JPS63301962A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To enable a black color to be sharply recorded by using a black toner having a reflectance satisfying specified conditions, when white paper is coated in a specified thickness with a black toner obtained by blending >=2 kinds of pigments or dyes transmitting light in the wavelength region of >=750nm. CONSTITUTION:The black toner to be used has spectral characteristics having a reflectance of <=5% in the total visible light wavelength region and a reflectance of >=40% in the >=750mum wavelength region by using the noncoated white paper as the basis, when the white paper is coated in a thickness of 10-20mum with the black toner obtained by blending >=2 kinds of pigments or dyes transmitting light in the wavelength region of >=750nm. The black toner is prepared not by using a single colorant, such as carbon black, but by mixing plural colorants, such as yellow, magenta, and cyan colorants, and each of these colorants transmits light in the nonvisible wavelength region, and the obtained mixed colorants transmits light in the nonvisible wavelength region, and substantially and completely absorbs the visible light, thus permitting the obtained black toner to sharply record the black parts and the colored parts in good balance.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an electrophotographic toner that forms an image on a recording material using an electrophotographic method.

[Background of the invention]

In an image forming apparatus using an electrophotographic method or an electrostatic recording method, an electrostatic latent image is formed on an image forming member, and the image is developed with 1 hener, which is a charged particle. This device has been commercialized as a copier, printer, etc. Furthermore, multicolor images and composite images (overlaying multiple originals or image information with original images)
The above principle is utilized in the following way to obtain . That is, for image formation having a photoconductive layer on a conductive substrate,
This is achieved by performing charging, image exposure, and development two or more times (for example, in Japanese Patent Application No. 58-184).
No. 381). Alternatively, a method in which a transparent insulating layer is provided on the outside of the photoconductive layer is used as an image forming body, and ■-secondary charging ■secondary charging simultaneous image exposure ■uniform exposure ■development is performed two or more times as one cycle. , or a method in which (1)-secondary charging, (2) secondary charging, (2) image exposure, and (3) development are carried out twice or more in one cycle (for example, Japanese Patent Application No. 183152/1983). All of these methods enable multicolor development and image composition on the image forming body, and these superimposed images can be transferred to the transfer body in a single transfer process, so they have a simple configuration. This is a device that can obtain multicolor images and composite images. As a developing method for this purpose, for example, development is carried out using a developer consisting of a mixture of a non-magnetic toner and a magnetic carrier under the conditions described in Japanese Patent Application No. 58-57446 or No. 60-192712. It is necessary. This developing method is a type of magnetic brush developing method, and is characterized in that the magnetic brush is not brought into contact with the image forming body, and only the toner is caused to fly onto the latent image surface of the image forming body using an alternating current bias. An example of the above-mentioned image forming apparatus is one in which a latent image forming means forms latent images for each color, and each latent image is developed by a developing device using toner of a corresponding color. In such a multicolor image forming apparatus, an electrostatic latent image is formed by irradiating an image forming body (hereinafter also referred to as a photoreceptor) with a photoconductive substance on a conductive substrate with a beam of light such as a laser. A thing is representative. In such an apparatus, a multicolor image is formed as shown in chart 70 of FIG. Figure 4 shows the change in surface potential of the image forming body, where Pl+ is the exposed area of the image forming body, D is the unexposed area of the image forming body, and T1 is the surface potential of the image forming body during the first development. The toner T2 attached to the top is the toner attached to the image forming body during the second development, and DUP is the toner T2 attached to the image forming body during the first development in the exposure section 1.
, shows the increase in potential caused by the adhesion of . For the sake of explanation, the polarity of the latent image is assumed to be stop. (2) The image forming body is uniformly charged by a charger and has a constant positive surface potential E. (2) First image exposure is applied using a laser, cathode ray tube, or LED as an exposure source, and the potential of the exposure section 1 decreases in accordance with the amount of light. (2) The electrostatic latent image thus formed is developed by a developing device to which a positive bias approximately equal to the surface potential E of the unexposed area is applied. As a result, the positively charged toner T, (-1) is deposited on the exposed area P)l, which has a relatively low potential, and a first toner image is formed. Due to the adhesion of T1, the potential increases by DIIP, but normally it does not reach the same potential as the unexposed area. ■ Next, the surface of the image forming body on which the first toner image is formed is charged a second time by a charger. As a result, a uniform surface potential E is obtained regardless of the presence or absence of l~nana-1. ■ A second image exposure is applied to the surface of this image forming body to form an electrostatic latent image. ■ In the same manner as in (■) above, positively charged toner T2 of a color different from toner T1 is developed to obtain a second toner image. The same process is repeated as many times as necessary to form a toner image on the image forming body. A multicolor toner image is obtained. This is transferred to a transfer material and then heated or pressurized to fix it. A multicolor recorded image is obtained. In this case, the l.
The toner and charges are cleaned and used for the next multicolor image formation. The above process is not limited to multicolor images, but can also be applied to an apparatus that synthesizes toner images on an image forming body and transfers them all at once to form a recorded image.

