JP2021164999A - Image forming system and image forming method - Google Patents

Abstract

To provide an image forming system and an image forming method that can perform transfer to a paper sheet well by combining active ray-curable ink and an intermediate transfer body having good conforming property to sheets, thus improving quality of images.SOLUTION: An image forming method and an image forming system of the present invention use an image forming device configured to transfer an image formed on an intermediate transfer body with active ray-curable ink to a recording medium. The intermediate transfer body is a laminate including at least one layer of an elastic layer and a base material layer. With measurement of dynamic viscoelasticity of the laminate in a vertical direction, a loss elastic modulus at a temperature of 40°C and frequency of 0.1 Hz is 10000 Pa or greater, and a storage elastic modulus of the active ray-curable ink at the time of image transfer is greater than a storage elastic modulus of the intermediate transfer body.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming system and an image forming method. More specifically, by combining an active ray-curable ink and an intermediate transfer material that has flexibility and good followability to paper, good transfer to paper can be performed and image quality can be improved. The present invention relates to a possible image forming system and an image forming method.

In the conventional inkjet image forming system using an intermediate transfer body, in order to further improve the transferability, the surface of the silicone rubber is formed by using sandblasting or a rough surface mold to increase the surface roughness. By receiving ink droplets on the surface, measures have been proposed to prevent the droplets of water-based ink from becoming spherical and causing a repelling phenomenon, thereby suppressing an increase in dot diameter and image loss due to misalignment (for example, Patent Documents). See 1.).

In the water-based ink used in the technique disclosed in Patent Document 1, the solvent component in the ink permeates the paper at the time of transfer, and only the coloring component remains on the surface to form a dot image. Therefore, the increase in the dot diameter of the ink and the image defect due to the misalignment are caused by the diffusion phenomenon of the liquid at the time of penetrating into the paper.

Here, in the water-based ink, the solvent permeates or dries to form a thin layer, so that the problem of ink deformation due to pressing force at the time of transfer to paper does not become apparent.

However, on the other hand, when an active ray-curable ink, for example, an active ray-curable ink such as an ultraviolet curable ink, does not penetrate into the paper even during transfer to paper, intermediate transfer between paper and paper does not occur. Ink is present in the gaps between the belts (hereinafter, also simply referred to as "belts").

Therefore, if an excessive pressing force is applied during transfer to paper, the ink is deformed and the dots expand (the dot diameter increases), which may cause image loss.
In particular, there is a problem that an increase in the dot diameter of the highlight portion causes a decrease in gradation.

Japanese Unexamined Patent Publication No. 7-17030

The present invention has been made in view of the above problems and situations, and the problem to be solved is to combine an active ray-curable ink and an intermediate transfer material having flexibility and good followability to paper to make paper. It is an object of the present invention to provide an image forming system and an image forming method capable of performing good transfer and improving image quality.

The present inventors, in order to solve the above problems, From the perspective of the relative relationship between the storage modulus E of the active ray-curable ink for causing problems such as'_'ink and the storage elastic modulus E of the intermediate transfer member' In the process, they have found that the problem can be solved by setting the relative relationship to a specific relationship state, and have arrived at the present invention.

That is, the above problem according to the present invention is solved by the following means.

1. 1. An image forming system that uses an image forming apparatus that transfers an image formed by an active ray-curable ink on an intermediate transfer body to a recording medium.
The intermediate transfer body is a laminate having at least one of an elastic layer or a base material layer, and is a laminate.
In the vertical dynamic viscoelasticity measurement of the laminate, the loss elastic modulus at a temperature of 40 ° C. and a frequency of 0.1 Hz is 10,000 Pa or more, and
Image forming system, wherein the storage modulus E 'of the active ray-curable ink during the image transfer' _ink is the storage elastic modulus of the intermediate transfer body E 'greater than.

2. The image forming system according to item 1, wherein the horizontal tensile elastic modulus of the intermediate transfer member is 3 MPa or less.

3. 3. The image forming system according to item 1 or 2, wherein the contact angle of the surface of the intermediate transfer body with respect to pure water at a temperature of 40 ° C. is 70 ° or more.

4. The elastic layer of the intermediate transfer body contains at least silicone rubber and an additive having an average primary particle size of 200 nm or less, and the content ratio of the additive is reduced in the vicinity of the surface. The image forming system according to any one of items 1 to 3.

5. The image forming system according to any one of items 1 to 4, wherein the outermost surface layer of the intermediate transfer material contains at least a molecule having a rotaxane structure.

6. An image forming method using the image forming system according to any one of items 1 to 5.
_{The feature is that the storage elastic modulus E ″ ink} when the temperature at the time of transfer of the image formed on the intermediate transfer body is 40 ° C. is within the range of 3 × 10 ^{1 to} 3 × 10 ^{3 Pa.} Image formation method to be performed.

7. The image forming method according to Item 6, wherein the temperature specified at the time of transfer of the image formed on the intermediate transfer body is set to 40 ° C. ± 3 ° C.

8. The image forming method according to item 6 or 7, wherein an ink that does not substantially penetrate the paper is used as the active ray-curable ink.

9. 6. The item according to any one of items 6 to 8, wherein the image formed on the intermediate transfer body is exposed to ultraviolet rays before being transferred to adjust the viscosity of the active ray-curable ink. Image formation method.

By the above means of the present invention, by combining an active ray-curable ink and an intermediate transfer material having flexibility and good followability to paper, good transfer to paper can be performed and image quality can be improved. It is possible to provide an image forming system and an image forming method that can be achieved.

Although the mechanism of expression or mechanism of action of the effects of the present invention has not been clarified, it is inferred as follows based on the following findings and considerations.

For example, in the case of active ray-curable ink, which is a non-aqueous ink, when it is landed directly on paper, it has a feature that the penetration into paper is very small due to the characteristics of the active ray-curable ink, and as a result, it is printed on paper. Due to the swelling of the ink, the printed portion may have unevenness of ink.

As a countermeasure, an intermediate transcript may be used. As a result, an image with less unevenness can be obtained by wetting and spreading the active ray-curable ink on the surface of the intermediate transfer body, placing it on a flat plate, and then transferring the ink.

On the other hand, since the active ray-curable ink has viscosity, it has a characteristic of being deformed by an external force, and when an excessive pressing force is applied, the ink is deformed and the dots expand (the dot diameter increases).

In order to suppress the above problem, the difference in viscosity between the ink and the belt is important, and it is necessary that the ink is not deformed and the belt is deformed at the time of pressing.
For that purpose, it is considered necessary that the storage elastic modulus E ″ _ink of the ink is larger than the storage elastic modulus E ′ of the belt.
That is, it is considered that the belt needs to be deformed at the time of image transfer, and in particular, it needs to have viscosity in order to be deformed with respect to the transfer pressing force.

As a result of diligent studies based on the above findings and considerations, the loss elastic modulus at a temperature of 40 ° C. and a frequency of 0.1 Hz was 10,000 Pa or more and the image transfer was performed in the vertical dynamic viscoelasticity measurement of the intermediate transfer body belt. It has estimated that the effect capable of solving the above problems has been found by the state storage elastic modulus E '' _ink storage modulus E of the belt 'greater than the ink when.

Schematic diagram showing an exemplary configuration of the image forming apparatus according to the embodiment of the present invention.

The image forming system and the image forming method of the present invention are an image forming system using an image forming apparatus of a type in which an image formed by an active ray-curable ink on an intermediate transfer body is transferred to a recording medium, and the intermediate. The transfer body is a laminated body having at least one elastic layer or a base material layer, and in the vertical dynamic viscoelasticity measurement of the laminated body, the loss elastic modulus at a temperature of 40 ° C. and a frequency of 0.1 Hz is 10,000 Pa. or more, and wherein the storage modulus E 'of the active ray-curable ink during the image transfer' _ink is the storage elastic modulus of the intermediate transfer body E 'greater than.
This feature is a technical feature common to or corresponding to each of the following embodiments.

In the embodiment of the present invention, it is preferable that the tensile elastic modulus in the horizontal direction of the intermediate transfer body is 3 MPa or less from the viewpoint that the intermediate transfer body follows the stepped shape of the paper.

It is preferable that the contact angle of the surface of the intermediate transfer body with respect to pure water at a temperature of 40 ° C. is 70 ° or more from the viewpoint of modifying the wet spread of the ink.

The flexibility is that the elastic layer of the intermediate transfer material contains at least silicone rubber and an additive having an average primary particle size of 200 nm or less, and the content ratio of the additive is reduced in the vicinity of the surface. It is preferable from the viewpoint of improving the elasticity, adjusting the elastic modulus in the pushing direction of the entire layer, and the transparency of the additive.

It is preferable that the outermost surface layer of the intermediate transfer product contains at least a molecule having a rotaxane structure from the viewpoint of ensuring the motility of the molecular chain in the horizontal direction of the laminate and providing flexibility.

_{The present invention states} that the storage elastic modulus E ″ ink when the temperature at the time of transfer of the image formed on the intermediate transfer body is 40 ° C. is within the range of 3 × 10 ^{1 to} 3 × 10 ^{3 Pa.} It is preferable from the viewpoint of expressing the effect of the invention.

It is preferable that the temperature specified at the time of transfer of the image formed on the intermediate transfer body is 40 ± 3 ° C. from the viewpoint of exhibiting the effect.

As the active ray-curable ink, it is preferable to use an ink that does not substantially penetrate the paper from the viewpoint of exhibiting the effect.

From the viewpoint of exhibiting the effects of the present invention, it is preferable to perform ultraviolet exposure before transferring the image formed on the intermediate transfer body to adjust the viscosity of the active ray-curable ink.

The image forming system of the present invention is particularly preferably used in an image forming method using an active ray-curable ink.

Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described. In the present application, "~" is used to mean that the numerical values described before and after the value are included as the lower limit value and the upper limit value.

The "active ray-curable ink" is an ink containing an organic compound other than water as a main component, and contains, for example, an active ray-polymerizable compound, and the active ray-polymerizable property is obtained by irradiation with an active ray such as an ultraviolet ray or an electron beam. An ink in which a compound is polymerized, crosslinked, and cured.

[Overview of the image forming system and the image forming method of the present invention]
The image forming system of the present invention uses an image forming apparatus for transferring an image formed by an active ray-curable ink (hereinafter, also simply referred to as “ink”) on an intermediate transfer body to a recording medium. In the system, the intermediate transfer body is a laminate having at least one of an elastic layer or a base material layer, and in the vertical dynamic viscoelasticity measurement of the laminate, the temperature is 40 ° C. and the frequency is 0. loss modulus at 1Hz is not less 10000Pa or higher, and said the storage modulus E 'of the active ray-curable ink during the image transfer' _ink is the storage elastic modulus of the intermediate transfer body E 'greater than do.

The image forming method using an intermediate transfer member according to the image forming system of the present invention basically includes (1) a step of applying active ray-curable ink to the intermediate transfer body, and (2) an active ray-curable ink on a recording medium. Is divided into a step of transferring the ink and (3) a step of main curing the active ray-curable ink.
Details of each step will be described later.
Hereinafter, the components of the image forming system of the present invention will be described in detail.

