JP2012088493A - Optical fixing device, and electronic apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fixing device and an electronic apparatus using the same, which can obtain desired fixing performance with low power consumption.SOLUTION: An optical fixing device gathers light from a light source 2 onto a recording medium 6 using an irradiation optical system 3 and irradiates unfixed toner 4 on the recording medium 6 for fixing. The irradiation optical system 3 forms a light irradiation area with a power density I[W/cm] satisfying the following formula (1): I>20,000[W/cm] on the recording medium 6.

Description

  The present invention relates to an optical fixing device, and more particularly, to an optical fixing device for fixing an unfixed toner image recorded on a recording medium by irradiating light, and an electronic apparatus equipped with the optical fixing device.

  Conventionally, in an image forming apparatus such as a copying machine or a printer, as a method for transferring a toner image onto a recording medium, the toner is melted by an overheated fixing roller, pressurized by a pressure roller, and fixed on a recording medium. A heat press method is generally known.

  In the case of the hot press method, it takes time to raise the fixing roller to a temperature sufficient to melt the toner. Further, there is a problem in that the power consumption during standby is large because the roller needs to be kept at a constant temperature in order to shorten the rise time even during standby.

  To solve these problems, a light fixing method is proposed in which unfixed toner is irradiated with light, and the toner is melted and fixed on the recording medium using heat generated by the toner absorbing light. Has been. The light fixing method does not use the fixing roller used in the thermal pressurization method, and uses a laser or the like that can instantaneously turn on and off the thermal energy supply source for the toner as compared with the thermal pressurization method. In addition to shortening the time required to start up the apparatus, it is possible to reduce power consumption during standby.

  Patent Document 1 proposes an optical system that realizes the above-described optical fixing. In Patent Document 1, in a fixing device using an LD (Laser Diode) as a light source, the laser light from this laser element is an elliptical spot as shown in FIG. 5, and the irradiation region of the laser light is in the recording paper conveyance direction. A method of increasing the fixing efficiency by securing the irradiation time of the laser beam to the unfixed toner by disposing the toner so as to spread is disclosed.

JP 2007-57903 A

  However, the fixing device disclosed in Patent Document 1 has the following problems. That is, the amount of thermal diffusion to the recording paper or the atmosphere while the toner temperature is rising increases with time. For this reason, if the laser spot is elliptical with the light irradiation power held constant, the laser power per unit area will be low and the irradiation time will be long for fixing. The thermal energy loss that does not contribute to increases, resulting in an increase in power consumption.

  The present invention has been made in view of the above problems, and is an optical fixing device using a laser, a laser array, or the like as a light source, and capable of obtaining desired fixing performance with low power consumption. And an electronic device using the same.

An optical fixing apparatus according to the present invention is an optical fixing apparatus that focuses light on a recording medium by an irradiation optical system and irradiates unfixed toner on the recording medium for fixing.
The irradiation optical system is characterized in that a light irradiation region having a power density I [W / cm ² ] satisfying the following formula (1) is formed on the recording medium.

I> 20,000 [W / cm ² ] (1)
In the photofixing device according to the present invention, the area of the light irradiation region is S [cm ² ], and the energy required for melting the unfixed toner existing in the light irradiation region is Q [J]. Then, the irradiation optical system is characterized in that the light irradiation region in which the power density I satisfies the following formula (2) is formed on the recording medium.

I <(Q / S) × 10 ¹⁵ [W / cm ² ] (2)
In the light fixing device according to the present invention, when the particle size of the unfixed toner is D [cm], the irradiation optical system displays the light irradiation area satisfying the following formula (3) on the recording medium. It is characterized by forming in.

S> π × (D / 2) ² [cm ² ] (3)
Further, the optical fixing device according to the present invention is characterized in that the recording medium relatively moves along a minor axis direction of the light irradiation region.

  An electronic apparatus according to the present invention includes any one of the above-described optical fixing devices.

