JP2009086193A - Optical film and its manufacturing method, and backlight unit and display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film having good alignment between a lens structure having stripe lenses such as lenticular lenses in the top face side and a structure of a reflection layer on the backside, and having excellent use efficiency of light, and to provide a method for manufacturing the same. <P>SOLUTION: The optical film comprises: a lens film (1) having a lens structure face where cylindrical lenses, prism lenses or a collection of these (4) are formed in stripes on one surface of the film; and a light reflection layer (2) on the backside of the lens structure of the lens film (1), the reflection layer containing magnesium carbonate or clay as a pigment formed into stripes leaving apertures (2a) corresponding to a pattern of condensed light of parallel beams incident from the lens structure face side of the lens film (1). <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 referred to as a liquid crystal display) mainly using a liquid crystal display element, a manufacturing method thereof, a backlight unit and a display.

  Generally, as shown in FIG. 6, a liquid crystal display is not a self-luminous type like other image display devices (plasma display panel, organic EL display, field emission display, etc.). In most cases, it is necessary to refer to FIG. In that case, the power consumption of the backlight unit 40 is added to the power consumption necessary for driving the liquid crystal panel 30.

  Therefore, in order to reduce the power consumption of the backlight unit 40 as much as possible, an attempt has been made to reduce the total power consumption of the display by using the optical film 10 having a brightness enhancement function.

  In order to solve this problem, an optical film including a brightness enhancement film (BEF, a registered trademark of 3M USA) is widely used between a light source or a light guide plate and a liquid crystal panel.

  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 this light “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 prisms is arranged in only one direction, only redirection or recycling in the arrangement direction is possible. Therefore, in order to control the luminance of the display light in the horizontal and vertical directions, two sheets are overlapped 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 film 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. There are also 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 film provided with the BEF, the light intensity is highest in the viewer's visual direction (the angle with respect to the axial direction is 0 °), 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 overcome such drawbacks, an optical film 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 film 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 film to the liquid crystal panel.

  On the other surface of the optical film, there is provided a light reflecting layer patterned in a stripe shape so that the vicinity of the focal plane of the lens is an opening. When the unit lens is a semi-cylindrical convex cylindrical lens, the light reflecting layer is formed in a stripe shape so that an opening is formed corresponding to each unit lens in a ratio of 1: 1. Such a light reflection layer is formed by printing or transferring a mixture obtained by mixing a white pigment, for example, titanium dioxide powder, in a solution such as a transparent adhesive so as to form a predetermined pattern.

  When this optical film is incorporated in a backlight unit of a liquid crystal display, only the light emitted from the diffusion film that has passed through the opening between the light reflecting 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 film 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 light reflecting layer, returned to the diffusion film side, and guided to the reflecting plate. Then, the light is incident on the diffusion film again by being reflected by the reflection 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 film.

  In the backlight unit using such an optical film, by adjusting the size and position of the opening between the light reflecting 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.

Hereinafter, known prior art documents related to the present invention are described.
Japanese Patent Publication No. 1-378001 JP-A-6-102506 Japanese National Patent Publication No. 10-506500 JP 2000-284268 A

  In the conventional optical film, when misalignment occurs between the lenticular lens on the structural surface and the light reflecting layer and the opening on the back surface of the structural surface, moire and luminance unevenness occur, and the film does not function as a luminance enhancement film. For this reason, it is necessary to take alignment accurately with the structure of the front surface and the back surface, and there is a manufacturing problem.

For example, in the method in which the shapes of the front surface and the back surface are formed on separate films and then bonded and integrated, there is a problem in maintaining alignment accuracy. In addition, it is necessary to mold the lens and the light reflection layer separately, which increases the number of steps.

