JP2015001710A - Liquid developer set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid developer set that has high fixing quality and can provide desired image quality.SOLUTION: There is provided a liquid developer set that includes a black developer including first toner particles and a chromatic color developer including second toner particles, where the first toner particles include a first resin and black colorant and the second toner particles include a second resin and chromatic color colorant, and the first resin and second resin are each a urethane-modified polyester resin in which at least two polyesters are joined with a constitutional unit derived from a compound having an isocyanate group and satisfy the formula 3000≤Mk<Mc≤50000 and the formula Uc<Uk, where Mk represents the number average molecular weight of the first resin; Mc represents the number average molecular weight of the second resin; Uk represents the urethane group density of the first resin; and Uc represents the urethane group density of the second resin.

Description

  The present invention relates to a liquid developer set.

  Various liquid developers (also called wet developers) used in electrophotographic image forming apparatuses are known. For example, Japanese Patent Application Laid-Open No. 2004-287314 (Patent Document 1) discloses a liquid developer containing toner particles made of a binder resin and a colorant, and the binder resin made of a polyurethane resin and a crystalline resin. Disclosure.

JP 2004-287314 A

  The liquid developer has an advantage that the particle size of toner particles is about 0.5 μm to 3 μm, and the particle size of toner particles is smaller than that of a dry developer. As a result, the liquid developer can achieve high image quality while reducing the adhesion amount of toner particles.

  In electrophotographic color image formation, a liquid developer set including a black developer and a chromatic developer such as a cyan developer is used. That is, a plurality of color liquid developers are simultaneously used in the image forming apparatus, and a color image is formed on the recording material by superimposing, transferring, and fixing the toner images of the respective colors onto the recording material.

  In consideration of such usage as a liquid developer set, the liquid developers of each color included in the liquid developer set can be fixed under the same temperature condition and have the same fixing quality between the color materials. It is desirable.

  Further, from the viewpoint of making the image density of each color uniform, it is desirable that the adhesion amount of toner particles be the same in each color liquid developer.

  However, as will be described below, in the prior art, the toner particles attached to the black developer and the toner particles attached to the other chromatic developer are kept at the same temperature while the toner particles are attached to the same amount. It was extremely difficult to fix under the conditions and obtain the same fixing quality.

  Generally, the coloring power of the colorant is different in each color liquid developer. For example, carbon black generally used as a black colorant tends to have a lower coloring power than chromatic colorants such as copper phthalocyanine, which is a cyan colorant, and carmine 6B, which is a magenta colorant. Therefore, when a black developer and, for example, a cyan developer are used as a liquid developer set, the colorant content of toner particles in the black developer is the colorant content of toner particles in the cyan developer. It is required to design higher than However, since the toner particles are difficult to melt when the content of the colorant is increased, the temperature range in which the black developer can be fixed is shifted to a higher temperature side. For this reason, it is difficult to fix the black developer and the cyan developer under the same temperature condition.

  In particular, in the liquid developer, since the particle size of the toner particles is small as described above, the influence of the colorant content on the fixing temperature is large, and there is a difference in the fixing temperature between the black developer and the other chromatic developer. There was a tendency to become even larger.

  Furthermore, carbon black, which is a black colorant, has insufficient electrical characteristics required for electrophotographic image formation, and may be used in combination with other organic colorants. As a result, the colorant content of the toner particles in the black developer is further increased, and the fixing temperature range is further shifted to a higher temperature side than other chromatic color developers.

  By the way, in an electrophotographic image forming apparatus, in order to form a color image by simultaneously using a plurality of color liquid developers, the fixing temperature is set according to the highest fixing temperature among them. It is common. Therefore, the fixing temperature of the image forming apparatus is set in accordance with the fixing temperature of the black developer. In this case, the chromatic color developer other than the black developer is exposed to a temperature higher than an appropriate fixing temperature in the fixing step. As a result, in the color image after fixing, the chromatic color has a lower gloss than black. Accordingly, since the glossiness varies among the color materials, a desired fixing quality cannot be ensured as the liquid developer set.

  In order to cope with such a problem, in the conventional liquid developer set, a method of adjusting the fixing temperature range by changing the molecular weight of the resin constituting the toner particle for each color has been used. However, it has been found that when the resin molecular weight of the toner particles is simply lowered for the purpose of lowering the fixing temperature of the black developer, the carrier liquid tends to remain between the molecules. In such a case, since the carrier liquid remains in the toner film even after the fixing process, the strength of the toner film is lowered, and sufficient fixing strength cannot be obtained. Therefore, depending on this method, the fixing strength varies among the color materials, so that a desired fixing quality cannot be ensured as a liquid developer set.

  Thus, when the black developer adhesion amount and the chromatic color developer adhesion amount are the same, it is impossible to ensure the desired fixing quality.

  Patent Document 1 is directed to improving the fixing strength and the like in a monochromatic liquid developer, and does not provide a sufficient solution to the problems related to the liquid developer set as described above. .

  The present invention has been made in view of such a situation, and the object of the present invention is to have the same amount of toner particles attached to the black developer and toner particles of the chromatic developer. However, an object of the present invention is to provide a liquid developer set having high fixing quality and capable of obtaining a desired image quality.

  As described above, by adjusting the resin molecular weight of the toner particles contained in the black developer to be lower than the resin molecular weight of the toner particles contained in the other chromatic developer in the liquid developer set, It is possible to match the fixing temperature range with the color developer. However, when the fixing temperature range of the black developer is adjusted by such a method, there arises a new problem that the fixing strength of the black developer is lowered.

  As a result of earnest investigation of the cause of the decrease in fixing strength by the above method, the present inventor has found that the intermolecular van der Waals force is weakened due to a decrease in the resin molecular weight, and the intermolecular binding force is weakened. In addition, it is found that the carrier liquid easily enters the gaps of the toner, and further, the carrier liquid that has entered the gaps between the molecules tends to remain even after the fixing process. It was found that the strength of the film was reduced.

  And as a result of earnestly examining the means for suppressing the entry of the carrier liquid, the present inventor has found that the urethane-modified polyester resin has a structure in which the carrier liquid is difficult to enter. Furthermore, the present inventor has not limited to this, and has examined the configuration of the liquid developer set in more detail. As a result, the urethane-modified polyester resin that constitutes the black toner particles and the urethane-modified polyester resin that constitutes the other chromatic toner are used. By adjusting the molecular weight and the urethane group concentration, the adhesion amount can be made the same, and the fixing temperature range of the black developer and the chromatic developer can be made the same without reducing the glossiness of the chromatic color. I came up with an idea. The inventor has completed the present invention by further studying based on this idea.

  That is, the liquid developer set of the present invention is a liquid developer set including a black developer including first toner particles and a chromatic color developer including second toner particles, and the first toner particles include 1 resin and a black colorant, the second toner particles include a second resin and a chromatic colorant, and each of the first resin and the second resin has at least two polyesters each having an isocyanate group It is a urethane-modified polyester resin bonded by a structural unit derived from the above, and satisfies the following formulas (1) and (2).

3000 ≦ Mk <Mc ≦ 50000 (1)
Uc <Uk (2)
In formula (1), Mk represents the number average molecular weight of the first resin, and Mc represents the number average molecular weight of the second resin. In formula (2), Uk represents the urethane group concentration of the first resin, and Uc represents the urethane group concentration of the second resin.

  Here, the first resin and the second resin include a common structural unit in the molecular structure, and the common structural unit occupies 80% or more of the total structural units in each molecular structure. Is preferred.

  The first resin and the second resin may be substantially the same polymer species.

  Furthermore, it is preferable that the liquid developer set satisfies the following condition 1 and / or condition 2.

  Condition 1: The first toner particles have a core-shell structure in which shell particles containing a shell resin are attached to or coated on the surface of the core particles containing the core resin, and the core resin is the first resin. .

  Condition 2: The second toner particles have a core-shell structure in which shell particles containing a shell resin are attached to or coated on the surface of the core particles containing the core resin, and the core resin is the second resin. .

  Since the liquid developer set of the present invention has the above-described configuration, even if the adhesion amount of the toner particles of the black developer and the adhesion amount of the toner particles of the chromatic developer are the same amount, a desired amount can be obtained. It has an excellent effect that an image density can be obtained and a higher fixing quality can be obtained.

1 is a schematic conceptual diagram of an electrophotographic image forming apparatus.

Hereinafter, embodiments according to the present invention will be described in more detail.
<Liquid developer set>
The liquid developer set of the present embodiment includes a black developer and a chromatic developer. Here, at least one chromatic color developer is included, and a plurality of chromatic color developers may be included.

  Note that the chromatic color means a color other than black, white, and gray. Typical examples of such chromatic colors include cyan, magenta, yellow, and the like.

<Liquid developer>
The liquid developer included in the liquid developer set of the present embodiment includes at least an insulating liquid (carrier liquid) and toner particles, and the toner particles are dispersed in the insulating liquid. Such a liquid developer can contain other arbitrary components as long as these components are contained. Other components include, for example, a toner dispersant (in contrast to a pigment dispersant described later contained in the toner particles, a dispersant contained in the insulating liquid for dispersing the toner particles. And a charge control agent, a thickener, and the like.

  The mixing ratio of the liquid developer can be, for example, 10 to 50% by mass of toner particles, and the remainder can be an insulating liquid or the like. If the blending amount of the toner particles is less than 10% by mass, the toner particles are likely to settle, and the stability over time during long-term storage tends to decrease. In addition, a large amount of liquid development is required to obtain the required image density. It is necessary to supply the agent, the amount of the insulating liquid adhering to the recording material such as paper increases, it becomes necessary to dry it at the time of fixing, and the generated vapor may cause environmental problems. is there. On the other hand, when the blending amount of the toner particles exceeds 50% by mass, the viscosity of the liquid developer becomes too high, which tends to be difficult in production and handling.

