JP2019078885A - Curable liquid developer - Google Patents

Abstract

To provide a curable liquid developer that has high developability and sufficient fixability and has good storage stability.SOLUTION: A curable liquid developer contains a radical polymerizable liquid monomer, a photopolymerization initiator, and toner particles. The molar average functional group number of the radical polymerizable liquid monomer is 1.02 or more and less than 1.40, and the content of the photopolymerization initiator is 0.10 parts by mass or more and 5.00 parts by mass or less based on 100 parts by mass of the radical polymerizable liquid monomer.SELECTED DRAWING: None

Description

  The present invention relates to a liquid developer used in an image forming apparatus utilizing an electrophotographic method such as electrophotography, electrostatic recording, electrostatic printing and the like.

In the electrophotographic method, the surface of an image carrier such as a photosensitive member is uniformly charged (charging step), and an electrostatic latent image is formed on the surface of the image carrier by exposure (exposure step). The latent electrostatic image is developed with a developer composed of colored resin particles (developing step), the developer image is transferred to a recording medium such as paper or plastic film (transfer step), and the transferred developer image is transferred to the recording medium Fixing (fixing step) is a method of obtaining a printed matter.
In this case, the developer is a dry developer using colored resin particles composed of a coloring agent such as a pigment and a material containing a binder resin in a dry state, and a liquid developer in which colored resin particles are dispersed in an electrically insulating liquid And roughly divided.
2. Description of the Related Art In recent years, needs for colorization and high-speed printing have been increasing for image forming apparatuses such as copying machines, facsimiles, and printers that use an electrophotographic method.
In color printing, high-resolution and high-quality images are required, and therefore developers that can form high-resolution and high-quality images and that can cope with high-speed printing are required.
A liquid developer is known as an advantageous developer in terms of color image reproducibility. In the liquid developer, fine toner particles can be used because aggregation of the colored resin particles in the liquid developer during storage is unlikely to occur. Therefore, the liquid developer is likely to obtain characteristics excellent in thin line image reproducibility and tone reproducibility.
Development of high-quality, high-speed digital printing apparatus utilizing electrophotographic technology using a liquid developer taking advantage of these excellent features is becoming popular. Under such circumstances, there is a need for the development of liquid developers having better properties.
Heretofore, as a liquid developer, one in which colored resin particles are dispersed in an electrically insulating liquid such as a hydrocarbon-based organic solvent or silicone oil is known. However, when the electrically insulating liquid remains on the recording medium such as paper or a plastic film, the image quality may be significantly reduced, and it has been necessary to remove the electrically insulating liquid.
For removing the electrically insulating liquid, a method of volatilizing and removing the electrically insulating liquid is generally applied by applying thermal energy. However, at that time, it is not necessarily preferable from the viewpoint of environment and energy saving, such as the possibility that the vapor of the organic solvent may be released to the outside of the apparatus and that a large amount of energy is required.
As a measure against this, a method of curing an electrically insulating liquid by photopolymerization has been proposed.
As a photocurable liquid developer, a monomer or an oligomer having a reactive functional group is used as an electrically insulating liquid, and a photopolymerization initiator is used to be dissolved.
The photocurable liquid developer is irradiated with light such as ultraviolet light to be reacted with a reactive functional group to be cured, and high speed response is also possible.

Patent Document 1 proposes such a photocurable liquid developer. In patent document 1, acrylate monomers, such as a urethane acrylate, are illustrated as a monomer which has a reactive functional group.
Patent Document 2 discloses an ink composition containing a polymerization accelerator containing an amine compound.

Unexamined-Japanese-Patent No. 2003-57883 JP, 2002-274004, A

In the case of using a radically polymerizable monomer such as an acrylate monomer as a photopolymerizable liquid proposed in Patent Document 1, if oxygen is present in the monomer, a side reaction by oxygen occurs to inhibit polymerization. It has been known.
In order to prevent this polymerization inhibition by oxygen, in Patent Document 2, a specific amine compound is added as a polymerization accelerator. The amine compound scavenges an oxygen-derived hydroxyper radical which causes polymerization inhibition, so that the photopolymerizable property of the radically polymerizable monomer can be improved.
However, in the liquid developer, when an amine compound as used in Patent Document 2 is used, the volume resistivity of the liquid developer decreases and the image density decreases, and defects such as image blurring and the like occur. There is a risk that image defects will occur, for example, if In addition, the fixability and storage stability may be reduced.

The present invention provides a curable liquid developer that solves the above-mentioned problems.
Specifically, the present invention provides a curable liquid developer having high developability, sufficient fixability, and good storage stability.

