JP2011110702A - Inkjet recording paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide inkjet recording paper of a non-coated paper type which suppresses cockling upon printing by an inkjet recording system, suppresses strike through and blotting of ink, and print irregularity, and which has high whiteness and high surface strength. <P>SOLUTION: The inkjet recording paper of a non-coated paper type is made by manufacturing paper by using raw material containing pulp and filler, wherein the pulp contains mechanical pulp, a content of the mechanical pulp is 20 to 60 mass% of the total pulp content, the ash content in the recording paper is 10 to 30 mass%, the whiteness of the recording paper is 80% or more, the recording paper contains ink fixation improving agent and an anion demand is 0.02 meq or more per 1 g of the recording paper. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an uncoated paper type ink jet recording paper having good ink jet recording suitability. More specifically, non-coated paper type ink jet capable of high-speed full-color recording, excellent cockling, whiteness, ink back-through, blurring, printing unevenness, and surface strength that can withstand offset printing. It relates to recording paper.

  The ink jet recording method records images, characters, and the like by causing micro droplets of ink to fly and adhere to a recording sheet such as paper according to various operating principles. Further, an image formed by a multicolor ink jet recording method can obtain an image that is comparable to a multicolor printing image by a plate making method or an image by a color photographic method. In applications where the number of copies to be produced is small, the inkjet recording method is being widely applied because the cost of the inkjet recording method is lower than that of the plate making method and the color photographic method.

  As the recording paper used in the ink jet recording system, high-quality paper or coated paper used for normal printing or writing is used. However, with the improvement in the performance of inkjet recording methods such as higher printing speed, higher definition, and full color, and the expansion of applications, more advanced characteristics are required for recording paper.

  With recent high-definition ink jet recording methods, the amount of ink discharged onto recording paper tends to increase. Since most of the ink components used in the ink jet recording method are water, the ink jet recording paper is produced so as to have properties that are rich in water absorption and moisture absorption. However, due to the property of being rich in water absorption and hygroscopicity, inkjet recording paper has a large dimensional variation due to a change in humidity, and the dimensional variation is a fatal defect in applications that require dimensional accuracy. In addition, in ink jet recording printing, cockling occurs due to the expansion and contraction of the recording paper due to the penetration of the ink, which not only significantly deteriorates the image quality, but the ink head may come into contact with the recording paper and the ink head may be damaged. is there.

  In order to solve the cockling of the recording paper due to the penetration of the ink, (1) a technique that defines the physical property value of the recording paper (for example, see Patent Documents 1 and 2), (2) the recording paper is cured, or a film (3) Technology for suppressing the occurrence of cockling itself using chemicals that inhibit the binding between pulp fibers of recording paper (For example, see Patent Documents 6, 7, and 8). Further, (4) a technique (for example, see Patent Document 9) that suppresses the occurrence of cockling itself using mechanical pulp that is difficult to form an interfiber bond.

  However, in the case of the technique (1), it is difficult to perform specific production management for defining physical property values. In the case of the technique (2), it becomes difficult to recycle when it is used. Further, the technique (3) has a drawback that the surface strength of the recording paper is remarkably lowered. Furthermore, the technique (4) has a drawback that the surface strength of the recording paper and the whiteness of the recording paper are lowered.

  Recently, commercial printing applications for printing full-color images by an inkjet recording method are increasing. In commercial printing applications, in order to place importance on production costs per hour, inkjet recording is performed at a higher speed, and therefore, faster ink absorbability is required for recording paper.

  In order to adapt to such a use, there is a recording sheet having a high ink absorbability (see, for example, Patent Documents 10 and 11). However, these recording papers do not have sufficient ink absorbability. Further, if the size of the recording paper is simply lowered in order to increase the ink absorbability, the ink penetrates deeply in the thickness direction of the recording paper, and ink breakthrough occurs. If the show-through occurs, it cannot be used for double-sided recording. Further, the ink spreads in the surface direction of the recording paper, causing blurring and printing unevenness in the mixed color portion, and the image quality is remarkably impaired.

