JP2009181068A - Optical sheet, backlight device, display device, and optical sheet production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent detachment of an optical diffusion film and an optical film, which are provided to an optical sheet, even when these films are integrated. <P>SOLUTION: The optical sheet 31 includes the optical diffusion film 32 where one side serves as a light incoming side 32b for receiving light from a light source part and another side serves as a light outgoing side and which diffuses light of the light source part, a translucent base material 36 having a light outgoing side 36a which is arranged on the outgoing side 32a and transmits and emits light from the optical diffusion film 32, and a plurality of optical elements 37 which are integrated to the outgoing side 36a of the translucent base material 36 and collect light outgoing from the outgoing side 36a. The optical diffusion film 32 and translucent base material 36 are made of the same resin material and are integrated with the peripheral parts welded in the side direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical sheet, a backlight device including the optical sheet, a display device, and a method for manufacturing the optical sheet.

A conventional display device such as a liquid crystal television, which has been reduced in thickness, includes a backlight device that emits planar light toward an image display unit such as a liquid crystal panel as disclosed in Patent Document 1, for example. There is. This type of backlight device includes, for example, a light source, a light diffusion film that diffuses light from the light source, and a lens that focuses the diffused light so as to be directed in a specific direction (for example, a normal direction to the display screen). It is comprised from the optical sheet which laminated | stacked the sheet | seat (optical film).
In general, in an optical sheet, a light diffusion film and a lens sheet are made of different materials.
JP 2007-76069 A

  By the way, in patent document 1, although the optical sheet which bonded and integrated the light-diffusion film and the lens sheet is proposed, since the light-diffusion film and the lens sheet are comprised with a different material, these The characteristics of warping are different. For this reason, for example, when the optical sheet is heated by a light source when the optical sheet or the display device is manufactured or used as a display device, the light diffusion film and the lens sheet are subjected to thermal diffusion. There is a possibility that the film and the lens sheet may be separated from each other. In addition, when a light-diffusion film and a lens sheet peel from each other, the optical characteristic as an optical sheet will change.

  The present invention provides an optical sheet that can prevent the peeling even when the light diffusion film and the optical film are integrated, a backlight device including the optical sheet, a display device, and a method for manufacturing the optical sheet. With the goal.

In order to solve the above problems, the present invention proposes the following means.
The optical sheet of the present invention has a light diffusion film that diffuses the light of the light source unit, with one surface serving as an incident surface on which light from the light source unit is incident and the other surface serving as a light exit surface. An optical film that is laminated on the exit surface of the diffusion film and controls light emitted from the exit surface, and the optical film is disposed on the exit surface side of the light diffusion film and from the light diffusion film A translucent substrate having an exit surface that transmits and emits light, and the translucent substrate provided integrally with the exit surface of the translucent substrate so as to protrude from the exit surface of the translucent substrate A plurality of optical elements that collect light emitted from the exit surface of the transmissive substrate, and the light diffusing film and the light transmissive substrate are made of the same material, and the light diffusing film and the light transmissive At least one of the peripheral edges in the surface direction. Characterized in that it is integrated by welding.

According to the optical sheet of the present invention, since the light diffusion film and the translucent base material are integrated, the process of incorporating the light diffusion film and the translucent substrate into the display device can be completed once, and the assembly process can be easily performed. it can.
Moreover, the improvement of the peeling strength between these can be aimed at by comprising the light-diffusion film and the translucent base material integrated with the same material. And, for example, the optical sheet is heated by the light source part when manufacturing the optical sheet or a display device including the optical sheet, and the light diffusion film and the translucent substrate are thermally deformed. Even if it occurs, since the warp characteristics of the light diffusion film and the translucent substrate are the same, no stress is generated between the light diffusion film and the optical film. Therefore, peeling of the light diffusion film and the optical film can be prevented, and a change in optical characteristics of the optical sheet can be prevented.

And in the said optical sheet, it is preferable to comprise the said light-diffusion film and the said translucent base material with the same resin material, and to weld the said light-diffusion film and the said translucent base material with a laser beam.
Furthermore, in the said optical sheet, it is more preferable that the same resin material which comprises the said light-diffusion film and the said translucent base material is a methyl methacrylate styrene copolymer (MS).

And in the said optical sheet, the level | step-difference part which protrudes in the said surface direction or the hollow may be formed in the peripheral part of the surface direction of the said light-diffusion film and the said optical film.
When manufacturing a display device including an optical sheet, the optical sheet is incorporated into a casing that supports the peripheral edge of the optical sheet. However, since the optical sheet according to the present invention has the stepped portion, the optical sheet with respect to the casing is formed. Can be easily recognized. Further, by forming a corresponding shape such as an engaging portion that engages with the stepped portion in the casing, the optical sheet can be easily positioned with respect to the casing. Therefore, the optical sheet can be easily incorporated into the housing.

In addition, the backlight device of the present invention includes the optical sheet and a light source unit that is disposed on the incident surface side of the light diffusion film and that emits light toward the incident surface.
Furthermore, the display device of the present invention includes the backlight device, and an image display unit that is disposed on the light exit surface side of the translucent substrate and displays an image using light from the backlight device as display light. It is characterized by becoming.
According to these backlight units and display devices, the same effects as those of the optical sheet described above can be obtained.

The display device includes a casing that supports the optical sheet at a peripheral portion thereof, and a part of the casing includes a thickness of the optical diffusion sheet and the welded portion of the light-transmitting substrate and the thickness of the optical sheet. You may distribute | arrange to the output surface side of the said translucent base material so that it may overlap with a horizontal direction.
According to the display device of the present invention, since the welded portion of the optical sheet is covered and covered by a part of the housing, the welded portion is discolored and the optical characteristics are different from other portions of the optical sheet. Even so, the viewer of the display device can visually recognize a video with no sense of incongruity.

