JPH0774914B2 - Toner for electrophotography - Google Patents

Description

TECHNICAL FIELD The present invention relates to a toner used in an electrophotographic method, an electrostatic printing method, and the like, and particularly to a color electrophotographic toner suitable for a heat fixing method.

BACKGROUND ART Conventionally, as electrophotographic methods, many methods are known as described in U.S. Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910 and Japanese Patent Publication No. 43-24748. In this electrophotographic method, in general, a photoconductive substance is used to form an electric latent image on a photoconductor by various means,
Next, the latent image toner is developed, the toner image is transferred to a transfer material such as paper, if necessary, and then the toner image is fixed by heating or pressure to obtain a copy.

Various developing methods are also known in which an electric latent image is visualized using toner.

For example, the magnetic brush method described in U.S. Pat.No. 2874063, the cascade developing method described in the 2615552 specification, and the powder method and the fur brush developing method described in the 2221776 specification, Many developing methods such as jumping developing method are known. As a toner used in these developing methods and the like, a fine powder in which a dye or a pigment is dispersed in a natural or synthetic resin has been conventionally used.
Further, it is known to use a developing powder to which a third substance is added for various purposes.

The toner image developed by such a developing method is fixed as an image transferred to a transfer material such as paper, if necessary.

As a method for fixing the toner image, a method of heating and melting the toner by a heater or a heat roller to fuse and solidify it on the support, a method of softening or dissolving the binder resin of the toner with an organic solvent and fixing it on the support, pressurization There is known a method of fixing the toner to the support by the method.

Although various methods and devices have been developed for the process of fixing the toner image on paper, the most general method at present is
This is a so-called thermal roll fixing method in which heat and pressure are applied at the same time. This is a method of fixing the toner image on the image receiving sheet by bringing the image receiving sheet carrying the toner image into contact with a heated roller. However, when such a fixing method is used, when the conventional toner (for the fixing method of heat alone) is used as it is, a problem such as so-called offset occurs. here,
Offset is an undesirable phenomenon in which a part of the toner carried on the image receiving sheet is transferred to the roller surface.

On the other hand, in recent years, with the efficiency of copying work, energy saving, downsizing, speeding up, and high performance of copying machines, heat roll type fixing system with good thermal efficiency has become the majority of commercially available copying machines. ing. Most of these copying machines fix toner onto paper by thermocompression bonding with a heating roller.

In such a thermocompression bonding method, compared to a non-contact type heating method using heat rays, it is possible to obtain a good fixed image by using a lower temperature heating member, and there are many advantages such as higher speed. However, this method also has various drawbacks. As one of the big ones, if the roller is kept at a temperature at which the toner is sufficiently fixed on the holding member such as paper, the toner is fused not only on the paper but also on the heat roll, which causes copying. There is a drawback that the heat roll becomes soiled as it is repeated. Such a fused toner on the roll cannot be sufficiently removed by a blade or a cleaning web for keeping the roll clean, and eventually the paper is also soiled (so-called high temperature offset), which is a contact method. Cause serious problems.

In order to solve or reduce the problem of such offset,
Although various measures have been tried from both the fixing device and the toner sides, it cannot be said that the problems have been sufficiently solved.

As an attempt to improve from the fixing device side, a device such as Teflon or silicone, which has excellent surface releasability, is used, or an oil such as silicone oil is applied to the roller. Most of the heat roller fixing devices of the copying machines that have been used have some form of oil coating. However, if a large amount of oil that can sufficiently prevent high-temperature offset is applied to the roller, it is not preferable because the image quality is poor due to oil stains on the sheet or oil marks, and troubles occur due to complication of the fixing device, or cost increase. The problem occurs.

