JP2016166990A - Liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve both low-temperature fixability of toner particles and scratch resistance of an image, and further increase fixing strength of toner particles to high-quality paper.SOLUTION: A liquid developer comprises an insulating liquid and toner particles dispersed in the insulating liquid. The toner particles have a core/shell structure. The core-shell structure includes a core particle including a core resin, and a shell resin that is provided at least a part on the surface of the core particle and is a resin different from the core resin. The core resin includes an aliphatic polyester resin in an amount of 5 mass% or more and 50 mass% or less, and an aromatic polyester resin in an amount of 50 mass% or ore and 95 mass% or less. The acid value of the core resin is 20 mgKOH/g or more and 100 mgKOH/g or less. The difference between the acid value of the aliphatic polyester resin and the acid value of the aromatic polyester resin is 0 mgKOH/g or more and less than 15 mgKOH/g.SELECTED DRAWING: None

Description

  The present invention relates to a liquid developer.

  Japanese Unexamined Patent Publication No. 2013-3197 (Patent Document 1) describes toner particles containing a polyester resin. This document describes that document offset can be prevented if the solid matter obtained by drying the liquid developer has a melting point of 55 ° C. or higher. It is derived from the structural unit derived from the acid component and the alcohol component. It is described that the melting point of the solid of the liquid developer is 55 ° C. or more when the total amount of the constituent units derived from the aliphatic monomer in both constituent units is 30 mol% or more.

  Japanese Unexamined Patent Application Publication No. 2009-96994 (Patent Document 2) and Japanese Unexamined Patent Application Publication No. 2014-66887 (Patent Document 3) describe toner particles having a core / shell structure.

JP 2013-3197 A JP 2009-96994 A JP 2014-66887 A

  Patent Document 1 describes that toner particles are fixed to a recording medium at 180 ° C., but liquid developers are required to be fixed at a lower temperature (low temperature fixability). Unlike the dry developer, the liquid developer can control the particle size of the toner particles to 2 μm or less. Therefore, the adhesion amount of the liquid developer to the recording medium can be significantly reduced than the adhesion amount of the dry developer to the recording medium. This is advantageous for low-temperature fixability. Further, as a method for realizing fixing at a low temperature, for example, use of a resin having a high sharp melt property (for example, a polyester resin) has been proposed.

  When an amorphous polyester resin is used as the resin contained in the toner particles, the softening point can be lowered by adjusting the molecular weight of the amorphous polyester resin. Therefore, fixing at a low temperature (for example, fixing at 90 ° C.) is possible. However, when the softening point of the amorphous polyester resin is lowered, its glass transition point is also lowered, which causes a reduction in heat resistance of the toner particles.

  On the other hand, the melting point of the crystalline polyester resin is lower than the softening point of the amorphous polyester resin. Therefore, when a crystalline polyester resin is used as the resin contained in the toner particles, fixing at a low temperature is possible without reducing the heat resistance of the toner particles. Therefore, it is preferable to use a crystalline polyester resin as the resin contained in the toner particles.

  By the way, the crystalline polyester resin is mainly composed of an aliphatic monomer, and the amorphous polyester resin is mainly composed of an aromatic monomer. Here, a resin made of an aliphatic monomer is softer than a resin made of an aromatic monomer, and therefore has a tendency to be weak against stress. For this reason, when a crystalline polyester resin is used as the resin contained in the toner particles, if the scratch test is performed on the image fixed on the recording medium, the image is scratched. That is, the scratch resistance of the image decreases.

  Further, it has been found that there is a difference in fixability of the liquid developer depending on the type of recording medium. Specifically, it was found that the fixing strength of the liquid developer on the high-quality paper is lower than the fixing strength of the liquid developer on the coated paper. The reason can be considered as follows. Since the coat layer is not formed on the surface of the high quality paper (the surface of the high quality paper on which the image is formed), there are irregularities due to the fibers constituting the high quality paper. Therefore, it is difficult to adhere the toner particles to the surface of the fine paper. In addition, since the particle size of the toner particles contained in the liquid developer is small, it is difficult to apply pressure (fixing pressure) to the irregularities formed on the surface of the fine paper via the toner particles. As described above, when the liquid developer is used, it is very difficult to ensure the adhesive strength of the toner particles to the fine paper.

  The present invention has been made in view of such a point, and the object thereof is to achieve both improvement in low-temperature fixability of toner particles and improvement in scratch resistance of images, and furthermore, toner particles on high-quality paper. It is to increase the fixing strength.

  A resin made of an aromatic monomer is harder than a resin made of an aliphatic monomer. For this reason, if an aromatic polyester resin is used as the resin contained in the toner particles, it is considered that the scratch resistance of the image is improved. However, if fixing is performed at a low temperature using only an aromatic polyester resin as the resin contained in the toner particles, the heat resistance of the toner particles is reduced.

  On the other hand, when only an aliphatic polyester resin is used as the resin contained in the toner particles, only the crystalline polyester resin is used as the resin contained in the toner particles. Therefore, the toner particles can be fixed at a low temperature without reducing the heat resistance of the toner particles. However, the scratch resistance of the image decreases.

  From the above, the present inventors can fix the toner particles at low temperature without reducing the heat resistance of the toner particles by using both aliphatic polyester resin and aromatic polyester resin as the resin contained in the toner particles. Further, it was thought that the scratch resistance of the image could be improved. Therefore, toner particles were formed using both an aliphatic polyester resin and an aromatic polyester resin, and the characteristics of the toner particles were examined. As a result, it has been found that when fine paper is used as the recording medium, the fixing strength of the toner particles on the fine paper may be reduced.

  In order to find out the cause of such a result, the present inventors analyzed toner particles having low fixing strength on high-quality paper and toner particles having high fixing strength on high-quality paper. As a result, in the toner particles having low fixing strength on the fine paper, the acid value of the polyester resin contained in the toner particles is low, or the aliphatic polyester resin and the aromatic polyester resin are not compatible. On the other hand, in the toner particles having high fixing strength on the fine paper, the acid value of the polyester resin contained in the toner particles is high, and the aliphatic polyester resin and the aromatic polyester resin are compatible.

  Generally, in order to increase the fixing strength of toner particles on a recording medium, it is necessary to increase the adhesive strength between the recording medium and the toner particles. In addition, since the adhesive strength is reduced due to the presence of the insulating liquid, it is necessary to further increase the adhesive strength when a liquid developer is used compared to when a dry developer is used. Further, for the reasons described above, such a requirement becomes conspicuous when high-quality paper is used as a recording medium.

  However, if the acid value of the polyester resin contained in the toner particles is low, the affinity between the polyester resin and the insulating liquid increases, so that the insulating liquid easily enters between the polyester resin and the fine paper. . As a result, the adhesion strength of the toner particles to the high-quality paper is decreased, and as a result, the fixing strength of the toner particles to the high-quality paper may be decreased.

  Further, if the aliphatic polyester resin and the aromatic polyester resin are not compatible, the insulating liquid is easily held at the interface between the aliphatic polyester resin and the aromatic polyester resin. Or it becomes easy to penetrate | invade between an aromatic polyester resin and fine paper. As a result, the adhesion strength of the toner particles to the high-quality paper is decreased, and as a result, the fixing strength of the toner particles to the high-quality paper may be decreased.

  Further, when toner particles having a core / shell structure are used, the fixing strength of the toner particles on the high-quality paper decreases as the amount of the insulating liquid present on the surface of the high-quality paper decreases at the time of fixing the toner particles. I found out that it would be expensive. Based on the above considerations, the liquid developer of the present invention was completed.

  The liquid developer of the present invention includes an insulating liquid and toner particles dispersed in the insulating liquid. The toner particles have a core / shell structure. The core / shell structure includes a core particle including a core resin and a shell resin that is provided on at least a part of the surface of the core particle and is a resin different from the core resin. The core resin contains 5% by mass or more and 50% by mass or less aliphatic polyester resin and 50% by mass or more and 95% by mass or less aromatic polyester resin. The acid value of the core resin is 20 mgKOH / g or more and 100 mgKOH / g or less. The difference between the acid value of the aliphatic polyester resin and the acid value of the aromatic polyester resin is 0 mgKOH / g or more and less than 15 mgKOH / g.

  The “shell resin that is a resin different from the core resin” means that at least one of the chemical structure and the molecular weight is different between the core resin and the shell resin.

  The polyester resin is synthesized by a condensation polymerization reaction of carboxylic acid (a structural unit derived from an acid component) and alcohol (a structural unit derived from an alcohol component). Therefore, the part derived from carboxylic acid becomes a structural unit derived from the acid component, the part derived from alcohol becomes the structural unit derived from the alcohol component, and the polyester resin is configured by repeating these structural units.

  The term “aliphatic polyester resin” means that the content ratio of the structural unit derived from the aliphatic monomer in both the structural unit derived from the alcohol component and the structural unit derived from the acid component is 50% by mass or more. Means. The content ratio of the structural unit derived from the aliphatic monomer in both the structural unit derived from the alcohol component and the structural unit derived from the acid component is preferably 70% by mass or more, more preferably 80% by mass. It is above, More preferably, it is 90 mass% or more.

  The “structural unit derived from the alcohol component” means a unit in which a hydrogen atom is removed from the hydroxyl group (OH group) of the alcohol, and includes a unit in which a hydrogen atom is removed from at least one hydroxyl group contained in the alcohol. The “constituent unit derived from the acid component” means that the hydroxyl group is removed from the carboxyl group (COOH group) of the carboxylic acid, and the hydroxyl group is removed from at least one carboxyl group contained in the carboxylic acid. Including. “Aliphatic monomers” include aliphatic carboxylic acids, lower alkyl esters of aliphatic carboxylic acids, acid anhydrides of aliphatic carboxylic acids, and aliphatic alcohols. “Aliphatic carboxylic acid” means a carboxylic acid having no aromatic ring in the molecule. “Fatty alcohol” means an alcohol having no aromatic ring in the molecule.

  “Aromatic polyester resin” means that the content ratio of the structural unit derived from the aromatic monomer in both the structural unit derived from the alcohol component and the structural unit derived from the acid component is 50% by mass or more. Means. The content ratio of the structural unit derived from the aromatic monomer in both the structural unit derived from the alcohol component and the structural unit derived from the acid component is preferably 70% by mass or more, more preferably 80% by mass. It is above, More preferably, it is 90 mass% or more.

  “Aromatic monomers” include aromatic carboxylic acids, lower alkyl esters of aromatic carboxylic acids, acid anhydrides of aromatic carboxylic acids, and aromatic alcohols. “Aromatic carboxylic acid” means a carboxylic acid having an aromatic ring in the molecule. “Aromatic alcohol” means an alcohol having an aromatic ring in the molecule.