  According to the present invention, it is possible to realize an optical fixing device capable of obtaining desired fixing performance with low power consumption, and an electronic apparatus using the same.

It is a block diagram of an optical fixing device. It is a figure which shows the light irradiation area | region by the condensed light which concerns on Embodiment 1. FIG. FIG. 3 is a diagram illustrating a relationship between power density and fixing efficiency in Embodiment 1. FIG. 6 is a diagram illustrating a relationship between power density and fixing efficiency in Embodiment 2. It is a figure which shows the irradiation area | region of the conventional optical fixing device.

  Embodiments of the present invention will be described below.

<Embodiment 1>
FIG. 1 is a configuration diagram of an optical fixing device 1 according to the first embodiment. The optical fixing device 1 includes a light emitting unit 2 that is a light source that melts an unfixed toner image, a condensing unit 3 that collects diffused light Z1 emitted from the light emitting unit 2, and a moving unit 7 that moves a recording medium 6. Has been. On the recording medium 6, an unfixed toner image 4 is formed by the toner particles 5, and the focused light flux Z <b> 2 from the light collecting unit 3 is irradiated to fix the image.

  The light emitting unit 2 uses a light semiconductor such as an LD (Laser Diode) or LED (Light Emitting Diode) as a light source, and is used as a light source for melting the unfixed toner image 4. These optical semiconductors have the advantage of being capable of high-frequency driving that switches on / off of the light source and high / low of the output at high speed, in addition to the small size, high luminous efficiency, and long life. Yes.

  The wavelength of the diffused light Z1 emitted from the light emitting unit 2 is preferably a wavelength that is well absorbed by the unfixed toner image 4 described later and is easily converted into thermal energy. Further, if the unfixed toner image 4 absorbs visible light, it is likely to change in quality due to long-term storage, which is not preferable from the viewpoint of storing and using a fixed matter on which the toner is fixed as a printed matter for a long time. Therefore, the wavelength of the diffused light Z1 is preferably 800 nm to 1000 nm, and near infrared light of around 850 nm is preferable. In particular, near-infrared light having a wavelength of around 850 nm can be efficiently obtained by a general-purpose semiconductor laser, the price of the semiconductor laser itself is low, and the performance is stable.

  Further, as the material of the toner particles 5 that form the unfixed toner image 4, it is necessary to use a material that has a characteristic of absorbing light in the above wavelength band emitted from the light emitting unit 2. The toner particles 5 are fine particles of, for example, about several μm to tens of μm, and are deposited on the recording medium 6 so as to form a single layer or a plurality of layers. The toner particles 5 on the surface layer of the unfixed toner image 4 absorb the light irradiated by the light emitting unit 2. The absorbed light is converted into heat energy, and the temperature of the toner particles 5 rises. Further, the temperature of the toner particles 5 existing on the recording medium 6 side of the inner layer of the unfixed toner image 4, that is, the surface layer, rises due to heat transfer from the toner particles 5 on the surface layer that has reached a high temperature. Eventually, the temperature of the entire toner particles 5 reaches the melting point, and the melted toner penetrates into the recording medium 6 to be fixed on the recording medium 6.

  The condensing unit 3 includes an irradiation optical system, and an optical lens, a galvano mirror, a polygon mirror, or the like made of glass or transparent resin is used alone or in combination. The diffused light Z1 emitted from the light emitting unit 2 is collected by the light collecting unit 3, and is collected on a recording medium 6 such as paper as a condensed light beam Z2.

  On the recording medium 6, an unfixed toner image 4 is formed in advance in a step before the fixing step. The toner particles 5 forming the unfixed toner image 4 are melted after absorbing the condensed light flux Z2 and heated, and penetrated into the recording medium 6 and fixed.

  The recording medium 6 is disposed on the moving unit 7. In the present embodiment, as shown in FIG. 1, a method of transporting the recording medium 6 by the moving unit 7 is adopted.

