JPH0695486A - Developing method - Google Patents

Abstract

PURPOSE:To obtain a developing method to always obtain good visible images by one-component contact developing method using a monolayer developing roller. CONSTITUTION:The developing roller has a monolayer structure having an elastic layer with R1 (OMEGA.m<2>) resistance around a conductive shaft. A toner layer 2 of one-component having dt (m) thickness, q (C/kg) charge amt. and epsilont dielectric const. (C<2>/Nm<2>) is formed on the surface of the roller, and the developing roller 1 is rotated at the rotation speed k times as fast that of an electrostatic latent image holder having dp (m) thickness and c dielectric const. (C<2>/Nm<2>) to bring the toner layer 2 into contact with the electrostatic latent image holder. A developing bias voltage is applied to the conductive shaft of the developing roller 1. The surface voltage V0 (V) of the electrostatic latent image holder, thickness and dielectric const. are determined to satify the relation of formula, in formula Vmax and Vmin are the max. and min. surface voltage, respectively, and A=dp/epsilonp+dt/epsilont.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method for visualizing an electrostatic latent image with toner in an electrophotographic apparatus or an electrostatic recording apparatus.

[0002]

2. Description of the Related Art Conventionally, various developing methods have been known for visualizing an electrostatic latent image in an electrophotographic apparatus or an electrostatic recording apparatus. Among them, a developing roller is used which has an elastic conductive layer or a semi-conductive layer integrally arranged on the peripheral surface of a conductive shaft, and a toner layer of one-component toner is formed on the peripheral surface of the developing roller. In the one-component contact development method in which the electrostatic latent image is visualized by bringing the toner layer into contact with the electrostatic latent image holder, the developing electrode remarkably approaches the electrostatic latent image surface. It is attracting attention because it can improve the image quality of optical printers.

In the above-mentioned one-component contact developing method, the conditions for obtaining a good visible image, specifically, the electric resistance value of the developing roller, the relationship between other physical quantities and the developing characteristics, etc. are also clarified. Has been. For example, in the one-component contact development method using a developing roller of a laminated type in which a semi-conductive elastic layer and a conductive layer are laminated on the peripheral surface of a conductive shaft, the optimum development conditions are examined, selected and set by Japa.
n Hardcopy'89 Proceedings p.25 (1989) and JP-A-1-168605
It is disclosed in the publication.

[0004]

However, the above disclosure regarding the electrical resistance value of the developing roller, the relationship between other physical quantities and the developing characteristics, etc. as conditions for obtaining a good visible image is not disclosed. In the case of the one-component contact developing method using a developing roller having a laminated structure in which a semi-conductive elastic layer and a conductive layer are sequentially arranged on the peripheral surface of a conductive shaft, the development using a developing roller having a single layer structure is performed. It cannot be directly adapted to the method. That is, due to the difference in the structure of the developing roller, the electrical characteristics and the like cannot be equated with those of the developing roller having a laminated structure. On the other hand, in the case of a single-layer type developing roller, compared with the case of a multi-layer type developing roller, the structure is simple, the manufacturing is easy, and the cost is advantageous. Many benefits are expected.
Then, regarding the developing method using the developing roller having the single-layer structure, the examination, selection and setting of the developing conditions for obtaining a good visible image are raised as new problems. That is, while taking advantage of the advantages of the single-layer type developing roller itself, it is possible to clarify the developing conditions for obtaining a good visible image, such as the electric resistance value of the developing roller and the relationship between other physical quantities and the developing characteristics. desired.

The present invention has been made to solve the above problems of the prior art, and provides a developing method capable of always obtaining a good visible image by a one-component contact developing system using a developing roller having a single-layer structure. With the goal.