The optical sheet manufacturing method of the present invention includes a light diffusing film that diffuses incident light, a translucent substrate that transmits light emitted from the light diffusing film material, and the light transmissive light that is emitted from the light. A plurality of optical elements that are integrally provided on the light emitting surface of the light transmissive substrate so as to protrude from the light emitting surface of the light transmissive substrate and collect light emitted from the light emitting surface of the light transmissive substrate. A film preparation step for preparing an optical film, and a laminate for forming a plate material for an optical sheet by superimposing the light diffusion film and the optical film so that the light transmissive substrate is disposed on the light diffusion film side. The film preparation comprising: a step and a laser cutting step of irradiating the optical sheet plate material with laser light to cut the optical sheet plate material so as to die-cut individual optical sheets from the optical sheet plate material Process Oite, and forming by the light diffusing film and the light-transmissive base same resin material material.
When cutting the optical sheet plate with laser light, the light diffusion film and the cut portion of the translucent substrate are heated by the laser light, so that the optical sheet is used as a peripheral portion in the surface direction of the optical sheet. On the cut surface of the plate material, the light diffusion film and the translucent substrate are welded to each other.

  The method for producing an optical sheet of the present invention includes a light diffusing film that diffuses incident light, a translucent substrate that transmits light emitted from the light diffusing film material, and the light emitted from the light diffusing film. A plurality of optical elements that are integrally provided on the exit surface of the translucent substrate so as to protrude from the exit surface of the translucent substrate and collect light emitted from the exit surface of the translucent substrate; A film preparation step for preparing an optical film comprising: a plate material for an optical sheet by superimposing the light diffusion film and the optical film so that the light transmissive substrate is disposed on the light diffusion film side A laminating step, a welding step of welding the light diffusion film and the optical film, and a die cutting step of die-cutting individual optical sheets from the optical sheet plate material. diffusion And forming a Irumu and the transparent substrate by the same resin material.

According to the manufacturing method of the optical sheet concerning these inventions, the above-mentioned optical sheet can be manufactured.
In addition, according to these optical sheet manufacturing methods, the optical sheet is stamped at the same time as or after the welding, so that after the light diffusion film and the optical film are individually stamped into the shape of the optical sheet, There is no need to position them by overlapping them, and the optical sheet can be easily manufactured.
When cutting the optical sheet plate with laser light, the optical sheet can be cut from the optical sheet plate and simultaneously the light diffusion film and the translucent substrate can be integrated. The production efficiency of the optical sheet can be improved by reducing the number.

  In the optical sheet manufacturing method, in the laser cutting step or the die cutting step, a stepped portion that protrudes or is recessed in the surface direction from the peripheral edge in the surface direction may be integrally formed on the optical sheet. . In the case where the step portion is formed in the laser cutting step, the step portion can be formed with high accuracy.

  According to the present invention, the optical sheet can be easily incorporated into the display device. Moreover, peeling of a light-diffusion film and a translucent base material can be prevented, and it becomes possible to prevent the change of the optical characteristic of an optical sheet.

Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, an optical sheet according to an embodiment of the present invention will be described together with a backlight device and a display device using the optical sheet.
(First embodiment)
As shown in FIG. 1, the display device 100 according to the first embodiment is configured by providing a liquid crystal display element (image display unit) 13 on the upper side of a backlight device 11 that emits light upward. The liquid crystal display device displays a planar image by emitting display light whose display is controlled by an image signal from the liquid crystal display element 13 upward.
Hereinafter, based on such an arrangement, the upper direction in FIG. 1 may be simply referred to as a display screen side, and the lower direction may be simply referred to as a back side.
The display device 100 is assumed to be a liquid crystal display device including the liquid crystal display element 13. However, if the display device 100 includes at least the optical sheet 31, a projection screen device, a plasma display, an EL display, etc. There is no limitation on the type of display device that displays an image with light.

The liquid crystal display element 13 is configured by sandwiching a liquid crystal 15 between two polarizing plates 17 and 19. The backlight device 11 includes a light source unit 21 and an optical sheet 31 that supplies light H from the light source unit 21 to the liquid crystal 15 of the liquid crystal display element 13.
The light source unit 21 includes a plurality of light sources 23 and a light reflection plate 25. As the light source 23, a light emitting element such as a fluorescent lamp, a halogen lamp, an LED, an EL, or a semiconductor laser can be used. In the case where the light emitting element is an LED, for example, an array of red, green, and blue LEDs may be used. In this case, the light from the LED array may be mixed with a diffuser plate or the like to obtain white light, and this white light may be emitted.
The light reflection plate 25 is arranged on the back side of the plurality of light sources 23, and the light source unit 21 of the backlight device 11 is configured by the plurality of light sources 23 and the light reflection plate 25.

The optical sheet 31 transmits light emitted from the light source 23 and enters the liquid crystal display element 13 and is formed in a substantially rectangular shape in plan view as shown in FIG.
A plurality of protrusions (steps) 34 projecting in the surface direction are formed on the peripheral edge of the optical sheet 31 in the surface direction. Three of these protrusions 34 are formed on a pair of sides (left and right sides in the figure) located on opposite sides. Further, the width dimension and the formation position of the projection 34 along each side are different between the pair of sides, and the width dimension of the projection 34 formed on the left side is the same as that of the projection 34 formed on the right side. It is larger than the width dimension. Further, all the protrusions 34 are formed in a substantially rectangular shape, but one protrusion 34A formed on the left side has a recess 35, and has a shape different from that of the other protrusions 34. .
By forming the protrusions 34 in this way, the front and back of the optical sheet 31 and the vertical and horizontal directions can be easily recognized.

As shown in FIG. 3, the optical sheet 31 is disposed between the light diffusion film 32 disposed between the light source 23 and the liquid crystal display element 13, and between the light diffusion film 32 and the liquid crystal display element 13. An optical film 33 laminated on the light diffusion film 32 is provided. Each of the light diffusion film 32 and the optical film 33 has a planar view shape of the optical sheet 31 described above.
The light diffusing film 32 diffuses light emitted from the light source 23 toward the display screen to reduce unevenness in luminance of the screen based on the plurality of light sources 23, and is formed in a sheet shape. One surface of the light diffusing film 32 forms an incident surface 32b on which light from the light source 23 is incident, and the other surface forms a light emitting surface 32a.

