JPH0255188A - Heat sensitive recording sheet - Google Patents

Abstract

PURPOSE:To improve recording sensitivity without generating base surface contamination by incorporating mechanical pulp and/or chemical pulp in total pulp composition and setting the measured value of the surface of a raw sheet by a normal reflection type smoothness meter to a specific value or more. CONSTITUTION:Raw sheet having 5wt.% or desirably 10wt.% or more of MP and/or CMP in total pulp composition is employed as the raw sheet. Further, the sheet is so processed that the measured value of the surface of the sheet by a normal reflection type smoothness meter (measuring pressure: 20kg/cm<2>) is 8% or more or desirably 14% or more. It is effective to smooth the surface of the sheet by a supercalender, gloss calendar, soft calendar composed of a metal roll and an elastic roll in an ON or OFF machine. Efficiently, the smoothing by the ON machine is desirably. In this case, a calendar composed of an elastic roll having 42-98 degrees of hardness Shore D is desirably employed.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a thermal recording paper, and particularly to a thermal recording paper that has a recording sensitivity that is sufficiently applicable to ultra-high-speed machines without causing background stains.

"Prior Art" Conventionally, heat-sensitive δCu utilizes a coloring reaction between a coloring agent and a coloring agent that develops color when it comes into contact with the coloring agent, and brings both coloring materials into contact with each other using heat to obtain a colored image. Mr. ♀ is well known.

Such thermal recording paper is relatively inexpensive, uses a non-impact recording method, is quiet, and has a fast recording speed, so it is widely used in facsimiles, thermal printers, and Herco printers.
- Widely used in Rahel printers, etc.

In addition, with the recent remarkable increase in 99 rf information, for example, development of the same speed 1 (GUIi) and even higher ultra-high speed a (GIV■) for facsimile is underway.

As the speed of such recording devices increases, the thermal recording paper used in these devices also needs to utilize minute amounts of thermal energy from the recording head more effectively to obtain high print density, and various improvements have been proposed for this purpose. ing.

"Problems to be Solved by the Invention" However, conventional depictions have focused on improving the materials that make up the recording layer, such as color formers, color formers, and thermofusible substances (sensitizers). However, improvements have not necessarily resulted in satisfactory results because new defects have been introduced. For example, if the recording sensitivity is increased to the extent that it can respond sufficiently to minute thermal energy, background stains will occur on the surface of the recording layer even before recording, which will not only deteriorate the appearance but also cause defects that will cause the recorded image to lack clarity. do.

As a result of intensive research into improving the above-mentioned drawbacks, the inventors of the present invention found that these drawbacks are largely caused by the characteristics of the base paper that makes up the thermal recording paper, especially the characteristics of the pulp that makes up the base paper. .

In other words, chemical pulp (hereinafter referred to as CP) with a pulp yield of 40 to 50% has traditionally been used as the pulp constituting the base paper, but even if the beating conditions and paper-making conditions are adjusted variously, Although we were not able to obtain satisfactory results, we were able to blend mechanical pulp or chemical mechanical pulp with a pulp yield of about 75 to 9:4 P%, and to improve the smoothness of the base paper surface as measured by a special smoothness meter. When adjusted to a specific value, thermal recording paper using that base paper will not suffer from background stains (recording sensitivity will be significantly improved, and as a result, thermal recording paper that can be used in ultra-high-speed machines will be easily obtained). The present invention was completed based on this discovery.

"Means for Solving the Problems" The present invention uses mechanical pulp (hereinafter referred to as M) in the entire pulp composition.
P) and/or chemical mechanical pulp (hereinafter referred to as CM
containing 5% by weight or more of
This heat-sensitive recording paper is characterized in that it uses a base paper having a carbon content of 8% or more.

"Function" The thermal recording paper of the present invention contains 5% by weight or more of MP and/or CMP, preferably 10% by weight, in the total pulp composition as a base paper.
Although it uses base paper containing more than % by weight, MP
Due to the combination of CP and CMP, the compression elasticity of the base paper becomes bluer compared to paper made of 100% CP, and its thermal conductivity is lower, so it cannot sufficiently handle the minute thermal energy from the recording head. Even if the recording sensitivity of the recording layer is increased, heat is concentrated at the contact point between the recording head and the recording paper, and it is difficult for the heat to be conducted outside of that contact point, resulting in high-sensitivity recording without causing background stains. It is assumed that Incidentally, if the content of MP or CMP is less than 5% by weight, a sufficient improvement effect cannot be expected.

