JP2021128235A - Optical sheet, liquid crystal display device, and manufacturing method for optical sheet - Google Patents

Abstract

To provide an optical sheet and a liquid crystal display device in which an adhesive between an optical function layer and a base material layer does not spread out of a cut surface of the optical sheet, and manufacture such an optical sheet.SOLUTION: An optical sheet is provided between a light source of a liquid crystal display device and a liquid crystal panel and includes: a first base material layer; an optical function layer stacked on the first base material layer and including a plurality of light transmission parts disposed with a predetermined space therebetween along the first base material layer and transmitting light, and a louver part disposed between the adjacent light transmission parts and reflecting or absorbing the light; a second base material layer disposed to face the first base material layer with the optical function layer held therebetween; and an adhesive layer disposed between the optical function layer and the second base material layer. The adhesive layer is formed of polyurethane resin.SELECTED DRAWING: Figure 4

Description

The present invention relates to an optical sheet arranged on the observer side of a light source, a liquid crystal display device using the optical sheet, and a method for manufacturing the optical sheet.

Liquid crystal display devices such as in-vehicle displays and liquid crystal televisions are provided with optical sheets having various functions in order to control the light emitted from the light source and provide high-quality light to the observer.

In Patent Document 1, a layer in which a prism portion (referred to as a light transmitting portion in the present specification) and a light absorbing portion (referred to as a louver portion in the present specification) are alternately arranged on one surface of a base film layer. There is disclosed an optical sheet which has the above and can suppress bending even if it is made thin.

Japanese Unexamined Patent Publication No. 2017-198735

When an optical sheet as described in Patent Document 1 is used in a liquid crystal display device, each module of the liquid crystal display device and the optical sheet are combined and mounted on a housing of the liquid crystal display device. When mounting an optical sheet as described in Patent Document 1, fixing is performed by adhesion or tightening with a frame of a housing, but depending on the fixing method, bending may occur due to the weight of the optical sheet or the like. Therefore, there is a problem that unevenness of light transmitted through the optical sheet occurs due to this bending.

In order to suppress such unevenness of light, it is conceivable to increase the rigidity of the optical sheet so that the optical sheet does not easily bend. In order to increase the rigidity, it is conceivable to further bond the second base film layer on the layer in which the prism portions and the light absorbing portions of the optical sheet are alternately arranged as described in Patent Document 1. However, when the ultraviolet curable acrylic adhesive conventionally used for adhering such an optical sheet is used for adhering the second base film layer, the optical sheet after adhering is cut and then adhered from the cut surface. The agent sometimes squeezed out. Such adhesive squeeze out is not preferable when mounting the optical sheet. In order to prevent the adhesive from squeezing out, it is conceivable to treat the end face of the optical sheet in a concave shape in advance to provide a margin for the adhesive squeeze out, but depending on the type of optical sheet, such end face treatment may be performed. It may not be possible. Further, depending on the type of the adhesive, the above-mentioned light unevenness may occur after the optical sheet is mounted on the liquid crystal display device even though the second base film layer is adhered.

The present invention has been made to solve the above-mentioned problems, and an optical sheet using an adhesive that is particularly suitable for use in a liquid crystal display device, particularly an in-vehicle liquid crystal display device, and an optical sheet thereof. It is an object of the present invention to provide a liquid crystal display device using a sheet and a method for manufacturing an optical sheet.

In order to achieve the above-mentioned object, the present invention is an optical sheet provided between a light source of a liquid crystal display device and a liquid crystal panel, which is laminated on a first base material layer and a first base material layer. It is an optical functional layer to be formed, and is arranged between a plurality of light transmitting portions arranged along the first base material layer at predetermined intervals to transmit light and adjacent light transmitting portions to reflect light. Alternatively, an optical functional layer having a louver portion for absorbing, a second base material layer arranged so as to face the first base material layer with the optical functional layer interposed therebetween, an optical functional layer, and a second base. It includes an adhesive layer arranged between the material layers, and the adhesive layer has a configuration of an optical sheet, which is a polyurethane resin.

Further, the polyurethane resin may be an acrylic polyol-polyurethane resin.

In order to achieve the above-mentioned object, the present invention is an optical sheet provided between a light source of a liquid crystal display device and a liquid crystal panel, which is laminated on a first base material layer and a first base material layer. It is an optical functional layer to be formed, and is arranged between a plurality of light transmitting portions arranged along the first base material layer at predetermined intervals to transmit light and adjacent light transmitting portions to reflect light. Alternatively, an optical functional layer having a louver portion for absorbing, a second base material layer arranged so as to face the first base material layer with the optical functional layer interposed therebetween, an optical functional layer, and a second base. It includes an adhesive layer arranged between the material layer and an optical sheet having a storage elastic coefficient of the adhesive layer of 1 × 10 ⁹ Pa to 2 × 10 ^{9 Pa at 85 ° C.}

Further, the second base material layer may be provided with a reflective polarizing film on the side in contact with the adhesive layer.

