JP2698097B2 - Method of manufacturing base paper for pressure-sensitive recording sheet - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a base paper for a pressure-sensitive recording sheet, and in particular, to effectively improve color stains without lowering the color developing ability, and to perform printing during printing. The present invention relates to a base paper processing method capable of producing a pressure-sensitive recording sheet having improved suitability and handleability extremely efficiently.

"Prior art" As a pressure-sensitive recording sheet, an "upper paper" in which a layer containing microcapsules containing an electron donating dye is applied to one side of a base paper, an electron which is colored by contact reaction with the electron donating dye "Lower paper" coated with a layer containing a receptive compound (developing agent),
`` Middle paper '' in which a layer containing microcapsules is applied on one side of the base paper and a layer containing a color developer is applied on the other side, and `` microcapsules and a color developer are laminated or mixed on the same side of the base paper '' Self-coloring papers "are known, and these are used in appropriate combinations.

Particularly, pressure-sensitive recording sheets known as carbonless paper and pressure-sensitive copying paper are disclosed in U.S. Pat. Nos. 2,711,375 and 2,730,457.
No., JP-B-47-20972, etc., and are widely used in practice.

"Problems to be Solved by the Invention" However, these pressure-sensitive recording sheets still have room for improvement in practical use.

One of them is a drawback that coloring smears occur on the surface coated with the color developer due to undesired friction other than the pressing force of writing or a typewriter. Therefore, a method of adding a water-soluble polymer to a paint (Japanese Patent Application Laid-Open No. 62-198492), a method of adding a latex (Japanese Patent Application Laid-Open No. 61-188184), and a method of adding a lubricant such as calcium stearate [ However, satisfactory results have not always been obtained due to the addition of new defects such as a reduction in color-forming ability with the improvement of coloring stains.

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

In addition, when the recording sheets are stacked as sheet sheets, the sheets are difficult to slip, and there is a disadvantage that the handling properties are lacking.In addition, when printing on the recording sheets, the surface of the upper sheet or the lower sheet is not smeared with paint, that is, When printing on the base paper surface, there is a disadvantage that the acceptability of the printing ink is poor and a sufficient printing effect cannot be obtained.

The present inventors have conducted intensive studies on the improvement of the above-mentioned drawbacks, and as a result, these drawbacks are largely attributed to the properties of the base paper constituting the pressure-sensitive recording sheet, and in particular, such as a machine calender conventionally applied to such base paper It was found that satisfactory results could not be obtained even if the processing conditions were variously adjusted in the processing by the smoothing device or the processing by the Yankee dryer or the like.

Based on this knowledge, as a result of further intensive research on the processing method of the base paper for the pressure-sensitive recording sheet, a metal roll was formed so that the smoothness of the base paper surface measured by a special smoothness meter became a specific value or more. When the base paper is subjected to a flattening process with a special pressure nip constituted by an elastic roll having a specific Shore D hardness, color stain due to undesired pressure on a recording sheet using the base paper lowers the color forming ability. The present invention was found to be improved effectively without any problem, and also improved in suitability for handling and printing, and completed the present invention.

“Means for Solving the Problems” The present invention relates to a metal roll such that the value measured by a regular reflection type smoothness meter on the base paper surface is 10% or more under a pressure condition of 20 kg / cm ^2.
A method for producing a base paper for a pressure-sensitive recording sheet, wherein the base paper is flattened by passing through a pressure nip composed of an elastic roll having a Shore D hardness of 42 to 98 degrees (ASTM standard, D-2240). It is.

"Action" The elastic roll used in the flattening treatment of the base paper in the method of the present invention is an elastic body having a specific value of 42 to 98 degrees in Shore D hardness specified in ASTM standard, D-2240 as described above. Be composed.

