Printing paper

Abstract

To provide Japanese printing paper excellent in printability and having Japanese feeling and touch.SOLUTION: Japanese printing paper excellent in printability and having Japanese feeling and touch, is manufactured by a method of making paper from plant fiber pulp to which a nanofiber of a natural origin (for example, a chitin nanofiber, a cellulose nanofiber or a chitosan nanofiber) is made to stick beforehand by ionic adsorption or the like (an internal addition method), or by a method of coating one or both surfaces of Japanese paper with a nanofiber of a natural origin (an external addition method).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a printing paper that retains the texture and feel of Japanese paper and has excellent printability. [Background technology]

[0002] Conventionally, papers for printing photographs using an inkjet printer or the like include glossy paper, matte paper, silk paper, and the like.

[0003] Glossy paper has a glossy surface and a smooth texture, and is commonly used as photo paper. When printing photos on glossy paper, the ink does not bleed as much and the colors come out well, making it the perfect photo paper for creating vivid photos.

[0004] Matte paper is a type of photo paper that has a matte surface and a soft texture, and is primarily used when you want to create a calm or classical impression.

[0005] Silk paper is a type of photo paper with a smooth surface that feels just like woven silk. Like matte paper, it has a subdued glossy surface with a fine, micro-grained surface and is primarily used when you want to create a calm and elegant atmosphere.

[0006] As such, there are many different types of paper for printing photographs, and since the expression of the photograph changes depending on the paper used, paper manufacturers are constantly developing products to meet the needs of a wide range of users.

[0007] For example, there is a recording medium (Patent Document 1) that has a matte feel (reduced surface gloss) by providing a top layer containing inorganic fine particles with an average secondary particle diameter of 1 to 10 μm. Furthermore, as this recording medium is considered to have an insufficient feel to the touch, there is also a recording medium (Patent Document 2) that has a matte feel and an excellent feel to the touch on the surface, and papers that meet various user needs are appearing every day.

[0008] Among these user needs, in recent years, there has been a demand from general users and professional users such as photographers to print photographs on washi paper using inkjet printers. The reason for this is that when photographs are printed on washi paper, the expression of monochrome gradations and the development of warm colors have a unique appeal. From the perspective of printing, washi paper has the advantage of having high ink absorption, which is necessary for printing characteristics, but on the other hand, the following three problems must be solved in a complex manner to use washi paper as printing paper. The first problem is that the surface of washi paper is uneven and has large voids, which often leads to poor ink dot formation. The second problem is that washi paper has long fibers and weak bonding strength between the fibers, which often leads to fiber fuzzing and bleeding. The third problem is that to improve the degree of color development, it is necessary for the pigment ink to remain on the surface layer, but washi paper has high liquid absorption, so the ink does not remain on the surface of the paper but penetrates deep into it, resulting in a decrease in the spectral reflectance, which indicates the degree of color development. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2005-231295 A [Patent Document 2] JP 2019-81325 A Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in consideration of the above problems, and its object is to provide a printing paper that has excellent printability while retaining the texture and feel of Japanese paper. And the manufacturing method of Japanese paper for printing The purpose is to provide. [Means for solving the problem]

[0011] In order to solve the above problems, the printing paper of the present invention is The printing washi paper uses one or more types of vegetable fiber pulp selected from the group consisting of paper mulberry pulp, gampi pulp, mitsumata pulp, Manila hemp, and wood pulp, and is characterized in that the printing washi paper is produced through the steps of: a first step of adding a cationic admixture to the dry weight of the vegetable fiber pulp at an appropriate concentration and uniformly mixing the mixture; a second step of adding chitin nanofiber to the dry weight of the vegetable fiber pulp at an appropriate concentration and uniformly mixing the mixture; a third step of adding a pigment to the dry weight of the vegetable fiber pulp at an appropriate concentration and uniformly mixing the mixture; and a fourth step of adding an anionic fixing agent to the dry weight of the vegetable fiber pulp at an appropriate concentration and uniformly mixing the mixture.

