JPH01288479A - Manufacture of original for pressure-sensitive recording sheet - Google Patents

Abstract

PURPOSE:To improve contamination of coloring performance due to unintended pressure without sacrifice of coloring capacity, by passing a paper through pressure nips comprising a metal roll and an elastic roll having specific hardness such that the smoothness on the surface of an original paper measured through a positive reflection smoothness meter will be higher than a predetermined level thus smoothing the surface of the original paper. CONSTITUTION:An elastic roll to be employed for smoothing an original paper is composed of an elastic member having Shore D hardness, regulated through ASTM regulation D-2240, of 42-98. A metallic roll constituting a pressure nip together with the elastic roll can be selected with no limitation. When the original paper is passed through the pressure nip, pressurizing conditions are regulated corresponding to various processing conditions including the hardness of the elastic roll to be employed, the type of the recording sheet, the paper pass speed, the temperature of the metallic roll, and the like. Since desired effect can not be achieved if the nip line pressure is lower than 20kg/cm, the surface of the original paper must be smoothed such that the smoothness measured through a positive reflection smoothness meter (measuring pressure; 20kg/cm<2>) is higher than 10% and preferably higher than 14%. In case of upper or lower sheet, the surface to be applied with paint is preferably contacted with the elastic roll.

Description

Detailed Description of the Invention: "Industrial Application Field" The present invention relates to a method for manufacturing base paper for pressure-sensitive recording sheets, and in particular, it is possible to effectively improve color development stains without reducing the color development ability, and to improve printing during printing. The present invention relates to a method for processing base paper that can extremely efficiently produce pressure-sensitive recording sheets with improved suitability and handling suitability.

``Prior art'' Pressure-sensitive recording sheets include ``top paper,'' which is a base paper coated with a layer containing microcapsules containing an electron-donating dye on one side; "Bottom paper" is coated with a layer containing a receptive compound (color developer), "middle paper" is coated with a layer containing microcapsules on one side of base paper, and a layer containing color developer is coated on the other side. Furthermore, "self-coloring paper" in which microcapsules and color developer are laminated or mixed on the same side of base paper is known, and these are used in appropriate combinations.

In particular, a pressure-sensitive recording sheet known as carbonless paper or pressure-sensitive copying paper is disclosed in US Pat. No. 2,711,375.

It is described in Japanese Patent Publication No. 2,730.457, Japanese Patent Publication No. 47-20972, etc., and has been widely put into practical use.

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

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, methods such as the method of adding a water-soluble polymer to the paint (Japanese Patent Application Laid-Open No. 62-198492), the method of adding latex [Japanese Patent Application Laid-open No. 61-188184], and the step
Improvements such as adding a lubricant such as calcium phosphate [Japanese Patent Application Laid-open No. 61-266291] have been proposed, but new defects such as a decrease in coloring ability accompany the improvement of coloring stains. Satisfactory results have not always been obtained.

In particular, since the color-forming stain and color-forming ability of the pressure-sensitive recording sheet 1- are contradictory characteristics, it would be extremely fraudulent to improve both in a well-balanced manner, and such improvement is strongly required.

In addition, when the recording sheets are piled up as sheets, they are difficult to slip and are not suitable for handling.Furthermore, when marking 11 on the recording sheets, the surfaces of the top and bottom sheets that have not been smeared with paint In other words, when printed on the base paper surface, the receptivity of printing ink is poor (it also has the disadvantage that sufficient printing effects cannot be obtained).

As a result of intensive research into improving the above-mentioned drawbacks, the inventors of the present invention have found that these drawbacks are largely caused by the characteristics of the base paper that constitutes the pressure-sensitive recording sheet, and in particular, machine calendaring, etc., which have conventionally been applied to such base paper, etc. It has been found that treatments using a smoothing device, a Yankee dryer, etc. do not give satisfactory results even after various adjustment of the processing conditions.

Based on this knowledge, we conducted further intensive research on the processing method for base paper for pressure-sensitive recording sheets.As a result, we developed a method for processing base paper for pressure-sensitive recording sheets, and as a result, we developed a method for processing base paper for pressure-sensitive recording sheets. When base paper is flattened using a special pressure nip made up of elastic rolls with a specific Shore D hardness, coloring stains on recording sheets made from the base paper due to unwanted pressure reduce the coloring ability. Kotona (
The present inventors have found that the present invention can be effectively improved, and that the handling suitability and printing suitability can also be improved.

