Color toner for flash fixing

[Technical field to which the invention belongs] The present invention utilizes an electrophotographic method.<u style="single">Regarding the image forming method, particularly regarding the image forming method of fixing the color toner on the recording medium by using the light energy from the flash light.</u>。

[0002] The electrophotographic method is a technique widely used in an image forming apparatus such as a copier, an electrophotographic facsimile, and an electrophotographic printer. As an electrophotographic method, a method using a photoconducting insulator is generally used, for example, as described in US Pat. No. 2,297,691. In this method, an electrostatic latent image is formed by irradiating a photoconducting insulator charged by a corona discharge or a charge supply roller with light such as a laser or an LED. Next, a resin powder (referred to as a colorant) colored with a pigment or dye called a toner is electrostatically adhered to the electrostatic latent image and developed to obtain a visualized toner image. Subsequently, this toner image is transferred onto a recording medium such as paper or film. However, since the toner image at this time is a powder image that is simply placed on the recording medium, it is necessary to fix the toner image on the recording medium. Therefore, as a final step, the toner is melted on the recording medium by heat, pressure, light, or the like and then solidified to finally obtain a toner image fixed on the recording medium.

[0003] As described above, toner fixing is generally performed by melting toner, which is a powder containing a thermoplastic resin (hereinafter referred to as a binder resin) as a main component, by heat and fixing it on a recording medium. is there. For that purpose, a heat roll method in which the recording medium on which the toner image is formed is directly heated and pressurized by a roller, and a flash fixing method in which the toner is fixed on the recording medium by irradiating a flash light such as a xenon flash lamp. Is well known.

[0004] Here, the flash fixing method is a method of melting the toner and fixing it on a recording medium by converting the light energy from the flash (flash light) of a discharge tube of a xenon flash lamp or the like into heat energy. is there.

[0005] Compared with the heat roll method, this flash fixing method has the following features when adopted in an image forming apparatus. (1) Since it is non-contact fixing, the resolution of the toner powder image formed on the photoconductive insulator layer is not deteriorated. (2) Quick start is possible without the need for warm-up time after turning on the power. (3) The material and thickness of the recording medium, such as glued paper, preprinted paper, and paper of different thickness, have little effect on fixing.

[0006] The process of fixing the toner on the recording medium by flash fixing is as follows. The flash light emitted from the discharge tube is absorbed by the toner image (powder image) on the recording medium and converted into thermal energy. As a result, the temperature of the toner rises, the toner softens and melts, and the toner adheres to the recording medium. After the flash light is emitted, the temperature drops, and the molten toner solidifies to form a fixed toner image.

[0007] However, for example, a xenon flash lamp generally used as a discharge tube for fixing a flash emits light over a wide range of wavelengths of 400 nm to 1400 nm, and in particular, is visible at 400 nm to 800 nm. The emission intensity in the near-infrared wavelength region of 800 nm to 1400 nm is remarkably stronger than the emission intensity in the region. Therefore, the toner to which flash fixing is performed is required to have high light absorption with respect to light in the near infrared wavelength region.

[0008] However, the binder resin, which is the main component of the toner, generally has extremely low light absorption in the visible and near infrared regions. Further, when the colorant is black, it exhibits high light absorption over the visible and near infrared regions. However, when the colorant is a colorant of a color toner such as yellow, cyan, magenta, red, blue, and green, it exhibits light absorption in the visible region but low light absorption in the near infrared region.

[0009] Therefore, it is difficult to fix the color toner containing the binder resin and the colorant for color with a flash light to the extent that the black toner is fixed. Therefore, it is necessary to supply strong light energy in order to fix the color toner.

[0010] Therefore, regarding fixing the color toner on the recording medium with flash light, a technique of adding an infrared light absorber having light absorption in the emission wavelength region of the xenon flash lamp in order to reduce the light energy. Has been proposed. For example, Japanese Patent Application Laid-Open No. 61-132959, Japanese Patent Application Laid-Open No. 6-18694, Japanese Patent Application Laid-Open No. 7-191492, and Japanese Patent Application Laid-Open No. 2000-147824 flash aminium-based compounds, diimonium-based compounds, and naphthalocyanine-based compounds. It discloses that it is contained in the fixing toner. Further, Japanese Patent Application Laid-Open No. 6-348056 discloses a technique for adhering resin particles containing anthraquinone-based, polymethine-based, and cyanine-based infrared light absorbers to the toner surface. Further, Japanese Patent Application Laid-Open No. 10-39535 discloses a technique for improving the fixability of a color toner by flash light by containing tin oxide and indium oxide.

[0011] The technique disclosed above improves the conversion of light energy to thermal energy by adding an infrared light absorber to the color toner, and increases the meltability of the binder resin as the main component. It is something that you try to make.

[0012] However, the binder resin has not yet been sufficiently melted only by the addition of the infrared light absorber. Further, the above-mentioned aminium-based compound, diimonium-based compound, etc. used as a preferable infrared light absorber are colored by themselves, and when used in a large amount, they adversely affect the saturation, hue, etc. of the color image after fixing. Therefore, it is preferable that the amount of the infrared light absorber used is as small as possible.

[0013] As described above, in the prior art, a large amount of light energy is still required in order to reliably fix the color toner with the flash light.

[0014] The present invention has been made in view of the above-mentioned circumstances. Therefore, the main object of the present invention is to reduce the light energy used and to reduce the amount of light energy used.<u style="single">An excellent image formation method using color toner for flash fixing</u>To provide.