[0012] According to the Japanese Industrial Standards (JIS), paper is defined as "something made by bonding together vegetable fibers and other fibers." This paper can be broadly categorized into Western paper and Japanese paper, and the present invention relates to the latter.

[0013] Western paper is, in brief, a paper made of short fibers laid out in a grid, and it can be said that it was originally developed for printing, so printability was considered the top priority, and various improvements and developments have been made to date. On the other hand, Japanese paper is a paper made of long fibers intertwined together, and because of its composition, the fibers can be seen under a microscope, and the fibers have an uneven texture that can be felt when touched, giving it characteristics that Western paper does not have, such as the texture and feel of Japanese paper. However, since it was not originally created for printing, the problems mentioned above arise when it is used as printing paper. In other words, if the printability of Japanese paper is improved, there is a high possibility that the texture and feel of Japanese paper will be lost, and maintaining the texture and feel of Japanese paper and improving printability are mutually exclusive requirements.

[0014] In order to solve the above problems, the method for producing printing Japanese paper of the present invention is a method for producing printing Japanese paper using plant fiber pulp consisting of one or more of paper mulberry pulp, gampi pulp, mitsumata pulp, Manila hemp or wood pulp, and is characterized by comprising a first step of adding a cationic admixture to the dry weight of the plant fiber pulp at an appropriate concentration and mixing uniformly, a second step of adding chitin nanofiber to the dry weight of the plant fiber pulp at an appropriate concentration and mixing uniformly, a third step of adding a pigment to the dry weight of the plant fiber pulp at an appropriate concentration and mixing uniformly, and a fourth step of adding an anionic fixing agent to the dry weight of the plant fiber pulp at an appropriate concentration and mixing uniformly. Effect of the Invention

[0020] According to the present invention, Japanese paper for printing And a method for manufacturing Japanese paper for printing In Using vegetable fiber pulp consisting of one or more of paper mulberry pulp, gampi pulp, mitsumata pulp, Manila hemp, or wood pulp, printing Japanese paper was manufactured through the following steps: a first step of adding a cationic admixture to the dry weight of the vegetable fiber pulp at an appropriate concentration and uniformly mixing; a second step of adding chitin nanofiber to the dry weight of the vegetable fiber pulp at an appropriate concentration and uniformly mixing; a third step of adding a pigment to the dry weight of the vegetable fiber pulp at an appropriate concentration and uniformly mixing; and a fourth step of adding an anionic fixing agent to the dry weight of the vegetable fiber pulp at an appropriate concentration and uniformly mixing. This makes it possible to satisfy two seemingly contradictory requirements: the texture and feel of Japanese paper, and excellent printability. [Brief description of the drawings]

[0021] [Figure 1] A graph showing a comparison of the spectral reflectance of inner-added washi paper and kozo washi paper. [Diagram 2] A graph showing a comparison of the spectral reflectance of additive-free washi paper and kozo washi paper. [Diagram 3] Enlarged image of the surface of additive-added washi paper. [Figure 4] Enlarged image of the surface of inkjet paper. [Diagram 5]Magnified surface observation image of the internally-added washi paper taken with a FE-SEM (Hitachi High-Tech Science). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, the embodiments of the present invention will be described in detail.

[0023] The printing Japanese paper in this embodiment was produced by using one or more of the vegetable fiber pulps used in Japanese paper, namely paper mulberry pulp, gampi pulp, mitsumata pulp, Manila hemp, or wood pulp, by the manufacturing methods described below, i.e., the internal addition method and the external addition method. Note that in this embodiment, chitin nanofibers obtained by further wet beating or wet pulverizing chitin obtained from crab shells with a water jet were used as the naturally derived nanofibers having a single fiber diameter (D) of 2 to 1,000 nm, and this chitin nanofiber was contained in an amount of 0.01 to 50 mass% based on the total amount of vegetable fiber pulp.

