JP4604785B2 - Image recording method and toner set for electrophotography - Google Patents

Description

The present invention relates to an image recording method and an electrophotographic Tonase' and.
Especially printing about the possible image recording method and the electrophotographic Tonase' preparative visible and invisible patterns.

  In general, optically readable code patterns such as bar codes and OCR characters are provided as means for optically reading information written on securities such as stock certificates, bonds, checks, gift certificates, lotteries, commuter passes, etc. It is often done. As a code pattern using optical reading, a barcode is widely used mainly in a physical distribution management system.

For example, barcodes are widely used as optical data carriers such as JAN codes for point-of-sale (POS) systems, delivery slips, shipping slips, and barcode tags for delivery. Further, in recent years, two-dimensional codes such as a data code, Vericode, CodeOne, Maxicode, and QR code that enable a huge data capacity and high-density printing are becoming widespread.
The use of barcodes is expected to become increasingly important because it makes it easier to manage product manufacturing information, distribution, card issuance, card defects and usage records, suspension, and reissue.

Conventionally, barcode printing has been performed on a product package, a product surface, or a card using an on-demand printing machine or the like.
As a light source light for optical reading with respect to these conventional code patterns, a semiconductor laser or a light emitting diode having an emission wavelength near 650 nm, 800 nm or 950 nm is mainly used.
However, since the wavelength range of the light source light is limited, the code pattern is an ink using carbon black having an absorption band in the visible light region or an ink having absorption characteristics in the red / infrared wavelength region of the cyan / green system. It is currently printed or printed by

The barcode printing method is letterpress, offset, flexo, gravure, silk printing or the like, and mass printing called source marking is mainly applied. Barcode printing methods are dot impact, thermal transfer, direct thermal, electrophotography, inkjet printing, etc., and are mainly applied to individual printing called in-store marking or the production of small-lot information code labels. .
However, the conventional bar code printer mainly uses a thermal transfer method using an ink ribbon, an ink jet method, a sublimation / melting heat transfer method, and the like, but has a problem that printing speed and resolution are low.

  Therefore, in recent years, printing by a toner fixing method using an electrophotographic method such as a laser beam method has been used from the viewpoint of simplicity. The electrophotographic recording system referred to here is a non-impact image recording system in which recording is performed by attaching toner to a recording medium (recording media such as paper or film) with a laser printer. An information medium is a medium that stores predetermined information and can communicate with or without contact with an external device. Personal identification information is printed directly from the surface of a product embedded with product information or printed on a package. Including, but not limited to, cards such as embedded magnetic cards, IC cards, and optical cards.

  As the visible barcode printing using the electrophotographic system, for example, a developer that can be fixed by flash fixing is disclosed for the toner used in the visible barcode printing using the electrophotographic system (see, for example, Patent Document 1). ), A toner that can read a printed matter with a barcode reader or the like.

However, flash fixing requires that a heat amount of 200 to 300 joules or more be applied when fixing the toner to the transfer member, and the fixing device becomes large.
In general, a low-melting resin is used for the toner for flash fixing. However, since the toner surface temperature rises to several hundred degrees Celsius or higher in a few milliseconds, it exists in a fixed image or on paper. Moisture evaporates instantaneously, and so-called voids that destroy the image may occur. For this reason, it is not suitable for printing for barcodes requiring precise resolution.

  Further, the image recording method using the electrophotographic toner has an essential problem that the scattering of the image toner cannot be avoided. Spattering causes blurring in the bar code line and causes misreading at the time of reading. In recent years, there has been a demand for high density and miniaturization of information, and a problem that stable reading cannot be performed on various recording information media.

  Toner scattering is also called “bleeding” or “blur”, and is image noise unique to electrophotography. Image blur can occur in each of the development process, the transfer process, and the fixing process. The generation mechanism will be described below by taking electrostatic transfer as an example.

In the electrophotographic image forming method, a toner image on an image carrier or an intermediate transfer member is electrostatically moved to a recording medium (such as paper or an intermediate transfer member). At that time, the toner image is moved in a state where they are always in contact. In the case of a configuration in which the toner particles are separated from each other, the moving distance of the electrostatically flying toner particles is greatly increased, resulting in toner image disturbance. This is because the electric field formed between the toner image on the image bearing member or the intermediate transfer member and the recording medium cannot be avoided, and is not an ideal parallel electric field in the pre-post nip region. Responsible.
Also, if a high voltage is applied in a state where the image carrier or intermediate transfer member is separated from the recording medium, a discharge occurs above a certain threshold value, and the effective electric field is reduced. Causes a charging phenomenon. These also cause image defects.

  For the above reasons, it is desirable to transfer the image carrier and the intermediate transfer member close to the recording medium. When the toner layer thickness on the image carrier or intermediate transfer member is made as thin as possible, the transfer electric field can be applied in an ideal form, which is advantageous in preventing toner scattering.

Next, image scattering and image thickening that occur in the fixing process will be described. In printers and copiers, as a method of fixing unfixed toner images attached to the surface of transfer materials such as paper and plastic, a pressure fixing method using only a pressure roll at room temperature, a heat roll method using a heating roll, and oven heating There are oven fixing methods, flash fixing methods using xenon lamps, electromagnetic wave fixing methods using microwaves, etc., solvent fixing methods using solvent vapor, etc., but with high thermal efficiency, the device can be designed compactly, easy to control heat, and Due to its high reliability, heat roll fixing or heat belt fixing has become the mainstream.
In this case, a material configuration such as a heating roll, a belt, and a pressure roll used for heat fixing, a fixing nip structure, and the like have a great influence on toner scattering. In addition to the configuration of the fixing roller, the toner layer thickness on the transfer material affects the scattering of the toner, the spread of the image, and the peelability of the transfer material from the roll.

When the toner layer thickness, that is, the image thickness is large, the proportion of the toner spreading in the lateral direction at the time of fixing increases, and when the line image is fixed, the line image becomes thick.
Further, when the image thickness is high, toner scattering becomes significant when an external force is applied, and further, an offset is likely to occur with respect to the heating roll, and defects such as image cutout are likely to occur.
Furthermore, if the image thickness is high, the durability of the image may be reduced, and these may all cause misreading.

  In addition to the situation of visible barcode printing using such an electrophotographic method, visible barcodes may impair the aesthetics of the product surface, and depending on the product, the visible barcodes cannot be printed due to the aesthetic destruction of the surface. In some cases.

In recent years, therefore, printing of invisible barcodes has been proposed. As the invisible barcode, a fluorescent ink, a type using a special ink designed to have absorption in a special wavelength range, and the like are known.
The invisible barcode cannot be substantially visually recognized by the naked eye, but has an optically identifiable pattern by absorbing infrared rays, and is printed as an information pattern, a detection mark, or the like.

  In other words, since the presence of barcodes cannot be determined from the outside, invisible barcodes have a design effect that does not impair the aesthetics of the surface of the information medium, and a security effect that barcode information does not easily leak outside. The

  However, invisible bar codes usually have unique numbers that are different from one to the other in serial numbers, and printing takes time.

There are various examples of the electrophotographic recording method using invisible toner. For example, an electrostatic latent image corresponding to image information is formed on a latent image carrier, and this electrostatic latent image is referred to as the electrostatic latent image. A method of forming an invisible toner image by developing with an insulating toner having a reverse polarity and high transparency, and forming the invisible image by transferring and fixing the invisible toner image on a transfer material is disclosed (for example, Patent Documents). 2).
Visualization of the invisible image obtained in this way is performed by charging only the insulating toner portion on the transfer material and developing it with colored toner.

  In addition, a colored region made of an infrared absorbing dye and a colored region made of an infrared reflecting dye are formed on a substrate in parallel or overlapped by an electrophotographic method, an electrostatic recording method or an ink jet recording method, and at least one of the colored regions is There is disclosed a method for recording an image such as a character, a number, a symbol, a pattern, and the like so that the two types of colored regions are substantially indistinguishable or difficult to distinguish with the naked eye (for example, Patent Document 3). And Patent Document 4).

The image recording method based on the same concept as described above has been disclosed in other documents (see, for example, Patent Document 5), but the electrophotographic toner has not been described in detail.
In the conventional technique for forming an invisible image, particularly, there has been little study on a recording material such as toner that forms an invisible image.

For this reason, when the development process, transfer process, and fixing process are performed by the image forming apparatus using the conventional invisible toner, similarly to the above-described visible pattern toner, the resolution of the toner scatters and blurs, and the invisible image is reduced. When it is formed, when it is mechanically read by infrared light irradiation as listed above, there is a problem that sufficient accuracy cannot be obtained, and various problems that various restrictions occur when forming an invisible image. May occur.
JP-A-8-15892 JP-A-1-225978 JP-A-6-171198 JP-A-6-122266 JP 2001-265181 A

  An object of the present invention is a visible image and an invisible image that can be machine-read / decoded, an image recording method capable of stably outputting for a long period of time, and recording high-density information, and a toner set for electrophotography And providing an image forming apparatus.

  As a result of intensive investigations in view of the above problems, the following invention has been solved.

<1> A charging step for charging the electrostatic latent image carrier, an exposure step for exposing the charged electrostatic latent image carrier to form a latent image, and the latent image with a visible toner and a near infrared light absorber. A developing step of developing with the invisible toner included to form a visible toner image and an invisible toner image on the electrostatic latent image carrier, and an unfixed transfer by transferring the invisible toner image together with the visible toner image onto a transfer material An image recording method comprising: a transfer step of forming an image; and a fixing step of fixing the unfixed transfer image transferred onto a transfer material,
The amount of toner applied to the unfixed transfer image is 4.5 g / m ² or less when the image area ratio is 100%,
The invisible toner includes a near infrared light absorber ;
The volume average particle diameter of not visible toner and visible toner is at 2μm or more 5μm or less,
A volume average particle size distribution index GSDv represented by the following formula (1) of the invisible toner is 0.02 or more and 0.3 or less smaller than a volume average particle size distribution index GSDv of the visible toner. .
Formula (1): GSDv = (D84v / D16v) ^0.5
[In the formula, D84v draws a cumulative distribution from the small diameter side in the particle size distribution and represents a particle size that is accumulated 84%, and D16v represents a particle size that accumulates 16%. ]

<2> the invisible toner is at least a binder resin, a releasing agent and the image recording how according to <1> to a colorant, characterized in that it comprises a near-infrared absorbent .

< 3 > The image recording method according to <1> or < 2 > , wherein the visible toner includes at least a binder resin, a release agent, and a colorant.

< 4 > The colorant contains at least one selected from the group consisting of a black pigment, a cyan pigment, a magenta pigment, a yellow pigment, a blue pigment, a red pigment, a green pigment, a gold pigment, and a silver pigment. The image recording method according to < 3 >, wherein the image recording method is characterized in that

<5> release agent is a synthetic wax, petroleum waxes, animal waxes include, and above, wherein the at least one selected from the group consisting of vegetable waxes such <3> or < 4 > The image recording method according to any one of the above.

<6> viewed including the invisible toner and a visible toner, the invisible toner an electrophotographic toner set transferred onto the transfer material with the visible toner,
The invisible toner includes a near infrared light absorber;
The invisible toner and the volume average particle size of the visible toner are 2 μm or more and 5 μm or less,
The volume average particle size distribution index GSDv represented by the following formula (1) of the invisible toner is 0.02 or more and 0.3 or less smaller than the volume average particle size distribution index GSDv of the visible toner. Toner set.
Formula (1): GSDv = (D84v / D16v) ^0.5
[In the formula, D84v draws a cumulative distribution from the small diameter side in the particle size distribution and represents a particle size that is accumulated 84%, and D16v represents a particle size that accumulates 16%. ]

< 7 > The toner set for electrophotography according to < 6 >, wherein the visible toner includes at least a binder resin, a release agent, and a colorant.

