JPH10282793A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent image haven a sufficient image density, without generation of a fog in supplying ink to an electrostatic latent image formed on an image carrier so as to form an image. SOLUTION: This image forming device comprises a latent image forming means 2 for forming the electrostatic latent image on the surface of the image carrier 1 and an ink developing means 3 for adjusting the thickness of the ink 32 held on the surface of an ink carrier 31 by a regulating plate 33 and bringing the ink into contact with the surface of the image carrier on which the electrostatic latent image is formed, to form an ink image. In this case, such a ink is used that when the system speed of the image forming device is defined as Vs [mm/s], the Young's modulus of the regulating plate is defined as E [kgf/mm<2> ], the length of the part coming into contact with the ink on the regulating plate is defined as L [mm] and the thickness of the regulating plate is defined as t [mm], viscosity η(γ) [cp] at a shear rate γ [/s] satisfies a condition of 44.8×10<-6> ×E×t<3> /(L<4> ×Vs)<=η(γ)<=902.8×10<-6> ×E×t<3> /(L<4> ×Vs).

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 which forms an electrostatic latent image on an image carrier and develops the latent image to form an image on a recording medium. The ink held on the surface of the carrier is brought into contact with the surface of the image carrier on which the electrostatic latent image is formed, so that an ink image corresponding to the electrostatic latent image is formed on the surface of the image carrier. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, as typified by an electrophotographic copying machine, an electrostatic latent image is formed on the surface of an image carrier, and after developing the electrostatic latent image, the electrostatic latent image is formed on a recording medium such as paper. 2. Description of the Related Art An image forming apparatus that transfers an image onto a recording medium and forms an image on a recording medium is used.

As one of such electrophotographic image forming apparatuses, colored resin particles (toner particles) are used to develop an electrostatic latent image as disclosed in Japanese Patent Application Laid-Open No. 7-271107. One using a liquid developer dispersed in a carrier liquid is known.

Here, the liquid developer used in the electrophotographic apparatus is generally one in which charged toner particles are dispersed in an insulating carrier liquid, and the toner particles become liquid developer as an image is formed. When this liquid developer is used, it is necessary to control the concentration of the toner particles in the carrier liquid, and the management is troublesome, and most of the carrier liquid is used. Since the liquid developer is used repeatedly, there is a problem that the liquid developer is easily deteriorated.

Further, in an electrophotographic apparatus using such a liquid developer, when an image is formed on a recording medium such as copy paper, a fixing device for fixing a toner image transferred onto the recording medium or the like is used. Is required, and there is a problem that the apparatus becomes complicated and large.

[0006] Conventionally, Japanese Patent Publication No. 52-45
As shown in JP-A-494, the ink held on the surface of the ink carrier is brought into contact with the surface of the image carrier on which the electrostatic latent image is formed, and an ink image corresponding to the electrostatic latent image is carried on the image carrier. There has been proposed an image forming apparatus that forms an image on a recording medium by forming the image on a recording medium by transferring the ink image onto a recording medium.

Here, the ink held on the surface of the ink carrier is brought into contact with the surface of the image carrier on which the electrostatic latent image is formed, and an ink image corresponding to the electrostatic latent image is carried on the image carrier. When forming on the surface of the body, if the amount of ink held on the surface of the ink carrier is small, the ink is not sufficiently supplied to the portion of the electrostatic latent image formed on the image carrier, and the formed image is While the density of the ink drops or white spots occur, if the amount of ink held on the surface of the ink carrier is too large, ink is also supplied to the portion where the electrostatic latent image is not formed, There are problems such as fogging of the formed image.

[0008]

SUMMARY OF THE INVENTION According to the present invention, an ink held on the surface of an ink carrier is brought into contact with the surface of the image carrier on which an electrostatic latent image is formed, and an ink corresponding to the electrostatic latent image is formed. It is an object of the present invention to solve the above-described problems in an image forming apparatus in which an image is formed on a surface of an image carrier.