  Such a liquid developer is useful as a developer for an electrophotographic image forming apparatus. More specifically, electrophotographic liquid developers, paints, electrostatic recording liquid developers, and ink jet printers used in electrophotographic image forming apparatuses such as copying machines, printers, digital printing machines, and simple printing machines. It can be used as an oil-based ink or an electronic paper ink.

<Toner particles>
The toner particles contained in the liquid developer include a resin and a colorant dispersed in the resin. Such toner particles can contain any other component as long as these components are contained. Examples of other components include pigment dispersants, waxes, charge control agents, and the like. Here, the blending ratio of the resin and the colorant may be determined so that the concentration expressed when the toner particles are applied in a desired adhesion amount becomes a desired concentration.

  In the present embodiment, the median diameter of the toner particles is preferably 0.5 μm or more and 5.0 μm or less. Such a median diameter is smaller than the particle diameter of toner particles of a conventional dry developer, which is one of the features of the present embodiment. However, when the median diameter is less than 0.5 μm, the particles are If the diameter is too small, the mobility in the electric field may be deteriorated and the developability may be deteriorated. If it exceeds 5 μm, the uniformity may be deteriorated and the image quality may be deteriorated. The median diameter here refers to D50. A more preferable median diameter is 0.5 μm or more and 2.0 μm or less.

  In the exemplary embodiment, the average circularity of the toner particles is preferably 0.85 or more and 0.95 or less, and the standard deviation of the circularity is preferably 0.01 or more and 0.1 or less. This is because the average circularity of the toner particles and the standard deviation of the circularity occupy such a range, thereby providing an effect of improving transferability and cleaning properties.

  The circularity referred to here is a numerical value obtained by dividing the perimeter of a circle having the same area as the particle area projected in two dimensions by the perimeter of the particle, and the average circularity is an arithmetic average value of the numerical values. Is shown.

  In the present embodiment, the median diameter, average circularity, and standard deviation of circularity of toner particles are all determined using a flow particle image analyzer (trade name: “FPIA-3000S”, manufactured by Sysmex Corporation). Can do. This apparatus is preferable because the insulating liquid can be used as a dispersion medium as it is, and thus the state of particles in an actual dispersion state can be measured as compared with a system in which measurement is performed in an aqueous system.

<Black developer and chromatic developer>
In the present embodiment, the black developer includes first toner particles, and the first toner particles include a first resin and a black colorant. The chromatic developer includes second toner particles, and the second toner particles include a second resin and a chromatic colorant.

<Urethane modified polyester resin>
In the present embodiment, the first resin and the second resin are urethane-modified polyester resins. Here, the urethane-modified polyester resin is a resin having a structure in which the end of the polyester is chain-lengthened with a urethane bond. That is, the urethane-modified polyester resin is a resin in which at least two or more polyesters are bonded by a structural unit derived from a compound having an isocyanate group. Such urethane-modified polyester resin preferably exhibits crystallinity.

  Such a urethane-modified polyester resin is obtained by first obtaining a polyester resin as a skeleton by polymerization, and chain-extending the terminal of the polyester resin with di (tri) isocyanate. Di (tri) isocyanate means diisocyanate and / or triisocyanate.

  In the liquid developer set of the present embodiment, when the number average molecular weight of the first resin is Mk and the number average molecular weight of the second resin is Mc, Mk and Mc satisfy the following formula (1), and When the urethane group concentration of the first resin is Uk and the urethane group concentration of the second resin is Uc, Uk and Uc satisfy the following formula (2).

3000 ≦ Mk <Mc ≦ 50000 (1)
Uc <Uk (2)
By having the above-described configuration, the liquid developer set of the present embodiment can fix the black developer and the chromatic color developer in the same fixing temperature region while keeping the same amount of adhesion of the black developer and the chromatic color developer, and The same fixing ability can be ensured, and the desired image quality can be realized. That is, it can have high fixing quality.

  Here, the urethane group concentration and the number average molecular weight are, for example, equivalent ratios between the acid group amount of the polycarboxylic acid component and the hydroxyl group amount of the polyol component ([[ Acid group] / [hydroxyl group]) and the equivalent ratio ([isocyanate group] / [hydroxyl group]) of the isocyanate group amount of the compound having an isocyanate group for bonding the polyester resins to the hydroxyl group amount of the polyester resin. By adjusting, it can control to a desired range.

  In the present embodiment, when the liquid developer set includes a plurality of chromatic color developers, the above formulas (1) and (1) are used between any one or more chromatic color developers and the black developer. If the relationship of 2) is satisfied, the effect of the present invention is shown. In addition, as long as the black developer and at least one chromatic color developer satisfy the above relationship, even if a chromatic color developer that does not satisfy the above relationship is included, the scope of the present invention is satisfied. It does not deviate.

  Here, if Mk is less than 3000, the resin becomes excessively soft and tends to cause an offset during fixing. If Mc exceeds 50000, the resin is difficult to melt, and the fixing strength decreases. It tends to be easy. Therefore, in this Embodiment, as shown to the said Formula (1), the number average molecular weight of 1st resin and 2nd resin needs to be 3000 or more and 50000 or less. In addition, the more preferable range of the number average molecular weight of 1st resin and 2nd resin is 10000-30000.

<Number average molecular weight (Mn) and weight average molecular weight (Mw)>
In the present specification, the number average molecular weight (hereinafter also referred to as “Mn”) and the weight average molecular weight (hereinafter also referred to as “Mw”) of a resin (excluding a polyurethane resin) are allowed to be tetrahydrofuran (hereinafter abbreviated as “THF”). The dissolved content was measured using gel permeation chromatography (GPC (Gel Permeation Chromatography), hereinafter abbreviated as “GPC”) under the following conditions. The Mn and Mw of the urethane-modified polyester resin are measured by this method.

Measuring device: “HLC-8120” manufactured by Tosoh Corporation
Column: “TSKgelGMHXL” (2) manufactured by Tosoh Corporation and “TSKgelMultiporeHXL-M” (1) manufactured by Tosoh Corporation
Sample solution: 0.25 mass% THF solution Injection amount of sample solution to the column: 100 μl
Flow rate: 1 ml / min Measurement temperature: 40 ° C
Detector: Refractive index detector Reference material: 12 standard polystyrene (TSK standard POLYSTYRENE) manufactured by Tosoh Corporation (Molecular weight: 500, 1050, 2800, 5970, 9100, 18100, 37900, 96400, 190000, 355000, 1090000, 2890000).

  Moreover, in this specification, Mn and Mw of a polyurethane resin are measured on condition of the following using GPC.

Measuring device: “HLC-8220GPC” manufactured by Tosoh Corporation
Column: “TSK guardcolumn α” (1) manufactured by Tosoh Corporation and “TSKgel α-M” (1) manufactured by Tosoh Corporation
Sample solution: 0.125 mass% dimethylformamide solution Injection amount of dimethylformamide solution to the column: 100 μl
Flow rate: 1 ml / min Measurement temperature: 40 ° C
Detector: Refractive index detector Reference material: 12 standard polystyrene (TSK standard POLYSTYRENE) manufactured by Tosoh Corporation (Molecular weight: 500, 1050, 2800, 5970, 9100, 18100, 37900, 96400, 190000, 355000, 1090000, 2890000).

  In the present embodiment, as shown in the above formulas (1) and (2), the resin molecular weight of the black toner particles is not simply lowered with respect to the resin molecular weight of the chromatic toner particles, but at the same time, the urethane of the black toner particles The base concentration is set higher than the urethane group concentration of the chromatic toner particles. By increasing the urethane group concentration, the resin becomes tough, so that entry of the carrier liquid between molecules can be suppressed. Therefore, the above-described configuration can compensate for the decrease in fixing strength accompanying the reduction in the molecular weight of the black toner particles, thereby achieving both the fixing strength of the black developer and the glossiness of the chromatic developer. be able to. That is, it can have high fixing quality. This makes it possible to achieve high image quality with a uniform image density even in an image in which a black toner image and a chromatic toner image are superimposed.

  In other words, the liquid developer set of the present embodiment can fix the black developer and the chromatic color developer in the same fixing temperature range while maintaining the same adhesion amount, and has high fixing quality. This is a liquid developer set that provides desired image quality.

<Urethane group concentration>
The “urethane group concentration (mass%)” means a value obtained by multiplying 100 by the value obtained by dividing the mass of the urethane group contained in the resin by the mass of the resin. Here, as for the urethane group concentration, Uc is preferably 0.5 or more from the viewpoint of maintaining elasticity at high temperature, and Uk is 8 or less from the viewpoint of heat resistance such as document offset resistance. Is preferred. Such urethane group concentration can be measured by the following method.

  For example, the urethane group concentration of the first resin and the second resin can be measured using a gas chromatograph mass spectrometer (GCMS). Specifically, the urethane-modified polyester resin that is the first resin or the second resin is pyrolyzed, and then the urethane group concentration of each resin is measured using GCMS under the following conditions. And the urethane group density | concentration in urethane modified polyester resin is computed using the ratio of the ionic strength detected from the thermally modified urethane modified polyester resin.

  In the present specification, the thermal decomposition of the urethane-modified polyester resin is performed under the following conditions.

Measuring device: “PY-2020iD” manufactured by Frontier Laboratories
Mass of measurement: 0.1 mg
Heating temperature: 550 ° C
Heating time: 0.5 minutes.

  In this specification, the urethane group concentration of the urethane-modified polyester resin is measured under the following conditions after thermal decomposition under the above conditions.

Measuring device: “QP2010” manufactured by Shimadzu Corporation
Column: “UltraALLOY-5” manufactured by Frontier Laboratories (inner diameter: 0.25 mm, length: 30 m, thickness: 0.25 μm)
Temperature range: 100 ° C to 320 ° C (held at 320 ° C)
Temperature increase rate: 20 ° C./min.

<Crystalline / Amorphous>
Moreover, it is preferable that the 1st resin and 2nd resin of this Embodiment show crystallinity. By making the resin structure exhibiting crystallinity, an excellent effect that high glossiness is easily obtained even at a low temperature is imparted.

