JP6003035B2 - Image forming method and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming method and an image forming apparatus.

  Conventionally, an electrophotographic image forming method using a liquid developer in which toner is dispersed in a carrier liquid as a developer has been performed. In image formation with the liquid developer, various fixing methods have been tried.

For example, an infrared heater is installed at a position between a plurality of electrophotographic printing units installed in the web flow direction, and an infrared ray is irradiated from the infrared heater to a portion located between the printing units of the web. An electrophotographic printer that partially removes evaporation and partially fixes toner is disclosed (for example, see Patent Document 1).
Also disclosed is an electrophotographic printer having transfer fixing means for transferring at least toner particles from an intermediate member to a copy sheet and simultaneously fixing the toner particles on the copy sheet in the form of an image to create a copy of an original document. (For example, refer to Patent Document 2).

In addition, the visible image formed on the surface of the photosensitive drum by the developing device is dried by the dry gas supplied from the spray nozzle, and the carrier liquid remaining in the visible image is evaporated on the surface of the intermediate transfer roller. A photographic apparatus is disclosed (for example, see Patent Document 3).
Further, when the viscoelastic dynamic measurement value of the toner image transferred to the image support is measured at a forced vibration of 1 Hz and an amplitude stress of 10 Pa, the storage elastic modulus is in the range of 1.0E5 Pa to 1.0E8 Pa, and the loss Viscoelasticity control means for controlling the elastic modulus to be from 1.0E5 Pa to 1.0E8 Pa. As the viscoelasticity control means, the temperature of the toner image that satisfies the conditions of the above viscoelastic dynamic measurement values is measured in advance. There has been disclosed a liquid electrophotographic apparatus in which a heater is built in an intermediate transfer member as an image support, and a toner image is heated to the temperature by the heater (see, for example, Patent Document 4).

  In addition, an image output apparatus using a liquid development method is disclosed in which dry air is blown and sucked along the surface of an output medium to which a liquid developer is adhered (for example, Patent Document 5). reference).

JP 2011-033650 A Japanese Patent No. 2614865 Japanese Patent No. 3563023 JP 2004-333633 A Japanese Patent Laid-Open No. 06-130823

  An object of the present invention is to provide an image forming method in which the suppression of the occurrence of hot offset during fixing and the suppression of the occurrence of document offset in a toner image are compatible.

The above object is achieved by the following invention.
The invention according to claim 1
A charging step for charging the surface of the electrostatic latent image holding member;
A latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image holder;
A developing step of developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member with a liquid developer in which a toner containing at least a thermoplastic elastomer is dispersed in a carrier liquid to form a toner image; ,
A transfer step of transferring the toner image to a recording medium;
The toner image on the recording medium is heated and pressurized to form a toner image fixed on the recording medium, and the remaining amount of the carrier liquid contained in the toner image is reduced to the first remaining amount. Fixing process;
A residual amount adjusting step for reducing the residual amount of the carrier liquid contained in the toner image after the fixing step to a second residual amount lower than the first residual amount, wherein the carrier liquid is fixed on the recording medium. A remaining amount adjusting step of heating the toner image from the opposite side of the recording medium ;
Have
In the image forming method, the first remaining amount is 15% by mass or more based on the total amount of the toner image.

The invention according to claim 2
The image forming method according to claim 1, wherein the second remaining amount is 12% by mass or less based on the total amount of the toner image.
The invention according to claim 3
An electrostatic latent image carrier;
A charging device for charging the surface of the electrostatic latent image holding member;
A latent image forming apparatus that forms an electrostatic latent image on the surface of the electrostatic latent image holding member;
A toner containing at least a thermoplastic elastomer containing a liquid developer dispersed in a carrier liquid is stored, and the electrostatic latent image formed on the surface of the electrostatic latent image holding member is developed with the liquid developer. A developing device for forming an image;
A transfer device for transferring the toner image to a recording medium;
The toner image on the recording medium is heated and pressurized to form a toner image fixed on the recording medium, and the remaining amount of the carrier liquid contained in the toner image is reduced to the first remaining amount. A fixing device;
A residual amount adjusting device for reducing a residual amount of a carrier liquid contained in the toner image after the fixing to a second residual amount lower than the first residual amount, wherein the residual amount adjusting device is fixed to the recording medium. A remaining amount adjusting device for heating the toner image from the opposite side of the recording medium ;
Have
In the image forming apparatus, the first remaining amount is 15% by mass or more based on the total amount of the toner image.

The invention according to 請 Motomeko 4,
The image forming apparatus according to claim 3 , wherein the second remaining amount is 12% by mass or less based on the total amount of the toner image.

  According to the first aspect of the invention, the liquid developer in which the toner containing the thermoplastic elastomer is dispersed in the carrier liquid is used, and the remaining amount of the carrier liquid contained in the toner image in the fixing step is set to the first amount. Compared to the case where the remaining amount is reduced to the second remaining amount lower than the first remaining amount in the remaining amount adjusting step after the fixing step, the hot offset at the time of fixing is not satisfied. Thus, an image forming method is provided in which the suppression of occurrence of toner and the suppression of occurrence of document offset in a toner image are compatible.

