JPH0229375A - Pressure sensitive copy sheet - Google Patents

Abstract

PURPOSE:To improve coloring contamination, coloring capacity by using raw paper having specific value or more of chemical-mechanical pulp in all pulp composition and specific value or more of measured value of surface of the raw paper by a normal reflection type smoothness meter. CONSTITUTION:Raw paper having 5wt.% or more of chemical-mechanical pulp(CMP) in all pulp composition and 8% or more of measured value of surface of the paper by a normal reflection type smoothness meter under pressurizing condition of 20kg/cm<2> is used. Concrete example of the CMP includes, for example, chemical refiner ground pulp, chemical ground pulp, chemical thermomechanical pulp, etc., and among them bleached chemical thermomechanical pulp is particularly satisfactory due to high whiteness, strong paper strength and less bounded fiber. Smoothing process of the surface of the paper employs a supercalendar composed of a metal roll and an elastic roll, a gloss calendar, a soft calendar, etc., to be used effectively in an ON machine or an OFF machine.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to pressure-sensitive copying paper, and in particular, it is possible to effectively improve color stains without reducing coloring ability, and to improve printability and handling suitability during printing. This invention relates to improved pressure sensitive copying paper.

``Prior art'' Pressure-sensitive copying paper is known as ``top paper,'' which is a base paper coated with a layer containing microcapsules containing an electron-donating dye on one side.
, ``lower paper'' coated with a layer containing an electron-accepting compound (developer) that develops color by contact with an electron-donating dye, and a layer containing microcapsules coated on one side of base paper, and a layer containing microcapsules coated on the other side. "Medium leaf paper" coated with a layer containing a color developer, and furthermore "middle leaf paper" coated with a layer containing a color developer, and furthermore, "medium leaf paper" in which microcapsules and a color developer are layered or mixed on the same side of base paper.
"Self-coloring paper" is known, and these are used in appropriate combinations.

``Problems to be Solved by the Invention'' However, there is still room for improvement in practical aspects of these pressure-sensitive copying papers.

One of the drawbacks is that colored stains may occur on the surface coated with the color developer due to unwanted friction other than the pressure of writing or typing with a typewriter. For this reason, there are methods of adding water-soluble polymers to paints [JP-A-62-198492], methods of adding latex [JP-A-61-188184], and methods of adding lubricants such as calcium stearate [JP-A-62-198492]. Kaisho 6
Although improvements such as No. 1-266291] have been proposed, satisfactory results have not always been obtained because improvements in color-forming stains are accompanied by new defects such as a decrease in color-forming ability.

In particular, since the color-forming stain and color-forming ability of pressure-sensitive copying paper are contradictory characteristics, it is extremely difficult to improve both in a well-balanced manner, and there is a strong demand for improvement.

In addition, when copy sheets are stacked as sheet sheets, the sheets are difficult to slip (and are not suitable for handling).Furthermore, when printing on recording sheet 1-, the paint on the top and bottom sheets is not smeared. When printing on the surface, that is, the surface of the base paper, there is also the drawback that the receptivity to printing ink is poor and sufficient printing effects cannot be obtained.

As a result of intensive research into improving the above-mentioned drawbacks, the inventors of the present invention discovered that these drawbacks are largely caused by the characteristics of the base paper that makes up the pressure-sensitive copying paper, especially the characteristics of the valves that make up the base paper. Ta.

In other words, chemical valves (hereinafter referred to as CP) with a valve yield of 40 to 50% have traditionally been used as valves constituting base paper, but even if the beating conditions and paper-making conditions are adjusted variously, Although we were not able to obtain satisfactory results, we added a chemical mechanical valve with a valve yield of about 75 to 90%, and the smoothness of the base paper surface measured with a special smoothness meter was adjusted to a specific value. The present inventors have discovered that, when adjusted, the color stains on copy paper using the base paper can be effectively improved without reducing the coloring ability, and the handling suitability and printing suitability are also improved, leading to the completion of the present invention.