  The light diffusion film 32 has a total light transmittance of 40% or more and 80% or less (in measurement according to JIS K7361-1) and a haze value of 98% or more (in measurement according to JIS K7136). In addition, it is desirable that the resin material is made of a light transmissive material. This is because when the total light transmittance is less than 40%, the luminance on the screen is greatly reduced, and when it exceeds 80%, the diffusion performance is insufficient. Moreover, if the haze value is less than 98%, the diffusion performance is still insufficient.

As the resin material used for the light diffusion film 32, a thermoplastic resin, a thermosetting resin, or the like can be used. In this embodiment, methyl methacrylate styrene copolymer (MS), acrylonitrile styrene copolymer are used. Thermoplastic resins well known in the art such as (AS), polycarbonate (PC), polyethylene terephthalate (PET), polystyrene (PS) are used.
The light diffusing film 32 may be configured, for example, by including light diffusing particles in a transparent resin material that transmits light. In this case, examples of the transparent resin material include those similar to the thermoplastic resin and the thermosetting resin described above.

Furthermore, as the light diffusing particles, transparent particles made of an inorganic oxide or a resin can be used. For example, transparent particles made of an inorganic oxide include particles made of silica, alumina or the like. The transparent particles made of resin include acrylic particles, styrene particles, styrene acrylic particles and cross-linked products thereof; melamine-formalin condensate particles; polytetrafluoroethylene (PTFE), perfluoroalkoxy resin (PFA), tetrafluoroethylene. -Fluoropolymer particles such as hexafluoropropylene copolymer (FEP), polyfluorovinylidene (PVDF), and ethylene-tetrafluoroethylene copolymer (ETFE); silicone resin particles and the like.
In the transparent resin material, only one type may be selected and dispersed from the exemplified light diffusion particles, but two or more types may be mixed and dispersed.

The optical film 33 plays a role of causing the light diffused in the light diffusing film 32 to enter the liquid crystal display element 13 in a specific direction, and is disposed on the emission surface 32a of the light diffusing film 32 and is light transmissive. And a plurality of unit lenses (optical elements) 37 provided integrally on the emission surface 36a. In addition, the emission surface 36a of the translucent substrate 36 indicates a surface on the liquid crystal display element 13 side from which the light K transmitted through the translucent substrate 36 is emitted, and is on the light source unit 21 side on which the light H is incident. The surface forms the incident surface 36 b of the translucent substrate 36.
The translucent substrate 36 is made of the same resin material as the light diffusion film 32. However, as long as the translucent base material 36 is the same resin material as the light diffusion film 32, it may be composed of only a transparent resin material that does not include light diffusion particles, for example, and has a function of diffusing light. It does not have to be.

  Each unit lens 37 collects light emitted from the emission surface 36a of the translucent substrate 36 in a specific direction, and is formed in a lens shape having a convex curved surface so as to protrude from the emission surface 36a. And extends in one direction along the emission surface 36a. 2 and 3, each unit lens 37 is extended in a direction (X direction) orthogonal to the side of the optical sheet 31 on which the projections 34 are formed. For example, the projections 34 are formed. You may extend in the direction (Y direction) parallel to a side. The plurality of unit lenses 37 are arranged at regular intervals in a direction (Y direction in FIG. 2) perpendicular to the extending direction of each unit lens 37 along the emission surface 36a. That is, in this embodiment, the unit lenses 37 each formed in a long shape are arranged in a plurality to constitute a lenticular array as a whole.

The unit lens 37 configured as described above may be molded using, for example, UV or radiation curable resin on the translucent substrate 36, for example, PET, PC, polymethyl methacrylate (PMMA). Further, it may be formed by a well-known extrusion molding method, injection molding method, or hot press molding method using cycloolefin polymer (COP), acrylonitrile styrene copolymer or the like.
And in this optical sheet 31, the light-diffusion film 32 and the translucent base material 36 are integrated by welding the peripheral part of these surface directions (direction along the output surface 32a and the incident surface 36b). Specifically, it is welded over the entire side surfaces 32c and 36c of the light diffusing film 32 and the translucent substrate 36 forming the peripheral edge. In FIG. 3, the welded portion is indicated by a thick line.

As shown in FIGS. 1 and 2, the display device 100 including the optical sheet 31 also includes a housing 41 formed in an annular shape having a substantially rectangular shape in plan view so as to support the optical sheet 31 at the peripheral edge in the surface direction. The housing 41 covers the peripheral edge of the optical sheet 31. Specifically, the housing 41 includes a rectangular cylindrical portion 42 that covers the side surfaces of the light diffusion film 32 and the translucent substrate 36, and a pair of rectangular lid portions 43 that protrude inward from both ends of the rectangular cylindrical portion 42. I have. The pair of rectangular lid portions 43 are respectively provided on the light-emitting film 32 and the light-transmitting substrate 36 at the peripheral edge so as to overlap the welded portion of the light diffusion film 32 and the light-transmitting substrate 36 in the thickness direction of the optical sheet 31. 36a and the incident surface 32b of the light diffusion film. Further, the housing 41 is formed with an engaging portion (not shown) such as a groove that engages with the protrusion of the optical sheet 31, so that the optical sheet 31 can be easily positioned with respect to the housing 41.
In the illustrated example, the housing 41 is configured to support only the optical sheet 31, but may be configured to support the light source unit 21 and the liquid crystal display element 13, for example.

Next, a method for manufacturing the optical sheet 31 will be described below.
When manufacturing the optical sheet 31, as shown in FIGS. 4 and 5, a light diffusion film 32 and an optical film 33 formed of the same resin material are prepared (film preparation step). Note that the light diffusion film 32 and the optical film 33 in this state are formed sufficiently larger than the optical sheet 31 in plan view. Next, the light diffusion film 32 and the optical film 33 are overlapped to form the optical sheet plate 38 so that the light transmissive substrate 36 is disposed on the light diffusion film 32 side (lamination step).

