JP6446983B2 - Liquid developer - Google Patents

Description

  The present invention relates to a liquid developer.

  Japanese Unexamined Patent Publication No. 2013-3197 (Patent Document 1) discloses toner particles including a resin obtained by mixing an aliphatic polyester resin and an aromatic polyester resin. Japanese Unexamined Patent Application Publication No. 2009-96994 (Patent Document 2) discloses a urethane-modified polyester resin as one of resins constituting the toner particles (hereinafter also referred to as “toner resin”).

JP 2013-3197 A JP 2009-96994 A

  According to Patent Document 1, since the toner resin contains an aliphatic polyester resin, the plasticization (swelling) of the toner resin due to the intrusion of the insulating liquid (carrier liquid) into the toner resin is suppressed, whereby the document It is said that offset can be prevented. The reason for this is considered to be that molecular chains are likely to be regularly arranged in the aliphatic polyester resin and the crystallinity is easily developed.

  Crystalline aliphatic polyester resins have the property of softening and liquefying rapidly when their melting point is exceeded (so-called sharp melt properties). Sharp melt properties are indispensable for low-temperature fixing of toner resins, but on the other hand, such resins cannot maintain elasticity at high temperatures, resulting in weak high-temperature offset resistance and image changes with temperature changes. There was a problem that the luster of the material changed. For example, in the case of a toner resin made of an aliphatic polyester resin, it has been confirmed that when the temperature of the fixing roller is lowered due to continuous paper passing, the elasticity of the toner resin changes greatly, thereby changing the gloss of the image.

  Patent Document 2 discloses a urethane-modified aromatic polyester resin as one of toner resins. Here, the urethane-modified aromatic polyester resin means a resin obtained by chaining an aromatic polyester with an isocyanate chain. The present inventor applied the technology to an aliphatic polyester resin to synthesize a urethane-modified aliphatic polyester resin (that is, a resin obtained by chaining an aliphatic polyester resin with an isocyanate chain), and investigated the properties in detail. It has been found that the modified aliphatic polyester resin has sharp melt properties, can maintain elasticity even at high temperatures, and has a small change in gloss accompanying a change in temperature.

  At the same time, however, it has also been found that urethane-modified aliphatic polyester resins have problems in storage performance under high temperature and high humidity (hereinafter also referred to as “HH storage property”). That is, it became clear that the molecular weight of the urethane-modified aliphatic polyester resin decreases when stored under high temperature and high humidity.

  Further, it was confirmed that the deterioration of the HH storage property tends to become remarkable as the acid value of the toner resin increases. Currently, in a liquid developer, the provision of an acid value to a toner resin is indispensable for securing adhesive force with a medium (for example, paper) in a state where an insulating liquid remains. Therefore, when a urethane-modified aliphatic polyester resin is used as the toner resin, it can be said that there is a problem in achieving both fixing strength (adhesive strength) and HH storage properties.

  The present invention has been made in view of the above problems. Therefore, an object of the present invention is to provide a liquid developer that has a small change in gloss of an image accompanying a change in temperature, and that is excellent in fixing strength and storage stability at high temperature and high humidity.

  As a result of intensive studies to solve the above problems, the present inventors have stored urethane-modified aliphatic polyester resins under high temperature and high humidity (HH), resulting in hydrolysis of the urethane-bonded portion. We obtained the knowledge that the molecular weight was decreasing. The present inventor has not limited to this, and through further research, has found a configuration of a toner resin capable of suppressing hydrolysis of the urethane-modified aliphatic polyester resin, and has completed the present invention.

That is, the liquid developer of the present invention is
[1] A liquid developer in which toner particles are dispersed in an insulating liquid. The toner particles include a toner resin and a colorant. The toner resin includes a urethane-modified aliphatic polyester resin and an aromatic polyester resin. In the toner resin, the proportion of the urethane-modified aliphatic polyester resin in the total of the urethane-modified aliphatic polyester resin and the aromatic polyester resin is 5% by mass or more and 40% by mass or less. Further, the acid value of the toner resin is 5 mgKOH / g or more and 100 mgKOH / g or less.

  [2] The acid value of the toner resin is preferably 20 mgKOH / g or more and 100 mgKOH / g or less.

  [3] The acid value of the urethane-modified aliphatic polyester resin is preferably 2 mgKOH / g or less.

  [4] The toner particles include core particles containing the toner resin and shell particles, and have a core / shell structure in which the shell particles are adhered or coated on the surface of the core particles. May be.

  According to the above, there is provided a liquid developer that has a small change in gloss of an image accompanying a change in temperature, and that is excellent in fixing strength and high-temperature and high-humidity storage properties.

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

  Hereinafter, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail, but the present embodiment is not limited thereto.

<Liquid developer>
The liquid developer according to the exemplary embodiment is useful as a developer used in an electrophotographic image forming apparatus (for example, a copying machine, a printer, a digital printing machine, or a simple printing machine). Such a liquid developer may be called, for example, an electrophotographic liquid developer, a paint, a liquid developer for electrostatic recording, an oil-based ink for an ink jet printer, an ink for electronic paper, or the like.

  The liquid developer is obtained by dispersing toner particles in an insulating liquid (carrier liquid). In addition to these components, the liquid developer can contain any component as long as it contains these components. For example, the liquid developer may further contain a dispersant, a charge control agent, a thickener, and the like. In the liquid developer, the blending ratio of the toner particles and the insulating liquid can be, for example, about 10 to 50% by mass of toner particles and about 50 to 90% by mass of insulating liquid.

<Toner particles>
The toner particles include a toner resin and a colorant (pigment). In addition to these, the toner particles may contain, for example, a pigment dispersant, a wax, a charge control agent, and the like. The colorant is present in a dispersed state in the toner resin. The blending ratio of the toner resin and the colorant may be determined so that when the toner particles are used at a predetermined adhesion amount, the concentration that is developed becomes a desired concentration.

  The median diameter of the toner particles is preferably from 0.5 μm to 5.0 μm. When the median diameter of the toner particles is less than 0.5 μm, the particle diameter is excessively small, so that the mobility in the electric field may be deteriorated and developability may be deteriorated. This is because there is a case where the image quality is deteriorated due to a decrease in performance. Here, the “median diameter” indicates a particle diameter (so-called D50) at an integrated value of 50% in a volume-based particle size distribution. The median diameter range is smaller than the particle diameter of toner particles in the conventional dry developer, and shows one of the characteristics of the liquid developer. The median diameter of the toner particles is more preferably 1.0 μm or more and 2.0 μm or less.

  The arithmetic average value (average circularity) of the circularity of the toner particles is preferably from 0.85 to 0.95, and the standard deviation of the circularity is preferably from 0.01 to 0.1. This is because when the average value and standard deviation of the circularity occupy the above ranges, the transfer property and the cleaning property are improved. Here, the “circularity” indicates a value obtained by dividing the perimeter of a circle having the same area as the particle area projected in two dimensions by the perimeter of the particle.

  The median diameter, average circularity, and standard deviation of the circularity of the toner particles can be measured using a flow type particle image analyzer (for example, trade name “FPIA-3000S”, manufactured by Sysmex Corporation). In “FPIA-3000S”, the insulating liquid contained in the liquid developer can be used as it is as a dispersion medium at the time of measurement. Therefore, when this apparatus is used, a result reflecting the actual dispersion state can be obtained more than in the case where the measurement is performed by redispersing the toner particles in an aqueous solvent.

