylphenol), 1,1,3
-Tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1,3-tris(2-
Methyl-4-hydroxy-5-cyclohexylphenyl)butane, 4,4'-thiobis(6-tert-butyl-2-methylphenol), 4,4'-diphenolsulfone, 4-isopropoxy-4'-hydroxy Diphenylsulfone, 4-benzyloxy-4'-hydroxydiphenylsulfone, 4,4'-diphenolsulfoxide, isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoate, benzyl protocatechuate,
Stearyl gallate, lauryl gallate, octyl gallate, 1,7-bis(4-hydroxyphenylthio)-
3,5-dioxaheptane, 1,5-bis(4-hydroxyphenylthio)-3-oxapentane, 1,3-bis(4-hydroxyphenylthio)-propane, 1,3
-bis(4-hydroxyphenylthio)-2-hydroxypropane, N,N'-diphenylthiourea, N,N'
-di(m-chlorophenyl)thiourea, salicylanilide, 5-chloro-salicylanilide, 2-hydroxy-
3-naphthoic acid, 2-hydroxy-1-naphthoic acid, 1
-Hydroxy-2-naphthoic acid, metal salts of hydroxynaphthoic acid such as zinc, aluminum, calcium, bis-
(4-hydroxyphenyl)acetic acid methyl ester, bis-(4-hydroxyphenyl)acetic acid benzyl ester,
1,3-bis(4-hydroxycumyl)benzene, 1,
4-bis(4-hydroxycumyl)benzene, 2,4'
-diphenolsulfone, 3,4-dihydroxy-4'
-methyldiphenylsulfone, 3,3'-diallyl-4
, 4'-diphenolsulfone, α,α-bis(4-hydroxyphenyl)-α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S, and the like.

In order to produce the heat-sensitive recording paper of the present invention, when a leuco dye and a color developer are bonded and supported on a support,
Various conventional binders can be used as appropriate, and specific examples include the following.

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, polyacrylic acid source DA, polyvinylpyrrolidone, acrylamide/acrylic acid ester copolymer, acrylamide/acrylic acid ester/methacrylic acid terpolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt, In addition to water-soluble polymers such as polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, polyacrylic ester, polymethacrylic ester, vinyl chloride/vinyl acetate copolymer, and ethylene/vinyl acetate copolymer Emulsions such as polymers, latex such as styrene/butadiene copolymers, styrene/butadiene/acrylic copolymers, etc.

In addition, in the heat-sensitive coloring layer, various heat-fusible substances can be used in combination with the leuco dye and color developer as heat sensitivity improvers, if necessary. Specific examples thereof include, for example, The following compounds may be mentioned.

Fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, zinc stearate, aluminum stearate,
Fatty acid metal salts such as calcium stearate, zinc palmitate, zinc behenate, p-benzylbiphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, β
-naphthoic acid phenyl ester, 1-hydroxy-2-
Naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid methyl ester, diphenyl carbonate, terephthalic acid dibenzyl ester, terephthalic acid dimethyl ester, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-di Benzyloxynaphthalene, 1,2-bis(phenoxy)ethane, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4
-methylphenoxy)ethane, 1,4-bis(phenoxy)butane, 1,4-bis(phenoxy)-2-butene, dibenzoylmethane, 1,4-bis(phenylthio)
Butane, 1,4-bis(phenylthio)-2-butene,
1,3-bis(2-vinyloxyethoxy)benzene,
1,4-bis(2-vinyloxyethoxy)benzene,
p-(2-vinyloxyethoxy)biphenyl, p-aryloxybiphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, 1,3-dibenzoyloxypropane, dibenzyl disulfide, 1,1-
diphenylethanol, 1,1-diphenylpropanol, p-(benzyloxy)benzyl alcohol, 1,
3-diphenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N
-octadecylcarbamoylbenzene, dibenzyl oxalate, p-chlorobenzyl oxalate, etc.

[0029] In the heat-sensitive coloring layer, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material,
For example, fillers, dispersants, color image stabilizers, antioxidants, antifoaming agents, light stabilizers, fluorescent whitening agents, surfactants, and the like can be used in combination. In this case, fillers include, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium and silica. Other examples include organic fine powders such as urea-formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin.

The heat-sensitive recording paper of the present invention is prepared by applying a heat-sensitive coloring liquid containing the above-mentioned components onto a support having the above-mentioned physical properties, applying water as a backing liquid to the non-thermosensitive surface, and then drying it. It is obtained by calendering.

[0031]

EXAMPLES Next, the present invention will be explained in more detail with reference to examples. Note that all parts and percentages shown below are based on weight.

Examples 1 to 3 and Comparative Examples 1 to 3 By using commercially available LBKP and NBKP and selecting the sizing agent and wet press pressure as shown in Table 1, the results shown in Table 2 were obtained. Basis weight 40-43 with various characteristics
g/m2, thickness 60-64μm, moisture 5.5-6.0%
The original paper was obtained.

[0033]

[Table 1] Note-1) Addition amount and wet press pressure are expressed as a ratio based on that of the comparative example (=1). -2) Chemical A Rosin emulsion B Alkyl ketene dimer C Higher fatty acid D Starch + PVA

Next, a mixture having the following composition was pulverized and dispersed to prepare [Liquid A] to [Liquid C]. [Liquid A] 3,3-bis(dimethylaminophenyl)-6
-Dimethylaminophthalide 60 parts 5%
Polyvinyl alcohol aqueous solution
60 copies
water

180 parts [Liquid B] 2,2-bis(p-hydroxyphenyl)propane 6
0 parts 5% polyvinyl alcohol aqueous solution

60 parts water

180 parts [Liquid C] Kaolin

60 parts Sodium hexametaphosphate
Part 6
montan wax

60 parts water

174 copies

0
[035] Next, 2 parts of [Liquid A], 5 parts of [Liquid B] and [C
[Liquid] Mix 3 parts, and add 2 parts of oxidized starch 15% aqueous solution to this.
1 part and stirred to prepare a thermosensitive coloring liquid.

Next, apply this heat-sensitive coloring liquid onto the base paper.
After applying with a wire bar so that the dry coating amount was 4 to 6 g/m2, water was applied to the non-thermal surface, dried, and calendered to prepare a thermal recording paper.

[0037] The thermal recording paper obtained as described above was
Voltage 13.3V with a thermal printing device manufactured by Matsushita Electronic Components Co., Ltd.
Macbeth Densitometer RD-914
It was measured with In addition, transmission and reception were performed using an α-20 machine manufactured by Ricoh Co., Ltd., and the tray storage properties of small-diameter rolls were examined. The evaluation results are shown in Table 2.

[0038]

[Table 2]

[0039]

[Effects of the Invention] Since the thermal recording paper of the present invention has the above-mentioned structure, it is difficult to curl up even when stored in small-diameter rolls for a long period of time, has excellent tray storage properties after recording, and has a high density. Provides clear images with less background fog.

Claims (1)

[Claims] 1. A heat-sensitive recording paper comprising a heat-sensitive coloring layer containing a leuco dye and a color developer as main components on a support, wherein J. TAPPI No. The transfer amount in the Bristow test according to No. 51 is 20 ml/m2 or less, and the difference in the transfer amount on the front and back sides is 2 ml/m2 or less, and the tension of the thermal recording paper is 0.9 g/cm3 or less, and the non-printing surface thereof J. TAPPI No. 1. A thermal recording paper characterized by a smoothness of 150 seconds or more according to 5B.