JP2011173325A - Intermediate transfer member for transfer-type inkjet printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate transfer body for transfer type ink jet recording which can achieve both high image retention and transferability.
An intermediate transfer member for transfer type ink jet recording, wherein the intermediate transfer member comprises a layer containing an addition type silicone rubber on the surface.
[Selection] Figure 1

Description

  The present invention relates to an intermediate transfer body for transfer type inkjet printing.

  Problems at the time of image formation by the inkjet method include bleeding in which adjacently applied inks are mixed, and beading in which ink that has landed first is attracted to ink that has landed later. There is also a problem of curling and cockling due to excessive absorption of the liquid content in the ink by the printing medium.

  In order to solve the problem, a step of ejecting ink onto the intermediate transfer member to form an image, and the intermediate transfer member on which the intermediate image has been formed is pressure-bonded to the substrate to be printed. A transfer type ink jet printing method has been devised which has a transfer step for transferring to a body.

  Here, as an intermediate transfer body used in the above-described transfer type ink jet printing method, a material having both image retention and releasability is generally required. That is, when the reaction liquid and the ink are applied to the surface of the intermediate transfer body, the obtained intermediate image can be held well (image retention), and the intermediate image can be more efficiently transferred to the printing medium. There is a need for materials that can be released (releasing properties). Patent Document 1 describes an image forming method including a step of performing plasma treatment and surfactant application treatment on an intermediate transfer body in order to achieve both image retention and transferability. In this method, a stable hydrophilic surface is formed on the intermediate transfer member by performing a plasma treatment and a surfactant application treatment. Thereby, it is possible to maintain good releasability while improving the retention of the reaction liquid and ink applied later.

Special registration No. 4054721

  In the above printing method, there is a case where a large number of transfer bodies are produced at a time and used for printing little by little in order to improve work efficiency. Particularly in recent years, the market demand for printing delivery such as immediate printing (print-on-demand) has been increasing, and it is preferable to prepare a transfer body in advance so that it can be used for immediate printing as needed. . For this reason, an intermediate transfer body to be used for the printing method is strongly required to have a property that the performance does not change even after being stored for a long period of time.

  Accordingly, an object of the present invention is to provide an intermediate transfer body for transfer type ink jet recording that can achieve both high image retention and transferability even when a long storage period has elapsed when the image forming method is used. is there.

  As a result of diligent study, the present inventor has found that the following configuration has better performance as a transfer-type inkjet recording intermediate transfer member, and has achieved the present invention. It was. That is, the step of applying plasma treatment and surfactant application to the intermediate transfer member, and the intermediate transfer member on which the plasma treatment and surfactant application treatment have been performed, the ink on the intermediate transfer member A step of applying a reaction liquid for reducing fluidity; a step of forming an image by ejecting ink onto the intermediate transfer body to which the reaction liquid has been applied; and an image formed on the intermediate transfer body. The present invention provides an intermediate transfer body for use in an image forming method comprising the step of transferring to a recording medium, wherein the intermediate transfer body contains an addition-type silicone rubber on the surface. Can be solved.

  The reason for such excellent performance is not clear, but the present inventors presume as follows. Generally, when a silicone rubber surface layer is subjected to plasma treatment, hydrophilic groups are introduced into a part of the rubber component, filler component, and oil component. Further, by adding a surfactant, it is considered that a more stable hydrophilic surface is obtained by adsorbing the surfactant on the surface that has become a high energy state by the plasma treatment.

  Silicone rubber is roughly classified into an addition type and a condensation type due to the difference in curing type. In the condensation type silicone rubber, the end of the base polymer undergoes a condensation reaction to form a Si—O—Si structure to produce the rubber. On the other hand, in the addition type silicone rubber, the vinyl group at the terminal of the base polymer undergoes an addition reaction to form a C—C bond to produce the rubber.

  When these are subjected to plasma treatment, it is conceivable that the hydrophilic group in the plasma treatment is different between the addition type and the condensation type. By the plasma treatment, SiOH generated from the Si—O—Si bond, COOH generated from the C—C bond, or a hydrophilic group composed of COH is generated on the surface. When a surfactant is adsorbed on these hydrophilic group components, it is considered that a hydrophilic group composed of COOH or COH can exist more stably than SiOH. Here, since the addition type has a higher proportion of C—C bonds than the condensation type, it is estimated that the addition type is less likely to lose hydrophilicity after a certain storage period than the condensation type. Is done.

