JP2014205795A - Printed matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed matter using an ink for lithographic printing excellent in flowability, onboard stability, printability and aging stability while considering global environment, and further capable of suppressing dry down amount and strike through amount of the printed matter at printing.SOLUTION: There is provided a printed matter obtained by printing an ink for lithographic printing on a paper containing 1 to 40 wt.% or pigment having a primary particle diameter of 10 nm to 500 nm and an absolute specific gravity of 2.0 to 5.0 for solving the problem.

Description

The present invention relates to a printed matter obtained by lithographic printing, and relates to a printed matter characterized by using a lithographic printing ink capable of suppressing a dry-down amount and a back-through amount of a printed matter at the time of printing.
In addition, low-quality printing paper such as comics and weekly magazines is used for the lithographic printed matter of the present invention in addition to those used for newspaper printing and the like.

In recent years, paper used for newspaper printing or the like has been reduced in the number of used papers and used paper. As the density decreases, the density of the paper becomes smaller, so the ink cannot be maintained on the surface of the paper, it can easily penetrate into the paper (dry down), and the ink can easily ooze out on the back (back) Missing).
For this reason, paper manufacturers have taken countermeasures by finely coating the surface or introducing extender pigments in the interior, but they have not been fully effective.

As described above, countermeasures have been studied from the ink side and the paper side for the problem of “through” where the paper side printed on the front side, which is a problem in newspaper printing, can be seen on the back side.

In addition, newsprint paper has been recycled from the environmental aspect, and the collected waste paper contains 60 to 100% of recovered waste paper. As the ratio of used paper increases and recycling progresses, the paper fibers of used paper become very short. Newspaper paper with a high recycling rate using these short fibers makes it difficult to retain ink on the paper surface, and easily penetrates into the paper, causing problems such as dry-down and back-through. It is coming.
As described above, the reduction of the paper reduces the paper surface quality in printing.

According to “Print Magazine” (Vol. 95, No. 11), newspaper paper has been reduced in terms of weight reduction and cost reduction. Lightweight paper (46.0 g / m ² ), ultralight paper (43.0 g / m ² ), ultra-lightweight paper (40.0 g / m ² ), and lighter weight has been developed, but there is also a problem of back-through, and now ultra-light paper is the mainstream, further lighter However, progress has been made in the future due to problems with behind-the-scenes, inking properties, and paper strength.

According to “Newspaper Technology” (Vol. 56, No. 2), when printing is performed using reduced paper, the level of strikethrough increases, so solving the issue of fallthrough through reduction is an issue. ing.

As described above, it is necessary to take measures against “dry-down” and “back-through”, and paper manufacturers, ink manufacturers, and the like are conducting various studies.

As an approach from paper, Japanese Patent Application Laid-Open No. 11-189995 discloses that the surface is finely coated with a pigment mainly composed of synthetic amorphous silica to suppress ink penetration as much as possible. However, since the ink is difficult to penetrate, the paper surface tends to become dirty, and the effect of through-through is not achieved with the reduction of the ink.

Further, as an approach from paper, International Publication No. WO 2004/085742 discloses a paper dust on a blanket of a printing press by including calcium carbonate having an average particle diameter of 0.5 to 5 μm as a filler for newsprint paper. However, the amount to be added has been limited in accordance with the recent decrease in the amount, and it has become difficult to obtain a sufficient through-through effect.

On the other hand, as an approach from the ink surface, Japanese Patent Application Laid-Open No. 2007-154182 discloses that the amount of ink required when printing at a standard printing density is reduced by using a conventional ink having a higher pigment content in ink. As a result, it is possible to reduce the penetration of ink into the paper and suppress “back-through”, but the degree of penetration of the ink into the paper does not change and the problem of dry-down has not been solved.

Further, as an approach from the printing method, by reducing the amount of ink at the time of printing by increasing the fine line, the show-through is suppressed. However, when the line becomes high and thin, there is a tendency that the paper quality does not have a sharp feeling. Therefore, the amount of ink is increased to give a sharp feeling, which hinders the suppression of showthrough.

