JP2011225747A - Offset printing ink, and printed matter using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide offset printing ink which is more bluish than conventionally used color carbon black for ink and is provided with dry down control while keeping equivalent printability such as print durability for providing stable printability and space quality on low density paper such as non-coated paper and finely coated paper with printing ink using specific carbon black, and to provide printed matters using the same.SOLUTION: The offset printing ink includes carbon black, a resin and a solvent. The carbon black has a dibutyl phthalate (DBP) oil absorption of 80-140 (cm/100g), an iodine adsorption of 30-100 (m/g) and the total content of iron and zinc of ≤60 ppm. There is also provided printed matters using the ink.

Description

  The present invention relates to an offset printing ink for printing on low-density paper such as non-coated paper and fine-coated paper, and further relates to a printed matter printed using the ink. More specifically, in the black ink for offset printing, the specific carbon black used for tires and rubber has a bluish and dryer color than the carbon black for color used in conventional printing ink applications. The present invention relates to an excellent offset printing ink and printed matter in which down is suppressed.

  In black ink for offset printing, carbon black is generally used as a pigment. In offset printing, since the ink film thickness on the paper after printing becomes thin, the blending ratio of carbon black is usually as high as 15 to 25% in order to ensure the printing density. Also, the hue of the printed image line exhibits a reddish or yellowish hue, but this hue is not preferred as a printing ink, and an expensive blue pigment or dye is added to adjust the hue to blue. Control (Non-Patent Documents 1 and 2).

  In black ink for offset printing, carbon black is generally used as a pigment. Carbon black has a complex agglomeration form in which spherical carbon particles called primary (basic) particles are fused and branch into chained or irregular chains, forming aggregates similar to bunch of grapes. ing. This aggregate is called an aggregate, and the degree of fusion of the primary particles forming this aggregate is called a structure. When carbon black is dispersed in an ink vehicle, it is impossible to disperse finer than an aggregate (Non-Patent Documents 2 and 3).

  Since high gloss is required for ink that requires high quality even in offset printing, carbon black with a small aggregate diameter is selected to increase the smoothness of the ink film surface even when the ink is thin. . However, in inks that print on low density paper, such as uncoated paper and finely coated paper, the carbon black sinks into the paper together with the ink vehicle, and the print density cannot be maintained. It is necessary to select carbon black having a large size (Non-patent Document 3).

  Considering the structure of carbon black in which spherical carbon particles are arranged in a grape shape, attention should be paid to the primary particle diameter and structure in order to select carbon black having a large aggregate diameter (Non-patent Document 3). That is, if the primary particle diameter and the structure are increased, the aggregate diameter is increased as a result, and offset printing with high blackness becomes possible.

  When primary particles are enlarged, the aggregate diameter is relatively large even if the structure is the same. The size of the primary particle diameter can be evaluated from the specific surface area of carbon black measured by a nitrogen adsorption method or an iodine adsorption method. The specific surface area measured by these adsorption methods is almost inversely proportional to the primary particle diameter, and the specific surface area becomes small when the primary particle diameter is large. However, when printing is performed with an ink using carbon black having a large primary particle size, that is, a small specific surface area, the hue of the printed image line exhibits a good bluish hue, while the ink called dry-down is used. In the process of drying, the print density decreases and the degree of the phenomenon that the print density of the image line differs immediately after printing and after drying is large. Insufficient blackness tends to be a problem in the printed matter after drying (Non Patents) Reference 3).

  For the purpose of preventing this dry-down, a method for processing paper as a base material, for example, disclosed in JP-A-6-192996, JP-A-10-131089, JP-A-2002-327393, etc. However, any of them seems to be effective for dry-down, but it is a special paper base material and is not practical in terms of productivity and cost.

  Further, when the structure is enlarged, the aggregate diameter becomes relatively large even if the primary particle diameter is the same. The size of the structure can be evaluated by a dibutyl phthalate (abbreviated as DBP in the present invention) oil absorption measurement method. That is, when the structure is large, the DBP oil absorption becomes large. When printing is performed with ink using carbon having a high DBP oil absorption, dry-down is reduced, and a good print density can be maintained even in a printed matter after drying, which is advantageous as the quality of the ink. However, when carbon with a high DBP oil absorption is used, the hue of the printed image line exhibits a yellowish hue, so an expensive blue pigment or dye must be added to make the hue bluish. It is a factor that raises. For this reason, a method using a special black pigment instead of carbon black is disclosed in Japanese Patent Application Laid-Open No. 2002-265837, but it is more expensive and less practical than carbon black.