Another aspect of the present invention for achieving the above-mentioned object is a liquid crystal display device including the above-mentioned optical sheet and a liquid crystal display device and a light source arranged so as to face each other across the optical sheet. be.

In addition, another aspect of the present invention for achieving the above-mentioned object is a first base material layer and an optical functional layer laminated on the first base material layer, which is the first base material. An optical functional layer having a plurality of light transmitting portions arranged along the layers at predetermined intervals to transmit light, and a louver portion arranged between adjacent light transmitting portions to reflect or absorb light. A second base material layer arranged so as to face the first base material layer with the optical functional layer interposed therebetween, and an adhesive layer arranged between the optical functional layer and the second base material layer. It is a method of manufacturing an optical sheet to be provided, and is a method of manufacturing an optical sheet using a polyurethane resin as an adhesive layer.

Further, the polyurethane resin may be an acrylic polyol-polyurethane resin.

In addition, another aspect of the present invention for achieving the above-mentioned object is a first base material layer and an optical functional layer laminated on the first base material layer, which is the first base material. An optical functional layer having a plurality of light transmitting portions arranged along the layers at predetermined intervals to transmit light, and a louver portion arranged between adjacent light transmitting portions to reflect or absorb light. A second base material layer arranged so as to face the first base material layer with the optical functional layer interposed therebetween, and an adhesive layer arranged between the optical functional layer and the second base material layer. A method for manufacturing an optical sheet to be provided, wherein an adhesive layer having a storage elasticity of 1 × 10 ⁹ Pa to 2 × 10 ⁹ Pa at 85 ° C. after completion of the optical sheet is used as the adhesive layer. This is a sheet manufacturing method.

Further, the second base material layer may be provided with a reflective polarizing film on the side in contact with the adhesive layer.

According to the present invention, it is possible to provide an optical sheet and a liquid crystal display device that prevent the adhesive from squeezing out and suppress unevenness of light. Moreover, it becomes possible to manufacture such an optical sheet.

It is an exploded perspective view of the liquid crystal display device which concerns on embodiment. It is an exploded view of the liquid crystal display device of FIG. It is an exploded view of the liquid crystal display device of FIG. It is an enlarged view paying attention to the optical sheet of FIG. It is explanatory drawing of the manufacturing process of the optical sheet of FIG. It is explanatory drawing of the manufacturing process of the optical sheet of FIG. It is explanatory drawing of the manufacturing process of the optical sheet of FIG.

Hereinafter, the optical sheet and the liquid crystal display device according to the embodiment will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components are designated by the same reference numerals as much as possible in each drawing, and duplicate description is omitted.

[composition]
First, the configuration of the optical sheet 30 and the liquid crystal display device 10 including the optical sheet 30 according to the embodiment will be described with reference to FIGS. 1 to 4. FIG. 1 is an exploded perspective view of the liquid crystal display device 10 according to the embodiment. 2 and 3 are exploded views of the liquid crystal display device 10. For the sake of simplicity, when the horizontal direction, the thickness direction, and the vertical direction are defined as shown in FIG. 1, FIG. 2 shows the liquid crystal display device 10 from the direction along the horizontal direction, and FIG. 3 shows the liquid crystal display device 10. , The liquid crystal display device 10 is shown from the direction along the vertical direction. FIG. 4 shows an enlarged view of the optical sheet 30 shown in FIG. 2 rotated 90 degrees counterclockwise when viewed from the cross-sectional direction in order to show the configuration of the optical sheet 30 shown in FIG. 2 and the like. It should be noted that the thickness of each layer shown may differ from the actual dimensions in order to give priority to the legibility of the figure.

The liquid crystal display device 10 is housed in a housing (not shown) together with a power supply, an electronic circuit, and the like. The liquid crystal display device 10 is provided in the passenger compartment of an automobile (not shown) and operates as a part of the navigation device. The liquid crystal display device 10 includes a liquid crystal panel 15, a surface light source device 20, and a functional film 40.

The liquid crystal panel 15 has a liquid crystal layer 12, an upper polarizing plate 13, and a lower polarizing plate 14. The upper polarizing plate 13 is arranged on the observer side, and the lower polarizing plate 14 is arranged on the surface light source device 20 side. The liquid crystal layer 12 is arranged between the upper polarizing plate 13 and the lower polarizing plate 14.

The upper polarizing plate 13 and the lower polarizing plate 14 decompose the incident light into two orthogonal polarizing components (P wave and S wave), and the polarizing component in one direction (direction parallel to the transmission axis) (for example, P). It has a function of transmitting a (wave) and absorbing a polarizing component (for example, an S wave) in the other direction (direction parallel to the absorption axis) orthogonal to the one direction. The lower polarizing plate 14 is an example of a polarizing film.

