JP6003702B2 - Laser fixing method, laser fixing device, and image forming apparatus - Google Patents

Description

  The present invention relates to a laser fixing method, a laser fixing device, and an image forming apparatus.

  Patent Document 1 discloses an image forming fine powder that contains a cyanine dye and is fixed by flash light at the time of fixing to a recording paper.

  Patent Document 2 discloses a polymerized toner containing at least a resin component, a colorant, and an infrared absorber, which uses particles obtained by agglomeration treatment of resin particles obtained by polymerization directly or further. The absorbent is finely dispersed and then added to the polymerization system or agglomeration system, and the infrared absorbent has a maximum absorption wavelength at a wavelength of 750 to 1100 nm, and the added amount of the infrared absorbent Discloses a polymer toner for flash fixing electrophotography, characterized in that is in the range of 0.01 to 3% by weight of the total toner weight.

  Patent Document 3 discloses an image forming method including a step of fixing an image on a fixing medium using a toner containing at least a wax and a binder resin having compatibility with the wax. Disclosed is an image forming method comprising a step of heating (melting) and fixing a toner by a non-contact heating fixing means to a fixing toner adhering (transfer) portion of the fixing medium at the time of fixing to a fixing medium. Has been. Further, it is disclosed that when laser heating fixing or flash heating fixing is used in this image forming method, a photodecolorable infrared absorber may be used (paragraph 0016).

JP 58-102247 A JP-A-11-125930 JP 2007-248819 A

  An object of the present invention is to provide a laser fixing method, a laser fixing device, and an image forming apparatus in which toner is fixed without being excessively heated.

The invention according to claim 1 in order to achieve the above object, using a toner that light absorption ratio is reduced with respect to the laser light of a specific wavelength after and toner melt becomes infrared absorber is aggregated dispersed in a binder resin This is a laser fixing method in which a toner image is fixed on the transfer target body by irradiating the transfer target body onto which the formed toner image has been transferred with laser light of the specific wavelength.

  The invention according to claim 2 is the laser fixing method according to claim 1, wherein the volume average particle diameter of the aggregate of the infrared absorbent is in the range of 1 nm to 1000 nm.

  A third aspect of the present invention is the laser fixing method according to the first or second aspect, wherein the specific wavelength is in a range of a wavelength of 700 nm to 1000 nm.

According to a fourth aspect of the present invention, an infrared absorber is agglomerated and dispersed in a binder resin, and is formed using a toner having a reduced light absorption rate for laser light having a specific wavelength after the toner is melted. A laser fixing device for fixing the toner image transferred to the transfer target body, the laser fixing apparatus including irradiation means for irradiating the transfer target body with the laser beam having the specific wavelength; A laser fixing device for fixing a toner image on the transfer medium;

According to a fifth aspect of the present invention, there is provided a latent image forming means for forming an electrostatic latent image by exposing the surface of a charged image carrier, an infrared absorber aggregated and dispersed in a binder resin, and a toner. Developing means for developing the electrostatic latent image with a developer containing toner whose light absorption rate for laser light having a specific wavelength decreases after melting, and forming a toner image on the image carrier; An image forming apparatus comprising: a transfer unit that transfers to a body; and a fixing unit that irradiates the transfer target with a laser beam having a specific wavelength to fix the toner image on the transfer target.

  According to the first, fourth, and fifth aspects of the invention, the toner is fixed without being heated excessively.

  According to the second aspect of the present invention, the change in the light absorptance is large and the setting of the specific wavelength is easy as compared with the case where the configuration of the present invention is not provided.

  According to the invention which concerns on Claim 3, the choice of an infrared absorber spreads compared with the case where the structure of this invention is not provided.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 4A is a schematic diagram illustrating a state of toner before melting. (B) is a schematic diagram showing the state of the toner after melting. It is a graph which shows the absorption spectrum in the dispersion state from which an infrared absorber differs. It is a graph which shows the reflection spectrum before the fixing of the conventional laser fixing toner. 6 is a graph showing reflection spectra before and after fixing of a toner for laser fixing according to an embodiment of the present invention.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

<Image forming apparatus>
First, the image forming apparatus will be described.
FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, the image forming apparatus 10 includes a paper supply unit 12, an image forming unit 14, an image fixing unit 16, and a paper discharge unit 18. The image fixing unit 16 fixes the toner image by a laser fixing method according to the present embodiment described later. The configuration of the image forming apparatus 10 is merely an example, and is not limited to the illustrated configuration as long as it is suitable for performing the laser fixing method according to the present embodiment. The paper is an example of a transfer target.

