JPH06161144A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To provide toner with wax of small grain diameter dispersed uniformly so as not to generate filming to a photosensitive body caused by the separation of wax, and black spots and fog caused by filming. CONSTITUTION:Electrophotographic toner for fixing a heat roll is formed of at least binding resin and offset preventing wax. This toner contains 1-7 weight parts of wax to 100 weight parts of the toner binding resin in such a state that the wax is incompatible with the binding resin, and the wax is substantially spherical and/or spindle-shaped, and dispersed in island shape. In the case of spherical dispersed wax, the average diameter (DW) of the wax and the average diameter (DT) of the toner satisfies the relation of DW=0.05DT-0.2DT. In the case of spindle-shaped dispersed wax, a relational expression (ab<2>)<1/3>=0.025 DT-0.1DT is satisfied, where (a) is the average of the major axes of the wax, and (b) is the average of minor axes of the wax.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner used in electrophotographic copying.

[0002]

2. Description of the Related Art A toner used for electrophotography is generally manufactured by melt-mixing a binder resin, a colorant and necessary additives, and crushing and classifying the melt-kneaded product. As a necessary additive, waxes that are incompatible with the binder resin are generally added to prevent the occurrence of high-temperature offset during heat roll fixing.

However, since the wax added is incompatible with the binder resin, it is difficult to uniformly disperse the wax in the binder resin in a small particle size, and the wax is removed from the toner particles during pulverization in the toner manufacturing process. Is easy to separate.

If the size of the wax separated from the toner particles is much smaller than the toner particle size,
Even if it is not removed in the classification step, even if it is not removed, the fine particles cling to the toner particles and fate together with the toner and do not adversely affect the photoconductor and the copy image. If it is near, the fine powder will not be cut even in the classification step and will be scattered in the toner product. Since the free wax thus mixed in the product does not contain a coloring agent or a charge control agent, its chargeability is significantly different from that of the product toner.

During the copying process, the wax adhered together with the toner particles on the electrostatic latent image on the photoconductor is not transferred even during the transfer process onto the copy paper, and free wax remains on the photoconductor. The wax remaining on the photoconductor is not cleaned by the cleaner blade in the cleaning step and remains fused on the photoconductor as it is. The fusion wax is further thinly stretched to form a film on the photoconductor.

Further, toner adheres to the filmed wax to form streaky black spots (black spots) on the photoconductor. This filming or black spot fusion product does not leak charge, so if fog occurs in the copied image or if toner is developed on them,
The toner is transferred to the paper and causes image noise.

In order to improve the vividness of an image, a toner has recently been made smaller in particle size. In the case of such a toner, it is particularly necessary to uniformly disperse the wax in a small particle size.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, in which wax is uniformly dispersed with a small particle diameter, and filming on a photoreceptor due to separation of wax and An object of the present invention is to provide a toner that does not cause black spots, fog, and the like.

[0009]

That is, the present invention relates to a heat roll fixing electrophotographic toner comprising at least a binder resin and an offset-preventing wax, in which the wax is incompatible with the binder resin. Resin 1
1 to 7 parts by weight per 100 parts by weight of the wax, and the wax is a substantially spherical and / or spindle-shaped dispersed in an island shape, and in the case of a spherically dispersed wax, the average diameter of the wax ( D _W ) and the average diameter (D _T ) of the toner satisfy the relationship of D _W = 0.05D _{T to} 0.2D _T , and in the case of a spindle-shaped dispersion wax, the following relational expression: (ab ² ) ^1/3 = 0.025D _{T to} 0.1D _T (wherein a represents the average of the major axis of the wax and b represents the average of the minor axis of the wax).

The electrophotographic toner of the present invention comprises at least a binder resin and a wax which is incompatible with the resin.

The binder resin used may be a commonly used thermoplastic resin such as styrene / acrylic copolymer resin or polyester resin.

