Due
to the defects of printing equipment, printing plate, ink and manual operation,
there will be deviation in the book
printing of QR code. It is precisely because the QR code may have poor
quality in the printing process, so we should detect the QR code before use,
otherwise we can't read the QR code, which will affect customers' trust in the
product. In the actual production of QR code printing, the following problems
need special attention
Color
contrast and registration
The
QR code can be monochrome black or multi-color overprint. The main factors
affecting the printing quality of QR code are color contrast and overprint error.
Color
contrast
Insufficient
color contrast of newspaper QR code will affect the recognition of QR code by
mobile phone software. Requirements for optical characteristics of bar code
printing symbols: in order to read reliably, there shall be obvious contrast
between lines and spaces in bar code after printing, and the reflectivity of
spaces shall be as large as possible, while the reflectivity of lines shall be
as small as possible. According to the national standard, the whiteness of
domestic newsprint is more than 50%, and the normal printing can meet the
recognition requirements of QR code. However, it should be noted that when
making QR codes in newspapers, editors should be reminded not to add shading to
prevent insufficient contrast from affecting reading.
2.
Overprint error
It
mainly refers to color QR code. The QR code must be neat and clear during book printing. Generally, we
specify that the maximum overprint error (overprint error between main tone and
picture) should be less than or equal to 0.4 times the nominal width of the
narrowest bar code.
According
to the national standard, the overprint error of newspapers is required to be
less than or equal to 0.3mm. In fact, some newspapers above the provincial
level with advanced printing equipment and high quality requirements can fully
meet the standards in this regard. For some local newspapers with unstable
overprint, it is recommended to use monochrome printing for QR code, so that
there is no overprint problem.
3.
Some elements lost in printing
When
printing, pay attention not to lose elements on the printing plate, so as not
to make it difficult to read the QR code. In printing, due to the printing
plate or blanket, it is easy to cause printing pattern defects. For the
slightly "fragmented" pattern of QR code, special attention should be
paid to pre printing plate making and post inspection.
4.
Printing ink problem
To
control the dimensional error of QR code symbols, the key in printing is to
control the ink color and book printing pressure to ensure the accurate restoration of QR code stripes. Under normal
conditions, we should ensure that the ink is "small in water and small in
ink", and ensure the necessary ink layer thickness. No fringes caused by
low pressure or insufficient ink color; There is no fringe diffusion caused by
high pressure or large ink.