< 8 > The colorant contains at least one selected from the group consisting of a black pigment, a cyan pigment, a magenta pigment, a yellow pigment, a blue pigment, a red pigment, a green pigment, a gold pigment, and a silver pigment. The toner set for electrophotography as described in < 7 > above, which is characterized in that

<9> The releasing agent is, synthetic waxes, petroleum waxes, animal waxes include, and above, wherein the at least one selected from the group consisting of vegetable waxes such <7> or The toner set for electrophotography as described in < 8 >.

According to the present invention, the machine to a read-decoding process visible images and invisible images possible, stably for a long period of time can be output over the image recording method and electrophotographic Tonase' preparative can record high density information it is possible to provide a.

  The present invention includes the following: (a) visible toner and developer containing visible toner, (b) invisible toner and developer containing invisible toner, (c) toner set for electrophotography, (d) image forming apparatus The image recording method and (e) the invisible image will be described in order.

  In the present invention, the simple term “toner” includes visible toner and invisible toner.

(A-1) Visible toner The visible toner according to the present invention has a volume average particle diameter of 2 to 5 μm, preferably 2 to 4.5 μm, more preferably 2 to 4 μm, and further preferably 2 to 3. 5 μm.
In the present invention, by setting the range of the volume average particle size to the above range, the toner weight in the 100% area area of the transfer image transferred onto the transfer material in the transfer step is 4.5 g / cm ² or less. Even in this case, fine line reproducibility is improved, and the problem of blurring of fine lines and fine dots that can generally occur when the toner weight is reduced is solved.

  In the visible toner according to the present invention, the volume average particle size distribution index GSDv represented by the following formula (1) is preferably 1.30 or less, more preferably 1.25 or less, still more preferably 1. 23 or less.

Formula (1): GSDv = (D84v / D16v) ^0.5

  The particle size distribution of the toner can be measured by various methods, and the measured particle size distribution is drawn from the smaller particle size side with respect to the divided particle size range (channel), and the particle size at which accumulation is 16% is volume averaged. The particle diameter is defined as D16v, and the particle diameter that is 50% cumulative is defined as the volume average particle diameter D50v (the volume average particle diameter of the fine particles described above indicates this). Similarly, the particle diameter that is 84% cumulative is defined as the volume average particle diameter D84v.

Using these, the volume average particle size distribution index (GSDv) is calculated as the square root of the ratio of 84 cumulative volume% to 16 cumulative volume% in the volume particle size distribution, that is, (D84v / D16v) ^0.5 .

  There is a high correlation between the particle size distribution and the scattering of the toner. When GSDv exceeds 1.30, the scattering of the toner tends to increase and it becomes difficult to improve the fine line reproducibility. GSDv has no lower limit, and basically a small numerical value is desirable.

Further, in the number particle size distribution, the cumulative number of visible toners having a particle size of 1 μm or less is preferably 15% by number or less, and the cumulative number of visible toners having a particle size of 5 μm or more is preferably 7.5% by number or less.
If the cumulative number of visible toners having a particle size of 1 μm or less exceeds 15% by number, image fogging or poor cleaning tends to occur. On the other hand, if the cumulative number of visible toners having a particle size of 5 μm or more exceeds 7.5% by number, it is difficult to achieve the improvement in fine line reproducibility that is the object of the present invention.

  The “reproducibility of fine lines” as used in the present invention means mainly whether or not fine lines with a width of 30 to 60 μm, preferably 30 to 40 μm can be faithfully reproduced, and further reproduce dots of the same diameter. This is also taken into consideration.

Further, the cumulative number% of visible toner particles exceeding 5.0 μm is used as a parameter for defining the large particle size side of the particle size distribution of the visible toner, but the reference particle size can be defined by other numerical values. .
Specifically, when the standard particle size is 4.0 μm, it is preferable that 75% by number or more of toner particles having a particle size of 4.0 μm or less are included in all visible toner particles.

  In view of the volume average particle size and particle size distribution of the toner of the present invention, when the cumulative number of particles of 4.0 μm or less in all toner particles is 75% by number or more, the particle size is 5.0 μm. In general, the cumulative number of toner particles exceeding 10 is 10% by number or less.

  The particle size distribution of the toner can be measured by various methods. In the present invention, the particle size distribution of colored particles of 1 μm or less is measured using a Coulter counter TA2 type (manufactured by Beckman Coulter, Inc.) with an aperture diameter of 50 μm. Only when the aperture diameter is 30 μm, the value is measured.

  Specifically, 2 to 3 drops of a dispersion (surfactant: Triton X100) and a measurement sample are added to an aqueous sodium chloride solution (10 g / liter), and after 1 minute of dispersion treatment with an ultrasonic disperser, the above The value when measured using an apparatus.

In order to obtain colored particles having such a particle size distribution, conditions for pulverization and classification may be set as appropriate when obtained by a pulverization method, and polymerization conditions may be set as appropriate when obtained by a polymerization method.
In order to reduce the particle size as much as possible by the usual pulverization method, the amount of loss increases. Therefore, a wet production method such as suspension polymerization, emulsion polymerization aggregation method, and submerged drying method is preferable. In order to obtain the production cost, suspension polymerization method, emulsion polymerization aggregation method and submerged dry granulation method are preferable, and toner adjustment method by emulsion polymerization aggregation is most preferable.

  A method for preparing a toner using an emulsion polymerization aggregation method is described in JP-A-6-250439. In this method, a resin fine particle dispersion is generally prepared by emulsion polymerization using a surfactant, and on the other hand, a dispersion that becomes a toner composition such as a colorant, a charge control agent, and a release agent is prepared. After mixing, a surfactant having an electric polarity opposite to that of the surfactant is added to aggregate the mixed particles until a desired particle size is obtained. After stabilization, the particles are fused at a temperature equal to or higher than the resin Tg to produce a toner.

  The visible toner according to the present invention preferably includes at least a binder resin, a release agent, and a colorant. The visible toner according to the present invention includes a visible toner for photofixing that is photofixed.

(A-2) Colorant In the visible toner used in the present invention, even if the visible toner weight per unit area of the image is reduced, sufficient image density can be achieved, and the water resistance, light resistance, or solvent resistance of the image can be achieved. In order to ensure the property, it is preferable to use pigment particles having high coloring power and excellent water resistance, light resistance, or solvent resistance as the colorant contained in the colored particles.

The colorant used in the visible toner of the present invention contains at least one selected from the group consisting of a black pigment, a cyan pigment, a magenta pigment, a yellow pigment, a blue pigment, a red pigment, a green pigment, a gold pigment, and a silver pigment. To do.
Specific examples of the colorant include carbon black, chrome yellow, hansa yellow, benzidine yellow, sren yellow, quinoline yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brillianthamine 3B, brilliantamine 6B. , Dapon oil red, pyrazolone red, risor red, rhodamine B rake, lake red C, rose bengal, aniline blue, ultramarine blue, calco oil blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green, malachite green oxalelate, titanium black Various pigments such as acridine, xanthene, azo, benzoquinone, azine, anthraquinone Various dyes such as thioindico, dioxazine, thiazine, azomethine, indico, thioindico, phthalocyanine, aniline black, polymethine, triphenylmethane, diphenylmethane, thiazine, thiazole, xanthene, etc. Can be used singly or in combination of two or more.

The visible toner used in the present invention has a small particle size, and a sufficient image density cannot be obtained with the same pigment concentration as that of a conventional toner having a particle size. The visible toner used in the present invention has a volume average particle diameter ranging from 2.0 μm to 5.0 μm, and the visible toner weight per unit area on the transfer material in a solid image (hereinafter referred to as “TMA”). Also, it is called “loading amount”).
Therefore, it is desirable to set the necessary pigment concentration according to TMA.

Assuming that the visible toner is formed in a single layer on the transfer material, TMA is determined by the volume average particle diameter D (μm) of the colored particles and the specific gravity a, and the pigment concentration C (%) in the colored particles. Preferably satisfies the following relational expression (2).
Formula (2): 30 ≦ a · D · C ≦ 90

  When the value of a · D · C (hereinafter abbreviated as “aDC”) is less than 30, the coloring power is not sufficient, and it is difficult to obtain a desired image density, and it is formed during development to obtain a desired image density. Increasing the amount of visible toner is not preferable because the thickness of the image increases, the reproducibility of fine lines decreases, and the transferability also decreases despite the fact that the folding angle is reduced.

  On the other hand, when the value of aDC exceeds 90, a sufficient image density can be obtained, but the background particles are likely to be stained due to scattering of visible toner to a small amount of non-image areas. It is not preferable because it may cause problems such as an increase in the fixing property and the like.

  In addition, when using a pigment having a low coloring power for a yellow pigment as compared with a black pigment, a cyan pigment, a magenta pigment, a blue pigment, a red pigment, etc., the optimum value of aDC may be different. Included in formula range. Of course, even in the case of pigments of the same color, the coloring power varies depending on the chemical structural formula and the like. Therefore, the pigment concentration is preferably set appropriately within the above range according to the type of pigment used.

The concentration C (%) of pigment particles in the visible toner depends on the amount of visible toner loaded on the paper, but is preferably 3% by weight to 50% by weight, and more preferably 4% by weight to 40% by weight. Preferably, 5% by weight or more and 20% by weight or less is most preferable.
If it is less than 3% by weight, the color density per unit weight of the visible toner tends to be insufficient. On the other hand, the larger the C, the higher the color density of the visible toner. However, when the amount exceeds 50% by weight, the background stain becomes noticeable even when a very small amount of visible toner is scattered on the non-image area, and coloring is caused by the reinforcing effect of the pigment. In some cases, the melt viscosity of the particles increases and the fixability decreases.

  As a method for dispersing the colorant, any method such as a general shearing method such as a rotary shearing homogenizer, a ball mill having a medium, a sand mill, or a dyno mill can be used, and is not limited at all. These colorant fine particles may be added together with other fine particle components in the mixed solvent at once, or may be divided and added in multiple stages.

(A-3) Release Agent The visible toner according to the present invention may use a release agent.
The release agent used in the present invention is preferably at least one selected from the group consisting of synthetic waxes, petroleum waxes, animal waxes, and plant waxes.
Specific examples of the release agent include low molecular weight polyolefins such as polyethylene, polypropylene, and polybutene; fatty acid amides such as silicones, oleic acid amide, erucic acid amide, ricinoleic acid amide, and stearic acid amide; carnauba wax Plant waxes such as beeswax, rice wax, candelilla wax, tree wax, jojoba oil, etc .; animal waxes such as beeswax; minerals such as montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, etc. And petroleum-based waxes, and modified products thereof.

The release agent is preferably added in an amount of 20% by mass or less with respect to the visible toner, more preferably 0.1% by mass to 15% by mass, and still more preferably 1% by mass to 12% by mass. is there.
If there are too many release agents, the release agent exposed to the surface of the visible toner or released to the outside of the visible toner will increase, causing problems in the fluidity and storage properties of the visible toner itself and filming. May be exacerbated. When combined with oilless fixing, the release agent is preferably contained in an amount of 6% by mass or more. If the amount of the release agent is too small, hot offset may occur or the peelability from the fixing device may be reduced.

  These waxes are dispersed in water together with polymer electrolytes such as ionic surfactants, polymer acids, and polymer bases, and are heated to the melting point or higher, and can be applied with a strong shearing force or pressure discharge type dispersers. Can be made into fine particles and a dispersion of particles of 1 μm or less can be prepared. These release agent fine particles may be added to the mixed solvent at the same time as other resin fine particle components, or may be divided and added in multiple stages.

