MXPA06005187A - Pigment compositions for oil-based lithographic printing ink systems - Google Patents

Abstract

Pigment compositions for oil-based lithographic printing ink systems are provided which comprise as colourant a mixture of an organic pigment and an organic dyestuff soluble in an organic solvent (solvent dye). The printing inks prepared from these pigment compositions show outstanding improvements in colour strength combined with improvements in both gloss and transparency of the prints obtained.

Description

PIGMENT COMPOSITIONS FOR OIL-BASED LITHOGRAPHIC PRINTING INK SYSTEMS Field of the Invention The present invention relates to pigment compositions suitable for use in oil-based lithographic printing inks. More particularly, the invention relates to pigment compositions containing a combination of an organic pigment and an organic coloring matter soluble in an organic solvent (solvent dye).

BACKGROUND OF THE INVENTION Lithographic printing is a process that uses a coated metal or polymeric plate that contains a hydrophobic image area that accepts hydrophobic-based ink and a water-free hydrophilic area that accepts water, that is, the source solution. Traditional inks based on pigments for lithographic transfer printing require as an rule an increased level of pigmentation in order to achieve high color strength. Increases in pigment loading result, however, in both manufacturing and performance problems. A high pigment loading can cause various difficulties, such as a reduced dispersibility of the pigment which results in oversize pigment particles and grains, or a poor wetting performance of the pigment. The poor wetting and poor dispersion lead, on the other hand, to poor color strength, and additionally, an increased proportion of shear stress is required during the processing of the inks to achieve the desired dispersion and to overcome the viscosity. Other problems arising from the high pigment loads and / or the high viscosity of the inks may be poor transfer and poor distribution in the rollers of the printing presses, and a considerable reduction in the film-forming properties of the printing presses. printing inks. And finally, inks with high pigment loading can lead to poor transparency and poor gloss. An alternative approach to increased color strength would be to increase the thickness of the ink film although this results in additional problems. The increased thickness of the film can result in prints that are more difficult to dry or cure, in addition a lower transparency and a reduced definition of the printed image can be observed. Another problem that can be caused by an increased thickness of the ink film is related to the achievement of a correct ink / water balance in the lithographic presses thus leading to printing capacity problems. And also, the increased thickness of the ink film results in greater expense since shorter runs of the press are possible only and more frequent changes in the ink supply are needed. It has now been found that these problems can be overcome and outstanding effects can be achieved with respect to eg increased color strength, but also increased brightness and increased transparency of the prints obtained, and increased print performance, when using the new ones solvent dye / organic pigment compositions, described hereinafter, in lithographic printing ink systems. Lithographic printing ink based only on solvent dye can be prepared but these do not show any strength advantage over pigment-based inks.