On the other hand, as an attempt of improvement from the toner side, in order to increase the releasability of the toner, a method of adding a small amount of wax such as polyethylene or polypropylene having a low molecular weight, which is sufficiently melted when heated, to the toner is used. If it is attempted to completely prevent the offset by adding such a wax, the binder resin and the above waxes have poor compatibility with each other.・ Projector) The film tends to become cloudy. Further, in general, addition of the above-mentioned waxes in an amount capable of sufficiently preventing offset causes adverse effects such as increase of toner cohesiveness, reduction of anxiety of charging characteristics, and deterioration of durability. However, it is hard to say that the improvement is practically sufficient.

As another toner improving method, various attempts have been made to improve the binder resin of the toner. For example
51-23354 proposes a toner using a crosslinked polymer (mainly a styrene resin) as a binder resin. According to this method, the offset resistance and the rust resistance of the toner are remarkably improved, but the fixing point of the toner is increased when the degree of crosslinking is increased. Such an increase in the fixing point of the toner remarkably deteriorates the image quality of the image, particularly when a color copy is obtained using the toner of each color. That is, not only the gloss and luster of the image, which are important characteristics as a color copy, are lost, but also the color reproducibility of the color tone deteriorates.

Further, such a crosslinked polymer has drawbacks such as poor dispersibility of a colorant such as a pigment.

As described above, a color toner having sufficient high-temperature offset resistance and releasability with respect to a heat fixing roller, and having a wide color reproducibility to give appropriate gloss as a color image has not yet been obtained. The current situation is not.

On the other hand, recently, low molecular weight amorphous polyester resins and epoxy resins have been attracting attention as materials for toner binders suitable for low-temperature fixing.

The main idea (previously) of preventing offset in a toner having such a polyester resin as a main binder is 3 as typified by JP-B-52-25420 or JP-B-59-11902. It is intended to improve the offset property at the time of fixing by mixing a polyol having a valency or more and polyacid to make the polymer non-linear and improving its viscoelasticity.

The present inventor has studied various examples of these publications, and it is confirmed that the non-linearity of these is effective for improving the offset resistance of the toner. Even in the non-linearization of (the same as in the improvement measures by the crosslinking in the styrene-based resin described above), if the excessive non-linearization is performed until sufficient offset resistance is achieved, the fixing point of the toner rises. As a result, the color reproducibility of the color toner deteriorates, the gloss disappears, and the OHP film becomes cloudy, resulting in a significant deterioration in image quality.

That is, according to the experiments of the present inventor, the offset resistance is improved to some extent by simply making the polyester resin extremely non-linear (especially for color copy).
It was difficult to prevent the deterioration of image quality.

Further, as disclosed in JP-A-58-211160, by defining the physical properties of the binder resin, particularly the pour point of the flow tester and the melt viscosity at a certain temperature, the offset resistance of the toner, Attempts have been made to improve the fixability. Although it is true that the melt viscosity at the time of fixing has a close relationship with the offset resistance and the fixability of the toner, as described above, the melt viscosity or pour point (macroscopic value) of the binder resin at a specific temperature is fixed. It was difficult to obtain both good fixability and offset resistance in an actual copying machine by simply specifying physical properties).
In fact, according to the experiments conducted by the present inventors, in the binder resin having the melt viscosity and the pour point in the specific ranges described in the above publication, it was found that the offset resistance was good but the fixing property was insufficient. ing.

OBJECT OF THE INVENTION An object of the present invention is to provide an electrophotographic toner having improved high temperature offset property.

Another object of the present invention is to provide an electrophotographic toner which gives a color copy image having sufficient gloss and gloss.

Another object is to provide a toner having a high image density and excellent durability that gives an image free of background fog.

Another object is to provide an electrophotographic toner which has an excellent color reproducibility and gives an image with high saturation.

Another object is to provide a toner having excellent powder characteristics such as fluidity and cohesiveness, and good replenishment and storability.

Another object of the present invention is to provide a toner which has a high degree of abrasion resistance against a mechanical load during the developing process and is also excellent in impact resistance.

Another object is to provide a toner that does not adhere to the toner holding member or the electrostatic latent image surface and is not contaminated.