[Means for Solving Problems]<u style="single">The above purpose is</u>, At least a color toner containing a binder resin, a colorant, and an infrared light absorber and fixed on a recording medium by flash light, and an infrared PAS spectrum obtained based on photoacoustic spectroscopy (PAS) analysis measurement. , PAS intensity integrated in the range of 1000 to 2000 nm is configured to be in the range of 0.01 to 0.2 when carbon black is 1.<u style="single">It is preferable to use the color toner</u>Achieved.

[0016] The photoacoustic spectroscopy (PAS) analysis method referred to in the present invention is Photoacoustic Spectroscopy, and this PAS analysis method irradiates a sample with intermittent light (flash light) to generate periodic heat in the sample. This is a method of finally detecting a change as a pressure change. This detection method can be measured in-situ (on the spot).

More specifically, the PAS analysis method used in the present invention will be described more specifically. First, when the modulated infrared light is absorbed by the sample, heat corresponding to the incident light is generated. This generated heat causes a pressure change in the surrounding gas layer, and this change is detected by a high-sensitivity microphone. Then, by Fourier transforming this, a spectrum similar to a normal infrared absorption spectrum is obtained.

[0018] The present invention uses the measurement results obtained by the PAS analysis method, and the PAS intensity of the color toner obtained by integrating the infrared PAS spectrum obtained based on the PAS analysis method in the range of 800 to 2000 nm is carbon black. It was found that the color toner in the range of 0.01 to 0.2 shows excellent fixability when 1 is set to 1. Such color toner can be fixed with low light energy, which is equivalent to the energy of flash light for fixing an image only with conventional black toner.

[0019] When the PAS intensity is less than 0.01, the light absorption of the color toner in the infrared region is low and the light-heat conversion efficiency is low, so that sufficient fixability cannot be obtained. Further, when the PAS intensity is greater than 0.2, sufficient fixability can be obtained, but a large amount of infrared light absorber is required to increase the PAS intensity, and the color image after fixing as described above is required. It has an adverse effect such as reducing the saturation of the image.

[0020] Also, claim<u style="single">3</u>1.<u style="single">Or 2</u>Described in<u style="single">Image formation method</u>The PAS strength of the color toner is preferably set to 0.2 to 0.9 times the PAS strength of the black toner to be fixed at the same time.

【0021】<u style="single">The above configuration</u>According to the above, the color toner fixed at the same time as the black toner on the recording medium by the image forming apparatus shows good fixability. That is, by setting the difference in PAS intensity between the color toner and the black toner within a predetermined range, the fixability of the color toner and the black toner can be made equal to each other.

[0022] When the PAS strength of the color toner is less than 0.2 times that of the black toner, the color toner becomes poorly fixed when flash-fixed with energy that gives the black toner good fixability. .. On the contrary, when the color toner is flash-fixed with energy that gives good fixability, the black toner has excessive flash light energy, and voids are generated due to excessive melting, resulting in deterioration of image quality. It ends up. As described above, when the PAS strength of the color toner is less than 0.2 times that of the black toner, it is difficult to satisfy the color toner and the black toner at the same time.

[0023] Further, when the PAS strength of the color toner is greater than 0.9 times that of the black toner, the fixability of the color toner and the black toner can be satisfied at the same time, but the infrared light absorber added to improve the PAS strength is added. In the case of a large amount, adverse effects such as a decrease in saturation of a color image occur.

[0024] Also, claim.<u style="single">4</u>1.<u style="single">From any of 3</u>Described in<u style="single">Image formation method</u>The PAS strength of the color toner is preferably set to 0.2 to 5 times the PAS strength of other color toners to be fixed at the same time.

【0025】<u style="single">The above configuration</u>According to the report, two or more kinds of color toners that are simultaneously fixed on a recording medium by an image forming apparatus show good fixability. That is, by setting the difference in PAS intensity of two or more types of color toners used at the same time within a predetermined range, the fixability of each color toner can be made equal.

[0026] Here, when the PAS strength of one color toner is less than 0.2 times that of other color toners, flash fixing is performed with energy that gives fixability to other color toners. , The color toner becomes poorly fixed. On the contrary, when the color toner is flash-fixed with energy that gives good fixability, the flash light energy of the other color toners is excessive, and voids are generated due to excessive melting, resulting in poor image quality. It will drop. As described above, when the PAS strength of the color toner is less than 0.2 times that of the other color toner, it is difficult to satisfy the color toner and the other color toner at the same time. Further, when the PAS strength of a certain color toner is more than 5 times that of another color toner, it is impossible to satisfy the fixability of the color toner and the other color toner at the same time.

[0027] Also, claim<u style="single">5</u>From claim 1 as described in<u style="single">4</u>Described in any of<u style="single">Image formation method</u>In the above, the configuration may contain at least two or more infrared light absorbers having different absorption wavelength spectra in the wavelength range of 800 to 2000 nm.

【0028】<u style="single">The above configuration</u>According to the above, the absorbance of the toner in the wavelength range of 800 to 2000 nm can be increased, thereby improving the PAS intensity of the color toner and realizing a good fixed image. Since the infrared light absorber as described above has an absorption peak in a specific range, the utilization efficiency of the irradiated light energy is poor even if the amount of one infrared light absorber is increased, and one infrared light absorption is further performed. If a large amount of the agent is used, problems such as poor saturation of the fixed image as described above occur. By using two or more infrared light absorbers with different absorption wavelength spectra together, the light energy irradiated can be used efficiently, and the fixed image quality deteriorates due to the use of a large amount of one infrared light absorber. Problems can also be reduced.

