JP2003280421A - Method for image forming - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a high image quality by suppressing the occurrence of the deformation of a toner image before/after fixing. <P>SOLUTION: In an image forming method, the toner image is preliminarily heated before thermal fixing and toner with which the rate of volume change Vt of the toner image before/after the fixing is set as ≤30% and the rate of area changes St is set as ≤20% is used as the toner. Vt=[(toner volume before passing the heating part)-(toner volume after passing the heating part)]/the toner volume before passing the heating part × 100. St=[(toner area after passing the heating part)-(toner area before passing the heating part)]/the toner area before passing the heating part × 100. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method used in digital copying machines, printers, facsimiles, etc.
The present invention relates to a fixing device and toner physical properties used for it.

[0002]

2. Description of the Related Art An image forming method using electrophotography is widely known and used in printers, copying machines and the like. No. 2,743,476 discloses that the physical properties of toner are specified.
A toner for roll fixing in which core particles made of a polyester resin and a wax having a polar group are coated with a resin to define the melt viscosity of the polyester resin and the wax. JP-A-3-122
661, Japanese Patent Application Laid-Open No. 4-85550, and Japanese Patent Publication No. 8
No. 16804 discloses a film comprising a specific polyester resin and a release agent, and defining the melt viscosity of the polyester resin at 80 to 120 ° C., the slope of a graph of the melt viscosity and the temperature, and the melt viscosity of the specific release agent. Toner for fixing. Japanese Examined Patent Publication No. 8-12459 discloses a polyester resin of 80 to 120, which comprises a specific polyester resin and a release agent.
Capsule toner for film fixing, which defines the melt viscosity at ℃, the slope of the graph of melt viscosity and temperature, and the melt viscosity of a specific release agent. Japanese Patent Publication No. 7-82250 contains a specific polyester resin, an organometallic compound, and a release agent,
A film fixing toner in which the melt viscosity of a polyester resin at 120 to 150 ° C., the slope of the graph of the melt viscosity and the temperature, and the melt viscosity of a specific release agent are specified. Japanese Patent Fair 7-72
No. 809, a toner made of styrene-acrylic resin which defines a relational expression between melt viscosity measured at 110 to 130 ° C. and temperature. Japanese Unexamined Patent Publication No. 10-246989 proposes a toner containing a specific charge control agent and defining an average viscosity gradient.

However, although these conventional techniques are effective for improving the fixing characteristics, they are not considered for improving the image quality such as the volume change and area change of the toner image. Further, Japanese Patent Laid-Open No. 6-230602 discloses that
A magnetic toner has been devised which prevents problems and offset during double-sided copying by controlling the ratio of the height of the toner image before fixing to that after fixing in a specific range. JP-A-7-44
No. 049 discloses that a toner having a small particle diameter is fixed to a fixing roller having a JIS hardness of 90 ° or less and a fixing roller having a JIS hardness of 95 ° or more.
A fixing method has been devised that obtains a fixed image having excellent fixability and less spread of the toner image by fixing in stages.

In Japanese Patent Laid-Open No. 10-307492, a method of obtaining a glossy and high-quality fixed image by devising a recording medium carrying a toner image by a belt which conveys the recording medium to a heat roller type fixing device is devised. Has been done. JP-A-11-
No. 1113060 proposes a fixing device in which the fixing property is improved by non-contact heating from the surface of a recording medium carrying a toner image on a belt which is conveyed to a heat roller type fixing device.

[0005]

Problems to be Solved by the Invention In recent years, the image quality has been further improved and the toner particle size tends to be smaller. It is known that when the toner particle size is small, even if pressure is applied between the fixing rollers, it is difficult to apply pressure to the toner particles, and thus the fixability deteriorates. This tendency becomes remarkable especially in the case of a fixing device having a low surface pressure. Further, when thin paper is used as the recording medium, the surface pressure is normal, so that the image quality is not particularly deteriorated. On the contrary, when thick paper is used, the toner is removed in the same manner as when the surface pressure is increased. After being crushed, the volume and area of the toner image after fixing change, and the image quality deteriorates. This phenomenon is particularly remarkable in the case of digital development, and the reproducibility of independent dots is greatly affected.

Further, in order to improve image quality, the fixing roller is often provided with an elastic layer. In this case, as compared with the fixing roller having no elastic layer, the phenomenon that the toner image spreads widely on the recording medium by fixing can be suppressed, but the fixing property deteriorates more severely when the surface temperature of the fixing roller drops. That is, it is more affected by the environment, recording medium, run mode, and the like. Therefore, in order to maintain sufficient fixability under various conditions, it may be unavoidable to set the fixing roller surface temperature higher than the optimum condition in the normal environment. As compared with the image before fixing, the spread of toner such as halftone dots of lines and dots becomes larger due to fixing, and smoothness and sharpness are deteriorated.

Under the above circumstances, the present invention provides an image forming method capable of preventing the spread of a toner image at the time of fixing and obtaining a sufficient fixing property, that is, suppressing deformation of the toner image before and after fixing, thereby improving the image quality. An object of the present invention is to provide an image forming method capable of obtaining a fixed image of high image quality.

