GB2035900A - Fixing toner images - Google Patents

Abstract

A toner fixing method particularly for use in electronic duplicating machines and preferably using a flash discharge lamp, wherein the light pulse width is selected to be in the range 0.5 to 2.5 msec. A light pulse width in this range results in a clearer copy of even a complicated character pattern, for example, a Chinese character, than otherwise obtained.

Description

SPECIFICATION Toner fixing method The present invention relates to a method of fixing a toner and is particularly applicable for use in electrostatic type recording instruments such as electronic duplicating machines.

Infra-red lamps and heaters have long been used for fixing toners in electronic duplicating machines. Recently radiation by light of flash discharge lamps has been proposed for this purpose. However a flash discharge lamp tends to result in illegibility of reproduced material, particularly of Chinese characters which have markedly complicated strokes. A close examination of reproduced Chinese characters under a microscope has revealed that their illegibility, when reproduced in a copying machine using a flash discharge lamp to fix the toner, is caused by scattering and something like a blur of the toner.

According to one aspect of the present invention there is provided a toner fixing method comprising fixing the toner by irradiating the toner by light for a duration in the range 0.5 to 2.5 milliseconds.

Preferably the irradiation is effected using a flash discharge lamp.

It will be seen that the present invention can provide a toner fixing method which suppresses the scattering and blurring effect of the toner previously experienced particularly when a flash discharge lamp was used.

According to a second aspect of the present invention there is provided a duplicating machine adapted so as to employ the method of the first aspect.

It has been shown experimentally that a light pulse having too small a width and too large a peak value causes scattering of a toner by an "explosion effect" due to rapid heating during flashing. On the other hand, a light pulse having a large width and a small peak value causes heating of copying paper thus resulting in characters being reproduced deformed or out of shape. In particular it has been found that a pulse width of less than 0.5 msec. causes marked scattering of the toner and that a pulse width exceeding 2.5 msec.

causes something like a blur and makes strokes of a reproduced character rather dim.

It has been found experimentally that illegibility of reproduced characters, particularly of Chinese characters, can be substantially prevented by defining the upper and lower limits of the pulse width of the light irradiation, and that if these limits are between 0.5 and 2.5 msec. very legible reproduction is achieved even with Chinese characters having complicated strokes.

For example, a legible reproduced Chinese character with very clear strokes can be produced using a flash discharge lamp having an arc length of 30cm at a discharge voltage of 1 500 volts and with a condenser capacitance of 300 1LF, which gives a resulting light pulse width of about 0.8 msec.

The pulse width mentioned herein is a pulse width corresponding to one third of the peak value of the light pulse.

1. A toner fixing method comprising fixing the toner by irradiating the toner by light for a duration in the range 0.5 to 2.5 milliseconds.

2. A toner fixing method according to claim 1 wherein the toner to be fixed is irradiated by light from a flash discharge lamp.

3. A toner fixing method substantially as hereinbefore described.

4. A duplicating machine adapted so as to employ the method of any one of the preced ing claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Toner fixing method The present invention relates to a method of fixing a toner and is particularly applicable for use in electrostatic type recording instruments such as electronic duplicating machines. Infra-red lamps and heaters have long been used for fixing toners in electronic duplicating machines. Recently radiation by light of flash discharge lamps has been proposed for this purpose. However a flash discharge lamp tends to result in illegibility of reproduced material, particularly of Chinese characters which have markedly complicated strokes. A close examination of reproduced Chinese characters under a microscope has revealed that their illegibility, when reproduced in a copying machine using a flash discharge lamp to fix the toner, is caused by scattering and something like a blur of the toner. According to one aspect of the present invention there is provided a toner fixing method comprising fixing the toner by irradiating the toner by light for a duration in the range 0.5 to 2.5 milliseconds. Preferably the irradiation is effected using a flash discharge lamp. It will be seen that the present invention can provide a toner fixing method which suppresses the scattering and blurring effect of the toner previously experienced particularly when a flash discharge lamp was used. According to a second aspect of the present invention there is provided a duplicating machine adapted so as to employ the method of the first aspect. It has been shown experimentally that a light pulse having too small a width and too large a peak value causes scattering of a toner by an "explosion effect" due to rapid heating during flashing. On the other hand, a light pulse having a large width and a small peak value causes heating of copying paper thus resulting in characters being reproduced deformed or out of shape. In particular it has been found that a pulse width of less than 0.5 msec. causes marked scattering of the toner and that a pulse width exceeding 2.5 msec. causes something like a blur and makes strokes of a reproduced character rather dim. It has been found experimentally that illegibility of reproduced characters, particularly of Chinese characters, can be substantially prevented by defining the upper and lower limits of the pulse width of the light irradiation, and that if these limits are between 0.5 and 2.5 msec. very legible reproduction is achieved even with Chinese characters having complicated strokes. For example, a legible reproduced Chinese character with very clear strokes can be produced using a flash discharge lamp having an arc length of 30cm at a discharge voltage of 1 500 volts and with a condenser capacitance of 300 1LF, which gives a resulting light pulse width of about 0.8 msec. The pulse width mentioned herein is a pulse width corresponding to one third of the peak value of the light pulse. CLAIMS

1. A toner fixing method comprising fixing the toner by irradiating the toner by light for a duration in the range 0.5 to 2.5 milliseconds.

2. A toner fixing method according to claim 1 wherein the toner to be fixed is irradiated by light from a flash discharge lamp.

3. A toner fixing method substantially as hereinbefore described.

4. A duplicating machine adapted so as to employ the method of any one of the preced ing claims.