What is Primary charge roller(PCR)?

Primary charge roller(PCR) is composed of a cylindrical metal stick and conductive rubber. Its main function is to give the OPC drum a uniform charge to absorb toner powder and to eliminate the residual potential on the OPC drum.

PCR adopts a new environmentally friendly charging method, which reduces the production of ozone, charges evenly and without noise. It is widely used in laser printers and also in low-speed copiers. The voltage of the laser printer charging roller is -600V to -700V, and there are also positive charging. The charging voltage of the charging electrode wire is relatively high, generally between 6000V and 8000V.

PCR Structure

The PCR is composed of a cylindrical metal  stick and an elastic rubber coated on the outside of the metal core. Its specific structure is roughly as follows:

1. The PCR is tightly coated with a low-hardness conductive elastic layer on the outside of the metal core, and a surface layer is coated on the outside of the elastic layer. 

The thickness of the surface layer is very thin, about several to tens of microns, and the resistance is relatively high.

2. The PCR only has a low-hardness conductive elastic layer on the outside of the metal core, but the outer surface has been specially treated.

3. The PCR is a surface layer outside the low-hardness conductive elastic layer. The surface layer is a rubber tube with high resistance, and the thickness ranges from tens 

of microns to 1 mm.

4. The PCR has a uniform electric layer between the low-hardness conductive elastic layer and the surface layer. The thickness of the electric layer is 1-3μm, and the 

thickness of the surface layer is 40-80μm.

The charging roller is a surface layer outside the low-hardness conductive elastic layer. The surface layer is a rubber tube with high resistance, and the thickness ranges from tens of 

microns to 1 mm. The entire charging roller is charged evenly and has stable performance during use, which provides good guarantee for printing.

PCRs are divided into soft rollers and hard rollers

Soft rollers: composed of metal shafts, conductive sponges and rubber sleeves

Hard rollers: composed of metal shafts and conductive rubber

In order for the charging device to achieve an ideal charging effect, the charging device is required to meet the following conditions:

1. It can make the surface of the photoconductor drum(opc drum) carry electrostatic charges with appropriate density, uniform distribution and correct polarity within a specified time.

2. Since the use conditions and the surrounding environment will change (temperature and humidity changes), the charging device is required to have a certain adjustment range, 

or the charging device should have a certain stability when the environment changes such as temperature and humidity changes, so as to eliminate, reduce or compensate for the 

impact of environmental factors on the quality of printing.

3. The charging device is required to be durable, safe and reliable.

4. When the power supply voltage fluctuates, the output characteristics of the charging device should remain basically unchanged.

5. The impedance of the charging device and the load (air gap, photoconductor, etc.) should match.

6. The photoconductor drum should not be damaged (broken down) or fatigue of the photoconductor drum should not be accelerated due to the charging device.

In addition, a high-quality charging roller should have: appropriate volume resistivity and uniform resistance distribution, appropriate hardness and surface roughness to ensure that 

the charging roller is in full contact with the photoconductor drum and the pressure is uniform, and the material constituting the charging roller is stable with environmental changes 

such as temperature and humidity, so that the required charging voltage is minimized, the charging is uniform, the charging roller has stable performance, and will not cause damage 

to the photoconductor drum, thereby obtaining good image effects and a long service life. The design service life of the original charging roller is 2-3 cycles, and it can be used for 

3-4 cycles if it is well maintained.