The present invention
A curable liquid developer comprising a radically polymerizable liquid monomer, a photopolymerization initiator, and toner particles,
The molar average functional group number of the radically polymerizable liquid monomer is 1.02 or more and less than 1.40,
The content of the photopolymerization initiator is 0.10 parts by mass or more and 5.00 parts by mass or less with respect to 100 parts by mass of the radical polymerizable liquid monomer.

  According to the present invention, it is possible to provide a curable liquid developer having high developability, sufficient fixability and good storage stability.

In the present invention, the descriptions of “more than or equal to or less than xxx” and “o to xxx” indicating numerical ranges mean numerical ranges including the lower limit and the upper limit which are end points unless otherwise noted.
Moreover, a monomer unit means the reacted form of the monomer substance in a polymer or resin.

The curable liquid developer of the present invention (hereinafter simply referred to as liquid developer) is
A curable liquid developer comprising a radically polymerizable liquid monomer, a photopolymerization initiator, and toner particles,
The molar average functional group number of the radically polymerizable liquid monomer is 1.02 or more and less than 1.40,
The content of the photopolymerization initiator is 0.10 parts by mass or more and 5.00 parts by mass or less with respect to 100 parts by mass of the radical polymerizable liquid monomer.

The inventors of the present invention conducted intensive studies on a curable liquid developer having both high developability and sufficient fixability, and found that the number of radically polymerizable functional groups possessed by the radically polymerizable liquid monomer is important.
Specifically, it was found that when the number of radically polymerizable functional groups possessed by the radically polymerizable liquid monomer is increased, the fixability is improved but the developability is lowered.
The reason for this is not clear, but it is believed that the fixability improves when the number of radically polymerizable functional groups is large, because the chance of association between the functional groups increases during radical polymerization and the radical reaction becomes easy to proceed.
On the contrary, the developability is lowered because the volume resistivity of the radically polymerizable liquid monomer is lowered.
When the number of radically polymerizable functional groups is increased, polarization occurs in the radically polymerizable liquid monomer molecule, and the molecule easily reacts to an electric field, so that the volume resistivity decreases.
From the above reasons, it is important to control the number of radically polymerizable functional groups of the radically polymerizable liquid monomer in order to obtain a curable liquid developer having both high developability and sufficient fixability.

The present inventors repeated studies on the number of radically polymerizable functional groups of the radically polymerizable liquid monomer, and when the molar average number of functional groups of the radically polymerizable liquid monomer is 1.02 or more and less than 1.40, the curable liquid It was found that the developability and fixability of the developer were compatible.
The molar average functionality is preferably 1.02 or more and 1.39 or less, and more preferably 1.04 or more and 1.39 or less.
When the molar average number of functional groups is less than 1.02, the fixability is insufficient.
On the other hand, when the molar average number of functional groups is 1.40 or more, the developability is lowered as the volume resistivity of the radically polymerizable liquid monomer is lowered.
The molar average number of functional groups can be adjusted by mixing radically polymerizable liquid monomers having different numbers of radically polymerizable functional groups per molecule in any ratio.

There are no particular restrictions on the type and number of radically polymerizable liquid monomers. However, the radically polymerizable liquid monomer contains a radically polymerizable liquid monomer having one radically polymerizable functional group per molecule, and a radically polymerizable liquid monomer having two radically polymerizable functional groups per molecule. It is preferable to do.
The radically polymerizable liquid monomer is composed of a radically polymerizable liquid monomer having one radically polymerizable functional group per molecule, and a radically polymerizable liquid monomer having two radically polymerizable functional groups per molecule. Is more preferred.
Furthermore, the molecular weight of the radically polymerizable liquid monomer having one radically polymerizable functional group per molecule and the molecular weight of the radically polymerizable liquid monomer having two radically polymerizable functional groups per molecule are all viscosities. From the viewpoint of adjustment, it is preferably 100 or more and 500 or less, and more preferably 100 or more and 400 or less. When the radically polymerizable liquid monomer is a high molecular weight monomer, the molecular weight may be weight average molecular weight (Mw) or number average molecular weight (Mn).

