JPS63301963A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To enable a black color to be sharply recorded by adding another pigment or a dye having a reflectance of <=3% in the wavelength region of 500-600nm to a black toner, 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 is prepared by blending >=2 kinds of pigments or dyes transmitting light in the wavelength region of >=750nm, and moreover, blending another pigment or dye transmitting light in the wavelength region of >=750nm, and having a reflectance of <=3% of that of noncoated white paper in the wavelength region of 500-600nm, when the white paper is coated in a thickness of 10-20mum with the black toner. The black toner is prepared not by using a signal 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 absorbs the visible light, and especially more perfectly absorbs the light in the wavelength region of 500-600nm, 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 electrophotography or electrostatic recording, an electrostatic latent image is formed on an image forming member and developed with toner, which is charged particles. This device has been commercialized as a copier, printer, etc. Further, in order to obtain a multicolor image or a composite image (superposition of a plurality of original documents or image information and an original image), the above-mentioned principle is utilized in the following manner. That is, it is realized by carrying out two or more cycles of (1) charging, (2) image exposure, and (3) development on an image formation having a photoconductive layer on a conductive substrate.
No. 81). Alternatively, using an image forming body with a transparent insulating layer provided on the outside of the photoconductive layer, ■-secondary charging■secondary charging simultaneous image exposure■uniform exposure■development is one cycle and two
There is a method in which the process is carried out two or more times, or a method in which one cycle consists of (1) - secondary charging, (2) secondary charging, (2) image exposure, and (3) development (for example, Japanese Patent Application No. 58-183152). 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 vc position where a multicolor image or a composite image can be obtained. 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 photoconductor) with a light beam such as a laser, which has a photoconductive substance on a conductive substrate. 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 PH is the exposed area of the image forming body, D^ is the unexposed area of the image forming body, and T is the area where the image is formed during the first development. The toner T2 attached to the body is the toner attached to the image forming body during the second development, and DUP is the toner T1 attached to the exposed area PH during the first development.
This shows the increase in potential caused by adhesion. 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 exposed portion PH 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 T1 adheres to the exposed portion P)I, which has a relatively low potential, and a first toner image is formed. In the area where this toner image is formed, the potential increases by DIP due to the adhesion of the positively charged toner T, but normally it does not have the same potential as the unexposed area D^. ■ Next, the surface of the image forming body on which the first toner image has been formed is charged a second time by a charger, and as a result, the toner T
Regardless of the presence or absence of 1, a uniform surface potential E is obtained. (2) A second image exposure is performed on the surface of this image forming body to form an electrostatic latent image. (2) Similarly to (2) above, positively charged toner T2 of a different color from toner T1 is developed to obtain a second toner image. Thereafter, the same process is repeated a necessary number of times to obtain a multicolor toner image on the image forming body. A multicolor recorded image can be obtained by transferring this to a transfer material and further fixing it by heating or applying pressure. In this case, the toner and charges remaining on the surface of the image forming member 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 explained above,
There are two methods: ■A method that does not directly overlap toners of different colors. ■A method in which toners of different colors are layered on top of each other. (2) By distributing multicolored toners T3 and T2 on the image forming body 1 without overlapping them as shown in FIG. 5(A),
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, toner of a different color is superimposed on a toner image of a certain color and developed to generate colors (subtractive color mixing). . 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 in that the toner image T1 partially blocks image exposure, and the amount of attached toner T2 to be 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 onto the previously developed toner T1, it is absorbed by the 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 becomes noticeably smaller. 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 α, a method has been proposed in which yellow and magenta are developed first using a laser beam or the like as an image exposure means (Japanese Patent Application No. 181087-1987).
, 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 black areas in the recorded image is reduced, the density is low, and character areas become unclear.

[Purpose 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 create a black toner by blending two or more types of pigments or dyes that both transmit light in the wavelength range of 750n+n or more, and that transmits wavelengths of 750n111 or more and spread the toner on a white paper to a thickness of 10%. This is achieved by an electrophotographic toner which is characterized in that a pigment or dye is separately added which gives a reflectance of 3% or less based on the uncoated state of the mortar paper in the wavelength range of 500 to 600 nm when coated at ~20 μm. Ru.