(A-4) Binder resin The resin fine particles used in the aggregating step are formed from a thermoplastic polymer that becomes a binder resin, and examples thereof include styrene, parachlorostyrene, and α-methylstyrene. Styrenes, methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate Esters with vinyl groups such as, vinyl nitriles such as acrylonitrile and methacrylonitrile, vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether, vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone, ethylene Homopolymers of monomers such as polyolefins such as propylene and butadiene, copolymers obtained by combining two or more of these, or mixtures thereof, as well as epoxy resins, polyester resins, polyurethane resins, polyamide resins, and cellulose resins , Polyether resins, non-vinyl condensation resins, mixtures of these with the vinyl resins, and graft polymers obtained when polymerizing vinyl monomers in the presence of these polymers. it can. These resins may be used alone or in combination of two or more. Among these resins, vinyl resins are particularly preferable. The vinyl resin is advantageous in that a resin fine particle dispersion can be easily prepared by emulsion polymerization or seed polymerization using an ionic surfactant or the like.

The method for preparing the dispersion of resin fine particles is not particularly limited, and a method appropriately selected according to the purpose can be adopted. For example, it can be prepared as follows.
When the resin in the resin fine particles is a homopolymer or copolymer (vinyl resin) of a vinyl monomer such as the ester having a vinyl group, the vinyl nitrile, the vinyl ether, or the vinyl ketone. Ionizes resin fine particles made of a vinyl monomer homopolymer or copolymer (vinyl resin) by emulsion polymerization or seed polymerization of the vinyl monomer in an ionic surfactant. It is possible to prepare a dispersion obtained by dispersing in a functional surfactant. Further, when the resin in the resin fine particles is a resin other than a homopolymer or copolymer of a vinyl monomer, the resin can be dissolved in an oily solvent having a relatively low solubility in water. The resin is dissolved in the oily solvent, and the dissolved product is added to water together with an ionic surfactant and a polymer electrolyte, and fine particles are dispersed using a disperser such as a homogenizer, and then heated or decompressed. Can be prepared by evaporating the oily solvent.

  When the resin fine particles dispersed in the resin fine particle dispersion are composite particles containing components other than the resin fine particles, the dispersion in which these composite particles are dispersed can be prepared, for example, as follows. it can. For example, each component of the composite particles is dissolved and dispersed in a solvent, and then dispersed in water together with an appropriate dispersant as described above, and the solvent is removed by heating or decompression, emulsion polymerization, It can be prepared by a method of immobilizing by performing mechanical shearing or electroadsorption on the latex surface prepared by seed polymerization. Moreover, when manufacturing resin fine particles, you may use the composite resin particle manufactured by adding a coloring agent and a mold release agent.

  The addition amount of the binder resin is preferably in the range of 60% by mass to 95% by mass and more preferably in the range of 70% by mass to 90% by mass with respect to the visible toner particles.

(A-5) Other additives When a visible toner is used as a magnetic toner, a magnetic powder is included. Examples of the magnetic powder used here include metals such as ferrite, magnetite, reduced iron, cobalt, nickel, manganese, and alloys. Or the compound containing these metals can be mentioned.
Furthermore, various charge control agents that are usually used, such as quaternary ammonium salts, nigrosine compounds and triphenylmethane pigments, may be added as necessary.

Furthermore, a conventional toner external additive can be contained in the visible toner.
As such external additives, inorganic particles and organic particles can be added as fluidity aids, cleaning aids, abrasives, and the like.

Examples of the inorganic particles include all particles usually used as an external additive on the toner surface, such as silica, alumina, titania, calcium carbonate, magnesium carbonate, tricalcium phosphate, and cerium oxide. These inorganic particles can be used by being dispersed with an ionic surfactant, a polymer acid, or a polymer base.
Among inorganic particles, it is preferable to add silica hydrophobized as an essential component.

Examples of the organic particles include all particles usually used as external additives on the toner surface, such as vinyl resins, polyester resins, silicone resins, and fluorine resins.
Further, a lubricant can be added. Examples of the lubricant include fatty acid amides such as ethylene bisstearylamide and oleic acid amide, and fatty acid metal salts such as zinc stearate and calcium stearate.

  The addition amount of these external additives is preferably in the range of 0.1% by mass to 10% by mass, more preferably in the range of 0.5% by mass to 8% by mass with respect to the visible toner particles.

  These external additives are mixed with a resin fine particle dispersion, a colorant dispersion, etc., and after preparing a uniform mixed particle dispersion, a soluble inorganic metal salt is added to the dispersion medium and mixed to obtain desired aggregated particles. obtain. At that time, resin fine particles, colorant, and if necessary, the above inorganic fine particles may be added at once, or the fine particle components are added step by step, and the structure of the aggregated particles is, for example, a core-shell structure, You may provide the structure which inclined the component to the radial direction of particle | grains. In that case, the resin fine particle dispersion, the colorant particle dispersion, the release agent fine particle dispersion and the like are mixed and dispersed, and the aggregated particles are grown until the particle size reaches a certain level.

  If necessary, additional resin fine particles may be added to the surface of the aggregated particles by adding a resin fine particle dispersion or the like. By covering the surface of the agglomerated particles with the additional resin fine particles, it is possible to prevent the colorant, release agent, etc. from being exposed to the toner surface, and it is effective in suppressing poor charging and uneven charging due to these exposures. is there.

(A-6) Developer containing visible toner An appropriate component composition can be taken according to the purpose. For example, the visible toner may be used alone to prepare as a one-component electrostatic image developer, or may be prepared as a two-component electrostatic image developer in combination with a carrier.

(A-7) Carrier The carrier is not particularly limited, and known carriers such as iron powder carriers and ferrite carriers can be used. For example, JP-A-62-39879 and JP-A-56. Known carriers such as the resin-coated carrier described in JP-11461A can be used.
The mixing ratio of the visible toner of the present invention and the carrier in the electrostatic image developer is not particularly limited and can be appropriately selected according to the purpose.

(B-1) Invisible toner In the present invention, the invisible toner refers to a toner having no color developability due to absorption of a specific wavelength in the visible light region.
Particularly in the present invention, the invisible toner contains a near infrared absorbent, that having a color in the near infrared region. More preferably, it includes at least a resin, a release agent, and a near infrared light absorber.
Furthermore, for the invisible toner, if the level of the colorant is clearly not confirmed, or if it is colored in accordance with the color of the background of the transfer material, or for the purpose of suppressing coloring by the near-infrared light absorber. A colorant may be added.
Therefore, the configuration of the invisible toner is basically similar to the configuration of the visible toner except that it does not contain a near infrared light absorber.
The invisible toner of the present invention includes an invisible toner for photofixing that is photofixed.

The average diameter of the invisible toner is 2 to 5 μm, preferably 2 to 4.5 μm, more preferably 2 to 4 μm, and further preferably 2 to 3.5 μm.
In the present invention, by setting the range of the volume average particle size to the above range, the toner weight in the 100% area area of the transfer image transferred onto the transfer material in the transfer step is 4.5 g / cm ² or less. Even in this case, fine line reproducibility is improved, and the problem of blurring of fine lines and fine dots that can generally occur when the toner weight is reduced is solved.

  The volume average particle size distribution index GSDv of the invisible toner is 1.28 or less, preferably 1.25 or less, and most preferably 1.23 or less. However, what is important at this time is the particle size distribution of the invisible toner. It is 0.02 or more and 0.3 or less smaller than the volume average particle size distribution index GSDv of the visible toner. Preferably, it is 0.03 or more and 0.25 or less small case, and 0.04 or more and 0.2 or less small case is more preferable.

  As described for the visible toner, the particle size distribution has a high correlation with toner scattering. In addition to this, when the invisible toner and the visible toner are simultaneously transferred, it has been found that the relationship between the average particle size distribution index of the invisible toner and the visible toner is extremely important.

When the average particle size distribution index of the invisible toner is 0.02 or more and 0.3 or less smaller than the average particle size distribution index of the visible toner, the scattering of the invisible toner is improved when transferring simultaneously with the visible toner. Reproducibility and resolution are improved, and reading of invisible information is improved.
Therefore, the image quality of the visible image is not impaired, and the invisible image is stable for a long period of time by mechanical reading / decoding processing by infrared light irradiation, and information can be stably recorded at a high density.

  When the difference in GSDv is less than 0.02, the scattering of invisible toner increases, and for the purpose of the present invention, this invisible stable reading cannot be performed.

(B-2) Near-infrared light absorber In this invention, a near-infrared light absorber refers to the material which has an at least 1 or more strong light absorption peak in the near-infrared area | region of the wavelength range of 800-1000 nm. .
The absorption rate of the invisible toner in the near-infrared light region of 800 nm to 1000 nm is preferably 20% or more, more preferably 30% or more, from the viewpoint of ensuring the reading intensity by the reading device such as a CCD and the accuracy at the time of decoding. . In addition, when a high-definition image incorporating higher-density information is formed and read by a CCD, it has an absorption peak (maximum absorption rate) in the wavelength range of 800 nm to 900 nm where the optical sensitivity of the CCD is high. Is preferred.

  The absorption rate (near infrared light absorption rate) of the invisible toner in the near-infrared region is determined by using a spectral reflectance measuring device (V-570, manufactured by JASCO Corporation). By measuring the spectral reflectance in the near infrared region as IT (i) and the spectral reflectance in the near infrared region of the recording medium (transfer material) as M (i), the following equation (3) is obtained. .

  Formula (3): Near-infrared light absorption rate of invisible toner = IT (i) -M (i)

  Further, in the same manner as described above, by measuring in the visible region, the absorption rate (visible light absorption rate) of the invisible toner in the visible light region can also be obtained. That is, by measuring the spectral reflectance in the visible light region of an image formed with invisible toner as IT (v) and the spectral reflectance of the recording medium (transfer material) as M (v), the following equation (4) is obtained. It is required as shown.

  Formula (4): Visible light absorption rate of invisible toner = IT (v) −M (v)

The maximum absorption rate in the visible light region (400 nm to 700 nm) of the near infrared light absorbent is preferably 15% or less, and more preferably 13.5% or less.
Furthermore, in order to increase invisibility in white paper generally used as a recording medium (transfer material), the maximum absorption rate in the wavelength region of 400 nm to 600 nm is preferably 8% or less, and preferably 4% or less. Further, the maximum absorption rate in the wavelength region of 600 nm to 700 nm is preferably 10% or less, and more preferably 7% or less.

  When the absorptance in the visible light region of 400 nm to 700 nm exceeds 15%, the invisibility of the image formed using the invisible toner is lowered and recognized by the naked eye as a matter of course. The quality of the visible image is deteriorated because the desired image is colored. In order to avoid such problems, a shielding layer is further provided on the surface of an image formed using invisible toner, and a visible image is formed on the surface, or a visible black image is visible. An image must be formed using invisible toner between the image and the surface of the recording medium. Therefore, an image cannot be formed using invisible toner regardless of the area on the recording medium surface where the visible image is formed.

Further, the maximum value ε (max) of the molecular absorption coefficient of the near-infrared light absorber is preferably 5 × 10 ⁴ (mol ⁻¹ · cm ⁻¹ · dm ³ ) or more, and more preferably 9 ×. 10 ⁴ (mol ⁻¹ · cm ⁻¹ · dm ³ ) or more.
Here, the maximum value ε (max) of the molecular absorption coefficient is determined by using a spectrophotometer “U-4000” manufactured by Hitachi, Ltd., in a near-infrared region in a solution that can dissolve a near-infrared light absorbent such as acetone or sulfuric acid. It is determined from the absorbance peak value measured by dissolving the light absorber.

