JPH08234483A - Toner for electrostatic charge development and image forming system using the same - Google Patents

Abstract

PURPOSE: To obtain a toner excellent in anti-offsetting property even when the dispersibility of a colorant is improved by high shear at the time of kneading because of superior kick-off of electrostatic charge and not causing fogging or contaminating the interior of a machine even in the case of recycling in a large quantity. CONSTITUTION: This toner contains a polyester resin having 300-700mgKOH/g saponification value and 30-80mgKOH/g acid value and contg. 0.5-20wt.% chloroform-insoluble component, a colorant and inorg. fine particles having 5-50nm vol. average primary particle diameter as an additive. The inorg. fine particles have free aggregates of >=47μm size, those of 20 to <47μm size and those of 2 to <20μm size by <=0.05%, 0.01-0.1% and <=1.0% of the weight of this toner, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for electrostatic charge development and a toner image forming system, and in particular, it is effective when used in a two-component reversal developing toner image forming system for performing image gradation correction control and toner recycling. And a toner for developing electrostatic charge.

[0002]

2. Description of the Related Art Recent trends in electrophotographic copying machines and printers are toward higher image quality and higher durability. As one of the means for achieving high image quality, a patch for checking the relationship between the exposure amount and the image density is formed on the photoconductor at the time of warming up or at a certain copy number, and based on the relationship, There is a system that maintains stable gradation by performing image gradation correction that adjusts the exposure amount to correct gradation. In this case, it is desirable to collect and reuse the patch image formed on the photoconductor without transferring it, because the toner consumption amount can be reduced, but since the amount of toner recycled is large, the charging start-up does not occur. It becomes worse, causing fogging and dirt inside the machine.

In the conventional electrostatic charge developing toner, the dispersibility of the colorant is aimed to be improved in order to improve the charge rising. For example, JP-A-1-137267 and 1-304467.
In No. 6, in the melt-kneading step, a high shearing force is applied to the binder resin to improve the dispersibility of the colorant. However, in such a method, the molecular chain of the binder resin is cut and a decrease in molecular weight occurs, It may cause a problem in offset performance.

[0004]

SUMMARY OF THE INVENTION The present invention has been made under the above circumstances, and an object thereof is to provide an offset even if the dispersibility of a colorant is improved by high shear at the time of kneading because of excellent charging rise. It is to provide a toner that has excellent performance and does not cause fog or stain inside the machine even if it is recycled in a large amount.

[0005]

The above object of the present invention is to provide a saponification number of 300 to 700 (KOHmg / g) and an acid number of 30 to 80 (KOHmg / g).
g), chloroform insoluble content of 0.5 to 20% by weight of polyester resin, colorant, and free aggregate amount of 47 μm or more is 0.05% or less with respect to toner weight, and 20 μm or less and less than 47 μm with respect to toner weight. 0.01-0.1%, 2
A toner for electrostatic charge development containing an inorganic fine particle external additive having a volume average primary particle diameter of 5 to 50 nm, which is 1.0% or less with respect to the number of toner and is not less than 20 μm, and to a charged photoconductive photoreceptor. A toner image forming system having a process of forming a toner image using the toner and the carrier when the charge is removed by exposure, performing image gradation correction control, and collecting and reusing the toner on the photoconductor, Achieved by

The present invention will be described in detail below.

<< Saponification Value and Acid Value of Polyester Resin >> The saponification value of the polyester resin according to the present invention is 300 to 700 (KOHm
g / g), preferably 400 to 600 (KOHmg / g). The acid value is 30 to 80 (KOHmg / g), preferably 40 to 70 (KOHmg / g).

Here, the saponification value refers to the number of milligrams of potassium hydroxide necessary for saponifying 1 g of the sample, and the acid value neutralizes the acid (carboxyl group existing at the molecular end) contained in 1 g of the sample. Says the number of milligrams of potassium hydroxide needed to. In the present invention, JISK0070 is used.
It shall be measured in accordance with.