Then, the optical sheet plate 38 is irradiated with the laser beam 51 from the laser irradiation device 50, and the optical sheet plate 38 is cut so that the individual optical sheets 31 are die-cut from the optical sheet plate 38 (laser cutting). Process). Examples of the laser irradiation apparatus 50 used here include a CO ₂ laser and an excimer laser.
In this laser cutting step, the protrusions 34 and the recesses 35 (see FIG. 2) are also formed integrally with the optical sheet 31. By cutting with the laser light 51, the protrusions 34 can be formed with high accuracy. In the laser cutting step, the cut portions of the light diffusing film 32 and the translucent substrate 36 are heated by the laser light 51, so that the optical sheet plate 38 serving as the peripheral portion in the surface direction of the optical sheet 31 is cut. On the surface 38c, the light diffusion film 32 and the translucent substrate 36 are welded to each other.

In this laser cutting process, dust may be generated during cutting and may adhere to the incident surface 32 b of the light diffusion film 32 or the surface of the unit lens 37. Therefore, in the manufacture of the optical sheet 31, between the end of the film preparation step and immediately before the laser cutting step, PET or PET is formed on the incident surface 32b of the light diffusing film 32 and the output surface 36a of the translucent substrate 36. A thin protective film 52 made of polypropylene (PP) is pasted (film pasting step).
These protective films 52 may be peeled off from the optical sheet 31 at least before the optical sheet 31 is incorporated into the display device 100. In addition, it can prevent that the incident surface of the light-diffusion film and the surface of the unit lens 37 are damaged in manufacture of the display apparatus 100 by peeling the protective film 52 after incorporating the optical sheet 31 in the display apparatus 100.

Further, when the display device 100 is manufactured using the optical sheet 31, the orientation of the optical sheet 31 with respect to the housing 41 is set with reference to the formation positions of the protrusions 34 and the recesses 35, and the optical sheet 31 is mounted on the housing. 41 can be incorporated. In this incorporation, the protrusion 34 of the optical sheet 31 may be engaged with the engaging portion of the housing 41.
In the optical sheet 31 incorporated in the display device 100, when the light H emitted from the light source 23 enters the light diffusing film 32, the light is diffused in the light diffusing film 32, and the diffused light is transmitted through the light transmissive base. It penetrates the material 36. The light transmitted through the translucent substrate 36 is directed by the unit lens 37 in a direction orthogonal to or close to the exit surface 36 a of the translucent substrate 36. That is, the light is directed to the front direction of the screen of the display device 100 which is the viewer's main visual direction, and the luminance in the front direction of the screen is improved.
In addition, since the welding part of the light-diffusion film 32 and the translucent base material 36 is covered with the housing | casing 41, it is not visually recognized by the viewer.

(Second Embodiment)
FIG. 6 shows an optical sheet 131 according to the second embodiment of the present invention. In this optical sheet 131, the same components as those of the optical sheet 31 according to the first embodiment shown in FIGS. 1 to 5 are denoted by the same reference numerals, description thereof is omitted, and different portions are mainly described.
The optical film 133 constituting the optical sheet 131 is a light reflecting material fixed to the incident surface 36b of the light transmissive substrate 36 in addition to the light transmissive substrate 36 and the plurality of unit lenses 37 similar to those in the first embodiment. A layer (light shielding layer) 61 is provided. In other words, the optical sheet 131 is configured to dispose the light reflection layer 61 between the light diffusion film 32 and the translucent substrate 36.

The light reflection layer 61 is configured to reflect light traveling from the light diffusion film 32 toward the light transmissive substrate 36. The light reflecting layer 61 has a plurality of openings 61a penetrating in the thickness direction. Each opening 61a is arranged at a position overlapping the top of the unit lens 37 in the thickness direction of the translucent substrate 36, and corresponds to each unit lens 37 formed in a long shape in the longitudinal direction. It is formed in an extending slit shape. That is, the plurality of openings 61 a are arranged in the Y direction at intervals like the plurality of unit lenses 37.
As a result, an air layer 62 defined by the opening 61 a is formed between the light diffusion film 32 and the translucent substrate 36. By defining the air layer 62 having a refractive index lower than that of the translucent substrate 36 in this way, the light is efficiently condensed when the light enters the translucent substrate 36 from the air layer 62. be able to.

The light reflecting layer 61 is constituted by, for example, a white layer. As a material for the white layer, a composite material in which a white pigment made of an inorganic substance such as titanium dioxide, barium sulfate, and magnesium oxide is mixed in a transparent resin material is used. The same resin material as that of the translucent substrate 36 is used as the transparent resin material.
The light reflecting layer 61 may be directly formed on the incident surface 36b of the translucent substrate 36 by printing or vapor deposition, or may be formed by transfer, for example.

When the light reflecting layer 61 is formed by transfer, for example, a photosensitive resin film is attached to the incident surface 36b of the translucent substrate 36, and the unit lens 37 and the translucent substrate 36 are interposed therebetween. The photosensitive resin film is exposed with ultraviolet rays. At the time of this exposure, the adhesive force of the photosensitive resin film is reduced only at the focal point of the unit lens 37 and the area in the vicinity thereof due to the light condensing action of the unit lens 37. Thereafter, the laminate of the translucent substrate 36 and the photosensitive resin film is pressed against the light reflecting layer 61 formed on the release paper, and then the laminate is released from the release paper. In this way, the light reflecting layer 61 having the opening 61a at the focal point of the unit lens 37 and the region in the vicinity thereof is obtained. Each opening 61a of the light reflecting layer 61 formed in this way is formed so that its central axis coincides with the optical axis of the corresponding unit lens 37.
Even when the printing method is used, for example, as described above, the light reflection layer 61 can be easily formed by printing by providing a step on the incident surface 36b when the light-transmitting substrate 36 is manufactured. .

  In the optical sheet 131 configured as described above, the light diffusing film 32 and the translucent base material 36 are welded and integrated at the peripheral portions in the plane direction, similarly to the optical sheet 31 of the first embodiment. Has been. However, the optical sheet 131 is welded over the entire side surfaces 32c, 61c, and 36c of the light diffusing film 32, the light reflecting layer 61, and the translucent substrate 36 that form the peripheral edge thereof. In FIG. 6, the welded portion is indicated by a thick line.

