JP5456590B2 - Positively chargeable toner - Google Patents

Description

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

  In recent years, miniaturization and speeding-up of electrophotographic apparatuses have been strongly demanded, and toners are required to have a minimum fixing temperature lowered and a fixing region temperature range expanded.

  To meet this demand, toner composed of two types of polyesters having different softening points, for example, a low softening point polyester having a softening point of 80 ° C. or higher and lower than 120 ° C. and a high softening point polyester having a softening point of 120 ° C. or higher and 170 ° C. or lower. Containing toner (see Patent Document 1), toner composed of two kinds of polyesters having a difference in softening point of 30 ° C. or more and 60 ° C. or less and a glass transition point of less than 10 ° C. (see Patent Document 2), softening point Has proposed a toner containing a resin having a softening point of 120 ° C. or more and 160 ° C. (see Patent Document 3).

  Also, a toner using two types of polyester using adipic acid having a weight average molecular weight of 4300 and a weight average molecular weight of 183,000, or a toner using two types of polyester using adipic acid having a weight average molecular weight of 6300 and a weight average molecular weight of 78000. (See Patent Document 4).

JP 2003-122059 A JP 2004-279842 A JP 2005-208552 A JP 2006-337847 A

  Since polyester has a strong negative chargeability, a large amount of a positively chargeable charge control agent needs to be blended for use as a binder resin for a positively chargeable toner. However, the present inventors have found that a toner using a low softening point polyester and a high softening point polyester has a large viscosity difference between the low softening point polyester and the high softening point polyester when a large amount of the charge control agent is blended. The present inventors have found that there is a problem that sufficient image quality cannot be obtained due to insufficient dispersion of the agent and generation of fogging and solid followability.

  An object of the present invention is to provide a positively chargeable toner that is excellent in low-temperature fixability and offset resistance, has a wide fixing temperature range, suppresses occurrence of fogging and solid followability, and is excellent in initial image density characteristics. There is to do.

  The present invention relates to a positively chargeable toner comprising a binder resin containing two kinds of polyesters having different softening points of 10 ° C. or more, a toner base particle containing a colorant and a positively chargeable charge control agent, and an external additive. The two kinds of polyesters are polyester A having a softening point of 105 to 140 ° C., a glass transition point of 30 to 55 ° C. and a weight average molecular weight of 10,000 to 45,000, a softening point of 140 to 170 ° C., and a glass transition point. Is a polyester B having a weight average molecular weight of 45000 to 150000 exceeding 55 ° C. and not higher than 80 ° C., and the polyester A is a polyester obtained by polycondensation of a carboxylic acid component containing an adipic acid compound and an alcohol component. The present invention relates to a chargeable toner.

  The positively chargeable toner of the present invention is excellent in low-temperature fixability and offset resistance, has a wide fixing temperature range, suppresses occurrence of fogging and solid followability, and has excellent effects on initial image density characteristics. Is.

  The positively chargeable toner of the present invention contains two kinds of polyesters having different softening points, and further has a feature that the glass transition points of these polyesters are different. By using polyester A having a softening point of 105 to 140 ° C., a glass transition point of 30 to 55 ° C., and a weight average molecular weight of 10,000 to 45,000, the low temperature fixability and low temperature offset resistance of the toner are improved. Moreover, high temperature offset resistance improves by using polyester B with a softening point of 140-170 degreeC, a glass transition point exceeding 55 degreeC and 80 degrees C or less, and a weight average molecular weight 45000-150000.

  In addition, in the production of positively chargeable toners, by controlling the softening points of the two types of polyesters within a certain range, it is possible to give an appropriate share during melt kneading of the raw materials, and to improve the dispersion of the charge control agent. As a result, the charging stability is improved, the generation of fog is suppressed, and the solid followability is improved.

  From the above viewpoint, the softening point of the polyester A having the lower softening point out of the two types of polyesters having different softening points is the viewpoint of improving the high temperature offset resistance of the toner, and the binder resin of the colorant and charge control agent. From the viewpoint of improving the dispersibility therein, it is 105 ° C. or higher, preferably 110 ° C. or higher, and more preferably 115 ° C. or higher. Further, from the viewpoint of improving the low-temperature fixability and low-temperature offset resistance of the toner, it is 140 ° C. or lower, preferably 135 ° C. or lower, more preferably 130 ° C. or lower. That is, when these viewpoints are taken together, the softening point of polyester A is 105 to 140 ° C, preferably 110 to 135 ° C, more preferably 115 to 130 ° C.

  On the other hand, the softening point of polyester B having a higher softening point is 140 ° C. or higher, preferably 145 ° C. or higher, and more preferably 150 ° C. or higher, from the viewpoint of improving the high temperature offset resistance of the toner. Further, from the viewpoint of improving the low-temperature fixability and low-temperature offset resistance of the toner and improving the dispersibility of the colorant and charge control agent in the binder resin, it is 170 ° C or lower, preferably 165 ° C or lower, 160 ° C. or lower is more preferable. That is, when these viewpoints are put together, the softening point of polyester B is 140-170 ° C, preferably 145-165 ° C, more preferably 150-160 ° C.

  The difference in softening point between polyester A and polyester B is 10 ° C. or higher, preferably 15 ° C. or higher, and more preferably 20 ° C. or higher from the viewpoint of improving the low-temperature fixability and low-temperature offset resistance and high-temperature offset resistance of the toner. . Further, from the viewpoint of improving the dispersibility of the colorant or charge control agent in the binder resin, it is preferably 65 ° C. or lower, more preferably 50 ° C. or lower, and further preferably 40 ° C. or lower. That is, taking these viewpoints together, the difference in softening point between polyester A and polyester B is 10 ° C. or higher, preferably 10 to 65 ° C., more preferably 15 to 50 ° C., and even more preferably 20 to 40 ° C.

  The softening point of polyester can be raised, for example, by increasing the reaction time for polyesterification or using a raw material monomer having a valence of 3 or more. For example, the softening point can be lowered by using a monovalent raw material monomer. Here, polyester means both polyester A and polyester B. The same applies to the following description.

  Furthermore, the glass transition point of polyester A is 30 ° C. or higher, preferably 33 ° C. or higher, and more preferably 35 ° C. or higher, from the viewpoint of improving the storage stability and high temperature offset resistance of the toner. Further, from the viewpoint of improving the low-temperature fixability and low-temperature offset resistance of the toner, it is 55 ° C. or lower, preferably 53 ° C. or lower, more preferably 52 ° C. or lower, and further preferably 50 ° C. or lower. That is, taking these viewpoints together, the glass transition point of polyester A is 30 to 55 ° C, preferably 33 to 53 ° C, more preferably 35 to 52 ° C, and further preferably 35 to 50 ° C. .

