JP2685794B2 - Multicolor image forming device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image forming apparatus using an electrophotographic system, and more particularly to a multicolor image forming apparatus using outline font data as a character font.

BACKGROUND OF THE INVENTION There is known an image forming apparatus in which character information is transferred as code data, which is converted into image data composed of pixels of 1 to several bits to form a visible image.

The data referred to in this conversion is called a font. Among the character fonts, outline font data handles only the outline information of characters, and this is converted into image data by using a dedicated data conversion means.

That is, the data of pixels inside the contour image data is created, and the embedded data is used as the image data.

Since the outline font is data only for the outline portion, character image data of any size can be created, and the data capacity is smaller than that of a dot font having a character image as a dot pattern.

[Problems to be Solved by the Invention] By the way, the above-mentioned conventional image forming apparatus is one which creates image data by using a character font and forms a black toner image based on the image data. .

Therefore, it is not possible to record the inside of the character at an arbitrary density, and there is no one that can record the color character. In particular, there is no disclosure of means for creating a color image using outline font data as a character font.

Although various types of image forming apparatuses for forming color images are known, the apparatus described in JP-A-58-184381, in particular, has a simple structure and is characterized by high speed which is a feature of electrophotography. It is an excellent one that takes advantage of the high image quality. The feature of this apparatus is that toner images are formed one by one on a photoconductor (image forming body).

Color reproduction in this apparatus is performed by forming a plurality of types of toner at the same position on the photoconductor in a superposed manner or by adjoining in the vicinity. However, when forming color characters with this apparatus, it was not clear how to form the image data of the characters. In particular, when the electrophotographic recording device as described above is used as the recording means, the following problems occur.

That is, such a recording apparatus has a drum-shaped image forming body to form a toner image of the first color, and then in the next process, a toner image of the second color is formed so as to be superimposed on the toner image of the first color. Such an image forming process is performed on all color separation images.

At the stage where all the image forming processes are completed, fixing and separation processes are performed, and the color original is copied and recorded on the ordinary recording paper.

In the case of using a recording unit configured to form a multicolor toner image by superimposing in this way, as will be described later in detail, the adhesion amounts of the toner images of the first color and the second color are different,
Color reproducibility deteriorates.

This problem is the same even when outline font data is used as a character font.

Therefore, in the present invention, such a point is taken into consideration, and in particular, a multicolor image forming apparatus capable of performing color recording by using outline font data as a character font and improving color reproducibility is provided. It is a proposal.

[Means for Solving the Problems] In order to solve the above problems, in the present invention,
Image input means for outputting at least character information, character size information and color information, and character coordinate information as image code data, and a plurality of types of outline font data are stored in advance, and the character information is also stored. The outline image data based on the outline font data, the character size information, and the color information, and a font storage unit that selects and outputs specific outline font data from the plurality of types of outline font data according to the character information. And a font data conversion unit for converting and outputting the image data for each recording color by adjusting the density inside the outline of the outline image data, and each recording color output from the font data conversion unit. It has a buffer memory that temporarily stores and outputs image data for each image, and uniformly charges the surface of the image forming body. Charging means, an exposing means for exposing the charged image forming body to form an electrostatic latent image based on image data for each recording color output from the buffer memory, and the electrostatic latent image. A developing means for developing is characterized in that a color toner image is formed on the image forming body by repeating charging, exposing and developing a plurality of times.

[Operation] The multicolor image forming apparatus according to the present invention incorporates a font, and characters and the like are recorded by an electrophotographic method capable of high density recording based on image data formed using the font.

In the multicolor image forming apparatus according to the present invention, a plurality of types of outline font data are stored in advance, and the outline font data corresponding to the character is selected and output from the plurality of types of outline font data according to the character information. I did it.

Then, in the font data conversion unit which has input the outline font data and the character size information and color information, contour image data is formed from these data and information, and the density inside the contour of the contour image data is adjusted. After being converted into image data for each recording color, the image data is output.

Based on the image data obtained in this way, a color toner image is formed on the image forming body by repeating charging, exposing and developing for each color component a plurality of times.

As a result, when one character is formed with a plurality of colors even with the same character, after the selected outline font data is formed into the contour image data, the density inside the contour of the contour image data is corrected for each recording color. Since the image data is formed, the toner image in the subsequent stage can be formed faithfully without being affected by the toner image in the previous stage, and a color character image with excellent color reproducibility can be formed.

