Optical: systems and elements – Glare or unwanted light reduction – Display window
Reexamination Certificate
1999-12-22
2001-08-14
Sikder, Mohammad (Department: 2872)
Optical: systems and elements
Glare or unwanted light reduction
Display window
C359S608000, C359S601000, C359S602000, C359S603000, C359S900000, C156S077000
Reexamination Certificate
active
06273573
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to the production of display windows. It particularly relates to a method for producing display windows, the moulding tool used in the method and the method of producing the moulding tool.
Communication devices like mobile phones are usually equipped with a display unit, preferably a Liquid Crystal (LCD)-display in combination with a display window. The display window protects the LCD display against damage. Sometimes the display window serves as a lens for slightly magnifying the information presented on the display.
Mobile phones are also used in cars and other vehicles. Typically, the display unit with display window are part of a handset which also has a keyboard, an earpiece and a microphone. The handset is connected to a box, containing other electronics of a mobile phone, that can be placed at any convenient place in the vehicle.
Display windows of communication devices are usually produced by an ejection moulding process. For a good visibility of information presented on the display the surface of the display window is shiny and smooth.
It is generally desirably to make phones as easy to use as possible. However, light reflections on the display window of a mobile phone may be distracting or annoying. For example, a user may have to change the position and/or orientation of the phone relative to light sources or their position relative to the phone, to minimise reflections. For phones used outside buildings, like in vehicles, the reflections of the sunlight can considerably restrict the use of the phone. Furthermore fingerprints on the surface of the display window can deteriorate the visibility of the information on the display.
SUMMARY OF THE INVENTION
According to the invention a method for producing a display window for a communication device covering a display element is disclosed. The method comprises the steps of
providing a moulding tool with a matt surface structure,
injecting fluid plastics,
cooling off the injected plastics and releasing the ready display window from the moulding tool.
With a matt surface of the display window light reflections on the display unit are drastically reduced and fingerprints are not problematic anymore. Furthermore, surprisingly, the visibility of information presented on a display is satisfactory if the outer surface of a display window covering a display element is matt.
Previously, to maximise visibility of the display, the surface roughness of display windows for communication devices was minimised and effectively negligible. The surface was shiny and smooth and therefore caused light reflections.
In technical terms matt may be defined as the surface roughness of the display window. The surface roughness is the collective variation in the height of a surface. Methods for effectively measuring surface roughness are known.
One advantage of the disclosed inventive method is that the display window and the outer surface of the display window are produced in one production step. The matt surface structure is part of the surface of the moulding tool and is copied to the display window during the moulding process. This is more advantageous than applying the matt surface in a second process step to a previously formed display window with a shiny and gloss surface.
Before the display window is released from the moulding tool it has to be cooled off until the plastics has become hard enough that it can be released from the tool without any deformation.
Experiment has shown that the surface roughness of the display unit should be around 1 &mgr;m or finer to obtain a good visibility of the information on the display. If the display window is very near to the display or the information presented on the display is very large the surface roughness could be higher then 1 &mgr;m but for a communication device with the usual dimensions a surface roughness of 1 &mgr;m or finer is optimal. It has to be noted that the surface roughness should not be so fine that light reflections again disturb the visibility of the information presented on the display element.
The display window is advantageously made of clear, hard and transparent plastic material to obtain best visibility. For this purpose the display window is for example made of acrylic.
The invention furthermore relates to a communication device comprising a display element and a separate display window covering the display element wherein at least a portion of the outer surface of the display window is matt.
The display element is for example a LCD display which presents information to the user and the transparent display window covers the LCD display and protects it against damage and dust. The display element can be fixed on a circuit board within the communication device and the display window is an integral part of the front cover of the communication device.
The display window may contain a view area covering the display element and another area, e.g. used for decoration purposes, with only the view area being matt. The view area of the display window is the area of the display window the user is looking through to see the information presented on the display element. Therefore the physical dimensions of the view area (length*width) are similar to the physical dimensions of the LCD display. The other area, which is situated for example around the view area or above or below the view area can be for example shiny or varnished as this does not affect the visibility of the presented information.
The display window is generally unitary, i.e. that the basic structure of the display window incorporating the view area and the matt outer surface is one part.
The invention furthermore relates to a moulding tool for producing a display window covering a display element. The moulding tool has a first part having a recess configured to define a front face of the display window wherein at least a portion of the first part of the moulding tool has a matt surface structure. The moulding tool also has a second part for defining the back part of the display window. The moulding tool has means for releasably bringing the first and second parts into co-operation and the first and second parts co-operate to define the shape and surface of the display window.
According to another aspect of the invention there is provided a method for manufacturing a moulding tool which is used for producing a display window with an outer surface and an inner surface by an injection moulding process. In a first step a recess is configured and dimensioned in the first part of the moulding tool to define a front face of the display window. In a second step electro-eroding is used to provide a matt surface structure on at least a portion of the first part of the moulding tool.
Electro-eroding is a well-known and cheap method to hollow out steel for moulding tools. Electro-eroding can be used to form the recess in the moulding tool and to give a finish to the surface of the moulding tool, i.e. applying a matt structure to the surface of the moulding tool, that will be copied to the front face of the display window during injection moulding.
REFERENCES:
patent: 5224049 (1993-06-01), Mushabac
patent: 5354397 (1994-10-01), Miyake et al.
patent: 5728328 (1998-03-01), Senda et al.
patent: 2548380 (1977-05-01), None
patent: 3345014 (1985-06-01), None
patent: 3421521 (1985-12-01), None
patent: 29613292 (1996-10-01), None
patent: 156246 (1985-10-01), None
patent: 0219700 (1987-04-01), None
patent: 0456822 (1991-11-01), None
patent: 0685247 (1995-12-01), None
patent: 58-003842 (1983-01-01), None
patent: 727920 (1995-01-01), None
patent: 7290652 (1995-11-01), None
patent: 9251188 (1997-09-01), None
patent: 10206603 (1998-08-01), None
patent: 10300902 (1998-11-01), None
Antonelli, Terry, Stotu & Kraus, LLP
Nokia Mobile Phone Limited
Sikder Mohammad
LandOfFree
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