JP2008090187A - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method and an image forming apparatus that is environmentally friendly, capable of firmly fixing toner particles to a recording medium and forming an image having superior tone. <P>SOLUTION: The image forming method for forming a color image on a recording medium includes a developing step of forming a plurality of monochromatic images, corresponding to the respective colors by using a plurality of liquid developers of different colors; a transfer step of transferring the monochromatic images of the respective colors onto the recording medium to form an unfixed color image on the recording medium; and a fixing step of fixing the unfixed color image on the recording medium. In the plurality of liquid developers of different colors, an insulating liquid, constituting a liquid developer corresponding to at least yellow, magenta and cyan, contains a fatty acid monoester that has ester coupling of a monohydric alcohol and a fatty acid and unsaturated fatty acid triglyceride. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

Conventionally, as a method for forming an image on a recording medium, a method using a liquid developer in which toner particles are dispersed in an insulating liquid is known.
In this method using a liquid developer, toner particles are more effectively prevented from agglomerating than dry toner using toner in a dry state, so that fine toner particles can be used. As described above, those having a low softening point (low softening temperature) can be used. As a result, an image forming apparatus using a liquid developer has characteristics that fine line image reproducibility, gradation reproducibility, and color reproducibility can be obtained. .

As the insulating liquid used for the liquid developer, petroleum-based hydrocarbons, silicone oils, and the like are generally used because of their high chemical stability.
However, the method using a liquid developer has a problem that the insulating liquid adhering to the surface of the toner particles at the time of fixing permeates into the recording medium and reduces the fixing strength. In addition, there is also a problem that it becomes difficult to add information to the recording medium with a ballpoint pen or the like due to this soaking.

In order to solve such a problem, an attempt has been made to remove the insulating liquid using a squeeze roller or the like before transferring the toner particles to the recording medium (see, for example, Patent Document 1).
However, with such a method, it is difficult to sufficiently remove the insulating liquid, and it is difficult to obtain a sufficient fixing strength. In order to improve the fixing strength of the toner, it may be possible to fix the toner particles by heating at a relatively high temperature for a long time, but this satisfies the recent demand for higher speed and energy saving of image formation. It was difficult.

JP 2004-286859 A

  An object of the present invention is to provide an image forming method and an image forming apparatus that are friendly to the environment, can firmly fix toner particles on a recording medium, and can form an image with excellent color tone. It is in.

Such an object is achieved by the present invention described below.
An image forming method of the present invention is an image forming method for forming a color image on a recording medium using a liquid developer in which toner particles are dispersed in an insulating liquid.
A development step of forming a plurality of single color images corresponding to each color using a plurality of liquid developers having different colors;
Transferring a plurality of monochrome images corresponding to each color to the recording medium, and forming an unfixed color image on the recording medium; and
A fixing step of fixing the unfixed color image on the recording medium,
A fatty acid in which a monohydric alcohol and a fatty acid are ester-bonded in the insulating liquid constituting the liquid developer corresponding to at least yellow, magenta, and cyan among the plurality of liquid developers having different colors A monoester and an unsaturated fatty acid triglyceride are contained.
Accordingly, it is possible to provide an image forming method that is friendly to the environment and can firmly fix the toner particles to the recording medium and can form an image with excellent color tone.

In the image forming method of the present invention, the content of the fatty acid monoester in the insulating liquid constituting the liquid developer corresponding to yellow, magenta, and cyan is X [wt%], and the unsaturated fatty acid triglyceride When the content of Y is defined as Y [wt%], it is preferable to satisfy the relationship of 0.01 ≦ X / Y ≦ 1.0.
By satisfying such a relationship, the permeability of the insulating liquid into the recording medium can be made higher, and the plastic effect of the fatty acid monoester on the toner particles can be sufficiently exhibited. As a result, the toner particles can be fixed more firmly, and a color image having a particularly excellent color tone can be formed.

In the image forming method of the present invention, it is preferable that in the fixing step, the color image is fixed to the recording medium by applying pressure while heating the recording medium on which the color image is formed.
Thereby, the toner particles can be firmly fixed on the recording medium.
In the image forming method of the present invention, it is preferable that the color image is irradiated with ultraviolet rays in the fixing step.
Thereby, the toner particles can be fixed to the recording medium at a lower temperature and at a higher speed.

The image forming apparatus of the present invention is an image forming apparatus that forms a color image on a recording medium using a liquid developer in which toner particles are dispersed in an insulating liquid.
A plurality of developing units that form a single color image corresponding to each color using a plurality of liquid developers having different colors;
An intermediate transfer unit that sequentially transfers the plurality of single-color images formed by the plurality of developing units and forms an intermediate transfer image formed by superimposing the transferred plurality of single-color images;
A secondary transfer unit that transfers the intermediate transfer image to the recording medium and forms an unfixed color image on the recording medium;
A fixing unit for fixing the unfixed color image on the recording medium,
A fatty acid in which a monohydric alcohol and a fatty acid are ester-bonded in the insulating liquid constituting the liquid developer corresponding to at least yellow, magenta, and cyan among the plurality of liquid developers having different colors A monoester and a fatty acid triglyceride are contained.
Accordingly, it is possible to provide an image forming apparatus that is friendly to the environment and can firmly fix the toner particles to the recording medium and can form an image with excellent color tone.

The image forming apparatus of the present invention is an image forming apparatus that forms a color image on a recording medium using a liquid developer in which toner particles are dispersed in an insulating liquid.
A plurality of developing units that form a single color image corresponding to each color using a plurality of liquid developers having different colors;
By transporting the recording medium, the plurality of monochrome images formed by the plurality of developing units are sequentially transferred to the recording medium, and an unfixed color image formed by superimposing the transferred plurality of monochrome images is A transfer portion formed on a recording medium;
A fixing unit for fixing the unfixed color image on the recording medium,
A fatty acid in which a monohydric alcohol and a fatty acid are ester-bonded in the insulating liquid constituting the liquid developer corresponding to at least yellow, magenta, and cyan among the plurality of liquid developers having different colors A monoester and a fatty acid triglyceride are contained.
Accordingly, it is possible to provide an image forming apparatus that is friendly to the environment and can firmly fix the toner particles to the recording medium and can form an image with excellent color tone.

In the image forming apparatus of the present invention, the fatty acid monoester content in the insulating liquid constituting the liquid developer corresponding to yellow, magenta, and cyan is X [wt%], and the fatty acid triglyceride content is When the amount is Y [wt%], it is preferable to satisfy the relationship of 0.01 ≦ X / Y ≦ 1.0.
By satisfying such a relationship, the permeability of the insulating liquid into the recording medium can be made higher, and the plastic effect of the fatty acid monoester on the toner particles can be sufficiently exhibited. As a result, the toner particles can be fixed more firmly, and a color image having a particularly excellent color tone can be formed.

In the image forming apparatus according to the aspect of the invention, it is preferable that the fixing unit includes an ultraviolet irradiation unit that irradiates the toner image with ultraviolet rays when the color image is fixed onto the recording medium.
Thereby, the toner particles can be fixed to the recording medium at a lower temperature and at a higher speed.
In the image forming apparatus according to the aspect of the invention, the fixing unit is installed to be opposed to the heat fixing roller that applies heat to the recording medium and the pressure that applies pressure to the recording medium. And having a roller
The linear pressure of the pressure roller with respect to the recording medium is preferably 500 g / cm or less.
Even with such a relatively low linear pressure, the toner particles can be firmly fixed to the recording medium. Further, since the linear pressure is relatively low, the driving power of the pressure roller and the heat fixing roller can be reduced, and energy saving can be achieved.

Hereinafter, preferred embodiments of the image forming method and the image forming apparatus of the present invention will be described.
<Image forming method>
The image forming method of the present invention uses a plurality of liquid developers of different colors to develop a plurality of single color images corresponding to each color, and transfers a plurality of single color images corresponding to each color to a recording medium. A transfer process for forming an unfixed color image on the recording medium; and a fixing process for fixing the unfixed color image on the recording medium.

<Liquid developer>
First, the liquid developer applied to the image forming method (image forming apparatus) of the present invention will be described in detail.
The liquid developer applied to the image forming method (image forming apparatus) of the present invention is one in which toner particles are dispersed in an insulating liquid.

[Insulating liquid]
First, the insulating liquid will be described.
The image forming method (image forming apparatus) of the present invention forms a color image on a recording medium using a plurality of liquid developers having different colors, and at least of the plurality of liquid developers having different colors, The insulating liquid constituting the liquid developer corresponding to yellow, magenta, and cyan contains a fatty acid monoester and a fatty acid triglyceride.

First, unsaturated fatty acid triglyceride will be described. An unsaturated fatty acid triglyceride is an ester (glyceride) of a fatty acid and glycerin, and includes an unsaturated fatty acid as a fatty acid component.
This unsaturated fatty acid component is an environmentally friendly component. Accordingly, it is possible to reduce the load on the environment of the insulating liquid due to leakage of the insulating liquid to the outside of the liquid developing device and disposal of the used liquid developer. As a result, an environment-friendly image forming method (image forming apparatus) can be provided.

  The unsaturated fatty acid component is a component that can contribute to improving the fixing strength of toner particles on a recording medium. More specifically, the unsaturated fatty acid component is a component having a function of being cured by being oxidized (by being oxidized at the fixing temperature at the time of fixing) and improving the fixing strength of the toner particles. . Further, since the unsaturated fatty acid component is cured, the fixed toner image can be easily and reliably added with an aqueous ballpoint pen.

  The unsaturated fatty acid constituting the unsaturated fatty acid triglyceride is not particularly limited, but is monovalent unsaturated such as crotonic acid, myristoleic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, erucic acid, nervonic acid Polyhydric acid such as fatty acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, eleostearic acid, stearidonic acid, arachidonic acid, sardine acid, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), etc. Examples thereof include unsaturated fatty acids of saturated fatty acids and derivatives thereof, and one or more selected from these can be used in combination.

Among these, when linoleic acid is used as the unsaturated fatty acid, the fixing strength of the toner particles to the recording medium is particularly excellent. In addition, since it has a high affinity with toner particles during fixing and does not hinder the melting of the toners, an image with a desired color tone can be easily obtained. Further, since the affinity with the toner particles is high, the toner particles can be stably dispersed in the liquid developer, and the storage stability of the liquid developer can be made particularly excellent.
Moreover, as a linoleic acid component, you may use what was comprised with the conjugated linoleic acid which has a conjugated double bond, for example. Thereby, the fixing strength of the toner particles on the recording medium can be made particularly excellent.

Although the content rate of linoleic acid with respect to the unsaturated fatty acid triglyceride total fatty acid component is not particularly limited, it is preferably 15 mol% or more, more preferably 25 mol% or more, and further preferably 45 mol% or more. If the linoleic acid content is less than the lower limit, the fixing strength of the toner particles on the recording medium may be lowered, and the storage stability of the liquid developer may be inferior.
Such unsaturated fatty acid triglycerides include, for example, safflower oil, rice oil, rice bran oil, rapeseed oil, olive oil, canola oil, soybean oil, linseed oil, castor oil and other animal-derived fats and oils such as cow oil. It can be efficiently obtained from naturally derived fats and oils such as fats and oils.