Specific examples of MP and CMP include unbleached and bleached mechanical pulps such as groundwood pulp, refined ground pulp, chem refiner pulp, chem ground pulp, thermomechanical pulp, chemothermomechanical pulp, and pressurized ground pulp. Among them, bleached chemi-thermomechanical pulp (hereinafter referred to as BCTMP), which is a highly bleached chemi-thermomechanical pulp, is particularly preferably used because it has high whiteness, strong paper strength, and less binding fibers.

Note that if the whiteness of MP or CMP is low, the whiteness of the thermal recording paper obtained will decrease, the sharpness of the color image will be lost, and the appearance will deteriorate.
123) is preferably 80% or more. Also, M
Bundled fiber pieces with a size of 0.1 m+++ or more included in P and CMP (undisintegrated fiber bundles in pulp)
If the amount exceeds 500 particles/g, the smoothness of the surface of the base paper may be significantly reduced, so it is desirable to perform a refiner treatment in the previous process of the paper machine.

For refiner treatment, a single disc refiner is more effective than a beater, conical refiner, or double disc refiner used in CP processing, etc., and the pulp concentration during treatment is determined by considering efficiency, power consumption, etc. 2 to 5% by weight is desirable.

In the thermal recording paper of the present invention, the above-mentioned
A base paper containing 20% by weight or more is used, and the surface of the base paper is measured using a specular reflection smoothness meter (measurement pressure: 20% by weight).
It is necessary to process so that the measured value in kg/cm") is 8% or more, more preferably 14% or more.

The specular reflection type smoothness meter referred to here is a device that measures the smoothness of paper by pressing it against the glass surface under constant pressure conditions, and according to the detailed study results of the inventors, - It is not affected by the air permeability of the paper like the air leak type smoothness measuring instruments such as the Beck smoothness meter and Parker Print Surf (and can provide measurement values that have an excellent correlation with the actual smoothness). , Moreover, this specular reflection type smoothness meter (measurement pressure;
It has become clear that the desired effect of the present invention can be determined very appropriately by the measured value at 20 kg/cm2),
The present invention has now been completed.

Incidentally, a specular reflection type smoothness meter (measurement pressure: 20 k
If the measured value in g/cm2) is less than 8%, even if the base paper contains 5% by weight or more of MP or CMP, the contact between the recording paper and the recording head will be uneven, and the density of the recorded image will decrease. Therefore, the desired effect of the present invention cannot be obtained.

For smoothing the surface of base paper, machine calenders consisting only of metal rolls installed at the rear of long or circular paper machines can also be used, but supercalendar gloss calenders consisting of metal rolls and elastic rolls, It is effective to use a soft calendar etc. on-machine or off-machine.

As the metal roll, for example, a chilled roll, an alloy chilled roll, a steel roll, or a metal roll whose surface is plated with hard chrome, etc. are selected and used as appropriate.As for the elastic roll, for example, natural rubber, styrene rubber, nitrile rubber, chloroprene, etc. are used. Various plastic resins such as rubber, chlorosulfonated ethylene rubber, butyl rubber, polysulfide rubber, silicone rubber, fluorine rubber, urethane rubber, aromatic polyamide resin, polyimide resin, polyether resin, polyester resin, polycarbonate resin, conton, paper, An elastic roll made of wool, wool, silica, or a mixture of these materials is appropriately selected and used.

Note that, in terms of efficiency, on-machine smoothing treatment is preferable, and in this case, a calender composed of elastic rolls having a Shore D hardness of 42 to 98 degrees (ASTM standard, D-2240) is particularly preferably used. Among them, elastic rolls made of urethane rubber, aromatic polyamide resin, a mixture of paper and wool, a mixture of wool and Tetron, a mixture of wool and nylon, a mixture of paper, wool and Tetron, a mixture of paper, wool and nylon, etc. Preferably, an elastic roll made of urethane rubber and aromatic polyamide resin is most preferably used because it is easy to handle, has a long roll life, and efficiently exhibits the desired effects of the present invention.