  In order to solve the problem of alignment of the front and back surfaces, a method of simultaneously molding the front and back surfaces is conceivable. However, when such a method is used, the number of members and processes is increased, which causes a decrease in yield and an increase in cost. In particular, there is a method of sandwiching a film with two molds for molding the front and back surfaces of the front and back lenses and the like when they are molded with a mold using a radiation curable resin. 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 sequentially molded and irradiated, and the back side structure is molded and irradiated, so that the resin is cured or shrunk during the first molding, etc. 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 surfaces, and cannot be practically adopted.

  An object of the present invention is to provide an optical film having a good alignment between a lens structure such as a lenticular lens on the front surface side and a structure such as a light reflecting layer on the rear surface side of the lens and a method for producing the optical film. It is to provide.

  According to a first aspect of the present invention, there is provided a lens film having a lens structure surface in which a cylindrical lens, a prismatic lens, or an assembly thereof is formed in a stripe shape on one surface, and is opposite to the lens structure surface. Striped openings corresponding to the stripe-shaped condensing shape formed on the back surface of the lens film by parallel light incident on the lens from the lens structure surface side of the lens film on the lens film back surface of the surface, And a light reflection layer containing at least magnesium carbonate formed in a stripe shape so as to correspond to both sides of each opening, or a pigment such as clay, titanium dioxide, barium sulfate, zinc oxide, alumina, or silver. It is an optical film.

  According to a second aspect of the present invention, in the optical film according to the first aspect, the lens film has a structure in which a transparent support film and a lens layer made of a radiation curable resin are laminated. It is an optical film.

  The invention according to claim 3 of the present invention is that, in the optical film according to claim 1 or 2, the compounding ratio of the magnesium carbonate or clay in the solid content of the light reflecting layer is 70% by weight or less. It is the optical film characterized.

  The invention according to claim 4 of the present invention is that, in the optical film according to claim 1 or 2, the compounding ratio of the magnesium carbonate or clay in the solid content of the light reflecting layer is 50% by weight or less. It is the optical film characterized.

  The invention according to claim 5 of the present invention is a manufacturing method for manufacturing the optical film according to any one of claims 1 to 4, wherein a cylindrical lens, a prismatic lens or a set of them is formed on one surface. A lens film having a lens structure surface on which a body is formed is prepared, and a light reflection forming layer containing at least magnesium carbonate or clay as a pigment is provided on the back surface of the lens film opposite to the lens structure surface of the lens film. Forming, irradiating near infrared wavelength laser light from the lens structure surface side of the lens film, and condensing the laser light in a stripe shape on the back surface of the lens film to a predetermined width by each lens, The light reflection forming layer portion corresponding to the light condensing portion is selectively removed by condensing laser light to form an opening, and a stripe is formed. Which is a method for producing an optical film according to any one of claims 1 to 4, characterized in that to leave the light reflection layer.

  Invention of Claim 6 of this invention is arrange | positioned at the back surface (back surface) side of the image display element which prescribes | regulates a display image, The optical film of any one of Claims 1 thru | or 4, A light-diffusion film, A backlight unit comprising a direct-type light source section arranged immediately below the light diffusion film in this order.

  The invention according to claim 7 of the present invention is characterized by comprising 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 6. It is a display.

  The invention according to claim 8 of the present invention is the display according to claim 7, wherein the light source part of the backlight unit is a light source part of a cold cathode ray tube, an organic EL, or an LED. is there.

  According to the optical film of the invention according to claim 1 of the present invention, it corresponds to the condensing shape of parallel light incident on the lens film from the lens structure surface side on the back surface opposite to the lens structure surface of the lens film. Since the light reflecting layer formed in a stripe shape is formed through the opening, the light use efficiency (light gain) of the light source for the backlight is high when used in the backlight unit for the image display element. It can be provided as an optical film.

  Further, according to the optical film of the invention according to claim 2, the optical film has a two-layer structure in which a transparent support film and a lens layer made of a radiation curable resin are laminated. The film thickness can be easily adjusted, and the stability and mechanical strength can be improved.