Further , according to the first aspect of the present invention, there is provided an image forming method in which melting of the fixed toner image is suppressed as compared with the case where the toner image is not heated from the opposite side of the recording medium in the remaining amount adjusting step. The

According to the invention of claim 3 , the liquid developer in which the toner containing the thermoplastic elastomer is dispersed in the carrier liquid is used, and the remaining amount of the carrier liquid contained in the toner image in the fixing device is set to the first amount. Compared to the case where the remaining amount adjusting device after fixing by the fixing device does not satisfy the requirement to reduce to the second remaining amount lower than the first remaining amount, the fixing amount is less The present invention provides an image forming apparatus in which the suppression of occurrence of hot offset and the suppression of occurrence of document offset in a toner image are compatible.

Furthermore , according to the invention of claim 3, there is provided an image forming apparatus in which the fixing of the fixed toner image is suppressed as compared with the case where the toner image is not heated from the opposite side of the recording medium in the remaining amount adjusting device. The

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows another example of the image forming apparatus of this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail.

<Image Forming Method and Image Forming Apparatus>
The image forming method according to the present embodiment includes a charging step for charging the surface of the electrostatic latent image holding member, a latent image forming step for forming an electrostatic latent image on the surface of the electrostatic latent image holding member, and the static image forming step. A developing step in which the electrostatic latent image formed on the surface of the electrostatic latent image holding member is developed with a liquid developer in which a toner containing at least a thermoplastic elastomer is dispersed in a carrier liquid to form a toner image; A transfer step of transferring a toner image to a recording medium, and heating and pressurizing the toner image on the recording medium to form a toner image fixed on the recording medium, and the carrier liquid contained in the toner image A fixing step for reducing the residual amount to the first residual amount, and a residual amount of the carrier liquid contained in the toner image after the fixing step to a second residual amount lower than the first residual amount. A remaining amount adjusting step .

  The image forming apparatus according to the present embodiment includes an electrostatic latent image holding member, a charging device that charges the surface of the electrostatic latent image holding member, and an electrostatic latent image on the surface of the electrostatic latent image holding member. A latent image forming apparatus for forming, and a liquid developer in which a toner containing at least a thermoplastic elastomer is dispersed in a carrier liquid and storing the electrostatic latent image formed on the surface of the electrostatic latent image holding member. A developing device that forms a toner image by developing with a liquid developer, a transfer device that transfers the toner image to a recording medium, and the toner image on the recording medium is heated and pressed to be fixed to the recording medium. A fixing device which forms a toner image and reduces the residual amount of carrier liquid contained in the toner image to a first residual amount, and the residual amount of carrier liquid contained in the toner image after the fixing. Second lower than the first remaining amount Having a residual amount adjusting apparatus for reducing to a residual amount.

  In electrophotographic image formation using a liquid developer, a liquid developer in which toner containing a thermoplastic elastomer is dispersed is used from the viewpoint of improving the bending resistance of the formed toner image. However, the thermoplastic elastomer has a high carrier liquid absorbability, the residual amount of the carrier liquid in the formed toner image increases, and the binder resin component in the toner image after being fixed on the recording medium melts to form the recording medium. May adhere to the back side of the paper or other printed matter and cause a document offset that results in an image defect. A method of increasing the temperature at which the toner is fixed on the recording medium and reducing the remaining amount of the carrier liquid is also conceivable. However, in this case, the molten toner is transferred to the fixing member at a higher temperature and the toner is transferred. Hot offsets that cause image division may occur.

  In contrast, in the image forming method and the image forming apparatus according to the present embodiment, in an aspect in which image formation is performed using a liquid developer in which a toner containing at least a thermoplastic elastomer is dispersed in a carrier liquid, The residual amount of carrier liquid contained in the toner image during fixing is reduced to the first residual amount, and the residual amount of carrier liquid contained in the toner image after the fixing is reduced to the first residual amount. Reduce to a second residual amount lower than the amount. Since the plasticizing effect is obtained by not excessively reducing the residual amount of the carrier liquid in the toner image at the time of fixing, the fixing is performed well without raising the temperature of the fixing member, and low temperature fixability is obtained. And the occurrence of hot offset is effectively suppressed. In addition, by reducing the amount of carrier liquid in the toner image after fixing, document offset caused by melting of the binder resin component in the finally obtained toner image is suppressed, and high image durability is achieved. Is done.

-First and second remaining amount-
In the fixing step (fixing device) that heats and pressurizes the toner image on the recording medium, the remaining amount of the carrier liquid contained in the toner image (first remaining amount) is 15 mass with respect to the total amount of toner. % Or more is preferable. By setting it as this range, generation | occurrence | production of a hot offset is suppressed more effectively.

  Further, in the remaining amount adjusting step after fixing (residual amount adjusting device), the residual amount of the carrier liquid (second residual amount) contained in the toner image is set to a range of 12% by mass or less with respect to the total amount of toner. It is preferable. By setting this range, the occurrence of document offset is more effectively suppressed in the finally obtained toner image.

-Measurement of remaining amount of carrier liquid-
The remaining amount of the carrier liquid in the toner image is measured by performing thermal analysis using TGA-50 manufactured by Shimadzu Corporation. More specifically, the amount of residual carrier liquid contained in the toner is determined by heating the toner at a rate of change of 10 ° C./min in the range of 25 ° C. to 500 ° C. and measuring the mass before and after that. Calculated as a mass ratio with respect to the toner mass.

