JP2015026090A - Image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve the appropriate level of transmissivity of an image formed and fixed on a recording medium.SOLUTION: An image forming method includes a first image forming step of forming a first developer image by using a white developer, a second image forming step of forming a second developer image by using a developer of a color other than white having a lower softening temperature than the softening temperature of the white developer and a lower outflow starting temperature than the outflow starting temperature of the white developer, and a fixing step of fixing the first developer image and second developer image onto a recording medium.

Description

  The present invention relates to an image forming method using an electrophotographic system.

  In order to make the color of the recording medium (transfer material) inconspicuous, a white toner image as a base is formed on the recording medium, and a color toner image is formed thereon, and then these toner images are fixed. An image forming apparatus is proposed (for example, see Patent Document 1).

JP 2002-236396 A

  However, since the white toner image after fixing has high light transmittance, there is a problem that the color of the recording medium is conspicuous and the image quality is deteriorated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method that can form an image with good image quality that is hardly affected by the color of a recording medium.

  An image forming method according to an aspect of the present invention includes a first image forming step of forming a first developer image using a white developer, a softening temperature lower than the softening temperature of the white developer, and white development. A second image forming step of forming a second developer image using a developer of a color other than white whose outflow start temperature is lower than the outflow start temperature of the agent, and the first developer image and the second developer image A fixing step of fixing the developer image to the recording medium.

  According to the present invention, it is possible to form an image that is hardly affected by the color of the recording medium and that has good image quality.

1 is a configuration diagram schematically illustrating a configuration example of a printer as an image forming apparatus according to a first embodiment of the present invention. It is a figure which illustrates the toner used for the test pattern and position for turbidity measurement, and printing of a test pattern. It is a figure which shows the haze value (Table 1) measured in Test 1. FIG. The figure which shows the result of having measured the powder hue of the developer printed on the transparent film in the test 1 on a black mount as a value (Table 2) on the (L *, a *, b *) color space coordinate axis. is there. The figure which shows the result (measurement) on the color space coordinate axis (Table 3) which measured the powder hue of the developer printed on the transparent film in the test 1 on a blue mount (L *, a *, b *). is there. It is a figure which shows the powder hue of the developer printed on the transparent film in Test 1 on the (L *, a *, b *) color space coordinate axis. It is a figure which shows the haze value (Table 4) measured in Test 2. FIG. The figure which shows the result of having measured the powder hue of the developer printed on the transparent film in the test 2 on a black mount as a value (Table 5) on the (L *, a *, b *) color space coordinate axis. is there. It is a figure which shows the powder hue of the developer printed on the transparent film in Test 2 on the (L *, a *, b *) color space coordinate axis. The figure which shows the result (measurement) on the color space coordinate axis (Table 6) which measured the powder hue of the developer printed on the transparent film in the test 4 on a blue mount (L *, a *, b *). is there. It is a figure which shows the powder hue of the developer printed on the transparent film in Test 4 on a (L *, a *, b *) color space coordinate axis. FIG. 5 is a configuration diagram schematically illustrating a configuration example of a printer as an image forming apparatus according to a second embodiment of the present invention.

<< 1 >> First Embodiment << 1-1 >> Configuration of First Embodiment <Printer 11>
FIG. 1 is a configuration diagram schematically illustrating a configuration example of a printer 11 as an image forming apparatus according to a first embodiment of the present invention. The printer 11 is a color printer using an electrophotographic system, for example. The printer 11 includes a medium cassette 12, an image forming unit 22 including image forming units 13, 14, 15, 16, and 17, a transfer unit 19, and a fixing device 20 as main components.

  The medium cassette 12 stores a medium (also referred to as “print medium”, “recording medium”, or “transfer material”) 21 in a stacked state. The medium cassette 12 is detachably attached to the lower part in the printer 11. The media 21 stored in the media cassette 12 are taken out one by one, and the taken-out media 21 travels in the direction of the arrow D1 along the media transport path and is sent to the image forming unit 22.

  The image forming unit 22 includes image forming units 13 to 17 that are detachably disposed along the medium conveyance path. The developer image (also referred to as “toner image”) formed by each of the image forming units 13 to 17 is transferred onto the upper surface of the medium 21 conveyed along the medium conveyance path by the transfer unit 19. The image forming units 13 to 17 arranged in series have the same configuration, but use different color toners. That is, the toners used in the image forming units 13 to 17 are white (W) toner, black (K) toner, yellow (Y) toner, magenta (M) toner, and cyan (C) toner, respectively. However, the number of image forming units and the type of toner are not limited to this example.

  The transfer unit 19 pairs the transfer belt 33 that electrostatically attracts and conveys the medium 21, the drive roller 34 that is rotated by the drive unit to drive the transfer belt 33, and the drive roller 34. A tension roller 35 that is stretched, transfer rollers 27 to 31 that are arranged to face the photosensitive drums 53 to 57 of the image forming units 13 to 17 and apply a voltage to transfer the toner image to the medium 21, and a transfer belt The transfer belt cleaning blade 38 scrapes and cleans the toner adhering to the toner 33 and the waste toner tank 39 that stores the toner recovered by the transfer belt cleaning blade 38.

