JPH03136076A - Electrophotographic printer - Google Patents

Abstract

PURPOSE:To make an amount of sticking toner proper in both graphic printing and line drawing printing by exposing parts, excluding a plane edge, one more time by means of a second exposure light source only in the case of picture information with equal or more prescribed area. CONSTITUTION:For an optical image corresponding to picture information, the entire picture information is written on a uniformly electrified, photoconductive insulated body 2 by means of a first exposure light source 4 based on data from a control part 3. In the case of the entire picture information with equal or more prescribed area, the parts irradiated by the first exposure light source 4, excluding the plane edge of the light source, are irradiated and exposed one more time by the second exposure light source 5 based on data from the control part 3. Since potential exerted on the edge of the optical image plane is almost equal to the entire potential excluding the potential of the edge, the edge effect in toner development is prevented. On the other hand, in the case of the entire picture information with equal or less prescribed area, exposure by means of the second exposure light source 5 is not carried out. Thus, even in the case of line drawing printing, toner is not developed excessively.

Description

[Detailed Description of the Invention] [Summary] Regarding an electrophotographic printer that improves the edge effect in printed matter, the purpose of this invention is to optimize the amount of adhered toner in both graphic printing and line drawing printing. An electrostatic latent image is formed by irradiating an insulator with a light image corresponding to image information, the electrostatic latent image is developed and visualized with toner, and the toner image is transferred onto a recording medium. 1. In an electrophotographic printer that fixes and prints an image, there is provided a control unit for irradiating a light image onto the photoconductive insulator for a length of 1 m according to the image information, and information on the planned image to be printed. control the light image corresponding to)? a first exposure light source that irradiates the photoconductive insulator based on data from iI; and a second exposure light source that irradiates the photoconductive insulator with the light image of a portion other than the edge portion of the surface image portion in the image information, overlapping the light image irradiated by the exposure light source. Configure.

[Industrial application field]

The present invention relates to an electrophotographic printer, and more particularly to a modified Q electrophotographic printer with edge effects in printed matter.

In recent years, electrophotographic printers have become faster, and as the process speed increases, edge effects tend to appear more strongly in graphic printing such as solid black. In addition, since the conditions of the i~lunar adhesion part are different between graphic printing and line drawing printing, it is required to make the printing state of the other side uniform by setting the conditions of A-. Therefore, it is necessary to optimize the amount of adhesion in both graphic printing and line drawing printing.

(Prior Art) In general, the electrophotographic method described in U.S. Pat. An electrostatic latent image is formed by charging the photoconductive insulator with an electrostatic charge such as -, and by irradiating a light image onto the photoconductive insulator by an exposure means. The latent image is developed and visualized with toner, and after the toner image is transferred to paper or the like as necessary, the toner image is fixed by pressure, heat, solvent vapor, light, etc. to obtain a copy or printed matter.

Here, development is performed by the electrically attractive force of charged toner adhering to the latent image formed on the photoconductive insulator. In this case, the normal forward method is when the charges on the toner and the photoconductive insulator have opposite polarities, and the reverse development method is when the charges on the toner and the photoconductive insulator are of the same polarity and use a bias potential. mainly,
The normal development method is used in copying machines, and the reversal development method is used in printers.

Therefore, the case of the reversal development method will be explained with reference to FIG.

FIG. 4 is a diagram for explaining the potential relationship of each part. First, when a photosensitive drum charged with, for example, a foreground potential of 600 (V) is irradiated with a light image, the potential of the irradiated part disappears, and becomes, for example, a printed part potential of 30 (V) (see Fig. 4).
A)). Here, the developing roll (which holds the toner)
For f) shown in the figure, for example, 3
A developing bias potential of 0.00 (V) is applied. During development, when the developing roll and the background part of the photosensitive drum (the part that is not irradiated with the light image) face each other, an electrical repulsive force acts on the toner from the photosensitive drum, and the toner is transferred to the photosensitive drum.
I don't do it. On the other hand, the developing roll and photosensitive drum printing section (
When the developing bias potential (300 (V)) is opposite to the photosensitive drum printed area potential (
30 (V)), the force moves in the direction in which the 1-ner (T) is transferred to the photosensitive drum, and the 1-ner (T) is attached to the photosensitive drum, and development is performed (FIG. 4 (B)).

