JP2023120831A - Method of forming image - Google Patents

Abstract

To solve a problem of degrading image quality because a coating defective place of a precoat layer on an intermediate transfer body generates a transfer failure.SOLUTION: A method of forming an image includes the steps of: forming a layer of wax on a surface of a surface layer of an intermediate transfer body having the surface layer; forming an ink image on a surface of the layer of wax; heating the surface layer after forming the ink image; and transferring the layer of wax and the ink image onto a recording medium. A static contact angle between the surface layer and the molten wax is 70° or lower, and the formula (1) and the formula (2) are satisfied when a heating temperature in the step of heating the surface layer is T1°C, a temperature of the surface layer just before the step of transferring is T2°C, and a melting point of the wax is Tm°C. T1>Tm (1). T1-T2≥20 (2).SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming method.

2. Description of the Related Art A transfer type image forming method is known in which an intermediate image is formed on an image forming surface of an intermediate transfer member with ink, and the intermediate image on the intermediate transfer member is transferred to a recording medium. In such an intermediate transfer type image forming method, a high transfer rate from the intermediate transfer member to the recording medium is generally required.

Therefore, a method has been developed in which a layer is formed on the surface of the intermediate transfer member to increase the transfer rate before intermediate image formation. Patent Document 1 discloses a method of forming an ink image after forming an ultraviolet curable precoat layer on an intermediate transfer member, and transferring the precoat layer and the ink image to a recording medium.

Examples of means for applying such a precoat layer include an inkjet method, a roll coating method, and a spray coating method.

JP 2019-130715 A

However, in the conventional coating process of the precoat layer, the surface of the intermediate transfer member could not be uniformly coated, resulting in coating defects in some cases. There is a problem that such a coating failure portion causes a transfer failure of the ink image in the subsequent transfer process, and the image quality of the image on the recording medium may be deteriorated.

According to the present invention, the step of forming a wax layer on the surface of the surface layer of an intermediate transfer member having a surface layer, the step of forming an ink image on the surface of the wax layer, and the step of forming the ink image. An image forming method comprising the step of subsequently heating the surface layer and the step of transferring the wax layer and the ink image to a recording medium, wherein the static contact angle between the surface layer and the molten wax is 70°. The heating temperature in the step of heating the surface layer is T1 [°C], the temperature of the surface layer immediately before the step of transferring is T2 [°C], and the melting point of the wax is Tm [°C]. Then, it is possible to provide an image forming method characterized by satisfying the following formulas (1) and (2).
T1>Tm (1)
T1-T2≧20 (2)

According to the present invention, it is possible to provide an image forming method in which transfer failure of an ink image is less likely to occur and a good image can be obtained.

1 is a schematic diagram showing an image forming apparatus used in an image forming method according to an embodiment of the invention; FIG.

FIG. 1 shows a schematic configuration of an image forming apparatus to which the present invention can be applied. In the image forming apparatus 100 of FIG. 1, an intermediate transfer member 107 is arranged on the outer peripheral surface of a rotatable drum-shaped support member. The intermediate transfer member 107 is rotationally driven in the direction of the arrow, and each mechanism arranged around it operates in synchronization with the rotation. The intermediate transfer member 107 may have any form as long as its image forming surface can come into contact with the recording medium 105, and may be, for example, a roller shape or an endless belt in accordance with the form of the image forming apparatus to be applied and transfer conditions to the recording medium. can be used.

The outline of the image forming method according to this embodiment will be described below.
First, image data is transmitted from an image supply device (not shown) to instruct the image forming device 100 to perform image recording.

As the intermediate transfer member 107 rotates, a wax coating device 106 forms a layer of wax on the surface of the intermediate transfer member 107 (hereinafter also simply referred to as a “wax layer”). This wax layer serves as a release layer for facilitating the release of the ink image from the intermediate transfer member in the subsequent transfer process.

The application device 106 may be any device capable of applying wax in a melted state to the surface of the intermediate transfer member 107, and conventionally known various devices can be appropriately used. Specific examples include roll coaters, gravure offset rollers, inkjet heads, die coaters, blade coaters, and spray coaters.

The wax used in the present invention is not particularly limited as long as it has a static contact angle of 70° or less with respect to the surface layer of the intermediate transfer member in a melted state. When the static contact angle to the surface layer is 70° or less, a portion of the molten wax penetrates into the surface layer when the wax is applied.

