JPH03294865A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To enhance durability and to prevent occurrences of poor fixing and offset by incorporating a specified styrene-acrylic copolymer as a fixing resin and specified carbon block as a colorant, and specifying the relaxation time. CONSTITUTION:The styrene-acrylic copolymer to be used as the fixing resin has in the gel permeation chromatogram for showing molecular weight distribution the maximum values above 1X10<5> and within 5X10<2> - 2X10<4> and the minimum value between the maximum values, and a ratio of the sum of the areas of both peaks within them to the area of the valley below a common tangent tying both peaks is <=0.30. As the colorant, the carbon black having an absorption of dibutyl phthalate of >=80 ml/100g is used, and the relaxation time at a frequency of 100kHZ is within 10 - 50 msec, thus permitting durability to be enhanced and occurences of poor fixing an offset to be prevented.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an electrophotographic toner, and more specifically, toner used in image formation using the so-called Carlson process, such as in electrostatic copying machines and laser beam printers. This invention relates to toner for electrophotography.

<Prior Art> Conventionally, when forming an image, a so-called magnetic brush is formed by first holding a developer containing an electrophotographic toner on the outer periphery of a developing sleeve having a magnetic pole inside. Next, this magnetic brush is brought into sliding contact with the photoconductor on which the electrostatic latent image is formed, and the electrophotographic toner in the developer is electrostatically attached to the electrostatic latent image, thereby creating a toner image. Visualize it. Next, the toner image is transferred from the surface of the photoreceptor onto paper and further fixed onto the paper by a fixing roller, thereby completing image formation.

The electrophotographic toner used for the above image formation is as follows:
A fixing resin containing a coloring agent such as carbon black, a charge control agent, etc., and granulated to a predetermined particle size is used.

The above-mentioned electrophotographic toner has problems such as the occurrence of so-called offset, such as show-through due to peeling from the paper, stains on the back side, and stains on the fixing roller, as well as poor fixation of the toner image on the paper (particularly when the fixing temperature is low). Problems such as deterioration of low-temperature fixing properties may occur.

Among the above-mentioned problems, deterioration in low-temperature fixability mainly occurs when the molecular weight of the fixing resin contained in the electrophotographic toner is high. On the other hand, offset mainly occurs when the molecular weight of the fixing resin is low.

Therefore, in order to solve the above problem, various electrophotographic toners have been proposed that use a combination of a low molecular weight resin and a high molecular weight resin as the fixing resin (for example, JP-A-56
-16144, JP-A-60-3644, etc.).

The electrophotographic toner described in JP-A-56-16144 is a polymer synthesized from vinyl monomers or a mixture of such polymers, and a chromatogram measured by gel permeation chromatography shows a molecular weight of 103. ~8x104 and molecular weight 105 ~2X1
A fixing resin having at least one maximum value in each area of ×105 is used.

In addition, the fixing resin used in the electrophotographic toner described in JP-A-60-3644 mainly contains A) a component with a weight average molecular weight of 500,000 or more, and B) a component with a weight average molecular weight of 20,000 to 200,000. components, and C) weight average molecular weight 1
A fixing resin composed of 000 to 20,000 components is used.

<Problems to be Solved by the Invention> However, as mentioned above, high molecular weight components have excellent offset resistance but reduce fixing properties, while low molecular weight components have excellent low temperature fixing properties but have poor offset resistance. Therefore, it is practically difficult to satisfy both low-temperature fixing properties and anti-offset properties at the same time by simply using both components together. Furthermore, in a system that uses a high molecular weight component and a low molecular weight component in combination, the resin composition becomes inhomogeneous, the cohesive force decreases, and the durability decreases, and the electrophotographic toner may be crushed during the development operation. There is a risk of Furthermore, there is also a risk that toner that does not contribute to image formation (spent toner) increases, accelerating deterioration of the developer.