Here, in addition to the development bias potential, an electric field acts from the spine part near the boundary i* (T-edge part) between the background part of the photosensitive drum and the printed part of the photosensitive drum. Since this electric field is higher than the developing bias potential, the amount of toner developed tends to be large only at the edge portions of the printed area. This is called the edge effect, and becomes more pronounced when the development process speed is high or when the electrical resistance of the developer is high.

By the way, the developed toner is transferred to the printed matter and fixed to form a print, but if the amount of developed toner does not exceed a certain level, it will not be fixed (sufficient blackness will not be achieved. If the amount is too large, a decrease in print resolution and poor fixing are likely to occur.

In other words, the field of toner transferred from the developing roll to the photosensitive drum is determined by various process conditions such as the potential difference between the printing area potential and the developing bias potential, the charge amount of the toner itself, the developing process speed, and the electrical resistance of the developing roll and developer. determined by Therefore, the optimal process can be achieved by printing line drawings, where most of the printing corresponds to edges, such as regular characters, and granoic printing, such as solid black drawings, which have edges and non-edges. selected.

[Problem to be solved by the invention]

However, when printing graphics with an electrophotographic printer that has an extremely high process speed, the edge effect becomes more pronounced as the process speed increases. A large amount of toner adheres, resulting in poor fixing. −
On the other hand, if the process conditions are set to be suitable for line drawing printing, there is a problem in that the amount of toner development in non-edge portions in graphic printing becomes insufficient and an edge effect appears.

Therefore, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an electrophotographic printer that can optimize the amount of adhered toner in both graphic printing and line drawing printing.

[Means to solve the problem]

FIG. 1 shows an explanatory diagram of the principle of the present invention. 1 In the electrophotographic printer 1 shown in FIG. Only the potential decreases. 3 is a control unit which controls the irradiation of a light image onto the photoconductive insulator 2 according to image information. 4 is a first exposure light source, which produces a light image corresponding to all image information to be printed by i! Il
Irradiate the photoconductive insulator 2 based on the data in Section 1.3. Reference numeral 5 denotes a second exposure light source, which overlaps the light image irradiated by the first exposure light source 4 based on the data of the control unit 3 when the total image information has a predetermined area or more, and displays a surface image portion in the image information. The photoconductive insulator 2 is irradiated with the optical image of the portion other than the T-junction.

[Effect]

As shown in FIG. 1, a photoconductive insulator 2 charged in a negative manner
Then, based on the data from the control unit 3, the entire image information is captured by the first exposure light source 4, which is a light image corresponding to the image information. When this total image information is larger than a predetermined area (graphic printing), the second exposure light source 5 further changes the surface area of the light source illuminated by the first exposure light source 4 based on the data from the control unit 3. An electrostatic latent image is formed by repeatedly exposing parts other than the edge parts. Then, the electrostatic fl image is developed and visualized with toner, and the toner image is transferred and fixed onto a recording medium to perform printing.

As a result, the overall potential caused by the potential acting from the back surface of the photoconductive insulator 2 on the edge portion of the optical image plane image and the potential of the portion other than the edge portion becomes approximately equal. Therefore, edge effects in toner development are prevented.

On the other hand, when the total image information is less than the predetermined area (line drawing printing), exposure by the second exposure light source 5 is not performed. This prevents toner from being excessively developed even in the case of line drawing printing.

In this way, in both graphic printing and line drawing printing, an appropriate amount of adhering toner is achieved, and thereby a uniform printing degree is achieved.

〔Example〕

FIG. 2 shows a configuration diagram of an embodiment of the present invention. In the electrophotographic printer 1 of FIG. 2, a photoconductive insulator (hereinafter referred to as "
It is called photosensitive drum 1. ) 2 rotates in the R1 direction in the figure while being positively charged by the charging unit 6 to which a predetermined positive voltage V+ is supplied.