  In this specification, “crystallinity” means the ratio (Tm / Ta) of the softening point of a resin (hereinafter abbreviated as “Tm”) and the maximum peak temperature of heat of fusion (hereinafter abbreviated as “Ta”) of the resin. ) Is 0.8 or more and 1.55 or less, and the results obtained by differential scanning calorimetry (DSC) do not show a stepwise endothermic change but a clear endothermic peak. It means having. In the present specification, “non-crystalline” means that the ratio of Tm to Ta (Tm / Ta) is larger than 1.55. Tm and Ta can be measured by the following method.

  In addition, it is preferable that Tm of the 1st resin and 2nd resin of this Embodiment is 40 degreeC or more, and it is preferable that it is 80 degrees C or less from a viewpoint of low temperature fixability.

  Tm can be measured using a Koka type flow tester (for example, “CFT-500D” manufactured by Shimadzu Corporation). Specifically, while a 1 g measurement sample is heated at a heating rate of 6 ° C./min, a load of 1.96 MPa is applied to the measurement sample by a plunger, and the measurement sample is pushed out from a nozzle having a diameter of 1 mm and a length of 1 mm. . Then, the relationship between “plunger descent amount (flow value)” and “temperature” is drawn on a graph. The temperature at which the plunger descending amount is ½ of the maximum value of the descending amount is read from the graph, and this value (temperature when half of the measurement sample is pushed out of the nozzle) is defined as Tm.

  Ta can be measured using a differential scanning calorimeter (for example, “DSC210” manufactured by Seiko Instruments Inc.). Specifically, first, a sample used for measuring Ta is pretreated. After the sample is melted at 130 ° C., the temperature is lowered from 130 ° C. to 70 ° C. at a rate of 1.0 ° C./minute, and then the temperature is lowered from 70 ° C. to 10 ° C. at a rate of 0.5 ° C./minute. Next, the sample is heated at a heating rate of 20 ° C./min by DSC method to measure the endothermic change of the sample, and the relationship between the “endothermic amount” and “temperature” is plotted on a graph. At this time, the temperature of the endothermic peak observed at 20 to 100 ° C. is Ta ′. When there are a plurality of endothermic peaks, the temperature of the peak with the largest endothermic amount is defined as Ta '. Then, the sample is stored at (Ta′-10) ° C. for 6 hours, and then stored at (Ta′-15) ° C. for 6 hours.

  Next, by the DSC method, the sample subjected to the pretreatment was cooled to 0 ° C. at a temperature decrease rate of 10 ° C./min, and then the temperature was increased at a temperature increase rate of 20 ° C./min to measure the endothermic change. The relationship between the "heat absorption and heat generation" and "temperature" is plotted on a graph. The temperature at which the endotherm takes the maximum value is taken as the maximum peak temperature (Ta) of heat of fusion.

  In order to obtain a urethane-modified polyester resin having crystallinity as described above, it is preferable to use, for example, a monomer having a linear alkyl skeleton having 4 or more carbon atoms as a constituent component of the resin. As such monomers, for example, aliphatic dicarboxylic acids and aliphatic diols are suitable. These are merely preferred examples, and may contain an aromatic dicarboxylic acid, an aromatic diol, or the like as long as crystallinity is exhibited.

Hereinafter, suitable examples of the monomer constituting the urethane-modified polyester resin will be described.
Preferred examples of the aliphatic dicarboxylic acid that is a starting material for the polyester resin include alkane dicarboxylic acids having 4 to 20 carbon atoms, alkene dicarboxylic acids having 4 to 36 carbon atoms, and ester-forming derivatives thereof. . More preferred aliphatic dicarboxylic acids are succinic acid, adipic acid, sebacic acid, maleic acid, fumaric acid and the like, or ester-forming derivatives thereof.

  Further, preferred as the aliphatic diol which is a starting material of the polyester resin is ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, or 1 , 10-decanediol.

  Next, a compound having an isocyanate group for making a urethane-modified polyester resin by bonding and linking polyester resins obtained by polymerizing the dicarboxylic acid monomer and the diol monomer as described above Will be described.

  As the compound having an isocyanate group of the present embodiment, a compound having a plurality of isocyanate groups in the molecule is preferable. Examples of such compounds include chain aliphatic polyisocyanates and cyclic aliphatic polyisocyanates.

  Examples of chain aliphatic polyisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (hereinafter abbreviated as “HDI”), dodecamethylene diisocyanate, 1,6,11-undecane triisocyanate, 2,2, and the like. 4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethylcaproate, bis (2-isocyanatoethyl) fumarate, bis (2-isocyanatoethyl) carbonate, and 2-isocyanatoethyl-2, Examples include 6-diisocyanatohexanoate, or a combination of two or more of these.

  Examples of the cycloaliphatic polyisocyanate include isophorone diisocyanate (hereinafter abbreviated as “IPDI”), dicyclohexylmethane-4,4′-diisocyanate (hereinafter also referred to as “hydrogenated MDI”), cyclohexylene diisocyanate, methylcyclohexyl. Silylene diisocyanate (hereinafter also referred to as “hydrogenated TDI”), bis (2-isocyanatoethyl) -4-cyclohexene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, and 2,6-norbornane diisocyanate, Or these 2 or more types combined use etc. are mentioned.

  In the present embodiment, the first resin and the second resin, which are urethane-modified polyester resins, include a common structural unit in the molecular structure, and the common structural unit is entirely configured in each molecular structure. It is preferable to occupy 80% or more of the unit. Thus, by approximating the molecular structures of the first resin and the second resin, it becomes possible to more precisely match the fixing temperature and glossiness of each liquid developer, and the present invention as described above. The excellent effect can be further enhanced.

  More preferably, the first resin and the second resin are substantially the same polymer species. Here, substantially the same polymer species indicates that the main components constituting the polymer are equal, and the first resin and the second resin have a common structural unit in the molecular structure as described above. This means that the common structural unit occupies 90% or more of the total structural units in each molecular structure.

<Method for producing toner particles>
The toner particles (that is, the first toner particles and the second toner particles) in the present embodiment can be manufactured based on a conventionally known technique such as a granulation method or a pulverization method.

  Here, the pulverization method is a method in which a resin and a colorant such as a pigment are previously melt-kneaded and pulverized. Such pulverization can be performed in a dry state or in a wet state in an insulating liquid.

  In addition, the granulation method includes suspension polymerization method, emulsion polymerization method, fine particle aggregation method, method of adding a poor solvent to a resin solution to precipitate, spray drying method, etc. There is also a manufacturing method in which the resin composition of the toner particles is made into a core / shell structure with different resins.

  The method for producing toner particles of the present embodiment is not particularly limited, but in order to obtain toner particles having a small diameter and a sharp particle size distribution, it is preferable to employ a granulation method rather than a pulverization method. This is because highly meltable resins and highly crystalline resins are soft and difficult to grind even at room temperature. According to the granulation method, even such a resin is suitable because a desired particle size can be easily obtained.

  In addition, among the above production methods, the resin is dissolved in a good solvent to form a core resin solution, and the core resin solution is mixed with an interfacial tension modifier for a poor solvent having an SP value different from that of the good solvent. After applying shear to form droplets, the good solvent is volatilized to form core resin fine particles.

  According to this method, the particle size and shape of the toner particles can be controlled to a high degree by appropriately adjusting the shearing method, the interfacial tension difference, or the interfacial tension adjusting agent (shell resin fine particles). This method is suitable as a method for obtaining toner particles having a particle size distribution and a shape.

<Core-shell type toner particles>
Features such as the median diameter and circularity of toner particles, which is one of the preferred aspects of the present embodiment described above, are realized by the toner particles being core-shell type toner particles having a core-shell structure. Cheap.

  Therefore, the first resin and / or the second resin of the present embodiment preferably has a core-shell structure in which shell particles containing a shell resin are attached to or coated on the surface of the core particles containing the core resin.

  In other words, the liquid developer set of the present embodiment preferably satisfies the following condition 1 and / or condition 2.

  Condition 1: The first toner particles have a core-shell structure in which shell particles containing a shell resin are attached to or coated on the surface of the core particles containing the core resin, and the core resin is the first resin.

  Condition 2: The second toner particles have a core-shell structure in which shell particles containing a shell resin are attached to or coated on the surface of the core particles containing the core resin, and the core resin is the second resin.

  Hereinafter, the core-shell type toner particles will be described. In the following description, for convenience, the core / shell type toner particles may be referred to as toner particles (C), and the liquid developer containing the toner particles (C) may be referred to as liquid developer (X).

  The toner particles (C) have a structure in which the shell particles (A) containing the shell resin (a) are attached to or coated on the surfaces of the core particles (B) containing the core resin (b).

  Here, in the present embodiment, the core resin (b) is the first resin or the second resin (that is, urethane-modified polyester resin), and the core particle (B) is the first toner particle or the second resin. 2 toner particles.

<Shell resin (a)>
The shell resin (a) in the present embodiment may be a thermoplastic resin or a thermosetting resin. Examples of the shell resin (a) include vinyl resin, polyester resin, polyurethane resin, epoxy resin, polyamide resin, polyimide resin, silicon resin, phenol resin, melamine resin, urea resin, aniline resin, ionomer resin, and polycarbonate resin. Etc. As the shell resin (a), two or more of the above listed resins may be used in combination.

  From the viewpoint of easily obtaining toner particles having the shape according to the present embodiment, it is preferable to use at least one of vinyl resin, polyester resin, polyurethane resin, and epoxy resin as the shell resin (a). More preferably, at least one of a polyester resin and a polyurethane resin is used.

<Vinyl resin>
The vinyl resin may be a homopolymer obtained by homopolymerizing a monomer having a polymerizable double bond (a homopolymer containing a bond unit derived from a vinyl monomer), or a polymerizable double bond. It may be a copolymer obtained by copolymerizing two or more monomers having a bond (a copolymer containing a bond unit derived from a vinyl monomer). Examples of the monomer having a polymerizable double bond include the following (1) to (9).

