JPH10319621A - Multicolor image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method to form such an image by using a toner that has uniform gloss and shows almost same high picture quality as a photograph on a printing paper by silver salt photography, and to form an image on which characters or marks can be written with a writing tool and tags can be easily stuck. SOLUTION: In this method, first, a latent image is formed on a latent image holding body by using light beams modulated according to the image information. Then a toner image is formed by using a powder toner of at least cyan, magenta and yellow colors on the latent image holding body. Then the toner image is transferred to a transfer body, and the toner image on the transfer body is fixed. Then the transparent layer is applied on the formed image surface. The transparent layer consists of an inorg. oxide fine particles having 1.40 to 1.60 refractive index and a water-soluble resin. The refractive index n of the binder resin which constitutes the powder toner, the refractive index N of the inorg. oxide fine particles above described, and the average thickness T (μm) of the transparent layer are controlled to satisfy the relation of -1.3<=(n-N)×T<=1.3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a multicolor image forming method for forming a multicolor image using a powder toner, such as electrophotography and electrostatic recording.

[0002]

2. Description of the Related Art Conventionally, when a multicolor image is formed by an electrophotographic system, for example, the following processing is performed. First, the reflected light from the document is color-separated by a color CCD and subjected to image processing and color correction by an image processing apparatus to obtain image signals of a plurality of colors. The signal is color-coded, for example, as a laser beam modulated using a semiconductor laser,
A plurality of electrostatic latent images are formed by irradiating an inorganic photoreceptor such as Se, amorphous silicon, or the like, or an organic photoreceptor using a phthalocyanine pigment, a bisazo pigment or the like for the charge generation layer a plurality of times, one color at a time. These electrostatic latent images are sequentially developed with, for example, four color toners of Y (yellow), M (magenta), C (cyan), and K (black), and the developed toner image is formed on the photoconductor surface. From the paper to a transfer body such as paper. Thereafter, the transferred unfixed toner image is heat-fixed by a heat fixing roll or the like to form an image.

[0003] The color toner is formed into particles having a particle size of 1 to 15 µm in which a pigment as a colorant is dispersed and contained in a binder resin such as a polyester resin, a styrene-acryl copolymer, a styrene-butadiene copolymer or the like. For example, a particle size of 5-1 of silicon oxide, titanium oxide, aluminum oxide, etc.
00nm inorganic fine particles, or polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF)
Can be obtained by attaching resin fine particles such as

Examples of the coloring pigment include: Y coloring agent: benzidine yellow, quinoline yellow, Hansa yellow M coloring agent: rhodamine B, rose bengal, pigment red C coloring agent: phthalocyanine blue, aniline blue, pigment blue K coloring agent : Carbon black, aniline black, a blend of color pigments and the like are used.

Japanese Patent Application Laid-Open No. Hei 4-242,752 discloses a method for obtaining a high-quality color image, in which a highly-dispersed pigment having a primary particle diameter substantially equal to the wavelength of visible light is contained in a resin. A method using a material that has been melt-dispersed so that aggregation does not occur is disclosed, and it is reported that color tone reproducibility is thereby improved.

By the way, in the color image formed on the transfer body by the above-described method or the like, the shape of the fixed toner particles remains, and the binder resin and the colorant are transferred to the transfer body (for example, paper). Due to the infiltration, the undulating shape of the transfer body itself remains, and the surface shape is irregularly rough as compared with a photographic paper image obtained by a silver halide photographic method. As a result, it is known that irregular reflection of light occurs on the image surface, and the gloss of the image surface becomes nonuniform between the image portion and the non-image portion.

The shape of the toner particles and the undulation of the transfer body itself due to the penetration of the binder resin greatly differ depending on the density of the image, and the type of the image such as a background portion, a low density portion, a high density portion, etc. As a result, the gloss and the graininess change, resulting in an unnatural image having less smoothness than a photographic paper image obtained by a silver halide photographic method. Further, the shape of the toner particles and the undulating shape of the transfer body greatly differ depending on the type of the transfer body, and it is difficult to obtain high image gloss and granularity with a transfer body having a surface.

In order to solve the above-mentioned problems, simply increasing the development weight of the toner can provide high gloss in a high density portion, but does not provide an effect in a non-image portion, and further reduces the charge amount. There is a drawback that fogging occurs in the non-image area due to reduction.

Incidentally, in order to solve the above problems, for example, Japanese Patent Application Laid-Open Nos.
JP-204670, JP-A-7-72669,
As described in JP-A-5-232840, a method of transferring and fixing a transparent toner on a transfer body in addition to a color toner, and JP-A-63-92964 and JP-A-63-92964.
As described in JP-A-92965, a method of coating a transfer member with a transparent resin in advance has been proposed. However, in these methods, the mechanical structure of the image structure, that is, the height of the toner layer remains between the developed portion and the blank portion, or the thickness of the transparent toner layer depends on the characteristics of the binder resin and the thickness of the transparent toner layer. It is difficult to control the mechanical undulating shape of the image surface, for example, the toner melts too much and soaks into the transfer body, or the toner particles do not melt sufficiently and the toner particle shape remains. The effect obtained is not sufficiently obtained.

