JPH0451156A - Heat fixing method and toner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a fixing method for fixing a visual image formed with toner in electrophotography, electrostatic printing, magnetic recording, etc. to a recording material, and a fixing method used in the fixing method. related to toner.

[Prior Art] Conventionally, as a method for fixing a toner image on a recording material, a heated roller maintained at a predetermined temperature and a pressure roller having an elastic layer and pressed against the heated roller are used.
A hot roll fixing method is often used in which a recording material holding an unfixed toner image is heated while being nipped and conveyed.

Further, a belt fixing method described in US Pat. No. 3.578.797 is known.

[Problems to be Solved by the Invention] However, in the above-mentioned hot roll fixing which has been frequently used in the past, (1) there is a so-called wait time, which is a period during which the image forming operation is prohibited until the hot roller reaches a predetermined temperature.

(2) The heating roller is maintained at an optimal temperature in order to prevent fixation failure and toner transfer to the heating roller due to fluctuations in the temperature of the heating roller due to passage of the recording material or other external factors. For this purpose, the heat capacity of the heating roller or heating body must be increased, which requires a large amount of electric power and also causes an increase in temperature inside the image forming apparatus.

(3) Since the roller is at a constant temperature, when the recording material passes through the heating roller and is discharged, the recording material and the toner on the recording material are slowly cooled, resulting in a highly sticky state and the roller Coupled with the curvature of the recording material, paper jams may occur due to offset or entrainment of the recording material.

(4) The high-temperature heating roller is directly touched by the hands, which may pose a safety problem or require a protective member.

Also, in the belt fixing method described in υSP3.578.797, the above-mentioned problems (1) and (2)
) has not been fundamentally resolved.

In Japanese Patent Application No. 62-147884, which was previously proposed by the present applicant, a toner image is heated via a heat-resistant sheet moved by a low-heat-capacity heating element that generates heat through pulsed electricity, and is fixed onto a recording material. An image forming apparatus with short wait time (low power consumption) has been proposed using a fixing device that uses
In No. 069, in a fixing device that heats and fixes a toner image onto a recording material via a heat-resistant sheet, the heat-resistant sheet has a heat-resistant layer and a release layer or a low-resistance layer, thereby effectively suppressing the offset phenomenon. A fixing device that prevents this problem has been proposed.

However, in order to realize a fixing method that achieves excellent fixation of toner images on recording materials, prevents offset, etc., and has a short wait time and low power consumption, it is necessary to use in addition to the above-mentioned fixing device. This is largely due to the characteristics of the toner.

An object of the present invention is to solve the above-mentioned problems, and has virtually no or extremely short wait time, low power consumption, no offset phenomenon, and good fixation of toner images on recording materials. The present invention provides a novel heat fixing method.

Another object of the present invention is to provide a toner for heat fixing that is preferably used in the heat fixing method provided in the present invention.

Still another object of the present invention is to provide a heat fixing method that does not require a special heat-resistant bearing because it does not use a high-temperature rotating roller.

Still another object of the present invention is to provide a heat fixing method that has a fixing device configuration that does not require direct hand contact with a high-temperature body, and is highly safe or does not require a protective member.

[Means for Solving the Problems] The present invention contains a polymer formed from one or more α,β-unsaturated ethylenic monomers as a binder resin, and the binder resin has a temperature in the range of 120 to 150°C. At any temperature of
Melt viscosity is 103 to 105 poise, and 12
When the logarithm (1!nη') of melt viscosity at 0°C and 150°C is plotted against temperature, the absolute value of the slope of the graph is o, 50I! A toner having a physical property of n(poise)/''C or less is brought into pressure contact with a heating body whose visible image is fixedly supported on a recording material, and the recording material is attached to the recording material via a film. and a pressure member brought into close contact with the heating body, and the heating member is characterized in that at least the surface of the film in pressure contact with the recording material has a critical surface tension of 30 dyne/cm and a surface electrical resistance of 010 Ωcm2 or less. The present invention relates to a heat fixing method that can be applied to a fixing method to solve the problems of the conventional fixing methods described above.