  On the other hand, the glass transition point of polyester B is more than 55 ° C., preferably 57 ° C. or more, and more preferably 60 ° C. or more from the viewpoint of improving the storage stability and high-temperature offset resistance of the toner. Further, from the viewpoint of improving the low-temperature fixability and low-temperature offset resistance of the toner, it is 80 ° C. or lower, preferably 75 ° C. or lower, and more preferably 70 ° C. or lower. That is, when these viewpoints are put together, the glass transition point of polyester B is more than 55 ° C. and 80 ° C. or less, preferably 57 to 75 ° C., more preferably 60 to 70 ° C.

  The difference in the glass transition point between polyester A and polyester B is preferably 5 ° C. or higher, more preferably 7 ° C. or higher, further preferably 8 ° C. or higher, from the viewpoint of improving the low temperature fixability and low temperature offset resistance of the toner. More preferably 10 ° C. or more. Further, from the viewpoint of improving the dispersibility of the colorant or charge control agent in the binder resin, it is preferably 40 ° C. or lower, more preferably 35 ° C. or lower, and further preferably 30 ° C. or lower. That is, taking these viewpoints together, the difference between the glass transition points of polyester A and polyester B is preferably 5 to 40 ° C, more preferably 7 to 35 ° C, still more preferably 8 to 35 ° C, still more preferably. It is 9-30 degreeC, More preferably, it is 10-30 degreeC.

  The glass transition point of polyester can be controlled by, for example, the composition of the raw material monomers. For example, the glass transition point can be increased by reducing the content of the aliphatic dicarboxylic acid compound in the carboxylic acid component of the polyester. In addition, the glass transition point can be lowered by using a divalent raw material monomer having a large carbon number, for example, a carbon number of 6 or more, or a monovalent raw material monomer.

  The weight average molecular weight of the polyester A is 10,000 or more, preferably 15,000 or more, from the viewpoint of improving the high temperature offset resistance of the toner and improving the dispersibility of the colorant or charge control agent in the binder resin. 20000 or more is more preferable. Further, from the viewpoint of improving the low-temperature fixability and low-temperature offset resistance of the toner, it is 45000 or less, preferably 40000 or less, and more preferably 35000 or less. That is, when these viewpoints are put together, the weight average molecular weight of polyester A is 10,000 to 45000, preferably 15000 to 40000, and more preferably 20000 to 35000. Further, from the same viewpoint, the number average molecular weight is preferably 2000 to 4000, more preferably 2400 to 3700, and further preferably 2800 to 3500. From the same viewpoint, the molecular weight peak is preferably 6000 to 8500, more preferably 6500 to 8200, and further preferably 7000 to 8000.

  On the other hand, the weight average molecular weight of polyester B is 45000 or more, preferably 50000 or more, more preferably 55000 or more, from the viewpoint of improving the high temperature offset resistance of the toner. In addition, from the viewpoint of improving the low-temperature fixability and low-temperature offset resistance of the toner and from the viewpoint of improving the dispersibility of the colorant and charge control agent in the binder resin, it is 150,000 or less, preferably 100,000 or less, preferably 80,000 or less. Is more preferable. That is, when these viewpoints are put together, the weight average molecular weight of polyester B is 45000-150000, Preferably it is 5000-100000, More preferably, it is 55000-80000. From the same viewpoint, the number average molecular weight is preferably 3500 to 8000, more preferably 3800 to 6500, and further preferably 4000 to 5000. Further, from the same viewpoint, the molecular weight peak is preferably 8000 to 12000, more preferably 8100 to 10,000, and further preferably 8200 to 9000.

  The molecular weight of the polyester can be increased, for example, by lengthening the reaction time for polyesterification or by using a trivalent or higher raw material monomer. Further, for example, the molecular weight can be lowered by using a monovalent raw material monomer.

  The storage elastic modulus of polyester A at 150 ° C. is from the viewpoint of improving the storage stability and high temperature offset resistance of the toner, and from the viewpoint of improving the dispersibility of the colorant and charge control agent in the binder resin. 100 Pa or more is preferable, 300 Pa or more is more preferable, and 500 Pa or more is more preferable. Further, from the viewpoint of improving the low-temperature fixability and low-temperature offset resistance of the toner, 2000 Pa or less is preferable, 1500 Pa or less is more preferable, and 1000 Pa or less is more preferable. That is, taking these viewpoints together, the storage elastic modulus of polyester A at 150 ° C. is preferably 100 to 2000 Pa, more preferably 300 to 1500 Pa, and even more preferably 500 to 1000 Pa.

  On the other hand, the storage elastic modulus of Polyester B at 150 ° C. is preferably 2500 Pa or more, more preferably 3000 Pa or more, and further preferably 3500 Pa or more, from the viewpoint of improving the storage stability and high-temperature offset resistance of the toner. Further, from the viewpoint of improving the low-temperature fixability and low-temperature offset resistance of the toner, and from the viewpoint of improving the dispersibility in the binder resin of the colorant and the charge control agent, preferably 20000 Pa or less, more preferably 15000 Pa or less, 10000 Pa or less is more preferable. That is, taking these viewpoints together, the storage elastic modulus of polyester B at 150 ° C. is preferably 2500 to 20000 Pa, more preferably 3000 to 15000 Pa, and further preferably 3500 to 10,000 Pa.

  The ratio of storage elastic modulus of polyester A and polyester B at 150 ° C. (storage elastic modulus of polyester B / storage elastic modulus of polyester A) improves the dispersibility of the colorant and charge control agent in the binder resin. From the viewpoint, 100 or less is preferable, 50 or less is more preferable, and 15 or less is more preferable.

  The storage elastic modulus of the polyester can be increased by, for example, increasing the reaction time for polyesterification or using a trivalent or higher raw material monomer. Further, the storage elastic modulus can be lowered by using a monovalent raw material monomer.

  The polyester is obtained by polycondensation of an alcohol component containing a divalent or higher alcohol and a carboxylic acid component containing a divalent or higher carboxylic acid compound as raw material monomers.

  Examples of the divalent alcohol include diols having 2 to 20 carbon atoms, preferably 2 to 15 carbon atoms, and formula (I):

(In the formula, RO and OR are oxyalkylene groups, R is an ethylene and / or propylene group, x and y indicate the number of added moles of alkylene oxide, each being a positive number, and the sum of x and y. 1 to 16, preferably 1 to 8, more preferably 1.5 to 4, and an alkylene oxide adduct of bisphenol. Specific examples of the diol having 2 to 20 carbon atoms include ethylene glycol, propylene glycol, 1,6-hexanediol, bisphenol A, hydrogenated bisphenol A, and the like.

