JP2005262512A - Manufacturing method of inkjet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably obtain an inkjet recording sheet excellent in gloss and image representing properties and also ink absorbency. <P>SOLUTION: In the manufacturing method of the inkjet recording sheet, in which a gloss developing layer including pigment and a binder is provided on at least one side of an air permeable support and is brought into contact with a solidifying liquid to solidify, and then pressure-welded under wet conditions against a heated mirror-finished surface and finally dried, the solid density of the gloss developing layer just before the contact with the solidifying liquid is controlled to be 25-75 mass%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing an ink jet recording sheet, and more particularly to a method for producing a recording sheet having high surface gloss and excellent ink absorbability.

  The ink jet recording system records images, characters, and the like by flying fine ink droplets according to various operating principles and attaching them to a recording sheet such as paper. The recording system has features such as high speed, low noise, easy multi-coloring, large flexibility of recording patterns, no need for development and fixing, and various uses as a printing device for various character graphics and color images. Is rapidly spreading. Furthermore, according to multicolor ink jet printing, it is possible to obtain a printed material that is comparable to silver salt color photographic printing, and the equipment required for printing is small and inexpensive. The ink jet recording method has been widely applied to the field of full-color image printing. Accordingly, an ink jet recording sheet having a high surface gloss has been strongly demanded from the conventional matte tone.

  As a method for imparting surface gloss to an ink jet recording medium, a method of smoothing the surface of a coating layer by using a calendar device such as a super calender or gloss calender and passing paper between rolls under pressure or temperature is generally used. It is. However, for the purpose of imparting surface gloss to the ink jet recording medium, calendering under high linear pressure improves the surface gloss, but the voids in the coating layer are reduced, leading to deterioration of ink absorbency. Become. Therefore, at present, it is difficult to satisfy the contradictory properties of surface gloss and ink absorbency by calendering.

  As a method for imparting surface gloss without using calendar treatment, a method for producing a high-gloss coated sheet for printing generally called cast-coated paper (hereinafter abbreviated as cast treatment) is known. This casting method includes a direct method in which the wet coating layer is pressed against the heated mirror-finished surface, and after the wet coating layer is dried, it is plasticized by rewetting and pressed onto the mirror-finished surface. And a solidification method in which a wet coating layer is solidified and pressed against a mirror-finished surface are known, and the production of an ink jet recording sheet by a cast processing method has already been proposed (for example, patent document) 1, Patent Document 2 and Patent Document 3).

  Among these casting methods, the direct method is such that when the wet coating layer is pressed against the mirror-finished surface, the water in the paint suddenly boils and destroys the coating layer. There is a problem that the temperature cannot be raised to high temperature and the low speed operation is forced. In addition, the rewet method also has a lower degree of plasticization than other methods in order to rewet the dried coating layer once, so the rewet coating layer adheres evenly to the mirror finished surface. Cannot be performed, and there is a problem such as poor uniformity of the coated surface.

  On the other hand, in the solidification method, the coating layer is pressed and dried to the mirror-finished surface in a plasticized solidified state without drying and solidifying the coating layer once as in the rewet method. It can adhere. Moreover, even if the temperature of the mirror finished surface is increased, the coating layer is not destroyed. Furthermore, since a bulky and porous coating layer can be formed, it is suitable as a method for producing an ink jet recording sheet among the casting methods.

  Various proposals have been made in order to obtain an ink jet recording sheet excellent in surface gloss using a coagulation method. For example, a combination of a resin in the coating layer and a coagulant that can coagulate the resin (see, for example, Patent Document 4, Patent Document 5, Patent Document 6, and Patent Document 7), and a gloss-expressing substance in the coagulation liquid. (For example, refer patent document 8) etc. can be mentioned.