[0029] As the infrared light absorber, for example, a first infrared light absorber (A) having an absorption peak in the wavelength range of 800 to 1100 nm and a second infrared light absorber (A) having an absorption peak in the wavelength range of 1100 to 2000 nm. It can be configured to be used in combination with the infrared light absorber (B).

[0030] And the claim<u style="single">1</u>As described in the above, an image forming method including a step of irradiating a color toner containing at least a binder resin, a colorant, and an infrared light absorber with flash light to fix the color toner on a recording medium.<u style="single">Of the color toner</u>The relationship between the PAS intensity (S) obtained by integrating the infrared PAS spectrum obtained based on photoacoustic spectroscopy (PAS) analysis measurement in the range of 800 to 2000 nm and the energy (E) of the flash light is the following equation (1). The above object can be achieved as an image forming method including the flash fixing step in the above.

0.03 E · S 0.15 ...... (1) Claim<u style="single">1</u>According to the invention described in the above, it is possible to realize color image formation having good fixability and less generation of voids.

[0032] The above equation (1) can be satisfactorily fixed even if the PAS intensity of the color toner is low when the flash light energy is high, and it is good if the PAS intensity is high when the flash light energy is low. It means that a good fixing property can be obtained.

[0033] That is, if the product E / S is less than 0.03, fixing is poor, and if it exceeds 0.15, excessive energy is applied to the color toner, so that voids are generated and a good fixing image is obtained. Cannot be obtained. That is, the present inventors have found that when flash fixing is performed so as to satisfy the condition of the above equation (1), a good fixed image can be obtained while reducing the light energy. To achieve image formation that satisfies these conditions,<u style="single">Said</u>It is desirable to use the color toner of.

[0034] In addition,<u style="single">Said</u>By using the color toner of the above, a suitable flash fixing image forming method for fixing the color toner image on the recording medium by exposure with flash light can be realized, and in this method, the energy of the flash light is 0.5 to 2.5 J / cm.²The light emission time can be set to 500 to 3000 μs. As described above, it is possible to form a color image with stable fixing property even with low light energy as compared with the conventional one and less generation of voids.

[Embodiments of the Invention] Hereinafter, the present invention<u style="single">In</u>The color toner for flash fixing will be described in more detail. The present invention<u style="single">In</u>The color toner for flash fixing contains at least a binder resin, a colorant and an infrared light absorber. In this color toner, the PAS intensity obtained by integrating the infrared PAS spectrum obtained based on photoacoustic spectroscopy (PAS) analysis measurement in the range of 800 to 2000 nm is within the range of 0.01 to 0.2 when carbon black is 1. It is in<u style="single">Is preferable</u>.. Such color toners can be suitably used in image forming devices such as copiers, printers, and facsimiles that employ an electrophotographic method.

[0036] Here, the PAS strength of the toner can be obtained, for example, as follows. After taking the toner in a stainless steel dish and setting the PAS measurement unit, the atmosphere is replaced with He gas under the conditions of 10 ml / s and 10 s, and FT-IR (manufactured by Mattson) is used as a device equipped with a predetermined Fourier transform function. Measure using. The infrared PAS spectrum is obtained by assuming that the number of integrations is 200, and the infrared PAS spectrum is integrated in the range of 800 to 2000 nm to obtain the PAS intensity. Carbon black, which has high light absorption in a wide wavelength range, is used as a reference substance, and the PAS intensity of the color toner is determined by the relative intensity with the PAS intensity of the carbon black as the reference 1.

[0037] The infrared light absorber has a function of converting the light energy of flash light into heat energy at a fixing portion in an image forming apparatus. This infrared light absorber is originally added to promote the melting of the binder resin. A general infrared light absorber absorbs light having a wavelength in the range of about 800 to 2500 nm and converts light energy into heat energy. For example, the naphthalocyanine compound that can be suitably used for the color toner of this example absorbs infrared light in the range of about 800 to 1100 nm.

[0038] The present inventors have conducted extensive research to search for an infrared light absorber capable of absorbing in a wide wavelength range of 800 to 2500 nm, preferably 800 to 2000 nm. However, it has not been possible to find a single infrared light absorber capable of absorbing a wide wavelength range. That is, it was concluded that when one infrared light absorber is used, sufficient fixability cannot be imparted to the color toner unless a large amount is added to obtain a very high concentration.

[0039] However, this wide wavelength range is divided, for example, a first infrared light absorber (A) having an absorption peak in the wavelength range of 800 to 1100 nm and an absorption peak in the wavelength range of 1100 to 2000 nm. It was found that when used in combination with the second infrared light absorber (B), the fixability of the color toner can be improved with lower light energy than before while keeping the concentration of the infrared light absorber low. ..

[0040] Then, in such a color toner, the PAS intensity obtained by integrating the infrared PAS spectrum in the range of 800 to 2000 nm is in the range of 0.01 to 0.2 when carbon black is set to 1.

[0041] Further, in the image forming apparatus that forms a color image, the black toner and the color toner are fixed at the fixing portion at the same time. In this case, by setting the PAS strength of the color toner to 0.2 to 0.9 times the PAS strength of the black toner to be fixed at the same time, the color toner and the black toner can be used while reducing the light energy used for flash fixing. It can be fixed efficiently and well.

