JPH07121610B2 - Base paper for pressure-sensitive copying paper - Google Patents

Description

The present invention relates to a base paper for pressure-sensitive copying paper, and in particular, it effectively improves color stains without lowering the color development ability, and is destroyed by unintentional pressure. The pressure-sensitive copying with improved printability and handling during printing, effectively preventing the phenomenon that the oil in the microcapsules migrates through the base paper to reach the surface coated with the color developer, causing unnecessary color development. The present invention relates to a base paper which provides paper very efficiently.

"Prior Art" As pressure-sensitive copying paper, "top paper" in which a layer containing microcapsules containing an electron-donating dye is coated on one side of a base paper, an electron that is colored by a contact reaction with the electron-donating dye "Lower paper" coated with a layer containing a receptive compound (developing agent), "Medium paper" coated with a layer containing microcapsules on one side of the base paper and a layer containing a developer on the other side, Further, "self-coloring paper" in which microcapsules and a color developer are laminated or mixed on the same surface of the base paper is known, and these are appropriately combined and used.

[Problems to be Solved by the Invention] However, there is still room for improvement in practical use for these pressure-sensitive copying papers.

One of them is a drawback that undesired friction other than the pressure of writing or typewriter causes color stain on the surface coated with the developer. Therefore, a method of adding a water-soluble polymer to the coating material [JP-A-62-198492], a method of adding a latex [JP-A-61-188184], and a method of adding a lubricant such as calcium stearate. [JP-A-61-266291] has also been proposed, but satisfactory results have not always been obtained because new defects such as a decrease in color-forming ability accompanying the improvement in color-developing stains are accompanied. In particular, since the color-developing stain and the color-developing ability of the pressure-sensitive copying paper are contradictory properties, it is extremely difficult to improve the both in a well-balanced manner, and the improvement is strongly demanded.

Further, for example, in the case of the mid-leaf paper, the microcapsules are destroyed by involuntary folding or impact, or by the printing pressure at the time of printing, and the oil containing the dye in the capsules migrates through the base paper and the developer on the opposite side It may reach the coated surface and cause unnecessary color development or fog. Also, when printing a roll-shaped sheet of medium-sized paper, a large amount of the ink vehicle used in the solid printing portion applied to the developer application surface migrated through the base paper and was slightly destroyed by the printing pressure. Extracting the oil in the capsule, causing unnecessary color development on the other developer coating surface that is in contact, or the oil in the capsule that is slightly broken on the capsule coating surface that is in contact with the solid printing portion, Similarly, a phenomenon of causing unnecessary color development on the surface coated with the color developer on the opposite side of the base paper occurs, and improvement thereof is strongly demanded.

In addition, when the copy sheets are stacked as single sheets, the sheets are less likely to slip, and there is a drawback that they are not suitable for handling. Furthermore, when printing on the recording sheet, the surface of the upper leaf paper or the lower leaf paper on which the paint is not spread, That is, when printing on the surface of the raw paper, there is a drawback that the acceptability of the printing ink is poor and a sufficient printing effect cannot be obtained.

As a result of earnest studies on the improvement of the above-mentioned defects, the present inventors have found that these defects are greatly affected by the characteristics of pulp fibers contained in the base paper constituting the pressure-sensitive copying paper, and are simply applied to the base paper. We found that satisfactory results could not be obtained even by adjusting the conditions of processing with a smoothing device such as a machine calendar or processing with a Yankee dryer.

Based on such knowledge, as a result of further research on pulp fibers constituting the base paper for pressure-sensitive copying paper, it was found that chemical pulp made from kenaf wood was used as a raw material, and the smoothness of the base paper surface measured by a special smoothness meter was measured. When the smoothing process is applied to obtain a specific value, the pressure-sensitive copying paper using the base paper can be effectively improved without causing color stains or color development due to unintentional pressure. The oil in the microcapsules destroyed by the migration migrates through the base paper and reaches the surface where the color developer is applied, which can effectively prevent the phenomenon that causes unnecessary color development and improves the printability and handleability during printing. This has led to the completion of the present invention.

"Means for Solving the Problem" The present invention contains 10 wt% or more of the chemical pulp from the kenaf wood part in the total pulp composition constituting the base paper, and a specular smoothness meter of the base paper surface. Measured value is 20 kg under pressure
The base paper for pressure-sensitive copying paper is characterized in that it is 8% or more in / cm ² .