<Image forming unit 13>
Next, the configuration of the image forming unit 13 including white (W) toner will be described. The image forming unit 14 includes black (K) toner, the image forming unit 15 includes yellow (Y) toner, the image forming unit 16 includes magenta (M) toner, and cyan (C) toner. The image forming unit 17 has the same configuration as the image forming unit 13 except that the type (color) of the toner is different. The image forming unit 13 includes a developing roller 40 as a developer carrying member, a supply roller 41 as a developer supply / recovery member, a developing blade 42 as a developer layer regulating member, and a developer container that contains toner 43. Toner cartridge 44, a photosensitive drum 53 as a latent image carrier, a charging roller 45 as a charging member, and a cleaning blade 46 as a developer removing member.

  The photosensitive drum 53 has a conductive support and a photoconductive layer covering the outer periphery thereof. As the conductive support, for example, an aluminum metal pipe is used, and as the photoconductive layer, for example, a structure in which a charge generation layer and a charge transport layer are sequentially laminated is used.

  The charging roller 45 is in contact with the peripheral surface of the photosensitive drum 53 and includes, for example, a metal shaft and a semiconductive epichlorohydrin rubber layer covering the outer periphery thereof.

  The LED head 47 as an exposure apparatus has, for example, a plurality of LED elements (light emitting diodes) and a lens array, and forms an image of the irradiation light output from the plurality of LED elements on the surface of the photosensitive drum 53. As the light source of the exposure apparatus, other light sources such as a laser light emitting element can be used.

  The developing roller 40 as a developer carrying member is disposed in contact with the peripheral surface of the photosensitive drum 53 and includes, for example, a metal shaft and a semiconductive urethane rubber layer covering the outer periphery thereof.

  The developing blade 42 in contact with the surface of the developing roller 40 is a leaf spring formed using stainless steel, phosphor bronze, or the like, and regulates the thickness of the developer layer on the surface of the developing roller 40.

  The medium 21 on which the toner image of each color is transferred by the image forming unit 22 is transported along the medium transport path in the direction of arrow D2 in FIG. The fixing device 20 includes, for example, a heat generating roller 48, a pressure roller 49, and a pressure belt 50.

<Toner 43>
Next, the toner 43 as the developer will be described. The toner 43 is obtained by appropriately treating the base particles containing at least a binder resin with an inorganic fine powder or an organic fine powder. This binder resin is, for example, a polyester resin, a styrene-acrylic resin, an epoxy resin, or a styrene-butadiene resin.

  The toner is produced by appropriately mixing or surface-treating known components such as a colorant, a release agent, a charge control agent, and a treatment agent as described below with a binder resin.

  As the colorant, dyes and pigments used as toner colorants for black (K), yellow (Y), magenta (M), and cyan (C) are used singly or in combination. be able to. Examples of the colorant include carbon black, iron oxide, permanent brown FG, pigment green B, pigment blue 15: 3, solvent blue 35, solvent red 49, solvent red 146, quinacridone, carmine 6B, naphthol, or disazo yellow. Isoindoline and the like can be used. The content of the colorant added to the binder resin is desirably 2 to 25 [parts by weight] with respect to 100 [parts by weight] of the binder resin, and more preferably 2 to 15 [parts by weight]. It is.

  Examples of the colorant for the white toner include titanium oxide, which may be surface-treated or used in combination. The content of the colorant added to the binder resin is desirably in the range of 20 to 100 [parts by weight] with respect to 100 [parts by weight] of the binder resin, and a more preferable range is 50 to 100. It is within the range of [parts by weight].

  As the release agent, for example, low molecular weight polyethylene, low molecular weight polypropylene, paraffin wax, carnauba wax, or the like can be used. The content of the release agent is preferably in the range of 0.1 to 20 [parts by weight] with respect to 100 [parts by weight] of the binder resin, and a more preferable range is 0.5 to 12 parts. It is within the range of [parts by weight], and a plurality of types of waxes may be used in combination.

  Examples of the charge control agent include a quaternary ammonium salt charge control agent in the case of a positive charge toner, and an azo complex charge control agent, a salicylic acid complex charge control agent in the case of a negative charge toner, or A calixarene charge control agent or the like can be used. The content of the charge control agent is desirably in the range of 0.05 to 15 [parts by weight] with respect to 100 [parts by weight] of the binder resin, and more preferably in the range of 0.1 to 10 [parts]. Parts by weight].

  The processing agent is added to improve environmental stability, charging stability, developability, fluidity, and storage stability, and silica, titania, alumina, or the like can be used. The content of the treatment agent is desirably 0.01 to 10 [parts by weight] with respect to 100 [parts by weight] of the binder resin, and a more preferable range is 0.05 to 8 [parts by weight]. .