  The content of the unsaturated fatty acid triglyceride in the insulating liquid in the present invention is preferably 20 to 90 wt%, more preferably 30 to 80 wt%, and further preferably 40 to 80 wt%. When the content of unsaturated fatty acid triglyceride in the insulating liquid is within the above range, an oxidative polymerization reaction of the unsaturated fatty acid component occurs moderately at the time of fixing, and as a result, the fixing strength of the toner image on the recording medium is increased. It can be made particularly excellent, and it becomes easier to obtain an image having a target color tone. On the other hand, if the content of unsaturated fatty acid triglyceride is less than the lower limit, the oxidative polymerization reaction of unsaturated fatty acid hardly occurs at the time of fixing, so that the fixing strength of toner particles to a recording medium may be reduced. is there. On the other hand, if the content of unsaturated fatty acid triglyceride exceeds the above upper limit value, an oxidative polymerization reaction with a large amount of unsaturated fatty acid occurs during fixing more than necessary, and solidification occurs around the toner particles. Depending on the case, the toner particles may not be melted when the toner particles are fixed on the recording medium, and it may be difficult to obtain an image having a target color tone.

Moreover, the saturated fatty acid component may be contained in the unsaturated fatty acid triglyceride. By including the saturated fatty acid component, it is possible to keep the chemical stability of the liquid developer and the electrical insulation of the insulating liquid even higher.
Examples of saturated fatty acids constituting such saturated fatty acid components include butyric acid (C4), caproic acid (C6), caprylic acid (C8), capric acid (C10), lauric acid (C12), and myristylic acid (C14). , Palmitic acid (C16), stearic acid (C18), arachidic acid (C20), behenic acid (C22), lignoceric acid (C24) and the like, and one or more selected from these are used in combination. be able to. Among the saturated fatty acids as described above, the number of carbon atoms in the molecule is preferably 6-22, more preferably 8-20, and even more preferably 10-18. . By including a saturated fatty acid component composed of such a saturated fatty acid, the effects as described above are exhibited more significantly.

As described above, the unsaturated fatty acid triglyceride undergoes oxidative polymerization and solidification in the vicinity of the toner particles at the time of fixing, and as a result, the fixing strength of the toner image can be increased. However, since unsaturated fatty acid triglycerides have low penetrability with respect to the recording medium, it is difficult to obtain sufficient fixing strength between the recording medium and toner particles simply by using an insulating liquid containing unsaturated fatty acid triglycerides. It was.
As a result of intensive studies, the present inventors have found that toner particles can be firmly fixed on a recording medium by using a liquid developer contained in an unsaturated fatty acid triglyceride and a fatty acid monoester.

Hereinafter, the fatty acid monoester will be described. The fatty acid monoester is an ester of a fatty acid and a monohydric alcohol.
Since the fatty acid monoester has a property of low molecular weight and low viscosity, it penetrates into the resin particles (toner particles) during the fixing process and exhibits a plastic effect. Due to this plastic effect, for example, when paper is used as the recording medium, the toner particles can easily enter the gaps between the paper fibers, so that the fixing strength of the toner particles can be increased and at a low temperature. Fixing can also be possible. In addition, since the toner particles enter the gaps between the fibers of the recording medium in this way, the resulting color image is smooth without any unevenness, and as a result, the gloss of the formed image is excellent. can do.

Further, due to such a plastic effect, toner particles corresponding to yellow, magenta, and cyan are suitably mixed at the time of fixing, and an image having a desired color tone can be suitably formed.
In particular, when a polyester resin is used as the resin material constituting the toner particles, the plastic effect as described above is remarkably exhibited, the fixing strength of the toner particles can be made particularly high, and a particularly excellent color tone can be obtained. Color images can be formed.

  In addition, since fatty acid monoester is a component that easily penetrates into the recording medium, the fatty acid monoester adhering to the vicinity of the surface of the toner particles quickly penetrates into the recording medium when the toner particles come into contact with the recording medium during fixing. To do. Along with the permeation of the fatty acid monoester, a part of the toner particles (resin material constituting the toner particles) melted by heat at the time of fixing penetrates into the inside of the recording medium, an anchor effect works, and the fixing strength is improved. . Further, along with the penetration of the fatty acid monoester, a part of the unsaturated fatty acid triglyceride existing near the surface of the toner particle also penetrates, and the toner particles are fixed more firmly by oxidative polymerization in this state.

Furthermore, since this fatty acid monoester is an environmentally friendly component, it is possible to reduce the environmental impact of the insulating liquid due to leakage of the insulating liquid outside the image forming apparatus and disposal of the used liquid developer. it can. As a result, an environment-friendly image forming apparatus can be provided.
The content of the fatty acid monoester in the insulating liquid is preferably 5 to 55 wt%, more preferably 10 to 50 wt%, and still more preferably 20 to 50 wt%. When the content of the fatty acid monoester is within the above range, the permeability of the insulating liquid into the recording medium can be made higher, and the plastic effect as described above can be sufficiently exhibited. . As a result, the toner particles can be fixed more firmly, and a color image having a particularly excellent color tone can be formed.

  Fatty acid monoesters that can be used in the liquid developer of the present invention are not particularly limited. For example, oleic acid, palmitoleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA), Unsaturated fatty acid alkyl (methyl, ethyl, propyl, butyl, etc.) monoesters such as eicosapentaenoic acid (EPA), butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, mytilic acid, palmitic acid, stearin Alkyl (methyl, ethyl, propyl, butyl, etc.) monoesters of saturated fatty acids represented by acid, arachidic acid, behenic acid, lignoceric acid, etc. are mentioned, and one or more selected from these are combined Can be used.

  As the fatty acid monoester, an unsaturated fatty acid monoester having an unsaturated fatty acid as the fatty acid component is preferably used. The unsaturated fatty acid component is a component that can contribute to improving the fixability of toner particles to a recording medium. More specifically, the unsaturated fatty acid monoester is oxidatively polymerized at the time of fixing, so that the unsaturated fatty acid monoester itself is cured, and the fixing strength between the toner particles and the recording medium can be particularly improved. As a result, not only unsaturated fatty acid triglycerides but also unsaturated fatty acid monoesters can contribute to oxidative polymerization, so that the anchor effect described above can be made particularly effective, and particularly excellent fixing strength can be obtained. it can.

The content of the unsaturated fatty acid component in the total fatty acid component in the fatty acid monoester is preferably 50 wt% or more, and more preferably 60 wt% or more. As a result, the above-described effect becomes particularly reliable, and a particularly strong fixing strength can be obtained.
The fatty acid component of the fatty acid monoester is preferably mainly composed of unsaturated fatty acids, but may partially contain saturated fatty acids. Thereby, the preservability and long-term stability of the insulating liquid can be further improved.

  The fatty acid monoester is an ester of a fatty acid and a monohydric alcohol, and this alcohol is preferably an alkyl alcohol having 1 to 4 carbon atoms. Thereby, the chemical stability of the liquid developer is excellent, and the storage stability and long-term stability of the liquid developer are further improved. Further, the viscosity of the insulating liquid can be made favorable, and the penetration of the liquid developer into the recording medium can be made more suitable. Examples of such alcohol include methanol, ethanol, propanol, butanol, isobutanol and the like.

  Moreover, it is preferable that the fatty acid monoester which comprises an insulating liquid is produced | generated by transesterification with fatty acid triglyceride and C1-C4 monohydric alcohol. Thereby, since the affinity between the fatty acid monoester and the fatty acid triglyceride is further increased, the viscosity of the insulating liquid becomes suitable, and the penetration of the liquid developer into the recording medium is further improved. Thereby, the fixing strength of the toner particles on the recording medium is excellent, and the liquid developer suitable for high-speed image formation can be suitably applied.

  As described above, the present invention is characterized in that at least an insulating liquid constituting a liquid developer corresponding to yellow, magenta, and cyan uses an unsaturated fatty acid triglyceride and a fatty acid monoester. Thus, an excellent effect can be obtained. On the other hand, when only one of fatty acid glycerides and fatty acid monoesters is contained in the insulating liquid, the effect of the present invention cannot be obtained.

  That is, when the fatty acid monoester is not contained in the insulating liquid, the plastic effect of the insulating liquid on the toner particles becomes insufficient at the time of fixing, and the toner particles do not easily enter the recording medium fiber. Furthermore, since the viscosity of the insulating liquid increases, the penetration of the carrier liquid (insulating liquid) into the recording medium is delayed, and as a result, the fixing strength of the toner particles on the recording medium cannot be made sufficient.

  On the other hand, when unsaturated fatty acid triglyceride is not contained in the insulating liquid, the plastic effect is exhibited, but the insulating liquid between the recording medium and the toner particles cannot be sufficiently solidified at the time of fixing, resulting in the recording medium. The fixing strength of the toner particles cannot be made sufficient. In addition, the viscosity becomes too low, and in the image forming apparatus, it becomes difficult to pump the liquid developer from the liquid developer reservoir with the liquid developer supply roller, and the resulting image is uneven. End up. Such unevenness of the image may make it difficult to form an image at high speed.

  The ratio between the fatty acid monoester and the fatty acid triglyceride in the insulating liquid is not particularly limited, but preferably satisfies the following relationship. That is, when the content of the fatty acid monoester in the insulating liquid is X [wt%] and the content of the fatty acid triglyceride is Y [wt%], the relationship of 0.01 ≦ X / Y ≦ 1.0 is satisfied. It is more preferable that the relationship 0.1 ≦ X / Y ≦ 1.0 is satisfied, and it is more preferable that the relationship 0.25 ≦ X / Y ≦ 1.0 is satisfied. By satisfying such a relationship, the permeability of the insulating liquid into the recording medium can be made higher, and the plastic effect as described above can be sufficiently exhibited. As a result, the toner particles can be fixed more firmly, and a color image having a particularly excellent color tone can be formed.

  In the present invention, the fatty acid monoester is contained in the insulating liquid. When the fatty acid monoester is present in the insulating liquid, the plasticizer effect of the fatty acid monoester on the toner particles is relatively small, and the stability of the toner particles during storage can be kept high. If the fatty acid monoester is simply contained as a constituent material of the toner particles, the toner particles are easily plasticized due to the plasticizer effect of the fatty acid monoester, resulting in poor stability of the toner particles during storage.

  The insulating liquid may contain components other than those described above. For example, Isopar E, Isopar G, Isopar H, Isopar L (Isopar; trade name of Exxon Chemical), Cielsol 70, Cielsol 71 (Cielsol; trade name of Ciel Oil), Amsco OMS, Amsco 460 solvent (Amsco; Spirits) Company name), mineral oil such as low viscosity / high viscosity liquid paraffin (Wako Pure Chemical Industries), fatty acid ester such as saturated fatty acid glyceride, medium chain fatty acid ester, fatty acid glyceride such as glycerin, fatty acid, octane, Examples include isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, mesitylene, and the like, and one or more of these can be used in combination.

  In the present invention, the unsaturated fatty acid triglyceride and the fatty acid monoester as described above may be contained at least in the insulating liquid constituting the liquid developer corresponding to yellow, magenta, and cyan. The unsaturated fatty acid triglyceride and the fatty acid monoester may or may not be contained in other colors such as black.

  Further, the liquid developer (insulating liquid) may contain an antioxidant having a function of preventing / suppressing the oxidation of the unsaturated fatty acid component. Thereby, the unintentional oxidation of the unsaturated fatty acid component in the liquid developer can be prevented. As a result, it is possible to prevent deterioration of the liquid developer (insulating liquid) over time, and to make the dispersibility of the toner particles and the fixing strength to the recording medium particularly excellent over a long period of time. it can. That is, the long-term stability (storability) of the liquid developer can be made particularly excellent.

