JP3187467B2 - Electrophotographic toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner, and more particularly, to an electrophotographic toner used in an electrophotographic image forming apparatus such as an electrostatic copying machine or a laser beam printer. It is about.

[0002]

2. Description of the Related Art When forming an image, first, a so-called magnetic brush is formed by holding a developer containing an electrophotographic toner on an outer periphery of a developing sleeve having a magnetic pole therein. Next, the magnetic brush is brought into sliding contact with the photoreceptor having the electrostatic latent image formed on the surface. Then, the electrophotographic toner is electrostatically attached to the electrostatic latent image, and is visualized as a toner image. This toner image is transferred from the photoreceptor surface onto paper,
Further, when fixing is performed on the paper by a fixing roller, an image corresponding to the electrostatic latent image is formed on the surface of the paper.

As the electrophotographic toner used in the above-described image formation, a toner obtained by mixing a coloring agent such as carbon black, a charge controlling agent, and the like in a fixing resin and granulating the mixture to a predetermined particle size is used. Can be In the above-described electrophotographic toner, so-called offset such as contamination of the back surface of the paper and contamination of the fixing roller due to the toner peeled off from the paper, or in particular, poor fixing of the toner image to the paper (low temperature) when the fixing temperature is low. (Deterioration of fixing property) may occur.

The deterioration of the low-temperature fixability mainly occurs when the molecular weight of the fixing resin contained in the electrophotographic toner is high. On the other hand, the offset mainly occurs when the molecular weight of the fixing resin is low. Therefore, in order to solve the above problem, various electrophotographic toners using a low molecular weight resin and a high molecular weight resin in combination as fixing resins have been proposed (for example, JP-A-56-16144, See JP-A-60-3644.

[0005]

However, all of the conventional electrophotographic toners have insufficient heat resistance.
In particular, there is a problem that blocking occurs in a low-speed image forming apparatus in which the temperature inside the image forming apparatus becomes high, causing toner loss, rainfall, cleaning failure, and the like.

[0006] Toner loss is caused by the fact that huge particles formed by agglomeration of toner due to blocking are caught between the photoreceptor and the paper at the time of transfer of the toner image to the paper, thereby creating a gap around the toner. Is a phenomenon in which transfer to the image is inhibited and a white portion is generated in the image. Also, in the rainfall, the toner fused to the surface of the photoconductor by blocking,
This is a phenomenon in which streaky marks are left on the formed image.

[0007] Further, the cleaning failure is caused by the blocking toner adhering to the blade for cleaning the photoreceptor drum, and causes the above-mentioned toner loss or rainfall.

[0008]

In order to solve the above-mentioned problems, the present inventors have determined the relationship between the physical properties of a styrene-acrylic copolymer as a fixing resin and the heat resistance of an electrophotographic toner. And found that heat resistance can be improved by increasing the intramolecular crosslinking of the styrene-acrylic copolymer and increasing the glass transition temperature. And, in the styrene-acrylic copolymer,
By limiting the molecular weight distribution to a predetermined range and increasing the acid value of the entire resin, which is a parameter for specifying the amount of intramolecular cross-linking, the glass transition temperature is increased while maintaining low-temperature fixability and offset resistance, thereby improving heat resistance. It was found that the properties could be improved, and the previous application was filed (Japanese Patent Application No. 2-197369).
In addition, the acid value referred to here is necessary to neutralize the free fatty acid contained in 1 g of the styrene-acrylic copolymer,
Shows the number of mg of potassium hydroxide (KOH).

After that, the present inventors have further studied the physical properties of the styrene-acrylic copolymer as a fixing resin. Then, while maintaining the molecular weight distribution and the acid value of the entire fixing resin at the same level as in the previous application, the intramolecular crosslinking (acid value) of the low molecular weight component in the fixing resin is reduced, and The inventors have found that lowering the glass transition temperature of the low molecular weight component can further improve the low-temperature fixability while maintaining high heat resistance, and completed the present invention.