That is, in the present invention, the ink held on the surface of the ink carrier is brought into contact with the surface of the image carrier on which the electrostatic latent image is formed, and an ink image corresponding to the electrostatic latent image is formed. In forming on the surface of the carrier, it is easy to appropriately adjust the thickness of the ink held on the surface of the ink carrier, and ink is supplied to the portion where the electrostatic latent image is not formed. Fogging does not occur in the image formed, and ink is not sufficiently supplied to the portion where the electrostatic latent image is formed, so that the density of the formed image does not decrease and white spots do not occur. It is an object of the present invention to stably obtain a good image having a sufficient image density without generation of the like.

[0010]

In the image forming apparatus according to the present invention, in order to solve the above-mentioned problems, a latent image forming means for forming an electrostatic latent image on a surface of an image carrier, an ink carrying device, The thickness of the ink held on the surface of the body is adjusted by a regulating plate, and the ink held on the surface of the ink carrier is brought into contact with the surface of the image carrier on which the electrostatic latent image has been formed to form an electrostatic latent image. And an ink developing means for forming an ink image corresponding to the image on the surface of the image carrier, the system speed of the image forming apparatus is set to Vs [mm /
s], and the Young's modulus of the regulating plate is E [kgf / m
m ² ], the length of the portion of the regulating plate that comes into contact with the ink is L [mm], and the thickness of the regulating plate is t [mm]. The viscosity η (γ) [cP] is 44.8 × 10 ⁻⁶ × E × t ³ / (L ⁴ × Vs) ≦ η (γ) ≦ 902.8 × 10
^An ink satisfying the condition of ⁻⁶ × E × t ³ / (L ⁴ × Vs) was used.

Here, as in the image forming apparatus of the present invention, an ink having a viscosity .eta. (. Gamma.) In the above-mentioned range at a shear rate .gamma. [/ S] is used, and an ink carrier holding the ink is used. When the thickness of the ink on the surface of the ink carrier is adjusted by the above-described regulating plate, the thickness of the ink on the surface of the ink carrier is adjusted to an appropriate thickness of about 5 to 20 μm.

Then, the ink held at an appropriate thickness on the surface of the ink carrier is brought into contact with the surface of the image carrier on which the electrostatic latent image has been formed, and an ink image corresponding to the electrostatic latent image is formed. Is formed on the surface of the image carrier, ink is suppressed from adhering to the surface of the image carrier on which the electrostatic latent image is not formed, and the ink sufficiently adheres only to a portion corresponding to the electrostatic latent image. The occurrence of fog in the formed image is suppressed, and a good image having a sufficient image density can be obtained.

Here, when using the ink having the viscosity η (γ) in the above range at the shear rate γ [/ s], as shown in FIG. 1, the ink 32 on the surface of the ink carrier 31 is used. That the thickness of the ink 32 on the surface of the ink carrier 31 is adjusted to an appropriate thickness of about 5 to 20 μm when the thickness of the ink carrier 31 is adjusted by the above-described regulating plate 33 will be described.

Here, the Young's modulus of the regulating plate 33 is expressed by E
[Kgf / mm ² ], the ink 3
The length of the portion in contact with 2 is L [mm].
Is assumed to be t [mm], and the distributed load applied to the regulating plate 33 by the flow of the ink 32 is represented by w, the amount of deflection h in the regulating plate 33 is h = 3 × w × L ⁴ / (2 × E × t ³ ) [1].

On the other hand, the regulation plate 3
3 is: w = η (γ) × γ (2), and the system speed of this image forming apparatus is Vs
[Mm / s], γ = Vs / h... [3] When this is substituted into the above equation [2], the distributed load w becomes: w = η (γ) × Vs / h. Becomes

Then, this distributed load w is calculated by the above equation [1].
And the amount of deflection h in the regulating plate 33 is obtained as follows: h = [3 × L ⁴ × η (γ) × Vs / (2 × E × t ³ )] ^1/2 . From this equation [5], the value of η (γ) is given by η (γ) = 2 × h ² × E × t ³ / (3 × L ⁴ × Vs) [6].