  The paper supply unit 12, the image forming unit 14, the image fixing unit 16, and the paper discharge unit 18 are arranged in the described order along the paper conveyance path 20 illustrated by a dotted line. Each of the paper supply unit 12, the image forming unit 14, the image fixing unit 16, and the paper discharge unit 18 is controlled by a control unit (not shown). In addition, the image forming apparatus 10 includes a plurality of transport rollers 26. The plurality of transport rollers 26 are arranged along the paper transport path 20. The plurality of transport rollers 26 transport the paper S according to the image forming operation.

  The paper supply unit 12 includes a paper storage unit 22 that stores the paper S, a supply mechanism that supplies the paper S from the paper storage unit 22 to the image forming unit 14, and the like. The supply mechanism includes a take-out roller 24 that takes out the paper S from the paper storage unit 22, a transport roller 26, and the like. Depending on the type and size of the paper S, a plurality of paper storage units 22 may be provided. The paper supply unit 12 supplies the paper S to the image forming unit 14 with the above configuration.

  The image forming unit 14 forms an image on the paper S by electrophotography. The image forming unit 14 includes at least one image forming unit. The image forming unit includes a photosensitive drum 30, a charging device 32, an exposure device 34, a developing device 36, a transfer device 38, a cleaning device 40, and the like. The photosensitive drum 30 is configured to rotate in the direction of arrow A.

  Specifically, the image forming unit 14 forms an image according to the following procedure. The photosensitive drum 30 is charged by the charging device 32. The exposure device 34 exposes the charged photosensitive drum 30 with light corresponding to the image. As a result, an electrostatic latent image corresponding to the image is formed on the photosensitive drum 30. The developing device 36 develops the electrostatic latent image formed on the photosensitive drum 30 with toner. The transfer device 38 transfers the toner image formed on the photosensitive drum 30 onto the paper S. The toner remaining on the photosensitive drum 30 without being transferred is cleaned by the cleaning device 40.

  The image fixing unit 16 is configured as an optical fixing unit including a laser light source 42 that emits laser light in the infrared region. In the present embodiment, the electrophotographic developer contains an infrared absorbing toner. The image fixing unit 16 irradiates the toner image transferred onto the sheet S with laser light in the infrared region emitted from the laser light source 42. Infrared absorbing toner absorbs laser light in the infrared region and generates heat. As a result, the toner image on the paper S is heated and melted and fixed on the surface of the paper S. The paper S on which the toner image is fixed is discharged to the paper discharge unit 18.

As the laser light source 42, an infrared laser having high directivity in the infrared region, such as a semiconductor laser, a dye laser, a titanium sapphire laser, or an optical parametric oscillator (OPO) is used. The light emission energy of the laser light source 42 may be in the range of 0.1 J / cm ² or more and 7.0 J / cm ² or less. Further 0.3 J / cm ² or more 6.0 J / cm ² may be less.

<Electrophotographic developer>
Next, the electrophotographic developer will be described.
The electrophotographic developer used in the laser fixing method according to the present embodiment includes the following infrared absorbing toner. The electrophotographic developer may be a one-component developer not containing a carrier, or a two-component developer containing a toner and a carrier. Examples of the carrier include a resin-coated carrier having a resin coating layer on the surface of the core material. As the core material, known magnetite, ferrite, and iron powder are used. A silicone resin or the like is used as a carrier coating agent.

(Infrared absorbing toner)
The infrared absorbing toner is a toner containing an “infrared absorber” having the strongest light absorption peak in the infrared region. The infrared absorbing toner contains a binder resin, a colorant, various additives and the like in addition to the infrared absorber. Each component will be described later. As described above, in the present embodiment, the infrared absorbing toner absorbs the laser beam in the infrared region and melts and is fixed on the surface of the transfer target. Here, the “infrared region” laser light is laser light having an oscillation wavelength of 700 nm to 1000 nm.

