JPH03227291A - Heat sensitive recording sheet - Google Patents

Abstract

PURPOSE:To extremely effectively improve coating propriety of a base sheet and to improve recording sensitivity for an ultrahigh speed machine by adjusting leakage propriety of the sheet and smoothness of its surface obtained by mixing regenerated pulp to specific ranges based on a certain special measuring method. CONSTITUTION:A base sheet in which 3wt.% or more of regenerated pulp obtained by deinking including a mechanically agitating step for applying compression force to waste sheet in the presence of deinking agent of surfactant, etc., is contained in entire pulp composition, its dynamic leakage value is -0.32 - +0.15g/m<2>, and a measured value by a surface normal reflection type smoothness meter is 12% or more under pressurizing condition of 20kg/cm<2> or less, is used. Its dynamic leakage value is adjusted to fall within a range of -0.32 - +0.15g/m<2>, more desirably -0.30 - +0.10g/m<2>. If the value exceeds +0.15g/m<2>, formation of smoothly coating surface becomes difficult, and a heat sensitive recording layer is reduced in thickness. However, if it becomes -0.32g/m<2> or smaller, its step coverage is reduced. Accordingly, in both cases, the sheet having desired recording sensitivity cannot be obtained.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention relates to heat-sensitive recording paper, and in particular, the pulp composition includes pulp recycled from OA waste paper, printing waste paper, etc. by deinking treatment accompanied by a seconding process. The present invention relates to a thermal recording paper which improves the coating suitability of the base paper made by the process and has a recording sensitivity sufficient to be suitable for ultra-high speed machines without causing background stains.

"Prior Art" Conventionally, heat-sensitive recording 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 a blue coloring substance is brought into contact with heat to obtain a colored image. Paper 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, barcode label printers, and the like.

In addition, with the remarkable increase in the amount of information in recent years, for example, high-speed machines (C, I [[[[[[[]] machines) and even higher speed machines (GIV machines) for facsimile are being developed.

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.

However, conventional proposals have focused on improving the materials that make up the recording layer, such as color formers, coloring agents, and thermofusible substances (sensitizers). Satisfactory results are not always obtained due to accompanying defects.

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.

On the other hand, with the recent progress in office automation (OA), contrary to what was said to be a "paperless" society, large amounts of information paper called OA paper are being discharged from offices and factories. The consumption of coated paper for printing is rapidly increasing due to the increase in the number of insert advertisements, magazines, and advertisements becoming more visual, colored, and more sophisticated, and the disposal of this rapidly increasing amount of paper waste is now an important issue. It has become a social problem.

Japan's waste paper recovery rate is approximately 50%, which is higher than other developed countries.
For example, 90% of used newspapers are recovered. Approximately 40% of the raw materials for newspaper production are supplied by recycled paper valves.

However, when waste paper valves are used as a raw material for OA paper, coated paper for printing, and uncoated paper, quality problems may occur, so they are not fully utilized as a raw material for these. Furthermore, since there is a limit to the amount of recycled paper that can be used as a raw material for conventional newspapers and cardboard, waste paper such as office automation paper and coated paper for printing, which are particularly difficult to recycle, is collected and incinerated. The reality is that each local government faces increasing incineration costs, landfill and other processing capacity limitations, global resource protection and forest resource reduction issues, and global warming caused by carbon dioxide generated by waste paper incineration. This phenomenon has developed into an international environmental problem.

Therefore, there is a strong demand for establishing a method for reusing waste paper valves as raw materials for OA paper, coated paper for printing, uncoated paper, and the like. However, it is very difficult to obtain valves similar to normal bleached pulp from used OA paper, waste coated paper for printing, etc.

This is because most used office paper such as printer paper for office computers, personal computers, word processors, faxes, etc. and copy paper are printed with toner containing resin components, and offset printing on printing paper also uses resin components. It is notorious for the fact that it is quite difficult to remove colored prints and printing pigments from the paper (especially in the case of rotary offset printing) because it is printed with printing ink containing a large amount of pigment.

