JP2008304518A - Optical sheet for display, manufacturing method therefor, backlight unit, and display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet having satisfactory alignment of lens structure such as a lenticular lens in a surface side with structure of a reflecting layer including an opening part in a reverse face side, and excellent in light using efficiency, and a backlight unit and a display using the same. <P>SOLUTION: The optical sheet 10 is constituted by forming the white reflecting layer 2 having the light transmitting opening part 2a in response to the central part including an optical axis of a unit lens, on a face opposite to a lens layer 4 of a lens sheet 1 having the lens layer 4 comprising a cylindrical lens of the unit lens, a prism or assembly thereof. The lens sheet 1 is obtained via the adhesive layer 2 having light reflexibility, on the face opposite to the lens layer 4 of the lens sheet 1 forming the two layers of reflecting layers 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical sheet mainly used for illumination light path control in a display backlight unit using a liquid crystal display element, a manufacturing method thereof, a backlight unit using the optical sheet, and a display device.

  As a display typified by a liquid crystal display (LCD), a display having a built-in light source (backlight) necessary for recognizing provided information is remarkably widespread. In particular, in a battery-type display device such as a laptop computer, the power consumed by the light source occupies a considerable portion of the power consumed by the entire device. For this reason, it is particularly desirable for battery powered displays to increase battery life by reducing the total power required to provide a given brightness.

In order to solve this problem, an optical sheet provided with a brightness enhancement film (BEF, a registered trademark of 3M USA) between a light source or a light guide plate and a liquid crystal panel is widely used.
BEF is a film in which unit prisms having a triangular cross section are periodically arranged in one direction on a transparent substrate. This prism is formed in a size (pitch) larger than the wavelength of light. BEF collects light from “off-axis” and redirects it “on-axis” or “recycle” toward the viewer. To do. When using the display (when observing), 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 viewer, and is generally a normal direction to the display screen.

  When the repetitive array structure of the prism is arranged in only one direction, only the light can be redirected or recycled in the direction of the arrangement. Therefore, in order to control the luminance of the display light in the horizontal and vertical directions, two sheets are stacked and combined so that the arrangement directions of the prism groups 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 disclose that a brightness control member having a repetitive array structure of prisms represented by BEF is used in a display (see, for example, Patent Documents 1 to 3).

  In an optical sheet using BEF as a brightness control member, light from a light source is emitted from the film at an angle controlled by refraction, and can be controlled to increase the intensity of light in the viewer's visual direction. However, there are unexpected light rays that are emitted in the horizontal direction without proceeding in the visual direction of the viewer. That is, regarding the intensity distribution of the light emitted from the optical sheet provided with the BEF, the light intensity in the viewer's visual direction (the angle with respect to the axial direction is 0 °) is the highest, but ± 90 with respect to the axial direction. There is also a problem that a small light intensity peak occurs in the vicinity of °, and the amount of light emitted unnecessarily 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 order to solve such a problem, an optical sheet having a repetitive array structure of unit lenses (also referred to as a lenticular lens) instead of a prism has been proposed (see, for example, Patent Document 4).
The surface of the optical sheet on the liquid crystal panel side has an array structure in which a plurality of unit lenses are repeatedly formed so as to guide light emitted from a light source and traveling through the optical sheet to the liquid crystal panel. On the other surface of the optical sheet, a reflective layer patterned in a stripe shape is provided so that the vicinity of the focal plane of the lens is an opening. In the case where the unit lens is a semi-cylindrical convex cylindrical lens, the reflective layer is formed in a stripe shape so that an opening is formed corresponding to each unit lens in a 1: 1 ratio. Such a reflective layer is formed by printing or transferring a mixture in which a white pigment, for example, titanium dioxide (TiO ₂ ) powder is mixed with a transparent resin or the like so as to form a predetermined pattern.

When such an optical sheet is incorporated into the backlight unit of a liquid crystal display, only the light emitted from the diffusion film that has passed through the opening between the reflective layers is incident on the lens and is condensed in a certain direction by the lens. After being emitted. Furthermore, the light emitted from the optical sheet enters the polarizing plate, and only the light having a predetermined polarization component is guided to the liquid crystal panel.
On the other hand, the light that has not passed through the opening is reflected by the reflection layer, returned to the diffusion film side, and guided to the reflection plate. Then, the light is incident on the diffusion film again by being reflected by the reflecting plate, and after being diffused again on the diffusion film, the incident light is incident on the lens through the opening after the incident angle is reduced. Is squeezed within a predetermined angle and emitted from the optical sheet.

