JP2019104190A - Inkjet recording paper - Google Patents

Abstract

To provide an inkjet recording paper having finish close to conventional off-set printing of non-coated printing paper, no generation of feathering, high in ink concentration and less in strike-through.SOLUTION: There is provided an inkjet recording paper manufactured by coating on both surfaces of a substrate with a surface treatment agent, and having (1) ash content of 5 to 25%, (2) Stoeckigt sizing degree of 5 sec. or less, (3) water absorbency of 20 to 200 sec. (4) contact angle of 30 to 80 degree, (5) Bekk smoothness of a surface and a rear surface of 50 to 100 sec., (6) coated amount of the surface treatment agent of 0.01 to 0.5 g/mper single surface, and (7) percentage of mechanical pulp of 10 to 50%.SELECTED DRAWING: None

Description

The present invention relates to an inkjet recording sheet close to the finish by offset printing.

In the non-coated printing paper, compared with the ink jet recording paper coated with the pigment, since the pulp fiber is exposed, the surface void is large, and in the ink jet printing of the aqueous ink, the ink absorption is too good and feathering There is a problem that ink density is hard to come out, strike-through, etc., and ink jet printing correspondence is awaited.

In the ink jet recording method, minute droplets of ink are caused to fly and adhere to a recording sheet such as paper according to various operation principles, thereby recording images, characters, and the like. Furthermore, it has become possible to obtain an image which is comparable to an image formed by a multi-color ink jet recording method, as compared with a multi-color printed image by a plate-making method or an image by a color photo method. In addition, since the ink jet recording method can reduce costs more than the plate making method in applications where the number of production copies is small, the ink jet recording method is widely applied.

Further, depending on the application, inkjet printing is required to be close to the finish by conventional offset printing. For example, in the case of a book with upper and lower volumes, when the reader purchases offset printing on one side and inkjet printing on the other side, the reader will feel uncomfortable due to the different finish.

Since the ink used in the ink jet recording system is aqueous, the paper for ink jet recording is prepared to have a property of being highly water-absorbent and hygroscopic. However, due to the properties of high water absorption and high hygroscopicity, the ink jet recording paper has a large dimensional change due to humidity change, and the dimensional change is a fatal defect in applications requiring dimensional accuracy. In the case of ink jet recording, cockling occurs due to the expansion and contraction of the recording sheet accompanying the penetration of the ink, and the image quality is significantly impaired, or in the worst case, the ink head contacts the recording sheet and the ink head is damaged. Sometimes.

As a technique for solving the cockling of the recording sheet accompanying the penetration of the ink, (1) a technique that defines physical property values of the recording sheet (for example, Patent Documents 1 and 2), (2) curing the recording sheet or Technology to make composite material with film and synthetic fiber (for example, patent documents 3, 4, and 5), (3) Technology to control the occurrence of cockling itself by using a chemical which inhibits the inter-pulp fiber bond of recording paper (For example, patent documents 6, 7, and 8) are mentioned. Furthermore, the technique (for example, patent document 9) which suppresses generation | occurrence | production itself of cockling is mentioned using (4) mechanical pulp which is hard to form the coupling | bonding between fibers.

However, in the case of the above technique (1), specific production control for defining physical property values is difficult. In the case of the above technique (2), there is a problem that the texture of the conventional non-coated printing paper described above is impaired and it is difficult to be accepted in the market. Further, in the case of the above technique (3), there is a disadvantage that the surface strength of the sheet is significantly reduced. Furthermore, in the case of the technique of (4), hardwood mechanical pulp is used, and since hardwood has a harder and denser structure than softwood, there is a problem that the power consumption unit becomes high in mechanical pulping. Therefore, in order to produce hardwood mechanical pulp, pretreatment with alkaline chemicals is required, and a dedicated grinding facility is necessary, and it is difficult to adopt it because it is necessary to modify the current mechanical pulp producing facility.

As described above, the paper that can be used for inkjet printing with non-coated printing paper is gradually accepted by the market, combined with the improvement of the ink on the printing machine side and the improvement of the printing machine itself, but the offset printing What is required is the same finish as in, and has not reached that level yet.