However, the quality of the surface gloss and ink absorbency of the ink jet recording sheet by such a casting method is affected by the components contained in the coating layer and the coagulating liquid. It is known that the quality greatly changes depending on the operating conditions such as the temperature, pressure to be pressed, and time to press. In particular, in the case of the solidification method, the process of solidifying the coated surface is also included in the quality variation factors, and there is a problem that much labor is required to obtain stable and sufficient characteristics.
Japanese Patent Publication No. 6-94229 Japanese Patent No. 2750534 Japanese Patent Publication No.8-1038 JP-A-9-59897 JP 2002-266282 A JP 2002-283597 A JP 2002-293004 A JP 2002-166645 A

  An object of the present invention is to solve these problems and to provide a production method for stably producing an ink jet recording sheet having excellent surface gloss and excellent ink absorbability.

As a result of intensive studies, the present inventors have invented a method for producing an inkjet recording sheet of the present invention that can solve the problems.
That is, a glossy expression layer containing a pigment and a binder is provided on at least one surface of a gas-permeable support, and a coagulating liquid is contacted to solidify the glossy expression layer. In a method for producing an inkjet recording sheet that is pressed against and dried on a mirror-finished surface heated while in a wet state, the solid content concentration of the glossy layer immediately before coming into contact with the coagulation liquid is controlled to 25 to 75% by mass. Was achieved.

  In the present invention, it is preferable to have at least one ink receiving layer between the air-permeable support and the glossy layer. Further, it is preferable to provide a glossy layer after drying the ink receiving layer.

  In the present invention, the difference between the 75 degree incident reflection angle gloss value and the 20 degree incident reflection angle gloss value on the surface of the glossy layer is preferably 50 or less.

  According to the present invention, it has been possible to solve the problem that stable quality cannot be obtained due to fluctuations in operating conditions, which has been a conventional problem in producing an ink jet recording sheet by a coagulation method, and an excellent surface. An inkjet recording sheet having gloss and excellent ink absorbability can be stably produced.

  In the present invention, a glossy expression layer containing a pigment and a binder is provided on at least one surface of a gas-permeable support, and a coagulation liquid is contacted to solidify the glossy expression layer. In a method for producing an ink jet recording sheet that is pressed against a heated mirror-finished surface and dried while the layer is in a wet state, the solid content concentration of the glossy developing layer immediately before contacting with the coagulating liquid is set to 25 to 75% by mass. Control. The solid content concentration of the glossy layer immediately before coming into contact with the coagulation liquid is measured immediately after the wet layer is peeled off from the support.

  The glossy layer of the ink jet recording sheet used in the present invention is composed of a coating composition mainly composed of colloidal particles and a binder. The colloidal particles according to the present invention are those which are suspended and dispersed in water to form a colloidal shape. For example, alumina sol such as colloidal silica, boehmite, pseudoboehmite, etc., colloidal alumina, cationic aluminum oxide or hydrate thereof, or colloidal silica particle surface as disclosed in Japanese Patent Publication No. 47-26959 is alumina. Inorganic particles such as coated particles, conjugated diene copolymers such as polystyrene, methyl methacrylate, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer, polymers or copolymers of acrylic acid esters and methacrylic acid esters Organic polymer fine particles such as microcapsules, urea resins, and melamine can be used, and two or more of these can be used in combination.

  The glossy layer can use one or more known white pigments in combination with colloidal particles. Since the white pigment generally has a large particle size and causes opacity, the mass ratio of the colloidal particles / the white pigment is 80/20 or more, more preferably 90/10 or more, depending on the particle size of the white pigment. It is.