  Further, according to the invention of claim 3, by making the blending ratio of magnesium carbonate or clay in the solid content of the light reflecting layer 70% by weight or less, compared with the case where titanium dioxide is 100%, light There is an effect of suppressing the fluctuation of the reflectance within 10%.

  According to the invention of claim 4, the workability equivalent to that in the case of 100% titanium dioxide is maintained by setting the blending ratio of magnesium carbonate or clay in the solid content of the light reflecting layer to 50% by weight or less. This has the advantage that the manufacturing process can be shared.

  According to the invention of claim 5, a lens film having a lens structure surface in which a cylindrical lens, a prismatic lens, or an assembly thereof is formed on one surface is prepared, and the back surface of the lens film (lens structure surface) On the other hand, by forming a light reflecting layer containing at least magnesium carbonate or clay as a pigment, an effect of suppressing the color development of the light reflecting layer during laser irradiation has been found. A good white layer can be obtained.

  Also, in the formation of the light reflecting layer, discoloration caused by laser irradiation occurs with white pigments made of titanium dioxide or zinc oxide, but with white pigments made of magnesium carbonate or clay, it is confirmed that the discoloration remains within a practical range. It was found that the same tendency was observed in the ink mixed with the binder resin or in the state of the light reflecting layer.

  Moreover, in the case of 100% blending of magnesium carbonate or clay, the whiteness is good, but on the other hand, it is accompanied by a decrease in workability and a decrease in white reflectance. Therefore, it becomes possible to clear these faults by setting it as the above-mentioned composition.

  Hereinafter, the present invention will be described in more detail. FIG. 1 is a partial sectional side view of an optical film according to an embodiment of the present invention. This optical film has a light reflecting layer containing a white pigment on the back surface (the surface opposite to the lens structure surface) of the lens film 1 having a structure such as a lenticular lens (repetitive array structure of striped semi-cylindrical convex cylindrical lenses). 2 is formed in a stripe shape. The opening 2a between the stripe-shaped light reflecting layers 2 is almost one in a condensing surface shape (stripe shape surface of a predetermined width) on the back surface of the lens film 1 of parallel light incident from the lens structure surface side of the lens film 1. I'm doing it.

  FIG. 2 is a cross-sectional view of an optical film according to another embodiment of the present invention. This optical film has a white pigment on the back surface (the surface opposite to the lens structure surface) of the lens film 1 in which a lens layer 4 having a structure such as a lenticular lens is formed on a transparent support film 3 such as polyethylene terephthalate (PET). Is formed in a stripe shape. In this case, the thickness of the support film 3 is set so that the back surface of the support film 3 is in the vicinity of the condensing position of the entire lens film 1. If the thickness of the support film 3 is set as described above, the parallel light incident from the structure surface side of the lens film 1 easily and with high accuracy through the openings 2a between the light reflecting layers 2 in the stripe shape. It can be adjusted to match the condensing shape. The thickness of the support film 3 is usually about 50 μm to 200 μm.

  As a material for the lens layer, it is desirable to use a radiation curable resin such as an ultraviolet curable resin or an electron beam curable resin, particularly when fine processing is required. As a radiation curable resin, the composition which added the reaction diluent, the photoinitiator, the photosensitizer, etc. to the urethane (meth) acrylate oligomer and / or the 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, It can be obtained by reacting with polyisocyanates such as isophorone diisocyanate, tolylene diisocyanate and xylene isocyanate.

  The epoxy (meth) acrylate oligomer is not particularly limited, but for example, epoxy resins such as 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. And can be obtained by reacting (meth) acrylic acid.

  The material of the light reflection forming layer is thermoplastic resin (for example, one or two-component type (main agent and curing agent) urethane resin (for example, polyurethane resin), acrylic resin (for example, polymethyl methacrylate resin), epoxy resin. Etc.) in which a white pigment (or filler) is dispersed. White pigments (or fillers) include magnesium carbonate, clay (for example, mineral powder based on hydrated aluminum silicate), glass powder, titanium dioxide, barium sulfate, zinc oxide, alumina, silver Etc. can be used. In addition, the thermoplastic resin material used for the light reflection forming layer is preferably a resin having a melting point lower than that of the resin used for the support film 3 (for example, polyethylene terephthalate).