Elastic rolls such as those mentioned above are softer than regular elastic rolls (and tend to generate heat even under stable working conditions, and this tendency is particularly noticeable with elastic rolls made of urethane rubber. The physical properties of the roll become unstable, and in extreme cases, the elastic body itself may be damaged by melting due to the accumulated heat, so it is a preferred practice to introduce a refrigerant inside the roll for cooling. Various measures are taken as appropriate, such as cooling from the outside, changing the roll diameter, and changing the thickness of the elastic body.

On-machine super calenders and on-machine soft calenders, which are composed of metal rolls and elastic rolls, are featured in Paper and Pulp Technology Times August 1985 issue (31) and 1986
It is introduced in the May issue (page 10), etc. In addition, the processing conditions are 2.

Line pressure 1. It is adjusted as appropriate depending on machine speed, etc.

Note that it is also possible to smooth the base paper surface by using a Yankee dryer whose dryer surface is mirror-treated with hard chrome plating, etc., as the dryer of the paper machine, but in any case, regular reflection type smoothing of the base paper surface is possible. It is necessary to reduce the value measured with a thermometer (measurement pressure: 20 kg 7 cm2) to 8% or more.

A heat-sensitive recording layer is formed on the base paper thus obtained according to a conventional method, and various combinations of coloring substances can be used to form the recording layer. Specifically, the following are exemplified. .

(a) A melting point of 100 to 100, which has a secondary alcoholic hydroxyl group and is described in Japanese Patent Publication No. 41-14510.
180°C compound, combination of sulfur and metal inorganic salts or metal acetates.

Examples of compounds having a secondary alcoholic hydroxyl group include benzoin compounds such as benzoin, 2-methoxyhenduin, 4-chlorobenzoin, 4-dimethylaminobenzoin, and 2-chloro-4'-dimethylaminobenzoin, and diphenyl carboxylic acid. Carbinols such as nol,
Resorcinol, pyrogallol, 3-hydroxytoluene-
Examples include phenolic compounds such as 4-sulfonic acid, 4-nitroresorcin, and 4,6-dibromoresorcin, fatty acid polyhydric alcohols such as erythritol, sorbitol, galactose, maltose, mannitol, and saccharose. Metal inorganic salts and metal acetates include a large number of metals that react with hydrogen sulfide to produce colored sulfides, such as copper, lead, tin, molybdenum, cobalt, chromium, nickel, manganese, Titanium, antimony, rhodium, osmium, mercury, iron, barium, bismuth, arsenic, magnesium, indium, iridium, etc.

(b) A combination described in Japanese Patent Publication No. 41-14511 in which various inorganic metal salts in the composition (a) are replaced with hexamethylenetetramine/metal salt adducts.

(C) A combination of carbohydrate and dehydrating agent described in Japanese Patent Publication No. 42-13237.

Here, carbohydrates include saccharose, fructose,
Examples of the dehydrating agent include galactose and starch, and examples of the dehydrating agent include sulfuric acid, acetic anhydride, anhydrous zinc chloride, and para-toluenesulfonic acid.

(d) Combinations of long chain fatty acid iron salts such as ferric stearate and ferric myristate with phenols such as tannic acid, gallic acid and ammonium salicylate.

(e) Organic acid heavy metal salts such as nickel, cobalt, lead, copper, iron, mercury, and silver salts such as acetic acid, stearic acid, and palmitic acid; and alkaline earth metal sulfides such as calcium sulfide, strontium sulfide, and barium sulfide. combination of,
Or a combination of the organic acid noble metal salt and an organic chelating agent such as S-diphenylcarbazide or diphenylcarbazone.

g) Combinations of heavy metal oxalates such as silver, lead, mercury and thorium oxalates with sulfur compounds such as Na-tetrathionate, sodium thiosulfate and thiourea.

((a) Fatty acid ferric salts such as ferric stearate and 3
．． Combination with aromatic polyhydroxy compounds such as 4-dihydroxytetraphenylmethane.

(h) A combination of a noble metal salt of an organic acid such as silver oxalate or mercury oxalate and an organic polyhydroxy compound such as polyhydroxy alcohol, glycerin, or glycol.

(i) A combination of a noble metal salt of an organic acid such as silver behenate or silver stearate with an aromatic organic reducing agent such as protocatechuic acid, spiroindane or hydroquinone.

(j) A combination of a fatty acid ferric salt such as ferric pelargonic acid or ferric lauric acid with thiosemicarbazide or isothiosemicarbazide derivative.

