JP4583784B2 - Binder resin for toner - Google Patents

Description

  The present invention relates to a binder resin for toner used for developing a latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method, and the like, and an electrophotographic toner containing the binder resin.

  In recent years, there has been a demand for a binder resin for toner that can be fixed at a lower temperature in response to demands for higher speed and downsizing of the apparatus. As the binder resin for toner, vinyl resin and polyester resin are generally used, but polyester is preferred from the viewpoint of low-temperature fixability. It is known that the softening point and glass transition temperature of the resin may be lowered to improve the low-temperature fixability, but on the other hand, the offset resistance, blocking resistance, etc. are poor. Therefore, both performances are achieved by using a resin having a low softening point and a resin having a high softening point. However, when the same type of resin is used in combination, the resins are compatible with each other, making it difficult to achieve both of the above performances, and the glass transition temperature of the resin is at most about 50 ° C.

In order to improve this and use a resin having a lower softening point and a lower glass transition temperature, an incompatible resin is encapsulated (see Patent Document 1) to obtain a resin composition having a domain-matrix structure (Patent Document) 2), etc., but the glass transition temperature of the low glass transition temperature resin used is 15 ° C. at most, and if it is lower than that, the blocking resistance and the like are lowered, and further low temperature fixability and resistance Both blocking properties are desired.
JP-A-6-130713 (Claim 1) JP-A-6-342225 (Claim 1)

  An object of the present invention is to provide a binder resin for a toner excellent in both low-temperature fixability and blocking resistance, and a toner containing the binder resin.

  In the binder resin having a domain-matrix structure, when the resin having a low glass transition temperature is used as a domain, the cause of lowering physical properties such as blocking resistance is more than the average particle size of the domain. It was found that the particles are large domain particles exceeding 2 μm in the domain, and that the glass transition temperature is a more important factor than the softening point for low-temperature fixability, and the present invention has been completed.

  The present invention is a binder resin for toner comprising a condensation polymerization resin (resin a) that forms a continuous phase and an addition polymerization resin (resin b) that forms a dispersed phase, and has a diameter of 2 μm or less in the resin cross section. The dispersed phase contains 90% or more of the entire cross-sectional area of the dispersed phase, the binder resin for toner having a glass transition temperature of resin b of 10 ° C. or lower, and the binder resin for toner and the colorant. The present invention relates to an electrophotographic toner.

  The binder resin for toner of the present invention and the toner containing the binder resin have an effect of being excellent in both low-temperature fixability and blocking resistance.

  The binder resin for toner of the present invention comprises a condensation polymerization resin (hereinafter also referred to as resin a) that forms a continuous phase and an addition polymerization resin (hereinafter also referred to as resin b) that forms a dispersed phase. One characteristic is that the dispersed phase having a diameter of 2 μm or less in the cross section is 90% or more, preferably 95% or more of the entire cross-sectional area of the dispersed phase. Here, the diameter in the resin cross section represents the dispersed particle diameter of the dispersed phase observed in the cross section, and is obtained as an average value of the major axis and the minor axis of the particle. If the disperse phase exceeding 2 μm in diameter in the cross section of the resin exceeds 10% of the area ratio, a uniform binder resin cannot be obtained, and the blocking resistance decreases when used as a binder resin for toner. Here, the diameter of the dispersed phase and the area ratio of the dispersed phase were determined by cutting a resin having a diameter of about 0.2 mm into a thickness of 100 to 300 nm with a microtome, and then obtaining the obtained flakes by a transmission scanning electron microscope (for example, JEOL ( JEOL Co., Ltd., “JEM-2000”) and image analysis can be performed by a well-known method.