  As the alcohol component, an alkylene oxide adduct of bisphenol represented by the formula (I) is preferable from the viewpoint of improving the charging stability of the toner and improving the fog and solid followability. Further, from the same viewpoint, the content of the alkylene oxide adduct of bisphenol represented by formula (I) is preferably 50 mol% or more, more preferably 70 mol% or more, and more preferably 90 mol% or more in the alcohol component. Further preferred.

  Examples of the trihydric or higher alcohol include trihydric or higher polyhydric alcohols having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms. Specific examples include sorbitol, 1,4-sorbitan, pentaerythritol, glycerol, trimethylolpropane, and the like.

  On the other hand, as the divalent carboxylic acid compound, the carbon number 3-30, preferably the carbon number 3-20, more preferably the carbon number 3-10 dicarboxylic acid, and their acid anhydride, carbon number 1-12 Examples thereof include derivatives such as alkyl esters. Specific examples of dicarboxylic acids include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid, succinic acid, fumaric acid, maleic acid, adipic acid, and alkyl groups or alkenyl groups having 1 to 20 carbon atoms. Examples include aliphatic dicarboxylic acids such as succinic acid.

  Examples of the trivalent or higher carboxylic acid compound include 4 to 30 carbon atoms, preferably 4 to 20 carbon atoms, and more preferably 4 to 10 carbon trivalent or higher polyvalent carboxylic acids, and acid anhydrides and carbons thereof. Derivatives such as alkyl esters of formula 1 to 12 can be mentioned. Specific examples include 1,2,4-benzenetricarboxylic acid (trimellitic acid).

  As the carboxylic acid component, aliphatic dicarboxylic acid compounds such as succinic acid, fumaric acid, maleic acid, adipic acid are used from the viewpoint of lowering the glass transition point of the polyester and improving the low-temperature fixability and low-temperature offset resistance of the toner. It is preferable to use each compound of succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms.

  Further, as the carboxylic acid component, it is preferable to use an adipic acid compound from the viewpoint of increasing the initial image density value of the toner and reducing the fluctuation range thereof, that is, improving the initial image density characteristics.

  The present invention is characterized in that the polyester A is a polyester obtained by condensation polymerization of a carboxylic acid component containing an adipic acid compound and an alcohol component. Polyester A using an adipic acid compound has moderate flexibility, and it is considered that the external additive adheres to the toner surface while being appropriately embedded in the external addition treatment step, and the adhesion strength is increased. On the other hand, since polyester A that does not have a soft segment such as adipic acid in the main chain does not have flexibility, it is considered that the external additive adheres to the toner surface with weak adhesion strength. Such a toner having a low adhesion strength of the external additive is stressed in the toner cartridge during printing, and the adhesion strength of the external additive gradually increases. As a result, the development amount increases and the image density gradually increases. As a result, the fluctuation range becomes large. On the other hand, the toner containing polyester A obtained by using an adipic acid compound has a sufficiently high development amount from the beginning of printing due to the strong adhesion strength of the external additive. As a result, the image density is high and the fluctuation range is also large. It is thought to be smaller.

  The content of the adipic acid compound in the carboxylic acid component of polyester A is from the viewpoint of lowering the glass transition point of polyester A, improving the low-temperature fixability and low-temperature offset resistance of the toner, and improving the initial image density characteristics. In the carboxylic acid component of polyester A, 15 mol% or more is preferable, 18 mol% or more is more preferable, 20 mol% or more is more preferable, 24 mol% or more is further preferable, and 28 mol% or more is more preferable. Further, from the viewpoint of improving the storage stability and high temperature offset resistance of the toner, it is preferably 60 mol% or less, more preferably 55 mol% or less, still more preferably 50 mol% or less in the carboxylic acid component of the polyester A, 45 The mol% or less is more preferable, and 40 mol% or less is more preferable. That is, taking these viewpoints together, the content of adipic acid is preferably 15 to 60 mol%, more preferably 18 to 55 mol%, still more preferably 20 to 50 mol% in the carboxylic acid component of polyester A. 24 to 45 mol% is more preferable, and 28 to 40 mol% is more preferable.

  The content of the adipic acid compound is the total amount of raw material monomers for polyester A from the viewpoint of lowering the glass transition point of polyester A, improving the low-temperature fixability and low-temperature offset resistance of the toner, and improving the initial image density characteristics. In other words, in the total amount of the carboxylic acid component and the alcohol component, 7 mol% or more is preferable, 8 mol% or more is more preferable, 9 mol% or more is more preferable, 10 mol% or more is further preferable, and 12 mol% or more is More preferably, from the viewpoint of improving the storage stability and high temperature offset resistance of the toner, it is preferably 28 mol% or less, more preferably 25 mol% or less, further preferably 22 mol% or less, further preferably 20 mol% or less, 18 mol% or less is more preferable. That is, taking these viewpoints together, the content of the adipic acid compound is preferably 7 to 28 mol%, more preferably 8 to 25 mol%, still more preferably 9 to 22 mol% in the total amount of raw material monomers of polyester A. 10 to 20 mol% is more preferable, and 12 to 18 mol% is more preferable.

  On the other hand, in the carboxylic acid component of polyester B, the content of the aliphatic dicarboxylic acid compound is 40% in the carboxylic acid component of polyester B from the viewpoint of increasing the glass transition point of polyester B and improving the high temperature offset resistance of the toner. Less than mol% is preferable, 30 mol% or less is more preferable, and 20 mol% or less is more preferable.

  The content of the adipic acid compound is preferably 1 mol% or more, more preferably 3 mol% or more, and further preferably 5 mol% or more in the carboxylic acid component of polyester B from the viewpoint of improving the initial image density characteristics of the toner. . Further, from the viewpoint of improving the storage stability and high temperature offset resistance of the toner, it is preferably 30 mol% or less, more preferably 25 mol% or less, and even more preferably 20 mol% or less in the carboxylic acid component of polyester B. That is, taking these viewpoints together, the content of adipic acid is preferably 1 to 30 mol%, more preferably 3 to 25 mol%, and even more preferably 5 to 20 mol% in the carboxylic acid component of polyester B.

