JP2013080254A - Toner for electrostatic charge image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide toner for electrostatic charge image development that has excellent grindability and fixability, and is less likely to cause filming.SOLUTION: Toner for electrostatic charge image development comprises high-softening point polyester having softening point of 120 to 160°C and low-softening point polyester having the softening point of 75 to 120°C, which are obtained by condensation polymerization of an alcohol component comprising substantially only aliphatic alcohol and a carboxylic acid component. Difference in the softening point between the high-softening point polyester and the low-softening point polyester is 10°C or more.

Description

  The present invention relates to an electrostatic charge image developing toner used for developing an electrostatic latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method or the like.

  Polyesters are essentially excellent in fixability, but for the purpose of further improving fixability, there are various binder resins for toner comprising polyesters obtained by using substantially only aliphatic alcohol as an alcohol component. It is being considered.

  For example, Patent Document 1, Patent Document 2, Patent Document 3 and the like include polyesters obtained by polycondensing a monomer mixture containing an aromatic dicarboxylic acid, an aliphatic diol, and a trivalent or higher polyvalent monomer. A toner contained as a binder resin is disclosed. However, with these toners, filming tends to occur although the fixability is good.

  Many toners have been reported in which a mixture of resins having different softening points is used as a binder resin to improve the defects of each resin, and among them, combinations of aromatic alcohol polyesters have been most studied (Patent Document 4, Patent Document 5, Patent Document 6, etc.). Patent Documents 7 and 8 also disclose toners in which aliphatic alcohol polyesters and aromatic alcohol polyesters are used as binder resins, but all of them have pulverizing properties, fixing properties, and filming resistance. It must be said that the improvement is insufficient, and further improvement in performance is desired for the toner for high-speed machines.

Japanese Patent Laid-Open No. 1-204065 Japanese Patent Laid-Open No. 2-161467 Japanese Patent Laid-Open No. 10-268558 JP-A-4-362956 JP-A-4-313760 JP-A-8-320593 JP-A-11-305486 Japanese Patent Laid-Open No. 12-39738

  An object of the present invention is to provide a toner for developing an electrostatic charge image that is excellent in grindability and fixability and hardly causes filming.

  The present invention relates to a high softening point polyester having a softening point of 120 to 160 ° C. and a softening point of 75 to 120 ° C., obtained by condensation polymerization of an alcohol component consisting essentially of an aliphatic alcohol and a carboxylic acid component. And a low-softening point polyester, wherein the difference in softening point between the high-softening point polyester and the low-softening point polyester is 10 ° C. or more.

  According to the present invention, it is possible to provide a toner for developing an electrostatic image that is excellent in grindability and fixability and hardly causes filming.

  The binder resin of the toner of the present invention contains a high softening point polyester and a low softening point polyester obtained by polycondensing an alcohol component consisting essentially of an aliphatic alcohol and a carboxylic acid component. Yes. Polyesters whose alcohol component consists essentially of aliphatic alcohols have much better fixing properties than polyesters using aromatic alcohols. Furthermore, since the compatibility with the wax is excellent, the characteristics of the wax can be sufficiently exhibited without causing filming even when the wax is contained as a release agent. In the present specification, the term “alcohol component consisting essentially of an aliphatic alcohol” means that the aliphatic alcohol in the alcohol component is 98 mol% or more, preferably 99 mol% or more, more preferably 100 mol%. It means what is contained.

  Aliphatic alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, Divalent polyhydric alcohols such as neopentyl glycol, dipropylene glycol, 1,4-butenediol, 1,4-cyclohexanedimethanol, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan , Pentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylol Examples include trihydric or higher polyhydric alcohols such as propane. Among these, carbon number Divalent straight or polyhydric alcohols and their dimers branched to 6 are preferred. Further, in order to obtain an amorphous polyester, the alcohol component preferably contains 2 to 5 kinds, more preferably 3 to 4 kinds of alcohol, and when a plurality of alcohols are contained. The content of each alcohol is preferably 1 to 70 mol%, more preferably 5 to 60 mol%.

  Examples of the divalent carboxylic acid compound include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; maleic acid, fumaric acid, adipic acid, succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, Aliphatic dicarboxylic acids such as succinic acid substituted by alkyl groups having 1 to 20 carbon atoms or alkenyl groups having 2 to 20 carbon atoms such as isododecenyl succinic acid, isooctyl succinic acid and isooctenyl succinic acid; and these An acid anhydride or a lower alkyl (1 to 3 carbon atoms) ester may be used. Among these, at least one polyester may be an aliphatic dicarboxylic acid from the viewpoint of fixability and compatibility with a wax. Is preferably contained, and maleic acid, fumaric acid and succinic acid are more preferably contained. The content of the aliphatic dicarboxylic acid is preferably 0.1 to 70 mol% and more preferably 0.1 to 50 mol% in the carboxylic acid component.

  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.

