JP2008255135A - Ink, method and device for forming image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink, which is capable of preventing poor transfer or transfer unevenness, maintains the fastness of the image such as abrasion-proof or waterproof properties, prevents the reduction of image quality caused by the unevenness of ejection speed from a nozzle, is easy with respect to the cleaning of the ink attached to a transferring body and is capable of preventing the uneven gloss of the image caused by a high boiling solvent; and to provide a method for forming an image and a device for the same. <P>SOLUTION: This method for forming the image comprises ejecting the ink containing at least a resin component and a coloring matter on an intermediate transfer body 12, absorbing the solvent component from the ink and transferring to a recording medium 36, and is characterized in that the resin component has ≥25% elongation at break at 25°C, and also the temperature of the intermediate transferring body 12 on transferring to the recording medium 36 is set at ≥25°C and at or lower than the lowest film-forming temperature of the resin component. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink, an image forming method, and an apparatus therefor, and more particularly to forming an image on an intermediate transfer member and then transferring the image formed on the intermediate transfer member to the recording medium. The present invention relates to an ink for forming an image, an image forming method using the ink, and an apparatus therefor.

  In recent years, with the rapid development of digital image technology such as digital cameras and inkjet technology, it has become possible to easily obtain high-quality photographic prints that surpass silver halide photography even in ordinary households. On the other hand, application and application of inkjet technology has begun in various fields including industrial and printing fields. However, in the field of industrial printing, speeding up is essential from the viewpoint of productivity, but there is still no ink or image recording method capable of printing high image quality like silver halide printing at high speed. Therefore, various recording methods that provide high-speed and high-quality images are being studied.

  In the conventional direct recording in which ink is directly ejected onto a recording medium for recording, the solvent component of the ink penetrates the recording medium, so that there is a problem that the print quality is impaired by the bleeding of the ink. There is also a problem that the print quality varies depending on the type of recording medium.

  In order to solve such a problem, Patent Document 1 proposes an intermediate transfer type apparatus in which an ink image is once formed on a transfer body, moisture in the ink image is evaporated, and then transferred to a recording medium. Yes. As a result, the deterioration in print quality due to bleeding and the difference in print quality due to the difference in recording medium were solved.

In Patent Document 1, an ink containing a resin emulsion having a minimum film forming temperature of 50 ° C. or higher is recorded on a transfer body heated to a surface temperature higher than the minimum film forming temperature. In addition to improving the film strength and adhesion of the ink image of the ink, enabling transfer at low pressure and increasing the operating environment temperature, it prevents the formation of a resin emulsion at the head nozzle and prevents nozzle clogging. ing. Furthermore, fastness such as water resistance is secured by forming a heated film of the ink image at the time of transfer.
JP 7-32721 A

  However, in the method of Patent Document 1, if the transfer body is heated to a temperature equal to or higher than the minimum film-forming temperature, the film strength and adhesive strength of the ink image increase, and at the same time, the adhesion between the transfer body and the ink image also increases. End up. As a result, the transfer rate at low pressure is improved, but in the solid image portion where the ink application amount increases, the adhesion between the transfer body and the ink image increases more than necessary, and there is a transfer unevenness in which a portion that is not transferred locally occurs. It will occur. Due to this transfer unevenness, an excessive load is generated for cleaning the ink image remaining on the transfer body. In addition, since the temperature of the transfer body is set in the range of 50 to 150 ° C., energy is excessively consumed. However, if the transfer body is repeatedly heated at such a temperature, the ink image remaining on the transfer body due to transfer failure. Since the adhesive force remains high, if the number of recordings is repeated, the residue remains stuck to the surface of the transfer member, and long-term reliability cannot be obtained. Even if the transfer body is cooled to avoid this problem, more energy must be required, and a system that repeats heating and cooling is very inefficient.

  Further, in the method of Patent Document 1, clogging of the nozzle can be avoided by using a resin emulsion having a minimum film forming temperature of 50 ° C. or more, but the viscosity of the ink liquid itself at the nozzle is increased by the effect of heating of the transfer body. Inevitable, the ejection speed varies depending on the nozzle location, there is a problem that ink droplets can not be ejected to the part to be ejected originally, ink droplets that did not adhere to the part to be ejected adhere to different places, the result As a result, there is a problem that the image quality is impaired.

  Furthermore, in a normal aqueous inkjet ink, a humectant such as glycerin is added to prevent volatilization of the solvent component of the nozzle, but as in Patent Document 1, the solvent component is removed by evaporation by heating the transfer body. Although a low boiling point solvent such as water can be removed, when heated to about 50 to 150 ° C., a high boiling point solvent such as glycerin is not easily evaporated and remains in the ink image. This high boiling point solvent component weakens the strength of the ink image and adversely affects various properties such as transferability and abrasion resistance. When a large amount of a humectant such as glycerin remains in the vicinity of the surface of the ink image, it affects the gloss of the image portion and causes uneven gloss. The gloss unevenness is a phenomenon in which a difference in gloss occurs between an image portion and a non-image portion (white background portion), or between image portions where the color material type and adhesion amount are different. Gloss unevenness is particularly a problem when using inkjet recording paper with high glossiness, so-called glossy inkjet recording paper. However, when a solid image is formed with this type of recording paper, gloss differences occur depending on the location, and the reflectance A large amount of high-boiling solvent remains in the portion where is high.

The present invention has been made in view of such circumstances, and in the intermediate transfer type recording system, it is possible to prevent transfer failure and transfer unevenness, maintain image fastness such as abrasion resistance and water resistance, Ink and image forming method capable of preventing deterioration of image quality due to variations in ejection speed from nozzles, facilitating cleaning of ink adhering to a transfer body, and preventing uneven glossiness of an image due to a high boiling point solvent, and its An object is to provide an apparatus.

  In order to achieve the above object, the invention described in claim 1 is an ink used for image formation that includes at least a resin component and a coloring material, and is transferred onto a recording medium after being discharged onto an intermediate transfer member. The resin component provides an ink having an elongation at break at 25 ° C. of 25% or more.

  In order to achieve the above object, the invention according to claim 2 is a recording medium in which an ink containing at least a resin component and a color material is ejected onto an intermediate transfer member, and then a solvent component is absorbed from the ink. In the image forming method of transferring to the recording medium, the resin component has an elongation at break of 25% or more at 25 ° C., and the temperature of the intermediate transfer member when transferring to the recording medium is 25 ° C. or more. Provided is an image forming method characterized in that the temperature is lower than the minimum film forming temperature.

  In the ink according to the present invention, the resin component contained in the ink is formed into a film, and contains an elongation at break of 25% or more when a tensile test is performed in an environment of 25 ° C.

  In the image formation, the temperature of the intermediate transfer body when transferring the ink that has absorbed the solvent component from the ink on the intermediate transfer body to the recording medium is 25 ° C. or higher and lower than the minimum film forming temperature (MFTα) of the resin component. Set. By setting the transfer body temperature within this temperature range, only the surface of the resin is fused, and it adheres to the surrounding colorant particles and resin components, thereby improving the film strength and adhesion only inside the ink image. is there. Here, if the temperature is not lower than the minimum film-forming temperature (MFTα), the film-forming proceeds so much that the particle shape cannot be retained, and the adhesion between the ink film and the transfer body becomes too high, resulting in undesirably uneven transfer. Also, the temperature of the image forming environment is increased, which causes an increase in ink viscosity at the nozzle portion, which is not preferable because the discharge speed is decreased.

  It is important to use a resin component having an elongation at break of 25% or more in order to develop an adhesive effect by fusion on the surface of the resin. When a tensile test is performed, the resin component which does not stretch at all and has a brittle property does not make sense because a ductile effect cannot be expected at all when fused. Even a slightly stretchable resin with an elongation at break of less than 25% is insufficient to increase the adhesion between particles and enhance the cohesive force of the entire interior of the ink image. The force that pulls the ink film from both due to the interaction between the adhesion between the transfer body and the ink film and the adhesion between the recording medium and the ink film causes the internal division of the ink film, which in turn lowers the transfer rate. In order to give an adhesive force that does not cause splitting inside the ink film and to perform good transfer, the elongation at break of at least 25% is required. Further, the effect of ductility is also exerted to the rub resistance of the fixed image.

  It is also important to remove the solvent component before transferring the ink to the recording medium. Only when non-solid content is positively removed from the ink image, the ink image is concentrated, and the particles made of the coloring material and the resin component are brought into contact with each other. . If a solvent component is present between the particles, the surface is hardly fused and the effect of the present invention is not exhibited. The means for removing the solvent component is more preferably a direct means such as an absorption roller for contacting the ink image. In the method of removing by evaporating the solvent component by heating the transfer body or blowing hot air, the high boiling point solvent tends to remain in the ink image, so the amount of the solvent component itself can be reduced regardless of the low or high boiling point component. A form that absorbs directly is more desirable.

  According to the first or second aspect of the present invention, in the intermediate transfer type recording system, it is possible to prevent transfer failure and transfer unevenness, maintain image fastness such as abrasion resistance and water resistance, and the nozzle. To obtain an ink or an image forming method capable of preventing deterioration in image quality due to variations in ejection speed from the toner, facilitating cleaning of the ink adhering to the transfer body, and preventing uneven glossiness of the image due to the high boiling point solvent Can do.