[0008]

Means for Solving the Problems As a result of earnest studies, the inventors of the present invention conducted non-contact heating of a toner image before fixing with a heat roller system and, as the toner, the area change rate and volume change rate of the toner image before and after fixing. It has been found that it is useful to select a material having a value equal to or less than a predetermined value, and the present invention has been completed. That is, the present invention includes (1) a latent image forming step of forming a latent image on a latent image carrier, a developing step of developing the latent image with a developer, and a transfer step of transferring a toner image onto a recording medium. An image forming method including a fixing step of fixing an unfixed toner image on a recording medium to a recording medium, comprising a rotatable fixing rotating body as a fixing device and a rotatable pressure rotating body in the fixing step. A recording medium having an unfixed toner image transferred thereon is nipped and conveyed in a nip formed between the fixing rotator and the pressure rotator, and at least the fixing rotator and the pressure rotator are provided. In an image forming method using a fixing device that heat-fixes the unfixed toner image on a recording medium by heating by a heating means provided inside either one, or both of the fixing rotator and the pressure rotator. Has an elastic layer on the surface layer of Before fixing, the toner image on the recording medium is irradiated with electromagnetic waves from the electromagnetic wave irradiating means to heat the toner image in a non-contact manner. As a developer, the volume change rate of the toner image on the recording medium before and after fixing is as follows. Vt defined in is less than 30%,
An image forming method using a toner having an area change rate St of 20% or less defined below. Vt = {(toner volume before passing through heating part)-(toner volume after passing through heating part)} / toner volume before passing through heating part × 100 St = {(toner area after passing through heating part) − (passing through heating part) Area of toner before)} / area of toner before passing through heating unit × 100 (2) Melt viscosity of the above toner at 100 ° C. η10
When the melt viscosity at 0 and 120 ℃ is η120, η100
And η120 satisfy the following formula: The image forming method described in (1) above. η100 / η120 = 6 to 10 (3) The toner has a THF insoluble content of 10 to 10 in the resin.
80% is contained, The image forming method of said (1) or (2) characterized by the above-mentioned. (4) The toner has a resin with an acid value of 10 to 100 mg KO
The image forming method according to any one of (1) to (3) above, wherein the H / mg polyester resin is contained in an amount of 50% by weight or more. (5) The toner has a resin with an acid value of 10 to 100 mg KO
The image forming method as described in any one of (1) to (4) above, which contains 50% by weight or less of a resin that is incompatible with H / mg of the polyester resin. (6) The image forming method according to any one of (1) to (5), wherein the toner contains magnetic fine particles. (7) The image forming method as described in any one of (1) to (6) above, wherein the toner contains an inorganic fine powder. (8) The image forming method as described in (1) to (7), wherein the toner contains an organic zirconium compound as a polarity control agent. (9) The toner contains an inorganic fine powder as an external additive
(1), which is characterized by containing 0% by weight or more.
The image forming method according to any one of (8). (10) The image forming method as described in (1) to (9) above, wherein the toner has a weight average particle diameter of 4 to 10 μm. (11) The melt viscosity at 100 ° C. of the toner is η
When the melt viscosity at 100 and 120 ℃ is η120, η10
A toner in which 0 and η 120 satisfy the following formula. Regarding η100 / η120 = 6 to 10.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a preferred example of a fixing device used in the image forming method of the present invention. The outer diameter of the fixing roller 1 is φ50, the material of the core metal 2 is aluminum, and the thickness thereof is 1 mm. An elastic layer 3 having a thickness of 300 μ is provided on the outer side thereof, and a fluorine resin layer 4 having a thickness of 30 μm is provided as a release layer on the surface layer thereof.
have. The fluororesin layer 4 uses PFA as a base material.
Silicone rubber was used for the elastic layer. A halogen heater 5 is provided inside the core metal 2. The outer shape of the pressure roller 6 is φ50, the material of the cored bar 7 is aluminum, and the thickness thereof is 1 mm. The elastic layer 8 is provided on the outer side thereof. Silicone rubber is used for the elastic layer.

The infrared lamp 10 of the electromagnetic wave irradiation means 9 has four
A 50 W halogen lamp is used, and at a position 5 cm upstream from the nip portion in the recording medium conveyance path, 1 mm from the recording medium.
Infrared reflection mirror 1 installed to irradiate cm away
An aluminum parabolic mirror was used as No. 1 and was installed above the halogen lamp. Infrared rays from the infrared lamp 10 directly irradiate the recording medium 12 and the toner image 13 on the recording medium 12, and at the same time, are reflected by the infrared reflection mirror 11 to irradiate the surface of the recording medium 12 and the toner image 13. The recording medium 12 which holds the toner image 13 in a semi-melted state by being irradiated with infrared rays is conveyed to a nip which is a contact portion between the fixing roller 1 and the pressure roller 6, and receives heat and pressure at the nip portion. The toner image 13 is fixed on the recording medium 12 and discharged.

Next, the behavior of the recording medium 12 will be described. The toner image 13 formed on the recording medium 12 by an image forming apparatus (not shown) enters the fixing device. The surface of the recording medium 12 is heated by the electromagnetic wave irradiating means 9, and the toner image 13 in a semi-melted state is conveyed to a fixing nip formed between the fixing roller 1 and the pressure roller 6. A drive (not shown) is applied to the fixing roller 1 and the pressure roller 6 to eject the recording medium 4 from the nip portion.

Next, the constitution of the toner used in the present invention will be shown. The toner used in the present invention comprises at least a resin and a wax, and a support carrying a toner image is preliminarily heated, and then is passed between heating members having elasticity to heat-fix the toner image. In the heat fixing device for performing the heat fixing, the volume change rate Vt of the toner image before and after the heat fixing is 30
% And the area change rate St is 20% or less, the toner can have a sufficient fixing property.

Vt and St are calculated by the following equations. Vt = {(toner volume before passing through heating part)-(toner volume after passing through heating part)} / toner volume before passing through heating part × 100 St = {(toner area after passing through heating part) − (passing through heating part) Previous toner area)} / Toner area before passing through heating unit × 100 Toner volume Vt and toner area St are measured by using an ultra-depth shape measuring microscope (VK-8500 type manufactured by Keyence Corporation). For the toner area, the area of the dot portion (φ 2.0 toner adhesion amount 1.2 ± 0.05 mg / cm ² ) before and after fixing is measured. The toner volume is obtained by measuring the height of the toner image (dots) before and after fixing and calculating from the previously measured area. When Vt and St exceed the predetermined value, the quality of the formed image is poor.

Further, in the present invention, when the melt viscosity at 100 ° C. of the toner is η100 and the melt viscosity at 120 ° C. is η120, η100 and η120 preferably satisfy the following formula. This makes it easy to secure the rate of change of Vt and St and the fixability. η100 / η120 = 6 to 10 When η100 / η120 is less than 6, the rate of change of Vt and St tends to increase, which is not preferable. Conversely, 100 / η1
When 20 exceeds 10, the fixing property tends to deteriorate, which is not preferable.