Further, since the correction is performed only inside the character font and the contour portion of the character is not adjusted, the contour does not collapse when the toner images are superposed.

As a result, not only black characters but also chromatic characters such as yellow, magenta, and cyan can be printed with high quality.

[Example] Next, an example of the multicolor image forming apparatus according to the present invention will be described in detail with reference to FIG.

FIG. 1 shows a block diagram of the basic configuration of the present invention.

The present invention has a font storage unit 1 in which fonts such as characters and symbols are stored.

The character font stored in the font storage unit 1 is outline font data.

Outline font data is the font data conversion unit
Supplied to 10.

As shown in FIG. 3, the font data converting unit 10 includes a contour image data forming unit 12 that forms contour image data from outline font data, and an internal image for filling the inside of the contour with pixels having a predetermined halftone. It is composed of an internal image data forming unit 13 that forms data.

The input means 2 for the font data conversion unit 10 inputs image information as a code, and this image code data is composed of at least a character, a character size, and character position information (coordinate information). .

Of the input image code data, the character information is decoded by the font data conversion section 10 and sent to the font storage section 1 having outline font data as its address signal.

The font storage unit 1 refers to the outline font data corresponding to the input address signal and outputs it to the font data conversion unit 10.

The font data conversion unit 10 converts the image code data into image data using information indicating the size of the character as a parameter, and forms character image data on a two-dimensional plane. The character density can be controlled from the outside based on a gradation control signal from the control unit 7.

Then, the character image data is stored in the corresponding area of the image buffer memory 5 according to the position information of the input image code data.

When one screen of image data relating to certain specific color information is formed, this image data is output according to a request signal from the electrophotographic recording unit 6.

In the electrophotographic recording unit 6, an electrostatic latent image is formed based on the sent image data, and toner of a color corresponding to the electrostatic latent image is attached and developed.

The processes from the creation of the image data to the development are sequentially performed in a frame-sequential manner to form a multicolor toner image, and then the fixing process is performed to record (copy) a desired color original. .

Outline font data is stored in the font storage unit 1 described above. For example, the katakana character "ka" is stored as outline information in a hollowed state as shown in FIG. 2A.

Therefore, if the outline font data in the hollowed-out state is used, the inside of the contour can be recorded at an arbitrary temperature by controlling the number of dots (halftone dots) of pixels as shown in FIG. 2B. it can.

Further, by changing the contents of the internal image data of the first color and the second color, it is possible to make a slight change in the adhesion amount of the toner images of the first color and the second color.

For example, when the character color is green G, the image forming colors are yellow Y and cyan C, and green G is reproduced by superimposing these. In this case, as shown in FIG.
By changing the density of the internal image data used for the first color (for example, yellow) and the second color of cyan C, the size of dots, and the like, the difference between the toner adhesion amounts of the two can be made small.

FIG. 3 shows an example of the configuration of the font data conversion unit 10 described above.

The character information forming the image code data is decoded by the decoder 11 and an address signal to the font storage unit 1 is created.

The outline font data corresponding to the character is referred to based on the created address signal, and this is sent to the contour image data forming unit 12.

The contour image data forming unit 12 forms contour image data of a character corresponding to the size of the input character from the transmitted outline font data and the information on the size of the input character. Then, the image data is sent to the internal image data forming unit 13 and the image data inside the character is created.

The internal image data is created as data corresponding to the designated halftone. The control unit 7 specifies what kind of halftone is to be used.

After the inside of the contour is formed with internal image data representing a predetermined halftone, these image data are stored in the line buffer 14
Sent to

The image code data indicating the size of the character is also supplied to the address signal forming unit 15. Address signal forming unit 15
Further, the image code data representing the position information of the characters is supplied to the, and an address signal indicating the recording position (coordinates) is formed by these.

This address signal and the image data in the line buffer 14 are correspondingly output, and the image data is stored in the area designated by the address signal.

Here, designation of a halftone representing the density of image data that fills the interior of the designated character will be described.

4th by the referenced outline font data
When the recording pixels (contour image data) as shown in the drawing are created, the image data in the area C surrounded by these recording pixels A and B is determined by the internal image data forming unit 13 according to the specified halftone. Created. That is, when multi-value recording is possible on a pixel-by-pixel basis, all of the pixels in the area C are made into the data of the designated gradation.