  According to a third aspect of the present invention, in the second aspect of the present invention, the intermediate transfer member temperature at the time of the transfer is set to be equal to or higher than the film formation start temperature of the resin component.

  According to the third aspect, by further setting the intermediate transfer member temperature at the time of transfer to a film forming start temperature (MFTβ) or higher, the adhesion effect between the particles can be further enhanced. In the present invention, the film formation start temperature (MFTβ) refers to the temperature at which the resin component begins to form a film, and the minimum film formation temperature (MFTα) refers to the temperature at which film formation is completely completed. Qualitatively, the film formation start temperature (MFTβ) is measured as a value lower than the minimum film formation temperature (MFTα).

  A fourth aspect of the invention is characterized in that, in the invention of the second or third aspect, the temperature of the recording medium at the time of the transfer is heated to a temperature equal to or higher than the film formation start temperature of the resin component.

  According to the fourth aspect, by setting the temperature of the recording medium to be equal to or higher than the film formation start temperature (MFTβ), the surface fusion effect of the resin can be promoted not only from the transfer body side but also from the recording medium side. Therefore, transferability can be improved.

  The invention according to claim 5 is characterized in that, in the invention according to any one of claims 2 to 4, the temperature of the recording medium at the time of transfer is heated to a temperature equal to or higher than the minimum film forming temperature of the resin component. To do.

  According to the fifth aspect, the adhesive force between the recording medium and the ink film can be improved by preliminarily heating the recording medium to be transferred to the minimum film forming temperature (MFTα) or higher. Furthermore, since the contact area between the recording medium after fixing and the ink image is increased, the fixing property is improved by the anchor effect.

  However, setting the heating temperature higher than necessary is not preferable because it leads to an increase in the temperature of the transfer body. A suitable temperature for heating the recording medium is a temperature that is 10 to 20 ° C. higher than the minimum film-forming temperature (MFTα). The appropriate heating temperature needs to be adjusted as appropriate because the thickness and porosity of the coating layer on the surface of the recording medium differ depending on the type of recording medium, for example, high-quality paper or coated paper.

  The invention described in claim 6 is characterized in that, in the invention described in any one of claims 2 to 5, the minimum film forming temperature of the resin component is 40 ° C. or higher and lower than 70 ° C.

  According to the sixth aspect of the present invention, it is considered that the temperature of the environment in which an image is formed becomes high due to fixing processing, apparatus driving energy, etc., and transfer is performed at a temperature slightly higher than room temperature (approximately 30 to 40 ° C.) in the transfer portion. Then, since the minimum film-forming temperature of the resin component is 40 ° C. or higher and lower than 70 ° C., the strength of the ink film can be increased and transfer can be performed satisfactorily without requiring heating of the transfer body. Here, if the minimum film-forming temperature is about 25 ° C. or less, which is too low, the film-forming progress speed at the nozzle portion will increase dramatically, causing nozzle clogging and further impairing the stability of the ink flying direction. This is not preferable. Even in the range of 25 to 40 ° C., there is a concern about the influence on the nozzle. In addition, at a temperature of 70 ° C. or higher, a high temperature of at least about 50 ° C. is required to develop the resin surface fusion effect. In this case, it is difficult to achieve both transferability and ink discharge speed maintenance, and energy is consumed for heating. Resulting in.

  The invention according to claim 7 is the invention according to any one of claims 2 to 6, wherein the particle size distribution (volume average particle size Mv / number) of the dispersed fine particles in the ink containing the resin component and the coloring material. The average particle diameter Mn) is 1.35 or more.

  According to claim 7, when the particle size distribution (Mv / Mn) of the dispersed fine particles in the ink is 1.35 or more, the particle distribution tends to be polydispersed, and the small particles fill the voids of the large particles. Therefore, the contact area between particles increases. Therefore, the adhesion effect between the fine particles can be further enhanced.

  The invention according to claim 8 is the invention according to any one of claims 2 to 7, wherein the resin component has a breaking strength at 25 ° C. of 5 MPa or more.

  According to the eighth aspect, since the ink film can be appropriately hardened by using a resin component having a breaking strength of 5 MPa or more when the tensile test is performed in an environment of 25 ° C., the transfer member is heated by the transfer member. It is possible to inhibit an increase in adhesion due to the adhesive effect that develops between the ink films. Further, even when a slight amount of ink image remains on the transfer body, the ink film can be appropriately hardened so that cleaning can be performed efficiently. Thus, since the strength of the ink film can be further strengthened by increasing the breaking strength, it is more effective with respect to the abrasion resistance by combining with the ductility imparting effect having a breaking elongation of 25% or more. The larger both values are, the better. However, the elongation at break and the strength at break are generally in a trade-off relationship, and it is difficult to increase both. Therefore, it is necessary to select and design a resin that balances both. Even if the elongation at break is increased too much, the stress does not work, so the break strength decreases. And even if the breaking strength is increased too much, the ductility is impaired and a problem is caused. Further, increasing the elongation at break leads to a decrease in the minimum film-forming temperature (MFTα) of the resin component, so it is necessary to adjust it so that it does not fall below 25 ° C.

  The invention according to claim 9 is the invention according to any one of claims 2 to 8, wherein the resin component includes an ionic bond whose counter ion is a metal ion or an organic amine ion.

  According to the ninth aspect, it is more preferable that the ink image on the transfer body has an ionic bond. Ion bonds are effective because the bonding direction of the resin particles is small, the electrostatic attractive force is optimized, and a close structure such as closest packing is easily formed. And the ionic bond has a very large bond strength order compared to the hydrogen bond and van der Waals force. For this reason, even if it is a resin material that is inherently hard and does not have ductility, by ionic crosslinking between molecules (chains), the ionic crosslinking point can act like a spring and impart ductility. A typical example of such a resin material is an ionomer resin.

  According to a tenth aspect of the present invention, in the invention according to any one of the second to ninth aspects, a treatment liquid is applied to the intermediate transfer member before discharging the ink, and the treatment liquid and the ink are added. The solid component and the solvent component are separated by the reaction of

  According to the tenth aspect of the present invention, it is effective to apply the treatment liquid and to separate the solid component and the solvent component by the reaction between the treatment liquid and the ink, thereby further enhancing the adhesion effect between the resin fine particles. .

  According to an eleventh aspect of the present invention, in the invention according to the tenth aspect, the treatment liquid contains a metal ion or an organic amine ion, and the coloring material or resin component of the ink has an anionic group. Features.

  According to the eleventh aspect, even if the resin component of the ink does not have an ionic bond as in the ninth aspect of the invention, anionic groups such as sulfonic acid groups and carboxylic acid groups are formed on the surface of the resin fine particles of the ink. The resin fine particles can be ion-bonded and aggregated with a cation component such as a polyvalent metal salt or organic amine contained in the treatment liquid. Therefore, the adhesion effect between the resin fine particles of the ink can be further enhanced.

  In order to achieve the above object, an invention according to claim 12 is an image forming apparatus in which an ink containing at least a resin component and a coloring material is ejected onto an intermediate transfer member, and then the ink is transferred to a recording medium. A liquid supply means for supplying the ink whose resin component has an elongation at break of 25% or more at 25 ° C., and the ink supplied from the liquid supply means is ejected in droplets onto the intermediate transfer member A liquid ejecting unit that absorbs the solvent component of the ink applied onto the intermediate transfer member by the liquid ejecting unit, and an ink that has absorbed the solvent component from the ink on the intermediate transfer member. Heating means for heating the intermediate transfer member at a temperature of 25 ° C. or higher and lower than the minimum film-forming temperature of the resin component, and pressurizing the ink heated by the heating means. To provide an image forming apparatus characterized by comprising a pressurizing means for transferring to a recording medium.

  According to the twelfth aspect of the present invention, in the intermediate transfer type image forming apparatus, transfer failure and transfer unevenness can be prevented, image fastness such as abrasion resistance and water resistance is maintained, and variation in ejection speed from the nozzles is achieved. In addition to preventing the image quality from being deteriorated due to the ink, the ink adhering to the transfer member can be easily cleaned, and the uneven glossiness of the image due to the high boiling point solvent can be prevented.

  In this specification, “recording medium” includes not only paper used in general apparatuses but also cloth, metal, plate, glass, ceramics, wood, plastic film, leather, and the like.

  In the present specification, the mechanical properties of the “breaking elongation” and “breaking strength” of the resin component are obtained by a tensile test based on JISK-6760.

  In this specification, “minimum film-forming temperature (MFTα)” means that a resin emulsion obtained by dispersing a resin component in water is thinly applied on a metal plate such as aluminum or stainless steel, and the temperature is increased. It means the temperature at which the formation of the transparent continuous film is completely completed, and the “film formation start temperature (MFTβ)” means the temperature at which the formation of the transparent continuous film starts. Specifically, a resin component dispersion is applied to a stainless steel plate with a temperature gradient to a thickness of 200 μm. Then, silica gel is installed as a desiccant, and the periphery is covered with a transparent plastic lid. After the coating is dried, the temperature at the boundary between the uniform continuous film portion and the cloudy portion is read. The temperature at which the cloudy part begins to appear is defined as “film formation start temperature (MFTβ)”, and the temperature at which the cloudy part completely disappears and is completely formed into a film is defined as “minimum film formation temperature (MFTα)”.