In order to smooth the surface of the transparent resin layer provided on the surface of the image, a fixing method of a heating and pressing contact method is used, but the transparent toner resin forming the transparent resin layer is of the same type as the color toner. There is a problem that the use of the above resin causes a phenomenon that the resin of the molten transparent toner is offset to the fixing member. For the purpose of preventing the offset phenomenon, a release agent such as oil is applied to the surface of the fixing member. In this case, however, there is a problem that the release agent is transferred onto the image surface after fixing.

In recent years, with the spread of electrophotographic full-color copying machines and printers becoming remarkable, a full-color image created by an electrophotographic system has a memorandum written on a surface of the image by a writing tool, similarly to an image produced by printing. In business documents, sticky notes are often attached to image surfaces. However, when the release agent such as oil remains on the surface of the image as described above, it is difficult to attach a sticky note for writing a memo, and for the same reason, characters or the like written by a writing instrument are not clear.

As a method of forming a transparent resin layer on an image surface without using a transparent toner, Japanese Patent Application Laid-Open No. 5-24 / 1993
Japanese Patent No. 9724 discloses a method in which only a transparent resin layer is transferred to an image surface by heating and pressing a film on which a transparent resin layer has been formed in advance. In this method, a transparent resin layer is provided as a post-processing on the surface of an image prepared in advance, and a high gloss image is obtained. In this method, since the resin forming the transparent resin layer does not directly contact the heating and pressing member, no problem such as offset occurs. However, since wax is added as a release agent to the inside of the transparent resin layer to prevent offset between the film and the transparent resin layer, in this method, similarly to the above, writing with a writing instrument and pasting of a sticky note are performed. A problem arises.

Further, JP-A-7-56409, 7
JP-A-56410 and JP-A-7-72695 disclose an image forming method in which an image is formed on a transparent film, a white sheet is attached from the image surface, and the transparent film surface becomes the image surface. . According to this method, an image having a high gloss surface can be obtained by using a film having a smooth surface. However, in the above-described method, a thermoplastic adhesive is used to adhere the white sheet and the image, but the image formed on the transparent film earlier at the time of heat bonding is dissolved in the adhesive,
The shape of the pixels of the original image formed on the transparent film is significantly disturbed. There is no problem of offset, but it is difficult to fill in depending on the type of writing instrument.

That is, in order to obtain a final image having a smooth and high-gloss image surface by using a transparent toner, it is necessary to use a heat and pressure contact fixing system. For this purpose, a step of transferring the surface shape of the heat and pressure fixing member having a smooth surface to the image surface is essential. However, in this step, the problem of offset caused by direct contact between the toner resin and the fixing member must be avoided,
To avoid this, it is necessary to form a release agent layer on the surface of the fixing member. As a result, the release agent is transferred to the surface of the produced image, so that it is difficult to attach a sticky note, and it is difficult to write clear characters or the like with a writing instrument. In the image production method using a transparent plastic film as the image surface, no offset problem occurs, but the problem remains that the shape of the pixels of the image is disturbed and writing with a writing instrument is difficult.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances in the prior art, and has been made to solve the problems. That is, an object of the present invention is to provide a method for producing a high-quality image close to a photographic paper photograph produced by a silver halide photograph having uniform glossiness over the entire image in a multicolor image forming method using powder toner. To provide. Another object of the present invention is to provide an image forming apparatus which does not generate an offset when forming a transparent layer on the entire surface of a powder toner image and forms an image on the surface where writing with a writing instrument and sticking of a sticky note can be easily performed. It is to provide a method.

[0016]

As a result of repeated studies of a method for achieving the above object, the present inventor has found that a photographic paper produced by a silver halide photographic method on a transfer member using a powder toner. In order to obtain a high quality image having an image surface with a uniform glossiness like a photograph, when forming a transparent layer on the entire image surface, the transparent layer is formed using a substance other than a powder toner resin or a plastic film. Thus, the present invention has been completed.

That is, the multicolor image forming method of the present invention comprises:
An exposure step of forming a latent image on the latent image holding member using light modulated by image information, and forming a toner image on the latent image holding member using a powder toner composed of at least cyan, magenta, and yellow toners; A developing step of forming, a transfer step of transferring the toner image onto a transfer body, and a fixing step of fixing an unfixed toner image on the transfer body, further comprising a step of providing a transparent layer on the surface of the formed image And the transparent layer has a refractive index of at least 1.40 to 1.60.
And the refractive index n of the binder resin used for the powder toner, the refractive index N of the inorganic oxide fine particles, and the average thickness T (μ) of the transparent layer.
m) satisfies the following expression (1). -1.3 ≦ (n−N) × T ≦ 1.3 (1) In the multicolor image forming method of the present invention, the oxidized inorganic fine particles used are silica fine particles, and the silica fine particles have an average primary particle diameter of 10 nm. The following is preferred. In the multicolor image forming method of the present invention, the water-soluble resin used is preferably polyvinyl alcohol. Further, in the multicolor image forming method of the present invention, the weight ratio of the mixture of the oxidized inorganic fine particles and the water-soluble resin for forming the transparent layer is preferably in the range of 1: 1 to 10: 1.