"Means for Solving the Problem" The present invention is based on a metal roll and a 42 to 98 degree shore so that the measured value of the base paper surface with a specular reflection type smoothness meter is 10% or more under a pressure condition of 20 kg/-. D hardness (A37M standard, D
This is a method for producing a pressure-sensitive recording sheet Kawahara paper, which is characterized by flattening the paper by passing it through a pressure nip constituted by an elastic roll having a diameter of -2240).

"Operation" The elastic roll used for flattening the base paper in the method of the present invention is made of an elastic material having a Shore D hardness of 42 to 98 degrees as defined in the A37M standard and D-2240, as described above. Consists of.

An elastic roll that is softer than 42 degrees requires excessive nip pressure in order to obtain sufficient surface smoothness of the base paper, which significantly shortens the life of the elastic body itself during operation. However, with elastic rolls harder than 98 degrees, it is difficult to obtain appropriate surface smoothness, so elastic rolls with Shore D hardness of 42 to 98 degrees, more preferably 70 to 95 degrees, are selectively used. be done.

The elastic body constituting such an elastic roll is not particularly limited as long as its hardness falls within the above specific range, and examples include natural rubber, styrene rubber, nitrile rubber, chloroprene rubber, corosulfonated ethylene rubber, Various plastic resins such as butyl rubber, polysulfide rubber, silicone rubber, fluorine rubber, urethane rubber, aromatic polyamide resin, polyimide resin, polyether resin, polyester resin, polycarbonate resin, cotton, paper, wool, Tetron, nylon, or these A specific example is a mixture of the following.

Among them, urethane rubber, aromatic polyamide resin, a mixture of vapor and wool (wool-n-baber), 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 preferable. In particular, an elastic roll using urethane rubber and an aromatic polyamide resin is most preferably used because it is easy to handle, has a long roll life, and efficiently exhibits the desired effects of the present invention.

The elastic rolls used in the present invention as described above are softer than ordinary elastic rolls, so they 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 includes external cooling, changing the roll diameter,
Various measures, such as changing the thickness of the elastic body, are adopted as appropriate.

The elastic rolls and metal rolls that make up the pressure nip are not particularly limited, and may include chilled rolls, alloy chilled rolls, copper-iron rolls used in flattening processing equipment such as normal super calenders and gross calenders, and even roll surfaces. A hard chrome-plated metal roll or the like is appropriately selected and used. In addition, the form of the pressurizing device, the number of pressurizing nips, etc. are appropriately adjusted according to a normal flattening processing device.

The pressure conditions when passing the base paper through the pressure nip depend on various processing conditions such as the hardness of the elastic roll used, the type of recording sheet, paper passing speed, number of nips, and temperature conditions of the metal roll. The nip linear pressure is adjusted as appropriate, but if the nip linear pressure is 20k
If it is lower than 400 g/am, it is difficult to obtain the desired effect.
If it exceeds 20 to 400 kg/cm, the heat generation phenomenon of the elastic roll itself will increase, making stable operation difficult.
It is desirable to adjust within a range of about cm.

Therefore, in the method of the present invention, the surface of the base paper after the flattening process has a value of 10% or more, more preferably 14% or more, as measured by a specular reflection type smoothness meter (measurement pressure: 20 kg/am"). However, the specular reflection type smoothness meter referred to here is a device that measures the smoothness of paper by pressing it against the glass surface under constant pressure conditions, and is a device that measures the smoothness of paper by pressing it against the glass surface under constant pressure conditions. According to the results, it is not affected by the air permeability of paper like the Beck smoothness meter and Parker Brint Surf, which are air leakage type smoothness measuring instruments used on boats, and has a close correlation with the actual smoothness. Excellent measurement values can be obtained, and
This specular reflection type smoothness meter (measurement pressure: 2Q kg/cm"
) It has become clear that the desired effect of the present invention can be determined very appropriately by the measured values, and the present invention has been completed.

Note that depending on the quality characteristics required for the recording sheet, the metal roll may be heated. In that case, the temperature of the metal roll is higher than the temperature of the base paper at 80°C or higher, preferably 110°C or higher. heated to. For heating the roll, a method using a medium such as electricity, steam, water, oil, etc. is appropriately selected and used.