  “The acid value of the core resin” refers to the method described in JIS K 0070: 1992 (acid acid value, saponification value, ester value, iodine value, hydroxyl value, and unsaponified test method for chemical products). The acid value of the measured core resin is meant and is based on the amount of carboxyl groups contained in the core resin. The “carboxyl group contained in the core resin” corresponds to the amount of the carboxyl group residue that has not reacted with the hydroxyl group in the condensation polymerization reaction when the aliphatic polyester resin and the aromatic polyester resin are synthesized.

  The “acid value of the aliphatic polyester resin” means the acid value of the aliphatic polyester resin measured according to the method described in JIS K 0070: 1992, and the carboxyl group contained in the aliphatic polyester resin. Based on quantity. The “carboxyl group contained in the aliphatic polyester resin” corresponds to the amount of the carboxyl group residue that has not reacted with the hydroxyl group in the condensation polymerization reaction when synthesizing the aliphatic polyester resin.

  The “acid value of the aromatic polyester resin” means the acid value of the aromatic polyester resin measured according to the method described in JIS K 0070: 1992, and the carboxyl group contained in the aromatic polyester resin. Based on quantity. The “carboxyl group contained in the aromatic polyester resin” corresponds to the amount of the carboxyl group residue that has not reacted with the hydroxyl group in the condensation polymerization reaction when the aromatic polyester resin is synthesized.

  The shell resin preferably contains 30% by mass or more and 90% by mass or less of a structural unit derived from a monomer having a long-chain alkyl group.

  The “long chain alkyl group” means an alkyl group having a carbon chain having 4 or more carbon atoms, preferably an alkyl group having a carbon chain having 4 to 30 carbon atoms, more preferably a carbon number. An alkyl group having 8 to 30 carbon chains. The “long-chain alkyl group” includes a case where the carbon chain is linear, a case where the carbon chain is branched, a case where the carbon chain has a cyclic structure based on a carbon skeleton, and the like. The “long-chain alkyl group” also includes a functional group in which one or more hydrogen atoms contained in the alkyl group are substituted with an atom (for example, a halogen atom) different from the hydrogen atom.

  “The shell resin includes a structural unit derived from a monomer having a long chain alkyl group” means that the chemical structure after polymerization of the monomer having a long chain alkyl group is included as a structural unit in the shell resin. To do. Using a TD-GC / MS (Thermal Desorption-Gas Chromatograph / Mass Spectroscopy) method (TD condition: 240 ° C., 10 minutes, GC condition: column (trade name “ZB-5” manufactured by Shimadzu GL Corporation), MS According to the conditions: ionization method (electron ionization), full scan mode, m / z = 33 to 500), the content of the structural unit in the shell resin can be determined. “The shell resin has a constitutional unit derived from a monomer having a long chain alkyl group in an amount of 30% by mass or more and 90% by mass or less” “having a long chain alkyl group relative to the total amount (mass) of the monomer constituting the shell resin In other words, the ratio of the amount (mass) of the monomer is 30% by mass or more and 90% by mass or less.

  In the present invention, it is possible to improve both the low-temperature fixability of the toner particles and the scratch resistance of the image, and to increase the fixing strength of the toner particles on the high-quality paper.

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

  Hereinafter, embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described with reference to the drawings. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

[Configuration of liquid developer]
The liquid developer of this embodiment is an electrophotographic liquid developer, paint, or electrostatic recording liquid used in an electrophotographic image forming apparatus (described later) such as a copying machine, a printer, a digital printing machine, or a simple printing machine. It is useful as a developer, oil-based ink for inkjet printers, or ink for electronic paper. The liquid developer of this embodiment includes an insulating liquid and toner particles dispersed in the insulating liquid, and preferably includes 10 to 50% by mass of toner particles and 50 to 90% by mass of an insulating liquid. The liquid developer of this embodiment may contain an arbitrary component different from the insulating liquid and the toner particles. Examples of such optional components include a toner dispersant, a charge control agent, and a thickener.

<Toner particles>
The toner particles of this embodiment have a core / shell structure. The core / shell structure includes a core particle including a core resin and a shell resin that is provided on at least a part of the surface of the core particle and is a resin different from the core resin. Since the toner particles of the present embodiment have a core / shell structure, the fixing strength of the toner particles on the high-quality paper can be increased. This will be described in detail later in <Shell Resin>.

  In the toner particles of this embodiment, the colorant is preferably dispersed in at least one of the core resin and the shell resin, more preferably 50 to 90% by mass of resin (core resin and shell resin) and 10%. And 50% by weight of a colorant. The toner particles of this embodiment may contain an arbitrary component different from the resin and the colorant. Examples of such optional components include pigment dispersants, waxes, charge control agents, and the like.

  Preferably, the median diameter D50 (hereinafter referred to as “toner particle median diameter D50”) when the particle size distribution of the toner particles is measured on a volume basis is 0.5 μm or more and 5.0 μm or less. This median diameter D50 is smaller than the particle diameter of toner particles contained in a conventional dry developer, and is one of the features of this embodiment. When the median diameter D50 of the toner particles is 0.5 μm or more, the particle diameter of the toner particles can be ensured, so that the mobility of the toner particles in the electric field is improved, and thus the developability can be improved. If the median diameter D50 of the toner particles is 5.0 μm or less, the dispersibility of the toner particles can be secured, and the image quality can be improved. More preferably, the median diameter D50 of the toner particles is 1.0 μm or more and 2.0 μm or less.

  For example, the median diameter D50 of the toner particles can be measured using a flow type particle image analyzer (product number “FPIA-3000S” manufactured by Sysmex Corporation). In this analyzer, it is possible to use the solvent as a dispersion medium as it is. Therefore, by using this analyzer, it is possible to measure the state of the toner particles in a state closer to the actual dispersed state than measured in the aqueous system.

  Preferably, the mass ratio [(mass of core resin) :( mass of shell resin)] of the core resin and the shell resin is 99: 1 to 30:70. In terms of uniformity of toner particle diameter and heat stability of the liquid developer, the mass ratio of the shell resin to the core resin is more preferably 98: 2 to 50:50, and still more preferably 97. : 3 to 80:20. When the mass of the shell resin is 1% by mass or more of the total mass of the core resin and the shell resin, the blocking resistance of the toner particles can be maintained high. If the mass of the shell resin is 70% by mass or less of the total of the mass of the core resin and the mass of the shell resin, the particle size uniformity of the toner particles can be maintained high.

<Core resin>
(Content of aliphatic polyester resin and content of aromatic polyester resin)
The core resin contains 5% by mass or more and 50% by mass or less aliphatic polyester resin and 50% by mass or more and 95% by mass or less aromatic polyester resin. If the content of the aliphatic polyester resin (the ratio of the mass of the aliphatic polyester resin to the mass of the core resin) is 5% by mass or more, the content of the resin having a low melting point (aliphatic polyester resin) can be secured, so that the temperature is low. It becomes possible to establish in. If the content of the aliphatic polyester resin is 50% by mass or less, the content of a hard resin (aromatic polyester resin) can be ensured, so that the scratch resistance of the image can be improved. Preferably, the content of the aliphatic polyester resin is 5% by mass or more and 30% by mass or less. Thereby, since the content of hard resin can be further ensured, the scratch resistance of the image can be further improved.

  If the content of the aromatic polyester resin (ratio of the mass of the aromatic polyester resin to the mass of the core resin) is 50% by mass or more, the content of the hard resin (aromatic polyester resin) can be ensured, so that the image resistance Scratch can be improved. If the content of the aromatic polyester resin is 95% by mass or less, the content of a resin having a low melting point (aliphatic polyester resin) can be ensured, so that fixing at a low temperature is possible. Preferably, the content of the aromatic polyester resin is 70% by mass or more and 95% by mass or less. Thereby, since the content of hard resin can be further ensured, the scratch resistance of the image can be further improved.

The content of the aliphatic polyester resin and the content of the aromatic polyester resin were determined by ¹ H-NMR analysis using a Fourier transform nuclear magnetic resonance apparatus (FT-NMR) (trade name: “Lambda400”, manufactured by JEOL Ltd.). And can be determined from the integration ratio. As the measurement solvent, a chloroform-d (deuterated chloroform) solvent can be used. The content ratio of the structural unit derived from the aliphatic monomer in both the structural unit derived from the alcohol component and the structural unit derived from the acid component, and the structure derived from the structural unit derived from the alcohol component and the acid component The content ratio of the structural unit derived from the aromatic monomer in both structural units with the unit can also be measured by the same method.

(Acid value of core resin)
In this embodiment, the acid value of the core resin is 20 mgKOH / g or more and 100 mgKOH / g or less. If the acid value of the core resin is 20 mgKOH / g or more, the amount of carboxyl group residue contained in the core resin is large, and therefore the core resin has polarity. Thereby, since the affinity between the core resin and the insulating liquid is lowered, it is possible to prevent an excessive amount of the insulating liquid from being supplied to the high-quality paper together with the core resin at the time of transfer. Accordingly, since the insulating liquid can be prevented from entering between the core resin and the fine paper, the adhesion strength of the toner particles to the fine paper can be increased. Therefore, even when toner particles having a small median diameter D50 are used (for example, when image formation is performed using a liquid developer), the fixing strength of the toner particles on the high-quality paper can be increased. it can.

  Preferably, the acid value of the core resin is 30 mgKOH / g or more. Thereby, since the polarity of the core resin is further increased, the fixing strength of the toner particles to the fine paper can be further increased even when toner particles having a small median diameter D50 are used. In fact, it is difficult to make the acid value of the core resin larger than 100 mgKOH / g. Even if the acid value of the core resin can be made larger than 100 mgKOH / g, it is difficult to control the thermophysical properties.

(Difference in acid value)
The difference between the acid value of the aliphatic polyester resin and the acid value of the aromatic polyester resin (hereinafter sometimes referred to as “acid value difference”) is 0 mgKOH / g or more and less than 15 mgKOH / g. If the difference in acid value is less than 15 mgKOH / g, the difference between the amount of carboxyl groups contained in the aliphatic polyester resin and the amount of carboxyl groups contained in the aromatic polyester resin can be kept small. The difference between the SP (Solubility Parameter) value of the resin and the SP value of the aromatic polyester resin can be kept small. This increases the affinity between the aliphatic polyester resin and the aromatic polyester resin. That is, the aliphatic polyester resin and the aromatic polyester resin are easily compatible.