In the liquid crystal layer 12, a plurality of pixels are arranged vertically and horizontally along the layer surface. By applying an electric field to each region forming one pixel, the orientation of the pixels in the region changes. As a result, the polarized light component (for example, P wave) parallel to the transmission axis transmitted through the lower polarizing plate 14 arranged on the surface light source device 20 side (that is, the light input side) is transmitted when passing through the pixel to which the electric field is applied. The polarization direction is rotated by 90 °, while maintaining the polarization direction as it passes through the pixels to which no electric field is applied. Therefore, depending on whether or not an electric field is applied to the pixels, the polarizing component (for example, P wave) transmitted through the lower polarizing plate 14 further transmits through the upper polarizing plate 13 arranged on the light emitting side, or the upper polarizing plate 13 is further transmitted. It is possible to control whether it is absorbed and blocked by.

As described above, the liquid crystal panel 15 is configured to control the transmission or blocking of light from the surface light source device 20 for each pixel and provide an image to the observer. Therefore, when irradiating light from the back surface side of the liquid crystal panel 15, a large amount of light having a polarizing component parallel to the transmission axis of the lower polarizing plate 14 is allowed to reach, so that the lower polarizing plate 14 is transmitted and the light is used. Efficiency can be increased.

Further, due to the nature of the liquid crystal panel 15, the contrast and efficiency (transmittance) of the emitted light are excellent with respect to the incident light from the normal direction of the liquid crystal panel 15. However, when the incident light is oblique to the normal direction of the liquid crystal panel 15 and the observer observes the light from an oblique direction, there are problems such as a decrease in contrast and low efficiency (transmittance). That is, in order to improve the light utilization efficiency, it is also effective to increase the incident light from the normal direction of the liquid crystal panel 15.

The type of the liquid crystal panel 15 is not particularly limited, and a known type of liquid crystal panel can be used. For example, as the liquid crystal panel 15, TN, STN, VA, MVA, IPS, OCB and the like can be used.

The surface light source device 20 is an illumination device that emits planar light to the liquid crystal panel 15. The surface light source device 20 is arranged on the side opposite to the observer side with respect to the liquid crystal panel 15. The surface light source device 20 is configured as an edge light type surface light source device, and includes a light guide plate 21, a light source 25, a light diffusion plate 26, a prism layer 27, a reflective polarizing plate 28, an optical sheet 30, and a reflective sheet 39. doing.

The light guide plate 21 has a base 22 and an optical element 23. The base 22 has a plate shape having a predetermined thickness. The base portion 22 guides light and is a base portion of the optical element 23. As the material forming the base 22 and the optical element 23, various materials can be used. However, a material that is widely used as a material for an optical sheet incorporated in a display device, has excellent mechanical properties, optical properties, stability, workability, and the like, and can be obtained at low cost can be used. This includes, for example, thermoplastic resins such as polymer resins having an alicyclic structure, methacrylic resins, polycarbonate resins, polystyrene resins, acrylonitrile-styrene copolymers, methyl methacrylate-styrene copolymers, ABS resins, and polyether sulfones. , Epoxy acrylate, urethane acrylate-based reactive resin (ionized radiation curable resin, etc.) and the like can be mentioned.

The optical element 23 is formed on the back surface side of the base portion 22 (the side opposite to the side on which the reflective polarizing plate 28 is arranged). The optical element 23 protrudes from the base 22 and has a triangular prism shape. The optical element 23 is formed so that the ridgeline of the protruding top extends in the horizontal direction. On the back surface side of the base portion 22, a plurality of optical elements 23 are arranged side by side at a predetermined pitch in the vertical direction. The optical element 23 has a triangular cross section, but is not limited to this, and may have any shape such as a polygon, a hemisphere, a part of a sphere, and a lens shape. The arrangement direction of the plurality of optical elements 23 is preferably the light guide direction. That is, the ridges of the optical elements 23 extend in the direction separated from the light source 25 and in the direction in which the light sources 25 are arranged, or in the direction in which the light source extends in the case of one long light source.

The light guide plate 21 having such a configuration can be manufactured by extrusion molding or by molding the optical element 23 on the base 22. In the light guide plate 21 manufactured by extrusion molding, the base portion 22 and the optical element 23 can be integrally formed. Further, when the light guide plate 21 is manufactured by molding, the optical element 23 may be the same resin material as the base 22 or a different material.

The light source 25 is arranged on one side surface of the side surface of the base portion 22 of the light guide plate 21 in the direction in which the plurality of optical elements 23 are arranged. The light source 25 is composed of a plurality of LEDs (light emitting diodes). The light source 25 is configured so that the lighting and extinguishing of each LED and / or the brightness at the time of lighting of each LED can be individually and independently adjusted by a control device (not shown).

The light diffusing plate 26 has a function of diffusing and emitting incident light. The light diffusing plate 26 is provided on the light emitting side of the light guide plate 21. As a result, the uniformity of the light emitted from the light guide plate 21 can be further enhanced, and the scratches existing on the light guide plate 21 can be made inconspicuous. Further, the light diffusing plate 26 functions as a support for the prism layer 27.

