JP2893660B2 - Recording paper consisting of multiple layers - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to recording paper excellent in printing strength, ink transfer rate, and rigidity, particularly printing paper A and electrophotographic paper.

[Prior Art] When recording information on paper, for example, when the recording material is in direct contact with the paper as in printing, there is a problem that an ink having a small adhesive strength on the surface of the paper due to the tack of the ink is burned. Even in electrophotography and other methods, the paper is often rubbed by a device for transporting the paper to the recording unit, and the strength of the paper surface is required.

In recent years, chips that are used as raw materials for pulp have been diversified at various destinations, and the use of hardwood containing many vascular elements as raw materials for chemical pulp has been inevitable. On the other hand, chemical pulp has been added to 10
Most of the printing on the printing paper A, which is 0%, is performed with the offset.

When offset printing is performed on the printing paper A containing a large amount of hardwood material in such a background, the duct elements on the surface of the paper are washed away by ink tack at the time of printing, and this remains on the blanket and becomes white for subsequent printing. A phenomenon (vessel pick) that remains as spots occurs, and if this phenomenon occurs frequently, the printer must stop the printing press and clean the blanket, which not only reduces productivity but also causes intermittent operation. This can cause problems, such as when the tone is not constant.

Conventionally for this vessel pick 1). To reduce the compounding ratio of the problematic chips, 2). Measures have been taken to increase the bond between the vessel and the fiber by adding a chemical that enhances paper strength in the wet end or size press.

However, these countermeasures have a problem in that there is a limit in the selection of raw material chips, and the selection of a specific chip and an increase in the distribution of chemicals not only increase costs but also limit their effects. In addition, a method of breaking down the vessel by beating to reduce the size of the vessel and increasing the bonding force between fibers can be considered, but in this method, the shrinkage of the paper due to drying increases, and the dimensional stability of the paper deteriorates. New problems arise, such as too high density and low opacity.

On the other hand, electrophotographic paper has the same whiteness as printing paper A,
Optical properties such as opacity are also required, but, unlike printing paper A, particularly important functions are running performance and image quality. One of the factors affecting the running reliability of paper in a copying machine is stiffness, and higher stiffness is desirable. In terms of material mechanics, bending stiffness is indicated by the product E × I of the elastic modulus E of the material and the second moment of area I, and is also applicable to paper. That is, the stiffness of the paper is proportional to the product of the elastic modulus of the paper and the cube of the thickness, and the stiffness increases as the basis weight and the paper thickness increase. In order to increase the paper thickness, there are methods such as lowering the density by loosening the beating and weakening the pressurization of finishing equipment such as a machine calendar. Therefore, the basis weight is often increased in practice. However, from the functionality of paper, light and thin paper is required, and increasing the basis weight is also a resource to reflect on,
This is not a preferable method because it increases the cost.

One of the factors affecting image quality is surface strength.If the surface strength of paper is low, the friction type feeder polishes the back surface of the paper with a retard roll, causing the fibers to fall off, resulting in paper powder and collected toner. May cause image trouble. Means for improving the surface strength include strengthening the beating and coating the starch with a size press.However, there is a problem that curling is likely to occur due to deterioration of dimensional stability and cost is increased, which adversely affects running performance. is there.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-described circumstances, and significantly improves print strength (vessel pick) without impairing dimensional stability, opacity and other qualities.
The task was to provide recording paper with an excellent ink transfer rate.

[Means for Solving the Problems] The above problem is achieved by forming a three-layer structure in which an outer layer mainly composed of pulp having a CSF value of 350 or less is provided on both surfaces of an inner layer mainly composed of pulp having a CSF value of 420 or more. It was solved by forming. Further, by using these recording papers as the printing paper A or the electrophotographic paper, the problems of the printing paper A and the electrophotographic paper could be solved.

For 100% chemical pulp paper, the quality of the paper is largely controlled by choosing the degree of beating of the pulp used. CSF is used as an index indicating the degree of beating.
Since (CANADIAN STANDARDFREENESS) is often used, the present invention also uses CSF as a measure of beating degree.