That is, the electrophotographic toner of the present invention comprises:
In a gel permeation chromatogram showing a molecular weight distribution, a molecular weight in the range of 1 × 10 ³ or more and less than 1 × 10 ⁵ ,
A styrene-acrylic copolymer having a maximum value of the molecular weight distribution within a range of a molecular weight of 1 × 10 ⁵ or more and 3 × 10 ⁵ or less, and having a minimum value of the molecular weight distribution between both maximum values is fixed. And the acid value of the entire fixing resin is 20 to 50 mg / g, while the ratio of styrene in the entire fixing resin is in the range of 40 to 80% by weight .
The acid value of the component having a lower molecular weight than the minimum value is 10 to 20 mg.
/ G and the acid value of the low molecular weight component is the whole of the fixing resin.
Is lower than the acid value of

As shown in FIG. 1, a styrene-acrylic copolymer which is a resin for fixing a toner has a high molecular weight side and a low molecular weight side in a gel permeation chromatogram showing a molecular weight distribution. maximum value P _H of the respective molecular weight distribution, has a P _L, and both the maximum value P _H, those having a minimum value V _M of the molecular weight distribution between P _L is used. The molecular weight of the maximum value P _H on the high molecular weight side is 1 × 10 ⁵ or more, 3 ×
It is limited to the range of 10 ⁵ or less. The molecular weight of less than 1 × 10 ⁵ maxima P _H, a styrene - the lack of high molecular weight component of the acrylic copolymer, excellent toner can not be obtained in offset resistance. Conversely, the molecular weight of the maximum value P _H is 3 ×
If it exceeds ^105, since likely the high molecular weight component is cut by the heat and mechanical shearing force is to be included in a large amount, rather the heat resistance is deteriorated. The molecular weight of the maximum value P _H of the high molecular weight side, 1.5 × 10 ⁵ ~2.5 × 1
0 is preferably in the ⁵ range of.

The molecular weight of the maximum value P _L on the low molecular weight side is 1 ×
It is limited to the range of 10 ³ or more and less than 1 × 10 ⁵ . A molecular weight of maximum value P _L is 1 × 10 ⁵ or more, styrene - a lack of components in the low molecular weight of the acrylic copolymer are not obtained toner having excellent low-temperature fixability. On the other hand, the maximum value P _L
If the molecular weight is less than 1 × 10 ³ , the shape retention of the styrene-acrylic copolymer is insufficient, and a toner having excellent durability cannot be obtained. The molecular weight of the maximum value P _L of the low molecular weight side is preferably in the range of ^{2 × 10 3 ~1 × 10 4} .

[0013] The molecular weight of the minimum value V _M of the molecular weight distribution, the both maximum values P _H, may be a middle value of the molecular weight of P _L. Both maximum value P _H, the area of the two peaks containing P _L S _H, S _L
Sum of, when connecting the two peaks with a common tangent L, ratio of lower than the tangential line L, from the area S _V of the valley containing the minimum value V _M, is guided by the following formula (V / P) Is styrene-
It shows how the molecular weight distribution curve of the acrylic copolymer approximates a quadrilateral shape formed by connecting the two maximum values with a common tangent L. The smaller the ratio (V / P), the more the quadrilateral shape Means that

[0014]

(Equation 1)

This is an index for indicating how much the component having an intermediate molecular weight between the high molecular weight component and the low molecular weight component. And, the smaller the ratio (V / P) is, the more components having an intermediate molecular weight are obtained, and a toner having an optimal combination of fixability, offset resistance and durability can be obtained. In the present invention, the ratio (V / P) is preferably not more than 0.30, and particularly preferably not more than 0.20.
It is preferably 0 or less. The ratio (V / P) is 0.30
If the ratio exceeds the range, the intermediate molecular weight component in the styrene-acrylic copolymer is insufficient, homogeneity is deteriorated, the durability of the toner is deteriorated, and the occurrence of poor fixing and offset may not be suppressed. There is.