  Examples of the antioxidant described above include vitamin E such as tocopherol, d-tocopherol, dl-α-tocopherol, acetic acid-α-tocopherol, dl-α-tocopherol acetate, tocopherol acetate, α-tocopherol and the like, dibutylhydroxy Examples include vitamin C such as toluene, butylhydroxyanisole, ascorbic acid, ascorbates, ascorbic acid stearate, green tea extract, fresh coffee extract, sesamol, sesaminol, etc., one or more of these Can be used in combination.

  Among the above, when vitamin E is used, the following effects are obtained. In other words, vitamin E is an environmentally friendly component, and is a component that has a small influence on the liquid developer due to oxidation of the substance itself, so that the liquid developer can be made more environmentally friendly. . Vitamin E can be suitably used as an antioxidant because of its high dispersibility in liquids (particularly glycerides) containing unsaturated fatty acid components and saturated fatty acid components as described above. Further, the combined use of vitamin E and glycerides as described above can further improve the affinity between the insulating liquid and the toner particles. As a result, the storage stability of the liquid developer, the fixing strength of the toner particles on the recording medium, and the like are particularly excellent.

  Moreover, among the above-mentioned, when vitamin C is used, the following effects are acquired. That is, like the above-mentioned vitamin E, vitamin C is an environmentally friendly component, and since it is a component having a small influence on the liquid developer caused by oxidation of itself, the liquid developer is more environmentally friendly. It can be friendly to you. In addition, since vitamin C has a relatively low thermal decomposition temperature, it can sufficiently exhibit its function as an antioxidant during storage of a liquid developer (including idling of an image forming apparatus). At the time of fixing, the function as an antioxidant can be reduced, and the oxidative polymerization reaction of unsaturated fatty acid components can be promoted.

The thermal decomposition temperature of the antioxidant is preferably not higher than the fixing temperature at the time of fixing. This effectively prevents deterioration of the insulating liquid during storage of the liquid developer, and at the time of fixing, thermally decomposes the antioxidant in the insulating liquid attached to the surface of the toner particles, The unsaturated fatty acid component can be effectively cured (oxidative polymerization reaction), and the fixing strength of the toner particles to the recording medium can be made sufficiently excellent.
Specifically, the thermal decomposition temperature of the antioxidant is preferably 200 ° C. or lower, and more preferably 180 ° C. or lower. Thereby, it is possible to more effectively improve the fixing strength of the toner particles while sufficiently retaining the function as an antioxidant.

  The content of the antioxidant in the insulating liquid is preferably 0.01 to 15 parts by weight and more preferably 0.1 to 7 parts by weight with respect to 100 parts by weight of the insulating liquid. 1 to 7 parts by weight is more preferable. This prevents the deterioration of the unsaturated fatty acid component due to oxidation during storage of the liquid developer more reliably, while efficiently curing the unsaturated fatty acid component (oxidation polymerization reaction) when necessary (fixing). Can be made.

Further, the liquid developer may contain an oxidative polymerization accelerator (curing accelerator) that accelerates the oxidative polymerization reaction (curing reaction) of the unsaturated fatty acid component described above. Thereby, the unsaturated fatty acid component can be effectively oxidatively polymerized (cured) when necessary (at the time of fixing). As a result, the fixing strength of the toner particles on the recording medium can be made particularly excellent.
When the liquid developer contains an oxidative polymerization accelerator, the oxidative polymerization accelerator is not particularly limited, but is substantially unsaturated fatty acid during storage (including idling of the image forming apparatus). It is preferable that it does not contribute to the oxidative polymerization reaction of the component and contributes to the oxidative polymerization (curing) reaction of the unsaturated fatty acid component when necessary (fixing). As a result, the fixing strength of the toner particles on the recording medium can be made particularly excellent while making the storage stability (long-term stability) of the liquid developer excellent.

  As such an oxidative polymerization accelerator, for example, it has a function of accelerating an oxidative polymerization reaction (curing reaction) of an unsaturated fatty acid component under heating conditions, and is substantially oxidative polymerization reaction of an unsaturated fatty acid component near room temperature. A substance having no function of promoting (curing reaction), that is, a substance having a relatively high activation energy in the oxidative polymerization reaction (curing reaction) of an unsaturated fatty acid component can be used.

  Examples of such a substance (oxidative polymerization accelerator) include various fatty acid metal salts and the like, and one or more of these can be used in combination. By using such a substance (oxidation polymerization accelerator), it is possible to effectively promote the oxidative polymerization of unsaturated fatty acid components during fixing while maintaining the stability of the liquid developer during storage. . In particular, fatty acid metal salts can accelerate the oxidative polymerization reaction of unsaturated fatty acid components by supplying oxygen during fixing, and therefore can effectively promote the oxidative polymerization reaction during heating such as during fixing. it can. Therefore, the oxidation polymerization reaction can be more effectively promoted at the time of fixing and the like while preventing the occurrence of the oxidation polymerization reaction more reliably during storage. Moreover, since the fatty acid metal salt is highly dispersible in the liquid (particularly glyceride) containing the unsaturated fatty acid component and the saturated fatty acid component as described above, it can be uniformly dispersed in the insulating liquid. At the time of fixing, the oxidative polymerization reaction can be efficiently advanced as a whole.

  Examples of such fatty acid metal salts include resin acid metal salts (for example, cobalt salts, manganese salts, lead salts, etc.), linolenic acid metal salts (for example, cobalt salts, manganese salts, lead salts, etc.), and metal octylates. Salt (for example, cobalt salt, manganese salt, lead salt, zinc salt, calcium salt, etc.), naphthenic acid metal salt (for example, zinc salt, calcium salt, etc.), etc. They can be used in combination.

  The oxidation polymerization accelerator may be contained in the insulating liquid in an encapsulated state. Thus, as described above, the oxidative polymerization accelerator does not substantially contribute to the oxidative polymerization reaction of the unsaturated fatty acid component during storage (including idling of the image forming apparatus) and the like when necessary. It can contribute to the oxidative polymerization (curing) reaction of unsaturated fatty acid components. That is, the oxidative polymerization reaction during storage of the liquid developer is more reliably prevented, and at the time of fixing, the oxidative polymerization accelerator and the unsaturated fatty acid component come into contact with each other by the capsule being crushed by the pressure at the time of fixing. In addition, the oxidative polymerization reaction of the unsaturated fatty acid component can surely proceed. Further, with such a configuration, the range of selection of the material for the oxidation polymerization accelerator is widened. In other words, even a highly reactive oxidative polymerization accelerator (an oxidative polymerization accelerator that contributes to the oxidative polymerization reaction of unsaturated fatty acid components at a relatively low temperature) can be suitably used. The fixing strength can be made particularly excellent.

  The content of the oxidation polymerization accelerator in the insulating liquid is preferably 0.01 to 15 parts by weight, more preferably 0.05 to 7 parts by weight, with respect to 100 parts by weight of the insulating liquid. More preferably, it is 0.1 to 5 parts by weight. As a result, the oxidative polymerization reaction of the unsaturated fatty acid component can proceed more reliably during fixing while sufficiently preventing the oxidative polymerization reaction during storage of the liquid developer.

  In the present invention, the iodine value of the insulating liquid is preferably 85 to 200, more preferably 85 to 180, and still more preferably 85 to 170. As a result, it is possible to easily form an image having a target color tone while improving the fixing of the toner particles to the recording medium. On the other hand, when the iodine value of the insulating liquid is less than the lower limit, the oxidative polymerization reaction of the unsaturated fatty acid component hardly occurs, and the fixing strength of the toner particles to the recording medium may be inferior. On the other hand, if the iodine value of the insulating liquid exceeds the upper limit, an oxidative polymerization reaction due to a large amount of unsaturated fatty acid components occurs more than necessary, and solidification occurs around the toner particles. In some cases, the particles cannot be melted and it is difficult to form an image having a target color tone.

The viscosity of the insulating liquid is not particularly limited, but is preferably 5 to 1000 mPa · s, more preferably 10 to 800 mPa · s, and still more preferably 100 to 500 mPa · s. When the viscosity of the insulating liquid is a value within the above range, an appropriate amount of the insulating liquid is added to the toner when the liquid developer is pumped from the liquid developer storage unit by the liquid developer supply roller in the image forming apparatus described later. The toner image can be adhered to the toner, and the developability and transferability of the toner image can be made particularly excellent. In addition, since an appropriate insulating liquid adheres to the toner particles on the recording medium, the fixing strength of the formed toner image can be made particularly excellent, and the toner particles melt due to the plastic effect, and the desired toner image is melted. A color image having a color tone can be formed more easily. In addition, aggregation and sedimentation of toner particles can be prevented, and dispersibility can be further improved. For this reason, in an image forming apparatus as will be described later, the liquid developer can be supplied more uniformly to the liquid developer supply roller, and the liquid developer dripping from the liquid developer supply roller or the like can be further reduced. It can be effectively prevented. However, the viscosity in this specification refers to a value measured at 25 ° C.
The electrical resistance of the insulating liquid as described above at room temperature (20 ° C.) is preferably 1 × 10 ⁹ Ωcm or more, more preferably 1 × 10 ¹¹ Ωcm or more, and 1 × 10 ¹³ Ωcm or more. More preferably.
The dielectric constant of the insulating liquid is preferably 3.5 or less.

[Toner particles]
Next, toner particles will be described.
-Constituent material of toner particles-
The toner particles (toner) include at least a binder resin (resin material).
1. Resin Material The toner constituting the liquid developer is composed of a material containing a resin material as a main component.

  In the present invention, the resin (binder resin) is not particularly limited, and for example, polystyrene, poly-α-methylstyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer. Polymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylic acid ester -Styrene resin such as methacrylic acid ester copolymer, styrene-α-crawler methyl acrylate copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, styrene-vinyl methyl ether copolymer, etc. Homopolymer or copolymer containing , Polyester resin, epoxy resin, urethane modified epoxy resin, silicone modified epoxy resin, vinyl chloride resin, rosin modified maleic acid resin, phenyl resin, polyethylene resin, polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene- Examples include an ethyl acrylate copolymer, a xylene resin, a polyvinyl butyral resin, a terpene resin, a phenol resin, an aliphatic or alicyclic hydrocarbon resin, and the like. One or more of these can be used in combination. Among these, since the polyester resin has high affinity with the insulating liquid as described above, the dispersibility of the toner particles in the liquid developer can be made particularly excellent. Moreover, the polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be made high.

  Although the softening temperature of resin (resin material) is not specifically limited, It is preferable that it is 50-130 degreeC, It is more preferable that it is 50-120 degreeC, It is further more preferable that it is 60-115 degreeC. In the present specification, the softening temperature is a measurement condition in a Koka type flow tester (manufactured by Shimadzu Corporation): temperature increase rate: 5 ° C./min, softening start temperature defined by a die hole diameter of 1.0 mm. Point to.

