JPH0885256A - Reversible thermosensitive recording paper - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a reversible thermosensitive recording paper for a word processor and a printer, which uses recycled paper waste. [Structure] The support, which is paper, uses 10% by weight or more of recycled pulp made from waste paper, the number average fiber length of the recycled pulp is 0.6 mm or more, and the Canadian standard freeness at 20 ° C. is 150 ml or more. And, if the dirt number on the surface of the recycled pulp is 0.08 mm ² or more, it is 1
30 pieces / m ² or less, total number of 0.03 mm ² or more is 125
A reversible thermosensitive recording paper, characterized in that it is 0 / m ² or less. [Effect] There is little wavy curl when coloring and decoloring are repeated by heating, and there is almost no decrease in whiteness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reversible thermosensitive recording paper capable of coloring and decoloring by heating, and more specifically to a reversible thermosensitive recording paper for word processors and printers using recycled pulp made from waste paper. It is a thing.

[0002]

2. Description of the Related Art A heat-sensitive recording material is generally composed of a colorless support or a light-colored electron-donating dye (hereinafter referred to as a color former) and an electron-accepting acidic substance (hereinafter referred to as a developer) on a support such as paper. A heat-sensitive recording layer containing as a main component is provided, and by heating with a thermal head, a heating pen, a laser beam, etc., a color developing agent and a color developing agent react instantaneously to obtain a recorded image. , Japanese Patent Publication No. 43-4160, No. 45-14039,
It is disclosed in, for example, JP-A-59-190886.
In such a heat-sensitive recording material, once an image is formed, that portion cannot be erased and returned to the state before the image was formed again. I had to add. Therefore, if the area of the heat-sensitive recording portion is limited, there is a problem that all necessary information cannot be recorded.

In recent years, a reversible thermosensitive recording material has been devised which can be repeatedly used for image formation and image erasure in order to cope with such a problem. For example, Japanese Patent Laid-Open No. 48-53734.
No. 48-71656, No. 52-73957, No. 57-82086, No. 57-82088, and No. 57-.
No. 109695, No. 57-117140, No. 62-2
57883, 63-130380, 63-28.
0684, JP-A-1-14077, 1-14144
No. 85, No. 1-133781, No. 1-163094.
No. 2-2089, 2-155786, 3-
253388, 3-274181, 4-298.
No. 387, No. 4-347684, No. 5-85047.
JP-A-5-85048, JP-A-5-104857, and the like, a reversible thermosensitive recording material composed of a resin matrix and organic small molecules dispersed in the resin matrix and repeatedly opaque and transparent by heating. And JP-A-55-15767
No. 7, No. 57-90085, No. 57-123283
No. 58-191190, 59-120492, 6
0-173028, 60-228589, 60
-264285, 61-9488, and 62-14.
No. 163, No. 62-138556, No. 62-1408.
81, 63-309490, 63-31528.
7, 63-315288, JP-A-1-12139.
No. 4, No. 2-188293, No. 3-213389,
No. 3-231888, No. 3-253387, No. 4-
No. 267190, No. 4-308790, No. 5-926.
No. 61, No. 5-294063, No. 6-210954.
JP-A-6-210955 and the like disclose a reversible thermosensitive recording material composed of a color former and a reversible developer and capable of repeating coloring and erasing by heating.

The purpose of use of these reversible thermosensitive recording materials is for cards and tickets, and there are few papers as a support, and most of them are synthetic resin coated papers or films coated on both sides of expensive paper. By the way, in recent years, the demand for paper has continued to increase unexpectedly, and the situation of pulp, which is the raw material for it, has become more severe worldwide, while the amount of paper contained in municipal waste is particularly large, and the global environment From the viewpoint of conservation and protection of forest resources, efforts must be made to expand the recycling of waste paper and increase the utilization rate. Almost 40% recycled paper made from recycled paper is used as newspaper (hereinafter referred to as recycled paper recycled pulp). However, if recycled paper recycled pulp is used for heat-sensitive recording paper, quality problems may occur, and especially for reversible heat-sensitive recording paper, deterioration of whiteness and deterioration of repeatability of coloring and erasing due to heating become the biggest problems. Apparently, it has not been put to practical use yet.

[0005]

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to use recycled pulp of waste paper, to prevent deterioration of whiteness and to have excellent repeatability of coloring and decoloring by heating, and to have both economic value and practical value. Another object is to provide a reversible thermosensitive recording paper for word processors and printers.