Furthermore, as copying machines become faster and consume less power, the fixing time has recently become shorter and the fixing temperature has tended to be lower than before, so the conventional fixing resins mentioned above are no longer used. The problems of poor fixing, increased tendency to offset, and shortened toner life have reoccurred with electrophotographic toners, and no effective solution to these problems has yet been found.

This invention has been made in view of the above circumstances, and eliminates the above-mentioned drawbacks of conventional electrophotographic toners, and is fully applicable to high-speed copying machines and copying machines equipped with low power consumption fixing sections. The purpose of the present invention is to provide an electrophotographic toner that can be used for electrophotography.

Means and Effects for Solving the Problems> In order to solve the above problems, the inventors conducted a comprehensive study on the molecular weight distribution of fixing resins and toner properties. As a result, when a styrene-acrylic copolymer is used as a fixing resin and a low-molecular-weight component and a high-molecular-weight component are used together as the styrene-acrylic copolymer, a common component of both components is In other words, it has been found that by increasing the amount of a component having a molecular weight intermediate between the two, homogeneity is improved and durability is improved, and the occurrence of poor fixing and offset can be suppressed.

However, by simply selecting the type of fixing resin and setting the molecular weight distribution, it is not possible to obtain an electrophotographic toner that can sufficiently respond to the faster fixing speeds and lower fixing temperatures that have come with recent advances in technology. It turned out that.

Therefore, we investigated factors other than the fixing resin and found that the dispersibility of the colorant carbon black in the fixing resin and the relaxation time of the electrophotographic toner are important for the occurrence of the above-mentioned poor fixing properties and offset. It was discovered that this is an important element in suppressing this, and as a result of further study, the present invention was completed.

Therefore, the electrophotographic toner of the present invention, as a fixing resin, has a molecular weight of 1 x 105 or more and a molecular weight of 500 to 500 in the gel permeation chromatogram showing the molecular weight distribution.
Within the range of 2 x 1 x 105, the maximum value of the molecular weight distribution and the minimum value of the molecular weight distribution between the two maximum values, and the sum of the areas of two peaks that include both maximum values, and the common value of both peaks. Contains a styrene-acrylic copolymer having a molecular weight distribution in which the ratio of the area of the valley including the minimum value below the tangent line to the area of the valley below the tangent line is 0.30 or less, and as a colorant, Dibutyl phthalate oil absorption 80ml/
Contains 100 g or more of carbon black, and
Relaxation time at frequency 100KHz is 10-50 m
sec. It is characterized by being within the range of

As shown in Figure 1, the styrene-acrylic copolymer used as the fixing resin has a molecular weight distribution on the high molecular weight side and low molecular weight side in the gel permeation chromatogram showing the molecular weight distribution. A molecular weight distribution having maximum values PH and PL and a minimum value vM of the molecular weight distribution between the two maximum values PH5PL is used.

The maximum molecular weight PII on the high molecular weight side needs to be a high molecular weight of I×10 5 or more. The molecular weight of the maximum value PH is 1
If it is less than ×105, the high molecular weight component in the styrene-acrylic copolymer is insufficient, and an electrophotographic toner with excellent offset resistance cannot be obtained.

In addition, the molecular weight of the maximum value PL on the low molecular weight side is 500 to 2
It needs to be within the range of X1×105.

When the maximum molecular weight PL exceeds 2×1×10 5 , the styrene-acrylic copolymer lacks low molecular weight components, making it impossible to obtain an electrophotographic toner with excellent low-temperature fixability. On the other hand, when the molecular weight of the maximum value P is less than 500,
The shape retention of the styrene-acrylic copolymer is insufficient, making it impossible to obtain an electrophotographic toner with excellent durability.

The molecular weight of the minimum value vM of the molecular weight distribution is not particularly limited as long as it is an intermediate value between the molecular weights of the two maximum values PH5PL.

