JPH0986041A - Double-side thermal recording paper and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide double-side thermal recording paper reduced in the permeation of printing from the rear surface thereof, reduced in the difference between the printing densities of the rear and upper surfaces thereof and excellent in machinery matching properties generating no overlap feed of cut sheets. SOLUTION: Thermal layers each based on a colorless or light-colored basic dye and a coupler forming a color along with the dye is applied to the upper and rear surfaces of base paper and surface finish is performed so that the upper and rear surfaces thereof respectively come into contact with an elastic roll and a chill roll. By setting ash in raw paper to 5-20%, the wt. basis thereof to 50-200g/m<2> and the opacity thereof to 80% or more, the double-side thermal recording paper reduced in the permeation from the rear surface thereof and excellent in machinery matching properties generating no overlap feed of cut sheets can be obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a double-sided thermal recording paper. In particular, the present invention relates to a double-sided heat-sensitive recording paper, which suppresses the difference in printability and sensitivity between the front and back sides, is excellent in device matching properties, and has little show-through on the reverse printing surface, and a method for producing the base paper and heat-sensitive layer.

[0002]

2. Description of the Related Art Various types of heat-sensitive recording materials have been published so far, which utilize a heat-coloring reaction of at least one colorless or light-colored basic dye with phenols, organic acid salts, etc. (Japanese Patent Publication No. It has been widely put into practical use. These thermosensitive recording materials are used in a wide range of fields such as measuring recorders, terminals for information communication such as computers and banks such as ATM / CD, facsimiles, ticket vending machines, word processors and labels used for foods, processes, clothing tags, etc. Has been applied to. These recording devices are equipped with a thermal element such as a thermal head or a hot pen, and by heating this element, a color can be developed to obtain a recording. In recent years, the performance and size of the apparatus have been increasing along with the diversification of applications, and with this, the quality required for the thermal recording paper has become wider.

For example, a conventional thermosensitive recording paper is generally a facsimile paper, but with the spread of applications in recent years, a word processor has appeared especially for individuals, and the thermal recording paper is used for reports and circulations in offices. It is becoming more common to print. Furthermore, high sensitivity is required due to downsizing and speeding up of the apparatus, and thermal recording paper is also provided with an undercoat layer in view of printability and sensitivity in accordance with this, and further, a sensitizer is used as a heat sensitive layer. It is improved by adding to.

However, with the advent of word processors, thermal printers have spread to the individual level,
The movement to save resources has been activated not only at government agencies and corporations but also at the individual level. As one of the movements for resource saving, there is a direction to increase the content rate of waste paper in paper, enhance paper recycling, and effectively utilize and protect forest resources.

Further, as a new direction in the future, the aspect of reducing the dust generation rate has been greatly highlighted, and resource saving of thermal recording paper having only one printing side, reduction of dust, page There is an increasing demand for a reduction in the number and realization of space saving for storage. Furthermore, the use has spread not only to postcards, papers, and reports but also to daily messages, memos, etc., and there has been a demand for double-sided printing as resource-saving thermal paper.

As described above, the advantages of the double-sided thermal paper are not only the resource saving of the paper but also the space saving such as the reduction of the number of sheets and the use of printing on both sides such as a postcard. Effective in some cases.

However, in spite of such demands, the present situation is that the double-sided thermosensitive recording paper is not popular in general. This is because the difference between the front and back is always a problem when manufacturing a double-sided heat-sensitive material. The cause of this difference is mainly due to the difference between the front and back sides of the base paper that is caused during the papermaking of the base paper.When the base paper is made by any of the fourdrinier paper machine and the twin wire paper machine, its formation, ash distribution rate, and size property And the like, and when the heat-sensitive recording layer is smeared on both sides, the printability and sensitivity are directly different from each other. As countermeasures against these problems, there are many methods such as sticking one-side smear products together using tack glue or EB resin, or simply changing the type of sensitizer or dye to eliminate the difference in sensitivity and printability. Improvement studies have been made. However,
When pasting one-side smeared products together using glue etc., the sensitivity may decrease due to the desensitizing action of the solvent etc. contained in the glue, and the fog on the background and the storage stability of the printed area may be reduced. It cannot be used for postcards. Furthermore, it is not something that individual users can use with confidence, such as peeling at the adhesive. In addition, if the material on one side is changed and handled, a difference in sensitivity, a problem of the color of the printed portion, and a difference in storability appear, so that the difference between the front and the back cannot be avoided.

