JP2007163681A - Binder resin for electrophotographic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a binder resin for an electrophotographic toner which exhibits satisfactory low temperature fixability and offset resistance even when used for an image forming apparatus equipped with a fixing machine of low press force at the time of fixing, and also is excellent in durability as well, an electrophotographic toner containing the binder resin, and also to provide an image forming method using the electrophotographic toner. <P>SOLUTION: There are provided: the binder resin for the electrophotographic toner in which the softening point (Tm<SB>1.96</SB>) measured under conditions of 1.96 MPa in the load by a flow tester is 110 to 130°C and the methyl ethyl ketone insoluble component is (Tm<SB>1,96</SB>-100)/2wt.% or more; the electrophotographic toner containing the binder resin; and the image forming method having a process of fixing the electrophotographic toner by using the toner for the image forming apparatus having the fixing machine of ≤600 N in the press force at the time of fixing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a binder resin for an electrophotographic 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, The present invention also relates to an image forming method using the electrophotographic toner.

  2. Description of the Related Art In recent years, toner image forming apparatuses have been strictly pursued for reduction in size and weight, speed, reliability, on-demand, and further energy saving.

  Therefore, in place of a conventionally used heat roll type fixing device, a fixing device of a belt nip type (see Patent Document 1) that can increase the thermal efficiency because the nip width of the fixing nip portion can be widened. An image forming apparatus has been reported.

On the other hand, as an attempt for a toner, a toner containing a polyester obtained by using an ethylene oxide adduct of bisphenol A is disclosed as a toner excellent in offset resistance (see Patent Documents 2 to 4).
JP-A-9-34291 JP 2005-49766 A JP 2001-265063 A Japanese Patent Laid-Open No. 2002-6555

  The belt nip type fixing machine has a smaller pressure applied to the toner at the time of fixing than the heat roll fixing type fixing machine, and it is difficult to maintain the low temperature fixing property (fixing strength). In addition, when the softening point of the binder resin is lowered in order to improve the low temperature fixability, the offset resistance is deteriorated. On the other hand, when the softening point of the binder resin is raised in order to improve the offset resistance, a high molecular weight component is obtained. Increases the low temperature fixability. Furthermore, it is extremely difficult to design a toner in consideration of durability in addition to compatibility between low-temperature fixability and offset resistance.

  An object of the present invention is to provide an electrophotographic apparatus that exhibits good low-temperature fixability and offset resistance and is excellent in durability even when used in an image forming apparatus equipped with a fixing machine having a low pressure during fixing. An object of the present invention is to provide a binder resin for toner, an electrophotographic toner containing the binder resin, and an image forming method using the electrophotographic toner.

The present invention
(1) For an electrophotographic toner having a softening point (Tm _1.96 ) of 110 to 130 ° C. and a methyl ethyl ketone insoluble content (Tm _1.96 -100) / 2% by weight or more measured with a flow tester under a load of _1.96 MPa. Binder resin,
(2) An electrophotographic toner comprising the binder resin described in (1) above, and (3) a fixing machine in which the applied pressure at the time of fixing the electrophotographic toner described in (2) is 600 N or less. The present invention relates to an image forming method including a step of fixing toner using an image forming apparatus having the above.

  The binder resin for electrophotographic toner of the present invention and the toner for electrophotography containing the binder resin are excellent in low temperature even when used in an image forming apparatus equipped with a fixing machine having a low pressure during fixing. It exhibits the effect of exhibiting fixing properties and offset resistance, as well as excellent durability.

  The binder resin for an electrophotographic toner of the present invention is characterized by a softening point and a methylethylketone insoluble matter.