1. 1. Intermediate transfer body The intermediate transfer body according to the present invention is a laminate having at least one elastic layer or a base material layer, and in the vertical dynamic viscoelasticity measurement of the laminate, the temperature is 40 ° C. and the frequency is 0. The loss elastic modulus at .1 HZ is 10,000 Pa or more.
The shape of the intermediate transfer body is not limited to a specific shape, but a belt-shaped intermediate transfer belt is preferable.

(1.1) Base material layer The base material layer of the intermediate transfer material according to the present invention includes aromatic polyimide (PI), aromatic polyamideimide (PAI), polyphenylene sulfide (PPS), and aromatic polyetheretherketone. Resins having structural units containing a benzene ring such as (PEEK), aromatic polycarbonate, and aromatic polyetherketone, polyvinylidene fluoride, and mixtures or copolymers thereof can be used.

Polyimide is preferably used as the base material of the intermediate transfer material. Due to its high mechanical strength, it may withstand long-term use.
Those that do not absorb ultraviolet (UV) light are also provided, and grades that can change the molecular skeleton are commercially available and can be used, but this is not preferable because the mechanical strength is lowered.
Mainly, by applying polyimide, a high-strength base material can be constructed.

(1.2) Elastic layer In the intermediate transfer material according to the present invention, in addition to the base material layer, silicone rubber (SR), chloropun rubber (CR), nitrile rubber (NBR) and epichlorohydrin rubber (on the side of the ink application surface) It may have an elastic layer containing rubber such as ECO), an elastomer, and an elastic resin.

It is preferable that the elastic layer contains at least silicone rubber and an additive having an average primary particle size of 200 nm or less, and the content ratio of the additive is reduced in the vicinity of the surface.

(1.2.1) Additives When the content ratio of the additive is reduced near the surface of the additive, the influence of the additive on the flexibility of the elastic layer is reduced, so that the flexibility near the surface of the intermediate transfer material is reduced. It is thought that it will improve. Further, the additive is preferably used because the tensile elastic modulus in the horizontal direction of the entire layer can be adjusted.

Further, the additive is preferably used for controlling the physical properties.
For example, it is possible to control the physical properties of the filler to be added, and it is also preferable to control the overall hardness (elasticity) with fine particles such as silica.

However, when UV light is irradiated through the intermediate transfer body (from the back surface side) to adjust the viscosity of the ink, transparency is required.
For that purpose, it is necessary to allow a filler having a small particle size to exist with a dispersion diameter shorter than the wavelength of light, and the average primary particle size is 200 nm or less, preferably 100 nm or less, and more preferably within the range of 10 to 50 nm. It is good that the dispersion diameter is.

In general, the effect of light scattering becomes smaller when the wavelength of light and the dispersion diameter are separated, so it is better that the wavelength and dispersion diameter used are different.

The content ratio of the additive in the elastic layer can be adjusted so that the amount of the additive added is reduced from the center toward the surface in the thickness direction of the elastic layer.
Further, the content ratio can be measured by a general surface analysis method such as X-ray photoelectron spectroscopy (XPS) or time-of-flight secondary ion mass spectrometry (TOF-SIMS).

(1.2.2) Followability of the elastic layer to the step of the paper and wet spread of ink The surface of the intermediate transfer body needs to have a function of wet spread of ink on the surface and obtaining an ink shape on a flat plate. ..
It is necessary for the elastic layer to ensure the ability to follow the step of the paper, and the viscoelastic body such as various rubber agents (silicone rubber is preferably used) usually used as the elastic layer is deformed at the time of pressing. Therefore, it is often used to improve the adhesion with paper, but the surface of the material is often hydrophobic, and problems may occur when the ink adheres to the surface.

For example, when the ink droplets adhere to the surface of the intermediate transfer belt, the ink droplets become spherical, the dot diameter of the ink is not stable, and the ink on the flat plate cannot be obtained.
The above may occur when applying a large step medium (paper with large irregularities such as Rezac paper), and the surface layer may not follow the shape. To improve transferability to paper, use ink on a flat plate. It is necessary to achieve both obtaining and ensuring the followability of the stepped shape of the paper.

In order to obtain the ink shape on the flat plate, it is preferable that the upper layer of the elastic layer is subjected to a surface layer for improving the wet spread of the ink or a rubber modification treatment to modify the wet spread of the ink. In that case, in order to obtain the ink shape on the flat plate, the contact angle with pure water is preferably 70 ° C. or less.

(1.3) Outermost surface layer The intermediate transfer material according to the present invention contains fluororesins such as polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), and polyvinylidene fluoride (PVDF), and acrylic resins. It may have an outermost surface layer.

(13.1) Followability of paper steps with respect to the outermost surface layer and wet spread of ink

It is necessary for the intermediate transfer body according to the present invention to ensure the ability to follow the stepped shape of the paper.
For this purpose, it is particularly important to give the intermediate transfer belt flexibility in the horizontal tensile direction, and it is important to ensure the motility of the molecular chain in the horizontal direction.

In order to have flexibility in the horizontal tensile direction, one is that the intermediate transfer body needs to have rubber elasticity. In this case, the ink spreads wet and spreads, and the function of obtaining the ink shape on the flat plate is obtained. Will be required.

Here, the tensile elastic modulus in the horizontal direction is preferably 3 MPa or less.

(1.3.2) It is also preferable to introduce a molecule having a rotaxane structure having a weak intermolecular interaction, for example, into the outermost surface layer of rotaxane, and the structure has two main chains and a flexible connection portion. It is like a rudder polymer with, and it is preferable to have strength and flexibility.
It is also preferable to lengthen the monomer before cross-linking to give it flexibility, and it is more preferable to add a small amount of rotaxane.

In "rotaxane", a rod-shaped molecule penetrates through a ring formed by a cyclic molecule, and bulky substituents are bonded to both ends of the rod-shaped molecule to form a rod-shaped cyclic molecule. A molecule having a structure that cannot be removed from the molecule.

(1.3.3) Precoat The outermost surface layer may be combined with the precoat.
Although the shape control of the ink is achieved by the present invention, a pretreatment on the surface of the intermediate transfer body may be performed for the purpose of assisting the transfer to paper.

For example, a surface modification treatment for imparting releasability or a means for installing a thin liquid layer on the surface for improving separability may be taken.

For example, the outermost surface layer may be concealed with glycerin or the like on the surface, and ink may be landed on the outermost layer. As a result, the outermost surface layer becomes a tear-off layer, and a part of the layer is transferred together with the ink, so that the transfer rate is improved. It is also possible to use such a surface treatment in combination with the present invention.

As the precoat liquid, liquid components such as water and a water-soluble organic solvent can be used. The precoat liquid may contain an adjusting agent for adjusting the surface tension and the viscosity. The viscosity of the precoat liquid is preferably 5% or more lower than the viscosity of the active ray-curable ink at room temperature (25 ° C.) (1 × 10 ^{3 to} 5 × 10 ⁴ mPa · s), preferably 0.95 ×. It is more preferably 10 ^{3 to} 4.75 × 10 ^{4 Pa · s.} The viscosity of the precoat liquid can be measured using a digital viscometer "LVDV2T" (manufactured by Brookfield). The viscosity of the precoat liquid at this time is the kinematic viscosity.

Examples of the water-soluble organic solvent include glycol, polyalkylene glycol, glycerin, or a polymer or copolymer thereof. Further, examples of the above-mentioned adjusting agent include a surfactant, a hydrophilic polymer and the like.

The precoat liquid is preferably applied to the entire surface of the intermediate transfer body by using a known liquid coating method such as spray coating, spiral coating using a nozzle or slit, dipping coating, and roll coater coating.

By applying the precoat liquid to the entire surface of the intermediate transfer body before applying the active ray-curable ink to the moving surface of the intermediate transfer body, the intermediate image is peeled off from the surface of the intermediate transfer body during transfer to the recording medium. It will be easier to do.

(1.3.4) Contact angle with pure water The contact angle with pure water at 40 ° C., which is the surface temperature of the intermediate transfer member according to the present invention (temperature at the time of image transfer), is that the ink has a contact angle of 70 ° C. or higher. It is preferable from the viewpoint of modifying the wet spread.

(Measuring method of contact angle with pure water)
The contact angle of the surface of the intermediate transfer material with respect to pure water is measured in accordance with JIS standard R3257: 1999, for example, using DMo-901 manufactured by Kyowa Surface Chemistry Co., Ltd. under the following conditions.
Conditions: The observed value is a droplet volume of 2 μL and a value 1 sec after the droplet is dropped. Observation is performed at a room temperature of 25 ° C. and the equipment temperature is maintained at 40 ° C. The measurement was performed 5 times, and the average value was taken as the contact angle with pure water.

(1.4) Vertical dynamic viscoelasticity measurement of laminated body (Measurement method of loss elastic modulus)
The intermediate transfer body (laminated body) according to the present invention is characterized in that the loss elastic modulus at a temperature of 40 ° C. and a frequency of 0.1 Hz is 10,000 Pa or more in a dynamic viscoelasticity measurement in the vertical direction.

The loss elastic modulus in the dynamic viscoelasticity measurement in the vertical direction was observed by pressing in the plane direction in the DMA measurement.
The specific method for measuring the loss elastic modulus will be described later.

(1.5) Measurement of tensile elastic modulus in the horizontal direction of the laminated body (Measurement method of tensile elastic modulus)
The horizontal tensile elastic modulus of the intermediate transfer body (laminated body) according to the present invention is preferably 3 MPa or less.
A specific method for measuring the tensile elastic modulus will be described later.

(1.6) Others The intermediate transfer material is polyethylene terephthalate (PET) film, 1,4-polycyclohexylene methylene terephthalate film, polyethylene naphthalate (PEN) film, polyphenylene sulfide film, polystyrene (PS) film, polypropylene. Resin films such as (PP) film, polysulfone film, aramid film, polycarbonate film, polyvinyl alcohol film, polyethylene (PE) film, polyvinyl chloride film, nylon film, polyimide film, and ionomer film, cellulose such as cellophane and cellulose acetate. It may be formed from a derivative.

The intermediate transfer material according to the present embodiment is preferably made of a material that transmits active rays (for example, ultraviolet rays) irradiated from the back surface side, and is not particularly limited as long as it is a material that transmits active rays (ultraviolet rays).

Further, the intermediate transfer material according to the present embodiment is preferably made of a material having a transmittance of 80% or more of active rays (ultraviolet rays) irradiated from the back surface side, and preferably 87% or more. , 92% or more, more preferably made of a material. When the transmittance of the intermediate transfer body is 80% or more, even if the active rays are irradiated from the back surface side of the intermediate transfer body, a sufficient amount of the active rays can reach the back surface side of the intermediate image, so that the back surface side can be reached. The hardness of the active ray-curable ink on the side can be increased to increase the viscosity of the active ray-curable ink on the surface side.

The transmittance of active rays in the intermediate transfer material can be measured using an optical spectrophotometer (for example, "U-3310" (Hitachi High-Technologies Corporation)). The measurement conditions are a spectral wavelength of 450 nm, a slit of 2 nm, and a% T mode.