Description of the Invention Accordingly, it is the main object of the present invention to provide new lithographic printing ink compositions comprising blends of solvent dye / organic pigment. Other objects of the present invention relate to processes for preparing these compositions, to prepare printing inks from these compositions, the printing inks obtained in this way, the use of the inks in the lithographic printing processes. These and other objects of the present invention will be described in the following. Thus, in a first aspect of the present invention, there is provided a lithographic printing ink composition, comprising a mixture of an organic pigment and an organic coloring matter soluble in organic solvents (solvent ink) and printing ink varnishes (vehicles of ink), solvents and other usual additives, varnishes or printing ink additives that are mixed or colored with the solvent dye either before or during the dispersion of the pigment. This particular combination of an organic pigment and a solvent dye (which is usually of the same hue), when incorporated into a printing ink for lithographic printing systems, results in an ink exhibiting synergistic effects, for example, with respect to to greater color strength and greater printing performance. The dispersion of the pigment should be considered as the process of disaggregation, wetting and incorporation of the pigment particles in a varnish medium such that the medium appears to be completely colored. The pigments are those that produce the four colors commonly used in the printing industry: specifically black, cyan (blue) magenta (red) and yellow. As a rule, they are compatible with the other components of the inventive ink compositions and constitute the base (dye) for forming the oil-based printing inks for lithographic printing processes, which are another object of the present invention. The organic pigments comprise, such as, without limitation, monoazo, disazo, azomethine, azocondensation, azocomplex-metal pigments, naphthol, metal complexes, such as phthalocyanines, dioxazone, nitro, perinone, quinoline, anthraquinone, hydroxyanthraquinone. , aminoanthraquinone, benzimidazolone, isoindoline, isoindolinone, quinacridone, anthrapyrimidine, indantrone, flavantrone, pyrantrone, antantrone, isoviolantrone, diketopyrrolopyrrole, carbazole, perylene, indigo or thioindigo. Mixtures of the pigments can also be used. Diazo pigments represent an important class of coloring materials commonly used for the preparation of lithographic printing inks. Preferably, they are yellow and orange diarylide pigments and orange disazopyrazolone pigments, including, for example, the yellow pigments C.I. (Color Index) 12, 13, 14, 17, 83, 174 and 188, as well as the Orange Pigments C.I. 13 and 34 which are frequently used as shading agents. Preferred blue pigments are, for example, metal complexes, such as copper phthalocyanine pigments (for example, Pigment Blue CI 15: 3), whereas red pigments are for example naphthol pigments, preferably β-pigments. - naphthol or β-oxinaphthoic acid (BONA) (for example, Red Pigments CI 57: 1). For further details regarding all these organic pigments reference is made to Industrial Organic Pigments, W. Herbst, K. Hunger, 2nd edition, VCH Verlagsgesellschaft, Weinheim, 1997. The pigments may have surface treatments in order to improve their performance within the chosen ink system. Typical additives for surface treatment are, for example, without limitation, rosin acids, ionic or nonionic surfactants and ionic coloring matters. The appropriate selection of the pigment additives and those for suitable surface treatments for the chosen ink system can be carried out by one skilled in the art. "Solvent Tint" is a term well known in the art and is defined in the color index (C.I.), published by the Society of Dyers and Colourists and the American Association of Textile Chemists and Colorists. As for the chemical constitution of solvent dyes, monoazo and disazo predominate, and also some polyazo dyes. Other important dyes are xanthene, triarylmethane, anthraquinone dyes, azine, thiazine and phthalocyanine. Representative red dyes include Red Solvents C.I. 19, 23, 24, 25, 26, 27 and 29 (which are all azo dyes, in addition the Red Solvents CI 1, 49, 52 and 111. Representative blue dyes include the Blue Solvents CI 14, 35, 36, 59 and 78. Representative yellow dyes include CI Yellow Solvents 7, 14, 33, 72, 94 and 114. Representative orange dyes include Solvent Oranges CI 1, 2 and 7. Mixtures of Solvent Dyes can also be used. Examples are 1: 1 (by weight) mixtures of the CI Redundant Solvents 26 and 27, or 1: 1: 1: 1 Red CI Mixes CI Solvents 23, 24, 26 and 27. The solvent / pigment dye ratios they comprise as a rule (99-1): (1-99), preferably (98-10): (2-90) and more preferred (95-30): (5: 70). Within this last interval, the ratio of (95-65): (5-35) is of special interest. Inventive pigment-based lithographic printing inks can contain from 0.1 to 70% by weight (all percentages mentioned below are by weight) of the solvent / pigment dye composition, inventive, the rest being custom printing ink varnishes (ink vehicles), solvents and other suitable and well-known additives. The range from 0.1 to 70% covers the printing inks concentrated and ready for use. For actual use, the concentrated printing inks are diluted with suitable solvents, resins, varnishes (ink vehicles) or ink vehicle components / varnishes. The percentages of 2 to 55%, more preferably 2 to 20%, are preferred for normal preparation methods (ready-to-use printing inks), the range of 12 to 18% is of special interest, while the range of 20 to 70%, preferably 20 to 55%, is for concentrated production. Within this range of preference of 20 to 55%, the concentrated production per bead mill is preferably carried out with the compositions of 20 to 35% solvent / pigment dye content; while for production with kneader, the corresponding preferred range is from 35 to 55%. These concentrates, which can also be prepared at various concentrations by extrusion, can be the basis for preparing the inks, for example, by dilution, used for actual printing processes. Another inventive modality comprises lithographic printing ink colorants, comprising a mixture of an organic pigment of an organic coloring matter soluble in an organic solvent (solvent dye) in which the organic pigment is coated with ink varnishes (ink vehicles) of printing, solvents and other usual additives, varnishes or printing ink additives that are mixed or colored with the solvent dye either before or during pigment processing. These lithographic printing ink colorants can be considered as surface treated (coated) pigment compositions comprising solvent dye / organic pigment (highly concentrated) combinations, for example containing about 60 to 95%, preferably of 70 to 90% of the combination, and approximately 40 to 5%, preferably 30 to 10%, of the usual printing ink varnishes, solvents and other additives mentioned hereinafter. The solvent / pigment dye ratio is as mentioned hereinabove. It can be prepared by surface coating (coating) of the organic pigment with a varnish (ink vehicle) or varnish component, solvent and other usual additives, vehicles (components) or additives that are mixed or colored with the solvent dye either before or during processing. The solvent dye may be present in dispersed or dissolved form. More particularly, the process for preparing these lithographic printing ink dyes (treated on the surface and concentrates), comprises: (a) incorporating the printing ink varnish, which is premixed or dyed with the solvent dye, in an aqueous slurry of the organic pigment, isolate it, and optionally dry it, or (b) add the printing ink varnish to an aqueous slurry of the solvent dye and then combine it with an aqueous slurry of the organic pigment, isolate it and optionally dry it , or (c) adding the printing ink varnish to an aqueous slurry of an organic pigment / solvent dye combination, isolating and optionally drying it. Printing inks for the actual printing process can be obtained, for example, by diluting the concentrates. The printing ink varnishes (ink vehicles) may comprise, among other components, for example, high-boiling distillates and / or vegetable oils, high-wetting alkyd resins plus highly-structured alkyd resins and vegetable resins, and mixtures thereof. the same; Additional monomers / oligomers / polymers that can be cured by UV radiation can also be used. The high-boiling distillates can be called mineral oil solvents comprising distillation fractions of aliphatic or aromatic