JPS59177583A - Magnetic latent image forming method - Google Patents

Abstract

PURPOSE:To reproduce half-tones by applying dot type heat inputs overlapping spatially on a magnetic latent image carrier, inverting the direction of an external applied magnetic field synchronously with a basic clock, and controlling the heat input application of every basic clock according to half-tone information. CONSTITUTION:Heating is performed during a basic cycle T1 in the presence of an applied electric field opposite in direction to the last magnetization and magnetism inversion corresponding to heating bit length shown by the uppermost stage is obtained on a beltlike magnetic body. Then, feeding is carried out in cycles T2 and T3 without heating and heating is carried out during T4 in the presence of the electric field in the opposite direction with the last magnetization. At this time, inverted magnetism M1 cirresponding to the feed amount (three times the half wavelength of basic magnetism inversion) of a magnetic latent image is formed in the period of the cycles T1-T4. Similarly, heating is performed again in cycles T5, T6 OFF, and T6. Further, five-fold and seven-fold operations are possible, and half-tones by a heat dot input magnetic latent image method are reproduced; and a solid part is reproduced uniformly and a magnetic latent image unit smaller than a heat input dot is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic copying method, more specifically, a method of forming a magnetic latent image on a magnetizable magnetic material by heat input from a thermal head, a laser, etc., which enables recording of intermediate tones. Regarding the forming method.

Conventionally, various methods have been proposed as a method for forming magnetic latent images in magnetic copying. Among them, chromium dioxide (Cr02), which has a Curie temperature at a high temperature relatively close to room temperature, is used as a magnetizable magnetic material. Using thermomagnetic materials such as , and adding dot-shaped thermal images with thermal head laser light.

A method is known in which a magnetic latent image is formed by applying an external magnetic field and by the cooperative action of heat and magnetic field due to the phenomenon of thermal remanent magnetization. In some cases, this method uses a thermomagnetic material that is uniformly magnetized in one predetermined direction. It is also possible to apply an external magnetic field so that the direction of magnetization is reversed at the heat input section.

Compared to the magnetic latent image formation method using a magnetic head, this method requires a longer length.It is possible to use a thermal head in which heating elements are lined up to the required image density or a laser optical system that can input high-density thermal images without contact. It is excellent in terms of increasing the density of the magnetic latent image and lowering the cost.

In the case of the magnetic dot method (in this case, halftones can be produced by changing the cycle of magnetization reversal formed as a magnetic latent image), but in the case of the above-mentioned method of reversing the magnetization of the thermal dot input section (in this case, Because the size of the heat dot is the smallest magnetic latent image unit.

It is a special feature to treat intermediate tones by changing the period of magnetization reversal.
This is difficult when using a relatively large heat dot such as a thermal head.

The present invention provides a method for forming a magnetic latent image by thermal residual magnetization by inputting a thermal dot while applying an external magnetic field.
The method of forming a magnetic latent image according to the present invention reproduces halftones (this provides a suitable method for forming a magnetic latent image). The externally applied magnetic fields are applied so that they overlap spatially on the image carrier, and the direction of the externally applied magnetic fields is reversed in synchronization with the basic clock.
This method is characterized by controlling the application of heat input in units of basic clocks in accordance with halftone information.

The present invention will be described in detail below with reference to one drawing.

FIGS. 1(a) to 1(d) are diagrams for explaining latent image formation performed by a heat input completely synchronized with a basic clock and a magnetic field reversal method.

In the figure, 1 is a nonmagnetic support layer, 2 is a thermomagnetic recording layer such as CrO2, 3 is a dot-shaped heat input region, and 4 is a preformed background magnetization in one direction. .

The magnetic latent image carrier moves in the direction of arrow 8. The movement may be performed intermittently or continuously using a stepping motor. First, as shown in FIG. Thermoremanent magnetization.

Next, the state shifts to the state shown in FIG. 1(b).At this time, the magnetic latent image carrier moves along the trajectory shown by the dashed line 9 in FIG. The thermal remanent magnetization is reversed as shown in 5, and the thermal remanent magnetization is in the opposite direction to that of 5.

By repeating the reversal of the direction of the external magnetic field as shown in Fig. 1 (c) and (d), the magnetic latent image carrier has 5Q.
, 5b-5 (-) is formed. In this case, in the final stage of magnetic latent image formation [Fig. 2 (d)], a cycle in which thermal magnetization in the same direction as the background remains remains. It is necessary to do so.