So far, the process of directly applying the active ray-curable ink to the moving surface of the intermediate transfer member has been described, but the present invention is not limited to this. Before the step of applying the active ray-curable ink to the moving surface of the intermediate transfer body, there may be a step of applying the precoat liquid to the surface of the intermediate transfer body.

2. Image forming method In the image forming method using the intermediate transfer body according to the image forming system of the present invention, (2.1) a step of applying an active ray curable ink (for example, an active ray curable ink) to the intermediate transfer body, (. It is divided into 2.2) a step of transferring the active ray-curable ink to a recording medium and (2.3) a step of main curing the active ray-curable ink.

As the active ray-curable ink according to the image forming method of the present invention, it is preferable to use an ink that does not substantially penetrate the paper from the viewpoint of exhibiting the effect.

(About "the ink does not substantially penetrate the paper")
Ink, which is a viscoelastic body, has a small penetration phenomenon into paper, needs to be transferred while riding on paper, and has a state of "substantially not penetrating into paper". Therefore, in the present application, "the ink does not substantially penetrate the paper" means a state in which the ink is laminated on the paper at the time of transfer.

As an index for defining this state, 0.1 cc of ink droplets are dropped on NPI high-quality paper with a syringe, and the droplet diameter is photographed (video) for 2 minutes starting from 10 ms later, and each time is taken. Observe the droplet area in (Observe under the same conditions as the contact angle measurement).

In the above observation, when the area of the droplet is S1 (at 10 ms) and S600 (after 2 minutes), a droplet having a ratio value S600 / S1 of both areas of 0.7 or more is substantially permeated. Do not use ink.
Hereinafter, an image forming method using an active ray-curable ink, which is a typical example of the active ray-curable ink, will be described.

(2.1) Step of Applying Active Ray Curable Ink to Intermediate Transfer In the step of applying active ray curable ink, the active ray curable ink is applied to the moving surface of the intermediate transfer body to produce an intermediate image. This is the process of forming.

(2.1.1) Composition of active ray-curable ink The active ray-curable ink according to the present embodiment contains an active ray-polymerizable compound and is irradiated with active rays such as ultraviolet rays and electron beams to produce the above-mentioned active rays. An ink in which a polymerizable compound is polymerized, crosslinked, and cured.
Further, in the active ray-curable ink, if necessary, a gelling agent, a polymerization initiator, a polymerization inhibitor, a coloring material such as a dye and a pigment, a dispersant for dispersing the pigment, and a pigment are fixed to a base material. It may contain a fixing resin, a surfactant, a pH adjuster, a moisturizing agent, an ultraviolet absorber, and the like.
As for the other components, only one kind may be contained in the above composition, or two or more kinds may be contained.

(Active ray-polymerizable compound)
The active ray-polymerizable compound is a compound that is crosslinked or polymerized by irradiation with active rays. Examples of active rays include electron beams, ultraviolet rays, α rays, γ rays, X-rays and the like. Among the above active rays, ultraviolet rays or electron beams are preferable, and ultraviolet rays are more preferable. Examples of the active ray-polymerizable compound include radical-polymerizable compounds, cationically polymerizable compounds, or mixtures thereof. Among the active ray-polymerizable compounds, a radical-polymerizable compound is preferable. The active ray-polymerizable compound may be any of a monomer, a polymerizable oligomer, a prepolymer, and a mixture thereof.

The radically polymerizable compound is a compound having an ethylenically unsaturated double bond group in the molecule. The radically polymerizable compound can be a monofunctional or polyfunctional compound. Examples of radically polymerizable compounds include (meth) acrylates, which are unsaturated carboxylic acid ester compounds. In the present invention, "(meth) acrylate" means acrylate or methacrylic acid, "(meth) acryloyl group" means acryloyl group or metaacryloyl group, and "(meth) acrylic" means acrylic. Or it means methacrylic.

Examples of monofunctional (meth) acrylates include isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, isomilstill (meth) acrylate, and isostearyl. (Meta) acrylate, 2-ethylhexyl-diglycol (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) ) Acrylate, methoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxy Ethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl phthal Includes acids, 2- (meth) acryloyloxyethyl-2-hydroxyethyl-phthalic acid and t-butylcyclohexyl (meth) acrylate.

Examples of polyfunctional (meth) acrylates include triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, and polypropylene glycol di. (Meta) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, Dimethylol-tricyclodecanedi (meth) acrylate, PO adduct di (meth) acrylate of bisphenol A, neopentyl glycol di (meth) acrylate of hydroxypivalate, polytetramethylene glycol di (meth) acrylate, polyethylene glycol diacrylate and Bifunctional (meth) acrylates such as tripropylene glycol diacrylate; trifunctional (meth) acrylates such as trimethylolpropantri (meth) acrylates and pentaerythritol tri (meth) acrylates; pentaerythritol tetra (meth) acrylates, di. Contains trifunctional or higher functional (meth) acrylates such as pentaerythritol hexa (meth) acrylate, ditrimethylol propanetetra (meth) acrylate, glycerin propoxytri (meth) acrylate and pentaerythritol ethoxytetra (meth) acrylate; polyester acrylate oligomers ( Meta) oligomers having an acryloyl group, modified products thereof, and the like are included. Examples of the modified product include ethylene oxide-modified (EO-modified) acrylate with an ethylene oxide group inserted and propylene oxide-modified (PO-modified) acrylate with a propylene oxide inserted.

The cationically polymerizable compound is a compound having a cationically polymerizable group in the molecule. Examples of cationically polymerizable compounds include epoxy compounds, vinyl ether compounds, oxetane compounds and the like.

Examples of the above epoxy compounds include 3,4-epoxycyclohexylmethyl-3', 4'-epoxycyclohexanecarboxylate, bis (3,4-epoxycyclohexylmethyl) adipate, vinylcyclohexene monoepoxyside, ε-caprolactone modified 3, 4-Epoxycyclohexylmethyl 3', 4'-epoxycyclohexanecarboxylate, 1-methyl-4- (2-methyloxylanyl) -7-oxabicyclo [4,1,0] heptane, 2- (3,4) -Epoxy Cyclohexyl-5,5-Spiro-3,4-Epoxy) Cyclohexanone-Meta-dioxane and alicyclic epoxy resins such as bis (2,3-epoxycyclopentyl) ether, diglycidyl ether of 1,4-butanediol , 1,6-Hexanediol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, ethylene glycol, propylene glycol, and glycerin. An aliphatic epoxy compound containing polyglycidyl ether, which is a polyether polyol obtained by adding one or more kinds of alkylene oxides (ethylene oxide, propylene oxide, etc.) to an aliphatic polyhydric alcohol, and bisphenol A or Di or polyglycidyl ether of the alkylene oxide adduct, di or polyglycidyl ether of the hydrogenated bisphenol A or the alkylene oxide adduct thereof, and aromatic epoxy compounds containing a novolak type epoxy resin and the like are included.

Examples of the vinyl ether compounds include ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, and isopropenyl. Monovinyl ether compounds including ether-o-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether, etc., as well as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether. , Butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, and di or trivinyl ether compounds including trimethylpropan trivinyl ether and the like.

Examples of the above oxetane compounds include 3-hydroxymethyl-3-methyloxetane, 3-hydroxymethyl-3-ethyloxetane, 3-hydroxymethyl-3-propyloxetane, 3-hydroxymethyl-3-normalbutyloxetane, 3 -Hydroxymethyl-3-phenyloxetane, 3-hydroxymethyl-3-benzyloxetane, 3-hydroxyethyl-3-methyloxetane, 3-hydroxyethyl-3-ethyloxetane, 3-hydroxyethyl-3-propyloxetane, 3 -Hydroxyethyl-3-phenyloxetane, 3-hydroxypropyl-3-methyloxetane, 3-hydroxypropyl-3-ethyloxetane, 3-hydroxypropyl-3-propyloxetane, 3-hydroxypropyl-3-phenyloxetane, 3 -Hydroxybutyl-3-methyloxetane, 1,4 bis {[(3-ethyl-3-oxetanyl) methoxy] methyl} benzene, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane and di [1- Ethyl (3-oxetanyl)] Methyl ether and the like are included.

The content of the active ray-polymerizable compound is, for example, preferably in the range of 1.0 to 97% by mass, preferably in the range of 30 to 90% by mass, based on the total mass of the active ray-curable ink. Is more preferable.

(Polymerization initiator)
The active ray-curable ink according to the present embodiment may contain a polymerization initiator. The polymerization initiator may be any as long as it can initiate the polymerization of the active ray-polymerizable compound by irradiation with active rays.
For example, when the active ray-curable ink has a radically polymerizable compound, the polymerization initiator can be a photoradical initiator, and when the active ray curable ink has a cationically polymerizable compound, polymerization initiation The agent can be a photocation initiator (photoacid generator).

The radical polymerization initiator includes an intramolecular bond cleavage type radical polymerization initiator and an intramolecular hydrogen abstraction type radical polymerization initiator.

Examples of intramolecular bond cleavage type radical polymerization initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1- (4-isopropylphenyl) -2. -Hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4) Acetphenone-based initiators including −methylthiophenyl) propan-1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, benzoin, benzoin methyl ether, benzoin isopropyl ether, etc. Includes benzoins, including 2,4,6-trimethylbenzoindiphenylphosphine oxides, acylphosphine oxide-based initiators, benzyl and methylphenylglycoesters, and the like.

Examples of intramolecular hydrogen abstraction-type radical polymerization initiators include benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl. 2-Isopropyl, a benzophenone-based initiator containing sulfide, acrylated benzophenone, 3,3', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, and 3,3'-dimethyl-4-methoxybenzophenone. A thioxanthone-based initiator containing thioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, etc., an aminobenzophenone-based initiator containing Michler ketone, 4,4'-diethylaminobenzophenone, etc. Includes 10-butyl-2-chloroacrydone, 2-ethylanthraquinone, 9,10-phenanslenquinone, and camphorquinone.

Examples of cationic polymerization initiators include photoacid generators.
Examples of photoacid generators include diazonium, ammonium, iodonium, sulfonium, and such aromatic onium compounds containing phosphonium ^{_{B (C 6 F 5) 4}} -, PF 6 -, AsF 6 -, SbF 6 -, CF Includes sulfonates that generate sulfonic acids, halides that photogenerate hydrogen halides, such as ₃ SO ₃ ^{-salts, and iron allen complexes.}

The content of the polymerization initiator can be arbitrarily set as long as the active ray-curable ink is sufficiently cured by irradiation with active rays and the ejection property of the active ray-curable ink is not deteriorated.
For example, the content of the polymerization initiator is preferably in the range of 0.1 to 20.0% by mass, and 1.0 to 12.0% by mass, based on the total mass of the active ray-curable ink. It is more preferable that it is within the range of.