hydrocarbons boiling points from 100 to 350 ° C, preferably 180 to 300 ° C, or vegetable oils. The vegetable oils for use in the printing ink vehicles of the invention are the commonly available vegetable triglycerides in which the fatty acid portions have a chain length of about 12 to 24 carbon atoms, preferably 18 to 22 carbon atoms. Of particular interest are those which have a substantial proportion of portions of di-unsaturated linoleic fatty acids and tri- unsaturated linoleic fatty acids, for example, soybean oil, coconut, cottonseed, flaxseed, safflower, sunflower, corn, sesame, naba and peanut or mixture thereof. Although the oils mentioned above may be employed in the raw state as they are originally expressed from the seed material, there are advantages in subjecting them to certain preliminary processing steps. For example, alkaline refining removes gums and phospholipids that can interfere with vehicle properties and final ink formulations. Alkaline refining also removes free fatty acids, which tend to reduce the hydrophobicity properties in ink formulations. Hydrocarbon distillation fractions are preferred, but vegetable oils are also important. Examples of the resins include long oil alkyd resins, medium oil alkyd resins, short oil alkyd resins, phenol modified alkyd resins, styrenated alkyd resins, aminoalkyl resins, oil free alkyd resins, alkyd thermosetting resins, resins UV curing, acrylic lacquer resins, acrylic polyol resins, polyester resins, epoxy resins, methylated or butylated melamine resins, vinyl acetate copolymers, styrene or styrene alkyd resins, styrene-diene copolymers, resins polyurethane, rosin (abietic acid), rosin salts (acids), such as alkali metal salt (sodium, potassium), and modified rosins such as resinates of rosin metals (acids) (copper, zinc, magnesium resinates), esters of rosin, such as rosin maleinized rosin of pentaerythritol or phenolic resins modified with rosin, and in addition rosin stears based on vegetable oils, such as esters of elevated oils or soybean oils (methyl, butyl), and also hydrogenated rosins, disproportioned rosins, dimerized, polymerized and partially polymerized rosins (crosslinked rosins, such as formaldehyde), or mixtures thereof. These compounds and their use in the printing compositions are well known in the art. They are not limiting. Examples of monomers that can be cured by UV radiation are, without limitation, acrylate monomers, such as 1,4-butanediol acrylate, propoxylated glycerol triacrylate and pentaerythritol triacrylate. UV curable monomers can be considered as an ink solvent for the solution of solvent dyes. After curing with UV then it can be considered that the solvent dye remains dissolved or dispersed in the cured resin. As the point of discrimination between the ink-solvent and ink-resin activity is the fluidity, for example, partially UV-cured oligomers can be classified as either a solvent or a resin. Additional details of lithographic printing inks (also known as transfer inks, oil-based inks, distillate-based inks or vegetable oil-based inks) can be found in "The Printing Ink Manual, "5th edition, edited by RH Leach and RJ Pierce, Blueprint (Chapman and Hall), chapter 6, pp. 342-452 (1993) .The mixture of pigment / solvent dye can be prepared by mixing (grinding) both In this last case, the solvent dye can be pre-dissolved or dispersed in an organic solvent that can be aliphatic, alicyclic and aromatic hydrocarbons, halogenated hydrocarbons, esters, ketones and alcohols. Oil-based printing systems for lithographic printing systems can be prepared by incorporating the pigment into the printing ink varnish by a variety of shear rate induction methods, such as mixing, beading, triple roller milling, kneading and extrusion; alternatively, heat induction methods can also be used. Examples of the typical methodology are triple roll mill, horizontal and vertical bead mill, cobra mill, mixer or mixer with Z-blades, extruder with single, double or triple screw and also a Müller glass plate dispersion apparatus. The coloring matter can be dissolved in the varnish by any method that allows the application of heat. This heat can be applied deliberately from an external source. For example, the laboratory scale incorporation of the dye can be carried out in a heated bead mill with water jacket or hot plate. During the incorporation process, agitation is an advantage although high shear stress is not essential. Alternatively, the heat may originate from the cutting and motility action of a viscous substrate. For example, the milling process with industrial-scale beads in a lithographic varnish often produces heat. This heat production is often higher during the tested pigment dispersion since the viscosity of the pigment / varnish mixture is higher. If the pigment incorporation method does not produce heat, the solvent dye is better incorporated by pre-dissolving in a mixture of the varnish medium, or one or more of the varnish components or solvents, by the addition of heat. The preferred method in the incorporation will be extrusion. In a vehicle of ink (or molten resin of ink vehicle) passed through this apparatus, the dispersion of the pigment (by high shear) and the solution of the dye (by generation of heat) can be achieved either in a manner simultaneous or sequential. The pigment can be applied either as a wet press cake, conglomerate, granule or dry powder. By extrusion, the use of granules is currently preferred due to the smaller dusting of this pigment form. The solvent dye can be applied in a similar way as a wet cake, conglomerate, granule or dry powder. In addition, the varnish can be pre-mixed or colored with the solvent dye and then added to a slurry of aqueous pigment. Alternatively, the varnish can be added to an aqueous slurry of the solvent dye or a mixed slurry of the pigment and solvent dye. The compositions obtained from lithographic printing ink can then be isolated by filtration and optionally dried; they are a basis for inventive pigment-based lithographic printing inks. Alternatively, the solvent dye (as a solid or solution in an organic solvent as mentioned) can also be incorporated by subsequent addition to the pigment-based finished printing ink followed by heating, if necessary to the complete solution. As a further alternative, the pigment-based lithographic printing inks can be prepared by a process comprising the rinsing of the pigment press cakes or pigment / dye mixtures in a varnish medium or a pre-dyed varnish medium ( printing ink varnish). Inventive pigment-based lithographic printing inks may further comprise customary additives known to those skilled in the art. Typical additives include drying enhancers, drying inhibitors, non-colored spreaders, opacifying fillers, antioxidants, waxes, oils, surfactants, rheology modifiers, wetting agents, dispersion stabilizers, transfer inhibitors and anti-foaming agents; promoters of additional adhesion, crosslinking agents, plasticizers, photoinitiators, light stabilizers, deodorants, biocides, lacquer forming agents and chelating agents. These additives are usually used in amounts from 0 to 10% by weight, particularly from 0 to 5% by weight, and preferably from 0.01 to 2% by weight, based on the total weight of the lithographic printing ink composition. The inventive pigment-based printing ink can be used in the lithographic printing process in a lithographic printing press whereby it is passed for example from a deposit by means of a roller duct system to the flat substrate to be printed. (ink plate). This plate is usually pre-treated with an aqueous source solution that frequently contains alcoholic components to aid the lithographic process. The printing processes are additional offers of the present invention. Inventive pigment-based lithographic printing inks lead to good overall print performance and produce unexpectedly increased color resistance prints (as compared to a pigment based ink alone), improved additional brightness and improved transparency in all types of inks of lithographic printing known in the art, for example, thermal curing, foil feeding, cold hardening or UV curing printing inks. The present invention is further described hereinafter with reference to particular examples thereof. It will be appreciated that these examples are presented for illustrative purposes and should not be construed as limiting the scope of the invention as described herein. In the following examples, the amounts are expressed as part by weight or percent by weight, unless stated otherwise. Temperatures are indicated in degrees centigrade.