"Another Means to Solve the Problem" The present invention incorporates chem-mechanical pulp into the entire valve composition.
A pressure-sensitive copying paper characterized by using a base paper containing at least 8% by weight and whose surface measured with a specular reflection smoothness meter is at least 8% under a pressure condition of 20 kg/cd. be.

"Function" The pressure-sensitive copying paper of the present invention contains 5% by weight of chemical mechanical pulp (hereinafter referred to as CMP) in the total pulp composition as a base paper.
As mentioned above, it is preferable to use a base paper having 10% by weight or more of agglomerates, but due to the addition of CMP, the compressive elastic modulus of the base paper is higher than that of paper made of 100% CP, and the friction pressure is buffered. It is presumed that colored stains on the color developer coated surface caused by undesired frictional pressure can be effectively improved. Incidentally, if the CMP content is less than 5% by weight, a sufficient improvement effect cannot be expected.

Specific examples of CMP include chem refiner ground valves, chem ground valves, chem thermomechanical valves, etc. Among them, bleached chem thermomechanical valves (hereinafter referred to as BCTMP), which are highly bleached chem thermomechanical, are white. It is particularly preferably used because it has a high paper strength and low binding fibers.

Note that if the whiteness of CMP is low, the whiteness of the resulting pressure-sensitive copying paper will decrease, the sharpness of the color image will be lost, and the appearance will deteriorate, so the whiteness of CMP (JIS P 8123) is 8.
It is desirable that it is 0% or more. In addition, if the amount of bundled fiber pieces (undisintegrated fiber bundles in the bulb) included in CMP exceeds 500'r/g, the smoothness of the base paper surface will be significantly reduced. Therefore, it is desirable to perform reflex inner processing in the front process of the paper machine.

For Ref 1 Inner processing, a single-day souffle refiner is more effective than the beater 1:1 Nical Ref Refiner and double-disease refiner used in processing such as CP, and the valve concentration during processing depends on efficiency and power consumption. Considering these factors, it is desirable to have 2-5% approval.

The pressure-sensitive copying paper of the present invention contains <5% by weight of CMP as described above.
A base paper containing the above content is used, but the surface of the base paper is further tested with a specular reflection type smoothness meter (measurement pressure: 20 kg/
cs") is 8% or more, more preferably 14
% or more.

Here, the specular reflection type smoothness meter is a device that measures the smoothness of paper by pressing it against the glass surface under constant pressure conditions.According to the detailed study results of the inventors, - It is not affected by the air permeability of the paper, unlike the Beck smoothness meter and Barker Print Surf, which are air leakage type smoothness measuring instruments, and provides measurement values that are highly correlated with actual smoothness. Furthermore, it has become clear that the desired effects of the present invention can be determined very appropriately from the measured values with this specular reflection type smoothness meter (measurement pressure: 20 kg/as"), and it is hoped that the present invention will be completed. reached.

By the way, a specular reflection type smoothness meter (measurement pressure: 20
If the measured value in kglon'' is less than 8%, it is not possible to effectively improve colored stains caused by undesired frictional pressure even if CMP is contained in the base paper in an amount of 5% by weight or more.

For smoothing the surface of base paper, a machine calender consisting only of metal rolls installed at the rear of the paper machine can also be used; It is effective to use a calendar etc. on-machine or off-machine.

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

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

The elastic rolls described above are softer than ordinary elastic rolls and tend to generate heat even under stable operating conditions, and this tendency is particularly noticeable in elastic rolls made of urethane rubber. The physical properties of the elastic body become unstable due to the heat generation phenomenon, and in extreme cases, the elastic body itself may be damaged by melting due to the accumulated heat. This is a preferred embodiment, and various measures such as cooling from the outside, changing the diameter of the roll, and changing the thickness of the elastic body are adopted as appropriate.

The on-machine super calender and on-machine soft calender, which are composed of metal rolls and elastic rolls, are featured in the August 1988 issue (page 31) and May 1988 issue (page 10) of the Gio Pulp Technology Times. Introduced. Further, processing conditions are appropriately adjusted depending on the number of nips, nip linear pressure, machine speed, etc.