(Polymerization inhibitor)
The active ray-curable ink may contain a polymerization inhibitor. Further, by using the polymerization inhibitor in combination with the above-mentioned polymerization initiator, storage stability can be improved.
By adding a polymerization inhibitor, the effect can be exhibited in cases where polymerization is started due to unexpected storage conditions (storage at high temperature, etc.).

Examples of the polymerization inhibitors include (alkyl) phenol, hydroquinone, catechol, resorcin, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiline, p-. Benzoquinone, nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyldisulfide, picric acid, cuperon, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, N- (3-oxyanilino) -1,3-Dimethylbutylidene) Aniline oxide, dibutyl cresol, cyclohexanone oxime cresol, guayacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxim, cyclohexanone oxime are included.

The content of the polymerization inhibitor can be in the range of 0.05 to 0.2% by mass with respect to the total mass of the ink.

(Gel agent)
Examples of gelling agents include dipentadecyl ketone, diheptadecyl ketone, dilignoceryl ketone, dibehenyl ketone, distearyl ketone, diicosyl ketone, dipalmityl ketone, dimyristyl ketone, lauryl myristyl ketone, lauryl. Alipid ketone compounds such as palmityl ketone, myristyl palmityl ketone, myristyl stearyl ketone, myristyl behenyl ketone, palmityl stearyl ketone, balmityl behenyl ketone and stearyl behenyl ketone; cetyl palmitate, stearyl stearate, behenyl behenate, icosan Icosyl acid, behenyl stearate, palmityl stearate, lauryl stearate, stearyl palmitate, myristyl myristate, cetyl myristate, octyldodecyl myristate, stearyl oleate, stearyl erucate, stearyl linoleate, behenyl oleate and linoleic acid An aliphatic ester compound such as arachidyl; an amide compound such as N-lauroyl-L-glutamate dibutylamide, N- (2-ethylhexanoyl) -L-glutamate dibutylamide; 1,3: 2,4-bis-O- Dibenzylidene sorbitols such as benziliden-D-glucitol; petroleum waxes such as paraffin wax, microcrystallin wax, petrolactam; candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, jojoba solid wax, and jojoba Plant waxes such as esters; Animal waxes such as honey wax, lanolin and whale wax; Mineral waxes such as montane wax and hydride wax; Hardened castor oil or hardened castor oil derivative; Montan wax derivative, paraffin wax derivative, micro Modified waxes such as crystallin wax derivatives or polyethylene wax derivatives; higher fatty acids such as bechenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, and erucic acid; higher alcohols such as stearyl alcohol and behenyl alcohol; Hydroxystearic acids such as 12-hydroxystearic acid; 12-hydroxystearic acid derivatives; lauric acid amides, stearic acid amides, bechenic acid amides, oleic acid amides, erucic acid amides, ricinolic acid amides, 12-hydroxystearic acid amides and the like. Fatty acid amide; N-stearyl stealic acid amide, N-oleyl palmitate amide N-substituted fatty acid amides such as N, N'-ethylenebisstearylamides, N, N'-ethylenebis-12-hydroxystearylamides, and special fatty acid amides such as N, N'-xylylenebisstearylamides; dodecyl Higher amines such as amines, tetradecylamines or octadecylamines; fatty acid ester compounds such as stearyl stealic acid, oleyl palmitic acid, glycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, ethylene glycol fatty acid esters, polyoxyethylene fatty acid esters; Sucrose fatty acid esters such as sucrose stearic acid and sucrose palmitic acid; synthetic waxes such as polyethylene wax and α-olefin maleic anhydride copolymer wax; polymerizable wax; dimer acid; dimer diol and the like are included. Only one type of these waxes may be used alone, or two or more types may be used in combination.

The content of the gelling agent is preferably in the range of 0.5 to 10.0% by mass with respect to the total mass of the active ray-curable ink, and is 1 with respect to the total mass of the active ray-curable ink. It is more preferably in the range of 0 to 10.0% by mass, and further preferably in the range of 2.0 to 7.0% by mass with respect to the total mass of the active ray-curable ink. The content of the gelling agent by 0.5 mass% or more, the storage elastic modulus E '' _ink droplet of active ray curable ink applied to the surface of the intermediate transfer member is increased sufficiently. Further, when the content of the gelling agent is less than 10.0% by mass, the uncured component is less likely to remain after irradiation with active rays. Further, the flexibility of the droplets of the active ray-curable ink before curing becomes relatively high.

(Color material)
The active ray-curable ink may contain a coloring material. Coloring materials include pigments and dyes. From the viewpoint of improving the dispersion stability of the active ray-curable ink and forming an image having high weather resistance, the coloring material is preferably a pigment. Examples of pigments include organic pigments and inorganic pigments. Examples of dyes include various oil-soluble dyes.

The pigment can be selected from, for example, red or magenta pigments, yellow pigments, green pigments, blue or cyan pigments and black pigments described in the color index, depending on the color of the image to be formed and the like.

The content of the pigment or dye is preferably in the range of 0.1 to 20.0% by mass, more preferably in the range of 0.4 to 10.0% by mass with respect to the total mass of the ink. preferable. When the content of the pigment or dye is 0.1% by mass or more with respect to the total mass of the ink, the color development of the obtained image is sufficient. When the content of the pigment or dye is 20.0% by mass or less with respect to the total mass of the ink, the viscosity of the ink does not increase too much.

(Dispersant)
The pigment may be dispersed with a dispersant. The dispersant only needs to be able to sufficiently disperse the pigment. Examples of dispersants include hydroxyl group-containing carboxylic acid esters, long-chain polyaminoamide and high molecular weight acid ester salts, high molecular weight polycarboxylic acid salts, long chain polyaminoamide and polar acid ester salts, and high molecular weight unsaturated acid esters. , Polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene Includes nonylphenyl ether and stearylamine acetate.

(Fixing resin)
The active ray-curable ink may contain a fixing resin in order to further enhance the abrasion resistance and blocking resistance of the coating film.

Examples of fixing resins include (meth) acrylic resin, epoxy resin, polysiloxane resin, maleic acid resin, vinyl resin, polyamide resin, nitrocellulose, cellulose acetate, ethyl cellulose, ethylene-vinyl acetate copolymer, urethane resin, polyester. Resins and alkyd resins are included.

The content of the fixing resin can be, for example, 1.0% by mass or more and 10.0% by mass or less with respect to the total mass of the active ray-polymerizable compound.

(Surfactant)
The active ray-curable ink may contain a surfactant.

The surfactant can adjust the surface tension of the ink to adjust the wettability of the ink after application to the substrate and suppress the coalescence between adjacent droplets.

Examples of surfactants include silicone-based surfactants, acetylene glycol-based surfactants, and fluorine-based surfactants having a perfluoroalkenyl group.

The content of the surfactant is preferably 0.001% by mass or more and 10% by mass or less, and 0.001% by mass or more and 1.0% by mass or less, based on the total mass of the active ray-curable ink. Is more preferable.

(Other ingredients)
In addition to the above components, the active ray-curable ink contains polysaccharides, viscosity modifiers, resistivity modifiers, film forming agents, ultraviolet absorbers, antioxidants, antifading agents, fungicides, etc., as required. It may contain a rust preventive or the like.

(2.1.2) Physical Characteristics of Active Ray Curable Ink The viscosity of the active ray curable ink is preferably in the range of ^{1 × 10 3 to} 5 × 10 ^{4 mPa · s at 40 ° C., 3 ×} It is more preferably in the range of 10 ³ to 1 × 10 ^{4 mPa · s.}
When the viscosity at the temperature of the intermediate transfer material at the time of ink application is 1 × 10 ³ mPa · s or more, the droplets of the active ray-curable ink applied to the intermediate transfer material are difficult to spread, and the droplets coalesce. hard. On the other hand, when the viscosity at the temperature of the intermediate transfer body at the time of applying ink ^{is less than 5 × 10 4} mPa · s, the ejection property from the inkjet head becomes good.

Further, from the viewpoint of further improving the ejection property from the inkjet head, the viscosity of the active ray-curable ink at 80 ° C. is preferably in the range of 3 to 20 mPa · s.
When the viscosity at 80 ° C. is in the range of 3 to 20 mPa · s, the composition is less likely to gel when the active ray-curable composition is injected from the inkjet head, so that the active ray-polymerizable compound can be more stably obtained. Can be ejected.
When the active ray-curable ink contains a gelling agent, the viscosity of the active ray-curable ink at 25 ° C. is from the viewpoint of sufficiently gelling the ink when it lands and cools to room temperature. Is preferably 1000 mPa · s or more.
When the viscosity at 25 ° C. is 1000 mPa · s or more, it is difficult for the ink droplets applied to the intermediate transfer material to spread, and it is difficult for the droplets to coalesce with each other.

Also, the storage modulus _{E '' ink} of the active ray-curable ink, at 40 ° C., preferably in the range of ^{3 × 10 1 Pa~3 × 10 3} Pa, 3 × 10 2 ~1 × 10 It is more preferably within the range of ^{3 Pa.}
When the storage elastic modulus E ″ _ink is 3 × 10 ¹ Pa or more, it is difficult for the droplets of the active ray-curable ink to coalesce with each other, and when the storage elastic modulus E ″ _ink is less than 5 × 10 ^{4 mPa.} , The droplets of active ray curable ink have moderate flexibility.
Therefore, when transferring from the intermediate transfer body to the recording medium, the active ray-curable ink and the recording medium tend to be in close contact with each other.
The "storage elastic modulus" is an index of the hardness of the material, and the smaller the value, the softer the material.

The viscosity of the active ray-curable ink at 40 ° C., the viscosity at 80 ° C., and the storage elastic modulus E ″ _{ink at} 40 ° C. are measured by measuring the temperature change of the dynamic viscoelasticity of the active ray-curable ink with a rheometer. Can be obtained by.
For example, the viscosity of the active ray-curable ink at 40 ° C. and the viscosity at 80 ° C. are determined by heating the active ray-curable ink to 100 ° C. with a rheometer and using a stress-controlled rheometer (Physica MCR301 manufactured by Antonio Par). While measuring the viscosity with a diameter: 75 mm, cone angle: 1.0 °)), cool the ink to 20 ° C under the conditions of a shear rate of 11.7 (1 / s) and a temperature lowering rate of 0.1 ° C / s. It is obtained by reading the viscosities at 40 ° C. and 80 ° C. on the temperature change curve of the obtained viscosity, respectively.
Further, the storage elastic modulus E ″ ink at 40 ° C. of the active ray-curable _ink is 5% strain and angular while changing the temperature from 90 ° C. to a temperature drop rate of 0.1 ° C./in in the oscillation mode. It is determined by measuring at a frequency of 10 radian / s and reading the _{storage elastic modulus E ″ ink at 40 ° C.}

(2.1.3) Method for preparing active ray-curable ink The active ray-curable ink contains the above-mentioned active ray-polymerizable compound, polymerization initiator, polymerization inhibitor, coloring material, and any other component. , Can be prepared by mixing under heating. At this time, it is preferable to filter the obtained mixed solution with a predetermined filter.
When preparing an ink containing a pigment, it is preferable to prepare a pigment dispersion liquid containing the pigment and an active ray-polymerizable compound, and then mix the pigment dispersion liquid with other components. The pigment dispersion may further contain a dispersant.