The prism layer 27 is provided on the liquid crystal panel 15 side of the light diffusing plate 26, and has a plurality of unit prisms 27a. The unit prism 27a projects toward the liquid crystal panel 15 side and extends in a direction orthogonal to the light guide direction of the light guide plate 21. As a result, the light can be focused in the direction in which the light is controlled by the optical function layer 32 (vertical direction in the present embodiment), and the light can be efficiently totally reflected by the optical function layer 32, so that the light utilization efficiency can be improved. ..

The reflective polarizing plate 28 decomposes the incident light into two orthogonal polarization components (P wave and S wave), and transmits the polarization component (for example, P wave) in one direction (direction parallel to the transmission axis). It has a function of reflecting a polarizing component (for example, an S wave) in the other direction (direction parallel to the reflection axis) orthogonal to the one direction. A known structure of such a reflective polarizing plate 28 can be used.

The optical sheet 30 is an optical functional layer laminated on one surface (the surface on the light guide plate 21 side in this embodiment) of the first base material layer 31a formed in a sheet shape and the first base material layer 31a. A second base material layer 31b, which is arranged so as to face the first base material layer 31a with the optical functional layer 32 interposed therebetween and is adhered to the optical functional layer 32 by the adhesive layer 37, is provided.

The first base material layer 31a and the second base material layer 31b are flat plate-shaped members that support the optical functional layer 32. Various materials can be used as the material forming the first base material layer 31a and the second base material layer 31b, but in the illustrated embodiment, the first base material layer 31a and the second base layer 31a The material layers 31b are all made of polyester film.

The optical functional layer 32 has a light transmitting portion 33 and a louver portion 34. The light transmitting portion 33 is a portion whose main function is to transmit light, and has a substantially trapezoidal cross-sectional shape in the cross sections shown in FIGS. 1, 2 and 4. As shown enlarged in FIG. 4, the light transmitting portion 33 extends in the horizontal direction while maintaining the cross section along the layer surfaces of the first base material layer 31a and the second base material layer 31b, and is vertically formed thereof. They are arranged in the direction at predetermined intervals. A groove 33a (see FIG. 6) having a substantially trapezoidal cross section is initially formed between the adjacent light transmitting portions 33, and the groove 33a is filled with a material described later to form the louver portion 34. Will be done. It should be noted that the structure shown in each drawing including FIG. 4 is a schematic one and does not necessarily match the dimensions of the actual product. In various products, the thickness of each layer may differ from the dimensional relationships shown. The method of forming the louver portion 34 will be described later with reference to FIG.

The light transmitting portion 33 maintains the cross section along the layer surface of the first base material layer 31a, extends in the front-back direction of the paper surface of FIG. 4, and extends in the direction perpendicular to the front-back direction (horizontal direction of FIG. 4). They are arranged at predetermined intervals (pitch: Pk). A groove having a substantially trapezoidal cross section is initially formed between the adjacent light transmitting portions 33, and the groove has a long lower bottom on the upper bottom side (light guide plate 21 side) of the light transmitting portion 33 and emits light. The transmission portion 33 has a trapezoidal cross section having a short upper bottom on the lower bottom side (liquid crystal panel side), and the louver portion 34 is formed by filling the transmission portion 33 with a necessary material described later. In this embodiment, the adjacent light transmitting portions 33 are connected by a long lower bottom side. In order to specify the structure of the optical functional layer 32, the following parameters are mainly used for the louver portion 34. Regarding the substantially trapezoidal shape of the louver portion 34 having a substantially trapezoidal cross section, the width of the short upper base is We, and the width of the long lower base is Wb. Let Dk be the thickness of the louver portion 34 (corresponding to the height of a substantially trapezoid).

The pitch of the light transmitting portion 33 described above (that is, the pitch of the louver portion 34) Pk is preferably 30 μm or more and 100 μm or less. Further, the angle formed by the interface between the louver portion 34 and the light transmitting portion 33 shown by θk in FIG. 4 and the normal of the layer surface of the optical functional layer 32 is preferably 1 ° or more and 10 ° or less. .. However, the angle may be outside this range, and may be, for example, 0 ° (that is, the hypotenuse coincides with the normal of the layer surface of the optical functional layer 32). The louver portion 34 shown in FIG. 4 has a substantially isosceles trapezoidal shape, but the length of one leg and the length of the other leg may be different. The thickness Dk of the louver portion 34 is preferably 50 μm or more and 150 μm or less, and more preferably 60 μm or more and 150 μm or less. The width We of the upper base and the width Wb of the lower base of the substantially trapezoidal portion of the louver portion 34 are appropriately selected so as to satisfy the relationship between the thickness Dk, the pitch Pk, and the angle θk of the louver portion 34 described above. By setting these parameters within a preferable range, the balance between light transmission and light absorption is often appropriate.