  The near-infrared light absorber used in the invisible toner according to the present invention is not particularly limited as long as it satisfies the absorptance in the visible light region as described above when manufactured as an invisible toner.

  Examples of organic near-infrared light absorbers include cyanine dyes, imonium dyes, diimonium dyes, triallylmethane dyes, naphthoquinone dyes, anthraquinone dyes, squarylium dyes, phthalocyanine dyes, and naphthalocyanine dyes. And dyes, anthraquinone dyes, nickel-dithiol complex dyes, and the like (Japanese Patent Laid-Open Nos. 51-135886, 56-143242, 58-1762, 58-13676). JP, 60-23451, JP 63-295578, JP 4-174402, JP 5-93160, JP 5-222302, JP 2-4881. No. publication, Japanese Patent Publication No. 6-18124 publication, etc.).

In the case of an organic near-infrared light absorber, the concentration of the near-infrared light absorber in the invisible toner is preferably in the range of 0.05% by weight to 3% by weight, preferably 0.2% by weight or more, 1 A range of not more than% by weight is more preferred.
When the concentration of the organic near-infrared light absorbing agent is less than 0.05% by weight, the near-infrared light absorbing ability may be insufficient, and when it is larger than 3% by weight, it is visible. The color tone of the image becomes stronger, and the invisibility of the image formed using the invisible toner may be impaired.

  As an inorganic near-infrared absorbing material, for example, transition metal ions that absorb at least near-infrared wavelengths in known glass network forming components that transmit visible wavelengths such as phosphoric acid, silica, and boric acid, Glass to which a material such as a pigment made of an inorganic and / or organic compound is added, crystallized glass obtained by crystallizing the glass by heat treatment, or the like can be used.

  In addition, in order to make preparation of the said glass and heat processing easy, you may add well-known glass network modification components, such as an alumina, an alkali oxide, an alkaline-earth oxide. In addition, such glass may be prepared by melting once and cooling it, but when adding a material such as a pigment made of an organic compound that absorbs near-infrared wavelengths to the glass raw material. Alternatively, it may be produced by a sol-gel method or the like that can produce glass without using a melting process that requires high-temperature heating.

  The average dispersion diameter of the near-infrared light absorbent composed of inorganic machine material particles is preferably in the range of 50 nm to 800 nm. When the average dispersion diameter is within the above range, the penetration of the binder resin into the surface of the recording medium can be suppressed within a range that does not impair the fixability.As a result, the image surface formed by the invisible toner is The smoothness is kept high and the glossiness is higher than that in the portion where the image is not formed. In this case, if the image formed using the invisible toner is held at an angle, the presence of the image portion formed by the invisible toner having a relatively high glossiness can be recognized without degrading the quality of the visible image. become.

Furthermore, in order to increase the near-infrared light absorption capability necessary for machine reading of an image formed with an invisible toner, the average dispersion diameter is preferably in the range of 100 nm to 600 nm, and more preferably in the range of 150 nm to 450 nm. In order to obtain a desired average dispersion diameter within the above-mentioned range, inorganic material particles pulverized or granulated so that the particle diameter falls within the above-mentioned range may be used.
When the average dispersion diameter is smaller than 50 nm, the image becomes translucent even in the near-infrared region and the image becomes blurred, so that recorded information cannot be read. On the other hand, when the average dispersion diameter is larger than 800 nm, the image quality is deteriorated or the pixels are rough, so that the density of recorded information is reduced or the image can be easily recognized visually. Therefore, there arises a problem that the quality of the visible image is impaired.

  As mentioned above, although the example of the near-infrared light absorber was given, what is necessary is just a material which has absorption in a near-infrared area | region, It is not limited to these.

The near-infrared light absorber is desirably added in a dispersed state in accordance with the toner production method. For example, in the case of a wet process toner, for example, a dispersion of near-infrared light absorbent particles is obtained using a media-type disperser such as a rotary shearing homogenizer, a ball mill, a sand mill, or an attritor, or a high-pressure counter-collision disperser. Can be prepared.
Further, the near-infrared light absorbing agent can be dispersed in an aqueous system by a homogenizer using a polar surfactant. At this time, by setting the average dispersion diameter of the near-infrared light absorber to a desired range, the light transmittance and the color developability are improved.

As an example, an inorganic material particle containing at least CuO and P ₂ O ₅ as a near infrared light absorber will be described in more detail, but the present invention is not limited thereto.

When inorganic material particles containing CuO and P ₂ O ₅ are used as a near-infrared light absorber, an image formed with an invisible toner is more invisible in the visible region, and becomes clearer when machine-read in the near-infrared region. Can be recognized.
It is presumed that the near-infrared light absorbing ability of such inorganic material particles is exhibited when the divalent copper ions contained in the inorganic material absorb near-infrared light.

  In particular, the CuO content concentration in the invisible toner particles is preferably in the range of 6% by mass to 35% by mass, and more preferably in the range of 10% by mass to 30% by mass. When the concentration of CuO is less than 6% by mass, the near-infrared light absorbing ability may be insufficient, and when it is greater than 35% by mass, the color tone from blue to green becomes strong, and the invisible toner. Invisibility of an image formed using may be impaired.

Furthermore, the inorganic material particles are CuO, Al ₂ O in order to obtain the uniform dispersibility of the inorganic material particles in the invisible toner and the appropriate negative triboelectric chargeability required as a recording material for electrophotography. ₃ , preferably made of copper phosphate crystallized glass containing P ₂ O ₅ and K ₂ O as essential constituent components. The composition of the copper phosphate crystallized glass is such that CuO is in the range of 20% by mass to 60% by mass, Al ₂ O ₃ is in the range of 1% by mass to 10% by mass, and P ₂ O ₅ is 30%. in the range of mass% to 70 mass%, K ₂ O is preferably in the range of 1 wt% to 10 wt%.

The content of CuO is preferably adjusted within the above range in order to obtain a suitable near-infrared light absorption ability, and the contents of P ₂ O ₅ and K ₂ O are the content of the former and the latter. The ratio is suitably adjusted within the above range so as to ensure the composition uniformity of the copper phosphate crystallized glass, and the content of Al ₂ O ₃ is within the above range for stabilizing divalent copper ions. It is suitably adjusted.

  As a method for producing a copper phosphate crystallized glass having such a composition, a glass raw material mixed with the above components is melted in a temperature range of 700 ° C. to 2000 ° C. until it is sufficiently homogeneous, Once cooled to near room temperature, it is vitrified. Next, the method of crystallizing this by heat-processing in the temperature range of 200 to 800 degreeC etc. is mentioned. In this case, mechanical pulverization may be performed before and after the crystallization process to perform a fine powder process. In addition, when the glass raw material is melted, it is possible to increase the abundance of divalent copper ions in the copper crystallized glass by adding an oxidizing agent or by performing a melting treatment in an oxidizing atmosphere. This is a method preferably used for enhancing the near-infrared light absorbing ability of phosphoric acid crystallized glass.

The average dispersion diameter of the near-infrared light absorber in the invisible toner is preferably in the range of 50 nm to 300 nm, preferably in the range of 75 nm to 250 nm, regardless of whether it is organic or inorganic. More preferred. When the average dispersion diameter is within the above range, infrared absorption can be increased as much as possible, and absorption of visible light can be reduced as much as possible.
Here, the “average dispersion diameter” means the average particle diameter of individual near-infrared light absorbers dispersed in the invisible toner. This average dispersion diameter was determined by TEM (transmission electron microscope: JEOL Datum Co., Ltd., JEM-1010) observation, about 1000 particulate near infrared light absorbers dispersed in the invisible toner. The particle size is calculated from each cross-sectional area and obtained from the average value.

(D-3) Binder Resin The binder resin used in the invisible toner of the present invention is not particularly limited when produced as an invisible toner. For example, materials listed below are used. be able to.

  For example, styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene and isoprene, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl acetate, methyl acrylate, ethyl acrylate, acrylic Α-methylene aliphatic monocarboxylic acid ester such as butyl acid, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate, vinyl methyl ether, vinyl ethyl ether, Examples include homopolymers or copolymers of vinyl ethers such as vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone.

  Particularly representative binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. A polymer, polyethylene, and polypropylene can be mentioned. Further examples include polyester, polyurethane, epoxy resin, silicon resin, polyamide, modified rosin, paraffin, and waxes.

(D-4) Release Agent As the release agent used for the invisible toner, those described for the visible toner can be applied.

(D-5) Colorant In particular, when an invisible image is formed on the surface of a recording medium (transfer material) having a high whiteness using an invisible toner, a white additive is added for the purpose of further increasing the invisibility of the image. It is preferable to use it. It is effective to use the above-mentioned titania particles as the white additive.
Titania particles can be used to increase the invisibility of the invisible toner by adding it to the inside of the invisible toner and / or adding it to the surface. It is desirable to be smaller than the average dispersion diameter of the agent. When the titania particle size is larger than the average dispersed particle size of the near-infrared light absorber, the whiteness of the invisible toner increases, but on the other hand, the light-hiding property also increases and the near-infrared light absorption ability is inhibited. There is a case.

  In addition, in order to increase invisibility, a colorant may be adjusted by adding a colorant to the invisible toner in accordance with a recording medium other than white. In addition, when an invisible image is overwritten on a visible image, a colorant may be appropriately added to adjust the color of the invisible image to the color of the visible image.

(B-6) Other Invisible Toner Composition Invisible toner is used by being contained and dispersed inside the invisible toner in addition to the binder resin, near-infrared light absorber, release agent, and in some cases, the colorant. As the internal additive, one or more kinds such as a charge control agent for adjusting the charge may be contained.

Furthermore, in order to further improve the long-term storability, fluidity, developability, and transferability of the invisible toner, inorganic powder and resin powder may be used alone or in combination as additives.
As this inorganic powder, for example, carbon black, silica, alumina, titania, zinc oxide, as resin powder, PMMA, nylon, melamine, benzoguanamine, fluorine-based spherical particles, and amorphous such as vinylidene chloride and fatty acid metal salts Powder.
The addition amount of these additives is preferably in the range of 0.2% by mass to 4% by mass and more preferably in the range of 0.5-3% by mass with respect to the invisible toner particles.

(B-7) Production method of invisible toner As for the production method of invisible toner, pulverization and classification conditions may be appropriately set when obtained by a pulverization method, and polymerization conditions may be appropriately set when obtained by a polymerization method. In addition, the production method of the invisible toner particles is not particularly limited, and a known method can be used. However, when the kneaded product is pulverized, for example, a micronizer, Ulmax, JET-O can be used. -It can be carried out by means of a mizer, KTM (krypton), turbome jet or the like.
Furthermore, as a subsequent process, using a hybridization system (manufactured by Nara Machinery Co., Ltd.), a mechano-fusion system (manufactured by Hosokawa Micron Corporation), a kryptron system (manufactured by Kawasaki Heavy Industries, Ltd.), etc. The toner shape can be changed. In addition, spheronization with hot air can also be mentioned.
Further, classification processing may be performed to adjust the toner particle size distribution.

The invisible toner was prepared by preparing a resin fine particle dispersion, a colorant particle dispersion, and a release agent particle dispersion, respectively, and adding a metal salt flocculant while stirring and mixing them at a predetermined ratio. The particles can be neutralized to form aggregated particles.
Next, an inorganic hydroxide is added to adjust the pH of the system from weakly acidic to a neutral range, and then the mixture is heated to a temperature equal to or higher than the glass transition point of the resin fine particles to be fused and united. After completion of the reaction, a desired invisible toner can be obtained through sufficient washing and solid-liquid separation and drying processes.