(Toner resin)
The toner resin includes a urethane-modified aliphatic polyester resin and an aromatic polyester resin. Here, “aliphatic polyester resin” refers to a polyester resin in which 90% or more of all structural units are occupied by structural units derived from aliphatic monomers, and “aromatic polyester resin” refers to 90% of all structural units. The polyester resin which the structural unit derived from an aromatic monomer accounts for the above is shown. The “urethane-modified aliphatic polyester resin” refers to a resin having a structure in which the main chain or terminal of the aliphatic polyester is chain-lengthed with a urethane bond.

  In general, aliphatic polyester resins tend to exhibit crystallinity because molecular chains are easily arranged regularly. On the other hand, in an aromatic polyester resin, irregular twisting or the like occurs in the molecular chain, and crystallization tends to be hindered. Therefore, the aromatic polyester resin tends to be amorphous.

  The urethane-modified aliphatic polyester resin is melted in a low-temperature region of 70 ° C. or lower because the aliphatic polyester resin as a constituent unit thereof shows crystallinity, and is chain-lengthed with isocyanate, whereby a high-temperature region of 100 ° C. or higher. But elasticity can be maintained. However, on the other hand, when urethane-modified aliphatic polyester resin is stored in an HH environment, the urethane bond portion is hydrolyzed and the molecular weight tends to decrease. In particular, when an acid value is imparted to the toner resin, hydrolysis tends to be promoted by the acid as a catalyst.

  In this embodiment, the toner resin is composed of a mixture of a urethane-modified aliphatic polyester resin and an aromatic polyester resin, thereby solving this problem. That is, by covering the urethane-modified aliphatic polyester resin with an aromatic polyester resin that is stable even in an HH environment, contact between water and the urethane-modified aliphatic polyester resin can be suppressed, and a decrease in molecular weight can be suppressed.

  Since the urethane-modified aliphatic polyester resin and the aromatic polyester resin have different molecular structures, they are hardly compatible with each other. Therefore, in the toner resin, by increasing the mass of the aromatic polyester resin more than the mass of the urethane-modified aliphatic polyester resin, it is as if the urethane-modified aliphatic polyester resin is in the “sea” made of the aromatic polyester resin. It is easy to have a “sea-island structure” interspersed as “,” and the contact between the urethane-modified aliphatic polyester resin and water can be efficiently suppressed.

  Specifically, the proportion of the urethane-modified aliphatic polyester resin in the total of the urethane-modified aliphatic polyester resin and the aromatic polyester resin is 5% by mass or more and 40% by mass or less. If the ratio is less than 5% by mass, the toner resin cannot be melted at a low temperature, and the low-temperature fixability may be impaired. Moreover, when the ratio exceeds 40 mass%, the hydrolysis of the urethane-modified aliphatic polyester resin may not be sufficiently suppressed. The ratio is more preferably 10% by mass to 35% by mass, and particularly preferably 15% by mass to 30% by mass.

  The acid value of the toner resin after mixing is 5 mgKOH / g or more and 100 mgKOH / g or less. This is because when the acid value is less than 5 mgKOH / g, sufficient fixing strength cannot be obtained, and when the acid value exceeds 100 mgKOH / g, the productivity decreases. The acid value of the toner resin is preferably as large as possible within the same range. The acid value of the toner resin is preferably 20 mgKOH / g or more, more preferably 30 mgKOH / g or more, and particularly preferably 40 mgKOH / g or more.

  At this time, the acid value of the urethane-modified aliphatic polyester resin is preferably 5 mgKOH / g or less. As described above, the urethane-modified aliphatic polyester resin is easily hydrolyzed in the presence of an acid. Therefore, hydrolysis can be more reliably suppressed by keeping the acid value of the urethane-modified aliphatic polyester resin low and allowing the aromatic polyester resin to bear the acid value selectively. The acid value of the urethane-modified aliphatic polyester resin is more preferably 2 mgKOH / g or less, further preferably 1 mgKOH / g or less, and most preferably 0 mgKOH / g.

  Here, the acid value of the resin is obtained by, for example, dissolving the resin (10 g) in a mixed solvent (100 ml) obtained by mixing toluene, acetone and methanol in toluene: acetone: methanol = 50: 25: 25 (mass ratio). It can be determined by titration with 0.1N potassium hydroxide ethanol solution using rain as an indicator.

  It is desirable that 90% by mass or more of the total amount of the toner resin is composed of a polyester resin (urethane-modified aliphatic polyester resin and aromatic polyester resin). This is because if the content of the resin other than the polyester resin exceeds 10% by mass, the regular arrangement of the urethane-modified aliphatic polyester resin may be inhibited. The toner resin may contain a resin other than the polyester resin as long as it is 10% by mass or less of the total amount. Examples of such resins include styrene-acrylic resins, urethane resins, and epoxy resins.

(Aliphatic polyester resin)
The aliphatic polyester resin is synthesized by a polycondensation reaction of a polyvalent carboxylic acid (acid component) and a polyhydric alcohol (alcohol component) in principle. Therefore, the aliphatic polyester resin is constituted by alternately repeating an acid component constituent unit derived from a polyvalent carboxylic acid and an alcohol component constituent unit derived from a polyhydric alcohol. In the aliphatic polyester resin, 90% or more of all the structural units are composed of an acid component structural unit derived from an aliphatic monomer and an alcohol component structural unit derived from an aliphatic monomer.

  Here, the content of each structural unit in the polyester resin is determined by performing 1H-NMR analysis using a Fourier transform nuclear magnetic resonance apparatus (FT-NMR) (trade name “Lambda400”, manufactured by JEOL Ltd.), Can be determined. As the measurement solvent, for example, a chloroform-d (deuterated chloroform) solvent may be used.

  Examples of the aliphatic monomer to be an acid component constituent unit include an aliphatic polyvalent carboxylic acid and a lower alkyl ester thereof or an acid anhydride thereof. More specifically, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelic acid, sebacic acid, 1,9-nonanedicarboxylic 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, 1,18-octadecanedicarboxylic acid, and These lower alkyl esters or acid anhydrides may be mentioned. Of these, adipic acid, sebacic acid, 1,10-decanedicarboxylic acid, and 1,12-dodecanedicarboxylic acid are preferable from the viewpoint of easily imparting crystallinity to the resin. The aliphatic monomer to be the acid component structural unit may be used alone or in combination of two or more.

  Aliphatic polyhydric alcohol etc. are mentioned as an aliphatic monomer which should become an alcohol component structural unit. More specifically, for example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octane Diol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecane Diol, 1,20-eicosanediol, etc. are mentioned. Among these, ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, and 1,10-decanediol are preferable from the viewpoint of easily imparting crystallinity to the aliphatic polyester resin. preferable. The aliphatic monomer to be the alcohol component constituent unit may be used alone or in combination of two or more.

(Urethane-modified aliphatic polyester resin)
The uretan-modified aliphatic polyester resin is a resin in which two or more aliphatic polyesters are bonded by a structural unit derived from a compound having an isocyanate group. The urethane-modified aliphatic polyester resin can exhibit crystallinity reflecting the crystallinity of the aliphatic polyester contained therein.

  The urethane-modified aliphatic polyester resin can be synthesized by first synthesizing an aliphatic polyester resin serving as a skeleton by a polycondensation reaction, and further lengthening the main chain or terminal of the aliphatic polyester resin with di (tri) isocyanate. Here, “di (tri) isocyanate” means at least one of diisocyanate and triisocyanate.