Japanese Patent Laid-Open No. 6-14396 JP 2005-280010 A JP-A-8-169174 JP-A-8-258408 JP 2000-263927 A JP 2002-103791 A Japanese Patent Laid-Open No. 2002-21958 JP 2004-66492 A JP 2007-10930 A Japanese Patent No. 3048580 Japanese Patent No. 3720075

  SUMMARY OF THE INVENTION An object of the present invention is to suppress cockling during printing by an ink jet recording method, suppress ink back-through, blurring and printing unevenness, and have high whiteness and high surface strength, and is an uncoated paper type ink jet. It is to provide recording paper.

  As a result of intensive studies, the inventor has determined that (1) the specific content of the pulp is mechanical pulp, (2) the ash content in the ink jet recording paper is in a specific range, and (3) the whiteness of the ink jet recording paper is specified. (4) containing an ink fixing improver, and (5) making the ink jet recording paper an anion requirement in a specific range, the above-mentioned problems of the present invention have been solved.

  That is, an object of the present invention is an uncoated paper type inkjet recording paper obtained by papermaking a raw material containing pulp and filler, wherein the pulp contains mechanical pulp, and the content of the mechanical pulp is all pulp. The content is 20 to 60% by mass, the ash content in the inkjet recording paper is 10 to 30% by mass, the whiteness of the recording paper is 80% or more, and the inkjet recording paper contains an ink fixing improver, This was achieved by an ink jet recording paper characterized in that the required amount of anion was 0.02 meq or more per gram of ink jet recording paper.

  Preferably, the mechanical pulp has a whiteness of 75% or more.

  Preferably, the ink jet recording paper contains cationic polyacrylamide.

  Preferably, the ink jet recording paper contains an ink fixing improver applied by a film transfer coater.

  According to the present invention, cockling, blurring and printing unevenness during printing by the ink jet recording method are suppressed, high whiteness is achieved, ink back-through is suppressed, double-sided printing quality is excellent, and offset printing is also possible. It is possible to provide an uncoated paper type ink jet recording paper having a tolerable surface strength.

  The ink jet recording paper of the present invention will be described in detail.

  The ink jet recording paper of the present invention is obtained by papermaking a raw material containing pulp and filler. Contains mechanical pulp as pulp. Examples of the mechanical pulp include groundwood pulp (GP), chemiground pulp (CGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), and bleached chemithermomechanical pulp (BCTMP).

  In the present invention, conventionally known wood pulp can be used as pulp other than mechanical pulp. For example, hardwood bleached kraft pulp (LBKP), softwood bleached kraft pulp (NBKP), hardwood bleached sulfite pulp (LBSP), softwood bleached Examples include chemical pulp such as sulfite pulp (NBSP) and waste paper pulp (DIP). Moreover, non-wood pulps such as bagasse, kenaf, bamboo, hemp, cotton, cocoon, cocoon, and husk can also be used.

  The content of mechanical pulp contained in the ink jet recording paper of the present invention is measured using the method defined in JIS-P8120. The content of mechanical pulp contained in the ink jet recording paper of the present invention is 20 to 60% by mass of the total pulp content. More preferably, it is 30-50 mass%. By setting it as the said range, the balance of the suppression effect of cockling and surface strength becomes favorable.

  The ash content in the ink jet recording paper of the present invention is measured using the method defined in JIS-P8251. The ash content in the ink jet recording paper of the present invention is 10 to 30% by mass. When the ash content in the recording paper is less than 10% by mass, the effect of suppressing ink back-through is small. A larger amount of ash in the recording paper is preferable in order to suppress ink back-through. However, as the ash increases, the surface strength of the recording paper decreases. If the ash content in the recording paper exceeds 30% by mass, troubles such as paper smearing and powder falling may occur during offset printing.