Japanese Patent Laid-Open No. 11-189995 International Publication No. WO2004 / 085472 JP 2007-154182 A

"Print magazine" Vol. 95, No. 11, Printing Society Press, November 15, 2012, pages 21-24 “Newspaper Technology” Vol. 56, No. 2, Japan Newspaper Association, published on June 25, 2012, pages 9-12

The present invention relates to a printed matter obtained by lithographic printing, and relates to a printed matter characterized by using a lithographic printing ink capable of suppressing a dry-down amount and a back-through amount of a printed matter at the time of printing.
In addition, low-quality printing paper such as comics and weekly magazines is used for the lithographic printed matter of the present invention in addition to those used for newspaper printing and the like.

  As a result of diligent research to reduce the amount of dry-down and back-through during printing, the amount of dry-down and back-through during printing can be obtained by incorporating extender pigments with specific particle sizes and specific gravity into lithographic printing inks. The inventors have found that the amount is greatly suppressed, and have reached the present invention.

That is, the present invention relates to a printed matter obtained by printing a planographic printing ink containing an extender pigment on a paper base material, which is the following (1) to (3).
(1) The primary particle diameter of the extender pigment is 10 nm to 500 nm and the true specific gravity is 2.0 to 5.0.
(2) 1 to 40% by weight of extender pigment is contained in the total amount of lithographic printing ink.
(3) The basis weight of the paper substrate is 46 g / m ² or less.

  In the printing of newspapers, books, leaflets, etc., the lithographic printing ink provided by the present invention can suppress the amount of dry-down and the amount of back-through than before, and can improve the paper quality and reduce the amount of ink. The industrial value is enormous.

  Next, the present invention will be described more specifically with reference to preferred embodiments.

In the present invention, the pigment having a primary particle diameter of 10 nm to 500 nm and a true specific gravity of 2.0 to 5.0 may be any pigment satisfying these.

In the present invention, an extender may be used as the pigment. Moreover, even if these pigment surfaces are treated, it is only necessary to satisfy the above particle diameter and true specific gravity.

Examples of extender pigments include calcium carbonate, barium sulfate, and titanium oxide.

Examples of the extender of the organic pigment include an organic white pigment obtained from a specific fluorescent brightening agent and a quaternary ammonium compound.

In the present invention, the amount of the extender pigment having a primary particle diameter of 10 nm to 500 nm and a true specific gravity of 2.0 to 5.0 is preferably 1 to 40% by weight, more preferably 5 to 5%, based on the total amount of ink. 15% by weight. If the amount is less than 1% by weight, the effect of suppressing “dry down” and “back-through” cannot be obtained. If the amount exceeds 40% by weight, the effect of the coloring component is inferior, and the dispersibility as a lithographic printing ink is reduced. Ink properties such as stability and fluidity cannot be maintained.

The primary particle diameter in the present invention was measured by a surface observation method using a scanning electron microscope (SEM). The average particle diameter was determined by the arithmetic average diameter [Σndp / Σn, n: number fraction of each particle diameter (dp)]. JSM-6390LA manufactured by JEOL Datum Co., Ltd. was used as the scanning electron microscope (SEM).

The mechanism of suppression of “dry down” and “back-through” by adding these pigments is as follows.
Commonly used color components of lithographic printing inks, such as yellow pigments, indigo pigments, red pigments, and carbon black, have a primary particle diameter of 100 nm to 1000 nm (0.1 μm to 1 μm) when dispersed as inks. ) And the true specific gravity is about 1.0 to 2.0.
When a specific amount of pigment in the primary particle diameter and true specific gravity range of the present invention is added to a lithographic printing ink, when printed, the specific gravity is heavier than yellow pigment, indigo pigment, red pigment, carbon black, etc., which are coloring components, It penetrates into the paper first. Since the pigment with a heavy specific gravity is fixed prior to the gap between the paper fibers, it is difficult for the pigment as the coloring component to penetrate later, so that “dry down” and “back-through” It is suppressed.

As a kind of the synthetic resin used in the present invention, any resin that can be applied to printing inks such as rosin-modified phenol resin, rosin-modified maleic resin, petroleum resin, alkyd resin, etc. may be used alone or in combination of two or more kinds. Although it can be used, it is preferably a rosin-modified phenolic resin.