One feature of the heat fixing method and toner structure of the present invention is that the binder resin of the toner used is
Melt viscosity at any temperature in the range of 102 to 105
poise, and when the logarithm (inη') of the melt viscosity at 120°C and 150°C is plotted against temperature, the absolute value of the slope of the graph is 0.50I! n(pois
e) have physical properties of less than /''C.

In the present invention, the viscosity was measured using an elevated flow tester (Shimadzu Flow Tester CFT-500 model: manufactured by Shimadzu Corporation) shown in FIG. A load of 10 kg-f was applied with plunger 1 at a constant temperature, and the diameter was 1 mm and the length was 1 m.
The amount of plunger descent (flow rate) of the flow tester was measured by extruding the liquid from the nozzle 4 of the flow tester. This outflow rate is measured at each temperature (temperature range from 120 DEG C. to 150 DEG C. at 5 DEG C. intervals), and from this value, the apparent viscosity n' can be determined by the following formula.

However, η: Apparent viscosity (poise) TW': Apparent shear reaction of the tube wall (dyne/cm2)
DW': Apparent shear velocity of pipe wall (1/5ee)Q
:Outflow velocity (cm”/5ec=n+f!/5ec)P
: Extrusion pressure (dyne/cm2) [10Kg=f
=980 x 105dynelR=nozzle radius (c
m) L: Nozzle length (cm) In the heat fixing method of the present invention, the viscosity and inclination of the binder resin are unique to each binder resin. It indicates the sensitivity of viscosity to temperature, and is involved in binding properties and toner particle deformation during fixed image formation.Especially in fixing methods using films, it has a strong correlation with the fixing process.12[ If the melt viscosity at 1°C to 150°C exceeds 106 poise, particle deformation occurs during heat fixing ((tackiness does not increase, causing poor fixing, and a large amount of energy is required to compensate for this. On the other hand, if it is less than 102 poise, bleeding on the transfer paper or seepage into the transfer paper is likely to occur.
poise)/"C", the particles are sensitive to temperature and exhibit rapid viscosity changes, making it impossible to maintain sufficient latitude in fixing temperature, which tends to cause poor fixing and seepage. Furthermore, the dependence on the fixing processing speed (mm/5ec) is large. Also, this "slope" ° is also involved in the viscosity change during cooling after particle melting during fixing, and the "slope" ° The absolute value is 0, 501!n (pois
e)/When it is larger than "C", there are disadvantages such as an increase in the offset phenomenon to the film, a noticeable gloss on the fixed image, and a decrease in image quality.

In the present invention, the gradient of viscosity is the value obtained by connecting the measurement point at t1°C and the measurement point at t0°C in the graph with a straight line, as shown in FIG. 2, and calculating the "slope" by This is approximated and used as the "inclination" of the slope.

(However, I!nr1m' indicates the value obtained by taking the natural logarithm of the viscosity at t1°C, and Rnηゎ' indicates the value at tt, "C.") In the present invention, in order to obtain a large amount of energy for heat fixing, When increasing the fixing temperature, there is a difficulty in increasing the heat resistance of the film that is in close contact with the heating element.Also, in order to lengthen the fixing time, attempts are made to widen the fixing nip. In some cases, the pressure from the pressure member increases, which poses a problem in terms of durability in terms of mechanical strength of the film that is pressed against the heating element by the pressure member. In order to lower the conveyance speed of the image forming operation, the speed of the image forming operation is regulated.

α and β constituting the binder resin of the toner applied to the present invention
- Unsaturated ethylenic monomers include, for example, styrene, α-methylstyrene, p-chlorostyrene and other styrenes and substituted products thereof, acrylic acid, methyl acrylate,
Ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate,
Monocarboxylic acids having double bonds such as butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, etc., or substituted products thereof, such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate, etc. dicarboxylic acids and substituted products thereof, such as vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate, etc.; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, etc., such as vinyl methyl ether; Vinyl monomers such as vinyl ethers such as , vinyl ethyl ether, vinyl isobutyl ether, etc. may be used alone or in combination.