The pigment dispersion liquid can be prepared by dispersing the pigment in an active ray-polymerizable compound. The pigment may be dispersed by using, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like. At this time, a dispersant may be added.

(2.1.4) Method of Applying Active Ray Curable Ink The method of applying the active ray curable ink to the moving surface of the intermediate transfer material is not particularly limited, and is not particularly limited, and is spray coating, dipping method, screen printing, and gravure. Known methods such as printing, offset printing, and inkjet method can be used.
In the present embodiment, in the step of applying the active ray-curable ink to the moving surface of the intermediate transfer body and forming the intermediate image, the active ray-curable ink is ejected from the inkjet head to form the intermediate transfer body. It is preferable to use an inkjet method that is applied to the moving surface.

The inkjet head used in the inkjet method may be either an on-demand method or a continuous method inkjet head.
Examples of on-demand inkjet heads include electro-mechanical conversion methods including single cavity type, double cavity type, bender type, piston type, shared mode type and shared wall type, and thermal inkjet type and bubble jet ( Bubble jet includes an electric-heat conversion method including a registered trademark of Canon Inc.).

Further, the inkjet head may be either a scan type or a line type inkjet head.
At this time, in order to improve the ejection property of the droplets of the active ray-curable ink, the active ray-curable ink in the inkjet head is heated to 40 to 120 ° C., and the heated active ray-curable ink is ejected. Is preferable.

When the active ray-curable ink contains a gelling agent, the temperature of the active ray-curable ink in the inkjet head should be set to a temperature 10 to 40 ° C. higher than the gelation temperature of the active ray-curable ink. Is preferable.
By setting the temperature of the active ray-curable ink in the inkjet head to the gelation temperature + 10 ° C or higher, the active ray-curable ink does not gel in the inkjet head or on the nozzle surface, and the active ray-curable ink is good. Can be ejected to.
Further, by setting the temperature of the active ray-curable ink in the inkjet head to less than the gelation temperature of the active ray-curable ink + 40 ° C., the thermal load of the inkjet head can be reduced.
In particular, in an inkjet head using a piezo element, performance deterioration is likely to occur due to a thermal load, so it is particularly preferable to keep the temperature of the active ray-curable ink within the above range.

When the active ray-curable ink contains a gelling agent, the active ray-curable ink applied to the surface of the intermediate transfer body is pinned by crystallizing the gelling agent.
As a result, the dots formed by applying the active ray-curable ink are less likely to get wet and spread, and the dots formed by the active ray-curable ink landing on the surface of the intermediate transfer body are united with each other. It can be suppressed.

At this time, in order to improve the pinning property of the active ray-curable ink, the surface temperature of the intermediate transfer material may be set to be near or lower than the gelling temperature of the gelling agent.

(2.1.5) Step of thickening active ray-curable ink The ink according to the present invention is preferably exposed to ultraviolet rays before being transferred to a recording medium to adjust the viscosity of the ink.
As the method, there are a first thickening step and a second thickening step as described below.
The steps of thickening the active ray-curable ink include a step of irradiating active rays from the back surface side of the intermediate transfer body to thicken the applied active ray-curable ink (first thickening step) and a transfer nip. It has a step (second thickening step) of irradiating active rays from the moving surface side of the intermediate transfer material to thicken the applied active ray-curable ink before passing through the ink. In this embodiment, it is preferable to use ultraviolet rays as active rays.

The front surface of the intermediate transfer body is the surface to which the active ray-curable ink is applied (the surface that comes into contact with the recording medium in the transfer process), and the back surface of the intermediate transfer body is the active ray-curable surface. This is the surface to which the mold ink is not applied (the surface that does not come into contact with the recording medium in the transfer process).

(1st thickening step)
The first thickening step is a step of irradiating active rays from the back surface side of the intermediate transfer body to thicken the active ray-curable ink applied to the surface of the intermediate transfer body.
In the first thickening step, the active rays irradiated from the back surface side of the intermediate transfer body pass through the intermediate transfer body and reach the back surface side of the intermediate image.
As a result, the intermediate image is cured from the back surface side, so that the hardness of the active ray-curable ink on the back surface side is increased and the hardness of the active ray-curable ink on the front surface side is decreased. can.

The front surface of the intermediate image is a surface that comes into contact with the recording medium when the image is transferred to the recording medium, and the back surface of the intermediate image is a surface that is in contact with the intermediate transfer body.

In the first thickening step, the exposure amount of the active rays (ultraviolet rays) irradiated to the back surface side of the intermediate transfer body is preferably 5 to ^{20 mJ / cm 2.}
When the exposure amount of the active ray (ultraviolet ray) is within the above range, the active ray-curable ink constituting the surface side of the intermediate image can maintain sufficient wettability with respect to the recording medium.
In addition, since the active ray-curable ink on the back side of the intermediate image is cured to some extent, it is easy to peel off from the intermediate transfer body during transfer, so that the intermediate image remains on the front surface of the intermediate transfer body (transfer leakage). Can be suppressed, so that the transferability can be improved.

(Second thickening step)
The second thickening step is a step of irradiating the moving surface of the intermediate transfer body with active rays to thicken the active ray-curable ink applied to the surface of the intermediate transfer body.
The second thickening step is continuously performed with the step of transferring the active ray-curable ink, which will be described later.
Here, "continuously" means that the second thickening step and the step of transferring the active ray-curable ink are performed separately and within a short period of time (for example, within 0.1 seconds), and It means that no other process is included between the two processes.

(others)

So far, the process of directly applying the active ray-curable ink to the moving surface of the intermediate transfer member has been described, but the present invention is not limited to this.
Before the step of applying the active ray-curable ink to the moving surface of the intermediate transfer body, there may be a step of applying the precoat liquid to the surface of the intermediate transfer body.

(2.2) Step of transferring active ray-curable ink In the step of transferring active ray-curable ink to a recording medium, irradiation of active rays from the moving surface side of the intermediate transfer body (second thickening step) and step of transferring the active ray-curable ink are performed. This is a step of continuously passing the transfer nip.
In particular, when transferring to a medium having a large step (concave-convex paper, rezac paper, etc.), transferability to the concave portion becomes a problem.

In order to ensure the followability of the stepped shape of the paper, it is necessary that the ink is not deformed during the image transfer and the belt is deformed.
If the storage elastic modulus E ″ _{ink of the ink} is larger than the storage elastic modulus E ′ of the belt, the belt is deformed before the ink.
At this time, since the ink is not collapsing, the temperature of the intermediate transfer member during image transfer within the storage modulus E '' _ink is ^{3 × 10 1 ~3 × 10 3} Pa of ink when the 40 ° C. Is preferable.

Both obtaining ink on a flat plate and ensuring followability to the stepped shape of paper may be achieved by modifying rubber or the like.
Further, it may be performed by installing a material layer for improving the wettability of the ink on the surface layer, but in that case, it is necessary that the material itself has flexibility.

Although the shape control of the ink is achieved by the present invention, pretreatment on the belt surface may be performed for the purpose of assisting the transfer to paper (combination with precoating is also possible).

For example, a surface modification treatment for imparting releasability or a means for installing a thin liquid layer on the surface for improving separability may be taken.

The series of methods is as described in (1.3) the outermost surface layer.

The step of transferring the active ray-curable ink to the recording medium is a step of continuously irradiating the active ray from the moving surface side of the intermediate transfer body (second thickening step) and passing the transfer nip.
In the present embodiment, after irradiating the surface side of the intermediate transfer body with active rays, the intermediate image is transferred to the surface of the recording medium by passing through a transfer nip. In the present embodiment, the step of transferring the active ray-curable ink to the recording medium is a step of pressurizing with a predetermined nip pressure by a support roller (pressurizing portion) located at the lower apex portion of the inverted triangle shape. Yes (see Figure 1).

In the second thickening step, the exposure amount of the active rays (ultraviolet rays) irradiated to the moving surface side of the intermediate transfer material is preferably ^{50 to 300 mJ / cm 2.}
By setting the exposure amount of the active rays (ultraviolet rays) within the above range, it is possible to improve the fine line reproducibility of the image, the transferability to the recording medium, and the fixability with the recording medium.

Here, the active ray-curable ink applied to the moving surface of the intermediate transfer body is the active ray-curable ink from the irradiation of the active ray (ultraviolet rays) to the surface side (second thickening step) to the entry into the transfer nip. The ink transfer time is longer than the time required for the kinematic viscosity of the active ray-curable ink to increase by 20% at 40 ° C. when the active ray (ultraviolet ray) irradiated from the surface side is ^{irradiated with an illuminance of 1 W / cm 2.} Is also preferable.

If the movement time is longer than the time required for the kinematic viscosity of the active ray-curable ink to increase by 20%, the active ray-curable ink must enter and pass through the transfer nip with the viscosity of the active ray-curable ink increased to some extent. Therefore, it is possible to suppress the disorder of the dot shape of the active ray-curable ink applied to the intermediate transfer body and improve the fine line reproducibility of the image. As a result, a high-definition image can be formed.

In addition, the active ray-curable ink applied to the moving surface of the intermediate transfer body from the irradiation of the active ray (ultraviolet rays) from the surface side (second thickening step) to the discharge from the transfer nip. The moving time is longer than the time required for the kinematic viscosity of the active ray-curable ink to increase by 30% at 40 ° C. when the active ray (ultraviolet ray) irradiated from the surface side is ^{irradiated with an illuminance of 1 W / cm 2.} Long is preferred.

When the moving time is within the above range, the viscosity of the active ray-curable ink applied to the intermediate transfer material is increased to some extent, so that the internal cohesive force of the active ray-curable ink can be increased. As a result, by increasing the internal cohesive force of the active ray-curable ink, it is possible to suppress the residual (transfer leakage) of the intermediate image on the surface of the intermediate transfer body even if the intermediate image is transferred to the recording medium. Therefore, the transferability can be improved.

In addition, the movement of the active ray-curable ink from the irradiation of the active ray (ultraviolet rays) from the surface side of the active ray-curable ink applied to the surface of the intermediate transfer body (second thickening step) to the entry into the transfer nip. The time is shorter than the time required for the kinematic viscosity of the active ray-curable ink to increase by 60% at 40 ° C. when the active ray (ultraviolet ray) irradiated from the surface side is ^{irradiated with an illuminance of 1 W / cm 2.} Is preferable.

When the moving time is within the above range, the active ray-curable ink may be deformed to some extent by being pressed by the transfer nip when the recording medium and the active ray-curable ink come into contact with each other in the transfer nip. Therefore, the followability to the recording medium is improved, and the fixability between the recording medium and the ink can be improved.

The kinematic viscosity of the above-mentioned active ray-curable ink is determined by using a dynamic viscoelastic device (DMA) stress-controlled rheometer (Physica MCR301 (cone plate diameter: 75 mm, cone angle: 1.0 °) manufactured by Antonio Par). Can be measured using.
The active ray-curable ink before irradiation with active rays (ultraviolet rays) is irradiated with ^{light for 100 ms at an illuminance of 1 W / cm 2} , and the time at which the viscosity increases at 40 ° C. is observed.
The viscosity of the active photocurable ink at this time is the kinematic viscosity.

