JP2009098566A - Optical sheet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a luminance controlling member which has constitution that a low refractive index layer such as an air layer is interposed at a place where light from a light source is made incident to avoid contact with other optical members and clear level difference (height difference) is provided to that place and around it and a side lobe is not produced in order to demonstrate a desired optical characteristic when applied to a back light unit for display. <P>SOLUTION: An optical sheet has a lot of unit lenses or prisms arranged in a row at an emission surface side and a rugged shape constituted by arranging a lot of projected parts and recessed parts in order at an incident surface side. The recessed parts at the incident surface side are arranged at a position corresponding to a light condensing shape of parallel light which is made incident from the unit lens or the prism at the emission surface side and light reflecting layers are formed on the whole surfaces of the projected parts. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical film used for applications such as illumination light path control in a backlight unit for a display (hereinafter, liquid crystal display) mainly using a liquid crystal display element, and a method for producing the same.

  In recent years, liquid crystal display devices using TFT liquid crystal panels and STN liquid crystal panels have been commercialized mainly for color notebook PCs (personal computers) in the OA field.

  Such a liquid crystal display device employs a so-called backlight method in which a light source is disposed on the back side of the liquid crystal panel and the liquid crystal panel is illuminated with light from the light source.

  As a backlight unit employed in this type of backlight system, a light source lamp such as a cold cathode fluorescent lamp (CCFT) is roughly divided into a flat light guide plate made of acrylic resin having excellent light transmittance. There are a “light guide plate light guide method” for reflecting (a so-called edge light method) and a “direct type method” that does not use a light guide plate.

  As a liquid crystal display device on which a light guide plate light guide type backlight unit is mounted, for example, the one shown in FIG. 1 is generally known.

  This is provided with a liquid crystal panel 72 sandwiched between polarizing plates 71 and 73 at the top, and a transparent base material such as a substantially rectangular plate-like PMMA (polymethyl methacrylate) resin or other acrylic resin on its lower surface side. A light guide plate 79 is provided, and a diffusion film (diffusion layer) 78 is provided on the upper surface (light emission side) of the light guide plate.

  Further, a scattering reflection pattern portion for efficiently scattering and reflecting the light introduced into the light guide plate 79 in the direction of the liquid crystal panel 72 is provided on the lower surface of the light guide plate 79 by printing or the like. A reflection film (reflection layer) 77 is provided below the scattering reflection pattern portion (not shown).

Further, the light guide plate 79 is provided with a light source lamp 76 at the side end, and further covers the back side of the light source lamp 76 so that the light from the light source lamp 76 can be efficiently incident on the light guide plate 79. Thus, a high-reflectance lamp reflector 81 is provided.
The scattering reflection pattern portion is a mixture containing white titanium dioxide powder printed in a predetermined pattern, for example, a dot pattern, dried and formed, and imparts directivity to light incident in the light guide plate 79, It leads to the light exit surface side, and is a device for increasing the brightness.

Further, recently, in order to increase the light utilization efficiency and increase the brightness, as shown in FIG. 2, a prism film (prism layer) having a light condensing function between the diffusion film 78 and the liquid crystal panel 72 is used. ) 74 and 75 are proposed.
The prism films 74 and 75 are configured to collect light emitted from the light exit surface of the light guide plate 79 and diffused by the diffusion film 78 on the effective display area of the liquid crystal panel 72 with high efficiency.

However, in the apparatus illustrated in FIG. 1, the distribution of the viewing angle is left only to the diffusibility of the diffusion film 78, and its control is difficult, and the center in the front direction of the display is bright.
The tendency to get darker as you go to the periphery is inevitable. For this reason, when the liquid crystal screen is viewed from the side, the luminance is greatly reduced, and the light utilization efficiency is reduced.
Furthermore, in the apparatus using the prism film illustrated in FIG. 2, two sheets are required to combine the prism film by changing the angle of the prism film. The increase also caused the cost to rise.

  On the other hand, the direct type is used for a display device such as a large liquid crystal TV in which it is difficult to use a light guide plate.

As a direct-type liquid crystal display device, a device illustrated in FIG. 3 is generally known.
This is because light emitted from a light source 51 made of a fluorescent tube or the like and diffused by an optical sheet such as a diffusion film 82 is incident on an effective display area of a liquid crystal panel 72 sandwiched between polarizing plates 71 and 73 in the upper part of the figure. The light is condensed on the liquid crystal panel 72 with high efficiency.
In order to efficiently use the light from the light source lamp 51 as illumination light, a lamp reflector 52 is disposed on the back surface of the light source 51.

  However, even in the apparatus illustrated in FIG. 3, the distribution of the viewing angle is left only to the diffusibility of the diffusion film 82, and its control is difficult. This trend is inevitable. For this reason, when the liquid crystal screen is viewed from the side, the luminance is greatly reduced, and the light utilization efficiency is reduced.

