JPS6055377A - Formation of magnetic latent image - Google Patents

Abstract

PURPOSE:To obtain the more uniform reproducibility of a solid and a dot image by impressing dot-shaped heat input such as thermal head and laser light so that they overlap each other spatially on a magnetic latent image carrier, and making an external impressed magnetic field opposite in direction synchronously. CONSTITUTION:The magnetic latent image carrier moves as shown by an arrow 8 to draw a track shown by a chain line 9. Simultaneously, an external magnetic field 7 is impressed firstly and then an external magnetic field 7' in the opposite direction is impressed; and the direction of the external magnetic field is inverted repeatedly to form magnetic latent images 5a, 5b... on the magnetic latent image carrier in alternate directions. An integral multiple of the length of magnetism produced in one heat cycle is one magnetic latent image unit, which is formed to an optional multiple of magnetism length. The solid image, therefore, consists of magnetic latent image units having a sufficiently large multiple of magnetisum length, and a magnetic field which has the magnetism length as basic repetition in free space is established in the solid, so the uniform sticking of magnetic toner and magnetic ink is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic copying method, more specifically, a method for forming a magnetic latent image on a magnetized magnetic material by heat input from a thermal head, L/-ff, and Ni. Regarding how to.

BACKGROUND OF THE INVENTION Conventionally, various methods have been proposed as methods for forming magnetic latent images in magnetic copying. Among them, thermomagnetic materials such as chromium dioxide (Cr0z), which has a high temperature relatively close to room temperature and -IJ temperature, are used to generate dot-shaped heat using a thermal head or laser beam. A method is known in which a magnetic latent image is formed by the cooperative action of heat and magnetic field by applying an external magnetic field while applying an image, thereby causing a thermal residual magnetization phenomenon ζ. In this method, depending on the case, it is also possible to use a thermomagnetic material that has been uniformly magnetized in one predetermined direction and apply an external magnetic field so that the direction of magnetization is reversed at the heat input section.

Compared to the magnetic latent image forming method that uses a magnetic head, this method uses a thermal head in which heating elements are arranged in a long length with the required pixel density, and a laser optical system that can input thermal images at high density without contact. It is superior in terms of increased image density and lower cost.

However, according to studies conducted by the present inventors, it has been found that with the above method, a complete solid image cannot be obtained during visualization due to magnetic toner, magnetic ink, etc., or that thermal dots cannot be reproduced as they are in the form of dots. It has been found that there are drawbacks such as a decrease in image quality.

This is thought to be due to the fact that in the above-mentioned method of forming a magnetic latent image, the direction force S of magnetization in the heated dot part is aligned in one direction. In other words, in magnetic copying, the magnetic latent image is transferred from the free space. Adhesion of magnetic toner and magnetic ink occurs in response to the magnetic field generated by the heating dot, so if the heating dot size is too large, the magnetic field will only form around the periphery of the heating dot, and the center of the heating dot may become hollow. If the reproducibility is such that the dot nature remains [see Figure 1 (, )], or if you try to reproduce it by dividing the solid into dot-sized pieces and heating and magnetizing them, as shown in Figure 1 (b) (see Figure 1 ()), only the periphery of the solid is reproduced.

OBJECTS OF THE INVENTION Accordingly, the present invention improves the drawbacks of image reproducibility in the above-mentioned thermal magnetic latent image forming method, and provides improved reproducibility of solid and dot images with more uniform reproducibility. An object of the present invention is to provide a method for forming a magnetic latent image.

In other words, the magnetic latent image forming method of the present invention applies dot-shaped thermal input from a thermal head or laser beam so as to spatially overlap on a magnetic latent image carrier, and in synchronization with this thermal input application. This is characterized by reversing the direction of the externally applied magnetic field. .

Hereinafter, the present invention will be described in detail with reference to the drawings.

In FIG. 2, 1 is a magnetic base layer, 2 is a thermomagnetic recording layer, 3 is a dot-shaped heat input region, and 4 is a previously formed background magnetization.

The magnetic latent image carrier moves in the direction of arrow 8. Move to Ste.
G may be performed intermittently using a pin motor or continuously. First, as shown in Figure 2 (,),
Under the application of an external magnetic field 7, it becomes thermally magnetized as shown in 5-a.

