JP3173737B2 - Thermal recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly, to a heat-sensitive recording material having an under layer containing non-foamable plastic hollow particles between a support and a heat-sensitive coloring layer.

It has long been known that a colorless or pale-colored leuco dye and a color developer such as an organic acid substance melt and react when heated to form a color. Examples of application are disclosed in JP-B-43-4160, JP-B-45-14039 and the like and are well known. These thermal recording sheets have been applied to a wide range of fields, such as measuring coders, terminal printers such as computers, facsimile machines, automatic ticket vending machines, and barcode labels. Accordingly, the required quality of the heat-sensitive recording sheet has become higher. For example, with the speeding up of the thermal head, there is a demand for a heat-sensitive recording sheet that can record a clear image at a high density even with a small amount of thermal energy and has good head matching properties such as sticking and head residue.

[0003] The color development of the heat-sensitive recording sheet is such that either or both of the color-forming leuco dye and the developer are dissolved and reacted by the thermal energy supplied from the thermal head. One of the
A method of adding a compound that melts at a lower temperature than the leuco dye and the developer and has a high ability to dissolve both (generally called a heat-fusible substance) is widely known. Is disclosed. For example, JP
JP-A-9-34842 discloses nitrogen-containing compounds such as acetamido, stearoamide, nitroaniline and dinitrile phthalate, JP-A-52-106746 discloses acetoacetic anilide, and JP-A-53-30139 discloses alkyl. Biphenylalkanes are disclosed. But,
In recent years, particularly in the field of facsimile thermal heads, speeding up has been advanced, and high-speed driving of the thermal head has become common. In this case, the background portion of the heat-sensitive recording sheet develops color during continuous recording due to heat storage around the head ( Because of the inconvenience of residual heat coloring), raising the coloring sensitivity has been an issue.

However, the above compounds improve the static color sensitivity, but do not provide sufficient dynamic color sensitivity unless added in a large amount to the thermosensitive coloring layer. If the amount of adhesion (head residue) is large, sticking occurs, or the melting point is too low, the storage stability (ground fog) of the heat-sensitive recording sheet is lowered, and a satisfactory result cannot be obtained.

[0005] One of the methods for improving the dynamic color sensitivity is to improve the smoothness of the surface of the heat-sensitive coloring layer or to include a component which does not participate in the coloring reaction in the coloring layer, such as a filler or a binder. There is also a method of reducing the amount and improving the density of the coloring component. The surface smoothness can be easily improved by calendering, usually using a super calender.However, the appearance of the recording paper due to the coloring of the background or the increase in the surface gloss is increased. I hate it. In addition, calcium carbonate, clay, urea, and the like are usually provided in the heat-sensitive coloring layer in order to maintain whiteness of the background, prevent adhesion of head residue, and prevent sticking.
Add a filler such as formalin resin, or add a water-soluble binder to fix the coloring component or its additive to the support, but to reduce the content of these, The above-described method causes deterioration of the quality and causes inconvenience, and such a method cannot provide a satisfactory result.

[0006] Further, for the purpose of effectively utilizing the energy from the thermal head, it has been proposed to provide an under layer having a high heat insulating property containing minute hollows between the support and the thermosensitive coloring layer. For example, JP-A-59-5
No. 093, it is possible to provide a layer containing fine hollow sphere particles as a main component between the support and the thermosensitive coloring layer, and JP-A-59-225987 discloses that the support and the thermosensitive coloring layer are provided. It has been proposed to provide a laminate of an intermediate layer A obtained by foaming an expandable plastic filler and an intermediate layer B containing a filler and a binder.

However, these are sometimes insufficient in foaming properties and have insufficient flexibility in the wall material, insufficient heat insulation, or insufficient adhesion between the thermal head and the heat-sensitive recording material. However, satisfactory results have not been obtained. Japanese Patent Application Laid-Open No. 62-5886 proposes that non-foamable fine hollow particles made of a thermoplastic resin be contained in an under layer. However, since a layer containing an oil-absorbing filler is further provided on the under layer containing the non-foamable plastic hollow particles, the heat insulating property is insufficient, and further, since the plastic hollow fine particles are contained, static electricity is generated. Transport trouble when used in thermal printing equipment.