The ratio of the area S _{H of the} peak containing the maximum value P _H on the high molecular weight side to the area S _{L of the} peak containing the maximum value P _L on the low molecular weight side is not particularly limited.
15:85 to 50:50, especially 20:80 to 4
It is preferably in the range of 5:55. In the styrene-acrylic copolymer having the above molecular weight distribution, the ratio of styrene in the whole is limited to 40 to 80% by weight for the following reason.

That is, if the proportion of styrene is less than 40% by weight, the glass transition temperature of the fixing resin does not sufficiently rise, and the heat resistance of the toner cannot be improved. On the other hand, if the proportion of styrene exceeds 80% by weight, the amount of the acrylic component having a —COO— group or the like, which affects the chargeability of the toner, relatively decreases, and the chargeability of the toner decreases, and the image density decreases. And fog due to toner scattering occurs. The ratio of the styrene is more preferably in the range of 60 to 80% by weight.

The acid value of the whole resin is 20 to 50 mg / g.
The range is limited for the following reason. That is, when the acid value of the entire resin is less than 20 mg / g, the glass transition temperature of the fixing resin does not sufficiently increase, and the heat resistance of the toner cannot be improved. On the other hand, the acid value of the entire resin is 5
If it exceeds 0 mg / g, a large amount of functional groups will be present in the fixing resin, and the moisture resistance of the toner will deteriorate.

Furthermore, the the minimum value V _M than the low molecular weight side of the acid number of component is limited within the range of 10-20 mg / g for the following reasons. That is, the acid value of the components of the low molecular weight side than the minimum value V _M is less than 10 mg / g, too glass transition temperature of the components of the low molecular weight side is low, the heat resistance is lowered. Conversely, if it exceeds 20 mg / g, the glass transition temperature of the component on the low molecular weight side cannot be lowered sufficiently,
The low-temperature fixability cannot be improved. And low molecular weight components
If the acid value is not lower than the acid value of the entire fixing resin,
The effect of further improving low-temperature fixability while maintaining high heat resistance
No result.

The styrene-acrylic copolymer is produced, for example, by uniformly melt-blending a plurality of styrene-acrylic copolymers having different molecular weight distributions so as to have the above-mentioned molecular weight distribution. According to this melt blending method, for example, as shown in FIG. 2, a styrene-acrylic copolymer having a molecular weight distribution shown in a curve A (low molecular weight) and a styrene-acrylic copolymer having a molecular weight distribution shown in a curve B The styrene-acrylic copolymer having a molecular weight distribution shown by curve C can be obtained by melt-blending an equal amount of the polymer (having a high molecular weight).

In the above melt-blending method, the acid value of the whole resin, and the acid value of the components of the low molecular weight side than the minimum value V _M, the adjusted within the range, the low molecular weight and high molecular weight which is a raw material The acid value of each of the styrene-acrylic copolymers may be adjusted. The acid value of the low-molecular-weight and high-molecular-weight styrene-acrylic copolymers can be easily adjusted by adjusting the ratio of the acrylate to the acrylic acid in the acrylic components in the copolymer.

The styrene-acrylic copolymer can be produced by a multi-stage polymerization method combining a plurality of polymerization methods. As the styrene monomer, in addition to styrene, vinyl toluene, α-methylstyrene and the like can be used. As the acrylic monomer, the following general formula
The one represented by (I) can be used.

[0023]

Embedded image

In the formula, R ¹ is a hydrogen atom or a lower alkyl group, and R ² is a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms, a hydroxyalkyl group, a vinyl ester group or an aminoalkyl group. The acrylic monomer represented by the general formula (I) includes acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate , Methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate,
β-ethyl hydroxyacrylate, propyl γ-hydroxyacrylate, butyl δ-hydroxyacrylate, β
-Ethyl hydroxymethacrylate, propyl γ-aminoacrylate, propyl γ-N, N-diethylaminoacrylate, ethylene glycol dimethacrylate,
Examples include tetraethylene glycol dimethacrylate.