Area SH of two peaks including the above maximum values PH and PL
, SL and the area S of the valley below the tangent ρ that includes the local minimum ■M when both peaks are connected by a common tangent g.
From v, the ratio (V/P) derived from the following formula is how the molecular weight distribution curve of the styrene-acrylic copolymer approximates a quadrilateral shape formed by connecting the two maximum values with a common tangent g. The smaller the ratio (V/P), the more similar it is to a quadrilateral. This is an indicator of how much there is a component with 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 with intermediate molecular weights are present, and an electrophotographic toner having an optimal combination of fixing properties, anti-offset properties, and durability can be obtained.

In the present invention, the ratio (V/P) needs to be 0.30 or less, and is particularly preferably 0.20 or less.

If the ratio (V/P) exceeds 0.30, styrene-
The lack of intermediate molecular weight components in the acrylic copolymer results in poor homogeneity, which deteriorates the durability of electrophotographic toners and makes it impossible to suppress the occurrence of poor fixing and offset.

In addition, the area SH of the peak including the maximum value PH on the high molecular weight side
The ratio of the area S of the peak containing the local maximum value P on the low molecular weight side is not particularly limited, but the ratio is 15, assuming a total of 100.
・85-50: 50, especially 20: 80-45
: Preferably within the range of 55.

In order to produce a styrene-acrylic copolymer having the above molecular weight distribution, dispersion of low molecular weight components (molecular weight distribution, M
-/M N ), a method of widening the dispersion of the high molecular weight component (M w / M N ), and a method of widening the dispersion of both components (M w / M N ). In short, the molecular weight distributions of both components overlap. It would be better to make it larger. In general, it is desirable to increase the dispersion (Mw/MN) of high molecular weight components from the viewpoint of various properties of an electrophotographic toner, and the dispersion (Mw/MN) of high molecular weight components is 2.
It is preferably in the range of 7 to 3.7, particularly 3.0 to 3.4. On the other hand, the dispersion (Mw/MN) of low molecular weight components is 1.
It is preferably in the range of 5 to 2.5, particularly in the range of 1.8 to 2.2.

The styrene-acrylic copolymer used in the present invention can be obtained by homogeneously melt-blending multiple types of styrene-acrylic copolymers with different molecular weight distributions, or by a two-stage polymerization method so as to have the molecular weight distribution described above. Manufactured using

For example, as shown in FIG. 2, a styrene-acrylic copolymer (low molecular weight) having a molecular weight distribution shown in curve A,
When equal amounts of a styrene-acrylic copolymer (high molecular weight) having a molecular weight distribution shown in curve B are melt blended, a styrene-acrylic copolymer having a molecular weight distribution within the range of the present invention shown in curve C can be obtained. .

Furthermore, suspension polymerization and emulsion polymerization generally produce higher molecular weight polymers than solution polymerization. Therefore, when producing a styrene-acrylic copolymer,
Multi-stage polymerization is performed by combining a suspension polymerization method or an emulsion polymerization method and a solution polymerization method in this order or in the reverse order,
Furthermore, by controlling the molecular weight at each stage, a styrene-acrylic copolymer having the above molecular weight distribution can be obtained. The molecular weight or molecular weight distribution can be adjusted by selecting the type and amount of the initiator, the type of solvent involved in chain transfer, the type of dispersant or emulsifier, etc.

As the styrene monomer, in addition to styrene, vinyltoluene, α-methylstyrene, etc. can also be used. As the acrylic monomer, those represented by the following formula (I) can be used.

In the formula, R1 is a hydrogen atom or a lower alkyl group, and R2 is a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms, a hydroxyalkyl group, a vinyl ester group, or an aminoalkyl group.

Examples of the acrylic monomers represented by general 2m above include acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, and methacrylate. Methyl acid, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-hydroxyacrylate, δ
-Butyl hydroxyacrylate, β-hydroxyethyl methacrylate, γ-aminopropyl acrylate, γ-N
, N-diethylaminopropyl acrylate, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and the like.

Styrene-acrylic copolymers suitable for the purpose of the present invention include styrene/methyl methacrylate/butyl acrylate copolymers, in particular 75 to 85% by weight of styrene, 0.5 to 5% by weight of methyl methacrylate, And those containing 10 to 20% by weight of butyl acrylate are preferably used.

