JP2005308890A - Toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner which is moderately controlled in gloss, permits excellent control of color development, and is excellent in low-temperature fixability and offset resistance. <P>SOLUTION: The toner contains a binder resin, a pigment, and inorganic particles, wherein the inorganic particles are 50 to 600 mL/100 g in oil absorption, 50 to 1,000 m2/g in BET surface area, 0.5 to 5.0 μm in average particle size, and 0.2 to 20wt% in content and the binder is a resin mixture composed of crystalline polyester of a melting point 180 to 280°C and amorphous polyester resin of a transition temperature 30 to 80°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a toner having a moderately controlled gloss, good color development, and excellent low-temperature fixability and hot offset resistance.

A dry development method is frequently used as a method for developing an electrostatic image in electrophotography or the like. In the dry development system, the toner is usually charged by friction with iron powder, glass beads, etc., called a carrier, which adheres to the electrostatic latent image on the photoreceptor by electrical attraction, and then transferred onto the paper, It is fixed by a heating roller or the like and becomes a permanent visible image.

In this heat fixing roller method, there is a demand for a toner that can be fixed at a lower temperature in order to improve economy such as power consumption and to increase the copying speed. However, when trying to improve the low-temperature fixability, an offset phenomenon is likely to occur in which a part of the toner adheres to the surface of the heat fixing roller and retransfers to the paper.

On the other hand, conventionally, for example, in a polyester-based toner, a polyfunctional monomer having three or more functional groups is copolymerized to form a chemically cross-linked structure in the polymer to maintain high temperature offset resistance. It was. However, in recent years, there is a tendency to reduce the melt viscosity of the resin and improve the low-temperature fixability of the toner by reducing the blending amount of the polyester having a crosslinked structure and increasing the ratio of the low-molecular weight polyester as the fixing component.

As described above, when a method for reducing the melt viscosity of the resin is adopted as a method for improving the low-temperature fixability of the toner, the obtained image is extremely glossy. However, in images used in business, if the gloss is too high, glare will appear, so a so-called matte tone image with low gloss is preferred. In particular, black is originally a black single color and has been used as a toner for copying machines and printers, and is particularly required to have a matte tone.

For example, Patent Document 1 discloses a dry toner containing 0.2 to 20% by weight of inorganic white particles having an average particle size of 40 μm or more and 300 μm or less in an adhesive resin. Toner is disclosed. This toner is excellent in low-temperature fixability and anti-blocking property, and the gloss of the fixed image is said to be low. However, in practice, when the average particle diameter of a commonly used toner is 5 to 15 μm, when mixing inorganic white particles of 40 to 300 μm, the particles may be crushed in advance with a three roll or a Banbury mixer. Necessary. The particle size distribution of the crushed particles is extremely wide. Large particles drop off and have a serious adverse effect on fixing properties, while small particles exhibit virtually no gloss reduction effect. do not do. Since the particle size distribution of the crushed particles varies depending on the kneading conditions, it must be said that it is very difficult to control the gloss by this method.

Patent Document 2 discloses an image capable of both multicolor image formation by overlapping toner images of different colors using a plurality of color toners including at least black and monochrome image formation using only black toner. The maximum transfer amount on the image of each color toner is 4 × 10 ⁻³ to
In the image forming method in the range of 8 × 10 ⁻³ kg / m ² , the image glossiness at the maximum transfer amount of black toner at the time of multicolor printing is GKC, and the image at the maximum transfer amount of chromatic color toner at the time of multicolor printing When the glossiness is GCC and the image glossiness at the maximum transfer amount of black toner during monochrome printing is GKM, 4 ≦ GKC ≦ 25 (%), 5 ≦ GCC ≦ 30 (%), 1 ≦ GKM ≦
10 (%), 0.5 ≦ GKC / GCC ≦ 0.90.1 ≦ GKM / GKC ≦ 0.7 GKM ≦
An image forming method that satisfies the relationship of GKC ≦ GCC is disclosed. Specifically, this is because the resin incompatible with the binder resin is 1 to 10 parts per 100 parts by weight of the binder resin.
By adding the weight part, the gloss of the black toner is reduced, the glossiness of the black part is suppressed for multicolor images, and a balanced and easy-to-view image is provided for the entire image, and the monochrome image is given to the user. It is said that this is an image forming method that gives a preferred matte image. However, in Comparative Example 1 of Patent Document 2, although sub-resin was added,
The gloss has not been suppressed. This is thought to be because the linear speed at the time of fixing is slowed down, so that the gloss is suppressed by means of controlling the transfer amount of the toner on the image rather than the matte effect by the toner itself. Conceivable. This is apparent from the fact that in Comparative Example 3, the gloss of only the black toner is sufficiently lowered even when no sub-resin is added. If so, it can be said that Patent Document 2 does not disclose any toner that can provide a matte image with reduced gloss.