(Isocyanate)
As the isocyanate, a compound having a plurality of isocyanate groups in the molecule is suitable. Examples of such compounds include chain aliphatic polyvalent isocyanates and cyclic aliphatic polyvalent isocyanates.

  Specific examples of the chain aliphatic polyvalent isocyanate include, for example, ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 1,6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate. Lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis (2-isocyanatoethyl) fumarate, bis (2-isocyanatoethyl) carbonate, 2-isocyanatoethyl-2,6-diisocyanatohexano Eight etc. can be illustrated. These may be used alone or in combination of two or more.

  Specific examples of the cycloaliphatic polyisocyanate include isophorone diisocyanate (hereinafter abbreviated as “IPDI”), dicyclohexylmethane-4,4′-diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis (2-isocyanatoethyl). ) -4-cyclohexene-1,2-dicarboxylate, 2,5-norbornane diisocyanate, 2,6-norbornane diisocyanate and the like. These may be used alone or in combination of two or more.

(Urethane group concentration)
The urethane group concentration (% by mass) of the urethane-modified aliphatic polyester resin is preferably 0.5% or more and 5% or less, and more preferably 1% or more and 3% or less. This is because if the urethane group concentration is less than 0.5%, elasticity at a high temperature may not be maintained, and if it exceeds 5%, there may be a problem in document offset property. Here, the “urethane group concentration” means a value obtained by dividing the mass of the urethane group contained in the urethane-modified aliphatic polyester resin by the total mass of the resin, as a percentage. The urethane group concentration can be determined by pyrolysis-GCMS (Gas Chromatography Mass Spectrometer). The following conditions are adopted for the measurement of the urethane group concentration in the present specification.

(Conditions for pyrolysis equipment)
Thermal decomposition apparatus: “PY-2020iD” manufactured by Frontier Laboratories
Mass of measurement: 0.1 mg
Heating temperature: 550 ° C
Heating time: 0.5 minutes.

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

(Number average molecular weight)
The number average molecular weight (hereinafter referred to as “Mn”) of the urethane-modified aliphatic polyester resin is preferably 10,000 or more and 50,000 or less. When Mn is less than 10,000, the resin is excessively soft and tends to cause an offset during fixing, and when Mn exceeds 50000, the resin is difficult to melt and the fixing strength tends to decrease. . The Mn of the urethane-modified aliphatic polyester resin is more preferably from 10,000 to 30,000.

  Here, Mn and weight average molecular weight (hereinafter referred to as “Mw”) of resins (excluding polyurethane resin) in this specification are gel permeation chromatography with respect to the soluble content of tetrahydrofuran (hereinafter abbreviated as “THF”). (GPC: Gel Permeation Chromatography) was measured under the following conditions (the Mn and Mw of the urethane-modified aliphatic polyester resin were also measured by this method).

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

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

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

  The urethane group concentration and Mn described above are equivalent ratios of [acid group amount of polyvalent carboxylic acid and hydroxyl group amount of polyhydric alcohol, for example, when synthesizing an aliphatic polyester resin ([acid group amount] / [hydroxyl group amount]). In addition, by adjusting an equivalent ratio ([isocyanate group amount] / [hydroxyl group amount]) of the isocyanate group amount of the compound having an isocyanate group and the hydroxyl group amount of the aliphatic polyester resin when urethane-modified, a desired range is obtained. Can be controlled.

(Aromatic polyester resin)
In the aromatic polyester resin, 90% or more of all the structural units are composed of an acid component structural unit derived from an aromatic monomer and an alcohol component structural unit derived from an aromatic monomer.

  Specific examples of the aromatic monomer to be an acid component constituent unit include, for example, terephthalic acid, isophthalic acid, orthophthalic acid, t-butylisophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, A trimellitic acid etc. can be illustrated. Among these, terephthalic acid, isophthalic acid, t-butylisophthalic acid and the like are preferable in view of availability.

  As an aromatic monomer which should become an alcohol component structural unit, for example, an alkylene oxide adduct of bisphenol A represented by the following chemical formula (I) can be exemplified.

In the above chemical formula (I), R ¹ and R ² each independently represent an alkylene group, and m and n each independently represent 0 or a positive integer, but the sum (m + n) of both is 1 to 16 is there.

  The Mn of the aromatic polyester resin is preferably from 1,000 to 10,000, and the Mw is preferably from 2,000 to 100,000. Mn and Mw of the aromatic polyester resin can be measured using GPC as described above.

(Crystalline and amorphous)
As described above, it is desirable that the urethane-modified aliphatic polyester resin is a crystalline resin and the aromatic polyester resin is an amorphous resin. In this specification, when the heat of fusion (H) of the DSC of the resin satisfies the following formulas (1) and (2), it is defined as a crystalline resin. 5 ≦ H1 ≦ 100 (1)
0.2 ≦ H2 / H1 ≦ 1.0 (2)
In the above formulas (1) to (2), H1 represents the heat of fusion (J / g) at the first temperature rise by DSC, and H2 represents the heat of fusion (J / g) at the second temperature rise by DSC. .

  H1 is an index of the melting rate of the resin. In general, a resin having heat of fusion exhibits a sharp melt property and can be melted with a small amount of energy. When the H1 of the resin exceeds 100, it is difficult to reduce the energy required for fixing, and the fixing property of toner particles is lowered. On the other hand, if the H1 of the resin is less than 5, the energy required for fixing is excessively reduced, and document offset is likely to occur. However, if the resin H1 satisfies the above formula (1), the occurrence of document offset can be prevented, and the fixing property can be prevented from being lowered. H1 is preferably 15 ≦ H1 ≦ 80, and more preferably 35 ≦ H1 ≦ 70.

  H2 / H1 in the above formula (2) is an index of the crystallization speed of the 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 problem occurs, the performance of the resin particles obtained by cooling may differ from the originally designed performance. From these circumstances, 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 resin crystallization speed is high, H2 / H1 approaches 1.0, and 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 DSC. Therefore, even when the actual measurement value (H2 / H1) by DSC exceeds 1.0, the above equation (2) is satisfied.

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

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

  Here, in order to synthesize the urethane-modified aliphatic polyester resin as a crystalline resin, for example, it is considered to use an aliphatic monomer having a linear alkyl skeleton having 4 or more carbon atoms. From the viewpoint of low-temperature fixability, the melting point of the urethane-modified aliphatic polyester resin is preferably adjusted to 40 ° C. or higher and 80 ° C. or lower.

<Method for producing toner particles>
The toner particles can be produced based on a conventionally known technique such as a granulation method or a pulverization method. Here, the pulverization method is a method in which a resin and a colorant such as a pigment are previously melt-kneaded and pulverized. Such pulverization can be performed in a dry state or a wet state (in an insulating liquid).

  Granulation methods include suspension polymerization method, emulsion polymerization method, fine particle aggregation method, method of adding a poor solvent to a resin solution for precipitation, spray drying method, and two different types of resins due to the difference in toner particle formation mechanism. Thus, the toner particles can be classified into a method having a core / shell structure, which will be described later.

  In the present embodiment, the method for producing toner particles is not particularly limited. However, in order to obtain toner particles having a small diameter and a sharp particle size distribution, the granulation method is preferable to the pulverization method. This is because a resin having a high melting property or a resin having a high crystallinity is soft and hardly pulverized even at room temperature. According to the granulation method, even such a resin is easily controlled to a desired particle size.

