JP4985091B2 - OPTICAL SHEET FOR DISPLAY, MANUFACTURING METHOD THEREOF, BACKLIGHT UNIT, AND DISPLAY DEVICE - Google Patents

Description

  In the present invention, an optical sheet in which a light reflecting layer is formed on a non-light condensing part of a non-lens surface of a lens sheet having a cylindrical lens or prism formed on one side in a stripe shape is integrated with a diffusion sheet. TECHNICAL FIELD The present invention relates to an optical sheet and a method for manufacturing the same, an optical sheet mainly used for illumination light path control in a display backlight unit using a liquid crystal display element, a method for manufacturing the optical sheet, a backlight unit using the optical sheet, and The present invention relates to 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 from the lateral direction is increased. 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 and luminance unevenness occur, Does not function as a brightness enhancement film. For this reason, it is necessary to accurately align the structure of the front side of the optical sheet having the lens layer, the reflective layer, and the back side of 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 above-described problem of alignment of the front and back structures, 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 a lens or the like on the front and back surfaces is to be molded with a mold using a radiation curable resin, it is necessary to sandwich a film with two molds for molding the front and back surfaces. 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 surfaces, and cannot be practically adopted.
In addition, when a linear light source such as a cold cathode tube is used as the light source of the backlight, a linear bright portion may be seen on the liquid crystal screen. In order to eliminate such uneven brightness, a plurality of diffusion sheets are used. However, the number of members increases, the configuration becomes complicated, and the number of assembly steps increases, which is an obstacle to cost reduction. There's a problem.
Usually, a diffusion sheet is used immediately above the light source of the backlight. By integrating the light scattering sheet and the lens sheet together with a pressure-sensitive adhesive or adhesive, it is possible to reduce costs by reducing the number of assembly steps. However, the use of pressure-sensitive adhesive or adhesive increases the cost. There is a problem that becomes a factor.

  The present invention has been made to solve the above-described conventional problems, and its purpose is to provide a lens structure such as a lenticular lens on the front surface side and a structure of a reflective layer (adhesive layer) including an opening on the back surface side. Provides an optical sheet with excellent alignment with light utilization efficiency, and the reflective layer on the back side of the lens sheet is used as a light-reflective adhesive layer to directly bond the optical sheet and the diffusion sheet together. An optical sheet, a manufacturing method thereof, a backlight unit using the optical sheet, and a display device are provided.

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, a light scattering sheet that scatters incident light to the exit surface side opposite to the entrance surface, and a support film a lens sheet which have a lens layer formed by arranging formed at a pitch one surface in the unit lens of certain of, is formed on the other surface of the supporting film, the light including the pressure-sensitive adhesive or adhesive containing a white pigment A reflective adhesive layer, the lens sheet and the light scattering sheet are integrated by adhering the exit surface of the light scattering sheet to the surface of the adhesive layer opposite to the support film, Corresponding to the central part including the optical axis of each unit lens, there is an opening for transmitting light, and the adhesive layer is on the adhesive surface of the adhesive layer with the light scattering sheet from the light scattering sheet side. light It characterized by having a high light reflectivity to reflect the light scattering sheet side reflecting surface.

  According to a second aspect of the present invention, in the optical sheet according to the first aspect, the unit lens is formed of a cylindrical lens or a prism, and the lens layer is formed of an assembly of the cylindrical lens or the prism.

The invention of claim 3 is a method of manufacturing an optical sheet used for illumination light path control in a backlight unit for display, wherein the lens is formed by arranging unit lenses on one surface of the support film at a constant pitch. A lens sheet having a layer is provided, a light-reflective adhesive layer containing a white pigment is formed on the other surface of the support film with a certain thickness, and the adhesive layer is irradiated with laser light from the lens layer side. The light condensing action of the unit lens creates an exposed area and an unexposed area in the adhesive layer, and the exposed area is removed to form an opening for light transmission, opposite to the support film of the adhesive layer. A light scattering sheet is adhered to the surface so as to cover the opening.

According to a fourth aspect of the present invention, in the method for manufacturing an optical sheet according to the third 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 of claim 5 is the method for producing an optical sheet according to claim 3, wherein the wavelength of the laser beam is 0.75 μm or more.

According to a sixth aspect of the present invention, in the method for manufacturing an optical sheet according to the third aspect, when the lens sheet forms the support film by a molten transparent resin extrusion method, the molten transparent resin is formed on the unit lens. It is manufactured by pressing against a mold having a shape opposite to the convex surface.
According to a seventh aspect of the present invention, in the optical sheet manufacturing method according to the third aspect, the lens sheet is formed by applying a transparent support film and an ultraviolet curable resin to the upper surface of the transparent support film, It is characterized by having a lens layer in which the lens shape of the mold is transferred to an ultraviolet curable resin by irradiating ultraviolet rays while pressing a mold having a shape opposite to the convex surface of the unit lens on the coating surface.