Patent Document 3 discloses a low-melting, low-gloss toner resin composition containing a non-crosslinked portion and a cross-linked portion, wherein the cross-linked portion is formed by fine gel particles cross-linked at high density. Disclosed is a toner resin composition that is primarily composed and contains the fine gel particles in an amount of about 20 to about 45% by weight of the toner resin. This is to reduce the gloss of the resulting image by incorporating fine gel particles in the binder resin. However,
Since there is a correlation between the content of the fine gel particles and the high temperature offset resistance, the gloss could not be lowered without actually affecting the fixability.

JP-A-61-117566 JP 2001-117277 A JP-A-6-130722

The present invention has been made in view of the above-described situation, and an object of the present invention is to provide a toner that can be appropriately controlled in gloss, can perform good color development, and has excellent low-temperature fixability and hot offset resistance.

The present invention is a toner containing a binder resin, a pigment, and inorganic fine particles, wherein the inorganic fine particles have an average particle diameter of 0.5 to 5.0 μm and a content of 0.2 to 20% by weight. Is a toner.
The present invention is described in detail below.

The toner of the present invention contains inorganic fine particles. As a result of intensive investigations, the inventors have formulated a certain amount of inorganic fine particles having a certain particle diameter, so that the gloss is appropriately controlled without impairing the low-temperature fixability and hot offset resistance, and good color development. As a result, the present inventors have found that the toner can be obtained.

The inorganic fine particles have a particle diameter lower limit of 0.5 μm and an upper limit of 5.0 μm. If it is less than 0.5 μm, it is too small for the average particle diameter of the toner, so that the effect of suppressing gloss cannot be sufficiently obtained. If it exceeds 5.0 μm, it is too large with respect to the average particle diameter of the toner, so that it may fall off in the toner production process, or the low-temperature fixability and hot offset resistance of the toner may be deteriorated. A preferred lower limit is 0.6 μm and a preferred upper limit is 4.0 μm.

The inorganic fine particles have a preferable lower limit of the oil absorption amount of 50 mL / 100 g and a preferable upper limit of 600.
mL / 100 g. If it is less than 50 mL / 100 g, the difference in polarity from the binder resin is too large, and thus the inorganic fine particles may not be uniformly dispersed in the binder resin. If it exceeds 600 mL / 100 g, the viscosity of the resulting toner increases and the low-temperature fixability may deteriorate. A more preferable lower limit is 80 mL / 100 g, and a more preferable upper limit is 450 mL / 100 g.

The inorganic fine particles have a preferable lower limit of the surface area measured by the BET method of 50 m ² / g and a preferable upper limit of 1000 m ² / g. If it is less than 50 m ² / g, the resulting toner may be inferior in transparency and color development may be deteriorated. If it exceeds 1000 m ² / g, the inorganic fine particles may not be uniformly dispersed in the binder resin. . A more preferable lower limit is 100 m.
² / g, and a more preferable upper limit is 800 m ² / g.

The inorganic fine particles are not particularly limited, and silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, quartz sand, clay, mica, wollastonite, Diatomaceous earth, chromium oxide, cerium oxide, pengala, antimony trioxide, magnesium oxide, zirconium oxide, parium sulfate,
Examples thereof include those made of barium carbonate, calcium carbonate, silicon carbide, and silicon nitride.
Among them, those made of silica are preferable because they do not hinder the transparency of the toner and can provide a toner with good color development.

The lower limit of the amount of the inorganic fine particles in the toner of the present invention is 0.2% by weight, and the upper limit is 20% by weight. If it is less than 0.2% by weight, a sufficient gloss suppressing effect cannot be obtained, and if it exceeds 20% by weight, the low-temperature fixability and hot offset resistance of the resulting toner are inferior. The preferred lower limit is 0
. 5% by weight, the preferred upper limit is 15% by weight.