  Hereinafter, the configuration of the image forming method and the image forming apparatus according to the present embodiment will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present embodiment.
The image forming apparatus 100 includes a photosensitive member (electrostatic latent image holding member) 10, a charging device 20, an exposure device (latent image forming device) 12, a developing device 14, an intermediate transfer member 16, a cleaner 18, a transfer fixing roller (transfer and transfer roller). The image forming apparatus includes a transfer fixing device (which also serves as fixing) 28 and a drying device (residual amount adjusting device) 32. The photosensitive member 10 has a cylindrical shape, and a charging device 20, an exposure device 12, a developing device 14, an intermediate transfer member 16, and a cleaner 18 are sequentially provided on the outer periphery of the photosensitive member 10 and transferred to the intermediate transfer member 16. A transfer fixing roller 28 is provided at a position where the toner image 26 transferred to the paper (recording medium) 30 is fixed, and a drying device (remaining amount) is provided downstream of the transfer fixing roller 28 in the traveling direction of the paper 30. An adjusting device) 32 is provided.
The operation of the image forming apparatus 100 will be briefly described below.

The charging device 20 charges the surface of the photoconductor 10 to a predetermined potential, and based on the image signal, the exposure device 12 exposes the charged surface with, for example, a laser beam to form an electrostatic latent image.
The developing device 14 includes a developing roller 14a and a developer storage container 14b. The developing roller 14a is provided such that a part thereof is immersed in the liquid developer 24 stored in the developer storage container 14b. The liquid developer 24 is formed by dispersing toner particles containing a thermoplastic elastomer in a carrier liquid.
In the liquid developer 24, the toner particles are dispersed. However, for example, the liquid developer 24 may be further stirred by a stirring member provided in the developer storage container 14b.

  The liquid developer 24 supplied to the developing roller 14a is conveyed to the photoconductor 10 in a state where the liquid supply 24 is limited to a constant supply amount by the regulating member, and at a position where the developing roller 14a and the photoconductor 10 are close (or in contact). It is supplied to the electrostatic latent image. As a result, the electrostatic latent image is visualized and becomes a toner image 26.

  The developed toner image 26 is conveyed to the photosensitive member 10 that rotates in the direction of arrow B in the figure, and is transferred to a sheet (recording medium) 30. In the present embodiment, before being transferred to the sheet 30, the recording medium The toner image is once transferred to the intermediate transfer body 16 in order to transfer the toner image to the toner image and fix the toner image. At this time, a peripheral speed difference may be provided between the photosensitive member 10 and the intermediate transfer member 16.

Next, the toner image conveyed in the direction of the arrow C by the intermediate transfer member 16 is transferred and fixed to the paper 30 at the contact position with the transfer fixing roller 28.
The transfer fixing roller 28 presses the toner image 26 with the sheet 30 interposed between the intermediate transfer body 16 and the toner image on the intermediate transfer body 16 is brought into close contact with the sheet 30. As a result, the toner image is transferred to the paper 30, and the toner image is fixed on the paper to become a toner image 29. The toner image 26 is fixed by providing a heat generating member on the transfer fixing roller 28 and applying pressure and heating.

  If the intermediate transfer body 16 has a roller shape as shown in FIG. 1, it forms a roller pair with the transfer fixing roller 28. Therefore, the intermediate transfer body 16 and the transfer fixing roller 28 respectively conform to the fixing roller and the opposing roller in the fixing device. It shows a fixing function. That is, when the paper 30 passes through the nip, the toner image is transferred and heated and pressed against the intermediate transfer member 16 by the transfer and fixing roller 28, and the binder resin in the toner particles constituting the toner image is changed. As the toner image softens, the toner image infiltrates into the fibers of the paper 30, and a toner image 29 fixed on the paper 30 is formed.

  In this embodiment, when the toner image 26 is fixed on the paper 30 by the transfer fixing roller 28, the remaining amount of the carrier liquid contained in the fixed toner image is reduced to the first remaining amount. The first remaining amount is preferably in the range of 15% by mass or more based on the total amount of toner as described above. The fixing temperature is usually adjusted in the range of 120 ° C. to 200 ° C., and the first remaining amount is adjusted by adjusting the fixing temperature.

  In this embodiment, the fixing is performed together with the transfer to the paper 30. However, the transfer process and the fixing process may be separately performed, and the fixing may be performed after the transfer. In this case, the transfer roller for transferring the toner image from the photoconductor 10 has a function according to the intermediate transfer body 16.

  A drying device (residual amount adjusting device) 32 is provided downstream of the transfer and fixing roller 28 in the paper 30 traveling direction. The drying device 32 is a plate-like heating device, and a heater is provided inside a plate-like body whose surface is made of metal. The sheet 30 is dried at the position of the drying device 32 and then conveyed to a discharge unit (not shown).

  The drying device (residual amount adjusting device) 32 reduces the residual amount of the carrier liquid contained in the toner image to the second residual amount. As described above, the second remaining amount is preferably set to a range of 12% by mass or less with respect to the total amount of toner. The temperature during drying is preferably adjusted in the range of 100 ° C. or more and 200 ° C. or less, and the second remaining amount is adjusted by adjusting the temperature and the drying time.