Paraffin waxes such as low molecular weight polypropylene, low molecular weight polyethylene, ethylene bisamide, microcrystalline wax, carnauba wax and beeswax are preferably used as the wax.
There is no particular limitation as long as it is incompatible with the thermoplastic resin used as the binder resin of the toner and has a releasing property.

In the present invention, "incompatible" means a state in which wax is dispersed in an island shape in the resin when melt-kneaded and is not incorporated in the molecular chain of the resin.

In the present invention, the wax is formed by dispersing substantially spherical particles and / or spindle-shaped particles in a binder resin.

Substantially spherical means that the ratio of the major axis a to the minor axis b is 1.
It may be / 1/1/3, the average diameter of the wax (D
w) was calculated from (a + b) / 2.

When such a substantially spherical wax is dispersed in the resin, the average diameter (D _W ) of the wax and the average diameter (D _T ) of the toner are 0.05 D _T ≤ D _W ≤ The particles are dispersed with a small particle size that satisfies the relationship of 0.2D _T.

The term "substantially spindle-shaped" means that the ratio (a / b) is in the range of 5/1 to 20/1, where a is the average of the long axes of the spindle and b is the average of the short axes. Say. If the major axis becomes too long compared to the minor axis, the free wax will be more likely to get scattered in the toner product. However, a / b is 1/1 to 1/1
And the substantially spherical shape, it is sufficient that the relationship between D _W and D _T is satisfied as described above.

When the spindle-shaped wax as described above is dispersed in the resin, it is dispersed so as to satisfy the following relational expression: (ab ² ) ^1/3 = 0.025D _{T to} 0.1D _T. There is. The expression (ab ² ) ^1/3 is statistically obtained from experimental results and approximately expresses the radius of the spindle-shaped wax.

When D _W is smaller than 0.05 D _T or (ab ² ) ^1/3 is smaller than 0.025 D _{T, the} effect of preventing high temperature offset becomes small, and the free wax is still classified by the product. It will adhere to the toner and be difficult to remove. On the other hand, when D _W is larger than 0.2 D _T or (ab ² ) ^1/3 is larger than 0.1 D _T , the free wax is scattered in the product toner, causing filming and black spots. .

The average diameter of the wax, the major axis and the minor axis are
The obtained toner is treated with a solvent that dissolves the binder resin but not the wax, is centrifuged, and the wax floating in the solvent is collected, and a scanning electron micrograph (SEM) is taken.
Observed by observing with any area (7.
It is a value obtained by arbitrarily extracting about 500 substantially spherical and spindle-shaped particles within 3 × 9.5 cm) and averaging them.

The average diameter of the toner is a value measured by the volume average diameter of a Coulter counter.

The wax produced in this manner is obtained in a state in which the substantially spindle-shaped wax and the spherical wax are randomly dispersed, but D _W and (ab ² ) ^1/3 satisfy the above-described relationship. If so, there is no particular problem.

In the toner of the present invention, it is desirable that the substantially spindle-shaped wax is 70% or less of the wax particles.

The toner of the present invention is manufactured by mixing a binder resin, a colorant, a wax and other additives, and kneading, pulverizing and classifying them. Wax is toner binder resin 10
1 to 7 parts by weight, preferably 2 to 6 parts by weight, are added to 0 parts by weight. If the amount is less than 1 part by weight, there is little effect on high temperature offset, and if it is more than 7 parts by weight, the amount of free wax increases and the filming black spots on the photoreceptor increase. The other additives may be used in usual amounts.

In order to uniformly disperse the wax with a small particle size as in the present invention, a mixer having a pulverizing ability, such as a ball mill or a Henschel mixer, is used in the mixing step, and kneading is performed in the kneading step. It is achieved by noting that the temperature is set as low as possible below the melting temperature of the resin and the shearing force of the resin is available.

The present invention will be further described below with reference to examples.