Specific examples of waxes include natural waxes such as beeswax, lanolin, carnauba wax, candelilla wax, and montan wax; petroleum waxes such as paraffin wax and microcrystalline wax; Fischer-Tropsch wax, polyethylene wax, polypropylene wax, oxidized wax, and the like. modified waxes such as urethane-modified waxes and alcohol-modified waxes; and α-olefin-maleic anhydride copolymer waxes. In particular, a wax having a polyolefin structure is suitable from the viewpoint of releasability from the surface layer of the intermediate transfer body. You may use these waxes individually or in combination of 2 or more types as needed.

The melting point Tm [°C] of wax can be measured according to the melting point test method described in JIS K2235:1991. The wax is preferably solid at room temperature (25°C), and preferably has a Tm of 40°C or higher and 120°C or lower. This is because, if the melting point of the wax is high, the temperature T1 in the heating process of the surface layer tends to be high, and the intermediate and the ink may be deteriorated by heat. More preferably, the temperature is 40°C or higher and 100°C or lower. Further, the contact angle between the melted wax and the surface layer of the intermediate transfer member can be measured using a contact angle meter.

As the next step, a treatment liquid for reducing the fluidity of the ink may be applied to the surface of the wax layer by the roll coater 101 . A treatment liquid that reduces the fluidity of the ink increases the viscosity of the ink as a whole by chemically reacting with or physically adsorbing the coloring material or resin that is part of the ink. It is a liquid that has the function of aggregating part of the ink.

The treatment liquid can contain conventionally known substances such as polyvalent metal ions, organic acids, cationic resins, porous fine particles, etc., as components that increase the viscosity of the ink, without particular limitations. Among these, polyvalent metal ions and organic acids are particularly suitable. It is also preferable to contain a component that increases the viscosity of a plurality of types of ink.

Examples of polyvalent metal ions include divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg 2+ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ , Fe ^{3+ , Cr 3+ ,} Y ³⁺ and Al ^{3+ .} trivalent metal ions such as In order to contain polyvalent metal ions in the treatment liquid, a polyvalent metal salt (which may be a hydrate) composed of a combination of polyvalent metal ions and anions can be used. Examples ^of anions include Cl ⁻ , Br ⁻ , I ⁻ , ClO − , ClO ₂ ⁻ , ClO ₃ ⁻ , ClO ₄ ⁻ , NO ₂ ⁻ , NO ₃ ⁻ , SO ₄ ²⁻ , CO ₃ ²⁻ , HCO _{3 Inorganic} ^anions such ^{as −} _{, PO 4} ^{3− , HPO} ₄ ^{2− ,} and H ₂ PO ₄ ⁻ _; ) ₂ , C ₆ H ₅ COO ⁻ , C ₆ H ₄ (COO ⁻ ) ₂ and CH ₃ SO ₃ ⁻ . When polyvalent metal ions are used, the content (% by mass) in terms of polyvalent metal salt in the treatment liquid is 1.00% by mass or more and 10.00% by mass or less based on the total mass of the treatment liquid. preferable.

The treatment liquid containing an organic acid has a buffering ability in the acidic region (pH less than 7.0, preferably pH 2.0 to 5.0), thereby converting the anionic groups of the components present in the ink into an acid form. agglomeration. Examples of organic acids include formic acid, acetic acid, propionic acid, butyric acid, benzoic acid, glycolic acid, lactic acid, salicylic acid, pyrrolecarboxylic acid, furancarboxylic acid, picolinic acid, nicotinic acid, thiophenecarboxylic acid, levulinic acid, and coumaric acid. monocarboxylic acids and their salts; dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, itaconic acid, sebacic acid, phthalic acid, malic acid, tartaric acid, and their salts and hydrogen salts; tricarboxylic acids such as citric acid and trimellitic acid and their salts and hydrogen salts; tetracarboxylic acids such as pyromellitic acid and their salts and hydrogen salts;

Examples of cationic resins include resins having a primary to tertiary amine structure and resins having a quaternary ammonium salt structure. Specific examples include resins having structures such as vinylamine, allylamine, vinylimidazole, vinylpyridine, dimethylaminoethyl methacrylate, ethyleneimine, and guanidine. In order to increase the solubility in the treatment liquid, a cationic resin and an acidic compound may be used together, or the cationic resin may be subjected to a quaternization treatment. When a cationic resin is used, the content (% by mass) of the cationic resin in the treatment liquid is preferably 1.00% by mass or more and 10.00% by mass or less based on the total mass of the treatment liquid.