2. Colorant The toner may contain a colorant. Examples of the colorant that can be used include pigments and dyes. Examples of such pigments and dyes include carbon black, spirit black, lamp black (CI No. 77266), magnetite, titanium black, chrome lead, cadmium yellow, mineral fast yellow, navel yellow, and naphthol yellow S. , Hansa Yellow G, Permanent Yellow NCG, Chrome Yellow, Benzidine Yellow, Quinoline Yellow, Tartrazine Lake, Red Mouth Lead, Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Benzidine Orange G, Cadmium Red, Permanent Red 4R, Watching Red Calcium salt, eosin lake, brilliant carmine 3B, manganese purple, fast violet B, methyl violet lake, bitumen, cobalt blue, al Reblue Lake, Victoria Blue Lake, First Sky Blue, Indanthrene Blue BC, Ultramarine, Aniline Blue, Phthalocyanine Blue, Calco Oil Blue, Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Lake, Phthalocyanine Green, Final Yellow Green G, Rhodamine 6G, quinacridone, rose bengal (C.I. No. 45432), C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modern Tread 30, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 184, C.I. I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Modern Blue 7, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 5: 1, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Basic Green 6, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 162, nigrosine dye (CI No. 50415B), metal complex dye, silica, aluminum oxide, magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, Examples thereof include metal oxides such as magnesium oxide, and magnetic materials containing magnetic metals such as Fe, Co, and Ni, and one or more of these can be used in combination.

3. Other Components The toner may contain components other than those described above. Examples of such components include waxes, charge control agents, magnetic powders, and the like.
Examples of the wax include hydrocarbon waxes such as ozokerite, cercin, paraffin wax, microwax, microcrystalline wax, petrolatum, Fischer-Tropsch wax, carnauba wax, rice wax, methyl laurate, methyl myristate, palmitic acid. Methyl, methyl stearate, butyl stearate, candelilla wax, cotton wax, wood wax, beeswax, lanolin, montan wax, fatty acid ester ester wax, polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax Olefin wax such as 12-hydroxystearic acid amide, stearic acid amide, amide anhydride such as phthalic anhydride, Lauro , Ketone waxes such as stearone, ether waxes, and the like, can be used singly or in combination of two or more of them.

Examples of the charge control agent include benzoic acid metal salt, salicylic acid metal salt, alkyl salicylic acid metal salt, catechol metal salt, metal-containing bisazo dye, nigrosine dye, tetraphenylborate derivative, quaternary ammonium salt, alkyl Examples include pyridinium salts, chlorinated polyesters, and nitrofunic acid.
Examples of the magnetic powder include magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, magnesium oxide, and other metal oxides, and magnetic materials such as Fe, Co, and Ni. The thing etc. which were comprised with the magnetic material containing a metal are mentioned.
In addition to the above materials, for example, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acid, fatty acid metal salt, etc. are used as the constituent material (component) of the kneaded product. May be.

-Toner particle shape, etc.-
The average particle size of the toner particles composed of the above materials is preferably 0.1 to 5 μm, more preferably 0.1 to 4 μm, and further preferably 0.5 to 3 μm. preferable. When the average particle diameter of the toner particles is a value within the above range, the resolution of an image formed by the liquid developer (toner) can be made sufficiently high.

The average value (average circularity) of the circularity R represented by the following formula (I) for the toner particles constituting the liquid developer is preferably 0.94 to 0.99, and preferably 0.96. More preferably, it is -0.99.
R = L ₀ / L ₁ (I)
(Where L ₁ [μm] is the circumference of the projected image of the toner particles to be measured, and L ₀ [μm] is the circumference of a perfect circle having an area equal to the area of the projected image of the toner particles to be measured) Represents length)

When the average circularity of the toner particles is in such a range, the insulating liquid can be appropriately contained in the unfixed toner image transferred onto the recording medium, and the fixing strength of the toner particles is higher. Can be.
The content ratio of the toner particles in the liquid developer is preferably 10 to 60 wt%, and more preferably 10 to 30 wt%.

  The liquid developer as described above may be obtained by any method. For example, an associated particle is obtained by adding an electrolyte to a dispersion liquid (including an emulsion liquid) in which a toner material is dispersed in a dispersion medium. And the toner particles obtained by pulverizing the associated particles are dispersed in an insulating liquid. Further, it may be produced by dispersing toner particles obtained by pulverizing a toner material by a pulverization method in an insulating liquid. Also produced by a method for producing a liquid developer using a dispersion obtained by dispersing a toner material in a dispersion medium (for example, a method as described in JP-A-2006-178117). It may be.

<Image forming apparatus>
Next, a first embodiment of the image forming apparatus of the present invention will be described.
The image forming apparatus of the present invention forms a color image on a recording medium using a plurality of liquid developers having different colors as described above.
FIG. 1 is a schematic diagram showing a first embodiment of the image forming apparatus of the present invention, FIG. 2 is a schematic diagram showing an example of a developing unit provided in the image forming apparatus of the present invention, and FIG. 3 is an image forming apparatus of the present invention. FIG. 3 is a cross-sectional view illustrating an example of a fixing device provided in the apparatus. In FIG. 1, the arrows indicate the vertical direction.

As shown in FIG. 1, the image forming apparatus 1000 includes four developing units 15Y, 15C, 15M, and 15K, an intermediate transfer unit 70, a secondary transfer unit (secondary transfer unit) 80, and a fixing device (described later). Fixing unit) F40.
The developing units 15Y, 15C, and 15M develop a latent image with a yellow (Y) liquid developer, a cyan (C) liquid developer, and a magenta (M) liquid developer, respectively. Have a function of forming a monochrome image. Further, the developing section 15K has a function of developing a latent image with a black (K) liquid developer to form a black (black) monochrome image.

Since the developing units 15Y, 15C, 15M, and 15K have the same configuration, the developing unit 15M will be described below.
As shown in FIG. 1, the developing unit 15M includes a photosensitive member 20M as an example of an image carrier, a charging unit 30M, an exposure unit 40M, a developing unit 50M, and a developing unit 50M along the rotation direction of the photosensitive member 20M. It has a next transfer unit 60M, a charge eliminating unit 73M, and a photoreceptor cleaning unit 75M.

The photoconductor 20M has a cylindrical base material and a photosensitive layer formed on the outer peripheral surface thereof, and is rotatable about a central axis. In the present embodiment, as shown by an arrow in FIG. Rotate clockwise.
The charging unit 30M is a device for charging the photoconductor 20M, and the exposure unit 40M is a device for forming a latent image on the photoconductor 20M charged by irradiating a laser. The exposure unit 40M includes a semiconductor laser, a polygon mirror, an F-θ lens, and the like, and charges the modulated laser based on an image signal input from a host computer (not shown) such as a personal computer or a word processor. The irradiated photoconductor 20M is irradiated.

The developing unit 50M is an apparatus for developing the latent image formed on the photoreceptor 20M using a magenta (M) liquid developer. Details of the developing unit 50M will be described later.
The primary transfer unit 60M is a device for transferring a single color image formed on the photoreceptor 20M to the intermediate transfer unit 70.

The primary transfer units 60Y, 60C, 60M, and 60K sequentially transfer the monochrome images corresponding to the respective colors formed by the developing units 15Y, 15C, 15M, and 15K, and superimpose the monochrome images corresponding to the respective colors. A full color developer image (intermediate transfer image) is formed on the transfer portion 70.
The intermediate transfer unit 70 is an endless belt stretched around a plurality of support rollers, and is rotationally driven while being in contact with the photoreceptors 20Y, 20C, 20M, and 20K.

The secondary transfer unit 80 is a device for transferring the intermediate transfer image formed on the intermediate transfer unit 70 to a recording medium F5 such as paper, film, or cloth.
The color image (transfer image) F5a transferred onto the recording medium F5 by the secondary transfer unit 80 is sent to a fixing device F40, which will be described later, and fixed.
The neutralization unit 73M is a device that removes residual charges on the photoreceptor 20M after the intermediate transfer image is transferred onto the intermediate transfer unit 70 by the primary transfer unit 60M.
The photoconductor cleaning unit 75M has a rubber photoconductor cleaning blade 76M in contact with the surface of the photoconductor 20M, and after the developer image is transferred onto the intermediate transfer unit 70 by the primary transfer unit 60M, This is a device for removing the liquid developer remaining on the photoconductor 20M by scraping it off with the photoconductor cleaning blade 76M.

In the image forming apparatus of the present invention, among the liquid developers in the plurality of developing units as described above, at least the insulating liquid constituting the liquid developer corresponding to yellow, magenta, and cyan colors is a fatty acid monoester. It is characterized in that it contains an ester and an unsaturated fatty acid triglyceride.
With such a configuration, when a color image is formed by superimposing single color images of the formed colors (yellow, cyan, magenta), it is suitably mixed by the plastic effect of the fatty acid monoester and has excellent color tone. Color images can be formed. In addition, the toner effect can be penetrated into the recording medium by the plastic effect, and the unsaturated fatty acid component is cured by the oxidative polymerization reaction in such a permeation state. It can be fixed. In addition, when the toner particles enter the inside of the recording medium in this way, the resulting color image is smooth without any unevenness, and as a result, an image with excellent gloss can be formed.
The insulating liquid constituting the black liquid developer may contain the fatty acid monoester and the unsaturated fatty acid triglyceride as described above. Thereby, the fixing strength of the obtained image can be made higher.

Next, the developing units 50Y, 50C, 50M, and 50K will be described in detail with reference to the accompanying drawings. In the following description, the developing unit 50M will be typically described.
As shown in FIG. 2, the developing unit 50M includes a liquid developer storage unit 530, a liquid developer supply roller 550, a lifting roller 540, a regulating blade 560, a developing roller 510, and a developing roller cleaning unit 570. have.

The liquid developer storage unit 530 has a function of storing the liquid developer D for developing the latent image formed on the photoconductor 20M.
Further, as shown in FIGS. 1 and 2, a reducing member 590 that reduces the oxidized unsaturated fatty acid component is provided in the liquid developer reservoir 530 of the developing unit 50M.
The reducing member 590 is disposed near the liquid surface of the liquid developer D so as to come into contact with the liquid developer D in the liquid developer reservoir 530.

Since the unsaturated fatty acid component in the liquid developer D stored in the liquid developer storage unit 530 is a component that undergoes oxidative polymerization, the liquid developer storage when stored in the liquid developer storage unit 530 for a long time. Depending on the temperature in the part 530 and the like, the oxidation may proceed with time. As a result, the function as the insulating liquid is lowered, and the obtained image quality may be lowered. In particular, this tendency is relatively strong in a liquid developer containing an oxidative polymerization accelerator.
Thus, by installing the reducing member 590 for reducing the oxidized unsaturated fatty acid component in the liquid developer reservoir 530 as described above, it is possible to prevent the deterioration of the function of the insulating liquid over a long period of time. As a result, it is possible to more effectively prevent the deterioration of the image quality of the obtained image.

The reducing member 590 is mainly composed of zeolite.
Zeolite has a condensed aluminosilicate structure, and is a crystal in which SiO ₄ tetrahedrons or AlO ₄ tetrahedrons substituted with Al instead of Si share oxygen atoms and are bonded in a three-dimensional network. It is.
Zeolite has a cation exchange ability, and it is considered that the oxidized unsaturated fatty acid component is reduced by this ability.

The reducing member 590 is a porous body. Such a porous body can be obtained by sintering zeolite powder.
When the reducing member 590 is a porous body, the contact area with the liquid developer D increases, and the unsaturated fatty acid component can be reduced efficiently. Further, oxygen contained in the liquid developer 1 can be taken into the pores, and oxidation of the unsaturated fatty acid component contained in the liquid developer D can be effectively prevented.