"Function" The chemical pulp from the kenaf wood part used in the present invention (hereinafter referred to as the kenaf wood part chemical pulp) is made from kenaf, which is an annual herb of the mallow family Hibiscus cultivated in Australia and Southeast Asia. Although it is a chemical pulp, kenaf is not simply used as a raw material, but after removing the bast portion constituting the surface layer, only the wood portion is chemically pulped and used.

In the present invention, this kenaf wood part chemical pulp is used as a part of the pulp that constitutes the base paper for pressure-sensitive copying paper, but the desired effect cannot be obtained with less than 10% by weight of the total pulp composition. Since it is not possible, it is necessary to contain 10% by weight or more in the total pulp composition.

The reason why the desired effect of the present invention is obtained by containing 10% by weight or more of kenaf wood part chemical pulp is not necessarily clear, but compared to hardwood chemical pulp, kenaf wood part chemical pulp has a fiber wall. Is extremely thin and has a short fiber length, and it is presumed that this characteristic greatly contributes to the achievement of the effect of the present invention.

Hardwood chemical pulp, softwood chemical pulp, high-yield pulp and the like are used as the pulp constituting the base paper for pressure-sensitive copying paper other than the kenaf wood portion chemical pulp. At the time of papermaking, various auxiliaries such as a papermaking filler, a sizing agent, an internal addition retention improver, a paper strength enhancer, a dye, a band, and an antifoaming agent are added to the papermaking machine by an acidic papermaking method or a neutral papermaking method. Raw paper is manufactured.

In the pressure-sensitive copying paper base paper of the present invention, the kenaf wood part chemical pulp is contained in the total pulp composition in an amount of 10% by weight or more as described above, and the base paper surface after the base paper surface smoothing treatment is specularly smoothed. Measurement value with a pressure meter (pressurization condition: 20 kg / c
m ² is a value measured at 20 kg / cm ² unless otherwise specified) is 8% or more, preferably 12% or more. The regular reflection type smoothness meter here is a device that presses paper against the glass surface under a constant pressure condition to measure the smoothness, and according to the detailed study results by the present inventors, general air It is not affected by the air permeability of the paper like the Beck's smoothness meter which is a leak type smoothness measuring instrument and Parker print surf etc., and the measured value excellent in the correlation with the actual smoothness is obtained. It has been clarified that the desired effect of the present invention can be judged extremely appropriately by the measured value by the regular reflection type smoothness meter.

For the surface smoothing treatment of the base paper, a machine calendar composed of only metal rolls provided at the end of the paper machine can be used, but a super calendar, gloss calendar, soft calendar, etc. composed of metal rolls and elastic rolls can be used. It is effective to use it 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 having a hard chrome plated roll surface is appropriately selected and used, and 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, cotton,
An elastic roll made of paper, wool, tetron, nylon, or a mixture thereof is appropriately selected. At that time, Shore D hardness of 42 to 98 degrees (ASTM standard, D-2240)
A calender composed of an elastic roll having is preferably used. Among them, urethane rubber, aromatic polyamide resin, a mixture of paper and wool, a mixture of wool and tetoron, a mixture of wool and nylon, a mixture of paper and wool and tetoron, an elastic roll consisting of a mixture of paper, wool and nylon, etc. are preferred, 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 roll as described above is softer than a normal elastic roll and easily causes a heat generation phenomenon even under stable operating conditions, and the tendency is remarkable especially in the elastic roll using urethane rubber. Due to the heat generation phenomenon, the physical properties of the elastic body become unstable, and in extreme cases, the accumulated heat of the elastic body itself may cause melting damage. This is a preferred embodiment, and measures such as external cooling, change in roll diameter, change in wall thickness of the elastic body, etc. are appropriately adopted.

The on-machine super calendar and on-machine soft calendar, which consist of metal rolls and elastic rolls,
Paper and Pulp Technology Times August 1987 issue (31 pages) and 63
It is introduced in the May issue (page 10). Further, the processing conditions are appropriately adjusted according to the number of nips, the pressure of the nips, the machine speed, and the like.