(1) Hydrocarbon having a polymerizable double bond The hydrocarbon having a polymerizable double bond is, for example, an aliphatic hydrocarbon having a polymerizable double bond represented by the following (1-1) or the following (1 -2) is preferably an aromatic hydrocarbon having a polymerizable double bond.

(1-1) Aliphatic hydrocarbon having a polymerizable double bond An aliphatic hydrocarbon having a polymerizable double bond is, for example, a chain having a polymerizable double bond represented by the following (1-1-1). It is preferably a hydrocarbon or a cyclic hydrocarbon having a polymerizable double bond represented by the following (1-1-2).

(1-1-1) Chain hydrocarbon having a polymerizable double bond Examples of the chain hydrocarbon having a polymerizable double bond include alkenes having 2 to 30 carbon atoms (for example, ethylene, propylene, butene). , Isobutylene, pentene, heptene, diisobutylene, octene, dodecene or octadecene); alkadienes having 4 to 30 carbon atoms (for example, butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene or 1,7-octadiene) Etc.).

(1-1-2) Cyclic hydrocarbon having a polymerizable double bond Examples of the cyclic hydrocarbon having a polymerizable double bond include mono- or dicycloalkene having 6 to 30 carbon atoms (for example, cyclohexene, vinyl, etc.). Cyclohexene or ethylidenebicycloheptene); mono- or dicycloalkadiene having 5 to 30 carbon atoms (for example, cyclopentadiene or dicyclopentadiene) and the like.

(1-2) Aromatic hydrocarbon having a polymerizable double bond As an aromatic hydrocarbon having a polymerizable double bond, for example, styrene; hydrocarbyl of styrene (for example, alkyl having 1 to 30 carbon atoms) , Cycloalkyl, aralkyl and / or alkenyl) substituted (eg, α-methyl styrene, vinyl toluene, 2,4-dimethyl styrene, ethyl styrene, isopropyl styrene, butyl styrene, phenyl styrene, cyclohexyl styrene, benzyl styrene, crotyl) Benzene, divinylbenzene, divinyltoluene, divinylxylene or trivinylbenzene); and vinylnaphthalene.

(2) Monomers having a carboxyl group and a polymerizable double bond and salts thereof Examples of the monomer having a carboxyl group and a polymerizable double bond include unsaturated monocarboxylic acids having 3 to 15 carbon atoms. [For example, (meth) acrylic acid, crotonic acid, isocrotonic acid, cinnamic acid, etc.]; unsaturated dicarboxylic acid having 3 to 30 carbon atoms (anhydride) [for example, (anhydrous) maleic acid, fumaric acid, itaconic acid, (Anhydrous) citraconic acid or mesaconic acid, etc.]; monoalkyl (1-10 carbon atoms) ester of unsaturated dicarboxylic acid having 3 to 10 carbon atoms (for example, maleic acid monomethyl ester, maleic acid monodecyl ester, fumaric acid) Monoethyl ester, itaconic acid monobutyl ester, citraconic acid monodecyl ester, etc.). As used herein, “(meth) acryl” means acrylic and / or methacrylic.

  Examples of the salt of the monomer include alkali metal salts (for example, sodium salt or potassium salt), alkaline earth metal salts (for example, calcium salt or magnesium salt), ammonium salts, amine salts, and 4 A grade ammonium salt etc. are mentioned.

  The amine salt is not particularly limited as long as it is an amine compound. For example, primary amine salt (for example, ethylamine salt, butylamine salt or octylamine salt); secondary amine salt (for example, diethylamine salt or dibutylamine salt) ); Tertiary amine salts (for example, triethylamine salt or tributylamine salt) and the like.

  Examples of the quaternary ammonium salt include tetraethylammonium salt, triethyllaurylammonium salt, tetrabutylammonium salt and tributyllaurylammonium salt.

  Examples of the salt of the monomer having a carboxyl group and a polymerizable double bond include sodium acrylate, sodium methacrylate, monosodium maleate, disodium maleate, potassium acrylate, potassium methacrylate, monopotassium maleate. , Lithium acrylate, cesium acrylate, ammonium acrylate, calcium acrylate, and aluminum acrylate.

(3) Monomers having a sulfo group and a polymerizable double bond and salts thereof (4) Monomers having a phosphono group and a polymerizable double bond and salts thereof (5) Hydroxyl groups and a polymerizable double bond (6) Nitrogen-containing monomer having a polymerizable double bond Examples of the nitrogen-containing monomer having a polymerizable double bond include the following (6-1) to (6-4): The monomer to show is mentioned.

(6-1) Monomer having an amino group and a polymerizable double bond Examples of the monomer having an amino group and a polymerizable double bond include aminoethyl (meth) acrylate and dimethylaminoethyl (meth) acrylate. , Diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, N-aminoethyl (meth) acrylamide, (meth) allylamine, morpholinoethyl (meth) acrylate, 4-vinylpyridine, 2-vinylpyridine, crotylamine N, N-dimethylaminostyrene, methyl-α-acetaminoacrylate, vinylimidazole, N-vinylpyrrole, N-vinylthiopyrrolidone, N-arylphenylenediamine, aminocarbazole, aminothiazole, aminoindole, aminopyrrole, Examples include minoimidazole and aminomercaptothiazole.

  The monomer having an amino group and a polymerizable double bond may be a salt of the monomers listed above. Examples of the salts of the monomers listed above include the salts listed as “Salts of the above monomers” in “(2) Monomers having a carboxyl group and a polymerizable double bond and their salts”. Can be mentioned.

(6-2) Monomer having an amide group and a polymerizable double bond Examples of the monomer having an amide group and a polymerizable double bond include (meth) acrylamide, N-methyl (meth) acrylamide, N -Butyl (meth) acrylamide, diacetone (meth) acrylamide, N-methylol (meth) acrylamide, N, N'-methylene-bis (meth) acrylamide, cinnamic acid amide, N, N-dimethyl (meth) acrylamide, N, N-dibenzyl (meth) acrylamide, (meth) acrylformamide, N-methyl-N-vinylacetamide, N-vinylpyrrolidone and the like can be mentioned.

(6-3) A monomer having 3 to 10 carbon atoms having a nitrile group and a polymerizable double bond As a monomer having 3 to 10 carbon atoms having a nitrile group and a polymerizable double bond, for example, (Meth) acrylonitrile, cyanostyrene, cyanoacrylate, and the like.

(6-4) Monomers having 8 to 12 carbon atoms having a nitro group and a polymerizable double bond As monomers having 8 to 12 carbon atoms having a nitro group and a polymerizable double bond, for example, Nitrostyrene etc. are mentioned.

(7) Monomer having 6 to 18 carbon atoms having an epoxy group and a polymerizable double bond (8) Monomer having 2 to 16 carbon atoms having a halogen element and a polymerizable double bond (9) Polymerization Ester having 4 to 16 carbon atoms having a polymerizable double bond Examples of the ester having 4 to 16 carbon atoms having a polymerizable double bond include vinyl acetate; vinyl propionate; vinyl butyrate; diallyl phthalate; diallyl adipate; Isopropenyl acetate; vinyl methacrylate; methyl-4-vinyl benzoate; cyclohexyl methacrylate; benzyl methacrylate; phenyl (meth) acrylate; vinyl methoxyacetate; vinyl benzoate; ethyl-α-ethoxy acrylate; Alkyl (meth) acrylate [for example, methyl Meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc.]; dialkyl fumarate (two alkyl groups have 2 to 8 carbon atoms) A linear alkyl group, a branched alkyl group or an alicyclic alkyl group); a dialkyl maleate (two alkyl groups are a linear alkyl group having 2 to 8 carbon atoms, a branched alkyl group or an alicyclic ring) Poly (meth) allyloxyalkanes (eg, diaryloxyethane, triaryloxyethane, tetraallyloxyethane, tetraallyloxypropane, tetraallyloxybutane or tetrametaallyloxyethane) ); A monomer having a polyalkylene glycol chain and a polymerizable double bond [for example, Polyethylene glycol (Mn = 300) mono (meth) acrylate, polypropylene glycol (Mn = 500) mono (meth) acrylate, methyl alcohol ethylene oxide (hereinafter “ethylene oxide” is abbreviated as “EO”) 10 mol adduct (meta ) Acrylate or lauryl alcohol EO 30 mole adduct (meth) acrylate, etc.]; poly (meth) acrylates {eg poly (meth) acrylates of polyhydric alcohols [eg ethylene glycol di (meth) acrylate, propylene glycol di ( Meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate or polyethylene glycol di (meth) acrylate]] and the like. In the present specification, “(meth) arylo” means alilo and / or metallo.

  Specific examples of the vinyl resin include, for example, a styrene- (meth) acrylic acid ester copolymer, a styrene-butadiene copolymer, a (meth) acrylic acid- (meth) acrylic acid ester copolymer, and a styrene-acrylonitrile copolymer. Copolymers, styrene- (maleic anhydride) copolymers, styrene- (meth) acrylic acid copolymers, styrene- (meth) acrylic acid-divinylbenzene copolymers, and styrene-styrenesulfonic acid- (meth) acrylic acid esters A copolymer etc. are mentioned.

  The vinyl resin may be a homopolymer or copolymer of a monomer having a polymerizable double bond as described in (1) to (9) above, or may be polymerized as described in (1) to (9) above. A polymer obtained by polymerizing a monomer having a double bond and a monomer (m) having a polymerizable double bond having a molecular chain (k) may be used. Examples of the molecular chain (k) include a linear or branched hydrocarbon chain having 12 to 27 carbon atoms, a fluoroalkyl chain having 4 to 20 carbon atoms, and a polydimethylsiloxane chain. The difference in SP value between the molecular chain (k) in the monomer (m) and the insulating liquid (L) is preferably 2 or less. In the present specification, the “SP value” is a method by Fedors [Polym. Eng. Sci. 14 (2) 152, (1974)].