When the adjustment is performed by the regulating plate 33 as described above, the thickness x [mm] of the ink 32 on the surface of the ink carrier 31 is about 0.6 times the deflection amount h of the regulating plate 33. Therefore, h = x / 0.6 is substituted into the above equation [6], and the thickness x of the ink 32 is in the range of 5 to 20 μm, that is, 5 × 10 ⁻³ ≦ x [mm].
In order to satisfy ≦ 20 × 10 ⁻³ , the ink 32 has a viscosity η (γ) at a shear rate γ [/ s].
It is necessary to use one satisfying the above conditions.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.

In the image forming apparatus according to this embodiment, as shown in FIG. 2, an electrophotographic photosensitive member having a photosensitive layer formed on the surface of a cylindrical conductive member is used as the image carrier 1. The image carrier 1 was rotated and an electrostatic latent image was formed on the surface of the image carrier 1 by the latent image forming means 2.

Here, when an electrostatic latent image is formed on the surface of the image carrier 1 by the latent image forming means 2, the surface of the rotating image carrier 1 is charged by the charging device 21 and thus charged. A suitable exposure device 2 on the surface of the image carrier 1
Exposure according to the image information is performed by means of the image carrier 1
To form an electrostatic latent image on the surface of the substrate.

On the surface of the image carrier 1 on which the electrostatic latent image is formed as described above, the ink 32
To form an ink image corresponding to the electrostatic latent image on the surface of the image carrier 1.

In this embodiment, when the ink 32 is supplied from the ink developing means 3 to the surface of the image carrier 1 on which the electrostatic latent image is formed, the ink is applied to the surface of the rotating ink carrier 31. The ink 32 held in the storage portion 34 is held, and the thickness of the ink 32 held on the surface of the ink carrier 31 is regulated by the regulating plate 33 in this manner. 32 was adjusted so as to have an appropriate thickness.

In adjusting the thickness of the ink 32 held on the surface of the ink carrier 31 by the regulating plate 33 to an appropriate thickness, the system speed of the image forming apparatus is reduced as described above. Vs [mm /
s], the Young's modulus of the regulating plate 33 is E [kgf / mm ² ],
When the length of the portion of the regulating plate 33 that comes into contact with the ink 32 is L [mm] and the thickness of the regulating plate 33 is t [mm], the viscosity η at the shear rate γ [/ s] is determined as the ink 32 described above. (Γ) [cP] is 44.8 × 10 ⁻⁶ × E × t ³ / (L ⁴ × Vs) ≦ η (γ) ≦ 902.8 × 10
^The ink 32 satisfying the condition of ⁻⁶ × E × t ³ / (L ⁴ × Vs) was used.

Here, when the thickness of the ink 32 held on the surface of the ink carrier 31 is regulated by the regulating plate 33 using the ink 32 having the viscosity η (γ) within the above range, the ink carrier The thickness of the ink 32 on the surface of No. 31 was regulated in the range of 5 to 20 μm.

When the thickness of the ink 32 held on the surface of the ink carrier 31 is adjusted by the regulating plate 33 as described above, as shown in FIG. Preferably, the surface of the ink carrier 31 is brought into contact with the surface of the ink carrier 31 along the tangential direction. That is, when the tip of the regulating plate 33 is brought into contact with the surface of the ink carrier 31 in this manner,
The thickness of the ink 32 held on the surface of the ink carrier 31 does not become uneven, and the ink 32 having a uniform and appropriate thickness is held on the surface of the ink carrier 31.

Here, as shown in FIG. 3 (B), when the tip of the regulating plate 33 is made to protrude further than the contact portion with the surface of the ink carrier 31, the portion of the regulating plate 33 thus protruding becomes A pulling force is generated in the ink 32 passing between the regulating plate 33 and the surface of the ink carrier 31, thereby causing a local unevenness in the thickness of the ink 32 on the surface of the ink carrier 31. However, the length of the regulating plate 33 protruding from the contact portion with the surface of the ink carrier 31 is 1 mm.
Within this range, the occurrence of local unevenness as described above is small.