[Problems to be Solved by the Invention] When expressing various colors using the method described in section 2 below, there are the following two methods. ■A method that does not directly overlap items 1 to 2 of different colors. ■A method of layering henna of different colors on top of each other. (2) is a multicolored toner T1. as shown in FIG. 5(A). By distributing T2 on the image forming body 1 without overlapping in principle,
This is to generate colors (additive color mixture) on the recording paper in a pseudo manner. (2) As shown in (B), by controlling the latent image potential and developing bias, toners 1 to 1 of different colors are developed on top of a toner image of a certain color to generate colors (subtractive color mixing). It is. However, in case (2), it is necessary to precisely align the image exposure with an accuracy of one pixel or less so that the toner images of each color do not overlap at the same position, and if the positional accuracy of the image exposure is incomplete, the previous stage There is a problem that the 1-hener image T1 partially blocks the image exposure, and the amount of the 1-hener T2 that is developed in the subsequent stage is significantly reduced as shown in FIG. 5(C). In this case, it is not possible to create a mixture of desired color tones. In addition, in case (2), even if light is irradiated from above the previously developed toner 1 to toner T1, it is absorbed by toner T1 and does not reach the photoconductive layer sufficiently, and a latent image is not completely formed. As shown in (D), the amount of toner T2 that was developed later is noticeably reduced. The above is a case where reversal development is performed, but when regular development is performed, on the contrary, the later toner T2 non-selectively adheres to the earlier toner T, causing color smearing. In order to avoid this problem, a method has been proposed in which yellow and magenta are developed first using a long wavelength laser beam as an image exposure means (Japanese Patent Application No. 59-181087,
181550 etc.). According to this method, the yellow image will be below the other colors on the image forming member and above the other colors on the transfer material. However, yellow has greater surface reflection than other colors, and in the multicolor image obtained by the above method, yellow is emphasized more than necessary, especially in colors to which yellow is added, such as green and red. For this reason, there was a problem in that color control was extremely difficult. In particular, this problem becomes a major obstacle when trying to express black color from yellow, magenta, and cyan toners. Therefore, it is preferable to use a special toner for expressing black. When forming a multicolor image from yellow, magenta, cyan, and black toners, conventional black toner absorbs most of the light, both visible and non-visible, so the black toner must be developed later. Since the amount of toner developed later is reduced, the number of dots in the recorded image is reduced, the density is low, and the character parts become unclear. OBJECTS OF THE INVENTION An object of the present invention is to provide a toner that can always record black clearly and express colors in a well-balanced manner.

[Structure of the invention]

The above purpose is to achieve the following by applying a toner obtained by blending two or more types of pigments or dyes, both of which transmit light in the wavelength range of 750 nm or more, to a thickness of 10 to 20 μm on white paper, based on the uncoated state of the white paper. 5% reflectance over the entire visible light range
The reflectance in the wavelength range of Q750nm or more is 4 or less.
This is achieved by an electrophotographic toner having spectral properties of 0% or more.

[Effect]

In the present invention, blacks 1 to 3 are not created using a single coloring agent such as carphone black, but are obtained by synthesizing a plurality of coloring agents such as yellow, magenta, and cyan. Each of these colorants is selected to have a component that transmits in the non-visible light range, so that the obtained black synthetic colorant also transmits in the non-visible light range. Also, visible light is substantially completely absorbed. The coloring agent thus obtained is used to produce L-ner. This l.na becomes black I.na. When this toner is used in the multicolor image forming method described above, the black toner can be developed first. At this time, the light source used for image exposure has a spectral distribution in the transmission wavelength range in the above-mentioned non-visible light range. As a result, a latent image can be formed superimposed on the black toner, and toners of other colors can be developed on the black 1-henner image. As a result, when the 1-henner image superimposed on the image forming body is transferred to a transfer material, black 1-toner is formed on the upper part of the transfer material, and the black part can be developed clearly and the chromatic color part can be developed in a well-balanced manner. .