  The infrared absorbing toner according to the present embodiment is configured such that the infrared absorbent is agglomerated and dispersed, and the light absorptance with respect to laser light having a specific wavelength for light fixing is lowered after the toner is melted. In other words, the specific wavelength for light fixing is selected from the infrared region so that the light absorption rate with respect to the laser light decreases after the toner is melted during light fixing.

  Here, the principle that the light absorption rate decreases will be described. FIG. 2A is a schematic diagram showing the state of the toner before melting. FIG. 2B is a schematic diagram showing the state of the toner after melting. As shown in FIG. 2A, in the infrared absorbing toner 50 according to the present embodiment, the infrared absorbent (molecules) 52 is dispersed in the binder resin 56 in the state of an aggregate 54 (see FIG. 2A). Aggregation dispersion). As shown in FIG. 2B, the infrared absorbent 52 is dissolved in the binder resin 56 when the toner is melted. That is, the infrared absorbent 52 is in a state of being molecularly dispersed in the binder resin 56 from the state of the aggregate 54 in the molten toner 50A (molecular dispersion). In short, “aggregation dispersion” is a dispersion state in which molecules are not dispersed.

  The absorption spectrum of the toner changes according to the dispersion state of the infrared absorbent. The absorption spectrum of the toner in which the infrared absorber is aggregated and dispersed has a broad absorption peak due to the influence of intermolecular interaction. For example, the wavelength of the light absorption peak having the strongest absorption spectrum is defined as “specific wavelength”. On the other hand, the absorption spectrum of the toner in which the infrared absorbent is molecularly dispersed has a sharp absorption peak. For this reason, when the infrared absorbent that has been aggregated and dispersed becomes molecularly dispersed, the wavelength of the strongest light absorption peak is shifted, and the light absorptance with respect to the laser light having a specific wavelength is lowered.

(Specific examples of spectrum changes)
Next, a specific example of spectrum change is shown.
In the measurement of the spectra of FIGS. 3 to 5, a perimidine-based squarylium compound represented by the following formula (1) was used as an infrared absorber.

  FIG. 3 is a graph showing absorption spectra in different dispersion states of the infrared absorber. The horizontal axis represents the wavelength. The unit is nm. The vertical axis represents the gram extinction coefficient. The unit is L / (g · cm). The Gram extinction coefficient is the absorbance when measured at a solution (dispersion) concentration of 1 g / L and an optical path length of 1 cm.

  As shown by a solid line in FIG. 3, the absorption spectrum of a solution in which an infrared absorbent is molecularly dispersed has a sharp maximum absorption peak in the vicinity of a wavelength of 810 nm. On the other hand, as shown by a dotted line in FIG. 3, the absorption spectrum of the suspension obtained by agglomerating and dispersing (fine particle dispersion) of the infrared absorbent has a broad absorption peak extending over a wavelength range of 750 nm to 880 nm and a wavelength of 870 nm. It has a maximum absorption peak in the vicinity.

  Therefore, if the specific wavelength is 870 nm, the wavelength of the strongest light absorption peak is shifted from 870 nm to 810 nm when the agglomerated and dispersed infrared absorber is molecularly dispersed. Absorption rate will decrease.

  FIG. 4 is a graph showing the reflection spectra before and after fixing of the toner in which the infrared absorbent represented by the above formula (1) is molecularly dispersed. FIG. 5 is a graph showing reflection spectra before and after fixing of the toner according to the embodiment of the present invention in which the infrared absorbent represented by the above formula (1) is aggregated and dispersed. The horizontal axis represents the wavelength. The unit is nm. The vertical axis represents the reflectance. The unit is%. The reflection spectrum was measured with a spectrophotometer U-4100 manufactured by Hitachi, Ltd.

A toner in which an infrared absorbent was molecularly dispersed was placed on a transfer medium and fixed by irradiating a laser beam having a wavelength of 810 nm. The irradiation time was 0.5 ms and the irradiation energy was 2.0 J / cm ² . As shown in FIG. 4, in the toner in which the infrared absorbent is molecularly dispersed, the reflection spectrum after fixing indicated by a solid line and the reflection spectrum before fixing indicated by a dotted line have substantially the same shape. The light absorptance with respect to the laser beam having a specific wavelength of 810 nm hardly changes before and after fixing. During fixing, the toner continues to absorb laser light having a wavelength of 810 nm with substantially the same light absorption rate.