In the present invention, the melt viscosity η100 at 100 ° C. is 1 × 10 ⁵ to 4 × 10 ⁵ Pa · S, and the melt viscosity η120 at 120 ° C. is 1 × 10 ^{4 to} 5 × 10 ⁴ Pa · S. It is more preferably S. η100 is 1 × 10 ⁵ Pa · S
When it is less than 1, the rate of change of Vt and St tends to increase, which is not preferable. On the contrary, the melt viscosity η100 is 4 × 10 ⁵
If it exceeds Pa · S, the fixing property tends to deteriorate, which is not preferable.

The melt viscosity of the present invention is a value measured by a flow tester CFT-500C (Shimadzu Corporation),
The measurement conditions are: extrusion pressure: 1.9612 MPa, heating rate: 6 ° C./min, die diameter: 1.0 mm, die length:
The measurement is performed under the condition of 1.0 mm. The melt viscosity η is calculated by the following formula. Melt viscosity η = τ / γ = πD ⁴ P / 128LQ where P: extrusion pressure (Pa) Q = X / 10 × A /
t D: Die diameter (mm) L: Die length (mm) t: Measurement time (s) X: Amount of piston movement (mm) with respect to measurement time t A: Cross-sectional area of piston (mm ² )

In the present invention, the THF-insoluble matter is contained in the resin in an amount of 1%.
The content of 0 to 80% is preferable because the rate of change of Vt and St can be reduced. When the THF insoluble content is less than 10%, the rate of change in Vt and St tends to increase,
Not preferable. On the other hand, if the THF insoluble content exceeds 80%, the fixing property tends to deteriorate, which is not preferable.
The present invention also has a resin having an acid value of 10 to 100 mg KOH /
It is preferable to contain 50 mg by weight or more of the polyester resin. Polyester resin is a binder resin suitable for the present invention because it is generally capable of low-temperature fixing while maintaining heat-resistant storage stability as compared with other resins.

The polyester resin used in the present invention is
Obtained by polycondensation of alcohol and carboxylic acid.
Examples of the alcohol used include glycols such as ethylene glycol, diene glycol, triethylene glycol, and propylene glycol, 1,4-bis (hydroxymeth) cyclohexane, and etherified bisphenols such as bisphenol A, and other divalent glycols. Examples thereof include alcohol monomers and trihydric or higher polyhydric alcohol monomers. Examples of the carboxylic acid include divalent organic acid monomers such as maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid and malonic acid, 1,2,4-benzenetricarboxylic acid, 1 2, 5
-Benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-
Dicarboxyl-2-methylenecarboxypropane,
Examples thereof include trivalent or higher polyvalent carboxylic acid monomers such as 1,2,7,8-octanetetracarboxylic acid. The Tg of the polyester resin is preferably 58 to 75 ° C.

The polyester resin has an acid value of 10 to 10.
It is preferable to contain a resin of 100 mgKOH / mg in an amount of 50% by weight or more. If the acid value is less than 10 mgKOH / mg, the chargeability may become unstable, the affinity with other materials may deteriorate, and the dispersibility may deteriorate, which is not preferable. If the acid value exceeds 100 mgKOH / mg, the environmental dependence of the charge amount may increase, which is not preferable.

In the present invention, the resin has an acid value of 10 to 10.
It is preferable to contain 50 wt% or less of a resin incompatible with 0 mg KOH / mg of the polyester resin. It is preferable to use an incompatible resin having a characteristic different from that of the polyester resin. By selecting each other's Tg, molecular weight, acid value, etc., it becomes incompatible with the polyester resin, the filler effect appears, and different characteristics are exhibited, ensuring Vt, St change rate, fixing property, etc. Will be easier. When they are not incompatible with each other, the average characteristics of the resins are exhibited, and the effect of improving Vt, St change rate, and fixability is reduced.

Further, in the present invention, it is preferable to contain fine magnetic particles as a toner component. Magnetic fine particles such as iron oxide, magnetite, and ferrite can be added as the magnetic fine particles. It is preferable that the rate of change of Vt and St tends to be small due to the filler effect by adding the magnetic fine particles. The amount of magnetic fine particles added is 5 to 60% by weight,
It is preferably 10 to 40% by weight. Further, in the present invention, it is preferable to contain an inorganic fine powder as a toner component. Examples of the inorganic fine powder include silica, aluminum oxides, and titanium oxides. The average particle size can be appropriately selected from the range of 0.001 to 1 μm, preferably 0.005 to 0.1 μm. Inorganic fine powders are also preferable because the rate of change in Vt and St tends to decrease due to the filler effect due to addition of magnetic fine particles. The addition amount is usually 0.1 to 10% by weight, preferably 0.2 to 5% by weight.

Further, in the present invention, it is preferable to contain an organic zirconium compound as a polarity control agent. Aromatic oxycarboxylic acid or a salt thereof as a charge control agent and a zirconium compound obtained from a compound containing zirconium or oxyzirconium react with a highly reactive portion of a resin to form a lightly crosslinked structure, thereby reducing Vt and St. It is preferable because the rate of change tends to be small. The amount of the polarity control agent used is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on the toner resin component.

In particular, the polar control agent has the following structural formula:

[Chemical 1] [Wherein R 1 is quaternary carbon, methine, or methylene,
N, S, O, P may contain a hetero atom, Y represents a cyclic structure linked by a saturated bond or an unsaturated bond, R2,
R3 are independently of each other an alkyl group, an alkenyl group, an alkoxy group, an aryl group which may have a substituent, an aryloxy group, an aralkyl group or an aralkyloxy group,
Halogen group, hydrogen, hydroxyl group, optionally substituted amino group, carboxyl group, carbonyl group, nitro group, nitroso group, sulfonyl group, cyano group, R4 represents hydrogen or an alkyl group, and 1 represents 0 Or an integer from 3 to 12, m
Is an integer from 1 to 20, n is an integer from 0 to 20, o is an integer from 0 to 4, p is an integer from 0 to 4, q is an integer from 0 to 3, r is an integer from 1 to 20, and s is 0. To an integer of 20] is preferable.