Therefore, as a conventional solution, as shown in FIG. 5, a brightness enhancement film (Brightness Enhancement Film BEF, a registered trademark of 3M USA) shown in FIG. 4 is disposed on the diffusion film 90, and light diffusion is further performed thereon. A method of arranging the film 300 is employed. Here, BEF is a film in which unit prisms having a triangular cross section are periodically arranged in one direction on a transparent member.
This prism has a size (pitch) larger than the wavelength of light. The BEF collects light from “off-axis” and redirects or recycles this light “on-axis” towards the viewer.

When using the display (when observing), the BEF increases the on-axis brightness by reducing the off-axis brightness. Here, “on-axis” is a direction that coincides with the visual direction of the observer, and is generally on the normal direction side with respect to the display screen.
When the repetitive array (arrangement) structure of prisms is arranged in only one direction, the direction of the parallel direction can only be changed or recycled. In order to control the luminance of display light in the horizontal and vertical directions, a prism group is used. The two sheets are stacked and combined so that their parallel directions are substantially orthogonal to each other.

The adoption of BEF allows display designers to achieve the desired on-axis brightness while reducing power consumption. Many patent documents that disclose that a brightness control member having a repetitive array structure of prisms represented by BEF is adopted for a display are known. Listed.
In the optical sheet using the BEF as a brightness control member as described above, the light from the light source is finally emitted from the film at a controlled angle by the refraction action, so that the visual direction of the observer can be improved. It can be controlled to increase the light intensity.

However, there are unexpected light rays that are unnecessarily emitted in the lateral direction without proceeding in the visual direction of the observer. For this reason, the light intensity distribution emitted from the optical sheet using BEF has the highest light intensity when the angle with respect to the visual direction of the observer is 0 °, but a small light intensity peak occurs around ± 90 ° from the front, That is, there is a problem in that light (side lobes) emitted wastefully from the lateral direction increases. A luminance distribution having such a light intensity peak is not desirable, and a smooth luminance distribution having no light intensity peak around ± 90 ° is more desirable.

  In addition, when only the on-axis brightness is excessively improved, the peak width of the curve of the brightness distribution is remarkably narrowed, and the viewing angle is extremely limited. Therefore, in order to appropriately widen the peak width, Requires a new light diffusing film as a separate member, which not only greatly reduces the amount of light due to absorption of the film, but also increases the number of members.

  As described above, this optical sheet is required not only to improve the light utilization efficiency but also to have various functions such as removing unevenness of the light source and securing the viewing area of the display. It is configured by overlapping sheets. However, if the number of optical sheets is large, the work for assembling the display becomes complicated, and there is a problem that it is affected by dust between the optical sheets and hinders miniaturization and thinning.

By the way, in such a liquid crystal display device, light weight, low power consumption, high brightness, and thinness are strongly demanded as market needs, and accordingly, the backlight unit mounted on the liquid crystal display device is also lightweight. In addition, low power consumption and high brightness are required.
In particular, in color liquid crystal display devices that have recently made remarkable progress, the transmittance of the liquid crystal panel is much lower than that of a monochrome-compatible liquid crystal panel. Therefore, improving the luminance of the backlight unit can reduce the consumption of the device itself. It is essential to get power.

  However, as described above, it is difficult to say that the conventional apparatus sufficiently satisfies the demand for high luminance and low power consumption, and the user has low price, high luminance, high display quality, and low power consumption. Development of a backlight unit and a display device that can realize a liquid crystal display device with electric power is awaited.

On the other hand, there is also a proposal for a transmissive liquid crystal display device including a backlight unit using a luminance control member having a repetitive array structure of unit lenses instead of a prism (see Patent Document 4). Shown in
The display device shown in FIG. 6 includes a liquid crystal panel and light source means for irradiating the liquid crystal panel with light from the back side. The light source means is provided with a lens layer for guiding light from the light source to the liquid crystal panel. And a light-shielding portion having an opening in the vicinity of the focal plane of the lens layer.

The display device shown in FIG. 6 is provided with a liquid crystal panel 12 sandwiched between polarizing plates 11 and 13 at the top, and a conductive plate made of a substantially rectangular plate-like PMMA (polymethyl methacrylate) resin or the like on the lower surface side. An optical plate 79 is disposed, and on the lower surface of the light guide plate 79, a scattering reflection pattern portion for efficiently scattering and reflecting the light introduced into the light guide plate 79 so as to be uniform in the direction of the liquid crystal panel 12. 83 is provided by printing or the like, and a reflection film (reflection layer) 77 is provided below the scattering reflection pattern portion.
A light source lamp 76 is attached to the light guide plate 79 along the side end portion. Further, the light source lamp 76 covers the back side of the light source lamp 76 so that the light from the light source lamp 76 is efficiently incident on the light guide plate 79. A high-reflectance lamp reflector 81 is provided.

The scattering reflection pattern portion 83 is formed by printing a mixture of white titanium dioxide powder or the like in a predetermined pattern, for example, a dot pattern. Light scattered by the scattering pattern portion 83 and the like is emitted from the upper surface of the light guide plate 79. A lens layer 15 composed of a plurality of lenses is disposed on the light emission side, and a light shielding layer 18 having an opening corresponding to each lens is provided in the vicinity of the focal plane of the lens constituting the lens layer 15.
The light emitted from the light guide plate 79 passes only through the opening of the light shielding layer 18 and enters the lens layer 15. Since the light shielding layer is disposed in the vicinity of the focal point, the light emitted from one point of the light shielding layer 18 is emitted from the lens layer 15 as light in a certain direction by the lens. Therefore, the direction of light emitted from the lens layer can be determined by the size of the opening of the light shielding layer 18.