  First, the moving unit 7 moves the recording medium 6 relative to the light irradiation area of the condensed light beam Z2 in the X direction shown in FIG. 1 to perform main scanning, and then moves the recording medium 6 to the condensed light beam Z2. Sub-scanning is performed by relatively moving the light irradiation area in the Y direction. Thereafter, the entire movement of the recording medium 6 is repeated by repeatedly performing the relative movement in the X direction and the relative movement in the Y direction. Irradiation with the condensed light beam Z2 fixes and fixes the toner particles 5 present at each position on the recording medium 6.

  Next, a method for fixing the unfixed toner image 4 to the recording medium 6 using the optical fixing device 1 will be described. In the present embodiment, as shown in FIG. 1, the optical axis of the light emitting unit 2 is disposed substantially perpendicular to the surface of the recording medium 6, and the diffused light Z1 from the light emitting unit 2 is collected by the condensing unit. 3 is condensed to be a condensed light beam Z2, and the recording medium 6 is irradiated.

Here, when the particle diameter of the toner particles 5 of the unfixed toner is D [cm], the sectional area of one toner particle 5 constituting the unfixed toner image 4 projected on the recording medium 6 is π X (D / 2) ² [cm ² ]. In order to heat one toner particle 5 as a whole and to melt the toner efficiently, the area S [cm ² ] of the light irradiation region formed on the recording medium 6 is set to one piece constituting the unfixed toner image 4. In other words, it is necessary to satisfy the following conditional expression (3).

S> π × (D / 2) ² [cm ² ] (3)
FIG. 2 is a diagram showing the light irradiation region 8 by the condensed light according to the present embodiment. In the present embodiment, the light irradiation area 8 by the condensed light beam Z2 on the recording medium 6 has an elliptical shape as shown in FIG. The size of the elliptical light irradiation region 8 in the major axis direction is 5 × 10 ⁻² [cm], and the size in the minor axis direction is 5 × 10 ⁻³ [cm]. Further, the toner used in the present embodiment is a dry toner used in a general thermal pressurization method, and the toner particle diameter D is about 5 × 10 ⁻⁴ [cm]. Therefore,
S [cm ² ] ≈1.96 × 10 ⁻⁴ [cm ² ]
π × (D / 2) ² [cm ² ] = 1.96 × 10 ⁻⁷ [cm ² ]
Thus, conditional expression (3) is satisfied. Note that the light irradiation region 8 may be circular as long as the entire toner particle 5 is irradiated with light. By doing so, the entire toner particle can be heated by light irradiation, and the toner can be efficiently melted. The melted toner penetrates into the recording medium 6 and is fixed and fixed on the recording medium 6.

  Next, the contents of a fixing experiment in which the power density I of the condensed light beam Z2 and the moving speed of the moving unit 7 are changed and the unfixed toner image 4 on the recording medium 6 is irradiated with light will be described. In addition, the power density in this invention refers to the power of the light irradiated per unit area. Here, the main moving direction of the moving unit 7 is a direction along the short axis direction of the light irradiation region 8 formed on the recording medium 6 as shown by an arrow in FIG. By doing so, the light irradiation time to the toner can be shortened, the thermal diffusion to the recording medium or the atmosphere while the toner temperature is rising can be suppressed, and the toner can be efficiently melted.

  FIG. 3 shows experimental results of toner fixing efficiency when the power density I of the condensed light flux Z2 irradiated to the toner is changed. The toner fixing efficiency in the present invention refers to the integrated irradiation light amount necessary for toner fixing per unit area. Here, if the numerical value of the toner fixing efficiency on the vertical axis of the graph is small, the power consumption required for fixing is small. Means. The numerical value on the vertical axis in FIG. 3 is a value when the fixing efficiency at point A is 1, and indicates the fixing efficiency obtained at each power density.