  If the aliphatic polyester resin and the aromatic polyester resin are compatible, since there is no interface between the aliphatic polyester resin and the aromatic polyester resin, it is possible to suppress the holding of the insulating liquid at the interface. This prevents an excessive amount of insulating liquid from being supplied to the high quality paper together with the core resin at the time of transfer, so that the insulating liquid penetrates between the aliphatic polyester resin or the aromatic polyester resin and the high quality paper. Can be prevented. Therefore, the adhesive strength of the toner particles to the high quality paper is increased. Therefore, even when toner particles having a small median diameter D50 are used (for example, when image formation is performed using a liquid developer), the fixing strength of the toner particles on the high-quality paper can be increased. it can.

  Moreover, if holding | maintenance of the insulating liquid in the interface of aliphatic polyester resin and aromatic polyester resin is suppressed, swelling of the aliphatic polyester resin or aromatic polyester resin by an insulating liquid can be prevented. This can also improve the scratch resistance of the image.

  Note that the present inventors have a toner particle core / shell structure, the acid value of the core resin is 20 mgKOH / g or more and 100 mgKOH / g or less, and the acid value difference is 0 mgKOH / g or more and 15 mgKOH / g. It is considered that the fixing strength of the toner particles on the high-quality paper can be increased if it is less than that (for example, see Comparative Examples 3 to 5 described later).

  Various methods are conceivable as a method for reducing the difference between the SP value of the aliphatic polyester resin and the SP value of the aromatic polyester resin. However, if the method of reducing the difference in acid value is adopted, the difference between the SP value of the aliphatic polyester resin and the SP value of the aromatic polyester resin can be effectively suppressed.

  If the difference in acid value is 0 mgKOH / g or more and less than 15 mgKOH / g, the acid value of the aliphatic polyester resin may be larger than the acid value of the aromatic polyester resin, or the acid value of the aromatic polyester resin It may be larger than the acid value of the aliphatic polyester resin. The difference in acid value is preferably 14 mgKOH / g or less, more preferably 10 mgKOH / g or less, and even more preferably 5 mgKOH / g or less.

  The acid value of the polyester resin can be adjusted according to the following method. For example, changing the type of structural unit derived from an alcohol component or the type of structural unit derived from an acid component, a mixed mole of a monomer serving as a structural unit derived from an alcohol component and a monomer serving as a structural unit derived from an acid component The ratio may be changed, or the conditions for the condensation polymerization reaction may be changed. By adopting any of these methods, the amount (molar amount) of the hydroxyl group contained in the monomer serving as the structural unit derived from the alcohol component is changed to the amount of the carboxyl group contained in the monomer serving as the structural unit derived from the acid component. More than the amount (molar amount). In this way, a polyester resin having hydroxyl groups at both ends (hereinafter referred to as “an intermediate of the polyester resin”) is synthesized. The polyester resin intermediate and the polycarboxylic acid are adjusted by adjusting the size relationship between the amount of hydroxyl group (molar amount) contained in the polyester resin intermediate and the amount of the carboxyl group contained in polycarboxylic acid (molar amount). Can be reacted to optimize the acid value of the polyester resin. Here, the “polycarboxylic acid” means a carboxylic acid having two or more functional groups (for example, a carboxyl group).

  For example, an intermediate of an aliphatic polyester resin is synthesized following a method for synthesizing an intermediate of a polyester resin. The intermediate of the synthesized aliphatic polyester resin is reacted with an aliphatic polyvalent carboxylic acid. At this time, if the amount (molar amount) of the carboxyl group contained in the aliphatic polyvalent carboxylic acid is larger than the amount (molar amount) of the hydroxyl group contained in the intermediate of the aliphatic polyester resin, the fatty acid having a high acid value Group polyester resin is obtained.

  Further, an intermediate of an aromatic polyester resin is synthesized in accordance with a method for synthesizing an intermediate of a polyester resin. The intermediate of the synthesized aromatic polyester resin is reacted with an aliphatic polyvalent carboxylic acid or an aromatic polyvalent carboxylic acid. At this time, the amount (molar amount) of the carboxyl group contained in the aliphatic polyvalent carboxylic acid or the aromatic polyvalent carboxylic acid should be less than the amount (molar amount) of the hydroxyl group contained in the intermediate of the aromatic polyester resin. Thus, an aromatic polyester resin having a low acid value can be obtained.

  Further, as will be described later, when a monomer containing three or more functional groups (for example, carboxyl groups) is used as the aliphatic monomer serving as a structural unit derived from the acid component, the acid value of the aliphatic polyester resin increases. Similarly, if a monomer containing three or more functional groups is used as the aromatic monomer that is a structural unit derived from the acid component, the acid value of the aromatic polyester resin is increased. A monomer containing three or more functional groups is used as an aliphatic monomer serving as a structural unit derived from an acid component, and three or more functional groups are used as an aromatic monomer serving as a structural unit derived from an acid component When the monomer is used, the acid value of the aliphatic polyester resin and the acid value of the aromatic polyester resin are increased, so that the acid value of the core resin can be increased.

(Structural unit)
Examples of the aliphatic monomer serving as a structural unit derived from the acid component include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelic acid, sebacic acid, and 1,9-nonane. Dicarboxylic acid, 1,10-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid An acid or 1,18-octadecanedicarboxylic acid etc. are mentioned. These lower alkyl esters may be used, and these acid anhydrides may be used. In terms of promoting the crystallinity of the polyester resin, it is more preferable to use adipic acid, sebacic acid, 1,10-decanedicarboxylic acid, or 1,12-dodecanedicarboxylic acid. As such an aliphatic monomer, any one of the above may be used alone, or two or more of the above may be used in combination.

  More preferably, as an aliphatic monomer that is a structural unit derived from an acid component, for example, butanetricarboxylic acid, cyclohexanetricarboxylic acid, hexanetetracarboxylic acid, octanetetracarboxylic acid, biphenyltetracarboxylic acid, and butanetetracarboxylic acid At least one of them (both monomers containing three or more functional groups). These acid anhydrides or lower alkyl esters thereof may be used. As a result, the acid value of the core resin is increased, so that the fixing strength of the toner particles on the fine paper can be increased.

  Examples of the aliphatic monomer serving as a structural unit derived from the alcohol component include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1 , 7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, , 14-tetradecanediol, 1,18-octadecanediol, 1,20-eicosanediol, and the like. From the viewpoint of promoting the crystallinity of the polyester resin, it is preferable to use ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, or 1,10-decanediol. . As such an aliphatic monomer, any one of the above may be used alone, or two or more of the above may be used in combination.

  Examples of aromatic monomers that are structural units derived from the acid component include aromatic polycarboxylic acids, lower alkyl esters of aromatic polycarboxylic acids, or acid anhydrides of aromatic polycarboxylic acids. Can do. Specific examples include terephthalic acid, isophthalic acid, orthophthalic acid, 5-tert-butylisophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, or trimellitic acid. . From the viewpoint of availability, terephthalic acid, isophthalic acid, or 5-tert-butylisophthalic acid is preferably used.

  More preferably, the aromatic monomer serving as a structural unit derived from the acid component is, for example, at least one of trimellitic acid, trimesic acid, naphthalenetricarboxylic acid, benzophenonetetracarboxylic acid, and pyromellitic acid (any As well as monomers containing three or more functional groups. These acid anhydrides or lower alkyl esters thereof may be used. As a result, the acid value of the core resin is increased, so that the fixing strength of the toner particles on the fine paper can be increased.

  An aromatic polyhydric alcohol etc. can be mentioned as an aromatic monomer used as the structural unit derived from an alcohol component. Specific examples include an alkylene oxide adduct of bisphenol A represented by the following formula (I).

In the above formula (I), R ¹ and R ² each independently represents an alkylene group having 2 or 3 carbon atoms. m and n each independently represent 0 or a positive integer. The sum of m and n is 1 or more and 16 or less.

The number average molecular weight (Mn) of the aliphatic polyester resin is preferably 1000 or more and 25000 or less, and the mass average molecular weight (Mw) of the aliphatic polyester resin is preferably 2000 or more and 200000 or less. The number average molecular weight (Mn) of the aromatic polyester resin is preferably 1000 or more and 25000 or less, and the mass average molecular weight (Mw) of the aromatic polyester resin is preferably 2000 or more and 200000 or less. The number average molecular weight and the mass average molecular weight can be measured by GPC (Gel Permeation Chromatography).

  The core resin may contain less than 10% by mass of a resin other than the aliphatic polyester resin and the aromatic polyester resin. Examples of the resin other than the aliphatic polyester resin and the aromatic polyester resin include styrene-acrylic resin, urethane resin, and epoxy resin. When the content is 10% by mass or more, it may be difficult to regularly arrange the molecular chains of the polyester resin.

(Crystalline and non-crystalline)
A polyester resin is defined as a crystalline resin when the heat of fusion of the polyester resin measured by DSC (Differential Scanning Calorimetry) satisfies the following mathematical formulas (1) and (2).
5 ≦ H1 ≦ 100 (1)
0.2 ≦ H2 / H1 ≦ 1.0 (2)
In the above formulas (1) and (2), H1 represents the heat of fusion (J / g) at the first temperature rise by the DSC method, and H2 is the heat of fusion (J / g) at the second temperature rise by the DSC method. ).

  H1 is an index of the melting rate of the polyester resin. In general, a resin having heat of fusion has a sharp melt property and therefore melts with a small amount of energy. If the H1 of the polyester resin exceeds 100, it is difficult to reduce the fixing energy. For this reason, the fixing property of the toner particles is lowered. On the other hand, if the H1 of the polyester resin is less than 5, the fixing energy becomes too small, and document offset is likely to occur. However, if the H1 of the polyester resin satisfies the above formula (1), the occurrence of document offset can be prevented, and the toner particle fixing property can be prevented from being lowered. Preferably 15 ≦ H1 ≦ 80, more preferably 35 ≦ H1 ≦ 70.

  H2 / H1 in the above formula (2) is an index of the crystallization speed of the polyester resin. In general, when a resin particle (resin particle) is used after being cooled and then cooled, if there is a non-crystallized portion in the crystal component in the resin particle, the resistance value of the resin particle is Inconveniences such as lowering or plasticization of the resin particles occur. When such a malfunction occurs, the performance of the resin particles obtained by cooling may differ from the originally designed performance. From the above, it is necessary to quickly crystallize the crystal component in the resin particles so as not to affect the performance of the resin particles. H2 / H1 is more preferably 0.3 or more, and further preferably 0.4 or more. Further, if the crystallization speed of the polyester resin is high, H2 / H1 approaches 1.0. Therefore, H2 / H1 preferably takes a value close to 1.0.

  Note that H2 / H1 in the above formula (2) does not theoretically exceed 1.0, but it may exceed 1.0 in the actual measurement value by the DSC method. Even when the actual measurement value (H2 / H1) by the DSC method exceeds 1.0, the above formula (2) is satisfied.