In the case of the luminance control member according to claim 3 of Patent Document 4, a light shielding layer (= light reflecting layer) 18 is formed on the flat surface on the incident portion side of the lens layer 15. Patent Document 4 does not describe a method for forming the light reflecting layer 18, but generally, various methods such as printing (coating), transfer, and photolithography are appropriately selected.
However, regarding the pattern formation on the flat surface, the thickness of the light reflecting layer 18 by the above-mentioned various methods is limited (at most, about several tens of μm), and the surface of the stripe-shaped light reflecting layer 18 and the lens layer 15 between them are formed. It is difficult to provide a clear step (level difference) with the opening.

  In FIG. 1 of Patent Document 4, the light reflection layer 18 side and the light guide plate 79 side of the brightness control member are stacked so as to face each other, but the light guide plate 79 is brought into contact with flat surfaces having no clear steps. When the boundary between the lens layer 15 and the lens layer 15 is not clear and the refractive indexes of the two are close to each other, a state in which the two are optically in close contact with each other occurs, and the incident light from the opening is at the intended angle. It becomes difficult to exhibit optical characteristics as designed by the lens layer 15 without entering the layer 15.

In addition, when the luminance control member is used in a direct type backlight unit that does not employ the light guide plate constituting the edge light type surface light source as described above, light diffusion is performed between the light source and the luminance control member. Generally, a configuration in which a layer (a light diffusing plate alone or a light diffusing film is used in combination) is interposed, but the same problem as described above is caused between the luminance control member and the light diffusing layer.
In particular, when adopting a configuration in which the brightness control member and the light diffusion layer are laminated and integrated through an adhesive layer or an adhesive layer, the adhesive layer or the adhesive layer fills between the opening and the light diffusion layer. Unexpected incident light components are likely to be generated (or the function is deteriorated by the light diffusion layer), and it becomes more difficult to achieve optical characteristics as designed.

Therefore, the brightness control member described in Patent Document 4 has an air layer or the like on the light source side in contact with the opening in order to achieve desired optical characteristics when applied to a backlight unit. It is desirable to interpose a low refractive index layer.
Therefore, in order to avoid contact with other optical members such as a light guide plate and a light diffusing layer, a configuration is also proposed in which a clear step (height difference) is provided between the opening and its periphery (see Patent Document 5). . A configuration according to the example is shown in FIG.

  The optical sheet shown in FIG. 7 is a lens sheet 2 having a lens portion in which unit lenses composed of semi-cylindrical convex cylindrical lenses are arranged in parallel on one side, and the other side faces the backlight light source side and reflects light. A light reflecting layer 1 that reflects light incident on the surface toward the backlight source, and the light reflecting layer 1 is provided for each unit lens of the lens sheet 2 described above. 1 is a stripe shape having an opening corresponding thereto, and a convex portion corresponding to the stripe shape is formed on the side opposite to the lens portion of the lens sheet 2.

The light reflecting layer 1 has a stripe shape having an opening corresponding to each unit lens of the lens sheet 2 described above, and corresponds to the stripe shape on the side opposite to the lens portion of the lens sheet 2. Since the structure is formed on the convex portion, the opening has a clear level difference (height difference) from its surroundings, and contact with other optical members such as the light guide plate and the light diffusion layer is reliably avoided. In addition, since the air layer is in contact with the opening, it is easy to realize a backlight unit that exhibits optical characteristics (viewing zone control) as designed.
Japanese Patent Publication No. 1-378001 JP-A-6-102506 Japanese National Patent Publication No. 10-506500 JP 2000-284268 A JP 2005-149079 A JP 2007-127932 A

An example of the proposed configuration shown in Patent Document 5 is shown in FIG.
In this configuration, the light incident on the recess 4 like the light rays A and B in FIG. 7 is emitted at a small emission angle (a direction close to the normal direction to the sheet surface). Further, the light incident on the light reflecting layer 1 at the top of the convex portion 3 like the light ray C is reflected by the light reflecting layer 1 and returned to the light source side to be reused.
However, when a clear step (height difference) is secured at the convex portion formed in a stripe shape as described above, when the light is incident from the side surface of the convex portion as shown by the light ray D in FIG. Therefore, there is a problem that the above-mentioned side lobe increases.

  Therefore, in the present invention, side lobes do not occur and a clear step (height difference) from the periphery of the opening is ensured, and contact with other optical members such as a light guide plate and a light diffusion layer is reliably avoided. The realization of a configuration in which the air layer reliably contacts the opening is a problem.