The base paper obtained is then coated with a microcapsule-containing coating liquid or a color developer-containing coating liquid according to a conventional method to produce "upper paper".
It can be finished as "upper paper", "middle paper", "self-coloring paper", etc., but there are no particular restrictions on the method of applying the coating liquid, such as air knife coater, roll coater, flade coater, ronto coater, curtain coater, etc. 2 to 1Qg/rn” in dry weight using a suitable coating device such as a coater
A certain amount of coating liquid is applied and dried.

The microcapsule-containing coating liquid is used for boat fishing by combining basic dyes such as tri'7-lylmethane lactones, spiropyrans, fluorans, diphenylmethanes, and azines with alkylated naphthalene, alkylated diphenyl, alkylated diphenylmethane, It is dissolved in a solvent consisting of synthetic oil such as alkylated terphenyl, vegetable oil such as cotton oil and castor oil, animal oil, mineral oil, or a mixture thereof, and various methods such as coacervation method, interfacial polymerization method, 1n-situ method, etc. It is prepared by including it in microcapsules using a capsule manufacturing method and dispersing it in a binder.

In addition, color developer-containing coating liquids include - For boat fishing, inorganic color developers such as acid clay, activated clay, attapal guide, various aliphatic carboxylic acids, benzoic acid, p-tert-butylbenzoic acid,
Phthalic acid, benzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-phenylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-methyl-5-benzylsalicylic acid, 3-phenyl-5-( α.

α-dimethylbenzyl)salicylic acid, 3,5-di(α
-methylbenzyl)salicylic acid, 2-t4'roxy1
- aromatic carboxylic acids such as benzyl-3-naphthoic acid,
Organic color developers such as phenolic resins such as p-phenylphenol-formalin resin and p-butylphenol-acetylene resin, and furthermore, these organic color developers and, for example, zinc,
It is prepared by dispersing various color developers, such as salts with polyvalent metals such as magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, in a binder.

Examples of binders include starches, celluloses, proteins, gum arabic, polyvinyl alcohol, styrene-maleic anhydride copolymer salts, styrene-butadiene copolymer emuldicine, acetic acid and maleic anhydride copolymer salts, and polyvinyl acetate. Acrylates and the like are appropriately selected and used.

For pressure-sensitive copying paper, see, for example, U.S. Pat. No. 2,505.
No. 470, No. 2.505.471, No. 2.505.4
No. 89, No. 2, 548.366, No. 2,712.50
No. 7, No. 2,730.456, No. 2.730.457
There are various forms as described in No. 3,418.250, No. 3,924.027, No. 4,010,038, etc., and the present invention is directed to the sensitivity of these various forms. This can be applied to pressure copy paper.

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

Further, "parts" and "%" in the middle indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 Whiteness (JIS P 8123) 83%, 0.1
Amount of bundled fiber pieces larger than ``vna'' is 3001 parts g
BCTMP (manufactured by Tescell Inc., 75% aspen material, 25% subluice material) was treated with a single disc refiner at a pulp concentration of 4% to adjust the amount of bundled fiber pieces to 500 pieces/g.

Double discret refiner in BCTMPS section after processing
LBKP7 each beaten to freeness 500cc with
Talc was added to the pulp suspension obtained by blending 5 parts of NBKP and 20 parts of NBKP so that the ash content was 6%, and 1.4% of rosin size was added as a sizing agent based on the bone dry pulp.

After adjusting the pH of this pulp slurry to 4.6 with a sulfuric acid band, paper was made using a long multi-cylinder cylinder dryer 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 to make it rrr, process it with a machine calender and make the basis weight 40g/
rtr, measured value with a specular reflection type smoothness meter (pressure condition 20k
A base paper for pressure-sensitive copying paper having a g/d) of 9% was obtained.

[Creation of top sheet]

Add 112.5 parts of water to 37.5 parts of a 20% aqueous solution of a copolymer consisting of 15 mol% vinyl sulfonic acid, 5 mol% styrene, 70 mol% acrylic acid, and 10 mol% ethyl acrylate, and add 20% NaOH aqueous solution. The p)l was adjusted to 4.6 and used as an aqueous medium for capsule production.