  In the granulation method, the resin is dissolved in a good solvent to form a core resin solution, and the core resin solution is mixed with a poor solvent having an SP value different from that of the good solvent together with an interfacial tension modifier to further give shear. There is also a method of forming core resin fine particles by forming droplets and finally evaporating a good solvent. In this method, the particle size and shape of the toner particles can be controlled to a high degree by adjusting the shearing method, the interfacial tension difference, or the interfacial tension adjusting agent (shell particles described later).

<Core / shell structure>
The toner particles may have a core / shell structure in which shell particles are attached or coated on the surface of the core particles containing the toner resin described above. By covering the surface of the core particles with shell particles, the hydrolysis of the urethane-modified aliphatic polyester resin can be further reliably suppressed.

(Shell particles and shell resin)
The shell particles are so-called polymer dispersants that have an action of adhering to the surface of the core particles and improving the dispersibility thereof. The shell particles are composed of a shell resin. The shell resin may be a thermoplastic resin or a thermosetting resin. Examples of resins that can be shell resins include vinyl resins, polyester resins, polyurethane resins, epoxy resins, polyamide resins, polyimide resins, silicon resins, phenol resins, melamine resins, urea resins, aniline resins, ionomer resins, and polycarbonate resins. can do.

  In consideration of circumstances such as easy control of the shape of the toner particles during production, vinyl resin, polyester resin, polyurethane resin and epoxy resin are preferably used for the shell resin, and vinyl resin is most preferably used. Shell resin may be comprised from 1 type of resin among these resins, and may be comprised from 2 or more types of resin. Hereinafter, a vinyl resin which is a preferred example of the shell resin will be described in detail.

(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 The hydrocarbon having a polymerizable double bond is, for example, an aliphatic hydrocarbon having a polymerizable double bond represented by the following (1-1), or the following (1-2): Aromatic hydrocarbons having a polymerizable double bond represented by

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

(1-1-1) Chain hydrocarbon having a polymerizable double bond As the chain hydrocarbon having a polymerizable double bond, for example, an alkene having 2 to 30 carbon atoms (for example, ethylene, propylene, butene, Isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.); alkadiene having 4 to 30 carbon atoms (for example, butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, etc.) ) And the like.

(1-1-2) Cyclic hydrocarbon having a polymerizable double bond Examples of the cyclic hydrocarbon having a polymerizable double bond include mono- or dicycloalkenes having 6 to 30 carbon atoms (for example, cyclohexene, vinylcyclohexene). Or ethylidenebicycloheptene); mono- or dicycloalkadiene having 5 to 30 carbon atoms (for example, monocyclopentadiene or dicyclopentadiene).

(1-2) Aromatic hydrocarbon having a polymerizable double bond As the aromatic hydrocarbon having a polymerizable double bond, for example, styrene; hydrocarbyl of styrene (for example, alkyl having 1 to 30 carbon atoms, Cycloalkyl, aralkyl, alkenyl) substituted products (for example, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, crotylbenzene, divinyl Benzene, divinyltoluene, divinylxylene, trivinylbenzene and the like); vinylnaphthalene and the like.

(2) Monomers having a carboxyl group and a polymerizable double bond and salts thereof Examples of the monomer having a carboxyl group and a polymerizable double bond include unsaturated monocarboxylic acids having 3 to 15 carbon atoms [for example, (meta ) Acrylic acid, crotonic acid, isocrotonic acid, cinnamic acid, etc.]; unsaturated dicarboxylic acid having 3 to 30 carbon atoms (anhydride) [for example, (anhydrous) maleic acid, fumaric acid, itaconic acid, (anhydrous) citraconic acid Or mesaconic acid, etc.]; monoalkyl (C1-10) ester of unsaturated dicarboxylic acid having 3 to 10 carbon atoms (for example, maleic acid monomethyl ester, maleic acid monodecyl ester, fumaric acid monoethyl ester, itacon) Acid monobutyl ester or citraconic acid monodecyl ester) and the like. In this specification, “(meth) acryl” means at least one of acryl and methacryl.

  Examples of the salt of the monomer include alkali metal salts (for example, sodium salt or potassium salt), alkaline earth metal salts (for example, calcium salt or magnesium salt), ammonium salts, amine salts, and quaternary ammonium salts. Etc.

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

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

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

(3) Monomers having sulfo group and polymerizable double bond and salts thereof (4) Monomers having phosphono group and polymerizable double bond and salts thereof (5) Monomers having hydroxyl group and polymerizable double bond Specific examples of (3) to (5) are not listed, but they can be used as monomers of vinyl resins in the same manner as the others.

(6) Nitrogen-containing monomer having a polymerizable double bond Examples of the nitrogen-containing monomer having a polymerizable double bond include monomers shown in the following (6-1) to (6-4).

(6-1) Monomer having an amino group and a polymerizable double bond Examples of the monomer having an amino group and a polymerizable double bond include aminoethyl (meth) acrylate, 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-dimethylamino Styrene, methyl-α-acetaminoacrylate, vinylimidazole, N-vinylpyrrole, N-vinylthiopyrrolidone, N-arylphenylenediamine, aminocarbazole, aminothiazole, aminoindole, aminopyrrole, amino Imidazole and amino mercaptothiazole and the like.

  Here, the monomer having an amino group and a polymerizable double bond may be a salt of the above-listed monomers. 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 Examples of the monomer having an amide group and a polymerizable double bond include (meth) acrylamide, N-methyl (meth) acrylamide, 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, N-vinylpyrrolidone, etc. are mentioned.

(6-3) Monomer having 3 to 10 carbon atoms having a nitrile group and a polymerizable double bond As a monomer having 3 to 10 carbon atoms having a nitrile group and a polymerizable double bond, for example, (meth) acrylonitrile , Cyanostyrene and cyanoacrylate.

(6-4) Monomers having 8 to 12 carbon atoms having a nitro group and a polymerizable double bond Examples of monomers having 8 to 12 carbon atoms having a nitro group and a polymerizable double bond include nitrostyrene and the like. Can be mentioned.

(7) Monomer having 6 to 18 carbon atoms having an epoxy group and a polymerizable double bond (8) Monomer having 2 to 16 carbon atoms having a halogen element and a polymerizable double bond (7) and (8) Although no specific example is enumerated, it can be used as a monomer of a vinyl resin as in the other cases.

(9) Ester having 4 to 16 carbon atoms having a polymerizable double bond Examples of the ester having 4 to 16 carbon atoms having a polymerizable double bond include vinyl acetate, vinyl propionate, vinyl butyrate, and 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; (E.g., methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate or 2-ethylhexyl (meth) Acrylate, etc.]; dialkyl fumarate (two alkyl groups are straight-chain alkyl groups, branched alkyl groups or alicyclic alkyl groups having 2 to 8 carbon atoms); dialkyl maleates (two The alkyl group is a linear alkyl group having 2 to 8 carbon atoms, a branched alkyl group or an alicyclic alkyl group); poly (meth) allyloxyalkanes (eg, diaryloxyethane, triaryloxy) Ethane, 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 Ruethylene oxide (hereinafter “ethylene oxide” is abbreviated as “EO”) 10 mol adduct (meth) acrylate or lauryl alcohol EO 30 mol adduct (meth) acrylate etc.]; poly (meth) acrylates {for example, polyvalent Poly (meth) acrylates of 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 etc.]} and the like. In this specification, “(meth) alillo” means at least one of alilo and metallo.