Further, in the case where it is desired to record a gradation that is larger than that which can be recorded in pixel units, the gradation data specified by the density pattern is formed. In this case, the area C may be formed in the recording pixels and the non-recording pixels at a specific ratio according to a predetermined rule.

FIG. 5 is an example of a density pattern. This example is a pattern in which the density is represented by the size of the dots. For example, a matrix of 4 rows and 4 columns (16 types in total, 16 gradations) is formed in advance, and the density to be recorded (gradation ), The image data of the corresponding density pattern is selected.

FIG. 6 shows the case where the area C, that is, the inside of the contour is filled with the density pattern.

FIG. 7 shows another example of the density pattern. This is an example in which the density is changed according to the density of the dots, and in this case as well, a pattern corresponding to the specified density is selected and multi-valued recording is performed.

When color characters are recorded by superimposing them, it is necessary to consider so that the color reproducibility is not deteriorated by superimposing the first color and the second color.

 It is based on the following reasons.

When a multicolor toner image is formed by superimposing as described above, when the photosensitive layer is made conductive by image exposure when the latent image of the second color is formed, absorption of laser light by the toner image of the first color and The problem is that the electric charge of the toner cannot be erased by light irradiation.

The factor of 1 is to reduce the effective exposure amount reaching the photosensitive layer,
This means that the charges on the photosensitive layer are not sufficiently erased, and the surface potential of the photoreceptor does not drop sufficiently.

The factor of 2 is that unless the toner is a special one having photoconductivity, its charge is not reduced by exposure. Therefore, this also causes the surface potential of the photoreceptor not to drop.

For these reasons, the surface potential difference between the exposed portion and the non-exposed portion in the area where the toner image is formed is small, and it is not possible to develop with a sufficient toner amount.

That is, when trying to reproduce a color by overlapping toners, the toner adhesion amount of the second and subsequent colors becomes small and the respective toner adhesion amounts become unbalanced, so that the color reproduction area becomes narrow.

Since the above two factors depend on the order of toner development, the spectral characteristics of image exposure light (laser light), the spectral characteristics of toner, the amount of charge of toner, etc., the color reproducibility changes depending on these values.

Since these tendencies become stronger in the order of yellow, magenta, cyan, and black, it is possible to eliminate the above-mentioned effects by making the thickness of the characters thinner or the content of the density pattern different in this order. Become.

For example, when recording green G, yellow Y and cyan C
Green G is recorded by superimposing the respective toner images of. In that case, as shown in FIG. 8, the content of the density pattern used for cyan C is different from the content of the density pattern used for yellow Y.

When color characters are recorded using density patterns having different data contents in this way, a portion where toner particles overlap and a portion where toner particles do not overlap always appear at a specific ratio. This is because the difference can be made small.

 FIG. 9 shows an example of the electrophotographic recording section 6.

As the electrophotographic recording unit 6, a color copying machine using a drum-shaped image forming body can be used.

In FIG. 9, reference numeral 20 is an image forming body having a photoconductive photoreceptor surface layer such as OPC and Se on the surface thereof. this is,
It is rotated in the direction of the arrow.

Reference numeral 21 is a charger that uniformly charges the surface of the image forming body 20. The image forming body 20 is subjected to image exposure of a color image for each color by the writing unit D.

22 to 25 are developing units in which toners of different colors such as yellow, magenta, cyan, and black are used as developers. Reference numerals 26 and 27 are for facilitating transfer of a color image formed by superimposing a plurality of color toner images on the image forming body 20 onto a recording paper (transfer material) P, or for facilitating separation of the recording paper P. A pre-transfer charger and a pre-transfer exposure lamp, which are provided as necessary.

28 is a transfer device for transferring a color image, 29 is a fixing device for fixing the toner image transferred onto the recording paper P, 30 and 31 are static elimination lamps and corona dischargers for static elimination, respectively. Or use both in combination.

Reference numeral 32 is a separating electrode, 33 is a cleaning device that comes into contact with the surface of the image forming body 20 after the color image is transferred and removes the residual toner on the surface, and the surface (part) on which the first development is performed. Has a cleaning blade 34 and a fur brush 35 which are separated from the surface of the image forming body 20.