The optical sheet 131 configured as described above can be incorporated into the housing 41 shown in FIGS. 1 and 2 to constitute a backlight device and a display device in the same manner as the optical sheet 31 of the first embodiment. it can.
Moreover, when manufacturing this optical sheet 131, it can manufacture in substantially the same way as the manufacturing method of the optical sheet 31 of 1st Embodiment. In the film preparation step, the light reflecting layer 61 is formed when the optical film 133 is manufactured. And in a laser cutting process, the light-diffusion film 32, the translucent base material 36, and the light reflection layer 61 are heated with the laser beam 51, and these are welded mutually.

Next, the operation of the optical sheet 131 will be described.
When the light H emitted from the light source 23 enters the light diffusion film 32, the incident light is diffused and reaches the emission surface of the light diffusion film 32. At this time, the light incident on the opening 61a of the light reflecting layer 61 from the light diffusion film 32 reaches the incident surface 36b of the translucent substrate 36 as it is, but the light not incident on the opening 61a is reflected on the light reflecting layer 61. The reflection is repeated between the light diffusion film 32 and the light reflection plate 25. Then, most of the light transmitted through the translucent base material 36 is directed by the unit lens 37 in a direction orthogonal to or close to the exit surface 36a of the translucent base material 36. That is, light is directed to the front direction of the screen of the display device 100, which is the viewer's main visual direction, thereby improving the luminance in the front direction of the screen.

Next, the results of a peel test on the peel strength between the light diffusing film 32 and the translucent substrate 36 or the light reflecting layer 61 in the optical sheets 31 and 131 having the above-described configuration will be summarized below.
In the peel test, as shown in FIG. 7, two test pieces 71 and 72 made of the same or different resin material are used. Each test piece 71, 72 is formed in a length of 15 cm, a width of 2 cm, and a thickness of 0.2 cm. Further, the two test pieces 71 and 72 are welded by cutting only a pair of side surfaces 70A extending in the longitudinal direction with the laser beam 51 in the state of being laminated in the thickness direction, similarly to the above embodiment. The end surfaces 70B of the two extending test pieces 71 and 72 are not welded.
In this peel test, a surface property measuring instrument (TYPE: HEIDON-14D) manufactured by Shinto Chemical Co., Ltd. is used, and one test piece 72 is moved 100 mm in the longitudinal direction at a speed of 95 mm / min. In addition, a vertical load of 500 g is applied to the direction in which one end of the other test piece 71 in the longitudinal direction is peeled off from the one test piece 72 (the arrow Z direction shown in FIG. 7B), and the peel strength when peeled is measured. did. In each of Examples 1 to 4 and Comparative Examples 1 to 4, this peel test was performed three times.
The peel strengths of Examples 1 to 4 and Comparative Examples 1 to 4 are summarized in [Table 1].

Example 1
Both test pieces 71 and 72 were produced by MS, and the peel test was performed three times on the two test pieces 71 and 72 cut and welded with the laser beam 51. In this case, although the variation in peel strength in each test was large, all showed a high value of 10 gf / cm or more.
(Example 2)
Both test pieces 71 and 72 were produced by AS, and the two test pieces 71 and 72 were cut and welded with the laser beam 51, and the peel test was performed three times. In this case, the variation in peel strength in each test was smaller than that in Example 1, and all showed a high value of 9 gf / cm or more.

(Example 3)
Both test pieces 71 and 72 were produced by PC, and the peel test was performed three times on the two test pieces 71 and 72 cut and welded with the laser beam 51. In this case, the variation in peel strength in each test was smaller than in the other examples, and all showed high values of 10 gf / cm or more.
Example 4
Both test pieces 71 and 72 were made of PET, and the two test pieces 71 and 72 were cut and welded with the laser beam 51, and the peel test was performed three times. In this case, although the variation in peel strength in each test was large, all showed high values of 17 gf / cm or more.
When the peel strength is large as in these Examples 1 to 4, even if an external force such as vibration or impact is applied to the two test pieces 71 and 72, the two test pieces 71 and 72 are difficult to peel off. Become.

(Comparative Example 1)
One of the two test pieces 71 and 72 was made by PC and the other was made by MS, and the peel test was performed three times on the two test pieces 71 and 72 cut and welded by the laser beam 51. In this case, although the variation in peel strength in each test was small, the average was a low value of 4.0 gf / cm.
(Comparative Example 2)
One of the two test pieces 71 and 72 was made by AS and the other was made by PC, and the two test pieces 71 and 72 were cut and welded with the laser beam 51, and the peel test was performed three times. In this case, although the peel strength in each test was constant, it showed a low value of 2.0 gf / cm.

(Comparative Example 3)
One of the two test pieces 71 and 72 was made of PET and the other was made of PC, and the two test pieces 71 and 72 were cut and welded with the laser beam 51, and the peel test was performed three times. In this case, although the peel strength in each test was constant, it showed a low value of 1.0 gf / cm.
(Comparative Example 4)
One of the two test pieces 71 and 72 was made by AS and the other was made by MS, and the two test pieces 71 and 72 were cut and welded with the laser beam 51, and the peel test was performed three times. In this case, although there was little variation in peel strength in each test, the average was as low as 4.3 gf / cm.
When the peel strength is small as in Comparative Examples 1 to 4, the two test pieces 71 and 72 are peeled from each other when an external force such as vibration or impact is applied to the two test pieces 71 and 72. Cheap.

As described above, according to the optical sheets 31 and 131 of the above embodiment, and the backlight device 11 and the display device 100 including the optical sheets 31, 131, the light diffusion film 32, the translucent base material 36, the light reflection layer 61, and the like. Since these are integrated, the process of incorporating them into the display device 100 can be completed once, and the incorporation process can be easily performed.
Moreover, the light diffusing film 32 to be integrated, the translucent base material 36 and the light reflecting layer 61 are made of the same material, whereby the peel strength between them can be improved. For example, the optical sheets 31 and 131 are heated by the light source 23 when the optical sheets 31 and 131 and the display apparatus 100 including the optical sheets 31 and 131 are used, or when used as the display apparatus 100. Even if thermal deformation occurs in the translucent base material 36 or the light reflecting layer 61, the light diffusion film 32 and the translucent base material 36 or the light reflecting layer 61 have the same warp characteristics. And no stress is generated between the optical films 33 and 133. Therefore, peeling of the light diffusion film 32 and the optical films 33 and 133 can be prevented, and a change in the optical characteristics of the optical sheets 31 and 131 can be prevented.