  The present invention has been made in view of the above problems, and the invention of claim 1 is an optical sheet used for illumination light path control in a backlight unit for display, and at least one arranged in a row on the exit surface side. Concave and convex shape in which a large number of unit lenses or unit prisms, convex portions projecting on the incident surface side, and concave portions having a height lower than the convex portions are sandwiched between the convex portions. The concave portion on the incident surface side is disposed at a position corresponding to a condensing shape of parallel light incident from the unit lens or unit prism on the output surface side, and the convex portion includes the convex portion The optical sheet is characterized in that a light reflection layer is formed on the entire surface including the top and sides of the convex portion, which is a region sandwiched between the boundary between the portion and the concave portion.

The invention according to claim 2 is the optical sheet according to claim 1, wherein the shape of the recess is a planar shape.
The invention according to claim 3 is the optical sheet according to claim 1, wherein the shape of the bottom surface of the recess is a plane.
The invention according to claim 4 is the optical sheet according to any one of claims 1 to 3, wherein the protruding amount of the top of the convex portion from the bottom surface of the concave portion is 1 μm or more and 95 μm or less. .
The invention according to claim 5 is characterized in that the amount of protrusion including the light reflecting layer from the bottom surface of the concave portion at the top of the convex portion is 6 μm or more and 100 μm or less. This is an optical sheet.
The invention according to claim 6 is the optical sheet according to any one of claims 1 to 5, wherein the unit lens or the unit prism, the convex portion and the concave portion are integrally molded. It is.

  According to a seventh aspect of the present invention, in an optical sheet used for illumination optical path control in a display backlight unit, at least one type of unit lenses or unit prisms arranged side by side on the exit surface side and projecting on the entrance surface side And a concave-convex shape in which a plurality of concave portions having a height lower than that of the convex portion are arranged in order, and the concave portion on the incident surface side is provided on the exit surface. A lens film disposed at a position corresponding to a condensing shape of parallel light incident from a unit lens or unit prism on the side, and a light reflecting layer is formed on the entire incident surface side of the lens film; Laser light is emitted from a unit lens or unit prism on the exit surface side of the film, and the light reflecting layer portion corresponding to the laser light condensing portion is selectively removed to produce light. The opening part without a projecting layer is formed, and the light reflecting layer is left on the entire other surface including the top part and the side part of the convex part. It is a manufacturing method of an optical sheet.

According to an eighth aspect of the present invention, the light diffusing sheet and the optical sheet according to any one of the first to sixth aspects are laminated and integrated on a surface on the light exit surface side, and the light diffusing sheet. Or it is the structure which has an air layer in the space enclosed by a contact bonding layer, the said light reflection layer, and the said recessed part, It is an optical sheet characterized by the above-mentioned.
The invention according to claim 9 is provided with the direct light source and the optical sheet according to any one of claims 1 to 6 or claim 8 on the back surface of the image display element that defines the display image. This is a display backlight unit.
The invention of claim 10 comprises an image display element comprising a liquid crystal display element that defines a display image in accordance with transmission / shielding in pixel units, and a backlight unit according to claim 9, wherein the direct light source is a cold cathode. It is a display characterized by being a tube, organic EL, or LED.

According to the invention of claim 1, the following three effects can be obtained.
(1) On the incident surface side of the optical sheet, a light reflecting layer having an opening corresponding to the condensing shape of the parallel light incident on the optical sheet from the surface side on which the unit lens or unit prism structure is formed is disposed. Therefore, an optical sheet with high light use efficiency when used in a backlight unit can be provided.
(2) Since the convex portion corresponding to the portion other than the opening is formed, the opening has a clear level difference (height difference) from the periphery thereof, and the light guide plate and the light diffusion layer This makes it easy to realize a backlight unit that exhibits optical characteristics (viewing angle control) as designed, because contact with other optical members such as the above is reliably avoided and the air layer reliably contacts the opening. .
(3) Since a light reflecting layer is formed on the entire surface including the top and side portions of the convex portion, which is a region sandwiched between the convex portion and the concave portion, light incident from the convex side surface portion The generated side lobe can be prevented, and an optical sheet with higher light utilization efficiency can be obtained.

  According to the second aspect of the invention, since the shape of the bottom surface of the concave portion is made flat, the light incident on the concave surface is uniformly distributed, so that an optical sheet with little brightness unevenness can be obtained.

  According to the invention of claim 3, by making the shape of the bottom surface of the concave portion into a curved surface including a curved surface convex toward the incident surface side, the light incident on the concave surface is collected and more light is emitted in a necessary direction. Can be collected. By adjusting the light collection direction, for example, the brightness in the observer direction can be increased.

  According to the invention of claim 4, the amount of protrusion from the bottom surface of the concave portion on the top of the convex portion is set to 1 μm or more, thereby preventing optical adhesion with optical members such as a diffusion film and a diffusion sheet that overlap the concave portion. In addition, when the protrusion amount from the bottom surface of the concave portion on the top of the convex portion is 95 μm or less, pattern processing of the light reflecting layer filled in the concave portion at the time of manufacture becomes easy, and the material cost can be reduced.