  H1 and H2 can be measured according to JIS-K7122 (1987) “Method for measuring the transition heat of plastic”. Specifically, first, 5 mg of a polyester resin is collected and placed in an aluminum pan. Using a differential scanning calorimeter (for example, a product number “RDC220” manufactured by SII Nano Technology Co., Ltd. or a product number “DSC20” manufactured by Seiko Instruments Inc.), the heating rate is 10 ° C./min. The temperature (melting point) at the endothermic peak of the polyester resin is measured to determine the endothermic peak area S1. And H1 is computable from the area | region S1 of the calculated | required endothermic peak. After calculating H1, after cooling to 0 ° C at a cooling rate of 90 ° C / min, the temperature (melting point) at the endothermic peak of the polyester resin due to melting was measured at a rate of temperature rise of 10 ° C per minute, and the endothermic peak The area S2 is obtained. And H2 is computable from the area | region S2 of the calculated | required endothermic peak.

  H1 and H2 can also be measured according to the following method using a differential scanning calorimeter (eg, product number “DSC210” manufactured by Seiko Instruments Inc.). First, the standard sample and the polyester resin are heated from 0 ° C. to 180 ° C. at a rate of 10 ° C./min, and the difference between the heat amount of the standard sample and the heat amount of the polyester resin is measured. The difference in the amount of heat measured is the heat of fusion H1 by the DSC method of the polyester resin. Then, after cooling to 0 ° C. at a cooling rate of 90 ° C./min, the standard sample and the polyester resin are heated from 0 ° C. to 180 ° C. at a rate of 10 ° C./min. Measure the difference. The difference in the amount of heat measured is the heat of fusion H2 of the polyester resin by the DSC method.

<Shell resin>
Shell resin has the effect | action which adheres to the surface of a core particle and improves the dispersibility of a core particle. That is, the shell resin functions as a polymer dispersant.

  As described above, since the toner particles of the present embodiment have a core / shell structure, the fixing strength of the toner particles on the fine paper can be increased. Although it cannot be determined as the reason, it can be considered as follows.

  When the glass transition point of the shell resin is sufficiently lower than room temperature, when the insulating liquid is not present on the surface of the core particles, the shell resin is integrated to form a film. In this specification, this phenomenon is expressed as “self-film forming property of shell resin”. As described above, since the self-film-forming property of the shell resin appears in the state where the insulating liquid is not present, the following effects can be obtained.

  When the liquid developer is heat-fixed on the fine paper, the insulating liquid present in the toner layer formed on the surface of the fine paper, or the interface between the toner layer and the fine paper (specifically, contained in the toner layer) The insulating liquid present at the interface between the core particles of the toner particles and the fine paper (the same applies hereinafter) evaporates or penetrates into the fine paper. As a result, the amount of insulating liquid present on the surface of the fine paper (specifically, the sum of the amount of insulating liquid present in the toner layer and the amount of insulating liquid present at the interface between the toner layer and the fine paper) The same applies to the following).

  Here, the toner particles contained in the liquid developer have a core / shell structure. Therefore, even after the toner layer is melted by heat fixing, the shell resin is present in a rich manner at the interface between the toner layer and the fine paper. That is, the amount of the insulating liquid present on the surface of the fine paper is reduced in a state where the shell resin is richly present at the interface between the toner layer and the fine paper. Therefore, the self-film forming property of the shell resin is manifested.

  When the self-film-forming property of the shell resin is developed at the interface between the toner layer and the fine paper, the adhesion strength of the toner particles to the fine paper is improved. Further, when the self-film-forming property of the shell resin is developed in the toner layer, the adhesive strength between the toner particles contained in the toner layer is improved. For these reasons, the fixing strength of the toner particles on the high-quality paper can be increased. In order to effectively obtain this effect, the shell resin has a long-chain alkyl group as a structural unit derived from a monomer having an affinity for an insulating liquid (hereinafter referred to as a “lipophilic structural unit”). It is preferable to contain 30% by mass or more of a structural unit derived from the monomer it has.

  Specifically, from the viewpoint of the toner particle manufacturing method and from the viewpoint of storage stability of the toner particles, the shell resin is a structural unit derived from a monomer having an affinity for the core resin (hereinafter referred to as “parent core”). And a parent oil constituent unit. If the shell resin contains 30% by mass or more of a structural unit derived from a monomer having a long-chain alkyl group as a lipophilic structural unit, the glass transition point of the shell resin is sufficiently lower than room temperature. The fixing strength of the toner particles can be further increased. More preferably, the shell resin contains 40% by mass or more of a structural unit derived from a monomer having a long-chain alkyl group as a lipophilic structural unit.

  Moreover, it is preferable that shell resin contains 90 mass% or less of the structural unit derived from the monomer which has a long-chain alkyl group as a lipophilic structural unit. Thereby, since content of the parent core structural unit in shell resin is securable, shell resin becomes easy to function as a polymer dispersing agent.

  Such a shell resin may be either a thermoplastic resin or a thermosetting resin. For example, vinyl resin, polyurethane resin, epoxy resin, polyamide resin, polyimide resin, silicon resin, phenol resin, melamine resin, urea A resin, aniline resin, ionomer resin, polycarbonate resin or the like is preferable. The shell resin may be a polyester resin made of a component different from the core resin.

  The shell resin is preferably a vinyl resin, a polyester resin, a polyurethane resin, or an epoxy resin, and more preferably a vinyl resin, from the viewpoint that the shape of the toner particles can be easily controlled during the production of the toner particles. Shell resin may be comprised from one of these resin, and 2 or more types of resin may be mixed and comprised. Hereinafter, the vinyl resin will be described.

(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 kinds of monomers (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 (1-1) Aliphatic hydrocarbon having a polymerizable double bond (1-1-1) Chained aliphatic hydrocarbon having a polymerizable double bond Polymerization Chain aliphatic hydrocarbons having an ionic double bond include, for example, alkenes having 2 to 30 carbon atoms (for example, ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.) Or an alkadiene having 4 to 30 carbon atoms (for example, butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, etc.).

(1-1-2) Cyclic aliphatic hydrocarbon having a polymerizable double bond Cyclic aliphatic hydrocarbon having a polymerizable double bond is, for example, a monocycloalkene having 6 to 30 carbon atoms or a dicycloalkene. A cycloalkene (such as cyclohexene, vinylcyclohexene or ethylidenebicycloheptene), or a monocycloalkadiene or dicycloalkadiene having 5 to 30 carbon atoms (such as monocyclopentadiene or dicyclopentadiene) Preferably there is.

(1-2) Aromatic hydrocarbon having a polymerizable double bond The aromatic hydrocarbon having a polymerizable double bond is, for example, styrene or a hydrocarbyl of styrene (for example, an alkyl having 1 to 30 carbon atoms). , Cycloalkyl, aralkyl or alkenyl) substituted (for example, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, crotylbenzene, Divinylbenzene, divinyltoluene, divinylxylene, trivinylbenzene, etc.) or vinylnaphthalene is preferred.

(2) Monomers having a carboxyl group and a polymerizable double bond and salts thereof Monomers having a carboxyl group and a polymerizable double bond are, for example, unsaturated monocarboxylic acids having 3 to 15 carbon atoms [for example, , (Meth) acrylic acid, crotonic acid, isocrotonic acid or cinnamic acid], unsaturated dicarboxylic acid (anhydride) having 3 to 30 carbon atoms [for example, (anhydrous) maleic acid, fumaric acid, itaconic acid, ( Anhydrous) citraconic acid or mesaconic acid], monoalkyl (carbon number 1 to 10) ester of unsaturated dicarboxylic acid having 3 to 10 carbon atoms (for example, maleic acid monomethyl ester, maleic acid monodecyl ester, fumaric acid) Acid monoethyl ester, itaconic acid monobutyl ester, citraconic acid monodecyl ester, etc.) It is preferable. As used herein, “(meth) acryl” means at least one of acrylic and methacrylic.

  Examples of the salt of the monomer include an alkali metal salt (for example, sodium salt or potassium salt), an alkaline earth metal salt (for example, calcium salt or magnesium salt), an ammonium salt, an amine salt, or a quaternary ammonium salt. A salt or the like is preferable.

  The amine salt is not particularly limited as long as it is an amine compound. For example, a primary amine salt (eg, ethylamine salt, butylamine salt or octylamine salt), secondary amine salt (eg, diethylamine salt or dibutylamine salt) Etc.) or a tertiary amine salt (for example, triethylamine salt or tributylamine salt).

  The quaternary ammonium salt is preferably, for example, a tetraethylammonium salt, a triethyllaurylammonium salt, a tetrabutylammonium salt, or a tributyllaurylammonium salt.

  Examples of the salt of a 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, acrylic Lithium acid, cesium acrylate, ammonium acrylate, calcium acrylate, aluminum acrylate, or the like is preferable.

(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) A hydroxyl group and a polymerizable double bond Monomer having (3) to (5) are not listed as specific examples, but can be used as monomers of vinyl resin.

(6) Nitrogen-containing monomer having a polymerizable double bond (6-1) Monomer having an amino group and a polymerizable double bond A monomer having an amino group and a polymerizable double bond is, for example, aminoethyl (meta ) Acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, t-butylaminoethyl methacrylate, 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, it is preferable that in such aminoimidazole or amino mercaptothiazole.

  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”.

(6-2) Monomer having an amide group and a polymerizable double bond Monomers having an amide group and a polymerizable double bond are, for example, (meth) acrylamide, N-methyl (meth) acrylamide, and N-butylacrylamide. , Diacetone acrylamide, N-methylol (meth) acrylamide, N, N′-methylene-bis (meth) acrylamide, cinnamic acid amide, N, N-dimethylacrylamide, N, N-dibenzylacrylamide, methacrylformamide, N— Methyl-N-vinylacetamide or N-vinylpyrrolidone is preferred.

(6-3) Monomer having 3 to 10 carbon atoms having nitrile group and polymerizable double bond Monomer having 3 to 10 carbon atoms having nitrile group and polymerizable double bond is, for example, (meta ) Acrylonitrile, cyanostyrene or cyanoacrylate is preferred.

(6-4) Monomer having 8 to 12 carbon atoms having nitro group and polymerizable double bond Monomer having 8 to 12 carbon atoms having nitro group and polymerizable double bond is, for example, nitrostyrene And the like.

(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 Above (7) and ( Although a specific example is not enumerated about 8), it can be used as a monomer of a vinyl resin.