Japanese Patent Application Laid-Open No. 6-143796 JP, 2005-280010, A JP-A-8-169174 JP-A-8-258408 JP, 2000-263927, A JP 2002-103791 A Unexamined-Japanese-Patent No. 2002-219858 Unexamined-Japanese-Patent No. 2004-66492 Japanese Patent Application Publication No. 2007-10930

An object of the present invention is to provide an ink jet recording sheet which is close to the finish by offset printing of a conventional non-coated printing sheet, does not cause feathering, has a high ink density, and has a low strike through.

As a result of intensive investigations on means for improving the ink jet suitability of ink jet recording paper, the present inventor finds that the above problems can be solved by specifying the paper manufacturing conditions and the characteristics of the paper, and completes the present invention. It reached.

The first invention of the present application is an ink jet recording sheet produced by applying a surface treatment agent to both sides of a paper-made substrate,
(1) 5 to 25% of ash content
(2) Stekhito size degree 5 seconds or less (3) water absorption 20 to 200 seconds on the front and back side (4) contact angle 30 to 80 degrees on the front and back side
(5) Beck smoothness on the front and back surfaces is 50 to 100 seconds (6) The amount of the surface treatment agent applied is 0.01 to 0.5 g / m ² per one surface
(7) Mechanical pulp ratio is 10 to 50%
It is characterized by being.

According to a second aspect of the present invention, in the first aspect, the ink jet recording sheet is provided to a paperback book.

According to the present invention, it is possible to provide an inkjet recording sheet which is close to the finish by offset printing, does not cause feathering, has a high ink density, and has a low strikethrough.

Hereinafter, embodiments of the present invention will be described.
In the production of the inkjet recording paper of the present invention, a paper machine comprising the steps of a wire part, a press part, a drier part and a reel part is used.

The ink jet recording paper according to the present invention is mainly made of kraft pulp as raw material pulp, and mechanical pulp, waste paper deinking pulp and the like can be used. As kraft pulp, softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), etc. can be used. As the mechanical pulp, stone ground pulp (SGP), pressurized groundwood pulp (PGW), refiner ground pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), etc. can be used. . As waste paper deinking pulp, deinking pulp (DIP) such as newsprint waste paper deinking pulp, high quality waste paper deinking pulp, etc. can be used.

A filler can be added to the ink jet recording sheet of the present invention. Specifically, calcium carbonate can be added or white carbon may be added. Since white carbon has a high ink absorption capacity, it contributes to feathering and the improvement of the opacity after printing, and calcium carbonate contributes to the improvement of the opacity, and can be made into an ink jet recording sheet without strike through.

In addition, the kind of filler to be used is not particularly limited, and fillers generally used for printing paper, such as inorganic fillers such as titanium dioxide, talc, clay and silica, and organic pigments can be used as necessary.

Here, the ash content of the inkjet recording paper of the present invention is 5 to 25%, preferably 10 to 25%. Low ash results in lack of opacity and worse strikethrough. If the ash content is too high, the contact angle decreases and ink bleeding is likely to occur.

In the ink jet recording paper of the present invention, a sulfuric acid band, a sizing agent, a paper strengthening agent, a retention aid, a dye and the like can be added to the pulp. As sizing agents, sizing agents such as rosin sizing agents, alkyl ketene dimers and alkenyl succinic anhydrides can be used. As a paper strengthening agent, cationized starch, polyacrylamide based resin, etc. can be used. In addition, additives such as slime control agents, pitch control agents and antifoaming agents can also be used.

Here, the degree of stationary size of the inkjet recording paper of the present invention is 5 seconds or less. If the size of the sticky person is higher than this, the tendency to feathering becomes strong and the setting of the ink becomes slow, so that the problem of hand transfer is likely to occur.

The ink jet recording sheet of the present invention is characterized in that the coating amount of the surface treatment agent is smaller than that of the conventional printing sheet. Specifically, the coating amount of the surface treatment agent is 0.01 to 0.5 g / m ² , preferably 0.1 to 0.5 g / m ² per one side. Many conventional printing papers are printed on an offset rotary press or an offset sheet-fed press. Offset printing requires higher surface strength than other printing methods, and the surface strength of paper is enhanced by surface treatment agents such as starch oxide, and problems due to insufficient surface strength such as paper loss and whitening are avoided. . It has been found that when ink jet printing is performed on such paper, the water-soluble ink bleeds sharply and the ink density decreases, which is not suitable for practical use. It is considered that the reason is that the hydrophilic starch increases the hydrophilicity of the paper surface, the contact angle decreases, and the ink spreads faster on the paper surface, so that the ink is likely to cause bleeding.