For this reason, various methods have been proposed for collecting waste paper such as office automation paper and printing paper.In particular, a hydrophilic surfactant-based deinking agent is used, and a machine is used to apply compressive force to the waste paper using a kneader or disperser. The so-called high-density kneading system method (hereinafter referred to as the HDK method), which performs deinking by selective stirring, is attracting attention because of its excellent deinking effect.

The present inventors conducted intensive research focusing on reusing the recycled pulp obtained by the HDK method as base paper for thermal recording paper, and found that the recycled pulp obtained by the HDK method can be used under heating and pressure. Because it is intensively treated with a special surfactant,
The resulting recycled pulp exhibits physical properties that are quite different from ordinary valve fibers, and it is difficult to use conventional virgin pulp or recycled pulp that does not involve the HDK method, as well as simple fibers obtained from common loss paper at paper mills and unprinted waste paper. It is clear that the coatability of the base paper is poorer than that of the base paper obtained by mixing and using a recovery valve, and that the recording sensitivity of the thermal recording paper obtained by coating this base paper with a heat-sensitive recording material is reduced. It became.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned defects when the base paper obtained by blending recycled pulp obtained by the HDK method is used as a base paper for thermal recording paper, especially the coating suitability of the base paper. It is an object of the present invention to provide a heat-sensitive recording paper which has a recording sensitivity that can be sufficiently applied to ultra-high-speed machines without causing background stains.

As a result of further intensive research into the above-mentioned defects, the inventors of the present invention found that the base paper obtained by blending the recycled pulp obtained by the HDK method is particularly poor in wettability to coating liquids and surface smoothness. It has been found that this causes a significant decrease in the recording sensitivity of thermal recording paper.

After further consideration of its improvement, H.
When the wettability and surface smoothness of base paper obtained by blending recycled pulp obtained by the DK method are adjusted to a specific range based on a specific measurement method, the coatability of the base paper can be extremely effectively improved. The present invention has been completed based on the discovery that the recording sensitivity for ultra-high-speed machines has been improved and that the initial objective of the present invention has been achieved.

[Means for Solving the Problems] The present invention provides a method for converting recycled pulp obtained through a deinking process that includes a mechanical stirring process in which compressive force is applied to waste paper in the presence of a surfactant-based deinking agent into whole pulp. Contains 3% by weight or more in the composition, has a dynamic wetting value of -0.32 to +0.15g/rn, and has a surface measured with a specular reflection type smoothness meter under a pressure condition of 20kg/cii. This heat-sensitive recording paper is characterized by using a base paper having a content of 12% or more.

"Function" Waste paper recycled pulp can be obtained by appropriately combining a disintegration process, a rough selection process, a selection process, a deinking process, and a bleaching process. Low concentration pulper, high concentration pulper, etc. are used in the disintegration process, screens, cleaners, etc. are used in the rough selection process and fine selection process, and flotation method, main selection method, compromise method, etc. are used in the deinking process. be selected depending on the quality of the material.

The HDK method for waste paper processing uses conventional sodium sulfite,
Using caustic soda together, earth pot high pressure cooking and cleaning method, solvent method,
Unlike deinking methods, which use pulper immersion cleaning method, pulper immersion flotation method, etc., to dissolve or emulsify and disperse printing ink and resin through the action of chemicals and heat, approximately 15%
The above-mentioned high-density paper stock is treated with strong and uniform interfiber friction such as kneading and a surfactant to separate printing ink from the pulp fibers, and uniformly convert foreign substances such as printing ink into ultra-fine particles. Method of removing by flotation method [Paper and Pulp Technology Association June 1983 issue, pages 1-17, Paper and Pulp Technology Times August 1988 issue, pages 25-31, Special Publication 1986-11
See Publication No. 353].

Furthermore, on page 29 of the August 1983 issue of Paper Valve Technology Times, there is a comparison of the quality of recycled pulp obtained using the HDK method and recycled pulp obtained without using the HDK method.
In particular, recycled pulp obtained using the HDK method has been shown to have increased water absorption and wettability. The cause of this is that the surfactant used as a deinking agent adsorbs to the surface of the recycled pulp or penetrates into the inside of the pulp fibers due to the compressive force of the kneading process, so it can be fully removed by washing and dehydration in the post-process. It is presumed that this is because it remains in the recycled pulp and imparts hydrophilicity to the pulp.