  A conventionally known white pigment is used as the filler used in the ink jet recording paper of the present invention, and can be used alone or in combination. Examples of white pigments include light calcium carbonate, heavy calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, diatomaceous earth, alumina, lithopone, Mention may be made of white inorganic pigments such as zeolite, magnesium carbonate and magnesium hydroxide. Furthermore, white organic pigments such as styrene plastic pigments, acrylic plastic pigments, polyethylene, microcapsules, urea resins, and melamine resins can be mentioned.

  The whiteness of the inkjet recording paper of the present invention is 80% or more. The adjustment of the whiteness of the ink jet recording paper to 80% or more can be achieved by bleaching the pulp, using a high whiteness white pigment such as titanium dioxide as a filler, or a conventionally known fluorescent whitening agent. Can be achieved by using or a combination of these, and it is preferable to bleach the pulp.

  The whiteness of the mechanical pulp contained in the ink jet recording paper of the present invention is preferably 75% or more. The whiteness of mechanical pulp can be 75% or more by bleaching mechanical pulp. By making the whiteness of the mechanical pulp 75% or more, the whiteness of the recording paper can be increased without reducing the surface strength.

  The ink jet recording paper of the present invention contains an ink fixing improver. The ink fixing improver referred to in the present invention is a primary to tertiary amine or a quaternary ammonium salt that dissociates and exhibits cationic properties when dissolved in water, such as dimethylamine / epibromohydrin polycondensate, dimethyl Amines and epihalohydrins such as amine / epiiohydrin polycondensate, dimethylamine / epichlorohydrin polycondensate, diethylamine / epibromohydrin polycondensate, diethylamine / epiiodohydrin polycondensate, diethylamine / epichlorohydrin polycondensate Polyamine epihalohydrin resins obtained by condensation polymerization with polyamines, polyamines such as diethylenetriamine and triethylenetetramine, polyvinylamine copolymers, dimethyl / diallyl / ammonium chloride resins, polyethyleneimine quaternary ammonium salt derivatives Can. A polyamine epihalohydrin resin and a polyvinylamine copolymer are preferable, and a dimethylamine / epichlorohydrin polycondensate is more preferable.

  In the ink jet recording paper of the present invention, the required amount of anion of the ink jet recording paper by the following measurement method is 0.02 meq or more per 1 g of ink jet recording paper. Preferably, the required amount of anion is 0.02 to 0.2 meq per 1 g of inkjet recording paper. The amount of anion required can be adjusted mainly by adjusting the content of the ink fixing improver. When the required amount of anion is less than 0.02 meq per gram of inkjet recording paper, the ink penetrates deeply in the thickness direction, resulting in ink see-through, and the ink spreads in the surface direction, causing blurring and uneven printing. There are things to do. On the other hand, when the required amount of anion is 0.02 meq or more per 1 g of inkjet recording paper, occurrence of ink back-through, blurring, and printing unevenness is suppressed. However, when the required amount of anion exceeds 0.2 meq per gram of inkjet recording paper, the suppression action reaches its peak, and the amount of ink fixing improver used is excessive, which is disadvantageous in terms of cost.

  The method for measuring the required amount of anion per gram of ink jet recording paper according to the present invention is as follows. The ink jet recording paper is dried in an oven at 105 ° C. for 3 hours, the water content of the ink jet recording paper is calculated from the mass before and after drying of the ink jet recording paper, and the water content is subtracted to weigh 1 g of the absolutely dry solid content of the ink jet recording paper. . The weighed inkjet recording paper is immersed in 500 ml of 1 / 10000N polyvinyl potassium sulfate (PVSK) and stirred for 5 minutes using a magnetic stirrer. Thereafter, the supernatant was filtered using a membrane filter (pore size: 0.47 μm), and 10 ml of the obtained filtrate was mixed with a colloid titrator PCD-03 (Mutech Co., Ltd.) to 1 / 10,000 N polydiallyldimethylammonium chloride ( The titration is performed using Poly-DADMAC), and the required amount of anion per 1 g of the ink jet recording paper can be measured from the amount of PVSK consumed in the ink jet recording paper.