In the backlight unit using such an optical sheet, by adjusting the size and position of the opening between the reflective layers, the ratio of the light emitted from the lens in the front direction is increased while improving the light utilization efficiency. Can be controlled to increase.
Japanese Patent Publication No. 1-378001 Japanese Examined Patent Publication No. 6-102506 Japanese National Patent Publication No. 10-506500 JP 2000-284268 A

In the conventional optical sheet, when misalignment occurs between the lenticular lens constituting the lens layer and the reflective layer and the opening formed on the surface opposite to the lens layer, moire or luminance unevenness occurs. , It will not function as a brightness enhancement film. For this reason, it is necessary to accurately align the structure on the front surface side having the lens layer and the back surface side having the reflective layer and the opening, which causes a manufacturing problem.
For example, in a method in which a lens layer or a reflective layer and an opening are formed on separate films and then these are bonded and integrated, there is a problem in maintaining alignment accuracy. In addition, it is necessary to mold the lens layer and the reflective layer separately, which increases the number of manufacturing steps.

  In order to solve the problem of the alignment of the front and back structures in the optical sheet as described above, a method of simultaneously molding the front and back structures can be considered. However, when such a method is used, it increases the number of members and processes, which causes a decrease in yield, which in turn increases a cost. In particular, when the shape of the lens on the front and back surfaces is to be molded with a mold using a radiation curable resin, it is necessary to sandwich the film with two molds for molding the front and back structures. However, since radiation irradiation is essential for curing the radiation curable resin, a method using two molds cannot be employed.

  On the other hand, for the same film, the surface side structure is molded and irradiated sequentially, and the back side structure is molded and irradiated with radiation. The deviation of the shape due to the above, particularly the deviation in the stripe width direction, becomes remarkable, adversely affects the alignment of the front and back structures, and cannot be practically adopted.

  The present invention has been made in order to solve the above-described conventional problems, and an object of the present invention is to align a lens structure such as a lenticular lens on the front surface side and a structure of a reflective layer including an opening on the back surface side. It is an object of the present invention to provide an optical sheet having good light utilization efficiency, a method for manufacturing the same, a backlight unit using the optical sheet, and a display device.

  The invention according to claim 1 of the present invention is an optical sheet used for illumination light path control in a display backlight unit, and a lens having lens layers formed by arranging unit lenses on one surface at a constant pitch. A sheet, and a reflection layer formed on a surface opposite to the lens layer of the lens sheet, and having a light transmission opening corresponding to a central portion including the optical axis of the unit lens, It is characterized by being configured in a two-layer structure stacked in the thickness direction.

According to a second aspect of the present invention, in the optical sheet according to the first aspect, the lens sheet includes a transparent support film, the lens layer is formed on one surface of the support film, and the lens layer is a radiation. It consists of a curable resin.
According to a third aspect of the present invention, in the optical sheet according to the first aspect, the layer on the lens sheet side of the reflective layer contains an infrared absorber.
According to a fourth aspect of the present invention, in the optical sheet according to the first aspect, the layer on the lens sheet side of the reflective layer contains an infrared absorber and is transmissive to visible light. .

According to a fifth aspect of the present invention, in the optical sheet according to the first aspect, a light diffusion film is laminated and adhered to the surface of the reflective layer opposite to the lens sheet so as to cover the opening. .
According to a sixth aspect of the present invention, in the optical sheet of the first aspect, the unit lens is composed of a cylindrical lens or a prism, and the lens layer is composed of an assembly of the cylindrical lens or prism.

  The invention according to claim 7 is a method of manufacturing an optical sheet used for illumination light path control in a display backlight unit, and has a lens layer in which unit lenses are arranged and formed at a constant pitch on one surface. A lens sheet is provided, two reflective layers are formed on the other surface of the lens sheet opposite to the lens layer, and the light condensing action of the unit lens is irradiated with laser light from the lens layer side to the reflective layer. Thus, an exposed area and an unexposed area are formed in the reflective layer, and an opening for light transmission is formed by removing the exposed area.