The porosity of the reducing member 590 is about 50 to 80 vol%, and preferably about 70 to 80 vol%. Thereby, an unsaturated fatty acid component can be reduced more efficiently. In addition, oxygen contained in the liquid developer D can be more efficiently taken into the pores.
In addition, the reducing member 590 can be attached and detached, so that the reducing member having reduced reducing ability and adsorption ability can be replaced with a new one.
In the configuration shown in the drawing, such a reducing member is provided in a developing unit (developing unit) containing (reserving) yellow, magenta, and cyan liquid developers. If necessary, the black developing unit 50K (developing unit 15K) may be provided.

The developer supply roller 550 has a function of supplying the liquid developer D to the developing roller 510.
Further, the developer supply roller 550 has a surface pressed against an elastic body layer described later of the developing roller 510 in order to appropriately transfer the liquid developer D on the developer supplying roller 550 to the developing roller 510. is doing. Further, the developer supply roller 550 can rotate around its central axis 550 a, and the central axis 550 a is below the rotation central axis of the developing roller 510. Further, the developer supply roller 550 rotates in a direction (clockwise in FIG. 2) opposite to the rotation direction of the developing roller 510 (counterclockwise in FIG. 2).

  Further, the liquid developer supply roller 550 is immersed in the liquid developer D accommodated in the liquid developer reservoir 530 with a part thereof exposed. Accordingly, when the liquid developer supply roller 550 rotates in such a situation, the liquid developer supply roller 550 enters the liquid developer D on the right side in FIG. 2 when viewed from the vertical plane A passing through the central axis of the liquid developer supply roller 550. Then, the liquid developer supply roller 550 advances from the liquid developer D on the left side in FIG.

The lifting roller 540 is configured such that, on the liquid surface of the liquid developer D, the liquid-side supply surface 580 on the side where the liquid developer-supply roller 550 rotates and enters the liquid developer D is the central axis of the liquid developer-supply roller 550. It has a function of making it higher than the horizontal plane B passing through 550a. The pumping roller 540 is a SUS roller and has a diameter of about 10 mm.
The pumping roller 540 has the liquid developer supply roller 550 arranged so that the axial direction of the central axis 540a is along the axial direction of the central axis 550a of the liquid developer supply roller 550 and when viewed from the vertical plane A described above. It is provided on the side that rotates and enters the liquid developer D (that is, the right side in FIG. 2 when viewed from the vertical plane A). Further, the central shaft 540 a of the liquid feeding roller 540 is positioned vertically below the central shaft 550 a of the liquid developer supply roller 550, and the upper end 540 b of the liquid lifting roller 540 is the liquid developer supply roller 550. It is located above the central axis 550a in the vertical direction. Further, the pumping roller 540 is separated from the liquid developer supply roller 550 with a width of about 2 mm.

Further, the pumping roller 540 is rotatable about its central axis 540a, and rotates in the same direction (clockwise in FIG. 2) as the rotation direction of the liquid developer supply roller 550 (clockwise in FIG. 2). The rotational speed of the pumping roller 540 is the same as the rotational speed of the liquid developer supply roller 550 and the linear speed.
The liquid raising roller 540 configured in this manner makes the entry side liquid level 580 higher than the horizontal plane B by rotating. For example, when the pumping roller 540 rotates while the entry side liquid level 580 is lower than the horizontal plane B, the rotation causes the liquid developer D around the pumping roller 540 to move, and the entry side The liquid level 580 becomes higher than the horizontal plane B.
The liquid lifting roller 540 has the above-described function, and moves the liquid developer D stored in the liquid developer reservoir 530 toward the liquid developer supply roller 550, so that the liquid developer D is transferred. It also has a function of supplying the liquid developer supply roller 550 and a function of stirring the liquid developer D in order to maintain the liquid developer D in an appropriate state.

  The regulating blade 560 contacts the surface of the liquid developer supply roller 550 and regulates the amount of the liquid developer D on the liquid developer supply roller 550. That is, the regulating blade 560 plays a role of scraping off excess liquid developer on the liquid developer supply roller 550 and measuring the liquid developer D on the liquid developer supply roller 550 supplied to the development roller 510. . The restriction blade 560 is made of urethane rubber as an elastic body, and is supported by a restriction blade support member 562 made of metal such as iron. Further, the regulation blade 560 is provided on the side where the liquid developer supply roller 550 rotates and advances from the liquid developer D when viewed from the vertical plane A (that is, the left side in FIG. 2 when viewed from the vertical plane A). It has been. The rubber hardness of the regulating blade 560 is about 62 degrees according to JIS-A, and the hardness (about 62 degrees) of the contact portion of the regulating blade 560 with the surface of the liquid developer supply roller 550 is about the development described later. The hardness of the elastic body layer of the roller 510 is lower than the hardness (about 85 degrees) of the pressure contact portion to the surface of the liquid developer supply roller 550.

  The developing roller 510 carries the liquid developer D and conveys it to the developing position facing the photoconductor 20M in order to develop the latent image carried on the photoconductor 20M with the liquid developer D. The developing roller 510 includes a conductive elastic layer on the outer peripheral portion of an inner core made of metal such as iron, and has a diameter of about 20 mm. The elastic body layer has a two-layer structure. As the inner layer, urethane rubber having a rubber hardness of about 30 degrees JIS-A and a thickness of about 5 mm is used, and as the surface layer (outer layer), the rubber hardness is JIS. A urethane rubber having a thickness of about 30 μm at about 85 ° A is provided. The developing roller 510 is in pressure contact with the liquid developer supply roller 550 and the photoconductor 20M in a state of being elastically deformed with the surface layer serving as a pressure contact portion.

  Further, the developing roller 510 can rotate around its central axis, and the central axis is below the rotational central axis of the photoconductor 20M. Further, the developing roller 510 rotates in a direction (counterclockwise in FIG. 2) opposite to the rotation direction of the photoconductor 20M (clockwise in FIG. 2). When developing the latent image formed on the photoconductor 20M, an electric field is formed between the developing roller 510 and the photoconductor 20M.

The developing roller cleaning unit 570 has a rubber developing roller cleaning blade 571 in contact with the surface of the developing roller 510, and the liquid developer remaining on the developing roller 510 after development is performed at the developing position. It is an apparatus for scraping and removing D by a developing roller cleaning blade 571.
In the developing unit 50M configured as described above, the liquid lifting roller 540 rotates around its central axis 540a, so that the liquid developer D stored in the liquid developer reservoir 530 is supplied to the liquid developer supply roller 550. The liquid developer D is supplied to the liquid developer supply roller 550.

The liquid developer D reaches the contact position of the regulating blade 560 by the rotation of the liquid developer supply roller 550. Then, when passing through the contact position, the excess liquid developer D is scraped off by the regulating blade 560, and the amount of liquid developer D supplied to the developing roller 510 is measured.
The liquid developer D held by the liquid developer supply roller 550 reaches the pressure contact position with the development roller 510 by further rotation of the liquid developer supply roller 550. The liquid developer D that has reached the pressure contact position is transferred from the liquid developer supply roller 550 to the development roller 510 by the action of pressure generated by the pressure contact between the liquid developer supply roller 550 and the development roller 510, and the development roller 510. A thin film of liquid developer D is formed thereon.

The thin film of the liquid developer D thus formed on the developing roller 510 reaches the developing position (that is, the pressure contact position with the photosensitive member 20M) facing the photosensitive member 20M by the rotation of the developing roller 510. The latent image formed on the photoconductor 20M is developed under an electric field of a predetermined magnitude at the development position. The liquid developer D on the developing roller 510 that has passed the developing position reaches the contact position of the developing roller cleaning blade 571 as the developing roller 510 further rotates. Then, when passing through the contact position, the liquid developer D adhering to the surface of the developing roller 510 is scraped off by the developing roller cleaning blade 571, and the liquid developer D scraped off is removed from the developing roller. The residual liquid developer is collected by the cleaning unit 570.
Note that the rotation of the liquid developer supply roller 550 is started in a state where the pumping roller 540 is rotating. That is, the liquid developer supply roller 550 is rotated after the pumping roller 540 is rotated.

Next, the fixing device will be described.
The fixing device (fixing unit) F40 fixes the unfixed toner image F5a formed in the developing unit, the transfer unit, and the like on the recording medium F5.
As shown in FIG. 3, the fixing device F40 includes a heat fixing roller F1, a pressure roller F2, a heat-resistant belt F3, a belt stretching member F4, a cleaning member F6, a frame F7, and an ultraviolet irradiation means F8. And a spring F9.

The heat fixing roller (fixing roller) F1 includes a roller base material F1b made of a pipe material, an elastic body F1c covering the outer periphery thereof, and a columnar halogen lamp F1a as a heating source inside the roller base material F1b. It can be rotated counterclockwise as indicated by an arrow in the figure.
Further, the pressure roller F2 has a roller base material F2b made of a pipe material and an elastic body F2c covering the outer periphery thereof, and is rotatable in the clockwise direction indicated by an arrow in the drawing.

  A PFA layer is provided on the surface layer of the elastic body F1c of the heat fixing roller F1. As a result, the elastic bodies F1c and 2c have different thicknesses, but the elastic bodies F1c and 2c are substantially uniformly elastically deformed to form a so-called horizontal nip, and with respect to the peripheral speed of the heat fixing roller F1 Since there is no difference in the conveyance speed of the heat-resistant belt F3 or the recording medium F5, which will be described later, extremely stable image fixing is possible.

  In addition, two columnar halogen lamps F1a and F1a constituting a heating source are built in the heat fixing roller F1, and the heating elements of these columnar halogen lamps F1a and F1a are arranged at different positions. Yes. Then, by selectively lighting each columnar halogen lamp F1a, F1a, a fixing nip portion where a heat-resistant belt F3, which will be described later, is wound around the heat-fixing roller F1, and a belt stretching member F4, which will be described later, are attached to the heat-fixing roller F1. The temperature controller is easily performed under different conditions from the sliding contact portion, different conditions between the wide recording medium and the narrow recording medium, or the like.

The pressure roller F2 is disposed so as to face the heat fixing roller F1, and is configured to apply pressure to a recording medium F5 on which an unfixed toner image is formed via a heat-resistant belt F3 described later. ing. By applying pressure, the insulating liquid as described above can be more efficiently permeated into the recording medium F5. As a result, the unsaturated fatty acid component contained in the insulating liquid can be more reliably cured inside the recording medium F5 by heat, ultraviolet irradiation, which will be described later, and the toner image F5a is more formed on the recording medium F5 by the anchor effect. It can be firmly fixed.
Further, the pressure roller F2 has a roller base material F2b made of a pipe material and an elastic body F2c covering the outer periphery thereof, and is rotatable in the clockwise direction indicated by an arrow in the drawing.

The aforementioned elastic body F1c of the heat fixing roller F1 and the elastic body F2c of the pressure roller F2 are subjected to substantially uniform elastic deformation to form a so-called horizontal nip. Further, since there is no difference in the conveyance speed of the heat-resistant belt F3 or the recording medium F5 described later with respect to the peripheral speed of the heat fixing roller F1, extremely stable image fixing can be performed.
The heat-resistant belt F3 is an endless annular belt that is stretched around the outer periphery of the pressure roller F2 and the belt stretching member F4 and is movable, and is sandwiched between the heat fixing roller F1 and the pressure roller F2. is there.