  The inkjet recording paper of the present invention contains mechanical pulp, the content of mechanical pulp is 20 to 60% by mass of the total pulp content, the inkjet recording paper contains an ink fixing improver, and the ash content of the inkjet recording paper Is 10 to 30% by mass, the whiteness of the ink jet recording paper is 80% or more, and the required amount of anion per 1 g of the ink jet recording paper is 0.02 meq or more. If the ink jet recording paper does not contain an ink fixing improver, or if any of the mechanical pulp content, ash content, or anion requirement of the ink jet recording paper is outside the scope of the present invention, cockling, blurring, ink back The effect of suppressing missing and printing unevenness cannot be obtained.

  The ink jet recording paper of the present invention preferably contains a paper strength enhancer. Examples of the paper strength enhancer include oxidized starch, cationized starch, amphoteric starch, anionic polyacrylamide, cationic polyacrylamide, amphoteric polyacrylamide, oxidized guar gum, cationized guar gum, and carboxymethyl cellulose. Preferred is a cationic polyacrylamide that does not interact with a cationic ink fixing improver.

  The inkjet recording paper of the present invention contains an ink fixing improver, for example, using an ink fixing improver using a size press, a gate roll coater, a film transfer coater, a blade coater, a rod coater, an air knife coater, a curtain coater, etc. It is applied and contained. In particular, it is necessary for an ink jet recording paper to contain an ink fixing improver on-machine by applying an ink fixing improver using a size press, gate roll coater, or film transfer coater installed in a paper machine. From this point, it is preferable. More preferably, the ink jet recording paper contains and contains an ink fixing improver using a film transfer coater. As a result, an ink fixing improver can be contained in the vicinity of the surface of the inkjet recording paper, and ink back-through, blurring, and uneven printing can be further suppressed.

  The ink jet recording paper of the present invention can contain conventionally known chemicals as other raw materials other than pulp and filler. Examples of the drug include pigment dispersants, thickeners, sizing agents, fluidity improvers, antifoaming agents, antifoaming agents, mold release agents, foaming agents, penetrating agents, colored dyes, colored pigments, UV absorbers, Antioxidants, antiseptics, antifungal agents and the like can be mentioned.

  In this invention, a conventionally well-known paper machine can be used as a paper machine which makes the paper containing the raw material containing a pulp and a filler. Examples of the paper machine include a long paper machine, a twin wire paper machine, a combination paper machine, a circular paper machine, and a Yankee paper machine.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
As a mechanical pulp, 45 parts of BCTMP having a whiteness of 75% and a freeness of 320 mlcsf is 45 parts, and as a pulp other than mechanical pulp, a pulp slurry comprising 55 parts of LBKP having a freeness of 320 mlcsf is used, and light calcium carbonate as a filler (trade name: TP-121, manufactured by Okutama Kogyo Co., Ltd.) 18 parts, amphoteric starch (trade name: Cato3210, manufactured by NSC Japan) 0.8 part, sulfuric acid band 0.8 part, alkyl ketene dimer type sizing agent (trade name: size pine) K903 (manufactured by Arakawa Chemical Co., Ltd.) was added, and the paper was made with a long paper machine and dried. Thereafter, dimethylamine / epichlorohydrin polycondensate (trade name: Jetfix 5052, manufactured by Satorita Chemical Co., Ltd.) as an ink fixing improver and cationic polyacrylamide (trade name: HG5304, manufactured by Seiko PMC) as a paper strength enhancer are mixed. liquid and respectively dry content with a film transfer coater so as to give a 1.5 g / ^{m 2} and 1.0 g / ^{m 2.} Thereafter, machine calendar treatment was performed to produce an ink jet recording paper of Example 1 having a basis weight of 81.4 g / m ² and a density of 0.75 g / cm ³ . At this time, the ash content of the ink jet recording paper was 10% by weight, the mechanical pulp content was 40% by weight of the total pulp content, and the anion requirement was 0.15 meq per gram of the ink jet recording paper.