<White (W) toner>
The white toner used in the first embodiment will be described. As the white toner, 100 [parts by weight] of a polyester resin as a binder resin and 1 Bontron E-84 (trade name) (manufactured by Orient Chemical Industry Co., Ltd.) as a charge control agent for the toner are used. 0.0 [parts by weight], 95 [parts by weight] titanium oxide as a colorant, and “CARNAUBA WAX (trade name)” (carnauba wax No. 1 powder, Kato Co., Ltd.) as a release agent. Yoji Co., Ltd.) (4.0 parts by weight) was mixed with a Henschel mixer, melt-kneaded with a twin screw extruder, cooled, and coarsely crushed with a cutter mill having a screen with a diameter of 2 [mm]. Thereafter, the mixture was pulverized using a collision type pulverizer, and further classified using an air classifier to obtain toner base particles.
Next, the obtained toner base particles are taken as 100 [parts by weight], and as an external addition step, hydrophobic silica R972 (trade name) (manufactured by Nippon Aerosil Co., Ltd., average particle size 16 [nm]) is 3.0 [weights]. Part] and stirring with a Henschel mixer for 3 minutes to obtain a white toner having an average particle size of 7.0 [μm].
In this white toner, the average particle diameter of the toner can be measured with a particle size distribution measuring device (Coulter Multisizer 3, manufactured by Beckman Coulter, Inc., aperture diameter 100 [μm]).

When the powder hue of this white toner was measured, (L *, a *, b *) color space coordinate axis,
L * = 94.64, a * = − 1.25, b * = 2.94
Met. The powder hue can be measured with a spectrocolorimeter (Nippon Denshoku Industries Co., Ltd., SE-2000, light source (2-degree visual field)). When measuring the powder hue, 5 g of toner was put in a powder measurement cell attached to the spectral color difference meter.

The loose apparent density of the white toner was measured and found to be 0.60 [g / cm ³ ]. The loose apparent density of the toner can be measured with a powder tester (manufactured by Hosokawa Micron Corporation, PT-S type, opening 710 [μm] sieve, 100 [cc] cup).

  Regarding the thermal properties of the white toner, the softening temperature Tsw is 81 [° C.], the outflow start temperature Tfw of the white toner is 98 [° C.], and the melting temperature Tmw of the white toner is 151 [° C.].

  The softening temperature Ts, the outflow start temperature Tf, and the melting temperature Tm, which are the thermophysical properties of the toner, are a flow characteristic evaluation device (manufactured by Shimadzu Corporation, CFT-500D, toner amount 1.0 [g], die diameter 1.0 [Mm], die length 1.0 [mm], load 10 [kg], starting temperature 50 [° C.], preheating time 300 [sec], heating rate 3 [° C./min], heating method) It can be measured. The physical properties of the toner are the temperature rising method flow curve obtained by measurement, the softening temperature Ts is the temperature at which the internal voids disappear and becomes one phase, the outflow start temperature Tf is the temperature at which the toner changes to a fluid state, The melting temperature Tm is a temperature calculated by the 1/2 method.

<Cyan (C) toner>
The cyan toner used in the first embodiment will be described. As the cyan toner, a polyester resin having a thermal characteristic different from that of the white toner is used as a binder resin, the binder resin is 100 [parts by weight], and a bontron E-84 (manufactured by Orient Chemical Industry Co., Ltd.) is used as a charge control agent. ) 0.5 [parts by weight], Pigment Blue 15: 3 (trade name) 4.0 [parts by weight] as a colorant, and Carnauba wax (trade name) (trade name Hiroyuki Kato) as a release agent Manufactured by Carnauba wax No. 1 powder) 4.0 [parts by weight], a Henschel mixer, melt kneaded by a twin screw extruder, cooled, and then a cutter mill having a screen with a diameter of 2 [mm] After that, the mixture was pulverized using an impact plate type pulverizer, and further classified using an air classifier to obtain toner base particles.

Next, as an external addition step, 3 parts of hydrophobic silica R972 (trade name) (manufactured by Nippon Aerosil Co., Ltd., R972, average particle size 16 [nm]) is used with respect to 100 [parts by weight] of the obtained toner base particles. 0.0 [parts by weight] was added, and the mixture was stirred with a Henschel mixer for 3 minutes to obtain a cyan toner having an average particle size of 7.0 [μm]. The apparent loose density of the toner was measured and found to be 0.35 [g / cm ³ ]. This cyan toner is referred to as cyan toner 1.

  Regarding the thermal properties of the cyan toner 1, the softening temperature Tsc was 80 [° C.], the toner outflow start temperature Tfc was 94 [° C.], and the toner melting temperature Tmc was 114 [° C.].

  Further, in the same manner as the manufacturing method of the cyan toner 1, by changing the kind of the colorant to be blended, black, magenta, and yellow toners can be obtained.

<Black (K) toner>
For black toner, carbon black is used as a colorant. The average particle diameter of the obtained black toner was 7.0 [μm], and the loose apparent density was 0.35 [g / cm ³ ]. This black toner is referred to as black toner 1. Regarding the thermal properties of the black toner 1, the softening temperature Tsk was 80 [° C.], the outflow start temperature Tfk of the toner was 94 [° C.], and the melting temperature Tmk of the toner was 114 [° C.].

<Magenta (M) toner>
For magenta toner, naphthol was used as a colorant. The obtained magenta toner had an average particle diameter of 7.0 [μm] and a loose apparent density of 0.35 [g / cm ³ ]. This is called magenta toner 1. Regarding the thermal properties of the magenta toner 1, the softening temperature Tsm was 81 [° C.], the toner outflow start temperature Tfm was 95 [° C.], and the toner melting temperature Tmm was 115 [° C.].