In addition to the binder resin component described above, the toner used in the present invention may contain the following compounds in a proportion smaller than the content of the binder resin component. For example, styrene-butadiene resin, silicone resin, polyester, polyurethane,
These include polyamide, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, and the like.

In addition, a release agent may be contained in the toner, such as polyfluorinated ethylene, fluororesin, fluorinated carbon foam, silicone oil, low molecular weight polyethylene, low molecular weight polypropylene, etc. in an amount of 0.1 to IO with respect to the toner. Used in % by weight.

When the toner used is a magnetic toner containing magnetic fine particles, the magnetic fine particles may be any material that exhibits magnetism or can be magnetized, such as metals such as iron, manganese, nickel, cobalt, and chromium, magnetite,
There are hematite, various ferrites, manganese alloys, and other ferromagnetic alloys, which have an average particle size of about 0.05~
A fine powder of 5 pm can be used. The amount of magnetic fine particles contained in the magnetic toner is 1 of the total weight of the magnetic toner.
It is preferably 5 to 70% by weight (more preferably 25 to 45% by weight).

Furthermore, various substances can be added to the toner used in the present invention for the purpose of coloring, controlling charge, etc.

Examples include carbon black, iron black, graphite, nigrosine, metal complexes of monoazo dyes, ultramarine blue, phthalocyanine blue, Hansa yellow, benzine yellow, and various quinacridone lake pigments.

Alternatively, colloidal silica or the like may be contained in the toner in an amount of 10 to 40% by weight as a fluidity improver. Of course, this fluidity improver may be used by being mixed outside the toner.
The amount added at this time is 0.2 to 5% by weight (based on the weight of the toner).

The toner used in the heat fixing method of the present invention is DS
As a result of measurement using C in the measurement range from 10°C to 200°C, the maximum value of the first endothermic peak that appears is from 40°C to 12°C.
Toners exhibiting a temperature of 0°C are preferred, particularly 55°C to 100°C.
More preferred are toners exhibiting the following characteristics.

Further, it is preferable that the temperature at which the film is peeled off from the surface to which the toner is fixed is higher than the endothermic temperature, more preferably 30°C or more (more preferably 40 to 140°C) higher than the endothermic temperature. It is preferable to peel it off under certain conditions.

The method of measuring the maximum value of the endothermic peak in the present invention is calculated based on ASTM D-3418-82. Specifically, 10 to 15 mg of toner is collected, heated in a nitrogen atmosphere from room temperature to 200°C at a temperature increase rate of 10°C/min, held at 200°C for 10 minutes, and then rapidly cooled. After toner pretreatment, the temperature is again 10℃.
20 minutes at a heating rate of 10°C/min.
Heat to 0°C and measure. - For boat fishing, the data shown in Figure 3 is obtained, and the maximum value of the first endothermic peak that appears is defined as the endothermic temperature (TD) in the present invention.

In the present invention, the heating body has a smaller heat capacity than a conventional heating roll and has a linear heating section, and the maximum temperature of the heating section is preferably 100 to 300°C.

Further, the film located between the heating body and the pressure member is preferably a heat-resistant sheet with a thickness of 1 to 100 μm, and these heat-resistant sheets include highly heat-resistant polyester, PET (polyethylene terephthalate), etc. ))PF
In addition to polymer sheets such as A (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, and polyamide, metal sheets such as aluminum, and laminates composed of metal sheets and polymer sheets. A sheet is used.

The structure of the film in the present invention is that these heat-resistant sheets have a release layer and/or a low resistance layer.

The surface characteristics of the surface of the film of the present invention that comes into pressure contact with the recording material are that it has a critical surface tension of 30 dyne/cm or less and a surface electrical resistance of 10 10 Ω/cm 2 or less.

