Tools for mechanical scribing are developed and manufactured in-house.
We conduct research on diamond-based tool materials, develop the best suited shape for the materials, and establish a processing technology for tool materials which are difficult to cut.
Glass scribing tools were conventionally made of cemented carbide. We have developed polycrystalline diamond (PCD) based tools to extend tool life.
PCD is a polycrystal diamond grit that is fused together with a catalytic metal such as cobalt (as a binder) under high-pressure condition. Depending on the grain size of the polycrystal diamond, type and ratio of the binder, and the manufacturing method, it can have various characteristics (physical properties). We have searched for materials that are suitable for scribing in terms of hardness, toughness, and so on.
We are still searching for new materials that are more suitable for scribing than PCD, from the viewpoint of better tool performance.
Development of shapes
Conventional glass cutting tools (glass cutters) have a diamond or carbide tip on its top edge, and the glass surface is machined by the tip. Contacting the tip at the correct angle and moving the glass cutter with the right force and speed enable refined cutting, which requires the so-called highly skilled artisanship. Glass cutters with a wheel-shaped tips was invented to achieve an easier cutting process.
When it became difficult to reverse panels due to the increase in size of LCD panels, a method for cutting LCD panels without reversing was demanded. Then, a tool called Penett®, which is a deep penetration scribing wheel, was developed. Since simultaneously scribing from the top and bottom makes the primary crack reach as far as 80% of the glass thickness, a significant improvement in productivity was realized without the reversing and break processes.
Furthermore, we have developed APIO®, which improves the quality of the glass edge and intersection, to deal with the increasing glass variations and thinning.
Currently, we are developing shapes suitable for glass materials, such as Ryu, which reduces chipping (small break of glass) during scribing, and SOLID-D®, a stationary blade for ultra-thin glasses with thickness of a few dozen μm.
Establishment of processing technology
The Mohs hardness of diamond (mono-crystal), which is structurally extremely hard, is 10. However, the hardness varies depending on the crystallite orientation. Since diamond has perfect cleavages, it can easily break in certain directions. Sintered diamond body is not prone to breakage due to crystallite orientation and is extremely difficult to cut because of its high hardness, since it is a polycrystalline diamond fused under high temperature and high pressure conditions in the presence of catalytic metals and such.
Special processing technologies are required to process extremely hard-to-cut materials like PCD into shapes of around 2 mm in diameter and to add μm-level processing onto its ridgeline. It is possible to provide high-quality processing by using diamond grindstones etc., which is time consuming. To achieve the projected mass production, reduction of processing time is essential.
In addition to the conventional polishing method using grindstones, by using laser processing technology, we have refined our technology for processing high-quality tools in a short time.
Tools with stable quality are manufactured in our own factory (Iida Plant) with increased process automatization.
Verification of prototype
When new materials and shapes are developed, it is essential to verify their performances.
Checks are carried out on the shapes and processed surfaces to the micron level by using methods such as SEM observation. All processed parts are checked to ensure that the target angles, lengths, surface roughness, and so on are achieved.
Also, tests are performed to verify the performance at the time of the actual cutting process. Checking of the scribe line with verification devices includes checks on the state of the primary crack, etc., as well as the surface line condition. Furthermore, for checking the tool life, verification is carried out by letting the tool run for a certain distance. By deliberately applying a load larger than usual, the level of wear is checked.
The result is passed on to the Development Department as feedback, the shapes and processing methods are reviewed, and the verification is carried out again. By repeating these processes, we develop tools that can achieve the target performance.