As a surface treatment agent for the inkjet recording paper of the present invention, a binder, a surface sizing agent,
Cationic polymers, water-soluble metal salts and the like can be used. As binders, in addition to binders based on starch such as cationized starch and starch oxide, binders such as polyacrylamide, polyvinyl alcohol, carboxymethyl cellulose and styrene butadiene based latex can be used. As a surface sizing agent, surface sizing agents, such as a styrene maleic acid type copolymer and a styrene acrylic acid type copolymer, can be used. As the cationic polymer and the metal salt, known ones can be used, and the ink jet printability can be improved by such means.

The water absorbency of the front surface and the back surface of the ink jet recording sheet of the present invention is set to 20 to 200 seconds, preferably 50 to 150 seconds. If the degree of water absorption is low, feathering will be severe, if it is high, the penetration of the ink will be slow, and the ink set will be poor, resulting in hand transfer.

The contact angle between the front surface and the back surface of the ink jet recording sheet of the present invention is 30 to 80 degrees, preferably 50 to 80 degrees. If the contact angle is low, feathering will be severe, and if it is high, ink penetration will be slow, and ink set will be poor, so that hand transfer is likely to occur.

In the production of the ink jet recording sheet of the present invention, the sheet is dried by a dryer and then smoothed by a calender device, but the calendering may be omitted if the target printability can be obtained. As a device for performing calendar processing, commonly used calendar devices such as chilled calendars, soft calendars, and gloss calendars can be used. Depending on the required smoothness, the number of nips, nip pressure, roll temperature, roll material, roll hardness and the like are set.

The Beck's smoothness of the ink jet recording paper of the present invention is 50 to 100 seconds on both sides. If the Beck smoothness is higher than this, the thickness is insufficient and the strike-through becomes severe.

The ink jet recording paper of the present invention has a mechanical pulp content of 10 to 50% by mass (including mechanical pulp derived from waste paper pulp). If it is less than 10% by mass, the opacity is insufficient. If it is higher than 50% by mass, feathering is likely to occur. It is desirable that the freeness of the mechanical pulp to be blended is adjusted to 75 to 120 ml CSF. If the freeness of the mechanical pulp is lower than 75 ml CSF, the dewatering ability of the paper machine will be poor, resulting in production problems such as a reduction in the paper speed. If the freeness is higher than 120 ml CSF, the proportion of fine fibers will be reduced and feathering will occur.

The ink jet recording paper of the present invention can be blended with waste paper deinked pulp within the range not against the specific matters of the present invention. The higher the content ratio of waste paper deinking pulp, the more desirable from the viewpoint of recycling, but the upper limit of the content ratio is determined also by the bulk, opacity and whiteness required for ink jet recording paper.

The basis weight of the inkjet recording paper of the present invention is about 50 to 150 g / m ² , and the basis weight can be set without limitation according to the intended use. For example, in the paperback application, the basis weight is preferably about 60 to 70 g / m ² . The opacity of the inkjet recording paper of the present invention is about 85 to 97%. An opacity of 90% or more is suitable for paperback applications.

The thickness of the inkjet recording paper of the present invention is about 60 to 150 μm, and can be set without limitation according to the intended application. For example, in the paperback application, the thickness is preferably 80 to 100 μm. If paper in this range is used, it is preferable to set the thickness to 80 to 100 [mu] m, for example, in paper-printer applications where paper-rolled books have good hand-feeling and page turnability.

The Clark stiffness (JIS P 8143: Paper-Stiffness Test Method-Clark Stiffness Tester Method) of the inkjet recording paper of the present invention varies depending on the blending ratio of the pulp and the basis weight, but for example, in the case of paperback application, Clark stiffness ( It is preferable that it is 40-60 cm < ³ > / 100 by length). If less than 40cm ^3/100, to thereby provide an inexpensive impression there is no firm hand Nikkan, less likely to turn the page after bookbinding. Above 60cm ^3/100, too hard as this, there is a problem that the handling is deteriorated.