[0042] Further, in an image forming apparatus that forms a color image, a color toner of a certain color (for example, red) and a color toner of another color (for example, blue) are fixed at the fixing portion at the same time. In this case, by setting the PAS intensity of one color toner to 0.2 to 5 times the PAS intensity of other color toners to be fixed at the same time, the light energy used for flash fixing can be reduced while reducing the light energy. Each color toner can be fixed efficiently and satisfactorily.

[0043] The toner having a predetermined relationship with respect to PAS intensity as described above contains at least two or more infrared light absorbers having different absorption wavelength spectra in the wavelength range of 800 to 2000 nm.<u style="single">In</u>The color toner can be appropriately adjusted and manufactured.

[0044] FIG. 1 is a diagram showing the absorbance characteristics of a color toner (red toner) which is an example of the present invention, and FIG. 2 is a diagram showing the absorbance of a conventional color toner (red toner) to which one infrared light absorber is added. It is a figure which shows the characteristic.

[0045] In FIG. 1, a first infrared light absorber (A) having an absorption peak in the wavelength range of 800 to 1100 nm and a second infrared light absorber having an absorption peak in the wavelength range of 1100 to 2000 nm. Since both (B) and (B) are contained, two absorption peaks are formed. Therefore, infrared light is used efficiently.

[0046] On the other hand, in the conventional color toner shown in FIG. 2, since only one absorption peak is formed in the infrared region, infrared light cannot be used efficiently. Therefore, in order to raise this one peak, it has been necessary to add a large amount of infrared light absorber.

The present invention<u style="single">In</u>As the first infrared light absorber (A) that can be used in the color toner, for example, a naphthalocyanine compound can be used as the most suitable material. Further, as the second infrared light absorber (B), for example, an aminium-based compound or a diimonium-based compound can be used as the most suitable material.

[0048] The naphthalocyanine compound is represented by the following general formula.

[0049] [Chemical 1]<img file="JP3680752B2_D0001.tif" />(In the formula, M represents a metal, a metal oxide or a metal halide, and each of R1 to R3 represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group or a carboxyl group). The system compound is represented by the following general formula.

[0050] [Chemical 2]<img file="JP3680752B2_D0002.tif" />(In the formula, each of R1 to R8 represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group or a carboxyl group, and X^-Represents an anion) Further, the diimonium-based compound is represented by the following general formula.

[0051] [Chemical 3]<img file="JP3680752B2_D0003.tif" />(In the formula, each of R1 to R8 represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group or a carboxyl group, and X^-In addition, as infrared light absorbers other than the above, polymethine compounds, cyanine compounds, anthraquinone compounds, phthalocyanine compounds, dithiol-nickel complexes, metal complex compounds of azocobalt complexes, squarylium compounds, Tin oxide, itterbium oxide, itterbium phosphate and the like can also be used.

[0052] It is preferable to use two or more kinds of the infrared light absorbers exemplified above in combination, and further, an infrared light absorber having an absorption peak in the wavelength range of 800 nm to 1100 nm and an infrared light absorber having a wavelength of 1100 nm to 2000 nm. It is particularly preferable to use an infrared light absorber having an absorption peak in the range.

[0053] The amount of the infrared light absorber used in the color toner of this example is preferably 0.1 to 10 parts by weight, more preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the toner. The addition amount here is the total addition amount of the infrared light absorber used in combination.

[0054] As described above, when the amount of the infrared light absorber added is large, the hue of the toner image after fixing largely deviates from the original hue of the colorant, causing problems such as a decrease in the saturation of the image. However, the present invention<u style="single">In</u>With color toner, the amount of infrared light absorber used can be suppressed more than before. That is, a large amount of addition is required to obtain a sufficient infrared light absorbing ability with one infrared light absorbing agent. Therefore, the above-mentioned problem of image deterioration after fixing is also introduced. However, by using two or more infrared light absorbers with different absorption wavelength spectra together, the total infrared light absorption capacity can be reduced with a total amount smaller than the total amount when one infrared light absorber is used. Can be improved. Furthermore, since different infrared light absorbers have different colors, the problem of image deterioration after fixing can be suppressed.

[0055] The present invention<u style="single">In</u>As the binder resin contained in the color toner, a conventional thermoplastic resin can be used. For example, epoxy resin, styrene acrylic resin, polyamide resin, polyester resin, polyvinyl resin, polyurethane resin, polybutadiene resin, etc. with a glass transition temperature of 40 to 80 ° C and a softening point of 80 to 140 ° C may be used alone or in combination. Can be done. If necessary, wax (for example, carnauba, montan, polyethylene, amide, polypropylene, etc.) may be added to the binder resin.

[0056] The colorant that can be contained in the color toner of this example is not particularly limited, and a known colorant can be used. For example, monoazo-based red pigments, disazo-based yellow pigments, quinacridone-based magenta pigments, anthraquinone dyes, niglosin-based dyes, quaternary ammonium salts, monoazo-based metal complex salt dyes, and the like can be used. Moreover, you may use these in combination as appropriate.