<Yellow (Y) toner>
For yellow toner, isoindoline was used as a colorant. The obtained yellow toner had an average particle diameter of 7.0 [μm] and a loose apparent density of 0.35 [g / cm ³ ]. This is called yellow toner 1. Regarding the thermal properties of the yellow toner 1, the softening temperature Tsy was 80 [° C.], the toner outflow start temperature Tfy was 94 [° C.], and the toner melting temperature Tmy was 114 [° C.].

  Note that black toner, cyan toner, magenta toner, and yellow toner, which are toners other than white toner, are collectively referred to as color toners.

<Toner adhesion amount>
In the first embodiment, the white toner is used such that the outflow start temperature Tf of the white toner is higher than the medium surface temperature Mt at the time of fixing. In the first embodiment, the range in which the adhesion amount of the white toner and the color toner (each single color developer) is good is 0.4 to 0.6 [mg / cm ² ] for the color toner, More preferably, it is 0.4-0.5 [mg / cm < ² >]. Moreover, the suitable adhesion amount of white toner is 0.8-1.1 [mg / cm < ² >], More preferably, it is 0.9-1.1 [mg / cm < ² >].

<< 1-2 >> Operation of First Embodiment Next, the operation of the printer 11 having the above-described configuration will be described. The photosensitive drum 53 is rotated at a constant peripheral speed in the direction of the arrow D5 by driving means such as a motor. The charging roller 45 provided in contact with the surface of the photosensitive drum 53 applies a DC voltage supplied from the high voltage power supply for the charging roller to the surface of the photosensitive drum 53 while rotating in the direction of the arrow D9. To charge. Next, the LED head 47 provided facing the photosensitive drum 53 irradiates the uniformly charged surface of the photosensitive drum 53 with light corresponding to the image signal, and light attenuates the potential of the light irradiation portion. To form an electrostatic latent image. The toner 43 is supplied with a voltage by a high-voltage power supply for a supply roller (not shown) and is supplied to the developing roller 40 from a supply roller 41 that rotates in the direction of arrow D3 in FIG.

  The developing roller 40 is disposed in close contact with the photosensitive drum 53, and a voltage is applied by a high voltage power supply for the developing roller. The developing roller 40 attracts the toner 43 conveyed by the supply roller 41 and conveys it in the direction of arrow D4 in FIG. In this conveyance process, the developing blade 42 disposed downstream of the supply roller 41 and in pressure contact with the developing roller 40 removes an excess portion from the toner adhering to the surface of the developing roller 40 as the developing roller 40 rotates. By scraping, a thin layer of toner is formed on the surface of the developing roller 40.

  Since a bias voltage is applied between the photosensitive drum 53 and the developing roller 40 by a high voltage power source, an electric field associated with the electrostatic latent image formed on the photosensitive drum 53 is generated between the developing roller 40 and the photosensitive drum 53. Occur. Therefore, the charged toner on the developing roller 40 adheres to the electrostatic latent image portion on the photosensitive drum 53 by electrostatic force, and this portion is developed to form a toner image. Note that this development process, which starts with the rotation of the photosensitive drum 53, is started at a predetermined timing.

  As shown in FIG. 1, the medium (for example, recording paper) 21 accommodated in the medium cassette 12 is taken out one by one from the medium cassette 12 along the medium guide in the direction of the arrow D <b> 1 and sent to the transfer unit 19. The image forming process described above is started at a predetermined timing while the medium 21 is conveyed in the direction of the arrow D1.

  Thereafter, the photosensitive drum 53 of the white (W) image forming unit 13 is disposed in opposition to the photosensitive drum 53 via the transfer belt 33, and a transfer roller 27 to which a voltage is applied by a transfer roller high voltage power source (not shown). A transfer process is performed in which the white toner image formed on the photosensitive drum 53 by the above-described development process is transferred onto the medium 21 that is conveyed by being electrostatically attracted to the transfer belt 33.

  Thereafter, the medium 21 travels along the direction of the arrow D6 on the transfer belt 33, and the image forming unit 14 and the transfer roller 28 perform a black process by the image forming unit 14 and the transfer roller 28 by a process similar to the developing process and the transfer process. A developer image is developed with a yellow developer image by the image forming unit 15 and the transfer roller 29, a magenta developer image is developed by the image forming unit 16 and the transfer roller 30, and a cyan developer is developed by the image forming unit 17 and the transfer roller 31. The agent image is sequentially transferred onto the medium 21. The medium 21 on which the developer images of the respective colors are transferred is conveyed in the direction of arrow D2 in FIG.

  The medium 21 on which the toner image of each color is transferred is conveyed to the heat roller 48, the pressure roller 49, and the pressure belt 50. The medium 21 onto which the developer image has been transferred is controlled by a temperature control means (not shown) and maintained at a predetermined surface temperature, and a heating roller 48 that rotates in the direction of arrow D11, a pressure roller 49 that rotates in the direction of arrow D12, The process proceeds between the pressure belts 50. Therefore, the heat of the heat generating roller 48 melts the toner image on the medium 21, and the toner image melted on the medium 21 is pressed by the pressure contact portion between the heat generating roller 48, the pressure roller 49, and the pressure belt 50. The toner image is fixed on the medium 21.