Furthermore, another feature of the present invention is the glass transition temperature of the resin b. That is, the glass transition temperature of the resin b is 10 ° C. or less, preferably 0 ° C. or less, more preferably −5 ° C. or less, still more preferably −10 ° C. or less. From the viewpoint of blocking resistance, It is 70 ° C. or higher, more preferably −50 ° C. or higher, and further preferably −25 ° C. or higher. Conventionally, in order to improve the blocking resistance, it is important that the glass point temperature of all the resins constituting the binder resin is not less than a certain value, not the whole binder resin, that is, the binder resin If even one of the constituent components has a component having a low glass transition temperature, it has been said that the fluidity is deteriorated due to melting of the component. However, in the binder resin of the present invention, as described above, the resin b having a low glass transition temperature exists as a dispersed phase that is extremely finely dispersed in the continuous phase. Therefore, reaggregation between resins having a low glass transition temperature is prevented, blocking resistance is maintained, and resin b having a low glass transition temperature finely dispersed at the time of fixing dissolves first. Melting is induced and excellent low temperature fixability is achieved. The glass transition temperature of the resin b can be adjusted by a known method in consideration of the raw material monomer species and the ratio thereof. For example, referring to “Polymer Handbook” (published by INTERSCIENCE), styrene, methyl methacrylate and the like as raw material monomers for increasing the glass transition temperature of the resin, butyl acrylate as raw material monomers for lowering the glass transition temperature of the resin, it can be used as appropriate acrylic acid 2-ethyl hexyl.

  The binder resin of the present invention comprising the resin a and the resin b is prepared by melt-kneading each resin in the presence of an initiator or the like, if necessary, dissolving and mixing each resin in a solvent. Although it may be produced by any method such as polymerization of a raw material monomer mixture, preferably, a polycondensation reaction and an addition polymerization reaction are performed using the raw material monomer of resin a and the raw material monomer of resin b. This is a resin obtained by performing the method (JP-A-7-98518).

  The resin a is preferably at least one selected from the group consisting of polyester, polyester-polyamide, and polyamide, and more preferably polyester.

  As a raw material monomer for polyester, an alcohol component composed of a divalent or higher alcohol and a carboxylic acid component composed of a divalent or higher carboxylic acid compound are used.

  Examples of the divalent alcohol include polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane and polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane. Formula (I):

(Wherein R is an alkylene group having 2 or 3 carbon atoms, x and y are positive numbers, and the sum of x and y is 1 to 16, preferably 1.5 to 5.0)
An aromatic diol such as an alkylene oxide adduct of bisphenol A represented by the formula: aliphatic diols such as ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, neopentyl glycol, polyethylene glycol, polypropylene glycol; hydrogen Additive bisphenol A etc. are mentioned.

  As the alcohol component, an alkylene oxide adduct of bisphenol A represented by the formula (I) is preferable. The content of the alkylene oxide adduct of bisphenol A is preferably 50 mol% or more, more preferably 80 mol% or more, and further preferably 100 mol% in the alcohol component.

  Examples of the trihydric or higher polyhydric alcohol include sorbitol, pentaerythritol, glycerin, trimethylolpropane and the like.

  Divalent carboxylic acid compounds include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, Aliphatic dicarboxylic acids such as succinic acid substituted by alkyl groups having 1 to 20 carbon atoms such as adipic acid, dodecenyl succinic acid, octyl succinic acid or the like, or alkenyl groups having 2 to 20 carbon atoms, preferably 8 to 16 carbon atoms; And anhydrides of these acids and alkyl (C 1 -C 3) esters of these acids.

  Among these, terephthalic acid, isophthalic acid, alkenyl succinic acid, adipic acid, fumaric acid and maleic acid are preferable. The total content of these suitable divalent dicarboxylic acid compounds is preferably 50 mol% or more, more preferably 80 mol% or more, and even more preferably 100 mol% in the divalent carboxylic acid compound.

  Examples of the trivalent or higher polyvalent carboxylic acid compound include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid and acid anhydrides thereof, and lower alkyl. (C1-C3) ester etc. are mentioned, Among these, trimellitic acid is preferable.

  The content of the trivalent or higher polyvalent carboxylic acid compound is preferably 5 to 30 mol% in the carboxylic acid component.