[0006]

The developing method according to the present invention is a developing roller having a single-layer structure in which an elastic layer having a resistance R ₁ (Ω · m ² ) is provided on the peripheral surface of a conductive shaft. On the peripheral surface of, the thickness d _t (m), the charge amount q (C / kg), the dielectric constant ε
a step of forming a toner layer of _t (C ₂ / Nm ₂ ) one-component toner, the developing roller has a thickness d _p (m), and a dielectric constant ε.
_The toner layer is brought into contact with the surface of the electrostatic latent image carrier while being rotated at a peripheral speed of k times that of the electrostatic latent image carrier of _p (C ₂ / Nm ₂ ), and development is performed on the conductive shaft of the developing roller. Applying a bias voltage, wherein the maximum value of the surface potential V ₀ (V) of the electrostatic latent image carrier is V _max , the minimum value is V _min , and A = d _p /
When ε _p + d _t / ε _t , the above physical quantities are

[Equation 2] It is characterized in that it is set to satisfy.

According to the present invention, in the developing method using the developing roller having a single-layer structure, the resistance value of the elastic layer of the developing roller, the amount of toner carried and the electrical characteristics, This has been achieved by empirically confirming the results of experiments and experiments that a high-quality image is output when the thickness and surface potential of the electrostatic latent image carrier are selected and set in a certain relationship.

[0008]

[Function] In the above formula, it is represented by the above physical quantities, 0.7 ×
When the value is in the range of 10 ^-2 to 2.0 x 10 ^-2 , it corresponds to the difference in toner adhesion amount between the image part and non-image part (background or white background part), and the contrast is high when the above formula is satisfied. It is possible to obtain a high-quality visible image with excellent resolution. That is, according to the present invention, it is possible to select and set the developing conditions for outputting a high-quality image in consideration of the characteristics of the developing roller having a single-layer structure, the characteristics of the toner, the characteristics of the electrostatic latent image holding member, and the like. Therefore, it is possible to stably obtain a high-quality image.

[0009]

EXAMPLE First, a developing equation is analytically derived based on a developing model in which the electrical configuration of the developing roller is taken into consideration, and the correlation between the resistance value of the developing roller and the developing characteristic will be described.

As schematically shown in FIG. 1, a toner layer 2 of a one-component non-magnetic toner is formed on the peripheral surface (front surface) of a developing roller 1 having elasticity or flexibility. The toner layer 2 is brought into contact with the electrostatic latent image surface of the electrostatic latent image holder 3 to perform reversal development. At this time, the toner is classified into the following according to the electric resistance value of the developing roller 1, as shown in FIG.
Analysis is performed based on the model in (d) and FIG.
However, in this analysis, the elasticity of the developing roller is not essential, and the discussion here can be applied, for example, even when a hard developing roller is brought into contact with a flexible photoconductor to perform development. It should be noted that reference numeral 4 in FIG. 1 denotes a toner layer thickness regulation flade that regulates the thickness of the toner layer 2 formed on the peripheral surface of the developing roller 1.

Conductive roller: As shown in FIG. 2 (a),
It forms a structure which is disposed an elastic conductive layer 1 _1b on the peripheral surface of the conductive shaft 1 _1a, a developing roller 1 ₁ which is adapted to supply a developing bias power 1 _1c from the conductive shaft 1 _1a.
Here, a laminated conductive roller having a surface further coated with a conductive layer and a roller having a structure in which only the surface layer is made conductive and a developing bias voltage is directly applied thereto are also included in the category of the conductive roller.

Semi-conductive roller: As shown in FIG. 2 (b), the semi-conductive elastic layer 1 is formed on the peripheral surface of the conductive shaft _12a.
A single layer type semi-conductive roller having a structure in which _2b is arranged, or a semi-conductive elastic layer 1 _{2b as} shown in FIG. 2 (c).
2 of laminated type semi-conductive roller having conductive layer _12d provided on the surface of
Any developing roller is conceivable. In the figure, reference numeral _12c is a developing bias power source.

Dielectric roller: As shown in FIG. 2 (d),
A conductive elastic layer 1 _3b is arranged on the peripheral surface of the conductive shaft 1 _3a , and a dielectric layer 1 _3d is further formed on the surface of the conductive elastic layer 1 _3a to supply a developing bias power source 1 _3c from the conductive shaft 1 _3a. This is the laminated type developing roller 1 ₃ .

FIG. 3 exemplifies a developing model at the developing position in the case of the dielectric roller having the most complicated layer structure. In the case of a conductive roller, the thickness of the dielectric layer _13d is set to zero, and in the case of a semi-conductive roller, an electric resistance is interposed between the surface of the roller and the developing bias power source. Can be applied.