Those having a large saponification value and acid value as defined in the present invention have a relatively large content of polar groups (ester bonds in the molecule or carboxyl groups present at the ends of the molecule). Therefore, the toner containing such a polyester resin as a binder resin has (1) a large dielectric constant and excellent charging characteristics (high charging speed), (2) a large cohesive force of the binder resin, and anti-offset properties. Excellent in
(3) The binder resin has a high affinity with the transfer material and is excellent in low-temperature fixability.

When the saponification value of the polyester resin is less than 300, the characteristics described in the above (1) to (3) cannot be imparted, and 70
When it exceeds 0, the polyester resin easily adsorbs water, and therefore when this is used as a binder for the toner, the charge holding power under high temperature and high humidity is deteriorated and the chargeability is apt to be deteriorated.

If the acid value of the polyester resin is less than 30, the properties described in the above (1) to (3) cannot be imparted.
When it exceeds 80, the polyester resin also easily adsorbs water, and therefore when this is used as a binder for the toner, the charge holding power under high temperature and high humidity becomes poor and the chargeability is apt to deteriorate.

<< Chloroform-insoluble matter of polyester resin >> The proportion of chloroform-insoluble matter of the polyester resin according to the present invention is 0.5 to 20% by weight, preferably 1.0 to 15% by weight.

Here, the chloroform-insoluble matter means a filter-paper-impermeable matter when a sample is dissolved in chloroform, and is obtained as follows.

The resin sample was finely pulverized, and 5.00 g of the sample powder that passed through a 40-mesh sieve was collected and placed in a container having a capacity of 150 ml together with 5.00 g of the filter aid Radiolite (# 700), and chloroform was placed in this container. Inject 100 g, place on a ball mill stand and rotate for 5 hours or more to sufficiently dissolve the sample in chloroform. On the other hand, the pressure filter has a diameter of 7 cm.
Filter paper (No. 2) was placed on it, 5.00 g of radiolite was uniformly precoated on it, and a small amount of chloroform was added to bring the filter paper into close contact with the filter, and then the contents of the container were filtered. Pour inside. Further, the container is thoroughly washed with 100 ml of chloroform and poured into a filter so that the deposits do not remain on the container wall. Then, the upper lid of the filter is closed and filtration is performed. Filtration is performed under a pressure of 4 kg / cm ² or less, and after the outflow of chloroform is stopped, 100 ml of chloroform is added to wash the residue on the filter paper, and pressure filtration is performed again. After the above operation is completed, put the filter paper, the residue on it, and the radiolite all on the aluminum foil and put it in the vacuum dryer. Temperature 80 ~ 100 ℃, pressure 100mm
After drying for 10 hours under the condition of Hg, the total weight a (g) of the dried product thus obtained is measured, and the chloroform insoluble matter x (% by weight) is determined by the following formula.

[0015]

[Equation 1]

When a polyester resin having a chloroform insoluble content of 0.5% by weight or more is used as a binder resin for the toner, the dispersibility of additives such as colorants is markedly improved.
Further, for example, by improving the dispersibility of the colorant such as carbon black, uneven distribution of the colorant is prevented, the surface state and the internal state of the toner are made uniform, and excellent charging characteristics are exhibited. It is possible to reliably prevent the occurrence of scattering.

Although it is not clear how the weight ratio of the chloroform-insoluble component affects the dispersibility of the additive, when the high-molecular-weight component that is the chloroform-insoluble component is present in a certain proportion or more, It can be presumed that the dispersibility is improved by crushing the aggregates of the additive due to the large shearing force of the resin containing the high molecular weight component during the kneading.

If the proportion of chloroform-insoluble matter in the polyester resin is less than 0.5% by weight, the dispersibility of the additive cannot be improved, and when it is used in the binder resin of the toner, for example, charging due to poor dispersion of the colorant is caused. It is easy to cause a decrease in amount (fogging and toner scattering). On the other hand, if the proportion of the chloroform-insoluble matter exceeds 20% by weight, the colorant is less likely to be distributed to the highly cross-linked chloroform-insoluble matter portion, and the dispersibility of the colorant is rather uneven.