【Example】

FIG. 1 shows an embodiment of a multicolor image forming apparatus configured to use the electrophotographic toner of the present invention. In the figure, 1 is an image forming body consisting of a photoreceptor that rotates in the direction of the arrow and has sensitivity in the infrared region, 21 is a corona charger, L is infrared image exposure light irradiated from a laser optical system 26, 5^, 5B
, 5C, 5D are developing devices having yellow, magenta, cyan, and black toners, 32 is a pre-transfer exposure lamp having an infrared light component, 33 is a transfer electrode, 34 is a separation electrode, P is a recording paper, and 36 is a recording paper. In the cleaning device, 36a is a fur brush, 36b is a toner collection roller, and 36c is a scraper. This forms a multicolor image in the following manner. The surface of the image forming body 1 is uniformly charged by a corona charger 21 comprising a Scoro I to Ron charge electrode. Subsequently, the image forming body 1 is irradiated with infrared image exposure light from the laser optical system 26 in accordance with the recorded data. In this way, an electrostatic latent image is formed. This electrostatic latent image is developed by the developing device 5D in which the first toners T1 are accommodated. The image forming body on which the L.color image has been formed is uniformly charged again by the corona charger 21 and receives image exposure light according to recorded data of another color component. The electrostatic latent image formed is the second
The toner T2 is developed by the developing device 5C in which the toner T2 is stored. As a result, a two-color toner image is formed on the image forming body 1 by the first toner T1 and the second toner T2. In the same manner, toner T, (developing device 511), and toner T4 (developing device 5^) are developed in a superimposed manner, and a four-color toner image is formed on the image forming body 1. The multicolor 1-toner image thus obtained on the image forming body 1 is exposed by the pre-transfer exposure lamp 32 and then transferred to the recording paper P by the transfer pole 33. Recording paper P is separated pole 3
The image forming member 1 is separated from the image forming member 1 by the image forming member 4, and is fixed by the fixing device 31. On the other hand, the image forming body 1 is cleaned by a cleaning device 36. Fur flap 36 of cleaning device 36
a is kept out of contact with the image forming body 1 during image formation,
When a multicolor image is formed on the image forming body 1, it comes into contact with the image forming body 1 after being transferred, and scrapes off the transfer residual toner while rotating in the direction of the arrow. When the cleaning is finished, the fur brush 36a leaves the image forming body 1 again. An appropriate bias is applied to the toner collection roller 36b while rotating in the direction of the arrow, and the toner T and the like are collected from the fur brush 36a. It is further scraped off by a scraper 36c"C'. The laser optical system 26 in the embodiment is shown in FIG.
7 is a semiconductor laser diode whose main emission wavelength is, for example, infrared 780 nn+, 38 is a rotating polygon mirror, and 39 is an fθ lens. FIG. 3 is a sectional view of the developing device 5^. In the figure, 51 is a housing, 53 is a sleeve, 54 is a developer conveying member, that is, a magnetic field generating means provided in the sleeve, and is a magnetic roll having N and S poles, 55 is a layer forming member, and 56 is a fixing member for this member. , 57 is a first stirring member, and 58 is a second stirring member. 59 is a sleeve cleaning member; 60 is a developing bias power source; 18 is a developing area; Toner and D represent developer. In this developing device, the two stirring members 57 and 58 are screw-shaped, and rotate in the direction of the arrow in the figure to stir and transport the developer. The stirring member 57 is shaped to be conveyed toward the front of the page, and the stirring member 58 is conveyed toward the back of the page. A wall 52 is provided so that the developer does not accumulate in the intermediate area between the two, and therefore the developer is exchanged in this area in the left-right direction in the drawing. Toner is replenished to the developing device 5 from the front side in FIG.
As a result, the toner and carrier are roughly circulated toward the front side of the page, and the toner and carrier are mixed uniformly. However, the position of toner replenishment is not particularly limited to this, and for example, a method of uniformly replenishing the toner to the sleeve shaft from the right side in FIG. 3 may be used. In this way, the developer mixture is sufficiently stirred and mixed, and is transported in the same direction as the rotational direction of the sleeve 53 by the transporting force of the sleeve 53 and the magnetic roll 54, which rotate in the direction of the arrow. A layer forming member 55 held by a fixing member 56 extending from the housing 52 is pressed against the surface of the sleeve 53 to regulate the amount of developer to be conveyed and form a developer layer. Other means for forming the developer layer when carrying out the development of this embodiment include, for example, a magnetic or non-magnetic regulating plate placed at a certain distance from the sleeve, or a magnetic or non-magnetic regulating plate placed close to the sleeve. Any conventionally known magnetic roll may be used. It is advantageous for the carrier and toner composing the developer to have small particle diameters from the viewpoint of image quality resolution and gradation reproducibility. For example, even when the carrier in the developer layer has a small particle size of 40 μm or less, by using means such as the layer forming member 55 described above, impurities and agglomerates in the developer can be automatically removed and a uniform length can be obtained. A magnetic brush can be formed. However, even if the carrier has a particle size as small as that of the toner, contamination of impurities can be similarly eliminated and a magnetic brush of uniform length can be formed. The sleeve cleaning roller 59 rotates in the direction of the arrow (FIG. 3) and scrapes off the developer that has passed through the developing area 18 and consumed the toner T from the sleeve 53. Therefore, the