Here, the determination of fixing was performed as follows. First, in a state where the fixing toner surface of the recording paper is lightly folded, a cylindrical weight of about 1 kg is reciprocated on the recording paper, then the crease is opened, and a weight is placed on the white paper on the crease. Holding the white paper and pulling on the fixing surface, it was visually determined whether or not the toner at the crease valley on the paper was removed. Note that the value of toner fixing efficiency also varies depending on physical properties such as toner density and toner melting point. The toner density ρ on the recording medium 6 used in this experiment was 0.41 [mg / cm ² ], the specific heat C of the toner was 1.42 [J / gK], and the melting point Tr of the toner was 110 [° C.]. .

  Since the integrated amount of light applied to the toner is determined by the product of the power density I and the light irradiation time, as the power density I increases, the moving speed of the relative moving portion is increased and the light irradiation time to the toner is shortened. . For example, the power density and fixing efficiency at points A, B, and C in FIG. As the power density increases, the light irradiation time required for toner fixing becomes shorter and the integrated irradiation light amount also decreases.

From the above experimental results, the following was found.
(I) When the power density I was increased and the irradiation time was shortened, the fixing efficiency decreased to almost point B.
(II) When the power density I is greater than 20,000 [W / cm ² ], the fixing efficiency becomes substantially the same as the minimum value, and the fixing efficiency becomes substantially constant even when the power density is increased.

In the region (I), the light irradiation time to the toner decreases as the power density I increases. For this reason, the thermal diffusion to the recording medium 6 or the atmosphere while the toner temperature is rising is reduced as the light irradiation time is shortened, and the heat generated by the light absorption is efficiently used for melting the toner. Accordingly, the fixing efficiency decreases as the power density increases.
Further, in the area (II), the moving speed of the relative moving portion is high, and the light irradiation time to the toner is 25 [μs] or less. Therefore, the heat generated by the light absorption to the recording medium or the atmosphere Thermal diffusion is almost negligible. Accordingly, when the power density I is greater than 20,000 [W / cm ² ], the fixing efficiency shows a minimum value. Accordingly, the power consumption required for toner fixing can be reduced by irradiating light in a region where the power density I [W / cm ² ] satisfies the following formula (1).

I> 20,000 [W / cm ² ] (1)
Further, the unfixed toner is melted by heat generated by light absorption of toner molecules. In general, in order for molecules to absorb light, 10 ⁻¹⁵ [s] or more is necessary, and therefore, the time for light irradiation to the toner also needs to be 10 ⁻¹⁵ [s] or more. Here, if the energy required to melt the toner existing in the elliptical light irradiation region S [cm ² ] in this embodiment is Q [J] and the light irradiation time is T [s], thermal diffusion is performed. In the state where can be ignored, the following relational expression holds.

I [W / cm ² ] × S [cm ² ] × T [s] = Q [J]
In the above formula, the light irradiation time needs to be 10 ⁻¹⁵ [s] or more,
Q / (I × S)> 10 ⁻¹⁵ [s]
Therefore, the upper limit value of the power density is defined by the following conditional expression (2).

I <(Q / S) × 10 ¹⁵ [W / cm ² ] (2)
In this embodiment, assuming that the room temperature is 20 ° C., from the toner density, specific heat, and area of the light irradiation region,
I <5.2 × 10 ¹⁰ [W / cm ² ] (4)
It becomes.

That is, even if the toner on the recording medium 6 is irradiated with light having a power density I exceeding the upper limit of the above formula (4), the light irradiation time cannot be shortened, so that the power consumption required for toner fixing is reduced. I can't. Further, if the toner is irradiated with light having a power density I exceeding the upper limit of the above formula (4) for 10 ⁻¹⁵ [s] or more, the toner is sublimated, resulting in poor fixing.

  As described above, according to the present embodiment, when unfixed toner is fixed and fixed, the power density I of the light applied to the toner, the light irradiation region 8, and the light irradiation time T are optimally set. Therefore, it is possible to achieve good fixability and high fixing efficiency.