[0027]

Example 1 Styrene / acrylic copolymer resin 100 parts by weight Number average molecular weight (Mn): 4500, Mw / Mn: 48 (Mw; weight average molecular weight) Glass transition point (Tg): 62 ° C. ・ Carbon black (MA # 8; Mitsubishi Kasei Co., Ltd.) 8 parts by weight Nigrosine dye (Bontron N-01; Orient Chemical Co., Ltd.) 3 parts by weight Low molecular weight polypropylene (Viscor 550P; Sanyo Kasei Co., Ltd.) 4 parts by weight

The above materials were placed in a ball mill, and 24
Mixed and crushed for hours. Further, it was sufficiently kneaded for 15 minutes using three rolls. At this time, the temperature of the two rolls inside and behind the three rolls is 140 ° C, and the temperature of the front roll is 120 ° C.
Set to.

The obtained kneaded product was taken out, gradually cooled to 90 ° C., and further cooled to 40 ° C. or lower with cold air. 2 cooling products
It was coarsely crushed to a size of less than mm square.

Next, the coarsely pulverized product was pulverized by a jet pulverizer to an average diameter of 8.4 μm, and coarse powder and fine powder were cut by a DS classifier to obtain particles having an average diameter of 9.1 μm.

Finally, the obtained particles are treated with hydrophobic silica (H
-2000; manufactured by Hoechst Co., Ltd.) 0.2% by weight was added to perform surface treatment to obtain a toner A.

Example 2 Polyester resin 100 parts by weight Number average molecular weight (Mn): 6800, Mw / Mn: 32 (Mw; weight average molecular weight) Glass transition point (Tg): 65 ° C. Carbon black (# 44; Mitsubishi Kasei Kogyo Co., Ltd.) 8 parts by weight Cr-containing gold oil-soluble dye (Bontron S-34; Orient Chemical Co., Ltd.) 2 parts by weight Low molecular weight polypropylene (Viscor TS-200; Sanyo Kasei Co., Ltd.) 4 parts by weight

The above material was made into a toner by the same method as in Example 1 to obtain a toner B having an average diameter of 8.2 μm.

Examples 3 to 5 Toners C to E having the particle sizes shown in Table 1 below were obtained in the same manner as in Example 1 except that the amount of the surface treatment agent was changed as follows.

[0035]

[Table 1] Particle size (μm) Surface-treated toner C 5.4 H-2000 0.3% by weight Toner D 12.1 H-2000 0.15% by weight Toner E 14.8 H-2000 0.1% by weight

Example 6 Toner F having an average diameter of 8.4 μm was prepared in the same manner as in Example 1 except that the low molecular weight polypropylene was replaced with Viscole 660P.
Got

Example 7 Toners G having the particle diameters shown in Table 2 below were prepared in the same manner as in Example 1 except that the low molecular weight polypropylene was added in the following amounts.
H was obtained.

[0038]

[Table 2] Low molecular weight polypropylene Particle size Toner G 1 part by weight 8.7 μm Toner H 5 parts by weight 9.2 μmToner I 7 parts by weight 8.6 μm

Comparative Example 1 The materials used in Example 1 were charged into a V blender with the same composition and the V blender was rotated for 15 minutes to uniformly mix the materials. Next, the mixture was charged into a continuous extrusion kneader and kneaded at a preset temperature of 160 ° C. The temperature of the discharged kneaded material is 178.
It was ℃. The obtained kneaded product was rapidly cooled to 40 ° C. or less with a cooling belt, and then pulverized to 2 mm square or less.

Comparative Example 2 The materials used in Example 2 were used with the same composition, and Comparative Example 1
A toner K having an average diameter of 8.5 μm was obtained by the same manufacturing method as described above.

Comparative Example 3 Toner L having an average diameter of 8.8 μm was obtained by using the same material as in Example 3 except that 8 parts by weight of low molecular weight polypropylene was used.