However, despite the many obstacles described above, the production of double-sided thermal papers by laminating single-sided thermal papers and changing the materials on both sides has been continued, and a complete improvement has been made. At present, there is no double-sided thermal paper having the basic characteristics. This is because there is currently no way to fundamentally solve the formation, ash distribution rate, and sizing degree that are derived from the difference between the front and back of the base paper. The result is lack of stable quality.

Further, when printing on both sides, it is required that the reverse side printing portion shows through the paper, that is, so-called opacity. Generally, as a method of improving opacity, a method of simply increasing the thickness or a filler in the base paper is used. The method of increasing the number is conventionally adopted.
However, thermal recording paper is mainly used in printers and the like, and increasing the thickness significantly impairs device matching. Further, if the filler is increased, the stiffness decreases so-called paper strain, and the printer section such as a word processor cannot perform feeding well and causes paper jam, so that the balance between thickness and opacity is important.

Furthermore, if the smoothness of the front and back is remarkably different, the alignment of the paper in the auto sheet feeder with a unit of several tens of cut sheets will be poor, and paper jam during printing, double feeding, etc. will occur, resulting in remarkable equipment matching. Be damaged.

[0011]

From the above points, the object of the present invention is to focus on the original difference between the front and back sides of the base paper, and apply the chilled surface of the calender to the thermosensitive recording layer smeared on the back surface of the base paper. By applying elastic roll finish to the one smeared on the surface, the BEKK smoothness is 200 seconds or more and the difference between the front and the back is within 100 seconds, so that the difference between the printability, the sensitivity and the storability is suppressed as much as possible. Moreover, there is no double feeding of cut sheets in the word processor, and it is excellent in equipment matching,
Furthermore, the opacity of the base paper is set to 80% or more, and the basis weight is 50 to 20.
The purpose of the present invention is to provide a double-sided heat-sensitive recording paper in which the show-through on the printed surface is suppressed to the utmost by setting it to 0 g / m ^2, and a method for producing the same.

[0012]

As a result of intensive studies, the present inventors have come to invent the thermal recording paper of the present invention. That is, a base paper having a filler content of 5 to 20% and an opacity of 80% or more and a basis weight of 50 to 200 g / m ² is colored by reacting with a colorless or light basic dye and the dye. In a thermosensitive recording paper coated on both sides with a water-soluble coating liquid containing a color developer, the thermal recording layer coated on the back side of the base paper should be chilled roll for calendar, and the one coated on the surface should be elastic roll finished. The double-sided thermal recording paper is characterized by having a BEKK smoothness of 200 seconds or more and a front-back difference of 100 seconds or less.

The thermal recording paper of the present invention will be described in detail below. In inventing the thermal recording paper of the present invention, a base material having a filler content of 5 to 20%, an opacity of 80% or more and a basis weight of 50 to 200 g / m ² is used, and a colorless or light basic dye and In a thermosensitive recording paper in which a water-soluble coating liquid containing a color developer capable of reacting with the dye is smeared on both sides, the thermosensitive recording layer smeared on the back side of the base paper is chilled roll finished with a calendar and further smeared on the surface. It has been found that by making an elastic roll finish on this side, it is possible to obtain a double-sided thermal recording paper that suppresses the difference between the front and back of the printability and sensitivity as much as possible and is excellent in device matching with a word processor.

In the present invention, the pulp used for the base paper of the double-sided thermal recording paper may be NBKP, LBKP, NBSP, LBSP, CGP, G regardless of whether it is dry pulp or wet pulp.
P, waste paper pulp, various non-wood pulp, and the like. In addition, a dye, a fixing agent, a polyacrylamide, a dry paper strength enhancer such as starch and the like, which are usually used in papermaking, are contained as necessary within a range that does not impair the effects of the present invention.

In the present invention, the content of the filler in the base paper is
5 to 20% by weight is required. If the content is less than 5% by weight, the difference in the smoothness between the front and back may be large and low, and the printability on the front and back may be remarkably different at the time of recording, and the printability may be remarkably deteriorated to cause uneven color development. Further, since the opacity is low, a so-called show-through phenomenon occurs in which the printed matter on the opposite side can be seen through. On the other hand, when the content of the filler exceeds 20% by weight, it causes pitch trouble during papermaking, and further weakens the strength of the paper, resulting in poor coating stability and other troubles during production. In addition, it may not be put to practical use because it may cause paper jams in the printer part such as a word processor, probably because the strength (stiffness) of the paper is lost.