  Another factor may be the difference in the amount of free oil components. During the plasma treatment, the Si—O—Si bond is partially broken and the oil component is released from the silicone rubber. Since the condensation type has more Si—O—Si bonds than the addition type, the amount of the free oil component is considered to be large. When a surfactant is applied to the plasma-hydrophilized silicone rubber surface, the surfactant is adsorbed on the hydrophilic group portion. However, if the amount of the free oil component is large, the surfactant is preferentially consumed for adsorption to the oil component, making it difficult to stably maintain the hydrophilicity of the silicone rubber surface. Therefore, it is considered that the addition-type silicone rubber having a relatively small amount of oil-releasing component is less likely to lose hydrophilicity after a certain storage period than the condensation-type silicone rubber.

  According to the present invention, it is possible to provide an intermediate transfer body for transfer type inkjet recording that can achieve both high image retention and transferability even after a long storage period.

It is a schematic diagram of a recording apparatus used in an image recording method to which the present invention can be applied.

  An aspect of the present invention includes a step of performing plasma treatment and surfactant application treatment on an intermediate transfer member, and an intermediate transfer member on which the plasma treatment and surfactant application treatment are performed. A step of applying a reaction liquid for reducing the fluidity of ink in the step, a step of forming an image by ejecting ink onto the intermediate transfer body to which the reaction liquid has been applied, and a formation on the intermediate transfer body And transferring the image to a recording medium. An outline of a printing method according to an embodiment of the present invention will be described below.

  First, a plasma treatment and a surfactant application treatment are performed on the intermediate transfer member.

<Intermediate transfer member>
The intermediate transfer member in the present invention holds a reaction liquid and ink and becomes a base material for forming an image. The structure includes a support member for handling the intermediate transfer member and transmitting a necessary force, and a surface layer member for forming an image. These may consist of a uniform member, or may consist of a plurality of independent members. Examples of the shape include a sheet shape, a roller shape, a drum shape, a belt shape, and an endless web shape. The size of the intermediate transfer member can be freely selected according to the target print image size.

  The support member for the intermediate transfer member is required to have a certain degree of structural strength from the viewpoint of conveyance accuracy and durability. The material is preferably metal, ceramic, resin, or the like. Among these, the following are preferable from the viewpoints of rigidity and dimensional accuracy that can withstand pressure during transfer, and characteristics required for reducing inertia during operation and improving control responsiveness. That is, aluminum, iron, stainless steel, acetal resin, epoxy resin, polyimide, polyethylene, polyethylene terephthalate, nylon, polyurethane, silica ceramic, alumina ceramic, and the like. It is also preferable to use these in combination.

  It is desirable that the surface layer member of the intermediate transfer body has a certain degree of elasticity in order to transfer the image by pressing the image on a printing medium such as paper. For example, when paper is used as the printing medium, the intermediate transfer member surface layer member preferably has a durometer type A (JIS K6253 compliant) hardness in the range of 10 to 100 °, particularly in the range of 20 to 60 °. Those are more preferred.

  As the material of the surface layer member, silicone rubber having excellent characteristics and processing characteristics is preferably used. This surface layer member may be formed by laminating a plurality of materials. For example, a laminated material in which silicone rubber is thinly coated on a polyurethane belt can be suitably used. Silicone rubbers are classified into heat vulcanization type silicone rubber, room temperature curable type silicone rubber and the like according to the production conditions. In particular, room temperature curable silicone rubber is preferably used because it does not require much labor when preparing the rubber, and silicone rubber can be obtained at low cost. In the present invention, addition type silicone rubber is used among silicone rubbers. The addition type silicone rubber is not particularly limited as long as it is formed by addition reaction. Generally, an organopolysiloxane having an unsaturated aliphatic group, an organopolysiloxane having active hydrogen bonded to silicon, and a platinum compound as a crosslinking catalyst are included.

  Silicone rubber can be further classified into one-component and two-component from the viewpoint of the product form, which can be arbitrarily selected from the viewpoint of characteristics and work. The silicone rubber may contain a filler. Silicone rubber fillers are expected to contribute to control of rubber hardness and thermal conductivity, reinforcement, and improvement of heat resistance, and also to assist hydrophilicity by plasma treatment. The type and amount of the filler can be appropriately selected according to workability and required rubber properties. For the purpose of the present invention, a filler made of silica is preferable, and the amount is 2% to 80 by volume ratio. % Is preferred.

<Surface modification>
Since the surface of the silicone rubber is generally water-repellent, the surface member is subjected to surface modification (hydrophilization treatment) in order to obtain image retention.