  In addition, the content of the adipic acid compound is preferably 1 mol% or more in the total amount of raw material monomers of polyester B, that is, in the total amount of the carboxylic acid component and the alcohol component, from the viewpoint of improving the initial image density characteristics of the toner. More preferably, mol% or more, more preferably 3 mol% or more, from the viewpoint of improving the storage stability and high temperature offset resistance of the toner, preferably 15 mol% or less, more preferably 12 mol% or less, and 9 mol% or less. Is more preferable. That is, taking these viewpoints together, the content of the adipic acid compound is preferably from 1 to 15 mol%, more preferably from 2 to 12 mol%, still more preferably from 3 to 9 mol%, based on the total amount of raw material monomers of polyester B. .

  Polyester is produced, for example, by polycondensing an alcohol component and a carboxylic acid component in an inert gas atmosphere at a temperature of about 180 to 250 ° C. in the presence of an esterification catalyst, a polymerization inhibitor or the like as necessary. can do. Examples of esterification catalysts include esterification catalysts such as tin compounds such as dibutyltin oxide and tin (II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolamate. The amount of the esterification catalyst used is preferably 0.01 to 1 part by weight, more preferably 0.1 to 0.6 part by weight, based on 100 parts by weight of the total amount of raw material monomers, that is, the carboxylic acid component and the alcohol component.

  In the present invention, the polyester may be a polyester modified to such an extent that the characteristics are not substantially impaired. Examples of the modified polyester include grafting and blocking with phenol, urethane, epoxy and the like by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, and the like. Polyester.

  The acid value of polyester A and polyester B is preferably 20 mgKOH / g or less, more preferably 15 mgKOH / g or less, and even more preferably 10 mgKOH / g or less, from the viewpoint of positive chargeability of the toner.

  The weight ratio of polyester A to polyester B (polyester A / polyester B) in the binder resin is 10/10 from the viewpoint of improving the low-temperature fixability and low-temperature offset resistance of the toner, and improving the initial image density characteristics of the toner. 90-99 / 1 is preferable, 15 / 85-99 / 1 is more preferable, and 20 / 80-99 / 1 is still more preferable. Further, from the viewpoint of improving the high temperature offset resistance of the toner, 1/99 to 80/20 is preferable, 1/99 to 70/30 is more preferable, and 1/99 to 50/50 is further preferable. Therefore, 10/90 to 80/20 is preferable, 15/85 to 70/30 is more preferable, and 20/80 to 50/50 is preferable from the viewpoint of expanding the fixing temperature range of the toner and improving the initial image density characteristics. Further preferred.

  The binder resin may contain a binder resin other than polyester A and polyester B as long as the effects of the present invention are not impaired. The total amount of polyester A and polyester B is 80% in the binder resin. % By weight or more is preferable, 90% by weight or more is more preferable, and substantially 100% by weight is further preferable. Examples of binder resins other than polyester A and polyester B include polyesters other than polyester A and B, vinyl resins, epoxy resins, polycarbonates, polyurethanes, and the like. From the viewpoint of improving low-temperature fixability, polyester A and Polyesters other than B are preferred.

  In all polyesters in the binder resin (polyester A, polyester B, and polyesters other than polyester A and polyester B), the content of the adipic acid compound is the total amount of raw material monomers of each polyester, that is, the carboxylic acid component and the alcohol component. From the viewpoint of improving the initial image density characteristics of the toner in the total amount, it is preferably 1 mol% or more, more preferably 2 mol% or more, further preferably 2.5 mol% or more, further preferably 3 mol% or more, more preferably 4 mol% or more. Is more preferable. Further, from the viewpoint of improving the storage stability and high temperature offset resistance of the toner, it is preferably 20 mol% or less, more preferably 18 mol% or less, and further preferably 16 mol% or less. That is, taking these viewpoints together, 1 to 20 mol% is preferable, more preferably 2 to 20 mol%, still more preferably 2 to 18 mol%, still more preferably 2.5 to 16 mol%, and still more preferably 4 to 16 mol%. Mol%.

  The content of the adipic acid compound in all the polyesters can be determined by a weighted average value of the content of the adipic acid compound in each polyester as shown in Table 2 described later.

  The toner base particles of the present invention contain at least a colorant and a positively chargeable charge control agent in addition to the binder resin.

  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, Isoindoline, Disazo Yellow and the like can be used. 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 either black toner or color toner.

  Examples of positively chargeable charge control agents include nigrosine dyes such as “Nigrosine Base EX”, “Oil Black BS”, “Oil Black SO”, “Bontron N-01”, “Bontron N-04”, “Bontron N-07 ”,“ Bontron N-09 ”,“ Bontron N-11 ”(manufactured by Orient Chemical Co., Ltd.), etc .; triphenylmethane dyes containing tertiary amines as side chains; quaternary ammonium salt compounds such as“ Bontron ” “P-51”, “Bontron P-52” (manufactured by Orient Chemical Co., Ltd.), “TP-415” (manufactured by Hodogaya Chemical Co., Ltd.), cetyltrimethylammonium bromide, “COPYCHARGEPXVP435” (manufactured by Hoechst), etc. Positive charge control agents that are not polymer compounds such as imidazole derivatives such as “PLZ-2001” and “PLZ-8001” (manufactured by Shikoku Kasei Co., Ltd.) and polyamine resins such as “AFP-B” (Orient Chemical) Manufactured by Kogyo Co., Ltd.), etc. Emissions acrylic resin, for example, "FCA-201-PS" (manufactured by Fujikura Kasei Co., Ltd.) positively chargeable charge control agent of the polymer compounds such as (hereinafter referred to as positively chargeable charge control resin) and the like.

  The content of the positively chargeable charge control agent is preferably 0.3 parts by weight or more with respect to 100 parts by weight of the binder resin, from the viewpoint of making the charge amount of the toner appropriate, suppressing fogging and improving the solid followability, 1 part by weight or more is more preferable, and 2 parts by weight or more is more preferable. From the same viewpoint, the amount is preferably 20 parts by weight or less, more preferably 18 parts by weight or less, and further preferably 15 parts by weight or less with respect to 100 parts by weight of the binder resin. That is, taking these viewpoints together, the content of the positively chargeable charge control agent is preferably 1 to 20 parts by weight, more preferably 2 to 18 parts by weight, and more preferably 3 to 15 parts by weight with respect to 100 parts by weight of the binder resin. Part by weight is more preferred.

  The content of the positively chargeable charge control agent that is not a polymer compound is 1 to 100 parts by weight of the binder resin from the viewpoint of making the charge amount of the toner appropriate, suppressing fogging and improving solid followability. 10 parts by weight is preferred, 1.5 to 8 parts by weight is more preferred, and 2 to 6 parts by weight is even more preferred.

  In addition, the content of the positively chargeable charge control resin is 3 to 20 parts by weight with respect to 100 parts by weight of the binder resin from the viewpoint of making the toner charge amount appropriate, suppressing fogging and improving the solid followability. Is preferred, 4 to 12 parts by weight is more preferred, and 5 to 10 parts by weight is even more preferred.

  A positively chargeable charge control agent that is not a polymer compound may be used in combination with a positively chargeable charge control resin. In that case, the content of the positively chargeable charge control agent that is not a polymer compound is the same from the same viewpoint. 1 to 10 parts by weight, preferably 1.5 to 8 parts by weight, and more preferably 2 to 6 parts by weight with respect to 100 parts by weight of the binder resin. Further, from the same viewpoint, the content of the positively chargeable charge control resin is preferably 3 to 20 parts by weight, more preferably 4 to 15 parts by weight, and 5 to 10 parts by weight with respect to 100 parts by weight of the binder resin. Is more preferable. From the same viewpoint, the total content of the positively chargeable charge control agent and the positively chargeable charge control resin that is not a polymer type is preferably 4 to 20 parts by weight with respect to 100 parts by weight of the binder resin, 18 parts by weight is more preferred, 6-15 parts by weight is more preferred, and 7-12 parts by weight is even more preferred.

  Further, in the positively chargeable toner, a negatively chargeable charge control agent may be used in combination as long as the positive chargeability of the toner is not impaired, but the negatively chargeable charge control agent is preferably not included. Even if it is, it is preferably 1 part by weight or less, more preferably 0.5 part by weight or less, with respect to 100 parts by weight of the binder resin.

  The toner base particles of the present invention preferably further contain a release agent from the viewpoint of improving the low-temperature fixability, high-temperature resistance and low-temperature offset property of the toner, and widening the fixing temperature range.

  As the release agent, low molecular weight polypropylene, low molecular weight polyethylene, low molecular weight polypropylene polyethylene copolymer, aliphatic hydrocarbon wax such as microcrystalline wax, paraffin wax, Fischer-Tropsch wax and oxides thereof, carnauba wax, Examples include montan wax, sazol wax and their deoxidized wax, ester waxes such as fatty acid ester wax, fatty acids, higher alcohols, fatty acid metal salts and the like. These may be used alone or in admixture of two or more.

  The melting point of the release agent is preferably 60 to 160 ° C., more preferably 70 to 150 ° C., from the viewpoint of improving the low temperature fixability, high temperature resistance and low temperature offset property of the toner.

  The content of the release agent is 0.5% with respect to 100 parts by weight of the binder resin from the viewpoint of improving the low temperature fixability, high temperature resistance and low temperature offset property of the toner, and improving the dispersibility in the binder resin. -10 parts by weight is preferable, 1-7 parts by weight is more preferable, and 1.5-4 parts by weight is more preferable.

  The toner base particles of the present invention preferably contain an amide compound as a release agent from the viewpoint of further improving the image durability of the toner.

  The amide compound in the present invention is preferably an amide compound having 10 to 70 carbon atoms, more preferably an amide compound having 20 to 60 carbon atoms, and an amide compound having 30 to 50 carbon atoms from the viewpoint of improving the image durability of the toner. Is more preferable. Examples of the amide compound include fatty acid amide compounds and aromatic amide compounds. Among these, fatty acid amides are preferable from the viewpoint of improving the image durability of the toner. 6-30 are preferable, as for carbon number of the fatty acid group in fatty acid amide, 12-24 are more preferable, and 16-22 are more preferable. Moreover, as an amide compound in this invention, a monoamide compound, a bisamide compound, a polyamide compound etc. are mentioned, Among these, the bisamide compound is preferable from the same viewpoint. Therefore, fatty acid bisamide is more preferred.

  Examples of the fatty acid amide compound preferably used in the present invention include fatty acid monoamide compounds such as lauric acid amide, stearic acid amide, and hydroxy stearic acid amide, ethylene bis lauric acid amide, ethylene bis stearic acid amide, ethylene bishydroxy stearic acid amide, hexa Examples include fatty acid bisamide compounds such as methylene bis lauric acid amide and hexamethylene bis stearic acid amide. Of these, stearic acid amide, hydroxystearic acid amide, ethylene bisstearic acid amide, and ethylene bishydroxystearic acid amide are preferable, and ethylene bisstearic acid amide and ethylene bishydroxystearic acid amide are more preferable.

  The melting point of the amide compound is preferably 70 to 200 ° C., more preferably 90 to 180 ° C., from the viewpoint of improving the durability of the image quality of the toner.

  The content of the amide compound is determined from the viewpoint of improving the low temperature fixability and high temperature resistance and low temperature offset property of the toner, improving the image durability, and improving the dispersibility in the binder resin. 0.5-5 weight part is preferable with respect to weight part, and 1-3 weight part is more preferable.

  The toner base particles of the present invention further include magnetic powder, fluidity improver, conductivity modifier, extender pigment, reinforcing filler such as fibrous substance, antioxidant, anti-aging agent, cleaning improver, etc. Additives may be contained as appropriate.

  In the present invention, the toner base particles can be produced by a known method such as a kneading and pulverizing method, a spray drying method, or a polymerization method, but from the viewpoint of productivity and dispersibility of the colorant, the pulverized toner by the kneading and pulverizing method is used. Is preferred. Specifically, raw materials such as a binder resin, a colorant, a charge control agent, and a release agent are uniformly mixed with a mixer such as a Henschel mixer, and then a sealed kneader, a single or twin screw extruder, and an open The toner can be produced by melt-kneading with a roll-type kneader or the like, cooling, pulverizing, and classifying. On the other hand, from the viewpoint of reducing the particle size of the toner, a toner by a polymerization method is preferable.

The volume median particle size (D ₅₀ ) of the toner base particles is preferably 3.0 to 11 μm, more preferably 3.5 to 10 μm, and even more preferably 4 to 9 μm, from the viewpoint of reducing toner consumption and improving the image quality. .

  In the toner of the present invention, from the viewpoint of increasing the initial image density value and reducing the fluctuation range, that is, improving the initial image density characteristics, an external additive to which an external additive is further adhered after the toner pulverization and classification steps. It is obtained by processing and externally adding an external additive to the toner base particles.

  For mixing the pulverized material and the toner base particles obtained after the classification step and the external additive, it is preferable to use a stirrer having a stirrer such as a rotary blade, and a more preferable stirrer is a Henschel mixer. .

  The toner of the present invention preferably contains polytetrafluoroethylene particles as an external additive from the viewpoint of improving the initial image density characteristics of the toner.