  According to the present invention, transfer defects and transfer unevenness can be prevented, image fastness such as abrasion resistance and water resistance is maintained, and deterioration in image quality due to variations in ejection speed from nozzles is prevented. At the same time, it is possible to provide an ink, an image forming method, and an apparatus for facilitating cleaning of ink adhering to a transfer body and preventing uneven glossiness of an image due to a high boiling point solvent.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  The ink of the present invention contains at least a resin component and a color material, and is used for image formation to be transferred onto a recording medium after being ejected onto an intermediate transfer body, and the resin component has an elongation at break at 25 ° C. Is 25% or more.

  The image forming method of the present invention is the image forming method in which after the ink containing at least the resin component and the color material is ejected onto the intermediate transfer member, the solvent component is absorbed from the ink and transferred to the recording medium. The resin component has an elongation at break at 25 ° C. of 25% or more, and the temperature of the intermediate transfer body when transferred to the recording medium is 25 ° C. or more and lower than the minimum film forming temperature of the resin component. Features.

  The image forming apparatus of the present invention is an image forming apparatus in which an ink containing at least a resin component and a colorant is ejected onto an intermediate transfer member, and then the ink is transferred to a recording medium. A liquid supply means for supplying the ink having a breaking elongation at 25% or more, a liquid discharge means for discharging the ink supplied from the liquid supply means to the intermediate transfer member in the form of droplets, Solvent absorbing means for absorbing the solvent component of the ink applied on the intermediate transfer body by the liquid discharge means, and the intermediate when transferring the ink that has absorbed the solvent component from the ink on the intermediate transfer body to the recording medium Heating means for heating the temperature of the transfer body in a range of 25 ° C. or more and less than the minimum film-forming temperature of the resin component, and pressurizing the ink heated by the heating means to transfer to the recording medium Characterized by comprising a pressure means.

  In this embodiment, an image forming method and apparatus for applying a treatment liquid before ejecting ink onto the intermediate transfer member will be described, but the present invention is not limited to this.

  First, the ink and the treatment liquid according to the present invention will be described in detail.

〔ink〕
The ink used in the present invention contains at least a pigment, polymer fine particles, a water-soluble solvent, and water.

[Color material]
Therefore, the color material used in the ink can be used by mixing a pigment or a dye and a pigment. From the viewpoint of aggregability at the time of contact with the treatment liquid, a pigment in a dispersed state in the ink is preferable because it aggregates more effectively. Among the pigments, a pigment dispersed by a dispersant, a self-dispersing pigment, a pigment whose surface is coated with a resin (microcapsule pigment), and a polymer graft pigment are particularly preferable. From the viewpoint of pigment aggregation, a form modified with a carboxyl group having a low dissociation degree is more preferable.

  The resin may be self-dispersible or soluble, or may have a function added by some means. For example, it may be a resin in which an anionic group such as a carboxyl group, a sulfonic acid group, or a phosphonic acid group is introduced by neutralization with an organic amine or an alkali metal. Further, it may be a resin into which one or two or more anionic groups of the same type or different types are introduced. In the present invention, a resin in which a carboxyl group is introduced by neutralization with a base is preferably used.

  Although it does not specifically limit as a pigment used for this invention, As a specific example, as a pigment for orange or yellow, C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185. Examples of red or magenta pigments include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the pigment for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  Examples of black pigments include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.

  The concentration of the color material contained in the ink used in the present invention may be selected to an optimum value depending on the color material used, but it should be in the range of 0.1% by weight to 40% by weight with respect to the total weight of the ink. Is preferred. More preferably, they are 1 weight%-30 mass%, More preferably, they are 2 weight%-20 mass%. If it is less than this range, sufficient image density cannot be obtained, and if it is too much, the ink viscosity becomes too high.

  The volume average particle diameter of the pigment particles is not particularly limited as long as the ink ejection properties are not impaired, but a range of 30 to 150 nm is particularly preferable. Although the effect of improving the color development and transparency of the resulting image on the recording medium can be expected by making the pigment finer, there are disadvantages such as a decrease in light resistance and an increase in ink viscosity. It is desirable to adjust.

[resin]
It is preferable to add a resin containing no colorant to the ink according to the present invention. In particular, an ink having high dispersibility and stability can be obtained by incorporating an anionic resin into the ink.

  Depending on the type of the resin, the resin forms a film with the recording material, and has an effect of improving the abrasion resistance and water resistance of the image.

  The addition form of the resin component used in the present invention may be dispersed in the ink as polymer fine particles composed of the resin component alone, or fine particles in which the color material and the resin are integrated so as to cover the pigment surface, that is, a microcapsule pigment It may be contained in the ink as particles.

  The method for dispersing the resin in the ink is not limited to emulsion, and it may be partially dissolved or may exist in a colloidal dispersion state.

  The resin component may be dispersed in the form of resin fine particles using an emulsifier, or may be dispersed without using an emulsifier. As the emulsifier, a low molecular weight surfactant is usually used, but a high molecular weight surfactant can also be used as an emulsifier. It is also preferable to use capsule type resin fine particles (core / shell type polymer fine particles having different compositions at the center and outer edge of the particle) whose outer shell is made of acrylic acid, methacrylic acid or the like.

  As a dispersion method, resin fine particles not using a low molecular weight surfactant are called soap-free latex, including polymer fine particles using a high molecular weight surfactant and polymer fine particles not using an emulsifier. For example, as described above, a polymer having a water-soluble group such as a sulfonic acid group or a carboxyl group (a polymer in which a solubilizing group is graft-bonded, a monomer having a solubilizing group and an insoluble portion). Resin fine particles using a block polymer obtained from a monomer as an emulsifier are also included.

  In the present invention, it is particularly preferable to use this soap-free latex. Compared to conventional resin fine particles polymerized using an emulsifier, the soap-free latex inhibits film formation of the resin fine particles, or the free emulsifier contains resin fine particles. There is no concern of moving to the surface after film formation and reducing the adhesion, that is, the fixability, between the image film mixed with the pigment and resin fine particles and the recording medium. Moreover, deterioration of water resistance can also be prevented.

  Resin components added to the ink include acrylic resins, vinyl acetate resins, styrene-butadiene resins, styrene isoprene resins, vinyl chloride resins, acrylic-urethane resins, styrene-acrylic resins, ethylene-acrylic resins. Examples thereof include, but are not limited to, resins, butadiene resins, styrene resins, acrylonitrile resins, and ionomer resins.

  From the viewpoint of imparting image fixability, those having a carboxyl group with a low degree of dissociation are more preferred.

  The resin component is preferably a polymer having both a hydrophilic part and a hydrophobic part. By having a hydrophobic portion, when in the form of resin fine particles, the hydrophobic portion is oriented on the inside, the hydrophilic portion is efficiently oriented on the outside, and a favorable anti-affinity effect is exerted on the water-repellent surface of the nozzle. It can be applied and prevents ink wetting around the nozzle hole.

  Any hydrophilic anionic group may be used as long as it has a negative charge, but it must be a phosphoric acid group, phosphonic acid group, phosphinic acid group, sulfuric acid group, sulfonic acid group, sulfinic acid group or carboxyl group. Is preferable, and a carboxyl group is more preferable.

  In the case of aggregation using pH change, it is more desirable to include not only an anionic group but also a cationic group. After the ink pH change, an anionic group on the surface of the colorant particle is generated and an attractive force is generated. The cohesive force can be increased.

  Examples of commercially available resins include Jonkrill (styrene-acrylic resin emulsion, manufactured by Johnson Polymer Co., Ltd.), Jurimer ET-410 (acrylic resin emulsion, manufactured by Nippon Pure Chemicals Co., Ltd.), A-104 (acrylic resin). Emulsions, manufactured by Toagosei Co., Ltd., Saixen (ethylene-acrylic resin emulsion, manufactured by Sumitomo Seika Co., Ltd.), Chemipearl (ethylene-acrylic resin emulsion, manufactured by Mitsui Chemicals), etc. Not what you want.

  The amount of the resin component added to the ink is preferably 2 to 40% by weight, more preferably 4 to 20% by weight. When it is less than 2% by weight, the effect of the present invention is insufficient. On the other hand, if it exceeds 40% by weight, the ink viscosity becomes too high, and the ejection reliability is impaired.

  The weight ratio of the amount of the resin component added to the pigment is preferably 2: 1 to 1:10, more preferably 1: 1 to 1: 5. If the weight ratio of the resin component added to the pigment is less than 2: 1, the effect of resin fusion is insufficient, and a sufficient effect on the abrasion resistance cannot be obtained. Moreover, even if the addition amount is more than 1:10, the viscosity of the ink becomes too high, and the ejection reliability and the like deteriorate.

  The molecular weight of the resin component added to the ink is preferably 5,000 or more in view of the adhesive force when fused. If it is less than 5,000, the effect of the image on the abrasion resistance and the fixing property is insufficient.

  The minimum film-forming temperature (MFTα) of the resin component used in the present invention is preferably 40 ° C. or more and less than 70 ° C. from the viewpoint of achieving both ejection properties and fixing properties. Generally, the minimum film-forming temperature means that a resin emulsion obtained by dispersing resin components in water is applied thinly on a metal plate such as aluminum or stainless steel, and when the temperature is raised, it is transparent and continuous. The temperature at which film formation is completely completed. In the temperature region below the minimum film-forming temperature, no film is formed and a white powder is formed.