[0019] "softening point of the polyester resin (T _sp)" softening point of the polyester resin employed in the present invention (T _sp) is 95
It is preferably ˜170 ° C. If T _sp is too small, the offset resistance of the toner decreases, and if T _sp is too large, the low temperature fixability of the toner tends to deteriorate. Here, T _sp is an elevated flow tester CFT-500 type (manufactured by Shimadzu Corporation), and measurement conditions are as follows: load 20 kg / cm ² , nozzle length 1 m.
m, preheating at 80 ° C for 10 minutes, heating rate of 6 ° C / min, sample amount of 1 cm ³ (weight expressed as true specific gravity × 1 cm ³ ) and recorded, flow plunger plunger drop-temperature The height of the S-shaped curve in the curve (softening flow curve) is h, and the temperature is h / 2.

<< Glass Transition Point of Polyester Resin (T
g) >> The glass transition point (Tg) of the polyester resin used in the present invention is preferably 50 to 80 ° C. If the Tg is too small, the blocking resistance and hot offset resistance of the toner will decrease, and if it is too large, the low temperature fixability of the toner will tend to deteriorate. Here, Tg is 3 at 100 ° C. using a differential scanning calorimeter DSC (manufactured by Seiko Denshi Kogyo Co., Ltd.).
After being left for a minute, a sample cooled to room temperature at a temperature lowering rate of 10 ° C./min was measured at a temperature rising rate of 10 ° C./min, and a baseline extension line below the glass transition point of the DSC thermogram in the glass transition region was used. It is the temperature at the intersection with the tangent line showing the maximum slope between the rising portion of the peak and the apex of the peak.

<< Molecular Weight of Polyester Resin >> Further, the polyester resin employed in the present invention has a weight average molecular weight M _{w of} tetrahydrofuran (THF) -soluble component of 10,000 to 5
0,000, number average molecular weight _Mn is 2,000 to 6,000, _Mw / _Mn is 4
It is preferably in the range of -12. M _w , M _n , M _w / M _n
If it is too small, the hot offset resistance tends to deteriorate, and if it is too large, the low temperature fixability tends to deteriorate. The molecular weight of the THF-soluble component is the value determined by gel permeation chromatography in light of a calibration curve obtained by using monodisperse standard polystyrene.

<< Synthesis of Polyester Resin >> The monomer used for synthesizing the polyester resin according to the present invention is (a) a divalent alcohol monomer constituting a main chain which is a basic skeleton of polyester. And a divalent carboxylic acid monomer, (b) a polyhydric alcohol monomer having a valence of 3 or more and / or a polyhydric alcohol having a valence of 3 or more, which is involved in the non-linearization (formation of a side chain / crosslinked structure) of the polyester Examples thereof include carboxylic acid monomers. Further, if necessary, a monomer other than (b) may be used in combination according to (a).

Examples of the dihydric alcohol monomer in the above (a) include polyoxypropylene (2,2) -2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene (3,3)-. 2,2-bis (4-hydroxyphenyl) propane,
Polyoxyethylene (2,0) -bis (4-hydroxyphenyl)
Propane, polyoxypropylene (2,0) -polyoxyethylene (2,0) -2,2-bis (4-hydroxyphenyl) propane,
Polyoxypropylene (6) -2, etherified bisphenols such as 2-bis (4-hydroxyphenyl) propane, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1, 4-butanediol, 1,4-butenediol, neopentyl glycol, 1,5-pentanediol,
Examples thereof include 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A, hydrogenated bisphenol A and the like.

Examples of the divalent carboxylic acid monomer in (a) include maleic acid, fumaric acid, citraconic acid,
Itaconic acid, glutaconic acid, phthalic acid, isophthalic acid,
Terephthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid, isododecenyl succinic acid,
Examples thereof include n-octyl succinic acid, n-octenyl succinic acid, anhydrides or lower alkyl esters of these acids, and the like.

Examples of the trihydric or higher polyhydric alcohol monomer in (b) include, for example, sorbitol, 1,2,3,5-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripenta. Erythritol, 1,2,4-butanetriol, 1,2,5-pentatriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1 Examples include 3,3,5-trihydroxymethylbenzene and the like.