  The primary average particle diameter of the polytetrafluoroethylene particles is preferably 100 nm or more, more preferably 200 nm or more, and even more preferably 300 nm or more from the viewpoint of imparting charge to the toner and improving the initial image density characteristics. In addition, from the viewpoint of improving the initial image density characteristics of the toner and suppressing in-machine contamination, 800 nm or less is preferable, 600 nm or less is more preferable, and 500 nm or less is more preferable. That is, taking these viewpoints together, the primary average particle size of the polytetrafluoroethylene particles is preferably from 100 to 800 nm, more preferably from 200 to 600 nm, and even more preferably from 300 nm to 500 nm.

  Examples of commercially available polytetrafluoroethylene particles having such an average particle size include “Lublon L2” (Daikin Industries, average particle size 0.3 μm), “Lublon L5F” (Daikin Industries, average particle size 200 nm). ), “KTL-500F” (manufactured by Kitamura Co., Ltd., average particle size 500 nm), and the like.

  The content of the polytetrafluoroethylene particles is preferably 0.05 parts by weight or more, more preferably 0.15 parts by weight or more, and more preferably 0.25 parts by weight with respect to 100 parts by weight of the toner base particles from the viewpoint of improving the initial image density characteristics of the toner. The above is more preferable. Further, from the viewpoint of improving the charging stability of the toner and improving the image quality such as fine line reproducibility, the amount is preferably 0.8 parts by weight or less, more preferably 0.6 parts by weight or less, and more preferably 0.45 parts by weight with respect to 100 parts by weight of the toner base particles. Part or less is more preferable. That is, taking these viewpoints together, the content of polytetrafluoroethylene particles is preferably 0.05 to 0.8 parts by weight, more preferably 0.15 to 0.6 parts by weight, and more preferably 0.25 to 0.45 parts by weight with respect to 100 parts by weight of the toner base particles. Part is more preferred.

  Further, the toner of the present invention can be used in combination with an external additive other than polytetrafluoroethylene particles. From the viewpoint of improving the initial image density characteristics of the toner, the content of polytetrafluoroethylene particles is In the additive, 1 to 50% by weight is preferable, 5 to 30% by weight is more preferable, and 10 to 25% by weight is further preferable.

  Other external additives include inorganic substances such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide from the viewpoints of improving the fluidity of the toner, improving the charging stability, and improving the initial density of the toner. Examples thereof include fine particles and organic fine particles such as resin fine particles other than polytetrafluoroethylene particles. Among these, from the same viewpoint, it is preferable to use silica together, and it is more preferable to use silica having an average particle diameter of less than 20 nm and silica having a particle diameter of 20 nm or more. When two types of silica are used in combination, the difference in average particle diameter is preferably 10 nm or more. In addition, in this invention, the average particle diameter of a silica is measured by the method as described in the below-mentioned Example.

  The softening point of the toner is preferably 115 ° C. or higher, more preferably 120 ° C. or higher, and further preferably 130 ° C. or higher from the viewpoint of improving the storage stability and high temperature offset resistance of the toner and improving the image quality durability. Further, from the viewpoint of improving the low-temperature fixability and low-temperature offset resistance of the toner, 155 ° C. or lower is preferable, 150 ° C. or lower is more preferable, and 140 ° C. or lower is further preferable. That is, taking these viewpoints together, the softening point of the toner is preferably 115 to 155 ° C, more preferably 120 to 150 ° C, and further preferably 130 to 140 ° C.

  The glass transition point of the toner is preferably 40 ° C. or higher, more preferably 45 ° C. or higher, and further preferably 50 ° C. or higher, from the viewpoint of improving the storage stability and high-temperature offset resistance of the toner and improving the image quality durability. More preferably, the temperature is 53 ° C. or higher. Further, from the viewpoint of improving the low-temperature fixability and low-temperature offset resistance of the toner, it is preferably 65 ° C. or lower, more preferably 63 ° C. or lower, still more preferably 62 ° C. or lower, further preferably 60 ° C. or lower, and further preferably 58 ° C. or lower. preferable. That is, when these viewpoints are put together, 40-65 degreeC is preferable, 45-63 degreeC is more preferable, 50-62 degreeC is further more preferable, 50-60 degreeC is further more preferable, 53-58 degreeC is further more preferable.

  The positively chargeable toner of the present invention is used as a one-component developing toner as it is or as a two-component developing toner used by mixing with a carrier in any one of the one-component developing method and the two-component developing method. be able to.

  The positively chargeable toner of the present invention is used in an image forming apparatus for positively chargeable toner. In particular, it is preferably used in an image forming apparatus equipped with a cleaner-less development system because it has excellent chargeability and transferability. Therefore, the present invention can provide an image forming method using the toner and the image forming apparatus for positively chargeable toner, particularly the image forming apparatus for positively chargeable toner having the cleanerless developing system.

[Softening point of resin and toner (Tm)]
Using a flow tester (Shimadzu Corporation, CFT-500D), a 1 g sample was heated at a heating rate of 6 ° C / min, and a 1.96 MPa load was applied by a plunger and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. . 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.

[Glass transition point (Tg) of resin and toner]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), 0.01 to 0.02 g of the sample was weighed into an aluminum pan, heated up to 200 ° C, and from that temperature to -10 ° C at a cooling rate of 10 ° C / min. Until cooled. Next, the sample was heated at a heating rate of 10 ° C./min and measured. The glass transition point is defined as the temperature at the intersection of the base line extension below the maximum peak temperature of endotherm and the tangent line indicating the maximum slope from the peak rising portion to the peak apex.

(Resin acid value (AV))
Measured by the method of JIS K0070. However, only the measurement solvent is changed from the mixed solvent of ethanol and ether specified in JIS K0070 to the mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

(Resin weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight peak (Mp))
The molecular weight distribution is measured by the gel permeation chromatography (GPC) method according to the following method, and the weight average molecular weight, number average molecular weight and molecular weight peak are determined.
(1) Preparation of sample solution Dissolve the sample in tetrahydrofuran at 25 ° C so that the concentration is 0.5 g / 100 ml. Next, this solution is filtered using a fluororesin filter having a pore size of 0.2 μm (manufactured by ADVANTEC, DISMIC-25JP) to remove insoluble components to obtain a sample solution.
(2) Molecular weight measurement Using the following measuring device and analytical column, tetrahydrofuran is flowed as an eluent at a flow rate of 1 ml / min, and the column is stabilized in a constant temperature bath at 40 ° C. Measurement is performed by injecting 100 μl of the sample solution. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. At this time, several types of monodisperse polystyrene (A-500 (5.0 × 10 ² ), A-1000 (1.01 × 10 ³ ), A-2500 (2.63 × 10 ³ ), A- 5000 (5.97 × 10 ³ ), F-1 (1.02 × 10 ⁴ ), F-2 (1.81 × 10 ⁴ ), F-4 (3.97 × 10 ⁴ ), F-10 (9.64 × 10 ⁴ ), F- 20 (1.90 × 10 ⁵ ), F-40 (4.27 × 10 ⁵ ), F-80 (7.06 × 10 ⁵ ), F-128 (1.09 × 10 ⁶ )) prepared as standard samples are used.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: GMHXL + G3000HXL (manufactured by Tosoh Corporation)