The light transmitting portion 33 has a refractive index of Nt. Such a light transmitting portion 33 can be formed by curing a predetermined composition, as will be described later. The value of the refractive index Nt is not particularly limited, but a material having an excessively high refractive index is often fragile, and light is appropriately reflected at the interface with the louver portion 34 on the slope of the trapezoidal cross section (total reflection). From the viewpoint of including), the refractive index is preferably larger than 1.47 and 1.65 or less, more preferably larger than 1.49 and 1.57 or less.

The louver portion 34 is formed by filling a groove 33a initially provided between adjacent light transmitting portions 33 with a material described later, and finally has a cross-sectional shape similar to the cross-sectional shape of the groove 33a before filling. It becomes. The louver portion 34 has a refractive index of Nr and is configured to be able to absorb light. Specifically, the light absorbing particles are dispersed in a transparent resin having a refractive index of Nr. The refractive index Nr is lower than the refractive index Nt of the light transmitting portion 33. In this way, by making the refractive index of the louver portion 34 smaller than the refractive index of the light transmitting portion 33, the light incident on the light transmitting portion 33 under predetermined conditions is appropriately totally reflected at the interface with the louver portion 34. Can be done. Further, even if the total reflection condition is not satisfied, some light is reflected at the interface. The value of the refractive index Nr is not particularly limited, but a material having an excessively high refractive index is often fragile, and from the viewpoint of appropriately performing the total reflection, it is preferably 1.47 or more and less than 1.65. More preferably, it is 1.49 or more and less than 1.57.

The difference between the refractive index Nt of the light transmitting portion 33 and the refractive index Nr of the louver portion 34 is not particularly limited, but is preferably greater than 0 and 0.14 or less, and 0.05 or more and 0.14 or less. It is more preferable to have. By increasing the difference in refractive index, more light can be totally reflected.

The optical functional layer 32 having such a structure and the second base material layer 31b are bonded to each other by an adhesive layer 37. This step will be described later with reference to FIG. The adhesive 370 constituting the adhesive layer 37 is a polyurethane resin, particularly a two-component curable acrylic polyol-polyurethane resin.

When the optical sheet 30 including the optical functional layer 32 having such a configuration is bent, unevenness of light when viewed from the user (observer) may occur. Specifically, in the optical sheet 30 shown in FIGS. 2 and 3, the deflection in the direction perpendicular to the surface of the optical sheet 30, that is, the direction shown as the thickness direction in FIGS. 2 and 3 is , Affects the occurrence of light unevenness when viewed from the user (observer). Among such bending directions of the optical sheet 30, in particular, bending in the thickness direction of the optical sheet 30 shown in FIG. 2, that is, a plurality of light transmitting portions 33 and louver portions 34 of the optical functional layer 32 are alternately arranged. Since the deflection in the direction orthogonal to the direction (the direction designated as the "vertical direction" in FIG. 2) in the paper surface of FIG. 2 changes the direction of the louver portion, it is viewed from the user (observer). It greatly affects the occurrence of light unevenness at the time.

The configuration of the liquid crystal display device 10 will be further described with reference to FIGS. 1 to 3. The functional film 40 is provided on the light emitting side of the liquid crystal panel 15 and has a function of improving the quality of image light and protecting the liquid crystal display device 10. For example, as the functional film 40, an antireflection film, an antiglare film, a hard coat film, a color tone correction film, a light diffusion film and the like can be used. Further, the functional film 40 may be formed by using a plurality of these films in combination.

[Method of manufacturing optical sheet]
Next, a method of manufacturing the optical sheet 30 will be described with reference to FIGS. 5 to 7. 5 to 7 are explanatory views of a manufacturing process of the optical sheet 30. Since these explanatory drawings show an outline of the production process, the dimensions and scale may differ from the actual configuration, such as the thickness and dimension of the optical sheet 30 and other films.

As described above, the first base material layer 31a of the optical sheet 30 and the optional second base material layer 31b are both made of polyester film. The polyester film can be obtained by condensing an arbitrary dicarboxylic acid with a diol. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and diphenylcarboxylic acid. Acid, diphenoxyetanedicarboxylic acid, diphenylsulfoncarboxylic acid, anthracendicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid Acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, Dimeric acid, sebacic acid, suberic acid, dodecadicarboxylic acid and the like can be used.

Examples of the diol include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, and 1,4. -Butandiol, 1,5-pentanediol, 1,6-hexadiol, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone and the like can be used.

As the dicarboxylic acid component and the diol component constituting the polyester film, one type or two or more types may be used, respectively. As the polyester resin constituting the polyester film, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and the like can be used, preferably polyethylene terephthalate and polyethylene naphthalate, and preferably polyethylene terephthalate. can. The polyester resin may contain other copolymerization components. From the viewpoint of mechanical strength, the proportion of the copolymerization component is preferably 3 mol% or less, preferably 2 mol% or less, and more preferably 1.5 mol% or less. These resins are excellent in transparency as well as thermal and mechanical properties. In addition, these resins can easily control the retardation Re by stretching.