Further, Japanese Patent Application Laid-Open No. 1-290981 discloses that a conductive agent is contained in any layer of a thermosensitive recording medium having an intermediate layer in which a foamable plastic filler is foamed to prevent generation of static electricity. However, when a conductive agent is added to the intermediate layer, generation of static electricity cannot be prevented so much.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording material having high dynamic sensitivity and free from transport trouble when used in thermal printing equipment.

[0010]

According to the present invention, an under layer and a thermosensitive coloring layer mainly composed of a leuco dye and a developer which causes the leuco dye to develop color when heated are successively laminated on a support. in becomes the heat-sensitive recording material, the under layer,
The average particle size is 2 to 10 μm and the hollowness is 90% or more.
The present invention provides a thermosensitive recording material characterized by containing non-foamable plastic hollow fine particles and further containing a conductive agent.

That is, the heat-sensitive recording material of the present invention contains non-expandable plastic hollow fine particles between the support and the heat-sensitive coloring layer, and further contains a conductive agent. Therefore, the dynamic color sensitivity is high, and there is no transport trouble during use. The non-expandable plastic fine hollow particles have an average particle diameter of those 2 to 10 [mu] m, hollow degree 90% or more.

The non-expandable plastic spherical fine particles in the under layer act as low-density hollow fine particles, that is, low heat conductive hollow fine particles, as in the case of the above-described prior art, and the entire under layer serves as a heat insulating layer. Having. Therefore, by providing the under layer, the heat energy given for image recording can be effectively used in the thermosensitive coloring agent layer, and a thermosensitive recording material having high heat sensitivity can be obtained. In addition, in the present invention, since the under layer contains a conductive agent, the electric resistance value is reduced, so that troubles due to static electricity during use are avoided, and a heat-sensitive recording material having high thermal sensitivity can be obtained.

In the present invention, an under layer containing non-foamable plastic hollow fine particles is provided. As the hollow fine particles in this case, those well-known in this type of heat-sensitive recording material can be used.

The non-foamable plastic hollow fine particles used in the under layer of the present invention are hollow fine particles which are made of thermoplastic resin grains, have a liquid or gas inside, and do not foam even when heated. The average particle size is 2 to 10 μm, and the hollowness is 90% or more. Here, the hollowness is a ratio of the outer diameter to the inner diameter of the hollow particles, and is represented by the following equation.

[0015]

The thermoplastic resin which becomes the grains of the plastic spherical hollow fine particles includes polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylate, polyacrylonitrile, polybutadiene or a copolymer thereof such as vinylidene chloride / Acrylonitrile and the like.

In the present invention, a conductive agent is contained in the undercoat layer mainly composed of non-foamable hollow fine particles and a binder in order to eliminate a transport trouble due to static electricity when used in a thermal printing apparatus.

As the conductive agent used in the present invention, conventionally known conductive agents can be used, and specific examples thereof include the following.

(I) Inorganic salts such as sodium chloride, potassium chloride, magnesium chloride, ammonium chloride, lithium chloride, aluminum chloride, zinc chloride, potassium bromide, zinc bromide, zinc phosphate and zinc acetate. (ii) Organic salts such as potassium formate and sodium oxalate. (iii) conductive metal oxides such as zinc oxide and tin oxide. (iv) Polymer anion salts such as polyacrylate, polymethacrylate, polystyrene sulfonate, calcium alkylbenzene sulfonate, sodium dioctyl sulfosuccinate. (v) The amount of the polymer cation salt such as a quaternary ammonium salt and a methylpyridinium salt, and the amount of the conductive agent used in the present invention is 10% or less and 1% or less with respect to the solid content of the layer containing the conductive agent. The degree is preferred.