  The medium 21 on which the toner image is fixed is conveyed in the direction of arrow D7 and is sent out of the printer 11.

  Some toner may remain on the surface of the photosensitive drum 53 after the transfer. The remaining toner is removed by the cleaning blade 46.

  Further, between the medium 21 during continuous paper passing and the next medium 21, some of the poorly charged toner may be transferred to the transfer belt 33 from the photosensitive drums 53 to 57 of the image forming units 13 to 17. is there. The toner transferred to the transfer belt 33 is removed from the transfer belt 33 by the transfer belt cleaning blade 38 and stored in the waste toner tank 39 when the transfer belt 33 rotates in the directions of arrows D6 and D8. .

<< 1-3 >> Test 1
In the image forming apparatus using the toner described above, the sheet passing speed is set to 200 [mm / sec], and a transparent film (OHP paper, CG3720, A4 size, 177 [g / manufactured by Sumitomo 3M Limited] is used as a print medium. m ² ]) to adjust the power supply voltage applied to the developing roller 40 and the supply roller 41, thereby controlling the toner development amount in the image forming units 13 to 17 and adjusting the toner adhesion amount on the print medium. Went.
In each color toner of the image forming units 14 to 17, the toner adhesion amount on the printing medium is 0.50 [mg / cm ² ] (= 100 [%] duty, duty = printing density, when the exposure apparatus is fully irradiated). Was set to be. Further, the amount of white toner adhering to the print medium in the image forming unit 13 takes into account the difference in loose apparent density from the color toner,
0.86 [mg / cm ² ]
(= 0.50 [mg / cm ² ] × (0.60 [g / cm ³ ] /0.35 [g / cm ³ ]))
Set to be.

  The fixing temperature of the fixing device 20 of the image forming apparatus is the same as that at the time of printing by heating the fixing device 20 in a state where the toner before passing through the medium 21 is not transferred and exposing the photosensitive drum from the exposure device. Then, the transparent film was conveyed, and the medium surface temperature Mt [° C.] immediately after fixing (immediately after passing through the transparent film) was measured as shown in FIG. The surface temperature measuring device 60 is a portable non-contact thermometer (Eurtron, IRtecP500 + Mk2, emissivity 0.95) as indicated by an arrow D9. Measurement was performed at a position 20 mm after discharging from the contact portion, and the medium surface temperature Mt immediately after fixing was an average value of measured values for ten media. As a result, the surface temperature of the heat generating roller 48 was 155 [° C.], and the medium surface temperature Mt was 85 [° C.].

Next, test patterns (test pattern 1 to test pattern 4) as shown in FIG. 2 were printed in order so that the white toner was transferred onto the medium and the color toner was transferred onto the white toner. . The turbidity (Haze value) at each position (1) to (4) in FIG. 2 was measured using a turbidimeter (Nippon Denshoku Industries Co., Ltd., Haze meter, NDH-2000).
The Haze value is the ratio of the diffuse light transmittance Td to the total light transmittance Tt, and the following formula Haze value [%] = (Td / Tt) × 100
Can be calculated.
The results are shown as Table 1 in FIG. From the measurement results of Test Pattern 1 to Test Pattern 4, the turbidity of the white toner is larger than that of any color toner, the image turbidity of the white toner single color is 88 [%], and the turbidity of the color toner YMCK is The degree was 70 [%] at the maximum. In addition, in the case of printing with the white toner overlaid, the turbidity was higher than the turbidity of the white toner alone.

In this printed medium, in order to confirm the influence of the background color on the printed image, color reproducibility was confirmed by placing colored paper as a lower mount. The printed surface of the transparent film printed at the time of measurement is black paper (made by Kishu Paper Co., Ltd., color fine paper, thick mouth, black, 90 [g / m ² ]) or blue paper (on the opposite side to the printed surface of the transparent film) Kishu Paper Co., Ltd., colored fine paper, thick mouth, blue color, 90 [g / m ² ]), and the hue at each position on the transparent film, XRite 528 (trade name) (manufactured by X-Rite, D50 light source ( Measured at 2 degrees visual field)). The measurement results are shown as Tables 2 and 3 in FIG. 4 and FIG. 5 and graphically in FIG. A point <1> indicated by a black circle “●” in FIG. 6 is a point of each color of YMCRGB which is black paper and does not overlap with white toner, and a point <2> indicated by a black triangle “▲” is a black paper on the mount. The point <3> indicated by the black square “■” in each color of YMCRGB with the white toner overlapped with the white toner is a point of each color of YMCRGB without the black toner overlapping with the white toner. The point <4> indicated by “” is a point of each color of YMCRGB in which the base paper is blue paper and is overlaid with white toner. From the results shown in FIG. 6, the color reproduction range becomes large when printing is performed by overlapping the white toner in each color of YMCRGB by comparing the points <1> and <2> or the points <3> and <4>. When a color reproduction result is obtained and white toner is not overprinted, the color reproduction range is narrow. In particular, when blue paper is used as a backing paper, the red color reproducibility has deteriorated, while the blue color reproducibility has not deteriorated. It is thought that it is greatly influenced by the color.