Examples of the trivalent or higher polyvalent carboxylic acid monomer in (b) include 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid and 1,2,4-naphthalenetricarboxylic acid. Acid, 1,2,4-butanetricarboxylic acid, 1,2,
5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxylic) methane, 1,2,7,8-octanetetra Examples thereof include carboxylic acid, pyromellitic acid, enpol trimer acid, anhydrides or lower alkyl esters of these acids, and the like.

The method for producing the polyester resin according to the present invention is not particularly limited, but it is preferable to produce the polyester resin according to the following conditions because the saponification value, the acid value and the ratio of chloroform-insoluble matter are controlled within a certain range. .

The polyester resin according to the present invention is 300 KOH
It is a resin having a large saponification value of mg / g or more and a high content of ester bonds, and in order to synthesize such a resin, it is necessary to synthesize it from a monomer having a relatively small molecular weight.

Further, the polyester resin according to the present invention is 30
A resin having an acid value of KOHmg / g or more, and in order to synthesize such a resin, in the alcohol monomer and the carboxylic acid monomer, the ratio of the carboxylic acid monomer (the ratio as a functional group) Should be increased.

From the viewpoint of controlling the saponification value and the acid value,
When the amount of monomer in the polymerization reaction system decreases due to scattering, sublimation, etc., it is preferable to carry out the reaction while successively replenishing the polymerization reaction system with a monomer corresponding to the decrease amount.

The proportion of chloroform-insoluble matter in the polyester resin according to the present invention is 0.5 to 20% by weight, and the following conditions are preferable for synthesizing such a resin.

The proportion of chloroform-insoluble matter can be controlled by adjusting the cooling rate of the product (polyester) after the termination of the conditional reaction.

The ratio of the chloroform-insoluble matter can be controlled by adjusting the ratio of the polyvalent monomer having a valence of 3 or more ((ii)). In order to set the ratio of chloroform insolubles to the range of 0.5 to 20% by weight, the ratio of trivalent or higher polyvalent monomers used should be 1 to 15 mol%, although it may vary depending on other synthesis conditions. preferable.

The polyvalent monomer having a valence of 3 or more may be added to the reaction system together with the divalent monomer ((a) above) to carry out the polymerization reaction. The number average molecular weight
After synthesizing a linear polyester of about 300 to 1400, add a polyvalent monomer having a valence of 3 or more to this system to cause a polymerization reaction between the linear polyester and the polyvalent monomer. You can also

<< Toner for Electrostatic Charge Development >> The toner of the present invention comprises the above polyester resin, a colorant, and an amount of free agglomerates of 47 μm or more of 0.05% or less with respect to the toner weight,
Less than 47μm 0.01 ~ 0.1% to toner weight
And 2% or more and less than 20 μm contains 1.0% or less of the number of toner particles and an inorganic fine particle external additive having a volume average primary particle diameter of 5 to 50 nm.

In the toner of the present invention, for the purpose of further improving the charging characteristics by further increasing the charging speed,
The amount of free aggregates of 47 μm or more is 0.05% of the toner weight.
Or less, preferably 0.005% or more and 20 μm or less 47
If it is less than μm, it is 0.01 to 0.1% of the toner weight, and if it is 2 μm or more and less than 20 μm, it is 1.
Inorganic fine particles of 0% or less, preferably 0.3% or more and having a volume average primary particle diameter of 5 to 50 nm are externally added.

The specific surface area of the inorganic fine particles by the BET method is 40
200 m ² / g is preferable, it is preferable mixing ratio of the inorganic fine particles is 0.05 to 5.0 wt% of the total toner.

Examples of the inorganic fine particles include silica, alumina, titanium oxide and the like. Among these, silica fine particles are preferable, and silica fine particles whose surface is hydrophobized are particularly preferable.

The inorganic fine particle external additive has an amount of free agglomerates of 47 μm or more of 0.05% or less based on the weight of the toner, and 20 μm or more of 4
If it is less than 7 μm, it is 0.01 to 0.1% of the toner weight, and if it is 2 μm or more and less than 20 μm, it is 1.
Toner that is present at 0% or less is relatively coarse (20
Since the inorganic fine particle agglomerates (μm or more and less than 47 μm) are contained in a free state, new inorganic fine particles are always replenished by loosening the agglomerates when stirred in the developing device. Therefore, even if the inorganic fine particles are buried, the fluidity does not decrease, and a stable charging rise is exhibited. 20 μm or more 47 μm
If the amount of free aggregates is less than 0.01% by weight, a stable charging start-up effect cannot be expected, and if it is more than 0.1% by weight, the change in the amount of charging becomes large. Further, when the amount of free aggregates of 47 μm or more is more than 0.05% by weight, the photoconductor is easily scratched, and when the amount of free aggregates of 2 μm or more and less than 20 μm is more than 1.0% by number, the filming layer is formed on the photoconductor. Are easily formed, and an error occurs on the image.