The research results of the present inventors have revealed that when a base paper with increased water absorption and wettability is used as a base paper for thermal recording paper, the recording sensitivity of the resulting recording medium is significantly reduced. .

For this reason, the recording sensitivity of the resulting thermal recording paper was determined by varying the measurement methods conventionally used to evaluate the water absorption of base paper, such as Klemm's water absorbency, Cobb's water absorbency, and Steckigt size. Although we conducted a detailed investigation into the correlation, no satisfactory correlation was found.

However, when the water absorption of the base paper was evaluated using a dynamic wetting value, it became clear that there was an extremely good correlation between the water absorption of the base paper and the recording sensitivity of the resulting thermosensitive recording paper.

The dynamic wettability value is an evaluation method that expresses the change in adhesion force to water over time as a measure of wettability, and in the present invention, it is expressed as a value measured with a dynamic wettability tester (NET-3000, manufactured by Resker). That is, the magnitude of wetting over time (adhesion force) is measured when a 2X5CI11 test piece is immersed in water at a speed of 16 mm/sec to a depth of 12 am for 10 seconds, and the magnitude of wetting (adhesion force) is measured. The dynamic wetting value (hereinafter referred to as dynamic wetting value) indicates that the larger the negative absolute value is, the harder it is to get wet, and the larger the positive value is, the easier it is to get wet.

As a result of further examination of this dynamic wetting value, we found that it has a very serious effect on the recording sensitivity of thermal recording paper, which can be obtained by measuring the wetting value 2 seconds after immersion in water as a temporal wetting value measured with this tester. It became clear that it was having an effect.

However, in the base paper for thermal recording paper of the present invention, this dynamic wetting value is in the range of -0.32 to +0.15 g/po, more preferably -0.30 to +0.10 g/po. It is adjusted to

Incidentally, when the dynamic wetting value is higher than +0.15g/rrl, the heat-sensitive coating liquid coated on the base paper rapidly penetrates into the fiber gaps of the base paper, making it difficult to form a smooth coated surface, making the heat-sensitive There is also a risk that the recording layer may become thinner. However, if it is less than -0.32 g/m2, the compatibility between the base paper and the thermal coating liquid decreases, resulting in a coating layer with weak surface strength and poor coverage, so in either case, the desired recording sensitivity cannot be achieved. It is not possible to obtain thermal recording paper with the following properties.

The dynamic wetting value of base paper can be controlled by, for example, pulp composition, beating conditions, type and amount of filler added, paper strength agent, internal sizing agent, pH1 surface sizing agent, surface treatment agent, paper density, and wire mesh. This is achieved by appropriately adjusting various conditions such as hydrofoil arrangement, paper filler distribution, smoother pressure conditions, press pressure conditions, and drying temperature conditions. However, since the various conditions mentioned above affect the paper making speed, it is natural that the optimum conditions should be appropriately selected depending on the paper machine used. Further, when increasing the blending amount of recycled pulp obtained by the HDK method, it is preferable to set the dynamic wetting value gradually lower accordingly.

In the heat-sensitive recording paper of the present invention, the dynamic wetting value of the base paper is adjusted to a specific range as described above, but at the same time, the value measured with a specular reflection type smoothness meter on the surface is under the pressure condition of 20 kg/c + I.
12% or more, more preferably 14% or more.

A specular reflection type smoothness meter is a device that measures the smoothness of a glass surface by pressing paper against the glass surface under certain pressure conditions. It is not affected by the air permeability of the paper as in Printsurf, and the minute smoothness of the paper surface can be appropriately evaluated.

Therefore, according to the detailed study results of the present inventors, especially for base paper containing recycled pulp obtained by the HDK method, the effect of improving the smoothness of the base paper surface and the recording sensitivity of thermal recording paper measured by this method is It became clear that there was an extremely good correlation between the two. Of course, it is not enough to simply increase the measurement value of the base paper surface with a specular reflection type smoothness meter to 12% or more; By combining the measurements of and identifying suitable base paper conditions, the initial improvement objective of the present invention was achieved for the first time.