  The heat-resistant belt F3 has a thickness of 0.03 mm or more, and its front surface (the surface on which the recording medium F5 comes into contact) is formed of PFA, and the rear surface (the pressure roller F2 and the belt stretching member F4 is in contact). The side surface is formed of a seamless tube having a two-layer structure formed of polyimide. The heat-resistant belt F3 is not limited to this, and can be formed of other materials such as a metal tube such as a stainless steel tube or a nickel electroformed tube, or a heat-resistant resin tube such as silicone.

The belt stretching member F4 is disposed upstream of the fixing nip portion between the heat fixing roller F1 and the pressure roller F2 in the conveyance direction of the recording medium F5, and has an arrow P around the rotation axis F2a of the pressure roller F2. It is arranged so that it can swing in the direction.
The belt stretching member F4 is configured to stretch the heat-resistant belt F3 in the tangential direction of the heat fixing roller F1 in a state where the recording medium F5 does not pass through the fixing nip portion. If the fixing pressure is large at the initial position where the recording medium F5 enters the fixing nip portion, the entry may not be smoothly performed and the recording medium F5 may be fixed in a state where the tip of the recording medium F5 is broken. By adopting a configuration in which F3 is stretched in the tangential direction of the heat fixing roller F1, an inlet port of the recording medium F5 through which the recording medium F5 enters smoothly can be formed, and the stable fixing nip portion of the recording medium F5 can be formed. Can enter.

  The belt stretching member F4 is fitted into the inner periphery of the heat-resistant belt F3 and cooperates with the pressure roller F2 to apply a tension f to the heat-resistant belt F3 (a heat-resistant belt F3 is a belt). Sliding on the tension member F4). This belt stretching member F4 is disposed at a position where the heat-resistant belt F3 is wound around the heat fixing roller F1 side from the pressing portion tangent L between the heat fixing roller F1 and the pressure roller F2 to form a nip. The protruding wall F4a protrudes from one end or both ends of the belt stretching member F4 in the axial direction. The protruding wall F4a is formed by the heat-resistant belt F3 when the heat-resistant belt F3 approaches one of the axial ends. The contact to the end of the heat-resistant belt F3 is regulated by contacting the wall F4a. A spring F9 is contracted between the end of the protruding wall F4a opposite to the heat fixing roller F1 and the frame, and the protruding wall F4a of the belt stretching member F4 is lightly pressed by the heat fixing roller F1, so that the belt tension is increased. The frame member F4 is positioned in sliding contact with the heat fixing roller F1.

The position where the belt stretching member F4 is lightly pressed against the heat fixing roller F1 is the nip initial position, and the position where the pressure roller F2 is pressed against the heat fixing roller F1 is the nip end position.
The linear pressure on the recording medium F5 at the nip end position, that is, the linear pressure of the pressure roller F2 on the recording medium F5 is preferably 500 g / cm or less, and more preferably 300 g / cm or less. Even at such a relatively low linear pressure, the toner particles can be firmly fixed to the recording medium F5 by applying the liquid developer of the present invention. Further, since the linear pressure is relatively low, the driving power of the pressure roller F2 and the heat fixing roller F1 can be reduced, and energy saving can be achieved.

  In the fixing device F40, the recording medium F5 on which the unfixed toner image F5a is formed enters the fixing nip portion from the nip initial position and passes between the heat-resistant belt F3 and the heat fixing roller F1, and the nip end position. As a result, the unfixed toner image F5a formed on the recording medium F5 is thermally fixed, and then discharged in the tangential direction L of the pressing portion of the pressure roller F2 to the heat fixing roller F1.

  The ultraviolet irradiation means F8 has a function of irradiating the surface of the recording medium F5 ejected as described above on which the toner image F5a is formed with ultraviolet rays. By adopting such a configuration, the unsaturated fatty acid component contained in the insulating liquid can be solidified more strongly by heat and ultraviolet irradiation, and as a result, the toner particles are more firmly fixed on the recording medium. Can be made. Further, since the toner particles can be firmly fixed on the recording medium without being heated to a particularly high temperature by the heat fixing roller F1 due to the irradiation of ultraviolet rays, the effect of using the liquid developer of the present invention can be obtained. Due to this synergistic effect, the toner particles can be fixed to the recording medium at a lower temperature and at a higher speed, and the toner particles can be more firmly fixed to the recording medium. Furthermore, since a large amount of heat is not required for fixing, the toner particles can be sufficiently fixed on the recording medium by irradiation with ultraviolet rays even if the time for passing through the fixing nip is relatively short. That is, since fixing does not take time, the printing speed can be further increased. Further, since a large amount of heat is not required for fixing, energy saving can be achieved. As a result, an environmentally friendly fixing device can be provided.

The cleaning member F6 is disposed between the pressure roller F2 and the belt stretching member F4.
The cleaning member F6 is in slidable contact with the inner peripheral surface of the heat-resistant belt F3 and cleans foreign matter, wear powder, and the like on the inner peripheral surface of the heat-resistant belt F3. In this way, by cleaning the foreign matter, wear powder, and the like, the heat-resistant belt F3 is refreshed, and the above-described instability factor of the friction coefficient is removed. Further, the belt stretching member F4 is provided with a recess F4f, and is configured to store foreign matter, abrasion powder, or the like removed from the heat-resistant belt F3.

  In order to stably drive the heat-resistant belt F3 by the pressure roller F2 and the belt stretching member F4 and stably drive the pressure roller F2, the friction coefficient between the pressure roller F2 and the heat-resistant belt F3 is determined by the belt tension. It is good to set larger than the friction coefficient of the frame member F4 and the heat-resistant belt F3. However, the friction coefficient is such that foreign matter enters between the heat-resistant belt F3 and the pressure roller F2 or between the heat-resistant belt F3 and the belt stretching member F4, or the heat-resistant belt F3, the pressure roller F2, and the belt stretching member. It may become unstable due to wear of the contact portion with F4.

  Therefore, the belt tension member F4 and the heat-resistant belt F3 have a winding angle smaller than the winding angle of the pressure roller F2 and the heat-resistant belt F3, and the diameter of the belt stretching member F4 is smaller than the diameter of the pressure roller F2. Set as follows. As a result, the length that the heat-resistant belt F3 slides on the belt stretching member F4 is shortened, which can be avoided from instability factors such as changes with time and disturbances, and the heat-resistant belt F3 is driven stably by the pressure roller F2. Will be able to.

  The time required for the toner particles to pass through the fixing nip portion (nip time) is preferably 0.02 to 0.2 seconds, and more preferably 0.03 to 0.1 seconds. Even when the time required for the toner particles to pass through the fixing nip portion is such a short time, the liquid developer of the present invention as described above can be sufficiently fixed, and the printing speed can be reduced. Further speedup can be achieved.

  Specifically, the heat (fixing temperature) applied by the heat fixing roller F1 is preferably 80 to 200 ° C, and more preferably 100 to 180 ° C. When the fixing temperature is within the above range, the oxidative polymerization reaction (curing reaction) of the unsaturated fatty acid component contained in the insulating liquid can proceed more effectively, and the toner particles can be recorded on the recording medium. Can be firmly fixed.

Next, a second embodiment of the image forming apparatus of the present invention will be described. In the following description, parts different from those of the above-described first embodiment will be mainly described, and description of similar parts will be omitted.
As shown in FIG. 4, the image forming apparatus 1000 ′ includes four developing units 15K, 15M, 15C, and 15Y, a transfer unit (conveying belt) 80 ′, and a fixing device (fixing unit) F40. .

The developing units 15K, 15M, 15C, and 15Y have the same configuration as that of the above-described embodiment.
The transfer section (conveyance belt) 80 ′ is an endless belt stretched around a plurality of support rollers, and has a function of conveying the recording medium F5.
Further, the transfer portion (conveyance belt) 80 ′ is rotationally driven while being in contact with the photoreceptors 20K, 20M, 20C, and 20Y.
The transported recording medium F5 is configured to pass through a contact portion between the transfer portion 80 ′ and each photoconductor.

The monochrome image formed by each developing unit is sequentially transferred to the recording medium F5 that passes therethrough.
As described above, the image forming apparatus 1000 ′ according to the present embodiment sequentially transfers the single color images formed by the developing units to the recording medium F5 conveyed through the transfer unit (conveying belt) 80 ′, thereby An unfixed color image formed by superimposing single color images is formed on the recording medium F5.
In the present embodiment, as shown in FIG. 4, black, magenta, cyan, and yellow single color images are sequentially transferred to the recording medium F5.
The unfixed color image formed as described above is fixed on the recording medium F5 by the fixing device F40 as described above.

Similar to the above-described embodiment, the image forming apparatus 1000 ′ of the present embodiment configures at least liquid developers corresponding to yellow, magenta, and cyan among the liquid developers in the plurality of developing units. The insulating liquid that contains the fatty acid monoester and the unsaturated fatty acid triglyceride.
Therefore, also in the image forming apparatus 1000 ′ having such a configuration, when forming a color image by superimposing single color images of the formed colors (yellow, cyan, magenta), it is preferable due to the plastic effect of the fatty acid monoester. It is possible to form a color image that is mixed and excellent in color tone. In addition, the toner effect can be penetrated into the recording medium by the plastic effect, and the unsaturated fatty acid component is cured by the oxidative polymerization reaction in such a permeation state. It can be fixed. In addition, when the toner particles enter the inside of the recording medium in this way, the resulting color image is smooth without any unevenness, and as a result, an image with excellent gloss can be formed.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, in the image forming method of the present invention, an optional process can be added as necessary.
In addition, each unit constituting the image forming apparatus of the present invention can be replaced with any one that exhibits the same function, or other configurations can be added.

Further, the image forming apparatus of the present invention is not limited to the one shown in the figure. For example, the arrangement of the developing units corresponding to the respective colors is not limited to the illustrated configuration, and may be different.
Further, in the image forming apparatus of the present invention, the fixing device is not limited to the above-described embodiment, and each part constituting the fixing device is replaced with any one that exhibits the same function, or other configuration is added. You can also
In the above-described embodiment, the fixing device having the ultraviolet irradiation unit has been described. However, the fixing device is not limited thereto, and for example, the ultraviolet irradiation unit may not be provided.
In the above-described embodiment, the heating is described from the fixing roller side. However, the heating may be performed from the pressure roller side.

[1] Production of liquid developer (yellow liquid developer Y-1)
First, 80 parts by weight of a polyester resin (softening temperature: 99 ° C.) and 20 parts by weight of a yellow pigment as a coloring agent (Pigment Yellow 93, manufactured by Dainichi Seika Co., Ltd.) were prepared. These components were mixed using a 20 L type Henschel mixer to obtain a raw material for toner production.

Next, this raw material (mixture) was kneaded using a twin-screw kneading extruder. The kneaded product extruded from the extrusion port of the biaxial kneading extruder was cooled.
The kneaded product cooled as described above was coarsely pulverized to obtain a powder (coarse pulverized product) having an average particle size of 1.0 mm or less. A hammer mill was used for coarse pulverization of the kneaded product.
Next, 100 parts by weight of the coarsely pulverized product of the kneaded product was added to 250 parts by weight of toluene, and the polyester resin of the kneaded product was dissolved by treating with an ultrasonic homogenizer (output: 400 μA) for 1 hour. A solution (toner material solution) was obtained.

On the other hand, an aqueous liquid in which sodium dodecylbenzenesulfonate as a dispersant: 1 part by weight and ion-exchanged water: 700 parts by weight were uniformly mixed was prepared.
The aqueous liquid was stirred with a homomixer (made by Tokushu Kika Kogyo Co., Ltd.) while adjusting the stirring rotation speed.
The toner material solution was dropped into the agitated aqueous liquid. As a result, an aqueous emulsion in which the dispersoid having an average particle size of 0.5 μm was uniformly dispersed was obtained.