The vegetable oil used in the present invention is preferably a semi-drying oil or non-drying oil such as soybean oil, rice bran oil or coconut oil, but a drying oil such as linseed oil or tung oil can be used in combination as required. As for the compounding quantity of vegetable oil, 10 to 60 weight% is desirable with respect to the printing ink whole quantity. If it is less than the lower limit of the above numerical value, the fluidity of the ink is insufficient due to insufficient solubility with the resin, and in some cases, there is a problem in on-machine stability. If the number exceeds the upper limit, the set deteriorates.

  Further, the lithographic printing ink composition of the present invention includes a gelling agent, a pigment dispersant, a metal dryer, a drying inhibitor, an antioxidant, a friction improver, an anti-set-off agent, and a nonionic type as necessary. Additives such as sea surface activators and polyhydric alcohols can be conveniently used.

The lithographic printing ink composition of the present invention is useful when printed on a paper base of 1 (m ² ) (hereinafter sometimes referred to as “basis weight”) of 46 (g / m ² ) or less. is there. In the case of a paper base of more than 46 (g / m ² ), the problem of the present invention does not occur because the paper does not dry down and the back-through is suppressed. On the other hand, when it is used for 43 (g / m ² ) ultra-light paper and 40 (g / m ² ) ultra-light paper, its usefulness becomes even more remarkable.

  EXAMPLES Next, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited by these Examples. In the examples, “parts” represents parts by weight.

(Phenolic resin production example 1)
P-octylphenol 1000 parts, 35% formalin 850 parts, 93% sodium hydroxide 60 parts and toluene 1000 parts are added to a four-necked flask equipped with a stirrer, a cooler and a thermometer, and reacted at 90 ° C. for 6 hours. . Then, 125 parts of 6N hydrochloric acid and 1000 parts of tap water were added, stirred and allowed to stand, and the upper layer part was taken out to obtain 2000 parts of a toluene solution of a resole type phenol resin having a nonvolatile content of 49%. X.

(Production Example 1 of rosin-modified phenolic resin)
A four-necked flask equipped with a stirrer, a condenser with a water separator, and a thermometer was charged with 1000 parts of gum rosin, dissolved at 200 ° C. while blowing nitrogen gas, added with 1400 parts of a resole solution, and toluene was removed. Then, after reacting at 230 ° C. for 4 hours, 100 parts of glycerin was charged, esterified until the oxidation became 20 or less at 250 to 260 ° C., and rosin modified phenolic resin A (hereinafter referred to as “30% by weight”). Resin A) was obtained.

(Production Example 2 of rosin-modified phenolic resin)
A four-necked flask equipped with a stirrer, a condenser with a water separator, and a thermometer was charged with 1000 parts of gum rosin, dissolved at 200 ° C. while blowing nitrogen gas, added with 1600 parts of resole solution, and toluene was removed. Then, after reacting at 230 ° C. for 4 hours, 120 parts of glycerin was charged, esterified at 250 to 260 ° C. until oxidation was 20 or less, and rosin-modified phenol resin B (hereinafter referred to as “tolerance”) having a weight average molecular weight of 100,000 and a tolerance of 24% by weight. Resin B) was obtained.

(Production Example 3 of rosin-modified phenolic resin)
A four-necked flask equipped with a stirrer, a condenser with a water separator, and a thermometer was charged with 1000 parts of gum rosin, dissolved at 200 ° C. while blowing nitrogen gas, added with 1800 parts of a resole solution, and toluene was removed. Then, after reacting at 230 ° C. for 4 hours, 110 parts of glycerin was charged, esterified at 250 to 260 ° C. until oxidation was 20 or less, and rosin-modified phenol resin C (hereinafter referred to as “tolerance”) having a weight average molecular weight of 130,000 and a tolerance of 17% by weight. Resin C) was obtained.