The treatment liquid may contain an appropriate amount of water and/or organic solvent. The water used in this case is preferably deionized water by ion exchange or the like. The organic solvent that can be used for the treatment liquid is not particularly limited, and any known organic solvent can be used. Various resins can also be added to the treatment liquid. By adding an appropriate resin, it is possible to improve the adhesion to the recording medium during transfer, and to increase the mechanical strength and glossiness of the final image, which is preferable. Materials to be used are not particularly limited as long as they can coexist with the ink viscosity increasing component. Further, a surface active agent or a viscosity modifier may be added to the treatment liquid to appropriately adjust its surface tension and viscosity. Materials to be used are not particularly limited as long as they can coexist with the ink viscosity increasing component. For example, it can be selected from cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, fluorine surfactants, silicone surfactants, and the like. It is also possible to use two or more of these materials in combination.

As the means for applying the treatment liquid, not only a roll coater but also a conventionally used technique such as a spray coater and a bar coater can be suitably used. Moreover, the method of applying using an inkjet head is also suitable.

As the next step, ink for image formation is selectively applied to the surface of the wax layer using the inkjet recording head 102 to form an intermediate image. When the treatment liquid is applied first, the applied ink chemically and/or physically reacts when it comes into contact with the treatment liquid on the surface of the wax layer, and the fluidity of the intermediate image is lowered.

Each component of the ink applied to this embodiment will be described.
(colorant)
A pigment or a dye can be used as a coloring material contained in the ink applied to this embodiment. The content of the coloring material in the ink is preferably 0.5% by mass or more and 15.0% by mass or less, and is 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink. is more preferable.

The type of pigment that can be used as a coloring material is not particularly limited. Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo-based, phthalocyanine-based, quinacridone, isoindolinone-based, imidazolone-based, diketopyrrolopyrrole-based, and dioxazine-based pigments. . One or more of these pigments may be used as necessary. The method of dispersing the pigment is not particularly limited. For example, resin-dispersed pigments dispersed with a resin dispersant, and self-dispersed pigments in which a hydrophilic group such as an anionic group is bonded directly or via another atomic group to the particle surface of the pigment can also be used. Of course, it is also possible to use a combination of pigments with different dispersion methods.

As the resin dispersant for dispersing the pigment, a known resin dispersant used for aqueous ink for inkjet can be used. Among them, in the aspect of the present embodiment, it is preferable to use an acrylic water-soluble resin dispersant having both a hydrophilic unit and a hydrophobic unit in the molecular chain. Forms of the resin include block copolymers, random copolymers, graft copolymers, combinations thereof, and the like.

The resin dispersant in the ink may be dissolved in the liquid medium or dispersed as resin particles in the liquid medium. In the present invention, the fact that the resin is water-soluble means that when the resin is neutralized with an alkali equivalent to the acid value, it does not form particles whose particle size can be measured by a dynamic light scattering method. do.

A hydrophilic unit (a unit having a hydrophilic group such as an anionic group) can be formed, for example, by polymerizing a monomer having a hydrophilic group. Specific examples of the monomer having a hydrophilic group include acidic monomers having an anionic group such as (meth)acrylic acid and maleic acid, and anionic monomers such as anhydrides and salts of these acidic monomers. . Examples of cations constituting salts of acidic monomers include ions such as lithium, sodium, potassium, ammonium and organic ammonium.

A hydrophobic unit (a unit having no hydrophilicity such as an anionic group) can be formed, for example, by polymerizing a monomer having a hydrophobic group. Specific examples of monomers having a hydrophobic group include monomers having aromatic rings such as styrene, α-methylstyrene, and benzyl (meth)acrylate; ethyl (meth)acrylate, methyl (meth)acrylate, butyl (meth)acrylate, etc. (ie, (meth)acrylic ester-based monomers) having an aliphatic group of .

