KONICA MINOLTA

About Konica Minolta

Giving Shape to Ideas

High-speed inkjet printheads

Background to development

Uses of industrial inkjet printers

Inkjet printers are a common sight in mass-market electronic retailers, and are widely used as consumer devices for home printing from personal computers. Industrial inkjet printers, on the other hand, are used in fields including textiles, industrial printing, and printed electronics (PE), and their range of uses is continuing to increase.

Signs and displays Outdoor notice boards, shop signs, and displays are output and produced by using wide-format inkjet printers.
Graphics Posters for use in restaurants and game stores are also output and produced by using wide-format inkjet printers.
Label printing Inkjet printers are suitable for printing bar codes, GS1 data bars, QR codes, name labels and other commercial labels.
Electronic materials Inkjet technology is now beginning to be used for printing electronic materials, such as color filter formation for liquid crystal displays (LCDs) and printed circuit boards.
Textile printing Inkjet printing of textiles is a rising trend in the apparel industry.

Demand for high-speed printing

Konica Minolta has developed inkjet printheads that utilize a type of piezoelectric element known as a shear mode piezo-element, and supplies these to manufacturers of industrial inkjet printers. Shear mode actuators apply an electric field to the piezoelectric material (PZT) that forms the ink channel walls, causing it to undergo a shearing deformation that changes the volume of the ink channels and eject ink from the nozzle. As it can be operated on low power, multiple channels can easily be used, enabling the use of a wide variety of inks with varying properties.

Industrial inkjet printers must be capable of printing at high speed without any loss of image quality, and inkjet printheads capable of operation at higher speed are particularly needed for single-pass printing, in which the printhead is fixed during printing and the medium is conveyed underneath it.

Goal

  • To develop inkjet printheads capable of high drive speed with no loss of image quality

Konica Minolta technology

Triple drive speed

Konica Minolta's own conventional printheads utilize the harmonica (HA) structure and incorporate a three-cycle drive system, in which the nozzles are divided into three groups that eject ink in sequence. This three-cycle drive system is useful for increasing ink density, but is of limited value for high-speed drives.
When an independent drive system with air channels on both sides of the ink channels is used then each channel can be driven individually, which is useful for high-speed drives, but it has the disadvantage of a lower nozzle density, which reduces image quality.

Two Types of Drive Mode

Konica Minolta has therefore developed a multi-row harmonica structure as a novel printhead actuator. This maintains the number of nozzles (1024) used in conventional printheads, while enabling the use of an independent drive system. As a result, the drive frequency has more than tripled from the 13 kHz of conventional printheads to 45 kHz for the new type, enabling high-speed operation.

Success

  • Creation of an inkjet printhead with the same number of nozzles but the drive frequency more than tripled to 45 kHz

Key technology

Precision machining technology enables four-row structure

Increasing the number of actuator rows enables the nozzle density to be increased, but supplying voltage and ink to the ink channels remains an issue, and until now only a maximum of two rows per printhead was possible.
Konica Minolta has now succeeded in producing a four-row HA structure by utilizing its hard-won expertise in high-precision machining, precision assembly, processing, and materials technologies.
For wiring boards, the ink supply holes must be formed with high precision so that the ink only enters the ink channels. The electrodes in the channels are drawn out of the tips of the wiring boards by means of high-precision wiring electrodes and connected to the drive IC to drive all four rows of channels. The distance between the rows of nozzles is extremely small to enable high-precision printing, and this also involves high-precision machining.

Ink circulation system

Similarly to the actuator, how the flow of ink is designed is extremely important for stable ejection.
The ink flow in the new printhead is extremely simple. A single ink chamber with two ink inlets sits above the four rows of ink channels. Any bubbles in the ink rise to the top, effectively removing them from the ink flow so they have no effect on ejection. The ink can be circulated from the inlet to the outlet, which is useful when using pigments with large particle size that tend to sink, such as ceramic inks.

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