  Thereafter, the toluene in the aqueous emulsion is removed under the conditions of temperature: 100 ° C. and atmospheric pressure: 80 kPa, and after cooling to room temperature, the concentration of the solid fine particles is adjusted by adding a predetermined amount of water. A dispersed aqueous dispersion was obtained. In the resulting aqueous dispersion, substantially no toluene remained. The obtained aqueous dispersion had a solid content (dispersoid) concentration of 20 wt%. The average particle size of the dispersoid (solid fine particles) dispersed in the suspension was 0.5 μm. The average particle size of the dispersoid was measured using a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.).

Next, 0.35 part by weight of a nonionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., trade name “Epan 450”) is added to 100 parts by weight of the obtained aqueous dispersion while stirring. did.
Next, while adjusting the stirring speed and setting the temperature to 30 ° C., 35 parts by weight of 3% aqueous ammonium sulfate solution was added dropwise to 100 parts by weight of the aqueous dispersion. As a result, an associated particle dispersion in which associated particles are dispersed was obtained.
From the obtained associated particle dispersion, the associated particles were separated by a centrifugal separator, washed, and then dried by a vacuum dryer to obtain associated particles. The average particle diameter of the obtained associated particles was 5.2 μm.

  Next, 4 mm carbon chromium beads are put into a 500 mL container, and then rapeseed oil fatty acid methyl produced by transesterification reaction between rapeseed oil and methanol (manufactured by Nisshin Oilio Co., Ltd.): 90 parts by weight, as a dispersant Polyamine fatty acid condensation polymer (manufactured by Nippon Lubrizol, trade name “Solsperse 13900”): 1.5 parts by weight were charged. In addition, content of the fatty acid monoester contained in rapeseed oil fatty acid methyl was 99.9 wt% or more. Rapeseed oil fatty acid methyl is mainly a fatty acid monoester mainly having unsaturated fatty acid monoesters such as methyl oleate, methyl linoleate and methyl α-linolenate and saturated fatty acid monoesters such as methyl palmitate and methyl stearate. It was composed of an ester.

Next, 90 parts by weight of the obtained associated particles were added, mixed for 10 minutes by a ball mill, and then crushed by a ball mill for 200 hours to obtain a toner dispersion.
After crushing, rapeseed oil (manufactured by Nisshin Oilio Co., Ltd., trade name “Nisshin Canola Oil Healthy Light”): 120 parts by weight and ascorbic acid stearate as an antioxidant (thermal decomposition temperature: 300 ° C. or higher): 2.0 parts by weight and encapsulated oxidation polymerization accelerator (manganese octylate): 1.25 parts by weight (1.0 part by weight as an oxidation polymerization accelerator) were added to disperse the toner particles. Dispersion was carried out for 24 hours by adding 1 mm beads using a ball mill. As a result, a liquid developer was obtained. In addition, content of the unsaturated fatty acid triglyceride contained in rapeseed oil was 98 wt%.

The average particle size of the toner particles in the obtained liquid developer was 1.5 μm, and the standard deviation of the particle size between the toner particles was 0.50 μm. Moreover, the viscosity of the liquid developer measured according to JIS Z8809 using a vibration viscometer at 25 ° C. was 265 mPa · s. Further, the electrical resistance of the insulating liquid was 2.6 × 10 ¹³ Ωcm, and the electrical resistance of the liquid developer was 3.1 × 10 ¹² Ωcm. The iodine value of the insulating liquid was 87.
The encapsulated oxidative polymerization accelerator used was prepared as follows.
First, 10 g of manganese octylate as an oxidative polymerization accelerator was dissolved in 15 ml of acetone, and the resulting solution was adsorbed on porous hydrophilic silica gel to obtain a core material.
Next, 10 g of the obtained core material and 20 g of polyethylene glycol (PEG) were heated and mixed to obtain a mixture.
Next, this mixture was put in 400 ml of AF6 solvent manufactured by Mitsubishi Oil Corporation, and sufficiently dispersed with a homomixer, and then slowly cooled to deposit PEG.

(Cyan liquid developer C-1)
A liquid developer C-1 was produced in the same manner as the liquid developer Y-1, except that a cyan pigment (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3) was used as the colorant.
(Magenta liquid developer M-1)
A liquid developer M-1 was produced in the same manner as the liquid developer Y-1, except that a cyan pigment (manufactured by Dainichi Seika Co., Ltd., Pigment Red 122) was used as the colorant.

(Black liquid developer K-1)
A liquid developer K-1 was produced in the same manner as the liquid developer Y-1, except that carbon black was used as the colorant.
(Yellow liquid developer Y-2)
Associated particles were obtained in the same manner as in the production of the liquid developer Y-1.

Next, 4 mm carbon chrome beads are put into a 500 mL container, and then rapeseed oil fatty acid methyl (manufactured by Nisshin Oillio Co., Ltd.): 60 parts by weight and a polyamine fatty acid polycondensation polymer (manufactured by Nippon Lubrizol Co., Ltd., Trade name “Solsperse 13940”): 1.5 parts by weight were charged.
Next, 90 parts by weight of the obtained associated particles were added, mixed for 10 minutes by a ball mill, and then crushed by a ball mill for 200 hours to obtain a toner dispersion.

  After crushing, rapeseed oil (Nisshin Oilio, trade name “Nisshin Canola Oil Healthy Light”): 150 parts by weight and ascorbic acid stearate as an antioxidant (thermal decomposition temperature: 300 ° C. or higher): 2.0 parts by weight and encapsulated oxidation polymerization accelerator (manganese octylate): 1.25 parts by weight (1.0 part by weight as an oxidation polymerization accelerator) were added to disperse the toner particles. Dispersion was carried out for 24 hours by adding 1 mm beads using a ball mill. As a result, a liquid developer was obtained.

The average particle size of the toner particles in the obtained liquid developer was 1.5 μm, and the standard deviation of the particle size between the toner particles was 0.52 μm. Moreover, the viscosity of the liquid developer measured according to JIS Z8809 using a vibration viscometer at 25 ° C. was 415 mPa · s. In addition, the electrical resistance of the insulating liquid was 3.4 × 10 ¹³ Ωcm, and the electrical resistance of the liquid developer was 4.2 × 10 ¹² Ωcm. The iodine value of the insulating liquid was 87.
As the encapsulated oxidative polymerization accelerator, one prepared in the same manner as the liquid developer Y-1 was used.

(Cyan liquid developer C-2)
A liquid developer C-2 was produced in the same manner as the liquid developer Y-2 except that a cyan pigment (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3) was used as the colorant.
(Magenta liquid developer M-2)
A liquid developer M-2 was produced in the same manner as the liquid developer Y-2 except that a cyan pigment (manufactured by Dainichi Seika Co., Ltd., Pigment Red 122) was used as the colorant.

(Black liquid developer K-2)
A liquid developer K-2 was produced in the same manner as the liquid developer Y-2 except that carbon black was used as the colorant.
(Yellow liquid developer Y-3)
A liquid developer Y-3 was produced in the same manner as the liquid developer Y-1, except that an epoxy resin (softening temperature: 128 ° C.) was used as the resin material.

(Cyan liquid developer C-3)
A liquid developer C-3 was produced in the same manner as the liquid developer Y-3 except that a cyan pigment (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3) was used as the colorant.
(Magenta liquid developer M-3)
A liquid developer M-3 was produced in the same manner as the liquid developer Y-3 except that a cyan pigment (manufactured by Dainichi Seika Co., Ltd., Pigment Red 122) was used as the colorant.

(Black liquid developer K-3)
A liquid developer K-3 was produced in the same manner as the liquid developer Y-3 except that carbon black was used as the colorant.
(Yellow liquid developer Y-4)
Associated particles were obtained in the same manner as in the production of the liquid developer Y-1.

Next, 4 mm carbon chrome beads are placed in a 500 mL container, and then rapeseed oil (Nisshin Oilio Co., Ltd., trade name “Nisshin Canola Oil Healthy Light”): 90 parts by weight, and polyamine fatty acid condensed as a dispersant. Polymer (trade name “Solsperse 13940” manufactured by Nippon Lubrizol Co., Ltd.): 1.5 parts by weight was charged.
Next, 90 parts by weight of the obtained associated particles were added, mixed for 10 minutes by a ball mill, and then crushed by a ball mill for 200 hours to obtain a toner dispersion.

  After crushing, rapeseed oil (manufactured by Nisshin Oilio Co., Ltd., trade name “Nisshin Canola Oil Healthy Light”): 120 parts by weight and ascorbic acid stearate as an antioxidant (thermal decomposition temperature: 300 ° C. or higher): 2.0 parts by weight and encapsulated oxidation polymerization accelerator (manganese octylate): 1.25 parts by weight (1.0 part by weight as an oxidation polymerization accelerator) were added to disperse the toner particles. Dispersion was carried out for 24 hours by adding 1 mm beads using a ball mill. As a result, a liquid developer was obtained.

The average particle diameter of the toner particles in the obtained liquid developer was 4.8 μm, and the standard deviation of the particle diameter between the toner particles was 1.50 μm. Moreover, the viscosity of the liquid developer measured according to JIS Z8809 using a vibration viscometer at 25 ° C. was 765 mPa · s. Moreover, the electrical resistance of the insulating liquid was 3.8 × 10 ¹³ Ωcm, and the electrical resistance of the liquid developer was 6.2 × 10 ¹³ Ωcm.

(Cyan liquid developer C-4)
A liquid developer C-4 was produced in the same manner as the liquid developer Y-4 except that a cyan pigment (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3) was used as the colorant.
(Magenta liquid developer M-4)
A liquid developer M-4 was produced in the same manner as the liquid developer Y-4 except that a cyan pigment (manufactured by Dainichi Seika Co., Ltd., Pigment Red 122) was used as the colorant.
(Black liquid developer K-4)
A liquid developer K-4 was produced in the same manner as the liquid developer Y-4 except that carbon black was used as the colorant.

[2] Image formation (Example 1)
Liquid developers Y-1, C-1, M-1, and K-1 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 as illustrated in FIG. A color image of a predetermined unfixed pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. 3 is used. And fixed.

  The fixing device is made of a heat fixing roller in which a release layer having a thickness of 30 μm is formed on the surface of an aluminum cored bar (outer diameter φ30 mm, length 240 mm, wall thickness 1 mm), and heat vulcanizing silicone rubber. A pressure roller having an outer diameter of 30 mm, a length of 240 mm, and a thickness of 7 mm was used. As the release layer, a layer composed of tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) was used.

Further, as a heating source in the heat fixing roller, a halogen lamp having a light emitting part length of 240 mm, a total length of 292 mm, and 850 watts was used. The linear pressure of the pressure roller against the recording medium was 480 g / cm, and the nip width was about 8 mm. The fixing temperature was set to 180 ° C. Further, the conveyance speed of the recording medium of the fixing device was 30 sheets / minute.
Further, a high pressure mercury lamp (100 W / cm ² ) was used as the ultraviolet irradiation means, and irradiation was performed from a distance of 2 cm from the recording medium.

(Example 2)
Liquid developers Y-2, C-2, M-2, and K-2 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 as illustrated in FIG. A color image of a predetermined unfixed pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. 3 is used. And fixed.