On the other hand, the photosensitive member 10 having the toner image 26 transferred to the intermediate transfer member 16 is conveyed to a contact position with the untransferred toner particle cleaner 18 and collected by the cleaner 18. If the transfer efficiency is close to 100% and residual toner is not a problem, the cleaner 18 may not be provided.
The image forming apparatus 100 may further include a neutralization device (not shown) that neutralizes the surface of the photoconductor 10 after the transfer and before the next charging.
The charging device 20, the exposure device 12, the developing device 14, the intermediate transfer member 16, the transfer fixing roller 28, the cleaner 18, and the drying device 32 provided in the image forming apparatus 100 are all synchronized with the rotational speed of the photosensitive member 10. Has been operating.

  Next, another aspect of the image forming apparatus according to this embodiment will be described in detail with reference to the drawings.

FIG. 2 is a schematic configuration diagram illustrating an example of another aspect of the image forming apparatus according to the present embodiment, and is a diagram illustrating a tandem image forming apparatus.
The image forming apparatus illustrated in FIG. 2 includes a cyan developing unit 101-C, a magenta developing unit 101-M, a yellow developing unit 101-Y, and a black developing unit 101-K. Each developing unit includes a developer tank 102, a developer supply roll 103, a supply amount regulating means 104, a developing roll (developing device) 105, a developing roll cleaner 106, a photosensitive member (electrostatic latent image holding member) 107, and a charging device 108. , An exposure device (latent image forming device) 109, a primary transfer device 110, and a photoreceptor cleaner 111. Further, an intermediate transfer member 125 is provided so as to be in contact with each of the photosensitive members 107 of the four developing units, and a secondary transfer device 124 that further transfers the toner image transferred to the intermediate transfer member 125 onto a sheet (recording medium) 127, 126 is provided. A fixing unit (fixing device) 131 is provided downstream of the secondary transfer devices 124 and 126 in the traveling direction of the paper 127, and a drying device (residual amount adjusting device) 135 is provided downstream of the fixing unit 131. It is done.

  The liquid developer 112 is maintained in a predetermined amount in the developer tank 102 by a developer circulation means (not shown), and is conveyed from the developer tank 102 to the developing roll 105 by the developer supply roll 103. The developer supply roll 103 includes a system in which the surface is charged and the developer is attached by an electrostatic force, and a system in which a groove or a recess is provided in the roll to convey the liquid so as to be supplied. 104 regulates the transport amount to a predetermined value. The photosensitive member 107 is charged by a charging device 108 so that the surface has a predetermined charging bias amount, and an electrostatic latent image is formed on the surface by a light beam from the exposure device 109 in accordance with an image signal sent from a host computer (not shown). It is formed. The liquid developer on the developing roll 105 is transferred to the photoreceptor 107 in accordance with the electrostatic latent image to form a toner image. Unnecessary developer is removed from the developer tank 102 by the developing roll cleaner 106 and a developer circulating means (not shown). Returned to

  The toner image formed on the photosensitive member 107 is transferred to the intermediate transfer member 125 by the primary transfer device 110. The intermediate transfer body 125 is supported by a drive roll 121, support rolls 122 and 123, and a secondary transfer device 124. The drive roll 121 drives the intermediate transfer body 125 in the direction of the arrow by a drive motor and a power transmission mechanism (not shown). Further, a tension determined by a spring mechanism (not shown) is applied to the intermediate transfer body 125. The primary transfer device 110 sequentially transfers cyan, magenta, yellow, and black toner images to the intermediate transfer member 125 by electrostatic force and pressure. The primary transfer device 110 for each color may make a difference in the set potential. The liquid developer remaining on the photoconductor 107 is removed by the photoconductor cleaner 111.

  The toner image transferred to the intermediate transfer member 125 is transferred to a sheet (recording medium) 127 by the secondary transfer devices 124 and 126 and further fixed by the fixing unit 131. The fixing unit 131 includes a roll pair of a heat roll 132 and a pressure roll 133 and a heater 134 provided inside each roll. The heat roll 132 and the pressure roll 133 form an elastic rubber layer and a release layer for releasing the toner on a metal roll, and a sheet 127 is formed by a pressure mechanism (not shown) so as to obtain a predetermined pressure and nip width. Is sandwiched.

  In this embodiment, when the toner image is fixed on the paper 127 by the fixing unit 131, the remaining amount of the carrier liquid contained in the fixed toner image is reduced to the first remaining amount. The first remaining amount is preferably in the range of 15% by mass or more based on the total amount of toner as described above. The fixing temperature is usually adjusted in the range of 120 ° C. to 200 ° C., and the first remaining amount is adjusted by adjusting the fixing temperature.

  A drying device (residual amount adjusting device) 135 is provided downstream of the fixing unit 131. The drying device 135 has a configuration in which a release layer is formed on the surface of a metal roll, and a heater is provided inside the metal roll. At the position of the drying device 135, the paper 127 is conveyed to a discharge unit (not shown) along a path so as to be wound around a roll.

  The drying device (residual amount adjusting device) 135 reduces the residual amount of the carrier liquid contained in the toner image to the second residual amount. As described above, the second remaining amount is preferably set to a range of 12% by mass or less with respect to the total amount of toner. The temperature during drying is preferably adjusted in the range of 100 ° C. or more and 200 ° C. or less, and the second remaining amount is adjusted by adjusting the temperature.

In addition, as shown in the drying device (residual amount adjusting device) 32 in FIG. 1 and the drying device (residual amount adjusting device) 135 in FIG. When used, it is desirable to contact and heat from the opposite side of the paper (recording medium).
Further, as the remaining amount adjusting device, a plate-like heating device is shown in FIG. 1 and a roll-like heating device is shown in FIG. 2, but the present invention is not limited to this. An irradiation device or the like that irradiates light may be applied.