  According to the invention of claim 5, when the protrusion amount including the light reflection layer from the bottom surface of the concave portion on the top of the convex portion is 6 μm or more, when integrated with an optical member such as a diffusion film or a diffusion sheet, An air layer can be easily secured, and the patterning of the light reflecting layer is facilitated by making the amount of protrusion including the light reflecting layer from the bottom surface of the concave portion on the top of the convex portion 100 μm or less, thereby reducing the material cost. Can be lowered.

  According to the invention of claim 6, since the unit lens or the unit prism and the convex part and the concave part are integrally molded, the production efficiency is good, and the problem comes from the environment such as dust mixing during product assembly. Can be reduced.

  According to the invention of claim 7, the light reflecting layer is formed on the entire incident surface side, the laser light is irradiated from the unit lens or the unit prism side, and the portion of the light reflecting layer corresponding to the condensing part of the laser light Is selectively removed to form an opening, and the light reflection layer is left on the entire surface including the top and sides of the first convex portion, so that the surface other than the entire top surface including the top and side portions of the first convex portion can be simplified. The light reflection layer can be removed, and a desired light reflection layer pattern can be obtained.

  According to the invention of claim 8, the light diffusion sheet and the optical sheet of any one of claims 1 to 6 of the present invention are laminated and integrated through the bonding layer, and the light diffusion sheet or bonding By having an air layer in a space surrounded by the layer, the light reflection layer, and the recess, it is possible to obtain a light diffusing / condensing function with a single sheet.

  According to the invention of claim 9, it is possible to realize a backlight unit capable of preventing side lobes and exhibiting optical characteristics (viewing angle control) as designed using an optical sheet with high light utilization efficiency. I can do it.

  According to the invention of claim 10, a display using a backlight unit capable of preventing side lobes and exhibiting optical characteristics (viewing angle control) as designed using an optical sheet with high light utilization efficiency. Can be realized.

Hereinafter, the present invention will be described in more detail.
FIG. 8 is a partial cross-sectional view of an optical sheet according to an embodiment of the present invention.
This optical sheet has a convex portion 3 on the back surface of the lens structure surface having a structure such as a lenticular lens (repetitive array structure of a striped semi-cylindrical convex cylindrical lens), and a convex portion 3 in a region sandwiched between the convex portions 3. Further, it has an uneven shape in which a plurality of planar recesses 4 having a lower height are arranged in order.
The concave portion 4 described above is disposed at a condensing position of parallel light incident from the lens surface side. The light reflecting layer 1 is formed on the entire side of the convex part 3 and the entire top part.

Light that enters the concave portion 4 like the light rays A and B is emitted at a small emission angle (a direction close to the normal direction to the sheet surface). Further, the light incident on the light reflecting layer 1 at the top of the convex portion 3 like the light ray C is reflected by the light reflecting layer 1 and returned to the light source side to be reused.
Light that is incident on the light reflecting layer 1 on the side of the convex portion 3 like the light ray D is reflected by the light reflecting layer 1 and enters the concave portion 4, and is emitted at a small emission angle.

  The lens sheet 2 is manufactured by a melt extrusion molding method using a thermoplastic resin such as PET (polyethylene terephthalate), PC (polycarbonate), PP (polypropylene), COP (cycloolefin polymer).

  The shape of the unit lens or unit prism of the lens sheet 2 may be appropriately selected depending on desired light distribution characteristics. The pitch of the unit lenses or unit prisms may be selected as appropriate, but in consideration of moire (interference fringes) with the liquid crystal panel, resolution, lens shape moldability, etc., 30 μm to 200 μm is suitable. .

At the top of the convex portion 3 of the lens sheet 2, the protruding amount from the bottom surface of the concave portion 4 is 1 μm or more and 95 μm.
It is as follows. The shape is not particularly limited, and may be appropriately selected from shapes that have a cross section of a rectangle, a triangle, a trapezoid, a part of a circle, or a part of an ellipse.

As another form, the concave portion 4 of the lens sheet 2 may have a curved shape including a convex curved surface on the incident surface side (FIG. 9).
Light that enters the concave portion 4 like the light rays A and B is emitted at a small emission angle (a direction close to the normal direction to the sheet surface).
Further, the light incident on the light reflecting layer 1 at the top of the convex portion 3 like the light ray C is reflected by the light reflecting layer 1 and returned to the light source side to be reused.
Light that is incident on the light reflecting layer 1 on the side of the convex portion 3 like the light ray D is reflected by the light reflecting layer 1 and enters the concave portion 4, and is emitted at a small emission angle.
The shape of the curved surface may be appropriately selected according to desired light distribution characteristics. For example, it is possible to select a part of a circular shape, a part of an elliptical shape, an aspherical shape with an elliptical surface as a reference plane and corrected by a higher order term.

As the material of the light reflecting layer 1, a material in which a white pigment is dispersed in a resin is used. As the white pigment, titanium dioxide, magnesium carbonate, clay, barium sulfate, zinc oxide, alumina, silver and the like can be used.
When the thickness of the light reflecting layer 1 exceeds 5 μm, a sufficient white color can be obtained and adjusted to a desired reflectance, and it has sufficient strength against rubbing and the like and does not easily peel / drop off. . Moreover, by making the thickness of the light reflecting layer 1 100 μm or less, it is possible to improve the pattern processing shape and reduce the material cost. Since the light reflection layer 1 having such a thickness can reflect light inside the layer, it can be said to be a volumetric light reflection layer.