In the present invention, the average thickness T of the transparent layer in the above relational expression (1) can be determined as follows. A portion including an image portion and a non-image portion is cut out of an image produced by the multicolor image forming method, and embedded in an embedding agent made of an epoxy resin. After the embedding agent is cured, the image is cut with a diamond knife and cut into ultrathin sections (thickness 0.05 to 0.20 μm). The cut ultrathin film section is mounted on a transmission electron microscope and observed. By performing this observation a plurality of times for each part of the prepared image, the average thickness of the transparent layer formed on the image surface can be measured from the cross-sectional structure of the fixed image.

Specifically, the observation image of the cross section of the image is photographed on a negative film, and then a transmitted light image is photographed with a CCD camera.
The captured image is converted into a digital signal and stored as digital data, or an image observed by a transmission electron microscope is directly captured by a CCD camera, and the captured image is converted into a digital signal and stored as digital data. The digital data of the stored image is subjected to image processing by a known image processing apparatus or a personal computer equipped with software capable of performing image processing, and the image structure is analyzed.

Next, a method for obtaining the average thickness T of the transparent layer will be described. First, the digital data is converted into an observation image and displayed on a display, and the embedding agent portion, the powder toner image portion, the transfer body portion, and the transparent portion are detected, and the respective boundaries are determined. Next, the observation image is arranged so that the powder toner image portion and the non-image portion on the image surface of the observation image have the same width. Next, the area of only the transparent layer portion was measured from the entire observation image, and the average thickness of the transparent layer in the observation image was divided by the added width of the powder toner image portion and the non-image portion displayed on the display. Ask for. By performing this operation for 10 points of the prepared image, the average thickness T of the transparent layer of the entire image can be obtained.

FIG. 1 illustrates the case, in which 11 is a transfer member, 12 is a powder toner image portion, 13 is a transparent layer, 14 is an embedding agent, and 1 is displayed on a display. The width of the powder toner image portion and the width of the non-image portion, L, are obtained by adding the widths of the powder toner image portion and the non-image portion.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the multicolor image forming method of the present invention will be described. First, using a light modulated by image information, an exposure step of forming a latent image on a latent image holding body by the exposure, and a powder toner comprising at least cyan, magenta and yellow toner on the latent image holding body Through a developing step of forming a toner image by using a toner, a transferring step of transferring the formed toner image onto a transfer body, and a fixing step of fixing an unfixed toner image on the transfer body. An image composed of a toner image is formed.

As the latent image holding member, an electrophotographic photosensitive member, a dielectric recording material, or the like is used, and an electrostatic latent image is formed by a known method. The formed electrostatic latent image is then developed using a powder toner composed of cyan, magenta, and yellow toners.
Magenta and cyan toners are obtained by dispersing a coloring agent such as a pigment or a dye in a binder resin. In the present invention, a black toner may be used.

As the colorant and the binder resin, conventionally known ones can be used, and there is no particular limitation. For example, the following are mentioned as coloring agents. Yellow colorant: Benzidine yellow, Quinoline yellow, Hansa yellow Magenta colorant: Rhodamine B, Rose Bengal, Pigment red Cyan colorant: Phthalocyanine blue, Aniline blue, Pigment blue Black colorant: Carbon black, Aniline black, blend of color pigments Are used.

Examples of the binder resin include styrene resin, acrylic resin, styrene-acryl resin, styrene-butadiene resin, vinyl chloride resin, vinyl acetate resin, polyester resin, polyurethane resin, polyamide resin, epoxy resin and the like. Although it can be used, the viscosity of the powder toner at the time of fixing is 10 ² Pa · s to 10 ⁵ Pa in consideration of fixing of the powder toner image on the transfer body.
S is preferred. If the viscosity of the powder toner at the time of fixing is less than 10 ² Pa · s, an offset to the fixing roll tends to occur when fixing is performed by the fixing roll. On the other hand, if it exceeds 10 ⁵ Pa · s, the powder toner does not melt and soften, and the adhesion to the transfer member and the adhesion between the toner particles become insufficient, so that sufficient fixing strength cannot be obtained.

In order to obtain more preferable color tone reproducibility, the colorant should have a primary particle size in the range of 0.01 to 1 μm, preferably 0.1 to 1 μm, and the same as the primary particle size. It is preferable to use a resin which is melted and dispersed in a resin.

The colorant melt-dispersed in the resin as used herein means that the resin is melted by heating or dissolved in a solvent, and a wet cake of the colorant obtained in the color material forming step is kneaded. A colorant is dispersed in a resin in the form of primary particles, solidified by cooling or removing a solvent, and then pulverized.