[0006]

As a result of extensive research and experiments, the present inventor has used 10% by weight or more of recycled pulp of waste paper for a paper support of a reversible thermosensitive recording paper, and has a number average of the recycled pulp. The fiber length is 0.6 mm or more, the Canadian standard freeness at 20 ° C (hereinafter referred to as "freeness") is 150 ml or more, and the dart number of the recycled pulp surface is 0.08 mm ² or more, 130 co / m ² or less. The present invention has been accomplished with the knowledge that the object can be achieved by setting the total number of 0.03 mm ² or more to 1250 co / m ² or less. The waste paper, which is a raw material of the recycled pulp used in the present invention, is, for example, old newspapers, white newspapers, and the like;
With special cut-out, cut-out, old-fashioned, old magazines such as magazines; white manila, register manila, color manila, top mount, normal mount, new Kamegomi,
Recycled paperboard such as Shinshin, upper ball, lower ball, card; wrapping paper waste such as top cut tea, plain tea, normal tea, cemen tea, miscellaneous tea bag, red wamp, wamp; corrugated tea, cutting, OCC, cardboard etc. Corrugated cardboard waste paper; printed white paper such as white, special white, whitewash, whitewash, upper register, imitation, color, blue imitation, white art, register art, color art, etc.

[0007] These waste papers are appropriately selected and combined for each step such as disintegration, dust removal, kneading, ripening, deinking and bleaching to obtain recycled pulp of waste paper. In the disaggregation process, the waste paper is treated with mechanical force and chemicals with a pulper to disintegrate it into fibers,
Peel off printing ink and ash from fibers. What is a dust removal process? Foreign substances (plastic etc.) and dust contained in waste paper are removed by a screen cleaner or the like. Kneading is a deinking agent (deinking agent) consisting of a surfactant prior to aging; a builder such as caustic soda and sodium silicate; a bleaching agent such as hydrogen peroxide is added to and mixed with waste paper and mechanical stirring is performed. , A step of separating and dispersing the ink from the pulp fiber. In the aging step, deinking of the waste paper after the kneading is promoted by a chemical reaction such as alkali swelling together with an additive chemical. The deinking process is called a deinking process, and the ink separated and dispersed from the fibers by kneading and aging is removed to the outside of the system by a flotation method (flotation method) or a washing method.

Means for controlling the number of residual inks in the recycled pulp of waste paper include the disintegration time in the disaggregation step and the amount of chemicals added, the load during kneading, and the amount of chemicals added in the deinking (deinking) step. There are many types of printing inks, such as penetrating type inks such as newspaper inks and book printing inks; oxidation polymerization type inks such as carton inks and porosity inks; gravure inks;
There are solvent type such as flexo ink; reaction curing type such as UV ink and EB ink; dye type such as jet ink; reaction color type such as heat sensitive ink and pressure sensitive ink. Chemicals used are caustic soda, sodium carbonate, sodium silicate. Alkali; α
-Surfactants such as olefin sulfonate and polyoxyethylene nonyl phenyl ether. Finally, bleaching is performed to improve whiteness. For bleaching recycled paper recycled pulp, hydrogen peroxide, hydrosulfite, and calcium hypochlorite, which are used for bleaching general pulp, are used.

The fiber length used in the present invention is a number average fiber length (hereinafter referred to as fiber length), and its measurement is an optical automatic measuring method. In the measurement method, a fiber suspension is passed through a capillary, and when the polarized light is projected on the fiber, the optical axis of the polarized light is rotated. Therefore, an image of only the fiber is captured by a photodiode by a polarization filter, and various fractions in various fractions are captured. Measure the length and number of fibers. The fiber length used in the present invention is 0.6 mm or more. 0.6
If it is less than mm, the tear strength is lowered. The repeatability of color development and erasing is most effective in the range of 0.6 to 0.9 mm. The degree of drainage is measured as freeness, and the value is 1
50 ml or more. If it is less than 150 ml, the above-mentioned tear strength is lowered, and the object of the present invention is not achieved.

The dart number referred to in the present invention is the number of printing ink left on the surface of the recycled pulp of the waste paper as black dots. These dart numbers can be adjusted by adjusting each step. However, the present inventors have a limit of 0.03 mm ² with an image analyzer using a microlens or a paper dirt analyzer as a measuring method.
It can be accurately evaluated by measuring the above-mentioned dirt numbers. The dart number on the surface of recycled pulp of the present invention is 0.08.
mm ² or higher at 130 U / m ² or less, 0.03 mm ² or more is 1250 U / m ² or less, Dart total area 80m
It is m ² / m ² or less. If 0.08 mm ² or more exceeds 130 cm / m ² , printed characters may be misread. On the other hand, when 0.03 mm ² or more exceeds 1250 co / m ² , the whiteness is lowered and a clear printed image cannot be obtained.