For example, as shown in Figure 1, when forming a magnetic latent image by reversing the magnetization of s, ), sl, , 5C, if the first heating cycle is aligned so that the magnetization is in the opposite direction to the background part, then Four heating cycles are always required.

According to this method, the basic repetition period of magnetization reversal can be made small even with a relatively large amount of manual heat dot power.

Now, the second method is to use the basic magnetization reversal achieved in this way as the fundamental wavelength and form magnetization reversal that is an odd number multiple of the fundamental wavelength.
Figure 2 and Figure 3 (This will be explained below. Figure 2 schematically shows the control for forming a magnetic latent image of odd wavelength magnetization reversal with respect to the basic cycle. Figure 2 (, ) and (b) is the signal corresponding to the basic cycle, (a) is the magnetic latent image sending signal, and (b) is the basic cycle heating enable (clock).It corresponds to the heating enable in (b) and is synchronized. Apply an external magnetic field to change the direction of the magnetic field (see Figure 2).

FIG. 2(d) shows a fundamental wave signal forming fundamental magnetization reversal. Fig. 2<e) shows a heating signal for forming a third harmonic, which is the next largest magnetization reversal wavelength after the fundamental wavelength. FIG. 2(f) shows a heating signal for forming the next thicker fifth harmonic wave. In this way, the magnetization reversal wavelength is the third harmonic,
5th harmonic, 7th harmonic, . . . (2n+1) harmonics and odd number multiples can be understood from the following Figure 3.

FIG. 3 is a diagram for schematically explaining how a third harmonic wave is formed.

At the time of basic cycle T1, heating is performed under an applied magnetic field (e.g., this is written as +H) in the opposite direction to the pre-magnetization, and the magnetic material marked in a strip shape corresponds to the heating bit length as shown in the top row. A magnetization reversal is formed.

Next - T2. At T3, the magnet is sent without heating, and at T4, it is heated under a magnetic field so that the direction is the same as that of the pre-magnetization.

At this time, reversal magnetization M1 is formed by the amount of magnetic latent image feeding between T1-T2-T2-T3 and T3-T4 (three times the half wavelength of basic magnetization reversal). Similar Qko T5, T6 OFF
, reheat at T7.

In this way, in order to form magnetization reversal with a longer wavelength in units of basic magnetization reversal, the direction of the applied magnetic field during heating should be +H1- when comparing the heating timings.
It needs to be reversed like H1+H [in the example in Figure 3 (T□, T4°T7, T!O,...T3n+1)]
. Also, the applied magnetic field during final heating is selected to be -H. That is, in the case of triple wavelength, T1-T4. (Half-wavelength reversal having three times the half-wavelength of the fundamental magnetization reversal) T1°T4, T7-T10 (11/2 length reversal having nine times the half-wavelength of the fundamental magnetization reversal) T1・T4. T7, T10, T13, T16 (24 wavelength reversal having 15 times the half wavelength of the fundamental magnetization reversal).

For the next longer wavelength, starting from T1, 10H1-H
, 10H, -H, we get T1, T6-Tll,
T16"' T5fi+1, and the allowed combinations are T□, T6 (5 times 514 wavelengths) T1, T6, Tl1-T16 (15 times, 11//2 wavelengths) T1. T6. T1□, Tl6- T2., T2
6 (25 times, 21/2 length), which is the fifth harmonic wave.

The same applies to the 7th harmonic wave, 9th harmonic wave, etc.0 The long wavelength magnetization reversal formed in this way is the magnetic latent image length that can be formed by changing the magnetic latent image feeding length in the basic cycle to t. is decided. In other words, the third harmonic is an odd multiple of 3t, 3t-
9t, 15t,..., 5t for 5th harmonic, 151.2
5t..., 7t for the 7th harmonic.

21L351. ...is... -10,000, the maximum allowed harmonic is the largest odd harmonic of f below L/, where L is the heating bit length.

When attempting to reproduce halftones, it is preferable to select the closest value such that the allowable magnetic latent image length of each odd harmonic falls within the above-mentioned maximum allowable harmonic.

The fact that intermediate tones are reproduced by magnetization reversals with different wavelengths formed in this way is that the magnitude and attenuation speed of the magnetic field leaking from the magnetic latent image into free space are determined by the magnetization reversal wavelength of the magnetic latent image (this It is explained by dependence.

The present invention will be explained below with reference to Examples.