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

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

  Examples of the monomer (m) having a polymerizable double bond having a molecular chain (k) include the following monomers (m1) to (m3). As the monomer (m), two or more of the monomers (m1) to (m3) may be used in combination.

  The monomer (m1) is a monomer having a straight hydrocarbon chain having 12 to 27 carbon atoms (preferably 16 to 25) and a polymerizable double bond. For example, mono-linear alkyl (alkyl having 12 to 27 carbon atoms) of unsaturated monocarboxylic acid and mono-linear alkyl (alkyl having 12 to 27 carbon atoms) of unsaturated dicarboxylic acid are monomers ( It corresponds to m1). Examples of the unsaturated monocarboxylic acid and unsaturated dicarboxylic acid include (meth) acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid and the like, a carboxyl group-containing vinyl monomer having 3 to 24 carbon atoms, etc. Is mentioned. Specific examples of the monomer (m1) include, for example, dodecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate and (meth) Examples include eicosyl acrylate.

  The monomer (m2) is a monomer having a branched hydrocarbon chain having 12 to 27 (preferably 16 to 25) carbon atoms and a polymerizable double bond. For example, a branched alkyl of an unsaturated monocarboxylic acid (alkyl having 12 to 27 carbon atoms) ester or an unsaturated dicarboxylic acid of a monobranched alkyl (alkyl having 12 to 27 carbon atoms) is used as the monomer (m2). Equivalent to. As unsaturated monocarboxylic acid and unsaturated dicarboxylic acid, the thing similar to what was enumerated as a specific example of unsaturated monocarboxylic acid and unsaturated dicarboxylic acid in a monomer (m1) is mentioned, for example. Specific examples of the monomer (m2) include, for example, 2-decyltetradecyl (meth) acrylate.

  The monomer (m3) is a monomer having a fluoroalkyl chain having 4 to 20 carbon atoms and a polymerizable double bond. Specific examples of the monomer (m3) include, for example, those obtained by substituting a hydrocarbon chain with a fluoroalkyl chain in the specific examples of the monomers (m1) and (m2).

(Melting point of shell resin)
The melting point of the shell resin is preferably 0 to 220 ° C, more preferably 30 to 200 ° C, and further preferably 40 to 80 ° C. Considering the particle size distribution and shape of the toner particles and the powder flowability, heat-resistant storage stability, and stress resistance of the liquid developer, the melting point of the shell resin should be equal to or higher than the temperature at which the liquid developer is produced. Is preferred. If the melting point of the shell resin is lower than the temperature at which the liquid developer is produced, it becomes difficult to control the coalescence or splitting of the toner particles during production, and it is also difficult to narrow the distribution width in the particle size distribution of the toner particles. This is because there is a possibility that the variation in the particle diameter of the toner particles may increase.

  Here, in this specification, the melting point of the resin was measured by a method based on “ASTM D3418-82” using a differential scanning calorimeter (“DSC20” or “SSC / 580” manufactured by Seiko Instruments Inc.). Value shall be indicated.

(Mn of shell resin)
The Mn of the shell resin (value measured by GPC described above) is preferably 100 to 5000000, more preferably 200 to 5000000, and particularly preferably 500 to 500000.

(SP value of shell resin)
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 .

(Method for producing shell particles)
The method for producing the shell particles is not particularly limited, and may be produced by any conventionally known method. For example, shell particles can be produced by the following methods [1] to [7]. [1] Shell resin is pulverized dry using a known dry pulverizer such as a jet mill. [2] Shell Disperse the resin powder in an organic solvent and pulverize it wet using a known wet disperser such as a bead mill or roll mill. [3] Spray and dry the shell resin solution using a spray dryer or the like. [4] Addition or cooling of a poor solvent to the shell resin solution causes the shell resin to supersaturate and precipitate. [5] Disperse the shell resin solution in water or an organic solvent. [6] Shell resin precursor. Polymerize by emulsion polymerization method, soap-free emulsion polymerization method, seed polymerization method or suspension polymerization method in water. [7] The shell resin precursor is polymerized by dispersion polymerization in an organic solvent. Of these, the methods [4], [6] and [7] are preferable, and the methods [6] and [7] are more preferable.

(Median diameter of shell particles)
The volume average particle diameter (median diameter) of the shell particles may be appropriately adjusted so that the particle diameter of the toner particles falls within a desired range. The median diameter of the shell particles is preferably 0.0005 to 3 μm. The upper limit of the median diameter of the shell particles is more preferably 2 μm, and even more preferably 1 μm. The lower limit of the median diameter of the shell particles is more preferably 0.01 μm, still more preferably 0.02 μm, and most preferably 0.04 μm. For example, when it is desired to obtain toner particles having a median diameter of 1 μm, the median diameter of the shell particles is preferably 0.0005 to 0.3 μm, more preferably 0.001 to 0.2 μm. For example, when it is desired to obtain toner particles having a median diameter of 10 μm, the median diameter of the shell particles is preferably 0.005 to 3 μm, more preferably 0.05 to 2 μm.

<Colorant>
The colorant is dispersed in at least one of urethane-modified aliphatic polyester resin and aromatic polyester resin. When the toner particles have a core / shell structure, the colorant is dispersed in at least one of the core particles and the shell particles. The particle size of the colorant is preferably 0.3 μm or less. When the particle size of the colorant exceeds 0.3 μm, the dispersibility is deteriorated, the glossiness is lowered, and a desired color may not be realized.

  Conventionally known pigments and the like can be used as the colorant without any particular limitation. However, for example, the following pigments are preferably used from the viewpoints of cost, light resistance, colorability and the like. In terms of color composition, these pigments are usually classified as black pigments, yellow pigments, magenta pigments, and cyan pigments. Basically, colors other than black (color images) are subtractive color mixtures of yellow pigments, magenta pigments, and cyan pigments. Is toned. Hereinafter, specific examples will be listed and explained for each pigment. These pigments can be used alone or in combination of two or more as required.

  Examples of the black pigment include carbon black such as furnace black, channel black, acetylene black, thermal black, and lamp black, carbon black derived from biomass, and magnetic powder such as magnetite and ferrite. Further, nigrosine, which is an azine compound which is a violet black dye, can be used alone or in combination with furnace black or the like. Nigrosine is exemplified by C.I. I. Solvent Black 7 or C.I. I. Selected from Solvent Black 5, etc.

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

  Examples of yellow pigments include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185.

  Examples of cyan pigments include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment blue 62, C.I. I. Pigment blue 66, C.I. I. And CI Pigment Green 7.

(Pigment dispersant)
The pigment dispersant has a function of uniformly dispersing the colorant in the toner particles, and it is preferable to use a basic dispersant. Here, “basic dispersant” refers to the one defined below. That is, a pigment dispersant (0.5 g) and distilled water (20 ml) are placed in a glass screw tube, further shaken for 30 minutes using a paint shaker, and then filtered to obtain a pH of the filtrate. Measured using a meter (trade name “D-51”, manufactured by HORIBA, Ltd.), and when the pH is higher than 7, the basic dispersant is used (if the pH is lower than 7, the so-called acidic dispersant) And).

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

  As a commercial item of a basic dispersant, for example, “Ajisper PB-821” (trade name), “Ajisper PB-822” (trade name), “Ajisper PB-881” (trade name) manufactured by Ajinomoto Fine Techno Co., Ltd., "Solspurs 28000" (trade name), "Solspurs 32000" (trade name), "Solspurs 32500" (trade name), "Solspurs 35100" (trade name), "Solspurs 37500" (trade name) manufactured by Nippon Lubrizol Etc.

  It is more preferable to select a pigment dispersant that does not dissolve in the insulating liquid (carrier liquid). For that reason, “Ajisper PB-821” (trade name), “Ajisper PB-822” (trade name), and “Ajisper PB-881” (trade name) manufactured by Ajinomoto Fine Techno Co. are more preferred. Although the detailed mechanism is unknown, when such a pigment dispersant is used, the shape of the toner particles tends to be easily controlled. A pigment dispersant may be used individually by 1 type, or may use 2 or more types together.

  The 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). When the addition amount is less than 1% by mass, the dispersibility of the colorant may be insufficient, and not only the necessary ID (image density) cannot be achieved but also the fixing strength may be lowered. If the added amount exceeds 100% by mass, more dispersant than necessary is added to the pigment, and the excess dispersant is dissolved in the insulating liquid, so that the chargeability and fixing of the toner particles are fixed. It may adversely affect strength.

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

  Hereinafter, although this embodiment is described further in detail using an example, this embodiment is not limited to these.

<Manufacture of liquid developer>
Various liquid developers were produced as follows, and the change in gloss with HH storage stability, fixing strength, and temperature was evaluated. In the following, “Mn”, “Mw” and “acid value” of the resin were measured according to the above-mentioned methods.

(Production Example 1) Synthesis of alkylene oxide adduct of bisphenol A Bisphenol A (228 parts by mass) and potassium hydroxide (2 parts by mass) are placed in an autoclave equipped with stirring and temperature control, and the temperature is increased to 135 ° C. After raising the temperature, propylene oxide (139 parts by mass) was introduced under a pressure condition of 0.1 to 0.4 MPa, and then allowed to react for 3 hours. The reaction product thus obtained was charged with an adsorbent (product name “KYOWARD 600”, manufactured by Kyowa Chemical Industry Co., Ltd.) (16 parts by mass) and stirred and aged for 30 minutes while maintaining at 90 ° C. . Thereafter, filtration was performed to obtain a propylene oxide adduct of bisphenol A. This propylene oxide adduct was a mixture of those in which the sum (m + n) of m and n in chemical formula (I) is 2 and 3.

(Production Example 2) Production of Aliphatic Polyester Resin (Resin D) In a four-necked flask equipped with a stirring rod, partial condenser, nitrogen gas inlet tube and thermometer, an aliphatic monomer to be a constituent unit of alcohol component ( 1,6-hexanediol) and an aliphatic monomer (adipic acid) to be an acid component constituent unit were added at a molar ratio of 1: 1, and a predetermined amount of acetone was further added. Nitrogen gas was introduced into the flask while stirring the mixture, and polycondensation was performed for 5 hours while maintaining the temperature at about 170 ° C.

  After the temperature was lowered to about 100 ° C., polycondensation was stopped by adding hydroquinone (0.012 parts by mass) as a polymerization inhibitor. Thus, a resin solution D in which the resin D, which is an aliphatic polyester resin, was dissolved was obtained.

Production Example 3 Production of Urethane Modified Aliphatic Polyester Resin (Resin A) IPDI (63 parts by mass) was added to a resin solution D (1000 parts by mass) and reacted at 80 ° C. for 6 hours. Thus, when the NCO value became 0 (zero), a resin A which was a urethane-modified aliphatic polyester resin was obtained. Next, resin A (800 parts by mass) and acetone (1200 parts by mass) were placed in a beaker and stirred to uniformly dissolve resin A in acetone. Thus, a resin solution A was obtained. Resin A had Mn of 25000, Mw of 45000, and acid value of 0 mgKOH / g.

Production Example 4 Production of Urethane Modified Aliphatic Polyester Resin (Resin B) A predetermined amount of phthalic anhydride was added to the resin solution A and reacted at 180 ° C. for 1 hour. Thereby, resin B which is a urethane-modified aliphatic polyester resin was obtained. Next, resin B (800 parts by mass) and acetone (1200 parts by mass) were placed in a beaker and stirred to uniformly dissolve resin B in acetone. Thus, a resin solution B was obtained. Resin B had Mn of 25000, Mw of 45000, and an acid value of 2 mgKOH / g.

Production Example 5 Production of Urethane Modified Aliphatic Polyester Resin (Resin C) A predetermined amount of phthalic anhydride was added to the resin solution A and reacted at 180 ° C. for 1 hour. As a result, a resin C which is a urethane-modified aliphatic polyester resin was obtained. Next, resin C (800 parts by mass) and acetone (1200 parts by mass) were placed in a beaker and stirred to uniformly dissolve resin C in acetone. Thus, a resin solution C was obtained. Resin C had Mn of 20000, Mw of 40000, and an acid value of 4 mgKOH / g.

(Production Example 6) Production of aromatic polyester resin (resin a) In a four-necked flask equipped with a stirring rod, partial condenser, nitrogen gas inlet tube and thermometer, an aromatic monomer (to be a constituent unit of alcohol component) A propylene oxide adduct of bisphenol A obtained in Production Example 1) and an aromatic monomer (isophthalic acid) to be an acid component constituent unit are added in a molar ratio of 1: 1, and a predetermined amount of acetone is further added. Was added. Nitrogen gas was introduced into the flask while stirring the mixture, and polycondensation was performed for 5 hours while maintaining the temperature at about 170 ° C. In this way, a solution of resin a which is an aromatic polyester resin (resin solution a) was obtained. Resin a had an Mn of 3500 and an acid value of 4 mgKOH / g.

(Production Example 7) Production of aromatic polyester resin (resin b) In a four-necked flask equipped with a stirring rod, a partial condenser, a nitrogen gas inlet tube and a thermometer, an aromatic monomer (to be a constituent unit of alcohol component) A propylene oxide adduct of bisphenol A obtained in Production Example 1) and an aromatic monomer (isophthalic acid) to be an acid component constituent unit are added in a molar ratio of 1: 1, and a predetermined amount of acetone is further added. Was added. Nitrogen gas was introduced into the flask while stirring the mixture, and polycondensation was performed for 5 hours while maintaining the temperature at about 170 ° C. In this way, a solution of resin b (resin solution b), which is an aromatic polyester resin, was obtained. Resin b had an Mn of 3000 and an acid value of 7 mgKOH / g.

(Production Example 8) Production of aromatic polyester resin (resin c) In a four-necked flask equipped with a stirring rod, a partial condenser, a nitrogen gas inlet tube and a thermometer, an aromatic monomer (to be a constituent unit of alcohol component) A propylene oxide adduct of bisphenol A obtained in Production Example 1 and an aromatic monomer (isophthalic acid and trimellitic acid) to be an acid component constituent unit, a propylene oxide adduct of bisphenol A: isophthalic acid: tri Mellitic acid was added at 1: 0.95: 0.05 (molar ratio), and a predetermined amount of acetone was further added. Nitrogen gas was introduced into the flask while stirring the mixture, and polycondensation was performed for 5 hours while maintaining the temperature at about 170 ° C. Thus, a solution of resin c (resin solution c), which is an aromatic polyester resin, was obtained. Resin c had an Mn of 2700 and an acid value of 25 mgKOH / g.

(Production Example 9) Production of Aromatic Polyester Resin (Resin d) In a four-necked flask equipped with a stirring rod, a partial condenser, a nitrogen gas inlet tube and a thermometer, an aromatic monomer (to be a constituent unit of alcohol component) A propylene oxide adduct of bisphenol A obtained in Production Example 1 and an aromatic monomer (isophthalic acid and trimellitic acid) to be an acid component constituent unit, a propylene oxide adduct of bisphenol A: isophthalic acid: tri Mellitic acid was added at 1: 0.95: 0.05 (molar ratio), and a predetermined amount of acetone was further added. Nitrogen gas was introduced into the flask while stirring the mixture, and polycondensation was performed for 5 hours while maintaining the temperature at about 170 ° C. Thus, a solution (resin solution d) of resin d which is an aromatic polyester resin was obtained. Resin d had Mn of 2400 and an acid value of 40 mgKOH / g. The structure of each resin obtained above is shown in Table 1.

Production Example 10 Production of Colorant Dispersion Solution In a beaker, copper phthalocyanine (trade name “FASTOGEN Blue FDB-14”, manufactured by DIC Corporation) (20 parts by mass) and a colorant dispersant (trade name “Azisper PB-821”). “Ajinomoto Fine Techno Co., Ltd.) (5 parts by mass) and acetone (75 parts by mass) were added and stirred and dispersed uniformly. Further, a colorant dispersion was obtained by finely dispersing copper phthalocyanine using a bead mill. In this colorant dispersion, the volume average particle diameter of the colorant (copper phthalocyanine) was 0.2 μm.

(Production Example 11) Production of shell resin In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a cooling tube and a nitrogen introduction tube, dodecanedicarboxylic acid (286 parts by mass) and 1,6-hexanediol (190 Part by weight) and titanium dihydroxybis (triethanolaminate) (1 part by weight) as a condensation catalyst, and the reaction is performed for 8 hours under a nitrogen stream at 180 ° C. while distilling off the water produced. It was. Then, it was made to react over 4 hours under nitrogen stream, distilling off the water to produce | generate, heating up gradually to 220 degreeC. Thereafter, a polyester resin was obtained by further reacting under reduced pressure of 0.007 to 0.026 MPa for 1 hour. When the melting point of this polyester resin was measured in accordance with the provisions of “ASTM D3418-82”, the melting point was 68 ° C. Moreover, Mn of this polyester resin was 4900 and Mw was 10,000.

  In a glass beaker, 2-decyltetradecyl methacrylate (80 parts by mass), methyl methacrylate (10 parts by mass), methacrylic acid (10 parts by mass), diethyl acrylamide (0.1 parts by mass), An equimolar reaction product (10 parts by mass) of an isocyanate group-containing monomer (trade name “Karenz MOI”, manufactured by Showa Denko KK) and the polyester resin obtained above, and azobismethoxydimethylvaleronitrile (0.11 parts by mass) ) And stirred and mixed at 20 ° C. to obtain a monomer solution.

  THF (195 parts by mass) was placed in 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, and the monomer solution obtained above was placed in the dropping funnel. After replacing the gas phase part of the reaction vessel with nitrogen, the monomer solution was dropped into THF at 70 ° C. for 1 hour in a sealed state. Three hours after the completion of the dropping of the monomer solution, a mixture of azobismethoxydimethylvaleronitrile (0.05 parts by mass) and THF (5 parts by mass) was added to THF and reacted at 70 ° C. for 3 hours. . The reaction was then cooled to room temperature. A copolymer solution was thus obtained.

  The copolymer solution (400 parts by mass) obtained above was dropped into an insulating liquid (trade name “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.) (600 parts by mass) under stirring, and 40 ° C., 0.039 MPa. The THF was distilled off under reduced pressure. A shell resin dispersion was thus obtained. The Mw of the shell resin contained in this dispersion was 100,000.

Example 1
Resin solution A (5 parts by mass) and resin solution d (95 parts by mass) were mixed to obtain a core resin solution. Into a beaker, the core resin solution (40 parts by mass) and the colorant dispersion (20 parts by mass) are added, and stirred at 8000 rpm using a TK auto homomixer (manufactured by Primix) at 25 ° C., and uniformly dispersed. It was.

  Into another beaker, the insulating liquid (trade name “IP Solvent 2028”, manufactured by Idemitsu Kosan Co., Ltd.) (67 parts by mass) and the dispersion (11 parts by mass) of the shell resin obtained above are introduced and uniformly dispersed. I let you. Next, while stirring this dispersion at 10000 rpm using a TK auto homomixer, the core resin solution (60 parts by mass) in which the colorant was dispersed was added and stirred for 2 minutes to obtain a mixed solution. Further, this mixed solution was put into a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, and a solvent removal device, heated to 35 ° C. and maintained at the same temperature under a reduced pressure of 0.039 MPa. Acetone was distilled off until the concentration was 0.5% by mass or less. Thus, a liquid developer according to Example 1 was obtained. In this liquid developer, the toner particles have a core / shell structure in which shell particles composed of a shell resin are attached to or coated on the surfaces of core particles composed of a mixture of a resin A and a resin d (toner resin). I had it.

(Examples 2 to 7 and Comparative Examples 1 to 4)
As shown in Table 2, various liquid developers were obtained in the same manner as in Example 1 except that the combination of various resins was changed.

<Evaluation of liquid developer>
The liquid developer was evaluated as follows.

(Evaluation of toner particles)
The median diameter of toner particles contained in the liquid developer was measured using FPIA-3000S (manufactured by Sysmex Corporation). The results are shown in Table 2. The pretreatment of the measurement sample was performed according to the following procedure. In the measurement, the same IP solvent 2028 as the carrier liquid was used as the flow solvent. First, a sample (50 mg) was collected and charged into IP solvent 2028 (20 g) to which S13940 (manufactured by Nippon Lubrizol) (30 mg) was added as a dispersant. Further, the suspension was subjected to a dispersion treatment for about 5 minutes with an ultrasonic disperser “Ultrasonic Cleaner Model VS-150” (manufactured by Wellbo Clear) to obtain a measurement sample.

(Evaluation of HH storage properties)
Each liquid developer (50 ml) was placed in a screw bottle and stored for one week in an HH environment at 50 ° C. and 85% humidity with the lid open. Mn was measured before and after storage, and the value of Mnb / Mna was calculated from Mn before storage (referred to as Mna) and Mn after storage (referred to as Mnb), and evaluated according to the following three levels. The results are shown in Table 2. A: 0.95 ≦ Mnb / Mna ≦ 1.00
B: 0.90 ≦ Mnb / Mna <0.95
C: Mnb / Mna <0.9
Here, the larger the value of “Mnb / Mna”, the better the HH storage property.

(Image forming device)
Actually, an image was formed from a liquid developer, and the change in gloss with a change in fixing strength and temperature was evaluated. First, the configuration and operation of the image forming apparatus used for the evaluation will be described. FIG. 1 is a schematic conceptual diagram illustrating an example of the configuration of the image forming apparatus 100. Referring to FIG. 1, liquid developer 6 is placed in developing tank 5. The liquid developer 6 is pumped up by the anilox roller 22 and sent to the leveling roller 21. Excess liquid developer 6 on the surface of the anilox roller 22 is scraped off by the anilox regulating blade 23 before reaching the leveling roller 21 so that the liquid developer has a uniform layer thickness on the surface of the leveling roller 21. Adjusted. Thereafter, the liquid developer is transferred from the leveling roller 21 to the developer carrier 24.