That is, the binder resin of the present invention has a softening point (Tm _1.96 ) of 110 to 130 ° C., preferably 112 to 128 ° C., more preferably 115 to 125, as measured by a flow tester under a load of _1.96 MPa. ° C. The binder resin of the present invention further has an insoluble content of methyl ethyl ketone of (Tm _1.96-100 ) / 2% by weight or more, preferably (Tm _1.96-100 ) / 2% by weight to (Tm _1.96-30 ) / It is 2% by weight, more preferably (Tm _1.96 -90) / 2% by weight to (Tm _1.96 -40) / 2% by weight. Here, the methyl ethyl ketone insoluble matter means the proportion of the high molecular weight component contained in the binder resin. From the viewpoint of securing offset resistance, particularly a non-offset region, it is desirable that the binder resin has a high viscosity even after melting. Therefore, the inclusion of a high molecular weight component is important for improving the offset resistance. The amount of the high molecular weight component can be easily measured as an insoluble content in a solvent, but a component having an extremely high molecular weight has a low cooperation with other resin components and does not lead to an increase in the melt viscosity of the entire resin. Therefore, as a result of examining the relationship between the amount of insoluble matter in various solvents and the improvement in offset resistance, the present inventors have found that the proportion of methyl ethyl ketone insoluble matter is an index of the amount of high molecular weight components effective in improving offset resistance. found. However, on the other hand, the high molecular weight component adversely affects the low-temperature fixability. Therefore, as a result of further examination of the relationship between the softening point and the high molecular weight component and the effect thereof on low-temperature fixability and offset resistance, the present inventors have found that when the softening point and methyl ethyl ketone insolubles satisfy the above conditions simultaneously, It was found that both low-temperature fixability and offset resistance were achieved, and the durability was further improved.

Furthermore, the binder resin of the present invention has a softening point (Tm _1.96 ) measured under a load of _1.96 MPa with a flow tester and a softening point (Tm _0.49 ) measured under a load of 0.49 MPa with a flow tester. The ratio (Tm _0.49 / Tm _1.96 ) is preferably 1.10 to 1.30, more preferably 1.14 to 1.23. Since Tm _0.49 / Tm _1.96 is related to the pressure dependency at the time of fixing of the binder resin, the resin within such a range can further improve the low-temperature fixability at low-pressure fixing.

The softening point (Tm _1.96 and Tm _0.49 ) and methyl ethyl ketone insolubles in the binder resin of the present invention can be adjusted by the type of raw material monomer and the degree of polymerization of the resin. For example, in a hybrid resin containing a polyester or polyester component described later, the use of an ethylene oxide adduct of bisphenol A as an alcohol component is effective for lowering the softening point at the same molecular weight.

  The type of the binder resin of the present invention is not particularly limited, but from the viewpoint of low-temperature fixability, a polyester obtained by polycondensation of an alcohol component and a carboxylic acid component, and a polyester raw material containing the alcohol component and a carboxylic acid component A resin (hereinafter referred to as a hybrid resin) obtained using a monomer and a raw material monomer of an addition polymerization resin is preferable.

（式中、ＲＯはアルキレンオキサイドであり、Ｒは炭素数2又は3のアルキレン基、ｘ及びｙはアルキレンオキサイドの平均付加モル数を示す正の数であり、ｘとｙの和は1〜16、好ましくは1.5〜5である）
で表されるビスフェノールＡのアルキレンオキサイド付加物が好ましい。かかるビスフェノールＡのアルキレンオキサイド付加物の含有量は、アルコール成分中、40モル％以上が好ましく、60モル％以上がより好ましく、80モル％以上がさらに好ましい。 As the alcohol component of the polyester, from the viewpoint of storage stability of the toner, the formula (I):

(In the formula, RO is an alkylene oxide, R is an alkylene group having 2 or 3 carbon atoms, x and y are positive numbers indicating the average added mole number of alkylene oxide, and the sum of x and y is 1 to 16) (Preferably 1.5 to 5)
An alkylene oxide adduct of bisphenol A represented by The content of the alkylene oxide adduct of bisphenol A is preferably 40 mol% or more, more preferably 60 mol% or more, and still more preferably 80 mol% or more in the alcohol component.

  Examples of propylene oxide adducts of bisphenol A represented by the formula (I) include polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane and other ethylene oxide adducts having 2 carbon atoms such as R, Polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane and the like include propylene oxide adducts having 3 carbon atoms such as R. Among these, the softening point and the methyl ethyl ketone insoluble matter balance From the viewpoint of the above, an ethylene oxide adduct of bisphenol A is preferable. The ethylene oxide adduct of bisphenol A is an alcohol that is preferably used in the present invention because the molecular weight can be increased without increasing the softening point, that is, the methyl ethyl ketone insoluble matter can be increased. The content of the bisphenol A ethylene oxide adduct is preferably 60 mol% or more, more preferably 70 mol% or more, further preferably 80 mol% or more, further preferably 90 mol% or more in the alcohol component.