  Examples of binders used in the glossy layer include starch derivatives such as oxidized starch, etherified starch, and phosphate esterified starch, cellulose derivatives such as carboxymethylcellulose, hydroxymethylcellulose, and hydroxyethylcellulose, casein, gelatin, soy protein, polyvinyl alcohol, Conjugated diene copolymers such as silane-modified polyvinyl alcohol, modified polyvinyl alcohol such as acetoacetyl-modified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyvinylpyrrolidone, maleic anhydride resin, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer Acrylic polymer latex such as a polymer latex or an acrylic polymer such as a polymer latex or a copolymer or copolymer of acrylic acid ester and methacrylic acid ester, ethylene Vinyl-based polymer latex such as vinyl acid copolymer, or functional group-modified polymer latex with functional group-containing monomers such as carboxyl groups of these various polymers, thermosetting synthetic resins such as melamine resin, urea resin, etc. Water-based adhesives, polymers or copolymer resins of acrylic acid esters and methacrylic acid esters such as polymethylmethacrylate, polyurethane resins, unsaturated polyester resins, vinyl chloride-vinyl acetate copolymers, polyvinyl butyral, alkyd resins, etc. System adhesives and the like. As a compounding quantity of a binder, it is 5-70 mass parts with respect to 100 mass parts of pigments, Preferably it is 5-50 mass parts, and if it is less than 5 mass parts, the coating layer intensity | strength of a gloss expression layer is insufficient, and 70 masses. If it exceeds the area, the ink absorbability is lowered.

  For the glossy layer, as additives, dye fixing agents, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, foam suppressors, mold release agents, foaming agents, penetrants, colored dyes, colored pigments , Fluorescent whitening agents, ultraviolet absorbers, antioxidants, preservatives, antibacterial agents, water resistance agents, wet paper strength enhancers, dry paper strength enhancers, and the like can be appropriately blended.

Examples of the coating device for the glossy layer include various blade coaters, roll coaters, air knife coaters, bar coaters, rod blade coaters, curtain coaters, short dwell coaters, and size presses. The coating amount of the gloss developing layer varies depending on the smoothness and size of the support and the required surface gloss, but it may be ² g / m ² or more. In addition, after applying the glossy layer, it is possible to correct the curl by spraying humidified air or humidified steam onto the back surface of the glossy layer sandwiching the support.

  In the present invention, the glossy expression layer formed on the support is subjected to a coagulation treatment by bringing a coagulation liquid into contact therewith. Various coagulants in the coagulation liquid, including formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid, nitric acid, phosphoric acid, malic acid, acrylic acid, etc., calcium, zinc, barium, lead, magnesium, cadmium, aluminum, etc. Examples thereof include metal salts and ammonium salts, boric acid, borates, borax and the like, and one kind or a mixture of plural kinds can be used.

  In the present invention, a glossy expression layer containing a pigment and a binder is provided on at least one surface of a gas-permeable support, and the solid content concentration of the glossy expression layer immediately before contact with the coagulation liquid is 25 to 75. It is controlled so as to be mass%, more preferably 40 to 70 mass%. As a method for controlling the solid content concentration of the coating layer, for example, a coating liquid having a solid content concentration lower than 25% by mass is coated on the support, and the running speed and drying conditions of the support, for example, the infrared dryer temperature. Are controlled so as to obtain a desired solid content concentration, but are not particularly limited.

  When the solid content concentration of the gloss developing layer immediately before contact with the coagulation liquid is lower than 25% by mass, coagulation of the gloss developing layer after the coagulation treatment is insufficient, It is difficult to obtain a softly solidified glossy layer on the transport roll or to obtain a good glossy layer. In addition, when the glossy layer is pressed against the heated mirror-finished surface, the pressed part is squeezed out and the surface shape of the glossy layer is disturbed, so it is difficult to obtain a good glossy surface. When the solid content concentration is higher than 75% by mass, the solidified gloss developing layer becomes too hard. Therefore, when the gloss developing layer is pressed against the heated mirror finished surface, the glossy surface of the mirror finished surface is changed. It is difficult to obtain a good glossy surface because of insufficient copying. In addition, since the voids in the glossy layer are reduced, the ink absorbability is deteriorated.