When developing with toner, an inorganic powder, for example, as a fine particle imparting fluidity, may be adhered to the surface of the toner particles. Examples of the inorganic powder include silica, titanium oxide, tin oxide, and aluminum oxide commonly used in the art, and have a particle size of 0.001 to 0.001.
Those having a range of 0.1 μm can be used. Further, the inorganic powder adhered to the surface of the toner particles may be treated with various treating agents in order to impart stability to the charging environment.

Further, the particle diameter of the powder toner used in the present invention is preferably in the range of 1 to 9 μm in order to improve the granularity. When the toner particle diameter is larger than 9 μm, the toner particles are recognized and the granularity is remarkably disturbed, so that the effect of the present invention cannot be sufficiently obtained.
On the other hand, if the toner particle size is less than 1 μm, the number of toner particles charged to the opposite polarity increases, causing fogging to the background portion, and a satisfactory image cannot be obtained.

In the present invention, as a method for transferring the powder toner image formed on the latent image holding member onto the transfer member, any known method such as electrostatic transfer and adhesive transfer can be used. be able to.

As a method for fixing the unfixed toner image on the transfer member, a known fixing method using a fixing device having a heating means such as oven fixing, radiant fixing, and roll fixing can be used.

Further, as a material of a transfer body for forming a powder toner image, any material capable of transferring a toner image, such as a paper sheet of wood pulp fiber, processed paper, synthetic paper, plastic sheet, metal sheet, etc. Any one may be used.

A transparent layer is provided on the surface of the image formed of the powder toner image formed on the transfer member. Examples of the inorganic oxide fine particles forming the transparent layer include silica fine particles, colloidal silica and calcium silicate. , Zeolite,
Kaolinite, halosite, muscovite, talc, calcium carbonate, calcium sulfate, boehmite, zinc oxide, barium carbonate and the like can be mentioned, but from the viewpoint of not lowering the transparency, the refractive index is 1.40 to 1.60. It is necessary to use those in the range. In the present invention, the inorganic oxide fine particles have an average primary particle diameter of 10 n.
m, particularly preferably 1 to 9 nm.

When the refractive index exceeds 1.60, the refractive index difference from air becomes large, and the illumination light is scattered on the surface of the transparent layer, and the color tone is remarkably compared with the image before forming the transparent layer. Inferior image. If the refractive index is less than 1.40, the difference in refractive index from the binder resin used for the powder toner becomes large, and the illumination light incident from the image surface at the boundary between the powder toner image and the transparent layer is scattered. The color tone is remarkably inferior to the image before forming the transparent layer. From the viewpoint of not lowering the transparency, silica fine particles which are inorganic oxide fine particles having a refractive index in the range of 1.40 to 1.60 are preferable, and fine particles having an average primary particle diameter of 10 nm or less, particularly an average primary particle diameter of 1 nm or less. Silica fine particles having a refractive index of 1.45 to 9 nm are preferable.

The method for producing the silica fine particles includes a wet method and a dry method. The most commonly used wet method is a method in which activated silica is generated by acid decomposition of silicate, which is appropriately polymerized and coagulated and settled to obtain hydrous silica. In general, a dry method is a method in which anhydrous silica is obtained by high-temperature gas-phase hydrolysis of silicon halide, or a method in which silica sand and coke are heated and reduced by an electric arc in an electric furnace and oxidized with air. This is a method of obtaining anhydrous silica.

As the resin used for the transparent layer, a water-soluble resin which does not cause an offset problem with the fixing member is used from the viewpoint of applying heat and pressure when fixing the transparent layer on the image surface.
Examples of the water-soluble resin include polyvinyl alcohol, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyethylene glycol, and polyvinyl ether. Among them, from the viewpoint of transparency, polyvinyl alcohol is particularly preferable when silica fine particles are used as the inorganic oxide fine particles. Although polyvinyl alcohol has a hydroxyl group in the structural unit, it is considered that this hydroxyl group forms a hydrogen bond with a silanol group on the surface of the silica fine particles, and a three-dimensional network structure having a secondary particle of the silica fine particles as a chain unit is likely to be formed. .

The weight ratio of the inorganic oxide fine particles to the water-soluble resin is preferably in the range of 1: 1 to 10: 1. If the weight ratio of the inorganic oxide fine particles to the water-soluble resin exceeds 10, the mechanical strength of the transparent layer becomes insufficient, or the transparent layer cracks during drying in the fixing step of the transparent layer. In addition, when it is less than 1, the gap between the three-dimensional network structures decreases, so that a writing instrument,
In particular, it is difficult to write with a writing instrument using a water-soluble or oil-based ink. In consideration of the mechanical strength of the transparent layer and the writing property with a writing instrument, the weight ratio of the inorganic oxide fine particles to the water-soluble resin is more preferably in the range of 2: 1 to 5: 1.