  Here, the image retention will be described. Good image retention means that when an ink or a reaction liquid is applied to the surface of the intermediate transfer member, the applied ink image does not repel or cause bleeding on the transfer member. A state formed in the street. This image retention is affected by the correlation between the intermediate transfer member and the surface free energy of the ink / reaction liquid. For example, when the surface free energy on the surface of the transfer body is low (strong water repellency), the applied ink is difficult to spread on the transfer body, so the size of the ink dots is reduced (the occurrence of repelling) and the desired image is obtained. It is difficult to obtain an ink image. Furthermore, inks applied adjacent to each other may mix and cause bleeding. Therefore, in order to obtain good image retention, it is preferable that the surface of the transfer member has a relatively high surface free energy. In order to simply evaluate the surface free energy of the intermediate transfer member, the static contact angle of water on the surface of the transfer member may be measured.

  Generally, the static contact angle of water on the surface of a silicone rubber that has not been subjected to any treatment is about 110 °. With this level of water repellency, it is difficult to obtain image retention. In the present invention, it is preferable to adjust the material composition and various surface modification conditions so that the static contact angle of water on the surface is approximately 95 ° or less.

  In the present invention, surface modification is performed by plasma treatment and surfactant treatment. First, the process of performing plasma treatment on the silicone rubber surface will be described. As the plasma processing means, a type in which processing is performed under atmospheric pressure or a reduced pressure atmosphere is generally used, and both are preferably used. The plasma treatment mentioned here includes corona discharge treatment that can activate oxygen in the atmosphere and generate hydroxyl groups on the surface. At this time, if an addition type silicone rubber is included on the surface, there are few oil components liberated by plasma treatment, and hydrophilic groups having relatively high stability such as -COOH and -COH are formed from the C-C bond. It is thought.

  Further, the surface of the plasma-treated surface is treated with a surfactant. Any surfactant can be used, for example, general cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, fluorine surfactants. , And silicone surfactants can be used. The means for imparting the surfactant can be selected arbitrarily from roll coating, doctor coating, spray coating, and dip coating.

  If the surface contains an addition type silicone rubber, the surfactant is oriented without waste because the free oil component is small, and the hydrophilic groups such as -COOH and -COH are stabilized by the surfactant. Conceivable.

<Storage>
The transfer material that has undergone surface modification can, of course, be used in the next process, but in order to improve work efficiency, the transfer material is surface-modified in large quantities at once, and the transfer that has been modified until printing is started. In some cases, the body is stored.

  Details of the mechanism by which the surface characteristics of the intermediate transfer member change during storage are not clear. However, according to the present invention, since a sufficient amount of the surfactant is stably oriented on the surface of the silicone rubber that has been increased in energy by the plasma treatment, fluctuations in the surface characteristics due to long-term storage can be suppressed to a smaller range. It is considered possible.

  In this case, it is preferable to store the surfactant in a state in which a certain amount or more is adhered to the surface because the storage stability is further improved. In general, the low molecular weight oil component contained in the rubber itself gradually oozes out on the rubber surface over time. This is because by adsorbing the oil component from which the surplus surfactant exudes during storage, it is possible to suppress the oil component from re-adsorbing to the hydrophilic group and reducing the hydrophilicity of the rubber surface.

  Further, it is possible to reduce contamination due to dust, oil, etc. floating outside, and to reduce the fact that the transfer bodies adhere to each other when the transfer bodies are stored in an overlapping manner.

  Then, the process of providing a reaction liquid is performed.

<Reaction solution>
The reaction liquid in the present invention contains a component that lowers the fluidity of the ink. Here, reducing the fluidity of the ink has the following meaning. That is, a color material, a resin, or the like, which is a part of the composition constituting the ink, chemically reacts or physically adsorbs by coming into contact with a component that lowers the fluidity of the ink. This is the case where an increase in the overall viscosity is observed. Furthermore, it includes a case where a viscosity increase locally occurs due to aggregation of a part of the ink composition such as a color material.

  This component has the effect of reducing bleeding and beading during image formation by reducing the fluidity of a part of the ink and / or ink composition on the intermediate transfer member. That is, in image formation using an ink jet device, the amount of ink applied per unit area may be large. In such a case, bleeding and beading, which are ink bleeding and mixing, are likely to occur. However, since the reaction liquid is applied onto the intermediate transfer member, the fluidity is lowered when an image is formed with ink, so that bleeding and beading hardly occur, and as a result, the image is formed and maintained satisfactorily. It will be.

  The component that lowers the fluidity of the ink to be used is desirably selected appropriately depending on the type of ink used for image formation. For example, it is effective to use a polymer flocculant for dye-based inks, and for pigment-based inks in which fine particles are dispersed, a liquid containing polyvalent metal ions or an acid buffer It is effective to use a pH adjusting agent such as a liquid. As an example of a component that lowers the fluidity of another ink, a compound having a plurality of ionic groups such as a cationic polymer may be used. It is also effective to use two or more of these compounds in combination.

  Specific examples of the polymer flocculant that can be used as a component that lowers the fluidity of the ink include, for example, cationic polymer flocculants, anionic polymer flocculants, nonionic polymer flocculants, and amphoteric polymers. A flocculant etc. are mentioned.

Specific examples of metal ions that can be used as a component that lowers the fluidity of the ink include the following. That is, divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ , trivalent metal ions such as Fe ³⁺ , Cr ³⁺ , Y ³⁺ and Al ^3+, etc. It is. Of course, it is not limited to these. And when apply | coating the liquid containing these metal ions, applying as a metal salt aqueous solution is desirable. Examples of the anion of the metal salt include the following. That is, Cl ⁻ , NO ₃ ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ , I ⁻ , Br ⁻ , ClO ₃ ⁻ , HCOO ⁻ , RCOO ⁻ (where R is an alkyl group) and the like can be mentioned, but are not limited thereto. It is not something.

  The metal salt concentration of the metal salt aqueous solution is preferably 0.01% by mass or more, and more preferably 0.1% by mass or more. Moreover, 20 mass% or less is preferable.

  In addition, an acidic solution having a pH of less than 7 is preferably used as a pH adjuster that can be specifically used as a component that lowers the fluidity of the ink. Examples include inorganic acids such as hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid, boric acid, succinic acid, polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid , Citric acid, tartaric acid, lactic acid, pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, and other organic acids. In addition, derivatives of these compounds or solutions of these salts can also be preferably used.

  In addition, an acid buffer (buffer) having a pH buffering ability is very preferably used because the reactivity with the ink does not deteriorate because the pH does not fluctuate little even if the apparent reaction liquid concentration is lowered by the ink. In order to obtain pH buffering capacity, it is preferable to contain a buffer in the reaction solution. Specific examples of buffers that can be used include acetates such as sodium acetate, potassium acetate, and lithium acetate, hydrogen phosphates, bicarbonates, or polyvalent carboxylic acids such as sodium hydrogen phthalate and potassium hydrogen phthalate. Acid hydrogen salts can be used. Furthermore, specific examples of polycarboxylic acids include, besides phthalic acid, malonic acid, maleic acid, succinic acid, fumaric acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, adipic acid, sebacic acid, dimer acid , Pyromellitic acid, trimellitic acid and the like. In addition to this, any conventionally known compound that exhibits a buffering effect on pH by addition can be suitably used.

  The reaction solution according to the present invention may contain an appropriate amount of water or an organic solvent. A component that lowers the fluidity of the ink as described above is dissolved in water or an organic solvent. Examples of the aqueous medium include water or a mixed solvent of water and a water-soluble organic solvent. Specifically, for example, alkanediols such as 1,3-butanediol, 1,5-pentanediol, 1,2-hexanediol, and 1,6-hexanediol. Glycol ethers such as diethylene glycol monomethyl (or ethyl) ether and triethylene glycol monoethyl (or butyl) ether. Alkyl alcohols having 1 to 4 carbon atoms such as ethanol, isopropanol, n-butanol, isobutanol, secondary butanol and tertiary butanol; Carboxylic acid amides such as N, N-dimethylformamide and N, N-dimethylacetamide. Ketones such as acetone, methyl ethyl ketone, 2-methyl-2-hydroxypentan-4-one, or keto alcohol. Cyclic ethers such as tetrahydrofuran and dioxane. Glycerin. Alkylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2- or 1,3-propylene glycol, 1,2- or 1,4-butylene glycol, polyethylene glycol; Polyhydric alcohols such as thiodiglycol, 1,2,6-hexanetriol, and acetylene glycol derivatives; Sulfur-containing compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and dimethyl sulfoxide are preferably used. Also, two or more kinds of these can be selected and mixed for use. In addition to the above components, the reaction solution can be appropriately added with an antifoaming agent, an antiseptic agent, an antifungal agent and the like in order to impart desired properties as required.

  Various resins may be added to the reaction solution in order to improve transferability or to improve the fastness of the finally formed image. By adding a resin, it is possible to improve the adhesiveness to the recording medium during transfer or to increase the mechanical strength of the ink film. Depending on the type, the water resistance of the image can be improved. The material to be used is not limited as long as it can coexist with a component that lowers the fluidity of the ink. For example, organic polymers such as polyvinyl alcohol and polyvinyl pyrrolidone are preferably used. Resins that react with the components contained in the ink and crosslink are also suitable. Examples include oxazolines and carbodiimides that react and crosslink with carboxylic acids frequently used to disperse colorants in the ink.

  These resins may be dissolved in the reaction solution solvent, or may be added in an emulsion state or a suspension state.

  The reaction solution can be used by adding a surfactant and adjusting the surface tension as appropriate. As the surfactant, known substances such as ionic, nonionic, cationic and anionic can be appropriately selected and used as necessary. However, it goes without saying that certain surfactants affect the reaction solution and ink and may affect image formation.

<Reaction liquid application>
As a method for applying the reaction solution, various conventionally known methods can be appropriately used. Examples include die coating, blade coating, gravure roller, and a combination of these with an offset roller. It is also suitable to use an ink jet device as a technique that can be applied at high speed and high accuracy.

  Subsequently, a step of forming an image by discharging ink is performed.

<Drawing>
Subsequently, ink is applied onto the intermediate transfer body to which the reaction liquid has been applied using an inkjet device.

  As an inkjet device applied to the present invention, for example, a mode in which ink is ejected by forming a bubble by causing film boiling in the ink by an electro-thermal converter, a mode in which ink is ejected by an electro-mechanical converter, electrostatic There is a form of discharging ink using Any of various ink jet devices proposed in the ink jet liquid ejection technique can be used. Among these, those using an electro-thermal converter are preferably used from the viewpoint of high-speed and high-density printing.

  Moreover, there is no restriction | limiting in particular as a form of the whole inkjet device. A line head type inkjet head in which ink discharge ports are arranged in the traveling direction of the intermediate transfer member (axial direction in the case of a drum shape), or a shuttle that performs recording while scanning the head perpendicular to the traveling direction of the intermediate transfer member A shaped head can also be used.

<Ink>
As the ink in the present invention, an ink widely used as an inkjet ink, specifically, various inks in which a coloring material such as a dye, carbon black, or an organic pigment is dissolved and / or dispersed can be used. Among these, carbon black and organic pigment ink are particularly preferable because an image having good weather resistance and color developability can be obtained.

  From the viewpoint of environmental load and odor during use, water-based inks containing water as a component are suitable. In particular, an ink containing 45% or more of water in the component and an ink whose main component is water are very preferable.

  Further, the color material content of the ink is preferably 0.1% or more, and more preferably 0.2% or more. Moreover, it is preferable that it is 15.0% or less, and it is more preferable that it is 10.0% or less.

  Examples of the color material include dyes, carbon black, organic pigments, and accompanying resins, and the following materials can be used.

  Examples of the dye include C.I. I. Direct Blue 6, 8, 22, 34, 70, 71, 76, 78, 86, 142, 199, C.I. I. Acid Blue 9, 22, 40, 59, 93, 102, 104, 117, 120, 167, 229, C.I. I. Direct Red 1, 4, 17, 28, 83, 227, C.I. I. Acid Red 1, 4, 8, 13, 14, 15, 18, 21, 26, 35, 37, 249, 257, 289, C.I. I. Direct Yellow 12, 24, 26, 86, 98, 132, 142, C.I. I. Acid Yellow 1, 3, 4, 7, 11, 12, 13, 14, 19, 23, 25, 34, 44, 71, C.I. I. Food Black 1, 2, C.I. I. Acid Black 2, 7, 24, 26, 31, 52, 112, 118 and the like. In addition to the above, known dyes can be used.

  The carbon black is, for example, a carbon black pigment such as furnace black, lamp black, acetylene black, or channel black. For example, the following commercially available products can be used. The carbon black that can be used in the present invention is not limited to these, and a known carbon black can be used. Further, magnetic fine particles such as magnetite and ferrite, titanium black and the like may be used.

  Ray Van: 7000, 5750, 5250, 5000, 3500, 2000, 1500, 1250, 1200, 1190 ULTRA-II, 1170, 1255 (above Colombia). Black Pearls: L, Legal: 400R, 330R, 660R, Mougl: L, Monak: 700, 800, 880, 900, 1000, 1100, 1300, 1400, Vulcan: XC-72R (above Cabot). Color black: FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex: 35, U, V, 140U, 140V, Special Black: 6, 5, 4A, 4 (manufactured by Degussa). No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical).