In the present invention, the basis weight of the base paper is 50 to 2
A range of 00 g / m ² is appropriate. If the grammage is less than 50 g / m ² , the paper cannot be fed satisfactorily by a word processor due to the occurrence of wrinkles, and if the grammage exceeds 200 g / m ² , smoothing is achieved even with calendering. Cannot be obtained, and the printability and print density are extremely reduced, and satisfactory quality cannot be obtained.

In the present invention, the filler contained in the base paper has to be changed depending on the pH of the papermaking system. For calcium carbonate, for example, light calcium carbonate, wet ground heavy calcium carbonate, dry ground heavy calcium carbonate. Further, talc or the like can be used alone or if necessary, and two or more kinds may be used in combination.
Further, in addition to the case where it is added as a filler, it may be brought in from waste paper pulp, broke paper disaggregation raw material or the like.

In the present invention, as the sizing agent used for the base paper, an internally added sizing agent such as alkyl ketene dimer, alkenyl succinic acid dimer, rosin, or neutral rosin can be added. The sizing agent needs to be added in an amount of 0.05 to 1.5% by weight based on the pulp. The amount added
If it is less than 0.05% by weight, sufficient size cannot be obtained,
Application of the aqueous liquid becomes extremely difficult, and when it exceeds 1.5% by weight, further size effect cannot be obtained, and troubles due to the pitch of the sizing agent are remarkably surfaced.

Further, for the purpose of improving the sizing property of these sizing agents, a sulfuric acid band at an appropriate pH and system,
Also, a yield improving agent and the like can be added. Sulfuric acid bands have been widely used in papermaking systems for the purpose of fixing dyes and chemicals, improving freeness of water in the wire part and improving dewaterability in the press part, adjusting pH, and preventing deposits. Is.

In the present invention, the base paper is surface-treated by a size press etc., if necessary, with or without starch, a water-soluble binder such as PVA, a latex such as SBR and a styrene-maleic anhydride copolymer. Can be primed with size, coating, etc.

In the present invention, on-machine calendering or super calendering may be applied as necessary in order to impart smoothness to the base paper.

The pulp used in the base paper of the present invention includes:
NBKP, LBKP, NBSP, LBSP, CGP, G
P, waste paper pulp, various non-wood pulp, and the like. Further, a dye, a fixing agent, a dry paper strength enhancer and the like, which are usually used in papermaking, are contained as necessary within a range not impairing the effects of the present invention.

The raw material for the waste paper pulp referred to in the present invention is as follows:
Top white, ruled white, cream white, special white, medium white, imitation, fair white, Kent, white art, special cut, extra cut shown in the standard standard table for used paper at the Waste Paper Recycling Promotion Center. ,newspaper,
Examples include magazines. More specific examples include printer paper such as non-coated computer paper, thermal paper and pressure-sensitive paper, which are information-related paper, and OA waste paper such as PPC paper, art paper, coated paper, lightly coated paper, fancy paper, and medium. Waste paper such as quality paper, newsprint, waste paper, supermarket wrapping paper, imitation paper, pure white roll paper, uncoated paper such as milk carton and waste paper such as paperboard, chemical pulp paper, high yield pulp containing paper etc. are used However, it is not particularly limited to printing, copying, printing, and non-printing.

In addition, the used paper pulp is generally (1) disaggregated: treated with mechanical force and chemicals in the used paper pulp to disintegrate into a fibrous form, and the printing ink is separated from the fibers. (2) Dust removal: Remove foreign substances (plastic etc.) and dust contained in used paper with a screen cleaner. (3) Deinking ... The printing ink separated from the fiber using a surfactant is removed from the system by a flotation method or a cleaning method. (4) Bleaching ...- The whiteness of the fiber is increased by using the oxidizing action and the reducing action. It is made from a combination of 4 steps.

In the present invention, the colorless or light-colored basic dyes constituting the recording layer of the heat-sensitive recording material may be used alone or in admixture of two or more, if necessary. Any of those applied to the heat-sensitive material of, for example, triallylmethane-based, fluoran-based, thiazine-based, spiropyran-based, lactam-based dye leuco compounds are preferably used, especially fluoran-based leuco dyes Is widely and generally used, and specific examples thereof include the following.