For black (K) toner, the saturation c * = (a * ² + b * ² ) ^1/2 when the mount is black paper.
In comparison with the presence or absence of the overlap with the white toner, c * = 1.3 is the same. But,
When the base paper is blue paper, c * = 3.8 without white toner overlap, c * = 2.9 with white toner overlap, and the saturation c * is smaller when overlapped with white toner. The black (K) toner was able to reproduce a black color.

  From this result, the image turbidity with a white toner single color is 88 [%] (value of W in FIG. 3) or more, and the image turbidity with a color toner single color is 70 [%] (Y, M, C, K in FIG. 3). By printing with white (W) toner overlaid with color (Y, M, C, K) toner, the color reproduction on the transparent film is good and the influence of the background color is small. Can be obtained.

  Next, in the same measurement location, the glossiness was measured using a gloss meter (Murakami Color Research Laboratory Co., Ltd., GM-26D, light receiving angle: 75 degrees). From this result, the glossiness of the color (Y, M, C, K) toner was 35%, and good glossiness was obtained. The color image has a glossiness of 25% or more, preferably 30% or more.

  Next, by adjusting the surface temperature of the fixing roller (heating roller) 48 of the fixing device 20, the medium surface temperature Mt immediately after fixing was changed.

  When the surface temperature of the fixing roller was 145 [° C.], the medium surface temperature Mt immediately after fixing was 81 [° C.]. At this time, the glossiness of the color toners was 30%, and good glossiness was obtained.

  When the surface temperature of the fixing roller was 135 [° C.], the medium surface temperature Mt immediately after fixing was 77 [° C.]. At this time, the glossiness of the color toners was 18%, and the glossiness was insufficient.

  When the fixing roller surface temperature was 175 [° C.], the medium surface temperature Mt immediately after fixing was 94 [° C.]. At this time, the glossiness of the color toners was 45%, and good glossiness was obtained.

  When the surface temperature of the fixing roller was 185 [° C.], the medium surface temperature Mt immediately after fixing was 99 [° C.]. At this time, when the printing medium is peeled off from the fixing roller immediately after fixing, a hot offset occurs in which part of the toner adheres to the fixing roller, resulting in non-uniform glossiness on the printed image and poor image quality, making it impossible to measure the glossiness. It was.

  From the viewpoint of glossiness, good glossiness was obtained by setting the medium surface temperature Mt immediately after fixing to 81 [° C.] or higher and 94 [° C.] or lower. When the surface fixing temperature of the printing medium is lower than the softening temperature Ts [° C.] of the color toner, the surface of each toner particle does not become uniform, but the toner layer on the medium becomes uniform above the softening temperature Ts [° C.]. Therefore, the surface gloss of the fixed toner becomes high, and if it is larger than the outflow start temperature Tf [° C.], the internal cohesive force of the toner on the medium becomes weak, and a part of the toner comes to adhere to the fixing roller. The toner on the medium is in a rubbery state below the toner outflow start temperature Tf and can be fixed within a range where no fixing offset occurs.

<< 1-4 >> Test 2
In Test 1, white toner was produced in the same manner as in the production of the white toner, except that the same polyester resin as the color toners other than the white toner (black toner 1, cyan toner 1, magenta toner 1, yellow toner 1) was used. did. The average particle diameter of the obtained white toner was 7.0 [μm], and the loose apparent density was 0.60 [g / cm ³ ]. This is called white toner 2. The thermal properties of the white toner 2 were a softening temperature Tsw = 82 [° C.], a toner outflow start temperature Tfw = 97 [° C.], and a toner melting temperature Tmw = 116 [° C.]. When the powder hue of the white toner was measured at this time, the value on the (L *, a *, b *) color space coordinate axis was
L * = 94.51, a * =-1.17, b * = 2.78.
In the same manner as in Test 1, except that the white toner 2 was used in place of the white toner 1, a printing test was performed by setting the medium surface temperature Mt immediately after fixing to 85 [° C.]. The turbidity of the white toner was 70%, which was the same as that of the color toner. The results are shown as Tables 4 and 5 in FIGS. 7 and 8, and as shown in the graph on the (L *, a *, b *) color space coordinate axis in FIG. A point <1> indicated by a black circle “●” in FIG. 6 is a point of each color of YMCRGB which is black paper and does not overlap with white toner, and a point <2> indicated by a black triangle “▲” is a black paper on the mount. Thus, it was confirmed that the color reproduction range was greatly narrowed in the case of Test 2 for each color of YMCRGB having an overlap with the white toner, compared to the case of Test 1. From Test 1 and Test 2, increasing the turbidity of the white toner increases the proportion of diffused light and makes it less susceptible to the underlying color. From the above results, if a white toner having a turbidity of 88% or more is formed under the color toner as a base, it can be made less susceptible to the color of the recording medium, and therefore the color reproducibility of the upper color toner. Is considered to be favorable.

<< 1-5 >> Test 3
In Test 1, the same polyester resin as that of the white (W) toner 1 was used in the production of the black (K) toner, the cyan (C) toner, the magenta (M) toner, and the yellow (Y) toner. A toner other than white was produced. The obtained toner had an average particle size of 7.0 [μm] and a loose apparent density of 0.35 [g / cm ³ ], respectively. The toners at this time are called black toner 2, cyan toner 2, magenta toner 2, and yellow toner 2, respectively.