The acid value of the resin dispersant is preferably 50 mgKOH/g or more and 550 mgKOH/g or less, more preferably 100 mgKOH/g or more and 250 mgKOH/g or less. Moreover, the weight average molecular weight of the resin dispersant is preferably 1,000 or more and 50,000 or less. The pigment content (% by mass) is preferably 0.3 times or more and 10.0 times or less in mass ratio (pigment/resin dispersant) to the resin dispersant content.

It is also suitable in the present embodiment to use a so-called self-dispersing pigment that is made dispersible by modifying the surface of the pigment itself without using a dispersant.
As the self-dispersing pigment, those in which an anionic group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group is bonded directly or via another atomic group (-R-) to the particle surface of the pigment is used. be able to. The anionic group may be in either an acid form or a salt form, and in the case of a salt form, it may be in a partially dissociated state or in a completely dissociated state. When the anionic group is in the salt form, examples of cations serving as counter ions include alkali metal cations, ammonium, organic ammonium, and the like. Further, specific examples of other atomic groups (-R-) include linear or branched alkylene groups having 1 to 12 carbon atoms, arylene groups such as phenylene groups and naphthylene groups, amide groups, sulfonyl groups, and amino groups. , a carbonyl group, an ester group, an ether group, and the like. Moreover, it is good also as a group which combined these groups.

Although the type of dye that can be used as a coloring material is not particularly limited, it is preferable to use a dye having an anionic group. Specific examples of dyes include azo dyes, triphenylmethane dyes, (aza)phthalocyanine dyes, xanthene dyes, and anthrapyridone dyes. One or more of these dyes can be used as necessary.

(resin particles)
The ink applied to this embodiment can contain resin particles. The resin particles need not contain a coloring material. Resin particles are preferable because they are effective in improving image quality and fixability.

The material of the resin particles that can be used in the present embodiment is not particularly limited, and known resins can be appropriately used. Specifically, resin particles composed of various materials such as olefin-based, polystyrene-based, urethane-based, and acrylic-based materials can be used. The weight average molecular weight (Mw) of the resin particles is preferably in the range of 1,000 or more and 2,000,000 or less. The volume average particle diameter of the resin particles measured by a dynamic light scattering method is preferably 10 nm or more and 1,000 nm or less, more preferably 100 nm or more and 500 nm or less. The content (% by mass) of the resin particles in the ink is preferably 1.0% by mass or more and 50.0% by mass or less, more preferably 2.0% by mass or more and 40.0% by mass or less, based on the total mass of the ink. It is below.

(aqueous medium)
The ink that can be used in this embodiment can contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. As water, it is preferable to use deionized water or ion-exchanged water. The water content (% by mass) in the water-based ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the ink. Also, the content (% by mass) of the water-soluble organic solvent in the water-based ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the ink. As the water-soluble organic solvent, alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing compounds, sulfur-containing compounds, and the like, which can be used for inkjet inks, can be used. A seed or two or more can be included.

(Other additives)
Ink that can be used in the present embodiment may optionally include antifoaming agents, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, antiseptics, antifungal agents, oxidizing Various additives such as inhibitors, anti-reduction agents and water-soluble resins may be contained.

As a next step, liquid may be removed from the intermediate image on the intermediate transfer member by the liquid remover 103 . By removing the liquid, it is possible to prevent the excessive liquid from overflowing or overflowing in the transfer process, which may cause image disturbance or transfer failure. As a method for removing the liquid component, any of various conventional methods can be suitably applied. Specifically, any of a heating method, a method of blowing low-humidity air, a method of reducing pressure, a method of contacting a liquid absorbing member, and a combination of these methods can be used. It is also possible to remove the liquid component by natural drying.

In the case of the method of pressing a liquid absorbing member containing a porous material, the liquid absorbing member may be formed on the outer peripheral surface of the roller, or the liquid absorbing member may be formed in the form of an endless sheet and run cyclically. It's okay. From the viewpoint of image protection, the liquid absorbing member may be moved by synchronizing the peripheral speed of the transfer member with the speed of the liquid absorbing member.

The liquid absorbing member may contain a porous body. The pore diameter of the porous body on the surface that contacts the ink image may be 10 μm or less in order to suppress adhesion of ink solids to the liquid absorbing member. Here, the pore diameter means the average diameter, and can be measured by known means such as mercury porosimetry, nitrogen adsorption, SEM image observation, and the like. The liquid component is not particularly limited as long as it does not have a fixed shape, is fluid, and has a substantially constant volume. Examples of liquid components include water and organic solvents contained in inks and treatment liquids.