Subsequently, the state shifts to the state shown in FIG. 21(b). At this time, the magnetic latent image carrier traces a trajectory as shown by the dashed line 9 in FIG. On the other hand, in (b), the direction of the external magnetic field is reversed as shown in 7', and the thermal residual magnetization becomes opposite to that in 5-a, as shown in 5-b.

Hereinafter, as shown in (c) and (d), by repeatedly reversing the direction of the external magnetic field, the magnetic latent image carrier has 5-a,
Magnetic latent images such as 5-b and 5-c are formed. In this case, in the final stage of magnetic latent image formation [Figure 2 (d)]
, the cycle must be such that the thermal magnetization in the same direction as the background part remains f6.

Therefore, for example, as shown in FIG.
In the case of forming a magnetic latent image by magnetization reversal of -c, four heating cycles are always required if the first heating cycle is aligned so that magnetization is in the opposite direction to the background part.

The length of magnetization formed in one heating cycle is 5-breath or 5
An integral multiple of -b or 5-c) constitutes one magnetic latent image unit, and a magnetic latent image unit is formed with an arbitrary multiple (generally an odd number) of magnetization length. Therefore, a solid image consists of a magnetic latent image unit consisting of a sufficiently large multiple of the magnetization length, and even in a solid, a magnetic field is generated in free space with the magnetization length basically (repetitively), so uniform magnetic toner and magnetic ink are generated. can be attached.

The length of magnetization formed in one heating cycle can be determined by the feeding speed of the magnetic latent image carrier, and is arbitrarily selected so as to ensure uniform reproducibility of solids and dots.

When using magnetic toner particles with an average particle diameter of about 10 μm as the visualization means, the magnetization depth is 5 μm to 2 μm.
00 μm1 is preferably about 30 μm to 120 μm. That is, in general, if the average particle diameter of the visualization particles is d, it is preferable that the initial magnetization length is about d/2 to 20 d.

Next, the method for forming a magnetic latent image of the present invention will be explained with reference to Examples.

Examples Commercially available chromium dioxide tape (US D
Upou' (trade name: CROLYN) was used. The magnetic layer of this tape was placed in contact with a commercially available thermal head (Telecopier 490 manufactured by Fuji Xerox Co., Ltd.), and the thermal head 10 was placed through the chromium dioxide tape.
A Sendust long magnetic head (number of turns: 300 turns) 11 having a track width of 30 tin and a gap length of 200 μm was placed at a position facing the magnetic head (see Fig. 3(a)).
.

After uniformly magnetizing the magnetic tape in one direction with a permanent magnet (not shown), it is heated with a thermal head (heating width of about 160 μm) so that the magnetization direction is opposite to that of the magnetic tape. Magnetized by a magnetic head, approximately 1
A reverse magnetization part of 60 μm was formed [FIG. 2(a)].

Next, after moving only the magnetic tape by 30 μm, it is heated again with a thermal head, and the magnetic field by the magnetic head is magnetized in a direction that forms thermal remanent magnetization in the opposite direction to the previous magnetization, that is, in the same direction as uniform magnetization. A reverse magnetization portion was formed [FIG. 2(b)].

After moving only the magnetic tape by 30 μm, it was heated again with a thermal head and magnetized in the opposite direction to the previous magnetization, that is, in the opposite direction to the uniform magnetization, to form the magnetization pattern shown in FIG. 2(c). Finally, in the same way, only the magnetic tape was used for 30 minutes.
After being moved by .mu.m, it was heated and magnetized in the opposite direction to the previous magnetization, that is, in the same direction as the uniform magnetization, forming a magnetization pattern with a magnetization reversal unit of 30 .mu.m as shown in FIG. 2(d). That is, after heating a magnetic tape that has been uniformly magnetized in one direction in advance and magnetizing it in the opposite direction, every time the magnetic tape is moved by 30 μm, the external magnetic field is heated and reversed to the same direction, the opposite direction, or the same direction as the uniform magnetization. Four heating cycles and four magnetization reversals were performed to form a magnetic latent image unit length 9 having a magnetization reversal unit of 30 μm.
A magnetic latent image of 0 μm was formed. When this magnetic latent image was developed with a magnetic brush using a one-component magnetic toner, transferred and fixed on transfer paper, it was possible to reproduce horizontal lines with a width of about 100 μm and uniform density.