The invention according to claim 8 is a backlight unit for display, the image display element defining a display image, a light source on the back of the image display element, and the optical sheet according to claim 1 or 2. It comprises at least an optical sheet manufactured by the method according to any one of 3 to 7.
According to a ninth aspect of the present invention, in the display backlight unit according to the eighth aspect, the image display element is a liquid crystal display element.

  The invention of claim 10 is a display device, wherein the image display element 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 element. 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. A light-reflective adhesive layer having an opening for light transmission is formed. 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 be provided.
Further, in the present invention, the lens sheet and the light diffusion sheet are directly bonded to and integrated with the surface of the lens sheet opposite to the lens layer via a light-reflective adhesive layer, whereby an adhesive or It is possible to reduce the materials and processes related to the adhesive, and when this optical sheet is used in a backlight unit for a display, the backlight unit has high light use efficiency and has no unevenness in brightness. A display device can be provided.

  Furthermore, in the method for producing an optical sheet according to the present invention, the light reflecting adhesive layer formed on the surface opposite to the lens layer of the lens sheet is irradiated with laser light from the lens layer side of the lens sheet. The light-collecting action creates an exposed area and an unexposed area in the adhesive layer, and by removing the exposed area, an opening for light transmission is formed, so that a desired shape such as a stripe shape can be formed by simple processing. A pressure-sensitive adhesive layer can be obtained.

(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 light scattering sheet 5 that is laminated in order from the incident light incident side and scatters incident light to the exit surface side opposite to the incident surface, and an adhesive or adhesive containing a white pigment. A light-reflective adhesive layer 2 made of an agent, and a lens sheet 1 in which unit lenses 1a are arranged on the surface opposite to the adhesive layer 2 at a constant pitch along the surface.
The lens sheet 1 can be manufactured by pressing a molten transparent resin against a mold having a shape opposite to the convex surface of the unit lens 1a when a film or sheet is formed by a melt extrusion method.
Further, on the surface opposite to the unit lens 1a of the 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 are formed. The light-reflective adhesive layer 2 containing a white pigment is formed in a stripe shape corresponding to the unit lens 1a. In addition, an opening 2a for light transmission is formed between the stripe-shaped adhesive layers 2 having light reflectivity, that is, in a portion 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.

(Second Embodiment)
FIG. 2 is a cross-sectional view of an optical sheet according to another embodiment of the present invention.
In FIG. 2, an optical sheet 10 includes a light scattering sheet 5 that is laminated in order from the incident light incident side and scatters incident light to the exit surface side opposite to the incident surface, and an adhesive or adhesive containing a white pigment. A light-reflective adhesive layer 2 made of an agent, and a lens layer 4 in which unit lenses 4a are arrayed at a constant pitch on one surface of the support film 3, and the other surface of the support film 3 is the adhesive. And a lens sheet 1 bonded to the light emitting surface of the light scattering sheet 5 via the layer 2.
The lens sheet 1 has a lens layer 4 in which unit lenses 4a such as lenticular lenses are arranged at a constant pitch on a transparent support film 3 such as polyethylene terephthalate (PET). On the surface opposite to 4a, a light-reflective adhesive layer 2 containing a white pigment is formed in a stripe shape corresponding to the unit lens 4a. In this case, the thickness of the support film 3 is set so that the back surface (adhesive 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, hexamethylene diisocyanate, 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, and examples thereof include 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, and fluorene epoxy resin. These epoxy resins can be obtained by reacting (meth) acrylic acid.

The light-reflective adhesive layer 2 is made of a resin composition containing a transparent resin binder and a white pigment as main components.
For transparent resin, vinyl acetate, vinyl alcohol, styrene, α-methylstyrene, (meth) acrylic acid, (meth) acrylic acid ester such as methyl methacrylate, fluorine-containing (meth) acrylic acid derivative, acrylonitrile, ethylene Polymers obtained by polymerizing at least one monomer selected from olefins such as propylene, butene and butadiene, cellulose derivatives such as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, ethyl cellulose, and nitrocellulose Polyamide, Polyamide, Polyethylene terephthalate, Polycarbonate, Polyarylate, Polysulfone, Polyacetal, Polyphenylene oxide, Polyurethane, Epoxy Examples thereof include transparent resins selected from fats, phenolic resins, petroleum resins, natural rubbers, synthetic rubbers such as butadiene rubbers, silicone resins, and polymers such as fluororesins. It can be used in combinations of more than one species. Moreover, in order to provide adhesiveness, the glass transition temperature of the transparent resin is preferably 20 ° C. or lower, and more preferably 0 ° C. or lower. In general, the resin composition contains at least one reactive group such as a hydroxyl group, a carboxylic acid group, and an epoxy group in order to mix a curing agent with the resin composition and partially crosslink the pressure-sensitive adhesive. It is preferable.