According to an eighth aspect of the present invention, in the optical sheet according to the seventh aspect, the lens sheet includes a transparent support film, the lens layer is formed on one surface of the support film, and the lens layer is a radiation. It consists of a curable resin.
The invention according to claim 9 is the method for producing an optical sheet according to claim 7, wherein the layer on the lens sheet side of the reflection layer contains an infrared absorber.
The invention of claim 10 is the method for producing an optical sheet according to claim 7, wherein the lens layer side layer of the reflective layer contains an infrared absorber and has transparency to visible light. Features.

According to an eleventh aspect of the present invention, in the optical sheet manufacturing method according to the seventh aspect, a light diffusing film is laminated and adhered to the surface of the reflective layer opposite to the lens sheet so as to cover the opening. Features.
According to a twelfth aspect of the invention, there is provided an optical sheet manufacturing method according to the seventh aspect, wherein the unit lens is formed of a cylindrical lens or a prism, and the lens layer is formed of the cylindrical lens or a prism or an assembly thereof.

The invention according to claim 13 is a backlight unit for display, comprising an image display element for defining a display image, a light source on the back of the image display element, and the optical according to any one of claims 1 to 6. A sheet or at least an optical sheet manufactured by the method according to any one of claims 7 to 12 is provided.
According to a fourteenth aspect of the present invention, in the display backlight unit according to the thirteenth aspect, the image display element is a liquid crystal display element.

  The invention of claim 15 is a display device, wherein the display device defines a display image according to transmission / light-shielding in pixel units, and a light source is provided on the back surface of the image display device. The display backlight unit is provided.

The optical sheet according to the present invention corresponds to the central portion including the optical axis of the unit lens on the surface opposite to the lens layer of the lens sheet having a cylindrical lens or prism as a unit lens or a lens layer made of an assembly thereof. Since the reflective layer having an opening for transmitting light is formed in two layers, when this is used for a backlight unit for a display, a backlight unit and a display device with high light utilization efficiency are provided. can do.
Moreover, in this invention, by making a reflection layer into two layers, the adhesiveness of a reflection layer can be improved and the durability with respect to a pressure, tension | tensile_strength, a temperature change, etc. can be improved.
Furthermore, the reflectance can be adjusted by taking the thickness of the two layers of the reflective layer and the balance between the two layers, and the range of material selection can be expanded.

In addition, according to the present invention, the lens sheet has a two-layer structure in which a transparent support film and a lens layer made of a radiation curable resin are laminated, thereby facilitating adjustment of the lens sheet thickness, Mechanical strength can also be improved.
In addition, according to the present invention, the whiteness of the outermost layer is maintained while improving workability using, for example, an infrared laser, by including an infrared absorber in the lens layer side layer of the reflective layer. It becomes easy.
Further, according to the present invention, the layer on the lens sheet side of the reflective layer includes an infrared absorber and is transparent to visible light, and further, the infrared absorbing layer does not need to contain a white pigment. As a result, the range of material selection is widened, and the binder-rich structure is obtained, and the mechanical strength of the reflective layer can be easily improved.
Workability can be maintained by the effect of the added infrared absorption layer, and there are great advantages such as the common manufacturing process.

Further, according to the present invention, a lens layer in which a cylindrical lens or a prism or an assembly thereof is formed is formed on one surface of the lens sheet, and two layers are formed on the other surface of the lens sheet opposite to the lens layer. By forming the reflective layer, it is possible to suppress the color development of the pigment generated during laser irradiation, and a white layer with good brightness can be easily obtained.
Further, according to the present invention, in addition to the effect of improving sensitivity with an infrared absorbent, it is possible to obtain the effect of adjusting the degree of dust generation during processing called debris and preventing discoloration due to exposure to high temperatures.

(First embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view of an optical sheet according to the first embodiment of the present invention.
In FIG. 1, an optical sheet 10 includes a lens sheet 1 in which unit lenses 1a having a structure such as a lenticular lens (repetitive array structure of a striped semi-cylindrical convex cylindrical lens) are arranged at a constant pitch. On the surface of the lens sheet 1 opposite to the unit lens 1a, two reflective layers 2 are formed in a stripe shape corresponding to the unit lens 1a. An opening 2a for transmitting light is formed between the reflective layers 2 adjacent to each other, that is, at a position corresponding to the central portion including the optical axis of the unit lens 1a. The opening 2a substantially matches the condensing shape of parallel light incident on the lens sheet 1 from the unit lens 1a side.
A light diffusion film 12 is laminated and adhered to the surface of the reflective layer 2 opposite to the lens sheet 1 with an adhesive 11 so as to cover the opening 2a.