As the support of the ink jet recording sheet used in the present invention, any support can be used as long as it has air permeability. Chemical pulp such as LBKP and NBKP, GP, PGW, RMP, TMP, CTMP, CMP, Mechanical pulp such as CGP, wood pulp such as waste paper pulp such as DIP, and non-wood pulp such as kenaf, bagasse, bamboo, and cotton and conventionally known pigments as the main components, binder, sizing agent and fixing agent, yield improvement A paper support produced by various apparatuses such as a long net paper machine, a circular net paper machine, and a twin wire paper machine, in which one or more various additives such as an agent, a cationizing agent and a paper strength enhancer are mixed. Furthermore, a paper support provided with a size press or an anchor coat layer with starch, polyvinyl alcohol or the like on a paper support, art paper with a coat layer thereon, DOO paper also includes coated paper support cast coated paper. Such a paper support and coated paper support may be directly provided with the glossy expression layer of the ink jet recording sheet of the present invention, and for the purpose of controlling flattening, a machine calendar, a TG calendar, a soft calendar, etc. Other calendar devices may be used. The basis weight of the support is usually 40 to 300 g / m ² , but is not particularly limited.

  The support used in the present invention is preferably provided with an ink-receiving layer on the paper support or coated paper support, if necessary. The ink receiving layer is composed of a coating composition mainly composed of a pigment and a binder. As the pigment used in the ink receiving layer, one or more known white pigments can be used. For example, light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, silicic acid, calcium, silicic acid Magnesium, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, hydrous halloysite, white inorganic pigments such as magnesium hydroxide, styrene plastic pigment, acrylic plastic pigment, polyethylene And organic pigments such as microcapsules, urea resins, and melamine resins. From the viewpoint of ink absorptivity, porous pigments are preferred, and synthetic amorphous silica that is particularly excellent in terms of color developability is preferably used.

  As the binder used in the ink receiving layer, starch derivatives such as oxidized starch, etherified starch, phosphate esterified starch, cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, casein, gelatin, soybean protein, polyvinyl alcohol or derivatives thereof, Polyvinyl pyrrolidone, maleic anhydride resin, styrene-butadiene copolymer, conjugated diene copolymer latex such as methyl methacrylate-butadiene copolymer, acrylate ester and methacrylate ester polymer or copolymer, etc. Acrylic polymer latex such as acrylic polymer, vinyl polymer latex such as ethylene vinyl acetate copolymer, or functional group-modified polymer latex with functional group-containing monomers such as carboxy groups of these various polymers, Melami Water-based adhesives such as resins, thermosetting synthetic resins such as urea resins, polymers or copolymer resins of acrylic acid esters and methacrylic acid esters such as polymethyl methacrylate, polyurethane resins, unsaturated polyester resins, vinyl chloride-vinyl acetate Examples thereof include synthetic resin adhesives such as copolymers, polyvinyl butyral, and alkyd resins. The blending amount of the binder is 3 to 70 parts by mass, preferably 5 to 50 parts by mass with respect to 100 parts by mass of the pigment. If the amount is less than 3 parts by mass, the coating layer strength of the ink receiving layer is insufficient. If the amount exceeds the mass part, the ink absorbability decreases.

  For the ink receiving layer, as additives, dye fixing agents, pigment dispersants, thickeners, fluidity improvers, antifoaming agents, antifoaming agents, mold release agents, foaming agents, penetrating agents, colored dyes, colored pigments , Fluorescent whitening agents, ultraviolet absorbers, antioxidants, preservatives, antibacterial agents, water resistance agents, wet paper strength enhancers, dry paper strength enhancers, and the like can be appropriately blended.

The coating amount of the ink receiving layer varies depending on the required surface gloss, ink absorption, type of support, etc., but is usually 1 g / m ² or more. In addition, the ink receiving layer can be applied by dividing a certain coating amount twice, and the surface gloss is improved as compared with coating the coating amount at once.

  Examples of the ink receiving layer coating apparatus include various blade coaters, roll coaters, air knife coaters, bar coaters, rod blade coaters, curtain coaters, short dwell coaters, size presses, etc., on-machine or off-machine Can be coated with machine.

  The ink receiving layer may not be calendered, but in order to obtain a particularly high surface gloss, it is desirable to calender the ink receiving layer. Examples of the calendar device include a machine calendar, a TG calendar, a super calendar, and a soft calendar. Among these, a soft calendering process is preferable because it causes little reduction in the absorption capacity of the ink receiving layer.