  Next, the liquid developer used in the image forming method and the image forming apparatus according to the present embodiment will be described.

[Liquid developer]
The liquid developer is obtained by dispersing a toner containing at least a thermoplastic elastomer in a carrier liquid. Further, other additives such as a binder resin other than the thermoplastic elastomer, a colorant, a wax, a charge control agent, silica powder, and a metal oxide may be contained. These additives may be added internally by, for example, kneading into a binder resin, or may be added externally by, for example, carrying out a mixing process after obtaining toner as particles. In general, a colorant is included, but when a transparent toner is used, the colorant may not be included.

[Toner particles]
-Thermoplastic elastomer-
Examples of the thermoplastic elastomer contained in the toner particles of this embodiment include those having rubber properties at normal temperature (25 ° C.) and softening properties similar to thermoplastics at high temperatures. Examples of the thermoplastic elastomer include polymethyl methacrylate-polybutyl butyl acrylate-polymethyl methacrylate block copolymer, polymethyl methacrylate-polydodecyl methacrylate-polymethyl methacrylate block copolymer, polymethacrylate. Examples include methyl methacrylate-polyethyl 2-ethylhexyl methacrylate-polymethyl methacrylate block copolymer, polymethyl methacrylate-polylauryl methacrylate-polymethyl methacrylate block copolymer, and the like.

  Examples of the styrenic thermoplastic elastomer include polystyrene-polybutadiene-polystyrene, polystyrene-polybutadiene / butylene-polystyrene, polystyrene-polyethylene / butylene-polystyrene, polystyrene-polyisoprene-polystyrene, polystyrene-hydrogenated polybutadiene-polystyrene, polystyrene. -Hydrogenated polyisoprene-polystyrene, polystyrene-hydrogenated poly (isoprene / butadiene) -polystyrene and the like.

  Examples of the weight average molecular weight of the thermoplastic elastomer resin include a range of 30,000 to 300,000.

  The content of the thermoplastic elastomer in the toner particles is desirably 10% by mass or more in the total binder resin, and more desirably 50% by mass or less.

-Binder resin-
As the binder resin contained in the toner particles of the present embodiment, an acrylic thermoplastic resin is first mentioned. Examples of the acrylic thermoplastic resin include a vinyl copolymer containing a polymer of a methacrylic acid ester monomer or a polymer of an acrylate monomer as a constituent unit. Hereinafter, “(meth) acryl” means either or both of acrylic and methacrylic.
Examples of the (meth) acrylic acid ester monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic. In addition to alkyl esters of (meth) acrylic acid such as isobutyl acid, n-octyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl acrylate, stearyl (meth) acrylate, 2-chloroethyl acrylate, Phenyl (meth) acrylate, methyl α-chloroacrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, glycidyl (meth) acrylate Dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, Glycidyl methacrylate, polyethylene glycol dimethacrylate, etc. methacryloxyethyl phosphate. Among these, methyl methacrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, and the like are desirably used.

In addition to the above (meth) acrylic acid ester monomers, other vinyl monomers include acrylic acid such as acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, and α- or β-alkyl derivatives thereof. ; Unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, itaconic acid and the like, and monoester derivatives or diester derivatives thereof; succinic acid mono (meth) acryloyloxyethyl ester, (meth) acrylonitrile, acrylamide, etc. are used Also good.
Further, a copolymer with a styrene monomer may be used, and it is desirable to use it within 10% by mass of the entire resin.

  The vinyl polymer preferably has a weight average molecular weight (Mw) of 10,000 to 500,000. The molecular weight distribution (Mw / Mn) is preferably 2 or more and 20 or less.

  Examples of binder resins other than those described above contained in the toner particles include known binder resins. Examples thereof include polyester, polyethylene, polypropylene, polyurethane, epoxy resin, silicone resin, polyamide, and modified rosin.

  The content of the binder resin other than the thermoplastic elastomer in the toner particles is desirably 50% by mass or more and 90% by mass or less in the total binder resin.

  As the colorant, a known pigment or dye is used. Specifically, the following yellow, magenta, cyan, and black pigments are used.

As yellow pigments, compounds represented by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complex compounds, methine compounds, and allylamide compounds are used.
As the magenta pigment, condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds are used.
As cyan pigments, copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, basic dye lake compounds, and the like are used.
As the black pigment, carbon black, aniline black, acetylene black, iron black and the like are used.

  The wax is not particularly limited. For example, plant wax such as carnauba wax, wood wax, rice bran wax; animal wax such as beeswax, insect wax, whale wax, wool wax; mineral wax such as montan wax, ozokerite, etc. , Synthetic fatty acid solid ester waxes such as Fischer-Tropsch wax (FT wax) having ester in the side chain, special fatty acid ester, polyhydric alcohol ester; paraffin wax, polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, polyamide wax, and And synthetic waxes such as silicone compounds. Only one type of wax may be used, or two or more types of wax may be used.

  There is no restriction | limiting in particular as a charge control agent, A conventionally well-known charge control agent is used. For example, positively chargeable charge control agents such as nigrosine dye, fatty acid-modified nigrosine dye, carboxyl group-containing fatty acid-modified nigrosine dye, quaternary ammonium salt, amine compound, amide compound, imide compound, organometallic compound; oxycarboxylic acid And a negatively chargeable charge control agent such as a metal complex of an azo compound, a metal complex salt dye, or a salicylic acid derivative. Only one type of charge control agent may be used, or two or more types may be used.