To this was added 105 parts of diisopropylnaphthalene (trade name, Ni-113, manufactured by Kureha Chemical Co., Ltd.) in which 5 parts of crystal violet lactone was dissolved, and after emulsifying and dispersing it so that the average particle size was 5 μm, the temperature of the emulsion was lowered. The temperature was raised to 70°C.

Next, 20 parts of methylated methylolmelamine precondensate (trade name: Beckamine APM, 80% concentration, manufactured by Dainippon Ink Chemical Co., Ltd.) was added to the system, and the temperature of the system was maintained at 70°C for 1 hour while stirring was continued. After cooling, a milky white capsule dispersion was obtained.

A capsule coating liquid prepared by adding 70 parts of wheat starch and 20 parts of dissolved oxidized starch (solid content) to this capsule dispersion liquid was coated on the above-mentioned base paper to a dry weight of 4 g/rd and dried to form a pressure-sensitive copying paper. I created a paper for the paper.

[Creation of bottom leaf paper and middle leaf paper]

65 parts of aluminum hydroxide, 20 parts of zinc oxide, 3.5-
Mixture of zinc di(α-methylbenzyl)salicylate and α-methylstyrene/styrene copolymer (melt ratio 80/
20) Prepared by adding 20 parts (solid content) of carboxy-modified styrene-butadiene copolymer latex to a dispersion obtained by grinding 15 parts of polyvinyl alcohol aqueous solution (solid content) and 300 parts of water in a ball mill for 24 hours. The developer coating solution prepared above was applied to the above-mentioned base paper and dried to a dry weight of 5 g/rtr, followed by calendering to prepare a lower sheet for pressure-sensitive copying paper.

Next, the capsule coating solution was applied to the surface opposite to the developer-coated surface of the bottom sheet and dried to give a dry weight of 4 glrd to prepare a middle sheet for pressure-sensitive copying paper.

A performance comparison test was conducted using the top paper, middle paper, and bottom paper thus obtained, and the results are listed in the table.

Example 2 BCT M P (manufactured by Temcell Inc., aspen material 75%, subluce) with a whiteness (JIS P 8123) of 83% and an amount of bound fiber pieces with a size of 2 or more per day of 3000 pieces/g 25% product) to pulp density 4
% in a single disc refiner to adjust the amount of bundled fiber pieces to 300 pieces/g.

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

After adjusting the pH of this pulp slurry to 4.6 with sulfuric acid band, paper was made using a 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, then press the metal roll and elastic roll (Shore D hardness 91
Processed with an on-machine calendar consisting of 1 tsubo
A base paper for pressure-sensitive copying paper was obtained which had a value of 140 g/m and a value measured with a specular reflection type smoothness meter (pressure condition 20 kg/aJ) of 16%.

Top paper, middle paper, and bottom paper were prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted on them, and the results are listed in the table.

Example 3 BCTMP (manufactured by Ten+cell Inc., 75% aspen material, 25% subluice material) with a whiteness (JIS P 8123) of 83% and an amount of bundled fiber pieces with a size of 0.1 Tsuru2 or more of 2000 pieces/g. % product) with a pulp concentration of 4%
The fibers were treated with a single disc refiner to adjust the amount of bundled fiber pieces to 100 pieces/g.

To a pulp suspension obtained by blending 75 parts of BCTMP after treatment with 25 parts of N.BKP beaten to 500 cc of freeness using a double disk refiner, talc was added to a low ash content of 6%, and rosin size was added as a sizing agent. was added in an amount of 1.4% based on the bone-dry bulb.

After adjusting the pH of this valve slurry to 4.6 with a sulfuric acid band, paper was made using a multi-tube 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 slurry. /nf, and then press the metal roll and elastic roll (Shore D hardness 91
A base paper for pressure-sensitive copying paper having a basis weight of 40 glrd and a value measured with a specular reflection type smoothness meter (pressure condition 20 kg/cd) of 18% was obtained. .

