JP2001265055A - Nonmagnetic toner and method for forming image by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve both of the fixing property and stress resistance in a nonmagnetic single component developer which uses nonmagnetic toner. SOLUTION: The binder resin used in the nonmagnetic toner shows a patter in the distribution of molecular weight based on GPC measurement that at least one peak is present in each range of >=4×104 <7×104, >=7×104 to <12×104, and >=12×104 to <25×104.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-magnetic toner for developing an electrostatic latent image and an image forming method using the same, and more particularly, to controlling the molecular weight distribution of a binder resin of the non-magnetic toner to improve the fixing property. This is a technique for improving both the stress resistance.

[0002]

2. Description of the Related Art In OA equipment such as a copying machine, a printer, and a facsimile, an electrostatic latent image on the surface of a photoreceptor is converted into a toner image by a developer, and the toner image is transferred to a medium such as paper.
2. Description of the Related Art An image forming method using an electrophotographic method in which a medium on which a toner image is transferred is passed between heating rollers and fixed is used.

As a developer, there are a two-component developer composed of a toner and a carrier, and a one-component developer composed of a toner without a carrier. One-component developer
The toner is kneaded in a binder resin. The toner includes a magnetic toner and a non-magnetic toner.

A magnetic toner is formed by mixing magnetic powder such as black magnetite into a binder resin as a main component, and is suitable for forming a monochrome image. However, when colorizing an image, the black color of magnetite hinders the use of the magnetic material, and there is an increasing demand for a non-magnetic one-component developer composed of a non-magnetic toner.

A non-magnetic toner constituting a non-magnetic one-component developer is prepared by kneading a colorant, a charge controlling agent (optional component), and a release agent (optional component) with a binder resin to form toner particles having a predetermined particle size. It is configured. Such toner particles include a fluidization improver,
Lubricants, abrasives, etc. are externally added.

[0006] The non-magnetic toner is charged during image formation in order to convert the electrostatic latent image formed on the surface of the photoreceptor into a toner image. The charging is generally performed by frictionally charging the non-magnetic toner conveyed to the developing roll by passing the non-magnetic toner between the tip of the elastic blade, the tip of which is pressed against the surface of the developing roll, and the surface of the developing roll. ing.

[0007] In the above-described method of imparting charge to non-magnetic toner,
The non-magnetic toner is strongly pressed when passing between the elastic blade and the surface of the developing roll, and may be crushed by the stress. Therefore, in an image forming method employing such a charging method, the nonmagnetic toner is required to have stress resistance.

On the other hand, from the viewpoint of increasing the speed of image formation, for example, an electrostatic latent image on the surface of a photoreceptor is converted into a toner image using a non-magnetic toner, and the toner image is transferred to a medium such as paper and then quickly fixed. Good fixability is required.

The improvement of the stress resistance can be solved by using a high molecular weight binder resin for the non-magnetic toner. On the other hand, in order to improve the fixability of the image forming method at a high speed, it is possible to solve the problem by using a low molecular weight binder resin for the non-magnetic toner.

However, when a high molecular weight binder resin is used for the purpose of improving stress resistance, the use of a high molecular weight
The permeability of the non-magnetic toner to the paper becomes poor, and the fixability decreases. That is, use of a binder resin having a high molecular weight is not preferable from the viewpoint of speeding up image formation.

On the other hand, if a low-molecular-weight binder resin is used for the purpose of improving the fixing property, on the other hand, the stress resistance is lowered and the pulverization becomes easy. The pulverized powder adheres to the elastic blade,
This may cause a thin film to adhere to the surface of the developing roll (called filming). Further, at the time of fixing, a part of the toner image easily adheres to the surface of the heating roller, which causes an offset phenomenon which is transferred at the next fixing and stains a medium such as paper. In addition, there is also a problem that the toner aggregates in the toner tank containing the developer and blocking easily occurs.

That is, the improvement of the stress resistance, the offset resistance, the filming resistance, the blocking resistance, and the improvement of the fixing property can be achieved by controlling the molecular weight of the binder resin. It can be said that they show opposite directions.

