Patent Application
20070258268
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.
Referring to
The protrusion 220 can have an appearance formed by inclined surfaces 221 and 222. In addition, an upper surface of the protrusion 220 can be formed as a rough surface. In a specific embodiment, the rough surface can have a predetermine curvature.
In embodiments, the protrusion 220 can have a triangular or trapezoidal cross-section.
In detail, the protrusion 220 can include a first surface 221 and a second surface 222, and a surface 223 formed on an upper portion of the protrusion having a plurality of furrows for refracting and scattering introduced light. The surface 223 in which the plurality of furrows is arranged can be formed rough because of the formation of predetermined curves, which can be formed regularly or irregularly.
In more detail, a plurality of protrusions 220 can be arranged in stripes on the body 210. A surface, in which a plurality of furrows having a fine size is arranged, can be formed on an upper portion of the protrusion 220. The surface in which the plurality of furrows is arranged is referred to as a ‘furrow pattern 223’.
The furrow pattern 223 can be consecutively formed in a length direction of the protrusion.
A method for manufacturing the furrow pattern 223 according to an embodiment of the present invention will be described with reference to
The surfaces 221 and 222 constituting the protrusion 220 can be provided in a shape inclined at a predetermined angle with respect to the surface of the body 210. The furrow pattern 223 can be formed in upper portions of the first and second surfaces 221 and 222.
The body 210 can include a plastic film formed of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), aligned polypropylene, polycarbonate, or triacetate, but is not limited thereto.
For example, a polyester film such as a Tetron™ film or a MELINEX™ film can be used as a substrate.
The protrusion 220 can be formed of ultraviolet (UV)-curable acrylate or a thermosetting resin and coated on a surface of the body 210.
The protrusion 220 condenses, diffuses, or reflects light introduced to the body 210. The light condensed or diffused by the protrusion 220 moves to the LC display panel. The light reflected by the protrusion 220 is reflected again by the body 210 or another portion of the protrusion 220, and condensed or diffused through the protrusion 220.
Since optical characteristics of light such as transmittance, brightness, refraction, and diffusion change depending on the shape of the protrusion formed on the optical sheet, the shape of the protrusion 220 of the optical sheet according to a first embodiment of the present invention will be described below.
Referring to
Referring to
The furrow pattern 223 can be formed parallel to a horizontal line, that is, parallel to one surface of the body 210 and has a rough surface. The furrow pattern 223 can have the rough surface with predetermined curves, and can be formed on the first surface 221 and/or the second surface 222.
In a further embodiment, a plurality of protuberances can be formed irregularly in a surface of the furrow pattern 223.
Accordingly, in an embodiment, an optical sheet can include a body 210 and a protrusion 220 formed on the body 210 having at least two surfaces 221 and 222. At least one surface of the protrusion 220 has a rough surface, so that upper portions of the surfaces 221 and 222 have a furrow pattern 223.
It is known that light incident on a surface of a medium is transmitted or refracted according to the relationship between the incident angle and a critical angle determined by the refractive index of the medium according to optical characteristics at a boundary between media having different refractive indexes.
In this aspect, examination of the optical characteristics of an optical sheet according to the present invention shows that light incident to the furrow pattern 223 is diffused and transmitted. That is, a portion of light having been introduced into the optical sheet according to an embodiment of the present invention moves to the furrow pattern 223 and is scattered and diffused to the LC display panel located above the optical sheet.
In the case where a predetermined defect is present inside an optical sheet, a predetermined dark spot, which is a region where diffusion or condensing of light by refraction of light is not swiftly performed and thus light is not emitted, may be observed. However, in an optical sheet having a furrow pattern 223 according to an embodiment of the present invention, light introduced to the furrow pattern 223 is scattered and emitted by the rough surface of the furrow pattern 223, and accordingly, a defect in the optical sheet can be supplemented.
Referring to
As described above, the furrow pattern 223 formed in the optical sheet according to an embodiment of the present invention increases a light-scattering effect and can supplement a defect that can exist inside the optical sheet.
The width ‘w1’ of the furrow pattern 223 and the lower width ‘w2’ of the protrusion 220 illustrated in
As described above, it can be expected that the optical sheets illustrated in
Table 1 shows measurement results obtained by carrying out an experiment on optical characteristics depending on the width of a furrow pattern in accordance with embodiments of the present invention. In the experiment described in Table 1, P1 is an optical sheet having a furrow pattern with a width ‘w1’ in the range of 12-15 μm, P2 is an optical sheet having a furrow pattern with a width ‘w1’ in the range of 7-10 μm, and P3 is an optical sheet having a furrow pattern with a width ‘w1’ in the range of 3-5 μm.