[0024] <Internal addition method> This is a method of making paper from chitin nanofibers that have been attached to plant fiber pulp in advance using ion adsorption, etc. Specifically, Japanese paper for printing was produced using the following method. Step 1: Pulp disintegration or beating One or more of the above-mentioned vegetable fiber pulps are dispersed in a suitable amount of water and beaten in a disintegrator or beader to the extent that the pulp can be made into paper in a papermaking machine. Step 2: Mixing cationic fixative Add an appropriate amount of the vegetable fiber pulp to the dry weight of the pulp and mix uniformly. Step 3: Chitin nanofiber mixing The solution is diluted in advance and added to the plant fiber pulp at an appropriate concentration based on the dry weight of the plant fiber pulp, and then mixed uniformly. Step 4: Pigment mixing The solution is diluted in advance and added to the plant fiber pulp at an appropriate concentration based on the dry weight of the plant fiber pulp, and then mixed uniformly. Step 5: Mixing anionic fixative Add an appropriate amount of the vegetable fiber pulp to the dry weight of the pulp and mix uniformly. Step 6: Creating the sheet The raw material that has been subjected to steps 1 to 5 is made into paper by a general papermaking method. The basis weight of the produced sheet is 15 g / m 2 ~150g / m 2 and more preferably 30 g / m 2 ~80g / m 2 is preferable, but is not particularly limited. Alternatively, an internal addition method may be used in which the ions are fixed without using a chemical that promotes controlled ion fixation in the plant fiber pulp used in steps 2 and 5. When steps 2 and 5 are not used, the ions are fixed only by adsorption due to weak surface ions inherent to the plant fiber pulp or by adsorption due to weak interactions with nanofibers, etc.

[0025] <External addition method> This method involves coating one or both sides of Japanese paper with chitin nanofibers. Specifically, the Japanese paper for printing was produced by the following method. · Step 1: Coating Mulberry Japanese paper (45g / m 2 ) is mixed with water-soluble chitin nanofiber and filler (high surface area silicate pigment) and then coated on the surface using a standard coating method. Step 2: Top coat application A typical water-soluble polymer is dissolved and adjusted to an appropriate concentration, and then coated using a typical coating method. Step 3: Drying the sheets Dry the sheet using a common sheet drying method such as a drum dryer. However, when the content of the filler is small, it is not necessary to use it.

[0026] In order to examine the printability of the printing paper produced by the internal addition method and the external addition method, the spectral reflectance was measured under the following conditions. For comparison, mulberry paper was used. <Printing conditions> Printer used: Canon pigment ink printer Pro2000 Color Chart: Black Red Blue Yellow <Spectral reflectance measurement conditions> Spectrophotometer used: Konica Minolta CM3700d Mode: Reflectance ·Measurement wavelength: 400-700nm Processing method: Specular reflection processing (SCI processing) Target mask: Φ25.4mm

[0027] The measurement results for printing washi paper produced by the internal addition method (hereafter referred to as "internal addition washi paper"), printing washi paper produced by the external addition method (hereafter referred to as "external addition washi paper"), and kozo washi paper under the printing and measurement conditions described above are shown in Figures 1 and 2.

[0028] <Printing suitability of internally added washi paper> Referring to Figure 1, the spectral reflectance of the three primary colors (red, yellow, blue) was higher for the doped washi paper compared to the kozo washi paper, and the color vividness was improved (higher spectral reflectance means more vivid colors). The increase in the spectral reflectance of each primary color was about 50% for red (660nm) compared to about 76% (26% up), and about 53% for yellow (560nm) compared to about 78% (25% up). Also, blue (460nm) compared to 31% for kozo washi compared to 37% (5% up). There was not much improvement in the color development of black. From these results, although the color development of black did not improve compared to the conventional kozo washi paper, there was improvement in other colors, and the printability was clearly improved.

[0029] <Printing suitability of additive-added washi paper> Referring to Figure 2, compared to kozo washi, the three primary color components (red, yellow, blue) have increased: red (660nm) from approximately 50% to approximately 66% (16% up), and the spectral reflectance of yellow (560nm) from approximately 52% to approximately 71% (19% up). Blue (460nm) has increased from 30% of kozo washi to 36% (6% up). There was not much improvement in the color development of black. From these results, it can be seen that although the color development of black was not improved compared to conventional kozo washi, there were improvements in other colors, and the printability has clearly improved.