(Example 2)
An ink jet recording paper of Example 2 was produced in the same manner as in Example 1 except that the light calcium carbonate content in Example 1 was changed to 30 parts. At this time, the ash content of the inkjet recording paper was 20% by mass, the mechanical pulp content was 40% by mass of the total pulp content, and the anion requirement was 0.15 meq per gram of the inkjet recording paper.

(Example 3)
An ink jet recording paper of Example 3 was produced in the same manner as in Example 1 except that the light calcium carbonate content in Example 1 was changed to 50 parts. At this time, the ash content of the ink jet recording paper was 30% by weight, the mechanical pulp content was 40% by weight of the total pulp content, and the anion requirement was 0.16 meq per gram of the ink jet recording paper.

Example 4
An inkjet recording paper of Example 4 was prepared in the same manner as Example 2 except that BCTMP having a whiteness of 80% and a freeness of 320 mlcsf was used as the mechanical pulp. At this time, the ash content of the inkjet recording paper was 20% by mass, the mechanical pulp content was 40% by mass of the total pulp content, and the anion requirement was 0.15 meq per gram of the inkjet recording paper.

(Example 5)
Except that the pulp slurry was prepared by using 25 parts of BCTMP having a whiteness of 75% and a freeness of 320 mlcsf as mechanical pulp and 75 parts of LBKP having a freeness of 320 mlcsf as a pulp other than mechanical pulp, the same as in Example 2. Thus, an inkjet recording paper of Example 5 was produced. At this time, the ash content of the ink jet recording paper was 20% by weight, the mechanical pulp content was 20% by weight of the total pulp content, and the anion requirement was 0.14 meq per gram of the ink jet recording paper.

(Example 6)
Example 2 except that a pulp slurry was prepared by using 65 parts of BCTMP having a whiteness of 75% and a freeness of 320 mlcsf as mechanical pulp, and 35 parts of LBKP having a freeness of 320 mlcsf as a pulp other than mechanical pulp. Thus, an inkjet recording paper of Example 6 was produced. At this time, the ash content of the inkjet recording paper was 20% by mass, the mechanical pulp content was 60% by mass of the total pulp content, and the anion requirement was 0.16 meq per gram of the inkjet recording paper.

(Example 7)
An ink jet recording paper of Example 7 is produced in the same manner as in Example 2, except that the dry content of the ink fixing improver is 0.2 g / m ² by coating using a film transfer coater. did. At this time, the ash content of the inkjet recording paper was 20% by mass, the content of mechanical pulp was 40% by mass of the total pulp content, and the required amount of anion was 0.02 meq per 1 g of the inkjet recording paper.

(Example 8)
An ink jet recording paper of Example 8 is produced in the same manner as in Example 2 except that the dry content of the ink fixing improver is applied by using a film transfer coater so as to be 2.0 g / m ^2. did. At this time, the ash content of the inkjet recording paper was 20% by mass, the mechanical pulp content was 40% by mass of the total pulp content, and the anion requirement was 0.20 meq per gram of the inkjet recording paper.

Example 9
An ink jet recording paper of Example 9 is prepared in the same manner as in Example 2 except that the dry content of the ink fixing improver is 3.0 g / m ² by coating using a film transfer coater. did. At this time, the ash content of the inkjet recording paper was 20% by mass, the content of mechanical pulp was 40% by mass of the total pulp content, and the required amount of anion was 0.30 meq per 1 g of the inkjet recording paper.

(Example 10)
An ink jet recording paper of Example 10 was produced in the same manner as Example 2 except that a polyvinylamine copolymer (trade name: Himax SC-700, manufactured by Hymo Co., Ltd.) was used as the ink fixing improver. At this time, the ash content of the inkjet recording paper was 20% by mass, the mechanical pulp content was 40% by mass of the total pulp content, and the anion requirement was 0.18 meq per gram of the inkjet recording paper.