The film applied to the present invention is made of a heat-resistant material such as polyimide, polyetherimide, PES, PFA, etc. as the heating body pressure contact surface, and PTF on at least the surface image contact side.
E. A multilayer coat comprising a low-resistance mold release layer having a surface electrical resistance of 1010 Ω/cm2 or less by adding and dispersing a conductive material into a binder resin such as PAF having a critical surface tension of 30 dyne/cm or less. Films are more preferably used. Conductive materials for controlling surface electrical resistance that are preferably used in the present invention include carbon black, graphite, and inorganic oxides.

When the critical surface tension of the surface of the film used in the heat fixing method of the present invention that comes into pressure contact with the recording material exceeds 30 dyne/cm, the so-called offset phenomenon in which toner adheres to the film surface becomes noticeable. Furthermore, when the surface electrical resistance exceeds 1010 Ω/cm, an electrostatic offset phenomenon in which toner electrostatically adheres to the film surface becomes significant.

The method for measuring surface electrical resistance in the present invention conforms to JIS standard 6911.

The critical surface of the surface that comes into pressure contact with the recording material in the present invention was determined by measuring the contact angle θ exhibited by various organic liquids (hydrocarbons and others) with different surface tensions γ on the film surface and performing Zisman plotting.

Hereinafter, preferred embodiments of the present invention will be described based on the accompanying drawings, but this is not intended to limit the present invention in any way.

FIG. 4a shows a structural diagram of the fixing device of this embodiment.

Reference numeral 11 denotes a low heat capacity linear heating element that is fixedly supported on the device, and as an example, has a thickness of 1.0 mm, a width of 10 mm, and a longitudinal length of 2.
A resistance material 13 is placed on a 40 mm alumina substrate 12 with a width of 1.0 mm.
It is coated with a thickness of mm and is energized from both ends in the longitudinal direction.

The current is supplied with a pulse-like waveform of DC 100V with a cycle of 20 m5 ec to a desired temperature controlled by the thermometer 14.
A pulse is given by changing the pulse width depending on the amount of energy released. Approximate pulse width is 0.5m5ec~5m5e
c. The fixing film 15 moves in the direction of the arrow in the figure while coming into contact with the heating body 11 whose energy and temperature are controlled in this manner. For example, this fixing film has a thickness of 20 pm.
heat-resistant film, such as polyimide on the side that contacts the heating element,
PTFE on the imide image contact side.

A release layer containing carbon black as a conductive material is added to the
It is an endless film coated with a thickness of 0 μm.

The critical surface tension of the surface of this film that comes into pressure contact with the recording material is
20dyne/cm, and the surface electrical resistance is 1×10
It was 6Ω/cm2.

Generally the total thickness is less than 100μ, preferably less than 40μ. The film is driven by the driving roller 16 and the driven roller 17 and tension to move the film in the direction of the arrow without wrinkles.

Reference numeral 18 denotes a pressure roller having a rubber elastic layer with good mold releasability such as silicone rubber, which presses the heating body through the film with a total pressure of 4 to 20 kg and rotates in pressure contact with the film. The unfixed toner 20 on the transfer material 19 is guided to the fixing section by the entrance guide 21 and is heated as described above to obtain a fixed image.

The above was explained using an endless belt, but as shown in Figure 4b (,
The sheet feeding shaft 24 and the winding shaft 27 may be used, and the fixing film may be a film with ends.

Further, as an image forming apparatus, the present invention is applicable to all the fixing devices of apparatuses that form images using toner, such as copying machines, printers, and facsimiles.

When the temperature detected by the temperature measuring element 14 in the low heat capacity linear heating element 11 is T1, the surface temperature T2 of the film 15 facing the resistance material 13 is about 10 to 30 degrees Celsius lower than T. Further, the film surface temperature T3 at the portion where the film 15 is peeled off from the toner fixed surface is approximately equal to the temperature T2.

[Example] Example 1 Styrene-butyl acrylate copolymer (120°C 3X
lO'poise, slope 0.11fn (poise)
/”C) 100 parts by weight, 50 parts by weight of magnetic material, and 2 parts by weight of nigrosine dye.