With an elastic roll softer than 42 degrees, an excessive nip pressure is required to obtain sufficient surface smoothness of the base paper, which significantly shortens the life of the elastic body itself during operation. However, since it is difficult to obtain appropriate surface smoothness with an elastic roll harder than 98 degrees, an elastic roll having a Shore D hardness of 42 to 98 degrees, more preferably 70 to 95 degrees, is selectively used. Is done.

The elastic body constituting such an elastic roll is not particularly limited as long as the hardness falls within the above-mentioned specific range. 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, cotton, and paper , Wool, tetron, nylon, or mixtures thereof.

Among them, urethane rubber, aromatic polyamide resin, a mixture of paper and wool (wool paper), a mixture of wool and tetron, a mixture of wool and nylon, a mixture of paper and wool and tetron, a mixture of paper, wool and nylon, and the like, In particular, elastic rolls using 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 roll used in the present invention as described above is softer than a normal elastic roll, and therefore easily generates heat even under stable operation conditions. In particular, the tendency is remarkable in an elastic roll using urethane rubber. The physical property of the elastic body becomes unstable due to the heat generation phenomenon, and in the extreme case, the elastic body itself may be melted and damaged by the accumulated heat. This is a preferred embodiment, and various countermeasures such as cooling from the outside, a change in the roll diameter, and a change in the thickness of the elastic body are appropriately adopted.

The elastic roll and the metal roll constituting the pressure nip are not particularly limited, and chill rolls, alloy chill rolls, copper iron rolls, and further roll surfaces used in flattening processing devices such as a normal super calender and a gloss calender are used. Hard chrome plated metal rolls or the like are appropriately selected and used. In addition, the form of the pressure device, the number of pressure nips, and the like are appropriately adjusted according to a normal flattening device.

The pressure conditions for passing the base paper through the pressure nip are as follows:
The hardness of the elastic roll to be used, the type of recording sheet, the paper passing speed, the number of nips, the temperature conditions of the metal roll, etc. are adjusted as appropriate according to various processing conditions, but the nip linear pressure is 20 kg.
If it is lower than / cm, it is difficult to obtain the desired effect, and if it exceeds 400 kg / cm, the heat generation phenomenon of the elastic roll itself increases, and stable operation becomes difficult.Therefore, it is necessary to adjust in the range of about 20 to 400 kg / cm. desirable.

Thus, in the method of the present invention, the surface of the base paper after the flattening treatment has a regular reflection type smoothness meter (measuring pressure; 20 kg / cm ² ) of 10% or more, more preferably 14% or more. The specular reflection type smoothness meter referred to here is an apparatus for measuring the smoothness of a paper by pressing the paper against the glass surface under a constant pressure condition. According to the results, it is not affected by the air permeability of the paper as in the case of a Beck smoothness meter or Parker print surf, which is a general air leak type smoothness measuring instrument, and has a very strong correlation with the actual smoothness. It is clear that excellent measured values can be obtained, and the desired effects of the present invention can be judged very appropriately by the values measured with this specular reflection type smoothness meter (measuring pressure: 20 kg / cm ² ). The invention has been completed.

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

When the base paper is passed through the pressure nip, whether the wire side or the felt side of the base paper is brought into contact with the elastic roll is not particularly limited, but in the case of the upper paper and the lower paper, a paint is applied. Preferably, the surface is in contact with an elastic roll.

In the method of the present invention, a pressure nip composed of a metal roll and an elastic roll having a specific Shore D hardness is:
For example, it is used as a pressure nip of a suitable flattening treatment device such as a super calender, soft calender, etc.
In particular, it is preferable to employ a pressure nip for an on-machine super calender or an on-machine soft calender. As for the on-machine super calendar and the on-machine soft calendar, for example, the pulp and paper technology Times, August 1987 (p. 31) and May 1988 (10
Page) etc.