  As one of means for solving these problems, carbon black having a large particle diameter and carbon black having a large structure may be used in combination (for example, Japanese Patent Application Laid-Open No. 7-18200, Example 2). When production is performed, a plurality of silos for carbon black are required, and the load on the equipment and the process in printing ink production is required, such as complicated measurement work.

  In addition, when carbon with a large particle size and structure is used, the aggregate diameter becomes too large, so the required dispersibility cannot be maintained in offset printing with a thin ink film thickness in the print line, This is not preferable because significant gloss deterioration and a problem that carbon particles accumulate on a plate, a guide roller, or the like during printing occur.

  Further, JP-A-7-18200 and JP-A-8-176463 disclose carbon black for printing ink, and preparation of lithographic newspaper offset rotary ink using carbon black for printing ink is disclosed. However, JP-A-7-18200 and JP-A-8-176463 only describe “resin varnish” as a resin component necessary for the ink, and it is substantially a printing ink and its production. Method Further, there is no disclosure about the printed matter formed with the manufactured printing ink, and there is doubt about the disclosed ink suitability.

Japanese Patent Application Laid-Open No. 11-349911 discloses carbon black having good dispersibility in mineral oil having a low polycyclic aromatic component content. However, when an ink is produced, such a mineral is simply used. Just having good dispersibility in oil does not always mean good physical properties as an ink.
Furthermore, the following examples can be given as examples in which carbon black is used as the black pigment as in the present invention and rosin-modified phenol resin is used as the resin varnish.

  That is, JP-A-9-25444 uses carbon black as a black pigment, rosin-modified phenolic resin as a resin varnish, and an example of using a black ink composition for offset printing using a pigment dispersant. It is disclosed. However, although the stability (dispersibility) of the printing ink is improved, a high-quality printed matter cannot be obtained simply by selecting carbon black.

Japanese Patent Application Laid-Open No. 2004-269572 discloses a printing ink produced from carbon black having a specific physical property and a resin varnish. As a physical property of carbon black, a DBP absorption amount (oil absorption amount) is 30. ~65 ^(cm 3 / 100g) a is defined to be, but if the DBP oil absorption is ⁸⁰ (cm 3 / 100g) or less, when printing on non-coated paper or fine coated paper, dry-down There is a possibility that blackness is insufficient after printing.

  Furthermore, JP-A-2004-107585 discloses an ink composition produced from carbon black and resin varnish having specific physical properties. However, although a rosin-modified phenolic resin is disclosed as a resin varnish, the DBP oil absorption and particle size alone cannot be used as an ink that requires high quality, and with the disclosed particle size, Printing density cannot be maintained when printing on non-coated paper or finely coated paper.

  In JP-A-2002-322407, JP-A-2002-322408, and JP-A-2002-327143, carbon black and a resin varnish that is solid at room temperature are preliminarily dry-ground and added with a solvent or the like. A method of mixing and manufacturing is disclosed. Moreover, although it is described that specific carbon black is used, when these carbons are used and this manufacturing method is performed, the structure is destroyed, such as uncoated paper or finely coated paper. It is not suitable for low-grade paper applications.

  In general, the blackness of carbon black increases as the aggregate diameter decreases, but the fluidity decreases as the aggregate diameter decreases. For this reason, Japanese Patent Application Laid-Open No. 2001-72912 discloses a surface treatment method of carbon black with aminosilane. However, although the dispersibility of carbon black is improved, there is a problem that the drying property of ink is lowered.

Furthermore, Japanese Patent Laid-Open No. 2001-192484 discloses that carbon black is produced without surface treatment and without performing surface treatment that improves the dryness, which is a defect of surface oxidized carbon black. Methods and printing ink compositions are disclosed. However, DBP oil absorption amount of carbon black being produced is at all 80 (cm 3 ^/ 100g) or less, in this case, when printing on non-coated paper or fine coated paper, large dry-down, after printing Blackness deficiency may occur.