2 parts by weight of low molecular weight polyethylene was melt-kneaded using a twin-screw kneading extruder, cooled, pulverized using a pneumatic pulverizer, and classified using a pneumatic classifier to obtain a black fine powder with an average particle size of 8 pm. Toner A was obtained by externally adding 0.5 parts by weight of silica powder to 100 parts by weight of this black fine powder.

This toner A was transferred to a commercially available copying machine, Canon NP-121.
5 (manufactured by Canon) was applied to a modified machine to produce an unfixed toner image.

This was applied to a fixing device having the configuration described above (see FIG. 4a).

The critical surface tension of the surface of this fixing film that comes into pressure contact with the recording material is 20 cfyne/am, and the surface electrical resistance is l.
Xl0'Ω/cm.

In this fixing device, the temperature measuring element surface temperature T of the heating body,
is 130℃, the power consumption of the resistance material of the heating part is 150W,
The total pressure of the pressure roller is 5 kg, the nip between the pressure roller and the film is 3 mm, the fixing speed is set to 25 mm/see, and the heat-resistant sheet is made of PTF on the contact surface with the recording material.
A polyimide film having a thickness of 20 pm and having a low-resistance release layer in which a conductive substance (carbon black) was added to E was used. At this time, the temperature sensing element surface temperature T1 of the heating body is 1
The time required to reach 30°C was about 0.5 seconds. Furthermore, the temperature T2 at this time is 126°C, and the temperature T is 126
It was ℃. As a recording material, commercially available copy machine paper Canon New Dry Paper (Canon Sales Co., Ltd. 54 g/m") was used.
was used.

The resulting image was free from toner penetration into the paper and set-off, had good fixing properties, and had no offset onto the film.

Further, when a continuous fixing test was carried out on 2000 sheets under the same fixing conditions, the fixing performance was good, and a good fixed image was obtained without causing any offset phenomenon to the film.

Example 2 Styrene-butyl acrylate copolymer (120°C 5
105poise, slope 0.15jl'n (pois
e)/”C) 100 parts by weight, 4 parts by weight of carbon black, 2 parts by weight of nigrosine dye, 2 parts by weight of low molecular weight polyethylene
A fine black powder having an average particle size of 13 μm was obtained in the same manner as in Example 1 using parts by weight. Toner B was obtained by externally adding 0.9 parts by weight of silica powder to 100 parts by weight of this black fine powder.

300 g of ferrite resin coated carrier was mixed with 36 g of this toner to prepare a two-component developer B'.

When this two-component developer B' was evaluated in the same manner as in Example 1, even in the fixing test of 5,000 continuous sheets,
A good image was obtained that did not cause any offset phenomenon, had excellent fixing properties, and was free from toner penetration into the recording paper, set-off, and image bleeding.

In addition, the surface temperature T1 of the temperature measuring element of the heating body in this fixing test is as follows:
The temperature was set at 175°C. Also, the process conditions at this time are:
Process speed 100mm/sec, nip 3mm
It is.

Example 3 Styrene-butyl acrylate copolymer (120°C 5X
105poise, slope 0.22Rn (poise)
/''C) 100 parts by weight, 3 parts by weight of the negative charge control agent, and 4 parts by weight of the phthalocyanine pigment to obtain a blue fine powder with an average particle size of 94 tm in the same manner as in Example 1.
A full color cyan toner C was obtained by externally adding 0.8 parts by weight of negatively chargeable colloidal silica.

300 g of ferrite resin coated carrier was mixed with 24 g of this toner to prepare a two-component developer C'.

This two-component developer C' is applied to a commercially available copying machine, Canon CLC.
-500 (manufactured by Canon) was applied to a modified machine to produce an unfixed toner image.

When this unfixed image was evaluated in the same manner as in Example 1, an image with excellent fixability was obtained without causing any offset phenomenon.

In this fixation test, the surface temperature T of the temperature measuring element of the heating body is as follows:
Set the temperature to 170℃ and the process speed of the fixing machine to 100℃.
mm/sec, nip 5mm, and the recording material is:
Commercially available color leather copier paper (Canon Sales) was used.