The polyester film can be obtained according to a general manufacturing method. Specifically, a non-oriented polyester obtained by melting a polyester resin and extruding it into a sheet is stretched in the vertical direction at a temperature equal to or higher than the glass transition temperature by utilizing the speed difference of the rolls, and then laterally stretched by a tenter. A stretched polyester film can be obtained by stretching, heat-treating, and if necessary, relaxing treatment. The stretched polyester film may be a uniaxially stretched film or a biaxially stretched film. For example, the polyester film used in Example 1 described later is stretched in the vertical direction and then in the horizontal direction at a temperature of 90 to 120 ° C., and the stretching ratio in the vertical direction is 2.0 times and the horizontal direction. The draw ratio in the direction is 4.5 times. Further, it is known that as the draw ratio increases, the breaking strength in that direction increases.

The thickness of the polyester film is arbitrary and can be appropriately set, for example, in the range of 15 to 300 μm, preferably in the range of 30 to 200 μm.

The light transmitting portion 33 is formed on one surface of the first base material layer 31a, which is the polyester film formed as described above. As shown in FIG. 5, a first mold roll R1 having a shape (groove) on which the shape of the light transmitting portion 33 can be transferred and a nip roll R2 arranged so as to face the mold roll R1 The polyester film 310 to be the base material layer 31a is inserted. At this time, while supplying the composition 330 constituting the light transmitting portion 33 (see FIGS. 1, 4, etc.) between the polyester film 310 and the mold roll R1, the mold roll R1 and the nip roll R2 are shown in FIG. Rotate in the direction indicated by the arrow at 5. As a result, the groove formed on the surface of the mold roll R1 (the shape obtained by reversing the shape of the light transmitting portion 33) is filled with the composition 330, and the composition 330 conforms to the surface shape of the mold roll R1. Become.

As the composition 330 constituting the light transmitting portion 33, for example, an ionizing radiation curable resin such as an epoxy acrylate-based resin, a urethane acrylate-based resin, a polyether acrylate-based resin, a polyester acrylate-based resin, or a polythiol-based resin can be used.

The composition 330 sandwiched between the mold roll R1 and the polyester film 310 and filled therein is irradiated with light rays (ultraviolet rays or the like) from the polyester film 310 side by the light irradiating device 61. As a result, the composition 330 is cured. Then, the mold roll R3 is used to release the pre-filling sheet 36a composed of the polyester film 310 and the molded light transmitting portion 33 from the mold roll R1.

Next, the louver portion 34 is formed. In order to form the louver portion 34, as shown in FIG. 6, the composition 340 constituting the louver portion 34 is excessively supplied to the groove 33a between the adjacent light transmitting portions 33 of the pre-filling sheet 36a. Then, the excess composition 340 is scraped off with a blade 62 or the like. Then, the composition 340 remaining so as to fill the groove 33a is irradiated with light rays (ultraviolet rays or the like) from a light source (not shown). As a result, the composition 340 is cured, the louver portion 34 is formed, and the intermediate sheet 36b is obtained.

As the composition 340 constituting the louver portion 34, for example, a photocurable resin such as urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, and butadiene (meth) acrylate can be used. Further, those resins in which colored light absorbing particles are dispersed can also be used.

Further, instead of dispersing the light absorbing particles, the entire louver portion can be colored with a pigment or dye. When light absorbing particles are used, light absorbing colored particles such as carbon black are preferably used, but the present invention is not limited to these, and a specific wavelength is selectively absorbed according to the characteristics of the image light. Colored particles may be used. Specific examples thereof include organic fine particles colored with metal salts such as carbon black, graphite and black iron oxide, dyes and pigments, and colored glass beads. In particular, colored organic fine particles are preferably used from the viewpoints of cost, quality, availability, and the like. The average particle size of the colored particles is preferably 1.0 μm or more and 20 μm or less.

A second base material layer 31b is further attached to the intermediate sheet 36b thus produced by using an adhesive 370. Specifically, as shown in FIG. 7, the intermediate sheet 36b is sent out from the roll R4, and the polyester film 310 serving as the second base material layer 31b is sent out from the roll R5 in the same direction. At this time, by aligning the flow directions of the first base material layer 31a and the second base material layer 31b (polyester film 310) contained in the intermediate sheet 36b and sticking them together, the disturbance of polarization based on the phase difference can be caused. Therefore, it is possible to prevent the occurrence of color unevenness and the decrease in transmittance. The intermediate sheet 36b and the polyester film 310 are guided by rollers 380 so as to approach each other and are integrated. At this time, the polyester film 310 is arranged so as to face the first base material layer 31a with the light transmitting portion 33 and the louver portion 34 interposed therebetween. Then, a mixed two-component curable acrylic polyol-polyurethane resin adhesive 370 can be introduced between the intermediate sheet 36b and the polyester film 310 from an adhesive supply unit (not shown), and both can be bonded together. Then, the optical sheet 30 completed by this bonding is wound around the roll R6. When the optical sheet 30 is wound by a predetermined length, the optical sheet 30 is cut, and the wound roll R6 is replaced with a new roll R6 to start the next winding.