Further, the moving time of the active ray-curable ink from the above-mentioned second thickening step to the entry into the transfer nip and the moving time of the active ray-curable ink from the second thickening step to the discharge from the transfer nip are as follows. It can be adjusted by the moving time of the intermediate transfer body, the distance between the position where the second thickening step is performed and the position of the transfer nip, the size (width) of the transfer nip, and the like.

(Ink viscosity during transfer)
The viscosity of the active ray-curable ink during transfer of the image formed on the intermediate transfer body is defined as follows.
The ink is applied on a PET sheet to a thickness of 10 μm with a wire bar or the like, and the temperature is adjusted to the temperature at the time of transfer.
It is good to adjust the temperature with a hot plate set to the same temperature as the environmental temperature at the time of transfer, and perform DMA measurement in this state.
In addition, when UV light is exposed before transfer, light irradiation is performed at a predetermined UV light amount and exposure time at this time, and the material preparation is completed.

Normally, it is sandwiched between cylindrical cells of 25 mmΦ, and dynamic viscoelasticity is measured while applying a pressing load with 1 g. The value shown.

After that, after transferring to paper, a curing process for immobilizing on paper is performed, and a state in which the ink is completely cured and permanently immobilized on paper is realized.
At the time of transfer, it is important to anchor and cure the paper in a deformed state.

(2.3) Step of main-curing active ray-curable ink In the step of main-curing active ray-curable ink, the active ray-curable ink (intermediate image) transferred to a recording medium is irradiated with active rays (ultraviolet rays). Then, it is a step of main curing the active ray curable ink (intermediate image).

In the step of main curing the active ray-curable ink, the active ray-curable ink (intermediate image) transferred to the recording medium is irradiated with active rays (for example, ultraviolet rays) to obtain the active ray-curable ink (intermediate image). This is the main curing process.
As a result, a target high-definition image is formed on the surface of the recording medium. The exposure amount of the active rays (ultraviolet rays) irradiated in the step is preferably ^{30 to 500 mJ / cm 2.}

3. 3. Image forming apparatus FIG. 1 is a schematic view showing an exemplary configuration of an image forming apparatus 100 for an inkjet according to an embodiment of the present invention.

The image forming apparatus 100 according to the present embodiment has an ink applying portion 120 that applies active ray-curable ink to the moving front surface of the intermediate transfer body 110, and an intermediate transfer body 110 that irradiates active rays from the back surface side. The first thickening portion 130 that thickens the active ray-curable ink applied to the moving surface and the moving surface side of the intermediate transfer body 110 are irradiated with active rays to the moving surface of the intermediate transfer body 110. It has a second thickening portion 131 for thickening the applied active ray-curable ink, and a transfer nip 140 (transfer portion) for transferring the active ray-curable ink to a recording medium. The image forming apparatus 100 further cures (mainly cures) the support rollers 150, 151, and 152 on which the intermediate transfer body 110 having the shape of an endless belt is stretched, and the active ray-curable ink constituting the intermediate image. The cured portion 170 that irradiates the surface of the transport path 160 toward the surface of the transport path 160, and the active ray-curable ink that remains on the surface of the intermediate transfer body 110 without being transferred to the recording medium 180 are removed from the surface of the intermediate transfer body 110. It has a cleaning unit 190 and a cleaning unit 190.

The intermediate transfer body 110 is stretched and rotationally moved by the support rollers 150, 151 and 152, and the intermediate image formed on the surface of the intermediate transfer body 110 by the intermediate image forming unit 121 is transferred to the transfer nip 140 (transfer unit). Transport.

Of the three support rollers 150, 151 and 152, at least one roller is a drive roller, which rotates the intermediate transfer body 110 in the A direction.

The intermediate transfer member 110 is preferably made of a material that transmits the active rays (ultraviolet rays) irradiated from the back surface side, and is not particularly limited as long as it is a material that transmits the active rays (ultraviolet rays). Further, the intermediate transfer body 110 is preferably made of a material having a transmittance of 80% or more of active rays (ultraviolet rays) irradiated from the back surface side, preferably 87% or more, and 92% or more. It is even more preferred to consist of certain materials.
Since the details of the composition of the intermediate transfer body and the constituent materials have been described above, they are omitted here.

The portions of the intermediate transfer body 110 stretched over the support rollers 150, 151, and 152 located at the left and right apex portions of the inverted triangle shape serve as the landing surface of the active ray-curable ink applied from the ink applying portion 120. ing. The support roller 150 located at the lower apex portion of the inverted triangular shape of the intermediate transfer body 110 is a pressurizing roller that pressurizes the intermediate transfer body 110 toward the transport path 160 by a predetermined nip pressure, and is an ink application unit. It functions as a pressurizing unit 141 that transfers an intermediate image formed by applying the active ray-curable ink ejected from 120 to the recording medium 180.

In the present embodiment, the intermediate image forming unit 121, which is also the ink applying unit 120, is an ink applying unit that forms an intermediate image by the inkjet method, and is Y (yellow), M (magenta), C (cyan), and K (respectively). It has inkjet heads 120Y, 120M, 120C and 120K for ejecting an active ray-curable composition (inkjet ink) of each color (black) from a nozzle and applying it to the surface of the intermediate transfer member 110. The inkjet heads 120Y, 120M, 120C and 120K apply the active ray-curable inks of the above colors to positions on the surface of the intermediate transfer member 110 according to the image to be formed to form an intermediate image.

In the first thickening portion 130, the back surface side of the intermediate transfer body 110 is irradiated with active rays (ultraviolet rays) while the intermediate image formed by the intermediate image forming portion 121 is conveyed to the transfer nip 140 (transfer portion). .. The exposure amount of the active rays (ultraviolet rays) to irradiate the back surface side of the intermediate transfer member 110 is preferably 5 to ^{20 mJ / cm 2.} As a result, the back side of the intermediate image can be uniformly irradiated with active rays (ultraviolet rays), so that the intermediate image is cured from the back side, and the hardness of the active ray-curable ink on the back side is increased, so that the front surface is hardened. The thickness is increased so that the hardness of the active ray-curable ink on the side becomes low.

In the first thickening portion 130, the exposure amount of the active rays (ultraviolet rays) irradiated to the back surface side of the intermediate transfer member 110 is set to 5 to 20 mJ / cm ² , so that the front surface side of the intermediate image is sufficient for the recording medium. Wetness can be maintained, and it is possible to prevent a part of the intermediate image from remaining on the surface of the intermediate transfer body during transfer.

The second thickening portion 131 is located on the downstream side of the first thickening portion 130 and on the upstream side of the transfer nip 140 (transfer portion), and irradiates the moving surface side of the intermediate transfer body with active rays. .. The exposure amount of the active rays (ultraviolet rays) to irradiate the moving surface side of the intermediate transfer member 110 is preferably ^{50 to 300 mJ / cm 2.} As a result, the active rays can be uniformly irradiated on the surface side of the intermediate image. Further, it is possible to improve the fine line reproducibility of the image, the transferability to the recording medium, and the fixability with the recording medium.

In the second thickening portion 131, the moving time of the intermediate image from the passage of the first thickening portion 130 to the entry into the transfer nip 140 (transfer portion) is an illuminance of ^{1 W / cm 2 for the active line (ultraviolet rays).} When irradiated, it is preferable to arrange the ink at 40 ° C. so that the kinematic viscosity of the active ray-curable ink becomes longer than the time until the kinematic viscosity increases by 20%. By arranging the second thickening portion 131 at such a position, the active ray-curable ink enters the transfer nip 140 in a state where the viscosity of the active ray-curable ink is increased to some extent. It is possible to suppress the disorder of the dot shape of the curable ink and improve the fine line reproducibility of the image. As a result, a high-definition image can be formed.

Further, in the second thickening portion 131, the moving time of the active ray-curable ink from the passage of the first thickening portion 130 to the discharge from the transfer nip 140 (transfer portion) is 1 W / W of the active ray (ultraviolet ray). When irradiated with an illuminance of cm ² , it is preferable to arrange the ink at a position such that the kinematic viscosity of the active ray-curable ink increases by 30% at 40 ° C. By arranging the second thickening portion 131 at such a position, the viscosity of the active ray-curable ink applied to the intermediate transfer body 110 is increased to some extent, so that the internal cohesive force of the active ray-curable ink is enhanced. be able to. As a result, even if the intermediate image is transferred to the recording medium 180, the residual of the intermediate image on the surface of the intermediate transfer body (transfer leakage) can be suppressed, so that the transferability can be improved.

Further, in the second thickening portion 131, the moving time of the active ray-curable ink from the passage of the first thickening portion 130 to the entry into the transfer nip 140 (transfer portion) is 1 W / W of the active ray (ultraviolet ray). When irradiated with an illuminance of cm ² , it is preferable to arrange the ink at a position where the kinematic viscosity of the active ray-curable ink becomes shorter than the time required to increase by 60% at 40 ° C. When the moving time is within the above range, when the recording medium and the ink come into contact with each other in the transfer nip, the active ray-curable ink can be deformed to some extent by being pressed by the transfer nip, so that the recording medium can be deformed to some extent. It is possible to improve the adhesiveness between the recording medium and the active ray-curable ink by improving the followability to the ink.

The transfer nip 140 (transfer portion) is a portion where the intermediate transfer body 110 and the transfer path 160 are closest to each other, and the intermediate transfer body 110 is urged in the direction of the transfer path 160 by the support rollers 150, 151 and 152. This pressurizes the surface of the transport path 160 in contact with the intermediate transfer body 110. On the intermediate image containing the active ray-curable ink formed on the surface of the intermediate transfer body 110 and conveyed by the first thickening portion 130 and the second thickening portion 131, and on the surface of the conveying path 160. The recording medium 180 that has been arranged and conveyed is brought into contact with the transfer nip 140 (transfer portion) and is pressurized from the intermediate transfer body 110 to the transfer path 160 side via the support roller 150, so that the recording medium 180 Is transferred to.

At this time, due to the irradiation by the first thickening portion 130, the intermediate image has a higher hardness of the active ray-curable ink on the back surface side that is pressed in contact with the intermediate transfer body 110, and is in contact with the recording medium 180. The ink is thickened so that the hardness of the active ray-curable ink on the surface side is lower. Therefore, the intermediate image is less likely to be crushed by pressing during transfer, and has sufficient wettability with respect to the recording medium 180 during transfer, so that the fixability to the recording medium 180 tends to increase.

Further, it is possible to suppress the disorder of the dot shape of the active ray-curable ink applied to the intermediate transfer body 110 by the irradiation by the second thickening portion 131, and to improve the fine line reproducibility of the obtained image. Further, since it has the ability to follow the recording medium while increasing the internal cohesive force of the active ray-curable ink, it is possible to improve the transferability and fixability to the recording medium.