The binder resin of the toner of the present invention is not particularly limited, and styrene, ethylene, methyl methacrylate, normal butyl methacrylate, 2-ethylhexyl methacrylate, vinyl chloride, acrylonitrile, α-methylstyrene, 2-vinylpyridine, butadiene, Homopolymers of vinyl monomers such as butyl acrylate and propylene, or copolymers thereof; any of those used as a binder resin for ordinary toners such as polyester can be used. In particular, when a polyester resin that is excellent in low-temperature fixability and tends to be highly glossy is used, a particularly high effect can be obtained.

As the polyester that can be used as the binder resin, those usually used as a binder resin in a toner can be used. Above all, the melting point is 18
When a mixed resin of a crystalline polyester having a temperature of 0 to 280 ° C. and an amorphous polyester having a glass transition temperature of 30 to 80 ° C. is used, it has excellent low-temperature fixability and storage stability and good offset resistance. A toner having the same can be obtained. This is because when such a mixed resin is used, the crystalline components in the high melting crystalline polymer form a physical cross-linked structure in the amorphous polyester, while the high melting crystalline polymer A non-crystalline component and non-crystalline polyester are entangled to form a kind of network structure. By forming such a network structure, there is little decrease in viscosity at high temperature, and low temperature fixability and storage This is considered to be because good offset resistance can be exhibited without lowering the properties.
In the present specification, the crystalline polyester means a polyester having a sharp and clear melting point peak when the differential heat is measured by a differential scanning calorimeter and having a crystallinity of more than 10%, which is non-crystalline. The polyester means a polyester having a crystallinity of 10% or less without showing a sharp and clear melting point peak when differential heat is measured by a differential scanning calorimeter.

The crystalline polyester can be obtained by condensation polymerization of dicarboxylic acid and diol.
Examples of the dicarboxylic acid include o-phthalic acid, terephthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, octyl succinic acid, cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid, fumaric acid, maleic acid, and itacone. Examples include acids, decamethylene carboxylic acids, anhydrides and lower alkyl esters thereof. Among these, terephthalic acid, naphthalenedicarboxylic acid, and anhydrides and lower alkyl esters thereof are preferably used for imparting crystallinity.

Examples of the diol include ethylene glycol, 1,3-propanediol, 1,
4-butanediol, diethylene glycol, 1,5-pentanediol, 1,6-hexanediol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-butanediol, 2,3 -Butanediol, neopentyl glycol (2,2-dimethylpropane-1,3-diol), 1,2-
Aliphatic diols such as hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol; 2 , 2-bis (4-hydroxycyclohexyl) propane, 2,2-
Alkylene oxide adduct of bis (4-hydroxycyclohexyl) propane, 1,4
-Alicyclic diols such as cyclohexanediol and 1,4-cyclohexanedimethanol.

Among the crystalline polyesters, polybutylene terephthalate (PBT),
Polyethylene terephthalate (PET) is preferred.
Since polybutylene terephthalate (PBT) has a high crystallization rate and a high degree of crystallization, a toner obtained using this has excellent offset resistance. Further, since the compatibility with the amorphous polyester is also excellent, the toner obtained using the polyester has excellent low-temperature fixability.
Since polyethylene terephthalate (PET) has a high crystalline melting point, the toner obtained using this has excellent offset resistance at high temperatures. Polyethylene terephthalate (PET) is inferior to polybutylene terephthalate (PBT) in terms of crystallization speed and crystallinity, but these points can be improved by adding a crystal nucleating agent.
These crystalline polyesters may be used alone or in combination of two or more.

The non-crystalline polyester can be obtained by polycondensing a dicarboxylic acid and a diol.
The glass transition temperature of non-crystalline polyester is such that aromatic dicarboxylic acids such as terephthalic acid improve the glass transition temperature, and long-chain aliphatic dicarboxylic acids such as sebacic acid and adipic acid lower the glass transition temperature. Since it has a function, the target glass transition temperature can be achieved by appropriately combining these dicarboxylic acids. However, even if an objective glass transition temperature can be achieved by appropriately combining an aromatic dicarboxylic acid and a long-chain aliphatic dicarboxylic acid, the softening temperature tends to be too high.
Therefore, the non-crystalline polyester comprises a polyvalent carboxylic acid and a polyhydric alcohol containing at least either a divalent bending monomer capable of introducing a bent molecular structure into the molecular chain or a divalent monomer having a branched chain. It is preferable to polymerize the monomer mixture containing.
A polymer obtained by polymerizing a monomer mixture containing these divalent bending monomers and divalent monomers having a branched chain can easily achieve both a desired glass transition temperature and a low softening temperature, and can be crystallized. It can be effectively suppressed.