(Second Embodiment)
FIG. 2 is a sectional view of an optical sheet according to another embodiment of the present invention.
In FIG. 2, the optical sheet 10 is formed by arranging unit lenses 4a having a structure such as a lenticular lens (repetitive array structure of a striped semi-cylindrical convex cylindrical lens) on one surface of a support film 3 at a constant pitch. The lens sheet 1 having the lens layer 4 is provided. On the surface of the lens sheet 1 opposite to the unit lens 1a, two reflective layers 2 are formed in stripes corresponding to the unit lens 1a. . An opening 2a for transmitting light is formed between the reflective layers 2 adjacent to each other, that is, at a position corresponding to the central portion including the optical axis of the unit lens 1a. The opening 2a substantially matches the condensing shape of parallel light incident on the lens sheet 1 from the unit lens 1a side. In this case, the thickness of the support film 3 is set so that the back surface (the reflective layer 2 side) of the support film 3 is in the vicinity of the light collection position of the entire lens sheet 1.
If the thickness of the support film 3 is set as described above, the light transmitting opening 2a formed between the stripe-shaped light-reflective adhesive layers 2 can be easily and accurately formed in the lens sheet 1. It can be adjusted to coincide with the condensing shape of the parallel light incident from the unit lens 4a side. Incidentally, the thickness of the support film 3 is usually about 50 μm to 200 μm.

  As a material for the lens layer 4, it is desirable to use a radiation curable resin such as an ultraviolet curable resin or an electron beam curable resin when particularly fine processing is required. As a radiation curable resin, the composition which added the reaction diluent, the photoinitiator, the photosensitizer, etc. to urethane (meth) acrylate and / or an epoxy (meth) acrylate oligomer can be used, for example.

The urethane (meth) acrylate oligomer is not particularly limited. For example, ethylene glycol, 1,4-butanediol, neopentyl glycol, polycaprolactone polyol, polyester polyol, polycarbonate diol, polytetramethylene glycol, and the like, hexamethylene diisocyanate, and isophorone. It can be obtained by reacting with a polyisocyanate such as diisocyanate, tolylene diisocyanate and xylene isocyanate.
The epoxy (meth) acrylate oligomer is not particularly limited. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, terminal glycidyl ether of bisphenol A type propylene oxide adduct, fluorene epoxy resin, etc. These epoxy resins can be obtained by reacting (meth) acrylic acid.

As the material of the reflective layer 2, a material in which a white pigment is dispersed in a resin is used. As the white pigment, TiO ₂ , BaSO ₄ , ZnO, Al ₂ O ₃ , Ag, or the like can be used.
By setting the thickness of the reflective layer 2 to 5 μm or more, a sufficient white color can be obtained and adjusted to a desired transmittance, and it has sufficient strength against rubbing and the like and does not easily peel / drop off. . Moreover, by making the thickness of the reflective layer 2 100 μm or less, it is possible to improve the processing shape of the pattern and reduce the material cost. Since the reflective layer 2 having such a thickness can reflect light inside the layer, it can be said to be a volumetric reflective layer.

As the curing agent, for example, polyfunctional isocyanate, polyfunctional epoxy compound, or metal chelate is used.
Further, examples of the white _pigment, and the like can be used _{TiO 2, BaSO 4, ZnO,} Al 2 O 3, Ag. When the thickness of the light-reflective adhesive layer 2 is 5 μm or more, a sufficient white color can be obtained and adjusted to a desired transmittance, and it has sufficient strength against rubbing and is easily peeled / It will not drop out. Further, by setting the thickness of the light-reflective adhesive layer to 100 μm or less, the pattern processing shape can be improved and the material cost can be reduced. The adhesive layer 2 having such a thickness and having light reflectivity can reflect light inside the layer, and thus can be called a volumetric reflective layer.

  Next, with reference to FIG. 3 and FIG. 4, an example of the manufacturing method of the lens sheet which concerns on this invention, and the adhesive layer with light reflectivity is demonstrated.