When the thickness of the light reflecting layer exceeds 5 μm, sufficient white color can be obtained and adjusted to a desired transmittance, and it has sufficient strength against rubbing and can be easily peeled / dropped off. Disappear. Moreover, by making the thickness of the light reflecting layer 100 μm or less, it is possible to improve the processing shape of the pattern and reduce the material cost. Since the light reflecting layer having such a thickness can reflect light inside the layer, it can be referred to as a volumetric light reflecting layer.

  As described above, the blending ratio of magnesium carbonate or clay in the solid content of the light reflecting layer is preferably 70% by weight or less, more preferably 50% by weight or less.

  Next, with reference to FIG. 3 and FIG. 4, 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. As shown in FIG. 3, a transparent support film 3 is supplied from an unwinding roll 101, and an ultraviolet curable resin is applied to the surface of the support film 3 by a coating device 102 to form a lens forming layer. The support film 3 is passed between a lens forming roll 103 having a reverse shape of a lenticular lens formed on the surface and a pressure roll 103 ′ (between the nips of a predetermined gap) and supported on the peripheral surface of the lens forming roll 103. While the film 3 and the lens forming layer (ultraviolet curable resin) are in circumferential contact, the shape of the lens structure is transferred to the ultraviolet curable resin on the support film 3. While the shape is being transferred, the lens forming layer (ultraviolet curable resin) is cured by irradiating ultraviolet rays from the ultraviolet irradiating device 104, and the support film 3 and the lens forming layer bonded and cured to the film 3 are formed into a lens molding roll. The lens layer 4 is formed by peeling from the circumferential surface 103.

  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 4 is formed is subjected to an easy-adhesion treatment with an ultraviolet curable resin. Examples of the material for the support film 3 include high-melting-point polyethylene terephthalate (PET), polycarbonate (PC), and polyvinyl chloride (PVC).

  Although the ultraviolet curable resin coating apparatus 102 is not particularly limited, 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 thickness of the lens layer 4 to be formed and the lens shape of the lens layer 4 such as a lenticular lens or a prismatic lens, but is suitably 0.02 to 0.2 mm. is there. 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.

  As the lens molding roll 103 having a concave shape of the lens layer 4 such as a lenticular lens or a prismatic lens formed on the surface, a metal mold obtained by cutting the peripheral surface of the lens molding roll 103 into a concave shape of the reverse shape, It is possible to use a resin-shaped concave mold made of a reverse shape, which is duplicated from a regular mold part of the lens layer 4 by a predetermined method, on the roll surface.

  Next, a light reflection forming layer containing a white pigment is formed on the back surface (flat surface) of the lens structure surface of the lens film 1, and the light reflection forming layer corresponds to each lens 4 a in the stripe pattern shape of the lens layer 4. Thus, the removed portion of the light reflection forming layer is formed as the opening 2 a, and the remaining portion is formed as the light reflection layer 2. If the raw material of the light reflection forming layer 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 convenient for 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 light reflection forming 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 light reflection forming layer for forming the light reflection layer 2 is preferably more than 5 μm and not more than 100 μm. When the thickness of the light reflection forming layer exceeds 5 μm, sufficient white color can be obtained and adjusted to a desired reflectance, and has sufficient strength against rubbing against the light reflection layer 2 after formation, It will not easily peel off or fall off. If the thickness of the light reflecting layer is 100 μm or less, the processed shape of the pattern can be improved and the material cost can be reduced.