Examples The following table shows a selection of red solvent dyes (of the class of phenylazophenylazo-beta-naphthol) to be used in the present invention; Table 1 Ri R2 3 R4 X SYNONYMS OF DYE H H H H OH Red Solvent C.I. 23 Sudan III 1- ((4-phenylazo) phenyl) azo-2-naphthol CH3 H CH3 H OH Red Solvent C.I. 24 Sudan IV 1- (4-o-tolylazo-o-tolylazo) -2-naphthol CH3 H CH3 CH3 OH Red Solvent C.I. 26 Red Oil EGN 1- ((2,5-dimethyl-4- ((2-methylphenyl) azo) phenyl) azo) -2-naphthol CH3 CH3 CH3 CH3 OH Red Solvent C.I. 27 Red Oil O 1- ((4- (dimethylphenyl) azo) -dimethylphenyl) azo) -2-naphthol H CH3 H CH3 OH Red Solvent C.I. 25 Red Sudan B 1- ((3-methyl-4- ((3-methylphenyl) azo) phenyl) azo) -2-naphthol H H H H NH- Red Solvent C.I. 19 CH2CH Red Sudan 7B N-ethyl- ((4- (phenylazo) phenyl) azo) -2- naphthylamine Additional dyes can be found in "The Color Index published by The Society of Dyers and Colourists". The numbers C.I. for these red dyes are 26000-26150. The structure of an additional applicable red dye (Solvent Red C.I. 29) found within this selection of numbers C.I. it is shown below (Formula 2).