Another object of the present invention is to provide a toner having almost no carrier-contaminating property in a two-component developer due to adhesion to the carrier, fusion or the like.

SUMMARY OF THE INVENTION As a result of earnest research, the present inventor has found that when applied to an actual copying machine, in order to provide a fixed image having both excellent offset resistance and fixing property and good gloss,
It was found that not only the respective values of the apparent viscosities of the toners at three temperatures are important, but also the slope of the apparent viscosity-temperature curve between these temperatures is very important.

The toner for electrophotography of the present invention is based on the above findings, and more specifically, the apparent viscosity η (90) at 90 ° C.,
And apparent viscosity η (100) at 100 ° C are 1 × 10 ⁵ <η (90) <5 × 10 ⁶ (poise) and 1 × 10 ^{5 respectively.}
<Η (100) <1 × 10 ⁶ (poise), and the ratio of these apparent viscosities is 0.05 <η (100) / η (90) <1.0
It is characterized by being.

The reason why the above-described effect is achieved in the toner of the present invention is not always clear, but according to the knowledge of the present inventor, it is presumed as follows.

That is, in the conventional toner, since the sharp melting property of the binder resin is large and the intramolecular cohesive force in the binder resin is weak, the slope of the apparent viscosity-temperature curve at 90 ° C. and 100 ° C. is excessive. It is estimated that there was.

Therefore, in such a conventional toner, even if the apparent viscosity at any of the above temperatures is within the proper range, the apparent viscosity at the other temperature is out of the proper range, and the offset resistance, It is estimated that either the fixability or the glossiness of the image (at least one of them) was not satisfied.

On the other hand, in the toner of the present invention, the apparent viscosities at 90 ° C. and 100 ° C. are both within a suitable range, and the ratio of these apparent viscosities (ie, apparent viscosity-gradient of temperature curve) is Since it is within a certain range, the above-mentioned inconvenience in the conventional toner does not occur, and therefore, both the offset resistance and the fixing property are excellent,
Moreover, it is estimated that an image with good glossiness can be obtained.

Hereinafter, the present invention will be described in more detail with reference to the drawings as necessary. In the following description, the quantitative ratio is represented.
"%" And "parts" are based on weight unless otherwise specified.

DETAILED DESCRIPTION OF THE INVENTION In the electrophotographic toner of the present invention, the apparent viscosity η (90) at 90 ° C. is 1 × 10 ⁵ <η (90) <5 × 10 ⁶ (poise), and the apparent viscosity η (100) at 100 ° C. 100) is 1 × 10 ⁵ <
η (100) <1 × 10 ⁶ (poise), and the ratio of these apparent viscosities is 0.05 <η (100) / η (90) <1.0
(More preferably 0.07 ≦ η (100) / η (90) <1.0, particularly preferably 0.1 <η (100) / η (90) <1.0. This apparent viscosity is the apparent viscosity of the entire toner including the binder resin and the colorant (additives and the like as necessary) described later.

When η (90) is 1 × 10 ⁵ poise or less, high temperature offset control becomes difficult. On the other hand, when η (90) is 5 × 10 ⁶ poise or more, the high temperature offset is greatly improved, but the gloss of the image is almost lost and only a matte image is obtained.

Further, when η (100) is 1 × 10 ⁵ poise or less, high temperature offset occurs. On the other hand, when η (100) is 1 × 10 ⁶ poise or more, the glossiness of the image is lowered and the color toner is used. However, the color mixture between the superposed toners is deteriorated.

Further, if the above η (100) / η (90) is 0.05 or less, it becomes difficult to suppress high temperature offset.

In the toner of the present invention, η (90), η (10
A more preferable range of 0) and η (100) / η (90) is
1.2 × 10 ⁵ <η (90) <1 × 10 ⁶ poise, 1.0 × 10 ⁵ <η (1
00) <1 × 10 ⁶ poise and 0.2 <η (100) / <η (9
0) <1.0 (particularly preferably 0.3 <η (100) / η (90) <
1.0).