[0030] The above measurement results show that both the internally and externally added washi paper have clearly improved printability compared to conventional mulberry washi paper.

[0031] Next, for the internally and externally added Japanese papers that showed this improved printability, we investigated whether the texture and feel of the Japanese paper remained by observing the condition of the surface. The results are shown in Figures 3 to 5.

[0032] Figures 3 and 4 are magnified images (200x) of the surface of each paper taken with a digital microscope, in which the same image (in this embodiment, an image of a flower) was printed and three randomly selected points were measured. Figure 3 is a magnified image of the additive-added washi paper, and Figure 4 is a magnified image of Canon's inkjet paper. Comparing these images, in the image of Figure 4, overlapping fibers and surface irregularities could not be seen, and it was observed that inorganic materials were laid out, but in the additive-added washi paper, overlapping fibers and surface irregularities were clearly observed. From these results, it can be seen that the additive-added washi paper has improved printability compared to conventional washi paper as described above, while maintaining the texture and feel of washi paper.

[0033] Figure 5 is a magnified image (10,000x) of the surface of the internally-added washi paper taken with a Hitachi High-Tech field emission scanning electron microscope (FE-SEM). In this image, chitin nanofiber fibers (chitin NF fibers) can be clearly observed between the gaps in the plant fiber pulp (pulp fibers). In particular, overlapping pulp with chitin nanofiber entangled was observed in the area marked with a circle. From these results, it can be seen that internally-added washi paper maintains the texture and feel of washi paper while achieving improved printability compared to conventional washi paper, as mentioned above.

[0034] From the above, the internal addition method established conditions for improving the spectral reflectance, an index of color vividness measured with a colorimeter, by internally adding a composite of nanofibers and titanium oxide or silica to papermaking mulberry fibers or hemp-based fibers before papermaking. The external addition method established conditions for improving the spectral reflectance, an index of color vividness measured with a colorimeter, by externally coating washi paper with a composite of nanofibers and nanosilicic acid filler. As a result, by using washi fiber to make paper or coat washi paper using the internal or external addition method, it was possible to obtain washi paper for printing that had a spectral reflectance of each primary color that was improved by 5% at the lowest and 26% at the highest (improving ink color development) without compromising the unevenness of the fiber surface, which is a characteristic of washi paper.

[0035] In this embodiment, chitin nanofibers were used as the naturally derived nanofibers. However, cellulose nanofibers and chitosan nanofibers are also applicable, and therefore these examples were also verified and will be described below along with comparative examples.

[0036] <Example 1> This sheet was produced by attaching chitin nanofibers using the internal addition method. Specifically, the printing paper was produced by the following method. Step 1: Pulp disintegration or beating 60 kg of hemp fiber pulp is dispersed in water and beaten in a beader until it can be used in a papermaking machine to prepare 2% raw pulp (hereinafter referred to as raw pulp). Step 2: Mixing cationic fixative Prepare a 10% cationic fixative solution of Phylex R104 c, add 2 L to the raw pulp, and mix uniformly. Step 3: Chitin nanofiber mixing Add 1 L of 2% chitin nanofiber aqueous solution (manufactured by Sugino Machine Co., Ltd.) to the raw pulp prepared in steps 1 and 2 and mix uniformly. Step 4: Pigment mixing Add 1 L of 1% Reolosil (Tokuyama) aqueous solution to the raw pulp prepared in steps 1 to 3 and mix uniformly. Step 5: Mixing anionic fixative Prepare a 10% anionic fixing agent, Phylex M solution (manufactured by Meisei Chemical Industry Co., Ltd.), add 2 L to the raw pulp prepared in steps 1 to 4, and mix uniformly. Step 6: Sheet making The raw pulp that has been subjected to steps 1 to 5 is made into paper using a general papermaking method, and the sheet has a basis weight of 50 g / m 2 A printing paper (Example 1) was prepared with the above-mentioned properties.