The electrophotographic toner of the present invention is produced by blending the above styrene-acrylic copolymer with carbon black as a colorant, a charge control agent and other conventionally known additives, and is Frequency 10, which represents charging characteristics
Relaxation time at 0 KHz is 10-501 Ilsec,
Must be within the range. Relaxation time is 10111se
If it is less than c, the charge of the toner adhering to the photoreceptor disappears in a short time, resulting in poor transferability and poor image formation.

Furthermore, electrophotographic toner with poor charging properties tends to scatter in the developing section of an image forming apparatus, causing stains on paper, blurring of formed images, and the like. On the other hand, the relaxation time is 50 msec. If the amount exceeds 1, it becomes difficult for the charge to be removed, and the removability from the surface of the photoreceptor, so-called cleaning performance, deteriorates. In addition, the relaxation time is 50 msec. Electrophotographic toner that exceeds 100% is likely to adhere to the fixing roller when subjected to friction by the fixing roller, etc., resulting in defective images,
This causes dirt inside the image forming device.

The above relaxation time can be defined within the above range by appropriately selecting the type, particle size, blending ratio, etc. of carbon black, as will be described later.

The carbon black has a dibutyl phthalate oil absorption amount (JIS
80 ml
/ Must be 100 g or more, especially 90~
Preferably, it is within the range of 120 ml/100 g. If the carbon black has an oil absorption amount of dibutyl phthalate of less than 80 ml/100 g, the dispersibility in the styrene-acrylic copolymer will be insufficient, which may impede the homogeneity of the electrophotographic toner and deteriorate its durability. Alternatively, carbon black separated from the destroyed resin contaminates the carrier constituting the developer together with the electrophotographic toner, promoting deterioration of the developer. Also,
Dibutyl phthalate oil absorption of carbon black is 80
ml less than 71002, the charge tends to escape to the outside through carbon black that is not sufficiently dispersed in the styrene-acrylic copolymer, and the relaxation time decreases.
The aforementioned 10 msec. As a result, the electrophotographic toner becomes difficult to charge. Furthermore, the influence of carbon black exposed from the surface of toner particles without being sufficiently dispersed tends to stain the roller during fixing and cause toner aggregation.

The particle size of carbon black is not particularly limited, but is 10~
It is preferably within the range of 50 mμ.

If the particle size exceeds 50 mμ, carbon black may inhibit the granulation of electrophotographic toner.

Furthermore, if the particle size of carbon black is less than 10 mμ, the dispersibility in the styrene-acrylic copolymer will decrease, resulting in the aforementioned problems associated with deterioration of durability, carrier contamination, and deterioration of chargeability. There is a risk of causing this.

In addition, the blending ratio of carbon black in the electrophotographic toner is not particularly limited, but the proportion of carbon black in the electrophotographic toner is 3 to 3.
It is preferably within the range of 20% by weight. If the blending ratio of carbon black is less than 3% by weight, the relaxation time of the electrophotographic toner may be 50 msec. There is a risk of exceeding.

On the other hand, when the blending ratio of carbon black exceeds 20 parts by weight, the relaxation time is 10 msec. There is a risk that it will be less than

The above carbon black includes furnace black,
Various conventionally known carbon blacks such as channel black, thermal black, gas black, oil black, acetylene black, and black can be used.

The charge control agent includes oil-soluble dyes such as nigrosine dye and spirone black; metal soaps such as naphthenic acid metal salts, salicylic acid metal salts, octylic acid metal salts, fatty acid metal salts, and resin acid metal salts; metal azo dyes. , pyrimidine compound,
Examples include alkyl salicylic acid metal chelates.

The blending ratio of the charge control agent in the electrophotographic toner is not particularly limited, but it is preferably within the range of 0.1 to 5% by weight in the electrophotographic toner.