The upper limit of the value measured by a specular reflection type smoothness meter for base paper is not particularly stipulated, but if this value is set high, streaks, It is preferable to keep it below 30% because scratches, etc. tend to occur (and the paper thickness tends to be low).In addition, if on-machine size press is performed on the base paper or an undercoat is applied with a coater, is defined as the measured value under that condition.

In order to control the measured value of the base paper surface with a specular reflection type smoothness meter within the above specific range, the pulp composition, beating conditions, wire mesh, felt mesh, press pressure, smoothing roll treatment, etc. are adjusted. It is most preferable to carry out the smoothing treatment in the wet part of the papermaking process, but a smoothing device such as a machine calender, soft calender, gloss calender, or supercalendar may be used on-machine or off-machine.

Note that it is also possible to smooth the base paper surface by using a Yankee dryer whose surface has been treated with hard chrome plating, etc. as the paper machine dryer, but in any case, the surface of the base paper is specularly reflective. The measured value with a smoothness meter (measurement pressure: 20 kg/cm") is 12
% or more.

In the pulp composition constituting the base paper for thermal recording paper of the present invention, 3% by weight or more of recycled pulp obtained by the HDK method,
It is preferably contained in an amount of 10% by weight or more,
If the content is less than 3% by weight, the desired effects of the present invention cannot be obtained. Furthermore, if the content exceeds 10% by weight, the compressive elastic modulus of the base paper will be low and the thermal conductivity will be low. , heat is concentrated at the contact point between the recording head and the recording paper, and is difficult to conduct to areas other than that contact point, resulting in high-sensitivity recording without causing background stains.

The recycled pulp obtained by the HDK method in the present invention refers to the recycled pulp obtained by the methods described in the above-mentioned Paper and Paper Technology Association Journal, Paper and Pulp Technology Times, patent publications, etc., and in particular, 15% or more This process involves mechanically treating waste paper while applying compressive force using a refiner, kneader-1 twin-shaft mixer, divider, etc. under conditions where one or more types of surfactant-based deinking agents are present at a pulp concentration of This is a pulp obtained by the Sumi method. Incidentally, as surfactants, those having an HLB value of 11 to 14 are often used in order to obtain high whiteness.

The waste paper used as raw materials includes information-related paper such as uncoated printer paper for computers, personal computers, word processors, faxes, etc., printer paper such as thermal paper, pressure-sensitive copying paper, etc.
So-called OA waste paper such as Xerox copy paper, art paper,
Coated paper such as coated paper, lightly coated paper, matte paper, high-quality paper, colored high-quality paper, notebooks, stationery, wrapping paper, fancy paper, medium-quality paper, newsprint, saragi, super paper, Used paper and paperboard such as imitation paper, white roll paper, milk cartons and other uncoated paper, acidic or neutral paper, chemical pulp paper, high-yield pulp (SGP, BSGP, BCTMP, TMP, etc.)
RGP, CNP, etc.) containing paper, waste paper standard quality specification table;
Used paper as described in the Waste Paper Recycling Promotion Center Summary is used, but it is not particularly limited, regardless of whether it is printed, copied, printed, or non-printed.

Please note that if the obtained recycled pulp is blended without treatment, the smoothness of the base paper surface and the paper strength of the base paper may decrease.
It is preferable that the paper be treated with a beating machine in the pre-process of the paper machine to reduce the Canadian Standard freeness in the range of about 30 to 150 cc.

If the beating is less than 30 cc, a sufficient effect of improving the smoothness cannot be obtained, and if the beating is more than 150 cc, the compressive elastic modulus of the obtained base paper becomes high, and the desired effect of the present invention is not achieved. There is a risk that it will become smaller. In addition,
As the refining machine, a conical refiner, a single disc refiner, a double disc refiner, etc. are used, but in consideration of power, it is more preferable to use a double disc refiner.

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.
A combination consisting of a 180°C compound, sulfur and metal inorganic salts or metal acetates.