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-methylindole -3-yl)
-5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl)- Triallylmethane dyes such as 6-dimethylaminophthalide, 6 '-[ethyl (3-methylbutyl) amino] -3'-methyl-2'-(phenylamino) -spiro [isobenzylfuran-1-9 ' −
Xanthen] -3-one, 3-dibutylamino-6-methyl-7-anilinofluoran, 3- (N-methyl-N
-Propylamino) -6-methyl-7-anilinofluoran, 3- (N-cyclohexyl-N-methylamino)
-6-methyl-7-anilinofluoran, 3-dimethylamino-6-methyl-7-chlorofluorane, 3-dimethylamino-7-methyl-7-chlorofluoran, 3-
Dimethylamino-6-methyl-7-anilinofluoran, 3,3-bis (4-dimethylaminophenyl) 6-
Diethylaminophthalide, 3-diethylamino-7 (2
-Chloroanilino) fluoran, 3-dibutylamino-
Fluoran dyes such as 7 (2-chloroanilino) fluoran; thiazine dyes such as benzoyl leucomethylene blue and p-nitribenzoyl leuconnetylene blue;
Spiropyrans such as -methyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran And lactam dyes such as rhodamine (p-nitroanilino) lactam and rhodamine (o-chloroanilino) lactam.

Further, in the present invention, various binders as shown below are applied as the binder for binding and supporting the thermosensitive coloring layer on the support.

Derivatives of polyvinyl alcohol, starch and its derivatives, methyl cellulose, hydroxymethyl cellulose, carboxymethyl cellulose, ethyl cellulose, polyvinyl pyrrolidone, polyacrylamide, sodium polyacrylate, acrylamide / acrylic ester copolymer, acrylamide / acrylic ester / Methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, sodium alginate, gelatin, casein, gum arabic and other water-soluble polymers,
Aqueous emulsions such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, polymethacrylate, vinyl chloride / vinyl acetate copolymer, ethylene / vinyl acetate copolymer, polybutyl methacrylate, etc. Can be used as

The heat-sensitive recording material of the present invention contains, in the heat-sensitive color forming layer, together with the above-mentioned basic dye and developer, if necessary,
Auxiliary additives commonly used in this type of heat-sensitive recording material, such as fillers, surfactants and lubricants, can be used in combination.
In this case, as the filler, for example, calcium carbonate,
Inorganic fine powder such as silica, aluminum hydroxide, magnesium carbonate, talc, barium sulfate, zinc oxide, titanium oxide, surface-treated calcium and silica, urea / formalin resin, styrene / methacrylic acid copolymer,
An organic fine powder such as polystyrene can be used. As the lubricant, for example, in addition to higher fatty acids or their esters, amides or metal salts, various waxes, condensates of aromatic carboxylic acids with amines, benzoic acid phenyl esters, higher linear glycols, and other heat-fusible organic compounds Compounds.

It is also possible to provide an under layer between the base paper and the heat sensitive layer. As an apparatus used for coating the under layer and the heat-sensitive recording layer, a coater head such as a blade coater, an air knife coater, a roll coater, a rod coater, a curtain coater or a gravure coater can be used.

If necessary, one or more barrier layers (overcoat layer) mainly composed of a water-soluble polymer may be provided on the heat-sensitive layer for the purpose of protecting the heat-sensitive layer or the back surface of the support. Various well-known techniques in the field of producing a thermosensitive recording medium can be added, such as providing a protective layer on the underside of the support, and further applying an adhesive to the back surface of the support.

The coating amount for providing the under layer is not particularly limited, but 3 to 20 g / m ^{2 is} preferable, and 5 to 10 g / m ² is suitable. The coating amount of the thermosensitive recording layer on the support is not limited, but is usually 3 to 1
5 g / m ² preferably from 4~10g / m ^2.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In addition, all the parts and% shown below are based on weight.

Example 1 (blend paper formulation) LBKP (freeness; 300 ml, csf) 85 parts by weight NBKP (freeness; 300 ml, csf) 15 parts by weight Light calcium carbonate 12 parts by weight AKD 0.5 parts by weight Positive starch 0.7 parts by weight Using the pulp slurry having the above composition, a base paper having a basis weight of 50 g / m ² was produced with a Fourdrinier paper machine having a paper making speed of 700 m / min. This paper machine has three presses installed in front of the dryer. After drying with a multi-cylinder dryer, the density is 0.7
The thickness was adjusted with a machine calendar so as to be 0 g / m ³ . (Composition of Size Press Liquid) This base paper was subjected to size press treatment with the following composition so that the solid adhesion amount was 1.2 g / m ² . Oxidized starch 5 parts by weight Water 94.8 parts by weight

Preparation of Heat Sensitive Layer (1) Preparation of Solution A Liquids A and B having the following component compositions were obtained by dispersing for 10 hours. 10% Polyvinyl alcohol solution 100 parts by weight 3-Dibutylamino-6-methyl-7-anilinofluorane 100 parts by weight Water 150 parts by weight A solution using Dynomill (manufactured by Shinmaru Enterprises Co., Ltd.) volume average, 0.8 μm Crushed into (2) Preparation of liquid B 15% styrene maleic anhydride copolymer ammonium salt 35 parts by weight 4,4′-isopropylidenediphenol 55 parts by weight 2-benzyloxy-naphthalene 40 parts by weight N-methylolstearic acid amide 10 parts by weight Part water 200 parts by weight Solution B was pulverized to a volume average of 0.8 μm using Dynomill (manufactured by Shinmaru Enterprises).