On this photosensitive drum 2, a first
A light image corresponding to image information is emitted from the exposure light source 4 and the second exposure light source 5. Then, the toner T from the developing roll 7a of the developing section 7 is deposited on the optical image area of the photosensitive drum 2. In this case, the toner T is charged with the same polarity as the photosensitive drum 2, and is biased at a predetermined voltage value between the photosensitive drum 2 and the developing roll 7a (f, not shown).

The photosensitive drum 2 to which the toner particles 1 to 4 are attached is transferred to a sheet of paper 9, which is a fed recording medium, at a transfer section 8 to which a negative voltage V2 of a predetermined value is supplied, and the sheet 9 is transferred to a sheet of paper 9, which is a recording medium, at a fixing section 10. 1° where the image is defined, while the photosensitive drum 2 is
After excess charge is removed by the static eliminator 12 supplied with the AC power source 11, the surface is cleaned by the cleaning part 13a, and the static electricity is removed again by the optical static eliminator 13b.

Here, the first exposure light source 4 and the second exposure light source 5 are, for example, a predetermined number of dot glue, L (light emitting diode) elements arranged in one chip on a ceramic substrate.
ED/'ray is used.

Next, the principle of operation of the electrophotographic printer 1 will be explained with reference to FIG. First, based on data from 1 control unit 3,
All image information is read in by the first exposure light source 4 with relatively weak exposure energy (Fig. 3(A) edge portion electrical information). In this case, the control unit 3 determines whether the area of the screen of all image information is greater than or equal to a predetermined value (e.g., determined based on exposure pattern information), and if it is equal to or greater than a predetermined value, the second exposure light source 5 performs exposure. If the value is less than a predetermined value, the second exposure light source 5 is controlled not to perform exposure.

In other words, when the area of the screen image is equal to or larger than a predetermined value, the t, 1Jla section 3 displays the light image PI irradiated by the first exposure light source 4.
Overlapping with step s14, a portion of the screen image other than the edge portion 15 (non-edge portion 16) is irradiated with the second exposure light source 5 (
FIG. 3(A) Non-edge portion 16 potential). At this time, since the potential of the photoimage area 14 on the surface of the photosensitive drum 2 tends to be lower when it receives a stronger exposure energy, the potential of the image area of the edge area 15 is lower than that of the non-edge area 16. (FIG. 3(A): Difference between the potential of the edge portion 15 and the potential of the actual edge portion 16). Therefore, the toner particles adhere to the photosensitive drum 2 by the electric attraction force (potential difference between the toner particles and the photoimage area 14 on the photosensitive drum 2) from the developing roll 7a of the developing section 7 at a predetermined bias potential (see Fig. 3). (B)). At this time, even if a stronger electric field acts on the edge portion 15 than the background portion of the photosensitive drum 2, toner particles do not adhere excessively to the 172 portion 15 and are uniformly adhered. Then, the image formed by the toner is transferred onto the paper 9 by the transfer section 8, and the fixed neck section 1
Even if printing is performed after fixing at 0, the -[tsuji effect does not occur.

On the other hand, when the area of the screen image of the image information is less than a predetermined value (line drawing printing), irradiation exposure is performed only with the first exposure light source 4, and the light image portion 14 is focused with relatively weak exposure energy. . Therefore, a large amount of toner T does not adhere to the photosensitive drum 2 and the paper 9 and cause fixing failure.

Next, in the electrophotographic printer 1, the specific ri1
1ifJ is shown and compared with the conventional example. , First, in the electrophotographic printer 1 of the present invention, the process speed is set to 850
IWri/S, and the first exposure light '#4 is 480 dpi.
1~ED array, wavelength 630 liters, light amount 0.8μJ
/cm3, and the second exposure light source 5 is 240dpi
7 LEDs with a wavelength of 63 nm and a light transmission of 1.4 μJ/c
m3rd56゜Also, photosensitive drum 2 (selenium drum)
Set the surface potential to 680V, and set the developing bias to 300V.
450■, and the developer has an electrical resistance of 105Ω and an average particle size of 45μ.
Toner a 6wt%, charge amount 12
μC/g. Then, we printed inch-square graphics (solid black) and line drawings (characters) consisting of 1-dot and 2-dot lines, and after fixing the dots with flash, we measured and compared the toner thickness of each part of the print using a fibrometer. It is something.