In the reversible thermosensitive recording material of the present invention, a paper support containing 10% by weight or more is used in order to utilize the recycled paper recycled pulp as an effective means, but it is used in addition to recycled paper recycled pulp. General pulp is NBKP, LB
KP, NBSP, LBSP, GP, TMP and the like are mixed singly or in combination of two or more. The paper support used in the present invention is a white filler such as talc, kaolin, titanium dioxide or bentonite; anionic, nonionic, athionic or amphoteric retention improver; paper strength enhancer; internal addition such as internal sizing agent. Auxiliary agents are used, for example, polyvalent metal compounds other than Fe such as Al, Sn and Zn (sulfuric acid band, aluminum chloride) and various starches, polyacrylamide, polyethyleneimine, polyamine, polyamide resin, hydrophilic crosslinked polymer particle dispersion And one or more kinds of these derivatives or modified products are mixed.

If desired, a fluorescent dye, a pH adjusting agent,
Using internal additives for papermaking such as defoaming agent, pitch control agent, slime control agent, etc.
The acidic paper of 0.5 is produced by a Fourdrinier paper machine, a twin wire paper machine, a combination paper machine, a round net paper machine, and a Yankee paper machine. Furthermore, starch is applied to the surface of the acidified paper that has been produced by conventional size press, gate roll size press or size press of metering blade system, bill blade, short dwell coater, etc.
Various surface sizing agents such as polyvinyl alcohol, latex emulsion, maleic anhydride-based sizes, styrene-acrylic acid-based sizes; dimensional stabilizers such as ethylene urea resins; wetting agents such as polyethylene glycol and polyoxyethylene polyglyceryl ether; surfactants; Apply white pigment.

The color former, which is the main component of the reversible thermosensitive layer provided on the surface of the paper support of the present invention, is a phthalide type, diphenylmethane type, fluorane type, thiazine type, which is used for general pressure sensitive recording paper and heat sensitive recording paper. It is represented by spiropyran compounds and the like. Examples of the phthalide compound include 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,
3-bis (p-dimethylaminophenyl) phthalide,
3,3-bis (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 (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3 -Bis (2
-Phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-
(1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like can be mentioned.

Examples of fluoran compounds include 3-
Diethylamino-7-dibenzylaminofluorane, 3
-Diethylamino-7-octylaminofluorane, 3
-Diethylamino-7-phenylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino)
Fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7. -Anilino Fluoran, 3-
(N-ethyl-N-tolyl) amino-6-methyl-7-
Phenethylfluorane, 3-diethylamino-7- (4
-Nitroanilino) fluorane, 3-dibutylamino-
6-methyl-7-anilinofluorane, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamyl) amino-6- Methyl-7-anilinofluorane, 3- (N-
Methyl-N-cyclohexyl) amino-6-methyl-7
-Anilinofluorane, 3- (N-ethyl-N-tetrahydrofuryl) amino-6-methyl-7-anilinofluorane and the like.

Examples of thiazine compounds include benzoyl leuco methylene blue and p-benzoyl leuco methylene blue. Examples of the spiropyran-based compound include 3-methylspirodinaphthopyran, 3-ethylspironaphthopyran, 3,3′-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3
-Methylnaphtho- (3-methoxybenzo) spiropyran, 3-propylspirobenzopyran and the like can be mentioned, and one kind or a mixture of two or more kinds is used.

The color-forming agent used in the present invention and the reversible color-developing agent capable of coloring and decoloring by heating are described in JP-A-6-171225.
6-210954, 6-210955, 6-
Although described in JP-A-227125, a particularly preferred reversible developer is N- (4-hydroxyphenyl) -N'-.
Alkylurea, specifically N- (4-hydroxyphenyl) -N'-octylurea, N- (4-hydroxyphenyl) -N'-nonylurea, N- (4-hydroxyphenyl) -N '. -Decyl urea, N- (4-hydroxyphenyl) -N'-undecyl urea, N- (4-hydroxyphenyl) -N'-dodecyl urea, N- (4-hydroxyphenyl) -N'-tridecyl urea, N -(4
-Hydroxyphenyl) -N'-tetradecyl urea, N
-(4-hydroxyphenyl) -N'-pentadecylurea, N- (4-hydroxyphenyl) -N'-hexadecylurea, N- (4-hydroxyphenyl) -N'-heptadecylurea, N- (4-hydroxy Phenyl)-
N'-octadecyl urea, N- (4-hydroxyphenyl) -N'-nonadecyl urea, N- (4-hydroxyphenyl) -N'-icosyl urea, N- (4-hydroxyphenyl) -N'-henicosyl urea Etc.