  Furthermore, from the viewpoint of molecular weight adjustment and the like, a monovalent alcohol or a monovalent carboxylic acid compound may be appropriately contained in the alcohol component and / or carboxylic acid component as long as the effects of the present invention are not impaired.

  Examples of the raw material monomer for forming an amide component in polyester-polyamide or polyamide include polyamines such as ethylenediamine, pentamethylenediamine, hexamethylenediamine, diethylenetriamine, iminobispropylamine, phenylenediamine, xylylenediamine, and triethylenetetramine. , Aminocarboxylic acids such as 6-aminocaproic acid and ε-caprolactam, and aminoalcohols such as propanolamine, among which hexamethylenediamine and ε-caprolactam are preferable.

  40-80 degreeC is preferable from a viewpoint of blocking resistance, and, as for the glass transition temperature of resin a, 50-65 degreeC is more preferable. The glass transition temperature of the resin can be easily adjusted by the raw material monomer species and the ratio thereof, the catalyst species, the reaction conditions, and the like.

  On the other hand, the resin b is preferably a vinyl resin obtained by radical polymerization reaction.

  Examples of the raw material monomer for the vinyl resin include styrene compounds such as styrene and α-methylstyrene; ethylenically unsaturated monoolefins such as ethylene and propylene; diolefins such as butadiene; halovinyls such as vinyl chloride; vinyl acetate; Vinyl esters such as vinyl propionate; alkyl (carbon number 1 to 18) esters of (meth) acrylic acid, esters of ethylenic monocarboxylic acids such as dimethylaminoethyl (meth) acrylate; vinyl ethers such as vinyl methyl ether Vinylidene halides such as vinylidene chloride; N-vinyl compounds such as N-vinylpyrrolidone and the like, and styrene, butyl acrylate, 2-ethylhexyl acrylate, and the like from the viewpoints of reactivity, grindability and charge stability; Methyl methacrylate is preferred, still And / or alkyl esters of (meth) acrylic acid, a raw material monomer in the vinyl resin, 50 wt% or more, and more preferably preferably is contained 80 to 100 wt%.

  In addition, when polymerizing the raw material monomer of the vinyl resin, a polymerization initiator, a crosslinking agent, or the like may be used as necessary.

  The weight ratio of the resin a to the resin b (resin a / resin b) in the binder resin of the present invention is preferably 50/50 to 95/5 from the viewpoint of achieving both low-temperature fixability and blocking resistance. -95/5 is more preferable, and 70 / 30-90 / 10 is more preferable.

  The weight ratio of the raw material monomer of the resin a to the raw material monomer of the resin b (the raw material monomer of the resin a / the raw material monomer of the resin b) is preferably 55/45 to 95/5 from the viewpoint of forming a continuous phase with the resin a. 60/40 to 95/5 are more preferable, and 70/30 to 90/10 are more preferable.

  The binder resin of the present invention preferably has, as a structural unit, a monomer that reacts with both the raw material monomer of resin a and the raw material monomer of resin b (hereinafter referred to as a bireactive monomer). Therefore, in the present invention, the condensation polymerization reaction and the addition polymerization reaction are preferably performed in the presence of both reactive monomers. As a result, the resin a and the resin b are partially bonded via the both reactive monomers, and a resin in which the resin b is more finely and uniformly dispersed in the resin a is obtained.

  Both reactive monomers have at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, an epoxy group, a primary amino group and a secondary amino group in the molecule, preferably a hydroxyl group and / or carboxyl. A monomer having a group, more preferably a carboxyl group and an ethylenically unsaturated bond is preferred. Specific examples of the both reactive monomers include, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid and the like, and these hydroxyalkyl (C1-3) esters may be used. In view of the above, acrylic acid, methacrylic acid and fumaric acid are preferable.

  In the present invention, among both reactive monomers, a monomer having two or more functional groups (polycarboxylic acid or the like) and a derivative thereof are used as a raw material monomer for the resin a, and a monomer having one functional group (monocarboxylic acid or the like) and The derivative is treated as a raw material monomer for the resin b. The amount of both reactive monomers used is 1 to 2 in the raw material monomer of the resin a for monomers having 2 or more functional groups and derivatives thereof, and 1 in the raw material monomer of the resin b for monomers having 1 functional group and derivatives thereof. 10 mol% is preferable and 4-8 mol% is more preferable.

