Positive plates and negative plates have significant differences in a number of aspects, these differences are mainly reflected in the imaging principle, the characteristics of the negative, solarization process, application characteristics and printing effect.

The following is a detailed description of the differences between positive plates and negative plates:

1, The imaging principle

- Positive plates:

When imaging, the image on the positive plates and the same as the original, that is, the blank part of the original on the negative completely transparent, and black (or other colors) lines or text on the negative is still black.

In the tanning process, laser or light irradiation film, transparent part of the light allowed to pass and irradiated to the plate on the light-sensitive layer, so that the light-sensitive layer of the decomposition of the light-sensitive part of the formation of the blank part of the offset printing plate; and black lines or text part of the blocking of the light, so that the light-sensitive layer did not change, constituting the printing plate of the printed part of the graphic.

- Negative plates :

When imaging, the image on the negative plates is the opposite of the original, i.e., the blank portion of the original is completely black on the negative, while the black (or other color) lines or text are completely transparent on the negative.

In the process of solarization, laser or strong light irradiation film, transparent part of the light allowed to pass through and irradiated to the plate photographic layer, so that the photographic layer of chemical changes (such as cross-linking, curing, etc.), the formation of the printing plate of the printed part; and the black part of the light blocking, so that the photographic layer to maintain the original state in the subsequent processing is removed, the formation of the blank portion of the printing plate.

2. The characteristics of the negative

- Positive plates:

The image on the negative is consistent with the original and is intuitive and easy to understand.

It is easy to check the correctness of the negative before solarization, and it is convenient for manual imposition.

It is not necessary to block the four sides of the negative with masking paper, and the process is easy to operate.

- Negative plates:

The image on the negative is opposite to the original and requires some adaptation and conversion process.

It may be relatively complicated to check the negatives for correctness before solarization.

The need for solarization of the negative map outside the location of the negative with a black paper cover, in order to avoid non-printing area exposure.

3. The tanning process

- Positive plates:

The solarization process is relatively simple and easy to operate.

Applicable to most modern printing equipment.

- Negative plates:

Tanning process is relatively complex, requiring additional shading and positioning steps.

However, in some specific cases (such as the need for high print resistance of the plate), negative film tanning may have an advantage.

4. Application characteristics

- Positive plates:

It is widely used in various printing scenarios, especially in commercial printing and package printing.

Due to its easy operation and low cost, it has become the mainstream choice in the printing industry.

- Negative plates:

In some specific application scenarios (e.g., plates requiring high print resistance and high resolution), negative film tanning may be more advantageous.

However, due to the complexity and high cost of the process, the use of negative film tanning in the printing industry is relatively small.

5. Printing results

- Positive plates:

Stable and reliable printing effect, suitable for most printing needs.

Printing plate print resistance is moderate, to meet the general requirements of the printing volume.

- Negative plates:

Printing results can be more detailed and of higher quality, especially when high resolution and high print resistance are required.

However, due to process complexity and cost factors, the improvement in printing results may not always be significant or economically viable.

In summary, positive plates and negative plates in the imaging principle, negative characteristics, solarization process, application characteristics and printing effect, there are significant differences. When choosing offset printing plates, you can select suitable one according to the specific printing needs and equipment conditions for comprehensive consideration.