In the present invention, it is preferable that the inorganic fine powder is contained in an amount of 1.0% by weight or more as an external additive. Specific examples of the inorganic fine powder include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, silica sand, clay, mica, wollastonite, Examples thereof include diatomaceous earth, chromium oxide, cerium oxide, pengal, antimony trioxide, magnesium oxide, zirconium oxide, parium sulfate, barium carbonate, calcium carbonate, silicon carbide and silicon nitride.

The primary particle diameter of this inorganic fine powder is from 5 mμ to
It is preferably 2 μm, particularly 5 mμ to 500 mμ
Is preferred. The specific surface area by the BET method is preferably 20 to 500 m ² / g. The use ratio of this inorganic fine powder is preferably 1.0% by weight or more of the toner. If less than 1.0% by weight, Vt,
This is not preferable because the rate of change in St tends to increase.
Such an inorganic fine powder can be surface-treated to increase its hydrophobicity and prevent deterioration of flow characteristics and charging characteristics even under high humidity. For example, a silane coupling agent, a silylating agent, a silane coupling agent having a fluorinated alkyl group, an organic titanate-based coupling agent, an aluminum-based coupling agent and the like can be mentioned as preferable surface treatment agents.

In the present invention, the weight average particle diameter is 4 to 10 μm.
m toner is preferably used. When the weight average particle diameter of the toner is less than 4 μm, there is no problem in the rate of change of Vt and St, but even if pressure is applied between the fixing rollers, it is difficult to apply pressure to the toner particles, so the toner image should be fixed uniformly. Becomes difficult. Particularly in the case of a fixing device having a low surface pressure, this tendency becomes remarkable, which is not preferable. On the other hand, when it exceeds 10 μm, there is no particular problem with the fixing property, but the resolution is poor, which is not preferable. The toner particle size is measured by Coulter
MULTISIZER IIe was used. The aperture diameter is 100 μm.

For the toner of the present invention, resins other than polyester resin can be used. As the other resin used in the present invention, a conventionally known resin is used. For example,
Styrene, poly-α-stillyl styrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer,
Styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-
Styrene type such as maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl acrylate copolymer, styrene-acrylonitrile-acrylic acid ester copolymer Resin (styrene or styrene-substituted homopolymer or copolymer), epoxy resin, vinyl chloride resin, rosin-modified maleic acid resin, phenol resin,
Examples thereof include polyethylene resin, polypropylene resin, petroleum resin, polyurethane resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, polyvinyl butyrate resin, and the like. These resins may be used in combination with polyester resin and epoxy resin. Good, but can be used alone. Also, two or more kinds may be used in combination. The method for producing these resins is not particularly limited, and any of bulk polymerization, solution polymerization, emulsion polymerization and suspension polymerization can be used.

In the present invention, a wax component may be used in order to improve releasability at the time of fixing. For example, polyolefin wax such as polypropylene wax and polyethylene wax, and natural wax such as candelilla wax, rice wax and carnauba wax can be used. The amount of the wax component added is preferably 0.5 to 10 parts by weight. Other than the organozirconium compound as the polarity control agent, for example, nigrosine dyes, quaternary ammonium salts, amino group-containing polymers, metal-containing azo dyes, salicylic acid complex compounds, phenol compounds and the like can be mentioned.

As the colorant used in the present invention, all of the pigments and dyes conventionally used as colorants for toner can be applied. Specifically, carbon black,
Lamp black, iron black, ultramarine, nigrosine dye, aniline blue, chalco oil blue, oil black, azo oil black and the like are not particularly limited. The amount of colorant used is 1 to 10 parts by weight, preferably 3 to 7 parts by weight.

The method for producing the toner of the present invention may be a conventionally known method, in which a binder resin, a colorant, a wax component, and in some cases, a charge control agent and the like are mixed using a mixer or the like, and the resulting mixture is heated on a hot roll. After kneading with a kneader such as an extruder, the mixture is cooled and solidified, and then crushed by crushing with a jet mill or the like, and then classified. Further, for example, when the toner of the present invention is used as a two-component dry toner, as a carrier to be mixed and used, glass, iron, ferrite, nickel, zircon, silica or the like as a main component, particle diameter 30 to 1000 μm Powder, or styrene-acrylic resin, silicon resin with the powder as a core material,
It can be appropriately selected and used from those coated with a polyamide resin, a polyvinylidene fluoride resin, or the like.

[0031]

Examples Example 1 (Toner formulation) Styrene-butyl acrylate copolymer 55 parts by weight (weight average molecular weight 320,000) Styrene-n-butyl methacrylate copolymer 30 parts by weight (weight average molecular weight 35000) Carbon black (Mitsubishi Kasei # 44) 10 parts by weight Charge control agent (Spilon Black TR-H: Hodogaya Chemical Co., Ltd.) 2 parts by weight Low molecular weight polypropylene 3 parts by weight At a low temperature kneading with a twin-screw extruder at a temperature of 50 ° C., pulverization and classification. After adjusting the weight average particle size to 11 μm, a fine silica powder (R-97
2: Clariant Japan) 0.3 parts by weight are mixed,
A toner of the present invention was obtained. This toner, average particle size 80 μm
A carrier having a toner concentration of 4.0 parts by weight is prepared from the spherical ferrite particles of No. 1 with a silicone resin-coated carrier.