(Example 3)
Liquid developers Y-3, C-3, M-3, and K-3 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 as illustrated in FIG. A color image of a predetermined unfixed pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. 3 is used. And fixed.

Example 4
Liquid developers Y-1, C-1, M-1, and K-4 are respectively charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 as illustrated in FIG. A color image of a predetermined unfixed pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. 3 is used. And fixed.

(Example 5)
Liquid developers Y-2, C-2, M-2, and K-4 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 as shown in FIG. A color image of a predetermined unfixed pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. 3 is used. And fixed.

(Example 6)
Liquid developers Y-3, C-3, M-3, and K-4 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 as shown in FIG. A color image of a predetermined unfixed pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. 3 is used. And fixed.

(Example 7)
Liquid developers Y-1, C-1, M-1, and K-1 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 ′ as shown in FIG. Then, an unfixed color image of a predetermined pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. Fixing.

(Example 8)
Liquid developers Y-2, C-2, M-2, and K-2 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 ′ as shown in FIG. Then, an unfixed color image of a predetermined pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. Fixing.

Example 9
Liquid developers Y-3, C-3, M-3, and K-3 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 ′ as shown in FIG. Then, an unfixed color image of a predetermined pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. Fixing.

(Example 10)
Liquid developers Y-1, C-1, M-1, and K-4 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 ′ as shown in FIG. Then, an unfixed color image of a predetermined pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. Fixing.
Table 1 shows the color of the liquid developer introduced into each developing unit and the presence or absence of an oxidation polymerization accelerator for each of the above Examples and Comparative Examples.

(Example 11)
Liquid developers Y-2, C-2, M-2, and K-4 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 ′ as shown in FIG. Then, an unfixed color image of a predetermined pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. Fixing.

(Example 12)
Liquid developers Y-3, C-3, M-3, and K-4 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 ′ as shown in FIG. Then, an unfixed color image of a predetermined pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. Fixing.

(Comparative Example 1)
Liquid developers Y-4, C-1, M-1, and K-4 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 as illustrated in FIG. A color image of a predetermined unfixed pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. 3 is used. And fixed.

(Comparative Example 2)
Liquid developers Y-4, C-1, M-1, and K-1 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 as illustrated in FIG. A color image of a predetermined unfixed pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. 3 is used. And fixed.

(Comparative Example 3)
Liquid developers Y-4, C-4, M-4, and K-4 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 as shown in FIG. A color image of a predetermined unfixed pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. 3 is used. And fixed.

(Comparative Example 4)
Liquid developers Y-4, C-1, M-1, and K-4 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 ′ as shown in FIG. Then, an unfixed color image of a predetermined pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. Fixing.

(Comparative Example 5)
Liquid developers Y-4, C-1, M-1, and K-1 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 ′ as shown in FIG. Then, an unfixed color image of a predetermined pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. Fixing.

(Comparative Example 6)
Liquid developers Y-4, C-4, M-4, and K-4 are charged into the developing units 15Y, 15C, 15M, and 15K of the image forming apparatus 1000 ′ as shown in FIG. Then, an unfixed color image of a predetermined pattern is formed on a recording medium (“J paper” manufactured by Fuji Xerox Office Supply and “Nina Bond paper” manufactured by Kimberly-Clark), and then a fixing device as shown in FIG. Fixing.
In each Example and each Comparative Example, Table 1 shows the configuration of the insulating liquid constituting the liquid developer charged in each developing unit.

[3] Evaluation (3-1) Fixing strength Eraser (Lion 261-11, made by Lion Business Machine Co., Ltd.) erases the fixed color image on the recording medium obtained in each of the above examples and comparative examples. After rubbing twice with a pressing load of 1.0 kgf, the residual ratio of image density was measured by “X-Rite model 404” manufactured by X-Rite Inc, and evaluated according to the following five-step criteria.
A: Image density residual ratio is 95% or more.
A: Image density residual ratio is 90% or more and less than 95%.
○: Image density remaining rate is 80% or more and less than 90%.
Δ: Image density remaining rate is 70% or more and less than 80%.
X: Image density remaining rate is less than 70%.

(3-2) Evaluation of Glossiness (Gloss) of Formed Color Image The glossiness (gloss) of the fixed color image on the recording medium obtained in each of the above Examples and each Comparative Example was measured with an incident angle of 60 ° and reflection. Measurement was performed using LAB-GLOSS manufactured by Macbeth under the condition of an angle of 60 °, and the evaluation was performed according to the following five-step criteria.
◎: 20 or more ◎: 15 or more and less than 20 ○: 10 or more and less than 15 Δ: 5 or more and less than 10 ×: less than 5 These results are shown in Table 2.

As is apparent from Table 2, in each of the examples, both the fixing strength and the gloss were excellent. In each example, a clear and excellent color image was obtained. On the other hand, in each comparative example, a satisfactory result was not obtained.
Further, when the fixing temperature of the fixing device was changed to 160 ° C., 140 ° C., 120 ° C., 100 ° C., and 80 ° C. and the fixing strength was evaluated in the same manner as described above, the same results were obtained. This shows that the image forming method and the image forming apparatus of the present invention can be suitably fixed at low temperature.

Further, when the conveyance speed of the recording medium of the fixing device was increased from 30 sheets / minute to 40 sheets / minute, 50 sheets / minute, and 60 sheets / minute, and the fixing strength was evaluated in the same manner as described above, similar results were obtained. was gotten. This shows that the image forming method and the image forming apparatus of the present invention are suitable for high-speed printing.
Further, when the linear pressure by the pressure roller of the fixing device was changed from 480 g / cm to 240 g / cm and the fixing strength was evaluated in the same manner as described above, the same result was obtained. This shows that a sufficient fixing strength can be obtained without applying a high linear pressure.

1 is a diagram illustrating a first embodiment of an image forming apparatus of the present invention. FIG. 2 is a schematic diagram illustrating an example of a developing unit provided in the image forming apparatus of the present invention. 1 is a cross-sectional view illustrating an example of a fixing device applied to an image forming apparatus of the present invention. It is a figure which shows 2nd Embodiment of the image forming apparatus of this invention.

Explanation of symbols

  1000, 1000 '... Image forming apparatus 15Y, 15M, 15C, 15K ... Developing unit 20Y, 20M, 20C, 20K ... Photoconductor 30Y, 30M, 30C, 30K ... Charging unit 40Y, 40M, 40C, 40K ... Exposure unit 50Y, 50M, 50C, 50K ... Developing unit 60Y, 60M, 60C, 60K ... Primary transfer unit 70 ... Intermediate transfer unit 73Y, 73M, 73C, 73K ... Static elimination unit 75Y, 75M, 75C, 75K ... Photoconductor cleaning unit 76Y, 76M , 76C, 76K ... Photoconductor cleaning blade 80 ... Secondary transfer unit 80 '... Transfer section (conveyance belt) 510 ... Developing roller 530 ... Liquid developer reservoir 540 ... Liquid roller 540a ... Central shaft 540b ... Upper end 550 ... Developing Agent supply roller 550a ... Mandrel 560 ... Regulating blade 562 ... Regulating blade support member 570 ... Developing roller cleaning unit 571 ... Developing roller cleaning blade 580 ... Entry side liquid level 590 ... Reducing member F40 ... Fixing device F1 ... Heat fixing roller (heating roller) F1a ... Column shape Halogen lamp F1b ... Roller base material F1c ... Elastic body F2 ... Pressure roller F2a ... Rotating shaft F2b ... Roller base material F2c ... Elastic body F3 ... Heat-resistant belt F4 ... Belt stretch member F4a ... Projection wall F4f ... Concavity F5 ... Recording medium F5a ... Color image F6 ... Cleaning member F7 ... Frame F8 ... Ultraviolet irradiation means F9 ... Spring

Claims (9)

An image forming method for forming a color image on a recording medium using a liquid developer in which toner particles are dispersed in an insulating liquid,
A development step of forming a plurality of single color images corresponding to each color using a plurality of liquid developers having different colors;
Transferring a plurality of monochrome images corresponding to each color to the recording medium, and forming an unfixed color image on the recording medium; and
A fixing step of fixing the unfixed color image on the recording medium,
A fatty acid in which a monohydric alcohol and a fatty acid are ester-bonded in the insulating liquid constituting the liquid developer corresponding to at least yellow, magenta, and cyan among the plurality of liquid developers having different colors An image forming method comprising a monoester and an unsaturated fatty acid triglyceride.   The content of the fatty acid monoester in the insulating liquid constituting the liquid developer corresponding to yellow, magenta, and cyan is X [wt%], and the content of the unsaturated fatty acid triglyceride is Y [wt%]. The image forming method according to claim 1, wherein a relationship of 0.01 ≦ X / Y ≦ 1.0 is satisfied.   3. The image forming method according to claim 1, wherein in the fixing step, the color image is fixed to the recording medium by applying pressure while heating the recording medium on which the color image is formed.   4. The image forming method according to claim 1, wherein in the fixing step, the color image is irradiated with ultraviolet rays. An image forming apparatus for forming a color image on a recording medium using a liquid developer in which toner particles are dispersed in an insulating liquid,
A plurality of developing units that form a single color image corresponding to each color using a plurality of liquid developers having different colors;
An intermediate transfer unit that sequentially transfers the plurality of single-color images formed by the plurality of developing units and forms an intermediate transfer image formed by superimposing the transferred plurality of single-color images;
A secondary transfer unit that transfers the intermediate transfer image to the recording medium and forms an unfixed color image on the recording medium;
A fixing unit for fixing the unfixed color image on the recording medium,
A fatty acid in which a monohydric alcohol and a fatty acid are ester-bonded in the insulating liquid constituting the liquid developer corresponding to at least yellow, magenta, and cyan among the plurality of liquid developers having different colors An image forming apparatus comprising a monoester and a fatty acid triglyceride. An image forming apparatus for forming a color image on a recording medium using a liquid developer in which toner particles are dispersed in an insulating liquid,
A plurality of developing units that form a single color image corresponding to each color using a plurality of liquid developers having different colors;
By transporting the recording medium, the plurality of monochrome images formed by the plurality of developing units are sequentially transferred to the recording medium, and an unfixed color image formed by superimposing the transferred plurality of monochrome images is A transfer portion formed on a recording medium;
A fixing unit for fixing the unfixed color image on the recording medium,
A fatty acid in which a monohydric alcohol and a fatty acid are ester-bonded in the insulating liquid constituting the liquid developer corresponding to at least yellow, magenta, and cyan among the plurality of liquid developers having different colors An image forming apparatus comprising a monoester and a fatty acid triglyceride.   The fatty acid monoester content in the insulating liquid constituting the liquid developer corresponding to yellow, magenta, and cyan is X [wt%], and the fatty acid triglyceride content is Y [wt%]. The image forming apparatus according to claim 5, wherein a relationship of 0.01 ≦ X / Y ≦ 1.0 is satisfied.   The image forming apparatus according to claim 5, wherein the fixing unit includes an ultraviolet irradiation unit that irradiates the toner image with ultraviolet rays when the color image is fixed to the recording medium. The fixing unit includes a heat fixing roller that applies heat to the recording medium, and a pressure roller that is disposed to face the heat fixing roller and applies pressure to the recording medium.
The image forming apparatus according to claim 5, wherein a linear pressure of the pressure roller with respect to the recording medium is 500 g / cm or less.

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