The base paper thus flattened is coated with a coating solution containing microcapsules and a developer containing a microcapsule in accordance with a conventional method, such as "upper paper,""lowerpaper,""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 blade coater, a rod coater, a dry coating weight of ^{2 to} 10 g / m ² by a suitable coating device such as a curtain coater.
About a coating liquid is applied and dried. In the case of "lower paper", if necessary, a flattening process using a super calendar or the like may be further performed.

Microcapsule-containing coating liquids are generally prepared by converting basic dyes such as triarylmethane lactones, spiropyrans, fluorans, diphenylmethanes, and azines into alkylated naphthalenes, alkylated diphenyls, alkylated diphenylmethanes, and alkylated dyes. Dissolved in solvents such as synthetic oils such as phenyl, vegetable oils such as cotton oil and castor oil, animal oils, mineral oils or mixtures thereof, and produced various capsule manufacturing methods such as coacervation method, interfacial polymerization method and in-situ method To be contained in microcapsules and dispersed in a binder.

Further, the developer-containing coating liquid is generally an acidic clay, an activated clay, an inorganic developer such as attapulgite, various aliphatic carboxylic acids, benzoic acid, p-tert-butylbenzoic acid, phthalic acid, and gallic. 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-hydroxy-1
Aromatic carboxylic acids such as -benzyl-3-naphthoic acid,
Organic developers such as phenolic resins such as p-phenylphenol-formalin resin and p-butylphenol-acetylene resin, and furthermore, these organic developers and zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, etc. And various developers such as salts with polyvalent metals are dispersed in a binder.

As the binder, for example, starches, celluloses, proteins, gum arabic, polyvinyl alcohol, styrene-maleic anhydride copolymer salt, styrene-
A butadiene copolymer emulsion, a vinyl acetate-maleic anhydride copolymer salt, a polyacrylate and the like are appropriately selected and used.

For pressure-sensitive recording sheets, for example, U.S. Pat.
470, 2,505,471, 2,505,489, 2,548,366
No. 2,712,507, 2,730,456, 2,730,457,
As described in JP-A Nos. 3,418,250, 3,924,027, and 4,010,038, there are various forms, and the present invention can be applied to these various forms of pressure-sensitive recording sheets.

"Examples" Hereinafter, the present invention will be described more specifically with reference to examples, but is not limited thereto. In the examples, "parts" and "%" indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 [Preparation of base paper] An on-machine soft calender having a pressure nip composed of a metal roll having a diameter of 420 mm having a hard chrome-plated surface and an elastic roll having a Shore D hardness of 78 degrees and a diameter of 400 mm, and a specular reflection type Measured value with smoothness meter (Pressure condition 20kg
/ cm ² ) 8% of pressure sensitive recording sheet base paper (40 g / m ² tsubo) is flattened (nip pressure 80 kg / cm) and the specular reflection smoothness is 2
A 0% pressure-sensitive recording sheet base paper was prepared.

[Creating upper paper]

112.5 parts of water was added to 37.5 parts of a 20% aqueous solution of a copolymer composed of 15 mol% of vinyl sulfonic acid, 5 mol% of styrene, 70 mol% of acrylic acid, and 10 mol% of ethyl acrylate, and 20% NaO
The aqueous medium whose pH was adjusted to 4.6 with an H aqueous solution was used as an aqueous medium for producing capsules.

To this was added 105 parts of diisopropylnaphthalene (trade name: K-113, manufactured by Kureha Chemical Co.) in which 5 parts of crystal violet lactone was dissolved, and the mixture was emulsified and dispersed so that the average particle size became 5 μm. The temperature was raised to 70 ° C.

Next, 20 parts of methylated methylol melamine precondensate (trade name: Becamine APM, 80% concentration, manufactured by Dainippon Ink and Chemicals, Inc.) was added to the system, and the temperature of the system was increased to 70 ° C. while stirring was continued.
, And cooled to obtain a milky white capsule dispersion.

A capsule coating solution prepared by adding 70 parts of wheat starch and 20 parts (solid content) of dissolved oxidized starch to this capsule dispersion was applied onto the base paper and dried to a dry weight of 4 g / m ² , followed by pressure-sensitive recording. An upper sheet for a sheet was created.