Top paper, middle paper, and bottom paper were prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted on them, and the results are listed in the table.

Example 4 Whiteness (JIS P 8123) 77%, 0.1m
BCT M P (manufactured by Temcell Inc., 100% stainless steel material) with a size of 2,500 f/g or more is treated with a single disc refiner at a pulp concentration of 4% to obtain bundled fiber pieces. quantity 400
It was adjusted to

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

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 Tamago Cornstarch Co., Ltd.) was added to the slurry. /rrf, then press the metal roll and elastic roll (Shore D hardness 8
Base paper for pressure-sensitive copying paper processed with an on-machine calender (7 degrees) and has a basis weight of 40 g/d and a value measured with a specular reflection type smoothness meter (pressure condition 20 kg/CIA) of 16%. I got it.

Top paper, middle paper, and bottom paper were 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 listed in the table.

Example 5 BCTMP (manufactured by Temcell 1.ne, made by Temcell 1.ne, 20% asben material, subluce material) with a whiteness (JIS P 8123) of 82% and an amount of bundled fiber pieces of 0.1 Tsuru 1 or larger size of 2500 care g 80% product) to 4% bulb concentration
The fibers were treated with a single disc refiner to adjust the amount of bound fiber pieces to 1000 care g.

After treatment, 10 parts of BCTMP are each beaten to a freeness of 500 cc using a double disc refiner.
Talc was added to a valve suspension obtained by blending 70 parts of KP and 20 parts of NBKP so that the 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 the second valve slurry to 4.6 with a sulfuric acid band, paper was made using a fourdrinier cylinder dryer paper machine, and an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Tamago Cornstarch Co., Ltd.) was added in 1. It is size pressed to a weight of 5g/-, and then processed with an on-machine calendar consisting of a metal roll and an elastic roll (Shore D hardness 78 degrees) to a basis weight of 4.
A base paper for pressure-sensitive copying paper was obtained which had a value of 0 g/rd and a value measured with a specular reflection type smoothness meter (pressure condition: 20 kg/cnf) of 10%.

Top paper, middle paper, and bottom paper were prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted on them, and the results are listed in the table.

Example 6 Whiteness (JIS P8123) 83%, 0.1mm
BCT M P (manufactured by Temeell Inc., 75% aspen material, 25% stainless steel material) with a bundled fiber piece amount of 3000 care g of the size larger than 1.
% in a single disc refiner to adjust the amount of bundled fiber pieces to 3'00 care g.

BCTMP after treatment: 10 parts of LBK each beaten to a freeness of 500 cc using a double disc refiner
A pulp suspension obtained by blending 70 parts of P and 20 parts of NBKP was added with heavy calcium carbonate (trade name: Laughton 1).
20O, manufactured by Teihoku Funka Co., Ltd.) was added so that the ash content was 6%, and sulfuric acid was added at 0°5% relative to the bone dry valve.
0.5% of cationic starch (trade name, CATO-F, manufactured by Tamago National Co., Ltd.) was added to the bone-dry bulb, and alkyl ketene dimer (trade name,
SPK902. After adding 0.2% of oxidized starch (manufactured by Kanyo Kagaku Co., Ltd.) to the bone-dry pulp, paper was made using a fourdrinier multi-tube cylinder dryer paper machine, and an aqueous solution of oxidized starch (trade name: Ace A, manufactured by Tamago Cornstarch Co., Ltd.) was added. It is size-pressed to 1.5 g/rrf, processed with an on-machine calendar consisting of a metal roll and an elastic roll (Syria hardness: 91 degrees), and then processed into a size of 1.5 g/rrf. A base paper for pressure-sensitive copying paper was obtained which had a value of 40 g/rtl and a value measured with a specular reflection type smoothness meter (pressure condition: 20 kg/cd) of 15%.

Top paper, middle paper, and bottom paper were prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted on them, and the results are listed in the table.

Example 7 Whiteness (JIS P 8123) 83%, Q, 1m
BCT M P (manufactured by Temeell Inc., product with 75% asben material and 25% stainless steel material) having a binding fiber piece amount of 3000 care g with a size of
% in a single disc refiner to adjust the amount of bundled fiber pieces to 300 pieces/g.