(k) Combinations of organic acid lead salts such as lead caproate, lead pelargonate, lead behenate and thiourea derivatives such as ethylenethiourea and N-dodecylthiourea.

(+) Combination of higher fatty acid heavy metal salts such as ferric stearate, stearin M, copper and zinc dialkyldithiocarbamate.

(ITI) Those that form oxazine dyes, such as combinations of resorcinol and nitroso compounds, or those that form azo dyes.

(n) Those forming azo dyes, such as combinations of diazonium salts and coupler compounds.

(0) A combination of a colorless or light-colored basic dye such as crystal violet lactone and a coloring agent such as bisphenol A.

Among the above-mentioned various combinations, the combination of a basic dye and a coloring agent is most preferably used and will be explained in more detail below.

Various kinds of basic dyes are known, and the following are exemplified.

3.3-bis(p-dimethylaminophenyl)6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2- dimethylindol-3-yl)
Phthalide, 3-(p-dimethylaminophenyl)-3-
(2-methylindol-3-yl)phthalide, 3.3
-bis(1,2-dimethylindol-3-yl)=5
-dimethylaminophthalide, 3,3-bis(12-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarboxol-3-yl)
yl)-6-'; Methylaminophthalide, 3,3-bis(2-phenylindol-3-yl)-6-dimethylaminophthalide, 3 p-dimethylaminophenyl-
Triallylmethane dyes such as 3-(1-methylpyrrol-3-yl)-6-dimethylaminophthalide, 4.4'
-bis-dimethylaminobenzhydrylbenzyl-ester, N-halophenyl-leucoolamine, N-2,4
, diphenylmethane dyes such as 5-trichlorophenylleucoauramine, hendiylleucomethylene blue,
Thiazine dyes such as p-nitropenzoyl, icomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-
Spiro dyes such as ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-hensyl-spiro-dinaphthopyran, 3-methyl-naphtho(6'-methoxyhenzu)spiropyran, 3-propyl-suvirodihenzopyran, rhodamine Lactam dyes such as B-anilinolactam, rhodamine (p-nitroanilino)lactam, rhodamine (0-chloroanilino)lactam, 3-dimethylamino-7-methoxyfluoran, 3
-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6
-Methyl-merchlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-(N-ethyl-
p-Toluidino)-7-methylfluorane, 3-diethylamine-7-〉J acetyl-N-methylaminofluorane, 3-diethylamine-7-N-methylaminofluorane, 3-diethylamino-merdihendylaminofluorane , 3-diethylamino-7-N-methyl-N-hensylaminofluorane, 3-diethylamino-7-N-
Chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3-
(N-ethyl-p-toluidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-p-1
luidino)-6-methyl-7-(p-1 luidino)fluoran, 3-diethylamino-6-methyl-7-phenylaminofluoran, 3-dibutylamino-6-methyl-7-phenylaminofluoran, 3- Diethylamino-7-(2-carbomethoxy-phenylamino)fluorane, 3-(N-cyclohexyl-N-methylamino)
-6-methyltophenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane,
3-Piperidino-6-methyl-7-phenylaminofluorane, 3-diethylamine-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluorane, 3-dibutylamino-
7-(0-chlorophenylamino)fluorane, 3-pyrrolidino-6methyl-7-p-butylphenylaminofluorane, 3-(N-methyl-Nn-amyl)amino 6-methyl-7-phenylaminofluorane , 3-(N
-ethyl-Nn-amyl)amino-6methyl-7-phenylaminofluorane, 3(N-ethyl-N-isoamyl)amino-6-methyl-7-phenylaminofluorane, :3-(Nmethyl-N -n-hexyl)amino-6
-Methyl-7-phenylaminofluorane, 3-(N-ethyl-N-n-hexyl)amino-6-medy-7-phenylaminofluorane, 3-(N-ethyl-N-β-
ethylhexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-cyclopentyl) )
Fluoran dyes such as amino 6-methyl-7-phenylaminofluorane, etc. Of course, the dyes are not limited to these dyes, and two or more types of dyes can be used in combination.

Furthermore, various compounds are known as coloring agents used in combination with the above-mentioned basic dyes, for example, the following are exemplified.