Evaluation Method of Fixability The fixing device of the digital copying machine imagio MF6550 (manufactured by Ricoh Co., Ltd.) is removed, and an unfixed toner image is formed on the transfer paper, and the unfixed toner image is shown in FIG. It was fixed with the fixing device of the invention. A fixing tape (manufactured by 3M Co.) is attached to the fixed image, a certain pressure is applied, and then the image is slowly peeled off. The image density before and after that is measured by a Macbeth densitometer, and the fixing ratio is calculated by the following formula. By gradually lowering the surface temperature of the fixing roller, the fixing ratio shown by the following formula becomes 80
The fixing temperature is defined as the temperature at which the temperature becomes less than or equal to%. Fixing rate (%) = image density on tape / image density × 100 Evaluation of granularity

Using the fixing device having the structure shown in FIG.
After fixing at the fixing temperature of + 10 ° C., the gray scale (halftone portion) of the obtained image is read at 1000 dpi with a GenaScan 5000 scanner manufactured by Dainippon Screen Co., Ltd. to obtain image data. The image data was converted into a density distribution and the granularity was evaluated. [Here, when explaining the granularity, the halftone density should be uniform, but if microscopic density unevenness occurs, it gives a rough impression when viewed with the naked eye, and the image quality of the appearance is increased. Lower. Here, the physical evaluation value of roughness is the granularity (GS). First, noise is the Wiener spectrum (Wiener spectrum)
Spectrum: WS). G (u) = ∫g (x) exp (-2πiux) dx Equation 1 WS (u) = F (u) 2 Equation 2 u is the spatial frequency Is. The granularity GS is a value obtained by integrating the product of WS and a visual frequency characteristic (Visual Transfer Function: VTF), and is expressed by the following equation. GS = exp (-1.8 <D>) ∫WS (u) (1/2) VTF (u) du Formula 3 Exp (-1.8 <D>) is the difference between the density and the brightness perceived by humans. Is a coefficient for correcting. <D> represents the average value of the density. Granularity is highly correlated with subjective evaluation of image smoothness and roughness. The smaller the granularity value, the smoother the image quality becomes, and conversely, the larger the granularity value, the rougher and poorer the image quality becomes. It is generally known that the granularity is preferably 0.7 or less, and when the granularity exceeds 1.0, an image with a bad impression is not obtained, which is not preferable. ]

Comparative Example 1 Using the developer used in Example 1, a digital copying machine ima was used.
By removing the fixing device of Gio MF6550 (manufactured by Ricoh Co., Ltd.), an unfixed toner image is formed on the transfer paper, and the unfixed toner image is heated by the fixing device of the present invention shown in FIG. Was fixed in the cut state. A fixing tape (manufactured by 3M Co.) is attached to the fixed image, a certain pressure is applied, and then the image is slowly peeled off. The image density before and after that is measured by a Macbeth densitometer, and the fixing ratio is calculated by the following formula. The surface temperature of the fixing roller is lowered stepwise, and the temperature at which the fixing ratio shown by the following formula becomes 80% or less is the fixing temperature. Fixing rate (%) = Adhesion image density on tape / Image density × 100 Evaluation of granularity Fixing is performed at the above fixing temperature + 10 ° C. in a state where heating before fixing is cut off in the fixing device having the configuration shown in FIG. Next, the grayscale (halftone part) of the obtained image is read at 1000 dpi with a GenaScan 5000 scanner manufactured by Dainippon Screen Co., Ltd. to obtain image data. The image data was converted into a density distribution and the granularity was evaluated.

Example 2 (Toner Formulation) Styrene-butyl acrylate copolymer 75 parts by weight (weight average molecular weight 253000) Styrene-n-butyl methacrylate copolymer 10 parts by weight (weight average molecular weight 23000) Carbon black (Mitsubishi Kasei # 44 ) 10 parts by weight Charge control agent (Spilon Black TR-H: Hodogaya Chemical Co., Ltd.) 2 parts by weight Low molecular weight polypropylene 3 parts by weight The above formulation was used to knead at low temperature at 40 ° C. using a twin-screw extruder, pulverize and classify. After adjusting the average particle size to 10.5 μm, a Henschel mixer was used to obtain fine silica powder (R-97
2: Clariant Japan) 0.4 parts by weight are mixed,
A toner of the present invention was obtained. This toner, average particle size 80 μm
A carrier having a toner concentration of 4.0 parts by weight is prepared with the carrier obtained by coating the spherical ferrite particles of No. 1 with a silicone resin.
The method of Example 1 was used to evaluate the fixability and the granularity.

Comparative Example 2 Using the developer used in Example 2, a digital copying machine ima was used.
The fixing device of Gio MF6550 (manufactured by Ricoh Co., Ltd.) is removed to form an unfixed toner image on the transfer paper, and the unfixed toner image is heated by the fixing device of the present invention shown in FIG. Was fixed in the cut state. The method of Comparative Example 1 was used to evaluate the fixability and the granularity.

[0037]   Example 3 (Toner prescription) Styrene-butyl acrylate copolymer 50 parts by weight (Weight average molecular weight 350,000) Styrene-n-butyl methacrylate copolymer 33 parts by weight (Weight average molecular weight 39000) Carbon black (Mitsubishi Kasei # 44) 10 parts by weight Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 2 parts by weight Carnauba wax 5 parts by weight

Using the above-mentioned prescription, heating 2 rolls was used.
Knead at low temperature at 0 ℃, crush, classify, weight average particle size 10.5
After the particle size was adjusted to μm, 0.4 part by weight of silica fine powder (R-972: manufactured by Clariant Japan) was mixed using a Henschel mixer to obtain a toner of the present invention. The toner and a carrier in which spherical ferrite particles having an average particle diameter of 80 μm are coated with a silicone resin prepare a developer having a toner concentration of 4.0 parts by weight. The fixability and the granularity were evaluated in the same manner as in Example 1. The evaluation results are listed at the end.

Comparative Example 3 Using the developer used in Example 3, a digital copying machine ima was used.
The fixing device of Gio MF6550 (manufactured by Ricoh Co., Ltd.) is removed to form an unfixed toner image on the transfer paper, and the unfixed toner image is heated by the fixing device of the present invention shown in FIG. Was fixed in the cut state. The method of Comparative Example 1 was used to evaluate the fixability and the granularity.