The radically polymerizable liquid monomer is not particularly limited as long as it is a liquid having high volume resistivity and electrical insulation. The radical polymerizable liquid monomer works as a carrier liquid of the curable liquid developer.
The carrier liquid may use only a radically polymerizable liquid monomer, or may be a mixture with a non-aqueous solvent other than the radically polymerizable liquid monomer as long as the effects of the present invention are not impaired. The radically polymerizable liquid monomer may be used alone or in combination of two or more.
When the carrier liquid is composed of only a radically polymerizable liquid monomer, the radically polymerizable liquid monomer itself in the curable liquid developer plays a role as a carrier liquid for dispersing toner particles.
Among the radically polymerizable liquid monomers, as a curable material curable by light such as ultraviolet light, acrylate compounds having a carbon-carbon double bond, thiol / ene composition (mixed composition of polythiol compound and polyene compound), etc. Can be mentioned.
As the curable material,
Polymer compounds such as polyethylene glycol diacrylate, polypropylene glycol diacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polyester acrylate, polyester methacrylate;
Styrene, 1,2-butadiene; tetrahydrofurfuryl acrylate, 2-hydroxyethyl acrylate, 2-ethylhexyl acrylate, N, N-dimethyl acrylamide, 4-hydroxybutyl acrylate, tricyclodecane methacrylate, cyclohexyl methacrylate, 2-hydroxyethyl methacrylate N-vinyl pyrrolidone, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol di Methacrylate, 1,9-nonanediol dimethacrylate, neopentyl glycol dimethacrylate, diethylene glycol dimethacrylate 1,4-butanediol dimethacrylate, EO-modified bisphenol A diacrylate (manufactured by Toagosei Co., Ltd.: M211B); monofunctional or 2 Kan'no monomeric compounds, such as
Multifunctional monomers such as pentaerythritol triacrylate, pentaerythritol tetraacrylate (manufactured by Toagosei Co., Ltd .: M-450), dipentaerythritol hexaacrylate, and trimethylolpropane triacrylate;
Mention may be made of methacryl modified silicone, silicone compounds in which an acryloyl group or methacryloyl group has been introduced, such as acrylic modified silicone, and the like.
Among them, the radically polymerizable functional group of the radically polymerizable liquid monomer is preferably an acryloyl group or a methacryloyl group.

The viscosity of the radically polymerizable liquid monomer at 25 ° C. is preferably 0.1 mPa · s or more and 200.0 mPa · s or less from the viewpoint of adjusting the viscosity of the curable liquid developer to a desired value, and 0. It is more preferably 1 mPa · s or more and 150.0 mPa · s or less, further preferably 0.1 mPa · s or more and 75.0 mPa · s or less, and is 0.1 mPa · s or more and 35.0 mPa · s or less Is particularly preferred.
Further, the volume resistivity of the carrier liquid is preferably 1.0 × 10 ¹⁰ Ω · cm or more and 1.0 × 10 ¹⁴ Ω · cm or less, and is 1.0 × 10 ¹⁰ Ω · cm or more. It is more preferable that it is 10 ¹³ Ω · cm or less.

The curable liquid developer contains a photopolymerization initiator that initiates the curing reaction of the radically polymerizable liquid monomer.
Examples of the photopolymerization initiator include benzophenone, benzoin isobutyl ether, benzoin ethyl ether, methyl benzoylbenzoate, benzyl, 4-chlorobenzophenone, 4-phenylbenzophenone, 4p-trithiobenzophenone, 2-hydroxy-2, 2 -Dimethylacetophenone, 2,2-diethoxyacetophenone, 2,4,6-trimethyl benzoyl phenyl ethoxy phosphine oxide, Lucillin TPO and Lucillin TPO-L manufactured by BASF, Irgacure 1850, Irgacure 1700, Irgacure 819, Irgacure 369 etc. Be
Among them, a photopolymerization initiator which strongly functions to accelerate the curing reaction of the radically polymerizable liquid monomer and which does not cause yellowing is preferable. For example, acyl phosphine oxide photopolymerization initiators (IRGACURE 819 described above; 2,4,6-trimethyl benzoylphenyl ethoxy phosphine oxide containing phosphorus in the molecular structure), alkylphenone photopolymerization initiators (Irgacure 369 described above), etc. Can be mentioned.
The said photoinitiator can be used individually by 1 type or in combination of 2 or more types.
Further, the photopolymerization initiator may be selected according to the radically polymerizable liquid monomer to be used.

The content of the photopolymerization initiator is 0.10 parts by mass or more and 5.00 parts by mass or less with respect to 100 parts by mass of the radical polymerizable liquid monomer.
The content of the photopolymerization initiator is preferably 0.50 parts by mass or more and 4.50 parts by mass or less with respect to 100 parts by mass of the radical polymerizable liquid monomer.
When the content of the photopolymerization initiator is less than 0.10 parts by mass, the amount of the photopolymerization initiator is insufficient, the reaction of the radically polymerizable liquid monomer is insufficient, and the fixability is lowered.
On the other hand, when the content of the photopolymerization initiator exceeds 5.00 parts by mass, a large amount of the photopolymerization initiator acts on the radically polymerizable liquid monomer with time to accelerate the curing reaction, and hence the curing type The storage stability of the liquid developer is reduced.