amount of toner T conveyed to the development area can be kept constant, and the development conditions are stabilized. Next, the structure of the developer of this embodiment used in the above-mentioned developing method will be described. (Developer formulation) Toner composition: Polyester resin 100 parts by weight Parifast 0.2〃 (Charge control agent) Colorant 21-24〃 The above composition is mixed, kneaded and classified to obtain the desired toner. ing. Carrier (resin coated carrier) composition: Core: 7 Elite Coating Resin: Styrene/acrylic (4:6) Magnetization: 27e u/g Particle size: 30 μl Specific gravity: 5.2 g/cy3 Specific resistance: 10I3Ωcz or more Mix the above composition, After grinding and classifying, the mixture was treated with hot air to make it spherical and used as a carrier. Conventionally known colorants are used as colorants for chromatic (yellow, magenta, cyan, etc.) toners. As the colorant for the black toner, a mixture of multiple types of colorants is used. Conditions for the plurality of colorants to be mixed include the following. (1) The absorption ranges complement each other in the entire visible light range (wavelengths from 360 to 700 nm). (2) There is a common wavelength range that transmits in the wavelength range of 750 parts m or more. According to condition (1), black is expressed. can. Also condition (2)
Since light in the common wavelength range is transmitted through the black toner, as described above, when such light is used for image exposure, latent image formation can be performed well. The inventor mixed the following pigments and measured their spectral characteristics. (Example 1) ■ Pigment Yellow+ 13 (Hoechst); 7 parts ■ Pigment Orange 43
(Hoechst); Part 7■ Pigment Blue
15:3 (Hoechst), Part 7■ Pigment Re
d 57:1 (Sumitomo Chemical): 3 parts (Example 2) ■ PiFlment Yellow+ 13;
Part 7■ Disperse Red 5; Part 7■ Pigment Blue 15:3;
Part 7 (Example 3) ■Pigment Yellow+ 17; 7
Part■Pigment Orange 43; 7
Part 5 Olvent Green 26; 7 parts Pigment Red 57:] 3 parts Above pigment Main resin (polyester resin), 100 parts Release agent (wax): 4 parts Pigment
, 5 to 30 parts, and then melted, kneaded, crushed and classified. The average particle size of the pigment used was 0.2 μm, and the average particle size of the prepared toner was 11 μl. The particle size of the pigment is preferably in the range of 0.1 to 1 μM. As the particle size of the pigment increases, it becomes easier to disperse or the density of the toner decreases. The method for measuring spectral characteristics is as follows. ■ Spread the prepared toner onto a white adhesive sheet of Maitatsu Clabel ML-10 (manufactured by Chiban Co., Ltd.) to a thickness of 10 to 20 μm.
Apply to a thickness of . (2) Measure the spectral reflectance using a spectrophotometer (IIITAcIll Model 330), setting the reflectance when nothing is coated on the pressure-sensitive adhesive sheet as 100%. The spectral reflectance of the pigment of Example 1 measured by the method described above is shown in FIG. As is clear from the figure, the reflectance in the visible region was 4% or less, and the reflectance increased rapidly from 740 parts m in the infrared region, reaching 90% at 850 parts m. The spectral reflectance of the toner with the pigment of Example 2.3.4 was also approximately the same as that shown in FIG. At the same time as this measurement, ordinary carbon black black toner (main resin (polyester 120P): 100 parts, release agent (wax): 4 parts, carbon fluff: 10 parts; manufactured by U-BiX) is the same as in 1. As a result of measurements, it was confirmed that a good black color could be obtained if the reflectance was 5% or less over the entire visible range. If the reflectance near a wavelength of 550 nm, which is the maximum visibility for humans, is 2% or more higher than the reflectance in other visible regions, the color tone will appear greenish. Therefore, by blending a dye or pigment that has a reflectance in the range of 500 to 600 nm that is lower than the reflectance in other visible ranges, a visually good black color can be obtained. When creating a toner that is a mixture of several types of dyes or pigments as described above, one is created by mixing toners created for each dye or pigment, and the other is a toner created by mixing each dye or pigment first and then mixed with other toners. When the toner compositions were mixed, kneaded, and classified, the latter yielded a toner with a more stable black tone. The step of preparing a developer with a toner concentration of 7% and a charge amount Q/M+18 μc/g using the toner made of the pigment of Example 1 and the carrier described above, and developing it by overlapping the toner of T1°T2 shown in the flow chart of FIG. Charging→image exposure→development→charging→image exposure, etc.) were carried out, and the surface potential was measured in each case, and the following results were obtained. In Table 1, FIG. 7, and the above Table 1, vL■: surface potential after image exposure, vL■: surface potential when imagewise exposed to the toner image area of the first color. When a black toner made of carbon black was used in the same process, the surface potential was as follows. From the results shown in Table 2 and above, it was confirmed that the blended toner according to the present invention has sufficient translucency for writing laser light (780 nm). Furthermore, when such a toner is used in the apparatus shown in FIG. 1 under conditions not shown in Table 3, what happens when the reflectance is 40% or more, preferably 60% or more at the main wavelength of image exposure 780 nm? A latent image with high contrast was obtained regardless of the color tone. Therefore, if such black toner is developed first, in the case of reversal development, toner of other colors can be superimposed on it, and pre-transfer exposure is also effective, so the transfer material of the 1-toner image is Transfer to the toner was also improved, and a multicolor image with good color balance was obtained, and the black color was appropriately emphasized on the transfer material, resulting in better fixing properties than black toner made of carbon black. Furthermore, the reflectance in the wavelength range of 500nm to 600nm is 3%.
or less, and the reflectance in the wavelength range of 750 nm or more is 60
% or higher, the color balance is good when using Table 3. Writing resolution: 16 dots/mm, writing level: binary