[0037] <Example 2> The sheet was produced under the same conditions as in Example 1, except that step 3 in Example 1 was changed to 2% chitosan nanofiber (manufactured by Sugino Machine Co., Ltd.), and the basis weight of the sheet was 50 g / m 2 A printing paper (Example 2) was prepared with the above-mentioned properties.

[0038] <Comparative Example 1> The sheet had a basis weight of 50 g / m2 under the same conditions as in Example 1, except that the vegetable fiber pulp used in step 1 of Example 1 was changed to paper mulberry fiber pulp. 2 The paper was then adjusted to the above value (Comparative Example 1).

[0039] <Comparative Example 2> The sheet had a basis weight of 50 g / m under the conditions of steps 1 and 6 of Example 1 (steps 2 to 5 were not performed). 2 A hemp washi paper (Comparative Example 2) was prepared with the above-mentioned adjustment.

[0040] The results of measuring the spectral reflectance of the Japanese printing paper produced as described above are shown in Table 1 below. JPEG0007603958000001.jpg39143

[0041] Referring to Table 1, it can be seen that the spectral reflectance of each color in Example 1 is higher than those in Comparative Examples 1 and 2 for all colors, and color vividness is improved, resulting in better color development.

[0042] In addition, a sensory evaluation of the texture of the produced washi paper was conducted with the following criteria: if it was unchanged compared to the texture of kozo washi paper, it was rated as "◎"; if there was a slight change but the texture of washi paper was still there, it was rated as "○"; if the texture was reduced, it was rated as "△"; and if the texture was lost, it was rated as "×". The sensory evaluation of the washi paper texture of Example 1 was also rated as "◎".

[0043] Furthermore, to evaluate the printing characteristics, a sensory evaluation was performed on the surface fuzziness, with the following marks assigned: "◎" if there was no fuzz and if rubbing with a finger did not produce any fuzz; "○" if there was no fuzz; "△" if there was some fuzz; and "×" if there was fuzz like Japanese paper. The sensory evaluation of the fuzziness of Example 1 was "○".

[0044] Similarly, when Example 2 was compared with Comparative Examples 1 and 2, it was found that the spectral reflectance of each color was higher than those of Comparative Examples 1 and 2 for all colors, and it was confirmed that the color vividness was improved and the color development was better.

[0045] In addition, the texture and fluffiness of the Japanese paper were also evaluated for Example 2, and the results were rated as "Excellent" and "Good", similar to Example 1.

[0046] Next, a comparative study was conducted on washi paper produced using the external additive method.

[0047] <Example 3> This sheet was produced by attaching cellulose nanofibers using an external addition method. Specifically, the printing paper was produced by the following method. · Step 1: Coating Kozo washi paper (50 g / m) produced by the method of Comparative Example 1 2 ) is coated with 2% cellulose nanofiber (manufactured by Sugino Machine Ltd.) using a bar coater to a coating thickness of 10 μm. Step 2: Top coat application In Example 3, no topcoat was applied. Step 3: Drying the sheets The paper was dried in a drum dryer to produce Japanese paper for printing (Example 3).

[0048] <Example 4> · Step 1: Coating Kozo washi paper (50 g / m) produced by the method of Comparative Example 1 2 ) is coated with 2% chitosan nanofiber (manufactured by Sugino Machine Ltd.) using a bar coater to a coating thickness of 10 μm. Step 2: Top coat application In Example 4, no topcoat was applied. Step 3: Drying the sheets The paper was dried in a drum dryer to produce Japanese paper for printing (Example 4).

[0049] <Example 5> · Step 1: Coating Kozo washi paper (50 g / m) produced by the method of Comparative Example 1 2 ) is coated with 2% chitin nanofiber (manufactured by Sugino Machine Co., Ltd.) using a bar coater to a coating thickness of 10 μm. Step 2: Top coat application In Example 4, no topcoat was applied. Step 3: Drying the sheets The paper was dried in a drum dryer to produce Japanese paper for printing (Example 5).

