Around 1989, our firm worked on a major project. As an original equipment manufacturer, we were asked by a certain major liquid crystal projector manufacturer "H" to produce projection screens, and participated in a tender for the development of screen materials with other several companies.
At that time, because the output of liquid crystal projectors was insufficient, screen gain was a major factor, and high-brightness projection screens were most sought after. In specifying, only brightness values were talked about and screen materials were sought without regard for diffusion. Though we received an order for the projection screens, we had a number of difficult problems with the fabrication of materials and assembly at the factory because the production of high-brightness screen materials had poor yield rates (defective rate). With mask coating applied, screen materials looked acceptable momentarily. However, we faced problems in a few days or weeks because of lost flatness. During shipping inspections, the defects of screen materials were not detected. But several weeks after delivery to the client, changes occurred to screen materials and they caused a major internal problem to the "H" company. This problem was resolved after stopping the application of mask coating and starting printing masks.
Screen materials at that time had the same conditions. Several companies tried to find a market for their materials as new projection screens, and we were offered many samples and trial products from them. However, as a projection screen manufacturer, we could only propose to them to improve screen gain for new projection screen materials. Though we sensed that glare and uneven brightness were more important issues, we did not have a way of expressing these theoretically and numerically.
Our current ultra bead screens had been jointly developed with our subcontractors since around 1991. In developing them, we reconfirmed an unexpected thing. At that time, CRT projectors were widely used. When we were making evaluations at our factory together with engineers from a major manufacturer "S" of CRT projectors, we found that *color shifts were generated. Screen surfaces that were applied with glass beads in the most uniform manner prevented the glass beads from coming off, and the desired high screen gain (2.4) was achieved. However, we learned that this uniformity and regularity (uniform particle diameters of beads) could have caused defects to projection screens in a different aspect.
We also sold projection screens that utilized the characteristics of polarized light from liquid crystal projectors. However, the projection screens that were on display at home electronics wholesalers had color shifts caused by liquid crystal projectors that had polarized lights in three different directions. Because the projection screens were very expensive, and our intention of planning and developing them was not accomplished, that was no laughing matter. In a certain magazine on audiovisual equipment, one of their readers expressed his opinion about our reflective type of projection screen, "Though I spent a large sum on the screen, wrinkles in the screen started bothering me recently. Is the screen supposed to have such wrinkles?" The reader's opinion made us feel keenly the need for the accountability of projection screen manufacturers like our firm for the precise use of projection screens.
*color shifts:The phenomenon in which a color tone shifts with the degree of incidence angle of light.