A toner in which an infrared absorbent was agglomerated and dispersed was placed on a transfer medium, and fixed by irradiating a laser beam having a wavelength of 870 nm. The irradiation time was 0.5 ms and the irradiation energy was 2.0 J / cm ² . As shown in FIG. 5, in the toner in which the infrared absorbent is agglomerated and dispersed, the reflection spectrum after fixing indicated by a solid line and the reflection spectrum before fixing indicated by a dotted line are significantly different in shape in the infrared region. That is, the light absorptance with respect to the laser beam having a specific wavelength of 870 nm is greatly reduced after fixing. Note that the light absorptivity decreases as the reflectance increases. By fixing, the light absorption rate of the toner with respect to the laser beam having a wavelength of 870 nm is greatly reduced.

(Overheating suppression principle)
Next, the principle that excessive heating is suppressed will be described.
In laser fixing, a laser beam is uniformly applied to a toner image on a transfer target. However, the light absorption rate varies depending on the content of the toner image (the amount of toner per unit area), and the time required to absorb the energy required for fixing varies. A toner image having a higher light absorption rate absorbs energy necessary for fixing in a shorter time. A toner image having a larger amount of toner per unit area has a higher light absorption rate.

  For example, a multi-color toner image formed so that toners of a plurality of colors overlap each other has a higher light absorption rate than a primary color toner image formed with a single-color toner. Further, a solid toner image has a higher light absorption rate than a halftone toner image. On the other hand, a toner image having a small amount of toner per unit area such as isolated toner has a low light absorption rate, and it takes time to absorb energy necessary for fixing.

  In the case of a normal toner in which an infrared absorber is molecularly dispersed, when toner images having different light absorption rates are mixed, other toners are absorbed until the energy required for fixing is absorbed in the toner image having the lowest light absorption rate. The image is continuously irradiated with laser light. As a result, a part of the toner is excessively heated, and fixing failure such as a rough image surface called a void occurs.

  In the infrared-absorbing toner according to the present embodiment, when the toner is melted, the agglomerated and dispersed infrared absorbent is molecularly dispersed, and the light absorptance with respect to laser light of a specific wavelength is lowered. After the toner is melted, the amount of absorption of the laser beam having a specific wavelength is reduced, and it becomes difficult to be heated.

  Therefore, even when toner images with different light absorption ratios are mixed, the absorption peak of each laser image is absorbed and fixed, and the absorption peak shifts. Therefore, a part of the toner image is prevented from being excessively heated.

-Infrared absorber-
The perimidine-based squarylium compound represented by the above formula (1) has been exemplified as the infrared absorber, but the infrared absorber is not limited to the compound represented by the above formula (1). When the state of aggregation dispersion is changed to the state of molecular dispersion, it is only necessary that the light absorptance with respect to a laser beam having a specific wavelength is lowered, and a known infrared absorber may be used. Examples thereof include infrared absorbers such as squarylium dyes, croconium dyes, naphthalocyanine dyes, cyanine dyes, and aminium dyes.

  The volume average particle diameter of the aggregated and dispersed aggregated particles may be in the range of 1 nm to 1000 nm. Desirably, it may be in the range of 10 nm to 500 nm. More desirably, the range may be 50 nm or more and 200 nm or less. When the volume average particle size of the aggregated particles is too small, the difference from the molecular dispersion state is lost. On the other hand, if the volume average particle size of the aggregated particles is too large, it becomes difficult to produce the toner. The volume average particle size of the agglomerated particles is set so that the light absorptance with respect to the laser light of a specific wavelength is lowered when the state is changed from the agglomerated dispersion state to the molecular dispersion state in consideration of compatibility with the binder resin. Is done.

  The “volume average particle diameter” here is a volume average particle diameter (D50v). The volume average particle diameter (D50v) is measured using an LS Coulter (a particle size measuring device manufactured by Coulter, Inc.). In the particle size distribution of the measured particles, a cumulative distribution is drawn from the smaller diameter side with respect to the divided particle size range (channel), and the particle size that becomes 50% cumulative is the volume average particle size (D50v). It is defined as The volume average particle diameter of the aggregated particles (pigment particles) of the infrared absorbent in the toner is substantially the same as the volume average particle diameter of the pigment particles in the “pigment particle dispersion” used for toner production. Have confirmed. For this reason, the volume average particle diameter of the pigment particles measured for the “pigment particle dispersion” is defined as the volume average particle diameter of the aggregated particles (pigment particles) in the toner.