In addition, by forming the protrusions 34 and the recesses 35 in the optical sheets 31 and 131, the orientation of the optical sheets 31 and 131 relative to the housing 41 can be easily recognized when the optical sheets 31 and 131 are assembled into the housing 41. be able to. Further, since the housing 41 is formed with an engaging portion that engages with the protrusion 34, the optical sheets 31 and 131 can be easily positioned with respect to the housing 41. Therefore, the optical sheets 31 and 131 can be easily incorporated into the housing 41.
Further, according to the display device 100, the welded portions of the optical sheets 31 and 131 are obscured by the rectangular lid portion 43 of the housing 41, so that the welded portions are discolored and the other parts of the optical sheets 31 and 131 are changed. Even if the optical characteristics are different from each other, the viewer of the display apparatus 100 can visually recognize a video with no sense of incongruity.

Furthermore, according to the manufacturing method of the optical sheets 31 and 131 of the above-described embodiment, the optical sheets 31 and 131 are punched at the same time as or after the welding, so that the light diffusion film 32 and the optical films 33 and 133 are formed. The optical sheets 31 and 131 can be easily manufactured after it has been individually cut into the shape of the optical sheets 31 and 131, and it is not necessary to superimpose them for positioning.
When the optical sheet plate 38 is cut by the laser beam 51, the optical sheets 31 and 131 are cut out from the optical sheet plate 38 and at the same time, the light diffusion film 32 and the translucent substrate 36 or the light reflection layer 61 are used. Since the number of steps can be reduced, the manufacturing efficiency of the optical sheets 31 and 131 can be improved.
Further, by cutting the optical sheets 31 and 131 with the laser beam 51, the projections 34 of the optical sheets 31 and 131 can be formed with high accuracy.

Moreover, when the light reflection layer 61 is provided between the light diffusion film 32 and the translucent substrate 36 as in the second embodiment, the light emitted from the emission surface 32a of the light diffusion film 32 is opened. It can squeeze in the part 61a. That is, since the light component having a large incident angle with respect to the unit lens 37 among the light emitted from the light diffusion film 32 can be cut at the opening 61a, the light emitted unnecessarily in the horizontal direction of the screen of the display device 100 is emitted. It becomes possible to reduce.
Furthermore, since the light that has not entered the translucent substrate 36 can be reused by being repeatedly reflected between the light reflecting layer 61 and the light diffusion film 32 or the light reflecting plate 25, the light source 23. The utilization efficiency of light from can be increased.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the display device 100, an optical sheet that achieves a diffusion / condensing effect by light refraction / transmission / reflection / polarization may be disposed between the liquid crystal display element 13 and the optical sheets 31 and 131. . In addition, as this optical sheet, a light-diffusion film, a prism sheet, a polarized light separation reflection sheet etc. are mentioned, for example. Even when configured in this manner, the same effects as those of the above-described embodiment can be obtained.
Moreover, in the said embodiment, although the display apparatus 100 is taken as the liquid crystal display device provided with the liquid crystal display element 13, if it uses the optical sheets 31 and 131 at least, such as a projection screen apparatus, a plasma display, an EL display, etc. As described above, the type of display device that displays an image with light is not limited.

  In addition, the light diffusion film 32 and the translucent base material 36 or the light reflection layer 61 are integrated by welding the entire peripheral edge thereof, but at least a part of the peripheral edge covered by the housing 41 is used. What is necessary is just to weld and integrate. Specifically, for example, as shown in FIGS. 8 and 9, the light exit surface 32 a of the light diffusion film 32 and the light entrance surface 36 b of the translucent substrate 36 may be welded. The welded portion 81 may be formed in a dot shape as in the illustrated example, but may be formed in a line shape, for example. Moreover, although the dotted | punctate welding part 81 may be formed in each corner | angular part vicinity of the optical sheet 31 like the example of illustration, you may form in the middle part of the side of the optical sheet 31, for example.

When the optical sheet 31 having this configuration is manufactured, the same film preparation process and laminating process as in the above embodiment are performed, and the light diffusion film 32 and the optical film 33 are welded (welding process), and then the optical sheet plate material. It is necessary to die-cut individual optical sheets 31 from 38 (die-cutting step).
In the welding step, for example, as shown in FIG. 9, the exit surface 32 a of the light diffusion film 32 and the entrance surface 36 b of the translucent substrate 36 can be welded with the laser beam 51. In this case, the laser beam 51 may be irradiated so that the focal point of the laser beam 51 is located at or near the contact surface between the light diffusion film 32 and the translucent substrate 36. Moreover, what is necessary is just to adjust the output of the laser beam 51 so that the area | region of the contact surface heated by the laser beam 51 may be restrict | limited. Furthermore, in the die cutting process, a laser cutting process similar to that in the above embodiment may be performed, but for example, a punching process may be performed.
In addition, although the welding method mentioned above described welding of the light-diffusion film 32 and the translucent base material 36, it is applied also to welding of the light-diffusion film 32 and the light reflection layer 61 like 2nd Embodiment, for example. can do.

In the above embodiment, the protrusions 34 formed on the optical sheets 31 and 131 are formed in a substantially rectangular shape that is symmetrical in the width direction. For example, as shown in FIG. It may be formed. Specifically, one side surface of the protrusion 34 is orthogonal to the side on which the protrusion 34 is formed, while the other side surface is inclined with respect to the same side. In addition, each projection 34 may be formed with a hole 34 a penetrating in the thickness direction, and the shape, number, and size of the hole 34 a may be different depending on each projection 34. Thus, even if the shape of the protrusion 34 formed on the optical sheet 31 is devised, the orientation of the optical sheet 31 can be easily recognized.
When forming the hole 34 a in the optical sheet 31, it is preferable to perform a die cutting process by punching, and the hole 34 a can be formed simultaneously with the die cutting of the optical sheet 31 including the protrusions 34.