(Example 11)
An inkjet recording paper of Example 11 was produced in the same manner as Example 10 except that oxidized starch (trade name: MS # 3800, manufactured by Nippon Shokuhin Kako Co., Ltd.) was used as a paper strength enhancer. At this time, the ash content of the inkjet recording paper was 20% by mass, the mechanical pulp content was 40% by mass of the total pulp content, and the anion requirement was 0.12 meq per gram of the inkjet recording paper.

(Example 12)
An inkjet recording paper of Example 12 was produced in the same manner as Example 10 except that cationized starch (trade name: CHARGEMASTER R462, manufactured by Grain Processing Corporation (USA)) was used as a paper strength enhancer. At this time, the ash content of the inkjet recording paper was 20% by mass, the mechanical pulp content was 40% by mass of the total pulp content, and the anion requirement was 0.17 meq per gram of the inkjet recording paper.

(Example 13)
An inkjet recording paper of Example 13 was produced in the same manner as Example 2 except that it did not contain a paper strength enhancer. At this time, the ash content of the ink jet recording paper was 20% by weight, the mechanical pulp content was 40% by weight of the total pulp content, and the anion requirement was 0.13 meq per gram of the ink jet recording paper.

(Example 14)
An ink jet recording paper of Example 14 was produced in the same manner as Example 2 except that oxidized starch (trade name: MS # 3800, manufactured by Nippon Shokuhin Kako Co., Ltd.) was used as a paper strength enhancer. At this time, the ash content of the inkjet recording paper was 20% by mass, the content of mechanical pulp was 40% by mass of the total pulp content, and the required amount of anion was 0.09 meq per gram of the inkjet recording paper.

(Example 15)
An ink jet recording paper of Example 15 was produced in the same manner as in Example 2 except that cationized starch (trade name: CHARGEMASTER R462, manufactured by Grain Processing Corporation (USA)) was used as the paper strength enhancer. At this time, the ash content of the inkjet recording paper was 20% by mass, the mechanical pulp content was 40% by mass of the total pulp content, and the anion requirement was 0.14 meq per gram of the inkjet recording paper.

(Example 16)
An ink jet recording paper of Example 16 was produced in the same manner as in Example 2 except that the ink fixing improver and the paper strength enhancer were applied and contained using a gate roll coater. At this time, the ash content of the inkjet recording paper was 20% by mass, the mechanical pulp content was 40% by mass of the total pulp content, and the anion requirement was 0.15 meq per gram of the inkjet recording paper.

(Example 17)
An ink jet recording paper of Example 17 was produced in the same manner as in Example 2 except that the ink fixing improver and the paper strength enhancer were applied and contained using a size press. At this time, the ash content of the inkjet recording paper was 20% by mass, the mechanical pulp content was 40% by mass of the total pulp content, and the anion requirement was 0.15 meq per gram of the inkjet recording paper.

(Example 18)
CGP having a whiteness of 60% and a freeness of 320 mlcsf was used as the mechanical pulp, titanium dioxide (trade name: A-110, manufactured by Sakai Chemical Industry Co., Ltd.) was used as the filler, and the number of blended parts of titanium dioxide was 60 parts. Except for the above, an ink jet recording paper of Example 18 was produced in the same manner as Example 2. At this time, the ash content of the inkjet recording paper was 20% by mass, the mechanical pulp content was 40% by mass of the total pulp content, and the anion requirement was 0.14 meq per gram of the inkjet recording paper.

(Comparative Example 1)
An inkjet recording paper of Comparative Example 1 was produced in the same manner as Example 2 except that a pulp slurry was prepared using 100 parts of LBKP having a freeness of 320 mlcsf as a pulp. At this time, the ash content of the ink jet recording paper was 20% by mass, and the required amount of anion was 0.12 meq per gram of the ink jet recording paper.