Example 1 Ink A 24 g of 1- ((4- ((dimethylphenyl) azo) dimethylphenyl) azo-2-naphthol are incorporated in 141.75 g of a commercial heat-curing varnish composition by bead milling with high shear stress which leads to the composition experiencing a temperature of 80 ° C for a period of 15 minutes.

Ink B 27 g of a Red Pigment C.I. 57: 1 composition adjusted for the use of heat hardening is incorporated in 141.75 g of a commercial heat-hardening varnish by a method identical to Ink A.

Ink C 23 g of 1- ((2,5-dimethyl-4- ((2-methylphenyl) azo) phenyl) azo) -2-naphthol are incorporated in 141.75 g of a commercial heat-hardening varnish by a method identical to Ink A.

Ink mixtures The mixtures of the inks A and B plus also mixtures of the inks B and C are prepared by 2 series of 25 revolutions in a Müller glass plate dispersion apparatus. The instrumental resistance at 510-550 nm for each mixture is compared to the normal pigment-only B ink (which is given the figure of 100%) by Prufbau printing. Key Prufbau impressions are also usually compared and resistance figures are assigned against the norm in increments of 5%.

Table 2 Pigment / Solvent Dye Blend, Benefits Additional As examples of the additional benefits achievable by the incorporation of even relatively small amounts of coloring matter, the prints of the B / ink A 90/10 and 80/20 ink blends show slightly improved brightness and slightly improved transfer with respect to B ink alone.

Additionally, a mixture of ink B / 80/20 ink shows reduced emulsification in water and reduced coloration in the bleed compared to pure ink B. Similar effects are found for ink B / ink C 90/10 and 80/20 blends. Additionally, the ink B / ink C 70/30 mix exhibits a significant improvement in both brightness and transparency with respect to ink B alone.