  Carbon black contains foreign matter such as iron rust coming from devices such as coke grains, furnace strips, heat exchangers, etc., which are generated when carbon black is called a grid. Although it is removed using a micron separator as a foreign matter removal, the carbon black for rubber has a larger amount of grid than the carbon black for non-rubber (carbon black for color). If there are many grid components, there will be a problem of wear resistance at the time of printing and a problem of abrasion resistance that scrapes the image area of the plate, which cannot be used for printing ink. Furthermore, these metallic foreign matters are generated during the production of carbon black, and are difficult to remove when mixed in the details of the carbon particles. For this reason, it is necessary to control the amount of foreign matter contained in the carbon black, but there has been no discussion of metal species, content, and effective analysis methods. Japanese Patent Application Laid-Open No. 2008-169309 defines the hardness of granulated particles (indicating the hardness of carbon black beads for rubber by a measurement method according to JISK6219) (3 to 20 cN). Even if carbon black is used, the printing durability cannot be solved.

Further, JP 2006-282774, carbon black ratio tinting strength: 80~95 (%), DBP oil ^{absorption: 80~120 (cm 3 / 100g)} , nitrogen adsorption specific surface area: 60 to 120 (m An ink for offset printing having a blue hue using ² / g) has been disclosed, but is insufficient for the blue hue.

  At present, the color tone of the printing ink is controlled by adding an expensive blue complementary color pigment instead of carbon black alone to enhance the black feeling, but the cost of the printing ink by the complementary color pigment is large. Therefore, there is a demand for offset printing inks that use carbon black that exhibits a bluish tone without the addition of complementary pigments, and can be used for offset printing on low-density paper such as uncoated paper and finely coated paper. Development of printed materials and manufacturing methods is desired. Thereby, the amount of expensive complementary color pigments can be reduced.

JP-A-6-192996 Japanese Patent Laid-Open No. 10-131089 JP 2002-327393 A JP 2002-265837 A Japanese Patent Laid-Open No. 7-18200 JP-A-8-176463 Japanese Patent Laid-Open No. 11-349311 Japanese Patent Laid-Open No. 9-25444 JP 2004-269572 A JP 2004-107585 A JP 2002-322407 A JP 2002-322408 A JP 2002-327143 A JP 2001-72912 A JP 2001-192484 A JP 2006-282774 A JP 2008-169309 A

“Printing and Paper 2000” issued on March 5, 2000, Issuing Paper Industry Times, Inc. “Carbon Black Yearbook No. 58 (2008)” edited by Carbon Black Association "Carbon Black Handbook" April 15, 1995, 3rd edition, Editorial publisher Carbon Black Association

  The present invention is to provide a printed matter obtained by offset printing on low density paper such as non-coated paper and fine coated paper. As offset printing ink, the amount of carbon black is increased, and the ink viscosity is increased. Ink for offset printing having a bluish tone and suppressing dry-down by containing specific carbon black without adding an expensive complementary color pigment while maintaining blackness without increasing, and this It aims at providing the printed matter formed by printing with the ink for offset printing.

  As a result of intensive studies to solve the above problems, the ink for offset printing containing specific carbon black, rosin-modified phenol and solvent has a bluish tone without adding expensive complementary color pigments, and is dry-down. The inventors have found that the above can be suppressed, and have reached the present invention.

That is, the present invention
Dibutyl phthalate (DBP) oil absorption 80-140 (cm3 / 100 g),
Iodine adsorption amount 30-100 (m2 / g)
Carbon black having a total content of iron and zinc of 60 ppm or less,
The present invention relates to an offset printing ink characterized by containing a resin and a solvent.

  The present invention also relates to the above offset printing ink, wherein the resin is at least one selected from rosin-modified phenolic resins, petroleum resins and alkyd resins.

  Furthermore, the present invention relates to the above offset printing ink, wherein the rosin-modified phenol resin has a weight average molecular weight of 20,000 to 300,000.

The present invention also relates to the above offset printing ink, wherein the solvent is at least one selected from petroleum solvents and vegetable oils.
Furthermore, the present invention relates to the above offset printing ink, wherein the petroleum solvent has an aniline point of 65 to 110 ° C.

The present invention also relates to the above offset printing ink, wherein the offset printing ink is a permeation dry type.
Furthermore, the present invention relates to a printed matter obtained by printing the above offset printing ink on uncoated paper or finely coated paper.

  According to the present invention, it is possible to obtain an offset printing ink having a bluish hue and suppressing dry-down. That is, the offset printing ink containing the specific carbon black of the present invention has a bluish tone without adding a complementary color pigment, and suppresses dry-down. Can be eliminated or eliminated. Moreover, the offset printing ink of the present invention can be applied to low-density paper such as non-coated paper and fine-coated paper, and further can provide a stable and high-quality printed matter because dry-down is suppressed. The industrial value of the present invention is enormous.

  Hereinafter, the form for implementing this invention is demonstrated concretely.