  Next, with reference to FIGS. 10-12, an example of the manufacturing method of the optical film which concerns on this invention is demonstrated.

First, a lens film is manufactured as shown in FIG. The lens sheet 2 is formed by a melt extrusion molding method using an extruder 60 as shown in FIG.
The extruder 60 includes, for example, a hopper 61 for introducing a molding resin, a screw 62 for extruding the resin while melting and kneading the resin, a plurality of barrels (not shown) for heating the resin, and a die 63 for extruding the resin into a sheet shape. It is a device provided.
Using this extruder 60, thermoplastic transparent resin pellets for forming a lens sheet are introduced from a hopper 61, heated to a predetermined temperature in a barrel to be in a molten state, and extruded from a die 63 as a sheet 80. Then, it is transported horizontally and guided to the mold rolls 64 and 65 arranged opposite to each other.
As shown in FIG. 11, the mold rolls 64 and 65 have a mold surface 64 a corresponding to the lens surface 5 and a mold surface 65 a corresponding to the convex part 3 and the concave part 4, respectively. The lens sheet 2 is continuously molded by rotating while pressing the upper and lower surfaces of the sheet 80 by the mold surfaces 64a and 65a.

As the molding rolls 64 and 65 having the lenticular lens or the reverse shape of the concavo-convex portion formed on the surface, a cut metal mold or a resin mold replicated from the metal mold by a predetermined method is arranged on the roll surface. What is provided can be used.
Next, the light reflection layer 1 containing a white pigment is formed on the lens back surface of the lens sheet 2 (not shown). If the raw material of the light reflection layer 1 can be supplied as a liquid white ink in which a white pigment is dispersed in a resin solution, a printing method, a coating method, a transfer method, and the like can be used, which is advantageous in production. . If necessary, the resin may be dried / cured using a dryer or the like after forming the light reflecting layer.

  As the printing method, a gravure printing method, a silk printing method, an offset printing method, a flexographic printing method, or the like can be selected. Since it is solid printing, a reflective layer having a required thickness may be formed by overprinting several times. As a coating method, a roll coater, a die coater, a curtain coater, or the like can be selected. When the transfer method is used, a transfer foil is used, and a thermal transfer method, a transfer method using adhesion or adhesion, or the like can be used.

Next, the light reflecting layer is striped by the method shown in FIG. As shown in FIG. 12, the laser light 7 is irradiated as parallel light from the unit lens or unit prism structure surface side of the lens sheet 2, and the portion of the light reflecting layer 1 corresponding to the condensing portion of the laser light 7, that is, the recess 4. While selectively removing the light reflecting layer 1, the laser beam 7 is moved relative to the lens sheet 2 in the stripe length direction (direction perpendicular to the paper surface) to form the opening 6.
By repeating this operation by moving the laser beam 7 relative to the lens sheet 2 along the stripe arrangement direction (left and right direction on the paper surface), the entire surface including the side portions and the top portions of the convex portions 3 is applied. The stripe-shaped light reflecting layer 1 to be formed can be left. In this way, a concave / convex pattern in which the light reflecting layer 1 is formed on the entire surface including the concave portion 4 corresponding to the structure of the lens sheet 1 and the side portions / top portions of the convex portion 3 can be obtained.

  The wavelength of the laser beam 7 is not particularly limited as long as sufficient energy can be given to the light reflection layer 1. However, in consideration of the transmittance of the lens film, the absorption rate of the light reflection layer 1, and the like, a laser beam having a wavelength of 0.8 μm or more obtained by a YAG laser (wavelength 1.064 μm) or LD can be used. Laser light with a near infrared wavelength is preferred.

  It is also effective to irradiate radiation such as ultraviolet rays in order to fix the light reflecting layer 1 after the stripe processing. By irradiating with a sufficient amount of ultraviolet rays and sufficiently curing the resin on the front and back surfaces, it is possible to stabilize the production and obtain a product with little deterioration even after long-term use.

  The optical sheet that has been subjected to the final processing may be wound up once in the winding unit, or may be connected to a line for bonding / adhering to the diffusion plate as it is to proceed with the next step.

  The optical sheet is integrated with a diffusion plate or diffusion film having a light diffusion function by bonding or bonding, and this is combined with a member such as a light source to constitute a backlight unit, and further combined with a liquid crystal panel to display a liquid crystal display. Can be manufactured.

    FIG. 13 shows an example of the configuration of the liquid crystal display. A lamp house 21 including a plurality of light sources 20 and a lamp reflector 22 are provided, and a diffusion plate 42 and a diffusion film 43 are overlaid thereon. On the diffusion film 43, an optical element having a stripe-like uneven structure on the back surface of the lens structure surface of the lens sheet 2 through the opening 6, and the light reflecting layer 1 is formed on the entire surface of the convex portion 3. Sheets 10 are stacked. The backlight unit 19 is comprised by these members. A liquid crystal panel 30 sandwiched between polarizing plates 31 and 32 is provided on the lens structure surface side of the optical sheet 10. These members constitute a liquid crystal display.