  The degree of decrease in the light absorptance with respect to the laser light having a specific wavelength is such that the light absorptance in the molecular dispersion state is 5% or more and 80% or less when the light absorption rate in the aggregation dispersion state is 100%. What should I do. It is desirable that the light absorption rate in each state has a large difference, but it may be determined in consideration of the degree of freedom in selecting the wavelength of the light source used for fixing. Further, even if the light absorption rate is not made extremely small as compared with the time of aggregation and dispersion, it is expected that overheating due to heat radiation can be avoided depending on the state of the toner image and the recording medium.

  The addition amount of the infrared absorber may be in the range of 0.05 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner. Desirably, it may be in the range of 5 to 10 parts by mass with respect to 100 parts by mass of the toner.

-Binder resin-
A thermoplastic resin is used as the binder resin. As the thermoplastic resin to be used, a thermoplastic resin made of a naturally-derived polymer and a thermoplastic resin made of a synthetic polymer are used without particular limitation. For example, an epoxy resin, a styrene-acrylic resin, a polyamide resin, a polyester resin, a polyvinyl resin, a polyolefin resin, a polyurethane resin, a polybutadiene resin, or the like may be used alone or in combination. Among these thermoplastic resins, a styrene-acrylic resin or a polyester resin may be used from the viewpoint of dispersibility of the infrared absorber and thermal fixing efficiency.

  The weight average molecular weight of the binder resin may be 1000 or more and 100,000 or less. Desirably, it is good also as 5000 or more and 50000 or less. When the weight average molecular weight is less than 1000, there is a tendency for offset and fusion to occur as compared with the case where the weight average molecular weight is within the above range, and when it exceeds 100,000, the weight average molecular weight is within the above range. Compared to the case, the amount of heat required for fixing increases, and there is a tendency that fixing cannot be performed with laser light.

  The glass transition temperature (Tg) of the binder resin may be 50 ° C. or higher and 150 ° C. or lower. Desirably, it is good also as 55 degreeC or more and 70 degrees C or less. When the glass transition temperature is in the above range, the thermoplastic resin is melted with an appropriate amount of heat and the infrared absorbing toner is fixed, as compared with the case where the glass transition temperature is out of the above range. By using the thermoplastic resin, the toner becomes a toner that can obtain a sufficient fixing effect with a small amount of light irradiation even when the amount of the infrared absorber used is reduced.

-Colorant-
A known colorant is used as the colorant. In order to impart a necessary color, a cyan pigment, a magenta pigment, a yellow pigment, or the like is used.

-Additive-
You may further contain a charge control agent, an offset prevention agent, etc. as needed. As the charge control agent, there are a positive charge agent and a negative charge agent. For the positive charge, there are quaternary ammonium compounds. For negative charging, alkylsalicylic acid metal complexes, resin-type charge control agents containing polar groups, and the like can be used. As the offset preventing agent, low molecular weight polyethylene, low molecular weight polypropylene or the like is used.

  In addition, inorganic powder particles or organic particles may be added to the toner surface as external additives in order to improve fluidity, powder storage stability, triboelectric charge control, transfer performance, and cleaning performance. Examples of the inorganic powder particles include known ones such as silica, alumina, titania, calcium carbonate, magnesium carbonate, calcium phosphate, cerium oxide and the like. Further, a known surface treatment may be applied to the inorganic powder particles according to the purpose. Examples of the organic particles include emulsion polymers and soap-free polymers having vinylidene fluoride, methyl methacrylate, styrene-methyl methacrylate and the like as constituent components.

<Method for producing infrared absorbing toner>
Next, a method for producing the infrared absorbing toner will be described.
Common toner production methods include a wet polymerization method and a kneading pulverization method. The infrared absorbing toner according to the present embodiment may be manufactured by a wet polymerization method or a kneading pulverization method.

  In the wet polymerization method, after a toner component dispersion is mixed, the components are aggregated while heating and stirring under pH adjustment to grow aggregated particles. Next, the grown aggregated particles are further heated to fuse and coalesce the aggregated particles. In the present embodiment, the aggregated particles are fused and united at a temperature not higher than the glass transition temperature of the binder resin so that the infrared absorber is aggregated and dispersed. Thereafter, the suspension is filtered, the obtained particles are washed and dried, and an external additive is attached to the surface of the particles to obtain toner particles.