As the next step, the surface layer of the intermediate transfer body 107 is heated. Assuming that the temperature (heating temperature) of the surface layer in this step is T1 [° C.], the expression (1) must satisfy the relationship of T1>Tm. This is because the mobility of the wax molecules is enhanced and the uniformity of penetration into the surface layer of the intermediate transfer member is enhanced. Preferably, the relationship T1-Tm≧20 is satisfied. Although the heating means is not particularly limited, such as a hot air heater or an infrared heater, a heating means using electromagnetic waves containing near-infrared rays with a wavelength of about 900 to 2500 nm is preferable from the viewpoint of energy efficiency, responsiveness, and the like. In the apparatus illustrated in FIG. 1, the near-infrared heater 108 is arranged so as to heat the surface layer of the intermediate transfer member 107 .

As the next step, the recording medium 105 is pressed against the surface layer of the intermediate transfer member 107 to transfer the intermediate image and the wax layer to the recording medium 105 . In the apparatus illustrated in FIG. 1, the intermediate transfer member 107 and the recording medium 105 are pressed against each other using the pressure roller 104 to transfer the intermediate image and the wax layer.

In the present invention, where T2 [° C.] is the temperature of the surface layer of the intermediate transfer member immediately before the transfer step, the expression (2) must satisfy the relationship T1−T2≧20. In order to satisfy this relationship, there may be a step of cooling the surface layer of the intermediate transfer member before the transfer step, or natural cooling may be performed between steps. For the temperatures T1 and T2, a known method for measuring the surface temperature of an object is used. For example, the surface of an intermediate transfer member after ink image formation can be measured by infrared thermography.

By setting T1>Tm, the mobility of the wax molecules penetrating into the surface layer of the intermediate transfer member is increased, and by setting T1−T2≧20, the solubility of the surface layer in wax is lowered. Therefore, wax molecules with high mobility exude from the surface layer as the temperature decreases. As a result, even if the wax layer on the surface layer has a coating defect, it is compensated for by the wax exuded from the surface layer. T1-T2≧30 is preferable, and by satisfying this relationship, the wax exudes more efficiently. As a result, it is possible to reduce the transfer failure of the ink image in the transfer process, and reduce the deterioration of the image quality. The wax layer that functions as a release layer does not have to be completely transferred, and part of it may remain on the surface layer.

Further, it is preferable that 70≦T1≦160. If it is higher than this range, the ink or intermediate transfer body may be denatured by heat, and if it is lower than this range, it is difficult to obtain the effect of heating. Further, it is preferable that 50≦T2≦120. If it is higher than this range, the recording medium may be denatured by heat, and if it is lower than this range, transferability to the recording medium may deteriorate.

Further, the intermediate transfer member 107 may be repeatedly used continuously, in which case the surface may be washed and regenerated before forming the next intermediate image. As the cleaning and regenerating means, any of various conventionally used techniques can be suitably applied. A method of applying a shower of cleaning liquid to the surface of the intermediate transfer member, a method of contacting the surface of the intermediate transfer member with a wet molton roller to wipe it off, a method of contacting the surface of the cleaning liquid, and applying various energies to the surface of the intermediate transfer member. methods and the like can also be suitably used. Of course, a method of combining a plurality of these is also suitable.

When the image data transmitted from the image supply device is processed as described above, the image forming procedure ends. As an additional step, the recording medium on which the image recording has been performed may be pressed with a fixing roller after the transfer to increase the surface smoothness. Further, at this time, the fixing roller may be heated to impart fastness to the image.

Next, the intermediate transfer member used in the present invention will be described in more detail.
The intermediate transfer member in the present invention preferably has appropriate elasticity because the intermediate image is pressed onto a recording medium such as paper for transfer. Therefore, when plain paper is used as a recording medium, at least a portion of the intermediate transfer member is preferably made of an elastic material. The portion made of the elastic material preferably has a durometer type A hardness (in accordance with JIS K6253) of 10 degrees or more and 100 degrees or less, more preferably 20 degrees or more and 80 degrees or less.