The toner particles preferably contain a binder resin and a colorant.
As the binder resin contained in the toner particles, known binder resins can be used as long as they are fixable to an adherend such as paper or a plastic film and are insoluble in the radical polymerizable liquid monomer.
Here, being insoluble in the radically polymerizable liquid monomer is an index that the toner particle component or binder resin to be dissolved is 1 part by mass or less with respect to 100 parts by mass of the radically polymerizable liquid monomer at a temperature of 25 ° C. .
Specific examples of the binder resin include vinyl resin, polyester resin, polyurethane resin, epoxy resin, polyamide resin, polyimide resin, silicon resin, phenol resin, melamine resin, urea resin, aniline resin, ionomer resin, polycarbonate resin, etc. Be
Among these, vinyl resins, polyester resins, polyurethane resins and epoxy resins are preferable, and polyester resins and vinyl resins are more preferable.

  Examples of the vinyl resin include methacrylic resin, acrylic resin, styrene acrylic resin, styrene methacrylic resin, polyethylene resin, ethylene methacrylic resin, ethylene acrylic resin and the like.

The polyester resin is not particularly limited, but is preferably a condensation product of a diol and a dicarboxylic acid. In addition, monohydric or trihydric or higher alcohols and carboxylic acids may be used to adjust the acid value and the SP value.
As diol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, neopentyl glycol, 1,4-butenediol, 1,4-cyclohexanedimethanol, ethylene oxide addition of bisphenol A And / or propylene oxide adducts and the like.
Examples of the monohydric alcohol include n-butanol, isobutanol, sec-butanol, n-hexanol, n-octanol, lauryl alcohol, 2-ethylhexanol, decanol, cyclohexanol, benzyl alcohol and dodecyl alcohol.
As trihydric or higher alcohols, aromatic alcohols such as 1,3,5-trihydroxymethylbenzene; pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentane Aliphatic alcohols such as triol, glycerin, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane and the like can be mentioned.

As a dicarboxylic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecenyl succinic acid, isodo Decenyl succinic acid, n-dodecyl succinic acid, isododecyl succinic acid, n-octenyl succinic acid, n-octyl succinic acid, iso octenyl succinic acid, isooctyl succinic acid, anhydrides of these acids and lower alkyl esters thereof It can be mentioned.
Examples of monovalent carboxylic acids include benzoic acid, naphthalenecarboxylic acid, salicylic acid, 4-methylbenzoic acid, 3-methylbenzoic acid, phenoxyacetic acid, biphenylcarboxylic acid, acetic acid, propionic acid, butyric acid, octanoic acid, decanoic acid and dodecane Examples of the acid include monocarboxylic acids such as stearic acid.
Examples of trivalent or higher carboxylic acids include aromatics such as 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, and pyromellitic acid. Aliphatic carboxylic acids such as aliphatic carboxylic acids, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, etc. And the lower alkyl esters thereof.

The acid value of the binder resin is preferably 5 mg KOH / g or more and 100 mg KOH / g or less, and more preferably 5 mg KOH / g or more and 50 mg KOH / g or less.
These resins can be used alone or in combination of two or more.
The SP value of the binder resin is preferably 9.0 or more and 15.0 or less, and more preferably 9.5 or more and 13.0 or less.
The SP value is a value obtained by calculation from the evaporation energy and molar volume of atoms and group by Fedors described in Fundamentals and Engineering of Coatings (page 53, Yuji Harasaki, Processing Technology Research Association). The unit of the SP value is (cal / cm ³ ) ^1/2 , but 1 (cal / cm ³ ) ^1/2 = 2.046 × 10 ³ (J / m ³ ) ^1/2 . m ³ ) It can be converted to a unit of ^1/2 .