  In the kneading and pulverization method, the toner constituents are heated and melt-kneaded. In the present embodiment, melt kneading is performed while controlling dissolution of the infrared absorbent in the binder resin so that the infrared absorbent is aggregated and dispersed. Next, the kneaded product is pulverized into particles. Finally, an external additive is attached to the surface of the obtained particles to obtain toner particles.

<Laser fixing conditions>
In the laser fixing method according to the present embodiment, laser light having a specific wavelength for fixing is irradiated to fix the toner image transferred onto the transfer target. Infrared absorbing toner absorbs and melts laser light of a specific wavelength and is fixed on the surface of the transfer target. The specific wavelength is selected from a range of 700 nm to 1000 nm. The irradiation time is selected from a range of 0.1 ms to 1000 ms, for example. Irradiation energy is selected from, for example, 0.1 J / cm ² or more 10J / cm ² or less.

  Hereinafter, the laser fixing method of the present embodiment will be specifically described with reference to examples, but the present invention is not limited to these examples. Further, unless otherwise specified, “part” represents “part by mass” and “%” represents “mass%”.

(Example)
<Synthesis of Binder Resin (1)>
-Bisphenol A ethylene oxide 2-mole adduct: 216 parts-Ethylene glycol: 38 parts-Terephthalic acid: 200 parts-Tetrabutoxy titanate (catalyst): 0.037 parts

  The above components were placed in a heat-dried two-necked flask, and nitrogen gas was introduced into the container and the temperature was raised while stirring in an inert atmosphere, followed by a copolycondensation reaction at 160 ° C. for 7 hours, and then gradually up to 1333 Pa. The temperature was raised to 220 ° C. while reducing the pressure to 4 hours. Once the pressure was returned to normal pressure, 9 parts of trimellitic anhydride was added, the pressure was gradually reduced to 1333 Pa again, and held at 220 ° C. for 1 hour to synthesize a binder resin.

<Preparation of resin particle dispersion (1)>
Binder resin (1): 160 parts Ethyl acetate: 233 parts Sodium hydroxide aqueous solution (0.3N): 0.1 parts

  The above components were placed in a 1000 ml separable flask, heated at 70 ° C., and stirred with a three-one motor (manufactured by Shinto Kagaku Co., Ltd.) to prepare a resin mixture. While further stirring this resin mixture, 373 parts of ion exchange water was gradually added, phase-inverted and emulsified, and the solvent was removed to obtain a resin particle dispersion (1) (solid content concentration: 30%).

<Preparation of release agent dispersion (1)>
・ Polyethylene wax: 50 parts (manufactured by Toyo Petrolite Co., Ltd., polywax 600 (PW600))
・ Anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., Neogen RK): 1.0 part ・ Ion-exchanged water: 200 parts

  The above mixture was mixed and heated to 140 ° C. and dispersed using a homogenizer (Ultra Turrax T50, manufactured by IKA). A release agent dispersion (solid content concentration: 20%) prepared by dispersing release agent particles having a diameter of 0.22 μm was prepared.

<Preparation of pigment particle dispersion>
-Compound (pigment) represented by the formula (1): 100 parts-Anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., Neogen RK): 1.5 parts-Ion-exchanged water: 900 parts

  The above is mixed and dispersed for about 1 hour using an emulsifying and dispersing machine Cavitron (manufactured by Taiheiyo Kiko Co., Ltd., CR1010) to disperse the compound (pigment) particles represented by the formula (1). A liquid (solid content concentration: 10%) was prepared.

<Production of toner>
Resin particle dispersion (1): 450 parts Release agent dispersion (1): 50 parts Pigment particle dispersion: 21.74 parts Nonionic surfactant (IGEPAL CA897): 1.40 parts Ion Exchanged water: 500 parts

  The above material was placed in a 2 L cylindrical stainless steel container, and dispersed and mixed for 10 minutes while applying a shearing force at 4000 rpm with a homogenizer (manufactured by IKA, Ultra Tarrax T50). Next, 1.75 parts of a 10% nitric acid aqueous solution of polyaluminum chloride as a flocculant was gradually added dropwise, and the homogenizer was rotated at 5000 rpm for 15 minutes and mixed to obtain a material dispersion.