As the divalent bending monomer, an aromatic dicarboxylic acid in which the ortho position or the meta position is substituted with a carboxyl group, an aromatic diol in which the ortho position or the meta position is substituted with a hydroxyl group,
Polycarboxylic aromatic dicarboxylic acids having a carboxyl group at an asymmetric position, polycyclic aromatic diols having a hydroxyl group at an asymmetric position, and other monomers that can introduce a molecular structure bent into the molecular chain of the polymer are limited to dicarboxylic acids and diols. For example, it may be an anhydride or lower ester of a dicarboxylic acid, a monohydroxymonocarboxylic acid, etc., for example, phthalic anhydride, o-phthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,7 Dicarboxylic acids such as naphthalenedicarboxylic acid and anhydrides and lower esters thereof; monohydroxymonocarboxylic acids such as salicylic acid and 3-hydroxy-2-naphthalenecarboxylic acid; catechol,
Examples include diols such as 1,4-cyclohexanedimethanol.

A divalent monomer having a branched chain effectively suppresses crystallization of the polymer due to steric hindrance of the branched chain. Examples of the monomer having a branched chain that can effectively suppress crystallization include an aliphatic diol having a branched alkyl chain and an alicyclic diol having a branched alkyl chain. The alicyclic diol is preferably an alicyclic diol in which a plurality of alicyclic diols are linked by a branched alkylene chain.
The divalent monomer having a branched chain is not particularly limited. For example, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, neopentyl glycol (2,2-dimethylpropane- 1,3-diol), 1,2-hexanediol, 2,5
-Hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1
Aliphatic diols such as 1,3-propanediol and 2,4-diethyl-1,5-pentanediol; 2,2-bis (4-hydroxycyclohexyl) propane and 2,2-bis (4-hydroxycyclohexyl) propane And alicyclic diols such as alkylene oxide adducts.
Among them, terephthalic acid, neopentyl glycol, ethylene glycol and / or
Alternatively, an amorphous polyester obtained by polymerizing a monomer mixture containing 1,4-butanediol as a main component is preferable because it is excellent in low-temperature fixability and transparency.

The amorphous polyester preferably contains two types of amorphous polyesters having different average molecular weights. The melt viscosity of the amorphous polyester is determined by its molecular weight. If a low molecular weight polyester is used as the non-crystalline polyester, the melt viscosity of the toner is lowered, so that excellent low-temperature fixability can be obtained. However, when an amorphous polyester having a small molecular weight is used, the high temperature offset resistance and storage stability are inferior, and kneading with the crystalline polyester becomes difficult.

The combination of two types of non-crystalline polyesters having different weight average molecular weights includes non-crystalline polyesters having a weight average molecular weight of 3000 to 20,000 as low average molecular weights, and weight average molecular weights as high average molecular weights. A non-crystalline polyester of 20,000 to 300,000 is used.
When the weight average molecular weight of the non-crystalline polyester having a small average molecular weight is less than 3000, the strength of the polyester resin composition for the toner is lowered, resulting in insufficient durability of the toner. In addition, it cannot exhibit low-temperature fixability. A more preferred upper limit is 8000.
When the weight average molecular weight of the non-crystalline polyester having a large average molecular weight is less than 20,000, the resulting toner has insufficient high-temperature offset resistance, storage stability and kneadability with the crystalline polyester. Further, the low-temperature fixability of the toner becomes insufficient. A more preferred lower limit is 3
A more preferable upper limit is 200,000.

Non-crystalline polyester having a weight average molecular weight of 3000 to 20,000 and a weight average molecular weight of 30,000 to
As a compounding ratio with the non-crystalline polyester which is 300,000, the weight average molecular weight is 3000-2.
The weight average molecular weight is 30,000 to 3 with respect to 40 to 90% by weight of non-crystalline polyester.
It is preferable that the non-crystalline polyester which is 100,000 is 10 to 60% by weight. When the blending amount of the amorphous polyester having a weight average molecular weight of 3000 to 20,000 is less than 40% by weight,
The low-temperature fixability of the toner may be insufficient, and if it exceeds 90% by weight, the high-temperature offset resistance, storage stability, and kneadability with the crystalline polyester may be insufficient.

When the crystalline polyester and the amorphous polyester are used in combination, the crystalline polyester and the amorphous polyester are preferably compatible with each other. When the crystalline polyester and the non-crystalline polyester are compatible, the polyester resin composition for toner becomes colorless and transparent, and is suitable as a polyester resin composition for color toners that can perform good color development. In addition, since it has a high resin strength, it can be suitably used as a polyester-based resin composition for toner having excellent high-temperature offset resistance.
The term “compatible” refers to a state in which the crystalline polyester and the non-crystalline polyester are uniformly mixed. These may be completely compatible or partially compatible. .

The pigment used in the toner of the present invention is not particularly limited. For example, carbon black such as furnace black, lamp black, thermal black, acetylene black, channel black; aniline black, phthalocyanine blue, quinoline yellow lamp black, rhodamine-B, Azo pigment, perylene pigment, perinone pigment, anthraquinone pigment, dioxazine pigment, isoindoline pigment, isoindolinone pigment, selenium pigment, indico pigment, quinophthalone, diketopyrrolopyrrole, quinacridone, etc. It is done.
The preferable lower limit of the amount of the pigment in the toner of the present invention is 1 part by weight with respect to 100 parts by weight of the binder resin, and the preferable upper limit is 10 parts by weight.

The toner of the present invention contains conventionally known additives such as a wax, a release agent, a charge control agent, a magnetic material, a rubbery polymer, a carrier, and a cleaning property improver as long as the object of the present invention is not impaired. Also good.

The particle size of the toner of the present invention is not particularly limited, but usually about 5 to 10 μm is used. When the thickness is 5 μm or less, particularly high image quality can be obtained.
The moisture content of the toner of the present invention is not particularly limited, but the preferred lower limit is 0.01% by weight.
The preferred upper limit is 0.2% by weight. If it is less than 0.01% by weight, production becomes difficult due to problems in production, and if it exceeds 0.2% by weight, sufficient charging stability may not be obtained.
The repose angle of the toner of the present invention is not particularly limited, but the preferred lower limit of the repose angle at 23 ° C. and 60% humidity is 1 degree, and the preferred upper limit is 30 degrees. If it is less than 1 degree, handling of the toner may be difficult, and if it exceeds 30 degrees, the fluidity of the toner may be insufficient. The angle of repose of the toner can be measured by, for example, a powder tester (for example, PT-N type manufactured by Hosokawa Micron Corporation).

The method for producing the toner of the present invention is not particularly limited. For example, inorganic fine particles, pigments, and additives to be added as necessary are added to the binder resin, kneaded with a twin-screw extruder or the like, rolled,
Examples of the method include coarse pulverization and fine pulverization after cooling.

The toner of the present invention can appropriately control the gloss and does not hinder the transparency, so that a good color can be produced. Further, by limiting the average particle size and content of the inorganic fine particles, the toner has excellent low temperature fixability and hot offset resistance, which are the most basic performances of the toner.

According to the present invention, it is possible to provide a toner whose gloss is moderately controlled, good color development can be performed, and which is excellent in low-temperature fixability and hot offset resistance.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Example 1)
Polyester mixed resin 8 comprising 10% by weight of crystalline polyester having a melting point of 230 ° C. and 90% by weight of amorphous polyester having a glass transition temperature of 55 ° C. as a binder resin
6% by weight of inorganic fine particles made of silica (average particle size 3.0 μm, oil absorption 325 mL / 1
00 g, specific surface area 300 m ² / g) 6% by weight, carnauba wax 3% by weight, charge control agent (
S-34: manufactured by Orient Chemical Co., Ltd.) 1% by weight and 5% by weight of carbon black were added, mixed thoroughly with a Henschel mixer, then melt-mixed at 120 ° C. using a twin screw extruder, cooled,
Coarsely pulverized. Thereafter, the resultant was finely pulverized with a jet mill (Lab Jet: manufactured by Nippon Pneumatic Co., Ltd.) to obtain a toner powder having an average particle size of about 10 μm. Furthermore, the toner powder is classified into a classifier (MD
S-2: manufactured by Nihon Pneumatic Co., Ltd.) to obtain toner fine powder having an average particle size of about 9 μm. Toner was manufactured by uniformly mixing (externally adding) 1.0 part by weight of hydrophobic silica (R972: manufactured by Nippon Aerosil Co., Ltd.) to 100 parts by weight of the toner fine powder.