(B-8) Developer containing invisible toner The developer containing the invisible toner in the invention preferably contains a carrier and the invisible toner. The developer containing the invisible toner can be obtained by mixing the carrier and the invisible toner according to the present invention by a known method.
In the developer containing the invisible toner according to the present invention, the invisible toner is preferably nonmagnetic, and is preferably a two-component developer obtained by mixing a carrier having magnetism.

(C) Electrophotographic Toner Set The electrophotographic toner set of the present invention includes the invisible toner and the visible toner.
Here, as described above, the volume average particle size of the invisible toner and the visible toner is 2 μm or more and 5 μm or less, and the volume average particle size distribution index GSDv of the invisible toner is 0.02 or more and 0 from the GSDv of the visible toner. .3 or less is characteristic.

Here, when a toner image is formed using invisible toner, an invisible image is obtained, and when visible toner is used, a visible image is obtained.
In the present invention, an “invisible image” is an image that can be recognized by a reading device such as a CCD in the infrared region.
In general, since invisible toner does not have color developability due to absorption of a specific wavelength in the visible light region, an invisible image cannot be visually recognized in the visible region. However, this should be suppressed when printing according to the color of the recording medium (transfer material) or overlying the image formed with visible toner, and even when the near-infrared light absorber is slightly colored. For the purpose, a colorant may be added after adjusting depending on the color to be printed or colored. An image formed under these conditions cannot be visually recognized, but it may be visually recognized in the case of different conditions such as printing on a recording medium of another color or overlapping different colors. Can do. Even in such a case, if it can be recognized by a reading device such as a CCD in the infrared region, an invisible image is obtained.

  Further, the “visible image” can be visually recognized (that is, visible) in the visible region because the visible toner that forms the visible image has color developability due to absorption of a specific wavelength in the visible light region. Means an image.

(D-1) Image Recording Method and Image Forming Apparatus In the image recording method of the present invention, a charging step for charging the electrostatic latent image carrier, and exposing the charged electrostatic latent image carrier to form a latent image. An exposure process; a development process for developing the latent image with toner to form a toner image; a transfer process for transferring the toner image onto a transfer material to form an unfixed transfer image; and a transfer process on the transfer material. And a fixing step of fixing the unfixed transfer image, wherein the toner includes an invisible toner and a visible toner, and the volume average particle size of the invisible toner and the visible toner is 2 μm or more. The volume average particle size distribution index GSDv represented by the above formula (1) of the invisible toner is 5 μm or less, and is 0.02 or more and 0.3 or less smaller than the volume average particle size distribution index GSDv of the visible toner. And

The image forming apparatus of the present invention includes an electrostatic latent image carrier, a charging device that charges the electrostatic latent image carrier, and exposure that exposes the charged electrostatic latent image carrier to form a latent image. A developing device that develops the latent image with toner and forms the toner image on the electrostatic latent image carrier, and a transfer device that transfers the toner image onto a transfer material to form an unfixed transfer image. And a fixing device that fixes the unfixed transfer image transferred onto the transfer material, wherein the developing device includes an invisible toner and a visible toner. The volume average particle size of the toner is 2 μm or more and 5 μm or less, and the volume average particle size distribution index GSDv represented by the above formula (1) of the invisible toner is less than the volume average particle size distribution index GSDv of the visible toner. The developing device is smaller than 02 and smaller than 0.3 However, it is characterized in that a toner image is formed with a loading amount of invisible toner in an unfixed transfer image on a transfer material being 4.5 g / m ² or less when the image area ratio is 100%.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image recording method of the present invention will be described in detail with reference to the drawings with respect to an embodiment using the image forming apparatus of the present invention.

  FIG. 1 is a schematic diagram illustrating a configuration example of an image forming apparatus for forming a visible image and an invisible image. The illustrated image forming apparatus 100 includes an image carrier (electrostatic image carrier) 101, a charger (charging device) 102, an image writing device (exposure device) 103, a developing device (developing device) 104, a transfer roll (transfer device). ) 105, a cleaning blade 106, a fixing roll (fixing device) 107, and the like.

The image carrier 101 is formed in a drum shape as a whole, and has a photosensitive layer on its outer peripheral surface (drum surface). The image carrier 101 is provided to be rotatable in the direction of arrow A.
The charger 102 charges the image carrier 101 uniformly. The image writing device 103 forms an electrostatic latent image by irradiating image light onto the image carrier 101 uniformly charged by the charger 102.

The developing device 104 supplies toner to the surface of the image carrier 101 on which the electrostatic latent image is formed by the image writing device 103, performs development, and forms a toner image on the surface of the image carrier 101.
Here, the developer contained in the developer is an invisible toner only, a yellow toner only, a magenta toner only, and a cyan toner only, respectively. In general, a method called a tandem method can be used.

The transfer roll 105 is formed on the surface of the image carrier 101 while sandwiching the recording paper (recording medium, transfer material) conveyed in the direction of arrow B by a paper conveyance unit (not shown) with the image carrier 101. The toner image is transferred onto a recording sheet.
The cleaning blade 106 is for cleaning (removing) the electrophotographic toner remaining on the surface of the image carrier 101 after the transfer.
The fixing roll (fixing device) 107 includes at least a pair of rolls, one of which may be a pressure roll and the other a heating roll. The recording sheet onto which the toner image has been transferred is sandwiched between the pair of fixing rolls. The toner image transferred to the surface of the recording paper is fixed.

  In this way, when the image forming apparatus 100 using the electrophotographic method records an invisible image and a visible image such as a character, number, symbol, pattern, picture, or photographic image on the surface of the recording paper, the invisible / visible image is used. Since the formation is carried out consistently, it is possible to provide technology with excellent productivity and confidentiality management.

Furthermore, an image forming apparatus for simultaneously forming a visible image together with an invisible image will be described.
FIG. 2 is a schematic diagram showing a configuration example of an image forming apparatus for simultaneously forming a visible image together with an invisible image by the image recording method of the present invention.
The illustrated image forming apparatus 200 includes an image carrier (electrostatic image carrier) 201, a charger (charging device) 202, an image writing device (exposure device) 203, a rotary developing device 204, and a primary transfer roll (transfer device) 205. , A cleaning blade 206, an intermediate transfer member 207, a plurality of (three in the figure) support rolls 208, 209, 210, a secondary transfer roll 211, a fixing roll (fixing device) 212, and the like.

  The image carrier 201 is formed in a drum shape as a whole, and has a photosensitive layer on its outer peripheral surface (drum surface). The image carrier 201 is rotatably provided in the direction of arrow C in FIG. The charger 202 charges the image carrier 201 uniformly. The image writing device 203 forms an electrostatic latent image by irradiating the image carrier 201 uniformly charged by the charger 202 with image light.

The rotary developing device 204 includes five developing devices 204Y, 204M, 204C, 204K, and 204F that respectively accommodate yellow, magenta, cyan, black, and invisible toners. In this apparatus, since toner is used as a developer for image formation, yellow toner is used for the developing device 204Y, magenta toner is used for the developing device 204M, cyan toner is used for the developing device 204C, and cyan toner is used for the developing device 4K. The black toner and the invisible toner are accommodated in the developing device 204F, respectively.
The rotary developing device 204 is driven to rotate so that the five developing devices 204Y, 204M, 204C, 204K, and 204F sequentially approach and oppose the image carrier 201, whereby electrostatic latent images corresponding to the respective colors. The toner is transferred to the surface to form a visible toner image and an invisible toner image.

  Here, the developing devices other than the developing device 204F in the rotary developing device 204 may be partially removed according to the required visible image. For example, a rotary developing device including four developing devices such as the developing device 204Y, the developing device 204M, the developing device 204C, and the developing device 204F may be used. Further, a developing device for forming a visible image may be used after being converted to a developing device containing a developer of a desired color such as red, blue, or green.

  The primary transfer roll 205 sandwiches the intermediate transfer member 207 with the image carrier 201 and transfers the toner image (visible toner image or invisible toner image) formed on the surface of the image carrier 201 to an endless belt-like intermediate transfer. Transfer (primary transfer) is performed on the outer peripheral surface of the body 207. The cleaning blade 206 is for cleaning (removing) the toner remaining on the surface of the image carrier 201 after the transfer. The intermediate transfer member 207 has its inner peripheral surface stretched by a plurality of support rolls 208, 209, and 210, and is supported so as to be able to rotate in the direction of arrow D and in the opposite direction. The secondary transfer roll 211 is a toner image transferred to the outer peripheral surface of the intermediate transfer member 207 while sandwiching a recording sheet (recording medium) conveyed in the direction of arrow E by a sheet conveying unit (not shown) with the support roll 210. Is transferred (secondary transfer) to the recording paper.

  The image forming apparatus 200 sequentially forms a toner image on the surface of the image carrier 201 and transfers it on the outer peripheral surface of the intermediate transfer member 207, and operates as follows. That is, first, after the image carrier 201 is rotationally driven and the surface of the image carrier 201 is uniformly charged by the charger 202, the image carrier 201 is irradiated with image light from the image writing device 203 to statically. An electrostatic latent image is formed. The electrostatic latent image is developed by the yellow developing device 204Y, and then the toner image is transferred to the outer peripheral surface of the intermediate transfer member 207 by the primary transfer roll 205. At this time, the yellow toner remaining on the surface of the image carrier 201 without being transferred onto the recording paper is cleaned by the cleaning blade 206. Further, the intermediate transfer member 207 on which the yellow toner image is formed on the outer circumferential surface temporarily moves in the direction opposite to the arrow D direction while holding the yellow toner image on the outer circumferential surface, and then moves to the next magenta. A color toner image is provided at a position where the toner image is laminated and transferred onto the yellow toner image.

  Thereafter, with respect to each color of magenta, cyan, and black, similarly to the above, charging by the charger 202, irradiation of image light by the image writing device 203, formation of toner images by the developing devices 204M, 204C, and 204K, outer periphery of the intermediate transfer member 207 The transfer of the toner image to the surface is sequentially repeated.

  When the transfer of the four color toner images to the outer peripheral surface of the intermediate transfer member 207 is completed in this manner, the surface of the image carrier 201 is then uniformly charged by the charger 202 again, and then from the image writing device 203. Irradiation with image light forms an electrostatic latent image. This electrostatic latent image is developed by an invisible developing device 204F, and then the toner image is transferred to the outer peripheral surface of the intermediate transfer member 207 by the primary transfer roll 205. As a result, both the full color image (visible toner image) and the invisible toner image in which the four color toner images are superimposed are formed on the outer peripheral surface of the intermediate transfer member 207. The full color visible toner image and invisible toner image are collectively transferred to the recording paper by the secondary transfer roll 211. Thereby, a recording image in which a full-color visible image and an invisible image are mixed is obtained on the image forming surface of the recording paper. In the image recording method of the present invention using the image forming apparatus 200, in the region where the visible image on the image forming surface overlaps the invisible image, the invisible image includes the visible image forming layer, the recording paper surface, , Formed between.

  In the image recording method of the present invention using the image forming apparatus 200 shown in FIG. 2, the formation of a full-color visible image and the embedding of additional information by forming an invisible image can be performed simultaneously on the surface of the recording paper. An effect is obtained.

  Further, by making the resolution of the invisible image different from the resolution of the visible image at the time of image formation, for example, a filter that cuts a frequency component corresponding to the resolution of the visible image as data processing after reading the invisible image By performing the processing, it is possible to efficiently separate the signal (data) resulting from the invisible image and the noise signal resulting from the visible image, and to easily read the invisible image. Incidentally, the resolution at the time of image formation can be adjusted by controlling the writing frequency of the electrostatic latent image by the image writing device 203.