  Thereafter, the material dispersion is transferred to a polymerization vessel equipped with a stirrer using a two-paddle stirring blade for forming a laminar flow, and a thermometer, and is started to be heated with a mantle heater at a stirring speed of 810 rpm. The growth of aggregated particles was promoted at 54 ° C. At this time, the pH of the material dispersion was controlled in the range of 2.2 to 3.5 with 0.3N nitric acid or 1N aqueous sodium hydroxide solution. The agglomerated particles were formed by maintaining the above pH range for about 2 hours. At this time, the volume average particle diameter of the aggregated particles measured using Multisizer II (aperture diameter: 50 μm, manufactured by Beckman-Coulter) was 10.6 μm.

  Next, 100 parts of resin particle dispersion (1) was additionally added, and the resin particles of the binder resin were adhered to the surface of the aggregated particles. The temperature was further raised to 56 ° C., and aggregated particles were prepared while confirming the size and form of the particles with an optical microscope and Multisizer II.

  After arranging the aggregated particles, 35 parts of isopropyl alcohol was added. Thereafter, the pH was raised to 8.0 in order to fuse the aggregated particles, and then the temperature was raised to 63 ° C. Further, the pH was lowered to 6.0 while maintaining at 63 ° C., and the heating was stopped after 2 hours, and the mixture was cooled at a temperature lowering rate of 1.0 ° C./min. Thereafter, the mixture was sieved with a 20 μm mesh, washed repeatedly with water, and then dried with a vacuum dryer to obtain toner particles. The obtained toner particles had a volume average particle diameter of 12.5 μm.

Hydrophobic silica (produced by Nippon Aerosil Co., Ltd., RY50) with respect to 100 parts of the toner particles obtained
Was mixed for 30 seconds at 10,000 rpm using a sample mill. Thereafter, the toner was prepared by sieving with a vibrating sieve having an opening of 45 μm. At this time, the volume average particle size of the toner measured using Multisizer II (aperture diameter: 50 μm, manufactured by Beckman-Coulter) was 10.4 μm.

<Creation of carrier>
Ferrite particles (volume average particle size: 35 μm): 100 parts Toluene: 14 parts Perfluoroacrylate copolymer (critical surface tension: 24 dyn / cm): 1.6 parts Carbon black: 0.12 parts (Product) Name: VXC-72, manufactured by Cabot, volume resistivity: 100 Ωcm or less)
Cross-linked melamine resin particles (average particle size: 0.3 μm, toluene insoluble): 0.3 parts

  First, carbon black was diluted in toluene and added to a perfluoroacrylate copolymer and dispersed with a sand mill. Next, the above components other than the ferrite particles were dispersed therein with a stirrer for 10 minutes to prepare a coating layer forming solution. Next, this coating layer forming liquid and ferrite particles were put into a vacuum degassing type kneader and stirred at a temperature of 60 ° C. for 30 minutes, and then the pressure was reduced and toluene was distilled off to form a resin coating layer to obtain a carrier. .

<Production of developer>
The toner: 8 parts and the carrier: 100 parts were put into a 2 liter V blender, stirred for 20 minutes, and then sieved at 212 μm to prepare a developer.

(Comparative example)
After preparing the agglomerated particles, a developer of a comparative example was produced in the same manner as in the example except that toner particles were obtained by the following procedure. After preparing the aggregated particles, the pH was raised to 8.0 in order to fuse the aggregated particles, and then the temperature was raised to 85 ° C. Further, the pH was lowered to 6.0 while maintaining at 85 ° C., the heating was stopped after 2 hours, and the mixture was cooled at a temperature lowering rate of 1.0 ° C./min. Thereafter, the mixture was sieved with a 20 μm mesh, washed repeatedly with water, and then dried with a vacuum dryer to obtain toner particles. The obtained toner particles had a volume average particle diameter of 12.5 μm.

(Spectrum measurement)
A toner image was formed on a paper using toner particles before being mixed with the carrier, and the reflection spectrum of the obtained toner image was measured. As shown in FIG. 4, the toner particles of the comparative example showed no noticeable change in the reflection spectrum before and after fixing. That is, there was no difference in the absorptance with respect to the laser beam having a specific wavelength of 810 nm before and after fixing. On the other hand, as shown in FIG. 5, the reflection spectrum before and after fixing of the toner particles of the example changed significantly. That is, the absorptance with respect to the laser beam having a specific wavelength of 870 nm was lower after fixing than before fixing.