[0057] Specifically, as the colorant, for example, aniline blue (CINo.50405) and calco oil blue (CINo.azoic) Blue3), Chrome Yellow (CINo.14090), Ultramarine Blue (CINo.77103), DuPont Oil Red (CINo.26105), Kinolin Yellow (CINo.47005), Methylene Blue Chloride (CINo.52015), Tartrazine Blue (CINo. 74160), Malakite Green Oxalate (CINo.42000), Edible Red No. 2 (Amaranth, CINo.16185), Edible Red No. 3 (Erythrosin, CINo.45430), Edible Red No. 40 (Arla Red AC, CINo.16035), Edible Red No. 102 (Ponceau 4R, CINo.16255), Edible Red No. 104 (Floxin, CINo.45410), Edible Red No. 105 (Rose Bengal, CINo.45440), Edible Red No. 106 (Acid Red, CINo.45100) , Edible Yellow No. 4 (Tartrazine, CINo.19140), Edible Yellow No. 5 (Sunset Yellow FCF, CINo.15985), Edible Green No. 3 (First Green FCF, CINo.42053), Edible Blue No. 1 (Brilliant Blue FCF) , CINo.42090), Edible Blue No. 2 (Indigo Carmine, CINo.73015), etc. can be used.

[0058] The content of the colorant is 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the toner.

[0059] As described above, in the color toner of the present invention, when the entire color toner is 100 parts by weight, for example, the binder resin is 75 to 95 parts by weight, and the colorant is 0.1 to 20 parts by weight, preferably 0.5 parts by weight. It is recommended to include ~ 10 parts by weight and 0.1 to 10 parts by weight, preferably 0.1 to 3 parts by weight of the infrared light absorber.

[0060] Further, the present invention.<u style="single">In</u>A charge control agent may be added to the color toner for the purpose of imparting chargeability and reducing the change in the amount of charge in different temperature and humidity environments. As the charge control agent, a colorless or light-colored one is recommended.

[0061] As the charge control agent, known positive charge and negative charge control agents such as a quaternary ammonium salt compound, a salicylic acid compound, a boric acid complex, and a carboxylic acid compound can be used.

[0062] The present invention<u style="single">In</u>The color toner can be produced by the same production method as before. At least, a binder resin, a colorant, and at least two or more kinds of infrared light absorbers having different absorbance characteristics in the wavelength range of 800 to 2000 nm are prepared, and if necessary, a charge control agent and a wax are added as raw materials. This raw material is kneaded and uniformly dispersed by, for example, a pressure kneader, a roll mill, an extruder or the like. Then, for example, it is pulverized and finely pulverized by a pulverizer, a jet mill, etc., and classified by a wind absorber or the like to obtain a color toner having a desired particle size distribution.

[0063] At the time of kneading, for example, as disclosed in Japanese Patent Application Laid-Open No. 7-191492, an infrared light absorber and a charge control agent are kneaded into separate resins, and then both are kneaded again. You may adopt the method of doing.

[0064] Further, the present invention<u style="single">In</u>In order to improve the fluidity of the color toner, the toner surface may be coated with inorganic fine particles (hereinafter referred to as an external additive). Here, the external additive that can be used has a particle size in the range of 2 nm to 500 nm, preferably 5 nm to 200 nm. In addition, the specific surface area by the BET method is 20 m.²/ g ~ 500m²It is preferably / g.

[0065] The present invention<u style="single">In</u>The ratio of the external additive mixed with the color toner is 0.1 to 5 parts by weight, preferably 0.1 to 2.0 parts by weight, based on 100 parts by weight of the toner. Examples of such an additive include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, silica ash stone, and silica soil. Fine particles of chromium oxide, cerium oxide, red iron oxide, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbonate, silicon nitride and the like can be used. Among these, it is preferable to use silica fine particles. It is more preferable to use an external additive whose surface is previously hydrophobically treated.

[Examples] Hereinafter, examples are shown to indicate the present invention.<u style="single">Image formation method</u>Will be described more specifically.

[0066] The present invention<u style="single">Used for</u>The color toners shown in Examples 1 to 7 were produced as color toners. The case where the infrared light absorber is used alone and the comparative example in which the addition amount is changed are also shown. (Example 1) Bending resin: Polyester resin (NCP-001J; manufactured by Nippon Carbide) 91 parts by weight Infrared light absorber (A): Naphthalocyanine compound (YKR-5010; manufactured by Yamamoto Kasei Co., Ltd.) (Maximum absorption wavelength 880nm) 1 part by weight Infrared light absorber (B): Aminium salt compound (NIR-AM1; manufactured by Teikoku Kagaku Sangyo Co., Ltd.) (Maximum absorption wavelength 1550nm) 1 part by weight Colorant: Copper phthalocyanine pigment (Lionol Blue ES; Toyo Ink (Manufactured by the manufacturer) 5 parts by weight Negative charge control agent: E-89 (manufactured by Orient Chemical Co., Ltd.) 2 parts by weight The above materials were put into a Henschel mixer, pre-kneaded, kneaded with an extruder, and then roughly pulverized with a hammer mill. Further, this was finely pulverized by a jet mill and classified by an air flow classifier to obtain a blue toner having a volume average particle size of about 8.5 μm. Next, 0.5 parts by weight of hydrophobic silica fine particles (H2000 / 4; manufactured by Clariant) were added as an external additive, and the external addition treatment was performed with a Henschel mixer to obtain a blue toner whose surface was coated with the external additive.