  First, as shown in FIG. 3, the support film 3 is supplied from the unwinding roll 101, and an ultraviolet curable resin is applied to the surface of the support film 3 by the coating device 102. The support film 3 is passed between a lens forming roll 103 having a reverse lenticular lens shape on the surface and a pressure roll 103a, and the lens structure is transferred to the ultraviolet curable resin on the support film 3. Thereafter, ultraviolet rays are irradiated from the ultraviolet irradiation device 104 to cure the ultraviolet curable resin, thereby forming the lens layer 4 as shown in FIG.

  The support film 3 is preferably a transparent resin film having ultraviolet transparency, and it is more preferable that the surface on which the lens layer is formed is subjected to an easy-adhesion treatment of the ultraviolet curable resin. Examples of the material of the support film 3 include polyethylene terephthalate (PET), polycarbonate (PC), and polyvinyl chloride (PVC).

The ultraviolet curable resin coating apparatus 102 is not particularly limited, but a doctor blade, a die coater, or the like is desirable. The thickness of the UV curable resin applied to the support film 3 varies depending on the shape of the lenticular lens to be formed, but is suitably 0.02 to 0.2 mm. The coating thickness of the ultraviolet curable resin can be adjusted by the viscosity of the resin, the feeding speed of the support film, and the like.
Further, as the lens forming roll 103 having a shape opposite to that of the lenticular lens formed on the surface of the support film 3, a cut metal mold or a resin mold duplicated from the metal mold by a predetermined method is arranged on the roll surface. The one set up is used.

  Next, as shown in FIG. 4, the reflective layer 2 containing a white pigment is formed on the surface (flat surface) opposite to the lens layer 4 of the lens sheet 1 (not shown). If the raw material of the reflective layer 2 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, etc. 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 reflective layer 2. Further, in order to make the reflective layer 2 into two layers, it can be easily obtained by repeating the above process while changing the material.

As a printing method for the reflective layer, 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 necessary thickness may be formed by several printings. 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 can be used, and a thermal transfer method, a sublimation transfer method, a transfer method using adhesion or adhesion, and the like can be used.
The thickness of the reflective layer 2 is preferably more than 5 μm and not more than 100 μm. When the thickness of the pressure-sensitive adhesive layer 2 exceeds 5 μm, a sufficient white color can be obtained and adjusted to a desired transmittance, and it has sufficient strength against rubbing and the like and does not easily peel / drop off. Moreover, if the thickness of the reflective layer 2 is 100 μm or less, the processed shape of the pattern can be improved and the material cost can be reduced.

  Next, as shown in FIG. 4, laser light 6 is irradiated as parallel light from the lens layer 4 side of the lens sheet 1. In this state, the laser beam 6 is moved relative to the lens sheet 1 in the stripe length direction (direction perpendicular to the paper surface), so that the unit lens 4a constituting the lens layer 4 collects the reflecting layer 2 by the light collecting action. An exposed area and an unexposed area are generated, and the exposed area is removed to form an opening 2a for light transmission. By repeating this operation by moving the laser beam 6 relative to the lens sheet 1 along the stripe arrangement direction (arrow direction), the stripe-shaped reflective layer 2 can be left. In this way, a stripe pattern of the reflective layer 2 corresponding to the structure of the lens sheet 1 can be obtained.

The wavelength of the laser beam 6 is not particularly limited as long as sufficient energy can be given to the reflective layer 2. However, in consideration of the transmittance of the lens sheet 1 and the absorptivity of the reflective layer 2, it is preferable to use a laser beam having a wavelength of 0.8 μm or more obtained with a YAG laser (wavelength 1.064 μm) or LD.
It is also effective to irradiate with radiation such as ultraviolet rays in order to fix the reflective layer after processing the striped reflective layer. 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 lens sheet that has undergone final processing may be wound at the upper winding portion with the separator film laminated, or may be directly connected to a line for bonding / adhering to the diffusion plate to proceed with the next process. .

  The optical sheet 10 can be formed by bonding or adhering the lens sheet 1 configured as described above to a diffusion plate or a diffusion film having a diffusion function. This can be combined with a member such as a light source (backlight) to form a backlight unit, and further combined with a liquid crystal panel to produce a liquid crystal display.