In the present invention, the apparent viscosity (η (90), η (10
As 0)), a flow tester CFT-500 type (manufactured by Shimadzu Corporation) is used, and the value measured under the following conditions is used.

That is, about 1.0 g of a sample (toner) was weighed as a granular material that passed through a 60 mesh sieve, and the sample was put into the molding machine attached to the flow tester and pressed for 1 minute with a load of 100 Kg / cm ^2. Use as a pressure sample.

Using this pressurized sample, the above flow tester CFT-500
The outflow rate of the sample is measured according to the mold under the following conditions, and the apparent viscosity (η) is determined from the Hagen-Poiseuille equation by flow tester measurement to obtain the apparent viscosity-temperature curve used in the present invention.

(Measurement conditions) Temperature rising rate (RATE TEMP): 6.0D / M (℃ / min) Initial temperature (SET TEMP): 70.0 DEG (℃) Maximum temperature (MAX TEMP): 200.0 DEG Interval (INTERVAL): 3.0 DEG Preheat time (PRE HEAT): 300.0 SEC (second) Load (LOAD): 20.0 KG (Kg) Capillary diameter (DIE (DIA)): 1.0 MM (mm) Capillary length (DIE (LENG)): 1.0 MM (Mm) Plunger bottom area (PLUNGER): 1.0 CM ² (cm ² ) The electrophotographic toner of the present invention having the above-mentioned viscosity characteristics has a colorant dispersed (dissolved in the adhesive resin). It's not meant to be excluded).

The binder resin used in the toner of the present invention can be used without particular limitation, including known ones, as long as it gives the above-mentioned apparent viscosity as the toner, and examples thereof include polystyrene, polychlorostyrene, and poly-α-. Methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene -Acrylic acid ester copolymer, (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer,
Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc., styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-methacrylic acid) Styrene resins such as ethyl acid acid acid copolymer, styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, and styrene-α-chloroacrylonitrile-acrylic acid ester copolymer (styrene or styrene substitution product) Containing a vinyl chloride resin, rosin-modified maleic acid resin, phenol resin, epoxy resin, polyester resin, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, Ethylene resin Ethylene - ethyl acrylate copolymer, xylene resin, polyvinyl butyral resin or the like, can be used alone or in combination.

Among the above resins, in the present invention, styrene-
Acrylic ester resin (especially weight average molecular weight 5,000
~ 100,000) or polyester resin is preferably used.

Further, in the present invention, the diol component represented by the following formula and at least one of a divalent or higher carboxylic acid, or an acid anhydride thereof, or a lower (for example, 1 to 12 carbon atoms) alkyl ester thereof. A polyester resin obtained by copolycondensation with a carboxylic acid component is particularly preferably used.

(In the formula, R is an ethylene or propylene group, and x, y
Are each an integer of 1 or more, and the average value of x + y is 2 to 10. ) In the above-mentioned divalent or higher carboxylic acid component (used to include esters and acid anhydrides), the ratio of the molar amount of the trivalent or higher carboxylic acid component to the total molar amount thereof is 0 to
40 mol% (further 0-30 mol%) is preferable from the viewpoint of obtaining a polyester having suitable properties.

As the carboxylic acid component, specifically, fumaric acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, or the like, or their anhydrides or lower alkyl esters are required. According to the above, two or more kinds are preferably used in combination.

Such a polyester resin can be obtained by polycondensing the diol component and the carboxylic acid component according to a conventional method.

On the other hand, as the colorant that constitutes the toner of the present invention together with the binder resin, known pigments or dyes can be used without particular limitation (combined as necessary).