  Next, stripe processing of the light reflection forming layer is performed. For example, according to the method shown in FIG. 4, the laser light 6 [point light, ultraviolet region, visible region, infrared region (near infrared region, far infrared region)] is converted into parallel light as the lens structure of the lens film 1. Irradiated from the surface side, the lens layer 2 causes the laser light 6 to be condensed in a stripe shape on the condensing portion on the back surface of the lens film 1 (the surface opposite to the lens layer 2), and the light reflected from the portion corresponding to the condensing portion The formation layer is selectively irradiated with focused laser light, instantaneously (strobe irradiation) or continuously, and melted, pyrolyzed, sublimated, burned, blown, scraped (scraped by friction). Alternatively, the laser beam 6 is moved relative to the lens film 1 in the stripe length direction (direction perpendicular to the drawing) while being removed by a removal operation such as ablation to form the opening 2a. In addition, the residue which remains in the condensing part of the lens film 1 after removal operation is removed by an air blow system, a water injection system, etc. with the injection pressure of the grade which does not damage the light reflection layer 2. In addition, the removal operation temperature (for example, instantaneous irradiation temperature) provided to a light reflection formation layer at the time of laser irradiation is 300-400 degreeC, for example.

  By repeating this operation by moving the laser beam 6 relative to the lens film 1 along the stripe arrangement direction (left and right direction in the drawing), a stripe pattern is formed on the entire surface of the light forming layer on the back surface of the lens film 1. The light reflecting layer 2 can be left. Thus, a stripe pattern of the light reflecting layer 2 corresponding to the lens structure of the lens film 1 can be obtained. Thereby, the optical film of the present invention is manufactured.

  The wavelength of the laser beam 6 is not particularly limited as long as sufficient energy can be given to the light reflection forming layer on the back surface of the lens film 1. However, in consideration of the transmittance of the lens film 1 and the absorption rate of the light reflection layer, a laser beam (thermal laser) having a wavelength of 0.8 μm or more obtained with a YAG laser (wavelength 1.064 μm) or LD is used. Is preferred. Laser light with a near infrared wavelength is preferred.

  Note that the parallel light of the laser light 6 applied to the light reflection forming layer does not limit the incident direction as long as a reaction occurs. The pigment to be contained in the light reflecting layer 2 (light reflecting forming layer) is based on magnesium carbonate or clay, and by adjusting the blending with other pigments (such as titanium dioxide) as necessary, for example, a film The reflectance can be controlled while the thickness is fixed and the optical / geometric shape is fixed.

  In order to fix the light reflecting layer 2 after the light reflecting layer 2 is striped, it is also effective to irradiate radiation such as ultraviolet rays. By irradiating with a sufficient amount of ultraviolet rays to sufficiently cure the resin on the front and back surfaces of the lens layer 4, it is possible to stabilize the production and obtain a product with little deterioration even after long-term use.

  The optical film that has been subjected to final processing may be taken up by a take-up section, or may be connected to a line for bonding / adhesion with a diffusion plate as it is, and the next process may be advanced.

The optical film according to the present invention is integrated with a diffusion plate or diffusion film having a diffusion function by bonding or bonding, and this is combined with a member such as a light source (backlight) to constitute a backlight unit. A liquid crystal display can be manufactured in combination with a panel.

  Next, as shown in FIG. 5, the image display element 33, the backlight unit 34, and the image display body 35 (display) in the present invention will be described. As the image display elements, for example, a configuration of a liquid crystal image display element 33, a backlight unit 34, and an image display body (display) 35 is shown. An optical film 10 having each light reflecting layer 2 formed in a stripe shape on the back surface of the lens film opposite to the lens structure surface (lens layer 4 side) of the lens film 1 with openings 2a on both sides. The adhesive 11 is adhered to the light diffusion film 12. Further, on the lens structure surface side of the lens film 1, a liquid crystal display panel 30 is provided as an image display panel sandwiched between polarizing plates 31 and 32, and an image display element 33 is configured. Further, a lamp house 21 including a plurality of light sources 20 and a light reflection plate 22 (light reflection surface on the upper inner surface side) are provided on the back surface side (directly below) of the light diffusion film 12 to constitute an illumination (light source) unit 35. Has been. The optical film 10, the light diffusion film 12, and the light source unit 35 constitute a backlight unit 34. These members constitute a liquid crystal image display as an image display 36 (image display device).