  As alcohol components other than the alkylene oxide adduct of bisphenol A, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, neopentyl glycol, polyethylene glycol, polypropylene glycol, bisphenol A, hydrogenated bisphenol A, sorbitol , Pentaerythritol, glycerol, trimethylolpropane and the like.

  Examples of the carboxylic acid component include dicarboxylic acids such as fumaric acid, maleic acid, phthalic acid, isophthalic acid, terephthalic acid, and succinic acid, n-dodecenyl succinic acid, isododecenyl succinic acid, n-dodecyl succinic acid, Succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms such as isooctenyl succinic acid and isooctyl succinic acid, 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2 , 5,7-naphthalenetricarboxylic acid, pyromellitic acid, anhydrides and lower alkyl (carbon number 1 to 3) esters of these acids, and the like. Such acids, anhydrides of these acids, and alkyl esters of these acids are collectively referred to herein as carboxylic acid compounds.

  Furthermore, the alcohol component and / or the carboxylic acid component may appropriately contain a monovalent alcohol and a monovalent carboxylic acid compound from the viewpoint of adjusting the molecular weight.

  The polyester or hybrid resin is a hybrid resin containing a cross-linked polyester or cross-linked polyester component obtained using a trivalent or higher monomer as an alcohol component and / or carboxylic acid component from the viewpoint of adjusting the softening point and methyl ethyl ketone insoluble matter. It is preferable that The content of the trivalent or higher monomer is preferably 2 to 20 mol%, more preferably 4 to 18 mol% in the total amount of the alcohol component and the carboxylic acid component. As the trivalent or higher monomer, 1,2,4-benzenetricarboxylic acid (trimellitic acid) and its anhydride are preferable.

  A polyester can be obtained by polycondensing an alcohol component and a carboxylic acid component at a temperature of 180 to 250 ° C., for example, in an inert gas atmosphere, if necessary, using an esterification catalyst.

  On the other hand, the hybrid resin is a mixture of, for example, a polyester raw material monomer and an addition polymerization resin raw material monomer, and preferably a mixture of both reactive compounds capable of reacting with both the polyester raw material monomer and the addition polymerization resin raw material monomer. It can be obtained by performing a condensation polymerization reaction and an addition polymerization reaction in parallel.

  Examples of the raw material monomer for polyester include the same alcohol component and carboxylic acid component as those of the polyester.

  Representative examples of addition polymerization resins include vinyl resins 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 (1-18) 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. The alkyl ester of styrene and / or (meth) acrylic acid is 50% by weight or more, preferably 80 to 100% by weight. % Content is desirable.

  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.

  In the hybrid resin in the present invention, the weight ratio of the raw material monomer of the polyester to the raw material monomer of the addition polymerization resin is preferably 50/50 to 95/5 because the continuous phase is preferably polyester, 60/40 to 95/5 is more preferable.

  The bi-reactive compound capable of reacting with both the polyester raw material monomer and the addition polymerization resin raw material monomer comprises a hydroxyl group, a carboxyl group, an epoxy group, a primary amino group, and a secondary amino group in the molecule. A compound having at least one functional group selected from the group and an ethylenically unsaturated bond is preferred, and by using such a reactive compound, the dispersibility of the resin serving as the dispersed phase is further improved. be able to. Specific examples of the both reactive compounds include acrylic acid, fumaric acid, methacrylic acid, citraconic acid, maleic acid, 2-hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, and the like. Of these, acrylic acid, methacrylic acid and fumaric acid are preferred.

  The amount of the both reactive compounds used is preferably 0.1 to 10 mol%, more preferably 1 to 8 mol% in the carboxylic acid component. In addition, the usage-amount of both reactive compounds is also contained in the carboxylic acid component here.

  From the viewpoint of dispersibility of the release agent in the toner, the hybrid resin is preferably produced by performing a condensation polymerization reaction and an addition polymerization reaction in the presence of the release agent. Examples of mold release agents include synthetic waxes such as polypropylene wax, polyethylene wax, and Fischer-Tropsch wax, petroleum waxes such as paraffin wax, coal-based waxes such as montan wax, alcohol-based waxes, and the like. Is preferred.