The colorant contained in the toner particles is not particularly limited, and examples thereof include known organic pigments and inorganic pigments.
As specific examples of the pigment, for example, the following may be mentioned as those exhibiting yellow.
C. I. Pigment yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185; I. Bat Yellow 1, 3, 20.
Examples of red or magenta color include the following.
C. I. Pigment red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48: 2, 48: 3, 48: 4, 49, 50, 51, 52, 53, 54, 55, 57: 1, 58, 60, 63, 64, 68, 81: 1, 83, 87, 88, 89, 90, 112, 114, 122, 146, 147, 150, 163, 184, 202, 206, 207, 209, 238, 269; I. Pigment violet 19; C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35.
Examples of pigments exhibiting blue or cyan include the following.
C. I. Pigment blue 2, 3, 15: 2, 15: 3, 15: 4, 16, 17; C.I. I. Bat Blue 6; C.I. I. Acid Blue 45, a copper phthalocyanine pigment in which 1 to 5 phthalimidomethyl groups are substituted to a phthalocyanine skeleton.
Examples of pigments exhibiting a green color include the following.
C. I. Pigment green 7, 8, 36.
The following may be mentioned as pigments exhibiting an orange color.
C. I. Pigment orange 66, 51.
The following may be mentioned as pigments exhibiting a black color.
Carbon black, titanium black, aniline black.
The following are mentioned as a specific example of a white pigment.
Basic lead carbonate, zinc oxide, titanium oxide, strontium titanate.
For dispersing the pigment, for example, a dispersing apparatus such as ball mill, sand mill, attritor, roll mill, jet mill, homogenizer, paint shaker, kneader, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, etc. is used. be able to.
The content of the coloring agent is preferably 1 part by mass to 100 parts by mass and more preferably 5 parts by mass to 50 parts by mass with respect to 100 parts by mass of the binder resin.

It is also possible to add a pigment dispersant when dispersing the pigment.
As pigment dispersants, hydroxyl group-containing carboxylic acid esters, salts of long chain polyaminoamides and high molecular weight acid esters, salts of high molecular weight polycarboxylic acids, high molecular weight unsaturated acid esters, high molecular weight copolymers, modified polyacrylates, fats Group polyvalent carboxylic acid, naphthalene sulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester, pigment derivative and the like. It is also preferred to use commercially available pigment dispersants such as the Lubrizol Solsperse series.
Moreover, it is also possible to use a synergist corresponding to various pigments as a pigment dispersion aid.
The addition amount of the pigment dispersant and the pigment dispersion aid is preferably 1 part by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the pigment.

A curable liquid developer can also use a toner particle dispersant, if necessary.
The toner particle dispersant is one for stably dispersing toner particles in the curable insulating liquid.
The type of the toner particle dispersant is not particularly limited as long as the toner particles can be stably dispersed. In addition, it may be one that dissolves in a curable insulating liquid, or one that disperses without being dissolved.
The toner particle dispersant can be used singly or in combination of two or more.
Examples of the toner particle dispersing agent include Ajispar PB 817 (manufactured by Ajinomoto Fine Techno Co., Ltd.), Solspers S11200, S13940, S17000, S18000 (manufactured by Nippon Lubrisol Co., Ltd.) and the like.
The toner particle dispersant may be added in an amount of about 0.5 to 30 parts by mass with respect to 100 parts by mass of the toner particles.

The curable liquid developer may optionally contain a charge control agent. Known charge control agents may be used.
Specific compounds include the following.
Oils such as linseed oil and soybean oil; alkyd resins, halogen polymers, aromatic polycarboxylic acids, acid group-containing water-soluble dyes, oxidation condensates of aromatic polyamines, cobalt naphthenate, nickel naphthenate, iron naphthenate, naphthene Metal soaps such as zinc acid, cobalt octylate, nickel octylate, zinc octylate, cobalt dodecylate, nickel dodecylate, zinc dodecylate, aluminum stearate, cobalt 2-ethylhexanoate; petroleum-based metal sulfonates, Sulfonic acid metal salts such as metal salts of sulfosuccinic acid esters; phospholipids such as lecithin and hydrogenated lecithin; salicylic acid metal salts such as t-butylsalicylic acid metal complex; polyvinylpyrrolidone resin, polyamide resin, sulfonic acid-containing resin, hydroxybenzoic acid Derivatives etc

In the toner particles, if necessary, a charge adjuvant may be contained in order to adjust the chargeability of the toner particles. A publicly known thing can be utilized as said charge adjuvant.
Specific compounds include zirconium naphthenate, cobalt naphthenate, nickel naphthenate, iron naphthenate, zinc naphthenate, cobalt octylate, nickel octylate, zinc octylate, cobalt dodecylate, nickel dodecylate, zinc dodecylate And metal soaps such as aluminum stearate, aluminum tristearate and cobalt 2-ethylhexanoate; metal salts of petroleum-based metal salts of sulfonic acids and metal salts of sulfosuccinic esters; and phosphorus metal salts such as lecithin and hydrogenated lecithin Lipids; salicylic acid metal salts such as t-butylsalicylic acid metal complex; polyvinyl pyrrolidone resins, polyamide resins, sulfonic acid-containing resins, and hydroxybenzoic acid derivatives.

In addition to the above, even if various known additives are used in the curable liquid developer according to the purpose of recording medium compatibility, storage stability, image storability, and other performance improvements, as needed. Good.
For example, polymerization inhibitors, surfactants, lubricants, fillers, antifoaming agents, ultraviolet absorbers, antioxidants, anti-fading agents, anti-flashing agents, anti-rust agents, etc. may be mentioned, and these are appropriately selected and used be able to.