When passing the base paper through the pressure nip, the wire side of the base paper,
There is no particular limitation as to which side of the felt should be brought into contact with the elastic roll, but in the case of top paper or bottom paper, it is preferable that the surface to be coated with the paint should be brought into contact with the elastic roll.

In the method of the present invention, a metal roll and a specific shore D
A pressure nip composed of an elastic roll having hardness is used as a pressure nip in a suitable flattening device such as a super calender or a soft calender, but is especially suitable for an on-machine super calender or an on-machine soft calender. It is preferable to employ it as a pressurizing device. The on-machine super calendar and the on-machine soft calendar are introduced, for example, in the August 1988 issue (page 31) and the May 1988 issue (page 10) of Paper and Pulp Technology Times.

The base paper that has been subjected to the flattening treatment is then coated with a microcapsule-containing coating liquid or a color developer-containing coating liquid in accordance with conventional methods to produce "top paper,""bottompaper,""middlepaper,""self-coloringpaper," etc. However, the method of applying the coating liquid is not particularly limited, and for example, an air knife coater, a roll coater, a plate coater, a rod coater, a curtain coater, etc.
A coating liquid of about g/d is applied and dried. In addition, "Shimohagami"
In this case, a flattening process using a supercalender or the like may be further performed if desired.

Coating liquids containing microcapsules are generally prepared by combining basic dyes such as realylmethane lactones, spiropyrans, fluorans, diphenylmethanes, and azines with alkylated naphthalenes, alkylated diphenyls, alkylated diphenylmethanes, and alkyl dyes. It is dissolved in a solvent consisting of synthetic oil such as terphenyl ester, vegetable oil such as cotton oil or castor oil, animal oil, mineral oil, or a mixture thereof, and various methods such as coacervation method, W solid state method, and 1n-situ method are used. 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 generally include inorganic color developers such as acid clay, activated clay, and attapulgide, various aliphatic carboxylic acids, benzoic acid, p-t, ert-butylbenzoic acid, and phthalic acid. , gallic acid, salicylic acid, 3-isopropylsalicylic acid, 3-phenylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5-tert-butylsalicylic acid, 3-methyl-5-benzyllilysalicylic acid, 3
-phenyl-5-(α.

α-dimethylbenzyl)salicylic acid, 3,5-di(α
-methylbenzyl)salicylic acid, 2-hydroxy-1-
Aromatic carboxylic acids such as benzyl-3-naphthoic acid, p
- Organic color developers such as phenolic resins such as phenylphenol-formalin resin and p-butylphenol-acetylene resin;
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, cellulose, protein M, gum arabic, polyvinyl alcohol, styrene-anhydrous 71 Twin M1 combined salt, styrene-butadiene copolymer emulsion, acetic acid and maleic anhydride copolymer salt, and polyacrylic. Acid salts and the like are appropriately selected and used.

Regarding pressure-sensitive recording sheets, for example, U.S. Pat.
No. 5.470, No. 2.505.471, No. 2,505
, No. 489, No. 2,548,366, No. 2,712,
No. 507, No. 2,730,456, No. 2,730,4
No. 57, No. 3,418.250, No. 3,924゜02
There are various types of pressure-sensitive recording stickers as described in No. 7 and No. 4,010,038, and the present invention can be applied to these various types of pressure-sensitive recording stickers.

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

In addition, "part J" and "%" in the examples indicate "1-fold Y part" and "heavy breakage %", respectively, unless otherwise specified.

Example 1 [Preparation of base paper] On-machine soft calender with a pressure nip consisting of a hard claw 1, a metal roll with a diameter of 420 mm with a peeled surface, and an elastic roll with a diameter of 400 M and a Chicor D hardness of 78 degrees. Pressure-sensitive recording sheet base paper (40 g/rrf) with a measurement value (pressure condition of 20 kg/cTA) using a reflection type smoothness meter of 8% was flattened using a grain pressure of 80%.
(kg/cm) A base paper for a pressure-sensitive recording sheet having a specular reflection type smoothness of 20% was prepared.