Comparative Example 1 A fixing test was conducted in the same manner as in Example 1, except that the low-resistance release layer on the surface of the fixing film used in Example 1 was replaced with a polyethylene terephthalate carbon black dispersion layer. The critical surface tension of the surface of this film that comes into pressure contact with the recording material is 41
dyne/cm, and the surface electrical resistance is 10? Ω/cf
It was f12.

As a result, an offset phenomenon occurred in a continuous fixing test of 2,000 sheets, and the image fixability was also poor.

Comparative Example 2 A fixing test was conducted in the same manner as in Example 1, except that the low-resistance release layer on the surface of the fixing film used in Example 1 was made by reducing the amount of carbon black in the PTFE and increasing the surface electrical resistance.

The critical surface tension of the surface of this film that comes into pressure contact with the recording material is 19 dyne/cm, and the surface electrical resistance is 10207
cm”.

As a result, an offset phenomenon occurred in a continuous fixing test of 2,000 sheets, and the image fixability was also poor.

[Effects of the Invention] According to the toner and heat fixing method of the present invention, the toner image is well fixed on the recording material, there is no offset phenomenon of the toner to the fixing film, and there is no permeation of the toner onto the recording material. Set-off (provides sharp images with no smearing,
Moreover, the power consumption is low and the wait time is extremely short.

[Brief explanation of drawings]

FIG. 1 shows a schematic cross-sectional view of an elevated flow tester for measuring the melt viscosity of toner or binder resin. Second
The figure is a graph showing the slope of the natural logarithm of the viscosity of toner or binder resin with respect to temperature. FIG. 3 is a graph showing the endothermic peak of toner. FIG. 4a is a diagram showing a schematic cross-sectional view of a fixing device for carrying out the fixing method of the present invention. FIG. 4b shows a schematic cross-sectional view of a fixing device for carrying out another aspect of the fixing method of the present invention. l...Piston (plunger) 2...Cylinder 3...Sample 4...Gui (nozzle) 5...Gui holder 11...Heating body 12...Alumina substrate 13...Resistance material 14...Temperature measuring element 15...Fixing film 16...Drive roller 17...Followed roller 18...Pressure roller 19...Recording material 20...Unfixed toner carried on recording material Visual image 21
... Fixing device entrance guide 24 ... Sheet feed shaft 27 ... Winding shaft

Claims (2)

[Claims] (1) In a method of heating and fixing a toner image on a recording material using a fixedly supported heating body and a pressure member that is in opposing pressure contact with the heating body and brings the recording material into close contact with the heating body through a film. , the toner contains a polymer formed from one or more α,β-unsaturated ethylenic monomers as a binder resin, and the binder resin has a melt viscosity at a temperature in the range of 120 to 150°C. 10^2～10^6poise
and the logarithm of the melt viscosity at 120°C and 150°C (
It has physical properties such that when plotting lnη') against temperature, the absolute value of the slope of the graph is 0.50 ln (poise)/°C or less, and is located between the heating body and the pressure member. A heat fixing method characterized in that at least the surface of the film in pressure contact with the recording material has a critical surface tension of 30 dyne/cm or less and a surface electrical resistance of 10^1^0 Ω/cm^2 or less. (2) Through a fixedly supported heating element and a film having at least a critical surface tension of 30 dyne/cm or less and a surface electrical resistance of 10^1^0 Ω/cm^2 as characteristics of the surface that comes into pressure contact with the recording material. A toner used in a method of heating and fixing a toner image on a recording material by means of a pressure member that presses against the heating body and brings the recording material into close contact with the heating body, wherein the binder resin used in the toner is 120% ~15
At any temperature in the range of 0°C, the melt viscosity is 10^3~
10^5 poise, and when the logarithm (lnη') of the melt viscosity at 120°C and 150°C is plotted against temperature, the absolute value of the slope of the graph is 0.50ln (
1. A toner characterized in that it is a polymer formed from one or more α,β-unsaturated ethylenic monomers having a physical property of not more than 100 ml of α, β-unsaturated ethylenic monomer.