  In the present invention, the condensation polymerization reaction and the addition polymerization reaction are preferably performed in the same reaction vessel. In addition, the progress and completion of each polymerization reaction do not need to be simultaneous in time, and the reaction temperature and time may be appropriately selected according to each reaction mechanism to advance and complete the reaction.

  Specifically, a step (A) of performing a condensation polymerization reaction in parallel with the addition polymerization reaction under a temperature condition suitable for the addition polymerization reaction, and a step of maintaining the reaction temperature under the above conditions to complete the addition polymerization reaction A method having (B) and a step (C) of further increasing the reaction temperature and further performing a polycondensation reaction is preferable.

  In the step (A), it is preferable that the mixture containing the raw material monomer of the resin a is dropped and reacted in the mixture containing the raw material monomer of the resin a.

  Here, although the temperature conditions suitable for the addition polymerization reaction depend on the type of the polymerization initiator used, a temperature range of 50 to 180 ° C. is preferable. Moreover, 190-270 degreeC is preferable as the temperature range at the time of raising reaction temperature and performing a polycondensation reaction further. In this way, a binder resin in which two types of resins are effectively mixed and dispersed can be obtained by a method in which two independent reactions proceed in parallel in a reaction vessel.

  The softening point of the binder resin for toner of the present invention is preferably from 80 to 160 ° C, more preferably from 90 to 150 ° C, from the viewpoints of fixability and blocking resistance. The softening point of the binder resin can be easily adjusted by adjusting the raw material monomer composition, the polymerization initiator, the catalyst amount, etc., or selecting the reaction conditions.

  Furthermore, the present invention provides an electrophotographic toner containing the toner binder resin and a colorant.

  In the toner of the present invention, a low softening point resin and a high softening point resin are preferably used in combination as a binder resin from the viewpoint of low-temperature fixability. The softening point of the low softening point resin is preferably 80 to 120 ° C., more preferably 85 to 110 ° C. from the viewpoint of low-temperature fixability, and the softening point of the high softening point resin is from the viewpoint of offset resistance. The temperature is preferably higher than 120 ° C and not higher than 160 ° C, more preferably 130 to 155 ° C. The difference in softening point between the low softening point resin and the high softening point resin is preferably 20 to 60 ° C, and more preferably 30 to 50 ° C.

  Therefore, it is preferable that a resin having a high softening point or a resin having a low softening point is further contained as a binder resin, depending on the softening point of the binder resin for toner of the present invention. Both are preferably the binder resins of the present invention. The content of the binder resin of the present invention is preferably 30 to 100% by weight, more preferably 50 to 100% by weight, and still more preferably 90 to 100% by weight in the total amount of the binder resin in the toner.

  In the toner of the present invention, the binder resin used in combination with the toner binder resin of the present invention is for conventional toners such as polyester, vinyl resin, epoxy resin, polycarbonate, polyurethane, and a hybrid resin composed of two or more resins. Any resin known as a binder resin may be used, but in the toner of the present invention, a hybrid resin composed of two or more kinds of resins is preferable.

  As the colorant, all of dyes and pigments used as toner colorants can be used, such as carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, rhodamine-B base, Solvent Red 49, Solvent Red 146, Solvent Blue 35, Quinacridone, Carmine 6B, Disazo Yellow and the like can be used alone or in combination of two or more. The toner of the present invention is a black toner, color Either toner or full color toner may be used. The content of the colorant is preferably 1 to 40 parts by weight and more preferably 3 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  The toner of the present invention further includes a release agent, a charge control agent, a magnetic powder, a conductivity modifier, an extender pigment, a reinforcing filler such as a fibrous substance, an antioxidant, an anti-aging agent, a fluidity improver, Additives such as a cleaning property improving agent may be appropriately contained.

  As the release agent, low molecular weight polypropylene, low molecular weight polyethylene, low molecular weight polypropylene polyethylene copolymer, aliphatic hydrocarbon waxes such as microcrystalline wax, paraffin wax, Fischer-Tropsch wax and their oxides, carnauba wax, Examples include ester waxes such as montan wax, sazol wax and their deoxidized wax, fatty acid amides, fatty acids, higher alcohols, fatty acid metal salts, etc. Among these, from the viewpoint of releasability and stability Therefore, an aliphatic hydrocarbon wax is preferable.

  The melting point of the release agent is preferably 60 to 120 ° C, more preferably 100 to 120 ° C, from the viewpoint of offset resistance and durability.

  The content of the release agent is preferably 0.5 to 10 parts by weight and more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the binder resin.

  Charge control agents include nigrosine dyes, triphenylmethane dyes containing tertiary amines as side chains, quaternary ammonium salt compounds, polyamine resins, imidazole derivatives and other positively chargeable charge control agents and metal-containing azo dyes, copper Examples include negatively chargeable charge control agents such as phthalocyanine dyes, metal complexes of alkyl derivatives of salicylic acid, and boron complexes of benzylic acid.

  The content of the charge control agent is preferably 0.1 to 5 parts by weight and more preferably 0.5 to 2 parts by weight with respect to 100 parts by weight of the binder resin.

Magnetic powder includes ferromagnetic materials such as cobalt, iron and nickel, alloys of metals such as cobalt, iron, nickel, aluminum, lead, magnesium, zinc and manganese, Fe ₃ O ₄ , γ-Fe ₃ O ₄ , cobalt Examples thereof include metal oxides such as added iron oxide, various ferrites such as Mn—Zn ferrite and Ni—Zn ferrite, magnetite and hematite. Furthermore, those surfaces may be treated with a surface treatment agent such as a silane coupling agent or a titanate silane coupling agent, or may be polymer-coated.

  The primary average particle diameter of the magnetic powder is preferably 0.05 to 0.5 μm, more preferably 0.1 to 0.3 μm from the viewpoint of dispersibility.

  In the case of a magnetic toner, the content of the magnetic powder is preferably 30% by weight or more, and more preferably 30 to 60% by weight in the toner. The magnetic powder may be contained as a black colorant.

The method for producing the toner may be any conventionally known method such as a kneading and pulverization method using the binder resin of the present invention as one of the raw materials, a phase inversion emulsification method, an emulsion dispersion method, and a suspension polymerization method. The kneading and pulverizing method is preferable because of easy production. For example, in the case of a pulverized toner by a kneading and pulverizing method, a binder resin, a colorant, and the like are uniformly mixed with a mixer such as a Henschel mixer, and then melt-kneaded with a hermetic kneader or a uniaxial or biaxial extruder. It can be produced by cooling, pulverization and classification. The weight average particle diameter (D ₄ ) of the toner is preferably 3 to 15 μm, and more preferably _{4 to 8} μm.

  The toner containing the binder resin obtained according to the present invention can be used for both one-component developing toner and two-component developing toner, but it is difficult to achieve low-temperature fixability. Is preferred.

[Softening point of binder resin]
Using a Koka type flow tester (manufactured by Shimadzu Corporation, CFT-500), a 1 g sample was heated at a heating rate of 6 ° C./min, a load of 1.96 MPa was applied by a plunger, a diameter of 1 mm, A nozzle with a length of 1 mm is pushed out, and this draws a plunger drop amount (flow value) -temperature curve of the flow tester. When the height of the S-shaped curve is h, the temperature corresponding to h / 2 (resin The temperature at which half of the effluent flowed out) is taken as the softening point.

[Glass transition temperature (Tg) of condensation polymerization resin (resin a) and addition polymerization resin (resin b)]
Using a differential scanning calorimeter (DSC210, manufactured by Seiko Denshi Kogyo Co., Ltd.), the sample was heated to 200 ° C. and cooled to 0 ° C. at a rate of temperature decrease of 10 ° C./min. The temperature at the intersection of the base line extension below the maximum peak temperature of the heat of fusion and the tangent that indicates the maximum slope from the peak rise to the peak apex is defined as the glass transition temperature. When there are two or more peaks of the glass transition temperature, the glass transition temperature calculated by the Fox method from the composition of the raw material monomers for the addition polymerization resin can be used as an aid in determining the peak assignment.

Resin production example 1 (resins A to R)
The raw material monomer and catalyst of the condensation polymerization resin shown in Tables 1 and 2 were put into a 5-liter four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple, and 160 ° C. in a nitrogen atmosphere. The mixture of the raw material monomer of the addition polymerization resin and the polymerization initiator shown in Tables 1 and 2 was added dropwise from the dropping funnel over 1 hour. After maintaining at 160 ° C. for 2 hours, the temperature was raised to 230 ° C. and a condensation polymerization reaction was performed until a desired softening point was reached, thereby obtaining resins A to R.

Resin Production Example 2 (Resin S)
(1) After reacting 140 g of styrene, 60 g of butadiene, 15 g of benzoyl peroxide and 500 g of toluene at 85 ° C. for 10 hours, 20 g of maleic acid was added. Further, after addition polymerization, a small amount of water was added to cause ring opening to obtain a resin S1 solution. Resin S1 had a softening point of 95 ° C. and a glass transition temperature of 32.1 ° C.

(2) Polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) 90 mol parts of propane, 10 mol parts of ethylene glycol, 75 mol parts of terephthalic acid and 20 mol parts of fumaric acid are condensed to form a resin. S2 was obtained. Resin S2 had a softening point of 121.3 ° C. and a glass transition temperature of 60.1 ° C.

(3) In a 2-liter four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple, 700 g of the resin S1 solution obtained in (1) and 470 g of resin S2 were mixed, and benzoyl 0.1 g of peroxide was added, and the temperature of the mixed solution was raised to 80 ° C. and reacted for 5 hours. Further, toluene was removed at 120 ° C. and 60 Torr over 5 hours to obtain Resin S. The obtained resin S had a softening point of 110.6 ° C. and a glass transition temperature of 40.5 ° C. The disperse phase having a diameter of 2 μm or less in the resin cross section was 62% of the entire cross-sectional area of the disperse phase.

Examples 1-8, Comparative Examples 1-5 (Example 4 is a reference example)
100 parts by weight of binder resin shown in Table 3, 66 parts by weight of magnetic powder “MTS106HD” (manufactured by Toda Kogyo Co., Ltd.), 0.5 part by weight of charge control agent “T-77” (manufactured by Hodogaya Chemical Co., Ltd.), polyethylene wax 1 part by weight of “C-80” (manufactured by Sasol, melting point: 82 ° C.) and 1 part by weight of polypropylene wax “NP-105” (manufactured by Mitsui Chemicals, melting point: 140 ° C.) are sufficiently mixed with a Henschel mixer, and then kneaded. Melting and kneading were performed using a co-rotating twin screw extruder having a total length of 1560 mm, a screw diameter of 42 mm, and a barrel inner diameter of 43 mm. The heating temperature in the roll was 140 ° C., the roll rotation speed was 150 rotations / minute, the mixture supply speed was 20 kg / hour, and the average residence time was about 18 seconds.
The obtained kneaded material was rolled with a cooling roll, mechanically pulverized, and classified to obtain a powder having a weight average particle diameter (D ₄ ) of 6 μm.

  To 100 parts by weight of the obtained powder, 2 parts by weight of hydrophobic silica “R-972” (manufactured by Nippon Aerosil Co., Ltd.) and strontium titanate “ST” (manufactured by Fuji Titanium, primary average particle size: 0) .97 μm) 1 part by weight was added and mixed with a Henschel mixer to obtain a magnetic toner.

Test example 1
250 g of magnetic toner was mounted on a magnetic one-component developing device “Laser Jet 4200” (manufactured by HP), and an unfixed image (2 cm × 12 cm) having a toner adhesion amount of 0.6 mg / cm ² was obtained.
The obtained unfixed image was converted to 100 using a fixing machine (fixing speed: 200 mm / sec) improved so that the fixing machine of the copying machine “AR-505” (manufactured by Sharp Corporation) can be fixed off-line. The fixing test was performed while gradually increasing from 10 ° C. to 240 ° C. in 10 ° C. steps. As the fixing paper, “CopyBond SF-70NA” (manufactured by Sharp Corporation, 75 g / m ² ) was used.

“UNICEF Cellophane” (Mitsubishi Pencil Co., Ltd., width: 18 mm, JISZ-1522) was attached to the image fixed at each temperature, passed through the fixing roll of the fixing machine set at 30 ° C., and then the tape was peeled off. The optical reflection density of the image after tape peeling was measured using a reflection densitometer “RD-915” (manufactured by Macbeth). The optical reflection density is also measured for the image before applying the tape in advance, and the temperature of the fixing roll whose ratio (after tape peeling / before tape application ) first exceeds 80% is set as the minimum fixing temperature. The low-temperature fixability was evaluated according to the evaluation criteria. The results are shown in Table 3.

〔Evaluation criteria〕
A: The minimum fixing temperature is less than 170.degree.
A: The minimum fixing temperature is 170 ° C. or higher and lower than 190 ° C.
○: The minimum fixing temperature is 190 ° C. or higher and lower than 210 ° C.
X: The minimum fixing temperature is 210 ° C. or higher and lower than 240 ° C.
XX: Minimum fixing temperature is 240 ° C. or higher.

Test example 2
After 4 g of the toner was allowed to stand for 1 week in an environment of a temperature of 50 ° C. and a humidity of 60%, the degree of aggregation was measured using a powder tester, and blocking resistance was evaluated according to the following evaluation criteria. The results are shown in Table 3.

〔Evaluation criteria〕
A: No aggregation is observed.
○: Aggregation is hardly observed.
X: Aggregation is recognized.

  From the above results, it can be seen that the toners of Examples 1 to 8 achieve both low-temperature fixability and anti-blocking properties. On the other hand, from Comparative Examples 1 to 5, the toner that does not contain a resin having a glass transition temperature of 10 ° C. or lower of the resin that forms the dispersed phase as the binder resin has either low-temperature fixability or blocking resistance. It turns out that it becomes insufficient.

  The binder resin for toner of the present invention is used as a binder resin for toner used for developing a latent image formed in electrophotography, electrostatic recording method, electrostatic printing method and the like.

Claims (5)

Presence of a monomer comprising a condensation polymerization resin (resin a) that forms a continuous phase and an addition polymerization resin (resin b) that forms a dispersed phase, and reacts with both the raw material monomer of resin a and the raw material monomer of resin b A binder resin for toner obtained by performing a condensation polymerization reaction and an addition polymerization reaction below, wherein the dispersed phase having a diameter of 2 μm or less in the resin cross section is 90% or more of the entire cross-sectional area of the dispersed phase, and the resin a The glass transition temperature of the resin is 50 to 65 ° C., the glass transition temperature of the resin b is −18.7 to 10 ° C., and the weight ratio of the resin a to the resin b is 50/50 to 95/5. Landing resin.   The binder resin for toner according to claim 1, wherein the resin a is polyester and the resin b is a vinyl resin. Using the raw material monomer of resin a and the raw material monomer of resin b in a weight ratio of the raw material monomer of resin a to the raw material monomer of resin b in the range of 55/45 to 95/5, a condensation polymerization reaction and an addition polymerization reaction are performed. The binder resin for toner according to claim 1 or 2 , obtained by An electrophotographic toner comprising the toner binder resin according to any one of claims 1 to 3 and a colorant. The binder resin contains a high softening point resin having a softening point difference of 20 to 60 ° C. and a low softening point resin, and at least one of the high softening point resin and the low softening point resin. The toner for electrophotography according to claim 4 , wherein is the binder resin for toner according to any one of claims 1 to 3 .