  Although it does not specifically limit as a monomer (m) which has a polymerizable double bond which has a molecular chain (k), For example, the following monomers (m1)-(m3) etc. are mentioned. As the monomer (m), two or more monomers (m1) to (m3) may be used in combination.

Monomer (m1) having a linear hydrocarbon chain having 12 to 27 carbon atoms (preferably 16 to 25 carbon atoms) and a polymerizable double bond
Examples of such a monomer (m1) include mono-linear alkyl of unsaturated monocarboxylic acid (alkyl having 12 to 27 carbon atoms) ester and mono-linear alkyl of unsaturated dicarboxylic acid (alkyl Examples thereof include esters having 12 to 27 carbon atoms. Examples of the unsaturated monocarboxylic acid and unsaturated dicarboxylic acid include (meth) acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, and other carboxyl group-containing vinyl monomers having 3 to 24 carbon atoms. Examples include masses.

  Specific examples of the monomer (m1) include, for example, dodecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate and ( (E.g., meta) eicosyl acrylate.

Monomer (m2) having a branched hydrocarbon chain having 12 to 27 carbon atoms (preferably 16 to 25 carbon atoms) and a polymerizable double bond
Examples of such a monomer (m2) include a branched alkyl of an unsaturated monocarboxylic acid (alkyl having 12 to 27 carbon atoms) and a monobranched alkyl of an unsaturated dicarboxylic acid (the carbon number of alkyl is 12-27) Ester etc. are mentioned. As said unsaturated monocarboxylic acid and unsaturated dicarboxylic acid, the thing similar to what was enumerated as a specific example of unsaturated monocarboxylic acid and unsaturated dicarboxylic acid in a monomer (m1) is mentioned, for example.

  Specific examples of the monomer (m2) include, for example, 2-decyltetradecyl (meth) acrylate.

  Other examples include a monomer (m3) having a fluoroalkyl chain having 4 to 20 carbon atoms and a polymerizable double bond.

<Melting point>
Melting | fusing point of shell resin (a) becomes like this. Preferably it is 0-220 degreeC, More preferably, it is 30-200 degreeC, More preferably, it is 40-80 degreeC. From the viewpoints of particle size distribution and shape of the toner particles, powder flowability of the liquid developer (X), heat-resistant storage stability and stress resistance, the melting point of the shell resin (a) is the same as that of the liquid developer (X). It is preferable that it is more than the temperature at the time of manufacture. If the melting point of the shell resin is lower than the temperature at which the liquid developer is produced, it may be difficult to prevent the toner particles from uniting with each other, and it may be difficult to prevent the toner particles from splitting. . In addition, the distribution width in the particle size distribution of the toner particles is difficult to be narrowed. In other words, there is a possibility that the variation in the particle size of the toner particles becomes large.

  In the present specification, the melting point is measured in accordance with a method prescribed in ASTM D3418-82 using a differential scanning calorimeter (such as “DSC20” or “SSC / 580” manufactured by Seiko Instruments Inc.). It is a thing.

<Mn (number average molecular weight)>
The Mn (obtained by GPC measurement) of the shell resin (a) is preferably 100 to 5000000, preferably 200 to 5000000, and more preferably 500 to 500000.

<SP value>
The SP value of the shell resin (a) is preferably 7 to 18 (cal / cm ³ ) ^1/2 , more preferably 8 to 14 (cal / cm ³ ) ^1/2 .

<Shell particles (A)>
Shell particles (A) in the present embodiment include shell resin (a). Any known method can be adopted as the method for producing the shell particles (A), and the method is not particularly limited. For example, the following methods [1] to [7] can be mentioned [1]: Shell resin (a) is pulverized dry using a known dry pulverizer such as a jet mill [2]. : Disperse the powder of shell resin (a) in an organic solvent and pulverize it wet using a known wet disperser such as a bead mill or roll mill [3]: Solution of shell resin (a) using a spray dryer or the like [4]: Addition or cooling of a poor solvent to the shell resin (a) solution to supersaturate and precipitate the shell resin (a) [5]: Shell resin (a) [6]: The precursor of the shell resin (a) is polymerized in water by an emulsion polymerization method, a soap-free emulsion polymerization method, a seed polymerization method, or a suspension polymerization method. [7]: Shi Le precursor of the resin (a) is polymerized by such dispersion polymerization in organic solvents.

  Of these methods, the methods [4], [6] and [7] are preferable from the viewpoint of ease of production of the shell particles (A), and more preferably the methods [6] and [7]. Is preferred.

<Volume average particle diameter>
In this case, the volume average particle diameter of the shell particles (A) can be appropriately adjusted so as to be a particle diameter suitable for obtaining toner particles (C) having a desired particle diameter. The volume average particle diameter of the shell particles (A) is preferably 0.0005 to 3 μm. The upper limit of the volume average particle diameter of the shell particles (A) is more preferably 2 μm, and even more preferably 1 μm. The lower limit of the volume average particle diameter of the shell particles (A) is more preferably 0.01 μm, still more preferably 0.02 μm, and most preferably 0.04 μm. For example, when it is desired to obtain toner particles (C) having a volume average particle diameter of 1 μm, the volume average particle diameter of the shell particles (A) is preferably 0.0005 to 0.3 μm, more preferably 0.001. ~ 0.2 μm. For example, when it is desired to obtain toner particles (C) having a volume average particle size of 10 μm, the volume average particle size of the shell particles (A) is preferably 0.005 to 3 μm, more preferably 0.05 to 2 μm. It is.

<Core resin (b) and core particle (B)>
As described above, in the present embodiment, when the toner particles (C) are core / shell type toner particles, the core resin (b) is the urethane-modified polyester resin. And core particle (B) contains core resin (b).

<SP value>
The SP value of the core resin (b) may be adjusted as appropriate. The SP value of the core resin (b) is preferably 8 to 16 (cal / cm ³ ) ^1/2 , more preferably 9 to 14 (cal / cm ³ ) ^1/2 .

<Core shell structure>
As described above, the resin contained in the toner particles of the present embodiment is such that the shell particles (A) containing the shell resin (a) are attached or coated on the surfaces of the core particles (B) containing the core resin (b). It is preferable to have a core-shell structure.

  The mass ratio [(A) :( B)] of the shell particles (A) and the core particles (B) is preferably 1:99 to 70:30. From the viewpoint of the uniformity of the particle diameter of the toner particles (C) and the heat resistance stability of the liquid developer (X), the ratio [(A) :( B)] is more preferably 2:98 to 50:50. More preferably, it is 3: 97-35: 65. If the content (mass ratio) of the shell particles (A) is too low, the blocking resistance of the toner particles may be lowered. If the content (mass ratio) of the core particles is too high, the particle size uniformity of the toner particles may decrease.

  From the viewpoint of the particle size distribution of the toner particles (C) and the heat stability of the liquid developer (X), the core-shell structure of the toner particles (C) is 1 to 70 masses relative to the mass of the toner particles (C). % (More preferably 5 to 50% by mass, more preferably 10 to 35% by mass) of shell particles (A) and 30 to 99% by mass (more preferably 50 to 95% by mass, still more preferably 65 to 90% by mass). %) Core particles (B).

  From the viewpoint of the fixing property of the toner particles (C) and the heat stability of the liquid developer (X), the content of the toner particles (C) in the liquid developer (X) is preferably 10 to 50% by mass. More preferably, it is 15-45 mass%, More preferably, it is 20-40 mass%.

<Additives>
The toner particles (C) in the present embodiment preferably contain a colorant in at least one of the shell particles (A) and the core particles (B), and additives other than the colorant (for example, a pigment dispersant, A wax, a charge control agent, a filler, an antistatic agent, a mold release agent, an ultraviolet absorber, an antioxidant, an antiblocking agent, a heat stabilizer, a flame retardant, and the like.

<Colorant>
The colorant contained in the toner particles of the present embodiment is dispersed in the resin (shell particles (A) and / or core particles (B)). The volume average particle size of such a colorant is preferably 0.3 μm or less. If the volume average particle size of the colorant exceeds 0.3 μm, dispersion may be deteriorated, resulting in a decrease in glossiness and the inability to achieve a desired color.

  As such a colorant, conventionally known pigments and the like can be used without any particular limitation, but from the viewpoint of cost, light resistance, colorability, and the like, for example, the following pigments are preferably used. In terms of color composition, these pigments are usually classified as black pigments, yellow pigments, magenta pigments, and cyan pigments. Basically, colors other than black (color images) are subtractive color mixtures of yellow pigments, magenta pigments, and cyan pigments. Is toned.

  Examples of the pigment (black pigment) contained in the black colorant include carbon black such as furnace black, channel black, acetylene black, thermal black, and lamp black, carbon black derived from biomass, and magnetite, Magnetic powder such as ferrite is also used. Further, nigrosine, which is an azine compound which is a purple black dye, can be used alone or in combination. Nigrosine includes C.I. I. Solvent Black 7 or C.I. I. Selected from Solvent Black 5, etc.

  Examples of the pigment (magenta pigment) contained in the magenta colorant include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the pigment (yellow pigment) contained in the yellow colorant include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185.

  Examples of the pigment (cyan pigment) contained in the cyan colorant include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment blue 62, C.I. I. Pigment blue 66, C.I. I. And CI Pigment Green 7.

  These colorants can be used alone or in combination of two or more as required.

<Pigment dispersant>
The pigment dispersant has a function of uniformly dispersing the colorant (pigment) in the toner particles, and it is preferable to use a basic dispersant. Here, the basic dispersant is defined as follows. That is, 0.5 g of pigment dispersant and 20 ml of distilled water are placed in a glass screw tube, shaken for 30 minutes using a paint shaker, and then filtered, and the pH of the filtrate obtained is filtered with a pH meter (product) Name: “D-51” (manufactured by HORIBA, Ltd.) and the case where the pH is higher than 7 is defined as a basic dispersant. In addition, when the pH is smaller than 7, it shall call an acidic dispersing agent.