In forming the under layer of the present invention, conventionally known water-soluble polymer type resins and / or aqueous emulsion type resins are used as binders. That is, examples of the water-soluble polymer type resin include polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylic acid Ester copolymer, acrylamide / acrylate / methacrylic acid ternary copolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein And the like. Examples of the aqueous emulsion type resin include styrene / butadiene copolymer latex, styrene / butadiene / acrylic copolymer latex, vinyl acetate resin, vinyl acetate / acrylic acid copolymer, styrene / acrylic ester copolymer, and acrylic resin. Emulsions such as acid ester resins and polyurethane resins are exemplified.

In order to provide the under layer on a support,
The non-expandable plastic spherical hollow particles and a conductive agent,
It is obtained by dispersing in water together with a known binder such as a water-soluble polymer or an aqueous polymer emulsion, applying this to the surface of a support, and drying. In this case, the coating amount of the non-expandable plastic spherical hollow particles is 1 m ² of the support.
At least 1 g per hit, preferably about 2 to 15 g,
The coating amount of the binder resin may be an amount that strongly bonds the under layer to the support, and is usually 2 to 2 with respect to the total amount of the plastic spherical hollow particles and the binder resin.
50% by weight.

In the present invention, the binder used for forming the under layer is appropriately selected from conventionally known water-soluble polymers and / or aqueous polymer emulsions. Specific examples thereof include, as water-soluble polymers, for example, polyvinyl alcohol, starch and derivatives thereof,
Cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylic ester copolymer, acrylamide / acrylic ester / methacrylic terpolymer, styrene / Examples include maleic anhydride copolymer alkali salts, isobutylene / maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, casein and the like. Examples of the aqueous polymer emulsion include latexes such as styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, vinyl acetate resin, vinyl acetate /
Emulsions of acrylic acid copolymers, styrene / acrylic ester copolymers, acrylic ester resins, polyurethane resins, and the like can be given.

In the under layer according to the present invention, together with the non-foamable plastic spherical hollow particles and the binder, if necessary, auxiliary additives commonly used in this type of heat-sensitive recording material, for example, fillers, A heat-fusible substance, a surfactant and the like can be used in combination. In this case, specific examples of the filler and the heat-fusible substance include various substances described below in relation to the thermosensitive coloring layer component.

Further, in order to smooth the surface of the underlayer formed on the support as described above, the flat surface may be smoothed by a calendering process after the formation of the undercoat layer.

The leuco dye used in the thermosensitive coloring layer of the present invention may be used alone or as a mixture of two or more types. As such a leuco dye, those applied to this type of thermosensitive material may be arbitrarily applied. For example, leuco compounds of dyes such as triphenylmethane type, fluoran type, phenothiazine type, auramine type, spiropyran type and indolinophthalide type are preferably used. Specific examples of such leuco dyes include, for example, 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 -Dimethylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran, 3-
Diethylamino-7,8-benzfluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-
(Np-tolyl-N-ethylamino) -6-methyl-
7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluoran, 2- {3 6-bis (diethylamino)-
Lactam 9- (o-chloroanilino) xanthylbenzoate, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-di- n-butylamino-7- (o-chloroanilino) fluoran, 3-N-methyl-N, n-amylamino-6-
Methyl-7-anilinofluoran, 3-N-methyl-N
-Cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 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'-chloro-5'-methylphenyl) phthalide, 3-
(N-ethyl-N-tetrahydrofurfuryl) amino-
6-methyl-7-anilinofluoran, 3-N-ethyl-N- (2-ethoxypropyl) amino-6-methyl-
7-anilinofluoran, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluoran 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluoran, 3-pyrrolidino- 7-trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluor Oran, 3-diethylamino-5-chloro-7- (α-phenylethylamino)
Fluoran, 3- (N-ethyl-p-toluidino) -7
-(Α-phenylethylamino) fluoran, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluoran, 3-diethylamino-5-methyl-
7- (α-phenylethylamino) fluoran, 3-diethylamino-7-piperidinofluoran, 2-chloro-3- (N-methyltoluidino) -7- (pn-butylanilino) fluoran, 3-di- n-butylamino-
6-methyl-7-anilinofluoran, 3,6-bis (dimethylamino) fluorenespiro (9,3 ')-6'
-Dimethylaminophthalide, 3- (N-benzyl-N-
(Cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4′-bromofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino -4 ', 5'
-Benzofluoran, 3-N-methyl-N-isopropyl-6-methyl-7-anilinofluoran, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluoran, 3-diethylamino -6-methyl-7-
(2 ′, 4′-dimethylanilino) fluoran and the like.

As the color developer used in the thermosensitive coloring layer of the present invention, various compounds having an electron-accepting property or a oxidizing agent which develop the color of the leuco dye upon contact are applied. Such materials are conventionally known, and specific examples thereof include the following.

4,4'-isopropylidenebisphenol, 4,4'-isopropylidenebis (o-methylphenol), 4,4'-secondarybutylidenebisphenol 4,4'-isopropylidenebis (2-tert-butylphenol) ), Zinc p-nitrobenzoate,
1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 2,2- (3,4'-dihydroxydiphenyl) propane, bis (4-hydroxy-3 -Methylphenyl) sulfide, 4- {β- (p-methoxyphenoxy) ethoxy} salicylic acid, 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane, 1,5-bis (4- (Hydroxyphenylthio) -5-oxapentane, monobenzyl phthalate monocalcium salt,
4,4'-cyclohexylidenediphenol, 4,4 '
-Isopropylidenebis (2-chlorophenol),
2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-butylidenebis (6-
Tert-butyl-2-methyl) phenol, 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-methyl) phenol, 4,4'-diphenolsulfone, 4-isopropoxy-4'-hydroxydiphenylsulfone, 4-benzyloxy-4'-hydroxydiphenylsulfone, 4,4 '-Diphenol sulfoxide, isopropyl P-hydroxybenzoate,
Benzyl P-hydroxybenzoate, benzyl protocatechuylate, stearyl gallate, lauryl gallate, octyl gallate, 1,3-bis (4-hydroxyphenylthio) -propane, N, N′-diphenylthiourea,
N, N'-di (m-chlorophenyl) thiourea, salicylanilide, bis- (4-hydroxyphenyl) acetic acid methyl ester, bis- (4-hydroxyphenyl) acetic acid benzyl ester, 1,3-bis (4-hydroxy Cumyl) benzene, 1,4-bis (4-hydroxycumyl)
Benzene, 2,4'-diphenol sulfone, 2,2'-
Diallyl-4,4'-diphenolsulfone, 3,4-
Dihydroxyphenyl-4′-methyldiphenylsulfone, zinc 1-acetyloxy-2-naphthoate, zinc 2-acetyloxy-1-naphthoate, zinc 2-acetyloxy-3-naphthoate, α, α-bis (4 -Hydroxyphenyl) -α-methyltoluene, an antipyrine complex of zinc thiocyanate, tetrabromobisphenol A,
Tetrabromobisphenol S, 4,4'-thiobis (2-methylphenol), 4,4'-thiobis (2-
Chlorophenol) and the like.

In the heat-sensitive coloring layer of the present invention, various conventional binders can be appropriately used for coating the leuco dye and the developer on the under layer.
Specific examples thereof include those similar to those exemplified in the above-described under layer coating.

In the heat-sensitive coloring layer of the present invention, together with the leuco dye and the color developing agent, if necessary, auxiliary additives commonly used in this type of heat-sensitive recording material, for example, fillers, heat-fusible materials Substances, surfactants and the like can be used in combination. In this case, as the filler, for example,
Calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay,
In addition to inorganic fine powders such as talc and surface-treated calcium and silica, organic fine powders such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin can be used. Examples of the active substance include higher fatty acids or esters, amides, and metal salts thereof, various waxes, condensates of aromatic carboxylic acids and amines, phenyl benzoate, higher linear glycols, 3,4- 5 such as dialkyl epoxy-dialkyl hexahydrophthalate, higher ketone, and other heat-fusible organic compounds
Those having a melting point of about 0 to 200 ° C. are mentioned.