Next, using the prepared [solution A] and [solution B],
A thermosensitive color developing layer coating solution comprising the following components was prepared, and first dried on the surface of the above-mentioned base paper with an air-knife coater at 400 m / min so that the dry weight was 5 g / m ² , and then on the back side. The thermosensitive coloring layer was dry-coated in the same manner as the surface. Polyvinyl alcohol solution (10% aqueous solution) 50 parts by weight Calcium carbonate 10 parts by weight Solution A 10 parts by weight Solution B 35 parts by weight 40% zinc stearate dispersion 4 parts by weight Water 25 parts by weight

The coated paper was calendered so that the chilled surface was contacted with the back surface coating layer and the elastic roll surface was contacted with the surface coating layer, and the Bekk smoothness of the front and back surfaces was 200 to 400 seconds and the difference between the front and back surfaces was within 100 seconds. The double-sided heat-sensitive recording paper of the present invention was obtained by finishing as follows.

Examples 2 to 3 Thermal recording papers were obtained in the same manner as in Example 1 except that the amounts of light calcium carbonate added were 7 parts by weight and 27 parts by weight, respectively, in the base paper formulation of Example 1. Double-sided thermosensitive recording papers of Examples 2 and 3 were obtained from these samples in order from the one having the smaller amount of light calcium carbonate added.

Example 4 The composition of the base paper and thermosensitive coloring layer of Example 1 was finished so that the BEKK smoothness after calendering was 400 to 600 seconds and the difference between the front and back sides was within 100 seconds. A double-sided thermosensitive recording paper was obtained.

Example 5 In the base paper formulation of Example 1, 35 parts by weight of LBKP,
A double-sided thermosensitive recording paper of Example 7 was obtained in the same manner as in Example 1 except that NBKP was 15 parts by weight and the artificial waste paper was 50 parts by weight.

Example 6 Both sides of Comparative Example 8 were carried out in the same manner as in Example 1 except that the base paper of Example 1 and the thermosensitive coloring layer were blended so that the basis weight of the base paper was 200 g / m ^2. A thermosensitive recording paper was obtained.

Comparative Example 1 A double-sided thermosensitive recording paper of Comparative Example 1 was obtained in the same manner as in Example 1 except that the calender conditions were changed so that the chilled roll surface was in contact with both the front and back surfaces.

Comparative Example 2 A double-sided thermosensitive recording paper of Comparative Example 2 was obtained in the same manner as in Example 1 except that the calender conditions were changed so that both the front and back surfaces were contacted by the elastic roll surface.

Comparative Example 3 Example 1 was repeated except that the calendering conditions were changed so that the chilled roll contacted the front surface and the elastic roll surface contacted the back surface.
A double-sided thermosensitive recording paper of Comparative Example 3 was obtained in the same manner as in.

Comparative Examples 4 to 5 Thermal recording papers were obtained in the same manner as in Example 1 except that the amount of light calcium carbonate added was 6 parts by weight and 28 parts by weight in the base paper formulation of Example 1. From these samples, double-sided thermosensitive recording papers of Comparative Example 4 and Comparative Example 5 were obtained in order from the one having the smallest addition amount of light calcium carbonate.

Comparative Example 6 Comparative Example 6 was carried out in the same manner as in Example 1 except that the base paper and the thermosensitive coloring layer of Example 1 were blended so that the BEKK smoothness was 100 to 200 seconds on both sides. To obtain double-sided thermal paper.

Comparative Example 7 Comparative Example 7 was carried out in the same manner as in Example 1 except that the base paper and the thermosensitive color developing layer of Example 1 were blended so that the difference in BEKK smoothness between the front and the back was 150 seconds or more. I got double-sided thermal paper

Comparative Example 8 Comparative Example 8 Both sides of Comparative Example 8 were carried out in the same manner as in Example 1 except that the base paper of Example 1 and the thermosensitive coloring layer were blended so that the basis weight of the base paper was 250 g / m ^2. A thermosensitive recording paper was obtained.