Here, as the charger 21, since the charging is performed by superposing on the surface of the image forming body 20 which is already charged, the scorotron corona as shown in the figure can give stable charging with little influence of the previous charging. It is preferable to use a discharger.

Next, an example of a process for forming a multicolor image using the electrophotographic recording unit 6 will be described with reference to FIG.

Here, since the image forming body 20 has a photoconductive layer on a conductive substrate, the latent image forming means is a charger 21 that uniformly charges the surface of the image forming body 20 and the image forming body 20 with a light beam such as a laser. It is configured by a combination with an image exposure device D that illuminates the top and performs image exposure.

Now, FIG. 10 shows changes in the surface potential of the image forming body 20, where T1 is the toner image developed for the first time and T2 is 2
The toner image developed the second time is shown. Note that, for convenience of explanation, the polarity of the latent image is positive.

1. The image forming body 20 is uniformly charged by the charger 21, and the surface potential becomes E.

2. Image exposure of the first color is performed by the image exposure device D, and the potential of the exposed portion decreases according to the amount of light emitted. Thus, an electrostatic latent image is formed.

3. The electrostatic latent image is developed by any of the developing devices 22 to 25 to which a positive bias which is approximately equal to the surface potential E of the unexposed portion is applied.

As a result, the toner (T1) having a positive charge adheres to the portion (exposure portion) having a relatively low potential, and the toner image T1 of the first color is formed.

4. The image forming body 20 is uniformly charged by the charger 21 with the toner image attached, and the surface potential of the image forming body 20 becomes E regardless of the presence or absence of toner.

5. Image exposure of the second color is performed by the image exposure device D, and the potential of the exposed portion PH decreases according to the amount of light emitted. Thus, an electrostatic latent image is formed.

When the toner-attached area is exposed again in the development of the first color, the potential becomes approximately equal to the potential after the development.

Develop with a different color toner from the first color toner as in 6.3. As a result, two color toner images T1 and T2 are obtained on the image forming body 20.

Thereafter, the same process is repeated a required number of times to obtain a multicolor toner image on the image forming body 20. After that, a fixing separation process is performed, and a color document is recorded on the recording paper P.

When the recording unit (multicolor printer) 6 processed in FIGS. 9 and 10 is used, the advantage of the electrophotographic method, that is, high speed and high resolution, is utilized, and the configuration is simple and downsized. It has the advantage of being easy.

[Effects of the Invention] As described above, since the character font used is outline font data, the contents of the image data inside the contour can be freely specified from the outside.

Therefore, since the character can be recorded in any halftone, it is possible to easily obtain the character having the desired density.

Further, even when a color character is recorded, the internal image data can be easily changed, so that a color character having good color reproducibility can be obtained.

Therefore, the multicolor image forming apparatus according to the present invention is extremely suitable for application to an electrophotographic color copying machine or the like.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of a multicolor image forming apparatus according to the present invention, FIG. 2 is a diagram showing an example of contour image data and internal image data, and FIG. 3 is a specific example of a font data conversion unit. 4 to 7 are diagrams for explaining the internal image data, FIG. 8 is a diagram showing an example of a density pattern, FIG. 9 is a configuration diagram showing an example of an electrophotographic recording unit, and FIG. The figure is an illustration of the image forming process. 1 ... Font storage unit 2 ... Input means 5 ... Image buffer memory 6 ... Electrophotographic recording unit 7 ... Control unit 10 ... Font data conversion unit 12 ... Contour image data formation unit 13 ... Internal image data Forming part

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Claims (1)

(57) [Claims] 1. An image input means for outputting at least character information, character size information and color information, and character coordinate information as image code data, and a plurality of types of outline font data are stored in advance. A font storage unit for inputting the character information, selecting and outputting specific outline font data from the plurality of types of outline font data according to the character information, and the outline font data, character size information, and color information. A font data conversion unit that forms contour image data by, and adjusts the density inside the contour of the contour image data to convert the image data into the image data for each recording color and output the image data; and output from the font data conversion unit. The image forming body surface has a buffer memory for temporarily storing and outputting image data for each recording color to be recorded. Charging means for uniformly charging the surface, and exposing means for forming an electrostatic latent image by exposing the charged image forming body on the basis of image data for each recording color output from the buffer memory, A multicolor image forming apparatus, characterized in that a developing means for developing the electrostatic latent image forms a color toner image on the image forming body by repeating charging, exposure and development a plurality of times.