  The high softening point polyester is preferably a cross-linked resin, and is preferably a resin obtained using a trivalent or higher monomer. The content of the trivalent or higher monomer is preferably 0.1 to 40% by mole, more preferably 5 to 30% by mole in the carboxylic acid component of the high softening point polyester.

  The polycondensation of the alcohol component and the carboxylic acid component is, for example, polycondensation of the alcohol component and the carboxylic acid component at a temperature of 180 to 250 ° C. using an esterification catalyst as necessary in an inert gas atmosphere. Can be manufactured.

  The polyester in the present invention comprises a high softening point polyester and a low softening point polyester. The softening point of the high softening point polyester is 120 to 160 ° C, preferably 125 to 160 ° C, more preferably 135 to 160 ° C, and the softening point of the low softening point polyester is 75 to 120 ° C, preferably 80 to 115 ° C. ° C. The high softening point polyester improves offset resistance and the like, and the low softening point polyester improves fixing property and grindability. However, in the present invention, the alcohol component of the polyester consists essentially of an aliphatic alcohol. In addition, the high softening point polyester and the low softening point polyester are easily entangled, and in particular, both properties are more effectively exhibited in terms of pulverization, fixing properties, and filming resistance.

  The difference in softening point between the high softening point polyester and the low softening point polyester is 10 ° C. or higher, preferably 20 to 80 ° C., more preferably 30 to 60 ° C.

  In the present invention, both the high softening point polyester and the low softening point polyester are preferably amorphous polyesters, and the difference between the softening point and the glass transition point is preferably 20 ° C. or more, and 30 to 100 ° C. More preferred.

  The softening point and glass transition point of the polyester can be adjusted by the monomer composition, the degree of crosslinking, the molecular weight, and the like.

  The acid value of the polyester is preferably 3 to 60 mgKOH / g, more preferably 5 to 50 mgKOH / g, regardless of the high softening point polyester and the low softening point polyester. The hydroxyl value is 5 to 60 mgKOH / g, preferably 10 to 50 mgKOH / g.

  The weight ratio of the high softening point polyester to the low softening point polyester (high softening point polyester / low softening point polyester) is preferably 20/80 to 90/10, more preferably 20/80 to 70/30.

  The content of the polyester in the binder resin is preferably 50 to 100% by weight, more preferably 80 to 100% by weight, and particularly preferably 100% by weight. The binder resin may appropriately contain a resin such as styrene-acrylic resin, epoxy resin, polycarbonate, polyurethane.

  The toner of the present invention preferably further contains a wax. In the present invention, since the low softening point polyester excellent in compatibility with the wax and the high softening point polyester for improving the dispersibility of the wax are used in combination, even if the wax is contained as a release agent, The characteristics of the wax are sufficiently exhibited without causing problems such as ming. As waxes, polyolefin waxes such as polypropylene wax, polyethylene wax, polypropylene polyethylene copolymer wax, carnauba wax, ester waxes such as haze wax, beeswax, whale wax, montan wax, synthetic waxes such as Fischer-Tropsch wax And amide waxes such as fatty acid amide waxes. The content of the wax is preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  Further, in addition to the binder resin, the toner of the present invention includes a colorant, a charge control agent, a release agent, a fluidity improver, a conductivity modifier, an extender pigment, a reinforcing filler such as a fibrous substance, an oxidation agent, Additives such as an inhibitor, an anti-aging agent, and a cleaning property improver may be appropriately contained.

  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, and these can be used alone or in admixture of two or more. It can be used as either toner or full color toner. The content of the colorant is preferably 1 to 60 parts by weight and more preferably 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  The toner of the present invention is preferably a pulverized toner obtained by a kneading and pulverizing method. For example, after a binder resin, a colorant, and the like are uniformly mixed with a mixer such as a ball mill, a sealed kneader or a uniaxial or biaxial It can be produced by melt-kneading with an extruder or the like, cooling, pulverizing and classifying. The volume average particle diameter of the toner is preferably 3 to 15 μm. Furthermore, a fluidity improver such as hydrophobic silica may be added to the surface of the toner as an external additive.

  The electrostatic image developing toner of the present invention contains a magnetic fine powder alone as a developer, and a non-magnetic fine powder as a non-magnetic one-component developer or mixed with a carrier. Can be used as a two-component developer.

  Since the toner for developing an electrostatic image of the present invention has good fixability and filming resistance, the linear velocity is 280 mm / sec or more, preferably 370 mm / sec or more, and 160 mm / sec or more, preferably It can be suitably used for a laser beam printer of 280 mm / sec or more.

[Softening point]
Using a Koka-type flow tester “CFT-500D” (manufactured by Shimadzu Corporation), a 1 g sample was heated at a heating rate of 6 ° C./min. A nozzle of 1 mm is pushed out, thereby drawing a plunger tester descending amount (flow value) -temperature curve, and when the height of the S-shaped curve is h, the temperature corresponding to h / 2 (half of the resin) Is the softening point.

[Glass transition point]
A differential scanning calorimeter “DSC210” (manufactured by Seiko Denshi Kogyo Co., Ltd.) is used for measurement at a heating rate of 10 ° C./min.