  In the image recording method of the present invention, a) an invisible image and a visible image are sequentially laminated on the surface of the recording medium, and b) the invisible image and the visible image are separately provided in different areas on the surface of the recording medium. The image recording method includes at least an image of a) or b), and the invisible image of a) or b) has a two-dimensional pattern.

Since the invisible image formed by the image recording method of the present invention is formed using the electrophotographic toner of the present invention, machine reading / decoding processing can be stably performed over a long period of time by infrared light irradiation. Thus, information can be recorded with high density.
In addition, since the invisible image has no color developability in the visible range and is invisible, any region on the image forming surface regardless of whether or not a visible image is provided on the image forming surface of the recording medium. Can be formed.

(D-2) Development Step In the image recording method of the present invention, the visible toner and the invisible toner described above are applied.
In the image recording method of the present invention, the applied amount (TMA) of the invisible toner and the visible toner in the unfixed transfer image is 4.5 g / m ² or less when the image area ratio is 100%. It is preferably 3.5 g / m ² or less, more preferably 3.0 g / m ² or less.
When the toner loading is 4.5 g / m ² or less, the image obtained as described above is improved in image quality and the releasability of the transfer material from the heating roll is improved, so that the toner adheres to the heating roll. This is preferable because troubles such as an offset phenomenon caused by the toner and a paper jam caused by the toner following the heating roll do not occur.
However, in order to ensure sufficient color development of the toner in the obtained image, TMA at an image area ratio of 100% is preferably 1 g / m ² or more, more preferably 1.5 g / m or more.

Furthermore, when forming an image by superimposing the three colors, it is preferably 14 g / m ² or less, more preferably 13 g / m ² or less, further preferably 12 g / m ² or less, including invisible toner. It is.
When the toner loading amount is 14 g / m ² or less, the image obtained by superimposing three colors as described above is improved in image quality and the releasability of the transfer material with respect to the heating roll is improved. This is preferable because troubles such as an offset phenomenon caused by adhering to the toner and a paper jam caused by the visible toner following the heating roll do not occur.

(D-3) Charging step, exposure step and transfer step The image recording method of the present invention charges the electrostatic latent image carrier in addition to the developing step of developing the latent image with toner to form a toner image. An exposure process for exposing the electrostatic latent image carrier to form a latent image, a transfer process for transferring the toner image onto a transfer material to form an unfixed transfer image, and a transfer onto the transfer material. And a fixing step for fixing the unfixed transfer image.

  In the present invention, any of the charging step, the exposure step method and the transfer step can be carried out by a known method employed in the conventional image forming method.

(D-4) Fixing Step The good releasability with respect to the fixing heating roll and the reduction in the occurrence of toner offset due to the small amount of applied toner can be advantageously achieved by combining a fixing device having a fluororesin on the outermost surface layer of the fixing device. Expressed.

  The fixing device in which a fluororesin layer such as PFA or PTFA is formed on the surface of the fixing roll or belt has a common problem that the toner peelability from the surface of the fixing device is lowered. This is because the surface of the fluororesin layer has low elasticity, so that it is impossible to ensure effective roll surface distortion for releasing the toner. However, a small-diameter toner with a small amount of applied toner can use a fixing roll or belt having a fluororesin surface, and can achieve both image quality and roll durability.

  In the recording method of the present invention, a heating contact type fixing device can be given as a specific example of the fixing device used for fixing the toner image. As the heating contact type fixing device, for example, a heating roller having a rubber elastic layer on a cored bar and, if necessary, a surface layer of a fixing member, and a rubber elastic layer on a cored bar are used. Correspondingly, a heat roller fixing device comprising a pressure roller having a surface layer of a fixing member, and a combination of the above roller and roller, a combination of a roller and a belt, or a combination of a belt and a belt. Instead, a heat belt fixing device or the like can be used, and among these, silicon rubber, fluororubber, and fluororesin are used for the surface layer, and among them, fluororesin is excellent in terms of wear resistance. As the fluororesin, a resin containing a large amount of fluorine such as polytetrafluoroethylene (PTFE) or a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (PFA) is suitable.

  In the image recording method of the present invention, a fixing device comprising a known release agent coating means can be used, and a so-called oilless fixing device without a release agent coating means can also be used. When using a fixing device comprising the release agent coating means, the supply amount of the release agent may be appropriately selected, but is preferably 2 mg / A4 or less.

  For the rubber elastic layer in the heat contact type fixing device, heat-resistant rubber such as silicone rubber or fluoro rubber is used. The thickness is preferably 0.1 to 3 mm, and the rubber hardness is preferably 60 mm or less. . By providing the rubber elastic layer on the roller which is a fixing member, the fixing member is deformed following the unevenness of the toner image on the transferred material, and the smoothness of the image surface after fixing can be improved. If the rubber elastic layer is too thick, the heat capacity of the fixing member increases, and it takes a long time to heat the fixing member, and the energy consumption may increase. The deformation of the fixing member may not be able to follow the unevenness of the toner image, so that melting unevenness may occur, or the rubber elastic layer may not have a strain effective for peeling.

  Silicone rubber, fluororubber, or fluororesin is used for the fixing member surface layer. Among these, fluororesins are excellent in terms of wear resistance. As the fluororesin, a resin containing a large amount of fluorine such as polytetrafluoroethylene (PTFE) or a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether (PFA) is suitable.

As the base material (core) of the fixing member, a material having excellent heat resistance, strong strength against deformation, and excellent thermal conductivity is selected. In the case of a roll-type fixing device, for example, aluminum, iron, Copper or the like is selected, and in the case of a belt-type fixing device, for example, a polyimide film, a stainless steel belt, or the like is selected.
The rubber elastic layer and the surface layer provided in the fixing member such as the roller may contain various additives according to the purpose. For example, for the purpose of improving wear resistance, controlling the resistance value, etc. You may contain ceramic particles, such as black, a metal oxide, and SiC. A release agent such as silicone oil can be applied to the fixing member for the purpose of further improving the releasability and wear resistance. There is no restriction | limiting in particular as said mold release agent, For example, liquid mold release agents, such as heat resistant oils, such as a dimethyl silicone oil, a fluorine oil, and a fluoro silicone oil, modified oils, such as an amino modified silicone oil, are mentioned.

(D-5) Other steps The image recording method of the present invention can also be applied to an electrophotographic system including a toner recycling step. The toner recycling process is a process of transferring the toner collected in the cleaning process to the developer layer. The present invention can also be applied to a recycling system in which the cleaning process is omitted and toner is collected simultaneously with development.

(F) Specific Example of Invisible Image Next, the toner set, the image recording method, the image configuration of the invisible image formed by the image forming apparatus, the visual recognition of the invisible image, the machine reading of the invisible image, etc. This will be specifically described.

  The invisible image is formed using the electrophotographic toner of the present invention, and is not particularly limited as long as it is machine-readable by irradiation with near infrared light, but is not limited to letters, numbers, symbols, patterns, pictures. Of course, the image may be a two-dimensional pattern such as a known barcode called JAN, standard ITF, Code 128, Code 39, NW-7, or the like.

  When the invisible image has a two-dimensional pattern such as a barcode, the serial number for identifying the image forming apparatus that has formed the image on the recording medium, or the visible image formed on the recording medium surface together with the invisible image is displayed. It can be used as a copyright certification number. Moreover, when the visible image formed with an invisible image takes the form of a confidential document, securities, a license, a personal ID card, etc., it can also be used effectively to detect the identification of these counterfeits.

In addition to the above barcode examples, in the present invention, the two-dimensional pattern is not particularly limited as long as it is a known recording method conventionally used as a visible and recognizable image.
For example, as a method of forming a two-dimensional pattern in which minute area cells are geometrically arranged, a two-dimensional barcode called a QR code can be cited. In addition, as a method of forming a two-dimensional pattern in which minute line bitmaps are geometrically arranged, a code forming method using a plurality of patterns with different rotation angles, which is a technique described in Japanese Patent Laid-Open No. Hei 4-233683 Is mentioned.

  By forming such an invisible image consisting of a two-dimensional pattern on the surface of a recording medium, it is possible to embed large amounts of information, such as music information, electronic files of text application software, etc. Thus, it is possible to provide a technique for creating a harder confidential document or a digital / analog information sharing document.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

<Developer of Example 1>
(Preparation of resin fine particle dispersion (L1))
-Oil layer 1-
・ Styrene (manufactured by Wako Pure Chemical Industries) ・ ・ ・ ・ 15.3 mass parts ・ n-butyl acrylate (manufactured by Wako Pure Chemical Industries) ・ ・ ・ ・ 0.46 mass parts ・ β-carboethyl acrylate (manufactured by Rhodia Nikka) -0.6 parts by mass-Dodecanethiol (manufactured by Wako Pure Chemical Industries) ... 0.2 parts by mass-oil layer 2-
・ Styrene (manufactured by Wako Pure Chemical Industries) ・ ・ ・ ・ 15.3 mass parts ・ n-butyl acrylate (manufactured by Wako Pure Chemical Industries) ・ ・ ・ ・ 0.46 mass parts ・ β-carboethyl acrylate (manufactured by Rhodia Nikka)・ 0.6 parts by mass ・ Dodecanethiol (manufactured by Wako Pure Chemical Industries) ・ ・ ・ ・ 0.4 parts by mass-water layer 1-
・ Ion-exchanged water ・ ・ ・ ・ 17.5 parts by mass ・ Anionic surfactant (manufactured by Rhodia) ・ ・ ・ ・ 0.35 parts by mass-water layer 2-
・ Ion-exchanged water ・ ・ ・ ・ 40 parts by mass ・ Anionic surfactant (manufactured by Rhodia) ・ ・ ・ ・ 0.05 part by mass ・ Ammonium persulfate (manufactured by Wako Pure Chemical Industries) ・ 0.3 part by mass

Half of the components described in the oil layer 1 and the water layer 1 are placed in a flask and mixed by stirring to obtain a monomer emulsified dispersion 1. Similarly, half of the oil layer 2 and the remaining water layer 1 are mixed by stirring. A mass emulsified dispersion 2 was obtained. The components of the aqueous layer 2 were put into a reaction vessel, and the inside of the vessel was sufficiently substituted with nitrogen and stirred, and then heated in an oil bath until the temperature in the reaction system reached 75 ° C.
First, the monomer emulsion dispersion 1 was dropped into the reaction vessel over 2 hours, and then the monomer emulsion dispersion 2 was dropped over 1 hour to carry out emulsion polymerization. Polymerization was further continued at 75 ° C. after completion of the dropping, and the polymerization was terminated after 3 hours to prepare a resin fine particle dispersion (L1).

The resin fine particles in the obtained dispersion were ₂₉₀ nm when the number average particle diameter D _50n was measured with a laser diffraction particle size distribution analyzer (LA-700, manufactured by Horiba, Ltd.).
It was 52 degreeC when the glass transition point of resin was measured with the temperature increase rate of 10 degree-C / min using the differential scanning calorimeter (The Shimadzu Corporation make, DSC-50).

Using a gel permeation chromatography molecular weight measuring instrument (HLC-8020, manufactured by Tosoh Corporation), the number average molecular weight (in terms of polystyrene) was measured using THF as a solvent.
In GPC measurement, two columns of “TSKgel, SuperHM-H (6.0 mm ID × 15 cm, manufactured by Tosoh Corporation)” were used, and the sample concentration was 0.5%, and the flow rate was 0.6 ml / min. The sample injection volume was 10 μl, and the measurement temperature was 40 ° C. The calibration curve is “polystylen standard sample TSK standard” manufactured by Tosoh Corporation: “A-500”, “F-1”, “F-10”, “F-80”, “F-380”, “A-2500”. , “F-4”, “F-40”, “F-128”, and “F-700”. The data collection interval in sample analysis was 300 ms.