Further, as shown in FIG.
If only the corners of the tip of 3 are brought into contact with the surface of the ink carrier 31, unevenness in the corners of the tip of the regulating plate 33 causes streak-like unevenness in the thickness of the ink 32 on the surface of the ink carrier 31. Will occur. However,
When the angle between the tip of the regulating plate 33 and the tangent line of the ink carrier 31 at the portion where the tip comes into contact is within 5 °, the occurrence of such streak-like unevenness is small.

Then, the ink 32 regulated by the regulating plate 33 as described above and having an appropriate thickness on the surface of the ink carrier 31 is applied to the surface of the image carrier 1 on which the electrostatic latent image is formed. At the same time, in this embodiment, a bias voltage is applied to the ink carrier 31 from a power supply (not shown) to apply the ink 32 to the portion of the electrostatic latent image formed on the surface of the image carrier 1. And an ink image corresponding to the electrostatic latent image was formed on the surface of the image carrier 1.

Next, the ink image formed on the surface of the image carrier 1 as described above is transferred to the transfer paper 5 by the transfer roller 4.
The ink is transferred onto the transfer paper 5 to form an ink image on the transfer paper 5. After the transfer, the ink 32 remaining on the surface of the image carrier 1 is removed from the surface of the image carrier 1 by the cleaning device 6. The surface of the image carrier 1 is irradiated with light from an eraser lamp 7 to
The potential remaining on the surface of the sample was removed, and the above-described operation was repeated to form an image.

By doing so, a satisfactory image having sufficient image density on the transfer paper 5 and free from fogging or the like could be formed.

[Experimental Example] In this experimental example, first, a specific ink was used, and the shear rate γ and the viscosity η (γ) of the ink were used.
Was examined, and the results are shown in FIG.

As a result, when the shear rate γ changes, the viscosity η (γ) of the ink also changes accordingly.

Next, as the regulating plate 33, the Young's modulus E is 2
SU having 1600 kgf / mm ² , a length L of 5 mm and a thickness t of 0.188 mm in a portion contacting the ink 32.
S & T, while the ink 32 is T & K
A viscosity modifier [T & K: NO. 2 ML reducer] and adjusted to a predetermined viscosity.

Then, the system speed Vs of the image forming apparatus
Is set to 20 mm / s, and the thickness of the ink 32 held on the surface of the ink carrier 31 by the regulating plate 33 is adjusted, and the viscosity η of the ink 32 is adjusted.
The relationship between (γ) [cP] and the amount of deflection [μm] of the regulating plate 33 was examined, and the results are shown in FIG.

Here, when the ink 32 having a viscosity η (γ) of about 4000 cP at a shear rate γ of 1000 / s is used, the amount of deflection of the regulating plate 33 becomes about 20 μm. The thickness of the ink 32 held on the surface of the base 31 could be reduced to about 12 μm.

The system speed Vs of the image forming apparatus is set to 50 mm / s, and the thickness of the ink 32 held on the surface of the ink carrier 31 by the regulating plate 33 is adjusted. Of viscosity η (γ)
The relationship between [cP] and the amount of deflection [μm] of the regulating plate 33 was examined, and the results are shown in FIG.

Here, if the ink 32 having a viscosity η (γ) of about 800 cP at a shear rate γ of 5000 / s is used,
The amount of deflection of the regulating plate 33 was about 10 μm, and the thickness of the ink 32 held on the surface of the ink carrier 31 by the regulating plate 33 could be reduced to about 6 μm.

When the ink image formed on the surface of the image carrier 1 as described above is transferred onto the transfer paper 5 by the transfer roller 4 to form an ink image on the transfer paper 5, The ink image formed on the surface of the body 1 is the transfer paper 5
In order to transfer the toner efficiently on the surface, the viscosity η (γ) at a shear rate γ of 2 / s is 5,000 to 50,000c.
P ink 32 was preferred.