In the step schematically shown in FIG. 7, before the polyester film 310 is sent out from the roll R5, the surface of the polyester film 310 that faces the intermediate sheet 36b, that is, the surface that comes into contact with the adhesive layer of the adhesive 370. It is also possible to attach a reflective polarizing film in advance. In this case, the second base material layer 31b includes a polyester film 310 and a reflective polarizing film (not shown). By providing such a configuration, the optical sheet can also have the role of the reflective polarizing plate 28. Therefore, since it is not necessary to use the reflective polarizing plate 28 as a separate member, the number of parts of the liquid crystal display device can be reduced and the overall thickness can be reduced, and the member can suppress the occurrence of uneven light. It is possible to reduce the weight and thickness of the.

As described above, in manufacturing the optical sheet, there is a transfer of the optical sheet between a plurality of rolls, that is, a roll-to-roll step, and the optical sheet is finally wound up on the roll again.

(Example)
The specific shape of the optical sheet according to the embodiment is as follows.

<First base material layer>
-Material: Polyester film-Thickness: 80 μm
<Optical functional layer>
-Pitch (see FIG. 4): Pk = 39 μm
・ Louver upper bottom width: 4 μm (Wa in Fig. 4)
・ Lower bottom width of louver: 10 μm (Wb in FIG. 4)
-Slope angle: 0 ° on one side and 3 ° on the other (θk in Fig. 4)
-Thickness of the louver (see FIG. 4): Dk = 102 μm
-Thickness of optical functional layer: 125 μm
-Material and refractive index of the light transmitting part: UV-curable urethane acrylate with a refractive index of 1.57-Material and refractive index of the louver part: UV-curable urethane acrylate with a refractive index of 1.49 and acrylic beads with an average particle size of 4 μm 20% by mass of black beads containing carbon black on the surface layer <second base material layer>
The following second base material layer was further bonded to the surface of the optical functional layer opposite to the first base material layer with an adhesive described later.
-Material: Polyester film-Thickness: 80 μm
<Adhesive>
As an example of the polyurethane resin, the following two-component curable acrylic polyol-polyurethane resin was used as an adhesive for adhering the optical functional layer and the second base material layer.
Main agent: Seikadyne TS241 primer (Dainichiseika Kogyo)
Hardener: Seikadyne TS241 Hardener (Dainichiseika Kogyo)
The main agent and the curing agent were mixed in a ratio of main agent: curing agent = 20: 1.
The thickness of the adhesive layer is 25 μm.

(Comparative Example 1)
In the optical sheet according to the example, the material of the adhesive for adhering the optical functional layer and the second base material layer is changed to an acrylic adhesive (PD-S1 manufactured by Panac) to prepare the optical sheet according to Comparative Example 1. bottom.

(Comparative Example 2)
In the optical sheet according to the embodiment, the material of the adhesive for adhering the optical functional layer and the second base material layer is changed to an acrylic adhesive (CS9861US manufactured by Nitto Denko) different from that of Comparative Example 1, and Comparative Example 2 An optical sheet according to the above was prepared.

In order to confirm the storage elastic modulus of the adhesive layer of the optical sheet, the adhesive squeezing out from the cut surface due to the cutting of the optical sheet, and the occurrence of light unevenness after mounting the optical sheet on the liquid crystal display device, the above-described embodiment , The optical sheets of Comparative Example 1 and Comparative Example 2 were confirmed and tested as described below, respectively.

[Storage modulus test]
The samples of Examples, Comparative Example 1 and Comparative Example 2 were cross-sectionally adjusted with a microtome (REM-710 manufactured by Daiwa Kouki Kogyo Co., Ltd.), fixed to the stage, and the nanoviscoelasticity of the adhesive layer was measured by the following evaluation method. This was performed to obtain a storage elastic modulus.
Equipment: Environmental control nano-indentation equipment Made by Nissan Ark Indenter used: Spherical indenter (tip radius 1 μm)
Measurement atmosphere: Vacuum (10 ^-3 Pa or less)
Measurement temperature: 85 ° C
Measurement frequency 250 to 1 Hz

[Confirmation of adhesive squeeze out]
The samples of Example, Comparative Example 1 and Comparative Example 2 were punched by a press cutter (Thomson cutter), tested at 95 ° C. for 1000 hours, and then examined under a microscope for the presence or absence of adhesive squeeze out at the end of the cut surface. It was visually confirmed by using.

[Confirmation of uneven light]
Regarding the occurrence of light unevenness, the optical sheets of each example and comparative example were mounted on a 12.3 inch IPS liquid crystal display for 1000 hours in an environment of a temperature of 95 ° C. and 1000 hours in an environment of a temperature of 65 ° C. and a humidity of 95%. The presence or absence of light unevenness when operating the liquid crystal display subjected to the reliability test for 1000 hours in an environment of −45 ° C. was visually confirmed.