The inkjet recording method includes a piezo method and a thermal method as an ink discharge method. The piezo method is a method in which a piezo element is attached to a micro tube filled with ink, and a voltage is applied to the piezo element to deform the ink, thereby discharging the ink to the outside of the tube. The thermal method is a method in which bubbles are generated in the ink in the tube by the heating of the heater and the ink is discharged.

The inkjet recording sheet of the present invention is more effective for thermal inkjet printing. The reason is that the thermal ink has a lower viscosity than the piezo ink, and the tendency of feathering and strikethrough is strong, and additionally, the thermal ink has a lower ink density, so the amount of ink is large. It is thought that there is a tendency to

Hereinafter, the effects of the present invention will be specifically described by examples and comparative examples. In addition,% represents mass% unless there is particular notice, and the addition amount is represented by solid content or an active ingredient with respect to 100 mass parts of bone-dry pulp.

Example 1
A pulp dispersion consisting of 30 parts by mass of thermomechanical pulp (80 ml CSF) and 70 parts by mass of hardwood bleached kraft pulp (420 ml CSF), 2.0 mass% of sulfuric acid band, cationized starch (manufactured by GS L Japan Co., Ltd., product Name: Geltron 24) 0.5% by mass, retention improver (Hymo Co., Ltd., trade name: Hymoloc ND-260) 200 ppm added, light calcium carbonate added as filler, ash content about 20% Paper was made to be As a surface treatment agent, a mixture of oxidized starch (manufactured by Oji Cornstarch Co., Ltd., trade name: Oji Ace A) and calcium chloride so as to have a solid content mass ratio of 5: 1 is a total coating amount of 0 on both sides. It coated by the gate roll coater so that it might become .60 g / m < ² > (the same coating amount as front and back). Calendar conditions were set so that the Bekk smoothness was about 80 seconds, and an inkjet recording sheet with a basis weight of 65 g / m ² was obtained.

(Example 2)
A surface treatment agent was further added with a water resistant agent (trade name: DK6810, manufactured by Starlight PMC Co., Ltd.) as a cationic polymer, and mixed so as to be starch oxide: calcium chloride: water resistant agent = 5: 1: 1. An ink jet recording sheet was obtained in the same manner as in Example 1 except that the product was coated with a gate roll coater so that the coated amount would be 0.70 g / m ² (the same coated amount on the front and back) in total on both sides.

(Example 3)
A surface sizing agent (Shokko PMC Co., Ltd., trade name: SS2718) is further added to the surface treating agent, and oxidized starch: calcium chloride: water resistant agent: surface sizing agent = 5: 1: 1: 0.3 An ink jet recording sheet was obtained in the same manner as in Example 1 except that the mixture was coated by a gate roll coater so that the total coating amount would be 0.73 g / m ² (the same coating amount on the front and back). The .

(Example 4)
An inkjet recording sheet was obtained in the same manner as in Example 2 except that the coating amount of the surface treatment agent was 1.0 g / m ² (the same coating amount on the front and back) in both sides in total.

(Example 5)
As a surface treatment agent, a coating of starch oxide: calcium chloride: water resistance agent = 5: 2: 2 is coated so that the coating amount becomes 0.90 g / m ² (the same coating amount on the front and back) in total on both sides. An ink jet recording sheet was obtained in the same manner as in Example 1 except that the work was carried out.

(Example 6)
The raw material pulp composition is 10 parts by mass of thermomechanical pulp (80 ml CSF) and 90 parts by mass of hardwood bleached kraft pulp (420 ml CSF), and the coated amount of the surface treatment agent is 0.20 g / m ² (total on both sides) An ink jet recording sheet was obtained in the same manner as in Example 5 except that the same coating amount was applied to the front and back sides).

(Comparative example 1)
Ink jet recording was carried out in the same manner as in Example 1 except that the ash content was about 3% and that the coating amount of the surface treatment agent was 1.2 g / m ² (the same coating amount on the front and back) in total on both sides. I got the paper.