(Example 2)
A toner was obtained in the same manner as in Example 1 except that the amount of inorganic fine particles composed of silica was changed from 6% by weight to 14% by weight in the production of the toner powder.

(Example 3)
In the production of toner powder, inorganic fine particles made of silica (average particle size 3.0 μm, oil absorption) instead of inorganic fine particles made of silica (average particle size 3.0 μm, oil absorption 325 mL / 100 g, specific surface area 300 m ² / g) A toner was obtained in the same manner as in Example 1 except that the amount was 500 mL / 100 g and the specific surface area was 600 m ² / g.

(Comparative Example 1)
Example 1 except that inorganic fine particles made of silica were not added in the production of the toner powder.
A toner was obtained in the same manner as above.

(Comparative Example 2)
A toner was obtained in the same manner as in Example 1 except that the amount of inorganic fine particles composed of silica was changed from 6 wt% to 25 wt% in the production of the toner.

(Comparative Example 3)
In the production of the toner, inorganic fine particles composed of silica (average particle size 3.0 μm, oil absorption 32
Instead of 5 mL / 100 g, specific surface area 300 m ² / g), inorganic fine particles made of silica (
A toner was obtained in the same manner as in Example 1 except that an average particle diameter of 10 μm, an oil absorption of 300 mL / 100 g, and a specific surface area of 300 m ² / g were used.

(Evaluation)
The toners produced in Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated by the following methods.
The results are shown in Table 1.

(Glossiness evaluation)
A developer was prepared by mixing 6.5 parts by weight of toner with 93.5 parts by weight of a ferrite carrier. Using a Konica UBIX4160AF as an electrophotographic copying machine, 100 A4 paper
The glossiness was measured using an image obtained by fixing a% density black image at a fixing temperature of 180 ° C. The measurement was performed at three arbitrary points per sheet, and the average value of the three points was used as the value of one image. The glossiness was measured with a gloss meter (manufactured by Nippon Denshoku Industries Co., Ltd.) at an incident angle of 60 degrees. In general, an image accepted in the market as having little glare shows a glossiness of less than 10%. Therefore, when the glossiness is less than 10%, it can be said that the image is sufficiently matte.

(Measurement of high temperature offset temperature and low temperature offset temperature)
6.5 parts by weight of toner was mixed with 93.5 parts by weight of a ferrite carrier to prepare a developer. As the electrophotographic copying machine, a UBIX4160AF manufactured by Konica was used so that the set temperature of the heat fixing machine roller could be changed up to 250 ° C.
The set temperature of the heat fixing roller was changed stepwise to obtain a copy in which the unfixed toner image was fixed on the transfer paper by the heat fixing roller at each set temperature.
It was observed whether the blank portion of the obtained copy and the fixed image were stained with toner, and a temperature region where no contamination occurred was defined as a non-offset temperature region. Further, the maximum value in the non-offset temperature region was set as the high temperature offset temperature, and the minimum value was set as the low temperature offset temperature.

(Measurement of minimum fixing temperature)
In the same way as the measurement of the high temperature offset temperature and the low temperature offset temperature, copying is performed by changing the set temperature of the heat fixing roller of the electrophotographic copying machine step by step. When the fixed image is not soiled with toner, and the fixed image of the obtained copy is rubbed with a sand eraser for typewriters, it is determined that the fixing is good when the decrease in density of the fixed image is less than 10%, The lowest temperature at which good fixing was obtained was determined. The image density was measured using a Macbeth photometer.

According to the present invention, it is possible to provide a toner whose gloss is moderately controlled, good color development can be performed, and which is excellent in low-temperature fixability and hot offset resistance.

Claims (6)

A toner containing a binder resin, a pigment, and inorganic fine particles, wherein the inorganic fine particles have an average particle diameter of 0.5 to 5.0 μm and a content of 0.2 to 20% by weight. Features toner. The toner according to claim 1, wherein the inorganic fine particles have an oil absorption of 50 to 600 mL / 100 g. The toner according to claim 1, wherein the inorganic fine particles have a surface area measured by the BET method of 50 to 1000 m ² / g. The toner according to claim 1, wherein the inorganic fine particles are made of silica. The toner according to claim 1, wherein the binder resin is a polyester resin. The binder resin is a mixed resin composed of a crystalline polyester having a melting point of 180 to 280 ° C and an amorphous polyester having a glass transition temperature of 30 to 80 ° C. 4. The toner according to 4.