The method for producing the curable liquid developer is not particularly limited, and examples thereof include known methods such as coacervation and wet grinding.
As a general production method, a colorant, a binder resin and other additives, and a dispersion medium are mixed and pulverized using a bead mill or the like to obtain a dispersion of toner particles. A method of producing a curable liquid developer by mixing the obtained dispersion of toner particles, a photopolymerization initiator, a radically polymerizable monomer and the like can be exemplified.
The coacervation method is described in detail, for example, in JP-A-2003-241439, WO2007 / 000974, or WO2007 / 000975.
In the coacervation method, a pigment, a resin, a solvent that dissolves the resin, and a solvent that does not dissolve the resin are mixed, and the solvent that dissolves the resin is removed from the mixed solution, and the resin is in a dissolved state. The pigment particles can be dispersed in a solvent in which the resin is not dissolved.
On the other hand, the wet grinding method is described in detail, for example, in WO 2006/126566 or WO 2007/108485.
In the wet pulverizing method, the pigment and the binder resin are kneaded at a temperature higher than the melting point of the binder resin and then dry pulverized, and the pulverized product obtained is wet pulverized in an electrically insulating medium to obtain toner particles as an electrically insulating medium. It can be dispersed in it.
Such known methods can be used in the present invention.

The toner particles preferably have a volume average particle diameter of 0.05 μm or more and 5 μm or less, more preferably 0.05 μm or more and 1 μm or less, from the viewpoint of obtaining a high definition image.
The concentration of toner particles in the curable liquid developer is not particularly limited, but is preferably about 1% by mass to 70% by mass, and more preferably about 1% by mass to 50% by mass It is more preferable that the content be about 2% by mass to 40% by mass.

The curable liquid developer is preferably adjusted to have the following physical property values and used. That is, the viscosity at 25 ° C. of the curable liquid developer is preferably 0.1 mPa · s or more and 200.0 mPa · s or less from the viewpoint of obtaining appropriate electrophoretic mobility of the toner particles. More preferably, the viscosity is s or more and 150.0 mPa · s or less, and still more preferably 0.1 mPa · s or more and 75.0 mPa · s or less and 0.1 mPa · s or more and 35.0 mPa · s or less Is particularly preferred.
Further, the volume resistivity of the curable liquid developer is preferably 1 × 10 ⁹ Ω · cm or more and 1 × 10 ¹⁵ Ω · cm or less, and preferably 1 × 10 ¹⁰ Ω · cm or more, from the viewpoint of developability. × 10 ¹
More preferably, it is ³ Ω · cm or less.

The curable liquid developer can be suitably used in a general electrophotographic image forming apparatus.
As a curing method of the liquid developer, there are a method using ultraviolet light and a method using electron beam (EB).
In the curing method using ultraviolet light, after the liquid developer is transferred to the recording medium, the image is fixed by rapidly irradiating the ultraviolet light and curing it.
Here, a mercury lamp, a metal halide lamp, an excimer laser, an ultraviolet laser, a cold cathode tube, a hot cathode tube, a black light, an LED (light emitting diode), etc. are applicable as a light source for irradiating an ultraviolet ray. Among these, a strip-shaped metal halide lamp, a cold cathode tube, a hot cathode tube, a mercury lamp, a black light, or an LED is preferable.
The dose of ultraviolet rays is preferably 0.1~1000mJ / cm ^2, when considering power saving of the image forming apparatus is more preferably 0.1~500mJ / cm ^2.
In the curing method using ultraviolet light, heat fixing and ultraviolet light fixing may be used in combination. The heat fixing method is not particularly limited, such as heat roll fixing, back surface fixing, warm air fixing, and the like.

The measurement method used in the present invention is described below.
<Method of measuring volume resistivity>
For volume resistivity, put 25 mL of the sample into the liquid sample electrode SME-8330 (manufactured by Nichioki Electric Co., Ltd.) using a digital ultra-high resistance / micro-ammeter R8340A (manufactured by Advantest) and apply 1000 V DC at 25 ° C. Measure with

<Structural determination of compounds etc.>
The structure determination of compounds etc. uses the following method.
The spectrum measurement of < ¹ > H-NMR and < ¹³ > C-NMR is performed using JEOL Co., Ltd. ECA-400 (400 MHz).
The measurement is carried out at 25 ° C. in a deuterated solvent containing tetramethylsilane as an internal standard substance. Chemical shift values are shown as ppm shift values (δ values) where tetramethylsilane, which is an internal standard substance, is zero.

<Method of measuring viscosity>
The viscosity is measured as follows using a viscoelasticity measuring apparatus (Physica MCR 300, manufactured by Anton Paar Co., Ltd.).
About 2 mL of a sample is filled in a measuring device equipped with a cone-plate type measuring jig (75 mm diameter, 1 °) and adjusted to 25 ° C. The viscosity is measured while continuously changing the shear rate from 1000 s ⁻¹ to 10 s ^−1, and the value at 10 s ⁻¹ is taken as the viscosity.

<Method of measuring the number of polymerizable functional groups per molecule of the radically polymerizable liquid monomer, and the number of molar average functional groups>
In the present invention, the molar average number of functional groups means the number of moles of each compound component constituting the mixed system, that is, the average number of functional groups per molecule averaged in terms of the number of molecules in the mixed system of compounds.
Here, when one polymerizable functional group is present in one molecule of the radically polymerizable liquid monomer, the number of polymerizable functional groups per molecule is expressed as “1” (or monofunctional), and n are present. When it does, the number of polymerizable functional groups per molecule is expressed as "n" (or n functional).
The number of polymerizable functional groups per molecule of the radically polymerizable liquid monomer in the curable liquid developer and the molar average functional group are determined by the following method.
(1) The curable liquid developer is centrifuged to precipitate toner particles, and the supernatant is extracted.
(2) The molecular weight and content of the content are determined by measuring the supernatant with liquid chromatography and a mass spectrometer, and separated for each molecular weight component.
(3) The chemical structure of each component is identified by performing spectrum measurement of ¹ H-NMR and ¹³ C-NMR on each of the separated components, and the contained radically polymerizable liquid monomer The molecular weight, the content, and the number of polymerizable functional groups per molecule are determined.
Furthermore, although the chemical structure is identified here by ¹ H-NMR and ¹³ C-NMR spectrum measurement, known analytical methods such as infrared spectroscopy and gas chromatography may be used in combination as necessary. It is also possible.
(4) From the molecular weight and content of each component and the number of polymerizable functional groups per molecule calculated in the above (3), the molar average number of functional groups is determined according to the following formula.

For example, when two types of radically polymerizable liquid monomer A and radically polymerizable liquid monomer B are mixed as the radically polymerizable liquid monomer,
The number of polymerizable functional groups per molecule of the radically polymerizable liquid monomer A is (Af), the molecular weight is (Amw), and the content is (Awt) parts by mass,
When the number of polymerizable functional groups per molecule of the radically polymerizable liquid monomer B is (Bf), the molecular weight is (Bmw), and the content is (B wt) parts by mass,
Molar average functional group number of radically polymerizable liquid monomer =
{(Af × Awt / Amw) + (Bf × Bwt / Bmw)} / {(Awt / Amw) + (Bwt / Bmw)}
The above is a calculation formula in the case where the radically polymerizable liquid monomer is contained in two types of radically polymerizable liquid monomer A and radically polymerizable liquid monomer B, but also in the case where three or more types are contained. It can be similarly obtained by extending to a three-component system or more.

  Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited thereto. In the following description, “parts” and “%” mean “parts by mass” and “% by mass” unless otherwise noted.

  The types and physical properties of the radically polymerizable liquid monomer used in the examples are shown in Table 1.

<Production Example of Hardened Liquid Developer (D-1)>
(Preparation of Radically Polymerizable Liquid Monomer)
70 parts of B-1 and 30 parts of B-3 were mixed to prepare a radically polymerizable liquid monomer.
(Preparation of Toner Particle Dispersion)
In a separable flask, 25 parts of Nucrel N 1525 (ethylene-methacrylic acid resin, manufactured by Mitsui DuPont Chemical Co., Ltd.) and 80 parts of a radically polymerizable liquid monomer are charged, and stirred at 200 rpm using a three-one motor. The temperature was raised to 130 ° C. in a bath over 1 hour.
After holding at 130 ° C. for 1 hour, it was gradually cooled at a temperature drop rate of 15 ° C. per hour to prepare a binder resin dispersion. The obtained binder resin dispersion was in the form of a white paste.
59.40 parts of the binder resin dispersion, Pigment Blue 15: 3 (4.95 parts) as a pigment, 0.20 parts of aluminum tristearate as a charge aid, Solsperse S13940 (polyethylene polyamine and 12 hydroxy as a toner particle dispersant Planetary bead mill (Classic line P- with a 0.5 mm diameter zirconia beads, a reaction product with a stearic acid self-condensing product, 0.5 parts of Nippon Lubrisol Co., Ltd., and 34 parts of a radically polymerizable liquid monomer 6, filled with Fritsch, and wet ground at room temperature at 200 rpm for 4 hours to obtain a toner particle dispersion (solid content: 20% by mass).
The toner particles contained in the obtained toner particle dispersion had a volume average particle diameter (D50) of 0.85 μm. In addition, the dynamic light scattering method (DLS) particle-size-distribution measuring apparatus (Nanotrac 150, product made by Microtrack Bell, Inc.) was used for the measurement of volume average particle diameter.
(Preparation of liquid developer)
100 parts of a toner particle dispersion, 0.10 parts of hydrogenated lecithin (Resinol S-10, manufactured by Nikko Chemicals Co., Ltd.) as a charge control agent, 20 parts of a radically polymerizable liquid monomer, Irgacure 369 (BASF as a photopolymerization initiator) A 0.50 part of an α-aminoalkylphenone photopolymerization initiator (manufactured by Japan Co., Ltd.) was mixed to obtain a curable liquid developer (D-1). The prescription is shown in Table 2.