Example 2 A colored ink vehicle is prepared by combining together 42.0 g of a commercial lithographic heat-cure varnish with 0.80 g of 1- ((4- (dimethylphenyl) azo) dimethylphenyl) azo) -2-naphthol and heated to a temperature between 80 ° C and 105 ° C for a period of 15 minutes. Then 0.856 g of this ink vehicle are combined with 0.144 g of a Red Pigment C.I. 57: 1, composition adapted for use of heat hardening using 2 series of 75 revolutions in a Müller glass plate dispersion apparatus.

Example 3 The procedure of Example 2 is repeated with 1- ((4- (dimethylphenyl) azo) dimethylphenyl) azo) -2-naphthol which is replaced by 1- ((2,5-dimethyl-4- ((2-methylphenyl) ) azo) phenyl) azo) -2-naphthol.

Example 4 The procedure of example 2 is repeated with 1- ((4- (dimethylphenyl) azo) dimethylphenyl) azo) -2-naphthol which is replaced by 1- (4-o-tolylazo-o-tolylazo) -2-naphthol .

Example 5 The procedure of Example 2 is repeated with 1- ((4- (dimethylphenyl) azo) dimethylphenyl) azo-2-naphthol which is replaced by 1- ((4-phenylazo) phenyl) azo-2-naphthol.

Example 6 (Comparative Example) 42. Og of a lithographic commercial heat cure varnish is heated to a temperature between 80 ° C and 105 ° C for a period of 15 minutes to mimic the conditions experienced in Examples 2-5. 0.840 g of this heated material are combined with 0.160 g of a Red Pigment C.I. 57: 1 composition adapted for use of heat hardening using two series of 75 revolutions in a Müller glass plate dispersion apparatus.

Results of Examples 2-5: Examples 2, 3, 4 and 5 are each plotted and visually assessed against Comparative Example 6 as a standard. All show superior color resistance to the norm.

Example 7 (Comparative Example, for Examples 8 and 9) 27.00 g of a Red Pigment composition C.I. 57: 1 adapted for the use of heat hardening are incorporated in 141.92 g of a commercial heat-hardening varnish by a method comprising bead milling at high shear stress which leads to the composition experiencing a temperature of 60 ° C during more than 30 minutes.

Example 8 Comparative Example 6 is repeated where 10% of the pigment is replaced by a 1: 1 mixture of 1- ((3-methyl-4- ((3-methylphenyl) azo) phenyl) azo-2-naphthol and 1- ((2,5-dimethyl-4- ((2-methylphenyl) azo) phenyl) azo) -2-naphthol In printing, the ink gives an increase in strength of 15% with respect to Comparative Example 7.

Example 9 Comparative Example 7 is repeated where 10% of the pigment is replaced by a 1: 1: 1: 1 mixture of 1 ((4-phenylazo) phenyl) azo-2-naphthol, 1- (4-o-tolylazole) -o-tolylazo) -2-naphthol, 1- ((3-methyl-4- ((3-methyl) azo) phenyl) azo) -2-naphthol and 1- ((2,5-dimethyl-4- ( (2-methylphenyl) azo) phenyl) azo) -2-naphthol. In printing, the ink gives an increase in resistance of 20% with respect to Comparative Example 7.

Claims (22)