Optical sheets having a size used for a 17-inch LCD device are used for the experiment, and the distance ‘w2’ between the protrusions is about 25 μm.
The optical sheets illustrated in
Because the furrow pattern according to an embodiment of the present invention has a roughly formed surface on an upper portion of the protrusion, the width ‘w1’ of the furrow pattern may not be maintained constant. Accordingly, the width ‘w1’ of the furrow pattern can be described to have a predetermined range. For example, the width ‘w1’ can be described as 12-15 μm, 3-5 μm, or 7-10 μm according to embodiments of the present invention.
Referring to Table 1, as the width ‘w1’ of the furrow pattern is reduced, that is, the furrow pattern is formed in a decreasing size on the upper portion of the protrusion, haze and brightness increase rate both increase, but transmittance gradually reduces.
That is, according to an embodiment of the present invention, it may be desirable that the furrow pattern has a width ‘w1’ of 3-5 μm in order to enhance brightness of the LCD device even more.
Table 2 shows results obtained by measuring a viewing angle for optical sheets P1, P2, and P3 used in Table 1.
Referring to Table 2, as the width ‘w1’ of the furrow pattern gradually reduces, that is, the area of the protrusion that is occupied by the furrow pattern gradually reduces, the horizontal viewing angle and the vertical viewing angle become reduced.
Therefore, it may be desirable to use an optical sheet according to an embodiment of the present invention, such as P1 having a width ‘w1’ of 12-15 μm, in order to widen the viewing angle of an LCD device. As described above, it may be desirable to use an optical sheet according to an embodiment of the present invention, such as P3 having a width ‘w1’ of 3-5 μm, in order to enhance the brightness of the LCD device.
Detailed numerical values are given by the graphs shown in
Referring to
In detail, the optical sheet 300 can include a plurality of protrusions 320 protruding to a predetermined height on the body 310, where the protrusions 320 are separated a predetermined distance from each other.
Also, a protrusion 320 can include surfaces 321 and 322 inclined at a predetermined angle with respect to the surface of the body 310, and a first furrow pattern 323 formed to a predetermined height of the surfaces 321 and 322, where the first furrow pattern 323 has a rough surface.
A second furrow pattern 330 for increasing a scattering effect of moving light can be formed in a predetermined space between the protrusions 320. The second furrow pattern 330 can be described as being formed in a portion of the surface of the body 310.
The cross-section observed along a line 17A-17B of
Referring to
First, referring to
The lamp unit 440 can include a lamp 441 for generating light, and a lamp reflector 442 surrounding the lamp 441. The light generated by the lamp 441 is incident to a light guide plate 420 of the light plate.
The lamp reflector 442 reflects light generated by the lamp 441 to the light guide plate 420, thereby increasing an amount of light incident to the light guide plate 420.
Also, the light guide unit according to an embodiment of the present invention can include a reflector 430, the light guide plate 420, and an optical sheet 410. The optical sheet 410 may be an optical sheet according to the first embodiment or the second embodiment as described with respect to
The light guide plate 420 can be provided on one side of the lamp unit 440 to guide the light generated from the lamp unit 440 to the LC display panel.
The reflector 430 can be provided on a lower surface of the light guide plate 420 to reflect light leaking from the light guide plate 420 back to the light guide plate 420.
An optical sheet 410 for enhancing optical characteristics of the light guided by the light guide plate 420 can be provided at an upper surface of the light guide plate 420.
Referring to
In this embodiment, two optical sheets 511 and 512 according to the first embodiment or the second embodiment of the present invention as shown in
The graphs regarding experiment results shown in
Table 3 shows a brightness increase rate for the case where one P3 optical sheet whose furrow pattern has a width ‘w2’ of 3-5 μm is used, a brightness increase rate for the case where two P3 optical sheets are used, and a brightness increase rate for the case where a diffusion sheet+a BEF™+a protection sheet are used.
Here, the combination of the diffusion sheet+the BEF™+the protection sheet denotes optical sheets used for a related art backlight assembly. The BEF™ is a prism sheet by 3M Co.
The measurement results show brightness for the case where one optical sheet according to an embodiment of the present invention is used is 1.40, and brightness for the case where two optical sheets according to an embodiment of the present invention is used is 1.43, which is relatively greater.
Also, it is revealed that the case where one optical sheet according to an embodiment of the present invention is used shows almost the same brightness increase rate as that of the case where the diffusion sheet and the protection sheet are used together with the prism sheet by 3M Co.