  Carbon black, which is the first essential component according to the present invention, is a carbon black for rubber (Non-Patent Documents 2 and 3) generally used for tires and rubbers, and has the following physical properties. This is different from non-rubber carbon black (commonly referred to as color carbon black) that has been used for printing inks.

  The demand for carbon black (on a supply basis) is about 910,000 tons / year in 2007. Among them, carbon black for rubber is about 95%, 860,000 tons / year, and carbon black for non-rubber used for printing ink is about 5%, 50,000 tons / year. Large supply of black. Of these carbon blacks for rubber, those having specific physical properties can be used for printing inks to produce excellent offset printing inks.

Physical properties required in the carbon black for rubber according to the present invention, it is necessary to DBP oil absorption amount to the first (measured according to ASTM D-2414) is in the range of 80~140 ^(cm 3 / 100g) . More ^{preferably, 90~130 (cm 3 / 100g)} , more preferably it is necessary that 95~125 ^(cm 3 / 100g). When the ink for printing the low density of the sheet, DBP oil absorption amount is 80 (cm 3 ^/ 100g) be smaller than the paper quality deterioration due blackness shortage after dry down is large printing occurs. Further, DBP oil absorption amount ¹⁴⁰ (cm 3 / 100g) reduced larger than ink fluidity thereof significantly, not obtained good dispersibility.

Furthermore, as a characteristic of the carbon black of the present invention, the iodine adsorption amount (measured in accordance with ASTM D-1510) needs to be in the range of 30 to 100 (m ² / g), preferably 40 to It is necessary to be 95 (m ² / g), more preferably 45 to 90 (m ² / g). The physical property value of iodine adsorption is common in carbon black for rubber. As described above, the amount of adsorbed iodine is in an inversely proportional relationship with the primary particle diameter. When the numerical value is small, the particle diameter increases and the aggregate diameter increases. In the case of ink for printing on low density paper, the larger the aggregate diameter, that is, the smaller the iodine adsorption amount, the more advantageous for dry-down, but the iodine adsorption amount is 30 (m ^2). / G), the aggregate diameter is too large, so that the dispersibility is deteriorated and the friction resistance is deteriorated. In addition, when the iodine adsorption amount is larger than 100 (m ² / g), the aggregate diameter is decreased, which causes a problem of dry-down.

Furthermore, as a further characteristic of the carbon black of the present invention, the total content of iron and zinc in 1 g of carbon black needs to be 60 μg (60 ppm) or less, and the smaller the amount, the more desirable.
Furthermore, the total content is a problem regardless of which content of iron and zinc is high.

  The metal content in the carbon black is measured by ICP (Inductively Coupled Plasma) emission analysis.

  Moreover, as described above, carbon black contains foreign matters such as iron rusts coming from devices such as furnace strips and heat exchangers generated during production. If there are a lot of foreign objects, it will cause problems such as inking deterioration during printing and frictional problems that scrape the image area of the plate, resulting in insufficient printed matter and damage to the printing press. Cannot be used as printing ink. The content and the plate wearability are directly proportional to each other. If the content exceeds 60 ppm, the plate wear that the image portion is missing occurs. Furthermore, the addition amount of the carbon black of the present invention is preferably 10 to 30% by weight in the printing ink.

  As the resin used in the present invention, in addition to the rosin-modified phenol resin, rosin-modified maleic acid resin, alkyd resin, petroleum resin, and the like can be used alone or in combination of two or more. The weight average molecular weight of the resin is preferably 20,000 to 300,000. If the weight average molecular weight is less than 20,000, the ink has insufficient viscoelasticity, and if it exceeds 300,000, the fluidity of the ink becomes insufficient.

  The resin (rosin-modified phenolic resin, rosin-modified maleic acid resin, alkyd, petroleum resin, etc.) is a solvent that is at least one selected from petroleum solvents and vegetable oils, and in some cases a gelling agent such as an aluminum chelate compound It is used as what was melt | dissolved at about 190 degree | times and varnished. The addition amount of the resin is 20% to 50% by weight with respect to the total amount of the printing ink composition.

  The vegetable oils in the present invention are vegetable oils and compounds derived from vegetable oils. In the triglycerides of glycerin and fatty acids, at least one fatty acid is a fatty acid having at least one carbon-carbon unsaturated bond, and triglycerides thereof. Fatty acid monoesters comprising esterification reaction with saturated or unsaturated alcohols can be mentioned.