(Comparative Example 2)
Except that the pulp slurry was prepared with 15 parts of BCTMP having a whiteness of 75% and a freeness of 320 mlcsf as mechanical pulp and 85 parts of LBKP having a freeness of 320 mlcsf as 85 parts of pulp other than mechanical pulp, the same as in Example 2. Thus, an inkjet recording paper of Comparative Example 2 was produced. At this time, the ash content of the ink jet recording paper was 20% by weight, the mechanical pulp content was 10% by weight of the total pulp content, and the anion requirement was 0.13 meq per gram of the ink jet recording paper.

(Comparative Example 3)
Inkjet of Comparative Example 3 was the same as Example 2 except that a pulp slurry was prepared by using 85 parts of BCTMP having a whiteness of 75% and a freeness of 320 mlcsf and 15 parts of LBKP having a freeness of 320 mlcsf as a mechanical pulp. Recording paper was prepared. At this time, the ash content of the inkjet recording paper was 20% by mass, the mechanical pulp content was 80% by mass of the total pulp content, and the anion requirement was 0.17 meq per gram of the inkjet recording paper.

(Comparative Example 4)
An inkjet recording paper of Comparative Example 4 was produced in the same manner as Example 2 except that it did not contain an ink fixing improver and a paper strength enhancer. At this time, the ash content of the inkjet recording paper was 20% by mass, the content of mechanical pulp was 40% by mass of the total pulp content, and the required amount of anion was −0.02 meq per 1 g of the inkjet recording paper.

(Comparative Example 5)
An ink jet recording paper of Comparative Example 5 was produced in the same manner as Example 2 except that the dry content of the ink fixing improver was 0.1 g / m ² by coating using a film transfer. . At this time, the ash content of the inkjet recording paper was 20% by mass, the content of mechanical pulp was 40% by mass of the total pulp content, and the required amount of anion was 0.01 meq per 1 g of the inkjet recording paper.

(Comparative Example 6)
An inkjet recording paper of Comparative Example 6 was produced in the same manner as in Example 1 except that the light calcium carbonate content in Example 1 was changed to 8 parts. At this time, the ash content of the ink jet recording paper was 5% by weight, the mechanical pulp content was 40% by weight of the total pulp content, and the anion requirement was 0.14 meq per gram of the ink jet recording paper.

(Comparative Example 7)
An inkjet recording paper of Comparative Example 7 was produced in the same manner as in Example 1 except that the light calcium carbonate content in Example 1 was changed to 55 parts. At this time, the ash content of the ink jet recording paper was 35% by weight, the mechanical pulp content was 40% by weight of the total pulp content, and the anion requirement was 0.16 meq per gram of the ink jet recording paper.

(Comparative Example 8)
An inkjet recording paper of Comparative Example 8 was produced in the same manner as Example 2 except that it did not contain an ink fixing improver. At this time, the ash content of the ink jet recording paper was 20% by weight, the mechanical pulp content was 40% by weight of the total pulp content, and the anion requirement was 0 meq per gram of the ink jet recording paper.

<Cock ring>
After cutting the inkjet recording paper into A4 size, a black 100% solid printing pattern (width 150 mm × length 200 mm) was printed using an inkjet printer PIXUS iP4100 (manufactured by Canon Inc.), and the inkjet recording paper 1 hour after printing The waving was visually evaluated. A rating of 3 or higher is a level that is practically acceptable.
5: There is no cock ring.
4: Almost no cockling 3: Slightly cockling occurs.
2: A little cockling has occurred.
1: Cockling occurs frequently.

<Whiteness>
The whiteness of the ink jet recording paper was measured using the whiteness measurement method defined in JIS-P8148.