The reversible heat-sensitive layer of the present invention is formed by mixing a binder and a white pigment, and the binder is a highly water-soluble binder such as starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein and polyvinyl alcohol. Molecule; polyvinyl acetate, polyurethane, polyacrylic acid ester, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, latex of ethylene / vinyl acetate copolymer and the like. Examples of white pigments include clay, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium dioxide, zinc oxide, silicon dioxide, aluminum hydroxide, magnesium hydroxide, barium sulfate, aluminum oxide, zinc stearate, calcium stearate. , Urea-formaldehyde resin, polystyrene and the like, and one kind or a mixture of two or more kinds is used.

In the present invention, if desired, waxes such as carnauba wax and paraffin wax; water resistant agents such as formaldehyde, glyoxal, epoxy resin, melamine, and melamine-folimaldehyde resin; UV absorbers typified by benzophenone A wetting agent such as sodium dialkyl sulfosuccinate; a dispersant such as sodium polyacrylate, styrene maleic anhydride copolymer ammonium and an alkylene glycol mixture; a defoaming agent or the like is appropriately added as an auxiliary agent for the reversible thermosensitive layer A coating solution, which is applied by an air knife, curtain, bar, gravure, roll coater, or the like so that the applied amount is 1 to 10 g / m ² (dry weight solid content), particularly preferably ² to 5 g / m ^2. A reversible thermosensitive layer is provided by coating and drying.

The reversible thermosensitive recording paper of the present invention is heated to
Color development and erasing are repeated, and in order to prevent deterioration of the reversible thermosensitive layer, a water-soluble polymer, latex or the like is applied to the upper layer of the reversible thermosensitive layer to provide a protective layer. Further, in order to further improve the color density, a porous white pigment, an organic polymer or the like is applied between the support and the reversible thermosensitive layer to provide an intermediate layer. Further, in order to improve the print density and the resolution thereof, it is preferable to smooth the surface of the reversible thermosensitive layer and the protective layer with a smoothing device such as a super calender and a soft calender.

[0020]

The preferred embodiments of the present invention and excellent effects will be specifically described below with reference to the most typical examples. The following parts are all parts by weight, and% means% by weight.

Example 1 [Preparation of recycled pulp from waste paper] Caustic soda 1 was added to 680 parts of water.
After dissolving the parts, 120 parts of commercial imitation waste paper was mixed, and 15% of the waste paper solid content was disaggregated with a lab high-concentration pulper for 20 minutes. Next, concentrate 15% of this waste paper solid content to 30%, and further use 1 part of caustic soda and 2 parts of sodium silicate as a builder.
Part, hydrogen peroxide 1.2 parts as a bleaching agent, deinking agent (Kao;
Add 0.08 part of the deinking agent 600R) and knead 1000 times with a lab PFI mill. After completion of the kneading, the waste paper dispersion was packed in a polyethylene bag and heated at 60 ° C. for 2 hours. The waste paper dispersion after the warm bath was diluted to 1.2% solids with water and subjected to flotation for 5 minutes with a lab flotator. During this period, the foam layer is scraped once every 90 seconds and 210 seconds. After the flotation, after washing on a 100-mesh wire net, the fiber length measured by a Kajaani fiber length measuring instrument (FS-200) was 0.6 with a double disc refiner.
mm, and beaten so as to have a freeness of 150 ml to obtain recycled pulp of waste paper. [Preparation of acidic paper using 20% recycled pulp] LBKP (fiber length 0.85 mm, freeness 350 ml) 60 parts NBKP (fiber length 0.84 mm, freeness 350 ml) 20 parts Waste paper recycled pulp 20 parts Talc 2 parts Rosin emulsion size 1 0.5 part Sulfate band 3 parts Amphoteric starch 1 part A 1% slurry of the above formulation was made into paper by a Fourdrinier paper machine, the wet paper obtained was pressed at 5 Kg / cm ² , and then 90 ° C.
And dried for 2 minutes to obtain an acid paper having a basis weight of 70 g / m ² . A 6% aqueous solution of oxidized starch was applied to this acidic paper in an amount of 1.2 g / m ²
A conventional size press was performed so as to obtain (dry weight solid content) to obtain an acid paper for reversible thermosensitive recording paper.