Next, a liquid crystal display device including a backlight unit using the optical sheet of the present invention will be described with reference to FIG.
In FIG. 5, a liquid crystal display device 100 includes a liquid crystal panel 30 (corresponding to an image display element described in claims), and a backlight unit 40 arranged facing the light incident side of the liquid crystal panel 30. Is provided.
The backlight unit 40 is configured to include an optical sheet 10 for controlling an illumination light path and a direct light source 23 disposed so as to face the light incident side of the liquid crystal panel 30. The optical sheet 10 is configured in the same manner as in the case shown in FIG. 1 (or in the case shown in FIG. 2), and thus the description of the configuration is omitted.

The direct type light source 23 is disposed to face the light incident surface of the light scattering sheet 5 constituting the optical sheet 10, and a plurality of light sources arranged to face the light incident surface of the light scattering sheet 5. 20, a lamp house 21 that houses the light source 20, and a light reflection plate 22 that is disposed so as to cover the light source 20 including the lamp house 21 from the opposite side of the light scattering sheet 5.
The liquid crystal panel 30 is disposed on the lens sheet 1 on the side facing the lens layer 4. The liquid crystal panel 30 is polarized so that the liquid crystal panel 30 is sandwiched between the front and back surfaces of the liquid crystal panel 30. Plates 31 and 32 are provided. Thus, a liquid crystal display, that is, a liquid crystal display device is configured.

The material of the light diffusion film 12 having a diffusion function is a material that is transparent with respect to the wavelength of the image light, and can be used without limiting what is used for the optical member. Is preferably used. As this plastic film, if polyethylene terephthalate (PET) is used, it is easy to handle from experience and preferable. However, acrylic resins such as polymethyl methacrylate, polycarbonate resins, acrylic-styrene copolymers, styrene resins, polyvinyl chloride Etc. can also be used.
Further, the material of the light diffusion film 12 having a diffusion function may have a transmittance and mechanical strength that can be practically used for reproduction of projected images. Main plastic materials include methacryl styrene resin, acrylic resin, and polycarbonate. Resin or the like can be used. 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 concerning this invention can be used also for uses other than a liquid crystal display device. For example, the stripe-shaped reflective layer of the optical sheet can be appropriately colored and used. In particular, the stripe-shaped reflective layer can be colored black and bonded / adhered to an appropriate light diffusion film to be used for a transmission screen.

Next, examples of the present invention will be described.
Example 1
In Example 1, an optical sheet having the structure shown in FIG. 2 was manufactured. Further, a polyethylene terephthalate (PET) film (Toyobo A4300) having a thickness of 75 μm was used as the support film 3.

  In the optical sheet manufacturing method shown in FIG. 3, an ultraviolet curable resin is applied on the support film 3, and the lens structure of the lens molding roll 103 is transferred to the ultraviolet curable resin, and then irradiated with ultraviolet rays. Is cured to form a lens layer. Thereby, a lens sheet was produced. The shape of the unit lens was an aspherical shape with a pitch of 140 μm and an ellipsoidal surface as a reference surface and corrected by higher order terms. When unit lenses are formed at a pitch of 140 μm in this way, the vicinity of the back surface of the support film 3 made of PET having a thickness of 75 μm becomes the focal plane of the laser light used for stripe processing of the reflective layer.

On the surface opposite to the lens layer of the lens sheet thus obtained, first, a pigment having two thicknesses of 5 μm in which two kinds of pigments (titanium oxide and barium sulfate are 1: 1) as the first layer of the two reflective layers. A reflective layer was formed, and after the coating / drying treatment, a second reflective layer containing 100% titanium oxide as a pigment was formed.
Next, the reflective layer was striped by the method shown in FIG. A laser beam 6 having a wavelength of 1064 nm emitted from a YAG laser is irradiated from the lens layer side of the lens sheet 1 and scanned with the laser, whereby one of the reflection layers 2 corresponding to the condensing portion of the laser beam 6 by the unit lens is scanned. The exposed portion was exposed and the exposed portion was selectively removed to form a stripe pattern of the reflective layer 2.

In this case, the influence on the pattern formation was examined by variously changing the incident angle of the laser beam to the lens sheet 1. Specifically, the tilt angle of the laser beam in the direction of the stripe length of the lens with respect to the vertical direction was changed to 0 degrees, 10 degrees, 20 degrees, and 30 degrees, but a stripe pattern can be obtained under any conditions. It was.
Further, as a first layer of the two reflective layers, a reflective layer having a thickness of 5 μm in which only an acrylic binder is blended with an IR absorber (organic absorber) is formed, and after coating / drying treatment, 100% titanium oxide is pigmented Similar results were obtained even when the second reflective layer was formed.