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.

If necessary, an infrared absorber can be added for the purpose of converting the energy of parallel light such as irradiated laser light into heat energy with high efficiency. The infrared absorber is not particularly limited as long as it is a material having absorption in an infrared region having a wavelength of 0.75 μm or more. For example, organic dyes such as imonium compounds, diimonium compounds, aminium salt compounds, perlin compounds, nickel complex compounds, phthalocyanine compounds, fluorine-containing phthalocyanine compounds, naphthalocyanine compounds, polymethine compounds, and phosphorus containing iron And at least one selected from a cobalt component, a neodymium component, an erbium component, a magnesium component, a calcium component, a strontium component, and a barium component in a phosphoric acid compound containing copper, a copper sulfate compound, or a copper-containing phosphate compound A compound obtained by containing a seed, a reaction product obtained by reacting a thiourea derivative with a copper compound or a lead compound, a reaction product obtained by reacting tungsten hexachloride with a trialkyl or triaryl phosphate, and , Ytterbiu Particles of oxides, YbPO 4 _(ytterbium phosphate), a compound of ytterbium, such as sulfuric acid ytterbium or acetic ytterbium, other metal oxide fine particles, there may be mentioned a number of organic compounds such as group IV transition metal carbides and inorganic compounds such as it can. These materials can be used alone or in combination of two or more. The content of these infrared absorbers is preferably 0.001 wt% or more, and more preferably in the range of 0.005 wt% to 10 wt%. If it is less than 0.001 wt%, the light reflective adhesive layer does not sufficiently absorb the light energy of the laser, has little effect of photothermal conversion, and cannot be molded satisfactorily.

The thickness of the pressure-sensitive adhesive layer 2 is preferably 5 μm or more and 100 μm or less. When the thickness of the pressure-sensitive adhesive layer is 5 μm or more, a sufficient white color can be obtained and adjusted to a desired transmittance, and a sufficient peel strength can be obtained . Further, by setting the thickness to 100 μm or less, it is possible to improve the pattern processing shape and reduce the material cost. The pressure-sensitive adhesive layer having such a thickness can be called a volume pressure-sensitive adhesive layer because it can reflect light inside the 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, a light-reflective adhesive layer 2 containing a white pigment is formed on the surface (flat surface) opposite to the lens layer 4 of the lens sheet 1. If the raw material for the adhesive 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, or the like can be used, which is advantageous in production. In addition, if necessary, the resin may be dried / cured using a dryer or the like after forming the adhesive layer 2.

  As a printing method for the adhesive 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 pressure-sensitive adhesive 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. Further, if the thickness of the light-reflective adhesive layer 2 is 100 μm or less, the pattern processing shape 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, by moving the laser beam 6 relative to the lens sheet 1 in the stripe length direction (direction perpendicular to the paper surface), the light condensing action of the unit lens 4a constituting the lens layer 4 is applied to the adhesive layer 2. An exposed area and an unexposed area are generated, and the exposed area is removed to form an opening 2a for light transmission. This operation is repeated by moving the laser beam 6 relative to the lens sheet 1 along the stripe arrangement direction (left and right direction on the paper surface) to leave the stripe-shaped reflective layer, that is, the adhesive layer 2. Can do. In this manner, a reflective layer corresponding to the structure of the lens sheet 1, that is, a stripe pattern of the adhesive layer 2 can be obtained.

The wavelength of the laser beam 6 is not particularly limited as long as sufficient energy can be given to the pressure-sensitive adhesive layer 2 that is a reflective layer. However, in consideration of the transmittance of the lens sheet 1 and the absorption rate of the adhesive layer 2 which is a reflective layer, a laser beam having a wavelength of 0.8 μm or more obtained with a YAG laser (wavelength 1.064 μm) or LD is used. Is preferred.
In addition, by incorporating an infrared absorber in the light reflecting layer in the present invention, the light reflecting layer efficiently absorbs the light energy of the laser and converts it into thermal energy, so that laser molding can be performed efficiently. . In particular, when titanium oxide (TiO ₂ ) is used as the white pigment of the pressure-sensitive adhesive layer 2 that is a reflective layer, it is effective to use laser light having a wavelength of 0.75 μm or more.
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.

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 scattering sheet 5 having a diffusing function is a material that is transparent with respect to the wavelength of the image light and can be used without limiting the material 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 scattering sheet 5 having a diffusing function only needs to have a transmittance and mechanical strength that can be practically used to reproduce a projected image. Main plastic materials include methacrylstyrene 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 pressure-sensitive adhesive layer, which is 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 scattering sheet 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 adhesive layer.