Here, the electrostatic latent image carrier 3, for example, the photosensitive layer of the photosensitive drum, the toner layer 2 and the dielectric layer _13d each have a thickness of 50 μm or less and a developing nip of 2 mm or more. Considering that, each layer is regarded as a parallel plate,
A good approximation can be obtained by considering only the force acting in the direction perpendicular to these (the X direction in FIG. 3). However, the electrostatic latent image carrier 3 is a negative charging type laminated organic photoreceptor layer,
The toner is a negative charging type insulating one-component non-magnetic toner.
Further, the toner layer 2 is regarded as a homogeneous dielectric layer in which charges are uniformly distributed inside, and the charges are not present inside the electrostatic latent image holding member (photoreceptor layer) 3 and the dielectric layer 1 _3d. However, it is assumed that electric charges of areal density σ _p and σ _i exist only on the surface. In contact development, the van der Waals forces acting on the toner act in both the positive and negative directions of the X axis, and therefore cancel each other out.

The amount of toner adhering to a unit area on the surface of the developing roller is m ₀ (kg / m ² ), and the speed ratio between the developing roller and the photosensitive drum (electrostatic latent image holding member) is k (= developing roller circumference). Speed / peripheral speed of photoconductor drum), the amount of toner existing at the developing position is km ₀ (kg / m ² ). In particular, this assumption is considered to give a good approximation when developing a solid latent image. At the developing position,
Although it is difficult to actually measure the thickness d _t of the toner layer, since the toner layer on the surface of the developing roller is a thin layer and the developing roller is pressed against the photosensitive drum, the thickness d _{t of the} toner layer is Can be regarded as always equal to the average particle diameter of the toner regardless of the speed ratio k between the developing roller and the photosensitive drum.

In the following, first, the development equations for the dielectric roller shown in FIG. 2 (d) are derived, and by deforming the equations, the development equations for the conductive roller and the semiconductive roller are sequentially derived.

1. Dielectric Roller The Poisson's equation is applied to each layer shown in FIG. 3, in which the electrostatic latent image carrier (photoreceptor layer) 3 and the dielectric layer _13d do not have internal charges, and the toner Since there is a charge having a volume charge density p _t inside the layer 2,

[Equation 3]

[Equation 4]

[Equation 5] The boundary condition of the electric field at the interface of each layer is

[Equation 6]

[Equation 7]

[Equation 8]

[Equation 9] The continuous condition of potential is

[Equation 10]

[Equation 11]

[Equation 12]

[Equation 13] However, the volume charge density ρ _t of the toner layer 2 and the surface charge surface densities σ _p and σ of the electrostatic latent image carrier 3 and the dielectric layer 13 _d.
i is expressed as follows using the charge / weight ratio q _{t of the} toner, the surface potential V _{0 of} the electrostatic latent image carrier 3 and the surface potential V _i of the dielectric layer 13 _d , which are easy to measure. .

[0019]

[Equation 14]

[Equation 15]

[Equation 16] Solving the boundary value problem from the above, and finding the electric field inside the toner layer 2,

[Equation 17] However, A is the value of the following equation.

[0020]

[Equation 18] The toner layer 2 is divided at the surface x = x ₀ where the electric field inside the toner layer 2 is zero, and the development is performed.

[Formula 19] Is introduced, and the toner amount m _i attached per unit area on the surface of the electrostatic latent image carrier 3 is expressed as follows using x ₀ .

[0021]

[Equation 20] Further, according to the formulas (17) and (18), the electrostatic latent image holding member 3
As a function of the developing potential (V ₀ −V _b ) of the toner amount m _i adhering to the surface, a developing equation showing the developing characteristic of the dielectric roller can be expressed as follows.

[0022]

[Equation 21] 2. Conductive Roller In the above equation (19), by setting the thickness d _i of the dielectric layer and the surface potential V _i to zero, the following development equation of the conductive roller is obtained. However, the toner adhesion density on the surface of the electrostatic latent image holder 3 is m _c .

[0023]

[Equation 22] 3. Semi-conductive roller Based on the development equation of the conductive roller, it is analyzed by adding resistance to it. First, the electric resistance value (roller resistance) of the development roller is defined, and then single layer type and laminated type The following two development equations of the semiconductive roller are derived.

Of the electrical characteristics relating to the developing roller having the elastic layer, the most important practical point is not the volume resistance or surface resistance of the elastic layer, but the resistance between the conductive shaft and the developing roller surface. Here, assuming that an electric resistance value between the shaft and the surface measured by attaching an electrode having an area S to the surface is R ₀ , S and R ₀ are in an inversely proportional relationship, and S ×
R ₀ = const. And the product is R ₁ (Ω · m ² ), then SR ₀ = R ₁ . R ₁ (Ω ・
m ² ) represents a resistance value specific to the developing roller that does not depend on the area of the measurement electrode, that is, a roller resistance. In other words,
It can be said that R ₁ is the resistance between the shaft and the surface, which is measured by bringing an electrode having a unit area into close contact with the surface. On the other hand, if the thickness of the semiconductive elastic layer is a, the volume resistance ρ (Ω
From the definition formula R ₀ = ρa / S of m), R ₁ = SR ₀ = ρ
a holds, and the resistance R ₁ is equal to the product of the volume resistance ρ and the thickness a. That is, the volume resistance ρ does not include information about the thickness a of the semiconductive layer and is not practically useful. Therefore, the volume resistance ρ × the thickness a of the semiconductive elastic layer is defined as the roller resistance. Define and interpret as R ₁ . Further, in the laminated type semi-conductive roller 1 ₂ shown in FIG. 2 (c), since the conductive layer 1 _2d is present on the surface of the semi-conductive elastic layer 1 _2b , the R
₁ = SR ₀ = ρa, the electrode area S is always the conductive layer 1
_It is equal to the surface area S _r of _2d and is independent of the measuring electrode area.
Therefore, the roller resistance R ₂ in this case is the measured value R _0.
Is defined as R ₂ = S _r R ₀ .

When the laminated type semi-conductive roller shown in FIG. 2 (c) is unfolded, the conductivity of the developing roller 1 ₂ is set to d _i = 0 and V _i = 0 in the model of FIG. the layer 1 _2d, as shown in FIG. 4, the addition of an equivalent resistance R ₀ being measured in a semi-conductive elastic body layer 1 _2b. in this case,
By developing a current transfer of the toner results, the potential difference across the resistor R ₀ is generated, the potential of the developing roller 1 ₂ surface, i.e. the effective developing bias must be considered to vary.

In the one-component contact development, the toner particles having a frictional charge in advance are contacted with the toner layer thickness regulating blade and the surface of the developing roller 1 and the electrostatic latent image holding member 3 surface and the toner particles are held at the developing position. By contacting the surface of the developing roller 1 ₂ , further electric charge is acquired. Here, the electric charge q ₀ previously held by the toner on the surface of the developing roller 1 _{2, the} frictional band charge q _p due to the contact with the electrostatic latent image holding member 3 at the developing position, and the friction due to the contact with the surface of the developing roller 1 ₂ If the electrostatic charge is q _r , the total amount of charge q held by the toner after passing through the developing position is q = q ₀ + q _p + q _r (21). Note that these charge amounts are generally the same as those of the developing roller 1.
₂ depends on the rotation speed, and in many cases, the absolute value of the electric charge tends to increase as the speed increases.

The developing toner is transferred to the electrostatic latent image holding member 3 surface by, the current I _p which is observed when the developing roller 1 ₂ moves away, the charge the toner stored in advance q
₀ , and the frictional band charge q _r due to contact with the surface of the developing roller 1 ₂ contributes, but the frictional band charge q _p due to contact with the electrostatic latent image carrier 3 does not participate. That is, q _p is an electric charge generated by frictional charging between the electrostatic latent image holding member 3 and the toner,
This is because current is not observed unless the photoconductor 3 and the toner are separated.

Since the laminated semiconductive roller shown in FIG. 2 (c) has the conductive layer 1 _2d on the surface of the semiconductive elastic layer 1 _2b , the resistance value is different between the surface direction and the radial direction. The different electrical anisotropy must be considered. That is, the developing current is 1 on the entire surface of the developing roller 1 _2.
Considering the total amount of charges flowing in and out per second, it is considered that this current flows toward the developing bias power source 1 _2c via the measured value R = R ₂ / S _r of the resistance between the surface and the shaft. The current I _p observed when the toner is transferred to the surface of the electrostatic latent image holding member 3 and moves away from the developing roller 1 ₂ is the toner amount m _s2 attached to the unit area of the electrostatic latent image holding member 3 in units. Let S be the area of the image portion that passes through the developing nip in time (= area of the toner adhering portion on the electrostatic latent image surface).

[Equation 23] However, both toner and photoconductor are negatively charged,
The current flowing from the electrostatic latent image holder 3 to the developing roller 1 ₂ is positive.

On the other hand, after the negative charge q _p is obtained by the contact with the surface of the electrostatic latent image carrier, it does not transfer to the surface of the electrostatic latent image carrier but remains on the surface of the developing roller and moves away from the electrostatic latent image carrier. The toner (hereinafter, referred to as residual toner) consequently takes a negative charge from the surface of the electrostatic latent image holding member. Therefore, the developing current I _r due to the residual toner is S ₀ , where the total electrostatic latent image area passing through the developing nip per unit time is

[Equation 24] And the total developing current I is given by the following equation.

[0030]

[Equation 25] Due to this developing current I, the resistance of the developing roller R ₂ / S _r
Potential difference occurs at both ends of the effective developing bias V _e

[Equation 26] Becomes Then, when the effective developing bias V _e is applied, the toner amount m _s2 transferred to the electrostatic latent image holding member is determined by the developing equation (20) of the conductive roller. That is, V _b is replaced with V _e in the equation (20).

[0031]

[Equation 27] Intuitively, the fluctuation of the effective developing bias V _e due to the development causes a change of the developing toner amount m _s2 , and as a result, the effective developing bias V _e changes again. Development toner amount m _s2
Is understood. Actually, it is considered that the transfer amount of toner is determined according to this process at the moment when the electrostatic latent image surface and the developing roller surface are separated, but analytically, the above equations (25) and (26) are simultaneous equations. As an equation, an equivalent developing toner amount can be calculated by solving for m _s2 , and a developing equation for the laminated semiconductive roller as shown in the following equation can be obtained.

[0032]

[Equation 28] On the other hand, in the case of the single-layer type semi-conductive roller, since the electric resistance is isotropic, the inflow and outflow of charges per unit area will be considered. The amount of toner m _s2 adhering to a unit area of the electrostatic latent image carrier surface, the moving speeds of the electrostatic latent image carrier surface and the developing roller surface are V _p and V _r , respectively, and the speed ratio k (= V _r / V _p ), The currents I _p and I _r due to the developing toner and the residual toner per unit area on the surface of the developing roller are given by the following equations.

[0033]

[Equation 29]

[Equation 30] Then, the total developing current I per unit area is

[Equation 31] And the toner amount m _s1 transferred to the electrostatic latent image carrier under the effective developing biases V _e and V _e is expressed as follows.

[0034]

[Equation 32]

[Expression 33] Here, by solving the simultaneous equations (31) and (32), the development equation of the single-layer semiconductive developing roller of the following equation can be obtained.

[0035]

[Equation 34] In the development model, the development equation of the semi-conductive roller was derived by adding resistance to the conductive roller. Strictly speaking, however, the combined static of the electrostatic latent image holding member (photoreceptor layer) and the toner layer is stricter. The relaxation phenomenon due to the capacitance and the CR circuit formed by the roller resistance must be taken into consideration. That is,
When the surface of the developing roller enters the developing nip, an electric charge is induced on the surface of the developing roller through a resistor to charge or discharge the above capacity. It is necessary to satisfy the condition that the time required for inducing the charge is sufficiently shorter than the developing time, that is, the condition that the time constant is sufficiently shorter than the developing time. Here, the time required for one point on the developing roller to pass through the developing nip is defined as the developing time.

In the case of this single-layer type semiconductive roller, consider the product C ₁ R ₁ of the electrostatic capacity C ₁ per unit area in the developing nip and the roller resistance R ₁ . The electrostatic capacities of the photoconductor layer (electrostatic latent image carrier) and the toner layer are respectively C _p ,
If C _t , developing time is T _d , developing nip width is N, and length is L,

[Equation 35] Where C ₁ R ₁ <T _d (T _d is much larger than C ₁ R ₁ )

[Equation 36] Therefore, when the roller resistance R ₁ satisfies this condition, the above model gives a solution exactly.

On the other hand, in the case of the laminated type semi-conductive roller, since the surface is covered with the conductive layer, the electrostatic capacity of the entire developing roller must be taken into consideration. Since the electrostatic capacity in the area other than the position is considered to be extremely small, this is approximated by the electrostatic capacity C ₂ in the developing nip.

[0038]

[Equation 37] Also, from C ₂ R ₂ / S _r <T _d

[Equation 38] Therefore, the development model described above can be applied to the laminated semiconductive roller in a wider resistance range than that of the single layer semiconductive roller. For example, in the case of outputting a rectangular solid image that is long enough in the moving direction of the electrostatic latent image, after the relaxation time described above, the electrical state of the developing roller surface reaches an equilibrium state, and the developing equation is strictly Gives the correct amount of developing toner.

As described above, assuming that the developing equation of the conductive developing roller is the basic equation, the developing equations of various developing rollers are as follows, and the developing conditions are different depending on the constitution and type of the developing roller, and are good. It is important to select and set appropriate conditions in order to obtain various visible images.

In case of conductive roller

[Formula 39] For single-layer semi-conductive roller

[Formula 40] For laminated semi-conductive roller

[Formula 41] In case of dielectric roller

[Equation 42] However, the developing toner amounts m _c and m _i become negative and km
Due to the physical restriction that it cannot exceed ₀ , the developing toner amounts are 0 and km ₀ , respectively in these cases. The following numerical values were used for the calculation.

M ₀ = 0.48 × 10 ^-2 (kg / m ² ), k = 2.36,
d _p , d _t , d _i = 20, 11, 50 (μm), ε _p , ε _t , ε
_i = 3.4ε ₀ , 1.1ε ₀ , 6.5ε ₀ , ε ₀ = 8.85 × 10
^-12 , q = -11.0 mC / kg (K = 1.30), q = -14.3 mC / kg (K =
2.36), q = -15.5mC / kg (K = 3.32), q p = 2mC / kg, V
_p = 39.3 (mm / sec.), S _r = 1.13 × 10 ^-2 (m ² ), S _o =
0.79 × 10 ^-2 (m ² ), N = 2 mm, l = 0.2 m Based on the above development equation, the developing characteristics of a single layer type semiconductive roller were theoretically predicted and compared with the experimental results. However, it was as follows.

FIG. 5 shows the developing characteristics of the single-layer type semiconductive roller. The abscissa shows the developing potential, that is, the difference between the electrostatic latent image potential V ₀ and the developing bias potential V _b, and the ordinate shows the static. The toner amount m _s1 adhered per unit area of the electrostatic latent image surface, the solid line shows the calculated value by the development equation (39), and the broken line shows the experimental result.

The roller resistance R ₁ is 0 to 1.1 × 10 ⁵ Ω · m
^In the range of ² , in both theory and experiment, there is almost no difference in the developing characteristics due to the resistance value, but when R ₁ exceeds this value, the inclination of the linear portion of the characteristic curve tends to become gentle. . Therefore, when a steep characteristic curve is required, that is, when a binary development characteristic or low-potential development is required, a developing roller having a lower resistance is suitable. When it is desired to obtain a smooth intermediate output, a developing roller having a higher resistance is suitable.

FIG. 6 shows the change in the amount of developing toner due to the roller resistance R _{1. In} the region of 1 × 10 ⁵ Ω · m ² or less, the amount of developing toner hardly depends on the roller resistance. It is clearly shown that the amount of toner adhered decreases in the image area and exceeds the amount in the background when it exceeds. Theoretically, it is considered that the amount of adhered toner on the image portion and the background converges to the same value at 1 × 10 ⁹ Ω · m ² and the image disappears. From the consideration of the time constant, R ₁ is 10 ⁴ Ω ・
In a region exceeding m ² , the theoretical value may not always give a correct result, and the fringe effect of the electric field causes toner adhesion different from the theoretical value at the edge portion of the image, so that the image does not always disappear. However, from the comparison with the experimental results, it can be said that the drawing is qualitatively the theoretical drawing.

FIG. 7 (a) shows an example of an image obtained under appropriate developing conditions based on the above-mentioned developing characteristics. A solid image of uniform density and an electrostatic latent image charge distribution without unnecessary edge enhancement are shown. The output of the image was true to. In the figure, a conductive roller and a dielectric roller are used, and the formulas (38) and (41) are used.
Images obtained under appropriate developing conditions based on the development equations shown in (b) using a conductive roller and (c) using a dielectric roller are illustrated as reference examples.

Here, regarding the single-layer type semi-conductive roller, it is further pointed out that the relationship between the roller resistance R ₁ and the toner adhesion amount m _s1 is that when R ₁ exceeds 10 ⁵ Ω · m ² , the toner in the image area is The adhesion amount decreases, the background toner adhesion amount increases, and the image density contrast decreases. To obtain a practically sufficient contrast, the difference in toner adhesion amount between the image area and the non-image area should be 0.7 × 10 ^-2 kg / m ² or more. Also,
If this difference is too large, the amount of toner adhering to the image portion becomes excessive, and the line image is crushed in the transfer process of the toner onto the recording paper and the fixing process, causing a reduction in resolution.
The difference in toner adhesion amount between the image area and non-image area is 2.0 × 10 ^-2
Set to less than kg / m ² . In other words, the equation [16] d _i = 0
As the maximum and minimum values of the surface potential V _o (V) of the electrostatic latent image holding member, that is, the surface potentials of the unexposed portion and the exposed portion of the electrostatic latent image holding member are V _max and V _min , respectively. Then, various physical quantities expressed by the above equations [1] and [2] may be calculated. Although the developing method using the single-layer type semi-conductive roller has been described above, even in the case of a single-layer type conductive roller or the like, optimization can be similarly achieved by satisfying the above relational expression. .

[0047]

As described above, according to the present invention, in developing an electrostatic latent image by a developing roller having a single-layer structure, which has many advantages in terms of simplicity of structure and cost, it is possible to develop the electrostatic latent image. It is possible to easily and surely optimize the relationship (developing condition) among the main physical quantities. That is, the process conditions are appropriately set according to the characteristics of the developing roller, the characteristics of the toner, the characteristics of the electrostatic latent image holder, etc., and a high-quality image having high image contrast and resolution is stably output. be able to.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main part of an embodiment of a developing method.

2A, 2B, 2C, and 2D are schematic views showing structural examples of different developing rollers used for carrying out the developing method.

FIG. 3 is a model diagram schematically showing an aspect of a developing position.

FIG. 4 is a schematic diagram showing a developing mode by a developing roller having a laminated structure.

FIG. 5 is a development characteristic diagram of a developing roller having a single-layer structure.

FIG. 6 is a characteristic diagram showing a relationship between a roller resistance and a toner adhesion amount of a developing roller having a single-layer structure.

FIG. 7 is an image diagram showing an example of the relationship between the structure of the developing roller and the obtained visible image.

Claims (1)

[Claims] _{1. A} resistance R ₁ (Ω ·
m ² ), a developing roller having a single-layer structure having an elastic layer disposed thereon has a thickness d _t (m), a charge amount q (C / kg),
A step of forming a toner layer of a one-component toner having a dielectric constant ε _t (C ₂ / Nm ₂ ), a developing roller having a thickness d _p (m), and a dielectric constant ε _p (C ₂ / C ₂ / Nm ₂ ).
The toner layer is brought into contact with the surface of the electrostatic latent image holding member while being rotated at a peripheral speed of Nm ₂ ) of the electrostatic latent image holding member, and a developing bias voltage is applied to the conductive shaft of the developing roller. And a maximum value of the surface potential V ₀ (V) of the electrostatic latent image holding member is V
_max , the minimum value is V _min , and A = d _p / ε _p + d _t
/ Ε _t , the above physical quantities are _expressed by the following equation: A developing method characterized by being set so as to satisfy the following.