4-tert-butylphenol, α-naphthol, β
-naphthol, 4-acetylphenol, 4tert
-octylphenol, 4.4'-5ec-phthylidene diphenol, 4-phenylphenol, 4.4'-dihydroxy-diphenylmethane, 4゜4'-isopropylidene diphenol, hydroquinone, 4.4'-cyclohexylidene diphenol Phenol, 4.4'-(1,3-
dimethylbutylidene) bisphenol, 2,2-bis(
4-hydroxyphenyl)-4-methyl-pentane, 4
, 4' dihydroxydiphenyl sulfide, 4.4'
-thiobis(6-tert-butyl-3-methylphenol), 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-methyldiphenylsulfone,
4-hydroxy-4'-methoxydiphenyl sulfone,
4-Hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy=3'4'-)limethylenediphenylsulfone, 4-hydroxy-3'4'
-tetramethylene diphenyl sulfone, 3,4-dihydroxy-4'methyldiphenyl sulfone, bis(3-allyl 4-hydroxyphenyl) sulfone, 1.3';
2-(4-hydroxyphenyl)-2-propyl]benzene, hydroquinone monobenzyl ether, bis(4-
hydroxyphenyl) acetic acid butyl ester, 4-hydroxybenzophenone, 2゜4-dihydroxybenzophenone, 2,4.4'-trihydroxybenzophenone,
2.2', 4゜4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-5
ec-butyl, pentyl 4-hydroxybenzoate, 4-
Phenyl hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenypropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, p-chlorobenzyl 4-hydroxybenzoate , 4-hydroxybenzoic acid-p-methoxyhensyl, novolac type phenolic resin, phenolic compounds such as phenol polymers, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl- 4-hydroxybenzoic acid, 3-cyclohexyl-4-
Hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3,5-di-t
er t-butylsalicylic acid, 3-benzylsalicylic acid, 3(α-methylhensyl)salicylic acid, 3-chlor5
-(α-methylbenzyl)salicylic acid, 3-phenyl-5
-(α,α-dimethylbenzyl)salicylic acid, 3,5-
Aromatic carboxylic acids such as di-α-methylbenzyl salicylic acid, their phenolic compounds, salts of aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, etc. organic acidic substances, etc. Note that, of course, two or more of these coloring agents can be used in combination as necessary.

The ratio of the basic dye and coloring agent to be used is appropriately selected depending on the type of basic dye and coloring agent used, and is not particularly limited, but in general, the ratio is based on 100 parts by weight of the basic dye. 100 to 700 parts by weight, preferably 150 to 700 parts by weight
About 400 parts by weight of coloring agent is used.

Preparation of coating liquids containing these generally uses water as a dispersion medium,
It is prepared by dispersing the dye and coloring agent together or separately using a stirring/pulverizing machine such as a ball mill, attritor, or sand mill.

Such coating liquids usually contain starches and binders as binders.
Hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene/maleic anhydride copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion, etc. have a total solid content. It is blended in an amount of about 2 to 40% by weight, preferably about 5 to 25% by weight.

Furthermore, various auxiliary agents can be added to the coating liquid.
Examples include dispersants such as dioctyl sodium sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, other antifoaming agents, fluorescent dyes, and coloring dyes.

Furthermore, inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, and activated clay may be added to improve the adhesion of residue to the recording head. Further, a dispersion or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax, etc. may be added to prevent sticking from contact with a recording device or a recording head.

Further, fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, coconut fatty acid amide, 22'-methylene bis(4-
methyl-6-tert-butylphenol), 44'-butylidenebis(5-LerL-butyl-3-methylphenol), 1.1.3-1-lis(2-methyl-4-hydroxy-5-tert-butylphenyl) Hindered phenols such as butane, p-benzylbiphenyl, ■
, 2-bis(phenoxy)ethane, ■, 2-bis(4-
Ethers such as methylphenoxy)ethane, 1,2-bis(3-methylphenoxy)ethane, and 2-naphtholhensyl ether, esters such as dibenzyl teretoclate, 1-hydroxy-2-naphthoic acid phenyl ester, 2- Ultraviolet absorbers such as (2'hydroxy-5'-methylphenyl)benzotriazole and 2-hydroxy-4-hensyloxybenzophenone, and various known thermofusible substances can also be used together as sensitizers. .

The method of forming the recording layer is not particularly limited, and can be formed according to conventionally well-known and commonly used techniques. For example, a suitable coating device such as an air knife coater, a blade coater, a bar coater, a gravure coater, a curtain coater, etc. can be used to apply a coating liquid for a heat-sensitive recording layer onto a base paper.

Further, the amount of the coating liquid to be applied is not particularly limited (generally adjusted in the range of 2 to 12 g/n in terms of dry weight, preferably 3 to log/rd).

It is also possible to provide an overcoat layer on the recording layer for the purpose of protecting the recording layer, etc. A protective layer may be provided on the back side of the base paper, or an undercoat layer may be provided between the base paper and the heat-sensitive recording layer. Of course, it is also possible to provide a heat-sensitive recording paper, and further, various known techniques in the field of heat-sensitive recording paper manufacturing, such as applying adhesive processing, can be added.

"Example" The present invention will be described in more detail with reference to Examples below, but it is of course not limited to these.

Note that parts and % in the examples indicate parts by weight and % by weight, respectively, unless otherwise specified.

Example 1 ■ Preparation of base paper Whiteness (JIS P 8123) 83%, 0.1m
BCT M P (manufactured by Temcell Inc., 75% aspen material, 25% stainless steel material) with an amount of bound fiber pieces of size 12 or more is 3000 pieces/g is pulp'1
It was treated with a single disc refiner at 72 degrees and 4% to adjust the amount of bound fiber pieces to 500 pieces/g.

Double discret refiner in BCTMPS section after processing
LBKP each beaten to a freeness of 500 cc.
Talc was added to the pulp suspension obtained by blending 75 parts of NBKP and 20 parts of NBKP so that the ash content was 6%,
Further, as a sizing agent, 1.4% of rosin size was added to the bone-dried pulp.

After adjusting the pH of this pulp slurry to 4.6 with a sulfuric acid hand, paper was made using a long multi-cylinder cylinder dryer paper machine, and 1.5 g of an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) was added. / m size press, machine calender processing to tsubo ff140
g/%, measured value with a specular reflection type smoothness meter (pressure condition 20k
A base paper for thermal recording paper having a g/cnl) of 9% was obtained.

■ Lacquer preparation A 3-(N-cyclohexyl-N-methylamino)6-methyl-7-phenylminofluorane 10 parts Methyl cellulose 5% aqueous solution 20 parts water
10 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ B Lacquer preparation Bisphenol A 30 parts Methylcellulose water 2
Part: This composition was ground in a sand mill until the average particle size was 3 μm.

■ Preparation of thermal recording paper 40 parts of liquid A, 80 parts of liquid B, silicon oxide pigment (oil absorption N: 1
80ml/100g) 30 parts, 20% oxidized starch aqueous solution 1
00 parts and 70 parts of water were stirred and mixed to prepare a coating liquid for heat-sensitive recording. The obtained coating liquid was applied and dried on the base paper obtained in step ① above so that the coating amount after drying was 7 g/ld,
Further, the paper was subjected to supercalender treatment to obtain heat-sensitive recording paper.

The thermal recording paper thus obtained was printed at a head voltage of 1 using an ultra-high-speed thermal printer (UP-103, manufactured by Sony).
Printing was performed at 5.5 volts and a pulse width of 5 ms, and the image density was measured using a Macbeth densitometer, and the results are shown in the table. Also,
The background stain on the surface of the recording layer was visually determined and the results are listed in the table. The evaluation criteria were 〔◎...excellent. ○
...Some dirt is observed. x: Significant staining was observed].

Furthermore, the sharpness of the recorded images was visually judged and the results are also listed in the table. The evaluation criteria were [◎: extremely excellent, ○: good, ×: poor].

Example 2 Whiteness (JIS P 8123) 8 3%, 0.1
BCT M P (manufactured by Temcell Inc.) with an amount of bundled fiber pieces of size 1.2 or more is 3000 pieces/g.
A product of 75% aspen material and 25% subluice material was treated with a single disc refiner at a pulp concentration of 4% to adjust the amount of bundled fiber pieces to 300 pieces/g.

Talc was added to a pulp suspension obtained by blending 10 parts of treated BCTMP with 70 parts of LBKP and 20 parts of NBKP, each beaten to a freeness of 500 cc using a double disc reflex burner, to give a low ash content of 6%. Furthermore, 1.4% of rosin size was added as a sizing agent to the bone-dry pulp.

After adjusting the PL+ of this pulp slurry to 4.6 with a sulfuric acid band, paper was made using a fourdrinier cylinder dryer paper machine, and 1.5 g of an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) was added to the pulp slurry. /m, then press the metal roll and elastic roll (Shore D hardness 91
Processed with an on-machine calendar consisting of
A base paper for thermal recording paper was obtained which had a fi4 0 g/rrr and a value measured with a specular reflection type smoothness meter (pressure condition 20 kg/cj) of 16%.

A thermosensitive recording paper was prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted, and the results are shown in the table.

Example 3 Whiteness (JIS P 8123) 8 3%, 0.1
The amount of bundled fiber pieces with a size of mm” or more is 2000 kel/g
BCT M P (manufactured by Temcell Inc., 75% aspen material, 25% soot material) was treated with a single disc refiner at a pulp concentration of 4% to adjust the amount of bundled fiber pieces to 100 pieces/g. .

Talc was added to a pulp suspension obtained by blending 75 parts of treated BCTMP with 25 parts of NBKP beaten to a freeness of 500 cC using a double-disuffle refiner to a low ash content of 6%, and further, as a sizing agent, the rosin size was completely reduced. It was added in an amount of 1.4% based on the dry pulp.

After adjusting the pH of this pulp slurry to 4.6 with a sulfuric acid hand, paper was made using a fourdrinier cylinder dryer paper machine, and 1.5 g of an aqueous solution of oxidized starch (trade name; manufactured by Ace A. Oji Cornstarch Co., Ltd.) was added to the pulp slurry. /%, and processed with an on-machine calender consisting of a metal roll and an elastic roll (Shore D hardness 291 degrees).
40 g/rl, measured value with a specular reflection type smoothness meter (
A base paper for thermosensitive recording paper was obtained under pressure conditions of 20 kg/CII of 18%.

A thermosensitive recording paper was prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted, and the results are shown in the table.

Example 4 Whiteness (JIS P 8123) 77%, 0.1f
BCT M P (manufactured by Temcell Inc., 100% stainless steel product) with a binding fiber piece amount of 2,500 pieces/g of 1" or more in size was treated with a single disc refiner at a pulp concentration of 4% and bundled. The amount of fiber pieces is 40
It was adjusted to 0 pieces/g.

After treatment, 10 parts of BCTMP are each beaten to a freeness of 500 CC using a double disc refiner.
To a pulp suspension obtained by blending 70 parts of KP and 20 parts of NBKP, talc was added so that the paper component was 6%, and rosin size was added as a sizing agent at 1.4% based on the bone-dry pulp.

After adjusting the pH of this pulp slurry to 4.6 with a sulfuric acid hand, paper was made using a fourdrinier cylinder dryer paper machine, and 1.5 g of an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Tamago Cornstarch Co., Ltd.) was added to the pulp slurry. /m, and then processed with an on-machine calender consisting of a metal roll and an elastic roll (Shore D hardness: 87 degrees) to obtain a size of
A base paper for thermosensitive recording paper was obtained, which had a roughness of 140 glrd and a value measured with a specular reflection type smoothness meter (pressure condition: 20 kg/c++l) of 16%.

A thermosensitive recording paper was prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted, and the results are shown in the table.

Example 5 BCT M P (manufactured by Temcell Inc., 20% asben material, carbon steel) with a whiteness (JTS P 8123) of 82% and an amount of bundled fiber pieces with a size of 0.1 甫-2 or more of 2500 pieces/g. A 80% blues material was treated with a single disc refiner at a pulp concentration of 4% to adjust the amount of bundled fiber pieces to 1000 pieces/g.

LB beaten to a freeness of 500 cc using a double disk refiner in the BCTMPIO section after processing.
Talc was added to the pulp suspension obtained by blending 70 parts of KP and 20 parts of NBKP so that the paper component was 6%, and 1.4% of rosin size was added as a sizing agent based on the bone dry pulp.

After adjusting the pH of this pulp slurry to 4.6 with a sulfuric acid band, paper was made using a long multi-cylinder cylinder dryer Shogiden, and an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Tamago Cornstarch Co., Ltd.) was added to a pH of 1.5. g/m, then processed with an on-machine calendar consisting of a metal roll and an elastic roll (Shore D hardness 78 degrees) to a final size of 340 g/m, measured using a specular reflection type smoothness meter. A base paper for thermosensitive recording paper having a value (pressure condition: 20 kg/co?) of 10% was obtained.

