Illumination – Revolving
Reexamination Certificate
2003-01-08
2004-08-10
Cariaso, Alan (Department: 2875)
Illumination
Revolving
C362S026000, C362S551000, C362S581000
Reexamination Certificate
active
06773127
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical film of a back light module, more particularly, to a positioning structure which can avoid wrinkles of the optical film when heated.
BACKGROUND OF THE INVENTION
With rapid advancement of the fabrication technology of thin film transistors, a liquid crystal display (LCD) is largely applied in various electronic products such as a Personal Digital Assistant (PDA) device, a notebook computer, a digital camera, a video camera, and a mobile phone due to the fact it has advantages of smaller size, lighter weight, lower power consumption and low radiation. Moreover, since manufacturers aggressively invest in research & development and employ large-scale fabricating equipment, the quality of the LCD is unceasingly improved and the price thereof is continuously decreased. That promptly broadens the applied fields of the LCD.
Since the LCD is not a light-emitting display apparatus, it can only perform a display function with the aid of a back light module. Please refer to
FIG. 1
illustrating a sectional view of the back light module
10
. The back light module
10
comprises a light guiding plate
11
, a reflective plate
12
, a lamp
13
, an optical film
14
consisting of a plurality of thin films and an aluminum back cover
15
. The light guiding plate
11
is an injected or extruded acrylic sheet and circular, hexagonal or square pellet patterns as diffusion dots
16
for scattering light are formed by screen printing or direct injection on the bottom surface thereof. The reflective plate
12
is disposed beneath the light guiding plate
11
and can reflect the light entering into the bottom surface of the light guiding plate
11
so as to return the light to the light guiding plate
11
to increase utilization of light. The lamp
13
is disposed at the side of the light guiding plate
11
and is generally composed by a cold cathode fluorescent lamp (CCFL) and sends light out into the light guiding plate
11
in a manner of end illuminating. The optical film
14
is placed on the top surface of the light guiding plate
11
and the composition and function thereof will be described thereinafter. The aluminum back cover
15
is mounted at the bottom and the side of the back light module
10
for protecting the back light module
10
and the elements therein.
Referring to
FIG. 2
, which is a schematic sectional diagram of the optical film
14
of the back light module
10
, the optical film
14
consists of a plurality of the thin films and is placed on the top surface of the light guiding plate
11
. The thin films include a lower diffusion sheet
141
, a prism sheet
142
, a reflective polarizing film
142
and an upper diffusion sheet
144
. The optical film
14
can be composed by appropriate thin films based on functions providing by the thin films and practical demands. Therefore, the composition of the thin films in
FIG. 2
is merely one type of combinations of the optical film
14
.
Since the optical film
14
is a thin film made of plastics and the thickness thereof is about between 0.1 and 0.2 mm, a positioning means is needed to fix the optical film
14
on the top surface of the light guiding plate
11
so as to avoid displacement or coming off resulting from transportation or assembly, and to reduce re-adjusting time of the optical film
14
during the back light module is assembled. Furthermore, when the back light module is conducted with a reliability test such as falling or vibration, etc., the optical film
14
is liable to displace and bad quality in appearances of pictures such as dark lines or bright lines is produced, if the fixing effect of the positioning means are not good.
Referring to
FIG. 3
, which is a schematic diagram (including a partially top view and a partially side view) of a positioning means for an optical film
30
in a first prior art, the optical film
30
is a rectangular planar thin film. At least one flange
33
is respectively disposed at two corresponding edges of the optical film
30
, i.e. a first edge
31
and a second edge
32
. By means of combination of the flanges
33
and the positioning means
34
, the optical film
30
is fixed on the light guiding plate
11
. In
FIG. 3
, two flanges
33
a
,
33
b
are respectively mounted near two ends of the first edge
31
of the optical film
30
, and a flange
33
c
is mounted in the middle of the second edge
32
. Certainly, the number and location of the flanges are merely one embodiment in the prior art. The optical film
30
can also have four flanges which are respectively disposed at the two edges of the optical film
30
in a manner of symmetry or other kinds of design. The positioning means
34
not only can carry the flanges
33
but also can has the function to fix the flanges
33
so as to prevent movement of the optical film
30
.
In
FIG. 3
, troughs
341
are mounted at locations of the positioning means
34
corresponding to two flanges
33
a
,
33
b
. The height of the troughs
341
is exactly equal to the thickness of the optical film
30
. Hence, after the flanges
33
of the optical film
30
is placed at the troughs
341
, the flanges and the height of the troughs
341
are at the same level. Then, adhesive tapes
35
are stuck on the top surface of the flanges
33
to have the optical film
30
fixed indeed without displacement. Since the manner of fixing the positioning means
34
is to firmly fix the flanges
33
by the tapes
35
in the troughs
341
, a relative displacement between the flanges
33
and the troughs
341
will not take place even if the temperature or humidity of the environment is changed. This results in unfree extension of any two sides of the optical film
30
due to fixation of the tapes, after the optical film
30
is heated. Hence, upwardly arched wrinkles will be produced in the middle of the optical film
30
, and thus uneven brightness of the image pictures of the LCD will happen.
Referring to
FIG. 4
, which is a schematic diagram (including a partially top view and a partially side view) of a positioning means for an optical film
30
in a second prior art, the same portion of the positioning means as that of the first prior art will not be reiterated. In
FIG. 4
, a first flange
36
at the first edge
31
of the optical film
30
has a round aperture
361
, and a second flange
37
along the direction of a Y axis has a slot
371
. Certainly, the locations of the round aperture
361
and the slot
371
therein can be interchanged. A positioning pin
342
is mounted at a trough
341
of the positioning means
34
corresponding to the round aperture
361
of the first flange
36
, and a guiding shaft
343
are mounted corresponding to the slot
371
of the second flange
37
. The fixing manner of the positioning means
34
for the optical film
30
is to have the first flange
31
and the second flange
37
of the first edge
31
respectively disposed in the corresponding troughs
341
, to have the positioning pin
342
and the guiding shaft
343
respectively inserted into the round aperture
361
and the slot
371
, and to have a third flange
38
of the second edge
32
disposed in the corresponding trough
341
. Furthermore, three bridges
39
are employed to respectively constrain the three flanges
36
,
37
, and
38
at the two edges of the optical film
30
in the troughs
341
, wherein enough gaps are retained between the bridges
39
and the top surface of the optical film
30
to provide deformation space of the optical film
30
along the direction of a Z axis perpendicular to the surface of the optical film
30
after the optical film
30
is heated. Appropriate gaps are also retained between the positioning means
34
and the first and second edges
31
,
32
of the optical film
30
to provide deformation space of the optical film
30
along the direction of an X axis after the optical film
30
is heated. In addition, the slot
371
of the second flange
37
mounted along the direction of a Y axis provides deformation space of the optical film
30
along
Cariaso Alan
HannStar Display Corp.
Troxell Law Office PLLC
Tsidulko Mark
LandOfFree
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