  The kind of such basic dispersant is not particularly limited. For example, an amine group, amino group, amide group, pyrrolidone group, imine group, imino group, urethane group, quaternary ammonium group, ammonium group, pyridino group, pyridium group, imidazolino group, and imidazolium group in the molecule of the dispersant And compounds having a functional group such as (dispersing agent). The dispersant usually corresponds to a so-called surfactant having a hydrophilic part and a hydrophobic part in the molecule, but as long as it has an action of dispersing a colorant (pigment) as described above, Compounds can be used.

  Commercially available products of such basic dispersants include, for example, “Ajisper PB-821” (trade name), “Azisper PB-822” (trade name), “Azisper PB-881” (product) manufactured by Ajinomoto Fine Techno Co., Ltd. Name) or “Solspers 28000” (product name), “Solspurs 32000” (product name), “Solspurs 32500” (product name), “Solspurs 35100” (product name), “Solspurs 37500” (product name) Product name).

  Further, it is more preferable to select a pigment dispersant that does not dissolve in the insulating liquid (carrier liquid). For that reason, “Ajisper PB-821” (trade name), “Ajisper PB-822” (trade name), and “Ajisper PB-881” (trade name) manufactured by Ajinomoto Fine Techno Co. are more preferred. Although the detailed mechanism is unknown, the use of such a pigment dispersant makes it easy to obtain a desired shape.

  The pigment dispersant is preferably added in an amount of 1 to 100% by mass with respect to the colorant (pigment). More preferably, it is 1-40 mass%. If it is less than 1% by mass, the dispersibility of the colorant (pigment) may be insufficient, the required ID (image density) may not be achieved, and the fixing strength may be reduced. On the other hand, if the amount exceeds 100% by mass, a dispersant more than the amount necessary for pigment dispersion is added, and the excess dispersant may be dissolved in the insulating liquid, which increases the chargeability and fixing strength of the toner particles. May have adverse effects.

  Such pigment dispersants can be used singly or in combination of two or more.

<Insulating liquid>
The insulating liquid contained in the liquid developer of the present embodiment may have a resistance value (approximately 10 ¹¹ to 10 ¹⁶ Ω · cm) that does not disturb the electrostatic latent image. Furthermore, a solvent having low odor and toxicity is preferred. In general, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes and the like can be mentioned. In particular, a normal paraffin solvent and an isoparaffin solvent are preferable in terms of odor, harmlessness, and cost. Specifically, Moresco White (trade name, manufactured by Matsumura Oil Research Co., Ltd.), Isopar (trade name, manufactured by ExxonMobil), Shellsol (trade name, manufactured by Shell Chemicals Japan Co., Ltd.), IP Solvent 1620, IP solvent 2028, IP solvent 2835 (both are trade names, manufactured by Idemitsu Kosan Co., Ltd.), and the like.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Production Example 1> [Production of polyester resin]
In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a cooling tube and a nitrogen introduction tube, 286 parts by mass of dodecanedioic acid, 190 parts by mass of 1,6-hexanediol and titanium dihydroxybis (triethanol as a condensation catalyst) Aminate) 1 part by mass was added and reacted at 180 ° C. under a nitrogen stream for 8 hours while distilling off the generated water. Next, while the temperature was gradually raised to 220 ° C., the reaction was performed for 4 hours while distilling off the generated water under a nitrogen stream. Furthermore, it was made to react under the reduced pressure of 0.007-0.026 MPa for 1 hour. Thereby, a polyester resin was obtained. About the obtained polyester resin, melting | fusing point was 68 degreeC, Mn was 4900, and Mw was 10,000.

In addition, the above-mentioned method was employ | adopted for the measurement of melting | fusing point, Mn, and Mw (it is the same below).
<Production Example 2> [Production of dispersion (W1) of shell particles (A1)]
In a beaker made of glass, 80 parts by mass of 2-decyltetradecyl methacrylate, 5 parts by mass of methyl methacrylate, 5 parts by mass of methacrylic acid, an isocyanate group-containing monomer (trade name: “Karenz MOI”, manufactured by Showa Denko KK) 20 parts by mass of an equimolar reaction product with the polyester resin obtained in Production Example 1 and 0.5 parts by mass of azobismethoxydimethylvaleronitrile were added and mixed by stirring at 20 ° C. Thereby, a monomer solution was obtained.

  Next, a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a solvent removal device, and a nitrogen introduction tube was prepared. 195 parts by mass of THF was put into the reaction vessel, and the monomer solution was put into a dropping funnel provided in the reaction vessel. After the gas phase portion of the reaction vessel was replaced with nitrogen, the monomer solution was added dropwise to THF in the reaction vessel over 1 hour at 70 ° C. in a sealed state. Three hours after the completion of the dropwise addition of the monomer solution, a mixture of 0.05 parts by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was placed in a reaction vessel, reacted at 70 ° C. for 3 hours, and then cooled to room temperature. . Thereby, a copolymer solution was obtained.

  Next, 400 parts by mass of the obtained copolymer solution was added dropwise to 600 parts by mass of IP solvent 2028 (made by Idemitsu Kosan Co., Ltd.) with stirring, and then THF was distilled off at 40 ° C. under a reduced pressure of 0.039 MPa. Thereby, a dispersion liquid (W1) of shell particles (A1) was obtained. The volume average particle diameter of the shell particles (A1) in the dispersion (W1) was 0.13 μm.

<Production Example 3> [Production of Core Resin (b1) Formation Solution (Y1)]
971 mass of polyester resin (Mn: 6000) obtained from sebacic acid, adipic acid and ethylene glycol (molar ratio 0.8: 0.2: 1) in a reaction vessel equipped with a stirrer, heating / cooling device and thermometer And 1300 parts by mass of acetone were added and stirred to dissolve uniformly. 29 parts by weight of IPDI was added to this solution and reacted at 80 ° C. for 6 hours. When the NCO value became 0, 28 parts by mass of phthalic anhydride was added and reacted at 180 ° C. for 1 hour to obtain a core resin (b1) which is a urethane-modified polyester resin. Next, 1000 parts by mass of the core resin (b1) and 1000 parts by mass of acetone were placed in a beaker and stirred to uniformly dissolve the core resin (b1) in acetone. As a result, a solution (Y1) for forming the core resin (b1) was obtained.

<Production Example 4> [Production of core resin (b2) forming solution (Y2)]
Polyester resin obtained from bisphenol A propion oxide 2-mole adduct, terephthalic acid, isophthalic acid (molar ratio 1: 0.6: 0.4) in a reaction vessel equipped with a stirrer, heating / cooling device and thermometer (Mn: 2000) 931 parts by mass and 1300 parts by mass of acetone were added and stirred to dissolve uniformly. 69 parts by weight of IPDI was added to this solution and reacted at 80 ° C. for 6 hours. When the NCO value became 0, 28 parts by mass of phthalic anhydride was added and reacted at 180 ° C. for 1 hour to obtain a core resin (b2) which is a urethane-modified polyester resin. Next, 1000 parts by mass of the core resin (b2) and 1000 parts by mass of acetone were placed in a beaker and stirred to uniformly dissolve the core resin (b2) in acetone. As a result, a solution (Y2) for forming the core resin (b2) was obtained.

<Production Example 5> [Production of core resin (b3) forming solution (Y3)]
957 masses of polyester resin (Mn: 4000) obtained from sebacic acid, adipic acid and ethylene glycol (molar ratio 0.8: 0.2: 1) in a reaction vessel equipped with a stirrer, heating / cooling device and thermometer And 1300 parts by mass of acetone were added and stirred to dissolve uniformly. 43 parts by weight of IPDI was added to this solution and reacted at 80 ° C. for 6 hours. When the NCO value became 0, 28 parts by mass of phthalic anhydride was added and reacted at 180 ° C. for 1 hour to obtain a core resin (b3) which is a urethane-modified polyester resin. Next, 1000 parts by mass of the core resin (b3) and 1000 parts by mass of acetone were placed in a beaker and stirred to uniformly dissolve the core resin (b3) in acetone. Thereby, a solution (Y3) for forming the core resin (b3) was obtained.

<Production Example 6> [Production of core resin (b4) forming solution (Y4)]
Polyester resin obtained from bisphenol A propion oxide 2-mole adduct, terephthalic acid, isophthalic acid (molar ratio 1: 0.6: 0.4) in a reaction vessel equipped with a stirrer, heating / cooling device and thermometer (Mn: 1200) 890 parts by mass and acetone 1300 parts by mass were added and stirred to dissolve uniformly. 110 parts by mass of IPDI was added to this solution and reacted at 80 ° C. for 6 hours. When the NCO value became 0, 28 parts by mass of phthalic anhydride was added and reacted at 180 ° C. for 1 hour to obtain a core resin (b4) which is a urethane-modified polyester resin. Next, 1000 parts by mass of the core resin (b4) and 1000 parts by mass of acetone were placed in a beaker and stirred to uniformly dissolve the core resin (b4) in acetone. Thereby, a solution (Y4) for forming the core resin (b4) was obtained.

<Production Example 7> [Production of core resin (b5) forming solution (Y5)]
956 mass of polyester resin (Mn: 4000) obtained from sebacic acid, adipic acid and ethylene glycol (molar ratio 0.8: 0.2: 1) in a reaction vessel equipped with a stirrer, heating / cooling device and thermometer And 1300 parts by mass of acetone were added and stirred to dissolve uniformly. 45 parts by weight of IPDI was added to this solution and reacted at 80 ° C. for 6 hours. When the NCO value became 0, 28 parts by mass of phthalic anhydride was added and reacted at 180 ° C. for 1 hour to obtain a core resin (b5) which is a urethane-modified polyester resin. Next, 1000 parts by mass of the core resin (b5) and 1000 parts by mass of acetone were placed in a beaker and stirred to uniformly dissolve the core resin (b5) in acetone. Thereby, a core resin (b5) forming solution (Y5) was obtained.