In the present invention, the relationship between the refractive index n of the binder resin used in the powder toner, the refractive index N of the inorganic oxide fine particles forming the transparent layer, and the average thickness T of the transparent layer is as follows.
It is necessary to be in the range of -1.3 ≦ (n−N) × T ≦ 1.3, and more preferably in the range of −1.0 ≦ (n−N) × T ≦ 1.0. . When the refractive index n, the refractive index N, and the average thickness T of the transparent layer do not satisfy the above relational expression, the incident light entering from the surface of the image is absorbed by the transparent layer so that a dark image is produced. Become.

As a method of forming a transparent layer on the surface of an image composed of a powder toner image, for example, the following method can be used. As a coating solution for forming a transparent layer, an average primary particle diameter of 10
The silica fine particles having a particle size of not more than 10 nm are added to water, and the homogenizer (manufactured by Nippon Seiki Co., Ltd.) is used.
After dispersing for 0 minute, an aqueous solution of polyvinyl alcohol is added, and the mixture is further dispersed under the above-mentioned conditions, and is applied onto an image composed of a powder toner image. As a method for applying the coating liquid, for example, a method using a known means such as a blade coater, a bar coater, a reverse roll coater or the like can be used.

The drying and fixing of the coating liquid applied on the image formed of the powder toner image is performed by a method of heating and pressing with a calender roll, or a method of pressing against a smooth metal surface and drying. be able to. In that case, the drying temperature at the time of drying is preferably lower than the softening point of the binder resin used for the powder toner. If calendering or pressing drying is performed at a temperature higher than the softening point, the image composed of the powder toner image formed on the transfer body is melted, and the pixels of the image before forming the transparent layer are remarkably disturbed. Significantly deteriorates the color tone and graininess.

In the present invention, there is no need to apply a release agent such as oil to the surface of the drying member since no offset occurs between the surface of the drying member and the above-mentioned coating solution during calendering and pressure drying. For this reason, since there is no release agent on the surface of the produced final image, it is possible to easily attach a sticky note to the image surface. The transparent layer formed as described above can be easily written on an image with a writing instrument, particularly a writing instrument using a water-soluble or oil-based ink.

The method for forming the transparent layer on the powder toner image is not limited to the method exemplified above, and various methods other than those described above can be adopted.

[0043]

EXAMPLES Specific examples of the present invention will be described below. Example 1 As a powder toner, Fuji Xerox's Acolor
Cyan, magenta and yellow toners.
The binder resin used for each toner was a linear polyester resin (linear polyester obtained from terephthalic acid / bisphenol A ethylene oxide adduct / cyclohexanedimethanol Tg = 62 ° C., Mn = 4,000, M
w = 35,000, acid value = 12, hydroxyl value = 25 (softening point = 110 ° C., refractive index 1.50).

O Image Creation Method An apparatus having the structure shown in FIG. 2 was used as the apparatus used in the present invention. In other words, Acolo manufactured by Fuji Xerox
A device modified from r630 was used. With this device,
The reflected light emitted from the illumination 21 to the original 22 is converted into a color CC.
The image was read by D23, color-separated into three color signals of yellow, magenta, and cyan by the image processing device 24, subjected to image processing, and output as a light signal from the semiconductor laser 25 in order for each color one by one. The optical signal was exposed to a photoreceptor 28 charged in advance by a charger 27 through an optical system 26 to produce an electrostatic latent image in which the image portion had a low potential. The developer containing the charged powder toner obtained by the above method is charged into the developing devices 29 to 31 and is developed by applying a developing bias, and the powder toner is statically charged on the photoreceptor by electrostatic force. Attached to the latent image. The formed powder toner image was transferred one by one to the transfer member 34 electrostatically attracted to the transfer drum 33 by the electric field provided by the transfer corotron 35. This is yellow, magenta,
This was repeated three times in the order of cyan to obtain an unfixed powder toner image on the transfer member. This was heated and fixed by an electric oven 37 to obtain a powder toner image. The weight of the developed toner was the same for each color, and was 6.5 (g / m ² ) in the image portion having an area ratio of 100%. The transfer member used was OK Super Art Paper (Shin Oji Paper Co., Ltd.).

Preparation of Transparent Layer Forming Coating Solution A Dry silica fine particles 10 parts by weight (average primary particle diameter: 7 nm, refractive index 1.45, A300, manufactured by Nippon Aerosil Co., Ltd.) polyvinyl alcohol 4 parts by weight (PVA217EE, 146 parts by weight of ion-exchanged water Among the above compositions, first, an aqueous solution of polyvinyl alcohol was prepared by dissolving 4 parts by weight of polyvinyl alcohol in 96 parts by weight of ion-exchanged water. Next, dry silica fine particles were added to 50 parts by weight of ion-exchanged water (the remainder after preparing an aqueous polyvinyl alcohol solution), and a homogenizer (manufactured by Nippon Seiki Co., Ltd.)
After stirring at 15000 rpm for 30 minutes using an aqueous solution of polyvinyl alcohol, an aqueous solution of polyvinyl alcohol was added. Thereafter, the mixture was stirred under the same conditions as above to obtain a coating liquid A for forming a transparent layer.