[Making lower and middle paper]

65 parts of aluminum hydroxide, 20 parts of zinc oxide, mixed melt of zinc 3,5-di (α-methylbenzyl) salicylate and α-methylstyrene / styrene copolymer (mixing ratio 80/20) 1
5 parts, polyvinyl alcohol aqueous solution 5 parts (solid content) and water 300 parts were crushed with a ball mill for 24 hours to obtain a dispersion obtained by carboxy-modified styrene / butadiene copolymer latex.
A developer coating solution prepared by adding 20 parts (solid content) is applied to the above-mentioned base paper so as to have a dry weight of 5 g / m ² , dried and calendered, and then subjected to a lower leaf for a pressure-sensitive recording sheet. Created paper.

Next, the capsule coating solution was applied to the surface of the lower paper opposite to the surface to which the developer was applied so as to have a dry weight of 4 g / m ² and dried to prepare a middle paper for a pressure-sensitive recording sheet.

A performance comparison test was performed using the upper, middle, and lower sheets thus obtained, and the results are shown in the table.

Example 2 Specular reflection smoothness was 18% in the same manner as in Example 1 except that the elastic roll of the on-machine soft calender was replaced with an elastic roll having a Shore D hardness of 87 degrees and the nip pressure was 160 kg / cm.
Is prepared in the same manner as in Example 1 except that the base paper for pressure-sensitive recording sheet is prepared and the obtained base paper is used.
A lower sheet was made.

Example 3 The regular reflection type smoothness was 12% in the same manner as in Example 1 except that the elastic roll of the on-machine soft calender was changed to an elastic roll having a Shore D hardness of 91 degrees and the nip pressure was set to 91 kg / cm.
Is prepared in the same manner as in Example 1 except that the base paper for pressure-sensitive recording sheet is prepared and the obtained base paper is used.
A lower sheet was made.

Comparative Example 1 A normal machine calender composed of a combination of chilled rolls was used in place of an on-machine soft calender to prepare a base paper for a pressure-sensitive recording sheet having a regular reflection type smoothness of 12%, and the obtained base paper was used. Except for this, upper paper, middle paper and lower paper were prepared in the same manner as in Example 1.

Comparative Example 2 A base paper for a pressure-sensitive recording sheet having a regular reflection type smoothness of 9% was prepared in the same manner as in Example 1 except that the nip pressure of the on-machine soft calender was changed to 0 kg / cm. Except for using, upper and lower sheets, middle and lower sheets were prepared in the same manner as in Example 1.

[Color development test]

Lay the middle paper and the lower paper together so that the capsule-coated surface of the middle paper and the developer-coated surface of the lower paper face each other, and apply 600 kg / cm
The density of the color image obtained under a load of ² was measured with a Macbeth densitometer (RD-914, filter visual).

[Coloring stain test]

Lay the middle paper and the lower paper together so that the capsule-coated surface of the middle paper and the developer-coated surface of the lower paper face each other, and apply 4 kg / cm ²
5 times with the load applied to determine the degree of color stain on the developer-applied surface.

"Evaluation criteria" A: Almost no contamination.

 Δ: Slightly dirty.

 X: remarkably dirty.

(Printability)

0.1 cc of New Nippon Ink Co., Ltd. black ink was printed on the base paper of the upper paper using an RI tester manufactured by Akira Seisakusho to determine the acceptability of the ink.

"Evaluation criteria" A: extremely good.

 ；: Good ×; bad

[Effect] As is clear from the results in the table, the pressure-sensitive recording sheet obtained by using the base paper for a pressure-sensitive recording sheet obtained by the method of the present invention has improved coloring stains and coloring ability in a very well-balanced manner. The handleability was good, and the acceptability of the printing ink was excellent.

Claims (5)

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