Comparative Example 4 4 parts by weight of low molecular weight polypropylene (Viscole 330P; manufactured by Sanyo Chemical Industry Co., Ltd.) was melted and dispersed during the solution polymerization reaction of the styrene-acrylic copolymer resin. Next, the obtained melt was desolvated in a high vacuum to obtain a resin. The obtained resin has a number average molecular weight of 5,200 and a dispersity (Mw / Mn) of 4
6. The glass transition point was 61 ° C.

100 parts by weight of the above resin Carbon black (MA # 8; manufactured by Mitsubishi Kasei Co., Ltd.) 8 parts by weight Nigrosine dye (Bontron N-01; manufactured by Orient Chemical Co., Ltd.) 3 parts by weight Implemented using the above materials Same as example 1, average diameter 8.4μ
m toner M was obtained.

Toners A prepared in Examples and Comparative Examples
M was dissolved in chloroform and centrifuged. After 10 minutes, the wax floating on the surface was collected, and an SEM photograph was taken to measure the particle size of the wax. The results are shown in Table 3 below.

[0045]

[Table 3]

The obtained toners A to M were sufficiently mixed with a separately prepared binder type carrier (average diameter 62 μm) and charged. Copier EP8600 for negatively charged toner
(Minolta camera), in the case of positively chargeable toner, copying machine EP860 in which the photoconductor was changed to an organic laminated photoconductor.
0 was used to perform a printing durability test. The results are shown in Table 4 below.

[0047]

[Table 4]

The ranking in the above table was performed as follows. Filming of photoconductor ◎: No filming at all ○: A little filming but no problem in practical use ×: Filming occurs and fog occurs Black spot fusion (black spot (BS)) ○: Black spot fusion No adhesion was observed. △: Black spot fusion occurred on the photoconductor, but it did not occur on the copy image. ×: Black spots appeared on the copy image.

The obtained toners A to M were sufficiently mixed with a separately prepared binder type carrier (average diameter 62 μm) and charged. Copier EP8600 for negatively charged toner
(Manufactured by Minolta Camera Co., Ltd.), in the case of positively chargeable toner, the copying machine EP8600 was modified, and the photosensitive member was changed to an organic laminated photosensitive member, and a printing durability test was conducted. The fixing test was performed at a system speed of 13 cm / sec, and images with densities of ID1.2 and ID0.6 were copied.
The copied image was shaved with a sand eraser under the conditions of a load of 1 kg and 3 reciprocations, and the ratio to the reflection density before scraping was expressed in%. At the same time, the high temperature offset generation temperature was measured. The results are shown in Table 5 below.

Practically, the ratio of reflection densities is required to be 80% or more for an image of ID1.2 and 65% or more for an image of ID0.6. The temperature at which high temperature offset occurs is practically 230
A temperature of ℃ or above is required.

[0051]

[Table 5]

In the toner of the present invention, the wax having a small particle diameter is uniformly dispersed, and filming on the photoconductor due to the separation of the wax and a black spot associated therewith,
Fogging does not occur.

Claims (2)

[Claims] 1. A heat roll fixing electrophotographic toner comprising at least a binder resin and an offset preventing wax, wherein the wax is incompatible with the binder resin in an amount of 1 to 7 per 100 parts by weight of the toner binder resin. A toner in which the wax is substantially spherical and / or spindle-shaped and dispersed in an island shape in the case of a spherical dispersion wax, the average diameter (D _W ) of the wax and the average diameter of the toner are included. (D
_T ) satisfies the relationship of D _W = 0.05D _{T to} 0.2D _T , and in the case of a spindle-shaped dispersion wax, the following relational expression: (ab ² ) ^1/3 = 0.025D _{T to} 0.1D _T (In the formula, a represents the average of the long axis of the wax, and b represents the average of the short axis). 2. The toner for electrophotography according to claim 1, wherein a ratio (a / b) of the major axis a and the minor axis b of the spindle wax is 20/1 to 5/1.