(9) Ester having 4 to 16 carbon atoms having a polymerizable double bond Ester having 4 to 16 carbon atoms having a polymerizable double bond includes, for example, 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, 1 to 11 carbon atoms Alkyl (meth) acrylates having the following alkyl groups [for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate or 2-ethylhexyl ( Meth) acrylates, etc.], dialkyl fumarate (the two alkyl groups are straight, branched or alicyclic alkyl groups having 2 to 8 carbon atoms), dialkyl maleates (2 Each alkyl group is a straight chain alkyl group having 2 to 8 carbon atoms, a branched alkyl group or an alicyclic alkyl group), poly (meth) allyloxyalkanes (for example, diaryloxyethane, Triaryloxyethane, tetraallyloxyethane, tetraallyloxypropane, tetraallyloxybutane or tetrametaallyloxyethane), a monomer having a polyalkylene glycol chain and a polymerizable double bond [eg, polyethylene glycol (Mn = 300) Mono (meth) acrylate, polypropylene glycol (Mn = 500) monoacrylate , Methyl alcohol ethylene oxide (hereinafter, “ethylene oxide” is referred to as “EO”) 10 mol adduct (meth) acrylate or lauryl alcohol EO 30 mol adduct (meth) acrylate, etc.], or poly (meth) acrylates { For example, poly (meth) acrylates of polyhydric alcohols [for example, 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]} and the like. As used herein, “(meth) arylo” means at least one of alilo and metallillo.

  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. Polymer, styrene- (maleic anhydride) copolymer, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid-divinylbenzene copolymer, or styrene-styrenesulfonic acid- (meth) acrylic Examples include acid ester copolymers.

  When the shell resin is a vinyl resin, the vinyl resin may be a homopolymer or copolymer of a monomer having a polymerizable double bond as described in (1) to (9) above, but the above (1) to (9). The monomer (9) having a polymerizable double bond and a monomer having a long-chain alkyl group and a polymerizable double bond are preferably polymerized. Thereby, the fixing strength of the toner particles on the high-quality paper can be further increased.

  When the shell resin is a vinyl resin, the long chain alkyl group includes, for example, a linear hydrocarbon chain having 12 to 27 carbon atoms, a branched hydrocarbon chain having 12 to 27 carbon atoms, or carbon It is preferably a fluoroalkyl chain having a number of 4 or more and 20 or less. The difference between the SP value of the monomer having a long-chain alkyl group and a polymerizable double bond and the SP value of the insulating liquid is preferably 2 or less. In the present specification, the “SP value” is a method according to Fedors [Polym. Eng. Sci. 14 (2) 152, (1974)].

  The monomer having a long chain alkyl group and a polymerizable double bond is preferably, for example, the following first to third monomers. As a monomer having a long-chain alkyl group and a polymerizable double bond, any of the first to third monomers may be used, or two or more of the first to third monomers may be used in combination. There may be.

  The first monomer is a monomer having a linear hydrocarbon chain (long chain alkyl group) having 12 to 27 carbon atoms (preferably 16 to 25 carbon atoms) and a polymerizable double bond, for example, A mono-linear alkyl of an unsaturated monocarboxylic acid (alkyl having 12 to 27 carbon atoms) ester or a mono-linear alkyl of an unsaturated dicarboxylic acid (alkyl having 12 to 27 carbon atoms) ester. . The unsaturated monocarboxylic acid and unsaturated dicarboxylic acid are preferably vinyl monomers containing a carboxyl group and having 3 to 24 carbon atoms. For example, (meth) acrylic acid, maleic acid, fumaric acid, crotonic acid, itacone An acid or citraconic acid is preferred. Specific examples of the first monomer include, for example, dodecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate or (meth) acrylic. Examples include eicosyl acid.

  The second monomer is a monomer having a branched hydrocarbon chain (long chain alkyl group) having 12 to 27 carbon atoms (preferably 16 to 25 carbon atoms) and a polymerizable double bond. Mono-branched alkyl (alkyl having 12 to 27 carbon atoms) ester of unsaturated monocarboxylic acid or mono-branched alkyl (alkyl having 12 to 27 carbon atoms) ester of unsaturated dicarboxylic acid. The unsaturated monocarboxylic acid and unsaturated dicarboxylic acid are as described for the first monomer. Specific examples of the second monomer include 2-decyltetradecyl (meth) acrylate.

  The third monomer is a monomer having a fluoroalkyl chain (long chain alkyl group) having 4 to 20 carbon atoms and a polymerizable double bond. Specific examples of the third monomer include those in which the hydrocarbon chain is replaced with a fluoroalkyl chain in the specific example of the first monomer or the specific example of the second monomer.

  The Mn of the shell resin is preferably 100 or more and 5000000 or less, more preferably 200 or more and 5000000 or less, and further preferably 500 or more and 500000 or less. The Mn of the shell resin can be measured by GPC (Gel Permeation Chromatography).

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

  Such a shell resin may be formed in a particle shape on the surface of the core particle, or may be formed in a film shape. The shell particles (particles containing the shell resin) or the shell film (film containing the shell resin) may further contain a colorant or an optional component (for example, a pigment dispersant, a wax or a charge control agent).

  The median diameter D50 when the particle size distribution of the shell particles contained in the shell dispersion is measured on a volume basis so that the median diameter D50 of the toner particles falls within a desired range (hereinafter referred to as “the median diameter D50 of the shell particles”). ) Is suitably adjusted. The median diameter D50 of the shell particles is preferably 0.0005 μm or more and 3 μm or less. The upper limit of the median diameter D50 of the shell particles is more preferably 2 μm, and even more preferably 1 μm. The lower limit of the median diameter D50 of the shell particles is more preferably 0.01 μm, still more preferably 0.02 μm, and still more preferably 0.04 μm. For example, when it is desired to obtain toner particles having a median diameter D50 of 1 μm, the median diameter D50 of the shell particles is preferably 0.0005 μm to 0.3 μm, and more preferably 0.001 μm to 0.2 μm. is there. When it is desired to obtain toner particles having a median diameter D50 of 10 μm, the median diameter D50 of the shell particles is preferably 0.005 μm to 3 μm, and more preferably 0.05 μm to 2 μm.

  The median diameter D50 of the shell particles is determined by a laser diffraction particle size distribution measuring device (for example, product number “LA-920” manufactured by Horiba, Ltd. or product number “Multisizer III” manufactured by Beckman Coulter, Inc.) or an optical system. It can be measured using a particle size distribution measuring apparatus using a laser Doppler method (product number “ELS-800” manufactured by Otsuka Electronics Co., Ltd.). When the median diameter D50 of the shell particles is measured using different measurement measurements, if a difference occurs in the measured values, measurement with a particle size distribution measuring device (product number “ELS-800” manufactured by Otsuka Electronics Co., Ltd.) Adopt value.

<Colorant>
The colorant is dispersed in at least one of the aliphatic polyester resin and the aromatic polyester resin, and preferably has a particle size of 0.3 μm or less. If the particle size of the colorant is 0.3 μm or less, the dispersibility of the colorant can be further increased, so that the glossiness of the image can be further increased, and thus the desired color can be easily realized. Become.

  As the colorant, conventionally known pigments and the like can be used without any particular limitation, but the following pigments are preferably used from the viewpoints of cost, light resistance, and colorability. In terms of color composition, these pigments are usually classified into black pigments, yellow pigments, magenta pigments, and cyan pigments. Basically, colors other than black (color image) are toned by a subtractive color mixture of a yellow pigment, a magenta pigment, or a cyan pigment. The pigments shown below may be used alone, or two or more of the pigments shown below may be used in combination as required.

  As the pigment (black pigment) contained in the black colorant, for example, carbon black such as furnace black, channel black, acetylene black, thermal black, or lamp black may be used, or biomass-derived carbon black may be used. Alternatively, magnetic powder such as magnetite or ferrite may be used. Nigrosine (azine compound), which is a purple black dye, may be used alone or in combination. Nigrosine includes C.I. I. Solvent Black 7 or C.I. I. Solvent black 5 or the like can be used.

  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, or 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, or 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 or C.I. I. And CI Pigment Green 7.

<Arbitrary component in toner particles (pigment dispersant)>
An example of the optional component in the toner particles is a pigment dispersant. The pigment dispersant has a function of uniformly dispersing the colorant (pigment) in the toner particles, and is preferably a basic dispersant. A basic dispersing agent means what is defined below. That is, 0.5 g of pigment dispersant and 20 ml of distilled water were placed in a glass screw tube, and the glass screw tube was shaken for 30 minutes using a paint shaker and then filtered. The pH of the filtrate thus obtained is measured by a pH meter (trade name: “D-51”, manufactured by Horiba, Ltd.).
When the pH is higher than 7, the basic dispersant is used. 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. Basic dispersants are, for example, amine groups, amino groups, amide groups, pyrrolidone groups, imine groups, imino groups, urethane groups, quaternary ammonium groups, ammonium groups, pyridino groups, pyridium groups, imidazolino groups, or imidazoliums. A compound having a functional group such as a group in the molecule is preferred. In addition, as a dispersing agent, what is called surfactant which has a hydrophilic part and a hydrophobic part in a molecule | numerator normally corresponds. However, as long as it has an action of uniformly dispersing the colorant (pigment) in the toner particles, it is not limited to the surfactant, and various compounds can be used.

  As a commercial item of such a basic dispersant, for example, “Ajisper PB-821” (trade name), “Azisper PB-822” (trade name) or “Azisper PB-881” manufactured by Ajinomoto Fine Techno Co., Ltd. (Trade name) may be used, or “Solspers 28000” (trade name), “Solspurs 32000” (trade name), “Solspurs 32500” (trade name), “Solspurs 35100” manufactured by Nippon Lubrizol Co., Ltd. (Trade name) or “Solspers 37500” (trade name) may be used.

  It is more preferable to select a pigment dispersant that does not dissolve in the insulating liquid. In consideration of this point, use “Ajisper PB-821” (trade name), “Ajisper PB-822” (trade name) or “Ajisper PB-881” (trade name) manufactured by Ajinomoto Fine Techno Co., Ltd. Is more preferable. Although the detailed mechanism is unknown, it is easy to obtain toner particles having a desired shape by using such a pigment dispersant.

  Such a pigment dispersant is preferably added in an amount of 1 to 100% by mass, more preferably 1 to 40% by mass, based on the colorant (pigment). If the added amount of the pigment dispersant is 1% by mass or more, the dispersibility of the colorant (pigment) can be secured, so that the necessary ID (image density) can be achieved, and the fixing strength of the toner particles on the recording medium. Can be secured. If the addition amount of the pigment dispersant is 100% by mass or less, the addition amount of the pigment dispersant can be prevented from becoming excessive, so that the excess amount of the pigment dispersant can be prevented from dissolving in the insulating liquid. The chargeability of the toner particles or the fixing strength of the toner particles can be maintained in a good state. The pigment dispersant may be used alone, or two or more of the pigment dispersants may be used in combination as necessary.