(Manufacture of gel varnish for penetrating dry offset printing ink)
Stirrer, Liebig condenser, 4-neck flask with thermometer 40 parts by weight of resin A (weight average molecular weight 30000), 33 parts by weight of soybean oil, AF Solvent No. 5 (manufactured by Nippon Oil Corporation, aniline point 88 ° C. , Boiling point range 279-307 ° C.) was charged 26 parts by weight, heated to 190 ° C., stirred at the same temperature for 30 minutes, allowed to cool, and 1 part by weight of ethyl acetoacetate aluminum diisopropoxide as a gelling agent (river Kench Fine Chemical Co., Ltd. ALCH (hereinafter referred to as “ALCH”) was charged and stirred at 190 ° C. for 30 minutes to obtain a gel varnish 1 for osmotic drying type offset printing ink (hereinafter referred to as “varnish 1”).

  Furthermore, based on the composition of Table 1, the gel varnishes 2 and 3 (hereinafter referred to as varnishes 1 and 2) were obtained by the same gel varnish production method as above.

(Manufacture of base ink and ink for osmotic drying offset printing)
14 parts by weight of LIONOL BLUE FG7330 (manufactured by Toyocolor Co., Ltd.), 50 parts by weight of gel varnish 1, 12 parts by weight of SA-200 (manufactured by Takehara Chemical Co., Ltd., primary particle diameter 80 nm, true specific gravity 2.6), AF solvent No. 5 (manufactured by Nippon Oil Co., Ltd.) 5 parts by weight, 13 parts by weight of soybean oil, 94 parts by weight in total were placed on 3 rolls and kneaded twice with 3 rolls at 60 ° C. Dispersed to 7.5 μm or less to obtain base ink 1. When the amount of gel varnish 1 and AF solvent No. 5 was adjusted so that the viscosity of this base ink 1 was 5.0 ± 4 Pa · s and 100 parts by weight, 6 parts by weight of AF solvent 5 was added. About 100 parts by weight of the ink of Example 1 of 5.0 Pa · s was obtained.

  Using the same base ink preparation method as above, prepare the base ink with the formulation shown in Table 2, and adjust the viscosity of the ink to 5.0 ± 4 Pa · s by adjusting the amount of varnish and AF solvent No. 5 equivalently. As a result, about 100 parts by weight of the inks of Examples 2 to 7 and Comparative Examples 1 to 4 were obtained.

(Evaluation results)
Fluidity, on-machine stability, stability over time, paper peelability, dry-down amount, show-through property, printability (inking) in the osmotic drying type offset printing inks of Examples 1 to 7 and Comparative Examples 1 to 4 Evaluation was carried out on meat properties and piling properties), and the results are shown in Table 3.
As the paper base material, 43 (g / m ² ) paper was used.

<Measurement method of fluidity>
After 2.1 ml of ink is set in a hemispherical container, the ink is immediately dropped on an inclined plate inclined at 60 °, and the length of the ink flowing for 10 minutes is measured. Higher values indicate less ink tightness and better fluidity.
(Evaluation criteria)
○: 50 mm or more Δ: 30 mm or more and less than 50 mm ×: less than 30 mm

<Measurement method of on-board stability>
1.32 ml of ink is set in a digital incometer manufactured by Toyo Seiki Co., Ltd., and the time until the tack value reaches the maximum value at 40 ° C. and 1200 rpm is measured. The longer the time to reach the maximum value, the more slowly the ink tack value fluctuates, indicating that there is less ink viscosity increase and fluidity change on the printing press. Indicates that
(Evaluation criteria)
○: 20 min or more Δ: 15 min or more and less than 20 min ×: less than 15 min

<Measurement method of stability over time>
180 ml of the ink whose viscosity has been measured with a Raleigh viscometer (L-type viscometer (25 ° C.)) is weighed out into a sealed container of maximum 220 ml. The inside of the container is purged with nitrogen, then the lid is closed, and the container is stored in an oven at 70 ° C. for 1 week to accelerate. One week later, the product is taken out from the oven, the viscosity is measured again, and the viscosity difference (ΔPa · s) from the ink before storing in the oven is obtained. The smaller the amount of change in viscosity, the better the stability over time.
(Evaluation criteria)
○: Less than 1 Pa · s Δ: 1 Pa · s or more, less than 1.5 P · s ×: 1.5 Pa · s or more

<Measuring method of paper peelability>
When ink is applied to a newspaper renewal paper (20 × 25 cm) at 50 rpm with an RI tester (manufactured by Meisei Co., Ltd.) at 50 rpm, the ink is applied and the state for paper is visually evaluated. It has excellent inking properties and does not peel off.
(Evaluation criteria)
○: Good inking, not for paper.
(Triangle | delta): There is some incompletely-thickening defect and paper peeling is also confirmed slightly.
X: Poorly inset and paper peeling is conspicuous.