Commercially available chromium dioxide tape (US p.
Made by Upont, trade name: cRoLYN). The magnetic layer of this tape was placed in contact with a commercially available long-maru head (manufactured by Fuji Xerox Co., Ltd., for Telecopier 490) 10, and a track width of 30σ was formed at a position facing the thermal head through the chromium dioxide tape. Sendust long magnetic head with a gap length of 200 μm (number of turns 3)
00 turn) 11 was placed (see Figure 4).

The length of the heating element of the thermal head was about 160 μm, and the chromium dioxide tape was moved by a stepper (not shown) so as to move by io μm every 1 m5 ec of the basic cycle (heating enable 0.5 m5 ec).

As explained in the main text, 10μm-30μm (3rd harmonic),
50 μm (5th harmonic), 70 μm (7x i), 90p
m < 9th harmonic) + 110 μm (11th harmonic),
A solid of 1 cm x 1 cm was printed with a magnetization reversal length of 130 μm (13th harmonic) and 150 μm' (15th harmonic). To explain in detail, 10μm - 10μm x 100 basic cycles = lo
ooμm30μm... 30μm x 33 =
990μm50μm +++ 50μm X 21
= 1050μm70ttm -70ttm
15 = 1050/jm90μm +++ 90μt
n x 11 = 990μm110μm...
1) 0μm x 9 = 990μm 130μm...
・130μm x 7 = 910μm150μm
−150 μm x 7 = 1050 μm.

The magnetic latent image formed in this way has an average grain size of 0μ.
After developing the image with a single-component magnetic toner and fixing it on plain paper in a static ridge transfer, the image density was measured using a Macbeth reflection densitometer, and as shown in Table F, 8 steps of different densities were obtained. .

In the above embodiments, the external magnetic field is applied using a magnetic head. However, as shown in FIG. 5, a permanent magnet can also be used as the external magnetic field applying means. It is an elastic material coating such as silicone rubber that assists in adhesion between the magnet 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 17 is provided with a magnetic flux detection means such as a Hall element, and the heating enable start timing control is such that the applied magnetic field is in the opposite direction to the pre-magnetization, and the applied magnetic field of +H1-H has a value sufficient to cause thermal residual magnetization. It performs slice level detection, heating enable control, and clock generation control that determines the feeding timing of the magnetic material.

This method reduces the positioning accuracy of the thermal head magnetic field applying means compared to the method of applying an external magnetic field using a magnetic head.

As explained above, the present invention applies dot-shaped heat input using a thermal head, laser beam, or the like so that they overlap spatially on a magnetic latent image carrier.

Reverses the direction of the externally applied magnetic field in synchronization with the basic clock,
The present invention provides a magnetic latent image forming method that controls heat input application in basic clock units according to halftone information,
Heat input control is basic clock synchronous application, 3n+1 timing, 5n+1 timing + 7n+1 timing,...
(n represents an integer) 71), and one halftone latent image is formed by applying an even number of signals at each timing.

According to the present invention, it is possible to reproduce halftone reproduction using a thermal dot input magnetic latent image forming method such as a thermal head, it is possible to reproduce a solid uniformly, and it is possible to form a magnetic latent image unit smaller than the size of a heat input dot. It has the following features.

[Brief explanation of the drawing]

FIGS. 1(a) to (d) are explanatory diagrams of the principle of the magnetic latent image forming method of the present invention, and FIGS. 2(a) to (f) are fundamental waves, third harmonic waves,
Timing chart for printing 5th harmonic wave. Figure 3 is an explanatory diagram of the process of forming the third harmonic wave, Figure 4 is a configuration diagram of an embodiment using a magnetic head, and Figures 5 (,) and (b).
) is a configuration diagram and a schematic diagram of control of an embodiment using permanent magnets. Symbols in the figure: l... Support layer: 2... Magnetic layer; 3... Heating dot part; 4... Background magnetization; 5... Latent image magnetization; 7.
... External magnetic field; 7'... Reversal external magnetic field; 8... Movement direction; 9... Movement trajectory; 10... Thermal head;
11... Long magnetic head; 12... Externally applied magnetic field;
13... Magnetic recording body feed signal; 14... Heating enable; 15... Elastic body coating; 16... Hollow support: 17... Permanent magnet roll; 18... Magnetic field detection means. (3 others) fl! 1 figure

Claims (1)

[Claims:] A method for forming a magnetic latent image by dividing a magnetic recording body capable of thermal remanent magnetization into dot-shaped images, heating the same, and applying an external magnetic field. A magnetic latent image characterized by periodically reversing the magnetic field as the magnetic recording body moves, and heating the magnetic recording body every time the moving distance of the magnetic recording body corresponds to an odd multiple of the reversal period. Formation method.