<Insulating liquid>
The insulating liquid preferably has a resistance value that does not disturb the electrostatic latent image (about 10 ¹¹ to 10 ¹⁶ Ω · cm), and is preferably a solvent having low odor and toxicity. Examples of the insulating liquid generally include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, and polysiloxanes. In particular, from the viewpoint of low odor, low harm, low cost, etc., it is preferable to use a normal paraffin solvent or an isoparaffin solvent as the insulating liquid. More preferably, Moresco White (trade name, manufactured by Matsumura Oil Co., Ltd.), Isopar (trade name, manufactured by ExxonMobil) or Shellsol (trade name, manufactured by Shell Chemicals Japan Co., Ltd.) is used. 1620, IP solvent 2028 or IP solvent 2835 (both are trade names, manufactured by Idemitsu Kosan Co., Ltd.).

<Manufacture of liquid developer>
The method for producing the liquid developer of the present embodiment is not particularly limited, and examples thereof include conventionally known techniques such as a granulation method or a pulverization method. 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. A resin having a high melting property or a resin having a high crystallinity is soft even at room temperature and hardly pulverized. Therefore, in the pulverization method, the particle size of the toner particles may not be controlled to a desired particle size. However, in the granulation method, toner particles having a desired particle size can be obtained.

  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 toner particles, spray drying method, etc. Is included.

  More preferably, a method of depositing toner particles by adding a poor solvent to the resin solution is employed. In this method, first, the core resin is dissolved in a good solvent to obtain a core resin forming solution (dispersed phase). After the core resin forming solution is mixed with a poor solvent (SP value is different from a good solvent) together with an interfacial tension adjusting agent (for example, a shell resin (continuous phase)), droplets are formed by applying shear. Thereafter, when the good solvent is volatilized, a liquid developer containing toner particles is obtained. In this method, the particle size of the toner particles or the shape of the toner particles can be highly controlled by appropriately adjusting the shearing method, the difference in interfacial tension, or the interfacial tension adjusting agent (for example, shell resin). Therefore, this method is suitable as a method for obtaining toner particles having a desired particle size distribution and a desired shape.

  When the core resin forming solution is mixed with a shell resin in a poor solvent, it is preferable to mix the core resin forming solution with a dispersion liquid (shell dispersion liquid) in which shell particles containing the shell resin are dispersed in the poor solvent. . For example, shell particles are preferably produced by any one of the following methods [1] to [7]. From the viewpoint of easy manufacture of shell particles, it is preferable to manufacture shell particles by the method [4], [6] or [7], and to manufacture shell particles by the method [6] or [7]. Is more preferable.

[1] The shell resin is pulverized dry using a known dry pulverizer such as a jet mill. [2] The shell resin powder is dispersed in an organic solvent, and a known wet disperser such as a bead mill or a roll mill is used. [3] Spray the shell resin solution using a spray dryer and dry it. [4] Add a poor solvent to the shell resin solution or cool it to supersaturate the shell resin and precipitate. [5] Disperse the shell resin solution in water or an organic solvent. [6] Polymerize the precursor of the shell resin in water by emulsion polymerization, soap-free emulsion polymerization, seed polymerization or suspension polymerization. [7] The shell resin precursor is polymerized in an organic solvent by dispersion polymerization or the like.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to the following.
<Production Example 1> [Production of Aliphatic Polyester Resin (A-1)]
A reaction vessel equipped with a stirrer, a heating / cooling device, and a thermometer was charged with 432 parts by mass of hexanediol, 568 parts by mass of sebacic acid, and 2 parts by mass of titanium dihydroxybis (triethanolaminate) (condensation catalyst). While removing generated water, the reaction was carried out at 180 ° C. under a nitrogen stream for 8 hours.

  Next, it was made to react under nitrogen stream for 4 hours, raising temperature gradually to 220 degreeC and removing the produced | generated water. Then, it was made to react under the reduced pressure of 0.007-0.026 MPa for 1 hour. 66 parts by weight of trimellitic anhydride was further added to the reaction vessel and reacted at 180 ° C. for 1 hour. Thus, aliphatic polyester resin (A-1) was obtained. When Mn of the aliphatic polyester resin (A-1) and the acid value of the aliphatic polyester resin (A-1) were measured by the above-described methods, Mn was 2100 and the acid value was 36 mgKOH / g. .

<Production Example 2> [Production of Aliphatic Polyester Resin (A-2)]
An aliphatic polyester resin (A-2) was obtained according to the method described in Production Example 1 except that the amount of trimellitic anhydride was changed to 30 parts by mass. When Mn of aliphatic polyester resin (A-2) and the acid value of aliphatic polyester resin (A-2) were measured by the above-mentioned method, Mn was 2100 and the acid value was 17 mgKOH / g.

<Production Example 3> [Production of Aliphatic Polyester Resin (A-3)]
An aliphatic polyester resin (A-3) was obtained according to the method described in Production Example 1 except that the amount of trimellitic anhydride was changed to 83 parts by mass. When Mn of the aliphatic polyester resin (A-3) and the acid value of the aliphatic polyester resin (A-3) were measured by the above-mentioned method, Mn was 2200 and the acid value was 45 mgKOH / g.

<Production Example 4> [Production of Aliphatic Polyester Resin (A-4)]
An aliphatic polyester resin (A-4) was obtained according to the method described in Production Example 1 except that the amount of trimellitic anhydride was changed to 9 parts by mass. When Mn of the aliphatic polyester resin (A-4) and the acid value of the aliphatic polyester resin (A-4) were measured by the above-mentioned method, Mn was 2000 and the acid value was 5 mgKOH / g.

<Production Example 5> [Production of aromatic polyester resin (B-1)]
In a reaction vessel equipped with a stirrer, a heating / cooling device, and a thermometer, 728 parts by mass of an ethylene oxide 2-mole adduct of bisphenol A, 136 parts by mass of isophthalic acid, 136 parts by mass of terephthalic acid, and titanium dihydroxybis (triethanolamate) (Condensation catalyst) 2 parts by mass were added. While removing generated water, the reaction was carried out at 180 ° C. under a nitrogen stream for 8 hours.

  Next, it was made to react under nitrogen stream for 4 hours, raising temperature gradually to 220 degreeC and removing the produced | generated water. Then, it was made to react under the reduced pressure of 0.007-0.026 MPa for 1 hour. 40 parts by weight of trimellitic anhydride was further added to the reaction vessel and reacted at 180 ° C. for 1 hour. In this way, an aromatic polyester resin (B-1) was obtained. When Mn of the aromatic polyester resin (B-1) and the acid value of the aromatic polyester resin (B-1) were measured by the method described above, the Mn was 4300 and the acid value was 40 mgKOH / g.

<Production Example 6> [Production of aromatic polyester resin (B-2)]
An aromatic polyester resin (B-2) was obtained according to the method described in Production Example 5 except that the amount of trimellitic anhydride was changed to 22 parts by mass. When Mn of the aromatic polyester resin (B-2) and the acid value of the aromatic polyester resin (B-2) were measured by the method described above, the Mn was 4200 and the acid value was 22 mgKOH / g.

<Production Example 7> [Production of aromatic polyester resin (B-3)]
An aromatic polyester resin (B-3) was obtained according to the method described in Production Example 5 except that the amount of trimellitic anhydride was changed to 100 parts by mass. When Mn of the aromatic polyester resin (B-3) and the acid value of the aromatic polyester resin (B-3) were measured by the method described above, the Mn was 4400 and the acid value was 53 mgKOH / g.

<Production Example 8> [Production of core resin forming solution (1)]
192 parts by weight of aliphatic polyester resin (A-1), 208 parts by weight of aromatic polyester resin (B-1) and 600 parts by weight of acetone are stirred in a beaker, and these polyester resins are uniformly dissolved in acetone. It was. Thus, a core resin forming solution (1) was obtained. It was 40 mass% when solid content concentration of the obtained solution (1) for core resin formation was measured. The acid value of the solid content (corresponding to the acid value of the core resin; the same applies hereinafter) was 38 mgKOH / g.

<Production Example 9> [Production of core resin forming solution (2)]
24 parts by mass of the aliphatic polyester resin (A-1), 376 parts by mass of the aromatic polyester resin (B-1) and 600 parts by mass of acetone are placed in a beaker and stirred, and these polyester resins are uniformly dissolved in acetone. It was. Thereby, a core resin forming solution (2) was obtained. It was 40 mass% when solid content concentration of the obtained solution (2) for core resin formation was measured. Moreover, the acid value of solid content was 40 mgKOH / g.

<Production Example 10> [Production of core resin forming solution (3)]
100 parts by weight of aliphatic polyester resin (A-2), 300 parts by weight of aromatic polyester resin (B-2) and 600 parts by weight of acetone are placed in a beaker and stirred, and these polyester resins are uniformly dissolved in acetone. It was. Thus, a core resin forming solution (3) was obtained. It was 40 mass% when solid content concentration of the obtained solution (3) for core resin formation was measured. Moreover, the acid value of solid content was 21 mgKOH / g.

<Production Example 11> [Production of core resin forming solution (4)]
120 parts by mass of an aliphatic polyester resin (A-3), 280 parts by mass of an aromatic polyester resin (B-3) and 600 parts by mass of acetone are placed in a beaker and stirred, and these polyester resins are uniformly dissolved in acetone. It was. Thereby, a core resin forming solution (4) was obtained. It was 40 mass% when solid content concentration of the obtained solution for core resin formation (4) was measured. Moreover, the acid value of solid content was 51 mgKOH / g.

<Production Example 12> [Production of core resin forming solution (5)]
120 parts by mass of the aliphatic polyester resin (A-1), 280 parts by mass of the aromatic polyester resin (B-2) and 600 parts by mass of acetone are placed in a beaker and stirred, and these polyester resins are uniformly dissolved in acetone. It was. This obtained the core resin formation solution (5). It was 40 mass% when solid content concentration of the obtained solution (5) for core resin formation was measured. Moreover, the acid value of solid content was 26 mgKOH / g.

<Production Example 13> [Production of core resin-forming solution (6)]
100 parts by weight of aliphatic polyester resin (A-1), 300 parts by weight of aromatic polyester resin (B-1) and 600 parts by weight of acetone are stirred in a beaker, and these polyester resins are uniformly dissolved in acetone. It was. This obtained the core resin formation solution (6). It was 40 mass% when solid content concentration of the obtained solution (6) for core resin formation was measured. Moreover, the acid value of solid content was 39 mgKOH / g.