  FIG. 14 shows another example of the configuration of the liquid crystal display. The optical sheet 10 having a stripe-like uneven structure on the back surface of the lens structure surface of the lens sheet 2 through the opening 8 and having the light reflecting layer 1 formed on the entire surface of the convex 3 has an opening portion. The air layer 8 is held and bonded to the diffusion plate 42 through a bonding layer. A lamp house 21 including a plurality of light sources 20 and a light reflecting plate 22 are provided on the back side of the diffusion plate 42. The backlight unit 19 is comprised by these members. A liquid crystal panel 30 sandwiched between polarizing plates 31 and 32 is provided on the lens structure surface side of the optical sheet 10. These members constitute a liquid crystal display.

  In the configuration of the backlight unit 19 of FIG. 13 or FIG. 14 described above, a configuration in which a diffusion film is stacked on the optical sheet 10 (between the optical sheet 10 and the polarizing plate 32) is also effective.

  The material of the diffusion film 43 shown in FIG. 13 or FIG. 14 is a material that is transparent with respect to the wavelength of the image light and can be used as an optical member. However, in consideration of production efficiency, a plastic film is used. It is preferable. As a plastic, if a polyethylene terephthalate (PET) resin is used, handling is easy and preferable from experience, but acrylic resin such as polymethyl methacrylate, polycarbonate resin, acrylic-styrene copolymer, styrene resin, polyvinyl chloride resin Etc. can also be used.

  The material of the diffusing plate 42 only needs to have a transmittance and mechanical strength that can be practically used to reproduce the projected image, and methacrylstyrene resin, acrylic resin, polycarbonate resin, or the like may be used as the main plastic material. it can. In addition to the plastic plate, a glass plate (float glass, blue plate glass, BK7, etc.) can also be used.

In addition, the optical sheet which concerns on this invention can be used also for uses other than a liquid crystal display. For example, the stripes of the optical film can be appropriately colored and used. In particular, the stripes can be colored black and bonded / adhered to an appropriate diffusion plate for use in a transmission screen.

Hereinafter, the present invention will be described based on examples.
In this example, the optical sheet shown in FIG. 8 was manufactured.

  The lens sheet 2 was produced by melt extrusion molding using PC (polycarbonate) with an extruder shown in FIG.

  The shape of the lens 5 was an aspherical shape with a pitch of 140 μm and an ellipsoidal surface as a reference surface and corrected by higher order terms.

  The convex portion 3 was a rectangular shape having a width of 84 μm, and the concave portion 4 was a planar shape having a width of 56 μm. The amount of protrusion from the bottom surface of the concave portion 4 on the top of the convex portion 3 was 5 μm.

  The light reflecting layer 1 containing titanium dioxide as a white pigment was formed on the uneven surface of the lens sheet 2 obtained as described above. The thickness of the light reflecting layer 1 was 18 μm at the concave portion and 13 μm at the convex portion. The white ink for forming the light reflecting layer 1 contains a resin, and the ratio of the pigment in the ink is 80% by weight. The light transmittance of this light reflecting layer 1 was 15%.

  The removal process of the light reflection layer 1 in the recess 4 was performed by the method shown in FIG. The light reflecting layer in the concave portion 4 corresponding to the condensing portion of the laser light 7 by irradiating the laser light 7 emitted from the YAG laser with the wavelength 1064 nm from the lens structure surface side of the lens sheet 1 and scanning the laser. 1 was selectively removed, and a light reflecting layer was formed on the entire surface of the side and top of the convex portion 3. In addition, the scanning direction in FIG. 12 has shown the moving direction of the lens sheet 1 at the time of repeated irradiation.

At this time, the influence on the pattern formation was examined by changing the incident angle of the laser beam on the lens sheet 2 in various ways. Specifically, the inclination angle of the laser beam in the lens stripe length direction with respect to the normal direction was changed to 0 degree, 10 degrees, 20 degrees, and 30 degrees, but a stripe pattern can be obtained under any conditions. I was able to. In addition, the laser beam tilt angle in the direction perpendicular to the lens stripe length direction with respect to the normal direction was changed in the same manner as described above, but a stripe pattern can be obtained under any conditions. Thus, it is possible to adjust the position of the light reflection layer to be removed and the width of the opening by adjusting the tilt angle of the laser beam.

  The configuration described here is an example of the present invention, and the present invention is not limited to this.

The optical film and the manufacturing method thereof of the present invention are particularly useful for applications such as illumination light path control in a display backlight unit mainly using a liquid crystal display element.