  Typical vegetable oils are: Asa seed oil, flaxseed oil, eno oil, psyllium oil, olive oil, cacao oil, kapok oil, kaya oil, mustard oil, kyounin oil, kiri oil, kukui oil, walnut oil, poppy oil, sesame oil , Safflower oil, radish seed oil, soybean oil, daikon oil, camellia oil, corn oil, rapeseed oil, niger oil, nuka oil, palm oil, castor oil, sunflower oil, grape seed oil, gentian oil, pine seed oil Cottonseed oil, palm oil, peanut oil, dehydrated castor oil, and the like. Especially soybean oil, coconut oil, linseed oil and rapeseed oil are preferable.

  In the present invention, the vegetable oil esters used include fatty acid esters derived from vegetable oils such as soybean oil, cottonseed oil, linseed oil, safflower oil, tall oil, dehydrated castor oil, canola oil, and rapeseed oil. Examples of the fatty acid ester include monoalkyl ester compounds, and the fatty acid constituting the monoester is preferably a saturated or unsaturated fatty acid having 16 to 20 carbon atoms, stearic acid, isostearic acid, hydroxystearic acid, oleic acid, linol. Examples include acids, linolenic acid, eleostearic acid and the like. The alcohol-derived alkyl group constituting the fatty acid monoester preferably has 1 to 10 carbon atoms, and examples thereof include methyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, and 2-ethylhexyl. These fatty acid monoesters can be used alone or in combination of two or more. In the present invention, vegetable oils and fatty acid esters may be used alone or in combination as vegetable oil components. The amount of the solvent added is preferably 10 to 50% by weight in the ink.

  The petroleum solvents used in the present invention are paraffinic, naphthenic, and mixed solvents thereof, and the content of aromatic hydrocarbons in the solvent is preferably 1% by weight or less. The aniline point of the solvent is preferably 65 to 110 ° C. When a solvent having an aniline point higher than 110 ° C. is used, since the solubility with the resin used in the ink composition is poor, the fluidity of the ink becomes insufficient, and only a glossy printed matter can be obtained due to poor leveling. In addition, in an ink using a solvent having an aniline point lower than 65 ° C., the detachment of the solvent from the ink film at the time of drying may be poor, resulting in drying deterioration.

In the present invention, when carbon black is dispersed in the varnish, pigments other than carbon black such as organic bentonite, calcium carbonate, barium sulfate, clay, and silica can be added. can get.
As other auxiliaries used in the present invention, additives such as dispersants, gelling agents, drying inhibitors, antioxidants, antifriction agents (waxes) can be used as appropriate.

  In the present invention, the substrate to be printed may be anything as long as it meets the purpose of the offset printing ink of the present invention, which is a osmotic dry type (a substrate into which a solvent penetrates), but paper, particularly uncoated paper or Substrates that are osmotically dried, such as finely coated paper or re-paper, are suitable as the substrate for printing of the present invention.

  Next, the present invention will be described based on examples. However, the scope of the present invention is not limited to the following examples. In the present invention, “part” and “%” mean “part by weight” and “% by weight”, respectively, unless otherwise specified.

[Production example of rosin-modified phenolic resin varnish]
38.5 parts rosin modified phenolic resin (Arakawa Chemical Industries, Ltd.) having an average molecular weight of 80,000, an acid value of 20, and a softening point of 165 ° C., 30 parts of soybean oil, AF Solvent No. 5 (new) 30 parts of aniline (manufactured by Nippon Oil Co., Ltd., aniline point 88.2 degrees) were added, the temperature was raised to 180 ° C., stirred for 30 minutes at the same temperature, and then allowed to cool. 0.0 part (ALCH manufactured by Kawaken Fine Chemical Co., Ltd.) was charged and stirred at 180 ° C. for 30 minutes to obtain a rosin-modified phenolic resin varnish.

[Production example of gilsonite resin varnish]
Charge 42 parts of an aliphatic hydrocarbon resin (AMERICA GILSONITE COMPERY ER-125) extracted from gilsonite with a softening point of 120 to 125 ° C. and 58 parts of soybean oil, and heat and stir at 140 ° C. for 1 hour to obtain a gilsonite resin varnish. Obtained.

[Ink production example]
The obtained resin varnish, carbon black and solvent (AF Solvent No. 6 (manufactured by Shin Nippon Oil Co., Ltd., aniline point 93.6 ° C.)) were kneaded and mixed using the three rolls and mixer with the composition shown in Table 1. Ink of the comparative example was prepared using a digital incometer manufactured by Toyo Seiki Co., Ltd. so that the ink was adjusted to 3.5 to 4.0 under the conditions of 30 ° C., ink 1.32 cc and 400 rpm. did.