  The black toner 2 had a softening temperature Ts = 82 [° C.], a toner outflow start temperature Tf = 97 [° C.], and a toner melting temperature Tm = 146 [° C.]. The cyan toner 2 had a softening temperature Ts = 82 [° C.], a toner outflow start temperature Tf = 97 [° C.], and a toner melting temperature Tm = 146 [° C.]. In the magenta toner 2, the softening temperature Ts = 82 [° C.], the toner outflow start temperature Tf = 97 [° C.], and the toner melting temperature Tm = 146 [° C.]. The yellow toner 2 had a softening temperature Ts = 82 [° C.], a toner outflow start temperature Tf = 97 [° C.], and a toner melting temperature Tm = 146 [° C.]. When a printing test was performed using the above toners, all the toners had a single color and a glossiness of 11% or less, and the glossiness was low as in the case of the white toner 1, resulting in poor image quality in full-color printing.

<< 1-6 >> Test 4
In Test 1, the test was performed in the same manner as in Test 1 except that blue paper (Kishu Paper Co., Ltd., colored fine paper, thick mouth, blue paper, 90 [g / m ² ]) was used as the printing medium. When the fixing roller surface temperature was 165 [° C.], the medium surface fixing temperature was 85 [° C.]. At this time, the color reproduction range was as shown in Table 6 and FIG. 11 shown in FIG. 10, and good color reproducibility was obtained. A point <1> indicated by a black circle “●” in FIG. 11 is a point of each color of YMCRGB which is blue paper and does not overlap with white toner, and a point <2> indicated by a black triangle “▲” is a blue paper on the mount. And YMCRGB color points that are overlaid with white toner.

Further, instead of blue paper, yellow paper (manufactured by Kishu Paper Co., Ltd., colored fine paper, thick paper, yellow paper, 90 [g / m ² ]) and red paper (produced by Kishu Paper Co., Ltd., colored fine paper, thick B, red paper, 90 [g / m ² ]), a good color reproduction result was obtained.

<< 1-7 >> Test 5
In addition, the effect of using the following toner was confirmed.
White (W) toner: haze value = 91.1 [%], flow data Tsw = 82 [° C.], Tfw = 99 [° C.], Tmw = 155 [° C.], gloss value = 10.0, powder hue L * = 80,1, a * = − 2.5, b * = − 3.1
Black (K) toner: haze value = 59 [%], flow data Tsk = 70 [° C.], Tfk = 84 [° C.], Tmk = 101 [° C.], gloss value = 39.9, powder hue KL * = 14.0, a * = − 0.1, b * = − 1.3
Yellow (Y) toner: haze value = 59 [%], flow data Tsy = 70 [° C.], Tfy = 83 [° C.], Tmy = 101 [° C.], gloss value = 41.0, powder hue Y L * = 89.3, a * = − 9.9, b * = − 108.2
Magenta (M) toner: haze value = 60 [%], flow data Tsm = 71 [° C.], Tfm = 84 [° C.], Tmm = 102 [° C.], gloss value = 40.1, powder hue ML * = 38.0, a * = 63,2, b * = 7.9
Cyan (C) toner: haze value = 59 [%], flow data Tsc = 70 [° C.], Tfc = 83 [° C.], Tmc = 101 [° C.], gloss value = 41.0, powder hue CL * = 36.0, a * = 2.2, b * = − 50.3

When a toner having a turbidity of 88% is used, good color reproducibility can be realized when an image is formed on a transparent film. Therefore, even when the toner having a turbidity of 91.1 [%] is used as described above, good color reproducibility can be realized when an image is similarly formed on a transparent film. On the other hand, when a color toner having a turbidity of 70% or less is used, it has high glossiness and good color reproducibility can be realized. For this reason, the toner having a turbidity of about 60 [%] as described above can also have a high glossiness and a good color reproducibility.
If the turbidity of the white toner is 88% or more and the turbidity of the color toner is about 70% or less, it is difficult to be influenced by the color of the base and a high gloss image can be obtained.

<< 1-8 >> Effect of First Embodiment As described above, by making the turbidity of the white image higher than the turbidity of the image by the color toner, it is difficult to be affected by the color of the background and is high. A glossy image can be obtained. In other words, by making the turbidity of the white image relatively high, it can be made less susceptible to the influence of the background color, and if the turbidity of the image by the color toner is made relatively low, a higher gloss image can be obtained. Can be obtained. More desirably, when the turbidity of the white toner is 88% or more and the turbidity of a single color toner is 70% or less, a highly glossy image can be obtained without being affected by the underlying color. Can do. More desirably, if a medium fixing surface temperature not lower than the softening temperature Ts [° C.] of the color toner and not higher than the outflow start temperature Tf [° C.] is employed, the color of the medium is not limited, and the medium color is not easily affected. In addition, an image having high gloss can be obtained.