The CSF value of chemical pulp used for recording paper is generally about 300 to 500. The CSF value of the inner layer in the present invention is 4
It must be 20 or more, and the CSF value of the outer layer must be 350 or less. It is desirable that the CSF value of the inner layer and the CSF value of the outer layer are separated to some extent, and the larger the difference between the CSF values of the inner layer and the outer layer, the more the physical properties such as printing strength and rigidity are improved. However, if the difference is too large, drainage and internal strength tend to be weak, which is not preferable. Also, if the difference is too small, the effect of the present invention is naturally not exhibited.

As for specific numerical values, the CSF value and the basis weight of the inner layer and the outer layer are determined by experiments so as to satisfy the target recording paper quality.

As equipment for producing a multilayer paper for the purpose of the present invention,
There are two types: wet paper webs formed on a paper machine, which are widely used for conventional paperboard, etc., are combined in a pressing process, and the wet paper web is formed by the wire part of the paper machine. There is a limit to this, and with the current technology, only products having a basis weight higher than that of general recording paper can be manufactured. Therefore, as the latter equipment, a multi-layer head box is available from BELOIT, VAL
MET-KMW, etc., and it is possible to form the above-mentioned multilayer paper by replacing this multi-layer head box with a head box of a mechanism for discharging a single single raw material layer. It can be applied to the former equipment. In addition, the present invention further improves the quality by combining the addition of a polymer additive at a wet end and the application of a sizing agent by a size press, which are common techniques for adjusting various characteristics required as recording paper. Becomes possible.

[Operation] The physical properties of chemical pulp are important in terms of strength properties such as density and tensile strength, and optical properties such as opacity defined by whiteness and specific scattering coefficient.

These physical property values are related to the CSF value. A high CSF value results in a pulp having relatively low density and weak strength properties, but having high opacity and excellent dimensional stability. On the other hand, if the CSF value is lowered by further beating, the fibers become finer, the density is high and the strength properties are strong, but the opacity and dimensional stability deteriorate.

In the present invention, the outer layer having a CSF value of 420 or more, and thus having an excellent strength and a CSF value of 350 or less, which is less likely to cause vessel picking, is formed on both surfaces of the inner layer having excellent dimensional stability and opacity. The recording paper is strong and has high dimensional stability. Furthermore, the inner layer with a CSF value of 420 or more has low density and high compressibility, and the outer layer with a CSF value of 350 or less has fine fibers and high smoothness. The ink transfer rate is improved because the contact between the ink and the paper surface is improved. Further, since the inner layer has a low density and a bulky structure, and the outer layer has a high elastic modulus, the stiffness represented by the product E × I of the elastic modulus E of the material and the second moment of area I is large. In the multilayer papermaking of the present invention in which a material having a large elastic modulus is disposed in the outer layer portion, the size is increased.

[Examples] Representative examples of the present invention will be described below, but the present invention is not limited to the scope of the following examples. still,
The percentages used in the following Examples and Comparative Examples are solids weight percentages.

Example 1 A low CSF raw material for the outer layer, a high CSF raw material for the inner layer, and a raw material for the outer layer were sequentially supplied at a speed of 750 m / min by an ORIENTED SHEET FORMER manufactured by Kumagaya Riki Kogyo Co., Ltd., and dehydration and drying were performed. A three-layer paper consisting of different raw material layers was prepared in different directions, and the printing strength, ink transfer rate, and other paper qualities were evaluated.

The raw materials of the outer layer and the inner layer and the basis weight ratio are shown in Table 1.
All papers are made the total basis weight of 60 g / m ² as the target, Sample No. 1, 2 and 3 is the standard paper monolayer Extract consisting LBKP100%, Sample No. 4-12 has a LBKP of CSF530 the inner layer Place and CS on outer layer
F94,196,295 of LBKP is obtained respectively 5,10,15g / m ² is disposed. Sample Nos. 13 to 15 have the LBKP of CSF420 arranged in the inner layer, 13 has the LBKP of CSF94 in the outer layer of 5 g / m ² , and 14 has CLB in the outer layer of 14.
LBKP of SF196 is 10 g / m ² , and LBKP of CSF295 is 15 g /
m ² was placed.