Examples of compounds having a secondary alcoholic hydroxyl group include benzoin compounds such as benzoin, 2-methoxybenzoin, 4-chlorobenzoin, 4-dimethylaminobenzoin, and 2-chloro-4'-dimethylaminobenzoin, and diphenylcarbinol. Carbinols such as
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 many metals that react with hydrogen sulfide to produce colored sulfides, such as copper, lead, tin, molybdenum, cobalt, chromium, nickel, pine, These include titanium, antimony, rhodium, osmium, mercury, iron, barium, bismuth, arsenic, magnesium, indium, and iridium.

(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 dehydrating agents include galactose and starch, and examples of dehydrating agents include sulfuric acid, acetic anhydride, anhydrous zinc chloride, para-toluenesulfonic acid, and the like.

(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 balmitic acid, and alkaline earth metal sulfides such as calcium sulfide, strontium sulfide, and barium sulfide. combination of,
or a combination of the organic acid heavy metal salt and an organic chelating agent such as S-diphenylcarbazide or diphenylcarbazone; (f) a combination of a heavy metal salt such as silver, lead, mercury, or thorium oxalate and Na-tetrathionate; Combinations with sulfur compounds such as sodium thiosulfate and thiourea (6) Combinations of ferric fatty acid salts such as ferric stearate and aromatic polyhydroxy compounds such as 3,4-dihydroxytetraphenylmethane.

(c) 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 and an aromatic organic reducing agent such as protocatechuic acid, spirointane 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.

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

(Combination of higher fatty acid heavy metal salts such as ferric listearate and copper stearate and zinc dialkyldithiocarbamate.