(Formation of Transparent Layer) The coating liquid for forming a transparent layer prepared as described above was applied to the entire surface of the image formed of the powder toner image prepared by the above-mentioned method using a bar coater, and was heated at a furnace temperature of 90 ° C. An iron plate was pressed against the coated surface in an oven and dried by heating for 10 minutes. As a result, a transparent layer having an average thickness of 14.5 μm was obtained.

Example 2 The unfixed powdery toner image obtained in Example 1 was heated and pressed and fixed by a fixing device 36, and then the release agent on the image surface was removed with a cloth soaked with ethanol. In the same manner as in Example 1, a transparent layer was formed on the image surface composed of the powder toner image. By applying a larger amount of coating than in Example 1, a final image having an average thickness of the transparent layer of 24.5 μm after heating and drying was produced.

Example 3 Preparation of Transparent Layer Forming Coating Solution B 7 parts by weight of dry silica fine particles (average primary particle diameter: 7 nm, refractive index 1.45, A300, manufactured by Nippon Aerosil Co., Ltd.) 1 part by weight of polyvinyl alcohol (PVA217EE, manufactured by Kuraray Co., Ltd.) 92 parts by weight of ion-exchanged water Among the above compositions, first, an aqueous solution of polyvinyl alcohol was prepared by dissolving 1 part by weight of polyvinyl alcohol in 49 parts by weight of ion-exchanged water. Next, dry silica fine particles were added to 43 parts by weight of ion-exchanged water (the remainder after preparing an aqueous solution of polyvinyl alcohol), and the mixture was subjected to 1500 using a homogenizer.
After stirring at 0 rpm for 30 minutes, an aqueous solution of polyvinyl alcohol was added. Thereafter, the mixture was stirred under the same conditions as above to obtain a coating liquid B for forming a transparent layer. The unfixed powder toner image obtained in Example 1 was heated and fixed in an electric oven 37 to obtain an image composed of the powder toner image. A transparent layer was formed on the image surface in the same manner as in Example 1, and a final image having an average thickness of the transparent layer after drying by heating of 18.5 μm was produced.

Example 4 Preparation of Transparent Layer Forming Coating Solution C Dry Silica Fine Particles 3 parts by weight (Average primary particle diameter: 7 nm, refractive index 1.45, A300, manufactured by Nippon Aerosil Co., Ltd.) 4 parts by weight of polyvinyl alcohol (PVA217EE, manufactured by Kuraray Co., Ltd.) 134 parts by weight of ion-exchanged water Of the above composition, first, an aqueous solution of polyvinyl alcohol was prepared by dissolving 3 parts by weight of polyvinyl alcohol in 97 parts by weight of ion-exchanged water. Next, dry silica fine particles were added to 37 parts by weight of ion-exchanged water (the remainder after preparing an aqueous solution of polyvinyl alcohol), and the mixture was subjected to 1500 using a homogenizer.
After stirring at 0 rpm for 30 minutes, an aqueous solution of polyvinyl alcohol was added. Thereafter, the mixture was stirred under the same conditions as above to obtain a coating liquid C for forming a transparent layer. The unfixed powder toner image obtained in Example 1 was heated and fixed in an electric oven 37 to obtain an image composed of the powder toner image. A transparent layer was formed on the image surface in the same manner as in Example 1, and a final image having an average thickness of the transparent layer of 18.5 μm after heating and drying was produced.

Example 5 Preparation of Transparent Layer Forming Coating Solution D 3 parts by weight of dry silica fine particles (average primary particle diameter: 7 nm, refractive index: 1.45, A300, manufactured by Nippon Aerosil Co., Ltd.) Methyl cellulose (100 cp, Shonan) 4 parts by weight Ion-exchanged water 37 parts by weight Of the above composition, dry silica fine particles were converted to ion-exchanged water 37
15,000 parts by weight using a homogenizer.
After stirring for 30 minutes under the condition of rpm, an aqueous solution of methylcellulose was added. Thereafter, the mixture was stirred under the same conditions as above to obtain a coating liquid D for forming a transparent layer. The unfixed powder toner image obtained in Example 1 was heated and fixed in an electric oven 37 to obtain an image composed of the powder toner image. A transparent layer was formed on the image surface in the same manner as in Example 1, and a final image having an average thickness of the transparent layer of 22.5 μm after heating and drying was produced.

Example 6 Preparation of Transparent Layer Forming Coating Solution E 6 parts by weight of dry silica fine particles (average primary particle diameter: 16 nm, refractive index 1.45, A130, manufactured by Nippon Aerosil Co., Ltd.) 3 parts by weight of polyvinyl alcohol (PVA217EE, manufactured by Kuraray Co., Ltd.) 151 parts by weight of ion-exchanged water First, an aqueous solution of polyvinyl alcohol was prepared by dissolving 3 parts by weight of polyvinyl alcohol in 97 parts by weight of ion-exchanged water. Next, dry silica fine particles were added to 54 parts by weight of ion-exchanged water (the remainder after preparing an aqueous solution of polyvinyl alcohol), and 1500 parts were added using a homogenizer.
After stirring at 0 rpm for 30 minutes, an aqueous solution of polyvinyl alcohol was added. Thereafter, the mixture was stirred under the same conditions as above to obtain a coating liquid E for forming a transparent layer. The unfixed powder toner image obtained in Example 1 was heated and fixed in an electric oven 37 to obtain an image composed of the powder toner image. A transparent layer was formed on the image surface in the same manner as in Example 1 to prepare a final image having an average thickness of the transparent layer of 20.5 μm after heating and drying.