[0067] The PAS strength of the blue toner obtained as described above was measured. The measurement procedure is as follows. Take the blue toner on a stainless steel plate, set the PAS measurement unit (Photoacustic Model 300, manufactured by MTEC), replace the atmosphere with He gas under the conditions of 10 ml / s and 10 s, and then FT-IR (manufactured by Mattson). Was measured using. The infrared PAS spectrum was obtained by assuming that the number of integrations was 200, and the infrared PAS spectrum was integrated in the range of 800 to 2000 nm to obtain the PAS intensity. Carbon black was used as the reference material, and the PAS strength of the carbon black was used as the standard 1, and the PAS strength of the color toner was determined by the relative strength. The relative strength of this blue toner was 0.07.

Next, the blue toner was composed of a two-component developer, a toner image was formed on a recording medium using a flash fixing type printer, and the fixing property was evaluated.

[0069] A two-component developer was manufactured using a mixture of 4.5 parts by weight of the above blue toner and 95.5 parts by weight of a silicone-based resin-coated magnetite carrier (manufactured by Kanto Denka Kogyo Co., Ltd.) with a ball mill.

[0070] FIG. 3 is a diagram schematically showing a partial outline of an image forming apparatus 1 of a two-component developing method as an example. This device 1 is, for example, a high-speed development type with a process speed of 1100 mm / s, and has a charger 20, an exposure means 30, a developing means 40, a transfer device 50, a cleaner 60, and a static eliminator 70 around a photoconductor 10 made of amorphous silicon. , A flash fuser 80 or the like having a xenon flash lamp 81 is arranged. The developing means 40 includes a developing agent container 41, a developing roller 43, a stirring blade (not shown), and the like, and brings the toner particles TO and the carrier particles CA in the developing agent container 41 into contact with each other so that a predetermined amount of charge is applied to the toner. It has become.

In this embodiment, a laser printer (F676D; manufactured by Fujitsu Limited) that employs a xenon flash fixing method is used as an image forming apparatus to displace the bias potential applied to the flash lamp. As a result, the light energy emitted from the flash lamp can be changed per unit area of the recording medium (paper). Here, 1.8J / cm²A light energy with a light emission time of 1500 μsec was applied, and a powder image of blue toner was melted on paper and then solidified to obtain a fixed image. The fixability of this fixed image was evaluated.

[0072] The fixability was evaluated by a tape peeling test. In the tape peeling test, the fixed image is lightly attached with adhesive tape (Scotch Mending Tape; manufactured by 3M), and the cylindrical block is rolled in the circumferential direction so that the tape is brought into close contact with the image surface at a linear pressure of 250 g / cm. After that, the test method was performed without peeling off the tape, and the optical density ratio of the images before and after the tape was peeled off represented by the following formula was used as the fixing rate. A retention rate of about 70% was allowed. Fixation rate (%) = (Image density after tape peeling / Image density before tape peeling) × 100 The evaluation result of the blue toner in Example 1 was 90%, showing good fixability, and voids were generated due to excess light energy. Was not seen.

[0073] Here, the optical density of the fixed image is determined by measuring the reflected light in the wavelength range of 400 nm to 800 nm using a spectrophotometer (CM-3700d; manufactured by Minolta), and at the wavelength at which the absorbance is maximum. The absorbance value was taken as the optical concentration.

[0074] Since the fixing rate changes depending on the amount of toner on the paper, the fixing rate is measured when the amount of toner on the paper is 0.70 ± 0.05 g / cm.²The toner fixing rate (%), which is within the range of, was determined. (Example 2) A blue toner was produced in the same manner as in Example 1 except that the material composition of the color toner was as follows, and the PAS strength was obtained in the same manner. The PAS intensity of the blue toner of Example 2 was 0.05.

[0075] Further, as a result of performing the same fixing evaluation as in Example 1, the fixing rate was 80%, and good fixing property without void generation was shown.<img file="JP3680752B2_D0004.tif" />(Example 3) A blue toner was produced in the same manner as in Example 1 except that the material composition of the color toner was as follows, and the PAS strength was obtained in the same manner as described above. The PAS intensity of this toner was 0.02 with respect to carbon black 1.

[0076] Further, as a result of performing the same fixation evaluation as in Example 1, the fixation rate was 70%, and good fixation without the occurrence of voids was shown.<img file="JP3680752B2_D0005.tif" />(Comparative Example 1) A blue toner was produced in the same manner as in the examples except that the material composition of the color toner was as follows, and the PAS strength was obtained in the same manner as described above. The PAS intensity of this Comparative Example 1 toner was 0.005 with respect to carbon black 1. In addition, as a result of performing the same fixing evaluation as in Example 1, no voids were generated, but the fixing rate was as low as 50%, resulting in poor fixing.

[0077] This is because the PAS intensity of the toner of Comparative Example 1 is 0.005, which is much lower than that of each toner of the Example, and its energy utilization efficiency is high despite being irradiated with the same flash light. It can be inferred that it is bad.<img file="JP3680752B2_D0006.tif" />(Comparative Example 2) A blue toner was produced in the same manner as in Example 1 except that the material composition of the color toner was as follows, and the PAS strength was obtained in the same manner. The PAS intensity of the toner of Comparative Example 2 was 0.21.

[0078] Further, as a result of performing the same fixing evaluation as in Example 1, the fixing rate was as high as 90%, but a large amount of voids were generated and good fixing property could not be obtained.