[Preparation of reversible thermosensitive recording paper] 3-di-n-butylamino-6-methyl-7-anilinofluorane 40 parts N- (4-hydroxyphenyl) -N′-octadecylurea 100 parts 10 % Polyvinyl alcohol aqueous solution 112 parts (Nippon Gosei Kagaku Kogyo Co., Ltd., Gohsenol NM-11) water 448 parts The above-mentioned mixed dispersion is ball-milled to have an average particle diameter of 1 μm.
The resulting mixture was pulverized to obtain a color developer / reversible color developer mixed pulverized liquid. After mixing 2.5 parts of 40% sodium polyacrylate aqueous solution with 100 parts of water, calcium carbonate (Shiraishi Industry Co., Ltd.)
Manufactured by Brilliant-15) was gradually added and dispersed, and then 300 parts of a 10% polyvinyl alcohol (NM-11) aqueous solution was mixed to obtain a white pigment dispersion. Coloring agent / reversible color developer mixed pulverized liquid: white pigment dispersion was mixed with diluting water so that the dry weight solid content ratio was 12.5: 3.5 to prepare an 18% reversible thermosensitive layer coating liquid. . This coating solution is applied to the above-fabricated acidic paper having a basis weight of 70 g / m ^{2 with} an air knife coater so that the coating amount is 3.5 g / m ² (dry weight solid content), and then supercalendering is performed. , A reversible thermosensitive layer. Furthermore, a 5% aqueous solution of polyvinyl alcohol (NM-11) is applied to the upper layer with an air knife coater so that the applied amount is 1 g / m ² (dry weight solid content), and then super calendar finish is applied to reversible heat sensitivity. I made a chart paper.

Example 2 1 part of caustic soda at the time of disaggregation in the production of recycled pulp from waste paper of Example 1, disaggregation time of 20 minutes, fiber length of 0.6 mm and freeness of 1.5 parts caustic soda of 1.5 parts, disaggregation time of 10 minutes, fiber length of 0 0.75 mm and freeness 250 ml
Acid paper was obtained in the same manner as above, and reversible thermosensitive recording paper was prepared. Example 3 Disaggregation time 20 in making waste paper recycled pulp of Example 1
Minute, solid content of waste paper dispersion during flotation 1.2
%, Fiber length 0.6 mm and freeness 150 ml, disaggregation time 10 minutes, solid content 0.6% of waste paper dispersion during flotation, fiber length 0.85 mm and freeness 150 m
Acid paper was obtained in the same manner except that the amount was changed to 1, and reversible thermosensitive recording paper was prepared.

Example 4 Disaggregation time 20 in the production of recycled pulp from waste paper of Example 1
Min, 1000 times kneading with PFI mill, fiber length 0.6 mm and freeness 150 ml, disaggregation time 10
Min, 2000 times of kneading with a PFI mill, a fiber length of 0.6 mm and a freeness of 150 ml were used to obtain an acid paper, and a reversible thermosensitive recording paper was prepared. Example 5 An acid paper was obtained in the same manner as in Example 1 except that the acid paper containing 20% recycled paper recycled pulp was replaced with the acid paper containing 80% recycled waste pulp having the following composition, and a reversible thermosensitive recording paper was prepared. . NBKP (fiber length 0.95 mm, freeness 400 ml) 20 parts Waste paper recycled pulp 80 parts Talc 2 parts Rosin emulsion size 1.4 parts Sulfate band 3 parts Amphoteric starch 1.2 parts

Comparative Example 1 Acidic paper was obtained in the same manner as in Example 1 except that the disaggregation time of 20 minutes in the production of recycled paper pulp was shortened to 10 minutes.
Further, a reversible thermosensitive recording paper was prepared. Comparative Example 2 Fiber length of 0.6 m in making recycled pulp from waste paper of Example 1
Acid paper was obtained by the same method except that m was 0.5 mm, and reversible thermosensitive recording paper was prepared. Comparative Example 3 Freeness 15 in making recycled pulp from waste paper of Example 1
Acidic paper was obtained by the same method except that 0 ml was changed to 100 ml, and reversible thermosensitive recording paper was prepared. Comparative Example 4 An acid paper was obtained in the same manner as in Example 1 except that the acid paper containing 20% recycled paper recycled pulp was replaced with an acid paper containing no recycled paper recycled pulp having the following composition, and a reversible thermosensitive recording paper was prepared. LBKP (fiber length 0.80 mm, freeness 300 ml) 90 parts NBKP (fiber length 0.84 mm, freeness 300 ml) 10 parts Talc 2 parts Rosin emulsion size 1.4 parts Sulfate band 3 parts Amphoteric starch 0.8 parts