Thus, the smoothed base paper is coated with a microcapsule-containing coating liquid or a developer-containing coating liquid according to a conventional method, such as "top paper,""bottompaper,""mediumpaper,""self-developingpaper," etc. The dry weight is 2 to 2 by a suitable coating device such as an air knife coater, a roll coater, a blade coater, a rod coater and a curtain coater.
A coating solution of about 10 g / m ² is applied. In the case of "lower leaf paper", a smoothing process using a super calendar or the like may be further performed if desired.

Microcapsule-containing coating liquids are generally triarylmethane lactones, spiropyrans, fluoranes,
Basic dyes such as diphenylmethanes and azines, synthetic oils such as alkylated naphthalene, alkylated diphenyl, alkylated diphenylmethane, alkylated terphenyl, vegetable oils such as cotton oil and castor oil, animal oils, mineral oils or mixtures thereof. It is dissolved in a solvent consisting of, and prepared by various methods such as a coacervation method, an interfacial polymerization method, an in-situ method, and the like, which are contained in microcapsules and dispersed in a binder.

In addition, the developer-containing coating liquid is generally an inorganic clay such as acid clay, activated clay, or attapulgite, various aliphatic carboxylic acids, benzoic acid, p-tert-butylbenzoic acid, phthalic acid, gallic acid. 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-
Aromatic carboxylic acids such as 1-benzyl-3-naphthoic acid, organic developers such as phenolic resins such as p-phenylphenol-formalin resin and p-butylphenol-acetylene resin, and further organic developers such as zinc and zinc, for example. , A salt of a polyvalent metal such as magnesium, aluminum, calcium, titanium, manganese, tin, and nickel, and the like are dispersed in a binder.

Examples of the binder include starches, celluloses, proteins, gum arabic, polyvinyl alcohol, styrene-maleic anhydride copolymer salt, styrene-
Butadiene copolymer emulsion, vinyl acetate-maleic anhydride copolymer salt, polyacrylic acid salt, etc. are appropriately selected and used.

For pressure-sensitive copying paper, see, for example, US Pat.
No. 2,505,471, 2,505,489, 2,548,366,
2,712,507, 2,730,456, 2,730,457, 3,4
There are various forms as described in No. 18,250, No. 3,924,027, No. 4,010,038, etc., and the present invention is applicable to these various forms of pressure-sensitive copying paper.

[Examples] The present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto. "Part" in the example
And "%" are "parts by weight" unless otherwise specified.
And "% by weight" are shown.

Example 1 [Preparation of base paper] A wood part was collected from kenaf produced in Australia, and the wood part was subjected to kraft pulp cooking using a test autoclave to obtain unbleached pulp. This unbleached pulp was treated with a vibrating flat screen to remove undigested material. Pulp from which undigested material has been removed is chlorine, sodium hydroxide,
Bleached pulp was obtained by sequentially treating with sodium hypochlorite and chlorine dioxide. The Canadian Standard Freeness (hereinafter referred to as CSF) of the obtained pulp was 410 ml (hereinafter referred to as kenaf stock). 10 parts of this kenaf stock and a single disc refiner each have a pulp concentration of 4
% Was added to 70 parts of LBKP beaten up to 500 ml of CSF and 20 parts of NBKP, talc was added so that the paper ash content was 6%, and rosin size was added 1.4% to the absolutely dry pulp. After adjusting the pH of this stock to 4.6 with a sulfuric acid band, paper was made using a standard hand-making machine, and an aqueous solution of oxidized starch was size-pressed to 1.5 g / m ² and consisted only of metal rolls. It is processed with the model calendar that is used and the basis weight is 40 g /
A base paper for pressure-sensitive copying paper having a m ² value of 9% measured by a specular smoothness meter was obtained.

[Creation of top paper]

112.5 parts of water was added to 37.5 parts of a 20% aqueous solution of a copolymer consisting of 15 mol% of vinyl sulfonic acid, 5 mol% of styrene, 70 mol% of acrylic acid and 10 mol% of ethyl acrylate, and 20% NaOH was added.
What was adjusted to pH 4.6 with an aqueous solution was used as an aqueous medium for capsule production.

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

Next, 20 parts of methylated methylolmelamine initial condensate (trade name; Beckamine APM, 80% concentration, Dainippon Ink and Chemicals, Inc.) was added to the system, and the system temperature was maintained at 70 ° C for 1 hour while continuing stirring. After that, the mixture was cooled to obtain a milky white capsule dispersion liquid.