[0079] The toner of Comparative Example 2 uses two types of infrared light absorbers in combination, and it can be seen that if the amount of the toner added is too large, the toner melts too much.<img file="JP3680752B2_D0007.tif" />Further, the examples and comparative examples shown below also take into consideration the situation in which the color toner and the black toner are actually fixed in the image forming apparatus, and a case where the color toner and the black toner are fixed at the same time will be described. (Example 4) The following black toner (No. 1 black toner) was produced in the same manner as the blue toner of Example 1, and the PAS strength was obtained in the same manner. The PAS intensity of the black toner produced in Example 4 was 0.1.

[0080] Using the blue toner of Example 1 and the No. 1 black toner, a fixing test was conducted in which these two types of toner were simultaneously fixed on paper as in the case of Example 1. The PAS intensity of the blue toner is 0.07, and the PAS intensity of the No. 1 black toner is 0.1. The PAS intensity of the blue toner with respect to the PAS intensity of the black toner is 0.7 (= 0.07 / 0.1).

[0081] The fixing rate in this example was 90% for blue toner and 95% for black toner, both of which showed good fixing property without void generation.

[No.1 Black Toner] Bound resin: Polyester resin (NCP-001J; manufactured by Nippon Carbide) 88 parts by weight Carbon: (# 25; manufactured by Mitsubishi Chemical Co., Ltd.) 10 parts by weight Negative charge control agent: S-34 (Orient) (Manufactured by Kagaku Co., Ltd.) 2 parts by weight (Example 5) Black as in Example 4 except that the PAS strength 0.02 (0.2 against No. 1 black toner) blue toner used in Example 3 was used as the color toner. Evaluation was performed using toner. The fixing rate in this example was 70% for blue toner and 95% for black toner, both of which showed good fixability with no void generation. (<u style="single">Reference example</u>) As the black toner, use the following No. 2 black toner (PAS strength 0.13), and as the color toner, use the PAS strength 0.02 (0.15 for No. 2 black toner) blue toner used in Example 3, and fix the light. The evaluation was performed in the same manner as in Example 4 except that the energy was changed to 2.5 J / cm2. As a result, the fixing rate was 75% for blue toner and 95% for black toner, but voids were generated on the black toner side and good fixability could not be obtained.

[No.2 Black Toner] Bundling resin: Polyester resin (NCP-001J; manufactured by Nippon Carbide) 83 parts by weight Carbon: (# 25; manufactured by Mitsubishi Chemical Co., Ltd.) 15 parts by weight Negative charge control agent: S-34 (Orient) (Made by Chemical Co., Ltd.) 2 parts by weight<u style="single">Reference example</u>The No. 2 black toner used in 1 has a higher PAS strength than the No. 1 black toner. Therefore, the fixing light energy suitable for the color toner (blue) of this embodiment may be too strong depending on the type of black toner.

That is, as described above, in the relationship between the color toner and the black toner used simultaneously by the present inventors, the PAS strength of the color toner is 0.2 to 0.9 with respect to the PAS strength of the black toner fixed at the same time. It was confirmed that it is preferable to set it to about twice. In addition, similar results could be obtained with color toners of other colors such as red, green, magenta, cyan, and yellow.

[0083] Although not shown here as an example, the present inventors have described Examples 4 and 5 and the above-mentioned Examples 4 and 5.<u style="single">Reference example</u>Similarly, the relationship between color toners was also examined. As a result, it has been confirmed that the PAS intensity of each color toner used at the same time is preferably set to 0.2 to 5 times the PAS intensity of other color toners. (Comparison example<u style="single">3</u>) As the black toner, the No. 1 black toner was used. Moreover, the blue toner used in Example 1 was used as the color toner. However, regarding the infrared light absorber added to this blue toner, the infrared light absorber (A) and the infrared light absorber (B) were each made 5 parts by weight, and the total amount was increased to 10 parts by weight. Under other conditions, the blue toner was produced in the same manner as in Example 1. The PAS intensity of this blue toner was 0.095 (0.95 with respect to the No. 1 black toner).

[0084] These toners were evaluated in the same manner as in Example 4. As a result, the fixing rate was 90% for the blue toner and 90% for the black toner, but the saturation of the fixed image of the blue toner was lowered, and a good image could not be obtained.

[0085] In this comparative example, since the infrared light absorber is added in a large amount, the fixability is improved, but it can be seen that the colored infrared light absorber has an adverse effect on the saturation of the fixed image. Examples and Comparative Examples further shown below show a case where the light energy (fixing energy) for flash fixing using the toner of Example 1 is changed. (Example 6) The energy of the flash light is 0.5 J / cm.²The toner was evaluated in the same manner as in Example 1 above, except that the emission time was changed to 3000 μsec. In this example, the fixing rate was 70%, and good fixing property was shown without the occurrence of voids. (Comparison example<u style="single">4</u>) Flash light energy 0.4J / cm²The toner was evaluated in the same manner as in Example 1 above, except that the emission time was changed to 500 μsec. In this comparative example, the fixing rate was 60%, resulting in poor fixing. In this comparative example, it can be inferred that the irradiated light energy is insufficient. (Comparison example<u style="single">5</u>) Flash light energy 3.1J / cm²The toner was evaluated in the same manner as in the case of Example 1 except that the toner was changed to. In this comparative example, voids were generated and good fixability could not be obtained. In this comparative example, it can be inferred that the irradiated light energy is excessive. (Comparison example<u style="single">6</u>) Flash light energy 1J / cm²The toner was evaluated in the same manner as in the case of Example 3 except that the toner was changed to. In this comparative example, no voids were generated, but the fixing rate was 60%, resulting in poor fixing. In this comparative example, it can be inferred that the irradiated light energy is excessive. (Comparison example<u style="single">7</u>) Flash light energy 3J / cm²The toner was evaluated in the same manner as in the case of Example 1 except that the toner was changed to. In this comparative example, voids were generated and good fixability could not be obtained. In this comparative example, it can be inferred that the irradiated light energy is excessive.