Table 2 shows a property comparison table of carbon black (CB) used in the present invention.

  CB1 to CB11 are carbon black for rubber. CB12 is a color carbon black for ink.

  The contents of iron and zinc were measured with an ICP emission spectroscopic analyzer SPS4000 manufactured by SII Corporation.

[Printing evaluation test]
About the ink of the said Example and the comparative example, the monochrome printing and the halftone dot (1 to 100% of 10% increments) printing and normal character printing were performed on the following printing conditions.

[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 Manufacturing Co., Ltd.) 0.5% tap water
Liquid Printing speed: 100,000 copies / hour Plate: CTP plate (Fuji Film Co., Ltd.)
Number of copies: 100,000 copies

[Dry-down evaluation method]
The density values immediately after printing and after 24 hours were measured using a spectrophotometer SpectroEye manufactured by Gretag Macbeth Co., and the difference was calculated and evaluated by the following calculation formula (1). The larger the value, the greater the decrease in print density due to drydown.
Formula (1)

[Printed material measurement conditions]
Concentration: spectrophotometer SpectroEye manufactured by Gretag Macbeth
45/0, D50, 2 degree field of view, Status T

[Method of evaluating hue]
Color measurement was performed with the above spectrophotometer using a color developed print that had passed 24 hours after printing, and L ^* a ^* b ^* was measured. The hue was evaluated based on the measured b ^* value. b ^* represents a yellowish hue as the value is large, and a blue hue as the value is small.

[Method for evaluating printing durability]
The printed matter is sampled every 5,000 minutes, and the degree of the solid print portion and the Japanese character portion is evaluated, and the damage degree of the image portion of the CTP plate after printing 100,000 copies is based on the following evaluation criteria. Evaluation was performed.
(Evaluation criteria)
○: No damage in the CTP print line part: No deterioration of the printed material up to 100,000 parts.
Δ: Damaged CTP print line part: Confirmed deterioration of printed matter by 70,000 copies.
X: Damage of CTP printing line part severely: Confirmed deterioration of printed matter by 50,000 parts.

[Evaluation results]
Table 3 shows the evaluation results.

As a result, when the carbon black of Examples 1 to 4 and Comparative Examples 1 to 3 are compared, the dry-down amount and b ^* value indicating bluishness are almost the same, but the printing durability essential for printability is It is getting very bad. This is due to the high content of iron and zinc in the carbon blacks of Comparative Examples 1 to 3. Further, even when Examples 5 and 6 are compared with Comparative Examples 4 and 5, the same tendency is observed, the amount of dry-down is small and the hue is bluish, but the printing durability is poor. On the other hand, Comparative Example 6 has a low iron and zinc content, so there is no problem in printing durability compared with other carbon blacks, but the dry-down amount and b ^* value are high. This is because b ^* is high even though the iodine adsorption amount is low due to the influence of the printing paper because the dry-down is large due to the osmotic drying and the print density is greatly reduced.

  As described above, by using the carbon black for specific rubber of the present invention, it has a bluish and dryness while maintaining the printability such as printing durability equivalent to that of conventionally used powdery carbon black. Ink for offset printing and printed matter in which down is suppressed can be obtained, which can contribute to improvement and stabilization of paper surface quality.

Claims (7)

Dibutyl phthalate (DBP) oil absorption 80-140 (cm3 / 100 g),
Iodine adsorption amount 30-100 (m2 / g)
Carbon black having a total content of iron and zinc of 60 ppm or less,
An offset printing ink comprising a resin and a solvent.   The ink for offset printing according to claim 1, wherein the resin is at least one selected from a rosin-modified phenol resin, a petroleum resin and an alkyd resin.   The ink for offset printing according to claim 2, wherein the rosin-modified phenol resin has a weight average molecular weight of 20,000 to 300,000.   The ink for offset printing according to any one of claims 1 to 3, wherein the solvent is at least one selected from petroleum solvents and vegetable oils.   The ink for offset printing according to claim 4, wherein the petroleum solvent has an aniline point of 65 to 110 ° C.   The ink for offset printing according to any one of claims 1 to 5, wherein the ink for offset printing is a permeation drying type.   A printed matter obtained by printing the offset printing ink according to any one of claims 1 to 6 on uncoated paper or finely coated paper.