A thermosensitive recording paper was prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted, and the results are shown in the table.

Example 6 BCTMP (manufactured by Temcell Inc., asben material 75%, subluth 25% product) to pulp density 4
% in a single disc refiner to adjust the amount of bundled fiber pieces to 300 pieces/g.

BCTMP after treatment: 10 parts of LBK each beaten to a freeness of 500 cc using a double disc refiner
A pulp suspension obtained by blending 70 parts of P and 20 parts of NBKP was added with heavy calcium carbonate (trade name: Laughton 1).
200. (manufactured by Bihoku Hankasha) was added so that the paper content was 6%, and sulfuric acid was added to the bone dry pulp at 0.5%.
Then, 0.5% of cationic starch (trade name, CATO-F, manufactured by Tamago National Co., Ltd.) was added to the bone-dry pulp, and alkyl ketene dimer (trade name) was added as a neutral sizing agent.
SPK902. After adding 0.2% of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) to bone-dry pulp, paper was made using a fourdrinier multi-tube cylinder dryer paper machine. 1.5 g/rrf
It is size-pressed like a potato, and is made up of a metal roll and an elastic roll (Shore D hardness 91 degrees), processed with a famous on-machine calender, and has a thickness of 40 g/ni, as measured by a specular reflection type smoothness meter. (pressure condition 20kg/cd) is 1
A base paper for thermal recording paper having a concentration of 5% was obtained.

A thermosensitive recording paper was prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted, and the results are shown in the table.

Example 7 Whiteness (JIS P 8123) 83%, 0. In
BCT M P (manufactured by Ten+cell Inc,
A product of 75% aspen material and 25% soot material was treated with a single disc refiner at a pulp concentration of 4% to adjust the amount of bundled fiber pieces to 300 pieces/g.

After treatment, 10 parts of BCTMP are each beaten to a freeness of 500 cc using a double disc refiner.
To a pulp suspension obtained by blending 70 parts of KP and 20 parts of NBKP, talc was added so that the ash content was 6%, and rosin size was added as a sizing agent at 1.4% based on the bone-dry pulp.

After adjusting the pH of this pulp slurry to 4.6 with a sulfuric acid band, it was made into paper using a round-mesh monotube Yankee dryer paper machine, and the basis weight was 40 g/rtr, and the value measured with a regular reflection type smoothness meter (
Pressure condition (20kg/cn) is 30% on the cast side and 1 on the back side.
A base paper for thermal recording paper having a concentration of 0% was obtained.

A thermosensitive recording paper was prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted, and the results are shown in the table.

Comparative Example 1 Double Diffle Finer with Friness 500 each
A base paper for thermosensitive recording paper was obtained in the same manner as in Example 1, except that a pulp suspension consisting of 80 parts of LBKP and 20 parts of NBKP beaten to cc was used. Measurement value of this base paper with a specular reflection type smoothness meter (pressure conditions; 2Q kg/c
n2) was 9%.

A thermosensitive recording paper was prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted, and the results are shown in the table.

Comparative Example 2 Whiteness (JIS p 8123) 78%, 0.1m
10 parts of BCT M P (manufactured by Temcell Inc., made of 100% stainless steel material) with an amount of bundled fiber pieces of 3500 pieces/g or more, and LB beaten to a freeness of 500 Ce using a double disc refiner.
A base paper for thermosensitive recording paper was obtained in the same manner as in Example 1, except that a pulp suspension obtained by blending 70 parts of KP and 20 parts of NBKP was used. The measured value of this base paper using a specular reflection type smoothness meter (pressure conditions: 20 kg/cm'') was 7%.

A thermosensitive recording paper was prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted, and the results are shown in the table.

"Effects" As is clear from the results in the table, all of the thermal recording papers obtained in the examples of the present invention produced recorded images that were clear and had excellent image density without causing background stains.

table

Claims (2)

[Claims] (1) Contains 5% by weight or more of mechanical pulp and/or chemical mechanical pulp in the total pulp composition, and the value measured with a specular reflection type smoothness meter on the surface of the base paper is under pressure conditions of 20 kg/
A thermal recording paper characterized by using a base paper having a thickness of 8% or more in cm^2. (2) The thermosensitive recording paper according to claim (1), wherein the chemi-mechanical pulp is bleached chemi-thermomechanical pulp.