Therefore, in the granoic printing of this example, only the inner portion (non-edge portion 16) from the edge portion 15 in the order of 5 was exposed with the second exposure light source 5, and the developing bias potential was set to 300V. Conventional Example 1 is a case where the second exposure is not performed under the same conditions as this example, and Conventional Example 2 is a case where the developing bias [F] is set to 450 V under the conditions of Conventional Example 1, and these comparisons are lower. I was beaten to the front.

If the strength is insufficient and the toner thickness is about 20 μm, fixing failure is likely to occur.

As is clear from the table, in this example, the toner thickness after fixing is in the range of 10 to 15 μm in all print patterns, whereas in Conventional Example 1, the toner thickness after fixing is in the range of 10 to 15 μm.
In the non-1st edge portion of black solid printing, the development time is not 4 minutes, and the black 1α is reduced by this amount. In addition, in Conventional Example 2, the darkness of the non-edge portions of graphic (solid black) printing is sufficient and the degree of blackness is high, but on the other hand, in the 179 portions of text and black solid printing, the dove thickness exceeds 20 μm and it is fixed. The part that caused the defect was removed.

Thus, in this example, the dove thickness is 10-15 μm.
It is within the range of 100% to 100%, indicating that sufficient blackness can be obtained and good fixing properties can be obtained.

In addition, in the above 172 parts, the printing part potential of the non-edge part L:L
The appropriate value is determined by the process conditions H such as the pro-hysteresis speed and the electrical resistance of the developer, and if the process speed etc. change, the above-mentioned printed area potentials at the edge and non-edge areas will change.

In this way, even if the process speed is high, the edge effect does not appear, and the toner R developed on the 179 parts of the image and the non-edge parts is almost equal, and the appropriate amount of developing toner is used for both graphic printing and line drawing printing. It is possible to aim for In addition, in the present invention, since exposure is performed twice within one rotation of the photosensitive drum 2, the process speed is not affected and the process is simple.
One rabbit is never complicated.

In addition, in the above embodiment, the first and second exposure light sources 4.5
Although we have described the case in which the LED/'ray is constructed, the same effect can be obtained even if it is constructed with a laser beam or the like.

〔Effect of the invention〕

As described above, according to the present invention, by re-exposing parts of the image other than 172 parts with the second exposure light source only when the image information is larger than a predetermined area, it is possible to achieve both graphic printing and line drawing printing. It is possible to optimize the amount of valley toner, and as a result, the mark'? It is possible to make the concentration uniform.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the original press of the present invention, Fig. 2 is a configuration diagram of an embodiment of the present invention, Fig. 3 is a diagram for explaining the potential relationship of the present invention, and Fig. 4 is a diagram of the conventional FIG. 3 is a diagram for explaining the relationship. In the figure, 1 is an electrophotographic printer, 2 is a light [I insulator, 3 is υJll) section, 4 is a first exposure light source, 5 is a second exposure light source, 6 is a charging section, 7 is a developing section, 78 is a developing roll, 8 is a transfer section, 10 is a fixing section, 14 is a light image section, 15 is one edge, and 16 is a non-edge section. (A) (B) A(418
Figure 3: Figure 4: A diagram explaining the telegraph review of the monthly telegraph II

Claims (1)

[Claims] A uniformly charged photoconductive insulator (2) is irradiated with a light image corresponding to image information to form an electrostatic latent image, and the electrostatic latent image is developed and visualized with toner. In an electrophotographic printer that prints by fixing the toner image on the recording medium after transferring the toner image onto the recording medium, an optical image is transferred onto the photoconductive insulator (2) according to the image information. a control unit (3) for controlling the irradiation of the photoconductive insulator (2), and a control unit (3) for irradiating the photoconductive insulator (2) with a light image corresponding to the entire image information to be printed based on data from the control unit (3). 1 exposure light source (4) and when the total image information has a predetermined area or more,
Based on the data from the control unit (3), the light image of a portion other than the edge portion of the screen portion in the image information is overlapped with the light image irradiated by the first exposure light source (4). An electrophotographic printer comprising: a second exposure light source (5) that irradiates a conductive insulator (2).