<Production Example of Cured Liquid Developer (D-2) to (D-13)>
In the production example of the curable liquid developer (D-1), (preparation of radically polymerizable liquid monomer)
The curable liquid developer (D) was prepared in the same manner as in Table 2 except that the type and amount of the radically polymerizable liquid monomer in and the amount of the photopolymerization initiator in (Preparation of liquid developer) were changed to those described in Table 2. -2)-(D-13) were manufactured. Each prescription is shown in Table 2.

Examples 1 to 9 and Comparative Examples 1 to 4
The curable liquid developers (D-1) to (D-13) were evaluated by the following method. The results are shown in Table 2.

<Evaluation of fixability>
At 25 ° C, a curable liquid developer is coated on a polyethylene terephthalate film with a wire bar (No. 6) (thickness: 8.0 μm), and a lamp output of 120 mW / cm ^{2 using} a high pressure mercury lamp: 200 mJ / cm ² (measurement It irradiated the light quantity of wavelength 365nm, and formed the cured film. The film surface immediately after curing was touched to confirm the presence or absence of surface tack (tackiness).
Below, the evaluation criteria of fixability are shown.
A: No surface tack is observed at all.
B: Slight surface tack is observed.
C: Surface tack is observed but generally good.
D: The membrane is not peeled off or cured at the time of the finger.

<Evaluation of developability>
An electrostatic pattern was formed on the electrostatic recording paper with a surface charge of 500V.
The resulting electrostatic pattern was developed using a liquid developer with a roller developing machine (process speed: 20 mm / sec) equipped with a metal roller. The quality of the obtained image was visually confirmed. The evaluation criteria of developability are shown below.
A: High density and high definition images were obtained.
B: Slight uneven density or slight image blurring is observed.
C: It can be seen that although the unevenness in density and the image blur are scattered, the development is generally good. D: Extreme density unevenness and image blurring occurred, and development was insufficient or development was not possible.

<Evaluation of storage stability>
Place 10 mL of a curable liquid developer in a test tube (12 mm diameter, 120 mm length), and measure the settled depth (the distance from the liquid surface to the surface formed by the settling of toner particles) after standing for 10 days did. Below, the evaluation criteria of storage stability are shown.
A: The sedimentation depth is greater than 0 mm and 3 mm or less.
B: The sedimentation depth is greater than 3 mm and less than 5 mm.
C: Settling depth is greater than 5 mm.

Claims (5)

A curable liquid developer comprising a radically polymerizable liquid monomer, a photopolymerization initiator, and toner particles,
The molar average functional group number of the radically polymerizable liquid monomer is 1.02 or more and less than 1.40,
A curable liquid developer, wherein the content of the photopolymerization initiator is 0.10 parts by mass or more and 5.00 parts by mass or less with respect to 100 parts by mass of the radical polymerizable liquid monomer.   The radically polymerizable liquid monomer contains a radically polymerizable liquid monomer having one radically polymerizable functional group per molecule, and a radically polymerizable liquid monomer having two radically polymerizable functional groups per molecule. The curable liquid developer according to claim 1.   The molecular weight of the radically polymerizable liquid monomer in which the radically polymerizable functional group per molecule is 1 and the molecular weight of the radically polymerizable liquid monomer in which the radically polymerizable functional group per molecule is 2 are 100 or more. The curable liquid developer according to claim 2, which is the following.   The curable liquid developer according to any one of claims 1 to 3, wherein a radically polymerizable functional group of the radically polymerizable liquid monomer is an acryloyl group or a methacryloyl group. The curable liquid developer according to any one of claims 1 to 4, wherein a molar average functional group number of the radically polymerizable liquid monomer is 1.04 or more and 1.39 or less.