Examples of additives other than the charge control agent include offset inhibitors for preventing offset, such as various waxes such as paraffin wax, low molecular weight polypropylene, low molecular weight polyethylene, fatty acid amide, silicone oil, and the like.

The above-mentioned offset inhibitor is contained in an electrophotographic toner of 0.5
It is preferable to contain up to 10% by weight.

The particle size of toner for electrophotography is generally 5 to 20 μm, especially 7
The particle size is preferably in the range of ~13 μm, and a toner having this particle size can be obtained by pulverization, classification, suspension polymerization, or the like. Hydrophobic silica fine particles or carbon black may be sprinkled on the surface of the toner particles to improve their fluidity.

This toner can be mixed with a magnetic carrier such as ferrite or iron particles and used as a two-component developer for image formation by electrostatic image development, transfer, and fixing.

<Examples> The present invention will be described in detail below using Examples and Comparative Examples.

Example 1 Styrene (St)/methyl methacrylate (MMA)/butyl acrylate (B
A) Copolymer [St:MMA:BA-80:5:15(
Weight ratio) 1100 parts by weight, dibutyl phthalate oil absorption 100ml/100g.

8 parts by weight of carbon black with an average particle size of 22 mμ, 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, melted and mixed using a heating roll mill, and then cooled. Pulverization and classification were performed to produce an electrophotographic toner having a volume-based median diameter of 12 μm. Of the obtained electrophotographic toner,
The relaxation time at a frequency of 100KHz is 30 asec
,Met.

Molecular weight of molecular weight distribution maximum value PH: 597,000 maximum value P,
Dispersion of the peak containing the maximum value (M-/MN): 3.1 Area of the peak containing the maximum value PH (S) I): 25 Molecular weight of the maximum value PL: 12200 Dispersion of the peak containing the maximum value PL (M, /MN) ): 1. 95 Area of peak including maximum value PL (SL) Near 5 Molecular weight of minimum value vM: 130000 Minimum value vM
Valley area (Sv): 14 Ratio (V/P): 0.140 The dibutyl phthalate oil absorption amount of carbon black is based on JIS K
6221-1982 R Carbon Black Test Method for Rubber" The measurement was carried out in accordance with the method A described in "Test Method for Carbon Black for Rubber" according to the following procedure.

First, 20.00g of sample was dried at 105±2℃ for 1 hour.
Absolute meter [Braben
Manufactured by der), spring tension 2.68kg/a
a ] into the mixing chamber. Next, with the limit switch for measuring the torque of the rotary blade for sample stirring installed in the mixing chamber of the absolute meter set at 70% of the maximum torque, the rotary blade was
Rotate at rotational speeds of r, p, and m. At the same time, dibutyl phthalate (specific gravity 1
．． 045 to 1.050) was dropped into the mixing chamber at a rate of 4 ml/min, and the sample was allowed to absorb the oil. When the end of oil absorption approaches, the torque of the rotor increases rapidly and the limit switch is turned off. Then, the dibutyl phthalate consumed from the start of dripping until the limit switch is turned off) ff
i (Bml) and the weight of the dried sample (A-20
, 00g), dibutyl phthalate oil absorption JEE (ml/100g) was calculated using the following formula.

Example 2 As a prescription, in place of 100 parts by weight of the copolymer used in Example 1, styrene (St
)/methyl methacrylate (MMA)/butyl acrylate (BA) copolymer [S t : MMA : BA
An electrophotographic toner having a volume-based median diameter of 12 μm was prepared in the same manner as in Example 1 except that 1100 parts by weight of -7525:20 (weight ratio) was used. The relaxation time of the obtained electrophotographic toner at a frequency of 100 KHz was 26 msec. Met.