  The melting point of the release agent is preferably from 70 to 120 ° C., more preferably from 85 to 115 ° C., more preferably from 90 to 120 ° C., from the viewpoints of improvement in low-temperature fixability and non-offset region, particularly enlargement on the high temperature side and improvement in image density at the time of printing. 110 ° C. is more preferable. In the present invention, the compatibility of the release agent with respect to the resin is improved by combining the release agent having a low melting point with the hybrid resin. Furthermore, by adding a release agent together with the raw material monomer to the reaction vessel during the production of the hybrid resin and polymerizing the raw material monomer, it is possible to achieve high dispersion of a low melting point wax which is generally considered difficult.

  The compounding amount of the release agent is 100% by weight of the total amount of the polyester raw material monomer and the addition polymerization resin raw material monomer from the viewpoint of improving the low-temperature fixability and non-offset region, in particular, expanding the high temperature side and improving the image density at the time of printing. 1 to 15 parts by weight is preferred, 2 to 10 parts by weight is more preferred, and 3 to 9 parts by weight is even more preferred.

  In the production of hybrid resins, it is not necessary for the progress and completion of the condensation polymerization reaction and the addition polymerization reaction to be simultaneous in time. The reaction temperature and time are appropriately selected according to each reaction mechanism, and the reaction proceeds and is completed. You can do it.

  For example, in the method for producing a hybrid resin in the present invention, a raw material monomer for polyester, a raw material monomer for addition polymerization resin, an amphoteric compound, a release agent and the like are mixed, and first, mainly by radical polymerization reaction at 50 to 180 ° C. It is preferable to obtain an addition polymerization resin component having a functional group capable of polycondensation reaction, then raise the reaction temperature to 190 to 270 ° C., and then form a polyester component mainly by polycondensation reaction.

  The binder resin of the present invention may be a resin (hybrid resin) obtained by using polyester or a raw material monomer of polyester and a raw material monomer of an addition polymerization resin, or both may be used in combination.

  Furthermore, a toner containing the binder resin of the present invention is provided. The toner may contain a binder resin other than the binder resin of the present invention, but the content of the binder resin of the present invention is preferably 20% by weight or more in the total binder resin, and 30% by weight. % Or more is more preferable, 30 to 80% by weight is further preferable, and 40 to 60% by weight is further preferable.

  As the binder resin other than the binder resin of the present invention, a binder resin having a softening point of 80 to 100 ° C. measured by a flow tester under a load of 1.96 MPa from the viewpoint of low-temperature fixability of the toner is preferable. A binder resin of 82 to 98 ° C. is more preferable.

  Examples of the binder resin other than the binder resin of the present invention include known resins used for toners, for example, polyesters other than the polyester of the present invention, styrene-acrylic resins, epoxy resins, polycarbonates, polyurethanes, etc. From the viewpoint of compatibility with the binder resin of the invention, polyester is preferred.

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

  As the colorant, all of the dyes and pigments used as toner colorants can be used, such as carbon black, phthalocyanine blue, permanent brown FG, priestly first scarlet, pigment green B, rhodamine-B base. Solvent Red 49, Solvent Red 146, Solvent Blue 35, Quinacridone, Carmine 6B, Disazo Yellow, etc. can be used, and the toner of the present invention may be either black toner or color toner. The content of the colorant is preferably 1 to 40 parts by weight and more preferably 2 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

The toner of the present invention may be a toner obtained by any conventionally known method such as a melt-kneading method, an emulsion phase inversion method, or a polymerization method, but from the viewpoint of productivity and dispersibility of the colorant, A pulverized toner obtained by a melt kneading method is preferred. In the case of pulverized toner by melt kneading method, raw materials such as binder resin, colorant, charge control agent, etc. are uniformly mixed with a mixer such as a Henschel mixer, then a sealed kneader, a single or twin screw extruder, open It can be produced by melt-kneading with a roll-type kneader or the like, cooling, pulverizing and classifying. The volume median particle size (D ₅₀ ) of the toner is preferably 3 to 15 μm. In the present specification, the volume-median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% when calculated from the smaller particle size.