  The photosensitive member 1 is charged by the charging unit 14, and a latent image is formed on the photosensitive member 1 in the exposure unit 15. The toner particles contained in the liquid developer are charged by the development charger 26. The charged toner particles are transferred from the developer carrying member 24 to the photosensitive member 1 corresponding to the latent image on the photosensitive member 1, and development is performed. At this time, the liquid developer that has not transferred to the photoreceptor 1 is collected by the cleaning blade 25 installed downstream of the developing unit.

  The liquid developer developed on the photosensitive member 1 is electrostatically transferred to the intermediate transfer member 16 by the primary transfer unit 13. The liquid developer remaining on the photosensitive member 1 without being transferred to the intermediate transfer member 16 is collected by the cleaning blade 12 of the image carrier cleaning unit.

  The liquid developer 6 carried on the intermediate transfer member 16 is electrostatically secondary transferred onto the medium 40 (for example, paper) in the secondary transfer unit 11. A direction A in FIG. 1 indicates a conveyance direction of the medium 40. The liquid developer transferred to the medium 40 is fixed by a heat roller fixing device (not shown). Thus, the printed image is completed. The liquid developer remaining on the intermediate transfer member 16 without being transferred to the medium 40 is collected by the cleaning blade 19 of the intermediate transfer member cleaning unit. The photoreceptor 1 repeats the cycle of charging, exposure, and development again, and the printing operation is continued.

In this evaluation, the toner particles were charged to a positive polarity by the development charger 26. The potential of the intermediate transfer member 16 was −400V, and the potential of the transfer roller 30 was −1200V. The conveyance speed was 400 mm / s, and “OK Top Coat (128 g / m ² )” manufactured by Oji Paper Co., Ltd. was used as the medium 40 (paper).

(Measurement of fixing strength)
Using the image forming apparatus described above, an unfixed image (10 cm × 10 cm solid pattern) having a toner adhesion amount of 3 mg / m ² is created from each liquid developer, and a heat roller fixing device (heat roller temperature 100 ° C.) , NIP time 30 msec). At this time, the paper temperature during NIP was about 80 ° C.

The fixing strength of the solid part in the fixed image was evaluated by a tape peeling test. That is, after applying a tape (“Scotch Mending Tape” manufactured by 3M) to the fixed image, the tape is peeled off, and the image density (ID) of the image peeled off the tape is measured by a reflection densitometer (trade name “ X-Rite model 404 "(manufactured by X-Rite), and evaluated according to the following three levels. The results are shown in Table 2. A: Image density (ID) less than 0.1 B: Image density (ID) 0.1 or more and less than 0.15 C: Image density (ID) 0.15 or more Here, the peeled image The smaller the image density (numerical value), the higher the fixing strength.

(Measure gloss change with temperature change)
An unfixed image was prepared in the same manner as described above, and a fixed image fixed at a heat roller temperature of 90 ° C. and a fixed image fixed at a heat roller temperature of 110 ° C. were prepared. Next, the glossiness of each fixed image was measured with a 75 ° glossmeter (trade name “VG-2000”, manufactured by Nippon Denshoku Industries Co., Ltd.), and the gloss when the heat roller temperature was 90 ° C. was G90. The glossiness at a temperature of 110 ° C. was defined as G110, and | G110−G90 | was calculated and evaluated according to the following three levels. The results are shown in Table 2. A: | G110-G90 | ≦ 10
B: 10 <| G110-G90 | ≦ 15
C: 15 <| G110-G90 |
Here, it is shown that the smaller the value of | G110−G90 |, the smaller the change in gloss associated with the temperature change.

<Results and discussion>
From Tables 1 and 2, the toner resin contains a urethane-modified aliphatic polyester resin and an aromatic polyester resin, and the urethane-modified aliphatic polyester resin accounts for the total of the urethane-modified aliphatic polyester resin and the aromatic polyester resin. The liquid developer according to the example in which the ratio is 5% by mass or more and 40% by mass or less and the acid value (“total acid value” in Table 2) of the toner resin is 5 mgKOH / g or more and 100 mgKOH / g or less It can be seen that, in comparison with the liquid developer according to the comparative example that does not satisfy the conditions, excellent characteristics are exhibited in any of the evaluation items.

  Further, from Table 2, it can be said that the larger the acid value (total acid value) of the toner resin is, the more preferable in consideration of the fixing strength. Further, considering the HH storage property, it can be said that the smaller the acid value of the urethane-modified aliphatic polyester resin, the better.

  As mentioned above, although embodiment and the Example of this invention were described, it is also scheduled from the beginning to combine suitably the structure of above-described embodiment and each Example. The embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Photoconductor, 5 Developer tank, 6 Liquid developer, 11 Secondary transfer part, 12, 19, 25 Cleaning blade, 13 Primary transfer part, 14 Charging part, 15 Exposure part, 16 Intermediate transfer body, 21 Leveling roller, 22 Anilox roller, 23 Anilox regulating blade, 24 Developer carrier, 26 Developer charger, 30 Transfer roller, 40 Media, 100 Image forming apparatus, A direction.

Claims (5)

A liquid developer in which toner particles are dispersed in an insulating liquid,
The toner particles include a toner resin and a colorant,
The toner resin includes a urethane-modified aliphatic polyester resin and an aromatic polyester resin,
Of the total of the urethane-modified aliphatic polyester resin and the aromatic polyester resin, the proportion of the urethane-modified aliphatic polyester resin is 5% by mass or more and 40% by mass or less,
The acid value of the toner resin is 5 mgKOH / g or more and 100 mgKOH / g or less,
The urethane-modified aliphatic polyester resin is a resin in which two or more aliphatic polyesters are bonded by a structural unit derived from a compound having an isocyanate group,
The compound having an isocyanate group has a plurality of isocyanate groups in the molecule,
At least a part of the urethane-modified aliphatic polyester resin is covered with the aromatic polyester resin ;
The toner particles include core particles containing the toner resin and shell particles,
A liquid developer having a core / shell structure in which the shell particles are attached or coated on the surface of the core particles . A liquid developer in which toner particles are dispersed in an insulating liquid,
The toner particles include a toner resin and a colorant,
The toner resin includes a urethane-modified aliphatic polyester resin and an aromatic polyester resin,
Of the total of the urethane-modified aliphatic polyester resin and the aromatic polyester resin, the proportion of the urethane-modified aliphatic polyester resin is 5% by mass or more and 40% by mass or less,
The acid value of the toner resin is 5 mgKOH / g or more and 100 mgKOH / g or less,
The urethane-modified aliphatic polyester resin is a resin in which two or more aliphatic polyesters are bonded by a structural unit derived from a compound having an isocyanate group,
The compound having an isocyanate group has a plurality of isocyanate groups in the molecule,
A liquid developer , wherein a sea-island structure in which the urethane-modified aliphatic polyester resin is dispersed like islands is formed in the sea made of the aromatic polyester resin . The toner particles include core particles containing the toner resin and shell particles,
The liquid developer according to claim 2 , wherein the liquid developer has a core / shell structure in which the shell particles are attached to or coated on the surface of the core particles. 4. The liquid developer according to claim 1, wherein an acid value of the toner resin is 20 mgKOH / g or more and 100 mgKOH / g or less. The liquid developer according to any one of claims 1 to 4, wherein the urethane-modified aliphatic polyester resin has an acid value of 2 mgKOH / g or less.

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