[Preparation of upper paper] 112.5 parts of water is added 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. was added and the pH was adjusted to 4.6 with a 5.20% NaOH aqueous solution, which was 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 Bio I/Tutolactone had been dissolved, and after emulsifying and dispersing it so that the average particle size was 5 μm, the emulsion was The temperature was raised to 70°C.7 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 stirring was continued.j7 The temperature of the system was maintained at 70°C for 1 hour, and then cooled to obtain a milky white capsule dispersion.

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

(Creation of bottom paper and middle 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) Add 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 to a dry weight of 5 g/rrr and dried, followed by calendering to prepare a lower paper for a pressure-sensitive recording sheet.

Next, the capsule coating liquid was applied to the surface opposite to the color developer-coated surface of the bottom paper so as to have a dry weight of 4 g/rrf and dried to prepare a middle paper for a pressure-sensitive recording sheet.

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 Shore D elastic roll of on-machine soft calender
Changed to an elastic roll with a hardness of 87 degrees and set the nip pressure to 160 kg.
A base paper for a pressure-sensitive recording sheet having a specular reflection type smoothness of 18% was prepared in the same manner as in Example 1, except that the thickness was set to 18%. I made leaf paper, middle leaf paper, and bottom leaf paper.

Example 3 Shore D elastic roll of on-machine soft calender
Changed to an elastic roll with a hardness of 91 degrees and increased the nip pressure to 91 kg/
A base paper for a pressure-sensitive recording sheet having a specular reflection type smoothness of 12% was prepared in the same manner as in Example 1, except that the thickness was changed to cm. paper,
I created the middle leaf paper and the lower leaf paper.

Comparative Example 1 A base paper for a pressure-sensitive recording sheet having a specular reflection type smoothness of 12% was prepared using a regular machine calender consisting of a combination of chilled rolls instead of an on-machine soft calender, and the resulting base paper was used. Top paper, middle paper, and bottom paper were prepared in the same manner as in Example 1, except for the following.

Comparative example 2, the nip pressure of the on-machine soft calender was Okg/
A base paper for a pressure-sensitive recording sheet having a specular reflection type smoothness of 9% was prepared in the same manner as in Example 1, except that the thickness was changed to cm. Paper, middle leaf paper, and bottom leaf paper were created.

[Color development test] Layer the middle paper and the bottom paper so that the capsule-coated surface of the middle paper and the developer-coated surface of the bottom paper face each other, and heat for 600 k.
The density of the color image obtained by applying a load of g/ctM was measured using a Macbeth densitometer (model RD-914, Filter Visual).
It was measured with

[Color 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/c.
The degree of colored stain on the surface coated with the developer was determined by scrubbing five times under a load of +fl.

"Evaluation criteria" ◎; is hardly dirty.

Δ: Slightly dirty.

×: Significantly dirty.

[Printing suitability] Using an R1 tester made by Mei Seisakusho, 0.1% of New Champion black ink made by Dainippon Ink Co., Ltd. was applied to the base paper surface of the upper paper.
cc printing was performed to determine ink acceptability.

“Evaluation Criteria J ◎: Extremely good.

O; Good ×; Bad.

"Effect" As is clear from the results in the table, the pressure-sensitive recording sheets obtained using the base paper for pressure-sensitive recording sheets obtained by the method of the present invention have improved color development stains and color development ability in an extremely well-balanced manner. It had good handling properties and excellent printing ink receptivity.

table One person for patent Kanzaki Paper Co., Ltd.

Claims (1)

[Claims] (1) Shore D hardness of 42 to 98 degrees with a metal roll so that the value measured with a specular reflection type smoothness meter on the surface of the base paper is 10% or more under a pressure condition of 20 kg/cm^2. (ASTM standard,
A method for producing a base paper for a pressure-sensitive recording sheet, characterized in that the paper is passed through a pressure nip comprising an elastic roll having an elastic roll (D-2240) and flattened. (2) The manufacturing method according to claim 1, wherein the elastic roll has a Shore D hardness of 70 to 95 degrees. (3) The manufacturing method according to claim (1), wherein the metal roll is heated to at least 80°C or higher. (4) The manufacturing method according to claim (1), wherein the pressure nip is a pressure nip of an on-machine soft calender. (5) The manufacturing method according to claim (1), wherein the base paper is flattened so that the measured value with a specular reflection type smoothness meter is 14% or more.