Sectional drawing of the optical sheet which shows 1st Embodiment concerning this invention. Sectional drawing of the optical sheet which shows 2nd Embodiment concerning this invention. The schematic diagram which shows the manufacturing method of the lens sheet concerning this invention. The schematic diagram which shows the manufacturing method of the optical sheet concerning this invention. The schematic diagram which shows the structure of the liquid crystal display incorporating the optical sheet concerning this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Lens sheet, 1a ... Unit lens, 2 ... Adhesive layer, 2a ... Opening part, 3 ... Support film, 4 ... Lens layer, 4a ... Unit lens, 6 ... Laser beam, 10 ... ... optical sheet, 20 ... light source, 21 ... lamp house, 22 ... light reflector, 23 ... direct light source, 30 ... liquid crystal panel, 31, 32 ... polarizing plate, 101 ... unwinding roll, 102 ... Coating device, 103 ... Lens molding roll, 103a ... Pressure roll, 104 ... UV irradiation device.

Claims (15)

In an optical sheet used for illumination light path control in a backlight unit for display,
A lens sheet having a lens layer formed by arranging unit lenses on one surface at a constant pitch;
A reflection layer formed on a surface of the lens sheet opposite to the lens layer and having a light transmission opening corresponding to a central portion including the optical axis of the unit lens;
The reflective layer is configured in a two-layer structure stacked in the thickness direction.
An optical sheet characterized by that.   The optical system according to claim 1, wherein the lens sheet includes a transparent support film, and the lens layer is formed by laminating one surface of the support film, and the lens layer is made of a radiation curable resin. Sheet.   The optical sheet according to claim 1, wherein a layer on the lens sheet side of the reflective layer contains an infrared absorber.   The optical sheet according to claim 1, wherein a layer on the lens sheet side of the reflective layer contains an infrared absorber and has transparency to visible light.   The optical sheet according to claim 1, wherein a light diffusion film is laminated and adhered to the surface of the reflective layer opposite to the lens sheet so as to cover the opening.   2. The optical sheet according to claim 1, wherein the unit lens is composed of a cylindrical lens or a prism, and the lens layer is composed of an assembly of the cylindrical lens or prism. A method of manufacturing an optical sheet used for illumination light path control in a backlight unit for display,
A lens sheet having a lens layer formed by arranging unit lenses on one surface at a constant pitch is provided.
Forming a reflective layer in two layers on the other surface of the lens sheet opposite to the lens layer;
A laser beam is irradiated to the reflective layer from the lens layer side to cause an exposure area and an unexposed area in the reflective layer by the condensing action of the unit lens, and the exposed area is removed to open a light transmission opening. Formed part,
An optical sheet manufacturing method characterized by the above.   8. The optical system according to claim 7, wherein the lens sheet includes a transparent support film, and the lens layer is formed by laminating one surface of the support film, and the lens layer is made of a radiation curable resin. Sheet.   The method for producing an optical sheet according to claim 7, wherein a layer on the lens sheet side of the reflective layer contains an infrared absorber.   The method for producing an optical sheet according to claim 7, wherein the layer on the lens sheet side of the reflective layer contains an infrared absorber and has transparency to visible light.   8. The method of manufacturing an optical sheet according to claim 7, wherein a light diffusion film is laminated and adhered to the surface of the reflective layer opposite to the lens sheet so as to cover the opening.   8. The method of manufacturing an optical sheet according to claim 7, wherein the unit lens is formed of a cylindrical lens or a prism, and the lens layer is formed of the cylindrical lens or a prism or an assembly thereof. An image display element for defining a display image;
At least a light source and an optical sheet according to any one of claims 1 to 6 or an optical sheet manufactured by the method according to any one of claims 7 to 12 are provided on the back surface of the image display element.
A backlight unit for displays.   14. The display backlight unit according to claim 13, wherein the image display element is a liquid crystal display element. An image display element that defines a display image according to transmission / shading in pixel units;
15. A display device comprising a light source and a display backlight unit according to claim 13 or 14 on a back surface of the image display element.

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