[0086] Example 6 above<u style="single">And comparative examples 4 to 7</u>As shown in, when the color toner of this example is used, the energy of the flash light is 0.5 to 2.5 J / cm.²Therefore, it is possible to realize a flash fixing process in which the fixing energy is reduced as compared with the conventional case, with a light emitting time of 500 to 3000 μs.

Further, as shown below, the present inventors pay attention to the product (E · S) of the PAS intensity (S) and the energy (E) of the flash light for the color toner, and this E · S It was also confirmed that excellent fixing of color toner can be achieved if the fixing is performed so that the value satisfies the condition of the equation (1).

0.03 E · S 0.15 ...... (1) Table 1 below shows Examples 1 to 1 to above.<u style="single">6</u>The E / S values are shown for the good color toners shown in (1) and the comparative example color toners that had problems. Also shows the relationship between the E · S value and the fixing rate in FIG. From Fig. 4, it can be confirmed that if the E / S value is too low, fixing is insufficient, and conversely, if it is too high, voids occur. Therefore, it can be confirmed from this that it is preferable that the E / S values are in the range of the above equation (1).

[0089] [Table 1]<img file="JP3680752B2_D0008.tif" /> Example 1 ~<u style="single">6</u>The color toner of the above formula (1) satisfies the condition of the above formula (1) (indicated by in the evaluation in Table 1), and conversely, the color toner of each comparative example satisfies the condition of the above formula (1). It can be confirmed that there is no such thing.

[0090] In addition, Example 4 and Example 5, and<u style="single">Reference example</u>Since the toner of No. 1 is a case where the black toner and the blue toner are fixed at the same time, both toners need to be in good condition. Therefore,<u style="single">Reference example</u>Evaluation is not possible (x) for the toner of No. 1 because the black toner has voids.

[0091] Further, with respect to Examples 1 to 3 and Comparative Example 1 shown above, the state of the fixing rate (%) when the fixing energy (energy of flash light) is changed with the light emitting time set to 1500 μsec is summarized. It is shown in Fig. 5.

[0092] From FIG. 5, in the color toners of Examples 1 to 3, the toner of Comparative Example has a poor fixing property of 1.75 J / cm.²It can be confirmed that high fixing property can be obtained even with lower fixing energy. That is, it can be confirmed that the color toner according to the present invention is a toner capable of reducing the fixing energy in flash fixing.

[0093] In the above example, as an example of the color toner according to the present invention, blue and black are shown, and a case where these are manufactured and a fixing test is performed has been described. However, the present invention is not limited to blue, and other colors such as red, green, magenta, cyan, yellow, etc. can be fixed reliably while reducing the light energy for fixing. Can be provided.

[0094] Further, in the above-described embodiment, the fixing test is performed by the two-component development method, but it goes without saying that the color toner of the present invention can be used as a magnetic or non-magnetic one-component toner.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiment, and various within the scope of the gist of the present invention described in the claims. Can be transformed / changed.

[Effect of the Invention] As is clear from the above-mentioned details, according to the invention of claim 1, the light energy for fixing can be reduced.<u style="single">Image formation method</u>Can be provided as. like this<u style="single">With the image formation method</u>Can be reliably fixed even with weak light energy that may cause poor fixing in the past. Since the amount of the infrared light absorber used can be suppressed, it is possible to form a clear color image without deterioration of the color image after fixing.

[0106] Also, claim<u style="single">3</u>According to the described invention, it is fixed on the recording medium at the same time as the black toner, and exhibits good fixability.<u style="single">Image formation method</u>Can be provided.

[0107] Also, claim<u style="single">4</u>According to the described invention, they are fixed on the recording medium at the same time and show good fixability to each other.<u style="single">Image formation method</u>Can be provided.

[0108] Also, claim<u style="single">5</u>According to the described invention, the absorbance of the toner in the wavelength range of 800 to 2000 nm can be surely increased, thereby improving the PAS intensity of the color toner and realizing a good fixed image.

[0109] Further, since two or more infrared light absorbers are used in combination, the flash light can be used more efficiently and the light energy can be surely reduced. Further, since the amount of the infrared light absorber used can be suppressed as a total amount, the influence on the formed image can be suppressed more reliably.

[0110] Also, claim<u style="single">1</u>According to the invention described in the above, it is possible to realize color image formation having good fixability and no void generation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing the absorbance characteristics of a color toner (red toner) which is an example of the present invention.

FIG. 2 is a diagram showing the absorbance characteristics of a conventional color toner (red toner) to which one infrared light absorber is added.

FIG. 3 is a diagram schematically showing a partial outline of a two-component development type image forming apparatus shown as an example.

FIG. 4 is a diagram showing the relationship between the E / S value and the fixing rate for each color toner.

[Fig. 5] Fixing energy (J / cm) for each color toner²) And the retention rate (%).

[Description of Code] 1 Image Forming Device TO Toner CA Carrier