<Production Example 14> [Production of core resin-forming solution (7)]
400 parts by mass of the aromatic polyester resin (B-1) and 600 parts by mass of acetone were placed in a beaker and stirred, and the aromatic polyester resin (B-1) was uniformly dissolved in acetone. This obtained the core resin formation solution (7). It was 40 mass% when solid content concentration of the obtained solution (7) for core resin formation was measured. Moreover, the acid value of solid content was 40 mgKOH / g.

<Production Example 15> [Production of core resin forming solution (8)]
240 parts by mass of the aliphatic polyester resin (A-1), 160 parts by mass of the aromatic polyester resin (B-1), and 600 parts by mass of acetone are stirred in a beaker, and these polyester resins are uniformly dissolved in acetone. It was. As a result, a core resin forming solution (8) was obtained. It was 40 mass% when solid content concentration of the obtained solution (8) for core resin formation was measured. Moreover, the acid value of solid content was 38 mgKOH / g.

<Production Example 16> [Production of core resin forming solution (9)]
120 parts by mass of an aliphatic polyester resin (A-4), 280 parts by mass of an aromatic polyester resin (B-3) and 600 parts by mass of acetone are placed in a beaker and stirred, and these polyester resins are uniformly dissolved in acetone. It was. This obtained the core resin formation solution (9). It was 40 mass% when solid content concentration of the obtained solution (9) for core resin formation was measured. Moreover, the acid value of solid content was 17 mgKOH / g.

<Production Example 17> [Production of core resin forming solution (10)]
80 parts by mass of the aliphatic polyester resin (A-2), 320 parts by mass of the aromatic polyester resin (B-1), and 600 parts by mass of acetone are stirred in a beaker, and these polyester resins are uniformly dissolved in acetone. It was. This obtained the core resin formation solution (10). It was 40 mass% when solid content concentration of the obtained solution for core resin formation (10) was measured. Moreover, the acid value of solid content was 35 mgKOH / g.

<Production Example 18> [Production of core resin forming solution (11)]
152 parts by mass of the aliphatic polyester resin (A-1), 248 parts by mass of the aromatic polyester resin (B-1) and 600 parts by mass of acetone are placed in a beaker and stirred, and these polyester resins are uniformly dissolved in acetone. It was. As a result, a core resin forming solution (11) was obtained. It was 40 mass% when solid content concentration of the obtained solution (11) for core resin formation was measured. Moreover, the acid value of solid content was 38 mgKOH / g.

<Production Example 19> [Production of Shell Dispersion (C-1)]
In a glass beaker, 45 parts by mass of n-octyl methacrylate (monomer having a long chain alkyl group), 15 parts by mass of 2-decyltetradecyl methacrylate (monomer having a long chain alkyl group), 15 parts by mass of methacrylic acid and a piece 25 parts by mass of terminal methacryloylated polymethyl methacrylate oligomer (trade name “AA-6” manufactured by Toagosei Co., Ltd., Mn = 6000) and 0.1 part by mass of azobismethoxydimethylvaleronitrile were added and stirred at 20 ° C. did. Thereby, a monomer solution was obtained.

  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. 100 parts by mass of THF was placed in the reaction vessel, and the monomer solution was placed in a dropping funnel. After the gas phase part of the reaction vessel was replaced with nitrogen, the monomer solution was added dropwise to THF at 70 ° C. for 1 hour in a sealed state. Three hours after the completion of dropping of the monomer solution, a mixture of 0.05 parts by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was added to the monomer solution. After reacting at 70 ° C. for 3 hours, the mixture was cooled to room temperature. Thereby, a copolymer solution was obtained.

  200 parts by mass of the obtained copolymer solution was dropped into 300 parts by mass of an insulating liquid under stirring (trade name “IP Solvent 2028” manufactured by Idemitsu Kosan Co., Ltd.), and then at 40 ° C. under a reduced pressure of 0.039 MPa. THF was removed. In this way, a dispersion for shell (C-1) was obtained. It was 40000 when Mn of the shell resin contained in the dispersion liquid (C-1) for shell was measured by the above-mentioned method.

<Production Example 20> [Production of Shell Dispersion (C-2)]
According to the method described in Production Example 19, except that the amount of n-octyl methacrylate (monomer having a long chain alkyl group) was changed to 15 parts by mass and the amount of methacrylic acid was changed to 45 parts by mass. A dispersion for shell (C-2) was obtained. It was 40000 when Mn of the shell resin contained in the dispersion liquid (C-2) for shell was measured by the above-mentioned method.

<Production Example 21> [Production of Shell Dispersion (C-3)]
According to the method described in Production Example 19, except that the amount of n-octyl methacrylate (monomer having a long chain alkyl group) was changed to 5 parts by mass and the amount of methacrylic acid was changed to 55 parts by mass. A dispersion for shell (C-3) was obtained. It was 40000 when Mn of the shell resin contained in the dispersion liquid (C-3) for shell was measured by the above-mentioned method.

<Production Example 22> [Production of Colorant Dispersion Liquid (1)]
In a beaker, 25 parts by mass of copper phthalocyanine (trade name “Fastogen Blue FDB-14” manufactured by DIC Corporation) (colorant (pigment)) and a pigment dispersant (trade name “Ajisper PB-821 manufactured by Ajinomoto Fine Techno Co., Ltd.) “) 4 parts by mass and 75 parts by mass of acetone were added and stirred to uniformly disperse the copper phthalocyanine. Copper phthalocyanine was finely dispersed using a bead mill to obtain a colorant dispersion. The median diameter D50 of copper phthalocyanine in the colorant dispersion (1) was 0.2 μm.

<Example 1> [Production of liquid developer (1)]
In a beaker, 410 parts by mass of the core resin forming solution (1) and 190 parts by mass of the colorant dispersion (1) were added. The obtained solution was stirred at 16000 rpm at 25 ° C. using a TK auto homomixer (manufactured by PRIMIX Corporation). In this way, a resin solution in which the colorant was uniformly dispersed was obtained.

  In another beaker, 670 parts by mass of an insulating liquid (trade name “IP Solvent 2028” manufactured by Idemitsu Kosan Co., Ltd.) and 60 parts by mass of the dispersion liquid for shell (C-1) were placed. While stirring the obtained solution at 20000 rpm using CLEARMIX (M Technique Co., Ltd.) at 25 ° C., 600 parts by mass of the resin solution was added and stirred for 2 minutes.

  The obtained mixed liquid was put into a reaction vessel equipped with a stirring device, a heating / cooling device, a thermometer, and a solvent removal device, and the temperature was raised to 35 ° C. At the same temperature, acetone was removed from the mixed solution under a reduced pressure of 0.039 MPa until the acetone concentration became 0.5% by mass or less. Thereby, a liquid developer (1) was obtained. In the liquid developer (1), the content of the colorant (pigment) in the toner particles was 20% by mass, and the content of the toner particles in the liquid developer was 24% by mass.

<Example 2> [Production of liquid developer (2)]
A liquid developer (2) was obtained according to the method described in Example 1, except that the core resin forming solution (2) was used instead of the core resin forming solution (1). In the liquid developer (2), the content of the colorant (pigment) in the toner particles was 20% by mass, and the content of the toner particles in the liquid developer was 24% by mass.

<Example 3> [Production of liquid developer (3)]
A liquid developer (3) was obtained according to the method described in Example 1, except that the core resin forming solution (3) was used instead of the core resin forming solution (1). In the liquid developer (3), the content of the colorant (pigment) in the toner particles was 20% by mass, and the content of the toner particles in the liquid developer was 24% by mass.

<Example 4> [Production of liquid developer (4)]
A liquid developer (4) was obtained according to the method described in Example 1, except that the core resin forming solution (4) was used instead of the core resin forming solution (1). In the liquid developer (4), the content of the colorant (pigment) in the toner particles was 20% by mass, and the content of the toner particles in the liquid developer was 24% by mass.

<Example 5> [Production of liquid developer (5)]
Implemented except that the core resin forming solution (5) was used instead of the core resin forming solution (1) and the shell dispersion (C-2) was used instead of the shell dispersion (C-1). According to the method described in Example 1, a liquid developer (5) was obtained. In the liquid developer (5), the content of the colorant (pigment) in the toner particles was 20% by mass, and the content of the toner particles in the liquid developer was 24% by mass.

<Example 6> [Production of liquid developer (6)]
Implemented except that the core resin forming solution (6) was used instead of the core resin forming solution (1) and the shell dispersion (C-2) was used instead of the shell dispersion (C-1). According to the method described in Example 1, a liquid developer (6) was obtained. In the liquid developer (6), the content of the colorant (pigment) in the toner particles was 20% by mass, and the content of the toner particles in the liquid developer was 24% by mass.

<Example 7> [Production of liquid developer (7)]
A liquid developer (7) was obtained according to the method described in Example 6 except that the dispersion liquid for shell (C-3) was used instead of the dispersion liquid for shell (C-2). In the liquid developer (7), the content of the colorant (pigment) in the toner particles was 20% by mass, and the content of the toner particles in the liquid developer was 24% by mass.

<Comparative Example 1> [Production of Liquid Developer (8)]
A liquid developer (8) was obtained according to the method described in Example 1, except that the core resin forming solution (7) was used instead of the core resin forming solution (1). In the liquid developer (8), the content of the colorant (pigment) in the toner particles was 20% by mass, and the content of the toner particles in the liquid developer was 24% by mass.

<Comparative Example 2> [Production of Liquid Developer (9)]
A liquid developer (9) was obtained according to the method described in Example 1, except that the core resin forming solution (8) was used instead of the core resin forming solution (1). In the liquid developer (9), the content of the colorant (pigment) in the toner particles was 20% by mass, and the content of the toner particles in the liquid developer was 24% by mass.

<Comparative Example 3> [Production of Liquid Developer (10)]
A liquid developer (10) was obtained according to the method described in Example 1, except that the core resin forming solution (9) was used instead of the core resin forming solution (1). In the liquid developer (10), the content of the colorant (pigment) in the toner particles was 20% by mass, and the content of the toner particles in the liquid developer was 24% by mass.

<Comparative example 4> [Production of liquid developer (11)]
A liquid developer (11) was obtained according to the method described in Example 1, except that the core resin forming solution (10) was used instead of the core resin forming solution (1). In the liquid developer (11), the content of the colorant (pigment) in the toner particles was 20% by mass, and the content of the toner particles in the liquid developer was 24% by mass.

<Comparative Example 5> [Production of Liquid Developer (12)]
In a beaker, 410 parts by mass of the core resin forming solution (12) and 190 parts by mass of the colorant dispersion (1) were placed. The obtained solution was stirred at 16000 rpm at 25 ° C. using a TK auto homomixer (manufactured by PRIMIX Corporation). In this way, a resin solution in which the colorant was uniformly dispersed was obtained.