It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the structural example of the liquid crystal display device by a prior art. It is explanatory drawing which shows the perspective view of BEF by a prior art. It is explanatory drawing which shows the structural example of the optical sheet for liquid crystal displays by a prior art. It is explanatory drawing which shows the structural example of the optical sheet for liquid crystal displays by a prior art. It is explanatory drawing which shows the optical sheet cross section by a prior art. It is explanatory drawing which shows the optical sheet cross section which concerns on embodiment of this invention. It is explanatory drawing which shows the optical sheet cross section which concerns on the other embodiment of this invention. It is a schematic explanatory drawing explaining the lens sheet manufacturing method of the optical sheet which concerns on embodiment of this invention. It is sectional drawing explaining the type | mold roll which manufactures the lens sheet of the optical sheet which concerns on embodiment of this invention. It is a schematic explanatory drawing explaining the method of removing the light reflection layer of the optical sheet which concerns on embodiment of this invention. It is explanatory drawing which shows an example of a structure of the liquid crystal display device which concerns on embodiment of this invention. It is explanatory drawing which shows an example of a structure of the liquid crystal display device which concerns on embodiment of this invention.

Explanation of symbols

71 ... Polarizing plate 72 ... Liquid crystal panel 73 ... Polarizing plate 76 ... Light source lamp 77 ... Reflective film 78 ... Diffusion film 79 ... Light guide plate 81 ... Lamp reflector 51 ... Light source lamp 52 ... Lamp reflector 82 ... Diffusion film F ... Axial direction 90 ... Diffusion film 92 ... BEF
300 ... Diffusion film 11 ... Polarizing plate 12 ... Liquid crystal panel 13 ... Polarizing plate 15 ... Lens layer 18 ... Light shielding layer 83 ... Scattering reflection pattern part 1 ... Light reflection layer 2 ... Lens sheet 3 ... Convex part 4 ... Concave part 5 ... Lens surface 60 ... Extruder 61 ... Hopper 62 ... Screw 63 ... Die 64 ... Mold roll 65 ... Mold roll 80 ... Sheet 64a ... Lens surface mold 65a ... Convex / concave mold 6 ... Opening 7 ... Laser light 10 ... Optical sheet 42 ... diffusion plate 43 ... diffusion film 44 ... bonding layer 19 ... backlight unit 20 ... light source lamp 21 ... lamp house 22 ... lamp reflector 30 ... liquid crystal panel 31 ... polarizing plate 32 ... polarizing plate 8 ... opening

Claims (10)

  In an optical sheet used for illumination light path control in a backlight unit for display, at least one type of unit lens or unit prism arranged side by side on the exit surface side, a convex portion projecting on the incident surface side, and the convex And a concave-convex shape in which a plurality of concave portions having a height lower than the convex portion are arranged in order, and the concave portion on the incident surface side is a unit lens or unit on the output surface side It is arranged at a position corresponding to the condensing shape of the parallel light incident from the prism, and the convex portion includes a top portion and a side portion of the convex portion, which is a region sandwiched between the convex portion and the concave portion. A light reflecting layer is formed on the entire surface including the optical sheet.   2. The optical sheet according to claim 1, wherein the shape of the bottom surface of the recess is a flat surface.   2. The optical sheet according to claim 1, wherein the shape of the bottom surface of the concave portion is a curved surface shape including a convex curved surface on the incident surface side.   The optical sheet according to any one of claims 1 to 3, wherein an amount of protrusion of the top of the convex portion from the bottom surface of the concave portion is 1 µm or more and 95 µm or less.   The optical sheet according to any one of claims 1 to 4, wherein an amount of protrusion including the light reflecting layer from the bottom surface of the concave portion at the top of the convex portion is 6 µm or more and 100 µm or less.   6. The optical sheet according to claim 1, wherein the unit lens or the unit prism, the convex portion, and the concave portion are integrally molded.   In an optical sheet used for illumination light path control in a backlight unit for display, at least one type of unit lens or unit prism arranged side by side on the exit surface side, a convex portion projecting on the incident surface side, and the convex And a concave-convex shape in which a plurality of concave portions having a height lower than the convex portion are arranged in order, and the concave portion on the incident surface side is a unit lens or unit on the output surface side A lens film arranged at a position corresponding to a condensing shape of parallel light incident from a prism is prepared, a light reflection layer is formed on the entire incident surface side of the lens film, and a light reflecting layer on the exit surface side of the lens film is formed. Irradiate laser light from a unit lens or unit prism, and selectively remove the portion of the light reflecting layer corresponding to the condensing portion of the laser light so that there is no light reflecting layer. Forming a top portion of the convex portion, other method of manufacturing an optical sheet according to any one of claims 1 to 6, characterized in that to leave the light reflecting layer on the entire surface, including the side.   The light diffusion sheet and the optical sheet according to any one of claims 1 to 6 are laminated and integrated via a bonding layer, and the light diffusion sheet or the bonding layer, the light reflection layer, and the concave portion are combined. An optical sheet having an air layer in an enclosed space.   A backlight unit for a display, comprising: a direct light source; and the optical sheet according to any one of claims 1 to 6 or claim 8.   An image display element comprising a liquid crystal display element that defines a display image in accordance with transmission / shading in pixel units and the backlight unit according to claim 9, wherein the direct light source is a cold cathode tube, an organic EL, or an LED The display characterized by being.

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