[0050] <Example 6> · Step 1: Coating Kozo washi paper (50 g / m) produced by the method of Comparative Example 1 2 ) is mixed with 2% chitin nanofiber (manufactured by Sugino Machine Co., Ltd.) and 1% Rheolosil (manufactured by Tokuyama Co., Ltd.) in a 1:1 ratio, and the resulting solution is applied to the surface of the Japanese paper using a bar coater to a coating thickness of 10 μm. Step 2: Top coat application A 0.01% polyacrylamide aqueous solution (Alkox K2, Meisei Chemical Industry Co., Ltd.) is applied with a bar coater to a coating thickness of 10 μm. Step 3: Drying the sheets The paper was dried in a drum dryer to produce Japanese paper for printing (Example 6).

[0051] The results of measuring the spectral reflectance of the Japanese printing paper produced as described above are shown in Table 2 below. JPEG0007603958000002.jpg43142

[0052] Referring to Table 2, it can be seen that the spectral reflectance of each color in Example 3 is higher than that of Comparative Example 1 (same as that shown in Table 1 above) for all colors, and that the color vividness has been improved and the color development has become better.

[0053] The sensory evaluation of the texture of the Japanese paper of Example 3 was rated as "good", and the surface fuzziness was rated as "excellent".

[0054] Similarly, referring to Table 2, it can be seen that the spectral reflectance of each color in Example 4 is higher than that in Comparative Example 1, and the color vividness is improved and the color development is better. In addition, the sensory evaluation of the texture of the Japanese paper in Example 4 was "○", and the surface fuzziness was "◎".

[0055] Similarly, referring to Table 2, it can be seen that the spectral reflectance of each color in Example 5 is higher than that in Comparative Example 1, and the color vividness is improved and the color development is better. In addition, the sensory evaluation of the texture of the Japanese paper in Example 5 was "○", and the surface fuzziness was "◎".

[0056] Similarly, referring to Table 2, it can be seen that the spectral reflectance of each color in Example 6 is higher than that in Comparative Example 1, and the color vividness is improved and the color development is better. In addition, the sensory evaluation of the texture of the Japanese paper in Example 6 was "○", and the surface fuzziness was "◎".

[0057] As described above, even when cellulose nanofibers or chitosan nanofibers were attached using the internal addition method and the external addition method, printing Japanese paper was obtained that had improved spectral reflectance of each primary color without compromising the unevenness of the fiber surface, which is a characteristic of Japanese paper.

Claims

1. A printing washi paper using one or more types of vegetable fiber pulp selected from the group consisting of paper mulberry pulp, gampi pulp, mitsumata pulp, Manila hemp, and wood pulp, A first step of adding a cationic admixture to the plant fiber pulp at an appropriate concentration based on the dry weight of the plant fiber pulp and uniformly mixing the cationic admixture; A second step of adding chitin nanofibers to the plant fiber pulp at an appropriate concentration relative to the dry weight of the plant fiber pulp and uniformly mixing the chitin nanofibers; a third step of adding a pigment to the plant fiber pulp at an appropriate concentration relative to the dry weight of the plant fiber pulp and uniformly mixing the pigment; a fourth step of adding an anionic fixing agent in an appropriate concentration relative to the dry weight of the plant fiber pulp and uniformly mixing the anionic fixing agent; A printing paper produced through the first to fourth steps.

2. A method for producing Japanese paper for printing using one or more types of vegetable fiber pulp selected from the group consisting of paper mulberry pulp, gampi pulp, mitsumata pulp, Manila hemp, and wood pulp, comprising: A first step of adding a cationic admixture to the plant fiber pulp at an appropriate concentration based on the dry weight of the plant fiber pulp and uniformly mixing the cationic admixture; A second step of adding chitin nanofibers to the plant fiber pulp at an appropriate concentration relative to the dry weight of the plant fiber pulp and uniformly mixing the chitin nanofibers; a third step of adding a pigment to the plant fiber pulp at an appropriate concentration relative to the dry weight of the plant fiber pulp and uniformly mixing the pigment; a fourth step of adding an anionic fixing agent in an appropriate concentration relative to the dry weight of the plant fiber pulp and uniformly mixing the anionic fixing agent; A method for producing Japanese paper for printing, comprising the steps of:

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