  The toner of the present invention can be used as a one-component developing toner or mixed with a carrier as a two-component developer. However, since the toner of the present invention has excellent fixability, the magnetic toner contains a large amount of magnetic powder. Can also be used suitably. The content of the magnetic powder is preferably 30% by weight or more, more preferably 35 to 60% by weight in the toner. The magnetic powder may be contained as a black colorant.

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 electrophotographic toner of the present invention can achieve both good low-temperature fixability and offset resistance even in an image forming apparatus having a low total pressure during fixing. Therefore, the present invention provides an image forming method for fixing toner using an image forming apparatus having a fixing machine having a low pressure applied to toner during fixing, preferably a fixing machine having a pressing force of 600 N or less, more preferably 400 N or less. By using the toner of the invention, the effect of the present invention is more remarkably exhibited. An example of such a fixing machine having a low pressure applied to the toner during fixing is a belt nip type fixing machine.

  The image forming method of the present invention can form an image through a known process except that it has a feature in a fixing process for fixing a transferred toner image. Typical processes in the image forming method include a process of forming an electrostatic latent image on the surface of the photoreceptor (charging / exposure process), a developing process of developing the electrostatic latent image, and the developed toner image being transferred to paper or the like. There are a step of transferring to a material (transfer step), a step of removing toner remaining on a developing member such as a photosensitive drum (cleaning step), and the like.

[Softening point]
Using a flow tester (Shimadzu Corporation, CFT-500D), a 1 g sample is heated at a heating rate of 6 ° C / min, a load of 1.96 MPa or 0.49 MPa is applied by a plunger, and a nozzle with a diameter of 1 mm and a length of 1 mm Extruded from. The amount of plunger drop of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is taken as the softening point. The softening point measured under the condition of the plunger load of _1.96 MPa is expressed as Tm _1.96 and the softening point measured under the condition of _0.49 MPa is expressed as Tm _0.49 .

[Methyl ethyl ketone (MEK) insoluble matter (wt%)]
(1) Sample preparation
Using a JIS Z8801 sieve, collect a powder sample that passes through a 22 mesh sieve and does not pass through a 30 mesh sieve. When the sample is a lump or the like, it is pulverized using a commercially available hammer or coffee mill and sieved as a powder.

(2) Sample dissolution
2-1. Weigh 2.000 g of sample in a glass bottle (Made by Yoyo Glass Co., Ltd., M-140), add 95 g of MEK, and attach the inner and outer lids.
2-2. Stir for 5 hours in a ball mill (peripheral speed: 200 mm / sec).
2-3. Leave for 10 hours.

(3) Filtration
3-1. Prepare a glass filter (opening standard 11G-3) attached to a pre-weighed (thousandth of a gram) eggplant flask (weight A (g)). A rubber stopper that can be decompressed is used to seal the glass filter.
3-2. Absorb 20 ml from the supernatant of the lysate that has been allowed to stand for 10 hours in 2-3 with a mespiped, and filter under reduced pressure using the glass filter prepared in 3-1. The supernatant is 2 cm below the liquid level. The degree of vacuum in the eggplant flask before filtering the solution is adjusted to 40 kPa.
3-3. Absorb 20 ml of unused MEK with mespiped and filter the soluble matter adhering to the glass filter under reduced pressure.

(4) Drying
4-1. Remove MEK from the eggplant flask with an evaporator.
Water bath temperature: 70 ℃
Eggplant flask rotation speed: 200r / min
Decompression degree in eggplant flask during MEK removal: Adjust to 40-20 kPa Time: 10 minutes
4-2. After drying at 50 ° C and 1 torr for 12 hours, weigh the eggplant flask weight B (g).

(5) Calculation of MEK insoluble matter
5-1. Calculate MEK soluble content X (g) dissolved in 20 ml of MEK.
X = BA
5-2. MEK soluble content Y (g) dissolved in 95 g of MEK is calculated with the specific gravity of MEK being 0.805.
Y = X × 95 / (20 × 0.805)
5-3. Calculate the soluble content Z (% by weight) per gram of sample.
Z = Y / 2 × 100
5-4. MEK insoluble matter (wt%) = 100-Z
Note that the MEK insoluble content (% by weight) is the average of three measurements.

[Melting point]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), the sample was heated to 200 ° C and then cooled to 0 ° C at a temperature decrease rate of 10 ° C / min. The maximum peak temperature of heat of fusion is the melting point.