<< 2 >> Second Embodiment << 2-1 >> Configuration of Second Embodiment FIG. 12 is a block diagram schematically showing an image forming apparatus 211 according to the second embodiment of the present invention. In FIG. 12, the same reference numerals are given to the same or corresponding components as those in FIG. 1 (first embodiment). In the image forming apparatus 211 of the second embodiment, the cyan toner image forming unit 17 is disposed on the most upstream side in the recording medium conveyance direction, and the white toner image forming unit 13 is disposed on the most downstream side in the recording medium conveyance direction. This is different from the image forming apparatus of the first embodiment. In other words, the image forming apparatus 211 of the second embodiment has a configuration in which the cyan toner image forming unit and the white toner image forming unit in the image forming apparatus (printer) 11 of the first embodiment are interchanged. Except for this difference, the image forming apparatus 211 of the second embodiment is the same as the image forming apparatus 11 of the first embodiment.

<< 2-2 >> Operation of the Second Embodiment In Test 1 of the first embodiment, the printing speed is obtained by using iron print paper (for example, Quick Art Co., Ltd., light color ground transfer paper CR) as the print medium. Was set at 50 [mm / sec] and a medium fixing temperature of 90 [° C.], and color toner was transferred onto iron print paper, and then transferred and printed so that the white toner was the uppermost layer. The printed printing paper is stacked on a black polyester fabric, and the toner is transferred from the iron printing paper to the fabric at 170 [° C.], 20 [sec], and 500 [kg / cm ² ] with a press machine. It was. As a result, the toner was fixed on the fabric, and an image with good color reproducibility was obtained.

  In addition, when iron printing was performed with the same configuration as in Test 1 in the case where the positions of the image forming unit 13 and the image forming unit 17 were not interchanged, white toner was the top layer on the fabric, and a white image was formed overall. As a result, color reproducibility was impaired.

<< 2-3 >> Effects of Second Embodiment As described above, in the image forming apparatus of the first embodiment, it is possible to realize good printing on iron-printed paper simply by replacing the toner cartridge. it can.

<< 3 >> Other Usage Forms In the first and second embodiments, the case where the present invention is applied to a printer has been described. However, the present invention is not limited to a facsimile, a copying apparatus, a multifunction peripheral (MFP, Multi Function Peripherals), or the like. The present invention can also be applied to other apparatuses using such an electrophotographic system.

  DESCRIPTION OF SYMBOLS 11,211 Printer (image forming apparatus), 12 Medium cassette, 13-17 Image forming unit, 19 Transfer part, 20 Fixing device, 21 Medium, 22 Image forming part, 33 Transfer belt, 34 Drive roller, 35 Tension roller, 38 Transfer belt cleaning blade, 39 waste toner tank, 40 developing roller, 41 supply roller, 42 developing blade, 43 toner, 44 toner cartridge, 45 charging roller, 46 cleaning blade, 48 heating roller, 49 pressure roller, 50 pressure belt 53 to 57 Photosensitive drum, Mt Surface temperature at fixing of fixing device (or medium), Ts single color developer softening temperature, Tf single color developer flow start temperature.

An image forming method according to an aspect of the present invention includes: a first image forming step of forming a first developer image using a white developer; a white development with a melting temperature lower than a melting temperature of the white developer; A second image forming step of forming a second developer image using a developer of a color other than white whose outflow start temperature is lower than the outflow start temperature of the agent, and the first developer image and the second developer image A fixing step of fixing the developer image to the recording medium.

Claims (9)

A first image forming step of forming a first developer image using a white developer;
A second developer image is formed using a developer of a color other than white, the softening temperature of which is lower than the softening temperature of the white developer, and the outflow start temperature of which is lower than the outflow start temperature of the white developer. Two image forming steps;
An image forming method comprising: a fixing step of fixing the first developer image and the second developer image on a recording medium. The image forming method according to claim 1, further comprising a transfer step of transferring the first developer image and the second developer image to a recording medium. In the first image forming step, the first developer image is formed so that the density of the white developer per unit area is in a range of 0.8 to 1.1 [mg / cm ² ]. And
In the second image forming step, the second developer image is adjusted so that the density of the developer other than white per unit area is in the range of 0.4 to 0.6 [mg / cm ² ]. The image forming method according to claim 1, wherein the image forming method is formed. In the first image forming step, the first developer image is formed so that the density of the white developer per unit area is within a range of 0.9 to 1.1 [mg / cm ² ]. And
In the second image forming step, the second developer image is adjusted so that the density of the developer other than white per unit area is in the range of 0.4 to 0.5 [mg / cm ² ]. The image forming method according to claim 1, wherein the image forming method is formed.   5. The image forming method according to claim 1, wherein the second developer image is formed after the first developer image is formed on the recording medium. 6.   5. The image forming method according to claim 1, wherein the first developer image is formed after forming the second developer image on the recording medium. 6. The maximum value among the softening temperatures of the developer other than the white is expressed as Tsmax [° C.],
When the minimum value of the outflow start temperature of the developer other than white is expressed as Tfmin [° C.]
Mt [° C.] is a surface temperature at the time of fixing of the recording medium in the fixing step.
Tsmax [° C.] ≦ Mt [° C.] ≦ Tfmin [° C.]
The image forming method according to claim 1, wherein:   The image forming method according to claim 1, wherein the turbidity of the first developer image is higher than the turbidity of the second developer image. The turbidity of the first developer image is 88% or more in haze value,
9. The image forming method according to claim 1, wherein the turbidity of the second developer image is 70% or less in terms of a haze value.

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