Optical waveguides – Optical fiber bundle – Fiber bundle plate
Reexamination Certificate
2002-08-29
2004-09-28
Ullah, Akm Enayet (Department: 2874)
Optical waveguides
Optical fiber bundle
Fiber bundle plate
C385S147000, C359S290000, C365S120000
Reexamination Certificate
active
06798959
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display device and a method for producing the same. In particular, the present invention relates to a display device provided with a substrate which has actuator elements, an optical waveguide plate, crosspieces which is interposed between the optical waveguide plate and the substrate and which surround the actuator elements, and picture element assemblies which are joined onto the actuator elements. The present invention also relates to a method for producing the same.
2. Description of the Related Art
Those hitherto known as the display device include, for example, cathode ray tubes (CRT) and liquid crystal display devices.
Those known as the cathode ray tube include, for example, ordinary television receivers and monitor units for computers. Although the cathode ray tube has a bright screen, it consumes a large amount of electric power. Further, the cathode ray tube involves a problem such that the depth of the entire display device is large as compared with the size of the screen.
The liquid crystal display device is advantageous in that the device is thin, and the display device consumes a small amount of electric power. However, the liquid crystal display device involves such problems that it is inferior in brightness or luminance of the screen, and the field angle of the screen is narrow.
In the case of the cathode ray tube and the liquid crystal display device, it is necessary for a color screen to use a number of picture elements (image pixels) which is three times a number of picture elements used in a black-and-white screen. For this reason, other problems also arise such that the device itself is complicated, a great deal of electric power is consumed, and the cost is high.
In view of the above, in order to solve the problems as described above, a new display device
200
has been suggested. As shown in
FIG. 20
, the display device
200
comprises an actuator substrate
202
, an optical waveguide plate
204
, and a plurality of crosspieces
206
allowed to be interposed between the actuator substrate
202
and the optical waveguide plate
204
. The optical waveguide plate
204
and the crosspieces
206
are joined to one another by the aid of an adhesive
207
. The actuator substrate
202
has actuator elements
208
each of which is displaceable toward the actuator substrate
202
or toward the optical waveguide plate
204
at a position surrounded by the plurality of crosspieces
206
. A unit dot
212
is constructed by the actuator element
208
and a picture element assembly
210
which is provided on the actuator element
208
. The display device
200
is provided with a plurality of unit dots
212
.
In the display device
200
described above, the picture element assembly
210
is softened mainly due to the heat generated, for example, by the driving of the actuator element
208
, the light
214
introduced into the optical waveguide plate
204
, and the driving circuit related to the image display.
Further, the picture element assembly
210
is continuously pressed to make contact with the optical waveguide plate
204
in accordance with the driving of the actuator element
208
. As a result, the concave/convex shape or irregular texture on the surface of the picture element assembly
210
, which is formed in order to improve the response characteristics of the picture element assembly
210
to make the contact/separation with respect to the optical waveguide plate
204
, is progressively changed to be flat.
The adhesion suppressant, which is previously added to the picture element assembly
210
and which remains even after the curing of resin, gradually seeps out from the picture element assembly
210
in association with the contact/separation operation of the picture element assembly
210
with respect to the optical waveguide plate
204
. The adhesion suppressant adheres to the optical waveguide plate
204
, resulting in the occurrence of the white defect in which the adhered matter glows white.
As a result, the response performance of the contact/separation of the picture element assembly
210
with respect to the optical waveguide plate
204
may be deteriorated, and the picture element assembly
210
may fail to make separation from the optical waveguide plate
204
any longer to cause the change into the bright defect of such a state that the light is always emitted, or the white defect level on the display may be gradually changed to cause any fluctuation in the image display ability.
Problems will now be enumerated in detail below. In order to stabilize the image display, it is necessary that the surface shape of the picture element assembly
210
is not changed. Specifically, it is necessary that the surface shape is not changed in an atmosphere represented by a temperature (heat resistance) of about 60° C.
The heat resistance (Tg) of the resin after the curing is low in the present resin system (resin system of the picture element assembly
210
). Therefore, it is impossible to suppress the change in shape of the resin due to the heat even when the heating treatment is performed beforehand. As a result, when the driving of the actuator element
208
is continued after the heating treatment, the surface shape of the picture element assembly
210
is gradually changed.
When a resin of the thermosetting type is used as the picture element assembly, the heat resistance (Tg) of the resin is improved, if the heating treatment is performed. Therefore, it is inevitable to perform any heating treatment in the process steps. However, if a resin in an uncured state is directly subjected to the heating treatment, there are some problems.
Firstly, the viscosity of the resin and/or the adhesion suppressant in the picture element assembly precursor is strikingly lowered by the heating. Even when the adhesion suppressant seeps out from the resin due to the incompatibility between the resin and the adhesion suppressant, the mutual leveling is consequently caused without forming any concave/convex structure. As a result, the surface shape of the picture element assembly
210
becomes flat.
Secondary, if an adhesion suppressant, which is prepared to have a high viscosity, is added in order to suppress the leveling, the effect to suppress the adhesion may be lowered. Further, it is difficult to wash out the seeped adhesion suppressant having the high viscosity in the washing step to be performed thereafter. The white defect may be caused on the display.
Finally, the resin may be cured without any sufficient seepage of the adhesion suppressant from the resin, the surface shape of the picture element assembly
210
may become flat, and it is impossible to obtain any sufficient effect to cause the release from the optical waveguide plate
204
.
Consequently, a delay may occur in the response of the contact/separation of the picture element assembly
210
with respect to the optical waveguide plate
204
, or the state (bright defect), in which no separation takes place, may arise.
It has been revealed that the heat resistance of the resin itself has the greatest influence, as the factor to bring about the change in shape of the resin as described above.
The factor to cause the change in level of the white defect on the display includes the fact that the adhesion suppressant, which has remained in an excessive amount in the picture element assembly
210
, seeps out to remain on the optical waveguide plate
204
. This phenomenon is caused as follows. A large amount of the adhesion suppressant remains in the picture element assembly
210
. When the picture element assembly
210
is pressed to make contact with the optical waveguide plate
204
in accordance with the driving of the actuator element
208
, the adhesion suppressant gradually seeps out in such a way that the adhesion suppressant is squeezed out to adhere to the optical waveguide plate
204
. As a result, the fluctuation of the white defect level on the display (to gradually become white) is caused.
Further, the adhesion
Nanataki Tsutomu
Shimogawa Natsumi
Takeuchi Yukihisa
Yamamoto Kazuhiro
Burr & Brown
NGK Insulators Ltd.
Ullah Akm Enayet
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