The metal oxide is not particularly limited, and examples thereof include titanium oxide, aluminum oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, magnesium titanate, and calcium titanate. Only one type of metal oxide may be used, or two or more types may be used.
The components other than the acrylic thermoplastic elastomer and the acrylic thermoplastic resin are preferably 50% by mass or less.

-Toner Particle Manufacturing Method-
The method for producing the toner particles of this embodiment is not particularly limited. For example, the toner particles can be obtained by pulverizing a pulverized toner, a liquid emulsion-dried toner, or a toner produced by a polymerized toner production method in a carrier liquid.
For example, a binder resin containing a thermoplastic elastomer, a colorant, and if necessary, other additives are mixed in a mixing apparatus such as a Henschel mixer, and the mixture is mixed with a twin-screw extruder, a Banbury mixer, a roll mill, After melt-kneading with a kneader, etc., cool with a drum flaker, etc., coarsely pulverize with a pulverizer such as a hammer mill, and further finely pulverize with a pulverizer such as a jet mill, followed by classification using an air classifier, etc. Thus, a pulverized toner can be obtained.

  Also, a binder resin containing a thermoplastic elastomer, a colorant, and if necessary, other additives are dissolved in a solvent such as ethyl acetate and emulsified / suspended in water to which a dispersion stabilizer such as calcium carbonate has been added. After removing the solvent, the particles obtained by removing the dispersion stabilizer are filtered and dried to obtain an in-liquid emulsified dry toner.

  In addition, a polymerizable monomer, a colorant, and a polymerization initiator (for example, benzoyl peroxide, lauroyl peroxide, isopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichloroylbenzoyl peroxide) that form a binder resin , Methyl ethyl ketone peroxide, etc.) and other additives are added to the aqueous phase under agitation and granulated. After the polymerization reaction, the particles are filtered and dried to obtain a polymerized toner.

  The blending ratio of each material (binder resin containing thermoplastic elastomer, colorant, other additives, etc.) when obtaining toner takes into account the required bending resistance, scratch resistance, low temperature fixability, color, etc. To set. The obtained toner is finely pulverized in a carrier oil using a known pulverizer such as a ball mill, a bead mill, a high-pressure wet atomizer, etc., whereby the toner particles for liquid developer of this embodiment are obtained.

  The volume average particle diameter D50v of the toner particles is desirably 0.5 μm or more and 5.0 μm or less. The volume average particle diameter D50v of the toner particles is more desirably 0.8 μm or more and 4.0 μm or less, and further desirably 1.0 μm or more and 3.0 μm or less.

For the volume average particle size D50v, number average particle size distribution index (GSDp), volume average particle size distribution index (GSDv), etc. of the toner particles, a laser diffraction / scattering type particle size distribution measuring device, for example, LA920 (manufactured by Horiba Ltd.) is used. Measured. Draw a cumulative distribution from the smaller diameter side for each particle size range (channel) divided based on the particle size distribution, and particles with a cumulative particle size of 16%, volume D16v, number D16p, and cumulative 50% The diameter is defined as volume D50v, number D50p, and the particle diameter at 84% cumulative is defined as volume D84v, number D84p. Using these, the volume average particle size distribution index (GSDv) is calculated as (D84v / D16v) ^1/2 and the number average particle size distribution index (GSDp) is calculated as (D84p / D16p) ^1/2 .

[Carrier liquid]
The carrier liquid is an insulating liquid for dispersing the toner particles, and is not particularly limited. For example, an aliphatic hydrocarbon solvent such as paraffin oil (a commercially available product, Moresco White MT-manufactured by Matsumura Oil Co., Ltd.). 30P, Moresco White P40, Moresco White P70, Exxon Chemical Co. Isopar L, Isopar M, etc., hydrocarbon solvents such as naphthenic oils (exon products are Exxon Chemical Exxol D80, Exol D110, Exol D130) , Nippon Petrochemical Co., Ltd., Naphthezol L, Naphthezol M, Naphthezol H, New Naphthezol 160, New Naphthezol 200, New Naphthezol 220, New Naphthezol MS-20P, etc.), and aromatic compounds such as toluene are included in them. You may make it contain.

The flash point of the carrier liquid is preferably 50 ° C. or higher and 180 ° C. or lower, and more preferably 70 ° C. or higher and 140 ° C. or lower.
The flash point is measured according to JIS K 2265-4 (2007).

  Only one type of carrier liquid may be included in the liquid developer of this embodiment, or two or more types may be used. When the carrier liquid is used as a mixed system of two or more kinds, for example, a mixed system of paraffinic solvent and vegetable oil, a mixed system of silicone solvent and vegetable oil, and a mixed system of paraffinic solvent and vegetable oil are used. It is desirable to be.

  The carrier liquid is made of various auxiliary materials such as dispersants, emulsifiers, surfactants, stabilizers, wetting agents, thickeners, foaming agents, antifoaming agents, coagulants, gelling agents, anti-settling agents, charging agents. It may contain a control agent, an antistatic agent, an anti-aging agent, a softening agent, a plasticizer, a filler, a flavoring agent, an anti-tacking agent, a release agent and the like.