  In the present invention, a recording sheet having excellent surface gloss can be obtained. However, the difference between the gloss value of 75 ° reflection angle and the gloss value of 25 ° reflection angle (gloss value based on JIS Z8741) on the surface of the recording surface is 50. The following is preferred. In general, the specular gloss of paper or paperboard is measured at an incident / reflection angle of 75 °. However, the change in gloss value is small particularly in the case of high-gloss paper such as cast-coated paper. The visual glossiness can be quantified by measuring at the angle of reflection. Furthermore, the present inventors have found that taking the difference between the 75 degree incident reflection angle gloss value and the 20 degree incident reflection angle gloss value is more suitable for quantifying the glossiness, and when this difference is 50 or less. And found to have a higher surface gloss.

  Examples will be described below, but the present invention is not limited to these examples. In the examples and comparative examples, “parts” and “%” indicate “parts by mass” and “mass%”.

(1) Support The ratio of light calcium carbonate / heavy calcium carbonate / talc to 10 parts of wood pulp consisting of 80 parts of LBKP (freeness 400 mlcsf) and 20 parts NBKP (freeness 450 mlcsf) 10/10 / 10 pigment, 0.10 parts of commercially available alkyl ketene dimer, 0.03 parts of commercially available cationic polyacrylamide, 0.80 parts of commercially available cationized starch, 0.40 parts of sulfuric acid band, Paper making was performed at a basis weight of 90 g / m ² using a paper machine to obtain a support.

(2) Glossy expression layer On the surface of the support produced in (1), a glossy expression layer coating liquid (solid content concentration 16%) having the following composition is dried so as to have a dry coating amount of 10 g / m ^2. It was coated with an air knife coater.
Colloidal silica (Snowtex AK: manufactured by Nissan Chemical Industries) 100 parts polyvinyl alcohol (PVA117: manufactured by Kuraray Co., Ltd.) 30 parts Cationic fixing agent (Smileds resin 1001: manufactured by Sumitomo Chemical Co., Ltd.) 20 parts Fatty acid type mold release agent (DEF7100: Japan) New Chemical Research Laboratory) 5 parts

(3) Coagulation and cast treatment After the coagulation liquid having the following composition was heated and controlled at the running speed and the infrared dryer temperature to contact the gloss-expressing layer controlled so that the solid content concentration became 55% by mass, the coagulation treatment was performed. The ink jet recording sheet of Example 1 was manufactured by immediately pressing and drying at a press line pressure of 980 N / cm on a mirror roll heated to a surface temperature of 110 ° C.
Water 100 parts Borax 1 part Boric acid 1 part

  The inkjet recording sheet of Example 2 was produced in the same manner as in Example 1 except that the solid content concentration of the glossy layer immediately before being contacted with the coagulation liquid was 25% by mass.

  The inkjet recording sheet of Example 3 was produced in the same manner as in Example 1 except that the solid content concentration of the glossy layer immediately before contacting with the coagulation liquid was 75% by mass.

(Comparative Example 1)
The inkjet recording sheet of Comparative Example 1 was produced in the same manner except that the solid content concentration of the glossy layer immediately before contacting with the coagulation liquid in Example 1 was 20% by mass.

(Comparative Example 2)
The inkjet recording sheet of Comparative Example 2 was produced in the same manner except that the solid content concentration of the glossy layer immediately before contacting with the coagulation liquid in Example 1 was 80% by mass.

In Example 1, an air knife coater was applied to the surface of the support prepared in (1) so that the ink receiving layer coating solution (solid content concentration 16%) having the following composition was a dry coating amount of 8 g / m ^2. The ink jet recording sheet of Example 4 was produced in the same manner as in Example 1 except that a support provided with an ink receiving layer by coating and drying was used.
Synthetic amorphous silica (Fine Seal X37B: manufactured by Tokuyama) 100 parts Polyvinyl alcohol (PVA117: manufactured by Kuraray) 30 parts Cationic fixing agent (Smileds resin 1001: manufactured by Sumitomo Chemical) 20 parts

(Comparative Example 3)
An inkjet recording sheet of Comparative Example 3 was produced in the same manner except that the solid content concentration of the glossy layer in Example 4 was 20% by mass.