Examples of such dyes include CI direct red 1, CI direct red 4, CI acid red 1,
CI Basic Red 1, IC Modern Red 30, C.
I. Solvent Tread 49, CI Solvent Red 52, C.
I. Direct Blue 1, CI Direct Blue 2, CI
Acid Blue 9, CI Acid Blue 15, CI Basic Blue 3, CI Basic Blue 5, CI Basic Blue 7, CI Direct Green 6, CI Basic Green 4, CI Basic Green 6, CI Disperse Yellow 164, CI Solvent Yellow 77 and the like are used in combination of two or more, if necessary.

On the other hand, as pigments, yellow lead, cadmium yellow, mineral fast yellow, navel yellow, naphthol yellow S, Hanseello G, Resilien yellow TGL,
CI Pigment Yellow 17, Balifast Yellow
3120, Permanent Yellow NCG, Tartrazine Lake, Red Mouth Lead, Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Benzidine Orange G, Cadmium Red, CI Pigment Red 5, Permanent Red 4R, Watching Red Calcium Salt, Eosin Lake, Brilliate Carmine 3B, Manganese Purple, Fast Violet B, Methyl Violet Lake, Navy Blue, Cobalt Blue, Alkali Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue BC, Chrome Green,
Two or more kinds of chromium oxide, pigment green B, malachite green lake, final yellow green G, etc. may be used in combination as required.

These coloring agents are 0.3 to 100 parts by weight of the binder resin component.
It is preferable to use 12.0 parts.

When the toner of the present invention is a magnetic toner, magnetic fine particles may be added to the toner. The magnetic particles are used as a whole or a part of the coloring agent, and are used in combination with the dye or pigment, etc., if necessary.

As the magnetic substance, a material that exhibits magnetism or can be magnetized may be used. For example, fine metal powders of iron, manganese, nickel, cobalt, chromium and the like, various ferrites, alloys and compounds of manganese, and other ferromagnetic materials. Materials conventionally known as magnetic materials such as alloys and magnetite can be used in combination of two or more, if necessary.

These magnetic fine particles are 10 to 100 parts with respect to 100 parts of the binder resin.
It is preferable to use a part.

Further, in order to make the releasability to the heat fixing roll more complete, the toner of the present invention contains a small amount (for example, a binder) of polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene (within the above-mentioned apparent viscosity range). It is also possible to add to the toner about 10 parts or less with respect to 100 parts of the coating resin).

On the other hand, as a carrier used in combination with the toner of the present invention as necessary, either a substance having magnetism or a substance having no magnetism can be used.
Iron, steel, ferrite, Ba-Fe ferrite, Cu-Fe ferrite, Zn-Fe ferrite, Sr-Fe ferrite, and oxides of chromium, cerium and magnesium, or zircon, silicon, silicon dioxide and the like are used. These substances have an average particle size of 20 to 100 μm, preferably 25 to 70 μm.
m, more preferably 30 to 65 μm.

If desired, the toner of the present invention may be mixed with various additives such as a charge control agent, a lubricant, fine powder silica, PVDF (polyvinylidene fluoride) powder and the like.

The toner of the present invention has an average particle size of preferably 5.0 to 16. by kneading and dispersing the above-described colorant in a binder resin and pulverizing (and further classifying if necessary) according to a conventional method.
Obtained as 0 μm particles.

The toner of the present invention is preferably used in an image forming process having a heat roller fixing step, and is particularly preferably used in an image forming process having a heat roller surface temperature of 120 to 210 ° C (further, about 130 to 190 ° C).

EFFECTS OF THE INVENTION According to the present invention as described above, the apparent viscosities at respective temperatures of 90 ° C. and 100 ° C., and the ratio of these apparent viscosities are within a specific range, whereby offset resistance and fixability are improved. Provided is an electrophotographic toner which not only excels but also provides an image having sufficient gloss and luster.

The toner of the present invention is preferably used as a normal black toner, but is particularly preferably used as a color electrophotographic toner in which gloss and luster of an image are important factors.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but these do not limit the present invention in any way. All used parts are parts by weight.