(e) Those that form oxazine dyes, such as a combination of resorcinol and a nitroso compound, 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 various combinations mentioned above, 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(l,2-dimethylindol-3-yl)
-5-dimethylaminophthalide, 3,3-bis(1゜2
~dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazole-
3-yl)-6-dimethylaminophthalide, 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'
- and sudimethylaminobenzhydryl benzyl ether, N-halophenyl-leucoolamine, N-2,4
, 5-) diphenylmethane dyes such as IJ chlorophenyl leuco auramine, thiazine dyes such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3
- Spiro dyes such as ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo)spiropyran, 3-propyl-spirodibenzobilane, rhodamine B-anilinolactam,
Lactam dyes such as rhodamine (p-nitroanilino)lactam and rhodamine (0-chloroanilino)lactam, 3-dimethylamino-7-methoxyfluorane, 3-
Diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-
Methyl-7-chlorofluorane, 3-diethylamino-
6,7-dimethylfluorane, 3-(N-ethyl-p-
toluidino)-7methylfluorane, 3-diethylamino-7-N-acetyl-N-methylaminofluorane,
3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-N-methyl-N-benzylaminofluorane, 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-)luidino)-6-methyl-7-(p-toluidino)fluorane,
3-diethylamino-6-methyl-7-phenylaminofluorane, 3-dibutylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7-(
2-Carbomethoxyphenylamino)fluorane, 3-
(N-cyclohexyl-N-methylamino)-6-methyltophenylaminofluorane, 3-pyrrolidino6-
Methyl-7-phenylaminofluorane, 3-piperidino-6-methyl-7-phenylaminofluorane, 3-
Diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylamino)fluoran, 3-dibutylamino-7-(o-chlorophenylamino)fluoran, 3-pyrrolidino-6
-methyl-7-p-butylphenylaminofluorane,
3-(N-methyl-Nn-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-Nn-amyl)amino-6-methyl-7-phenylaminofluoran Oran, 3 (N-ethyl-N-isoamyl)
amino-6-methyl-7-phenylaminofluorane,
3-(N-methyl-N-n-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-n-hexyl)amino-6-methyl-7-phenylaminofluorane , 3-(N-ethyl-N-β-ethylhexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-phenylaminofluoran Fluoran dyes such as orane, 3-(N-ethyl-N-cyclopentyl)amino-6-methyl-7-phenylaminofluorane, and the like. 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, 4-tert
-Octylphenol, 4.4'-5ec-butylidene diphenol, 4-phenylphenol, 4.4'-dihydroxy-diphenylmethane, 4゜4'-isopropylidene diphenol, hydroquinone, 4,4'-cyclohexylidene diphenol ,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'-methoxydiphenylsulfone, 4
-Hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-3'4'-)limethylenediphenylsulfone, 4-hydroxy-3',4'-tetramethylenediphenylsulfone, 3,4-dihydroxy-4'methyl Diphenyl sulfone, bis(3-allyl 4-hydroxyphenyl) sulfone, 1,3-di(2-
(4-hydroxyphenyl)-2-propyl]benzene, hydroquinone monobenzyl ether, bis(4-hydroxyphenyl)acetic acid butyl ester, 4-hydroxybenzophenone, 2゜4-dihydroxybenzophenone, 2.4.4'-trihydroxy Benzophenone, 2.
2', 4゜4'-tetrahydroxybenzophenone, 4
-dimethyl hydroxyphthalate, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-5e
c-Butyl, pentyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, 4-hydroxy phenethyl benzoate,
Phenolic compounds such as p-chlorobenzyl 4-hydroxybenzoate, p-methoxybenzyl 4-hydroxybenzoate, novolac type phenolic resin, phenol polymer, benzoic acid, p-tertbutylbenzoic acid, trichlorobenzoic acid, terephthalic acid , 3-sec-butyl-4
-Hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid! , folic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3,5-di-te
r t-butylsalicylic acid, 3-benzylsalicylic acid,
3-(α-methylbenzyl)salicylic acid, 3-chloro-
5-(α-methylbenzyl)salicylic acid, 3-phenyl-
5-(α,α-dimethylbenzyl)salicylic acid, 3,5
- Aromatic carboxylic acids such as di-α-methylbenzyl salicylic acid, and their phenolic compounds; salts of aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel; and other organic acidic substances. 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 is generally based on 100 parts by weight of the basic dye. 100-700 parts by weight, preferably 150-4
About 0.00 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 sodium dioctyl 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 resin, 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, 2,2'-methylene bis(4
-methyl-6-tert-butylphenol), 4.4
'-Ptylidenebis(6-tert-butyl-3-methylphenol), 1,1.3-)lis(2-methyl-4
Hindered phenols such as -hydroxy-5-tert-butylphenyl)butane, p-benzylbiphenyl, 1,2-bis(phenoxy)ethane, 1,2-bis(
Ethers such as 4-methylphenoxy)ethane, 1,2-bis(3-methylphenoxy)ethane, 2-naphtholbenzyl ether, dibenzyl terephthalate, 1-
Esters I such as hydroxy-2 naphthoic acid phenyl ester! , 2-(2'hydroxy-5'-methylphenyl)benzotriazole, 2-hydroxy-4-benzyloxybenzophenone, and various other known thermofusible substances may be used in combination as sensitizers. can.

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, and is generally adjusted in the range of 2 to 12 g/rrr, preferably 3 to Log/rrr in terms of dry weight.

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 A mixture of OA waste paper, high-quality coated paper, and uncoated printed paper was disintegrated in an alkaline aqueous solution using a pulper, and screened to remove foreign substances such as plastics and adhesives. was removed and dehydrated to a pulp concentration of 30%. In addition, NaOH 3%, NagSiO+ 4%, H,
0.3%, surfactant-based deinking agent [Product name: or6oo
, manufactured by Kao Corporation] was added thereto, and the mixture was compressed and stirred using a heating kneader, and then held at about 60° C. for 2 hours. Next, about 1
%, deinked by flotation treatment, and dehydrated to obtain recycled pulp with a whiteness of 78% and a freeness of 550 cc.

This recycled pulp was refined with a double disc refiner to a freeness of 500 cc, and 10 parts of LB were each refined to a freeness of 500 cc.
Talc was added to a valve suspension prepared by blending 70 parts of KP and 20 parts of NBKP so that the paper ash content was 6%, and 1.4% of rosin size was added as a sizing agent based on the bone dry valve.