  As the organic pigment, for example, the following can be used. Water-insoluble azo pigments such as Toluidine Red, Toluidine Maroon, Hansa Yellow, Benzidine Yellow, and Pyrazolone Red. Water-soluble azo pigments such as Ritolol Red, Helio Bordeaux, Pigment Scarlet, and Permanent Red 2B. Derivatives from vat dyes such as alizarin, indanthrone and thioindigo maroon. Phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green. Quinacridone pigments such as quinacridone red and quinacridone magenta. Perylene pigments such as perylene red and perylene scarlet. Isoindolinone pigments such as isoindolinone yellow and isoindolinone orange. Imidazolone pigments such as benzimidazolone yellow, benzimidazolone orange, and benzimidazolone red. Pilanthrone pigments such as pyranthrone red and pyranthrone orange. Indigo pigment. Condensed azo pigment. Thioindigo pigment. Flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet, etc.

  Moreover, when an organic pigment is shown by a color index (CI) number, the following can be used. C. I. Pigment Yellow: 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 151, 153, 154, 166 168. C. I. Pigment Orange: 16, 36, 43, 51, 55, 59, 61. C. I. Pigment Red: 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 170, 192, 215, 216, 217, 220, 223, 224, 226, 227 228, 238, 240. C. I. Pigment Violet: 19, 23, 29, 30, 37, 40, 50. C. I. Pigment Blue: 15, 15: 3, 15: 1, 15: 4, 15: 6, 22, 60, 64. C. I. Pigment Green: 7, 36. C. I. Pigment Brown: 23, 25, 26. In addition to the above, known organic pigments can be used.

  These pigments are not limited in form, and for example, any of self-dispersion type, resin dispersion type, microcapsule type and the like can be used. As the pigment dispersant used in this case, a water-soluble dispersion resin having a weight average molecular weight of about 1000 to 15000 can be preferably used. Specific examples include water-soluble vinyl resins, styrene and derivatives thereof, vinyl naphthalene and derivatives thereof, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid and derivatives thereof. Examples thereof include maleic acid and derivatives thereof, itaconic acid and derivatives thereof, block copolymers or random copolymers comprising fumaric acid and derivatives thereof, and salts thereof.

  In order to improve the fastness of the finally formed image, a water-soluble resin or a water-soluble crosslinking agent can be added. The material used is not limited as long as it can coexist with the ink component. As the water-soluble resin, the dispersion resin exemplified above can be used as it is. As the water-soluble crosslinking agent, oxazoline and carbodiimide are preferably used in terms of ink stability. In addition, reactive oligomers such as polyethylene glycol diacrylate and acryloylmorpholine can also be suitably used.

  Further, in the method using the intermediate transfer member according to the present invention, the ink when transferring to the printing material is almost only the color material and the high boiling point organic solvent, so that an appropriate amount of the organic solvent is included for improving transferability. It is effective. The organic solvent to be used is preferably a water-soluble material having a high boiling point and a low vapor pressure. For example, alkanediols such as 1,3-butanediol, 1,5-pentanediol, 1,2-hexanediol, and 1,6-hexanediol. Glycol ethers such as diethylene glycol monomethyl (or ethyl) ether and triethylene glycol monoethyl (or butyl) ether. Alkyl alcohols having 1 to 4 carbon atoms such as ethanol, isopropanol, n-butanol, isobutanol, secondary butanol and tertiary butanol; Carboxylic acid amides such as N, N-dimethylformamide and N, N-dimethylacetamide. Ketones such as acetone, methyl ethyl ketone, 2-methyl-2-hydroxypentan-4-one, or keto alcohol. Cyclic ethers such as tetrahydrofuran and dioxane. Glycerin. Alkylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2- or 1,3-propylene glycol, 1,2- or 1,4-butylene glycol, polyethylene glycol; Polyhydric alcohols such as thiodiglycol and 1,2,6-hexanetriol; A heterocyclic compound such as 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylmorpholine, a sulfur-containing compound such as dimethyl sulfoxide, and the like are preferably used. Also, two or more kinds of these can be selected and mixed for use.

  In addition to the above components, the ink according to the present invention may contain a pH adjuster, a rust inhibitor, an antiseptic, an antifungal agent, an antioxidant, an anti-reduction agent, a water-soluble resin neutralizer, a salt, as necessary. Various additives such as these may be contained.

  In addition, it is also preferable to add a surfactant as necessary to appropriately adjust the surface tension of the ink. The surfactant is not limited as long as it does not affect the storage stability of the ink. For example, anionic surfactants such as fatty acid salts, higher alcohol sulfates, liquid fatty oil sulfates, alkylallylsulfonates, polyoxyethylene alkyl esters, polyoxyethylene sorbitan alkyl esters, acetylene alcohols, acetylene Nonionic surfactants such as glycols are listed. Two or more of these can also be selected and used as appropriate.

