JPH06130851A - Image forming device - Google Patents

Abstract

PURPOSE:To perform high-density printing with low energy without emitting a bad smell by using toner whose temperature range where melt viscosity is a specified value and volume average particle size are regulated. CONSTITUTION:The small particle size toner whose temperature (melt temperature) attaining the viscosity of 10000 poise is 120-160 deg.C and whose volume average particle size including 3-15wt.% light absorption agent is within 4-10mum is fixed with flash light. In such a case, a flash lamp 1 such as a xenon lamp having flashing width in accordance with printing width and connected to a power source circuit and a reflector 2 for effectively guiding the flash light to paper are properly arranged so that the uniform distribution of light quantity may be obtained within a fixing area 3 on recording paper 5. When the lamp 1 radiates the flash light in the case the recording paper 5 to which the toner 4 is attached passes through the fixing area 3, the toner 4 in the fixing area 3 is melted by absorbing radiated energy, and solidified and fixed on the recording paper 5 when the temperature becomes low after finishing flashing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for visualizing an electrostatic latent image by toner such as electrostatic recording and electrophotography, and more particularly to an image forming apparatus equipped with a flash fixing device.

[0002]

2. Description of the Related Art As a device for fixing an image formed by powder toner in a copying machine, a printer or the like using an electrophotographic system, a flash fixing device for heating and fixing the toner by flash irradiation of a xenon lamp is known. Has been. In such a flash fixing device, when the amount of the adhered toner per unit area is increased in order to obtain a dark printed material, that is, when the image density before fixing is increased, the irradiation energy must be increased according to the increase of the adhered toner amount. Fixation becomes insufficient.

[0003]

Conventionally, an epoxy-based toner having a low viscosity and easy to melt is used so that a sufficient fixing strength can be obtained with a low energy. However, such a low-viscosity toner causes a flash of light. A phenomenon called a void occurs in which the paper surface is exposed by being irradiated and then agglomerating while melting and solidifying again, and the image density after fixing is greatly reduced. However, the image density after fixing could not be increased. Further, if the agglomeration is severe, the fixing strength may be lowered.

Further, in a general flash fixing device,
Since very high energy is irradiated in a short time, the surface of the toner is overheated and the temperature rises above the decomposition temperature to generate gas, so that it is necessary to take measures to prevent foul odors and stains.

In view of the above, as a method for obtaining a high image density, Japanese Patent Laid-Open No. 54-111356 discloses a toner fixing device that radiates radiant heat after flash light irradiation.
Japanese Patent Laid-Open No. 193155 proposes a flash fixing method using a specific binder resin, but none of them is said to be perfect.

An object of the present invention is to solve the above-mentioned problems, that is, a high image density can be obtained without a decrease in image density due to the occurrence of voids, and moreover, the energy required for fixing can be reduced and a bad odor can be obtained. An object of the present invention is to provide an image forming apparatus capable of excellent flash fixing.

[0007]

[Means for Solving the Problems] The object is to obtain a viscosity of 100.
The temperature at which it becomes 00 poise (hereinafter referred to as the melting temperature) is 12
This is achieved by fixing a small particle size toner having a volume average particle size of 0 to 160 ° C. and a volume average particle size of 4 to 10 μm containing 3% to 15% by weight of a light absorber by flashing.

Further, by preheating the image to a temperature of 100 ° C. or lower by the preheating means prior to the fixing, the image density can be further improved without causing deterioration such as wrinkles on the paper.

[0009]

As described above, by using a toner having a high melting temperature, generation of voids is suppressed and a high-density fixed image can be obtained.
The energy required for fixing can be reduced. Further, it is possible to suppress the generation of bad odor. Furthermore, by using preheating together, higher image density can be obtained.

[0010]

EXAMPLES As the light absorber added to the toner used in the image forming apparatus according to the present invention, black pigment or dye such as carbon black is used in the case of black toner, and red toner is also used in the case of color toner. In the case of a blue toner or a green toner, a red pigment or dye such as rhodamine is preferable, and it is preferable to use a blue or green pigment or dye such as copper phthalocyanine because it can satisfy the coloring of the toner at the same time. In this case, a light absorber, which is generally called a near infrared absorber, such as an aminium complex-based dye, a diionium-based dye, a cyanine-based dye, can be used in combination. If the amount of the light absorber added is less than 3% by weight, sufficient color density cannot be obtained, and if it exceeds 15% by weight, good chargeability cannot be obtained. Therefore, it is desirable to set the amount to 3% by weight to 15% by weight. .

As a result of a study using a toner containing 3% by weight to 15% by weight of carbon black as a light absorber, when the flash emission time is less than 0.5 ms (1/3 pulse width), the toner is scattered. It has been found that it is necessary to set 0.5 ms to 1.5 ms (1/3 pulse width) because the above phenomenon occurs and the energy loss increases when the light emission time exceeds 1.5 ms.