  In this embodiment, the unfixed toner image 4 fixed and fixed to the recording medium 6 absorbs light from the light emitting unit 2 and generates heat, and is fixed to the recording medium 6. However, phenomena other than heat generation occur. You may fix by. For example, fixing by a chemical reaction using the effect of ultraviolet rays may be used.

  In the present embodiment, the recording medium 6 is transported by the moving unit 7. However, the moving unit 7 and the light collecting unit 3 are configured such that the light collecting unit 3 is fixed and the moving unit 7 moves. Alternatively, the moving unit 7 may be fixed and the condensing unit 3 may move, or both the condensing unit 3 and the moving unit 7 may move relative to each other by moving at different speeds.

  Furthermore, the relative moving method of the recording medium 6 may be any configuration as long as it is a relative moving means that can irradiate the entire area of the recording medium 6 with the condensed light beam Z2. For example, a moving unit that moves the optical system constituted by the light emitting unit 2 and the light collecting unit 3 in the XY directions with respect to the recording medium 6 may be used, or a galvanometer mirror or polygon that constitutes the irradiation optical system. A system in which a condensed light beam Z2 is scanned on the recording medium 6 using a spatial light modulation element such as a mirror may be used.

<Embodiment 2>
In the present embodiment, a case where the toner density of the unfixed toner shown in the first embodiment is different will be described. Since the basic configuration other than the toner density is the same as that of the first embodiment, a detailed description of common portions is omitted.

  FIG. 4 shows experimental results of toner fixing efficiency when the power density I of the condensed light flux Z2 irradiated to the toner is changed. Here, if the numerical value of the toner fixing efficiency on the vertical axis of the graph is small, it means that the power consumption required for fixing is small. The numerical value on the vertical axis in FIG. 4 is a value when the fixing efficiency at the point D is 1, and indicates the fixing efficiency obtained at each power density.

The toner density ρ on the recording medium 6 used in this experiment is 0.063 [mg / cm ² ], the specific heat C of the toner is 1.42 [J / gK], and the melting point Tr of the toner is 110 [° C.] The toner fixing efficiency value also varies depending on physical properties such as toner density and toner melting point. Since the cumulative amount of light applied to the toner is determined by the product of the power density and the light irradiation time, as the power density I increases, the moving speed of the relative moving portion is increased and the light irradiation time to the toner is shortened. For example, Table 2 shows the light irradiation conditions and fixing efficiency at points D, E, and F in FIG.

From the experimental results, the following was found.
(I) When the power density I was increased and the irradiation time was shortened, the fixing efficiency decreased to the point E.
(II) When the power density I is greater than 20,000 [W / cm ² ], the fixing efficiency becomes substantially the same as the minimum value, and the fixing efficiency becomes substantially constant even when the power density is increased.

  In the region (I), the light irradiation time to the toner decreases as the power density I increases. For this reason, the thermal diffusion to the recording medium 6 or the atmosphere while the toner temperature is rising is reduced as the light irradiation time is shortened, and the heat generated by the light absorption is efficiently used for melting the toner. Further, since the toner density used in the present embodiment is smaller than the toner density used in the first embodiment, the interval between the toner particles 5 is wide, and the effect of reducing thermal diffusion due to shortening of the light irradiation time is great. . Further, as in the first embodiment, the fixing efficiency decreases as the power density increases.

Further, in the area (II), the moving speed of the relative moving portion is high, and the light irradiation time to the toner is 25 [μs] or less. Therefore, the heat generated by the light absorption to the recording medium or the atmosphere Thermal diffusion is almost negligible. Accordingly, when the power density I is greater than 20,000 [W / cm ² ], the fixing efficiency shows a minimum value. Accordingly, the power consumption required for toner fixing can be reduced by irradiating light in a region where the power density I [W / cm ² ] satisfies the following formula (1).