  In the present invention, the film formation start temperature (MFTβ) refers to a temperature at which formation of a transparent continuous film starts. When the minimum film-forming temperature is measured by the above method, a gap occurs between the minimum film-forming temperature (MFTα) and the film-forming start temperature (MFTβ), and the film-forming start temperature is measured lower than the minimum film-forming temperature.

  In the present invention, the resin component dispersion is applied to a stainless steel plate with a temperature gradient to a thickness of 200 μm. Immediately thereafter, silica gel is installed as a desiccant, and the periphery is covered with a transparent plastic lid. After the coating film is dried, the temperature at the boundary between the uniform continuous film portion and the cloudy portion is read to obtain the minimum film-forming temperature.

  In the present invention, the temperature at which the white turbid portion begins to appear is defined as the film forming start temperature (MFTβ), and the temperature at which the white turbid portion completely disappears and is completely formed into a film is defined as the minimum film forming temperature (MFTα).

  In the present invention, two or more kinds of resin components may be mixed and used in the ink. Each resin component may be dispersed alone in the ink, or may have a core-shell structure including a core portion and a shell portion. Moreover, not only the form which the shell part has coat | covered the core part completely, but the form which coat | covered a part of core part may be sufficient. Further, the second resin component layer may be dispersed and wrapped in islands in the first resin component layer, or the surface on which the first resin layer forms the surface layer may be A form in which resin particles are dispersed in a point may be used.

  In the present invention, the elongation at break of the resin component at 25 ° C. needs to be 25% or more. If it is less than 25%, sufficient adhesion cannot be exhibited when the resin surface is fused inside the ink image. From the viewpoint of improving transferability and abrasion resistance, 100% or more is more preferable.

  In order to further improve the toughness of the resin component and to give more abrasion resistance, and to reduce the cleaning load of the transfer body by appropriately hardening the resin component and reducing the adhesiveness, the breaking strength is 5 MPa. The above is preferable. If it is less than 5 MPa, there is a concern that the load of cleaning increases when the transfer member is used for a long time.

  From the viewpoint of rubbing resistance, when the ink image is rubbed particularly strongly, if it is too plastic, the image may be stretched and the image quality may be slightly impaired. In order to prevent this, it is desirable to use a characteristic that both the elongation at break and the strength at break are large, that is, a resin having high toughness.

  Mechanical properties such as breaking elongation and breaking strength of the resin component can be obtained by a tensile test based on JISK-6760. For film molding, the polymer fine particle liquid may be freeze-dried and formed into a film by a heat press, or may be coated on a plate so as to have a predetermined film thickness, and heat-treated to form a film.

  Each value of elongation at break and strength at break used in the present invention was obtained by forming a resin component into a film having a thickness of 100 μm by a heat press machine, making it a test piece size of 1 cm × 3 cm, 25 ° C. and humidity of 50%. What was measured with Tensilon at a tensile speed of 100 mm / min under the conditions was used.

  When the resin component is added to the ink in the form of dispersed particles, the volume average particle size of the dispersed particles is not particularly limited, but is particularly preferably 100 nm or less. If the particle size is small, the ink image becomes denser, and the effect of fusing the resin particle surface can be effectively expressed.

  The volume average particle diameter of the resin fine particles is preferably smaller than the volume average particle diameter of the pigment particles. When the resin fine particle size is smaller than the pigment particle size, the resin fine particles easily enter between the pigment particles, and the packing density of the ink image can be improved. Thereby, the pigment particles are connected to each other through the resin fine particles whose surfaces are fused, and the effect of improving the cohesive force of the entire ink image is further enhanced.

  In view of the above effects, the ratio of the volume average particle diameter of the pigment to the volume average particle diameter of the resin fine particles is preferably 1: 1 to 10: 1, more preferably 3: 1 to 10: 1. If it exceeds 10: 1 and the pigment particle size becomes too large, the adhesion effect between the pigment particles by the resin fine particles is insufficient.

  Regarding the particle size distribution of the dispersed particles in the ink, the ratio of the volume average particle size to the number average particle size (volume average particle size / number average particle size) is preferably 1 or more and 1.35 or more. When the particle size distribution is polydispersed, that is, when a large number of particles having different particle sizes are present in the ink, there is an effect of lowering the viscosity of the ink liquid compared to the case of monodisperse. A large amount of solid content can be added, and the effect of the present invention is further enhanced. In addition, in the ink image on the transfer body from which the solvent component has been removed after removal of the solvent, the filling structure of the internal structured particles can be made denser, which has the effect of assisting the adhesion effect. For the purpose of reacting with the dispersed particles in the ink before ink ejection, it is more preferable to apply a treatment liquid on the transfer body because the effect of increasing the packing density can be further enhanced.

  Examples of the method for measuring the particle size distribution including the volume average particle size and the number average particle size include a static light scattering method, a dynamic light scattering method, and a centrifugal sedimentation method. Among them, the dynamic light scattering method using the laser Doppler effect is particularly preferable because it can measure the particle size up to a small size. The particle size measurement by the dynamic light scattering method can be performed using, for example, Microtrac UPA (manufactured by Nikkiso Co., Ltd.). The volume average particle size is an average particle size weighted by the particle volume. In the set of particles, the sum of the diameter of each particle multiplied by the volume of the particle is divided by the total volume of the particle. Is represented by the following formula A.

Volume average particle diameter Mv = ΣFiMi ⁴ / ΣFiMi ³ (Formula A)
(However, Fi: number of particles whose particle system is Mi (fraction))
The number average particle diameter is a sum of diameters of individual particles divided by the total number of particles in a set of particles, and is represented by the following formula B.

Formula B; Number average particle diameter Mn = ΣFiMi / ΣFi (Formula B)
(However, Fi: number of particles whose particle system is Mi (fraction))
As the relationship between the volume average particle size and the number average particle size, the volume average particle size Mv is equal to or greater than the number average particle size Mn (volume average particle size ≧ number average particle size). is there. Therefore, in a set of particles having the same particle size, both values are equal, and the ratio of the volume average particle size Mv to the number average particle size Mn (volume average particle size Mv / number average particle size Mn) is 1. It becomes. In addition, the larger the ratio between the volume average particle size Mv and the number average particle size Mn, the wider the particle size distribution. The volume average particle number and the number average particle size are described in Soichi Muroi, “Polymer Latex Chemistry”, Polymer Publishing Association, page 119.

  When coarse particles are present in the resin fine particles in the ink, the ink ejection reliability may be greatly affected. In particular, when a resin having a film-forming property at room temperature is used as in the present invention, the influence of coarse particles becomes significant. In other words, if there are many coarse particles (≈ the particle size distribution shape is broad), an ink residue is formed in the vicinity of the nozzle due to the coarse particles, even if ejection failure occurs in the nozzle of the head, or even ejection failure does not occur. Variations occur in the droplet ejection direction.

  As a method for removing these coarse particles, a known centrifugal separation method, microfiltration method, or the like can be used.

  A commercially available centrifuge can be used as the centrifugation method. The magnitude of the centrifugal force to be applied is preferably 10 times to 1 million times the gravitational acceleration.

  As a filter used in the microfiltration method, various materials can be used. That is, cellulose, acetyl cellulose, polyvinylidene fluoride, polyethersulfone, polytetrafluoroethylene, polycarbonate, glass fiber, polypropylene, and the like are preferable. Moreover, as for the form of a filter, both a membrane filter and a depth filter are preferably used. The pore size of the filter used for filtration is preferably 0.1 to 10 μm, more preferably 0.2 to 5 μm, and most preferably 0.2 to 0.5 μm. Moreover, when filtering, after filtering with a filter with a large hole diameter, it is preferable to filter again with a filter with a smaller hole diameter.

  If there are many coarse particles and the filterability is poor, a dispersant can be added to the dispersion to improve the filterability.

  The ink of the present invention preferably contains a water-soluble organic solvent for the purpose of preventing clogging of the nozzles of the inkjet head due to drying. Such water-soluble organic solvents include wetting agents and penetrants.

  Examples of the water-soluble organic solvent include polyhydric alcohols, polyhydric alcohol derivatives, nitrogen-containing solvents, alcohols, sulfur-containing solvents and the like, as in the case of the treatment liquid. Specific examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, and glycerin. Examples of polyhydric alcohol derivatives include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and diglycerin. Examples include ethylene oxide adducts. Examples of nitrogen-containing solvents include pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, and triethanolamine. Examples of alcohols include alcohols such as ethanol, isopropyl alcohol, butyl alcohol, and benzyl alcohol. Thiodiethanol, thiodiglycerol, sulfolane, dimethyl sulfoxide and the like. In addition, propylene carbonate, ethylene carbonate, or the like can be used.

  The ink of the present invention can contain a surfactant.

  Examples of surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensates, Anionic surfactants such as oxyethylene alkyl sulfate esters, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylamines Nonionic surfactants such as glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Further, SURFYNOLS (Air Products & Chemicals), which is an acetylene-based polyoxyethylene oxide surfactant, is also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.