<Ink breakthrough>
After the inkjet recording paper is cut into A4 size, a black 100% solid printing pattern (width 100 mm × length 100 mm) is printed using an inkjet printer PIXUS iP4100 (manufactured by Canon Inc.), and the opposite side of the black 100% solid printing portion The whiteness was measured from the side, and the ink penetration of the ink jet recording paper was evaluated based on “whiteness of white portion without printing (%)” − “whiteness of black solid printing portion (%)”. The whiteness was measured using a Nippon Denshoku PF-10 with a sample placed on a standard plate and UV cut conditions. The smaller the value of the ink see-through, the better. A rating of 3 or higher is a level that is practically acceptable.
5: Less than 10%.
4: 10% or more and less than 13%.
3: 13% or more and less than 16%.
2: 16% or more and less than 19%.
1: 19% or more.

<Nijimi>
After cutting the inkjet recording paper into A4 size, a black fine line pattern was printed using an inkjet printer PIXUS iP4100 (manufactured by Canon Inc.), and the degree of blurring of the fine lines was visually evaluated. A rating of 3 or higher is a level that is practically acceptable.
5: There is no blurring.
4: There is almost no blurring.
3: Slight blurring occurs.
2: Slight blurring occurs.
1: There are frequent rainbows.

<Print unevenness>
After cutting the inkjet recording paper into A4 size, a solid print pattern (width 100 mm x length 100 mm) of green (100% each of magenta and cyan) is printed using an inkjet printer PIXUS iP4100 (manufactured by Canon Inc.) The degree of printing unevenness of the part was visually evaluated. A rating of 3 or higher is a level that is practically acceptable.
5: No printing unevenness.
4: There is almost no printing unevenness.
3: Print unevenness slightly occurs.
2: Some printing unevenness has occurred.
1: Printing unevenness occurs frequently.

<Surface strength>
Black ink solid printing was performed using an RI printing aptitude machine. Printing was performed under the following conditions.
Ink: IGT measurement ink, ink TV. 20 (made by DIC)
Ink amount: 1.0 cc
Printing rotation speed: 80rpm
Thereafter, the degree of picking of the printed surface was visually determined. A rating of 3 or higher is a level that is practically acceptable.
5: No picking at all.
4: Almost no picking.
3: Slight picking is observed.
2: A little picking is seen.
1: There is considerable picking.

  From the results of Examples 1 to 18, it can be seen that the ink jet recording paper of the present invention has an effect of suppressing cockling, ink back-through, blurring and printing unevenness, and high whiteness and surface strength. On the other hand, from the results of Comparative Examples 1 to 8, the ink jet recording paper in which any of pulp, ink fixing improver, ash content, whiteness, and anion requirement does not satisfy the present invention is cockling, ink breakthrough, blurring and printing. It can be seen that there is no unevenness suppressing effect and / or high whiteness and surface strength.

  From the results of Examples 2 and 18, when the whiteness of the mechanical pulp is 75% or more, a high whiteness of the recording paper can be obtained, and it has a higher surface strength than when high whiteness is obtained with the white pigment. Recognize.

  From the results of Examples 2, 13 to 15 and Examples 10 to 12, the inclusion of cationic polyacrylamide has a more excellent effect of suppressing ink penetration and printing unevenness and higher surface strength. Recognize.

  From the results of Examples 2 and 16 to 17, it can be seen that, by applying and containing an ink fixing improver using a film transfer coater, it has a more excellent ink back-through suppression effect and high surface strength.

Claims (4)

  A non-coated paper type ink jet recording paper obtained by papermaking a raw material containing pulp and filler, wherein the pulp contains mechanical pulp, and the content of the mechanical pulp is 20 to 60% by mass of the total pulp content The ash content in the recording paper is 10 to 30% by mass, the whiteness of the recording paper is 80% or more, the recording paper contains an ink fixing improver, and the required amount of anion is 0.00 per gram of the recording paper. Inkjet recording paper, characterized in that it is 02 meq or more.   The inkjet recording paper according to claim 1, wherein the whiteness of the mechanical pulp is 75% or more.   The inkjet recording paper according to claim 1, wherein the recording paper contains cationic polyacrylamide.   The ink jet recording paper according to claim 1, wherein the recording paper contains the ink fixing improver applied by a film transfer coater.