The resin composition of the pressure-sensitive adhesive layer having the following composition was sufficiently kneaded using a mixer such as a ball mill, and this was uniformly formed on the surface opposite to the lens layer of the lens sheet obtained above. And dried to form a reflective layer having a thickness of 11 μm.
In the following, “part” is based on mass.
(Adhesive resin composition with light reflectivity)
Adhesive resin (Toyo Ink Manufacturing Co., Ltd.) 90.2 parts Titanium oxide (DuPont Co., Ltd.) 52.6 parts Epoxy curing agent 0.36 parts Pigment dispersant BYK110 1.25 parts Methyl ethyl ketone 107.5 parts The pressure-sensitive adhesive is a resin mainly composed of an acrylic resin, has a non-volatile content of 25%, a Tg of about −40 ° C., and an acid value of about 26 mgKOH / g.
With the above formulation, an adhesive layer resin composition having a light reflectivity of 30% non-volatile content and 70% pigment weight concentration (PWC) was obtained.

With the optical sheet manufacturing method shown in FIG. 4, the white adhesive layer having light reflectivity was striped. A part of the adhesive layer 2 corresponding to the condensing part of the laser beam 6 is selected by irradiating the laser beam 6 with a wavelength of 1064 nm emitted from the YAG laser from the structural surface side of the lens sheet 1 and scanning the laser. The stripe pattern of the adhesive layer 2 was formed.
The lens sheet was directly bonded to a light scattering sheet having a diffusion function to produce an optical sheet integrated with the lens sheet and the light scattering sheet.

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, 3 ... Support film, 4 ... Lens layer, 4a ... Unit lens, 5 ... Light scattering sheet, 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 ... Polarizer, DESCRIPTION OF SYMBOLS 101 ... Unwinding roll, 102 ... Coating apparatus, 103 ... Lens molding roll, 103a ... Pressure roll, 104 ... Ultraviolet irradiation apparatus.

Claims (10)

In an optical sheet used for illumination light path control in a backlight unit for display,
A light scattering sheet that scatters incident light to the exit surface side opposite to the entrance surface;
A lens sheet which have a lens layer one unit lens in the plane formed by arranging formed at a constant pitch of the support film,
A light-reflective pressure-sensitive adhesive layer formed on the other surface of the support film and made of a pressure-sensitive adhesive or adhesive containing a white pigment;
The lens sheet and the light scattering sheet are integrated by adhering the exit surface of the light scattering sheet to the surface of the adhesive layer opposite to the support film,
The adhesive layer has an opening for light transmission corresponding to the central part including the optical axis of each unit lens,
The pressure-sensitive adhesive layer has a light-reflective reflecting surface that reflects light from the light-scattering sheet side to the light-scattering sheet side on the adhesive surface of the pressure-sensitive adhesive layer with the light-scattering sheet.
An optical sheet characterized by that.   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 at a constant pitch on one surface of the support film is provided.
A light-reflective adhesive layer containing a white pigment is formed on the other surface of the support film with a certain thickness,
The adhesive layer is irradiated with laser light from the lens layer side to cause an exposure area and an unexposed area in the adhesive layer by the condensing action of the unit lens, and the light transmission opening is formed by removing the exposed area. Forming part,
A light scattering sheet was adhered to the surface of the adhesive layer opposite to the support film so as to cover the opening,
An optical sheet manufacturing method characterized by the above.   4. The method of manufacturing an optical sheet according to claim 3, wherein the unit lens is formed of a cylindrical lens or a prism, and the lens layer is formed of an assembly of the cylindrical lens or prism.   The optical sheet manufacturing method according to claim 3, wherein the wavelength of the laser beam is 0.75 μm or more.   The lens sheet is manufactured by pressing the molten transparent resin against a mold having a shape opposite to the convex surface of the unit lens when the support film is formed by an extrusion method of a molten transparent resin. The method for producing an optical sheet according to claim 3.   The lens sheet is coated with a transparent support film and an ultraviolet curable resin on the upper surface of the transparent support film, and a mold having a shape opposite to the convex surface of the unit lens is pressed against the application surface of the ultraviolet curable resin. 4. The method for producing an optical sheet according to claim 3, further comprising a lens layer in which a lens shape of the mold is transferred to an ultraviolet curable resin by irradiating with ultraviolet rays. An image display element for defining a display image;
At least a light source and an optical sheet according to claim 1 or 2 or an optical sheet manufactured by the method according to any one of claims 3 to 7 are provided on a back surface of the image display element.
A backlight unit for displays.   9. The display backlight unit according to claim 8, 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;
10. A display device comprising a light source and a display backlight unit according to claim 8 or 9 on a back surface of the image display element.

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