[Effect]

In the present invention, the black toner is not created using a single colorant such as carbon black, but is obtained by synthesizing a plurality of colorants 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, especially from 500nm to 600++n+.
to more completely absorb light in the wavelength range. A toner is produced using the colorant thus obtained. This toner becomes black toner. 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 toner of another color can be developed on the black toner image. As a result, when the toner image superimposed on the image forming body is transferred to a transfer material, black toner is formed on the upper part of the transfer material, and black parts can be developed clearly and chromatic parts 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 rotates in the direction of the arrow and is an image forming body consisting of a photoreceptor having 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 7-ar 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 consisting of a suflotron electrode. Subsequently, the image forming body 1 is irradiated with infrared image exposure light according to the recording data from the laser optical system 26 . In this way, an electrostatic latent image is formed. This electrostatic latent image is developed by the developing device 5D containing the first toner T1. The image forming body on which the toner image has been formed is again charged by the corona charger 2.
1, and receives image exposure light I5 according to recording data of another color component. The electrostatic latent image formed is fJ
The toner T2 of S2 is developed by the developing device 5C containing the toner T2. As a result, the first toner T is deposited on the image forming body 1.
, and a two-color toner image is formed using #2 toner T2. Thereafter, toner T (developing device 5B) and toner T (developing device 58) are developed in a superimposed manner in the same manner, and a four-color toner image is formed on image forming body j. The multicolor 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
4 and is separated from the image forming body 1 and fixed by a fixing device 31. On the other hand, the image forming body 1 is cleaned by a cleaning device 36. Fur brush 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 with a scraper 36c. FIG. 2 shows the laser optical system 26 in this embodiment. In the diagram, 3
7 is a semiconductor laser diode whose main emission wavelength is, for example, infrared 780 nm, 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, that is, a region where the toner conveyed by the sleeve 53 can be transferred to the image forming body under electrostatic force, T is l·ner, D is represents a 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. This replenishment of 1 to toner to the developing device 5 is performed from the front side in FIG.
7, the toner and carrier are roughly circulated toward the front side of the paper, and the toner and carrier are mixed uniformly. However, the position of toner replenishment from 1 to 1 is not particularly limited to this, and for example, a method of uniformly replenishing 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 example 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 device such as a magnetic roll may be used. It is advantageous for the carrier and toner constituting 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. Moreover, even if the carrier has a particle size as small as that of the toner, impurities can be 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 one hener T from the sleeve 53. For this reason, the star of the toner T transported to the development area can be kept constant.
Development conditions become stable. Next, the composition of the developer used in the developing method of this embodiment will be described. (Developer formulation) Toner composition: Polyester resin 100 parts by weight Barriface l-0,2 horns (charge control agent) Colorant 21 to 24 tons The above composition is mixed, kneaded and classified to give the desired one to I'm trying to keep my energy up. Carrier (resin-coated carrier) composition: Core: Coating to Ferrai 1 Resin: Styrene/acrylic (4:6) Magnetization: 27 emu/g Particle size: 30 μm Specific gravity: 5.2 g 7 cm3 Specific resistance: 1013 ΩcjI or more The above composition was mixed, kneaded, and classified. The spheroidized product was then treated with hot air and used as a carrier. Conventionally known colorants are used as colorants for chromatic (yellow, magenta, cyan, etc.) toners. As the coloring agent for black 1 henna, a mixture of multiple types of coloring agents is used. Conditions for the plurality of colorants to be mixed include the following. (1) The absorption ranges complement each other in the visible range (wavelengths from 360 to 750 nm). (2) There is a common wavelength range that transmits light in the wavelength range of 750 nm or more. According to condition (1), black can be expressed. 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 prepared a black toner by mixing the following pigments. (Example 1) ■ Pigment Yellow+ 13 (hex l-); 7 parts ■ Pigment 0rang
e 43 (horn); Part 7 ■
4Hment 1)lue 15:3(horn
), 7 parts (Example 2) ■ Pigment Yellow…13; 7 parts ■ Pigment Orange 43;
Part 7■ I'igment Blue 15:
3; Part 7■ Pigment Itcd 57:
1 (Sumitomo Chemical); 3 parts of the above pigment, main resin (polyester resin), 100 parts of mold release agent (wax), 4 parts of pigment
; 5 to 30 parts of this are mixed and subjected to melt kneading, crushing and classification. The average particle size of the pigment used was 0.2μ, and the average particle size of the prepared toner was 1.
It was set to 1μ shoulder. The particle size of the pigment is preferably in the range of 0.1 to 1 μm. The larger the pigment, the easier it is to disperse, but 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 reflectance using a spectrophotometer (HITACHI Model 330) based on the state in which nothing is coated on the white adhesive sheet. FIG. 6 is a graph showing the spectral reflectance of the toner made using the pigment shown in Example 1, and FIG. 7 is a graph showing the spectral reflectance of the toner made using the pigment shown in Example 2. As shown in FIG. 6, the toner prepared using the pigment of Example 1 has a reflectance at 550 nm that is 2% higher than the reflectance at 400 nm to 500 nm or 600 nm to 700 nm, and appears greenish black. As a result of experiments conducted with a black toner made from carbon black, the conditions for the black toner to appear are that the reflectance is 5% or less in the entire visible light range and that the spectral reflectance is flat. When mixing various pigments to prepare black toner as described above, it is difficult to obtain flat characteristics over the entire visible light range. However, it has been found that visually good black color can be obtained by making the reflectance of 500 nm to 600 n +n lower than the reflectance of other regions. So especially 500
A magenta or red dye or pigment is added to reduce the reflectance in the wavelength range of nm to 600 nm. It goes without saying that this dye or pigment must also have high transmittance at 750 nm or more. Examples of pigments that satisfy the above conditions include Pigme
nt Red 57: ID1avesin Re
d I+ (Mitsubishi Kasei) DiavesinRedK (
u) DiavesinRedl15B(u)Diavesi
Examples include nViolet 8(u). FIG. 7 is a spectral reflectance curve of a black toner obtained with the pigment of Example 2 to which Pigment Red 57:1 was added. Comparing with the spectral reflectance curve shown in Figure 6, P
It can be seen that the effect of adding igment Red 57:1 appears. When such a toner is used in the apparatus shown in FIG. 1 under the conditions shown in Table 1, when the reflectance is 40% or more, preferably 60% or more at the main wavelength of image exposure, any number of colors can be obtained. A latent image with high contrast was obtained regardless of the condition. 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 toner image is transferred to the transfer material. The transfer 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 the black toner made of carbon black. Table 1□□□□----] Writing resolution: 16doL/Writing level:
binary