JP-A-5-6029 discloses that the molecular weight distribution of a resin component used as a binder resin is measured by gel permeation chromatography (GPC).
A region having a molecular weight of 5,000 or less is defined as less than 15%,
It is disclosed that the toner has a main peak in the range of 000 to 100,000 and has a weight average molecular weight of 5,000,000 or more to improve the fixing property, offset resistance, and filming resistance of the magnetic toner.

Japanese Patent Application Laid-Open No. 9-34172 discloses a technique of using a binder resin having a specific molecular weight distribution to provide a toner having excellent fixing properties, offset resistance and blocking resistance even in a high-speed system. Is disclosed.

Japanese Patent Application Laid-Open No. 11-119467 discloses a technique for improving the fixing property and the offset resistance in a two-component developer using a magnetic toner by using a binder resin having a specific molecular weight distribution. Have been.

[0016]

As described above, by using a binder resin having a specific molecular weight distribution pattern, the fixing property is improved, and at the same time, the offset resistance is incompatible with the improvement of the fixing property. Proposals for improving filming resistance and blocking resistance are disclosed in the above-mentioned publications, however, there is no description for improving both fixing property and stress resistance.

In an image forming method using a non-magnetic toner as a non-magnetic one-component developer, it is necessary to apply a charge by passing through an elastic blade, as described above, unlike the magnetic toner. There is a demand for an improvement in stress resistance against stress received during passage.

An object of the present invention is to improve both the fixing property and the stress resistance in a non-magnetic one-component developer using a non-magnetic toner.

[0019]

According to the present invention, there is provided a non-magnetic toner used for developing an electrostatic latent image formed on the surface of a photoreceptor, wherein the binder resin contained in the non-magnetic toner is a gel resin. In the molecular weight distribution based on the measurement of cation chromatography (GPC), the molecular weight is 4 × 10 ⁴ or more and 7 × 1
0 Low molecular weight region of less than ^4, the molecular weight region in less than 7 × 10 ⁴ or more 12 × 10 ^4, to each of 12 × 10 ⁴ or more 25 × 10 high molecular weight region of less than ^4, that at least one peak is present Features.

According to another aspect of the present invention, there is provided an image forming method for developing an electrostatic latent image formed on the surface of a photoreceptor with a one-component non-magnetic toner. It is characterized in that toner is used.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings and examples.

The non-magnetic toner of the present invention is formed by kneading a colorant, a charge controlling agent (optional component) and a release agent (optional component) into a binder resin to form toner particles having a predetermined particle size. Additives such as a fluidization improver and a cleaning agent may be externally added to the toner particles, or may be used by being mixed and dispersed in a binder resin.

As the colorant, for example, known pigments or dyes such as carbon black, chrome yellow, Hansa yellow, benzine yellow, rose bengara, aniline red, phthalocyanine blue, aniline blue, nigrosine dye, and aniline black are used. can do.

As the charge control agent, for example, a metal-containing (Cr) azo dye or the like can be used as a negative charge control agent.

As the releasing agent, for example, polypropylene, polyethylene, paraffin wax, carnauba wax, amide wax and the like can be used.

As the fluidity modifier, fine powders such as hydrophobic silica, titanium oxide, polyvinylidene fluoride, and soaps belonging to the group can be used. As a cleaning agent, zinc stearate, calcium stearate, magnesium stearate, polymethyl methacrylate, nylon,
Fine powders such as polytetrafluoroethylene and silicon carbide can be used.

Examples of the binder resin include known styrene resins such as polystyrene, styrene / butadiene copolymer, styrene / acrylate copolymer and styrene / methacrylate copolymer, epoxy resins and polyester resins. The toner resin can be used alone or in a mixed state.

[0028] Such binder resin, the molecular weight distribution of the binder resin in the toner measured by GPC, and the low molecular weight region of weight average molecular weight is less than 4 × 10 ⁴ or more 7 × 10 ^4, 7 × 1
Medium molecular weight region of at least 0 ^{4 and} less than 12 × 10 ⁴ , 12 × 10 ⁴
A molecular weight distribution pattern in which at least one molecular weight peak exists in each of the high molecular weight regions of less than 25 × 10 ⁴ is shown.