[Method for producing liquid developer]
In the liquid developer, the toner particles and the carrier liquid described above are mixed using, for example, a dispersing machine such as a ball mill, a sand mill, an attritor, or a bead mill, and pulverized to disperse the toner particles in the carrier liquid. Is obtained.
The dispersion of the toner particles in the carrier liquid is not limited to a disperser, and may be dispersed by rotating a special stirring blade at a high speed like a mixer, or by the shearing force of a rotor / stator known as a homogenizer. Alternatively, it may be dispersed by ultrasonic waves.

  The concentration of the toner particles in the carrier liquid is preferably in the range of 0.5% by mass to 40% by mass, and more preferably in the range of 1% by mass to 30% by mass.

  Thereafter, the obtained dispersion may be filtered using, for example, a membrane filter having a pore size of 100 μm to remove dust and coarse particles.

  Hereinafter, although an example is given and it demonstrates more concretely, the following example does not restrict | limit this invention.

Example 1
<Production of developer>
Cyan pigment C.I. was added to 60 parts by mass of styrene acrylic resin (FSR-051 manufactured by Fujikura Kasei Co., Ltd., weight average molecular weight 380,000). I. 40 parts by mass of Pigment Blue 15: 3 (manufactured by Clariant Co., Ltd.) was added and kneaded with a pressure kneader. The kneaded product was coarsely pulverized to prepare a cyan pigment master batch.

Next, a mixture having the following composition was kneaded with a Banbury mixer.
-Cyan pigment master batch: 25 parts by mass-Styrene acrylic resin (FSR-053 manufactured by Fujikura Kasei Co., Ltd., weight average molecular weight 320,000, acid value 10): 57 parts by mass-Styrenic thermoplastic elastomer (manufactured by Asahi Kasei Corporation SOE-L605 ",
Hydrogenated product of styrene / butadiene block copolymer): 18 parts by mass The above kneaded product was pulverized with a jet mill and classified to obtain cyan toner 1 having an average particle diameter of 16 μm. A mixture of 85 parts by mass of non-volatile paraffin oil (manufactured by Matsumura Oil Co., Ltd., Moresco White P40, flash point: 130 ° C.) was finely pulverized with a ball mill to 1:15 parts by mass of this cyan toner, and the average particle diameter was determined. A liquid developer 1 of 1.1 μm was obtained.

<Preparation of unfixed image>
After filtering onto a Teflon (registered trademark) filter (PTFE Membrane filter (pore size 0.2 μm, JGWP04700) manufactured by Millipore) using the above liquid developer 1 so that the toner amount per image unit area is 4 g / m ^2. A toner image was formed on Oji Paper's OK top coat +127 gsm.

<Preparation of fixed image and final toner image>
Fixing process A fixed image was produced using a fixing device having a roll pair with a diameter of 50 mm. Each fixing roll is formed of a silicone rubber having a thickness of 5 mm and a rubber hardness of 50 degrees (JIS-A) on the surface of a stainless steel core, and is covered with a fluororesin (PFA) layer having a thickness of 30 μm. A halogen heater is provided inside each roll to control heating of the roll surface temperature. The load is adjusted by a pressure mechanism so that the maximum pressure is 0.3 MPa and the nip width is 10 mm, and the unfixed image is inserted between the rolls when driven at a speed of 384 mm / s, A fixed image was obtained (the fixing temperature will be described later).

-Residual amount adjustment step Using the plate-shaped heating device shown in Fig. 1 as a drying device, adjusting the temperature and time of drying so that the second residual amount becomes the amount shown in Table 1 below, The fixed image was heated and dried.

<Measurement of remaining amount of carrier liquid>
The remaining amount of the carrier liquid in the fixed image (first remaining amount) and the remaining amount of the carrier liquid in the final toner image (second remaining amount) were respectively measured using the TGA-50 manufactured by Shimadzu Corporation. Measured by analytical method.

<Evaluation of fixed image and final toner image>
Fixing temperature The fixing temperature in the fixing step was set to a temperature at which the image gloss measured by using a 60-degree Micro-TRI-Gloss manufactured by BYK-Gardner as a gloss measuring device was 20. Based on this fixing temperature, evaluation was performed according to the following evaluation criteria.
○: 145 ° C or lower △: Over 145 ° C and 160 ° C or lower ×: 161 ° C

-Hot offset In the fixing step, whether or not a hot offset that causes transfer of the melted toner to the fixing member and the separation of the toner image is visually confirmed, and evaluated according to the following evaluation criteria.
○: Image adhesion is not confirmed on the paper downstream from the image fixing process. ×: Image adhesion is present on the paper downstream from the image fixing process.

Bending resistance The paper was bent with the surface on which the final toner image was formed on the inside, and the degree of destruction of the image after lightly wiping the bent portion was observed and evaluated according to the following evaluation criteria.
○: No peeling or slight discontinuous image peeling △: Discontinuous damage ×: Continuous damage

Document offset Using two paper samples on which the final toner image has been formed, the image surfaces deteriorated when the image surfaces were pressed against each other at a pressure of 400 Pa in a 50 ° C. and 50% RH environment and left for 1 week. The condition was observed and evaluated according to the following evaluation criteria.
○: No image deterioration △: Slight image peeling is observed ×: Significant image peeling is observed

-Comprehensive evaluation Based on the evaluation results for the fixing temperature, hot offset, bending strength, and document offset, the following evaluation criteria were used.
○: 4 items evaluated as “◯” △: 3 items evaluated as “◯”, 1 item evaluated as “△” ×: 1 item evaluated as “×”

[Example 2]
A liquid developer was prepared by the method described in Example 1, except that the carrier liquid to be mixed in Example 1 was changed from “Moleco White P40” to “Isopar M (flash point 92 ° C.) manufactured by Exxon Chemical Co., Ltd.”. Then, a fixed image and a final toner image were prepared and evaluated.