The transport path 160 is composed of, for example, a metal drum, and transports a recording medium 180 on which an intermediate image is transferred. The transport path 160 is arranged in contact with a part of the surface of the intermediate transfer body 110, and the transfer nip 140 (transfer portion) is formed by pressurizing the contacting surface of the intermediate transfer body 110 by the support roller 150. NS. The transport path 160 may have a claw (not shown) for fixing the tip of the recording medium 180. The transport path 160 transports the recording medium 180 to the transfer nip by fixing the tip of the recording medium 180 to the claw and rotating it in the counterclockwise direction in FIG.

The cured portion 170 is arranged on the downstream side of the transfer nip 140 (transfer portion) in the transport direction of the recording medium 180 by the transport path 160, and irradiates the surface of the transport path 160 with active rays (ultraviolet rays). As a result, the curing unit 170 irradiates the intermediate image transferred to the recording medium 180 with active rays to cure (mainly cure) the active ray-curable ink constituting the intermediate image. As a result, a target high-definition image is formed on the surface of the recording medium 180.

The cleaning unit 190 is a cleaning roller such as a web roller or a sponge roller, and comes into contact with the surface of the intermediate transfer body 110 on the downstream side of the transfer nip 140 (transfer unit). The cleaning unit 190 removes the residual composition (residual coating material) remaining on the surface of the intermediate transfer body 110 without being transferred to the recording medium 180 by the transfer nip 140 (transfer unit) by driving and rotating the cleaning roller. do.

In the above description, the intermediate image is formed on the moving surface of the intermediate transfer body by the inkjet method, but the method for forming the intermediate image is not particularly limited, and spray coating, dipping method, screen printing, gravure printing, and the like. A known method such as offset printing can be used. Among these methods, since an image formed by aggregating dots of droplets of active ray-curable ink is formed, crushing of droplets of active ray-curable ink is more likely to occur during image formation by the inkjet method. Curing that can suppress the crushing of the active ray curable ink by the above image forming apparatus is remarkably achieved.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Each active ray-curable inkjet ink 1 to 10 was prepared using the following compounds as components.
Each active ray-curable inkjet ink used below is an "ink that does not substantially penetrate paper" according to the present invention.

4. Preparation of active ray-curable inkjet ink (4.1) Photopolymerizable compound (monomer)
・ NK Ester A-400 (manufactured by Shin-Nakamura Chemical Co., Ltd.):
Polyethylene glycol diacrylate (ClogP value: 0.47)
-SR499 (manufactured by Sartomer):
6EO-modified trimethylolpropane triacrylate (ClogP value: 3.57)
-SR494 (manufactured by Sartomer):
4EO-modified pentaerythritol tetraacrylate (ClogP value: 2.28)
(Oligomer)
・ Urethane acrylate oligomer

(4.2) Gelling agent ・ Lunac BA (manufactured by Kao): behenic acid ・ Kao wax T1 (manufactured by Kao): distearyl ketone ・ stearic acid amide

(4.3) Photopolymerization Initiator ・ DAROCUR TPO (manufactured by BASF)
・ ITX (manufactured by DKSH Japan)
・ DAROCUR EDB (manufactured by BASF)
(4.4) Polymerization inhibitor ・ Irgastab UV10 (manufactured by Ciba Japan)

(4.5) Surfactant ・ KF-352 (manufactured by Shin-Etsu Chemical Co., Ltd.)

(4.6) Sensitizing aid ・ DEA (diethoxyanthracene, manufactured by Kawasaki Kasei Chemicals Co., Ltd.)

(Preparation of pigment dispersion)
The pigment dispersant, photopolymerizable compound, and polymerization inhibitor shown below were placed in a stainless beaker and heated and stirred for 1 hour while heating on a hot plate at 65 ° C.
-Pigment dispersant: Ajispar PB824 (manufactured by Ajinomoto Fine-Techno)
9 parts by mass ・ Photopolymerizable compound: APG-200 (tripropylene glycol diacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.) 70 parts by mass ・ Polymerization inhibitor: Irgastab UV10 (manufactured by Ciba Japan)
0.02 parts by mass

After cooling the above mixed solution to room temperature, 21 parts by mass of Pigment Red 122 (Chromofine Red 6112JC manufactured by Dainichiseika) was added thereto.

The mixed solution was placed in a glass bottle together with 200 g of zirconia beads having a diameter of 0.5 mm, sealed, and dispersed with a paint shaker for 8 hours. Then, the zirconia beads were removed to prepare a pigment dispersion liquid.

[Preparation of radical polymerization type inkjet ink]
The compositions of the active photocurable inkjet inks 1 to 10 containing each compound at the composition ratios shown in Tables I and II below were heated to 100 ° C. and stirred.
Then, the obtained liquid was filtered with a # 3000 metal mesh filter under heating.
This was cooled to prepare a radical curable inkjet ink.

The ink viscosity of the ink prepared by the above method was measured by the following method.
Ink was set in a temperature-controllable stress-controlled rheometer (Physica MCR300, manufactured by Antonio Par), and the ink was heated to 100 ° C.

Then, the viscosity and dynamic viscoelasticity were measured while cooling to 25 ° C. at a temperature lowering rate of 0.1 ° C./s. At this time, the share rate was set to 11.7s ^-1 . For the measurement, a cone plate (CP75-1, manufactured by Antonio Par) having a diameter of 75 mm and a cone angle of 1 ° was used.

The temperature was controlled by a Perche element type temperature control device (TEK150P / MC1) attached to the Physica MCR300.

From the temperature change curve obtained by the dynamic viscoelasticity measurement, the value of the storage elastic modulus at a temperature of 25 ° C. was read. The results obtained by the above method are shown in Table II.

5. Preparation of Intermediate Transcription Body 1 was prepared by the following procedure.

(5.1) Preparation of Intermediate Transfer 1 (Formation of Base Material Layer)
A leveling agent (KF-96 manufactured by Shin-Etsu Chemical Co., Ltd.) is added to a polyimide varnish (Spixeria HR003 (manufactured by Somar Corporation)) containing a polyimide resin precursor (polyamic acid) as a main component and having a solid content of 15% by mass with respect to the total weight of the polyimide varnish. A coating liquid for forming a substrate layer was prepared by adding 100 ppm and mixing using a mixer.

Next, a cylindrical stainless steel mold having a circumference of 2500 mm and a width of 800 mm on which a mold release agent is formed is rotated at 100 rpm around a cylindrical shaft, and the dispenser nozzle is moved in the direction of the cylindrical shaft to a total width of 700 mm after firing. A wet film was formed so that the thickness of the film was 750 μm.

Next, the solvent was volatilized by heating (baking) at 100 ° C. for 2 hours using a far-infrared drying device while rotating the cylinder shaft at 100 rpm so that the base material layer did not flow down.

Finally, the mold was introduced into a heating furnace, heated stepwise, and heat-treated (baked) for 90 minutes while being held at 380 ° C. It was sufficiently cooled to obtain a polyimide base material layer having a thickness of 750 μm.

The thickness of the base material layer was measured using FICHERSCOPE MMS PC2 (manufactured by Fisher Instruments).

(Formation of elastic layer)
The following components were dissolved in toluene in the following amounts so that the solid content concentration was 20% by mass, and then a coating liquid for forming an elastic layer was prepared.

(Coating liquid for forming elastic layer)
Matrix polymer:
KE2061-30A / B (Shin-Etsu Chemical Co., Ltd.) 100 parts by mass Organic flame retardant:
Trimethyl phosphate TPM (manufactured by Daihachi Chemical Industry Co., Ltd.) 30 parts by mass Resin cross-linking agent:
Phenol novolac type epoxy resin N-770 (manufactured by DIC Corporation)
10 parts by mass Conductive agent:
Tetrabutylammonium perchlorate QAP-01 (manufactured by Carlit Japan Co., Ltd.)
1 part by mass

Next, using the polyimide base material layer formed on the outer peripheral surface of the mold, the total width is 700 mm and the thickness after firing is 300 μm while rotating the dispenser nozzle at 200 rpm around the cylindrical axis and moving the dispenser nozzle in the cylindrical axis direction. The wet film was laminated so as to be.

Next, the mold was introduced into a heating furnace, and the temperature was gradually raised and heat-treated (vulcanized) for 60 minutes while being held at 180 ° C. It was cooled sufficiently. The thickness of the formed elastic layer was 300 μm.

(Formation of the outermost surface layer 1)
A polyfunctional acrylate resin: obbligato SS0051 (manufactured by AGC Cortec) was mixed and stirred with a main agent: curing agent = 5: 1 (part by mass ratio) to prepare an SS0051 resin solution.

The SS0051 resin liquid is arranged as an upper layer of the elastic layer formed above, and as a preliminary preparation, the surface of the elastic layer is surface-treated by excimer treatment.

Then, the SS0051 resin liquid was applied on the outer peripheral surface of the elastic layer by a spray method so that the solid content dry film thickness was 2 μm to form a coating film. Then, while rotating the obtained intermediate transfer belt, it was heated at 120 ° C. for 20 minutes to form the hardened outermost surface layer 1.

(Spray application conditions)
Nozzle scan speed: 1-10 mm / sec
Nozzle distance: 100-150 mm
Number of nozzles: 1
Coating liquid supply amount: 1 to 5 mL / min
O _{2 flow rate: 2 to 6} L / min.

(Formation of the outermost surface layer 2)
Polyfunctional acrylate resin: 2 parts by mass of an obligato SS0051 curing agent (manufactured by AGC Coatec) was added to 100 parts by mass of an obligato SS0051 main agent (manufactured by AGC Cortec) and stirred to prepare an SS0051 resin solution.

To 100 parts of this SS0051 resin liquid, 0.1 part by mass of rotaxane (SH2400P, manufactured by Advanced Soft Materials Co., Ltd.) as a cross-linking agent was added and stirred for 10 minutes to prepare a surface treatment liquid.

The produced endless belt with an elastic layer was subjected to a corona discharge treatment under the condition of 350 mW while rotating at 100 mm / s using a corona discharge device (manufactured by Kasuga Electric Co., Ltd.).

Immediately after the corona discharge treatment, the outermost surface treatment liquid is applied using a spray nozzle so that the entire belt surface is wet, and the belt is heated and dried at 120 ° C. for 60 minutes.

Then, the surface was washed with ion-exchanged water, dried, and aged for 12 hours to prepare an intermediate transcript 1.
As described above, the relationship between the outermost surface layers 1 and 2 formed as described above and the intermediate transcripts 1 to 10 is as shown in Table III.