The printing strength was measured using a Prüfbau printing suitability tester, and 200 μl of Dainippon Ink CAPS G-S Red was supplied to a blanket plate having a plate surface of 50 × 200 mm at a printing pressure of 600 N and a speed of 2.0 m / s at 22 ° C. Printing was performed in a room conditioned to 55%, and the number of white spots on the printed surface was counted. In the measurement of the ink transfer ratio, the same tester was used to calculate the ratio of the transferred ink under the condition that the amount of ink on the plate was 3.5 g / m ² from the weights of the plate and the ink before and after printing. The dimensional change is in a constant temperature and humidity chamber.
The dimensional change was measured by changing the relative humidity from 50% RH to 80% RH at 20 ° C. The results are shown in Table 2. In this example,
Since the sheet is made with ORIENTED SHEET FORMER, the fiber orientation is anisotropic, and the quality such as specific tear, tear length, and stiffness depends on the papermaking direction (Machine Direction MD) and its perpendicular direction (Cross-machine Direction CD). Is anisotropic. Therefore, these qualities were evaluated by the square root of MD × CD.

When the sample numbers 4 to 12 were compared with the standard paper 3 of 100% LBKP having the same density, the printing strength (surface strength) was increased without impairing the dimensional stability, and the ink transfer rate and the rigidity were improved. In addition, the CSF of the inner layer pulp is set to 420 and the strength is set to sample number 4 ~
In Sample Nos. 13 to 15, which were stronger than 12, the print strength and rigidity were improved without impairing the specific tear, tear length and dimensional stability as compared with the standard paper 2 having the same density. The standard paper 1 which has been beaten and has excellent print strength is inferior in dimensional stability and opacity.

Comparative Example 1 Samples obtained by mixing raw pulp at the same mixing ratio as Sample Nos. 7 to 9 of Example 1 and making a single layer in the same manner as Sample Nos. 1, 2, and 3 of Sample 1 (Sample Nos. 16 to 18) Was prepared and the quality was evaluated. The results are shown in Table 3.

The print strength (surface strength), stiffness, and ink transfer rate were all excellent in sample Nos. 7 to 9 made of multilayer paper.

Example 2 This is a common process for high quality paper and electrophotographic paper.
Table 5 shows the results of examining the effect of adding a polymer additive for enhancing the paper strength or performing size press treatment of external addition.

Using the same pulp mixing ratio as in Sample Nos. 8 and 9, 1% (0.67% based on the whole) of cationized starch was added to the inner layer pulp having a high CSF, and the same as that of Example 1 was made by Kumagaya Riki Kogyo ORIE.
NTED SHEET FORMER at a speed of 750m / min, a low CSF raw material for the outer layer, a raw material with high CSF for the inner layer added with cationic starch, and a raw material for the outer layer again supplied in order to dehydrate and dry, so that the thickness direction Sample Nos. 19 and 20 were three-layer papers made of different raw material layers. Sample No. 2
In Nos. 1 and 22, oxidized starch was applied to sample Nos. 8 and 9 by 2 g / m ² size press coating.

The addition of the cationized starch increases the general strength, and the coating strength of the oxidized starch increases as in Example 1.
Even better.

[Effects] The present invention relates to a recording paper containing 100% of chemical pulp, and an outer layer mainly composed of pulp having a CSF value of 350 or less on both sides of an inner layer mainly composed of pulp having a CSF value of 420 or more. By forming the above, it was possible to provide a three-layer recording paper excellent in printing strength, ink transfer rate, and rigidity.

Continuation of the front page (72) Inventor Etsushi Itaya 5-21-1, Oji, Kita-ku, Tokyo Jujo Paper Co., Ltd. Central Research Laboratory (56) References JP-A-62-289697 (JP, A)

Claims (2)

(57) [Claims] 1. A recording paper containing 100% of chemical pulp has a CSF (CANADIAN STANDARD FREENESS) value of 420.
A recording paper comprising three layers, wherein an outer layer mainly composed of pulp having a CSF value of 350 or less is formed on both sides of an inner layer mainly composed of pulp as described above. 2. The recording sheet according to claim 1, wherein the recording sheet is printing paper A or electrophotographic paper.