Further, when fixing an image having a relatively low density, the irradiation energy required to obtain the same fixing strength (hereinafter, referred to as fixing energy) is smaller for a toner having a lower viscosity, that is, a toner having a lower melting temperature. From the end
In the conventional flash fixing, the melting temperature is 100 ° C to 120 ° C.
Although toner of about ℃ was used, as a result of experiments conducted by the inventors, when fixing an image having a high density, as shown in FIG. 3, even if the image density before fixing is the same, the image is melted. It was found that the higher the temperature of the toner, the higher the image density after fixing. Accordingly, it has been found that in order to obtain a high image density in flash fixing, it is necessary to use a toner having a high melting temperature, which is disadvantageous in terms of fixing energy.

That is, in the case of flash fixing, the toner viscosity should be determined in consideration of not only the fixability but also the required image density, and the image density after fixing is 1.2.
When the above is required, the melting temperature needs to be 120 ° C. or higher. On the other hand, if the melting temperature exceeds 160 ° C, energy loss will occur. Therefore, the melting temperature of the toner is 12
The temperature is set to 0 ° C to 160 ° C, more preferably 130
It will be in the range of ℃ to 150 ℃.

As described above, the improvement of the image density is achieved by using a toner having a high viscosity, but at the same time, when it is attempted to reduce the fixing energy, it is necessary to use a method which does not affect the toner viscosity. As a result of various experiments conducted by the inventors, it has been found that it is effective to use a toner having a smaller particle diameter in combination.

FIG. 4 shows an example showing the effect of reducing the particle size. Unfixed images with the same image density were created with toners of different volume average particle sizes made using the same material, and flash fixing was performed with a flash emission time of 0.8 ms (1/3 pulse width). When the image density in the fixed state is 1.0 or less, the fixing energy is almost constant regardless of the toner particle size as shown by the dotted line, but when the image density in the unfixed state is increased to 1.0 or more, As indicated by the solid line, it was found that the smaller the toner particle size, the smaller the fixing energy. Further, as shown in FIG. 6, it was found that the small particle size toner was less in terms of generation of a bad odor.

Therefore, it is effective to reduce the particle size of the toner as much as possible in order to reduce energy and prevent bad odor, but a toner of less than 4 μm causes problems such as fogging and scattering at the time of development, and conversely 10 μm. If it exceeds, the energy reduction effect will decrease, and large voids will be generated,
Since the unevenness of the image is conspicuous and the image quality is deteriorated, the volume average particle diameter of the toner needs to be in the range of 4 μm to 10 μm, and more preferably in the range of 7 μm to 8 μm.

FIG. 5 is an embodiment showing the effect when the image preheating by the preheating means (heating means) is also used.
After preheating images of the same density formed using the same toner to a predetermined temperature and then performing flash fixing, it was found that the higher the preheating temperature, the higher the image density after fixing. Therefore, it is effective for high density fixing to raise the preheating temperature as much as possible, but the energy increase of the preheating device,
Since there are problems such as paper deterioration (wrinkles and yellowing), preheating causes wrinkles and yellowing when the image density exceeds 100 ° C, and conversely, when the temperature is below 60 ° C, the preheating effect disappears. It is desirable that the temperature be in the range of 100 ° C to 100 ° C.

The present invention will be described below based on specific examples.

(Embodiment 1) FIG. 1 is a schematic view of a fixing device used in this embodiment. A flash lamp 1 such as a xenon lamp having a flash width corresponding to a print width connected to a power supply circuit (not shown) and a reflector 2 for effectively guiding the flash to the paper are provided in a fixing area 3 on the recording paper 5. Are arranged appropriately so that a uniform light amount distribution can be obtained. When the flash lamp 1 irradiates a flash light when the recording paper 5 to which the toner 4 is attached passes through the fixing area 3, the toner 4 in the fixing area 3 is irradiated.
Absorbs the irradiation energy and melts, and after the flashing ends, the temperature drops and solidifies and is fixed on the recording paper 5. A continuous fixed image is obtained by repeating light emission at an appropriate light emission interval so that an incompletely fixed area does not occur on the recording paper 5 fed at an appropriate speed.

In this apparatus, an unfixed image having a reflection density of 1.5 was prepared by using a polyester black toner having a melting temperature of 140 ° C., a glass transition temperature of 65 ° C. and a volume average particle diameter of 8 μm containing 6% by weight of carbon black. Then, when a flash light having a light emission time of 0.8 ms (1/3 pulse width) was irradiated and fixing was performed, an image density of 1.3 after fixing and a fixing strength of 100% were obtained with an irradiation energy of 1.8 J / cm ^2. No bad odor was generated.

(Embodiment 2) As in Embodiment 1 above, FIG.
The melting temperature of 150 ° C and the glass transition temperature of 70
C., unfixed image with a reflection density of 1.7 made using styrene-acrylic black toner containing 6% by weight of carbon black and having a volume average particle size of 8 .mu.m has a light emission time of 0.8 ms (1 /
When fixing was carried out by irradiating a flash light of 3 pulse width), the image density after fixing was 1. ² with an irradiation energy of 2.2 J / cm ² .
4. A fixing strength of 100% was obtained and no bad odor was generated.