The binder resin having the molecular weight distribution pattern having such a constitution can be produced by various methods such as a solution polymerization method, a suspension polymerization method and an emulsion polymerization method. G
Peak of molecular weight distribution measured by PC is 4 × 10 ⁴ or more 7
A low molecular weight binder resin in a low molecular weight region of less than × 10 ⁴ ,
A medium molecular weight binder resin having a molecular weight distribution of 7 × 10 ⁴ or more and less than 12 × 10 ^4, and a high molecular weight binder resin having a molecular weight distribution peak of 12 × 10 ⁴ or more and less than 25 × 10 ^4. What is necessary is just to prepare separately the resin and the resin, and to melt and mix them.

Alternatively, a method of polymerizing a low molecular weight binder resin with a monomer to polymerize a medium molecular weight binder resin, and further polymerizing the monomer to polymerize a high molecular weight binder resin may be used. Further, the reverse method may be used. Further, a method of polymerizing a high molecular weight binder resin by monomer polymerization of a low molecular weight binder resin, and then polymerizing a monomer thereto to polymerize a medium molecular weight binder resin may be used.

In the above polymerization, the peak position and the peak height in the low molecular weight range, the medium molecular weight range, and the high molecular weight range are appropriately adjusted by adjusting the type and ratio of the monomers and the type and amount of the catalyst during the polymerization. Can be adjusted arbitrarily.

The molecular weight distribution of a chromatogram of the binder resin by GPC is measured as follows. A toner sample and tetrahydrofuran (THF) are mixed for about 0.5 m.
g (for example, about 2 mg / ml), left at room temperature for several hours, shake well, mix well, and leave at room temperature for 12 hours or more. At this time, the time from the mixing start time of the sample and THF to the end of standing is set to be 24 hours or more. Thereafter, the filtered filtrate is used as a measurement sample for GPC. The sample concentration was 0.5 to 5 mg / resin.
Make up to be ml.

In GPC, the column is stabilized in a heat chamber at 40 ° C., and THF is flowed through the column at this temperature as a carrier at a flow rate of 1 ml / min.
Inject μl of the THF sample solution with a micro cylinder to measure. In the measurement, a calibration curve prepared using several kinds of standard polystyrene samples is used.

In the GPC measurement, a sample resin is adsorbed on a gel in the column by passing a solution containing the sample resin through the column. The adsorption of the sample resin differs depending on the molecular weight of the sample resin. The sample resin having a higher molecular weight has less adsorption and is eluted earlier. A chromatogram can be created by associating the time axis indicating the elution time with the molecular weight.

In the state of the toner, the molecular weight distribution of the binder resin is represented by G
For measurement with a PC, a polar substance such as a charge control agent may be dissolved in a polar solvent such as methanol, and the polar solvent may be removed by Soxhlet extraction. Since the release agent such as polypropylene does not dissolve in THF, it can be filtered off at the time of filtration.

[0036]

EXAMPLES In this example, non-magnetic toners having the following compositions having peaks in various molecular weight ranges were prepared, and their fixing property and stress resistance were verified.

The manufacture of the non-magnetic toner was performed as follows. 94 parts by weight of a styrene / n-butyl methacrylate copolymer as a binder resin, 4 parts by weight of carbon black as a colorant, 4 parts by weight of polypropylene (TP32, manufactured by Sanyo Chemical Co., Ltd.) as a release agent, and 2 parts by weight of a control agent (Bontron E-84, manufactured by Orient Chemical Co., Ltd.)
The mixture is dry-mixed with a ball mill and then heated and kneaded with a kneader. After heating and kneading, the mixture was solidified by cooling, further pulverized by a jet mill, and classified to produce a non-magnetic toner having an average particle diameter of 9 μm.

[0038] To the produced non-magnetic toner, 1.2 parts by weight of Aerosil as a fluidizing agent and 0.2 parts by weight of zinc stearate as a lubricant are added to 100 parts by weight of the non-magnetic toner. did.