Resin production example 1
Raw material monomers of polyester shown in Table 1, release agent (paraffin wax) “HNP-9” (manufactured by Nippon Seiwa Co., Ltd., melting point: 79 ° C.) and esterification catalyst (tin octoate) are introduced into a nitrogen introduction tube, dehydration tube, Place in a 10-liter four-necked flask equipped with a stirrer and thermocouple, stir at 160 ° C in a nitrogen atmosphere, and from the dropping funnel, the vinyl-based resin raw material monomers, both reactive compounds and polymerization shown in Table 1 A mixture of initiators (dibutyl peroxide) was added dropwise over 1 hour. After aging the addition polymerization reaction for 2 hours while maintaining the temperature at 160 ° C., the temperature is raised to 230 ° C., and the condensation polymerization reaction is performed until the desired softening point is reached, and the resins A to E, G, H, J, and K are obtained. Obtained.

Resin production example 2
The raw material monomer of polyester and the esterification catalyst (tin octoate) shown in Table 1 were put into a 10 liter four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple. The resins F, I, and L were obtained by a condensation polymerization reaction at normal pressure until the desired softening point was reached.

Examples 1-12 and Comparative Examples 1-3
100 parts by weight of binder resin shown in Table 2, 67 parts by weight of magnetic powder “MTS106HD” (manufactured by Toda Kogyo Co., Ltd.), 1 part by weight of negative charge control agent “T-77” (manufactured by Hodogaya Chemical Co., Ltd.) and paraffin After mixing 2 parts by weight of wax “HNP-9” (manufactured by Nippon Seiwa Co., Ltd., melting point: 79 ° C.) with a Henschel mixer, it was melt-kneaded with a twin screw extruder and cooled. Furthermore, a pulverization and classification process was obtained to obtain a powder having a volume median particle size (D ₅₀ ) of 7 μm.

  To 100 parts by weight of the obtained powder, 1.5 parts by weight of hydrophobic silica “Aerosil R-972” (manufactured by Nippon Aerosil) and 1.0 part by weight of hydrophobic titanium oxide “TiSr” (manufactured by Fuji Titanium) were added. The magnetic toner was obtained by mixing with a Henschel mixer.

Example 13
Instead of magnetic powder “MTS106HD”, 7 parts by weight of carbon black “MOGUL L” (manufactured by Cabot) was used, and hydrophobic titanium oxide “TiSr” was not used. A magnetic toner was obtained.

Test Example 1 [low temperature fixability]
250 g of toners of Examples 1-12 and Comparative Examples 1-3 are applied to a magnetic one-component developing device “LaserJet4200” (manufactured by Hewlett-Packard), and a non-magnetic one-component developing device “MicroLine9300PS” (made by Oki Data) is used. Each of the 13 toners was mounted to obtain an unfixed image (2 cm × 12 cm) having a toner adhesion amount of 0.6 mg / cm ² .

  The unfixed image was stored for 20 seconds in a thermostat bath at each temperature while the temperature in the thermostat bath was gradually increased from 80 ° C to 10 ° C.

  “UNICEF Cellophane” (Mitsubishi Pencil Co., Ltd., width: 18 mm, JISZ-1522) was attached to the fixed image, passed through a fixing roller set at 30 ° C., and then the tape was peeled off. Measure the optical reflection density before and after applying the tape using a reflection densitometer "RD-915" (manufactured by Macbeth), and the ratio of both (after peeling / before sticking) first exceeds 90%. The temperature of the roller was set as the minimum fixing temperature, and the low temperature fixing property was evaluated according to the following evaluation criteria. The results are shown in Table 2.

〔Evaluation criteria〕
A: The minimum fixing temperature is less than 100 ° C.
○: The minimum fixing temperature is 100 ° C. or higher and lower than 120 ° C.
X: The minimum fixing temperature is 120 ° C. or higher.

Test Example 2 [Offset resistance]
250 g of toners of Examples 1-12 and Comparative Examples 1-3 are applied to a magnetic one-component developing device “LaserJet4200” (manufactured by Hewlett-Packard), and a non-magnetic one-component developing device “MicroLine9300PS” (made by Oki Data) is used. Each of the 13 toners was mounted to obtain an unfixed image (2 cm × 12 cm) having a toner adhesion amount of 0.6 mg / cm ² .