(Storage modulus of resin (G '))
The measurement is performed using a viscoelasticity measuring device (rheometer) ARES (manufactured by TA) (Strain: 0.05%, frequency: 6.28 rad / sec). The measurement equipment conditions are set as follows. A 25mm diameter parallel plate is heated / left at 140 ° C, and the sample is melted at 140 ° C and placed on the parallel plate so that the gap is 1.5-2.5mm. After cooling, heat up to 180 ° C at 5 ° C / min and determine the storage elastic modulus at 150 ° C. Specifically, the measurement device is set as follows.

AutoTension Adjustment = On
Mode = Apply Constant Static Force
AutoTension Direction = Compression
Initial Static Force = 10.0 [g]
AutoTension Sensitivity = 10.0 [g]
When Sample Modulus <= 100.0 [Pa]
AutoTension Limits = Default
Max Autotension Displacement = 3.0 [mm]
Max Autotension Rate = 0.01 [mm / s]
AutoStrain = On
Max Applied Strain = 20.0 [%]
Max Allowed Torque = 300.0 [g-cm]
Min Allowed Torque = 1.0 [g-cm]
Strain Adjustment = 20.0 [% of Current Strain]
Strain Amplitude Control = Default Behavior
Limit Minimum Dynamic Force Used = No
Minimum Applied Dynamic Force = 1.0 [gmf]

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

[Volume Median Particle Size (D ₅₀ ) of Toner Base Particles]
Measuring machine: Coulter Multisizer II (Beckman Coulter, Inc.)
Aperture diameter: 50μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) is dissolved in the electrolyte so as to have a concentration of 5% by weight.
Dispersion conditions: 10 mg of a measurement sample was added to 5 ml of the dispersion, and dispersed for 1 minute with an ultrasonic disperser, then 25 ml of the electrolyte was added, and further dispersed for 1 minute with an ultrasonic disperser. Prepare sample dispersion.
Measurement conditions: The dispersion is added to 100 ml of the electrolyte so that the particle size of 30,000 particles can be measured in 20 seconds, and 30,000 particles are measured. Determine the unit particle size (D ₅₀ ).

[Average particle diameter of external additive]
The average particle size refers to the average primary particle size, and the particle size (average value of major axis and minor axis) of 500 particles is measured from a scanning electron microscope (SEM) photograph, and the average value is referred to as the average particle size. To do.

Resin production example 1
Raw material monomers other than trimellitic anhydride shown in Table 1 and 20 g of 2-ethylhexanetin (II) as an esterification catalyst, 4 liters of 10 liters equipped with nitrogen introduction tube, dehydration tube, stirrer and thermocouple The flask was put into a flask, reacted at 235 ° C. for 7 hours under a nitrogen atmosphere, and then reacted at 8.3 kPa for 1 hour. Thereafter, the mixture was cooled to 210 ° C., trimellitic anhydride was added, reacted at normal pressure for 1 hour, reacted at 8.3 kPa, and when the desired softening point was reached, the reaction was terminated. Polyesters (resins A1 to A3, B1, B2, C1, C2, C4) having the physical properties shown in FIG.

Resin production example 2
As shown in Table 1, raw material monomers other than fumaric acid and trimellitic anhydride, and 20 g of 2-ethylhexanetin (II) as an esterification catalyst, equipped with a nitrogen inlet tube, a dehydrating tube, a stirrer, and a thermocouple The flask was put into a four-necked flask, heated to 235 ° C. in a nitrogen atmosphere, reacted for 5 hours, and then reacted at 8.3 kPa for 1 hour. Then, it cooled to 180 degreeC, the fumaric acid and trimellitic anhydride were thrown in, and it heated up from 180 degreeC to 210 degreeC over 4 hours. Thereafter, the reaction was carried out at 8.3 kPa, and when the softening point reached 122 ° C., the reaction was terminated to obtain a polyester (resin C3) having the physical properties shown in Table 1.

Examples 1-11 and Comparative Examples 1-7
100 parts by weight of binder resin shown in Table 2, 3.0 parts by weight of positively chargeable charge control agent “Bontron N-04” (Orient Chemical Co., Ltd.), positively chargeable charge control resin “FCA-201-PS” (Fujikura Kasei) 6.0 parts by weight, carbon black "REGAL 330R" (Cabot Specialty Chemicals, Inc.) 5.0 parts by weight, and release agent "Mitsui High Wax NP055" (Mitsui Chemicals, polypropylene wax, melting point: 140 parts) 1.5 parts by weight and release agent “Kao Wax EB-P” (made by Kao Corporation, ethylenebis stearamide, melting point: 144 ° C.) into a 75 L Henschel mixer (Mitsui Mining Co., Ltd.) After stirring and mixing for 1 minute, the mixture was melt kneaded using a twin screw extruder “PCM-45” (manufactured by Ikegai Co., Ltd.).

The resulting melt-kneaded product is coarsely pulverized with a pulperizer (manufactured by Hosokawa Micron), pulverized and classified with an IDS pulverizer (manufactured by Nippon Pneumatic Co., Ltd.), and the volume-median particle size (D ₅₀ ) is 7.6 μm. The positively charged toner base particles were obtained.

  100 parts by weight of the obtained toner base particles and a predetermined amount of external additive shown in Table 2, hydrophobic silica “TG-7120” (manufactured by Cabot Specialty Chemicals Inc., average particle size: 16 nm) 0.7 weight Part and hydrophobic silica “NA-50Y” (Nippon Aerosil Co., Ltd., average particle size: 40 nm) 1.0 part by weight in a 10 L Henschel mixer (Mitsui Mining Co., Ltd.) at 2500 r / min for 3 minutes, Obtained.

Test Example 1 [low temperature fixability]
The printer “HL-2040” manufactured by Brother Industries, modified to take unfixed images, is filled with toner and printed with a 2cm square solid unfixed image. The oilless fixing method “DL-2300” (Konica Fix by 5 ° C from 100 ° C to 230 ° C with an external fixing device (manufactured by Minolta Co., Ltd.) modified (fixing roll rotation speed set to 265mm / sec and variable fixing roller temperature in the fixing device) While increasing the temperature, this unfixed image was fixed at each temperature to obtain a solid image. The image obtained at each fixing temperature is rubbed 5 times with sand eraser under a load of 500 g. The image density ratio before and after rubbing (after rubbing / before rubbing x 100) first exceeds 90% at the minimum fixing temperature. And low-temperature fixability was evaluated. The results are shown in Table 3.