  Thereafter, ion-exchanged water was added to adjust the solid content concentration in the dispersion to 40%. The solid content concentration was calculated from the mass of the dried product remaining by weighing 3 g of the dispersion and heating it at 130 ° C. for 30 minutes to volatilize water.

(Preparation of black pigment dispersion (K1))
Carbon black (Cabot, Regal 330) 20 parts by weight Anionic surfactant (Daiichi Kogyo Seiyaku, Neogen R) 2 parts by weight, ion-exchanged water 78 parts by mass

Using a homogenizer (Ultra Turrax T50, manufactured by LKA), the above components were mixed with water at 3000 rpm for 2 minutes, further dispersed at 5000 rpm for 10 minutes, and then stirred for one day with a normal stirrer to remove. After foaming, a black pigment dispersion (MN1) was obtained by dispersing for about 1 hour at a pressure of 240 MPa using a high-pressure impact disperser Ultimateizer (manufactured by Sugino Machine Co., Ltd., HJP30006).
The number average particle diameter D _50n of the pigment in the dispersion was 106 nm. Thereafter, ion exchange water was added to adjust the solid content concentration of the dispersion to 15%.

(Preparation of black toner (toner K1))
-Resin fine particle dispersion (L1) ... 160 parts by mass-Release agent fine particle dispersion (W1) ... 33 parts by mass (10% by mass with respect to toner)
-Black pigment dispersion (K1)-60 parts by weight (9% by weight based on toner)
・ Polyaluminum chloride 10% by mass aqueous solution 15 parts by mass (Asada Chemical Co., Ltd., PAC100W)
・ 1 mass% nitric acid aqueous solution ... 3 parts by mass

  The above components were dispersed in a round stainless steel flask using a homogenizer (manufactured by LKA, Ultra Turrax T50) at 5000 rpm for 3 minutes, and then a stirring device having a magnetic seal in the flask, a thermometer and pH After covering with a meter, set a heating mantle heater, and adjust to the minimum number of revolutions at which the entire dispersion in the flask is stirred and heat to 48 ° C at 1 ° C / 1 min with stirring. The temperature was maintained at 48 ° C. for 30 minutes, and the particle size of the aggregated particles was confirmed with a Coulter counter (TA II, manufactured by Nikka Kisha Co., Ltd.).

  Then, while confirming the aggregated particle size with a Coulter counter every 15 minutes, the temperature in the flask was heated at 0.1 ° C./15 min, and the temperature was increased when the volume average particle size of the aggregated particles reached 3.0 μm. Was stopped and kept at that temperature. At this time, the aggregate had a volume average particle size of 3.0 μm. Immediately after the temperature increase was stopped, 50 parts by mass of the resin fine particle dispersion (L1) was added and held for 30 minutes. Then, an aqueous sodium hydroxide solution was added until the pH in the system reached 6.5, and then at 1 ° C./1 min. Heated to 97 ° C. After the temperature rise, an aqueous nitric acid solution was added to adjust the pH in the system to 5.0, and the aggregated particles were heated and fused by holding for 10 hours.

  Thereafter, the temperature in the system was lowered to 50 ° C., an aqueous sodium hydroxide solution was added to adjust the pH to 12.0, and the mixture was maintained for 10 minutes. Then, after removing from the flask, sufficiently filtering using ion-exchanged water, washed with water, dispersed in ion-exchanged water so that the solid content becomes 10% by mass, added nitric acid and stirred at pH 3.0 for 10 minutes. Thereafter, the slurry obtained by sufficiently filtering and washing with water through ion exchange water again was freeze-dried to obtain a black toner (toner K1).

  The volume average particle diameter D50v and the volume average particle size distribution index GSDv of the toner K1 were measured with a Coulter Counter TAII (manufactured by Nikka Kisha Co., Ltd.). The size of the aperture was 50 μm. For the calculation of the particle size distribution, the cumulative distribution is drawn from the smaller diameter side with respect to the divided particle size range, and the particle sizes that become 16%, 50%, and 84% are respectively set to D16v, D50v, and D84v. As sought.

  The particle size range was divided from 1.26 to 50.8 μm into 16 channels and 0.1 intervals on the log scale. Specifically, channel 1 is 1.26 μm or more and less than 1.59 μm, channel 2 is 1.59 μm or more and less than 2.00 μm, channel 3 is 2.00 μm or more and less than 2.52 μm, and the log value of the numerical value on the left side is It was divided so that (log 1.26 =) 0.1, (log 1.59 =) 0.2, 0.3, ... 1.6.

  When D50v and GSDv were measured by the above method, the volume average particle diameter D50v of the toner K1 was 3.5 μm, the volume average particle size distribution index GSDv was 1.25, and the water content was 0.28%.

Further, when the surface of the toner K1 was observed with a scanning electron microscope (SEM) and the cross section was observed with a transmission electron microscope (TEM), the resin, pigment, and other additives were fused as intended, and holes and irregularities were not observed. The pigment dispersion state was also good.
Further, when the shape factor SF1 of the toner K1 was measured with a Luzex image analyzer, it was 135, and no particular shape distribution was observed.

Reaction of the toner K1 with silica (SiO ₂ ) fine particles having a volume average particle diameter of 40 nm, which has been surface-hydrophobized with hexamethyldisilazane (hereinafter sometimes abbreviated as “HMDS”), metatitanic acid and isobutyltrimethoxysilane. The product, metatitanic acid compound fine particles having a volume average particle diameter of 20 nm, were added in an amount of 1% by weight and mixed with a Henschel mixer to prepare a clotner.

  As a carrier, toluene obtained by dissolving 0.8 parts by mass of a styrene / butyl methacrylate copolymer (mass average molecular weight = 120,000) having a copolymerization ratio of styrene / butyl methacrylate of 25/75 in 10 parts by mass of toluene. 100 parts by mass of Mn—Mg ferrite particles (average particle size 40 μm) were put into the solution, and vacuum drying treatment was performed while heating and stirring, whereby the styrene / butyl methacrylate copolymer was coated on the Mn—Mg ferrite particles. The carrier of Example 1 was obtained. Further, 8 parts by mass of the toner and 100 parts by mass of the carrier were mixed with a V blender to obtain the developer of Example 1 (Developer 1). Using the developer 1 thus obtained, an image forming test was performed using an image forming apparatus, and various evaluations were performed.

<Developer of Example 2>
(Adjustment of cyan pigment dispersion (C1))
Cyan pigment (manufactured by Dainichi Seika Kogyo Co., PB15: 3) ... 20 parts by mass (12% by mass with respect to toner)
・ Anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., Neogen R) ・ ・ ・ ・ 2 parts by mass ・ Ion-exchanged water ・ ・ ・ ・ 78 parts by mass

The above components were adjusted in the same manner as the black pigment dispersion (K1) to obtain a cyan pigment dispersion.
The number average particle diameter D _50n of the pigment in the dispersion was 121 nm. Thereafter, ion exchange water was added to adjust the solid content concentration of the dispersion to 15%.

(Preparation of cyan toner (toner C1))
A cyan toner was obtained in the same manner as the above clotner, except that it was changed to a cyan pigment dispersion. The cyan toner C1 had a volume average particle diameter D _50V of 3.0 μm and a volume average particle size distribution index GSDv of 1.24.
An external additive was externally added to this toner in the same manner as the black toner to obtain a cyan toner C1.

<Developers of Examples 3 to 7>
The type of pigment particles used, the pigment concentration, etc. were changed as shown in Table 1, and the pH adjusted with the nitric acid aqueous solution in the production of the toner K1 and the aggregation time were changed, and the same as in the toner of Example 1. Thus, toners of Examples 3 to 7 shown in Table 1 were prepared.
Specifically, a toner having a large volume average diameter was prepared by changing the aggregation time. A toner having a large GSDv was prepared by controlling the stirring speed during aggregation.
The same carrier as in Example 1 was used as the carrier used in Examples 3 to 7, and a developer was prepared in the same manner as in Example 1.

Table 1 shows the produced developer containing visible toner.

<Preparation of invisible toner and developer>
(Developer of Example 8)
55 parts by weight of linear polyester as a binder resin, 40 parts by weight of copper phosphate crystallized glass A as a near infrared light absorber, and 5 parts by weight of wax (Fischer-Tropsch wax) as an additive are 100 weights of ethyl acetate. In addition to the part, it was sufficiently dissolved to adjust the oil phase.
On the other hand, a 40 parts by weight aqueous solution of calcium carbonate (luminous: manufactured by Maruo Calcium Co., Ltd.) was stirred with a ball mill for 24 hours to obtain a calcium carbonate dispersion.
Moreover, 2.5 weight part aqueous solution of carboxymethylcellulose (CMC: Daiichi Kogyo Seiyaku Co., Ltd.) was prepared.
Finally, the calcium carbonate dispersion and the carboxymethyl cellulose solution were mixed to prepare an aqueous phase. The solid content concentrations finally adjusted were 12 parts by weight and 0.5 parts by weight, respectively.

  Next, 100 parts by weight of the oil phase and 120 parts by weight of the aqueous phase were emulsified at 8,000 rpm for 5 minutes using an Ultra Turrax (IKA) emulsifier. After removing the solvent under reduced pressure with a rotary evaporator and adding hydrochloric acid (24% by mass) to dissolve calcium carbonate, the solid-liquid separation was repeated with a centrifuge, followed by drying in a 40 ° C. oven for 17 hours and the volume average particle size Particles having an average particle diameter D50v of 3.5 μm and a GSDv of 1.23 were obtained.

The linear polyester is synthesized from terephthalic acid, bisphenol A / ethylene oxide adduct, and cyclohexanedimethanol, and has a glass transition point Tg = 63 ° C., a number average molecular weight Mn = 4200, and a mass. Average molecular weight Mw = 33000, acid value = 20, and hydroxyl value = 25.
As external additives, 0.7 parts by mass of rutile-type titania particles (average particle size 25 nm) (manufactured by Teika, MT150AW) and 1.2 parts by mass of silica particles (average particle size 40 nm) (manufactured by Nippon Aerosil Co., Ltd., OX50) Using an Henschel mixer, externally added to 100 parts by mass of the previously obtained particles, the invisible toner of Example 8 was obtained.
On the other hand, as a carrier, 0.8 part by mass of a styrene / butyl methacrylate copolymer (mass average molecular weight = 120,000) having a copolymerization ratio of styrene / butyl methacrylate of 25/75 is dissolved in 10 parts by mass of toluene. 100 parts by mass of Mn—Mg ferrite particles (average particle size: 40 μm) (F300, manufactured by Powdertech Co., Ltd.) were put into the toluene solution, and vacuum drying treatment was performed while heating and stirring. The carrier of Example 8 coated with a butyl methacrylate copolymer was obtained.

  Further, 8 parts by mass of the present toner and 100 parts by mass of the carrier were mixed with a V blender to obtain a developer of Example 8.

(Developer of Example 9)
52 parts by mass of linear polyester as a binder resin, 40 parts by mass of copper phosphate crystallized glass B as a near-infrared light absorber, and anatase-type titania particles (average particle size 35 nm) as an additive (manufactured by Sakai Chemical Co., Ltd.) , SSP-M) In the same manner as in Example 8 except that 3 parts by mass were used, particles having a volume average particle size of 3.1 μm and GSDv 1.21 were obtained.
The linear polyester is synthesized from terephthalic acid, bisphenol A / ethylene oxide adduct, bisphenol A / propylene oxide adduct, and cyclohexanedimethanol, and has a glass transition point Tg = 70 ° C. The number average molecular weight Mn = 4600, the mass average molecular weight Mw = 38000, the acid value = 11, and the hydroxyl value = 23.