The thermal recording materials described above were evaluated according to the following items.

[Calcium Carbonate Content] The calcium carbonate content of the base paper was measured according to the ash test method for paper and paperboard described in JIS-P-8128. 500 in the electric furnace
The values of the ash content (%) A when ashed by heating to ℃ and the ash content (%) B when ashed at 900 ° C. were obtained by substituting them into the mathematical formula represented by the formula 1.

[0051]

Calcium carbonate content = (A−B) × 2.273

[Measurement of Opacity] Measurement of opacity is described in J
According to IS-P8138, the ratio of the reflectance R of the standard plate with a whiteness of 89% Rw and the reflectance of the black standard plate Ro measured with a green filter with a Hunter reflectometer.
o / Rw was expressed as a percentage.

[Evaluation of Sensitivity and Printability] Regarding the above-mentioned thermal recording material, word processor W manufactured by Sharp Co., Ltd.
In the high-speed printing mode of D-A560, both sides were printed in solid black, the print densities of the background part and the image part at that time were measured, and the printability was visually judged. Print density is at least 1.0
More than OD is required. In addition, the judgment of the difference in print density between the front and back is 1) There is no problem if the difference in print density between the front and back is 0.05 OD or less. 2) When the print density difference between the front and back is 0.05 to 0.09 OD,
There is no problem in practice. 3) If the print density difference between the front and back is 0.10 OD or more, there is a problem because the difference can be clearly seen by visual inspection. And In addition, the evaluation of the printability should be at least as shown below, with Δ or more on both sides, and both sides should have the same evaluation result. The print density is Macbeth RD91.
8 was used to measure. ○: Color is evenly printed with no print unevenness. B: Some print unevenness is observed. X: A part that is not colored is observed.

[Evaluation of Double Feed] A genuine automatic sheet feeder for Toshiba Word Processor JW95GP A
When 4, 100 sheets were set and 99 sheets were printed, double feeding was confirmed. It must be at least Δ or higher. Example 7,
Regarding Comparative Example 8, 10 sheets were set as one set and evaluated 10 times. Judgment method ◎ ・ ・ ・ Good, no problem. ○: Occurred about 1 to 3 times. Δ: Occurred 4 to 6 times. ×: Frequent occurrence.

[Evaluation of show-through] Each heat-sensitive paper printed on both sides with a copying machine was copied, and it was evaluated whether or not a printed pattern on the opposite side of the copy side was found on the copied matter. ○: No show-through. Δ: The back print part appears on the copy slightly. X: The back side printing part appears on the copy to the extent that it can be clearly seen.

[0056]

[Table 1]

[0057]

[Table 2]

From the results shown in Tables 1 and 2, in the present invention, the content of the filler is 5 to 20%, the opacity thereof is 80% or more, and the base paper having the basis weight of 50 to 200 g / m ² is colorless or not. After a light-colored basic dye and a water-soluble coating liquid containing a color developing agent that reacts with the dye to coat the both surfaces, a chilled roll of a calender recording layer is coated on the back surface of the base paper.
The double-sided thermal recording paper, which has the surface of the back and front BEKK smoothness of 200 seconds or more and the difference within 100 seconds, has high sensitivity, printability and sensitivity. It was a double-sided thermal recording paper with minimal difference between the front and back sides, little printed image on the reverse side, and excellent equipment matching in word processors.

Claims (4)

[Claims] 1. A thermosensitive recording paper having a thermosensitive layer containing, as a main component, a colorless or pale basic dye and a developer capable of reacting with the dye to develop a color, and the thermosensitive layer is smeared on both sides of the base paper. A double-sided thermosensitive recording paper characterized in that the chilled surface of a calendar is applied to the thermosensitive recording layer smeared on the back side, and the surface of the smeared surface hits an elastic roll. 2. The BEKK smoothness after smearing is 20 on both sides.
The double-sided thermosensitive recording paper according to claim 1, wherein the difference between the front and back sides is 0 seconds or more and the front-back difference is 100 seconds or less. 3. JIS-P8128 as a filler in the base paper.
According to JIS-P8123, the opacity of the base paper is 5% to 20% by weight, and the basis weight is 5%.
It is 0-200 g / m ² , It is characterized by the above-mentioned,
The double-sided thermal recording paper described in 2. 4. The double-sided heat-sensitive recording paper according to claim 1, wherein the base paper contains waste paper pulp.