The colorant is not particularly limited, and conventionally used ones such as carbon black, nigrosine dye (CI No. 50415B), aniline blue (CI).
No.50405), Calco Oil Blue (CINo.azoic Blue
3), Chrome Yellow (CINo.14090), Ultramarine Blue (CINo.77103), DuPont Oil Red (C.
I.No.26105), quinoline yellow (CINo.47005), methylene blue chloride (CINo.52015), phthalocyanine blue (CINo.74160), malachite green (C.
I.No.42000), lamp black (CINo.77266), rose bengal (CINo.45435), a mixture of these, and others can be used, and 1 to 2 per 100 parts by weight of the binder resin.
It is preferable to use 0 parts by weight.

Further, if necessary, a low molecular weight polyolefin such as low molecular weight polyethylene or low molecular weight polypropylene, preferably a low molecular weight polyolefin having a softening point of 70 to 150 ° C., more preferably 120 to 150 ° C. by a ring and ball method, etc. And other additives may be contained.

The addition of the low molecular weight polyolefin further improves the offset resistance, and it may be contained in an amount of 1 to 10 parts based on 100 parts by weight of the binder resin.

An example of the method for producing the toner of the present invention is as follows: a binder resin component containing the above polyester resin;
By premixing the colorant, the low molecular weight polyolefin, and various other additives that are added as necessary, this mixed system is melt-kneaded, cooled, coarsely pulverized, finely pulverized, and then classified to obtain a desired mixture. A toner in the form of particle powder having a particle size is obtained.
Then, the inorganic fine particles are externally added to the toner with a mixer such as a Henschel mixer. The toner particle size is about 5 to 20 μm,
4 to 10 μm is particularly preferable in that high image quality can be obtained.

[0044]

The present invention will be described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto.

Example 1 << Synthesis of Polyester >>

[0046]

[Table 1]

In accordance with the formulation shown in Table 1, each of the dialcohol monomer, dicarboxylic acid monomer and tricarboxylic acid monomer was charged with a thermometer, a stainless steel stirrer, a glass nitrogen inlet tube and a flow-down condenser. 2l capacity
In a 4-necked flask, set this flask in a mantle heater, and introduced nitrogen gas from a glass nitrogen gas introduction tube to raise the temperature to 220 ° C. while keeping the inside of the reactor in an inert atmosphere. The polymerization reaction was carried out with stirring. When the amount of the monomer decreased due to scattering, sublimation, etc., the amount of the monomer corresponding to the decreased amount was replenished in the flask. The reaction system was appropriately sampled to measure the acid value, and the reaction was stopped when a predetermined acid value (shown in Table 2) was reached, and the reaction product was taken out from the flask into a vat.
It cooled to room temperature and each polyester (this invention polyester A-C and comparative polyester ac) was obtained. The saponification value and softening point (Ts
p), the glass transition point (Tg) and the proportion of chloroform insoluble matter were measured. Table 2 shows the results.

[0048]

[Table 2]