As external additives, 0.9 part by mass of rutile-type titania particles (average particle size 25 nm) (manufactured by Teika, MT150AW) and 1.0 part by mass of silica particles (average particle size 40 nm) (manufactured by Nippon Aerosil Co., Ltd., OX50) Using an Henschel mixer, externally added to 100 parts by mass of the previously obtained particles, the invisible toner of Example 9 was obtained.
Further, 8 parts by mass of this toner and 100 parts by mass of the carrier used in Example 8 were mixed with a V blender to obtain a developer of Example 9.
Using the developer thus obtained, an image forming test was performed using an image forming apparatus, and various evaluations were performed.

  Table 2 shows the compositions of the near-infrared light absorbers used in Examples 8 and 9.

(Developers of Example 10 and Example 11)
In the same manner as in Examples 8 and 9, the emulsification conditions were changed, and toners of Examples 10 and 11 were produced. Table 3 shows the composition and particle size distribution of the toner. Further, the same external additive as in Example 8 was added, and a developer was prepared using the same carrier as in Example 8.

(Developer of Example 12)
An invisible toner shown in Example 12 was produced in the same manner as in Example 8, except that the weight of the diimonium compound shown in Compound 1 below was changed to 20 parts by weight as a near infrared light absorber. The volume average particle diameter of the toner is 3.7 μm, and the GSDv is 1.26.
Further, a developer was prepared in the same manner as in Example 8.

(Developer of Example 13)
Other than changing the near-infrared light absorber to a vanadyl naphthalocyanine pigment (YKR-5010 (λmax; 925 nm, εmax; measured by dissolving in 9.3 × 10 ⁴ ml / g · cm sulfuric acid) manufactured by Yamamoto Kasei Co., Ltd.) Produced an electrostatic image developing toner 12 by the same composition and preparation method as in Example 8. When the obtained electrostatic image developing toner was measured based on the above-described measurement method, the average particle diameter was 3. .5 and the volume GSD was 1.25.
Further, a developer was prepared in the same manner as in Example 8.

(Developer of Comparative Example 1)
A mixture of toner raw materials consisting of 70 parts by mass of linear polyester as a binder resin and 30 parts by mass of copper phosphate crystallized glass A as a near infrared light absorber is kneaded with an extruder, pulverized, and then wind-powered Fine particles and coarse particles were classified by a classifier to obtain particles having a volume average particle size of 7.5 μm and a GSDv of 1.28.
The linear polyester is synthesized from terephthalic acid, bisphenol A / ethylene oxide adduct, bisphenol A / propylene oxide adduct, and cyclohexanedimethanol, and has a glass transition point Tg = 70 ° C. The number average molecular weight Mn = 4600, the mass average molecular weight Mw = 38,000, the acid value = 11, and the hydroxyl value = 23.

Next, as a second additive, rutile-type titania particles (average particle size 20 nm) (manufactured by Teika, MT150W-S) 1.0 part by mass and silica particles (average particle size 40 nm) (manufactured by Nippon Aerosil Co., Ltd., XOX515) The invisible toner of Comparative Example 14 was obtained by externally adding 0.8 parts by mass to 100 parts by mass of the previously obtained particles using a Henschel mixer.
Further, 8 parts by mass of the toner and 100 parts by mass of the carrier used in Example 8 were mixed with a V blender to obtain a developer of Comparative Example 1.

(Developer of Comparative Example 2)
A mixture of toner raw materials consisting of 60 parts by mass of linear polyester as a binder resin and 40 parts by mass of copper phosphate crystallized glass A as a near infrared light absorber is kneaded with an extruder, pulverized, Fine particles and coarse particles were classified by an equation classifier to obtain particles having a volume average particle size of 9.1 μm and a GSDv of 1.32.
The linear polyester is synthesized from terephthalic acid, bisphenol A / ethylene oxide adduct, bisphenol A / propylene oxide adduct, and cyclohexanedimethanol, and has a glass transition point Tg = 60 ° C. The number average molecular weight Mn = 3800, the mass average molecular weight Mw = 32,000, the acid value = 11, and the hydroxyl value = 23.
Next, as a second additive, rutile-type titania particles (average particle size 20 nm) (manufactured by Teica, MT150AW-S) 1.0 part by mass using a Henschel mixer, 100 parts by mass of the particles obtained previously Was added externally to obtain an invisible toner of Comparative Example 14. Further, 8 parts by mass of the present toner and 100 parts by mass of the carrier used in Example 8 were mixed with a V blender to obtain a developer of Comparative Example 2.

  The produced invisible toners of Examples 8 to 13 and Comparative Examples 1 and 2 are summarized in Table 3.

  Table 4 shows color toner sets obtained by combining the visible toners of Examples 1 to 7 and the invisible toners of Examples 8 to 13 and Comparative Examples 1 and 2.

<Invisible image formation by image forming apparatus>
A DocuColor 1250 manufactured by Fuji Xerox Co., Ltd. as shown in FIG. 1 was modified and used for an image formation test using visible toner and invisible toner prepared in each of Examples and Comparative Examples.
The invisible image is modified so that a standard ITF pattern can be output, and the invisible developer of the present invention is mounted in the yellow developer. In addition, as a recording medium used for the image formation test, A4 size white paper (Fuji Xerox, P-A4 paper, width: 210 mm, length: 297 mm) was used.

<TMA measurement>
A solid image with an area ratio of 100% was transferred onto a transfer material, and the weight of toner per unit area of the image area (TMA: g / m ² ) was measured.
As a specific measurement method, an unfixed solid image per 10 cm ² is formed on a transfer material, and this is weighed. Then, the toner on the transfer material is removed by air blow, and the weight of the transfer material alone is measured to measure the toner before and after the removal. TMA was measured from the amount.
The TMA measured for each developer is shown in Tables 1 and 3.

<Readability with barcode reader>
Each printed barcode is a THLS-6000 & TBR-6000 (using a 780 nm laser as the light source) as a barcode reader as a barcode reader, and an infrared light emitting diode (SHARP, GL480, peak emission wavelength 950 nm as a light source). ) Was used as a light receiving part (sharp, PD413PI, peak emission wavelength 960 nm).

  A reading test was performed 200 times with the above barcode reader, and evaluation was performed according to the following evaluation criteria. ◎ and ○ are practically acceptable ranges.

: All 200 times can be read.
◯: Can be read 198 to 199 times.
Δ: Can be read 196 to 197 times.
X: The number of times of reading is 195 times or less.

<Visibility>
The visibility of the invisible image was evaluated according to the following evaluation criteria. ○ is practically acceptable.
◯: Can hardly be confirmed with the naked eye.
Δ: Slightly visible with naked eyes.
X: Visible to the naked eye.

<Evaluation of absorption rate of invisible toner in visible light region>
A solid image of an invisible toner is formed on a recording medium, and the area where the solid image is formed and the surface of the recording medium on which no image is formed are measured with a spectral reflectance measuring machine (manufactured by JASCO Corporation, V- 570), and the spectral reflectance of each was substituted into formula (4) to obtain the visible light absorption rate (%) of the invisible toner.

<Fixing roll maintenance evaluation>
A durability test of 20,000 sheets was performed using the above-described image forming apparatus (Fuji Xerox Co., Ltd., DocuColor 1250 modified machine). After the durability test, the toner fixing property to the fixing roll was visually observed. ◎ is practically acceptable.

A: Adherence to the roll and contamination are not observed.
Δ: Some roll contamination.
×: Strong sticking occurs

<Readability with barcode reader after maintainability evaluation>
With the above-described image forming apparatus, the readability evaluation with a barcode reader was performed again after the durability test. The evaluation criteria were the same as described above.

<Evaluation of visible image quality>
The visual image quality was evaluated by visual comparison between the visible image of the recorded product 1 and the visible image of the recorded product 2 and the following criteria. The evaluation results are shown in Table 5.

○: There is no difference in the image quality of the visible images of the recorded matter 1 and the recorded matter 2 and there is no practical problem.
Δ: Compared with the visible image of the recorded matter 2, although the image quality of the visible image of the recorded matter 1 is slightly observed, there is almost no problem in practical use.
X: Compared with the visible image of the recorded matter 2, a clear image quality noise is confirmed in the visible image of the recorded matter 1, which causes a practical problem.

  The evaluation results obtained above are shown in Table 5.

  As shown in Table 5, in the image recording method and the image forming apparatus using the electrophotographic toner set of the present invention, an invisible image that can be machine-read / decoded by infrared light irradiation is stabilized over a long period of time. Thus, a visible image and an invisible image that can be output and information can be recorded at a high density can be obtained, and it has been revealed that it is extremely useful in practice.

1 is a schematic diagram illustrating a configuration of an image forming apparatus of the present invention. It is the schematic which shows the other structure of the image forming apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 101 Image carrier (electrostatic image carrier)
102 Charger (charging device)
103 Image writing device (exposure device)
104 Developer (Developer)
105 Transfer roll (transfer device)
106 Cleaning blade 107 Fixing roll (fixing device)
200 Image forming apparatus 201 Image carrier (electrostatic image carrier)
202 Charger (charging device)
203 Image writing device (exposure device)
204 Rotary developer (Developer)
204Y Yellow developer 204M Magenta developer 204C Cyan developer 204B Black developer 204F Invisible developer 205 Transfer roll (transfer device)
206 Cleaning blade 207 Intermediate transfer member 208, 209, 210 Support roll 211 Secondary transfer roll 212 Fixing roll (fixing device)

Claims (2)

A charging step for charging the electrostatic latent image carrier, an exposure step for exposing the charged electrostatic latent image carrier to form a latent image, and developing the latent image with a visible toner and an invisible toner to produce a visible toner image and an invisible toner. A developing process for forming a toner image on the electrostatic latent image carrier, a transfer process for transferring the invisible toner image together with the visible toner image onto a transfer material to form an unfixed transfer image, and on the transfer material A fixing step of fixing the unfixed transfer image transferred to the image recording method,
The amount of toner applied to the unfixed transfer image is 4.5 g / m ² or less when the image area ratio is 100%,
The invisible toner includes a near infrared light absorber;
The invisible toner and the volume average particle size of the visible toner are 2 μm or more and 5 μm or less,
A volume average particle size distribution index GSDv represented by the following formula (1) of the invisible toner is 0.02 or more and 0.3 or less smaller than a volume average particle size distribution index GSDv of the visible toner. .
Formula (1): GSDv = (D84v / D16v) ^0.5
[In the formula, D84v draws a cumulative distribution from the small diameter side in the particle size distribution and represents a particle size that is accumulated 84%, and D16v represents a particle size that accumulates 16%. ] Look including the invisible toner and a visible toner, there the invisible toner in electrophotographic toner set transferred onto the transfer material with the visible toner,
The invisible toner includes a near infrared light absorber;
The invisible toner and the volume average particle size of the visible toner are 2 μm or more and 5 μm or less,
The volume average particle size distribution index GSDv represented by the following formula (1) of the invisible toner is 0.02 or more and 0.3 or less smaller than the volume average particle size distribution index GSDv of the visible toner. Toner set.
Formula (1): GSDv = (D84v / D16v) ^0.5
[In the formula, D84v draws a cumulative distribution from the small diameter side in the particle size distribution and represents a particle size that is accumulated 84%, and D16v represents a particle size that accumulates 16%. ]

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