  Further, pages (37) to (38) of JP-A-59-157636, Research Disclosure No. The surfactants described in 308119 (1989) can also be used. In addition, fluorine (fluorinated alkyl) and silicone surfactants as described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are also used. Can do. These surface tension modifiers can also be used as antifoaming agents, and fluorine-based, silicone-based compounds, chelating agents represented by EDTA, and the like can also be used.

  The surface tension is lowered to increase the wettability on the intermediate transfer member or on the treatment liquid, and the cohesive action is effectively promoted by increasing the contact area between the two liquids.

  The surface tension of the ink of the present invention is preferably from 10 to 50 mN / m. When direct recording is performed, the penetrability to the permeable recording medium, and when recording is performed by the intermediate transfer method, the intermediate transfer member is used. From the viewpoint of achieving both the wettability above, the formation of fine droplets and the discharge properties, it is more preferably 15 to 45 mN / m.

  The viscosity of the ink of the present invention is preferably 1.0 to 20.0 cP.

  In addition, a pH buffer, an antioxidant, a fungicide, a viscosity modifier, a conductive agent, an ultraviolet absorber, and the like can be added as necessary.

[Treatment solution]
Preferable examples of the treatment liquid used in the present invention include a treatment liquid to which a polyvalent metal salt or polyallylamine is added. These compounds may be used alone or in combination of two or more. From the viewpoint of the crosslinking point, trivalent aluminum ions are more preferably used.

  A treatment liquid that aggregates pigments and polymer fine particles contained in the ink by changing the pH of the ink to produce an aggregate is also preferable.

  Treatment liquid components include 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, sulfonic acid, orthophosphoric acid, pyrrolidone It is preferably selected from carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof.

  The treatment liquid according to the present invention preferably has a pH of 1 to 6, more preferably 2 to 5, and particularly preferably 3 to 5 from the viewpoint of pH aggregation performance with the ink. .

  The addition amount of the component for aggregating the ink pigment and polymer fine particles in the treatment liquid according to the present invention is preferably 0.01% by weight or more and 20% by weight or less with respect to the total weight of the liquid. When the amount is 0.01% by weight or less, concentration dispersion does not proceed sufficiently when the treatment liquid and the ink are in contact with each other, and agglomeration due to pH change may not occur sufficiently. On the other hand, if it is 20% by weight or more, the dischargeability from the ink jet head may deteriorate.

  These solvents can be used alone or in combination with water and other additives.

  The content of water and other additive-soluble organic solvents is preferably 60% by weight or less based on the total weight of the treatment liquid. When the amount is more than 60% by weight or more, the viscosity of the treatment liquid increases, and the dischargeability from the inkjet head may deteriorate.

  The treatment liquid may further contain a resin component in order to improve fixability and abrasion resistance. The resin component may be any resin component that does not impair the ejection properties from the head when the treatment liquid is ejected by the ink jet method and has storage stability, and water-soluble resins and resin emulsions can be used freely.

  The coagulability may be further enhanced by adding polymer fine particles having a polarity opposite to that of the ink to the treatment liquid and aggregating with the pigment and polymer fine particles in the ink.

  In addition, a curing agent corresponding to the polymer fine particle component contained in the ink is contained in the treatment liquid, and after the two liquids contact, the resin emulsion in the ink component aggregates and crosslinks or polymerizes to increase the cohesiveness. Also good.

  The treatment liquid according to the present invention can contain a surfactant.

  Examples of surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensates, Anionic surfactants such as oxyethylene alkyl sulfate esters, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylamines Nonionic surfactants such as glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Further, SURFYNOLS (Air Products & Chemicals), which is an acetylene-based polyoxyethylene oxide surfactant, is also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.

  Further, pages (37) to (38) of JP-A-59-157636, Research Disclosure No. The surfactants described in 308119 (1989) can also be used. In addition, fluorine (fluorinated alkyl) and silicone surfactants as described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are also used. Can do. These surface tension modifiers can also be used as antifoaming agents, and fluorine-based, silicone-based compounds, chelating agents represented by EDTA, and the like can also be used.

  The surface tension of the treatment liquid according to the present invention is preferably 10 to 50 mN / m. When direct recording is performed, the penetrability into the permeable recording medium, or when recording is performed by an intermediate transfer method, From the viewpoint of achieving both wettability on the intermediate transfer member, fine droplet formation and ejection properties, it is more preferably 15 to 45 mN / m.

  The viscosity of the treatment liquid according to the present invention is preferably 1.0 to 20.0 cP.

  In addition, pH buffering agents, antioxidants, fungicides, viscosity modifiers, conductive agents, ultraviolet rays, absorbents, and the like can be added as necessary.

  If the difference in pH between the treatment liquid and the ink is 3 or less, the aggregation component in the treatment liquid may not sufficiently diffuse and move, and a sufficient agglomeration action may not be obtained to achieve the effect. In such a case, the surface potential drop of the dispersed particles in the ink due to neutralization is delayed, and the dispersed state of the particles in the ink is not sufficiently destroyed. As a result, image disturbance on the transfer body due to the flow of the pigment on the transfer body, and transfer failure due to the fact that the aggregate does not have sufficient cohesive force at the transfer stage are caused. If the difference in pH between the treatment liquid and the ink is 3 or more, sufficient diffusion movement occurs and a preferable aggregating action is obtained.

  Wax may be added to the treatment liquid used in the present invention from the viewpoint of improving transferability by imparting releasability or imparting adhesive force inside the ink film. More preferably, it is added in the form of an emulsion. The amount added is preferably 0.05% by weight or more in terms of the weight ratio of the solid content in the emulsion with respect to the total solid content of the ink in order to obtain a good release effect and an adhesive strength inside the ink film. If it is less than 0.05%, a sufficient release effect cannot be obtained. However, since the reliability of the ink is lowered by increasing the addition amount of the emulsion, the solid content is preferably suppressed to about 30% by weight with respect to the whole ink.

  As the wax, carnauba wax, paraffin wax, microcrystalline wax, montan wax, alcohol wax, polyethylene wax, polypropylene wax, PTFE wax, synthetic oxide wax, α-olefin-maleic anhydride copolymer, and the like can be used.

  Further, these waxes may be separately applied onto the transfer body before applying the treatment liquid or ink, and it is also desirable that the layer is formed by drying or agglomeration by contact with the treatment liquid / ink. It is a form.

[Overall configuration of image forming apparatus]
FIG. 1 is a schematic diagram illustrating a schematic configuration of an ink jet recording apparatus, which is an example of an image forming apparatus according to the present exemplary embodiment. As shown in the figure, the ink jet recording apparatus 10 of the present embodiment mainly includes an intermediate transfer body 12, a treatment liquid application section 14, an ink discharge section 16, and a transfer section 18, and further includes a solvent removal section 20, a transfer body heating. A unit 21, a cleaning unit 22, and an image fixing unit 24.

  The intermediate transfer body 12 is composed of an endless belt having a predetermined width, and is wound around a plurality of rollers 26. In the present embodiment, four rollers 26A to 26D are used as an example. There is also an aspect in which a drum-like member or a plate-like member is used as the intermediate transfer body 12.

  The power of a motor (not shown) is transmitted to at least one main roller among the plurality of rollers 26, and the intermediate transfer body 12 is driven outside the rollers 26 (26A to 26D) by the driving of the motor in FIG. It is configured to rotate in a rotating direction (hereinafter referred to as “transfer body rotation direction”).

  The processing liquid application unit 14 is provided with a recording head (processing liquid head) 30S corresponding to the processing liquid (S). The processing liquid head 30 </ b> S discharges the processing liquid from the discharge surface facing the intermediate transfer body 12. Thereby, the treatment liquid is applied onto the recording surface 12 a of the intermediate transfer body 12.

  The ink discharge unit 16 is disposed downstream of the treatment liquid application unit 14 in the transfer body rotation direction. The ink ejection unit 16 is provided with recording heads (ink heads) 30K, 30C, 30M, and 30Y corresponding to black (K), cyan (C), magenta (M), and yellow (Y) inks. Yes. Each of the ink heads 30K, 30C, 30M, and 30Y discharges the corresponding color ink from the discharge surface facing the intermediate transfer body 12. As a result, each color ink is applied onto the recording surface 12 a of the intermediate transfer body 12. Here, each color ink is an ink containing a resin and a colorant as described above.

  Each of the treatment liquid head 30S and the ink heads 30K, 30C, 30M, and 30Y has a large number of ejection ports (nozzles) over the maximum recording width (maximum recording width) of the image formed on the intermediate transfer body 12. It is a full line head formed. Image recording on the intermediate transfer body 12 is performed at a higher speed than a serial type recording in which a short shuttle head is reciprocally scanned in the width direction of the intermediate transfer body 12 (front and back in FIG. 1). Can do. Of course, the present invention is also suitable for a method capable of relatively high-speed recording even in the serial type, for example, a one-pass recording method in which one line is formed by one scan.

  In the present embodiment, the recording heads (the treatment liquid head 30S and the ink heads 30K, 30C, 30M, and 30Y) all have the same structure, and in the following, the recording head is represented by reference numeral 30. And In the implementation of the present invention, the recording heads are not limited to the same structure. For example, the treatment liquid head 30S and the ink heads 30K, 30C, 30M, and 30Y may have different structures. .