<< Production of Toner A >> 100 parts by weight of the obtained polyester A, 10 parts by weight of carbon black, 3 parts by weight of an aliphatic ester wax, and 3 parts by weight of carnauba wax were mixed by a Henschel mixer, Melt and knead with a twin-screw extruder, then cool, coarsely pulverize with a hammer mill, finely pulverize with a jet mill, and classify with an air classifier to obtain a volume average particle size of 8
Colored particles A having a size of 15 μm (15% by number or less having a particle size of 5 μm or less and 0% by volume having a particle size of 16 μm or more) were obtained. or,
Silica A having a volume average primary particle diameter of 16 nm was obtained by a known method utilizing a thermal decomposition oxidation reaction of silicon tetrachloride gas in an oxyhydrogen flame. This silica A was hydrophobized with octyltrimethoxysilane and then crushed. In the crushing step, first, crushing was performed so that the volume average particle diameter was 36 μm, and silica aggregate A was obtained. Further crushing was carried out to obtain treated silica A having an amount of aggregates of 10 μm or more of 1 vol% or less.
The particle size of the crushed silica is based on a Coulter counter. 100 parts by weight of colored particles, 0.5 parts by weight of treated silica A, and 0.1 parts by weight of silica aggregate A were mixed with a Henschel mixer for 20 minutes at a peripheral speed of 40 m / sec, and then mixed with a high-volter.
The resulting mixture was passed through a 25 mesh sieve and further collected by a cyclone to produce Toner A of the present invention. Table 3 shows the amount of free inorganic fine particle aggregates in this toner.

<< Production of Toners B and C >> In the same manner except that 100 parts by weight of each of polyesters B and C were used instead of polyester A, both had a volume average particle size of 8 μm (5
Toners B and C of the present invention having 15% by number or less of particles having a particle size of μm or less and 0% by volume of particles having a particle size of 16 μm or more were manufactured. The amounts of these free inorganic fine particle aggregates are shown in Table 3.

<Production of Toner D> 100 parts by weight of colored particles A, 0.5 parts by weight of treated silica B (volume average primary particle diameter 7 nm, amount of agglomerates of 10 μm or more is 1% by volume or less), obtained in the same manner. Silica aggregate B (volume average particle size 28 μm)
20 parts at a peripheral speed of 40 m / sec with a Henschel mixer
The toner D of the present invention was obtained by mixing for a minute. The amount of free inorganic fine particle aggregates in this toner is also shown in Table 3.

<Production of Toners a to c> The same procedures as in the production of Toner A except that 100 parts by weight of each of polyesters a to c were used instead of polyester A, and both had a volume average particle size of 8 μm (5 μm or less). With a particle size of 15% or less, 16
Comparative toner a having a particle size of μm or more of 0% by volume)
~ C were produced. The amounts of these free inorganic fine particle aggregates are also shown in Table 3.

<Production of Toner d> 100 parts by weight of colored particles a obtained in the same manner as in the production of colored particles A by using polyester a and 0.5 parts by weight of treated silica A were used in a Henschel mixer at a peripheral speed of 40 m / sec. After mixing for a minute, a comparative toner d was obtained. Table 3 shows the amount of free inorganic fine particle aggregates measured by the following measuring method.

<< Measurement of Amount of Aggregate of Free Inorganic Fine Particles >> 2 g of the toner was measured and sucked through a stainless steel 350 mesh (twill weave, wire diameter 25 μm, opening diameter 47 μm) sieve. Of the coarse particles remaining on the sieve, the coarse toner was washed off with methyl ethyl ketone, then the whole sieve was dried and weighed.
The weight of the sieve measured in advance was subtracted to obtain the aggregate weight of 47 μm or more (p mg), and the amount of aggregate of 47 μm or more = (p / 20
It was set to 00) x 100 (%).

Stainless steel 635mesh (twill weave,
Wire diameter 20 μm, opening diameter 20 μm)
Calculate the aggregate weight (q mg) of 20 μm or more,
Aggregate amount less than μm = {(q-p) / 2000} × 100 (%)
And For the amount of aggregates of 2 μm or more and less than 20 μm, 1000 or more of the scanning electron microscope images of the toner are observed, and the number of aggregates (n) of 2 μm or more and less than 20 μm present therein is calculated to be 2 μm.
The amount of aggregates of m or more and less than 20 μm (n / total number of toner particles observed (N)) × 100 (%).

[0056]

[Table 3]

<< Production of Developer >> Each toner obtained and a resin-coated carrier (volume average particle diameter 60 μm) in which the surface of ferrite particles is coated with an acrylic resin have a toner concentration of 6% by weight. Two-component developers A to D and developers a to d were prepared by mixing in proportions.