  In another beaker, 670 parts by mass of an insulating liquid (trade name “IP Solvent 2028” manufactured by Idemitsu Kosan Co., Ltd.) was added and stirred. Next, 600 mass parts of the resin solution was added and stirred for 2 minutes while stirring at 20000 rpm using CLEARMIX (M Technique Co., Ltd.) at 25 ° C.

  The obtained mixed liquid was put into a reaction vessel equipped with a stirring device, a heating / cooling device, a thermometer, and a solvent removal device, and the temperature was raised to 35 ° C. At the same temperature, acetone was removed from the mixed solution under a reduced pressure of 0.039 MPa until the acetone concentration became 0.5% by mass or less. As a result, a liquid developer (12) was obtained. In the liquid developer (12), the content of the colorant (pigment) in the toner particles was 20% by mass, and the content of the toner particles in the liquid developer was 24% by mass.

<Measurement of fixing strength (fixing strength of toner particles on fine paper)>
First of all, according to the method described below, solid pattern image (image density: 5g / m ²⁾ a high-quality paper (trade name "gold diamond", manufactured by Mitsubishi Paper Mills Ltd., 127.9g / m ²⁾ was formed on the surface of. As a result, a three-layer solid pattern image was formed on the surface of the fine paper. Thereafter, a three-layer solid pattern image was fixed on the surface of the fine paper using a heat roller. The set temperature of the heat roller was 120 ° C., the fixing NIP time was 50 msec, and the temperature of the fine paper immediately after passing through the heat roller fixing device was 90 ° C.

  After leaving the fine paper on which the three-layer solid pattern image was fixed for 1 hour at room temperature, a tape (trade name “Scotch Mending Tape”, manufactured by Sumitomo 3M Co., Ltd.) was attached to the measurement target portion of this fine paper . Then, the tape was peeled off from the measurement object part, and was affixed on the reference | standard paper (brand name "CF paper", Konica Minolta Co., Ltd. make). The image density (ID) of the portion where the tape was attached was measured using a reflection densitometer (trade name: “SpectroEye”, manufactured by X-Rite). In this way, the image density for evaluation was measured.

  Further, the tape was affixed to the reference paper without being affixed to high-quality paper, and the image density (reference image density) of the portion where the tape was affixed was measured. Then, a difference (ΔID) between the evaluation image density and the reference image density was obtained. The results are shown in Table 1.

  In Table 1, when ΔID is less than 0.1, it is described as “A1”, when ΔID is 0.1 or more and less than 0.15, it is described as “B1”, and ΔID is 0.15 or more. In this case, it is described as “C1”. It can be said that the lower the ΔID, the higher the fixing strength of the toner particles on the high-quality paper because the three-layer solid pattern image is less likely to be peeled off by the tape. Further, in this embodiment, the set temperature of the roller at the time of fixing is 120 ° C., and the temperature of the fine paper immediately after passing through the heat roller fixing device is 90 ° C. Therefore, if ΔID is low, fixing at a low temperature is realized. I can say that.

<Evaluation of scratch resistance>
Scratch resistance was evaluated using an image (three-layer solid pattern image) used for measuring the fixing strength. However, when the fixing strength is evaluated as C1, an image (three-layer solid pattern image) having a fixing strength evaluation of A1 or B1 is prepared by adjusting the fixing temperature, and the scratch resistance of the image is improved. evaluated.

  Specifically, a copper indenter having a radius of 2.5 mm was brought into contact with a three-layer solid pattern image (evaluation image). The evaluation image was moved 30 mm at a scanning speed of 5 mm / s while applying a load toward the evaluation image to the indenter. The load applied to the indenter was changed, and the minimum value (minimum weight) of “weight” when scratches formed on the surface of the evaluation image could be recognized with the naked eye was examined. Here, “weight” means the load applied from the indenter to the evaluation image, and includes the influence of the weight of the indenter itself. The results are shown in Table 1.

  In Table 1, when the minimum weight is 40 gf or more, “A2” is written. When the minimum weight is 20 gf or more and less than 40 gf, “B2” is written. When the minimum weight is less than 20 gf. “C2”. It can be said that the heavier the minimum weight, the better the scratch resistance.

<Image formation>
An image was formed using the image forming apparatus shown in FIG. The configuration of the image forming apparatus shown in FIG. The liquid developer 21 is pumped up from the developing tank 22 by the anilox roller 23. Excess liquid developer 21 on the anilox roller 23 is scraped off by the anilox regulating blade 24, and the remaining liquid developer 21 is sent to the leveling roller 25. On the leveling roller 25, the liquid developer 21 is adjusted to have a uniform and thin thickness.

  The liquid developer 21 on the leveling roller 25 is sent to the developing roller 26. The liquid developer 21 on the developing roller 26 is charged by the developing charger 28 and developed on the photoconductor 29, and excess liquid developer is scraped off by the developing cleaning blade 27. Specifically, the surface of the photoconductor 29 is uniformly charged by the charging unit 30, and the exposure unit 31 disposed around the photoconductor 29 emits light based on predetermined image information on the surface of the photoconductor 29. Irradiate. As a result, an electrostatic latent image based on predetermined image information is formed on the surface of the photoreceptor 29. By developing the formed electrostatic latent image, a toner image is formed on the photoreceptor 29. The excess liquid developer on the photoconductor 29 is scraped off by the cleaning blade 32.

  The toner image formed on the photosensitive member 29 is primarily transferred to the intermediate transfer member 33 in the primary transfer unit 37, and the liquid developer transferred to the intermediate transfer member 33 is recorded in the recording medium 40 (for example, high-quality paper) in the secondary transfer unit 38. ) Is secondarily transferred. The liquid developer remaining on the intermediate transfer member 33 without being subjected to the secondary transfer is scraped off by the intermediate transfer member cleaning unit 34.

In this embodiment, the surface of the photosensitive member 29 is positively charged by the charging unit 30, the potential of the intermediate transfer member 33 is −400 V, and the potential of the secondary transfer roller 35 is −1200 V. The conveyance speed of the recording medium 40 was 400 mm / s. The toner amount on the developing roller 26 was 1.5 g / m ² .

<Result>
The results are shown in Table 1.

In Table 1, “mixing ratio (mass%) ^{* 11} ” is the aliphatic polyester relative to the total (mass of core resin) of the blending amount (mass) of the aliphatic polyester resin and the blending amount (mass) of the aromatic polyester resin. It means the proportion of the amount (mass) of resin.

“Blend ratio (mass%) ^{* 12} ” is the ratio of the blending quantity (mass) of the aromatic polyester resin to the sum of the blending quantity (mass) of the aliphatic polyester resin and the blending quantity (mass) of the aromatic polyester resin. means.

“ΔAV ^{* 13} ” means the magnitude of the difference between the acid value of the aliphatic polyester resin and the acid value of the aromatic polyester resin (unit: mgKOH / g).

“Mixing ratio of monomer having long chain alkyl group (mass%) ^{* 14} ” is the ratio of the blending quantity (mass) of monomer having long chain alkyl group to the total blending quantity (mass) of monomer constituting shell resin. means. In this example, “n-octyl methacrylate” and “2-decyltetradecyl methacrylate” correspond to “monomer having a long-chain alkyl group”.

“Core / shell ^{* 15} ” means that the toner particles have a core / shell structure. “Non-core / shell ^{* 16} ” means that the toner particles do not have a core / shell structure. Each unit of “acid value” and “acid value of core resin” described in Table 1 is mgKOH / g.

<Discussion>
As shown in Table 1, in Comparative Example 1, the fixing strength (fixing strength of toner particles on fine paper) is lower than in Examples 1-7, and in Comparative Example 2, the image is compared with Examples 1-7. Scratch resistance decreased. From this result, it can be said that the core resin preferably contains 5% by mass to 50% by mass of aliphatic polyester resin and 50% by mass to 95% by mass of aromatic polyester resin.

  In Comparative Examples 3 to 5, the fixing strength was lower than that in Examples 1 to 7. From this result, it can be said that the acid value of the core resin is preferably 20 mgKOH / g or more, the difference in acid value is preferably less than 15 mgKOH / g, and the toner particles preferably have a core / shell structure.

  In Examples 1, 4 and 6, the fixing strength was higher than that in Example 2. In Examples 1, 4 and 6, compared to Example 2, the blending amount (mass) of the aliphatic polyester resin relative to the sum of the blending amount (mass) of the aliphatic polyester resin and the blending amount (mass) of the aromatic polyester resin. ) Is high. Therefore, it is considered that such a result was obtained.

  In Examples 1, 4 and 6, the fixing strength was higher than in Examples 3 and 5. From this result, it can be said that the acid value of the core resin is more preferably 30 mgKOH / g or more.

  In Examples 1, 4, and 6, the fixing strength was higher than that in Example 7. From this result, it can be said that the shell resin further preferably contains 30% by mass or more of a structural unit derived from a monomer having a long-chain alkyl group.

  In Examples 2 to 7, compared to Example 1, the scratch resistance of the image was further improved. From this result, it can be said that the core resin further preferably contains 70% by mass or more of the aromatic polyester resin.

  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 Developing tank, 3 1st roller, 5 2nd roller, 21 Liquid developer, 22 Developing tank, 23 Anilox roller, 24 Anilox control blade, 25 Leveling roller, 26 Developing roller, 27 Developing cleaning blade, 28 Developing charger, DESCRIPTION OF SYMBOLS 29 Photoconductor, 30 Charging part, 31 Exposure part, 32 Cleaning blade, 33 Intermediate transfer body, 34 Intermediate transfer body cleaning part, 35 Secondary transfer roller, 37 Primary transfer part, 38 Secondary transfer part, 40 Recording medium.

Claims (2)

A liquid developer comprising an insulating liquid and toner particles dispersed in the insulating liquid,
The toner particles have a core / shell structure;
The core / shell structure includes core particles containing a core resin, and a shell resin that is provided on at least a part of the surface of the core particles and is a resin different from the core resin,
The core resin includes 5% by mass or more and 50% by mass or less aliphatic polyester resin, and 50% by mass or more and 95% by mass or less aromatic polyester resin,
The acid value of the core resin is 20 mgKOH / g or more and 100 mgKOH / g or less,
A liquid developer, wherein a difference between an acid value of the aliphatic polyester resin and an acid value of the aromatic polyester resin is 0 mgKOH / g or more and less than 15 mgKOH / g.   The liquid developer according to claim 1, wherein the shell resin contains 30% by mass or more and 90% by mass or less of a structural unit derived from a monomer having a long-chain alkyl group.

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