[Acid value and hydroxyl value]
It is measured by the method of JIS K0070.

Resin Production Example The raw material monomers shown in Table 1 were reacted in the presence of dibutyltin oxide with stirring at 230 ° C. under vacuum in a nitrogen stream, and a softening point according to ASTM E28-67 was desired. The reaction was terminated when the softening point was reached. Table 1 shows the softening point, glass transition point, acid value, and hydroxyl value of the obtained resin.

Examples 1-6, Comparative Examples 1-10
Binder resin shown in Table 2, carbon black “Regal 330” (Cabot) 6 parts by weight, charge control agent “T-77” (Hodogaya Chemical) 1.5 parts by weight and release agent (low molecular weight polypropylene wax) , Melting point: 140 ° C.) 2 parts by weight were mixed using a Henschel mixer, and then melt-kneaded by a twin screw extruder. The obtained melt-kneaded product was pulverized and classified using a high-speed jet mill pulverizing and classifying machine “IDS-2 type” (manufactured by Nippon Pneumatic Co., Ltd.) so that the volume average particle diameter was 8.5 μm. When pulverizing and classifying, the pulverizing property was evaluated by the following method.

[Crushability]
A resin powder is obtained which passes through a 16-mesh sieve (aperture: 1.0 mm) but does not pass through a 22-mesh sieve (aperture: 710 μm). After pulverizing 30 g of classified resin powder for 10 seconds with a coffee mill (manufactured by PHILIPS, type HR-2170), it is applied to a 30-mesh sieve (opening: 500 μm), and the weight of resin powder that does not pass (A) g Weigh accurately. From this weight, the residual rate was determined by the following formula, and this operation was performed three times to determine the average value. The results are shown in Table 2.

Residual rate (%) = (A [g] /30.0 [g]) × 100

(Evaluation criteria)
A: The average residual rate is less than 10.0%.
○: The average remaining rate is 10.0% or more and less than 15.0%.
Δ: The average residual ratio is 15.0% or more and less than 20.0%.
X: The average residual rate is 20.0% or more.

  Next, 0.5 parts by weight of hydrophobic silica “R-972” (manufactured by Nippon Aerosil Co., Ltd.) was added to 100 parts by weight of the obtained powder and mixed with a Henschel mixer to obtain a toner.

Test example 1
The toner is mounted on a device (linear speed: 370 mm / sec) modified from the copier “AR-505” (manufactured by Sharp), and the image is output while the temperature of the fixing roller is gradually increased to 90 to 240 ° C. The toner fixability was evaluated from the minimum fixing temperature. The results are shown in Table 2. Here, the minimum fixing temperature is before and after rubbing 5 times on an image fixed on a sand eraser having a bottom surface of 15 mm × 7.5 mm by placing a load of 500 g through a fixing machine (100 to 240 ° C.). The temperature of the fixing roller when the optical reflection density is measured with a Macbeth reflection densitometer and the fixing rate exceeds 70% according to the following definition.
Fixing rate (%) = [(Image density after rubbing) / (Image density before rubbing)] × 100

Test example 2
The toner is mounted on an apparatus (linear speed: 370 mm / sec) modified from the copier “AR-505” (manufactured by Sharp), and 500,000 continuous printings are performed, and the residual toner is fused to the surface of the photosensitive drum. The occurrence of filming and the effect on the printed image were visually observed, and the degree of filming was evaluated according to the following evaluation criteria. The results are shown in Table 2.

〔Evaluation criteria〕
A: Not generated B: Toner fusion is slightly observed on the photoreceptor, but there is no influence on the image.
X: Ten or more points of toner fusion on the photosensitive member are observed, and the image is defective.

  From the above results, it can be seen that the toners of Examples 1 to 6 exhibit excellent performance in any evaluation as compared with the toners of Comparative Examples 1 to 10. In particular, a resin obtained by polycondensing an alcohol component consisting only of an aliphatic alcohol and a carboxylic acid component is a resin having a different softening point compared to a resin obtained using an alcohol component containing an aromatic alcohol. It can be seen that the combined use of cis significantly improves the grindability, fixability and filming resistance, and that the carboxylic acid component of the resin preferably contains an aliphatic carboxylic acid.

Claims (4)

  A high softening point polyester having a softening point of 120 to 160 ° C. and a low softening point of 75 to 120 ° C. obtained by condensation polymerization of an alcohol component consisting essentially of an aliphatic alcohol and a carboxylic acid component. An electrostatic charge image developing toner comprising a polyester, wherein a difference in softening point between the high softening point polyester and the low softening point polyester is 10 ° C. or more.   2. The electrostatic image developing toner according to claim 1, wherein the weight ratio of the high softening point polyester to the low softening point polyester (high softening point polyester / low softening point polyester) is 20/80 to 90/10.   The electrostatic charge image developing toner according to claim 1, wherein the high softening point polyester is a resin obtained by using a trivalent or higher monomer.   The electrostatic image developing toner according to claim 1, further comprising a wax.