I> 20,000 [W / cm ² ] (1)
Further, the unfixed toner is melted by heat generated by light absorption of toner molecules. Generally, since 10 ⁻¹⁵ [s] is required for molecules to absorb light, the light irradiation time to the toner needs to be 10 ⁻¹⁵ [s] or more. Here, if the energy required to melt the toner existing in the elliptical light irradiation region S [cm ² ] in this embodiment is Q [J] and the light irradiation time is T [s], thermal diffusion is performed. In the state where can be ignored, the following relational expression holds.

I [W / cm ² ] × S [cm ² ] × T [s] = Q [J]
In the above formula, the light irradiation time needs to be 10 ⁻¹⁵ [s] or more,
Q / (I × S)> 10 ⁻¹⁵ [s]
Therefore, the upper limit value of the power density is defined by the following conditional expression (2).

I <(Q / S) × 10 ¹⁵ [W / cm ² ] (2)
In this embodiment, assuming that the room temperature is 20 ° C., from the toner density, specific heat, and area of the light irradiation region,
I <8.1 × 10 ⁹ [W / cm ² ] (5)
It becomes.

That is, even if the toner on the recording medium 6 is irradiated with light having a power density I exceeding the upper limit of the above formula (5), the light irradiation time cannot be shortened, so that the power consumption required for toner fixing is reduced. I can't. Further, if the toner is irradiated with light having a power density exceeding the upper limit of the above formula (5) for 10 ⁻¹⁵ [s] or more, the toner is sublimated, resulting in poor fixing.

  As described above, according to the results of the present embodiment and the first embodiment, when fixing and fixing unfixed toner, regardless of the toner density, the power density I of the light applied to the toner, the light irradiation region 8, By setting the light irradiation time T optimally, good fixability and high fixing efficiency can be realized.

  By the way, as described above, the optical fixing device 1 in each of the above embodiments, when fixing and fixing unfixed toner on the recording medium 6, the power density I of the light applied to the toner, the light irradiation region 8, By setting the irradiation time optimally, the heat diffusion to the recording medium 6 or the atmosphere during the rise of the toner temperature can be ignored, and the heat generated by the light absorption is efficiently used for melting the toner. Thus, good fixability and high fixing efficiency can be realized, and power consumption required for toner fixing can be reduced.

  Therefore, when the optical fixing device 1 in each of the above embodiments is mounted on an electronic device such as a copying machine, a printer, or a facsimile, the toner exhibiting good fixability to the recording medium 6 and high fixing efficiency is provided on the electronic device. Therefore, the energy required for fixing can be reduced.

  The optical fixing device of the present invention is useful for reducing energy required for fixing and fixing, and can be used for electronic devices such as copying machines, printers, facsimiles, and exposure devices.

DESCRIPTION OF SYMBOLS 1 Light fixing apparatus 2 Light emission part 3 Condensing part 4 Unfixed toner image 5 Toner particle 6 Recording medium 7 Moving part 8 Light irradiation area Z1 Diffuse light Z2 Condensed light beam

Claims (5)

A light fixing device that focuses light from a light source on a recording medium by an irradiation optical system and irradiates unfixed toner on the recording medium for fixing.
The irradiation optical system forms on the recording medium a light irradiation region in which a power density I [W / cm ² ] satisfies the following formula (1):
I> 20,000 [W / cm ² ] (1) When the area of the light irradiation region is S [cm ² ] and the energy required to melt the unfixed toner existing in the light irradiation region is Q [J], the irradiation optical system is The light fixing device according to claim 1, wherein the light irradiation region having a power density I satisfying the following formula (2) is formed on the recording medium.
I <(Q / S) × 10 ¹⁵ [W / cm ² ] (2) 2. The irradiation optical system forms the light irradiation region satisfying the following formula (3) on the recording medium when the particle size of the unfixed toner is D [cm]. Or a light fixing device according to 2;
S> π × (D / 2) ² [cm ² ] (3)   4. The optical fixing device according to claim 1, wherein the recording medium relatively moves along a minor axis direction of the light irradiation region. 5.   An electronic apparatus comprising the optical fixing device according to claim 1.