The fixing machine of the copier "AR-505" (manufactured by Sharp Corporation) has been improved so that it can be fixed outside the machine, and adjusted so that the applied pressure is 40 kgf (392 N) (fixing speed 250 mm) / sec), a fixing test of an unfixed image was performed at each temperature while sequentially increasing from 100 ° C. to 240 ° C. by 10 ° C. The presence or absence of the occurrence of offset was visually confirmed, and the offset resistance was evaluated according to the following evaluation criteria. The results are shown in Table 2. The paper used for the fixing test is CopyBond SF-70NA (75 g / m ² ) manufactured by Sharp Corporation.

〔Evaluation criteria〕
A: Non-offset region (temperature region where no offset occurs) is 80 ° C. or higher.
○: The non-offset region is 50 ° C or higher and lower than 80 ° C.
X: The non-offset area is less than 50 ° C.

Test Example 3 [Durability]
250 g of toners of Examples 1-12 and Comparative Examples 1-3 are applied to a magnetic one-component developing device “LaserJet4200” (manufactured by Hewlett-Packard), and a non-magnetic one-component developing device “MicroLine9300PS” (made by Oki Data) is used. Each of the 13 toners was mounted, and after printing 50 images at a printing rate of 5% in an environment of 30 ° C and 90%, the optical reflection density was measured using a reflection densitometer “RD-915” (manufactured by Macbeth). And measured. Further, after printing 3000 sheets, the optical reflection density was measured again using a reflection densitometer “RD-915” (manufactured by Macbeth). The difference between the two image densities was calculated, and the durability was evaluated according to the following evaluation criteria. The results are shown in Table 2.

〔Evaluation criteria〕
A: The image density difference is less than 0.1.
○: Image density difference is 0.1 or more and less than 0.5.
X: The image density difference is 0.5 or more.

  From the above results, it can be seen that, in contrast to the comparative example, all of the examples are excellent in all of low-temperature fixability, offset resistance, and durability.

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

Claims (10)

Binder resin for an electrophotographic toner having a softening point (Tm _1.96 ) of 110 to 130 ° C. and a methyl ethyl ketone insoluble content (Tm _1.96 -100) / 2% by weight or more measured with a flow tester under a load of _1.96 MPa. . Binder resin, softening point load was measured under the conditions of 1.96MPa by a flow tester and (Tm _1.96), the ratio of the softening point load was measured under the conditions of 0.49MPa by a flow tester (Tm _0.49) (Tm _0.49 2. The binder resin for an electrophotographic toner according to claim 1, wherein / Tm _1.96 ) is 1.10 to 1.30. A polyester obtained by polycondensation of an alcohol component and a carboxylic acid component, or a resin obtained by using a raw material monomer of a polyester containing an alcohol component and a carboxylic acid component and a raw material monomer of an addition polymerization resin, the alcohol component Is the formula (I):

(In the formula, RO is an alkylene oxide, R is an alkylene group having 2 or 3 carbon atoms, x and y are positive numbers indicating the average added mole number of alkylene oxide, and the sum of x and y is 1 to 16) Is)
The binder resin for an electrophotographic toner according to claim 1, comprising 40 mol% or more of an alkylene oxide adduct of bisphenol A represented by the formula:   The binder resin for an electrophotographic toner according to claim 3, wherein the alcohol component contains 60 mol% or more of an ethylene oxide adduct of bisphenol A, wherein R is an alkylene group having 2 carbon atoms in the formula (I). .   An electrophotographic toner comprising the binder resin according to claim 1.   The toner for electrophotography according to claim 5, further comprising a binder resin having a softening point of 80 to 100 ° C. measured by a flow tester under a load of 1.96 MPa.   The toner for electrophotography according to claim 5 or 6, further comprising 20% by weight or more of magnetic powder in the toner.   The toner for electrophotography according to any one of claims 5 to 7, which is used in an image forming apparatus having a fixing device having a pressing force at fixing of 600 N or less.   9. The toner for electrophotography according to claim 8, wherein the fixing device is a belt nip type.   An image forming method comprising a step of fixing toner by using the electrophotographic toner according to claim 5 in an image forming apparatus having a fixing machine having a pressing force of 600 N or less during fixing.