The toner comprises a colorant,
It is manufactured by blending additives such as a charge control agent and a release agent (anti-offset agent) and granulating to an appropriate particle size. As a coloring agent, various coloring pigments, extenders, conductive pigments,
Examples include magnetic pigments and photoconductive pigments. These may be used alone or in combination of two or more depending on the application.

The following are preferably used as the coloring pigment. Black furnace black, channel black, thermal,
Carbon black such as gas black, oil black and acetylene black, lamp black, aniline black.

White zinc white, titanium oxide, antimony white, zinc sulfide. Red Bengala, Cadmium Red, Lead Red, Mercury Sulfide, Permanent Red 4R, Risor Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B.

Orange red-mouthed graphite, molybdenum orange, permanent orange GTR, pyrazolo orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK. Yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, Naples yellow, naphthol yellow S, Hanser yellow G, Hanser yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow Rake, permanent yellow NCG, tartrazine rake.

Green chrome green, chromium oxide, pigment green B,
Malachite Green Lake, Fanal Yellow Green G. Blue Navy Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue Partially Chlorinated, First Sky Blue, Indanthrene Blue B
C.

Purple manganese purple, first violet B, methyl violet lake. As extenders, barite powder, barium carbonate, clay, silica, white carbon, talc,
Alumina white and the like. Examples of the conductive pigment include conductive carbon black and aluminum powder.

As the magnetic pigment, various ferrites, for example,
For example, ferric oxide (Fe_ThreeO_Four), Iron sesquioxide (γ-Fe_TwoO
_Three), Zinc iron oxide (Zn Fe_TwoO_Four), Yttrium iron oxide
(Y _ThreeFe_FiveO₁₂), Cadmium iron oxide (Cd Fe_TwoO_Four),
Gatrinium iron oxide (Gd_ThreeFe _FiveO_Four), Iron oxide copper (Cu F
e_TwoO_Four), Lead iron oxide (Pb Fe₁₂O₁₉), Neodymium iron oxide
(Nd Fe O_Three), Barium iron oxide (Ba Fe₁₂O₁₉),acid
Magnesium iron fossil (MgFe_TwoO_Four), Iron manganese oxide (Mn
Fe_TwoO_Four), Iron lanthanum oxide (La Fe 2 O 3)_Three), Iron powder, ko
Baltic powder, nickel powder and the like can be mentioned.

Examples of the photoconductive pigment include zinc oxide, selenium, cadmium sulfide, cadmium selenide, and the like. The colorant is used in an amount of 1 to 30 with respect to 100 parts by weight of the binder resin.
It is used in a proportion of 2 parts by weight, preferably 2 to 20 parts by weight. As the charge control agent, one of two types of charge control agents for positive charge control and negative charge control is used according to the polarity of the toner.

As the charge controlling agent for controlling the positive charge, an organic compound having a basic nitrogen atom, for example, a basic dye, an aminopyrine, a pyrimidine compound, a polynuclear polyamino compound, an aminosilane, etc. Fillers and the like. Examples of the charge control agent for controlling the negative charge include a compound containing a carboxy group (for example, a metal chelate of alkyl salicylate), a metal complex dye, a fatty acid soap, a metal salt of naphthenic acid, and the like.

The charge control agent is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the binder resin. Examples of the release agent (anti-offset agent) include aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters or partially saponified products thereof, silicone oil, various waxes, and the like. Among them,
Aliphatic hydrocarbons having a weight average molecular weight of about 1,000 to 10,000 are preferred. Specifically, one or a combination of two or more of low-molecular-weight polypropylene, low-molecular-weight polyethylene, paraffin wax, and a low-molecular-weight olefin polymer composed of olefin units having 4 or more carbon atoms is suitable.