(5.1.1) Vertical dynamic viscoelasticity measurement of laminated body (intermediate transfer body 1) (Measurement method of loss elastic modulus)

The loss elastic modulus of the intermediate transfer material can be measured by a general dynamic viscoelasticity measurement.
That is, for example, a strip-shaped sample piece cut out from an intermediate transfer material to a width of 4 mm and a length of 35 mm is measured under the following conditions.
The measurement is performed under the following conditions while raising the temperature at a predetermined heating rate, and at this time, the loss elastic modulus at each temperature is calculated from the temperature-dependent profile of the obtained dynamic viscoelasticity.
In the dynamic viscoelasticity measurement, the thickness of the sample piece is measured in advance, and the cross-sectional area of the sample piece is calculated by inputting the values of the thickness of the sample piece and the width of the sample piece into the measuring device, and each value. Is calculated. In this experiment, the value of the temperature of 40 ° C. was adopted.
Frequency: 0.1Hz
Ramp rate: 3 ° C / min Axial force: 0 g
Sensitivity: 10g
Initial strain: 0.01%
Strain adjustment: 30.0%
Minimum strain: 0.01%
Maximum strain: 10.0%
Minimum torque (Minimum torque): 1 g · cm
Maximum torque (Maximum torque): 80 g · cm
Measurement interval (Sampling interval): 1.0 ° C./pt
When the loss elastic modulus of the intermediate transfer material 1 was measured under the above conditions, it was 12000 Pa.
In addition, the loss elastic modulus was measured by the same measuring method for the intermediate transcripts 2 to 10 below.
The measured values for each intermediate transcript are shown in Table III.

(5.1.2) Measurement of tensile elastic modulus in the horizontal direction of the laminated body (intermediate transfer member 1) (Measurement method of tensile elastic modulus)
The tensile elastic modulus was measured by a tensile test using a section obtained by cutting the intermediate transfer material into a dumbbell shape by the method of JIS K7161.

Measuring equipment: Tensilon universal material tester RTC-1250 (manufactured by A & D Co., Ltd.)
Measurement conditions: Test piece for tensile test: Shape conforming to JIS K7161
Tensile rate: 1 mm / s
Distance between chucks: 115 mm
Distance between gauge points: 100 mm
For the intermediate transfer material, the tensile elastic modulus after irradiation with ultraviolet rays was measured at ^{500 mW / cm 2} for 100 hours using a high-pressure mercury lamp.
When the tensile elastic modulus in the horizontal direction of the intermediate transfer material 1 was measured under the above conditions, it was 2.7 MPa.
In the following, the tensile elastic modulus was measured for the intermediate transfer bodies 2 to 10 by the same measurement method.
The measured values for each intermediate transcript are shown in Table III.

(5.1.3) Contact angle with pure water (contact angle and measurement method)
The contact angle of water on the surface of the intermediate transfer body 1 was measured in accordance with JIS standard R3257: 1999 using, for example, DMo-901 manufactured by Kyowa Surface Chemistry Co., Ltd. under the following conditions.
The amount of droplets was 2 μL.
The value of the contact angle 1 sec after dropping the droplet was used as the observed value.
Observations were carried out at a room temperature of 25 ° C. and the equipment temperature was maintained at 40 ° C.
The measurement was performed 5 times, and the average value was taken as the water contact angle.
When the contact angle of the intermediate transfer material 1 with respect to pure water was measured under the above conditions, it was 72 °.
The contact angle with respect to pure water was measured by using the same measuring method for the intermediate transcripts 2 to 10 below.
The measured values for each intermediate transcript are shown in Table III.

(5.2) Intermediate Transfer 2 to Intermediate Transfer 10
Intermediate Transfers 2 to 10 were prepared in the same manner as Intermediate Transfer 1 except that the types of additives were changed as shown in Table III. The content of the additive in the thickness direction of the elastic layer was changed by changing the amount of the additive at the time of addition to adjust the dynamic viscoelasticity and the contact angle with pure water.

6. Image formation (Examples 1 to 8, Comparative Example 1 and Comparative Example 2)
An image formation experiment was carried out by combining various inks produced above and various intermediate transfer members. Each experiment was designated as Example 1-8, Comparative Example 1 and Comparative Example 2 as shown in Table III.

(6.1) Step of Applying Active Ray Curable Ink to Intermediate Transfers An inkjet recording apparatus having an inkjet recording head equipped with a piezo-type inkjet nozzle for each of the inks 1 to 10 for each intermediate transfer. A square of 20 cm x 20 cm, respectively, under the condition of resolution of 720 x 720 dpi for each intermediate transfer material 1 to 10 introduced into "KM-1" (manufactured by Konica Minolta Co., Ltd.) and heated to 25 ° C. using a Perche cooling unit. A solid image (100% printing) was printed.
Each of the intermediate transcripts 1 to 10 used here has ultraviolet transparency.

The images printed on the intermediate transfer bodies 1 to 10 were irradiated with ultraviolet rays having a wavelength of 420 nm and an exposure amount of 10 mJ / cm ^{2 from the back surface side of the intermediate transfer bodies to thicken the respective inks.}
Then, ultraviolet rays having a ^{wavelength of 420 nm and an illuminance of 1 W / cm 2} were irradiated from the back surface side of each of the intermediate transfer bodies 1 to 10.

(6.2) Step of transferring active ray-curable ink to a recording medium (image transfer step)
Further, continuously, the ink was transferred to a recording medium (NPI128, manufactured by Oji Paper Co., Ltd.) by the transfer unit with the diameters of the upper and lower rollers being 80 mm and the nip width being 8 mm.
The pushing load at the time of transfer was usually a total surface pressure of 250 kPa / 515 mm.

(Dynamic viscoelasticity measurement during image transfer (measurement of ink storage elastic modulus))
Ink 1 was applied on a PET sheet to a thickness of 10 μm with a wire bar or the like, and the temperature at the time of transfer was adjusted to 40 ° C.
At this time, the temperature was adjusted with a hot plate set to the same temperature as the environmental temperature at the time of transfer.
DMA measurement was performed in this state.
When ink 1 was sandwiched in a cylindrical cell of 25 mmΦ and a dynamic viscoelasticity measurement was performed while applying a pressing load with 1 g, the storage elastic modulus E ″ _ink was 4000 Pa.

The intermediate transfer modulus 1 to 10 and the storage elastic modulus ratio (ink / belt) used for calculating the storage elastic modulus, temperature, and elastic modulus ratio of the ink during image transfer pre-exposure and image transfer in each ink 1 to 10 are It is as shown in Table IV.

(6.3) Step of main curing the active ray-curable ink At this time, the ink movement time from the irradiation of the active light beam from the front side to the entry into the nip by changing the apparatus configuration or the moving speed of the intermediate transfer body. (The movement time is 1) and the ink movement time (the movement time 2) from the irradiation of the active light beam from the front side to the discharge from the nip was changed for each test.

At the time of image formation, glycerin was used as a precoat solution. The viscosity of the precoat liquid at 25 ° C. was 2 × 10 ² mPa · s.
The viscosity of the precoat liquid can be measured using a stress-controlled rheometer (Physica MCR301 (cone plate diameter: 75 mm, cone angle: 1.0 °), manufactured by Antonio Par)).

The following method was used for the image formation using the inks 1 to 10.
(Image formation method)
The sheet on which the ink dots were landed was run (800 mm / s), and a UV exposure device was installed in front of the nip.
After 100 ms exposure, plain paper and uneven paper (Rezac 305 gsm) were used as the transfer paper that passed through the nip (upper and lower 80 mmΦ, nip width 8 mm) in contact with the transfer paper.

[evaluation]
Using inks 1 to 10, transferability and dot diameter were evaluated under the following conditions.

<Evaluation method of transferability>
A sheet with ink dots landed is run (800 mm / s), a UV exposure device (SPX-TA200, manufactured by REVOX) is installed in front of the nip (upper and lower 80 mmφ, width 8 mm), and after 100 ms exposure, transfer paper (unevenness). The nip was passed in contact with paper (Rezac 305 gsm).
Then, whether or not the ink was transferred from the intermediate transfer body to the recording medium was visually observed according to the following criteria.

(Evaluation criteria for transferability)
⊚: The transferability of the image is 90% or more.
◯: The transferability of the image is 80% or more and less than 90%.
X: The transferability of the image is less than 80%.

The ratio of the image area ratio after transfer to the area ratio of the original image is defined as the transfer ratio. The image area ratio can be measured from an optical microscope image.

<Evaluation method of dot diameter>
The enlargement of the dot diameter in the highlight part of the sheet on which the ink dots were landed was visually observed.
The dot diameter of the isolated dots in the image having a printing rate of 5% was observed, and the dot diameter before transfer and the rate of increase in the dot diameter after transfer marked with% were evaluated according to the following criteria.

(Evaluation criteria for dot diameter)
⊚: The rate of increase in dot diameter is less than 1%.
◯: The rate of increase in dot diameter is 1% or more and less than 5% ×: The rate of increase in dot diameter is 5% or more.

The diameter of the dots is taken as a value by observing the major axis on an optical microscope.

Table V shows the values and evaluation results obtained in Examples 1 to 8, Comparative Example 1 and Comparative Example 2.

表Ｖより、本発明の実施例の方が比較例より評価結果が優れていることがわかる。

From Table V, it can be seen that the examples of the present invention have better evaluation results than the comparative examples.

100 Image forming apparatus 110 Intermediate transfer body 120 Inking part 121 Intermediate image forming part 130 First thickening part 131 Second thickening part 140 Transfer nip (transfer part)
141 Pressurizing section 150, 151, 152 Support roller 160 Transport path 170 Hardened section 180 Recording medium 190 Cleaning section

Claims (9)

An image forming system that uses an image forming apparatus that transfers an image formed by an active ray-curable ink on an intermediate transfer body to a recording medium.
The intermediate transfer body is a laminate having at least one of an elastic layer or a base material layer, and is a laminate.
In the vertical dynamic viscoelasticity measurement of the laminate, the loss elastic modulus at a temperature of 40 ° C. and a frequency of 0.1 Hz is 10,000 Pa or more, and
An image forming system characterized in that the storage elastic modulus of the active ray-curable ink at the time of image transfer is larger than the storage elastic modulus of the intermediate transfer material. The image forming system according to claim 1, wherein the horizontal tensile elastic modulus of the intermediate transfer member is 3 MPa or less. The image forming system according to claim 1 or 2, wherein the contact angle of the surface of the intermediate transfer body with respect to pure water at a temperature of 40 ° C. is 70 ° or more. The elastic layer of the intermediate transfer body contains at least silicone rubber and an additive having an average primary particle size of 200 nm or less, and the content ratio of the additive is reduced in the vicinity of the surface. The image forming system according to any one of claims 1 to 3. The image forming system according to any one of claims 1 to 4, wherein the outermost surface layer of the intermediate transcript contains at least a molecule having a rotaxane structure. An image forming method using the image forming system according to any one of claims 1 to 5.
_{The feature is that the storage elastic modulus E ″ ink} when the temperature at the time of transfer of the image formed on the intermediate transfer body is 40 ° C. is within the range of 3 × 10 ^{1 to} 3 × 10 ^{3 Pa.} Image formation method to be performed. The image forming method according to claim 6, wherein the temperature specified at the time of transfer of the image formed on the intermediate transfer body is set to 40 ° C. ± 3 ° C. The image forming method according to claim 6 or 7, wherein an ink that does not substantially penetrate the paper is used as the active ray-curable ink. The invention according to any one of claims 6 to 8, wherein the image formed on the intermediate transfer body is exposed to ultraviolet rays before being transferred to adjust the viscosity of the active ray-curable ink. Image formation method.

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