  As a material of the light diffusion film 12 having a diffusion function, a material that is transparent with respect to the wavelength of the image light and can be used for an optical member without any particular limitation. Is preferably used. As the plastic, if polyethylene terephthalate (PET) is used, it is easy to handle from experience, but acrylic resins such as polymethyl methacrylate, polycarbonate resins, acrylic-styrene copolymers, styrene resins, polyvinyl chloride, and the like are also available. Can be used.

  The material of the light diffusing film 12 having a diffusing function is sufficient if it has practically sufficient transmittance and mechanical strength for reproducing the projected image. Main plastic materials such as methacryl styrene resin, acrylic resin, polycarbonate resin, etc. 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 film which concerns on this invention can be used also for uses other than a liquid crystal display. For example, the stripe-shaped light reflecting layer 2 of the optical film can be appropriately colored and used. In particular, the stripe-shaped light reflection layer 2 can be colored black and bonded to an appropriate diffusion plate (light diffusion film) and bonded to be used for a transmission screen.

  Hereinafter, the present invention will be described based on specific examples.

  In this example, an optical film having a lens structure surface in which lenticular lenses 4a are arranged in a stripe shape shown in FIG. 2 was manufactured.

  As the support film 3, a 75 μm thick polyethylene terephthalate (PET) film (Toyobo A4300) was used.

3, an ultraviolet curable resin (lens forming layer) is applied on the support film 3 and irradiated with ultraviolet rays while transferring the lens structure surface to the ultraviolet curable resin by the lens mold of the lens molding roll 103. Then, the ultraviolet curable resin (lens forming layer) was cured to form the lens layer 4, and the lens film 1 including the support film 3 and the lens layer 4 was produced. The lens shape of the lens layer 4 was an aspherical shape with a lens pitch of 140 μm, an elliptical surface as a reference surface, and shape correction by a high-order term algorithm. When the lens layer 4 is thus formed at a pitch of 140 μm, the vicinity of the back surface of the support film 3 made of PET having a thickness of 75 μm (the surface opposite to the lens layer 4) is a condensing surface for laser light used for stripe processing ( Focal plane).

  On the back surface of the lens film 1 thus obtained (opposite to the lens layer 4), magnesium carbonate and titanium dioxide or clay and titanium dioxide as a white pigment were mixed at a thickness of 13 μm. A light reflection forming layer was formed. The white ink for forming the light reflection forming layer contained a resin, and the ratio of the pigment in the ink was 75% by weight. The transmittance of this light reflection forming layer was 15%.

  Striping of the light reflection forming layer was performed by the method shown in FIG. Laser light 6 (beam light) having a wavelength of 1064 nm emitted from the YAG laser is irradiated from the lens structure surface (lens layer 4) side of the lens film 1, and the laser light 6 is subjected to light output (light quantity) and optical scanning. By adjusting the speed (or light irradiation time) and scanning along the length direction and width direction of each lens 4a of the striped lens layer 4, the laser light 6 condensing part (predetermined) of the lens film 1 is obtained. The light reflection forming layer corresponding to the stripe-shaped light condensing portion of the width is selectively laser-exposed to remove the exposed portion, and the stripe-shaped light reflecting layer 2 is applied to the laser unexposed portion other than the light condensing portion. Formed. In FIG. 4, the scanning direction X in the horizontal direction of the drawing indicates the moving direction in the lens width direction (horizontal direction of the screen) of the striped lens 4a of the lens film 1, and the scanning direction Y is the striped lens of the lens film 1. The movement direction in the lens length direction 4a (direction perpendicular to the drawing) is shown.