1. CLAIMS 1. Lithographic printing ink composition, characterized in that the composition comprises an organic pigment, an organic coloring matter soluble in an organic solvent (solvent dye), a printing ink varnish (ink vehicle) and a solvent, the printing ink varnish that is mixed or colored with the solvent dye either before or during the dispersion of the pigment. Composition according to claim 1, characterized in that the organic coloring matter is a solvent dye selected from the group consisting of Red Solvent C.I. 1, 19, 23, 24, 25, 26, 27, 29, 49, 52, 111, Solvent Blue C.I. 14, 35, 36, 59, 78, Yellow Solvent C.I. 7, 14, 33, 72, 94, 114, Orange Solvent C.I. 1, 2, 7 and mixtures thereof, selected preferably from the group consisting of Red Solvent C.I. 19, 23, 24, 25, 26, 27, 29 and mixture thereof. Composition according to claim 1 or 2, characterized in that the organic pigment is a disazo or naphthol pigment. Composition according to any of claims 1 to 3, characterized in that the pigment / solvent dye ratio is (99-1): (1-99), preferably (98-10): (2-90) ) and more preferred (95-30): 5-70). 5. Composition according to any of claims 1 to 3, characterized in that the ratio of pigment / solvent dye is (95-65): (5-35). Composition according to any one of claims 1 to 5, characterized in that it comprises a mixture of solvent dyes and / or a mixture of organic pigments. 7. Pigmented lithographic printing ink, characterized in that it comprises the composition according to any of claims 1 to 6. 8. Pigmented lithographic printing ink according to claim 7, characterized in that it comprises an organic pigment and a solvent dye in a total amount of 0.1-70%, preferably from 2 to 55% by weight, and the remainder being varnishes, solvents and other usual printing ink additives. 9. Pigmented lithographic printing ink according to claim 7 or 8, characterized in that it is a lithographic printing ink ready for use and comprises the organic pigment and the solvent dye in a total amount of 2 to 20%, so preferred from 12 to 18% by weight. 10. Pigmented lithographic printing ink according to claim 7 or 8, characterized in that it is an ink concentrate and comprises the organic pigment and the solvent dye in a total amount of 20 to 70%, preferably 20 to 55% by weight. 11. Pigmented lithographic printing ink according to any of claims 7 to 10, characterized in that it comprises, as printing ink varnishes, mixtures of high-boiling distillates and / or vegetable oils, high wetting alkyd resins, highly structured alkyd resins and vegetable resins, and mixtures thereof; or monomers / oligomers / polymers that can be cured by UV radiation. Process for the preparation of pigmented lithographic printing inks according to any of claims 7 to 11, characterized in that it comprises incorporating the pigment / solvent dye composition into a printing ink varnish, or one of its components, by methods of heat induction or shear rate, and optionally combine the components charged in the pigment / solvent dye with the other components of the varnish. Process for the preparation of pigmented lithographic printing inks according to any of claims 7 to 11, characterized in that it comprises incorporating the pigment and the solvent dye separately in a printing ink varnish, or one of its components , by heat induction or shear stress method, and optionally combine the components loaded in the pigment and solvent dye with the other components of the varnish. 14. Process for the preparation of pigmented lithographic printing inks according to any of claims 7 to 11, characterized in that it comprises incorporating the solvent dye as a solid or solution in an organic solvent to the finished printing ink, optionally followed by heating. Process for the preparation of pigmented lithographic printing inks according to any of claims 7 to 11, characterized in that it comprises the rinsing of the pigment press cakes or pigment / dye mixtures in a varnish medium or in a medium of pre-dyed varnish. 16. Lithographic printing process, characterized in that it comprises printing a flat substrate with the pigmented lithographic printing inks according to any of claims 7 to 11, or with the pigmented lithographic printing inks prepared according to the processes of claims 12. to 15. 17. Lithographic dye printing ink, characterized in that it comprises a solvent, an organic pigment, and an organic coloring matter soluble in an organic solvent (solvent dye), where the organic pigment is coated with an ink varnish of printing (ink vehicle) and the printing ink varnish is mixed or colored with the solvent dye either before or during pigment processing. 18. Colorant according to claim 17, characterized in that it comprises the organic pigment and the solvent dye in a total amount of 60 to 95% by weight, and 40 to 5% by weight, of printing ink varnishes (vehicles of ink), solvent and other usual additives. Colourant according to claim 17, characterized in that the pigment / solvent dye ratio is (99-1): (1-99), preferably (98-10): (2-90), and more preferred (95-30): (5-70). 20. Colorant according to claim 17, characterized in that the ratio of pigment / solvent dye is (95-65): (5-35). 21. Pigmented lithographic printing ink, characterized in that it comprises the dyes according to any of claims 17 to 20. 22. Process for the preparation of lithographic printing ink dyes according to any of claims 17 to 20, characterized in that understands (a) incorporating the printing ink varnish, which is premixed or dyed with the solvent dye, into an aqueous slurry of the organic pigment, isolating it, and optionally drying it, or (b) adding the printing ink varnish to a aqueous slurry of the solvent dye and then combine it with an aqueous slurry of the organic pigment, isolate and optionally dry it, or (c) add the printing ink varnish to an aqueous slurry of a combination of solvent dye / organic pigment , isolate it and optionally dry it.