(Comparative Example 4)
The inkjet recording sheet of Comparative Example 4 was produced in the same manner except that the solid content concentration of the glossy layer immediately before contacting with the coagulation liquid in Example 4 was 80% by mass.

  The inkjet recording sheet manufactured on the conditions of the above Examples 1-4 and Comparative Examples 1-4 was used for the following evaluation. The evaluation results are shown in Table 1.

[Operability]
The operability was evaluated by visual observation of dirt on the coagulating liquid application roll. ○ indicates that there is no contamination of the coagulating liquid application roll. Δ indicates a slight transfer of the glossy layer on the surface of the coagulating liquid application roll, but there is no practical problem. X is a level at which the glossy layer is transferred to the surface of the coagulating liquid application roll, and the portion where the glossy layer is peeled off is observed on the surface of the obtained inkjet recording sheet.

[Surface gloss]
The surface gloss was measured in accordance with JIS Z8741 · P8142, using a digital gloss meter GM-26D manufactured by Murakami Color Research Laboratory at an incident / reflection angle of 20 degrees and 75 degrees, respectively.

[Ink absorption]
Ink absorption was performed by printing an image using a printer “PM-900C (setting: super fine paper, clean)” manufactured by Seiko Epson. The image used for the evaluation is composed of a black, cyan, magenta, yellow, blue, red, green 100% solid printing portion, and a pattern in which white characters are provided. The ink absorption was evaluated by visually observing the uniformity in the solid print portion, the boundary portion between adjacent solid print portions, the sharpness of white characters, and the like. ○ indicates good ink absorption. Δ is a level where there is no problem in practical use, although non-uniformity of the solid print portion and crushing of white characters are observed. ○ △ is an intermediate level between ○ and △. X is a level at which printing failure due to insufficient ink absorption is observed.

Rating:
As apparent from Table 1, the production methods of the present invention of Examples 1 to 4 have good operability, and the obtained ink jet recording sheet has a 75-degree reflection angle gloss value and a 20-degree reflection angle gloss value. The difference was 50 or less, the surface gloss was high, and the ink absorbency was excellent. On the other hand, in Comparative Examples 1 and 3 in which the solid content concentration of the gloss developing layer immediately before contact with the coagulation liquid is lower than 25%, the coagulation treatment gloss developing layer is insufficiently coagulated. The transfer of the expression layer was observed, and many portions where the gloss expression layer was peeled were observed on the surface of the obtained ink jet recording sheet, and a high surface gloss could not be obtained. Further, in Comparative Examples 2 and 4 having a solid content concentration of more than 75%, the operability was good, but the gloss-expressing layer that had been solidified was too hard, so that the glossy surface of the heated mirror-finished surface was sufficient. It was not possible to obtain a good glossy surface. Further, since the voids in the glossy layer were reduced, the ink absorbability was poor.

Claims (4)

  A glossy expression layer containing a pigment and a binder is provided on at least one surface of a gas-permeable support, and a coagulating liquid is contacted to solidify the glossy expression layer so that the glossy expression layer is in a wet state. In the method of manufacturing an ink jet recording sheet that is pressed against a mirror-finished surface heated while being dried and dried, the solid content concentration of the glossy layer immediately before contacting with the coagulating liquid is controlled to 25 to 75% by mass. A method for producing an ink jet recording sheet.   2. The method for producing an ink jet recording sheet according to claim 1, wherein at least one ink receiving layer is provided between the gas-permeable support and the glossy expression layer.   The method for producing an ink jet recording sheet according to claim 2, wherein a glossy expression layer is provided after the ink receiving layer is dried.   The inkjet recording sheet according to any one of claims 1 to 3, wherein the difference between the gloss value at 75 degrees and the gloss value at 20 degrees on the surface of the glossy layer is 50 or less. Method.