  The blending ratio of the components constituting the ink is not limited, and can be appropriately adjusted within a range that allows ejection from the ejection force, nozzle diameter, and the like of the selected inkjet head. When ink is applied to the image forming surface of the intermediate transfer body to which the reaction liquid is applied using an ink jet device, the reaction liquid and the ink come into contact with each other on the surface, and an ink image in which the fluidity is reduced is an intermediate image. Formed as.

  Needless to say, when the intermediate image is formed, an image (mirror image) in which a desired image is inverted is formed on the intermediate transfer member.

<Moisture removal>
It is also preferable to provide a step of reducing the liquid content from the intermediate image. If the liquid content of the image is excessive, excess liquid will overflow or overflow in the next pressure-transfer transfer process, thereby disturbing the image or causing a transfer failure. Any of various conventional methods can be suitably applied as the method for removing moisture. A heating method, a method of blowing low-humidity air, a method of reducing the pressure, a method of bringing the absorber into contact with each other, and a method of combining them are preferably used. It is also possible to carry out by natural drying.

  Subsequently, a step of transferring the image formed on the intermediate transfer member to a recording medium is performed.

<Transfer>
Thereafter, the printing medium is pressure-bonded to the image, and the image is transferred from the intermediate transfer body to the printing medium, thereby obtaining a printed image. In this specification, the “printed body” refers to not only paper used in general printing, but also widely includes cloth, plastic, film and other printing media and recording media.

  In this case, it is preferable to apply pressure from both sides of the intermediate transfer body and the printing medium using a pressure roller because an image is efficiently transferred and formed.

  Also, multi-stage pressurization is preferable because it has an effect of reducing transfer defects.

<Cleaning>
Although the image formation is completed as described above, the intermediate transfer member may be repeatedly used continuously from the viewpoint of productivity. In this case, it is preferable to clean and regenerate the surface before the next image formation.

  As the means for performing the cleaning and regeneration, any of various methods conventionally used can be suitably applied. The method of applying the cleaning liquid in a shower form, the method of contacting and wiping the wet Molton roller to the surface, the method of contacting the surface of the cleaning liquid, the method of scraping with a wiper blade, the method of applying various energy, etc. are all suitably used. It is done. Of course, a method of combining a plurality of these is also suitable.

<Fixing>
As an additional step, the printing medium on which the post-transfer image recording has been performed may be pressed with a roller to enhance the surface smoothness. In this case, if the roller is heated, the fastness of the image may be improved, which is also preferable.

  As described above, by taking the aspect of the present invention, according to the present invention, it is possible to provide an intermediate transfer body for transfer type ink jet recording that achieves both image retention and transferability even when a certain storage period is provided. The inventor has found for the first time that this is possible.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples of an intermediate transfer body for transfer type ink jet printing according to the present invention. Of course, the present invention is not limited to the following examples.

  FIG. 1 shows an intermediate image forming step in which an intermediate image is formed by selectively applying ink onto an intermediate transfer body to which a reaction solution has been applied using an inkjet device, and an intermediate transfer in which the intermediate image is formed. It is a schematic diagram of an example of the present invention having a transfer step of transferring the intermediate image by pressure-bonding a body to a substrate.

  In FIG. 1, the intermediate transfer member includes a rotatable drum-shaped support member 12 and a surface layer member 11 fixed to the outer surface thereof. The support member 12 is driven to rotate in the direction of the arrow about the shaft 13, and each device arranged in the periphery operates in synchronization with the rotation.

The surface layer member 11 of the intermediate transfer member is a layer made of silicone rubber and a PET sheet, and is fixed to the support member 12 with a double-sided adhesive tape. In this example, a 0.5 mm thick PET sheet coated with silicone rubber to a thickness of 0.3 mm was used. This surface was subjected to surface modification under the following conditions using an atmospheric pressure plasma treatment apparatus (ST-7000 manufactured by Keyence Corporation).
Processing distance: 7mm
Plasma mode: High
Processing speed: 50mm / sec

  Further, after immersing this surface in a surfactant aqueous solution diluted with pure water to make 3% of a commercially available neutral detergent made of sodium alkylbenzene sulfonate, it is naturally dried with the surfactant attached. It was.

  The obtained transfer body was stored for a certain period of time. As for the storage environment, 50 sheets of the transfer material with the surface-modified surfactant adhered thereto were stacked and left under conditions of a temperature of 30 ° C. and a humidity of 50% RH.

  In this configuration, in addition to the rigidity and dimensional accuracy that can withstand pressure during transfer, and the characteristics required for reducing rotational inertia and improving control responsiveness, etc., the cylindrical shape made of aluminum alloy A drum was used as the support member 12 for the intermediate transfer member.