[0039]

[Table 1] Table 1 shows the results of the molecular weight distribution of the styrene / n-butyl methacrylate copolymer in the non-magnetic toner having the above-described configuration measured by GPC. In Table 1, the position of the main peak having the maximum peak height among the peaks in each of the low molecular weight region, the medium molecular weight region, and the high molecular weight region was appropriately moved within the individual molecular weight regions. 2, and 3. In the table, the low molecular weight main peak was designated as peak 1, the medium molecular weight main peak was designated as peak 2, and the high molecular weight main peak was designated as peak 3.

Further, at least one of the three main peaks which should be in the low molecular weight region, medium molecular weight region and high molecular weight region is
Comparative Examples 1 to 4 were constructed outside the range. Comparative Example 5
Means that no peak exists only in the low molecular weight region. Comparative Examples 6 and 7 are cases in which no peak is observed in the middle molecular weight region. Comparative Example 8 is a case where no peak is shown in the low molecular weight region and in the high molecular weight region, the main molecular peak region has a main peak having the maximum peak height, and the sub-peak is in a region larger than the high molecular weight region. This is the case.

Table 1 also shows the values of the weight average molecular weight (Mw) and the number average molecular weight (Mn) in each of the examples and comparative examples.

Using the non-magnetic toners of Examples 1 to 3 and Comparative Examples 1 to 8 in Table 1, an image forming method was carried out in the following manner, and the fixing property (%), the anti-offset property, Each of the stress resistances was evaluated.

The above evaluation was carried out by using an image forming apparatus whose main part is shown in FIG. 1 and evaluating an actually obtained image. As such an image forming apparatus, an apparatus capable of performing reversal development used in a printer or the like was used. As shown in FIG. 1, a charger 20, an exposure unit 30, a developing roll 40, a transfer charger 50, and a cleaner 60 are sequentially arranged on the peripheral surface of a negatively chargeable OPC photoreceptor 10 formed in a drum shape. And a developing roller 40 having a conductive shaft 41 and a conductive elastic layer 42 connected to a bias voltage source 70 in a developing area arranged opposite to the negatively chargeable OPC photoconductor 10 by a contact developing method. Reversal development is possible.

In this embodiment, the case where the negatively chargeable OPC photosensitive member 10 is formed in a drum shape will be described. However, the negatively chargeable OPC photosensitive member 10 does not have to be a drum shape. The belt-shaped configuration described above does not matter. In that case, devices such as the charger 20 and the exposure device 30 may be arranged according to a conventional configuration.

The surface of the negatively chargeable OPC photosensitive member 10 is uniformly negatively charged by the charger 20 while rotating at a constant peripheral speed. As the charger 20, a scotron for corona discharge may be used. In addition to corona discharge, roller charging, brush charging, or magnetic brush charging may be used.

The surface of the negatively chargeable OPC photoreceptor 10 whose surface is negatively charged in this way is further exposed to the exposure unit 3
0 to expose the negatively chargeable OPC photoconductor 10
A negative electrostatic latent image is formed on the surface of the substrate. For light image exposure (writing of a latent image) for forming an electrostatic latent image, a conventionally used printer light source such as a semiconductor laser or an LED light source is used.

The electrostatic latent image is a rotating negatively charged OPC
While being carried on the surface of the photoreceptor 10, the developing roll 40 is transported to a developing area opposed to the developing area. This electrostatic latent image is transferred to the developing roll 4 connected to the bias voltage source 70.
The toner image is visualized as a toner image by the non-magnetic one-component negatively-charged non-magnetic toner carried electrostatically on the surface of No. 0 and transported to the development area, and is subjected to reversal development.

The non-magnetic toner used for the development is shown in FIG.
As shown in (2), the toner is agitated by the agitator 44 in the toner hopper 43, and is carried on the surface of the rotating developing roll 40 and transported. As shown in FIG. 1, the non-magnetic toner carried on the surface of the developing roll 40 is conveyed to the elastic blade 80 pressed against the peripheral surface of the developing roll 40 at a predetermined pressure, and the lower side of the elastic blade 80 is When passing, it is charged.