Test Method (1) Measurement of Dirt Number and Total Area of Recycled Waste Paper Pulp 2% recycled waste paper prepared in Examples 1 to 4 and Comparative Example 1
The wet paper obtained by paper-making the slurry with a TAPII standard machine was pressed at 5 Kg / cm ² , and then 9
It was dried at 0 ° C. for 2 minutes to prepare a handmade paper having a basis weight of 70 g / m ² . This handmade paper is printed with a dry copier (Xerox).
It was transferred to a PC (copy paper) and a certain area was measured and quantified by transmitted light with a macro lens of an image analysis device (manufactured by Nicolet). With this macro lens, an area of 2.5 cm ²
Measured zero, appearing on PPC transfer image 0.08 mm ² or more and 0.03 mm ² or more dart number and total area mm ² / m ²
Table 1 shows the result of measurement.

(2) Measurement of Whiteness Handmade paper for measuring the dirt number of waste paper recycled pulp prepared in Examples 1 to 4 and Comparative Example 1 and Examples 1 to 5 and Comparative Examples 1 to 4
The reversible thermosensitive recording paper prepared in 1. was measured by a Hunter reflectance meter (manufactured by Toyo Seiki) and the results are shown in Tables 1 and 2.
The larger the value, the higher the whiteness. (3) Whiteness expressed by D value of reversible thermosensitive recording paper Table 2 shows the results measured by a densitometer (using RD100R / Amber filter manufactured by Macbeth Co., Ltd.). The smaller the value, the higher the whiteness. (4) Color density of word processor printing The color density printed by the high speed mode (density dial; max) of the word processor Shoin WD-A560 manufactured by Sharp Corporation was measured by a densitometer (same as above), and the results are shown in Table 2. The higher the value, the higher the print density.

(5) Decoloring property The sheet colored by the above word processor is passed through a heat roll at 110 ° C. to decolorize the coloring part, and the density of the decoloring part is measured by a densitometer (same as above). Shown in 2. The smaller the value, the better the erasability. (6) Repeatability The decolorized sheet is printed again under the same conditions as the above word processor. After the decoloring is repeated 10 times under the same conditions, the wavy curl (wrinkle) of the sheet is visually observed and evaluated by ○ and × marks. The results are shown in Table 2. O mark: Excellent without waviness ×
Signs are greatly inferior in waviness.

[0029]

[Table 1] : 0.08 mm ² or more co number of Dirt: 0.03 mm ² or more da - co number of bets

[0030]

[Table 2]

[0031]

INDUSTRIAL APPLICABILITY In a reversible thermosensitive recording paper in which a support such as paper is provided with a reversible thermosensitive layer, as is apparent from the present invention, the support is made of recycled pulp of 10% by weight or more of recycled pulp. Used, and the number average fiber length of the recycled pulp is 0.6 m
130 m / m ² when the dart number of the recycled pulp surface is 0.08 mm ² or more and the Canadian standard freeness at 20 ° C. is 150 ml or more.
By setting the total number of 0.03 mm ² or more to 1250 pcs / m ² or less, it is possible to provide a reversible thermosensitive recording paper for word processors and printers, which has almost no deterioration in whiteness and has excellent repeatability of coloring and decoloring. It was

Claims (1)

[Claims] 1. A reversible thermosensitive recording paper comprising a support such as paper containing a usually colorless to light-colored electron-donating dye and an electron-accepting acidic substance which causes the dye to undergo a reversible color change upon heating. The support uses 10% by weight or more of recycled pulp made from waste paper, the number average fiber length of the recycled pulp is 0.6 mm or more, the Canadian standard freeness at 20 ° C. is 150 ml or more, and the recycled pulp is 1 when the dirt number on the surface is 0.08 mm ² or more
30 pieces / m ² or less, total number of 0.03 mm ² or more is 125
A reversible thermosensitive recording paper, characterized in that it is 0 / m ² or less.