  However, as the support member for the intermediate transfer member, for example, a roller-like or belt-like member can be suitably used according to the form of the recording apparatus to be applied or the transfer to the printing medium.

  In any case, if a drum-like support member or a belt-like endless web-structured support member is used, the same intermediate transfer member can be used continuously and repeatedly. Become.

  In this configuration, a roller type coating device 14 is arranged as a device for applying the reaction liquid. As a result, the reaction liquid is continuously applied to the surface of the intermediate transfer member.

  In this example, an aqueous solution of a metal salt as a reaction solution, specifically, 0.3 part of acetylenol E100 (trade name) as a surfactant is appropriately added to a 28% by mass aqueous solution of calcium acetate ((CH3COO) 2Ca) to obtain a surface. The thing which adjusted tension was used. In addition, a metal seed | species and density | concentration can be suitably changed according to conditions.

  Next, ink for image formation is ejected from the inkjet device 15, and an intermediate image (image that is mirror-reversed) is formed on the intermediate transfer member. In this configuration, a device of an ink discharge type using an electrothermal conversion element is used.

In this example, a resin-dispersed pigment ink was prepared and used as the ink. The composition is shown below.
("Part" is part by mass)
Pigment coloring material: C.I. I. Pigment Blue 15 3.0 parts Dispersing resin: Styrene-acrylic acid-ethyl acrylate copolymer (acid value 100, weight average molecular weight 12000) 1.0 part non-aqueous solvent 1: glycerin 6.5 parts non-aqueous solvent 2: Ethylene glycol 5.0 parts Surfactant: Acetylenol E100 (trade name) 0.3 parts Ion-exchanged water: 84.2 parts

  In this configuration, the air blower 16 is disposed for the purpose of reducing the liquid content in the ink constituting the image on the intermediate transfer member. At the same time, a heater 17 for heating from the back side of the intermediate transfer member is also arranged. As a result, the liquid content in the ink image is dried, and the disturbance of the image during transfer is suppressed.

  A pressure roller 19 is disposed to bring the printing medium 18 into contact with the image formed on the intermediate transfer body and to transfer and form the image. In this configuration, the support member 12 and the pressure roller 19 apply pressure so as to sandwich the intermediate image and the printing medium 18, thereby realizing efficient image transfer.

  In this example, a surface hydrophilized pet film (thickness 50 μm) was used as the printing medium. As the shape of the printing material, a long and roll-shaped sheet is used in a prescribed shape in this example, but a sheet-cut sheet may be used.

  According to this embodiment, since the liquid component in the ink is already reduced on the intermediate transfer body at this stage and the fluidity is lowered, it is good to use a printing medium that hardly absorbs ink such as a pet film. An image can be formed.

  In the configuration as described above, Examples 1 to 3 and Comparative Examples 1 and 2 according to the present invention were performed. Table 1 shows the level of the intermediate transfer member used in each example.

(All silicone rubbers are manufactured by Momentive Performance Materials)
In Table 1, rubber hardness is a value measured with a type A durometer of JIS K6253. Image retention and releasability were evaluated by printing / transfer using samples stored for 8 months when printing without storage (from surface modification to printing for about 10 minutes). .

  The evaluation criteria are ◎ when 80% or more of the evaluators are judged to be good, ○ when judged that 50% or more and less than 80% are good, and 50% or more are bad. When it is judged that there is, it is marked with “X”.

  The evaluation results are shown in Table 2.

  In Examples 1 to 3, compared with Comparative Examples 1 and 2, the image retention after 8 months storage was better.

  As is clear from the above results, according to the present invention, it is possible to provide an intermediate transfer body for transfer type inkjet recording that can achieve both high image retention and transferability even after a long storage period. .

DESCRIPTION OF SYMBOLS 11 Surface layer member 12 Support member 13 Rotating shaft of support member 12 Roller type coating device 15 Inkjet device 16 Blower device 17 Heater 18 Printed material 19 Pressure roller 20 Cleaning unit

Claims (1)

The step of performing plasma treatment and surfactant application treatment on the intermediate transfer member, and the fluidity of ink on the intermediate transfer member on the intermediate transfer member subjected to the plasma treatment and surfactant application treatment A step of applying a liquid for reducing the liquid, a step of forming an image by ejecting ink onto the intermediate transfer member to which the liquid has been applied, and a transfer of the image formed on the intermediate transfer member to a recording medium An intermediate transfer member for use in an image forming method comprising the steps of:
An intermediate transfer member, wherein the intermediate transfer member contains an addition-type silicone rubber on the surface.