After adjusting the pH of this valve 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. /rrr, processed with a machine calendar to give a basis weight of 40g/m
A base paper for thermosensitive recording paper was obtained which had a dynamic wetting value of -0.20 g/a and a value measured with a specular reflection type smoothness meter (pressure condition 20 kg/cd) of 12%.

■ Afi preparation 3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-phenylaminofluorane 10 parts Methyl cellulose 5% aqueous solution 206B water
10 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ B-wave preparation Bisphenol A 30 parts Methyl cellulose 5% aqueous solution 70 parts water
20 parts of 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 I: 18
0 cc/100 g), 100 parts of a 20% oxidized starch aqueous solution, and 70 parts of water were stirred and mixed to prepare a coating liquid for thermal recording.

This heat-sensitive coating liquid was coated and dried on the base paper obtained in step (1) above so that the coated amount after drying was 1 g/rd, and then supercalendered to obtain heat-sensitive recording paper.

The heat-sensitive recording paper thus obtained was printed at a head voltage of 15 using an ultra-high-speed thermal printer (UP-103, manufactured by Sony).
．． Printing was performed with a 5 volt pulse width of 5 ms, and the image density was measured using a Macbeth densitometer, and the results are shown in the table.

In addition, background stains on the surface of the recording layer were visually determined and the results are listed in the table. The evaluation criteria were [◎...extremely excellent]. 0: Slight stains are 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]. O: good, ×: poor].

Example 2 The recycled pulp used in Example 1 was refined in a double disc refiner to a freeness of 450 cc. 50 parts of this recycled pulp has a freeness of 500 parts each.
Talc was added to a pulp suspension obtained by blending 30 parts of LBKP and 20 parts of NBKP beaten in CC so that the ash content was 6%, and rosin size was added as a sizing agent to 1.6% of the bone-dry pulp. Added.

This pulp slurry p! (After adjusting to 4.6 with a sulfuric acid band, paper was made using a long multi-cylinder cylinder dryer paper machine, and an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Oji Cornstarch Co., Ltd.) was added to a concentration of 1.5 g/rrr. size pressed and treated with an on-machine calender consisting of a metal roll and an elastic roll (Shore D hardness 91 degrees), with a basis weight of 46 g/m and a dynamic wettability value of -0.15 g/rrr.
Measured value with a specular reflection type smoothness meter (pressure condition 20kg/cd
) of 16% 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 3 The recycled pulp of Example 1 was refined using a double disc refiner to obtain a freeness of 430 cc.

To 50 parts of this recycled pulp, 500 c of freeness was added to each
A pulp suspension obtained by blending 30 parts of beaten LBKP and 20 parts of NBKP with c was added with talc having a low ash content of 6%.
Furthermore, 1.0% of rosin size was added as a sizing agent to 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 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. rd, size press the metal roll and elastic roll (Shore D hardness 91
Processed with an on-machine calender consisting of
, measured value with a specular reflection type smoothness meter (pressure condition 20 kg/c
A base paper for thermal recording paper having d) of 18% 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 4 The recycled pulp of Example 1 was refined in a double disc refiner to a freeness of 430 cc. To a pulp suspension obtained by blending 50 parts of this recycled pulp with 30 parts of LBKP and 20 parts of NBKP, each beaten to a freeness of 500 cc, talc was added so that the ash content was 6%, and rosin size was added as a sizing agent. It was added in an amount of 0.10% 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 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. size press so that it has a hardness of 8.
Processed with an on-machine calendar consisting of
) of 16% 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 5 A mixture of used newspaper and printed paper was disintegrated in an alkaline aqueous solution using a pulper, foreign substances such as plastics and adhesives were removed using a screen, and water was dehydrated to a pulp concentration of 25%.

To this, NaOH 2%, NazSiO +
4%, HzOz 3%, surfactant-based deinking agent [product name: DI 600R, manufactured by Kao Corporation] 0.4%, surfactant-based deinking agent [product name: 01300. Manufactured by Kao Corporation] 0.3
%, and after compression stirring treatment with a heating kneader, about 7
It was held at 0°C for 2 hours. Then, after further kneading treatment, it was diluted to about 1%, deinked by flotation treatment, and dehydrated to give a whiteness of 72% and a freeness of 350 c.
A recycled pulp of No.c was obtained.