In the present invention, a layer containing a filler, a binder, a heat-fusible substance or the like may be provided as an intermediate layer between the under layer and the thermosensitive coloring layer, if necessary. In this case, specific examples of the filler, the binder, and the heat-fusible substance include those similar to those exemplified in relation to the thermosensitive coloring layer or the under layer.

Further, in the heat-sensitive recording material of the present invention, it is possible to provide a protective layer on the heat-sensitive coloring layer for the purpose of improving the matching property of a thermal head or the like and further improving the storage stability of the recorded image. In this case, the above-mentioned filler, binder, surfactant, and heat-fusible substance can also be used as components constituting the protective layer.

The heat-sensitive recording material of the present invention is produced, for example, by applying the above-mentioned coating liquid for forming each layer on a suitable support such as paper, synthetic paper, plastic film and the like, and drying. Applied in the recording field.

[0034]

Next, the present invention will be described in more detail with reference to examples. The parts and percentages shown below are based on weight.

Example 1 [Solution A] 20 parts of 3- (N-methyl-3-N-cyclohexyl) amino 20 parts of 10% aqueous solution of 6-methyl-7-anilinofluoran polyvinyl alcohol 60 parts of water

[Solution B] 1,5-bis (4-hydroxyphenylthio) -3 10 parts-oxapentane polyvinyl alcohol 10% aqueous solution 25 parts calcium carbonate 15 parts water 50 parts

The mixture composed of the above-mentioned compositions was dispersed using a sand mill so that the average particle diameter was 2 μm or less and 2.5 μm or less, respectively, to prepare [Solution A] and [Solution B].

[Liquid C] Fine hollow particle dispersion (copolymer resin mainly composed of vinylidene chloride and 30 parts of acrylonitrile) (solid content: 32%) (average particle diameter: 5 μm, hollowness: 92%) Styrene / butadiene Polymer latex 10 parts (solid content concentration 47.5%) Conductive agent (aliphatic quaternary ammonium-substituted polystyrene, 1 part Trade name: Chemistat 6300: Sanyo Chemical Industry Co., Ltd. solid content 30%) Water 59 parts

The mixture having the above composition was stirred and dispersed to prepare an underlayer-forming solution, which was dried on a surface of a commercially available high-quality paper (basis weight: 52 g / m ² ) to have a weight of 5 g / m ^2. This was coated and dried to obtain an underlayer coated paper.

Next, the above-mentioned [Solution A] and [Solution B] were mixed and stirred at a weight ratio of 1:10 to prepare a thermosensitive coloring layer forming solution, and this was coated on the surface of the underlayer-coated paper. After drying, a thermosensitive coloring layer is formed by applying and drying so as to have a weight of 5 g / m ^2, and then subjected to a super calender treatment so as to have a Beck smoothness of 600 to 700 seconds. Obtained.

Example 2 Instead of the fine hollow particle dispersion in [Liquid C] of Example 1, another fine hollow particle dispersion (a copolymer resin mainly composed of vinylidene chloride and acryloniloryl; solid content: 30%) , An average particle diameter of 9 µm and a hollow ratio of 93%) in the same manner as in Example 1 to obtain a heat-sensitive recording material of the present invention.

Comparative Example 1 [Liquid D] 20 parts of a plastic solid particle dispersion (manufactured by Mitsui Toatsu Co., Ltd .: SPMM = HS, solid content 47%) Styrene / butadiene copolymer latex (solid content 47%) 10 parts Conductive agent (Chemistat 6300, Sanyo Chemical Industries, Ltd. 1 part, solid content concentration 30%) Water 69 parts Same as Example 1 except that [D liquid] was used in place of [C liquid] in Example 1. Thus, a heat-sensitive recording material for comparison was obtained.

Comparative Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the conductive liquid was not used in [C solution] of Example 1.

