Patent Application
20090268296
The present invention generally relates to coatings for lenses or display covers, and more particularly to a method for a coating a thin, supportive layer on a glass lens.
In many portable electronic devices, such as mobile communication devices, displays present video and text information to a user. These optical displays, for example touch panel displays, typically comprise a transparent protective layer including a high gloss reflective surface of glass or a polymer. Glass typically offers a higher scratch resistance. While these transparent protective layers have excellent transparency and are relatively physically strong, they may suffer physical damage due to harsh treatment by the user. This is particularly true for the displays of products which receive significant handling, such as personal digital assistants (PDAs) and cell phones.
In order to reduce distracting reflections from the surface of the transparent protective layer, conventional displays place either an antireflective coating or a decorative vacuum metallized coating over the surface by laminating a dry stack of adhesive polymer film, and a hard film such as titanium dioxide or silicon oxide onto the glass. Placement of these hard films directly onto the glass layer is known to decrease the impact or fracture strength of the glass due to the mismatch of the mechanical and structural properties of the glass and these coatings.
Accordingly, it is desirable to provide a method for applying a relatively thin antireflective or vacuum metallized coating onto glass that improves the impact or fracture strength of the glass. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.
Embodiments of the present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.
An optically clear polymer material disposed between a glass lens and an antireflective coating or a vacuum metallized optical coating improves the impact or fracture strength of the glass lens. The polymer material preferably is spin, spray, or meniscus coated so molecules of the polymer material attach to the glass lens, preferably at a thickness below 38 micrometers, and more preferably at a thickness below 25 micrometers. The application of the polymer material prior to deposition of the antireflective or vacuum metallized optical coating provides a soft coating and buffer-like quality, thereby allowing for the use of a thinner glass lens.
Referring to
In accordance with the exemplary embodiment, a thin layer 104 of a polymer material is formed on the glass layer 102. The layer 104 is preferably spin, spray, or meniscus coated so molecules of the polymer material attach to the glass. The thin layer 104 is disposed on the “inside” of the layer 102. In other words, the side 103 of the layer 102 faces the viewer of the lens 100. These methods allow for the layer 104 to be thin when compared to previously known methods, by having a thickness preferably less than 38 micrometers, and more preferably less than 25 micrometers, for example when maintaining anti-splinter characteristics. The polymer layer 104 may be any polymer, but preferably is one of a polyimide, siloxane, polyurethane, polyester, polycarbonate, and polyethylene material. A polyurethane layer has shown good anti-splintering qualities.
A coating 106, for example a metal or an alloy such as indium tin oxide, titanium oxide, or a conductive polymer, of either an antireflective material to reduce reflection or a vacuum metallization for decoration is deposited on the polymer layer 104. The coating 106 may have a thickness in the range of 0.05 to 0.25 micrometers, but preferably has a thickness of about 0.15 micrometers. The polymer layer 104 provides a buffer-like quality that maintains the fracture strength of the glass layer 102 when the coating 106 is applied. The combination of layers 102, 104, 106 has a light transmission value of 65-98% between the wavelengths of 400 to 700 nanometers to maintain the desired optical quality and an index of refraction that closely matches glass to reduce any optical aberrations or image distortion.
The layers 102, 104, 106 have the right balance of tensile strength, Young's Modulus, modulus of elasticity, and coefficient of thermal expansion to maintain the integrity of the layers 102, 104, 106 through environmental conditions while reducing the negative effects of the layers 104, 106 on the fracture and impact strength of the glass layer 102. Tensile strength of a material is the maximum amount of tensile stress that it can be subjected to before failure. Stress is a measure of the average amount of force exerted per unit area. It is a measure of the intensity of the total internal forces acting within a body across imaginary internal surfaces, as a reaction to external applied forces and body forces, and is measured in units of pascals (Pa), or Newtons per square meter. Young's modulus, synonymously with modulus of elasticity, is the ratio of tensile stress to the resulting strain, which reflects the resistance of a material to elongation. The higher the Young's modulus, the larger the force needed to deform the material.
This process produces a favorable situation where a relatively soft (low Young's Modulus) layer is interposed between the harder glass and optical coating layers. This allows for easier relative movement of the hard layers thereby reducing the possibility that these layers might fracture.
The method 200 of the exemplary embodiments is shown in
Although the apparatus and method described herein may be used with an exposed display surface for any type of device, the exemplary embodiment as shown in
The mobile communication device 300 has a first housing 302 and a second housing 304 movably connected by a hinge 306. The first housing 302 and the second housing 304 pivot between an open position and a closed position. An antenna 308 transmits and receives radio frequency (RF) signals for communicating with a complementary communication device such as a cellular base station. A display 310 positioned on the first housing 302 can be used for functions such as displaying names, telephone numbers, transmitted and received information, user interface commands, scrolled menus, and other information. A microphone 312 receives sound for transmission, and an audio speaker 314 transmits audio signals to a user.
A keyless input device 350 is carried by the second housing 304. The keyless input device 350 is implemented as a touchscreen with a display. A main image 351 represents a standard, twelve-key telephone keypad. Along the bottom of the keyless input device 350, images 352, 353, 354, 356 represent an on/off button, a function button, a handwriting recognition mode button, and a telephone mode button. Along the top of the keyless input device 350, images 357, 358, 359 represent a “clear” button, a phonebook mode button, and an “OK” button. Additional or different images, buttons or icons representing modes, and command buttons can be implemented using the keyless input device. Each image 351, 352, 353, 354, 356, 357, 358, 359 is a direct driven pixel, and this keyless input device uses a display with aligned optical shutter and backlight cells to selectively reveal one or more images and provide contrast for the revealed images in both low-light and bright-light conditions.
Referring to
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.