【Effect of the invention】

The present invention provides a toner that can always record black clearly, express colors in a well-balanced manner, has excellent fixing properties, and has good transfer.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a multicolor image forming apparatus using the image forming method of the present invention, Figure 2 is a diagram of the configuration of a laser optical system, Figure 3 is a sectional view of a developing device, and Figure 4 is an image forming body. Diagram showing the change in surface potential above, tIS
FIG. 5 is a block diagram showing the state of adhesion of toner on the image forming body, and FIGS. 6 and 7 are graphs showing the spectral reflectance of toner according to an embodiment of the present invention when applied to a blank sheet of paper. 1... Image forming body 5^, 58.5C, 5D... Developing device 21... Corona charger 26... Laser optical system 32... Pre-transfer exposure lamp 33... Transfer electrode 34... ...Separation electrode 36...Cleaning device T,, T2...)・Nar applicant Konishi Roku Photo Industry Co., Ltd. Figure 4 E: Surface potential PH: Exposed area DH: Unexposed area DUP:) Due to toner adhesion Potential increase molecule 1: Toner T2 2 Toner

Claims (2)

[Claims] (1) To create a black toner by blending two or more types of pigments or dyes that both transmit light in the wavelength range of 750 nm or more, apply the above toner to a thickness of 10 to 20 μm on white paper. 500 if
A toner for electrophotography, characterized in that a pigment or dye is separately added which has a reflectance of 3% or less based on the uncoated state of the white paper in a wavelength range of 600 nm. (2) The electrophotographic toner according to claim 1, wherein the pigment or dye added is a magenta or red pigment or dye.