That is, even in the case where only one optical sheet according to an embodiment of the present invention is used, a brightness increase similar to a brightness increase of the case where related art three sheets of the diffusion sheet, the prism sheet, and the protection sheet are used can be obtained. Furthermore, in the case where two optical sheets according to an embodiment of the present invention are used, greater brightness increase rate can be obtained.
Table 4 shows a viewing angle for the case where a P3 optical sheet is used, a viewing angle for the case where two P3 optical sheets are used, and a viewing angle for the case where related art diffusion sheet and protection sheet are used together with the prism sheet by 3M Co.
Measurement results show a horizontal viewing angle for the case where two optical sheets according to an embodiment of the present invention are used is relatively smaller than a horizontal viewing angle for the case where one optical sheet according to an embodiment of the present invention is used. However, a vertical viewing angle for the case where two optical sheets are used is relatively greater than a vertical viewing angle for the case where one optical sheet is used.
On the other hand, in the case where the diffusion sheet, the protection sheet, and the prism sheet are used, a horizontal viewing angle is widest but is not greatly different from a horizontal viewing angle for the case where one diffusion sheet according to an embodiment of the present invention is used.
Also, a vertical viewing angle for the case where one optical sheet according to an embodiment of the present invention is used is not greatly different from a vertical viewing angle for a related art case.
The backlight assembly 600 of an LCD device according to the third embodiment of the present invention can include a lamp unit 640 for generating light, and a light guide unit for guiding the light generated by the lamp unit 640 to an LC display panel. The lamp unit 640 can include a lamp 641 for generating light, and a lamp reflector 642 surrounding the lamp 641. The light guide unit can include a light guide plate 620 to which the light generated from the lamp 641 is incident, and a reflector 630 for reflecting the light leaking from the light guide plate 620 back to the light guide plate 620.
Two optical sheets 611 and 612 formed according to the first embodiment or the second embodiment as shown in
That is, as shown in
In another embodiment, referring to
An optical sheet 710 formed according to the first or second embodiment as shown in
Particularly, the optical sheet 710 is disposed such that the protrusion faces the light guide plate 720. Light that has passed through the light guide plate 720 is not incident to a body first, but incident to the protrusion and a furrow pattern formed in the optical sheet 710, and then emitted through the body.
Also, although not shown, a related art diffusion sheet, prism sheet, or protection sheet can be further provided in the backlight assembly.
However, since the optical sheet alone according to an embodiment of the present invention can sufficiently perform the function of the related art diffusion sheet or prism sheet, an excellent effect can be obtained in aspects of a viewing angle and brightness using the optical sheet of the present invention alone.
Referring to
The lamp unit 840 can include a lamp 841 for generating light, and a lamp reflector 842 surrounding the lamp 841. The light generated by the lamp 841 is incident on the light guide plate 820. For reference, the light guide plate 820 may also be called a diffusion plate, but is referred to as a light guide plate in this description.
The lamp reflector 842 reflects the light generated by the lamp 841 to the light guide plate 820 to increase an amount of the light incident to the light guide plate 820.
The diffusion unit includes the light guide plate 820 and an optical sheet 810. The light guide plate 820 is disposed on the upper surface of the lamp unit 840 to diffuse the light generated from the lamp unit 840 and guide the diffused light to an LC display panel.
Because the light guide plate 820 is disposed on the upper surface of the lamp unit 840, the light leaking from the light guide plate 820 can be introduced back to the light guide plate 820 by the lamp reflector 842.
Also, the optical sheet 810, which increases the optical efficiency of light directed by the light guide plate 820, can be disposed on the upper surface of the light guide plate 820. The optical sheet 810 can be an optical sheet formed according to the first or second embodiment as shown in
First, referring to
The guide rolls can include a first guide roll 930a, a second guide roll 930b, a third guide roll 930c, a fourth guide roll 930d, and a fifth guide roll 930e. The number and positions of the guide rolls can change depending on modifications to the apparatus.
The apparatus for manufacturing the optical sheet can further include a pattern molding unit 940 provided, for example, between the third guide roll 930c and the fourth guide roll 930d to coat a patterned coating solution on the base film 910. The pattern molding unit 940 can serve as a pattern roll.
In detail, the pattern molding unit 940 can include: a forming mold 942 having a pattern shape; a drum roll 944 for allowing an injected coating solution to stick on the forming mold 942, to pattern the coating solution using the pattern provided to the forming mold 942, and coat the patterned coating solution onto the base film 910; and pattern guide rolls 946a and 946b for transferring the forming mold 942 about the pattern molding unit 940.