Similarly, in order to form magnetic latent images of various unit lengths, experiments were conducted by varying the number of heating cycles and feeding length. That is, in addition to forming a magnetic latent image using the combinations shown in the table below, as a comparative example, the conventional method of not performing divided printing, that is, applying a magnetic field in one direction from a long magnetic head, results in the formation of a magnetic latent image. was formed.

Length - The round head is the length of the heating element (3) in Figures 1 and 2.
was approximately 160 μm, and the same signal was applied over 3 tyn in a direction orthogonal to the magnetic image carrier feeding direction.

In the case of the conventional method, the minimum length of the magnetic latent image unit is 160 μm since it is the length of the heating dot of the long head (160 μm).
0 μm x 3 cm horizontal line (number of heating cycles 1), 320 μ
Horizontal line of fnX311ffM (number of heating cycles 2, feed 1
60μm), 480/1m x 3cm horizontal line (1
60μm heating, 160μm non-heating, 160μm heating; number of heating cycles: 2, feed: 320μm), -, -3cIlt
X 36N solid ((160μm heated, 160μm unheated) x 94, number of heating cycles 94, feed 320μm)
A latent image was formed. This was developed with an electrophotographic component magnetic toner having an average particle size of 10 μm. These results are shown in the table.

In the above embodiment, a case has been described in which the external magnetic field is applied by a magnetic head, but a permanent magnet may also be used as shown in FIG. 4.

In the figure, 15 is an elastic covering such as silicone rubber,
Assists in the close contact between the thermal head and the magnetic material. In the hollow cylinder 16, a symmetrically magnetized cylindrical permanent magnet roll rotates at a constant speed.

This permanent magnet roll is provided with a magnetic flux detection means such as a Hall element to control the timing of the heating enable (clock) start, which applies a magnetic field in the opposite direction to that of pre-magnetization.
Slice level detection and heating enable control are performed so that the applied magnetic field of H has a value sufficient to cause thermal residual magnetization, and clock generation control is performed to determine the feeding timing of the magnetic body.

According to this external magnetization application method, the alignment accuracy between the thermal head and the magnetic field application means is reduced compared to a magnetic head.

As described in detail, the present invention applies a dot-shaped thermal input using a long head or a laser beam so as to spatially overlap on a magnetic latent image carrier, and synchronizes with the application of the thermal input by applying an externally applied magnetic field. This method provides a method of forming a magnetic latent image by reversing the direction of the dot, and has the features of uniformly reproducing a solid and being able to form a magnetic latent image unit smaller than the size of the heat input dot. It is something.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are explanatory diagrams of a conventional method for forming a magnetic latent image using heat; FIGS. 2(a) to (d) are explanatory diagrams of a method for forming a magnetic latent image according to the present invention; FIG. (a), (b) and FIG. 4 (a), (b) are block diagrams and schematic diagrams of control of an embodiment using a magnetic head and a permanent magnet as external magnetic field applying means, respectively. Symbols in the figure: l... Support layer; 2... Magnetic material Pi: 3... Heating dot part; 4... Background magnetization; 5... Latent image magnetization'
, 6... Magnetic toner; 7... External magnetic field; 7'...
Reversal external magnetic field; 8...Movement direction; 9...Movement trajectory;
10... Thermal head; 11... Long magnetic head; 12... Long magnetic head drive current; 13...
Thermal head heating enable; 14...Magnetic image carrier feeding signal; 15...Elastic coating layer; 16...Hollow support; 17...Permanent magnet roll; 18...Magnetic field detection means. 111 Figure 2 Figure 3

Claims (1)

[Claims] A method of forming a magnetic latent image by imagewise heating a magnetic recording body having a magnetic layer capable of thermoremanent magnetization on a support and applying a magnetic field, in which the direction of the magnetic field is reversed each time it is imagewise heated. A method for forming a magnetic latent image, characterized in that: