EP0888579A1

EP0888579A1 - Process and arrangement for optimising charge pattern formation on a photoconductor

Info

Publication number: EP0888579A1
Application number: EP97920571A
Authority: EP
Inventors: Volkhard Maess; Martin Schleusener
Original assignee: Oce Printing Systems GmbH and Co KG
Current assignee: Canon Production Printing Germany GmbH and Co KG
Priority date: 1996-03-29
Filing date: 1997-03-27
Publication date: 1999-01-07
Anticipated expiration: 2017-03-27
Also published as: DE59710268D1; US6167210A; WO1997037285A1; EP0888579B1

Abstract

The disclosure relates to a process for optimising charge pattern formation. In order to determine (step 3) an optimised exposure energy (H) for a given charging potential (Vc) of a photoconductor, a sensitivity factor (K) is calculated (step 3). In addition, a process is described whereby an optimised charging potential (Vc) is calculated on the basis of the sensitivity factor (K) for a given exposure energy (H).

Description

description

Method and arrangement for optimizing charge image generation on a photoconductor

The invention relates to a method for optimizing charge image generation on a photoconductor of electrophotographic printing and copying devices.

The user places considerably higher quality requirements on the print results which can be achieved by means of electrophotographic printing devices, compared to the results of copying which can be achieved by means of electrophotographic copiers. Copier results are therefore also accepted by users of the copying machines, which are somewhat poorer compared to the copy template.

However, since electrophotographic printing devices are mostly used in connection with EDP systems and the operator's options for influencing the print quality are insignificant, there are extremely high quality requirements for electrophotographic printing devices. In order to meet these high requirements, it is necessary to reduce the permissible tolerance ranges in electrophotographic processes.

Electrophotographic printing devices, for example, print single sheets or continuous paper by generating a latent image on a photo conductor, which is preferably in the form of a drum. For this purpose, the photoconductor is charged to a defined charging potential. A latent image is then generated on the photoconductor by means of an exposure device, which supplies energy to the photoconductor at certain points, by reducing the charge in the areas of the photoconductor by exposure to such an extent that these areas are subsequently printed out in the so-called "charged area" development "(CAD-) remain white or with the so-called "Discharged area development" (DAD) can be colored with toner. Following the exposure, toner is applied to the photoconductor with the aid of a developing device, which toner adheres to the charged areas (CAD process) or to the discharged areas (DAD process) of the photoconductor.

The toner image on the photoconductor is then transferred, for example, to paper or another recording medium and, in a downstream fixing station, is melted down by heating the recording medium or connected to it by the adhesive forces which arise when the toner image melts. After the toner image has been transferred to the recording medium, the photoconductor is completely discharged and cleaned of residual toner, in order to then be fully charged again to a fixed potential for the preparation of the next exposure.

As illustrated in FIG. 1, when the photoconductor is exposed, its potential increases from a charging potential V2, to which the photoconductor was charged before the exposure and which can be kept constant by means of a charge control, along a characteristic curve K 1 or K 2 Lich lower potential VD1 or VD2. The potential of exposed areas depends on the one hand on the level of the exposure energy, the exposure time and the level of the charging potential V2.

On the other hand, the discharge characteristics Kl, K2 and thus the level of the potential of exposed areas on the photoconductor are also affected, for example, by production-related fluctuations, the quality of the photoconductor, its age, its temperature and the current process state, for example influences the start of a printing process, longer pauses between individual printing processes or different environmental influences. This results in potential fluctuations VD1, VD2 in the exposed areas of the photo film. ters, due to the consequent different toner receptacle in the developer unit to quality Schwan ^¬ fluctuations cause a printed image to be produced.

To compensate for temperature fluctuations, it is known to keep the photoconductor at a constant temperature during the entire operation. In some cases, the photoconductor is even kept uninterrupted at a constant temperature. The disadvantage here is that a corresponding heating must be provided, which increases energy costs. In addition, only one of the above-mentioned influencing factors is influenced by the heating.

It is also known to vary the toner concentration in order to compensate for fluctuations in the quality of the printed image as a function of certain parameters. However, not all quality fluctuations can be compensated for in this way. In particular, raster or fine line reproductions cannot be kept constant in the same way by changing the toner concentration.

A method is known from Japanese document JP 6-230642 (A) and the associated Japanese patent application HEI 5-15327, in which the discharge characteristic of the photoconductor is dependent on the exposure energy by repeated measurement of the discharge potential in order to optimize the generation of charge images - tials at different exposure energies and a subsequent approximation between the measured values is determined. It is disadvantageous that both several measurements are required, and furthermore it has to be approximated in order to determine the optimal value for the exposure energy.

In US-A-4, 855, 766 a method for determining an optimal charging potential and an optimal exposure energy is explained, in which the charging potential or the exposure energy is gradually increased by a predetermined amount until a desired value is reached. Thus at this method, as a rule, carry out a plurality of iteration steps until the target value for the difference between the discharge potential and the charging potential or the target value for the increase in the discharge curve of the photoconductor is reached with an optimal exposure energy.

From DE-OS 27 41 713 a method for stabilizing a charge image is known, in which, given a given exposure energy, the optimal charging potential can be determined with one or two iteration steps, but previously coefficients of functions have to be determined which are derived from a model of the Photoconductor have been derived and therefore take into account a variety of factors. However, this makes the formulas very complex and increases the computing time for calculating the coefficients. Ultimately, six value groups of the charging potential and the discharging potential must be measured until the sought-after coefficients can then be determined by solving an equation system. The coefficients can then still have large errors. Alternatively, for the determination of one of the coefficients, the recording of a large number of measured values is proposed, from which the desired coefficients are then determined with the required accuracy using the methods known from linear optimization.

US-A-4, 502, 777 discloses a large number of physical relationships in a copying process and, based thereon, specifies a comparatively complex method for correcting the charging voltage or the current flowing through the charging unit, without measuring the charging potential or the discharge potential is carried out. When the physical relationships are explained, an iteration method for determining the charging potential or the current flowing through the charging device at constant exposure energy is also given. In addition to the iteration steps that have to be carried out several times, this iteration method has the _N downside that it assumes an approximately linear relationship between the discharge potential and exposure energy.

It is an object of the invention to provide a simple method for optimizing charge image generation on a photoconductor of electrophotographic printing and copying devices, in which the quality of printed images is independent of quality and temperature fluctuations of the photoconductor and independent of process state changes and a resulting change in characteristics of the photoconductor is.

According to the invention, this is achieved in a method for optimizing charge image generation on a photoconductor of electrophotographic printing and copying devices by the features of claim 1 or 6. Advantageous further developments are the subject of the subclaims which are directly or indirectly jerk-related to claim 1 or 6.

According to the method according to the invention, a residual or discharge potential present on a photoconductor on the photoconductor is set to a predetermined target value, from which slight deviations are only permissible within narrow limits.

In order to achieve an discharge potential which lies within the tolerance range defined by the predetermined desired value, for example a charging potential, which is the potential to which the photoconductor is charged before exposure, and / or an exposure energy used for exposing the photoconductor, is adapted . Such an adjustment of the charging potential and / or the exposure energy can be achieved, for example, using assignment tables; the assignment tables contain, for example, depending on various parameters, corresponding values to which the charging potential and / or the exposure energy are set. The parameters used are, for example, the temperature of the photoconductor, the discharge potential remaining after a test exposure and a calculated or determined sensitivity factor of the photoconductor layer.

The charging potential to be used to achieve optimum printing results and / or the exposure energy to be used are thus calculated or preferably taken from the assignment tables with the aid of one or more specific parameters. The tables contain, for example, empirically determined values or values calculated using formulas.

In the method for optimizing charge image generation on a photoconductor in electrophotographic printing and copying devices, the photoconductor is charged to a standard charging potential. Then, after the exposure using standard exposure energy, the discharge potential generated on the photoconductor and the temperature of the photoconductor are measured. Following this, a sensitivity factor and an exposure energy adapted on the basis of the sensitivity factor are determined, for example by means of a microprocessor.

In a development of the method according to the invention, it is checked whether the determined exposure energy lies between a maximum and a minimum allowable exposure energy. If this is the case, then the photoconductor is recharged to the predetermined charging potential, exposed with the determined, adjusted exposure energy, and then the generated discharge potential is measured or determined. If the discharge potential generated is in the range of the predetermined target value, the charge image is generated on the photoconductor charged with the standard charging potential by exposing it to the adjusted exposure energy.

If the discharge potential generated deviates too far from the specified setpoint ao, _* ιrd again the temperature of the photoconductor determined, a new sensitivity factor and a new adapted exposure energy is calculated and the subsequent checking process is repeated with regard to the generated discharge potential. An iteration loop formed in this way is run through until the discharge potential generated on the photoconductor after exposure is in the predetermined tolerance range, ie in the range of the predetermined target value, and a charge image can be generated.

Instead of defining a tolerance range with the aid of a predetermined setpoint, this can also be determined by means of a predetermined difference value, the difference value being calculated from the charging potential and the generated discharging potential. Apart from slight fluctuations, the distance between charged and discharged areas remains constant.

However, if the calculated, adapted exposure energy exceeds the predetermined maximum limit value, which is generally determined by the structure of the printer, the method steps specified in claim 6 are preferably carried out.

A discharge potential is generated and measured with a maximum exposure energy and the predetermined charging potential. An adjusted charging potential is then determined from the measured discharge potential, with which the photoconductor is charged, provided that the adjusted charging potential lies within a predetermined working range, which is also generally determined by the technology used.

In a further development, the photoconductor charged to the determined charging potential is again exposed to the maximum exposure energy and the newly generated discharge potential is determined. If this is within the specified tolerance range, the charge pattern is determined using the adapted charging tials and the maximum exposure energy generated on the photoconductor.

If, however, the generated discharge potential is not within the specified tolerance range, the adapted charge potential is redetermined and the above-explained steps are repeated in an iteration loop until the value of the generated discharge potential lies within the specified tolerance range.

If, after a predetermined number of iterations, the calculated adapted charging potential is nevertheless outside the defined working range, in another development of the invention, a charge image is generated by exposing a charged photoconductor with a minimal charging potential to the maximum exposure energy.

If, on the other hand, the adjusted exposure energy calculated according to the method according to the invention falls below the specified minimum limit value, the steps specified in claim 6 are preferably also carried out, however, the maximum exposure energy is used instead of the minimum exposure energy.

The photoconductor is charged with the specified charging potential and then exposed with minimal exposure energy. With the help of the discharge potential thus generated and subsequently measured, an adapted charge potential is calculated. If the adjusted charging potential lies within the specified working range, the photoconductor is charged to the adjusted charging potential, exposed with minimal exposure energy and then the discharging potential generated in this way is re-tuned.

If the newly determined discharge potential lies within a predetermined tolerance range, the charge pattern becomes generated using the adjusted charging potential and the minimum exposure energy.

However, if the generated discharge potential is not within the specified tolerance range, the adapted charge potential is redetermined and the steps explained above are carried out again. This iteration loop is repeated until the generated discharge potential lies within the predetermined tolerance range and the charge image can be generated with the adapted charging potential and the minimal exposure energy, or until the charging potential calculated at the beginning of the iteration loop is not within the working range . In the latter case, the charge image is generated using the maximum charging potential and the minimum exposure energy.

In the method according to the invention it is particularly advantageous that the influence of all influence factors which influence the characteristic of the photoconductor is taken into account. In addition, it is advantageous in the method according to the invention that the temperature of the photoconductor does not have to be kept constant and in this respect the operating costs of the electrophotographic printing device are lower.

Another advantage of the method according to the invention is that raster or feminine lines are reproduced with constant quality even with different characteristics of photoconductors. This also extends the useful life of photoconductors, since they can still be used and used even with less favorable characteristic curves due to aging.

Furthermore, data is acquired and the method according to the invention is carried out automatically. Since the method according to the invention runs very quickly, the critical parameters can be checked, preferably not only after switching on a printer, after pausing or after printing Replacement of a photoconductor, but also be carried out at suitable time intervals during the printing operation.

The invention also relates to an arrangement for optimizing charge image generation and in particular for carrying out the method according to the invention. The above-mentioned technical effects also apply to the arrangement which is preferably installed in a printer or copier.

The invention is explained below with reference to the accompanying drawings. Intestine show:

Figure 1 em potential-time diagram of different characteristics of a photoconductor, and

Figures 2a,

2b and 2c each show a flow diagram of a preferred one

Embodiment of the method according to the invention.

1 shows a potential-time diagram of different characteristic curves K1, K2 of a photoconductor, the potential V of the photoconductor being plotted on an ordinate and the process time t being plotted on the abscissa. Here, a time tQ indicates the start of charging a photoconductor to a potential V] _, which is reached at a time t \. At a time t2, the charge on the photoconductor can decrease due to environmental influences on a potential V2. From time t2, the photoconductor is exposed. As a result of the exposure, the potential present on the photoconductor decreases along a characteristic curve K1 or K2 in a time period from t2 to t3 to a potential Vr ^ i or Vτj2. At time t3, the development of the charge image using toner m of the developer station begins. _S omit are spot on the photoconductor after exposure to Zeit¬ t3 depending on characteristics Kl or K2 unter¬ schiedliche discharge potentials V _D} and V _D2 for the development ^¬ lung starting present. The characteristic curves K 1 and K 2 are exemplary characteristic curves, ie, after exposure, at time t _{3 there} may also be areas with other potentials deviating from Vp__ or Vj ₃ 2.

The different course of the characteristic curves K1 and K2 of one or more photoconductors depends, for example, on environmental conditions, such as the temperature, on production-related fluctuations, on the quality of the photoconductor, on its age or on the current process state, such as the start of the printing process or the length of a pause between individual printing processes. The characteristic curve K 1 describes, for example, a photoconductor that is relatively insensitive and / or cold. In contrast, the characteristic curve K2 describes a photoconductor which is more sensitive and / or warmer than the photoconductor described by the characteristic curve K1.

It can be seen from FIG. 1 that, depending on the characteristics K1 or K2, different residual or discharge potentials V _D1 or V _D 2 remain on the photoconductor after exposure. Because of these potential differences between exposed areas, quality fluctuations occur in the printed image. In contrast, ideally the potential after exposure or at time t3 is at a value V _D soll _f. A broken line shows the lowest achievable discharge potential V2j_ _m -

FIGS. 2a to 2c are flow diagrams of a preferred implementation of the method according to the invention. According to Figure 2a is a printing device after switching, charged to the standard Aufla- depotential V _c ^s in V (volts) after longer breaks or disturbances of the photoconductor (step la), which is kept constant by means of a known charging control. The exposure is then set to a standard exposure energy H ^s in μWs / cm ² and the photoconductor H ^{s is} exposed (step 1b). If the exposure process is completed before or at the latest at time t3 (see FIG. 1), the residual or discharge potential Vp is measured at time t3 (step 1c). The discharge potential V _D in V at time t3 corresponds, for example, to one of the values V _Q -I or V _j ^ 2 of a discharge potential which, depending on the characteristic curve K 1 or K 2 of a photoconductor, remains as a residual potential on the photoconductor after exposure ( see Figure 1).

The temperature T of the photoconductor is then measured in step 2. However, the temperature can also be measured at a later or earlier point in time.

Subsequently, a sensitivity factor K and, based on the sensitivity factor K, an adapted exposure energy H ^a in μWs / cm ^{2 are} calculated (step 3). The sensitivity factor K can be calculated, for example, as a function of the instantaneous charging potential V _Q , the temperature T, the instantaneous exposure energy H, the measured discharge potential V _Q and a deepest achievable discharge potential V ^ ^m as:

Instead of the temperature T, a temperature factor TF determined from this can also be used, which specifies the influence of the temperature on the sensitivity factor K more precisely.

An adapted exposure energy H ^a is then preferably calculated using equation (2) on the basis of the sensitivity factor K as: )

where V _D ^S ° H is the target value for the discharge potential V _D.

In the subsequent step 4, it is checked whether the matched in step 3 exposure energy H ^a smaller than the maximum or greater than the minimum, with the used or existing exposure unit adjustable Belichtungs¬ energy H ^max or H ^mιn or equal EMEM these limits. Is H ^a outside this range, then the later with reference to figures 2b and 2c performs steps described durchge.

Is the adapted exposure energy in the interval H ^a H ^mιn <H ^a <H ^max, then in a step 5a analogous to step la of the photoconductor again to the standard charging potential V _c ^s charged. After completion of the charging of the Foto¬ conductor is matched with the calculated exposure energy H ^a exposed (step 5b '). The discharge potential Vp generated on the photoconductor is then measured.

Then in step 6 the discharge potential V _D measured in step 5c is compared with the target potential V _D ^so11 (see FIG. 1).

If the generated discharge potential V _Q lies within a predetermined tolerance range, ie if the generated discharge potential V _D deviates only slightly from the target potential V _{D set} , a charge image is subsequently generated (step 7) by the photoconductor charged to the standard charging potential V _c ^s and then exposed with the adapted exposure energy H ^a .

If the discharge potential Vp generated in step 5c is not within the specified tolerance range, then the iteration cycle with the discharge potential measured in step 5c tial Vp and the adjusted exposure energy H ^a calculated in step 3, at which steps 2 to 6 are carried out again.

The iteration loop described above, in which steps 2 to 6 are carried out, is repeated until the generated discharge potential Vrj is within the tolerance range and step 7 can be carried out; ie em charge image by charging the photoconductor to the standard charging potential VQ ^S and exposing is generated with the entspre¬ accordingly adapted exposure energy H ^a.

If, however, the decision in step 4 is "no" in one of the iterations, the steps described below with reference to FIGS. 2b and 2c are carried out.

According to the part of the flowchart of the method according to the invention shown in FIG. 2b, a step 4 ′ will decide whether the adapted exposure energy H ^a calculated in step 3 (see FIG. 2 a) is greater than the maximum permitted exposure energy H ^max . If the decision made in step 4 'is "no", ie if the adjusted exposure energy is less than a minimally permissible exposure energy H ^min , the part of the flowchart described later with reference to FIG. 2c is carried out.

If the adjusted exposure energy H ^{a is} greater than the maximum exposure energy H ^max , the decision is "yes" and the photoconductor is charged to the standard charging potential Vς ^s in step 8a in accordance with step la and in contrast to steps Ib and 5b 'then exposed with maximum exposure energy H ^max (step 8b''). The discharge potential V _D generated on the photoconductor is then determined (step 8c). Then, in step 9, an adapted charging potential Vς ^{a is} determined, which for example either according to equation (3)

_γ a ₌ fasoll ^ Jj, _eχp ( _{κ TH} ™ ή _{+ Vlnn} ( ₃ )

or according to equation (4)

can be calculated. The instantaneous sensitivity factor K calculated on the basis of equation (1) is used in equations (3) or (4).

In step 10, a decision is made as to whether or not the adapted charging potential Vς ^a lies within a working range.

If the decision in step 10 is "yes", the photoconductor is charged with the adapted charging potential V _c ^a calculated in step 9 (step Ila '), then exposed with maximum exposure ^energy H ^rnax (step Ilb') and in step 11c the discharge potential V _D determined.

Then, in step 12, analogously to step 6, it is examined whether the discharge potential V _D lies within a predetermined tolerance range. If this is the case, the charge image is generated with the adapted charging potential Vς ^a and by exposure with maximum exposure energy H ^max (step 13).

If, however, the decision in step 10 is "no" already during the first pass or after passing through one or more iteration loops (steps 9 to 12), the fcto conductor is charged with a minimal charging ^potential V _Q mιn load and then exposed with maximum exposure energy H ^max (step 14).

The flow chart shown in FIG. 2c is carried out when the decision made in step 4 '(FIG. 2b) is "no", ie the adjusted exposure energy H ^a calculated in step 3 (FIG. 2a) is less than the minimum exposure energy H ^mιn is.

As can be seen from FIG. 2c, with the exception of steps 8b ''',9', Ilb '', 13 'and 14', steps 8a to 13 already shown in FIG. 2b are carried out. In step 8b ″ ’, in contrast to step 8b ^τ ′ m in FIG. 2b, the photoconductor is not exposed with maximum, but with minimum exposure energy H ^min . If the result of the decision in step 10 is "no", step 14 'is carried out in the part of the flowchart shown in FIG. 2c, with which charge image on the photoconductor charged to maximum charging potential V £ ^max by means of mini Maier exposure energy H ^m i ⁿ is generated.

Another difference between the part shown in FIG. 2b from step 8a and the part shown in FIG. 2c is the equation (3) used in step 9 '. Analogous to the above-described difference between the two parts in steps 8b ''',Ilb'',13' and 14 ', in which E ^{mιn is} used instead of the maximum eme, the calculation must be carried out instead of that in step 9 of the adapted charging potential Vς ^a used equation (3) the equation (3 ') are used, m which _H max is replaced by H ^min , equation (3') is therefore as follows:

r _c ^a 4r / ^{0 //} - O «φ (* TH ^max ) + r _hrn (3 ')

That this is an image generation with fixed and not by means of the optimization method according to the invention. driving certain values, a corresponding display can be activated to inform the user that the copying or printing device is not working under optimal operating conditions.

Claims

Expectations

1. A method for optimizing charge image generation on a photoconductor of an electrophotographic printing or copying device, in which

a) the photoconductor is charged to a predetermined charging potential (V _c ) (step la),

b) the charged photoconductor is exposed to a predetermined exposure energy (H) and thereby discharged (step 1b),

c) the discharge potential (VQ) of the exposed photoconductor is determined (step 1c),

d) the temperature (T) of the photoconductor is determined (step 2),

e) is determined from the charging potential (V ^), the exposure energy (H), the discharging potential (VQ) and the temperature (T) em sensitivity factor (K), which m a predetermined relationship between the discharge potential (VQ) and the Exposure energy (H) at a fixed temperature (T) the relationship between the

Discharge potential (VQ) and the exposure energy (H) (step 3)

f) from the charging potential (VQ), the temperature (T), the determined sensitivity factor (K) and a predetermined target value (VQ ^S ° Ü) for the discharge potential (VQ) in accordance with the predetermined relationship changed according to the exposure energy (H) a new exposure energy (K) is determined which is used instead of the previous exposure energy (step 3), g) and with which a charge image is generated with the determined exposure energy (H) and the predetermined charging potential (VQ) (step 7).

2. The method according to claim 1, characterized in that the sensitivity factor (K) according to the formula:

is determined, where K is the sensitivity factor,

TF em temperature factor determined from the temperature T,

H the exposure energy in μWs / cm ^,

V _{c is} the charging potential m V, VQ the discharge potential m V and ^v lιm ^the lowest achievable discharge potential in V.

3. The method according to claim 1 or 2, characterized in that the new exposure energy (H) according to the formula:

is determined, whereby

H the exposure energy,

TF em temperature factor determined from the temperature,

K αer sensitivity factor,

V _{c is} the charging potential in V,

V _D is the setpoint of the discharge potential m V and ^v lιm ^the lowest achievable discharge potential m V smc. 4. The method according to any one of the preceding claims, characterized in that after step f) according to claim 1, the following steps are carried out:

fl) after re-exposure of the photoconductor charged with the predetermined charging potential (V _Q ) with the exposure energy (H) last determined, the discharge potential (V _Q ) is determined again on the photoconductor and used instead of the previous discharge potential (V _D ) ( Steps 5a, 5b ', 5c),

f2) if the discharge potential (VQ) lies within a predetermined tolerance range, step g) is carried out according to claim 1 (step 6),

f3) if the discharge potential (VQ) is not within the tolerance range, steps d) to f3) or e) to f3) are repeated until the discharge potential (VQ) lies within the tolerance range (step 6).

5. The method according to any one of the preceding claims, characterized in that instead of the setpoint (V _Q ^S ° ^Ü ) for the discharge potential (V _Q ) em setpoint for the difference between the charging potential (V _c ) and the discharge potential tial (V _Q ) is used.

6. Method for optimizing charge image generation on a photoconductor of an electrophotographic printing or copying device, in which

A) the photoconductor is charged to a predetermined charging potential (V _c ) (step 8a),

B) the charged photoconductor is exposed to a predetermined exposure energy (H) and is then discharged (step 8b ''; 8b ''') C) the discharge potential (V _D ) of the exposed photoconductor is determined (step 8c),

D) the temperature (T) of the photoconductor is determined (step 2),

E) a sensitivity factor (K) is determined from the charging potential (VQ), the exposure energy (H), the discharge potential (VQ) and the temperature (T), which is given in a predetermined relationship between the discharge potential (VQ) and the exposure energy (H) determines the relationship between the discharge potential (VQ) and the exposure energy (H) at a fixed temperature (T) (step 9; 9 '),

F) from the exposure energy (H), the temperature (T), the determined sensitivity factor (K) and a predetermined target value (VQ ^S ° Ü) for the discharge potential (V _D ) according to the after the charging potential (V _c ) a predetermined charging relationship (VQ) is determined, which is used instead of the previous charging potential (VQ) (step 9; 9 '),

G) and in which a charge image is generated with the determined charging potential (V _c ) and the predetermined exposure energy (H) (step 13; 13 ').

7. The method according to claim 6, characterized in that the sensitivity factor (K) according to the formula:

K

is determined, where K is the sensitivity factor, TF em is the temperature factor determined from the temperature T, H the exposure energy in μWs / cm ² , V _c the charging potential in V, VQ the discharge potential in V and ^v lιm ^the lowest achievable discharge potential in V.

A method according to claim 6 or 7, characterized in that the new charging potential (V _Q ) according to the formula:

V, / should

- ('D -Vh, m J exp (K.TF H) + V _hrn

is determined, whereby

V _c the charging ^potential V _D ^so11 the discharge potential in V, ^v lιm the lowest achievable discharge potential m V;

TF em temperature factor determined from the temperature T,

K is the sensitivity factor and H is the exposure energy in μWs / cm ² .

9. The method according to emem of claims 6 to 8, characterized ge indicates that instead of the setpoint (V _Q ^S ° H) for the discharge potential (VQ) em setpoint for the difference between the charging potential (V _Q ) and the discharge potential (V _Q ) is used.

10. The method according to any one of claims 6 to 9, characterized in that after step F) the following steps are carried out:

FI) after re-exposure of the photoconductor charged with the determined charging potential (V _Q ) with the predetermined exposure energy (H), the discharge potential (VQ) is determined again on the photoconductor and used instead of the previous discharge potential (V _Q ) (steps Ila , llö \ 11c; Ila 'Ilb'', 11c), F2) when the discharge potential (V _D) lies within a ^pre-¬ given tolerance range, the step G) according to claim 6 is carried out (step 12),

F3) if the discharge potential (VQ) is not within the tolerance range, steps D) to F3) or E) to F3) are repeated until the discharge potential (V _Q ) lies within the tolerance range (step 12).

11. The method according to claim 10, characterized in that before the execution of step FI) it is checked whether the determined charging potential (V _Q ) lies in a predetermined working range (step 10),

step FI) is only carried out when the determined charging potential (V _Q ) is within the working range,

and that, instead of steps FI) to F3), a charge image is generated with the predetermined exposure energy (H) and with a predetermined charging potential (V _Q ), which is preferably at a limit of the working range when the determined charging potential (V _c ) lies outside the working range (step 14; 14 ').

12. The method according to any one of claims 6 to 10, characterized in that it is determined before the execution of said steps that an exposure energy (H) determined for em predetermined charging potential (V _c ) is above a maximum exposure energy (H ^max ) ( Steps 4, 4 '),

and that the predetermined exposure energy (H) is the value of the maximum exposure energy (H ^max ) nat. 13. The method according to any one of claims 6 to 11, characterized ge indicates that before the execution of the above-mentioned steps it is determined that an exposure energy (H) determined for a predetermined charging potential (VQ) is below a minimum exposure energy (H ^mιn ) lies (steps 4,4 '),

and that the predetermined exposure ^energy (H) has the value of the minimum exposure ^energy (H ^min ).

14. The method according to any one of the preceding claims, da¬ characterized in that the charging potential (V _Q ) according to the formula:

is determined, whereby

V _{c is} the charging potential,

VQ the discharge potential m V,

K is the sensitivity factor, TF em temperature factor determined from the temperature T,

H are the exposure energy m μWs / cm ² and ^v lιm the lowest achievable discharge potential in V.

15. The method according to the preceding claims, characterized in that the temperature (T) em temperature factor (TF) is determined using the following formula:

TF = a + bT + c T ² ,

where T is the temperature m degrees Celsius and where a, b and c are fixed coefficients.

16. The method according to the preceding claims, _αa _ αurcb characterized in that zαr Bescnleumgung αer procedural Assignment tables are created on the basis of the predefined relationship and / or the converted relationship.

17. The method according to any one of the preceding claims, da _¬ characterized in that to accelerate the procedural implementation assignment tables are created empirically printer-specific.

18. The method according to any one of the preceding claims, characterized in that after switching on, after printing pauses, after changing the photoconductor and / or during the printing operation is carried out at predetermined time intervals.

19. Arrangement for optimizing charge image generation and in particular for performing the method according to one of the preceding claims,

with a light-sensitive layer system,

a charging device for generating a charging potential (V _c ) on the light-sensitive layer system,

an exposure device for exposing the charged layer system to an exposure energy,

a temperature sensor for detecting the temperature of the layer system,

a potential sensor for detecting the discharge potential (V _D ) on the light-sensitive layer system after exposure,

and with a control unit for specifying the charging potential (V _c ) and the exposure energy (H), characterized in that the control unit, when specifying the charging potential (VQ) and / or the exposure energy (H), determines a sensitivity factor (K) which, in a predetermined relationship between the discharge potential (VQ) and the exposure energy (H) at a fixed temperature (T) defines the relationship between the discharge potential (VQ) and the exposure energy (H).

20. Printer according to claim 19, characterized in that it contains the arrangement.