[0040]   Example 4 (Toner prescription) Styrene-butyl acrylate copolymer 53 parts by weight (Weight average molecular weight 280000) Styrene-2 ethylhexyl acrylate-n-butyl methacrylate copolymer (Weight average molecular weight 31,000) 30 parts by weight Carbon black (Mitsubishi Kasei # 44) 10 parts by weight Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 2 parts by weight Carnauba wax 5 parts by weight

With the above-mentioned prescription, 10 rolls were formed by using two heating rolls.
Knead at low temperature at 0 ℃, crush, classify, weight average particle size 10.5
After the particle size was adjusted to μm, 0.4 part by weight of silica fine powder (R-972: manufactured by Clariant Japan) was mixed using a Henschel mixer to obtain a toner of the present invention. The toner and a carrier in which spherical ferrite particles having an average particle diameter of 80 μm are coated with a silicone resin prepare a developer having a toner concentration of 4.0 parts by weight. The fixability and the granularity were evaluated in the same manner as in Example 1. The evaluation results are listed at the end.

Comparative Example 4 Using the developer used in Example 4, a digital copying machine ima was used.
Gio MF6550 (manufactured by Ricoh Co., Ltd.) is removed, an unfixed toner image is formed on the transfer paper, and the unfixed toner image is turned on by the fixing device shown in FIG. Fixed in. The method of Comparative Example 1 was used to evaluate the fixability and the granularity.

[0043]   Example 5 (Toner prescription) Polyester resin 68 parts by weight (Weight average molecular weight 182000, THF insoluble content 20%, acid value 3 mg KOH / mg ) Polyester resin 15 parts by weight (Weight average molecular weight 53000, THF insoluble content 0%, acid value 5 mg KOH / mg) Carbon black (Mitsubishi Kasei # 44) 10 parts by weight Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 2 parts by weight Rice wax 5 parts by weight

The above-mentioned formulation was kneaded at low temperature at 60 ° C. using a twin-screw extruder, pulverized and classified to obtain a weight average particle size of 1
After adjusting to 0.5 μm, a Henschel mixer was used to obtain 0.4 of silica fine powder (R-972: manufactured by Clariant Japan).
By mixing parts by weight, a toner of the present invention was obtained. With this toner,
A carrier having a toner concentration of 4.0 parts by weight is prepared using a carrier obtained by coating spherical ferrite particles having an average particle diameter of 80 μm with a silicone resin. The fixability and the granularity were evaluated in the same manner as in Example 1. The evaluation results are listed at the end.

Comparative Example 5 Using the developer used in Example 5, a digital copying machine ima was used.
The fixing device of Gio MF6550 (manufactured by Ricoh Co., Ltd.) was removed, an unfixed toner image was created on the transfer paper, and the unfixed toner image was turned off by the fixing device shown in FIG. It was fixed in the state. In addition, evaluation of fixability,
The method of Comparative Example 1 was used to evaluate the granularity.

[0046]   Example 6 (Toner prescription) Polyester resin 68 parts by weight (Weight average molecular weight 182000, THF insoluble content 5%, acid value 35 mg KOH / mg ) Polyester resin 15 parts by weight (Weight average molecular weight 53000 THF insoluble matter 0%, acid value 5 mg KOH / mg ) Carbon black (Mitsubishi Kasei # 44) 10 parts by weight Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 2 parts by weight Rice wax 5 parts by weight

The above-mentioned formulation was kneaded at low temperature at 60 ° C. using a twin-screw extruder, pulverized and classified to obtain a weight average particle size of 1
After adjusting to 0.5 μm, a Henschel mixer was used to obtain 0.4 of silica fine powder (R-972: manufactured by Clariant Japan).
By mixing parts by weight, a toner of the present invention was obtained. With this toner,
A carrier having a toner concentration of 4.0 parts by weight is prepared using a carrier obtained by coating spherical ferrite particles having an average particle diameter of 80 μm with a silicone resin. The fixability and the granularity were evaluated in the same manner as in Example 1. The evaluation results are listed at the end.

Comparative Example 6 Using the developer used in Example 6, a digital copying machine ima was used.
Gio MF6550 (manufactured by Ricoh Co., Ltd.) is removed, an unfixed toner image is formed on the transfer paper, and the unfixed toner image is turned on by the fixing device shown in FIG. Fixed in. The method of Comparative Example 1 was used to evaluate the fixability and the granularity.

[0049]   Example 7 (Toner prescription) Polyester resin 63 parts by weight (Weight average molecular weight 182000, THF insoluble content 20%) Styrene-butyl acrylate copolymer 20 parts by weight (Weight average molecular weight 71,000 THF insoluble content 25%) Carbon black (Mitsubishi Kasei # 44) 10 parts by weight Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 2 parts by weight Carnauba wax 5 parts by weight

The above-mentioned formulation was kneaded at 120 ° C. using a twin-screw extruder, pulverized and classified to obtain a weight average particle size of 10.
After adjusting the thickness to 5 μm, 0.4 part by weight of silica fine powder (R-972: manufactured by Clariant Japan) was mixed using a Henschel mixer to obtain a toner of the present invention. A developer having a toner concentration of 4.0 parts by weight is prepared using the present toner and a carrier obtained by coating spherical ferrite particles having an average particle diameter of 80 μm with a silicone resin. The fixability and the granularity were evaluated in the same manner as in Example 1. The evaluation results are listed at the end.

Comparative Example 7 Using the developer used in Example 7, a digital copying machine ima was used.
The fixing device of Gio MF6550 (manufactured by Ricoh Co., Ltd.) was removed, an unfixed toner image was created on the transfer paper, and the unfixed toner image was turned off by the fixing device shown in FIG. It was fixed in the state. In addition, evaluation of fixability,
The method of Comparative Example 1 was used to evaluate the granularity.