  When the processing liquid is discharged from the processing liquid head 30S toward the intermediate transfer body 12, the region to which the processing liquid of the intermediate transfer body 12 is applied as the intermediate transfer body 12 rotates corresponds to the ink heads 30K. The ink moves sequentially directly below 30C, 30M, and 30Y, and the corresponding color inks are ejected from the ink heads 30K, 30C, 30M, and 30Y, respectively. The treatment liquid has a function of aggregating solvent-insoluble materials (coloring materials and the like) in the ink.

  The treatment liquid application amount and the ink application amount are preferably adjusted as necessary. For example, depending on the recording medium to be transferred, the application amount of the treatment liquid may be changed in order to adjust the physical properties such as viscoelasticity of the aggregate formed by mixing the treatment liquid and ink.

  Further, the treatment liquid may be applied prior to ink, or may be applied after ink droplet ejection.

  The solvent removal unit 20 is disposed on the downstream side of the ink discharge unit 16 in the rotation direction of the transfer body. In the solvent removal unit 20, a solvent removal roller 32 is provided at a position facing the roller 26 </ b> A across the intermediate transfer body 12. The solvent removal roller 32 is composed of a roller-like porous body and is disposed so as to contact the recording surface 12 a of the intermediate transfer body 12. As other modes, there are a method of removing excess solvent from the intermediate transfer body 12 with an air knife, a method of heating and evaporating the solvent, and the like.

  In the solvent removal unit 20, the solvent on the recording surface 12 a of the intermediate transfer body 12 is removed by the solvent removal roller 32. For this reason, even when a large amount of processing liquid is applied to the recording surface 12a of the intermediate transfer body 12, the solvent is removed by the solvent removal unit 20, so that a large amount of solvent (dispersed in the recording medium 34 by the transfer unit 18). Medium) is not transferred. Therefore, even when paper is used as the recording medium 34, there is no problem characteristic to the aqueous solvent such as curl and cockle.

  By removing the solvent from the ink aggregate by the solvent removing unit 20, the aggregate can be concentrated and the internal aggregating force can be further increased. Thereby, fusion of the resin particles contained in the aggregate is effectively promoted, and a stronger internal cohesive force can be imparted to the aggregate until the transfer step. Furthermore, the effective concentration of the ink aggregates by removing the solvent can impart good fixability and glossiness to the image even after transfer to the recording medium.

  In the transfer body heating unit 21, the temperature of the intermediate transfer body is heated so as to be in a range of 25 ° C. or higher and lower than the minimum film forming temperature of the resin. By setting the temperature of the intermediate transfer body 12 within this temperature range, as described above, only the surface of the resin is fused and adhered to surrounding colorant particles and resin components, and the film strength only inside the ink image. And has the effect of increasing the adhesive strength.

  The transfer unit 18 is disposed downstream of the solvent removal unit 20 in the rotation direction of the transfer body. The transfer unit 18 is provided with a pressure roller 36 at a position facing the roller 26B with the intermediate transfer body 12 interposed therebetween. A heater is provided inside the pressure roller 36, and the temperature of the outer peripheral surface of the pressure roller 36 is increased by the heater. The recording medium 34 is conveyed from the left side to the right side in FIG. 1 so as to pass between the intermediate transfer body 12 and the pressure roller 36. When passing between the intermediate transfer body 12 and the pressure roller 36, the surface side of the recording medium 34 is brought into contact with the recording surface 12 a of the intermediate transfer body 12, and pressure is applied by the pressure roller 36 from the back surface side of the recording medium 34. Thus, the image formed on the recording surface 12 a of the intermediate transfer body 12 is transferred and formed on the recording medium 34.

  In the present invention, the heating part is not limited to the transfer part of the transfer body, and the temperature of the recording medium 34 is not less than the film formation start temperature of the ink resin component at the time of ink transfer, preferably the ink resin. In order to make the temperature equal to or higher than the minimum film forming temperature of the component, it is preferable to provide the recording medium heating unit 25 in a portion before the recording medium 34 arrives at the transfer unit.

  As described above, since the recording medium 34 that is in direct contact with the ink image has already reached the desired transfer temperature, heat transfer can be efficiently performed in a shorter time during the transfer nip. Also, as compared with the case where heating is performed only at the transfer nip, the recording medium is preliminarily set at a desired transfer temperature, whereby the heating temperature of the recording medium where the ink aggregate and the surface of the recording medium are in contact with each other is preferably made of resin fine particles. By setting the film starting temperature (MFTβ) or higher, more preferably the minimum film forming temperature (MFTα), the resin fusing rate by heating during transfer can be further improved, and the medium surface is preheated. Therefore, when the ink image and the surface of the recording medium are in contact with each other at the transfer nip, the resin component in the ink image immediately melts and enters the irregularities and capillaries of the surface of the recording medium, thereby recording by the throwing effect due to the increase in the contact area. As a result, the adhesive force between the medium and the ink image is improved, and as a result, the transfer is performed well, and good fixing properties can be imparted to the image even after the transfer.

  This heating temperature can be freely adjusted according to the type of the recording medium 34. It is also possible to control the tackiness of the ink image by this temperature control. If there are many irregularities due to pulp fibers on the surface of plain paper or high-quality paper, and an anchor effect can be expected between the ink image and the surface of the recording medium, the adhesiveness of the ink image can be determined only by the heating temperature at the transfer section. In addition, by controlling and adjusting the heating temperature of the surface of the recording medium that is in direct contact with the transfer, good fixability can be imparted to plain paper or high-quality paper with the optimum adhesive strength of the ink image. For example, a recording medium having a smooth surface such as coated paper has a good heat transfer efficiency at the surface portion, and therefore the heating temperature can be set low. On the other hand, since recording media with irregularities on the surface, such as fine paper, tend to have an air layer between them and the ink image, an anchor effect due to an increase in the adhesive strength of the resin component can be expected when the heating temperature is set higher. preferable. The pressure at the time of transfer may be freely adjusted to a suitable condition depending on the recording medium and printing conditions.

  Further, the surface of the intermediate transfer body 12 may have a structure having a releasable surface layer as necessary. Since the surface of the releasability imparting transfer body has a low surface energy and a high releasability, it is possible to realize a high transfer rate. In the present invention, a sufficient transfer rate can be obtained without particularly providing releasability, but there is no problem if releasability is imparted to the surface of the intermediate transfer member from the viewpoint of cleaning load and the like. Here, the releasable surface described in the present invention refers to a surface having a critical surface tension of 30 mN / m or less or a contact angle with water of 75 ° or more. A material having releasability may be separately provided before image recording.

  Preferred materials used for the surface layer of the intermediate transfer body 12 include, for example, polyurethane resins, polyester resins, polystyrene resins, polyolefin resins, polybutadiene resins, polyamide resins, polyvinyl chloride resins, polyethylene resins. And known materials such as silicone resin, fluorine resin, and polyimide resin. In addition, a material obtained by blending these resins may be used. Specific examples include fluorosilicone resins and silicone-modified polyimide resins, but are not limited thereto.

  In order to perform good transfer on a recording medium having a rough surface shape such as high-quality paper or copy paper, it is preferable to follow the surface shape of the transfer medium with the surface shape of the recording medium, and it is more preferable to use a rubber material. Specific examples include silicone rubber, urethane rubber, fluorine rubber, nitrobutadiene rubber, styrene butadiene rubber, and natural rubber, but are not limited thereto.

  Then, the heated intermediate transfer body 12 is cooled by the transfer body cooling section 23 downstream of the transfer section 18 in the transfer body rotation direction after the transfer.

  The cleaning unit 22 is disposed downstream of the transfer body cooling unit 23 in the transfer body rotation direction and upstream of the treatment liquid application unit 14 in the transfer body rotation direction. In the cleaning unit 22, a cleaning roller 38 is provided at a position facing the roller 26 </ b> C across the intermediate transfer body 12, and is disposed so as to contact the recording surface 12 a of the intermediate transfer body 12. Residues after transfer on the surface 12a are removed.

  The cleaning roller 38 is made of a flexible porous member, and has a system for cleaning the surface of the intermediate transfer body (recording surface 12a) while soaking the cleaning liquid in the cleaning liquid applying means. The surface is provided with a brush, and the cleaning liquid is applied to the surface of the intermediate transfer body. There are a method of removing dust on the surface of the intermediate transfer member with a brush while applying to the surface, and a method of scraping off the residue on the surface of the intermediate transfer member by providing a flexible blade on the roller surface. The removal rate of the residue can be increased by setting the linear velocity on the surface of the cleaning roller 38 to be slower or faster than the linear velocity on the surface of the intermediate transfer member. A shearing force is generated on the surface of the intermediate transfer member according to the speed difference between the surface of the cleaning roller 38 and the surface of the intermediate transfer member, and the residue can be efficiently removed.

  In the present invention, after transferring the ink aggregate, an image fixing unit 24 may be separately provided as needed in order to give a strong fixing property to the recording medium.

  The image fixing unit 24 is disposed on the recording medium discharge side (right side in FIG. 1) of the transfer unit 18. The image fixing unit 24 is provided with two fixing rollers 40A and 40B on the front and back surfaces of the recording medium 34, and presses and heats the image transferred and formed on the recording medium 34 by the fixing rollers 40A and 40B. As a result, the fixability of the recorded image on the recording medium 34 can be improved. The fixing rollers 40A and 40B are preferably a pair of rollers including one pressure roller and one heating roller, but are not limited thereto.