The non-magnetic toner having a predetermined layer thickness charged when passing through the elastic blade 80 is pressed against the surface of the negatively chargeable OPC photoreceptor 10 at a predetermined linear pressure, thereby forming an electrostatic latent image. Contact development is performed by electrostatically adsorbing the image.

Either the negatively chargeable OPC photoreceptor 10 or the developing roll 40 is configured to have an elastic surface, and the negatively chargeable non-magnetic toner is appropriately pressed against the electrostatic latent image during the contact development. It has become so. For example,
At least the surface of the developing roll 40 is made of urethane or E
What is necessary is just to form with an elastic material, such as PDM, so that an elastic surface may be obtained.

Thus, the negatively chargeable OPC photosensitive member 10
The toner image formed on the surface of the transfer charger 5 is further transferred.
0 is conveyed to the transfer area arranged opposite to the transfer area. In the transfer area, a transfer material 51 such as paper is fed between the transfer charger 50 and the toner image so as to match the conveyance of the toner image, and the toner is transferred from the transfer charger 50 to the back surface of the transfer material. Charging with a polarity opposite to the charging polarity of the image (in this case, positive charging) is performed, and the toner image is transferred onto the transfer material 51.

The transfer charger 50 uses a corotron for corona discharge. Thereafter, the transfer material 51 onto which the toner image has been transferred is sent to the heat roll unit 52 with the heating roll and the pressure roll facing each other at a predetermined interval, and the toner image is compressed when passing between the heat roll units 52. The sheet is subjected to heat treatment and is fixed on a transfer material 51 by a heat roll. The fixing of the toner image may be performed by pressure fixing or oven fixing.

On the other hand, after the transfer of the toner image,
The surface of the PC photoreceptor 10 is configured so that the residual developer is removed by the cleaner 60. In the present embodiment, a conventional blade is used for the cleaner 60 so that the remaining negatively charged non-magnetic toner that has not been transferred to the surface of the negatively chargeable OPC photoconductor 10 can be scraped off. .

Using the above image forming apparatus, image formation was performed under the following conditions. As the negatively chargeable OPC photoreceptor 10, a drum-shaped OPC photoreceptor having a diameter of 30 mm is used, and a process speed ( _VP : also referred to as a peripheral speed) is set to 100 mm / sec.
c, and the surface potential (V ₀ ) was set to −550 V with a scotron. The residual potential ( _VL ) of the surface of the negatively chargeable OPC photoreceptor 10 after light image exposure was -50 V.

The developing roll 40 has a diameter (φ) of 20 mm.
A urethane rubber roll containing a conductive agent and a foaming agent having a volume resistance (R) of 10 ⁵ Ω · cm was used. While rotating the elastic developing roll 40 at a peripheral speed of 110 mm / sec, which is slightly faster than that of the negatively chargeable OPC photoconductor 10, 40 g
Contact development was carried out by pressing the negatively chargeable OPC photoreceptor 10 at a pressure (linear pressure) of / cm through a toner layer.

In the present embodiment, a bias voltage of -450 V, which is slightly lower than the surface potential V ₀ of the negatively chargeable OPC photosensitive member 10, is applied to the developing roll 40 in order to perform reversal development.

The thickness of the negatively charged non-magnetic toner layer is as follows:
A urethane blade is used as the elastic blade 80,
It is regulated to be 15 μm.

Further, for the transfer and fixing of the toner image, a corotron is used as the transfer charger 50 and the transfer material 5 is transferred.
1 using plain paper, fixing temperature 160 ° C, linear pressure 1Kg
The fixing was performed by heat roll fixing at a fixing pressure of / cm. In the cleaner 60, the negatively charged OPC photoconductor 10
A residual urethane blade was removed by contacting a urethane blade at a linear pressure of 300 g / cm with the surface of.