This recycled pulp was refined with a double disc refiner to give a freeness of 250 cc to 70 parts, and NBKP30 was refined to a freeness of 500 cc.
To the pulp suspension prepared by blending the above ingredients, heavy calcium carbonate was added so that the ash content was 6%, 0.5% of aluminum sulfate and 0.5% of cationic starch were added, and further as a sizing agent. Alkyl ketene dimer [trade name: Vercon, manufactured by Dick Vercules] 0.1%, polyacrylamide as a fixing agent [trade name: Percoll 155]
．． (manufactured by Allied Colloid) 0.02% was added.

The thus prepared pulp slurry of pos and o was made into paper using a multi-cylinder cylinder dryer paper machine, and 100 parts of oxidized starch and an acrylic surface sizing agent [trade name: Polymaron 482. Manufactured by Arayo Kagakusha] 2 parts of the mixed solution at 2g/m
It was size pressed and treated with an on-machine calendar consisting of a metal roll and an elastic roll (Shore D hardness 78 degrees) to give a basis weight of 40g/proof and a dynamic wetting value of -0.
A base paper for thermal recording paper was obtained which had a value of 10 g/rrr and a value measured with a specular reflection type smoothness meter (pressure condition: 20 kg/ci) of 14%.

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 The recycled pulp used in Example 1 was refined in a double disc refiner to a freeness of 430 cc. 50 parts of this recycled pulp has a freeness of 500 parts each.
To a pulp suspension obtained by blending 30 parts of beaten LBKP and 20 parts of NBKP to cc, talc was added so that the low ash content was 6%, and rosin size was added as a sizing agent to 1.8% based on the bone dry pulp. Added.

The pH of this pulp slurry was adjusted to 4.6 using a sulfuric acid band, and then paper was made using a round-mesh monotube Yankee dryer paper machine to yield a paper with a tsubo of 146 g/rrr and a dynamic wetting value of -0.28.
g/rd, measured value with a specular reflection type smoothness meter (pressure condition 20
A base paper for thermosensitive recording paper was obtained in which the cast surface was 30% and the back surface was 10%.

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 LBKP8 each beaten to a freeness of 500 cc
A base paper for thermosensitive recording paper was obtained in the same manner as in Example 1 except that a pulp suspension consisting of 0 parts of NBKP and 20 parts of NBKP was used. The dynamic wetting value of this base paper is -0.32g/rd
, Measured value with a specular reflection type smoothness meter (pressure condition; 20 kg
/Country 2) 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 Regenerated pulp was obtained in the same manner as in Example 1, except that in the regenerated pulping step of Example 1, a mixer was used instead of the kneader, and the stirring treatment was carried out at a pulp concentration of 10%. This recycled pulp has a whiteness of 70% and a freeness of 500 cc.
Met. This recycled pulp was made into paper in the same manner as in Example 2 to obtain a base paper for thermosensitive recording paper. The dynamic wettability value of this base paper was -0.35 g/m2, and the value measured with a specular reflection type smoothness meter (pressure condition; 20 kg/cta'') was 8%.

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 3 A base paper for thermosensitive recording paper was obtained in the same manner as in Example 2 except that the rosin size was changed from 1.6% to 0.01%. The dynamic wetting value of this base paper is +0.17g/resistance, the value measured with a specular reflection type smoothness meter (pressure condition: 20kg/ai")
was 14%.

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, the thermal recording paper obtained in each example of the present invention did not cause background staining and recorded images with clear and excellent image density were obtained. .

Claims (1)

[Claims] The total pulp composition contains at least 3% by weight of recycled pulp obtained through a deinking process that includes a mechanical stirring process that applies compressive force to waste paper in the presence of a surfactant-based deinking agent. The value is -0.32 to +0.15g/m^2, and the value measured with a specular reflection type smoothness meter on the surface is under pressure condition 20k.
A thermal recording paper characterized by using a base paper having a g/cm^2 of 12% or more.