【Effect of the invention】

The present invention provides an electrophotographic toner that can always record black clearly, express colors in a well-balanced manner, and perform good transfer.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a multicolor image forming apparatus using the image forming method of the present invention, Figure 2 is a configuration diagram of a laser optical system, Figure 3 is a sectional view of a developing device, @Figures 4 and 7. FIG. 5 is a diagram showing the state of toner adhesion on the image forming body, and FIG. 6 is a diagram showing the change in surface potential of the image forming body. It is a graph showing the spectral reflectance when applied. 1... Image forming body 5^, 5B, 5C, 5D... Developing device 21... Corona charger 26... Laser optical system 32... Pre-transfer exposure lamp 33... Transfer electrode 34.・・・
Separation electrode 36...Cleaning device W T l, T
2... Toner applicant Roku Konishi Photo Industry Co., Ltd. Figure 4 E: Surface potential PH: Exposed area DH: Non-exposed area DUP:) Potential increase due to toner adhesion Toner T2 2 Toner Figure 6 Heat loss (+ ,,yL) Figure 7

Claims (2)

[Claims] (1) When a toner obtained by blending two or more types of pigments or dyes that both transmit light in the wavelength range of 750 nm or more is coated on white paper to a thickness of 10 to 20 μm, the reflection is based on the uncoated state of the white paper. An electrophotographic toner having spectral properties in which the ratio is 5% or less over the entire visible light range and 40% or more in the wavelength range of 750 nm or more. (2) The toner for electrophotography according to claim 1, wherein the reflectance in the wavelength range of 500 nm to 600 nm is 3% or less, and the reflectance in the wavelength range of 750 nm or more is 60% or more.