Molecular weight at maximum pH of molecular weight distribution: 240,000 maximum pH
Dispersion of the peak containing the maximum value PH (M-/MN): 3.0 Area of the peak containing the maximum value PH (S□) = 32 Molecular weight of the maximum value PL 211,000 Dispersion of the peak containing the maximum value PL (M, /MN) 2 2, 2 Area of the peak including the maximum value PL (SL): 68 Molecular weight of the minimum value VM: 35000 Area of the valley including the minimum value vM (Sv): 4.8 Ratio (V/P): 0.048 Implemented Example 3 In place of 100 parts by weight of the copolymer used in Example 1, styrene (St
)/methyl methacrylate (MMA)/butyl acrylate (BA) copolymer [S t : MMA : BA-
80:10:10 (weight ratio) using 1100 parts by weight, dibutyl phthalate oil absorption amount 100ml/100g
, in place of 8 parts by weight of carbon black with an average particle size of 22 mμ, an oil absorption amount of dibutyl phthalate of 80 ml/100
An electrophotographic toner having a volume-based median diameter of 12 μm was prepared in the same manner as in Example 1, except that 7 parts by weight of carbon black having an average particle size of 20 μm was used.

The relaxation time of the obtained electrophotographic toner at a frequency of 100 KH2 was 24 msec. Met.

Molecular weight distribution Maximum value P, molecular weight: 105,000 Dispersion of peak including maximum value PH (M, /MN): 3.1 Area of peak including maximum value PH (So): 28 Molecular weight of maximum value PL: 12,500 Maximum value Dispersion of the peak containing the PL (MW/MN): 1.9 Area of the peak containing the maximum value PL (SL) near 2 Molecular weight of the minimum value vM: 45000 Area of the valley containing the minimum value ■3 (Sv): 20. 2 Ratio (V/P): 0.202 Example 4 As a prescription, dibutyl phthalate oil absorption amount 80ml/1
00 g, in place of 7 parts by weight of carbon black with an average particle size of 20 mμ, dibutyl phthalate oil absorption 100 ml/
An electrophotographic toner having a volume-based median diameter of 12 μm was produced in the same manner as in Example 3, except that 100 g of carbon black and 12 parts by weight of carbon black having an average particle size of 25 μm were used. The frequency of the obtained electrophotographic toner was 100KH.
The relaxation time in z was 121 sec.

Example 5 As a prescription, in place of 100 parts by weight of the copolymer used in Example 1, styrene (St
)/methyl methacrylate (MMA)/butyl acrylate (BA) copolymer [St:MMA:BA-85:
5:10 (weight ratio) using 1100 parts by weight, dibutyl phthalate oil absorption j 1100 ml / 100 g,
In place of 8 parts by weight of carbon black with an average particle size of 22 mμ, the oil absorption amount of dibutyl phthalate was 80 ml/100
An electrophotographic toner having a volume-based median diameter of 12 µm was prepared in the same manner as in Example 1, except that 7 parts by weight of carbon black having an average particle diameter of 20 mμ was used.

The relaxation time of the obtained electrophotographic toner at a frequency of 100 KH2 was 451 Ilsec.

Molecular weight of molecular weight distribution maximum value PH: 350000 maximum value PH
Dispersion of the peak containing the maximum value PH (M, /MN): 2.9 Area of the peak containing the maximum value PH (So): 21 Molecular weight of the maximum value PL 2620 Dispersion of the peak containing the maximum value PL (M, /MN) : 3.1 Area of the peak containing the maximum value PL (SL) Near 9 Molecular weight of the minimum value VM: 105,000 Area of the valley including the minimum value VM (Sv): 22 Ratio (V/P): 0.22 Comparative example 1 As a prescription, in place of 100 parts by weight of the copolymer used in Example 1, styrene (St
)/methyl methacrylate (MMA)/butyl acrylate (BA) copolymer [St:MMA:BA-80:
5:15 (weight ratio) Same as Example 1 except that 1100 parts by weight was used, but the volume-based median diameter was 1.
Two volumes of toner for electrophotography were produced. The relaxation time of the obtained toner for electronic photographic instruments at a frequency of 100 KHz is 2.
It was 9 11 seconds.