  In the present embodiment, the processing liquid is applied onto the intermediate transfer body 12 by discharging the processing liquid from the processing liquid head 30 </ b> S. However, the method of applying the processing liquid is particularly limited when the present invention is implemented. It is not something. As a modification of the present embodiment, there is an aspect in which the treatment liquid is applied onto the intermediate transfer body 12 using an application roller instead of the treatment liquid head 30S. The treatment liquid can be easily applied to almost the entire surface including the image area on which the ink droplet on the intermediate transfer body 12 is landed. In this modification, the thickness of the processing liquid on the intermediate transfer body 12 is preferably 1 to 5 μm. Means for making the thickness of the treatment liquid on the intermediate transfer body 12 constant may be provided. For example, there are a method using an air knife, and a method in which a member having a sharp corner is provided with a gap having a prescribed amount of processing liquid thickness between the intermediate transfer member 12. Further, it is not necessary to apply the treatment liquid on the intermediate transfer body 12.

  In the intermediate transfer type image forming apparatus as described above, the resin component of the ink can prevent transfer failure and transfer unevenness by using ink satisfying that the elongation at break at 25 ° C. is 25% or more. Maintains image robustness such as abrasion resistance and water resistance, prevents deterioration in image quality due to variations in ejection speed from nozzles, and facilitates cleaning of ink adhering to the transfer body, and has a high boiling point It is possible to prevent uneven gloss of the image caused by the solvent.

  The minimum film forming temperature (MFTα) of the resin component is preferably 40 ° C. or higher and lower than 70 ° C. Considering that the temperature of the image forming environment becomes higher due to fixing processing and apparatus driving energy, and transfer is performed at a temperature slightly higher than room temperature (approximately 30 to 40 ° C.) in the transfer portion, the minimum production of the resin component. When the film temperature is 40 ° C. or higher and lower than 70 ° C., the strength of the ink film can be increased and transfer can be performed satisfactorily without requiring heating of the transfer body. Here, if the minimum film-forming temperature is about 25 ° C. or less, which is too low, the film-forming progress speed at the nozzle portion will increase dramatically, causing nozzle clogging and further impairing the stability of the ink flying direction. This is not preferable. Even in the range of 25 to 40 ° C., there is a concern about the influence on the nozzle. In addition, at a temperature of 70 ° C. or higher, a high temperature of at least about 50 ° C. is required to develop the resin surface fusion effect. In this case, it is difficult to achieve both transferability and ink discharge speed maintenance, and energy is consumed for heating. Resulting in.

  Furthermore, it is preferable that the breaking strength at 25 ° C. of the resin component is 5 MPa or more. By using a resin component having a breaking strength of 5 MPa or more when a tensile test is performed in an environment of 25 ° C., the ink film can be appropriately hardened, and thus is developed between the transfer body and the ink film by heating the transfer body. An increase in adhesion due to the adhesive effect can be inhibited. Further, even when a slight amount of ink image remains on the transfer body, the ink film can be appropriately hardened so that cleaning can be performed efficiently. Thus, since the strength of the ink film can be further strengthened by increasing the breaking strength, it is more effective with respect to the abrasion resistance by combining with the ductility imparting effect having a breaking elongation of 25% or more. The larger both values are, the better. However, the elongation at break and the strength at break are generally in a trade-off relationship, and it is difficult to increase both. Therefore, it is necessary to select and design a resin that balances both. Even if the elongation at break is increased too much, the stress does not work, so the break strength decreases. And even if the breaking strength is increased too much, the ductility is impaired and a problem is caused. Further, increasing the elongation at break leads to a decrease in the minimum film-forming temperature (MFTα) of the resin component, so it is necessary to adjust it so that it does not fall below 25 ° C.

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

  Examples of the present invention will be described below, but the present invention is not limited thereto.

  The ink and treatment liquid used in the present invention were prepared according to the composition described below.

(Preparation of pigment dispersion of ink)
Components of the following composition are mixed so that the total amount becomes 500 parts by mass, and further 2 parts by mass of 2,2′-azobis (2,4-dimethylvaleronitrile) is added as a polymerization initiator, and nitrogen gas replacement is sufficiently performed. A resin synthesis mixture was obtained.

-Stearyl methacrylate 20% by mass
・ Styrene macromer 5% by mass
・ Styrene 10% by mass
-Polypropylene glycol (9) methacrylate 10% by mass
・ Methacrylic acid 10% by mass
・ 2-Mercaptoethanol 0.1% by mass
-Ion-exchanged water balance The above names mean the following.
Styrene macromer: manufactured by Toa Gosei Co., Ltd., trade name: AS-6 (styrene homopolymerized macromer, number average molecular weight: 6000, polymerizable functional group: methacryloyloxy group)
Polypropylene glycol (9) methacrylate: manufactured by NOF Corporation, trade name: BLEMMER PP-500 (propylene oxide addition moles: 9)
Next, 500 parts by mass of methyl ethyl ketone was heated to 75 ° C. with stirring in a nitrogen atmosphere. The resin synthesis mixture was added dropwise over 4 hours while stirring at 75 ° C. The reaction was further continued for 6 hours at 75 ° C. with stirring. Thereafter, the reaction product was naturally cooled to 25 ° C. and then diluted by adding methyl ethyl ketone so that the solid content was 50%, thereby obtaining a dispersed resin solution having an average molecular weight of 19000.

  15 parts by mass of the obtained 50% copolymer solution was neutralized by adding 2 parts by mass of a 5 mol / L sodium hydroxide aqueous solution, and Pigment Red 122 [manufactured by Ciba Specialty Chemicals Co., Ltd., trade name: CROMOPHTAL Jet Magenta DMQ 7.5 parts by mass were added and kneaded with a roll mill for 2 to 8 hours as necessary. The kneaded product was dispersed in 100 parts by mass of ion-exchanged water. The organic solvent was completely removed from the obtained dispersion under reduced pressure at 60 ° C., and further concentrated by removing water to obtain an aqueous dispersion of pigment-containing vinyl polymer particles having a solid content concentration of 20% by mass. .

Then, the following components were mixed to obtain an ink composition.
(Inks 1-7 and 10-12)
Pigment RED 122 4% by weight
・ Resin components 1 to 10 8% by weight
・ Glycerin 20% by weight

・ Diethylene glycol 10% by weight
・ Orphine E1010 (manufactured by Nissin Chemical Industry) 1% by weight
-Ion exchange water remainder The following were used about said resin components 1-10.

For the resin components 1, 8, 9, 10, and 12, the monomer components in Table 1 below were synthesized by emulsion polymerization at the respective weight ratios described.
Synthesis example:
Synthesis of resin component 1 (styrene-acrylonitrile-butyl acrylate-acrylic acid [41/21/35/3 = w / w / w]) Stirring apparatus, 1 liter three-necked flask equipped with a reflux condenser, Pionein A-43s (Takemoto Yushi Co., Ltd.) 8.1g and distilled water 236.0g were put, and it heated and stirred at 70 degreeC under nitrogen stream. 4.1 g of styrene, 2.1 g of acrylonitrile, 3.5 g of n-butyl acrylate, 0.3 g of acrylic acid, 1.0 g of ammonium persulfate and 40 g of distilled water were added and stirred for 30 minutes, and then 77.9 g of styrene and acrylonitrile 39 were added. A monomer solution consisting of 9.9 g, n-butyl acrylate 66.5 g and acrylic acid 5.7 g was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, an aqueous solution consisting of 0.5 g of ammonium persulfate and 20 g of distilled water was added and stirred at 70 ° C. for 4 hours, then heated to 85 ° C. and stirred for another 2 hours. The reaction solution was cooled, adjusted to pH 7 with a 1 mol / L sodium hydroxide aqueous solution, and then filtered through a 75 μm filter to obtain 505 g of the intended resin component 1.

  Moreover, the resin component which controlled various physical-property values was changed by changing a monomer composition, the amount of initiators, and the amount of surfactant, or adding a chain transfer agent.

  Commercially available products were used for the resin components 2 to 7 and 11.

(Inks 1, 8, and 9)
Regarding the values of Mv / Mn of inks 1, 8, and 9, when the centrifugal separation method is used to filter coarse particles after ink preparation, the number of rotations and the rotation time, or the case of using the microfiltration method, With an acetylcellulose membrane filter, the value was adjusted according to the pore size of the filter and the number of filtrations.

(Preparation of treatment liquid 1)
・ Glycerin 12.5% by weight
・ Diethylene glycol 10% by weight
2-pyrrolidone-5-carboxylic acid 10% by weight
・ Lithium hydroxide 1.95% by weight
・ Olfin E1010 1.5% by weight
・ Ion-exchanged water remaining (preparation of treatment liquid 2)
・ Glycerin 12.5% by weight
・ Diethylene glycol 10% by weight
・ Magnesium sulfate 5% by weight
・ Olfin E1010 1.5% by weight
・ Balance of ion exchange water (preparation of treatment liquid 3)
・ Glycerin 12.5% by weight
・ Diethylene glycol 10% by weight
-Aluminum ammonium sulfate 5% by weight
・ Olfin E1010 1.5% by weight
-Ion-exchanged water remainder Using inks 1 to 14, under the process conditions shown in Tables 2 to 4 of Figs. 2 to 4 (whether or not the solvent is removed, the temperature of the intermediate transfer member, and the heating temperature of the recording medium) Evaluation was performed.