<Production Example 8> [Production of core resin (b6) forming solution (Y6)]
914 mass of polyester resin (Mn: 2000) obtained from sebacic acid, adipic acid and ethylene glycol (molar ratio 0.8: 0.2: 1) in a reaction vessel equipped with a stirrer, a heating / cooling device and a thermometer And 1300 parts by mass of acetone were added and stirred to dissolve uniformly. 86 parts by weight of IPDI was added to this solution and reacted at 80 ° C. for 6 hours. When the NCO value became 0, 28 parts by mass of phthalic anhydride was added and reacted at 180 ° C. for 1 hour to obtain a core resin (b6) which is a urethane-modified polyester resin. Next, 1000 parts by mass of the core resin (b6) and 1000 parts by mass of acetone were placed in a beaker and stirred to uniformly dissolve the core resin (b6) in acetone. As a result, a solution (Y6) for forming the core resin (b6) was obtained.

<Production Example 9> [Production of core resin (b7) forming solution (Y7)]
975 mass of polyester resin (Mn: 6000) obtained from sebacic acid, adipic acid and ethylene glycol (molar ratio 0.8: 0.2: 1) in a reaction vessel equipped with a stirrer, heating / cooling device and thermometer And 1300 parts by mass of acetone were added and stirred to dissolve uniformly. 25 parts by weight of IPDI was added to this solution and reacted at 80 ° C. for 6 hours. When the NCO value became 0, 28 parts by mass of phthalic anhydride was added and reacted at 180 ° C. for 1 hour to obtain a core resin (b7) which is a urethane-modified polyester resin. Next, 1000 parts by mass of the core resin (b7) and 1000 parts by mass of acetone were placed in a beaker and stirred to uniformly dissolve the core resin (b7) in acetone. This obtained core resin (b7) formation solution (Y7).

<Production Example 10> [Production of Core Resin (b8) Formation Solution (Y8)]
973 mass of polyester resin (Mn: 6000) obtained from sebacic acid, adipic acid and ethylene glycol (molar ratio 0.8: 0.2: 1) in a reaction vessel equipped with a stirrer, heating / cooling device and thermometer And 1300 parts by mass of acetone were added and stirred to dissolve uniformly. 27 parts by mass of IPDI was added to this solution and reacted at 80 ° C. for 6 hours. When the NCO value became 0, 28 parts by mass of phthalic anhydride was added and reacted at 180 ° C. for 1 hour to obtain a core resin (b8) which is a urethane-modified polyester resin. Next, 1000 parts by mass of the core resin (b8) and 1000 parts by mass of acetone were placed in a beaker and stirred to uniformly dissolve the core resin (b8) in acetone. Thereby, a solution (Y8) for forming the core resin (b8) was obtained.

<Production Example 11> [Production of Core Resin (b9) Formation Solution (Y9)]
954 mass of polyester resin (Mn: 4000) obtained from sebacic acid, adipic acid and ethylene glycol (molar ratio 0.8: 0.2: 1) in a reaction vessel equipped with a stirrer, heating / cooling device and thermometer And 1300 parts by mass of acetone were added and stirred to dissolve uniformly. 47 parts by mass of IPDI was added to this solution and reacted at 80 ° C. for 6 hours. When the NCO value became 0, 28 parts by mass of phthalic anhydride was added and reacted at 180 ° C. for 1 hour to obtain a core resin (b9) which is a urethane-modified polyester resin. Next, 1000 parts by mass of the core resin (b9) and 1000 parts by mass of acetone were placed in a beaker and stirred to uniformly dissolve the core resin (b9) in acetone. This obtained core resin (b9) formation solution (Y9).

<Measurement of number average molecular weight and urethane group concentration>
The number average molecular weight and the urethane group concentration of the core resin (b1) to the core resin (b9) thus obtained were measured according to the method described above. The results are shown in Table 1.

<Production Example 12> [Production of Cyan Colorant Dispersion (P1)]
In a beaker, 20 parts by mass of acid-treated copper phthalocyanine (trade name: “Fastogen Blue FDB-14”, manufactured by DIC) as a cyan colorant, a pigment dispersant (trade name: “Azisper PB-821”, Ajinomoto Fine Techno ( Co., Ltd.) and 5 parts by mass of acetone and 75 parts by mass of acetone were added, stirred and uniformly dispersed, and then copper phthalocyanine was finely dispersed by a bead mill to obtain a cyan colorant dispersion (P1). The volume average particle diameter of copper phthalocyanine in the cyan colorant dispersion (P1) was 0.2 μm.

<Production Example 13> [Production of Black Colorant Dispersion (P2)]
In a beaker, 15 parts by mass of carbon black (trade name: “Mogal L”, manufactured by Cabot Corporation) as a black colorant, 5 parts by mass of acid-treated copper phthalocyanine (trade name: “Fastogen Blue FDB-14”, manufactured by DIC Corporation) , 5 parts by mass of a pigment dispersant (trade name: “Ajisper PB-821”, manufactured by Ajinomoto Fine Techno Co., Ltd.) and 75 parts by mass of acetone were stirred and uniformly dispersed, and then copper phthalocyanine was finely dispersed by a bead mill. Dispersion gave a black colorant dispersion (P2). The volume average particle diameter of copper phthalocyanine in the black colorant dispersion (P2) was 0.2 μm.

<Production Example 14> [Production of Cyan Developer (Z-1)]
Into a beaker, 40 parts by mass of the core resin (b1) forming solution (Y1) and 20 parts by mass of the cyan colorant dispersion (P1) were added, and a TK auto homomixer (manufactured by Primix Co., Ltd.) was used at 25 ° C. The mixture was stirred at 8000 rpm and dispersed uniformly to obtain a resin solution (Y1P1).

  Into another beaker, 67 parts by mass of an insulating liquid (trade name: “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.) and 11 parts by mass of the dispersion liquid (W1) of shell particles (A1) were added and uniformly dispersed. Next, while stirring at 10000 rpm using a TK auto homomixer at 25 ° C., 60 parts by mass of the resin solution (Y1P1) was added and stirred for 2 minutes. Next, this mixed solution was put into a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, and a solvent removal device. Acetone was distilled off from the resin solution (Y1P1) until the content became 5% by mass or less. As a result, a cyan developer (Z-1) having a colorant (pigment) content of 17% by mass in the toner particles (C-1) was obtained. The toner particles (C-1) had a core-shell structure in which the shell particles (A1) were attached or coated on the surface of the core particles (B1) made of the core resin (b1).

<Production Example 15> [Production of cyan developer (Z-2)]
In Production Example 14, the core resin (b1) formation solution (Y1) was changed to the core resin (b2) formation solution (Y2) to obtain a resin solution (Y2P1). Thus, a cyan developer (Z-2) having a colorant (pigment) content of 17% by mass in the toner particles (C-2) was obtained. The toner particles (C-2) had a core / shell structure in which the shell particles (A1) were adhered or coated on the surfaces of the core particles (B2) made of the core resin (b2).

<Production Example 16> [Production of Black Developer (Z-3)]
Into a beaker, 40 parts by mass of the core resin (b3) forming solution (Y3) and 20 parts by mass of the black colorant dispersion (P2) were charged, using a TK auto homomixer (manufactured by Primix Co., Ltd.) at 25 ° C. The mixture was stirred at 8000 rpm and uniformly dispersed to obtain a resin solution (Y3P2).

  Into another beaker, 67 parts by mass of an insulating liquid (trade name: “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.) and 11 parts by mass of the dispersion liquid (W1) of shell particles (A1) were added and uniformly dispersed. Next, while stirring at 10000 rpm using a TK auto homomixer at 25 ° C., 60 parts by mass of the resin solution (Y3P2) was added and stirred for 2 minutes. Next, this mixed solution was put into a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, and a solvent removal device. Acetone was distilled off from the resin solution (Y3P2) until the content became 5% by mass or less. As a result, a black developer (Z-3) having a colorant (pigment) content of 30% by mass in the toner particles (C-3) was obtained. The toner particles (C-3) had a core-shell structure in which the shell particles (A1) were adhered or coated on the surfaces of the core particles (B3) made of the core resin (b3).

<Production Example 17> [Production of Black Developer (Z-4)]
In Production Example 16, the same procedure as in Production Example 16 was conducted except that the core resin (b3) forming solution (Y3) was changed to the core resin (b4) forming solution (Y4) to obtain the resin solution (Y4P2). A black developer (Z-4) having a colorant (pigment) content of 30% by mass in the toner particles (C-4) was obtained. The toner particles (C-4) had a core / shell structure in which the shell particles (A1) were adhered or coated on the surfaces of the core particles (B4) made of the core resin (b4).

<Production Example 18> [Production of Black Developer (Z-5)]
In Production Example 16, the core resin (b3) formation solution (Y3) was changed to the core resin (b5) formation solution (Y5) to obtain a resin solution (Y5P2). A black developer (Z-5) having a colorant (pigment) content of 30% by mass in the toner particles (C-5) was obtained. The toner particles (C-5) had a core / shell structure in which the shell particles (A1) were adhered or coated on the surfaces of the core particles (B5) made of the core resin (b5).

<Production Example 19> [Production of Black Developer (Z-6)]
In Production Example 16, the same procedure as in Production Example 16 was conducted except that the core resin (b3) forming solution (Y3) was changed to the core resin (b6) forming solution (Y6) to obtain the resin solution (Y6P2). A black developer (Z-6) having a colorant (pigment) content of 30% by mass in the toner particles (C-6) was obtained. The toner particles (C-6) had a core / shell structure in which the shell particles (A1) were adhered or coated on the surfaces of the core particles (B6) made of the core resin (b6).

<Production Example 20> [Production of Black Developer (Z-7)]
In Production Example 16, the same procedure as in Production Example 16 was conducted except that the core resin (b3) forming solution (Y3) was changed to the core resin (b7) forming solution (Y7) to obtain a resin solution (Y7P2). A black developer (Z-7) having a colorant (pigment) content of 30% by mass in the toner particles (C-7) was obtained. The toner particles (C-7) had a core / shell structure in which the shell particles (A1) were adhered or coated on the surface of the core particles (B7) made of the core resin (b7).