In order to confirm the effects of the present invention, a polyester black toner having a low melting temperature of 110 ° C. and a large volume average particle diameter of 12 μm and a glass transition temperature of 60 ° C. containing 6% by weight of carbon black was prepared. Reflection density 1.
When the unfixed image of No. 7 was fixed by irradiating it with flash light with a light emission time of 0.8 ms (1/3 pulse width), the image density after fixing was increased even if the irradiation energy was increased to 2.5 J / cm ^2. Only 1.0 was obtained, and the fixing strength was as low as 90%.
In addition, a large amount of gas was generated and bad odor was severe.

(Example 3) As in the above example, using the apparatus shown in FIG. 1, a melting temperature of 130 ° C., a glass transition temperature of 63 ° C., a volume average particle diameter of 8 μm, 6% by weight of a rhodamine pigment as a light absorber, and Aminium-based near infrared absorber 1% by weight
For an unfixed image with a reflection density of 1.4 created using a polyester-based red toner to which is added a light emission time of 0.8 ms (1/3
When the fixing was carried out by irradiating a flash light of pulse width), the image density after fixing was 1.2 with the irradiation energy of 1.8 J / cm ² .
A fixing strength of 100% was obtained and no odor was generated.

(Embodiment 4) FIG. 2 is a schematic view of a fixing device used in this embodiment. As in FIG. 1, the flash lamp 1 and the reflector 2 are appropriately arranged so as to obtain a uniform light amount distribution in the fixing area 3, and further, an infrared heater for preheating an image before flash fixing. A heating device 6 is provided which is composed of a reflector 7, a reflector 8 and a power supply circuit (not shown).

The recording paper 5 to which the toner 4 is attached is preheated by the heating device 6 before the flash fixing, and the temperature is controlled so that the image density becomes 100 ° C. or less. After the preheating, the recording paper 5 to which the toner 4 is attached is irradiated with flash light when passing through the fixing area 3 to be fixed.

An unfixed image having a reflection density of 1.7, which was prepared by the above apparatus using a styrene acrylic black toner having a melting temperature of 150 ° C., a glass transition temperature of 70 ° C., a carbon black of 6% by weight and a volume average particle diameter of 8 μm. Was preheated to 60 ° C, and was then fixed by irradiating it with flash light with a light emission time of 0.8 ms (1/3 pulse width).
An image density of 1.5 after fixing and a fixing strength of 100% at cm ² were obtained, and no odor was generated.

In the above example, the reflection density was measured with a Macbeth densitometer RD-919 (manufactured by Macbeth Co.).

For fixing strength, a measuring tape (Type 810 manufactured by Sumitomo 3M Co., Ltd.) was lightly attached to an image of which reflection density was measured by a Macbeth densitometer, and the weight was 2 kg.
After reciprocally rolling the roll of 1 and making it adhere, the tape is peeled off,
The reflection density at the same place was measured again and the value was calculated by the following formula.

Fixing strength = (Reflected strength after peeling) / (Reflected strength before peeling) × 100 (%) As described above, the present invention has been described with reference to specific examples, but the present invention is not limited to these examples. However, for example, the toner resin to be used may be polyester, styrene-acrylic copolymer, epoxy or other resin generally used for toner, and an internal additive such as a charge control agent or a release agent. An external additive such as a fluidity improver may be added if necessary. Further, the number of flash lamps does not have to be one and may be a plurality of flash lamps. Further, the heating device used together is not limited to the infrared heater.

[0030]

As described above, if the toner according to the present invention is subjected to flash fixing at 120 ° C. to 160 ° C., there is an effect that no bad smell is generated with low energy and high density printing can be performed.

[Brief description of drawings]

FIG. 1 is a schematic view of a fixing device used in an embodiment of the present invention.

FIG. 2 is a schematic view of a fixing device used in another embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a melting temperature and an image density after fixing.

FIG. 4 is a diagram showing the effect of reducing the particle size.

FIG. 5 is a diagram showing the effect of preheating.

FIG. 6 is a diagram showing the relationship between the toner particle size and the generation of malodor.

[Explanation of symbols]

 1 Flash lamp 2 Reflector 3 Fixing area 4 Toner 5 Recording paper 7 Infrared heater 8 Reflector

Claims (2)

[Claims] 1. An image forming apparatus equipped with a flash fixing device has a melt viscosity of 10,000 poise at a temperature of 1.
20 to 160 ° C. and a volume average particle diameter of 4 to 10 μm
An image forming apparatus using a toner regulated in a range of m. 2. The image forming apparatus according to claim 1, further comprising a preheating unit that preheats an image to a temperature of 100 ° C. or less prior to the flash irradiation of the flash fixing device.