The release agent is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the binder resin. The toner is obtained by uniformly kneading the above components with a dry blender, a Henschel mixer, a ball mill, or the like, using a kneading apparatus such as a Banbury mixer, a roll, a single-screw or twin-screw extrusion kneader. After uniformly melt-kneading, the resulting kneaded material is cooled, pulverized, and classified if necessary, and can also be produced by a suspension polymerization method or the like.

The particle size of the toner is 3 to 35 μm, preferably 5 to 25 μm. The surface of the toner can be coated with a surface treatment agent to improve the fluidity and the chargeability. As the surface treatment agent, various conventionally known materials such as inorganic fine particles and fluororesin particles can be used, and in particular, silica-based surface treatment agents containing hydrophobic or hydrophilic silica fine particles, for example, ultrafine anhydrous silica and Colloidal silica or the like is preferably used.

The toner can be mixed with a magnetic carrier such as ferrite or iron powder and used as a two-component developer in an image forming apparatus.

[0038]

EXAMPLES The present invention will be described below based on examples and comparative examples. Has a molecular weight distribution of Example 1 below, 65 weight percentage of styrene in the entire resin, an acid value of the whole resin is 20 mg / g, and the acid value of components of the low molecular weight side than the following minimum value V _M Is 10
mg / g styrene-butyl acrylate copolymer 1
8 parts by weight of carbon black as a coloring agent, 1 part by weight of a negative polarity dye as a charge control agent, and 1 part by weight of low molecular weight polypropylene as an anti-offset agent were mixed with 00 parts by weight, followed by melt-kneading, followed by cooling and pulverization. , Classify,
An electrophotographic toner having a volume-based median diameter of 12 μm was prepared.

[0039] Molecular weight The molecular weight distribution maximum value P _H: 230000 Molecular weight of maximum value P _L: 6000 Molecular weight of the minimum value V _M: 24500 instead of 100 parts by weight of the copolymer used in Example 2 above Example 1, the following Having a molecular weight distribution of 70% by weight of styrene in the whole resin and an acid value of 30 mg / g in the whole resin.
In, and from the following minimum value V _M lower molecular weight acid number of component styrene is 20 mg / g - except for using butyl acrylate copolymer 100 parts by weight, the electrophotographic the same manner as in Example 1 A toner was prepared.

[0040] Molecular weight The molecular weight distribution maximum value P _H: 235000 Molecular weight of maximum value P _L: 5500 Molecular weight of the minimum value V _M: 24000 Example 3 in place of the 100 parts by weight of the copolymer used in Example 1, below Having a molecular weight distribution of 70% by weight of styrene in the whole resin and an acid value of 20 mg / g in the whole resin.
In, and from the following minimum value V _M lower molecular weight acid number of component styrene is 15 mg / g - except for using butyl acrylate copolymer 100 parts by weight, the electrophotographic the same manner as in Example 1 A toner was prepared.

[0041] Molecular weight The molecular weight distribution maximum value P _H: 240000 Molecular weight of maximum value P _L: 5000 Molecular weight of the minimum value V _M: 24500 instead of 100 parts by weight of the copolymer used in Comparative Example 1 Example 1, below Having a molecular weight distribution of 65% by weight of styrene in the whole resin and an acid value of 20 mg / g in the whole resin.
In, and from the following minimum value V _M lower molecular weight acid number of component styrene is 9 mg / g - except for using butyl acrylate copolymer 100 parts by weight, the electrophotographic the same manner as in Example 1 A toner was prepared.

[0042] Molecular weight The molecular weight distribution maximum value P _H: 240000 Molecular weight of maximum value P _L: 5000 Molecular weight of the minimum value V _M: 24000 instead of 100 parts by weight of the copolymer used in Comparative Example 2 Example 1, below Having a molecular weight distribution of 70% by weight of styrene in the whole resin and an acid value of 30 mg / g in the whole resin.
In, and from the following minimum value V _M lower molecular weight acid number of component styrene is 22 mg / g - except for using butyl acrylate copolymer 100 parts by weight, the electrophotographic the same manner as in Example 1 A toner was prepared.

[0043] Molecular weight The molecular weight distribution maximum value P _H: 235000 Molecular weight of maximum value P _L: 5500 Molecular weight of the minimum value V _M: 24500 Comparative Example 3 in place of the 100 parts by weight of the copolymer used in Example 1, below Having a molecular weight distribution of 30% by weight of the total resin and 30 mg / g of the acid value of the entire resin.
In, and from the following minimum value V _M lower molecular weight acid number of component styrene is 30 mg / g - except for using butyl acrylate copolymer 100 parts by weight, the electrophotographic the same manner as in Example 1 A toner was prepared.

[0044] Molecular weight The molecular weight distribution maximum value P _H: 240000 Molecular weight of maximum value P _L: 5000 Molecular weight of the minimum value V _M: 25000 Comparative Example 4 in place of the 100 parts by weight of the copolymer used in Example 1, below Having a molecular weight distribution of 90% by weight of styrene in the whole resin and an acid value of 25 mg / g in the whole resin.
In, and from the following minimum value V _M lower molecular weight acid number of component styrene is 25 mg / g - except for using butyl acrylate copolymer 100 parts by weight, the electrophotographic the same manner as in Example 1 A toner was prepared.

[0045] Molecular weight The molecular weight distribution maximum value P _H: 240000 Molecular weight of maximum value P _L: 5000 Molecular weight of the minimum value V _M: 24100 instead of 100 parts by weight of the copolymer used in Comparative Example 5 Example 1, below Having a molecular weight distribution of 70% by weight of styrene in the whole resin and an acid value of 15 mg / g in the whole resin.
In, and from the following minimum value V _M lower molecular weight acid number of component styrene is 15 mg / g - except for using butyl acrylate copolymer 100 parts by weight, the electrophotographic the same manner as in Example 1 A toner was prepared.

[0046] Molecular weight The molecular weight distribution maximum value P _H: 240000 Molecular weight of maximum value P _L: 5000 Molecular weight of the minimum value V _M: 24200 instead of 100 parts by weight of the copolymer used in Comparative Example 6 above Example 1, the following Having a molecular weight distribution of 70% by weight of styrene in the whole resin and an acid value of 60 mg / g in the whole resin
In, and from the following minimum value V _M lower molecular weight acid number of component styrene is 15 mg / g - except for using butyl acrylate copolymer 100 parts by weight, the electrophotographic the same manner as in Example 1 A toner was prepared.

[0047] Molecular weight The molecular weight distribution maximum value P _H: 240000 Molecular weight of maximum value P _L: 5000 Molecular weight of the minimum value V _M: 24300 instead of 100 parts by weight of the copolymer used in Comparative Example 7 Example 1, below Having a molecular weight distribution of 70% by weight of styrene in the whole resin and an acid value of 30 mg / g in the whole resin.
In, and from the following minimum value V _M lower molecular weight acid number of component styrene is 15 mg / g - except for using butyl acrylate copolymer 100 parts by weight, the electrophotographic the same manner as in Example 1 A toner was prepared.

[0048] Molecular weight The molecular weight distribution maximum value P _H: molecular weight 80,000 maxima P _L: 5000 Molecular weight of the minimum value V _M: 24000 instead of 100 parts by weight of the copolymer used in Comparative Example 8 Example 1, below Having a molecular weight distribution of 70% by weight of styrene in the whole resin and an acid value of 30 mg / g in the whole resin.
In, and from the following minimum value V _M lower molecular weight acid number of component styrene is 15 mg / g - except for using butyl acrylate copolymer 100 parts by weight, the electrophotographic the same manner as in Example 1 A toner was prepared.

[0049] Molecular weight The molecular weight distribution maximum value P _H: 240000 Molecular weight of maximum value P _L: 110000 Molecular weight of the minimum value V _M: 160000 hydrophobic toner 100 parts by weight for electrophotography obtained in the above respective Examples and Comparative Examples After mixing 0.2 parts by weight of silica, a ferrite carrier having an average particle diameter of 80 μm was blended and uniformly stirred and mixed to prepare a two-component developer having a toner concentration of 4.0%. The following tests were performed using the obtained developer.

Fixing test Electrophotographic copying machine manufactured by Mita Kogyo Co., Ltd., Model No. DC-20
The set temperature of the heating roller of the 55-model remodeling machine (heating pressure roll fixing system) is increased by 2.5 ° C. from 140 ° C. in increments of 2.5 ° C., and the transfer paper on which a toner image corresponding to a solid black original is formed is passed and fixed. The pressure-sensitive adhesive tape is pressed against the formed fixed image and then peeled off. The density of the fixed image before and after peeling is measured by the reflection densitometer. The minimum fixing temperature (F
₁ )

[0051]

(Equation 2)

Thereafter, the temperature was further increased, and the temperature at which the offset was generated was determined and set as the high-temperature offset occurrence temperature (F ₂ ). Blocking resistance test In an oven at a predetermined temperature, 20 g of the toner is placed in a cylindrical cylinder made of glass having an inner diameter of 26.5 mm.
A weight of 00 g was placed and left for 30 minutes. Thereafter, the cylinder was pulled out, the state of the toner was observed, and the temperature (B ₁ ) of the oven at which the toner did not collapse was recorded.

Observation of toner loss A mesh pattern in which a plurality of straight lines parallel to each other in the vertical and horizontal directions at an interval of about 0.57 mm is drawn in a square frame having a side length of 24 mm,
A mesh chart attached to 30 places on the surface of the A4 size blank paper was created. Using this mesh chart as an original, continuous copying is performed by an electrophotographic copying machine (Model No. DC-2055 manufactured by Mita Kogyo Co., Ltd.), and the first, 500th, 1000th, 2000th, 3000th, 4000th, 4000th From the first sheet and the 5000th sheet, the sheets on which the originals were copied were sampled every five sheets, and the presence or absence of toner loss was observed. The above results were evaluated according to the following criteria.

：: toner missing within 9 places ×: toner missing in 10 places or more Rain-free observation The above developer was used as a start developer in the same electrophotographic copying machine as described above, and was included in the developer. Using the same electrophotographic toner as the replenishing toner, 20,000 continuous copies of a solid black original were made. And
The presence or absence of rainfall in the 20,000th copy image was observed.

：: Not generated X: Measurement of spent ratio of generated toner The above developer was used as a start developer in the same electrophotographic copying machine as described above, and was the same as that contained in the developer. After performing 50,000 continuous copies of a black solid document using the electrophotographic toner as a replenishing toner, the developer is washed with a surfactant to remove the toner, and the washed carrier is dried. And weighed it (this is Xg). Next, the weighed carrier was washed with toluene to remove spent toner adhering to the carrier, and then the carrier was dried again and weighed (referred to as Yg). Then, the spent ratio (%) of the toner to the carrier was determined by the following equation.

[0056]

(Equation 3)

Moisture resistance test The above developer was used as a start developer in the same electrophotographic copying machine as described above, and the same electrophotographic toner contained in the developer was used as a replenishing toner. Observe the state of toner replenishment from the toner hopper to the developing device when 20,000 continuous copies of a solid black original were performed.
も の indicates that the toner was replenished without any problem, ○ indicates that the toner was slightly clogged, but did not cause any problem in toner replenishment, and x indicates that the toner was clogged.

Table 1 shows the above results.