LBK beaten to a freeness of 500 cc using a double disc refiner in the BCTMPIO section after processing.
To a pulp suspension obtained by blending 70 parts of P and 20 parts of NBKP, talc was added so that the ash content was 6%, and the rosin size was added to 1.4% based on the bone-dry pulp by coarsely sizing. did.

The pH of this valve slurry was adjusted to 4°6 with a sulfuric acid band, and then paper was made using a round-mesh monotube Yankee dryer paper machine to obtain a paper with a basis weight of 40 g/ld and a value measured with a specular reflection type smoothness meter (
Pressure condition (20kg/cd) is 30% on the cast side and 1 on the back side.
A base paper for pressure-sensitive copying paper having a concentration of 0% was obtained.

Top paper, middle paper, and bottom paper were prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted on them, and the results are listed in the table.

Comparative Example 1 Double Disc I/Finer, each freeness 5
A base paper for pressure-sensitive copying paper was obtained in the same manner as in Example 1, except that a valve suspension consisting of 80 parts of LBKP and 20 parts of NBKP beaten to 0.00 cc was used. Measurement value of this base paper with a specular reflection type smoothness meter (pressure condition i 20 kg
/esi”) was 9%.

Top paper, middle paper, and bottom paper were prepared in Example 17 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 listed in the table.

Comparative Example 2 BCT M P with a whiteness (JIS P 8123) of 78% and an amount of bundled fiber pieces with a size of 0.1 Tsuru 2 or more of 3500 pieces/g (manufactured by Tea+cell Inc., 100% stainless steel product) 10 parts of L were each beaten to a freeness of 500 cc using a double-day souffle refiner.
A base paper for pressure-sensitive copying paper was obtained in the same manner as in Example 1, except that a valve suspension obtained by blending 70 parts of BKP and 20 parts of NBKP was used. The measurement value of this base paper with a specular reflection type smoothness meter (pressure conditions: 20 kg/cm") is 7%.
Met.

Top paper, middle paper, and bottom paper were prepared in the same manner as in Example 1 except that this base paper was used, and a performance comparison test was conducted on them, and the results are listed in the table.

[Color development test]

Layer the middle paper and the bottom paper so that the capsule coated side of the middle paper and the developer coated side of the bottom paper face each other, and roll them for 600k.
The density of the color image obtained by applying a load of g/- was measured using a Macbeth densitometer (Model RD-914, Filter Visual).

[Color development stain test] Layer the middle paper and the bottom paper so that the capsule coated side of the middle paper and the developer coated side of the bottom paper face each other, and apply 4kg/-
The degree of colored staining on the surface coated with the color developer was determined by rubbing the surface 5 times under a load of .

"Evaluation criteria" ◎The gate is almost always clean.

○: Slightly dirty.

×: Significantly dirty.

[Printability]

Using a Mei Seisakusho 1 tester, 0.1.
cc printing was performed to determine ink acceptability.

"Evaluation criteria" ◎: Extremely good.

○; Good.

×; Bad.

[Appearance test]

The sharpness of the colored image obtained in the color development test was visually judged.

"Evaluation criteria" ◎: Extremely good.

O: Good.

×; Bad.

Table ``Effects'' As is clear from the results in the table, the pressure-sensitive copying paper obtained in the examples of the present invention has an extremely well-balanced (improved) appearance and handling ability in color development stains and color development ability. August 18, 1988 The suitability was good, and the acceptability of printing inks was also excellent.

Claims (2)

[Claims] (1) Base paper containing 5% by weight or more of chemical mechanical pulp in the total pulp composition, and the value measured by a specular reflection type smoothness meter on the base paper surface is 8% or more at a pressure condition of 20 kg/cm^2. Pressure-sensitive copying paper characterized by its use. (2) The pressure-sensitive copying paper according to claim (1), wherein the chemi-mechanical pulp is bleached chemi-thermomechanical pulp.