  At this time, the incident angle of the laser beam 6 on the lens film 1 was variously changed, and the influence on the pattern formation of the light reflecting layer 2 was examined. Specifically, the inclination angle of the laser beam 6 in the stripe length direction of each lens 4a with respect to the direction perpendicular to the horizontal plane of the lens film 1 was changed to 0 degrees, 10 degrees, 20 degrees, and 30 degrees. The stripe pattern of the light reflecting layer 2 could be obtained under any conditions.

  Further, the lens shape of the lens film 1 may be a striped prism shape, a striped prism shape having a curved surface at the apex, or a striped asymmetric shape (the lens surface on one side is linear with respect to the center of the lens width of each lens 4a (plane ) And the lens surface on the other side was changed to a curved shape (curved surface), but a stripe pattern could be obtained with any shape.

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

Sectional drawing of the optical film which concerns on one embodiment of this invention. Sectional drawing of the optical film which concerns on other embodiment of this invention. The schematic diagram which shows the manufacturing method of the lens layer of the optical film of this invention. The schematic diagram which shows the manufacturing method of the light reflection layer of the optical film of this invention. The schematic diagram which shows the structure of the image display tolerance (liquid crystal display) incorporating the optical film of this invention. The schematic diagram which shows the structure of a general liquid crystal display.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Lens film 2 ... Light reflection layer 2a ... Opening part 3 ... Supporting film 4 ... Lens layer 4a ... Striped lens 6 ... Laser beam 10 ... Optical film 11 ... Adhesive 12 ... Diffusion film 20 ... Light source 21 ... Lamp house 22 Light reflector 30 Image display element (liquid crystal panel)
31, 32 ... Polarizing plate 40 ... Backlight unit 101 ... Unwinding roll 102 ... Coating device 103 ... Lens molding roll 103 '... Pressure roll 104 ... Ultraviolet irradiation device

Claims (8)

  A lens film having a lens structure surface in which a cylindrical lens or a prismatic lens or an assembly thereof is formed in a stripe shape on one surface; and a lens film back surface opposite to the lens structure surface; Stripe openings corresponding to the stripe-shaped condensing shape formed on the back surface of the lens film by parallel light incident on the lens from the lens structure surface side, and stripes corresponding to both sides of the opening portions, respectively. And a light reflecting layer containing a pigment such as at least magnesium carbonate or clay, titanium dioxide, barium sulfate, zinc oxide, alumina, silver or the like.   The optical film according to claim 1, wherein the lens film has a lens structure in which a transparent support film and a lens layer made of a radiation curable resin are laminated.   The optical film according to claim 1 or 2, wherein a blending ratio of the magnesium carbonate or clay in the solid content of the light reflecting layer is 70% by weight or less.   The optical film according to claim 1 or 2, wherein a blending ratio of the magnesium carbonate or clay in the solid content of the light reflecting layer is 50% by weight or less.   5. A manufacturing method for manufacturing the optical film according to claim 1, wherein the lens has a lens structure surface in which a cylindrical lens, a prismatic lens, or an assembly thereof is formed on one surface. A film is prepared, and a light reflection forming layer containing at least magnesium carbonate or clay as a pigment is formed on the back surface of the lens film opposite to the lens structure surface of the lens film, and from the lens structure surface side of the lens film The light reflection forming layer corresponding to the condensing part is irradiated with laser light of near-infrared wavelength, and the laser light is condensed into a predetermined width on the condensing part on the back surface of the lens film by each lens. The portion is selectively removed by a focused laser beam to form an opening, leaving a striped light reflecting layer. Method of manufacturing an optical film.   An optical film according to any one of claims 1 to 4, a light diffusion film, and a light source unit directly underneath the light diffusion film, which is disposed on a back surface (back surface) side of an image display element that defines a display image. And a backlight unit characterized by being arranged in this order.   A display comprising: an image display element comprising a liquid crystal display element that defines a display image in accordance with transmission / shading in pixel units; and a backlight unit according to claim 6.   8. The display according to claim 7, wherein the light source unit of the backlight unit is a light source unit composed of a cold cathode ray tube, an organic EL, or an LED.

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