Furthermore, in the said embodiment, although the protrusion 34 is formed in a pair of edge | side of the optical sheet 31 located in the mutually opposite side, you may form in the mutually adjacent edge | side. For example, as shown in FIGS. 10 to 18, the protrusions 34 may be formed on all sides of the optical sheet 231.
Further, the projections 34 are formed on the peripheral edges in the surface direction of the optical sheets 31, 131, and 231. However, the present invention is not limited to this, and at least a step for recognizing the orientation of the optical sheets 31, 131, and 231. The part should just be formed. Therefore, for example, a dent that is recessed in the surface direction may be formed as a stepped portion in the peripheral portion in the surface direction of the optical sheets 31, 131, and 231.

  Further, in the case of the optical film 133 including the light reflecting layer 61, the light diffusion film 32 and the light reflecting layer 61 are not limited to be made of the same resin material, but are formed of different materials, for example, and they are peeled small. You may weld with strength. That is, the light diffusion film 32 and the light reflection layer 61 are temporarily fixed so that the light diffusion film 32 and the optical film 133 are integrated until the assembly of the optical sheet 131 into the housing 41 is completed. The light diffusion film 32 and the light reflection layer 61 may be peeled off by applying an external force such as vibration later.

  When the peel strength is set as described above, the light diffusion film 32 and the optical film 133 can be peeled when the display device 100 is used, that is, the light diffusion film 32 and the light reflection. A gap can be formed between the layer 61. In the display device 100 in this state, light is diffused in this gap in addition to the light diffusing film 32, so that luminance unevenness generated on the display screen based on the light source 23 can be reduced. In this peeled state, the amount of light reflected or absorbed by the light reflecting layer 61 is reduced, and the amount of light passing through the opening 61a is increased, so that the brightness on the display screen can be improved.

Note that the peel strength of the light diffusion film 32 and the light reflection layer 61 to be temporarily fixed is preferably, for example, 2 gf / cm or more and 8 gf / cm or less. Specific combinations of resin materials that satisfy this condition include, for example, those described in Comparative Examples 1, 2, and 4 described above. 7
In this case, the light reflecting layer 61 may be formed of a metal layer. As the metal layer, for example, a vapor deposition layer made of a material having high reflectivity and low light absorption such as silver and aluminum can be used.

Each unit lens 37 is extended in a direction parallel to any side of the optical sheet 31 formed in a substantially rectangular shape in plan view, but at least on the emission surface 36a of the translucent substrate 36. For example, as shown in FIGS. 10 to 12, it may be extended in a direction inclined with respect to the side of the optical sheet 231.
Furthermore, although the unit lens 37 is arranged on the emission surface 36a of the translucent substrate 36, it has a function of condensing at least light emitted from the emission surface 36a of the translucent substrate 36 in a specific direction. An optical element may be provided.

  That is, for example, as shown in FIG. 14, the exit surface 36 a of the translucent base material 36 has a curved surface from the top to one width direction end, and the other width direction end. An optical element 237 formed so as to be a flat surface inclined toward the exit surface 36a of the translucent substrate 36 may be disposed. For example, as shown in FIG. 15, an optical element 337 having a convex curved surface and having a V-shaped groove 337a formed on the top thereof may be arranged. Further, for example, as shown in FIG. 18, a prism-shaped optical element 437 may be arranged. In the case of the prism-shaped optical element 437, the apex angle is preferably 90 degrees.

  The optical elements 37, 237, 337, and 437 are not limited to being formed in a long shape to form a lenticular array. For example, the optical elements 37, 237, 337, and 437 are formed in a circular shape or a polygonal shape in plan view. It may be arranged in the surface direction of the emission surface 36a. As shown in the second embodiment and FIGS. 16 to 18, when the optical sheets 31 and 231 include the light reflecting layer 61, the planar view shape of each opening 61 a of the light reflecting layer 61 is also the optical element 37. , 237, 337, 437 may be formed in a shape corresponding to the shape in plan view. For example, when the optical elements 37, 237, 337, and 437 are formed in a circular shape in plan view, the opening 61a may be formed in a circular shape in plan view.

Furthermore, in the second embodiment, the light reflection layer 61 is provided between the light diffusion film 32 and the translucent substrate 36, but it is sufficient that at least a light shielding layer that blocks light is provided. It is only necessary that the opening 61a similar to that of the above embodiment is formed in this light shielding layer.
For example, as shown in FIG. 17, in the optical sheet 231 including the light reflecting layer 61, the light-transmitting base material 36 has an opening recess 36 d that is recessed from the incident surface 36 b and continues to the opening 61 a of the light reflecting layer 61. It may be formed. In this case, the air layer 63 is defined by the opening 61a of the light reflecting layer 61 and the opening recess 36d of the translucent substrate 36, but the thickness of the optical sheet 231 is changed by forming the opening recess 36d. Therefore, since the length of the air layer 63 along the thickness direction of the optical sheet 231 can be extended, the light scattering effect by the air layer 63 can be improved.

For example, as shown in FIG. 15, even in the optical sheet 231 that does not include the above-described light reflecting layer 61, the second concave portion 36 d is formed in the translucent base material 36 so as to be recessed from the incident surface 36 b. Similarly to the optical sheet 131 of the embodiment, an air layer 64 may be formed between the light diffusion film 32 and the translucent substrate 36.
In the optical sheet 231 shown in FIG. 15, one opening recess 36 d is formed at a position where the two optical elements 337 and the translucent substrate 36 overlap in the thickness direction. Similarly, in the optical sheets 131 and 231 provided with the light reflecting layer 61 as in FIGS. 16 and 17, one opening 61 a or opening recess is provided at a position where the plurality of optical elements 37 and the translucent substrate 36 overlap in the thickness direction. 36d may be formed.
In addition, the openings 61 a of the light reflecting layer 61 and the opening recesses 36 d of the translucent substrate 36 described in the second embodiment and FIGS. 15 to 17 are regularly arranged according to the arrangement of the optical elements 37 and 337. However, for example, the openings 61a of the light reflecting layer 61 shown in FIG. 18 may be irregularly arranged regardless of the arrangement of the optical elements 437.