[0059]

[Table 2] An image was actually formed using the image forming apparatus having the above configuration, and the fixing property of the obtained image was evaluated. The fixability was evaluated based on the tape fixability. Scotch mending tape 810 (trade name) manufactured by 3M was applied to the fixed image, and then the tape was peeled off, and the image density ratio before and after peeling the tape was measured.
For example, if the image density after tape peeling is 80% or more, it can be determined that the image density is excellent, if it is 75% or more, it is acceptable, and if it is less than 75%, it can be determined that it is not.

The evaluation of the offset resistance was performed by visually observing the offset in the non-image portion of the plain paper after fixing. In the evaluation 評 価, the offset was not confirmed at all, and in the evaluation △, the offset was slightly visible.

The evaluation of the stress resistance was performed based on the amount of toner adhered to the developing roll or the elastic blade. In the table,
The evaluation で indicates the case without toner adhesion, the evaluation △ indicates the case where the image does not appear even with the toner adhesion, and the evaluation × indicates the case where a vertical streak appears in the image.

From Table 2, it was found that the fixing property was excellent irrespective of the examples and the comparative examples. On the other hand, with respect to stress resistance, Examples 1-3 and Comparative Example 4 are excellent, but in Comparative Examples 1-3, the non-magnetic toner is pulverized when passing through the elastic blade 80. I understand.

From the above results, although there is an exception of Comparative Example 4, the overall tendency is that if any of the main peaks of the low molecular weight region, the medium molecular weight region, and the high molecular weight region is out of the range, the stress resistance is reduced. It can be said that the property decreases. Example 1
As can be seen from FIGS. 3 to 3, it can be seen that stress resistance is obtained by the presence of main peaks in each molecular region.

Also, in Comparative Examples 5 to 7, in which the main peak does not exist in any one of the low molecular weight region, the medium molecular weight region and the high molecular weight region, or in two regions, the stress resistance is inferior. . Examples 1 to 5 also show offset resistance.
3. It can be seen that Comparative Examples 1 to 4 and 8 are excellent but insufficient.

From the above results, as shown in Table 1, GPC
Peak in the molecular weight distribution of the binder resin measured in step 4
Low molecular weight region of × 10 ⁴ or more and less than 7 × 10 ⁴ , 7 × 10 ⁴
Above 12 × 10 molecular weight region in less than ^4, the 12 × 10 ⁴ or more 25 × 10 ⁴ of high molecular weight region, if it has a main peak, respectively, as shown in Table 2, fixability and stress that antagonizes this It turns out that the property becomes good.

[0066]

According to the non-magnetic toner of the present invention, fixability and
This is improved both in terms of competing stress resistance. Therefore, the toner is suitable for a non-magnetic one-component developing high-speed image forming method in which charging is imparted to the toner by an elastic blade and fixability to a medium is required immediately after transfer, or the image forming apparatus.

According to the image forming method of the present invention, since the non-magnetic toner having both improved fixing property and stress resistance is used as compared with the related art, the speed can be increased.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a main part of an image forming apparatus used in an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Negative charge OPC photoreceptor 20 Charger 30 Exposure device 40 Developing roll 41 Conductive shaft 42 Conductive elastic layer 43 Toner hopper 44 Stirrer 50 Transfer charger 51 Transfer material 52 Heat roll part 60 Cleaner 70 Bias voltage source 80 Blade

Claims (2)

[Claims] 1. A non-magnetic toner used for developing an electrostatic latent image formed on a surface of a photoreceptor, wherein a binder resin contained in the non-magnetic toner is used for measurement by gel permeation chromatography (GPC). Molecular weight distribution is 4 × 10 ⁴ or more and 7 × 10 ⁴
Wherein at least one peak exists in each of a low molecular weight region of less than 7 × 10 ⁴ or more and a medium molecular weight region of less than 12 × 10 ⁴ , and a high molecular weight region of 12 × 10 ⁴ or more and less than 25 × 10 ^4. Non-magnetic toner. 2. An image forming method for developing an electrostatic latent image formed on a photoreceptor surface with a one-component non-magnetic toner, wherein the one-component non-magnetic toner includes the non-magnetic toner according to claim 1. An image forming method characterized by being used.