<Production Example 21> [Production of black developer (Z-8)]
In Production Example 16, the core resin (b3) formation solution (Y3) was changed to the core resin (b8) formation solution (Y8) to obtain a resin solution (Y8P2), and the same as Production Example 16 A black developer (Z-8) having a colorant (pigment) content of 30% by mass in the toner particles (C-8) was obtained. The toner particles (C-8) had a core / shell structure in which the shell particles (A1) were adhered or coated on the surface of the core particles (B8) made of the core resin (b8).

<Production Example 22> [Production of black developer (Z-9)]
In Production Example 16, the same procedure as in Production Example 16 was conducted except that the core resin (b3) forming solution (Y3) was changed to the core resin (b9) forming solution (Y9) to obtain the resin solution (Y9P2). A black developer (Z-9) having a colorant (pigment) content of 30% by mass in the toner particles (C-9) was obtained. The toner particles (C-9) had a core / shell structure in which the shell particles (A1) were adhered or coated on the surfaces of the core particles (B9) made of the core resin (b9).

<Measurement of median diameter and average circularity>
The median diameter (volume distribution) and average circularity of the toner particles (C-1) to toner particles (C-9) obtained in this manner were measured using a flow particle image analyzer (trade name: “FPIA-3000S”, (Sysmex). The same IP solvent 2028 as the insulating liquid of each liquid developer was used as the flow solvent.

  Suspensions were prepared by adding 50 mg of each liquid developer into 20 g of IP solvent 2028 to which 30 mg of a dispersant (trade name: “S13940”, manufactured by Nippon Lubrizol Co., Ltd.) was added. Dispersion treatment was performed for about 5 minutes using a sonic disperser (trade name: “Ultrasonic Cleaner Model VS-150”, manufactured by Welbo Clear).

  Then, using this suspension, the median diameter (D50), circularity (circumference of circle equal to particle area / periphery of particle) and average circularity of the volume distribution of toner particles were measured. The results are shown in Table 2.

<Example 1>
A liquid developer set according to Example 1 was configured using the black developer Z-3 and the cyan developer Z-1 as the chromatic developer.

<Examples 2 to 4 and Comparative Examples 1 to 3>
As shown in Table 3, the liquids according to Examples 2 to 4 and Comparative Examples 1 to 3 were prepared by combining the black developer of the production example and the cyan developer (chromatic developer) of the production example. Each developer set was configured. In Table 3, the description such as “Z-3 / Z-1” shown in the “Liquid developer set” column indicates a combination of liquid developers constituting the liquid developer set. For example, “Z-3 / Z-1” means that the liquid developer set according to Example 1 includes the black developer Z-3 and the cyan developer Z-1.

<Evaluation>
<Image forming apparatus>
FIG. 1 shows a schematic conceptual diagram of an image forming apparatus used for producing an image for evaluation of a liquid developer set. The process conditions and process outline of this apparatus are as follows.

  In this evaluation, an image forming apparatus that performs primary transfer from the photosensitive member to the intermediate transfer member and then secondary transfer to the recording material is shown. However, the same effect can be obtained by the method of transferring directly from the photosensitive member to the recording material. can get.

  FIG. 1 shows a single-color image forming apparatus in order to simplify the explanation and make it easy to understand the explanation, but in actual evaluation, it has a plurality of developing tanks and transfer rollers. A multicolor image forming apparatus that forms a color image by superposing a plurality of developers was used.

  First, the liquid developer 6 is placed in the developing tank 5 of the image forming apparatus 100. The liquid developer 6 is pumped up by the anilox roller 22 and sent to the leveling roller 21. Excess liquid developer 6 on the surface of the anilox roller 22 is scraped off by the anilox regulating blade 23 before reaching the leveling roller 21, and the level of the liquid developer 6 is adjusted so that the liquid developer 6 has an equal layer thickness. The Next, the liquid developer 6 is transferred from the leveling roller 21 to the developer carrier 24.

  The photoreceptor 1 is charged by the charging unit 7 and a latent image is formed by the exposure unit 8. Corresponding to the image on which the latent image is formed, the liquid developer 6 is charged on the toner particles by the development charger 26 and then developed on the photoreceptor 1. The liquid developer 6 that has not transferred to the photoreceptor 1 is scraped off and collected by the cleaning blade 25 downstream of the developing unit.

  The liquid developer 6 developed on the photosensitive member 1 is electrostatically primary transferred to the intermediate transfer member 10 in the primary transfer unit 2. The liquid developer 6 (toner particles) carried on the intermediate transfer body 10 is electrostatically secondary transferred onto the recording material 12 in the secondary transfer unit 3. The liquid developer 6 (toner particles) transferred to the recording material 12 is fixed by a fixing device (not shown) and a printed image is completed.

  The liquid developer 6 that has not been transferred and remains on the photosensitive member 1 is scraped off by the cleaning blade 9 of the image carrier cleaning unit, and the photosensitive member 1 repeats charging, exposing, and developing steps to perform a printing operation. Similarly, the liquid developer 6 that cannot be completely transferred and remains on the intermediate transfer member 10 is scraped off by the cleaning blade 11.

  The toner particles are charged to a positive polarity by the development charger 26. The potential of the intermediate transfer member 10 was −400V, and the potential of the transfer roller 4 was −1200V. The conveyance speed was 400 mm / s.

In this evaluation, coated paper (trade name: “OK Top Coat” (128 g / m ² ), manufactured by Oji Paper Co., Ltd.) was used as the recording material.

<Evaluation of glossiness>
Using the image forming apparatus described above, a solid pattern (10 cm × 10 cm, toner particle adhesion amount: 2 g / m ² ) with cyan developer and black developer, the same adhesion amount, and the same recording material (coated paper) ) And subsequently fixed with a heat roller (120 ° C. × nip time 40 msec.).

  Thereafter, the glossiness of the cyan solid portion and the black solid portion of the fixed image obtained above was measured with a 75 ° gloss meter (trade name: “VG-2000”, manufactured by Nippon Denshoku Co., Ltd.). The results are shown in Table 3. In Table 3, when the “difference (absolute value)” is 10 or less in the “glossiness” column, the difference in glossiness is small and good.

<Evaluation of fixing strength>
The fixing strength of the cyan solid portion and the black solid portion of the fixed image obtained in the same manner as described above was evaluated by a tape peeling test of the fixed image. In other words, after affixing the tape to the measurement target site on the coated paper after image fixing, the tape is peeled off, and the image density (ID) of the image peeled off the tape is measured by a reflection densitometer (trade name: “X -Rite model 404 "(manufactured by X-Rite), and the following two-stage rank evaluation was performed. The results are shown in Table 3. As the tape, “Scotch Mending Tape” (trade name, manufactured by 3M) was used.
A: Less than image density (ID) of 0.1 B: Image density (ID) of 0.1 or more The smaller the image density value of the peeled image, the higher the fixing strength. Therefore, those in which “Cyan” and “Black” are both “A” have good fixing strength as a liquid developer set. On the other hand, one in which either “Cyan” or “Black” is “B” does not have sufficient fixing strength as a liquid developer set.

  As is apparent from Table 3, the liquid developer set includes a black developer containing the first toner particles and a chromatic developer containing the second toner particles, and the first toner particles include the first resin and the black resin. The second toner particles include a second resin and a chromatic colorant, and each of the first resin and the second resin is derived from a compound having at least two polyesters each having an isocyanate group. The liquid developer set of Example, which is a urethane-modified polyester resin bonded by units and satisfies the above formulas (1) and (2), has extremely good glossiness and fixing strength, and they are highly It is compatible. That is, it was confirmed that the liquid developer set of the example was a liquid developer set having a high fixing quality and a desired image quality.

  On the other hand, the liquid developer set of the comparative example that does not satisfy such conditions does not achieve both glossiness and fixing strength, and does not provide sufficient fixing quality.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Photoconductor, 2 Primary transfer part, 3 Secondary transfer part, 4 Transfer roller, 5 Developing tank, 6 Liquid developer, 7 Charging part, 8 Exposure part, 9 Cleaning blade, 10 Intermediate transfer body, 11 Cleaning blade, 12 recording material, 21 leveling roller, 22 anilox roller, 23 anilox regulating blade, 24 developer carrying member, 25 cleaning blade, 26 developing charger, 100 image forming apparatus.

Claims (4)

A liquid developer set comprising a black developer containing first toner particles and a chromatic developer containing second toner particles,
The first toner particles include a first resin and a black colorant,
The second toner particles include a second resin and a chromatic colorant,
Each of the first resin and the second resin is a urethane-modified polyester resin in which at least two or more polyesters are bonded by a structural unit derived from a compound having an isocyanate group,
A liquid developer set satisfying the following formulas (1) and (2).
3000 ≦ Mk <Mc ≦ 50000 (1)
Uc <Uk (2)
(In Formula (1), Mk represents the number average molecular weight of the first resin, Mc represents the number average molecular weight of the second resin. In Formula (2), Uk represents the urethane group concentration of the first resin. Uc represents the urethane group concentration of the second resin.)   The first resin and the second resin each include a common structural unit in a molecular structure, and the common structural unit occupies 80% or more of all the structural units in each molecular structure. The liquid developer set described in 1.   The liquid developer set according to claim 1, wherein the first resin and the second resin are substantially the same polymer species. The liquid developer set according to claim 1, wherein the liquid developer set satisfies the following condition 1 and / or condition 2.
Condition 1: The first toner particles have a core-shell structure in which shell particles containing a shell resin are attached to or coated on the surface of the core particles containing a core resin, and the core resin is the first resin. .
Condition 2: The second toner particles have a core-shell structure in which shell particles containing a shell resin are attached to or coated on the surface of the core particles containing the core resin, and the core resin is the second resin. .

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