Test Example 2 [Offset resistance]
The printer “HL-2040” manufactured by Brother Industries, modified to take unfixed images, is filled with toner and printed with a 2cm square solid unfixed image. The oilless fixing method “DL-2300” (Konica Fix the temperature of the fixing roll from 80 ° C to 230 ° C with a modified external fixing device (manufactured by Minolta Co., Ltd.) (fixing roll rotation speed is set to 265mm / sec and the fixing roll temperature in the fixing device is variable) The unfixed image was fixed at each temperature while increasing the temperature by 5 ° C., and a solid image was produced. After the solid image was printed at each temperature, the white paper was continuously passed through the fixing roll, and the temperature at which the toner stain occurred before the toner stain disappeared on the white paper was defined as the low temperature offset generation temperature. Further, the temperature of the fixing roll was further raised, and the temperature at which the toner stain occurred on the white paper was defined as the high temperature offset occurrence temperature. The results are shown in Table 3.

Test Example 3 [Fixing temperature range]
The fixing temperature region was determined for the examples and comparative examples having a minimum fixing temperature of 145 ° C. or lower. The difference between [low temperature offset generation temperature + 5 ° C.] and the minimum fixing temperature, whichever is higher, and [high temperature offset generation temperature−5 ° C.] was defined as a fixing temperature region. The results are shown in Table 3.

Test Example 4 [Charge amount]
After filling the printer “HL-2040” with a cleaner-less development system with toner and printing the entire surface, use the TR / MDEL 210HS q / m meter on the development roll. The toner was sucked at 10 locations, the charge and the unit mass of the toner were measured, and the charge amount (μC / g) was calculated. The results are shown in Table 3.

Test Example 5 [Fog]
A Brother Industries printer “HL-2040” equipped with a cleaner-less development system was filled with toner, and 5,000 images with a printing rate of 1% were printed on each page for 20 seconds intermittently. A white solid image was printed every 1000 sheets, and the power was turned off halfway. The toner on the surface of the photoconductor is attached to the mending tape, the color density is measured with an image density measuring instrument “SPM-50” (Gretag), and the difference from the color density of the tape before the toner is applied is determined. The average of five measurements from the 1000th sheet to the 5000th sheet was obtained. As the value is smaller, the fog is suppressed. The results are shown in Table 3.

Test Example 6 [solid follow-up performance]
A Brother Industries printer “HL-2040” equipped with a cleaner-less development system was filled with toner, and 10000 images with a printing rate of 1% were printed on one page for 20 seconds intermittently. At that time, a solid image was printed every 1000 sheets printed, the obtained image was visually observed, and the evaluation was performed by the number of sheets where the blur was observed for the first time. The larger the value, the better the solid followability. In addition, when no blur was observed on the 10000th sheet, it was set as 10000 <. The results are shown in Table 3.

Test Example 7 [Initial image density characteristics]
A Brother Industries printer “HL-2040” equipped with a cleaner-less development system was charged with toner, and 100 images with a printing rate of 1% were printed on one page for 20 seconds intermittently. At that time, every 1st, 10th, 20th, 50th, and 100th prints, a solid image of 2cm x 2cm square was printed, and the obtained image was used as an image density measuring instrument `` SPM-50 '' ( The image density was measured by Gretag). Further, the difference between the measured maximum value and the minimum value of the image density at the five points was defined as the fluctuation range. The larger the image density value and the smaller the fluctuation range value, the better the initial image density characteristics. The results are shown in Table 4.

From the above results, the toners of Examples 1 to 11 are excellent in low-temperature fixability and offset resistance, have a wide fixing temperature range, suppress the occurrence of fogging and solid followability, and further, the fluctuation range of the initial image density. It is clear that the initial image density characteristics are excellent. In particular, the toners of Examples 1 and 2 and 7 to 11 containing 200 to 800 nm of polytetrafluoroethylene as an external additive have high initial image density values and excellent initial image density characteristics.
On the other hand, in the toners of Comparative Examples 1 to 3 in which the softening point, glass transition point, and weight average molecular weight of the two polyesters are not within the predetermined ranges, the toner of Comparative Example 1 is inferior in the minimum fixing temperature and the low temperature offset occurrence temperature. The toners of Examples 2 and 3 are inferior in high temperature offset generation temperature, charge amount, fog, and solid followability, have a small initial image density value, a large fluctuation range, and inferior initial image density characteristics.
Although the softening point and glass transition point of the two polyesters are in the predetermined ranges, the toners of Comparative Examples 4 to 7 that do not contain adipic acid as the carboxylic acid component of polyester A have a small initial density value and a large fluctuation range. The initial image density characteristics are inferior.

  The positively chargeable toner of the present invention is used for development of a latent image formed in electrophotography, electrostatic recording method, electrostatic printing method and the like.

Claims (6)

  A positively chargeable toner comprising a binder resin containing two kinds of polyesters having different softening points of 10 ° C. or more, a toner base particle containing a colorant and a positively chargeable charge control agent, and an external additive, Two types of polyesters have a softening point of 105-140 ° C, a glass transition point of 30-55 ° C, a weight average molecular weight of 10,000-45,000, a softening point of 140-170 ° C, and a glass transition point of 55 ° C. A positively chargeable toner which is a polyester B having a weight average molecular weight of 45,000 to 150,000 exceeding 80 ° C., and wherein the polyester A is a polyester obtained by condensation polymerization of a carboxylic acid component containing an adipic acid compound and an alcohol component.   The positively chargeable toner according to claim 1, wherein a difference in glass transition point between polyester A and polyester B is 5 to 40 ° C.   The positively chargeable toner according to claim 1, wherein the polyester A is a polyester containing 15 to 60 mol% of an adipic acid compound in the carboxylic acid component of the raw material monomer.   The positively chargeable toner according to claim 1, wherein the weight ratio of polyester A to polyester B (polyester A / polyester B) is 10/90 to 80/20.   The positively chargeable toner according to claim 1, wherein the external additive contains polytetrafluoroethylene having an average primary particle size of 100 to 800 nm.   The positively chargeable toner according to claim 1, wherein the content of the positively chargeable charge control agent is 1 to 20 parts by weight with respect to 100 parts by weight of the binder resin.