Comparative Example 3 Instead of the fine hollow particles in [C solution] of Example 1,
Fine hollow particles with a hollow ratio of 75% and an average particle diameter of 0.4 μm
(Rohm and Haas: OP-62, solid content 3
7.5%) and no conductive agent
A heat-sensitive recording material was obtained in the same manner as in Example 1 .

Comparative Example 4[E liquid]  Foamable plastic filler (unfoamed) 14 parts (trade name: Matsumoto Microsphere F-30, actual solid content 70%, manufactured by Matsumoto Yushi Co., Ltd.) Conductive agent (described above) 1 part 10% aqueous polyvinyl alcohol solution 20 parts Water 65 parts The above-mentioned layered coating solution [E solution] is dried on the surface of commercially available high quality paper.
After adhesion amount is about 3g / m^TwoAnd then apply
Keep the coated paper in an immersion tank kept at about 140 ° C for about 2 minutes.
To dry the coated surface and expand the foam plastic
The underlayer was foamed to obtain an underlayer coated paper. Get more
Press the compressed underlayer coated paper with a super calender.
Force 30kg / cm^Two, Smoothing at a passing speed of 10 m / min
Was. Further, a heat-sensitive coloring layer was provided in the same manner as in Example 1, and
A calendering treatment was performed to obtain a thermosensitive recording material.

A printing test and a paper discharging test were performed on the six types of heat-sensitive recording materials obtained as described above. Further, the surface potential of the heat-sensitive recording material after the sheet was discharged was measured.

The test was performed using Rifax 131 [Co., Ltd.]
Ricoh's facsimile], and prints in a copy mode using the facsimile test chart No. 1 of the Institute of Image Electronics Engineers of Japan as a document. Using a Macbeth densitometer (R)
D-514; filter vratten-106), and the image reproducibility was evaluated as dot reproducibility. Further, in a 5 ° C., 30% RH environment, it was confirmed whether or not there was a paper discharge (recording paper discharge) trouble when 30 sheets were continuously repeated by the same method as the above-described print test.

The surface potential generated on the thermosensitive recording material at that time was also measured simultaneously with a Monroe surface electrometer. Table 1 shows the evaluation results of each test.

[Table 1] * 1: The evaluation of image uniformity is determined with respect to the reproducibility of printing dots. ◎: particularly excellent, ：: excellent, Δ: good, ×: slightly poor. * 2: The suitability for paper discharge was evaluated based on the occurrence of defects due to paper discharge problems in a continuous 30-sheet printing test. ：: not generated, Δ: generated twice or less, x: generated three or more times. Table 1 shows that the heat-sensitive recording material of the present invention has high dynamic color sensitivity, good image quality, and excellent paper discharge characteristics.

[0049]

According to the heat-sensitive recording material of the present invention, an under layer is provided between the support and the heat-sensitive coloring layer, and the under layer has an average grain size.
Since it contains non-foamable hollow fine particles having a diameter of 2 to 10 μm and a hollowness of 90% or more and a conductive agent, the dynamic color sensitivity is high, the electrostatic charge is improved, and transport trouble during use is reduced. It does not occur.

Continuation of the front page (56) References JP-A-1-285383 (JP, A) JP-A-3-147888 (JP, A) JP-A-1-113282 (JP, A) JP-A-2-164580 (JP) JP-A-1-291981 (JP, A) JP-A-63-34180 (JP, A) JP-A-59-145187 (JP, A) JP-A-59-5093 (JP, A) 4-201481 (JP, A) JP-A-4-129797 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/28-5/34

Claims (2)

(57) [Claims] 1. A heat-sensitive recording material comprising a support and an under layer and a thermosensitive coloring layer mainly composed of a leuco dye and a color developing agent capable of developing the leuco dye upon heating. , Average particle size is 2 to 10 μm and medium
A heat-sensitive recording material containing non-foamable plastic hollow fine particles having an airiness of 90% or more and further containing a conductive agent. 2. The heat-sensitive recording material according to claim 1, wherein the non-foamable plastic is a vinylidene chloride / acrylonitrile copolymer resin.