<Dry-down measurement method>
The density of the solid part immediately after printing and after 12 hours of the printed matter printed in <Printability test> below was measured, and the density retention from the density value immediately after printing was evaluated as the dry-down amount.
The concentration retention rate is obtained by the following formula.

Density retention (%) = (solid part density after 12 hours of printing) / (solid part density immediately after printing) × 100

Density measurement condition: Gretag Macbeth Spectro Eye (45/0, D50, 2 fields of view: Status T) Measure the density value of the printed matter.
(Evaluation criteria)
○: 100% to 90%
Δ: 90% to 80%
X: Less than 80%

<Three-through evaluation method>
Measure the density of the back of the solid paper 12 hours after printing in the <Printability Test> below and the density of the unprinted paper, and determine the transmittance from the density / opacity / transmittance conversion table. And introduce it into the following formula to obtain the strikethrough index.

Back-through degree (%) = (solid surface rear surface transmittance) / (unprinted surface transmittance) × 100

Density measurement condition: Gretag Macbeth Spectro Eye (45/0, D50, 2 fields of view: Status T) Measure the density value of the printed matter.
Back-through index conversion formula:
This value is (evaluation criteria)
○: 100% to 90%
Δ: 90% to 80%
X: Less than 80%

<Printability test>
Under the following printing conditions, single color solid and halftone dots (1 to 100% in 10% increments) printing and normal character printing were performed. The print density of the solid part is adjusted by adjusting the ink key so that the density value immediately after printing is in the range of 1.12 to 1.20.
Density measurement condition: Gretag Macbeth Spectro Eye (45/0, D50, 2 fields of view: Status T) Measure the density value of the printed matter.

[Printing conditions]
Printing machine: LITHOPIA BT2-800 NEO (Mitsubishi Heavy Industries, Ltd.)
Paper: Newspaper renewal: Super lightweight paper (43 g / m ² ) (Nippon Paper Industries Co., Ltd.)
(Colorimetric value: L ^* : 83, a ^* : -0.25, b ^* : 5.5)
Dampening solution: NEWSKING ALKY (Toyo Ink Co., Ltd.) 0.5% tap aqueous solution Printing speed: 100,000 copies / hour Plate: CTP plate (Fuji Film Co., Ltd.)
Number of printed copies: 50,000

[Incarnation]
The solidity of the solid portion and halftone dot portion on the paper surface when printing 50,000 copies is visually evaluated.
(Evaluation criteria)
○: Good meat setting.
Δ: Partially incompletely inked.
X: Poor meat

[Piling properties]
Visually evaluate the pileability of the paper surface when printing 50,000 copies.
(Evaluation criteria)
○: No piling.
Δ: There is some piling.
X: Piling is terrible.

  From the results in Table 3, fluidity, on-machine stability, aging stability, paper peelability, flash point, printability (fillability, piling property) are all well-balanced, dry-down amount is small, and there is a breakthrough. It was found that the examples were also excellent in properties.

The osmotic drying type offset printing ink according to the present invention is superior in stability on the printing press, inking property, and stability over time, has very little environmental impact, and can contribute to CO ₂ reduction in the atmosphere. Useful in the field of printing newspapers, magazines, flyers, etc.

Claims (1)

A printed matter obtained by printing a planographic printing ink containing extender pigment on a paper substrate, the printed matter being the following (1) to (3).
(1) The primary particle diameter of the extender pigment is 10 nm to 500 nm and the true specific gravity is 2.0 to 5.0.
(2) 1 to 40% by weight of extender pigment is contained in the total amount of lithographic printing ink.
(3) The basis weight of the paper substrate is 46 g / m ² or less.