Molecular weight of molecular weight distribution maximum value PH: 330000 maximum value PH
Dispersion of the peak containing the maximum value CM, /MN): 2.9 Area of the peak containing the maximum value PM (So): 31 Molecular weight of the maximum value PL: 16500 Dispersion of the peak containing the maximum value PL (M-/MN): 2 .2 Area of the peak including the maximum value PL (SL): 69 Molecular weight of the minimum value vM: 80000 Area of the valley including the minimum value V (Sv): 52.1 Ratio (V/P): 0.521 Comparative example 2 As a prescription, in place of 100 parts by weight of the copolymer used in Example 1, styrene (St
)/methyl methacrylate (MMA)/butyl acrylate) (BA) copolymer [S t : MMA : B
A-82:4:14 (weight ratio)] An electrophotographic toner having a volume-based median diameter of 12 μm was produced in the same manner as in Example 1, except that 1100 weight was used. The relaxation time of the obtained electrophotographic toner at a frequency of 100 KHz was 20 msec. Met.

Molecular weight of molecular weight distribution maximum value P: 85000 maximum value P)l
Dispersion of the peak containing the maximum value (M-/MN): 3.0 Area of the peak containing the maximum value PH (SH): 24 Molecular weight of the maximum value PL: 5000 Dispersion of the peak containing the maximum value P (M-/MN) : 2.3 Area of the peak including the maximum value P (SL) Near 6 Molecular weight of the minimum value vM : 10800 Area of the valley including the minimum value VM (Sv): 15.2 Ratio (V/P) : Q, 152 Comparative Example 3 As a prescription, dibutyl phthalate oil absorption amount 100ml/
100 g, 60 ml of dibutyl phthalate oil absorption in place of 8 parts by weight of carbon black with an average particle size of 22 mμ
/ 100 g, except that 8 parts by weight of carbon black with an average particle size of 24 mμ was used, in the same manner as in Example 1,
An electrophotographic toner having a volume-based median diameter of 12 μm was produced. The frequency of the obtained electrophotographic toner was 100
The relaxation time at KHz is 22 msec. Comparative Example 4 An electrophotographic toner having a volume-based median diameter of 12 μm was produced using the same recipe as in Example 1 by changing the crosstalk conditions. The relaxation time of the obtained electrophotographic toner at a frequency of 100 KHz was 60 m5ec.

Met.

Comparative Example 5 An electrophotographic toner having a volume-based median diameter of 12 μm was produced using the same recipe as in Comparative Example 3 by changing the crosstalk conditions. The relaxation time of the obtained electrophotographic toner at a frequency of 100 KHz was 81 sec.

Comparative Example 6 As a prescription, dibutyl phthalate oil absorption amount 80ml/10
0 g, and 7 parts by weight of carbon black with an average particle size of 20 mμ, dibutyl phthalate oil absorption 100 ml/100
An electrophotographic toner having a volume-based median diameter of 12 μm was prepared in the same manner as in Example 3, except that 20 parts by weight of carbon black having an average particle size of 22 μm was used.

The relaxation time of the obtained electrophotographic toner at a frequency of 100 KHz was 9 msec. Met.

After mixing 0.2 parts by weight of hydrophobic silica with 100 parts by weight of the electrophotographic toner obtained in each of the above Examples and Comparative Examples, a ferrite carrier having an average particle size of 80 μm was blended,
A two-component developer having a toner concentration of 4.0% was prepared by uniformly stirring and mixing. The following tests were conducted using the obtained developer.

Copyability Test After 20,000 copies were made using the above developer in an electrophotographic copying machine (model number DC-5585, manufactured by Sanda Kogyo Co., Ltd.), the presence or absence of dirt on the fixing roller was checked. Further, the transfer efficiency when copying 20,000 sheets was calculated using the following formula.