[0052]   Example 8 (Toner prescription) Styrene-butyl acrylate copolymer 45 parts by weight (Weight average molecular weight 280000) Styrene-2 ethylhexyl acrylate-n-butyl methacrylate copolymer   (Weight average molecular weight 31,000) 15 parts by weight Magnetic material (Toda Kogyo: EPT-1000) 30 parts by weight Carbon black (Mitsubishi Kasei # 44) 5 parts by weight Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 2 parts by weight Carnauba wax 3 parts by weight

The above formulation was kneaded in a twin-screw extruder at 130 ° C., pulverized and classified to obtain a weight average particle size of 10.
After adjusting the thickness to 5 μm, 0.4 part by weight of silica fine powder (R-972: manufactured by Clariant Japan) was mixed using a Henschel mixer to obtain a toner of the present invention. A developer having a toner concentration of 4.0 parts by weight is prepared using the present toner and a carrier obtained by coating spherical ferrite particles having an average particle diameter of 80 μm with a silicone resin. The fixability and the granularity were evaluated in the same manner as in Example 1. The evaluation results are listed at the end.

Comparative Example 8 Using the developer used in Example 8, a digital copying machine ima was used.
The fixing device of Gio MF6550 (manufactured by Ricoh Co., Ltd.) was removed, an unfixed toner image was created on the transfer paper, and the unfixed toner image was turned off by the fixing device shown in FIG. It was fixed in the state. In addition, evaluation of fixability,
The method of Comparative Example 1 was used to evaluate the granularity.

[0055]   Example 9 (Toner prescription) Polyester resin 60 parts by weight (Weight average molecular weight 75000 THF insoluble content 40%) Styrene-butyl acrylate copolymer 20 parts by weight (Weight average molecular weight 71,000 THF insoluble content 25%) Carbon black (Mitsubishi Kasei # 44) 10 parts by weight Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 2 parts by weight Carnauba wax 5 parts by weight

The above formulation was kneaded in a twin-screw extruder at 100 ° C., pulverized and classified to obtain a weight average particle size of 10.
After adjusting the thickness to 5 μm, 0.4 part by weight of silica fine powder (R-972: manufactured by Clariant Japan) was mixed using a Henschel mixer to obtain a toner of the present invention. A developer having a toner concentration of 4.0 parts by weight is prepared using the present toner and a carrier obtained by coating spherical ferrite particles having an average particle diameter of 80 μm with a silicone resin. The fixability and the granularity were evaluated in the same manner as in Example 1. The evaluation results are listed at the end.

Comparative Example 9 Using the developer used in Example 9, a digital copying machine ima was used.
The fixing device of Gio MF6550 (manufactured by Ricoh Co., Ltd.) was removed, an unfixed toner image was created on the transfer paper, and the unfixed toner image was turned off by the fixing device shown in FIG. It was fixed in the state. In addition, evaluation of fixability,
The method of Comparative Example 1 was used to evaluate the granularity.

[0058]   Example 10 (Toner prescription) Polyester resin 83 parts by weight (Weight average molecular weight 182000, THF insoluble content 30%, acid value 55 mg KOH / m g) Carbon black (Mitsubishi Kasei # 44) 10 parts by weight Charge control agent (organozirconium compound) 2 parts by weight Carnauba wax 5 parts by weight

The above-mentioned formulation was kneaded using a twin-screw extruder at 130 ° C., pulverized and classified to obtain a weight average particle size of 10.
After adjusting to 5 μm, 0.4 part by weight of silica fine powder (R-972: manufactured by Clarint Japan) was mixed using a Henschel mixer to obtain a toner of the present invention. A developer having a toner concentration of 4.0 parts by weight is prepared using the present toner and a carrier obtained by coating spherical ferrite particles having an average particle diameter of 80 μm with a silicone resin. The fixability and the granularity were evaluated in the same manner as in Example 1. The evaluation results are listed at the end.

Comparative Example 10 Using the developer used in Example 10, a digital copying machine im was used.
The fixing device of the agio MF6550 (manufactured by Ricoh Co., Ltd.) was removed, and an unfixed toner image was created on the transfer paper. The unfixed toner image was turned off by the fixing device shown in FIG. It was fixed in the state. The method of Comparative Example 1 was used to evaluate the fixability and the granularity.

[0061]   Example 11 (Toner prescription) Polyester resin 83 parts by weight (Weight average molecular weight 182000, THF insoluble content 30%, acid value 55 mg KOH / m g) Carbon black (Mitsubishi Kasei # 44) 10 parts by weight Charge control agent (organozirconium compound) 2 parts by weight Carnauba wax 5 parts by weight

The above formulation was kneaded using a twin-screw extruder at 130 ° C., pulverized and classified to obtain a weight average particle size of 10.
After adjusting the thickness to 5 μm, 1.5 parts by weight of silica fine powder (R-972: manufactured by Clariant Japan) was mixed using a Henschel mixer to obtain a toner of the present invention. A developer having a toner concentration of 4.0 parts by weight is prepared using the present toner and a carrier obtained by coating spherical ferrite particles having an average particle diameter of 80 μm with a silicone resin. The fixability and the granularity were evaluated in the same manner as in Example 1. The evaluation results are listed at the end.

Comparative Example 11 Using the developer used in Example 11, a digital copying machine im was used.
The fixing device of the agio MF6550 (manufactured by Ricoh Co., Ltd.) was removed, and an unfixed toner image was created on the transfer paper. The unfixed toner image was turned off by the fixing device shown in FIG. It was fixed in the state. The method of Comparative Example 1 was used to evaluate the fixability and the granularity.