It is a schematic sectional drawing which shows the display apparatus which concerns on 1st Embodiment of this invention. It is a schematic plan view which shows the optical sheet with which the display apparatus of FIG. 1 is equipped. It is a schematic sectional drawing which shows the optical sheet of FIG. It is a schematic perspective view which shows an example of the manufacturing method of the optical sheet of FIG. It is a schematic sectional drawing which shows an example of the manufacturing method of the optical sheet of FIG. It is a schematic sectional drawing which shows the optical sheet which concerns on 2nd Embodiment of this invention. The test piece for the peeling test which verifies the peeling strength in the optical sheet of this invention is shown, (a) is a schematic plan view, (b) is a schematic side view. It is a schematic plan view which shows an example of the manufacturing method of the optical sheet which concerns on other embodiment of this invention. It is an expanded sectional view which shows the welding part of a light-diffusion film and a translucent base material in the optical sheet of FIG. It is a top view which shows the state which looked at the optical sheet which concerns on other embodiment of this invention from the output surface side of the translucent base material. It is a top view which shows the state which looked at the optical sheet of FIG. 10 from the entrance plane side of the light-diffusion film. It is the side view which looked at the optical sheet of Drawing 10 from the A direction. It is the side view which looked at the optical sheet of Drawing 10 from the B direction. In the optical sheet of FIGS. 10-13, it is an enlarged side view which shows the state which looked at the example of the laminated structure from the formation part of protrusion. In the optical sheet of FIGS. 10-13, it is an enlarged side view which shows the state which looked at the example of the laminated structure from the formation part of protrusion. In the optical sheet of FIGS. 10-13, it is an enlarged side view which shows the state which looked at the example of the laminated structure from the formation part of protrusion. In the optical sheet of FIGS. 10-13, it is an enlarged side view which shows the state which looked at the example of the laminated structure from the formation part of protrusion. In the optical sheet of FIGS. 10-13, it is an enlarged side view which shows the state which looked at the example of the laminated structure from the formation part of protrusion.

Explanation of symbols

11 Backlight device 13 Liquid crystal display element (image display unit)
21 Light source part 23 Light source 31,131,231 Optical sheet 32 Light diffusion film 32a Output surface 32b Incident surface 32c Side surface (welded part)
33, 133 Optical film 34, 34A Protrusion (step)
36 Translucent base material 36a Outgoing surface 36b Incident surface 36c Side surface (welded portion)
37 Unit lens (optical element)
41 Case 51 Laser light 61 Light reflection layer (light shielding layer)
61a Opening 81 Welded portion 100 Display device 237, 337, 437 Optical element

Claims (11)

One surface forms an incident surface on which light from the light source unit is incident and the other surface forms a light output surface, and is laminated on the light diffusion film for diffusing the light from the light source unit and the light diffusion film. And an optical film that controls the light emitted from the emission surface,
The optical film is disposed on the light emission surface side of the light diffusion film and has a light transmission surface that transmits and emits light from the light diffusion film, and light emission of the light transmission substrate A plurality of optical elements that are provided integrally with the emission surface of the translucent substrate so as to protrude from the surface and collect light emitted from the emission surface of the translucent substrate; and
The light diffusion film and the translucent base material are made of the same material,
The optical sheet, wherein the light diffusing film and the translucent base material are integrated by welding at least a part of a peripheral portion in the surface direction. The light diffusion film and the translucent substrate are made of a resin material,
The optical sheet according to claim 1, wherein the light diffusion film and the translucent base material are welded by laser light.   The optical sheet according to claim 1 or 2, wherein the light diffusion film and the translucent base material are made of a methyl methacrylate styrene copolymer.   The step part which protrudes in the said surface direction, or is depressed in the said surface direction is formed in the peripheral part of the surface direction of the said light-diffusion film and the said optical film, The Claim 1 characterized by the above-mentioned. The optical sheet described. The optical sheet according to any one of claims 1 to 4,
A backlight device, comprising: a light source unit disposed on the incident surface side of the light diffusion film and irradiating light toward the incident surface.   The backlight device according to claim 5, and an image display unit that is disposed on an emission surface side of the translucent substrate and displays an image using light from the backlight device as display light. Display device. A housing that supports the optical sheet at its peripheral edge,
A part of the casing is arranged on the light emitting surface side of the light-transmitting substrate so that the light diffusion film and the welded portion of the light-transmitting substrate overlap the thickness direction of the optical sheet. The display device according to claim 6. A light diffusing film that diffuses incident light, a translucent base material that transmits light emitted from the light diffusing film material, and an output surface of the translucent base material from which the light exits A film preparation step of preparing an optical film provided with a plurality of optical elements that are integrally provided on the emission surface of the translucent substrate and collect light emitted from the emission surface of the translucent substrate;
A laminating step of superposing the light diffusing film and the optical film to form a plate for an optical sheet so that the light transmissive substrate is disposed on the light diffusing film side;
A laser cutting step of irradiating the optical sheet plate with a laser beam and cutting the optical sheet plate so as to die-cut individual optical sheets from the optical sheet plate;
In the film preparation step, the light diffusion film and the translucent substrate are formed of the same resin material.   9. The method of manufacturing an optical sheet according to claim 8, wherein in the laser cutting step, a stepped portion that protrudes or is recessed in the surface direction from a peripheral edge in the surface direction is integrally formed on the optical sheet. A light diffusing film that diffuses incident light, a translucent base material that transmits light emitted from the light diffusing film material, and an output surface of the translucent base material from which the light exits A film preparation step of preparing an optical film provided with a plurality of optical elements that are integrally provided on the emission surface of the translucent substrate and collect light emitted from the emission surface of the translucent substrate;
A laminating step of superposing the light diffusing film and the optical film to form a plate for an optical sheet so that the light transmissive substrate is disposed on the light diffusing film side;
A welding step of welding the light diffusion film and the optical film;
A die cutting step of punching individual optical sheets from the optical sheet plate, and
In the film preparation step, the light diffusion film and the translucent substrate are formed of the same resin material.   The method for producing an optical sheet according to claim 10, wherein, in the die cutting step, a stepped portion protruding or recessed in the surface direction from a peripheral edge portion in the surface direction is formed on the optical sheet.

Images