Comparative Example 1 In the preparation of the coating liquid for forming a transparent layer in Example 6, alumina fine particles (average primary particle diameter: 3) were used instead of silica fine particles.
Example 6 except that 0 nm and a refractive index of 1.75) were used.
A transparent layer was formed on the powder toner image in the same manner as in the above. The average thickness of the transparent layer was 4.5 μm. Comparative Example 2 Example 1 except that the average thickness of the transparent layer was 30.5 μm.
An image was produced in the same manner as described above.

Comparative Example 3 Production of transparent toner Binder resin: linear polyester resin (linear polyester obtained from terephthalic acid / bisphenol A ethylene oxide adduct / cyclohexanedimethanol; Tg = 62 ° C., Mn = 4) 000, Mw
= 35,000, acid value = 12, hydroxyl value = 25) The above resin was melt-kneaded with an extruder, pulverized with a jet mill, and then classified with an air classifier to produce particles having an average particle size of 7 μm. Then, 0.76% by weight of hydrophobic silica fine powder (R972, manufactured by Nippon Aerosil Co., Ltd., average particle size 0.016 μm) was added to the particle surface as a fluidizing agent, and mixed with a Henschel mixer to form a transparent toner. I got

Preparation of Developer for Transparent Toner The above-described transparent toner composition and a carrier made of ferrite having a particle size of about 50 μm coated with a methyl methacrylate-styrene copolymer were used. 8 parts by weight of the toner composition was added and mixed with a turbula shaker mixer to obtain a two-component developer containing a transparent toner. In the image forming method of Example 1, the developer containing the transparent toner is charged into the developing device 32, and the image area ratio is 100% on the powder toner image transferred onto the transfer body.
Is transferred and fixed by heating with a fixing device 36.
An image consisting of a powder toner image having a transparent resin layer on the surface was obtained. The average thickness of the transparent resin layer was 15.0 μm.

Comparative Example 4 A 15 μm-thick polyethylene terephthalate having an 8 μm-thick thermosetting acrylic resin adhesive formed on the surface as an adhesive was superimposed on the powder toner image produced by the method of Example 2. Then, a final image was produced by heating and bonding under the conditions of an adhesion temperature of 100 ° C. and a feed speed of 30 mm / s by the fixing device 36 from which the release agent was removed. The average thickness of the transparent layer is 22.5
μm.

Example 7 Example 1 was repeated except that a photograph including a person was used as the manuscript.
A final image was prepared using the methods of ６ to ６. Comparative Example 5 Comparative Example 1 was performed except that a photograph including a person was used as the manuscript.
A final image was prepared using the methods of.

Table 1 shows the evaluation results of the images produced in Examples 1 to 6 and Comparative Examples 1 to 4. The evaluation methods and evaluation criteria in the table were as follows.

(Average Transparent Layer Thickness) A method of analyzing the inside of an image to determine the average thickness of the transparent layer will be described. A plurality of process black images having a rectangular shape of 30 × 30 mm and an image area ratio of 100% are formed on the transfer body using a powder toner, and a transparent layer is formed on the entire surface. Next, a part of the image is cut out to include the boundary between the image part and the non-image part,
After embedding in an embedding agent made of an epoxy resin and curing, an ultra-thin section is prepared by cutting out 10 points along the boundary of the image with a diamond knife. The prepared ultrathin film section is loaded into a transmission electron microscope, and a transmission electron image is photographed on a negative film. The negative film after photographing is placed on frosted glass, and light from a fluorescent lamp is irradiated from the opposite side of the negative film to obtain a transmitted light image of the negative film.
Next, the transmitted light image is photographed by a CCD camera, and the photographed image is converted into a digital signal and stored as digital data.
Next, the digital data of the stored image is subjected to image processing by an image processing apparatus, and for the image produced by the method of the present invention, an image portion containing a colorant therein, a transfer body portion, and a transparent layer portion are detected. To determine each boundary. Next, the powder toner image portion and the non-image portion are arranged so as to have the same width in the image surface direction of the observed image, the area of only the transparent layer portion is measured from the entire observed image portion, and displayed on a display. The average thickness of the transparent layer in the observed image can be obtained by dividing the powder toner image portion and the non-image portion by the added width. By performing this operation on 10 points of the prepared image, the average thickness of the transparent layer of the entire image can be obtained. Further, in an image in which the transparent toner layer or the adhesive and the transparent plastic film produced in the comparative example were formed as a transparent layer on the image surface, the transparent layer portion was a transparent toner layer or an adhesive layer and a transparent plastic film, and the present invention The average thickness of the transparent layer is determined in the same manner as in the image prepared by the method described in (1).