<Evaluation> Each developer was subjected to an actual copying test under high temperature and high humidity (30 ° C., 80% RH), and low temperature fixing property, anti-offset property and charging property (contamination in the machine due to toner scattering, fog density) evaluated. An electrophotographic copying machine "4155" (manufactured by Konica Corporation) was used as a live-action test machine.
The digital reversing developing machine was modified to have an image gradation correction control mechanism and a toner recycling system.

Evaluation of In-machine Contamination Due to Toner Scattering After conducting an actual copying test of 100,000 copies of an A4 size original with a blackened area ratio of 7%, the contamination state in the copying machine was visually observed. When there is almost no in-machine contamination, it is "○", when there is toner stain on both ends of the developing device, it is "△", toner stain is found on the entire lower surface of the developing device, and black streaks appear on the copied image. When the occurrence was recognized, it was designated as "x". However, the actual copying test was performed with and without the image gradation correction control, and the collected toner amount was measured for each. The method of measuring the collected toner was to collect the collected toner from 50,000 copies to 51,000 copies and measure the weight to obtain the amount of collected toner per copy.

Fog Density At the time of the actual copying test, the relative density of a white background portion having a document density of 0.000 with respect to a copied image was measured by a “Sakura densitometer” (manufactured by Konica Corporation).

Offset resistance The temperature of the heat roller was stepwise increased from 120 ° C. to 240 ° C. in steps of 5 ° C., and the low temperature offset disappearance temperature and the high temperature offset generation temperature were measured. The presence / absence of the offset phenomenon can be determined by sending blank plain paper to a heat roller fixing device under the same conditions immediately after forming a copy image at each set temperature and visually observing whether or not toner stains occur. It was judged.

Low Temperature Fixability The temperature of the heat roller is increased stepwise by 5 ° C. from 120 ° C. to 240 ° C. to form a copied image. The copied image has a fixing ratio of 70% measured by the following method. The minimum setting temperature of the heat roller when the temperature exceeds the above is defined as the minimum fixing temperature.

(Measurement of Fixing Rate) The fixed toner was rubbed on the solid black part (image density 1.0) of the copied image by reciprocating a 1 kg weight wrapped with a bleaching cloth 15 times, and depending on the image density before and after rubbing (rubbing). The image density after rubbing / image density before rubbing) × 100 was defined as the fixing rate (%). The concentration was measured with a "Sakura densitometer" (manufactured by Konica Corporation).

<< Dispersion of Carbon Black >> Toner A to
For each of D and a to d, a transmission electron microscope (TE
The dispersibility of the carbon black was evaluated by observing the cross section of the toner particles by taking a photograph (magnification: 10,000 times) using M). In addition, the sample for dispersibility is processed by embedding the toner with epoxy resin and then using a diamond knife.
It was prepared by slicing to a thickness of 0.2 μm. For the evaluation of dispersibility, the number of carbon black agglomerates having a maximum diameter of 1 μm or more was determined for 10 toner particles, and when the number was 2 or less, “◯”, and when 3 to 5 Was evaluated as “Δ”, and the case of 6 or more was evaluated as “x”.

The above results are shown in Table 4.

[0066]

[Table 4]

[0067]

According to the first aspect of the invention, it is possible to obtain a toner which is excellent not only in charging characteristics but also in offset resistance and low-temperature fixing property, and which is free from fog and stains inside the machine even when recycled in large quantities.

Claims (2)

[Claims] 1. A saponification value of 300 to 700 (KOHmg / g) and an acid value of 30.
〜80 (KOHmg / g), Chloroform insoluble matter 0.5〜20wt%
20% of the polyester resin, the colorant, and the amount of free aggregates of 47 μm or more are 0.05% or less of the toner weight.
m or less and less than 47 μm is 0.01 to 0.1 with respect to toner weight
%, And the content of 2 μm or more and less than 20 μm is 1.0% or less with respect to the number of toner and contains an inorganic fine particle external additive having a volume average primary particle diameter of 5 to 50 nm. 2. A toner image is formed by using the toner and carrier according to claim 1 where the charge is removed by exposure to a charged photoconductive photoreceptor, and image tone correction control is performed. A toner image forming system having a process of collecting and reusing toner on a photoconductor.