(Comparative example 2)
The internal sizing agent (rosin emulsion sizing agent) was added so that the Stekhito size degree was 10 seconds, and the coating amount of the surface treatment agent was 1.2 g / m ^{2 in} total on both sides (coating amount same on front and back An ink jet recording sheet was obtained in the same manner as in Example 1 except that the above was used.

(Comparative example 3)
An ink jet recording sheet was obtained in the same manner as in Example 1 except that the surface treatment agent was not applied, and that the calender conditions were changed so that the Bekk smoothness was about 40 seconds.

(Comparative example 4)
An ink jet recording sheet was obtained in the same manner as in Example 1 except that the surface treatment agent was not applied, and that the calender conditions were changed so that the Bekk smoothness was about 120 seconds.

(Comparative example 5)
The raw material pulp composition was 60 parts by mass of thermomechanical pulp (80 ml CSF) and 40 parts by mass of bleached hardwood kraft pulp (420 ml CSF), and the coated amount of the surface treatment agent was 1.5 g / m ² (total on both sides) An inkjet recording sheet was obtained in the same manner as in Example 1 except that the same coating amount was applied to the front and back.

(Comparative example 6)
An inkjet recording sheet was obtained in the same manner as Comparative Example 1 except that only oxidized starch was coated as a surface treatment agent so that the coating amount was 1.2 g / m ² (the same coating amount on the front and back). The

Tables 1 and 2 show the evaluation results of the ink jet recording sheets of Examples 1 to 6 and Comparative Examples 1 to 6. The test method and evaluation method are as follows. The degree of water absorption and the contact angle are the values measured on the paper surface

(ash)
JISP 8251: 2003 Paper, paperboard and pulp-test method for ash-525 ° C combustion method (stoichit size degree)
JISP 8122: 2004 Paper, paperboard-Test method for size-Stekhito method (water absorption) JAPAN TAPPI paper pulp test method No. 32-2: 2000 Paper-Water absorption test method-Part 2: Dropping method The amount of water to be dropped was measured as 8 μl.
(Contact angle)
The contact angle after 0.1 sec was measured using a contact angle meter DMs 401 manufactured by Kyowa Interface Science Co., Ltd.
(Bekk smoothness)
JISP 8119: 1998 Paper and board-Smoothness test method by Beck smoothness tester

(Feathering, ink density, strike through evaluation)
Using the ink jet printer (manufactured by HP, ENVY 4520), the surface of the paper was printed under the conditions of pigment ink, thermal head, print quality: color maximum 4800 × 2000 dpi, print mode: standard, and evaluated as follows.

Feathering: Relatively evaluated in the following four steps visually.
優 れ る Excellent, ○ Good, や や Slightly inferior, × Poor

Ink density: The optical density of the black solid portion was measured at four points in the absolute mode using an optical densitometer (R730, manufactured by Ihara Denshi Kogyo Co., Ltd.).
◎ 1.35 or more, 1.251.25 or more and less than 1.35, 51.15 or more and less than 1.25, × 1.15 or less

Go through: Japan TAPPI No. Post-Print Opacity The opacity was measured according to the Post-Print Opacity Test Method and evaluated according to the following criteria.
◎ 91.0% or more, ○ 89.0% or more and less than 91.0%, Δ 88.0% or more and less than 89.0%, × less than 88.0%

As shown in Table 1, in Examples 1 to 6 of the present invention, an inkjet recording sheet having excellent evaluation of feathering, ink density and strike-through in inkjet printing is obtained. On the other hand, in Comparative Examples 1 to 6, any of these evaluations is worse.

Claims (2)

An ink jet recording sheet produced by applying a surface treatment agent to both sides of a substrate,
(1) 5 to 25% of ash content
(2) Stekhito size degree 5 seconds or less (3) water absorption 20 to 200 seconds on the front and back side (4) contact angle 30 to 80 degrees on the front and back side
(5) Beck smoothness on the front and back surfaces is 50 to 100 seconds (6) The amount of the surface treatment agent applied is 0.01 to 0.5 g / m ² per one surface
(7) Mechanical pulp ratio is 10 to 50%
An inkjet recording sheet characterized in that The ink jet recording sheet according to claim 1, wherein the ink jet recording sheet is to be provided in a paperback book.