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 is applied to the above-mentioned base paper at a dry weight of 4 g / m ² and dried to perform pressure-sensitive copying. I made a leaflet on paper.

[Creation of lower and middle paper sheets]

Aluminum hydroxide 65 parts, zinc oxide 20 parts, 3,5-di (α
-Methylbenzyl) zinc salicylate and α-methylstyrene / styrene copolymer blend (blend ratio 80/20) 15
Parts, polyvinyl alcohol aqueous solution 5 parts (solid content) and water
Carboxyl-modified styrene-butadiene copolymer latex 20 was added to the dispersion obtained by grinding 300 parts with a ball mill for 24 hours.
Part (solid content) is added to adjust the color developer coating solution to the above-mentioned base paper so that the dry weight becomes 4 g / m ^2, and then the paper is calendered to produce the bottom sheet of pressure-sensitive copying paper. did.

Next, the capsule coating solution was applied to the reflective surface of the developer-coated surface of the lower leaf paper at 4 g / m ² and dried to prepare a middle leaf paper of pressure-sensitive copying paper.

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

Example 2 Using 20 parts of the kenaf stock obtained in Example 1 and 20 parts of NBKP and 60 parts of LBKP beaten up to 450 ml of CSF at a pulp concentration of 4% with a double disc refiner, the stock obtained by using As with 1, do hand-making and size press,
Treated with a model super calender consisting of metal rolls and elastic rolls (Shore D hardness 91 degrees), basis weight 40g / m ²
A base paper for pressure-sensitive copying paper having a value measured by a regular reflection type smoothness meter of 17% was obtained.

Upper sheet, middle sheet, and lower sheet were prepared in the same manner as in Example 1 except that this base paper was used, and the performance comparison test was conducted, and the results are shown in the table.

Example 3 The kenaf stock obtained in Example 1 was beaten with a single disc refiner at a pulp concentration of 3.5% to CSF 300 ml and 50 parts of the kenaf beaten paper stock and a double disc refiner at 4% pulp to CSF 550 ml, respectively LBKP25. Department and
Using paper stock obtained by blending 25 parts of NBKP, papermaking and size press were performed in the same manner as in Example 1, and treated with a model super calender composed of metal rolls and elastic rolls (Shore D hardness 91 degrees). As a result, a base paper for pressure-sensitive copying paper having a basis weight of 40 g / m ² and a value measured by a regular reflection type smoothness meter of 22% was obtained.

Upper sheet, middle sheet, and lower sheet were prepared in the same manner as in Example 1 except that this base paper was used, and the performance comparison test was conducted, and the results are shown in the table.

Example 4 Using the stock material obtained by blending 75 parts of the kenaf stock material obtained in Example 1 and 25 parts of NBKP beaten up to 530 ml of CSF at a pulp concentration of 4% with a double disc refiner, Example 1
Similarly to the above, hand-making and size-pressing are performed, and processed with a model calender consisting of only metal rolls, basis weight 40 g /
A base paper for pressure-sensitive copying paper having a m ² of 17% as measured by a regular reflection type smoothness meter was obtained.

Upper sheet, middle sheet, and lower sheet were prepared in the same manner as in Example 1 except that this base paper was used, and the performance comparison test was conducted, and the results are shown in the table.

Example 5 20 parts of the kenaf stock material obtained in Example 1 and 60 parts of LBKP and 20 parts of NBKP beaten up to 450 ml of CSF at a pulp concentration of 4% with a double disc refiner were blended to prepare heavy calcium carbonate (Softon 1200, Bihoku powder). (Manufactured by K.K.) was added so that the paper ash content was 6%, and a sulfuric acid band was added to the absolutely dry pulp.
0.5% and cationic starch (CATO-F, manufactured by Oji National Co., Ltd.) were added to 0.5% of the absolutely dried pulp, and alkyl ketene dimer (SPK-902, manufactured by Arakawa Chemical Co., Ltd.) as a neutral sizing agent was made into the absolutely dried pulp. On the other hand, after adding 0.2%, paper was made using a standard handmade machine, and size press was performed in the same manner as in Example 1, and a metal roll and an elastic roll (Shore D hardness 91
To obtain a base paper for pressure-sensitive copying paper having a basis weight of 40 g / m ² and a value measured by a regular reflection type smoothness meter of 17%.