Example 1 (* Polyester resin obtained by polycondensing 100 parts of hydroxypropylated bisphenol A, 90 parts of fumaric acid, and 10 parts of trimellitic acid.) The components of the above formulation are kneaded using a three-roll mill, afterwards,
Particle size 5 to 30 μm by pulverizing with a jet mill and further classifying
Then, 0.3 part of finely powdered silica was added to obtain a red toner of the present invention.

The apparent viscosity-temperature curve of this red toner measured by the Flotester method is shown in the attached drawing.

Referring to the drawing, in this red toner, η (9
0) = 8.0 x 10 ⁵ poise, η (100) = 3.1 x 10 ⁵ poise, η
(100) / η (90) = 0.39.

90 parts of an iron powder carrier (average particle size: 50 μm) was mixed with 10 parts of the red toner to prepare a developer (starting agent). When this developer was applied to a color copying machine (trade name: Color T, manufactured by Canon Inc.) and a durability test was conducted on 10,000 sheets, the 10,000th sheet showed almost no change from the initial stage and high saturation. A good glossy image (specular gloss of 30%, gloss meter measurement) was obtained.

During this durability test, no high temperature offset was observed, and the contamination on the upper roller (the roller in contact with the toner transfer surface side of the paper) was very slight.

Example 2 A yellow toner and a developer were obtained in the same manner as in Example 1 except that the components described above were used.

The apparent viscosity-temperature curve of this yellow toner is shown in the drawing.

Referring to the drawing, η (90) = 3.0 × 10 ⁶ poise, η (10
0) = 2.1 × 10 ⁵ poise, η (100) / η (90) = 0.07.

This developer was applied to a color T (color copying machine), and a durability test of 15,000 sheets was conducted in the same manner as in Example 1. However, even after 15,000 sheets, no high temperature offset was observed. , A high-density image with sufficient gloss (specular gloss 23%) was obtained.

Comparative Example 1 A blue toner and a developer were obtained in the same manner as in Example 1 except that the components described above were used. The apparent viscosity-temperature curve of this blue toner is shown in the drawing.

In this blue toner, η (90) = 4.6 × 10 ⁵ poise and η (100) = 3.0 × 10 ⁴ poise.

When an image was formed using color T using the above-mentioned developer in the same manner as in Example 1, high-temperature offset had already occurred at the initial stage. Furthermore, due to the durability of only a few hundred sheets, the offset material accumulated on the upper roller dropped onto the image support passing through the fixing device, and the image was contaminated.

This is due to the remarkable high temperature offset phenomenon.

Comparative example 2 A yellow toner and a developer were obtained in the same manner as in Example 1 except that the components described above were used.

The apparent viscosity-temperature curve of this yellow toner is shown in the drawing.

Referring to the drawing, in this yellow toner, η (9
0) = 1.8 × 10 ⁷ poise and η (100) = 2.5 × 10 ⁶ poise.

When an image was printed with color T using the above-mentioned developer in the same manner as in Example 1, there was no high temperature offset at the initial stage, and no high temperature offset was observed even after running for 20,000 sheets. However, the image has poor gloss (specular gloss
3.8%) The image became matt. Further, with magenta toner and cyan toner having the same binder component,
When the three colors were overlaid, the color mixture of full color was poor, and only a poorly saturated image was obtained.

[Brief description of drawings]

The drawing is a graph showing the apparent viscosity-temperature curves of the toners of Examples and Comparative Examples, which were obtained by the flow tester method.

Claims (1)

[Claims] 1. An apparent viscosity η (90) at 90 ° C., and
The apparent viscosity η (100) at 100 ° C is 1 × 10 ⁵ <η (90) <5 × 10 ⁶ (poise) 1 × 10 ⁵ <η (100) <1 × 10 ⁶ (poise), respectively. Moreover, the ratio of these apparent viscosities is 0.05 <η (100) / η (90) <1.0, which is an electrophotographic toner.