[0059]

[Table 1]

[0060] From the results of Table 1, the toner of Comparative Example 1 minimum value V _M than the low molecular weight side of the acid number of the component having a molecular weight distribution is less than 10 mg / g has high spent rate, Therefore, heat resistance Turned out to be bad. Further, when the acid value is 20
The toner of Comparative Example 2 of greater than mg / g has a high minimum fixing temperature F _1, From this, it was found that the poor low-temperature fixing property.
Comparative Example percentage of the total resin of styrene is less than 40 wt% 3, Comparative Example Comparative Example 5 the acid value of the whole resin is less than 20 mg / g, the molecular weight of the maximum value P _H is less than 1 × 10 ⁵ 7, and the toner of Comparative Example 8 having a maximum molecular weight P _L of more than 1 × 10 ⁵ , the blocking temperature B _1.
Of the toner, and toner loss and fraying of the toner due to the occurrence of blocking were observed, indicating that the heat resistance was poor. The toner of Comparative Example 7 has a low high-temperature offset generating temperature F _2, it was found that easily offset.

The toners of Comparative Example 4 in which the ratio of styrene to the entire resin exceeds 80% by weight, Comparative Example 6 in which the acid value of the entire resin exceeds 50 mg / g, and the toner of Comparative Example 8 above all have the lowest fixing temperature. F ₁ is high, since this was found to be inferior in low-temperature fixability. Further, it was found that the toner of Comparative Example 6 had poor moisture resistance. On the other hand, it was found that all of the toners of Examples 1 to 3 having the constitution of the present invention were excellent in low-temperature fixability, offset resistance and heat resistance.

[0062]

According to the electrophotographic toner of the present invention,
By limiting the molecular weight distribution of the styrene-acrylic copolymer to a predetermined range, while maintaining low-temperature fixability and offset resistance, increasing the acid value of the entire resin and increasing the glass transition temperature of the entire fixing resin. At the same time, the acid value of the low molecular weight component is lowered to lower the glass transition temperature of the low molecular weight component. Therefore, the electrophotographic toner of the present invention is
It is excellent in offset resistance and heat resistance, and particularly excellent in low-temperature fixability.

[Brief description of the drawings]

FIG. 1 is a gel permeation chromatogram showing the molecular weight distribution of a styrene-acrylic copolymer.

FIG. 2 is a gel permeation chromatogram showing an example of a method for obtaining a styrene-acrylic copolymer having the molecular weight distribution of FIG.

Continuation of the front page (72) Inventor Takeshi Arakawa 1-2-2, Tamazo, Chuo-ku, Osaka City, Osaka Prefecture Inside Mita Industries Co., Ltd. (56) References JP-A-2-5070 (JP, A) JP-A-2-2- 235069 (JP, A) JP-A-60-150056 (JP, A) JP-A-63-214760 (JP, A) JP-A-62-9356 (JP, A) JP-A-2-168264 (JP, A) JP-A-63-218971 (JP, A) JP-A-2-66560 (JP, A) JP-A-56-16144 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (1)

(57) [Claims] 1. In a gel permeation chromatogram showing a molecular weight distribution, a molecular weight is in the range of 1 × 10 ³ or more and less than 1 × 10 ⁵ , and a molecular weight of 1 × 10 ⁵ or more and 3 × 10 ⁵ or less. An electrophotographic toner containing, as a fixing resin, a styrene-acrylic copolymer having a maximum value of the molecular weight distribution and a minimum value of the molecular weight distribution between the two maximum values, The ratio of styrene to the entire fixing resin is in the range of 40 to 80% by weight, the acid value of the entire fixing resin is 20 to 50 mg / g, and the acid value of the component having a lower molecular weight than the minimum value is 10 to 10 mg / g. 20 mg / g , and
The acid value of the low molecular weight component is lower than the acid value of the entire fixing resin.
Electrophotographic toner, characterized in that the decoction.