Upper sheet, middle sheet, and lower sheet were prepared in the same manner as in Example 1 except that this base paper was used, and the performance comparison test was conducted, and the results are shown in the table.

Example 6 30 parts of the kenaf stock obtained in Example 1 was beaten with a single disc refiner at a pulp concentration of 4% to CSF 300 ml, and bleached chemithermo-mechanical pulp 30 parts and a double disc refiner at a pulp concentration of 4% with CSF 550 ml, respectively. Using the stock obtained by blending 20 parts of LBKP and 20 parts of NBKP beaten up to this point, handmaking and size pressing were performed in the same manner as in Example 1,
Treated with a model super calender consisting of metal roll and elastic roll (Shore D hardness 91 degrees), basis weight 40g /
A base paper for pressure-sensitive copying paper having a m ² of 15% as measured by a regular reflection type smoothness meter was obtained.

Upper sheet, middle sheet, and lower sheet were prepared in the same manner as in Example 1 except that this base paper was used, and the performance comparison test was conducted, and the results are shown in the table.

Comparative Example 1 Pulp concentration of 4 using a double disc refiner
A base paper for pressure-sensitive copying paper was obtained in the same manner as in Example 1 except that the stock material obtained by blending 80 parts of LBKP and 20 parts of NBKP beaten to CSF of 500 ml was used. The basis weight of this base paper was 40 g / m ² , and the value measured by the regular reflection type smoothness meter was 9%.

Upper sheet, middle sheet, and lower sheet were prepared in the same manner as in Example 1 except that this base paper was used, and the performance comparison test was conducted, and the results are shown in the table.

Comparative Example 2 The paper materials obtained by blending in Example 1 were used, papermaking, size press and model calendering were conducted in the same manner as in Example 1, basis weight 40 g / m ² , specular reflection type smoothness meter. A base paper for pressure-sensitive copying paper having a measured value of 7% was obtained.

Upper sheet, middle sheet, and lower sheet were prepared in the same manner as in Example 1 except that this base paper was used, and the performance comparison test was conducted, and the results are shown in the table.

[Coloring test]

As the capsule coated surface and the developer-coated surface of the lower lobe paper middle lobe sheet are opposed, superposed middle lobe sheet and the lower sheet paper, 600 kg / cm ²
The density of the color image obtained by applying the load was measured with a Macbeth densitometer (RD-914 type, filter visual).

[Color stain test]

The middle leaf paper and the lower leaf paper are overlapped so that the surface of the middle leaf paper coated with the capsule and the surface of the lower leaf paper coated with the color developer face each other, and the color is developed 5 times by applying a load of 4 kg / cm ² for 5 times. The degree of color stain on the agent-coated surface was evaluated.

"Evaluation criteria" ◎: Almost no stain.

○: Slightly soiled.

X: Remarkably soiled.

[Printability]

The ink acceptability was judged by printing 0.1 cc of New Champion Ink manufactured by Dainippon Ink and Co., Ltd. using the RI tester manufactured by Akira Seisakusho on the base paper of the upper paper.

"Evaluation criteria" ◎: Very good.

○: Good.

×: Bad.

[Blank color stain test]

Place high-quality paper on the developer-coated surface of the medium-sized paper, type-print with an electric typewriter, sandwich it with a polyester film, and leave it at 100 ° C for 2 days. It was visually judged by the degree of color development of the printed part.

“Evaluation criteria” ⊚: Almost no stain (color development).

○: Slightly soiled (colored).

X: Remarkably soiled (colored).

[Effect] As is clear from the results in the table, the pressure-sensitive copy paper obtained by using the base paper for pressure-sensitive copy paper obtained in the examples of the present invention is
The color stain and color development were improved in a very well-balanced manner, the appearance and handling were good, and the print ink acceptability was also excellent.

Claims (1)

[Claims] 1. The total pulp composition of the base paper contains 10% by weight or more of chemical pulp derived from kenaf wood, and the surface of the base paper is measured under a specular smoothness meter under a pressure condition of 20.
A base paper for pressure-sensitive copying paper, which is 8% or more in kg / cm ² .