(Evaluation of fixability)
Using developers of Examples and Comparative Examples, the toner amount per unit area (TMA) is 4.5 g ^/ cm 2, the toner image of 9.0 g / cm ^2, 3 kinds of the toner image of the toner image of the isolated toner Was developed on a color / monochrome paper (C paper) by a cake printing method. A toner image of TMA 4.5 g / cm ² is an example of a toner image having a low light absorption rate. A toner image of TMA 9.0 g / cm ² is an example of a toner image having a high light absorption rate. The developed toner image was irradiated with laser light under the conditions shown in Table 1 with different wavelengths of laser light and irradiation energy, and the toner image was fixed on the transfer target.

  Note that cake printing is a simple development method. In cake printing, a potential difference is created between the mesh and the paper, and the toner is developed on the paper by electrostatic force by applying the toner over the mesh. The amount of toner to be developed is grasped by measuring the paper weight increment.

Evaluation of fixability was performed based on the fixability of the toner image and the roughness (void) of the image surface after fixing. Regarding the fixability of the toner image, the fixed image of the toner image was rubbed with flannel cloth, and the residual ratio of the toner image before and after rubbing was counted. The fixability of the toner images was evaluated for three types of toner images: TMA 4.5 g / cm ² , TMA 9.0 g / cm ² toner image, and isolated toner toner image. As for the roughness of the image surface (void), x and voids should be confirmed when voids due to overheating are visually confirmed for TMA 4.5 g / cm ² toner image and TMA 9.0 g / cm ² toner image. ○.

According to the results shown in Table 1, when the developer of the comparative example was used, no condition was found in which the toner image has good fixability and the image surface does not become rough after fixing regardless of the light absorption rate. . On the other hand, when the developer of the example is used, the toner image has good fixability and fixing regardless of the light absorption rate in the range of 1.5 J / cm ² or more and 1.75 J / cm ² or less. A condition was found in which the subsequent image surface roughness did not occur.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Paper supply part 14 Image forming part 16 Image fixing part 18 Paper discharge part 20 Paper conveyance path 22 Paper accommodating part 24 Extraction roller 26 Conveyance roller 30 Photosensitive drum 32 Charging device 34 Exposure device 36 Development device 38 Transfer device 40 Cleaning Device 42 Laser Light Source 50 Infrared Absorbing Toner 50A Molten Toner 52 Infrared Absorbing Agent 54 Aggregate 56 Binder Resin

Claims (5)

The specific material is transferred to a transfer object onto which a toner image formed by using a toner in which an infrared absorber is aggregated and dispersed in a binder resin and the light absorption rate of a laser beam having a specific wavelength decreases after the toner is melted. A laser fixing method for fixing a toner image on the transfer medium by irradiating a laser beam having a wavelength.   2. The laser fixing method according to claim 1, wherein a volume average particle size of the aggregate of the infrared absorbent is in a range of 1 nm to 1000 nm.   The laser fixing method according to claim 1, wherein the specific wavelength is in a range of a wavelength of 700 nm or more and 1000 nm or less. A toner image formed by using a toner in which an infrared absorbent is aggregated and dispersed in a binder resin and has a light absorption rate with respect to laser light having a specific wavelength after the toner is melted, and transferred onto a transfer medium, is transferred to the transfer target. A laser fixing device for fixing to a transfer body,
An irradiating means for irradiating the transferred body with laser light of the specific wavelength;
A laser fixing device that fixes a toner image on the transfer target body by irradiating a laser beam by the irradiation unit. Latent image forming means for exposing the surface of the charged image carrier to form an electrostatic latent image;
The electrostatic latent image is developed on the image carrier by developing the electrostatic latent image with a developer containing a toner in which an infrared absorbent is agglomerated and dispersed in a binder resin and the light absorptance with respect to laser light having a specific wavelength decreases after the toner is melted. Developing means for forming a toner image on
Transfer means for transferring the toner image to a transfer object;
Fixing means for fixing a toner image on the transfer body by irradiating the transfer body with a laser beam having a specific wavelength;
An image forming apparatus.