  Further, using the treatment liquids 1 to 3, the experiment No. in Table 2 of FIG. The following evaluations were performed under the process conditions of 8 (whether or not the solvent was removed, the temperature of the intermediate transfer member, and the heating temperature of the recording medium) (Table 5 in FIG. 5).

(Evaluation)
A modified PX-G930 manufactured by Seiko Epson Corporation was used as a drawing machine, and the evaluation ink was ejected onto the transfer body with a droplet ejection amount of 7 pl to form an image consisting of 100 solid areas of 5 mm × 5 mm size. .

  A silicone rubber sheet SR series 0.5 mm film thickness (manufactured by Tigers Polymer Co., Ltd.) was used as a transfer body.

  The pressure at the transfer unit was set to 1 MPa, the conveyance speed was set to 100 m / s, and the heating temperature was appropriately set when heating the transfer body.

  Solvent removal was performed by bringing a roller-shaped porous body (silicon carbide) into contact with the transfer body and sucking it.

  The recording medium was Tohoku Art (Mitsubishi Paper). When the recording medium was heated in advance, the heating temperature was appropriately set.

"Transcription evaluation"
[offset]
In 100 solid areas of 5 mm × 5 mm size, the locations where the ink images were split on the transfer member side and the recording medium side were counted and evaluated.

◎: Less than 3 ○: 3 or more and less than 10 △: 10 or more and less than 20 ×: 20 or more
[Transfer unevenness]
In 100 solid areas of 5 mm × 5 mm size, the locations where the ink image remained on the transfer body side were counted and evaluated.

◎: Less than 3 ○: 3 or more and less than 10 △: 10 or more and less than 20 ×: 20 or more “Image quality of transferred image”
The solid image after the transfer was visually observed and sensorially evaluated. When there was a problem in transferability due to the occurrence of offset / transfer unevenness, the evaluation was made with an image formed on the transfer body.

[Outline]
◎: Not concerned at all ○: Little concern △: Slightly conspicuous but within acceptable range ×: Very conspicuous out of acceptable range
[Graininess]
◎: Not concerned at all ○: Little concern △: Slightly conspicuous but within acceptable range ×: Very conspicuous out of acceptable range “Cleanability”
The evaluation image formed on the transfer body was not transferred, but was scraped with a urethane blade to evaluate the remaining degree of the ink image on the transfer body.

A: No residue at all. ○: Almost no residue. Δ: A small amount remains.

  X: A large amount remains.

"Abrasion resistance"
The special solid art paper was covered on the transferred solid image from above and rubbed 20 times with a load of 1.5 kg / cm ² to evaluate the color material peeling state of the coated sample. The color material density (magenta optical density OD (M)) adhering to the rubbed art paper was also quantitatively evaluated by measuring with X-Rite. The measured density includes art paper white background.

A: Color material peeling at the rubbed part is completely unknown. OD (M) value is less than 0.15 ○: Color material peeling is hardly recognized at the rubbed portion, and there is no problem in appearance. OD (M) value is 0.15 or more and less than 0.25 Δ: Color material peeling is confirmed to some extent in the rubbed portion, but is in an allowable range. OD (M) value is 0.25 or more and less than 0.35 x: There is a part exposed to the white background of the art paper surface, which is outside the allowable range. OD (M) value of 0.35 or higher “Gloss unevenness”
Using PM photographic paper <Glossy> (manufactured by Seiko Epson Corporation) as a recording medium, the gloss difference in the solid image after transfer was visually observed and sensorially evaluated.

  ◯: There is almost no gloss difference, and the maximum gloss difference is less than 5.

  X: Gloss difference is observed, and the maximum glossiness difference is 5 or more.

(result)
As can be seen from Experiments 1 to 17 in Table 2 of FIG. 2, the resin component of the ink has an elongation at break at 25 ° C. of 25% or more, absorbs the solvent component from the ink on the intermediate transfer member, and the solvent When the temperature of the intermediate transfer member when transferring the ink that absorbed the component to the recording medium was set to 25 ° C. or higher and lower than the minimum film-forming temperature (MFTα) for resin, a result of ◯ or higher was obtained in all evaluations. Has been obtained. In addition, Experiment No. 8 and 9, and Experiment No. From the comparison of 10 and 11, it can be seen that it is preferable to set the temperature of the transfer body at the time of transfer to be equal to or higher than the film forming start temperature (MFTβ) of the resin component of the ink.

  And experiment no. 1 and 18 and 20, and Experiment No. From comparison of 5, 19 and 21, it is preferable that the temperature of the recording medium at the time of transfer is heated to a temperature equal to or higher than the film formation start temperature (MFTβ) of the resin component of the ink, and the minimum film formation temperature (MFTα) of the resin component of the ink. It turns out that it is more preferable to heat above.

  In addition, Experiment No. From comparison of 22 to 24, it is understood that the minimum film-forming temperature (MFTα) of the resin component of the ink is preferably in the range of 40 ° C. or higher and lower than 70 ° C.

  And experiment No. of Table 3 of FIG. As can be seen from the comparison between 8, 25 and 26, the particle size distribution (Mv / Mn) of the dispersed fine particles in the ink is preferably 1.35 or more.

  In addition, in Experiment 4 of Table 4 of FIG. From comparison of 8, 14, 27 and 28, it is found that the breaking strength at 25 ° C. of the resin component of the ink is preferably 5 MPa or more.

  Furthermore, the experiment No. in Table 5 of FIG. From the comparison of 5 and 29 to 32, it is understood that it is preferable to apply the treatment liquid before ejecting the ink onto the intermediate transfer member and to separate the solid component and the solvent component by the reaction between the treatment liquid and the ink.

Schematic diagram showing the schematic configuration of an inkjet recording apparatus Illustration of measurement results Illustration of measurement results Illustration of measurement results Illustration of measurement results

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 12 ... Intermediate transfer body, 14 ... Processing liquid application part, 16 ... Ink discharge part, 18 ... Transfer part, 20 ... Solvent removal part, 22 ... Cleaning part, 24 ... Image fixing part, 26 ... Solvent Removal roller, 30 ... recording head, 30S ... recording head (treatment liquid head), 30K, 30C, 30M, 30Y ... recording head (ink head), 34 ... recording medium, 36 ... pressure roller, 38 ... cleaning roller 40A, 40B ... Fixing roller

Claims (12)

  An ink that includes at least a resin component and a color material, and is used for image formation that is transferred onto a recording medium after being ejected onto an intermediate transfer member, and the resin component has an elongation at break of 25% or more at 25 ° C. Ink characterized by that. In an image forming method in which an ink containing at least a resin component and a color material is ejected onto an intermediate transfer member, and then a solvent component is absorbed from the ink and transferred to a recording medium.
The resin component has an elongation at break at 25 ° C. of 25% or more,
An image forming method, wherein the temperature of the intermediate transfer member when transferring to the recording medium is 25 ° C. or higher and lower than the minimum film forming temperature of the resin component.   The image forming method according to claim 2, wherein an intermediate transfer body temperature at the time of transfer is set to be equal to or higher than a film forming start temperature of the resin component.   4. The image forming method according to claim 2, wherein the temperature of the recording medium at the time of transfer is heated to a temperature equal to or higher than a film forming start temperature of the resin component.   The image forming method according to claim 2, wherein the temperature of the recording medium at the time of transfer is heated to a temperature equal to or higher than a minimum film forming temperature of the resin component.   The image forming method according to claim 2, wherein the minimum film forming temperature of the resin component is 40 ° C. or higher and lower than 70 ° C. 6.   7. The particle size distribution (volume average particle size Mv / number average particle size Mn) of dispersed fine particles in the ink containing the resin component and the color material is 1.35 or more. The image forming method according to claim 1.   The image forming method according to claim 2, wherein the resin component has a breaking strength at 25 ° C. of 5 MPa or more.   The image forming method according to claim 2, wherein the resin component includes an ionic bond in which a counter ion is a metal ion or an organic amine ion.   10. The method according to claim 2, wherein a treatment liquid is applied to the intermediate transfer member before discharging the ink, and a solid component and a solvent component are separated by a reaction between the treatment liquid and the ink. The image forming method according to claim 1.   The image forming method according to claim 10, wherein the treatment liquid contains metal ions or organic amine ions, and the color material or resin component of the ink has an anionic group. In an image forming apparatus for transferring ink to a recording medium after ejecting ink containing at least a resin component and a coloring material onto an intermediate transfer member,
A liquid supply means for supplying the ink in which the resin component has an elongation at break of 25% or more at 25 ° C .;
Liquid ejection means for ejecting the ink supplied from the liquid supply means to the intermediate transfer member in the form of droplets;
A solvent absorbing means for absorbing a solvent component of the ink applied on the intermediate transfer member by the liquid discharging means;
Heating means for heating the temperature of the intermediate transfer member when transferring ink that has absorbed the solvent component from the ink on the intermediate transfer member to a recording medium in a range of 25 ° C. or higher and lower than the minimum film-forming temperature of the resin component; ,
An image forming apparatus comprising: a pressurizing unit configured to pressurize and transfer the ink heated by the heating unit to the recording medium.

Images