[0039]

As described in detail above, in the image forming apparatus of the present invention, the thickness of the ink held on the surface of the ink carrier is adjusted by the regulating plate, and the thickness of the ink held on the surface of the ink carrier is adjusted. When the ink is brought into contact with the surface of the image carrier on which the electrostatic latent image is formed to form an ink image corresponding to the electrostatic latent image on the surface of the image carrier, the system speed of the image forming apparatus is set to Vs [mm / s], the Young's modulus of the regulating plate is E [kgf / mm ² ], the length of the regulating plate in contact with ink is L [mm], and the thickness of the regulating plate is t [m].
m], the above ink has a shear rate γ
The viscosity η (γ) [cP] at [/ s] is 44.8 × 10 ⁻⁶
× E × t ³ / (L ⁴ × Vs) ≦ η (γ) ≦ 902.8 × 10 ⁻⁶ × E × t ³
/ (L ⁴ × Vs), the thickness of the ink on the surface of the ink carrier is 5 to 2
The thickness was adjusted to an appropriate thickness of about 0 μm.

As a result, according to the image forming apparatus of the present invention, the ink is held at an appropriate thickness on the surface of the ink carrier as described above, and thus the ink is held on the surface of the ink carrier. When the ink is brought into contact with the surface of the image carrier on which the electrostatic latent image is formed and an ink image corresponding to the electrostatic latent image is formed on the surface of the image carrier, the image carrier on which the electrostatic latent image is not formed is formed. The ink is suppressed from adhering to the surface of the body, the ink is sufficiently adhered only to the portion corresponding to the electrostatic latent image, and the occurrence of fog in the formed image is suppressed, and the sufficient image is formed. A good image having a density can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a state in which the thickness of ink held on the surface of an ink carrier is adjusted by a regulating plate in an image forming apparatus according to the present invention.

FIG. 2 is a schematic explanatory diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a mode in which the tip of a regulating plate is brought into contact with the surface of an ink carrier in the image forming apparatus according to the embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a shear rate γ and ink viscosity η (γ) in an experimental example of the present invention.

FIG. 5 is a diagram illustrating an experimental example of the present invention in which the system speed Vs of the image forming apparatus is set to 20 mm / s to adjust the thickness of the ink held on the surface of the ink carrier by the regulating plate; FIG. 7 is a diagram illustrating a relationship between γ) and the amount of deflection of a regulating plate.

FIG. 6 shows an experimental example of the present invention, in which the system speed Vs of the image forming apparatus is set to 50 mm / s to adjust the thickness of the ink held on the surface of the ink carrier by the regulating plate, and the viscosity η ( FIG. 7 is a diagram illustrating a relationship between γ) and the amount of deflection of a regulating plate.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image carrier 2 latent image forming means (discharge electrode) 3 ink developing means 31 ink carrier 32 ink 33 regulating plate

Claims (1)

[Claims] A first image forming device that forms an electrostatic latent image on the surface of the image carrier; a regulating plate that adjusts a thickness of the ink held on the surface of the ink carrier; An image forming apparatus comprising: an ink developing unit configured to contact the held ink with the surface of the image carrier on which the electrostatic latent image is formed to form an ink image corresponding to the electrostatic latent image on the surface of the image carrier. , The system speed of this image forming apparatus is set to Vs
[Mm / s], and the Young's modulus of the regulating plate is E [kgf /
mm ² ], the length of the portion of the regulating plate that comes into contact with the ink is L [mm], and the thickness of the regulating plate is t [mm]. The viscosity η (γ) [cP] is 44.8 × 10 ⁻⁶ × E × t ³ / (L ⁴ × Vs) ≦ η (γ) ≦ 902.8 × 10
An image forming apparatus using an ink satisfying a condition of ^-6 × E × t ³ / (L ⁴ × Vs).