Fixability test Electrophotographic copying machine manufactured by Sanda Kogyo Co., Ltd., model number DC-55
The set temperature of the heating roller of the 85 modified machine (heated pressure roll fixing method) was increased from 140°C in 2.5°C increments, and the transfer paper with the toner image corresponding to the solid black original was passed through and fixed. Press the adhesive tape against the formed fixed image and then peel it off. Measure the fixed image density before and after peeling off using a reflection densitometer (manufactured by Tokyo Juishoku Co., Ltd.), and calculate the fixing rate using the following formula. The lowest temperature at which the temperature increased and exceeded 90% was determined and defined as the lowest fixing temperature (F,). Thereafter, the temperature was further increased, and the temperature at which offset occurred was determined, which was defined as the high temperature offset occurrence temperature (F2).

Further, the difference (F2-i;', ) between the minimum fixing temperature (Fl) and the high temperature offset temperature (F2) was calculated and defined as the fixing temperature width (FΔ).

Blocking resistance test In an oven at 60°C, put 20g of toner into a glass cylinder with an inner diameter of 26.5mm, and place 10g of toner on top of the toner.
A weight of 0 g was placed on it and left for 30 minutes. After that, remove the cylinder and observe the state of the toner. If the toner has collapsed and returned to its original state, it is determined that there is no blocking.
).

Impact Resistance Test After the developer was thoroughly mixed before use for copying, the toner was removed from the developer and the amount of carbon CI in the carrier was measured. In addition, the amount of carbon in the carrier is reduced by removing toner from the developer after 20,000 sheets of continuous copying.
was measured. Then, the occurrence rate of spent toner (% formula %) was determined using the following formula % formula %.

The above results are shown in the table.

From the results in the table above, the electrophotographic toners of Examples 1 to 5 all had low minimum fixing temperatures (Fl), high transfer efficiency, and no roller stains, so they had excellent low-temperature fixing properties. It turned out to be something.

Further, the electrophotographic toners of Examples 1 to 5 have a high high temperature offset occurrence temperature (F2) and no blocking occurs in the blocking resistance test.
It was found to have excellent offset resistance. Furthermore, the electrophotographic toners of Examples 1 to 5 have a low spent toner occurrence rate S value, a high transfer efficiency, and no roller stains, so it is believed that they have excellent impact resistance. found. Therefore, the electrophotographic toners of Examples 1 to 5 above have a wide fixing temperature range (FΔ), and are therefore fully applicable to high-speed copying machines and copying machines equipped with low power consumption fixing sections. It turned out to be worth it.

In contrast, Comparative Example 1 in which any of the molecular weight distribution of the styrene/methyl methacrylate/butyl acrylate copolymer, the dibutyl phthalate oil absorption of carbon black, and the relaxation time at a frequency of 100 KHz was outside the range of the present invention.
It was found that samples No. 6 to No. 6 caused problems in any one of low-temperature fixing properties, blocking resistance, and impact resistance.

<Effects of the Invention> Since the electrophotographic toner of the present invention is configured as described above, it has excellent low-temperature fixing properties, anti-offset properties, and impact resistance, and can be used in high-speed copying machines and equipped with low power consumption fixing units. It can also be fully applied to copying machines.

[Brief explanation of the drawing]

Figure 1 is a gel permeation chromatogram showing the molecular weight distribution of a styrene-acrylic copolymer, and Figure 2 is a scale showing an example of a method for obtaining a styrene-acrylic copolymer having the above molecular weight distribution. This is a vermeation chromatogram. (1 other person)

Claims (1)

[Claims] 1. As a fixing resin, in the gel permeation chromatogram showing the molecular weight distribution, maximum values of the molecular weight distribution are present in the molecular weight range of 1 x 10^5 or more and in the range of molecular weight 500 to 2 x 10^4, respectively. The sum of the areas of two peaks that have a minimum value in the molecular weight distribution between the two maximum values and include both maximum values, and the minimum value below the tangent when both peaks are connected by a common tangent. Contains a styrene-acrylic copolymer having a molecular weight distribution in which the ratio to the area of valleys including
Contains carbon black of 0ml/100g or more, and has a relaxation time of 10 to 5 at a frequency of 100KHz.
0msec. An electrophotographic toner characterized by being within the range of