The intermediate transfer member may have a single layer structure or a multi-layer structure consisting of a plurality of layers. For example, an elastic compressible layer that is compressible under pressure and capable of returning to its original shape when the pressure is released, in order to even out the pressure when pressing and transferring onto a recording medium. may have

As the material for forming the compressible layer, various rubber materials or various elastomer materials can be used from the viewpoint of processing characteristics, etc., and an elastic layer can be provided as a continuous layer or a porous layer. Examples of elastomer materials and rubber materials include silicone rubber, fluorosilicone rubber, phenyl silicone rubber, fluororubber, chloroprene rubber, nitrile rubber, ethylene propylene rubber, natural rubber, styrene rubber, isoprene rubber, butadiene rubber, ethylene/propylene/butadiene. copolymer, nitrile butadiene rubber, and the like. It may also consist of multiple layers of these materials.

In addition, the image forming surface of the intermediate transfer member must have an appropriate surface free energy that satisfies both ink image forming properties and transfer properties. Therefore, the intermediate transfer member may have a surface layer made of a material having such properties. In order to obtain high-quality images, the surface layer is required to deform following the surface shape of the recording medium during transfer. Therefore, it is desirable that the storage elastic modulus of the material forming the surface layer is low. Specifically, it is 100 MPa or less. More desirably, it is 50 MPa or less. On the other hand, it is desirable to be 10 MPa or more from the viewpoint of durability.

As a material for forming the surface layer of the intermediate transfer member, various rubber materials or various elastomer materials can be used. , natural rubber, styrene rubber, isoprene rubber, butadiene rubber, ethylene/propylene/butadiene copolymer, nitrile butadiene rubber, and the like. Silicone rubber or fluororubber is preferably used. In particular, silicone rubber is desirable because it has appropriate surface free energy and heat resistance. Alternatively, it may be a condensate obtained by condensing an organic silicon compound having an appropriate surface free energy. The surface layer may also serve as the compressible layer described above.

Further, the intermediate transfer member may have a resin layer, a base fabric layer, a metal layer, etc., in order to impart elasticity, strength, thermal properties, and the like.

EXAMPLES Hereinafter, the present embodiment will be described in further detail using examples and comparative examples. The present invention is by no means limited by the following examples, as long as the gist thereof is not exceeded.
(Example 1)
[Preparation of Intermediate Transfer Body]
Unvulcanized silicone rubber mixed with known hollow fine particles is applied to the surface of the base material, which is laminated in the order of the first base fabric layer, the rubber sponge layer, and the second base fabric layer, using a knife coater. After coating with a film thickness, vulcanization was performed at 150° C. to form a sponge layer with a thickness of 500 μm.

Next, a known silicone rubber obtained by adding 5% by mass of a black masterbatch for silicone rubber to the silicone rubber is coated on the surface of the heat insulating layer using a knife coater and vulcanized at 150° C. to a thickness of 100 μm. to form a surface layer of Then, metal fittings for attachment to an image recording apparatus were attached to obtain an intermediate transfer member.

Next, the static contact angle with wax was measured. A mixture of microcrystalline wax and low-density polyethylene wax (Hi-Mic-1455 (trade name, manufactured by Nippon Seiro Co., Ltd.)) was used as the wax. DMo-701 (trade name) manufactured by Kyowa Interface Science Co., Ltd. was used as a contact angle meter, and the contact angle with the surface layer of the intermediate transfer member was measured in a state in which the wax was heated to 140°C and melted, and was 61°. Met.

[Image formation]
An image was formed using the produced intermediate transfer member.

First, wax was melted by a heated roller type applicator and applied to the surface of the intermediate transfer body to form a wax layer. The thickness of the wax layer was 0.5 mm. When the wax layer was observed with an optical microscope, it was observed that the surface layer of the intermediate transfer member was exposed, and coating defect portions were scattered.

Next, a treatment liquid for reducing the fluidity of the ink was applied to the surface of the wax layer using a roller type applicator. The composition ratio of the treatment liquid is as follows.
・Glutaric acid 55 parts by mass ・8N potassium hydroxide aqueous solution 20 parts by mass ・Glycerin 10 parts by mass ・Surfactant (acetylenol E100 (trade name, manufactured by Kawaken Fine Chemicals Co., Ltd.)) 1 part by mass ・Ion-exchanged water 14 parts by mass Next, ink of each color was applied to the surface of the wax layer by an ink jet recording head provided so as to face the intermediate transfer member. The composition components and composition ratio of each color ink were common except for the type of pigment. The composition of the ink is shown in Table 1.