[Comparative Example 1]
A liquid developer was prepared by the method described in Example 1 except that the “residual amount adjusting step” was not performed in Example 1, and a fixed image was produced and evaluated.

[Comparative Example 2]
A liquid developer was prepared by the method described in Example 2 except that the “residual amount adjusting step” was not performed in Example 2, and a fixed image was produced and evaluated.

[Comparative Example 3]
In Comparative Example 1, a liquid developer was prepared by the method described in Comparative Example 1 except that the fixing temperature was adjusted so that the first remaining amount after the fixing step was the amount shown in Table 1 below, and a fixed image was produced. And evaluated.

[Comparative Example 4]
In Comparative Example 2, a liquid developer was prepared by the method described in Comparative Example 2 except that the fixing temperature was adjusted so that the first remaining amount after the fixing step was the amount shown in Table 1 below, and a fixed image was produced. And evaluated.

In Comparative Examples 1 and 2 in which the remaining amount adjustment process is not provided after the fixing process, the occurrence of hot offset is suppressed, but the document offset occurs.
On the other hand, in Comparative Examples 3 and 4 in which the remaining amount adjusting process is not provided after the fixing process and the temperature at the time of fixing is higher than those of Comparative Examples 1 and 2, occurrence of document offset is suppressed, but hot offset is suppressed. Had occurred.
On the other hand, in Examples 1 and 2 provided with the remaining amount adjusting step, it was found that the occurrence of hot offset is suppressed and the occurrence of document offset is also suppressed.

10 Photoconductor (electrostatic latent image holder)
12 Exposure device (latent image forming device)
14 Developing Device 16 Intermediate Transfer Body 18 Cleaner 20 Charging Device 24 Liquid Developer 26 Toner Image 28 Transfer Fixing Roller (Transfer Fixing Device Combined with Transfer and Fixing)
29 Toner image 30 Paper (recording medium)
32 Drying device (residual amount adjusting device)
100 Image forming apparatus 101-C Cyan developing unit 101-M Magenta developing unit 101-Y Yellow developing unit 101-K Black developing unit 102 Developer tank 103 Developer supplying roll 104 Supply amount regulating means 105 Developing roll 106 Developing roll cleaner 107 Photoconductor (electrostatic latent image holder)
108 Charging Device 109 Exposure Device (Latent Image Forming Device)
110 Primary transfer device 111 Photoconductor cleaner 112 Liquid developer 121 Drive roll 122 Support rolls 124 and 126 Secondary transfer device 125 Intermediate transfer body 127 Paper (recording medium)
131 Fixing unit (fixing device)
132 Heat roll 133 Pressure roll 134 Heater 135 Drying device (residual amount adjusting device)

Claims (4)

A charging step for charging the surface of the electrostatic latent image holding member;
A latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image holder;
A developing step of developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member with a liquid developer in which a toner containing at least a thermoplastic elastomer is dispersed in a carrier liquid to form a toner image; ,
A transfer step of transferring the toner image to a recording medium;
The toner image on the recording medium is heated and pressurized to form a toner image fixed on the recording medium, and the remaining amount of the carrier liquid contained in the toner image is reduced to the first remaining amount. Fixing process;
A residual amount adjusting step for reducing the residual amount of the carrier liquid contained in the toner image after the fixing step to a second residual amount lower than the first residual amount, wherein the carrier liquid is fixed on the recording medium. A remaining amount adjusting step of heating the toner image from the opposite side of the recording medium ;
Have
The image forming method, wherein the first remaining amount is 15% by mass or more based on the total amount of the toner image. The image forming method according to claim 1, wherein the second remaining amount is 12% by mass or less based on the total amount of the toner image. An electrostatic latent image carrier;
A charging device for charging the surface of the electrostatic latent image holding member;
A latent image forming apparatus that forms an electrostatic latent image on the surface of the electrostatic latent image holding member;
A toner containing at least a thermoplastic elastomer containing a liquid developer dispersed in a carrier liquid is stored, and the electrostatic latent image formed on the surface of the electrostatic latent image holding member is developed with the liquid developer. A developing device for forming an image;
A transfer device for transferring the toner image to a recording medium;
The toner image on the recording medium is heated and pressurized to form a toner image fixed on the recording medium, and the remaining amount of carrier liquid contained in the toner image is reduced to the first remaining amount. A fixing device;
A residual amount adjusting device for reducing a residual amount of a carrier liquid contained in the toner image after the fixing to a second residual amount lower than the first residual amount, wherein the residual amount adjusting device is fixed to the recording medium. A remaining amount adjusting device for heating the toner image from the opposite side of the recording medium ;
Have
An image forming apparatus in which the first remaining amount is 15% by mass or more based on the total amount of the toner image. The image forming apparatus according to claim 3 , wherein the second remaining amount is 12% by mass or less based on the total amount of the toner image.