[0064]   Example 12 (Toner prescription) Polyester resin 63 parts by weight (Weight average molecular weight 182000, THF insoluble content 20%) Styrene-butyl acrylate copolymer 20 parts by weight (Weight average molecular weight 71,000 THF insoluble content 25%) Carbon black (Mitsubishi Kasei # 44) 10 parts by weight Charge control agent (Spiron Black TR-H: Hodogaya Chemical) 2 parts by weight Carnauba wax 5 parts by weight

The above-mentioned formulation was kneaded in a twin-screw extruder at 120 ° C., pulverized and classified to obtain a weight average particle diameter of 6.5.
After the particle size was adjusted to μm, 1.5 parts by weight of silica fine powder (R-972: manufactured by Clariant Japan) was mixed using a Henschel mixer to obtain a toner of the present invention. A developer having a toner concentration of 5.0 parts by weight is prepared using the present toner and a carrier obtained by coating spherical ferrite particles having an average particle diameter of 50 μm with a silicone resin. The fixability and the granularity were evaluated in the same manner as in Example 1. The evaluation results are listed at the end.

Comparative Example 12 Using the developer used in Example 12, a digital copying machine im was used.
The fixing device of the agio MF6550 (manufactured by Ricoh Co., Ltd.) was removed, and an unfixed toner image was created on the transfer paper. The unfixed toner image was turned off by the fixing device shown in FIG. It was fixed in the state. The method of Comparative Example 1 was used to evaluate the fixability and the granularity. The measurement results of the image fixability (fixing temperature C), granularity, toner volume change rate (Vt) and toner area change rate (St) of each of the examples and comparative examples are displayed.

[0067]

[Table 1] As is clear from Table 1, in the present invention, the volume of the toner image (dot) when the toner image (dot) preheated as the toner is heated and fixed by heating the toner image before fixing. By using a toner that can set the change rate and the area change rate to predetermined values, respectively, the fixing temperature can be lowered and the granularity is lowered as compared with the comparative example. This is because the toner image is in a semi-melted state due to the heating before fixing, so the surface temperature of the heating roller can be lowered by the amount that there is room for fixing, so the spread of the toner image caused by excessive heating of the toner layer is prevented. Therefore, it is possible to improve the granularity. 4 shows the melt viscosity of the toner of the example.

[0068]

[Table 2]

[0069]

As described above, according to the image forming method of the present invention, by heating the toner image before fixing, and the volume of the toner image (dots) preheated as the toner before and after fixing. Since the toner image is heated to a semi-melted state before fixing by the heat roller method by using a toner that can change the rate and area ratio to a predetermined value, the toner and the recording medium are fixed by the heat roller fixing. The time until the interface temperature is heated to the toner softening point or higher is shortened.
Therefore, sufficient fixing property can be secured even if the surface temperature of the fixing roller is low, and a high-quality fixed image can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a fixing device used in an image forming method of the present invention.

[Explanation of symbols]

1 fixing roller 6 pressure roller 9 Electromagnetic wave irradiation means 12 recording media 13 Toner image

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 9/097 G03G 9/08 344 321 (72) Inventor Tai Furuichi 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 Ricoh Co., Ltd. (72) Inventor Toshiaki Higaya 1-3-6 Nakamagome, Ota-ku, Tokyo Mitsuo Aoki (3) No. 3 Nakamagome, Ota-ku, Tokyo In stock company Ricoh (72) Inventor Kumi Hasegawa 1-3-6 Nakamagome, Ota-ku, Tokyo F-term inside Ricoh Company (reference) 2H005 AA01 AA02 AA06 AA08 CA08 CA25 CB13 DA01 EA03 EA10 2H033 BA01 BA25 BA58 BB03 BB05 BB06 BB29 BB30 BC02

Claims (11)

[Claims] 1. A latent image forming step of forming a latent image on a latent image carrier, a developing step of developing the latent image with a developer, a transfer step of transferring a toner image onto a recording medium, and a recording medium. An image forming method including a fixing step of fixing an unfixed toner image on a recording medium, comprising: a fixing rotating body which is rotatable as a fixing device in the fixing step; and a rotatable pressure rotating body, A recording medium on which an unfixed toner image has been transferred is nipped and conveyed in a nip formed between the fixing rotary member and the pressure rotating member, and at least one of the fixing rotary member and the pressure rotating member is conveyed. In an image forming method using a fixing device for thermally fixing the unfixed toner image onto a recording medium by heating by a heat generating means provided inside, a surface layer of either or both of the fixing rotator and the pressure rotator is formed. Has an elastic layer and records before fixing The toner image on the body is provided with a means for heating the toner image in a non-contact manner by irradiating the toner image with an electromagnetic wave, and the volume change rate of the toner image on the recording medium before and after fixing as a developer Vt defined below. Is 30% or less and an area change rate St defined below is 20% or less. Vt = {(toner volume before passing through heating part)-(toner volume after passing through heating part)} / toner volume before passing through heating part × 100 St = {(toner area after passing through heating part) − (passing through heating part) Area of toner before)} / area of toner before passing through heating unit x 100 2. When the melt viscosity of the toner at 100 ° C. is η100 and the melt viscosity at 120 ° C. is η120, η
The image forming method according to claim 1, wherein 100 and η 120 satisfy the following formula. 3. The image forming method according to claim 1, wherein the toner contains 10 to 80% of THF insoluble matter in the resin. 4. The toner as a resin has an acid value of 10 to 100.
The image forming method according to any one of claims 1 to 3, which contains 50% by weight or more of mgKOH / mg of a polyester resin. 5. The toner has a resin having an acid value of 10 to 100.
Resin that is incompatible with mgKOH / mg polyester resin 5
The image forming method according to claim 1, wherein the content is 0% by weight or less. 6. The image forming method according to claim 1, wherein the toner contains magnetic fine particles. 7. The image forming method according to claim 1, wherein the toner contains an inorganic fine powder. 8. The toner according to claim 1, wherein the toner contains an organic zirconium compound as a polarity control agent.
The image forming method described. 9. The toner according to claim 1, wherein the toner contains 1.0% by weight or more of an inorganic fine powder as an external additive.
The image forming method described in 8 above. 10. The toner has a weight average particle diameter of 4 to 10 μm.
The image forming method according to claim 1, wherein 11. A toner characterized in that η100 and η120 satisfy the following equation, where η100 is the melt viscosity at 100 ° C. and η120 is the melt viscosity at 120 ° C. η100 / η120 = 6-10