By applying the ink onto the intermediate transfer member, the treatment liquid reacted with the ink on the surface layer of the intermediate transfer member to form an intermediate image. After that, the surface layer of the intermediate transfer body was heated by a near-infrared heater provided so as to face the surface of the intermediate transfer body. The temperature was measured by infrared thermography to be 131°C.

Next, after the temperature of the surface layer was naturally cooled to 99° C., coated paper (Aurora Coat (trade name, manufactured by Nippon Paper Industries Co., Ltd.), basis weight 73.5 g/m ² ) used as a recording medium was pressed. A roller was pressed against the intermediate transfer member to transfer the ink image onto the recording medium.

[Evaluation of exudation]
The oozing property of the wax that had permeated the coating defect portion of the wax layer at the temperature immediately before the transfer of the surface layer was observed with an optical microscope. The exudative evaluation was carried out as follows.
A: Wax exuded to 80% or more of the coating defect B: Wax exuded to less than 80% of the coating defect C: No exudate was observed in the coating defect

[Image evaluation]
The image on the recording medium was observed with an optical microscope to evaluate the transferability at the coating defect portion of the resin layer. Evaluation of transferability was carried out as follows.
AA: Transfer rate to recording medium is 95% or more A: Transfer rate to recording medium is 90% or more and less than 95% B: Transfer rate to recording medium is 80% or more to less than 90% C: Transfer rate to recording medium is less than 80%

Each evaluation result is shown in Table 2.

(Examples 2 and 4)
Evaluation was performed in the same manner as in Example 1 except that SFM-40L (trade name), which is a fluororubber compound manufactured by 3M Japan Limited, was used as the surface layer of the intermediate transfer member. However, T1 and T2 during image formation were as shown in Table 2.

(Examples 3 and 5)
Evaluation was performed in the same manner as in Example 1 except that T1 and T2 were set as shown in Table 2.

(Example 6)
Evaluation was performed in the same manner as in Example 1, except that microcrystalline wax (Hi-Mic-2095 (trade name, manufactured by Nippon Seiro Co., Ltd.)) was used as the wax. However, T1 and T2 during image formation were as shown in Table 2.

(Example 7)
Dynion SFM-40L (trade name), which is a fluororubber compound manufactured by 3M Japan Co., Ltd., is used as the surface layer of the intermediate transfer body, and Hi-Mic, which is a microcrystalline wax manufactured by Nippon Seiro Co., Ltd., is used as the wax. Evaluation was performed in the same manner as in Example 1, except that -2095 (trade name) was used. However, T1 and T2 during image formation were as shown in Table 2.

(Comparative Examples 1 to 3)
Evaluation was performed in the same manner as in Example 1, except that the combination of the surface layer, wax, T1, and T2 shown in Table 3 was used. As the fluoroelastomer in Comparative Example 3, SIFEL2618 (trade name), which is a fluoroelastomer manufactured by Shin-Etsu Chemical Co., Ltd., was used.

REFERENCE SIGNS LIST 100 image forming apparatus 101 device for applying treatment liquid for reducing fluidity of ink 102 inkjet recording head 103 liquid removing device 104 pressure roller 105 recording medium 106 wax coating device 107 intermediate transfer member 108 infrared heater

Claims (5)

forming a wax layer on the surface of the surface layer of an intermediate transfer member having a surface layer; forming an ink image on the surface of the wax layer; and heating the surface layer after forming the ink image. and transferring the wax layer and the ink image to a recording medium, the method comprising:
The static contact angle between the surface layer and the molten wax is 70° or less, and the heating temperature in the step of heating the surface layer is T1 [°C], and the temperature of the surface layer immediately before the step of transferring. is T2 [°C], and the melting point of the wax is Tm [°C], the following formulas (1) and (2) are satisfied.
T1>Tm (1)
T1-T2≧20 (2) 2. The image forming method according to claim 1, wherein the formula (2) satisfies T1-T2≧30. 3. The image forming method according to claim 1, wherein the formula (1) satisfies T1−Tm≧20. The image forming method according to any one of claims 1 to 3, wherein the surface layer contains silicone rubber, and the wax contains a polyolefin structure. The image forming method according to any one of claims 1 to 4, wherein the wax has a melting point of 40°C or higher and 100°C or lower.

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