The forming mold 942 can be formed in a belt type by coating a patterned layer on a base layer of a film shape. Like the above-described pattern roll, the forming mold 942 patterns the coating solution.
Although
The forming mold 942 can be installed by surrounding an extending line connecting the drum roll 944 with the pattern guide rolls 946a and 946b using the forming mold 942 and connecting both ends of the forming mold 942.
Because a joint formed by connecting both ends of the forming mold 942 can have a remarkably longer period than that of a joint of a related art pattern roll, a period of a pattern defect generated at a joint portion can also be lengthened, so that yield of a completed optical sheet 912 can be improved.
It can be sufficient to form the forming mold 942 longer and form a longer interval between the drum roll 944 and the pattern guide rolls 946a and 946b in order to lengthen the period of the joint.
The apparatus for manufacturing an optical sheet according to an embodiment of the present invention can further include a coating solution injecting element 960 for injecting a coating solution to a region inserted into the pattern molding unit 940, and a curing element 970 for applying heat or illuminating ultraviolet (UV) to cure the coating solution.
An operation of an apparatus for manufacturing an optical sheet according to an embodiment of the present invention will be described below.
The base film 910 wound on the first roll 920 can be transferred towards the second roll 950 by the guide rolls 930a to 930e. In addition, the forming mold 942 provided to the pattern molding unit 940 can be transferred about the pattern molding unit 940 and rotated by being wound on the drum roll 944 and the pattern guide rolls 946a and 946b.
Also, since the drum roll 944 can be engaged with the third guide roll 930c and the fourth guide roll 930d, the base film 910 can contact the forming mold 942 through the third guide roll 930c.
Here, the third guide roll 930c can perform a gap control function of controlling the thickness of the coating solution coated on the base film 910 for controlling the thickness of the pattern layer of a completed optical sheet.
In detail, when the third guide roll 930c is closely attached on the drum roll 944, the thickness of the pattern layer of the optical sheet becomes thin. On the other hand, when the third guide roll 930c is separated apart from the drum roll 944, the thickness of the pattern layer of the optical sheet becomes thicker. The thickness of the pattern layer (e.g., a protrusion) of the optical sheet can be controlled using viscosity of the coating solution, pattering speed, and tensile force of the base film in addition to the interval between the third guide roll 930c and the drum roll 944.
The coating solution can be injected by the coating solution injecting element 960 to a predetermined region where the base film 910 is inserted between the third guide roll 930c and the drum roll 944. The coating solution is pushed into a space between the pattern of the forming mold 942 and fills the pattern.
Also, the coating solution can be uniformly distributed on the base film 910 by the pressure between the third guide roll 930c and the drum roll 944, so that pattern forming occurs. The coating solution distributed between patterns can then be cured using heat or UV emitted from the curing element 970.
The base film 910 on which the pattern-formed coating solution is cured and coated can be separated from the forming mold 942 while it is drawn out by the fourth guide roll 930d. The completed optical sheet 912 can be transferred by the fifth guide roll 930e and wound on the second roll 950.
Here, the fourth guide roll 930d separates the optical sheet 912 on which the coating solution has been coated from the forming mold 942. In other words, the fourth guide roll 930d separates the optical sheet 912 on which the pattern layer has been formed from the forming mold 942.
The above-described base film 910 and completed optical sheet 912 according to the above described embodiment of the present invention denote the same element, and their names are classified depending on whether the coating solution has been coated or not.
That is, the base film 910 means a state before the pattern is formed, and the optical sheet 912 means a state where the pattern-formed coating solution is coated on the base film while it passes through the pattern molding unit 940.
Also, although
The forming mold can have a two-story structure of a base layer 942a having a continuous flat surface of a relatively uniform thickness, and a pattern layer 942b including a fine shape carved on at least one surface of the base layer 942a. The pattern layer 942b should be provided in a shape reverse to the pattern of the optical sheet to be manufactured.
In this case, the pattern layer 942b illustrated in
The base layer 942b of the forming mold 942 can be formed of a transparent and flexible film having predetermined tensile strength and durability. In a specific embodiment, the base layer 942b can be formed of a polyethyleneterephthalate (PET).
In an embodiment, the resin material constituting the pattern layer 942b can be a mixture of high polymer such as oligomer and curing start agent.
The various embodiments of the present invention can obtain excellent effects in aspects of optical characteristics such as brightness and a viewing angle.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-41252 | May 2006 | KR | national |