(Granularity) The granularity was evaluated by forming a transparent layer on the surface of a 30 × 30 mm rectangular, 30% image area blue image formed on a transfer member using powder toner. Using the final image obtained, visual evaluation was performed. 20
For one evaluator: 1. very coarse;
2. coarse texture; Usually, 4. 4. Fine-grained Very fine-grained evaluations were obtained, and the average value was obtained. The case where the average value was less than 2 was evaluated as x, the case of 2 or more and less than 4 was evaluated as ○, and the case of 4 or more was evaluated as ◎.

(Uniformity of Glossiness) Regarding the uniformity of glossiness on the image surface, Gloss Meter GM-26 was used.
D (manufactured by Murakami Color Research Laboratory Co., Ltd.) was used to average the values obtained by measuring at 10 locations on the image surface, and the difference between the maximum or minimum value of the measured values and the average value was calculated as Those with 5 or more were evaluated as x, those with 2 or more and less than 5, and those with less than 2 were evaluated as ◎.

(Writing of writing instrument) Writing instrument writing was evaluated by writing letters and lines on the surface of the produced image using a felt pen using oil-based ink and water-based ink for 20 evaluators. Ease of writing, written characters
Evaluation was made from the viewpoint of line visibility and fixability of written characters and lines. The evaluation result was evaluated as "O" when the image was equivalent to an image produced by printing, "A" when the image was inferior to the image produced by printing, and "X" when writing with a writing instrument was impossible.

(Sticky Sticky Property) Regarding sticky sticky property, the prepared image was fixed on a desk, and then the adhesive coated surface of the sticky note (Post-it 500Y, manufactured by 3M) was put on the prepared image with a finger. The other end was fixed to a chuck of a digital force gauge DFG-2K (manufactured by Shinpo Kogyo KK). Move the digital force gauge in the direction perpendicular to the image surface to peel off the sticky note, measure the maximum load until the sticky note completely peels off from the image surface at five points on each part of the image surface, and measure the average value And
The average value is less than 30 gf or less x, 30 gf or more, 80 gf
Less than ○ was evaluated as ○, and 80 gf or more as ◎.

(Overall Image Quality) The final images produced in Examples and Comparative Examples were evaluated by visual evaluation for overall image quality. For 20 evaluators, 1. 1. very coarse and completely different from silver halide photography; 2. coarsely different from silver halide photography; 3. Smooth but different from silver halide photography 4. Smooth and close to silver halide photography Evaluations were categorized into five categories: very smooth and having a depth close to that of a silver halide photograph, and the average value was obtained. X when the average value is less than 3,
The case of 3 or more and less than 4 was evaluated as ○, and the case of 4 or more was evaluated as ◎.

[0064]

[Table 1] As is clear from the above results, in the embodiment of the present invention,
Overall, the evaluation of image quality is high.

[0065]

According to the present invention, which has the above-described structure, a multicolor image forming method using a powdery toner has a high image quality similar to that of a photographic paper photograph produced by a silver halide photograph having uniform gloss over the entire image. It is possible to produce a high quality image. Further, in the image forming method of the present invention, there is no occurrence of offset when forming a transparent layer on the entire surface of the powder toner image, and the created toner image is written on the surface with a writing tool or pasted on a sticky note. Can be easily performed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a method for obtaining an average thickness of a transparent layer, and is a schematic diagram showing measurement points on a cross section of a final image on which a transparent layer is formed.

FIG. 2 is a schematic view showing an example of an apparatus for implementing the present invention.

[Explanation of symbols]

Reference Signs List 11 transfer member, 12 powder toner image portion, 13 transparent layer, 14 embedding agent, 21 illumination, 22 original, 23 color CCD, 24 image processing device, 25 semiconductor laser, 26 Optical system, 27: charger, 28: photoconductor, 29
~ 32 developing device, 33 transfer drum, 34 transfer body, 3
5: transfer corotron, 36: fixing device, 37: electric oven.

Claims (1)

[Claims] 1. An exposure step of forming a latent image on a latent image carrier using light modulated by image information, and applying a powder toner comprising at least cyan, magenta and yellow toner on the latent image carrier. A multicolor image forming method including a developing step of forming a toner image using the toner image, a transfer step of transferring the toner image onto a transfer member, and a fixing step of fixing an unfixed toner image on the transfer member. And a step of providing a transparent layer at a refractive index of at least 1.
The refractive index n of the binder resin, the refractive index N of the inorganic oxide fine particles, and the average thickness T of the transparent layer, which are composed of inorganic oxide fine particles having a particle size of 40 to 1.60 and a water-soluble resin and are used in the powder toner. (M) satisfying the following expression. −1.3 ≦ (n−N) × T ≦ 1.3