Table 1 shows the measurement results of the storage elastic modulus, the confirmation result of the adhesive squeeze out, and the confirmation result of the light unevenness for each Example and Comparative Example.

As described above, with respect to the optical sheet using the acrylic adhesive as in Comparative Examples 1 and 2, the adhesive squeezed out and the light was uneven, whereas the optical sheet using the polyurethane resin as the adhesive was used. , It was found that the adhesive did not squeeze out and the light was not uneven.

The storage modulus of the adhesive layer when using an acrylic adhesive, such as Comparative Examples 1 and 2 is 0.8~1.0 × 10 ⁵ Pa, that protrusion of adhesive in these comparative examples occur Do you get it. As described above, the low storage elastic modulus of the adhesive layer suggests that the adhesive constituting the adhesive layer easily moves and easily protrudes from the end portion of the cut surface of the optical sheet.

The storage modulus of the adhesive layer when using an acrylic adhesive, such as Comparative Examples 1 and 2 is 0.8~1.0 × 10 ⁵ Pa, generation of light irregularity was observed in these comparative examples From this, it is suggested that the ease of movement of the adhesive constituting the adhesive layer causes an optical effect. That is, normally, the light transmitting portion and the louver portion are regularly arranged in the optical functional layer, but the arrangement of the light transmitting portion and the louver portion is disturbed by being dragged by the movement (shift) of the adhesive constituting the adhesive layer. As the viewing angle changes, unevenness of light tends to occur. In particular, since the amount of movement (deviation) of the adhesive differs between the central portion of the optical sheet and the outer peripheral portion of the optical sheet, it is considered that the slope angle of the louver portion changes depending on the location, and further unevenness of light occurs. Thus, the storage modulus of the adhesive layer becomes low as 0.8 to 1.0 × 10 ⁵ Pa as in Comparative Example is undesirable.

On the other hand, if an adhesive whose storage elastic modulus of the adhesive layer ^{greatly exceeds the range of 1 to 2 × 10 9} Pa as in the example is used, the rigidity of the adhesive layer is increased, and as a result, the rigidity of the entire optical sheet is increased. Is expected to increase. If the rigidity of the entire optical sheet becomes too high, the optical sheet may be cracked during winding on a roll in the manufacture of the optical sheet as described above. It is also not preferable that the storage elastic modulus of the adhesive layer is too large, because this leads to a decrease in manufacturing efficiency. In the above-described embodiment, there is no problem in roll-to-roll characteristics, and the processing speed is 10 m / min, so that there is no problem from the viewpoint of manufacturing efficiency.

That is, according to the optical sheet of the above-described embodiment and the liquid crystal display device using this optical sheet, it is possible to suppress the protrusion of the adhesive layer and the occurrence of uneven light, and further prevent a decrease in manufacturing efficiency. It becomes possible.

In the two-component curable acrylic polyol-polyurethane resin used as the adhesive in the above-mentioned examples, it is necessary to mix the main agent and the curing agent before use. Therefore, as compared with the acrylic adhesive used in each comparative example, the number of steps in its use increases. However, the use of the two-component curable acrylic polyol-polyurethane resin has a great advantage that it suppresses the protrusion of the adhesive layer and the occurrence of uneven light, and also prevents the production efficiency from being lowered.

In the above-mentioned examples, a two-component curable acrylic polyol-polyurethane resin was used as the polyurethane resin, but in addition to this, a polyether polyol-polyurethane resin, a polyester polyol-polyurethane resin, a polycarbonate-polyurethane resin and the like were used. It is also possible to use various polyurethane resins as adhesives.

Further, other adhesives can also be used as long as the adhesive can form an adhesive layer having a storage elastic modulus similar to that of the adhesive layer in the above-described embodiment.

Further, according to the manufacturing method of the above-described embodiment, it is possible to manufacture an optical sheet suitable for use in a liquid crystal display device, particularly an in-vehicle liquid crystal display device.

10 Liquid crystal display 14 Lower polarizing plate (polarizing film)
30 Optical sheet 31a First base material layer 31b Second base material layer 32 Optical functional layer 33 Light transmission part 34 Louver part 37 Adhesive layer

Claims (9)

An optical sheet provided between the light source of the liquid crystal display device and the liquid crystal panel.
The first base material layer and
An optical functional layer laminated on the first base material layer, which is adjacent to a plurality of light transmitting portions that are arranged along the first base material layer at predetermined intervals and transmit light. An optical functional layer having a louver portion arranged between the light transmitting portions and reflecting or absorbing light, and
A second base material layer arranged so as to face the first base material layer with the optical functional layer interposed therebetween.
An adhesive layer arranged between the optical functional layer and the second base material layer,
With
The adhesive layer is an optical sheet made of polyurethane resin. The optical sheet according to claim 1, wherein the polyurethane resin is an acrylic polyol-polyurethane resin. An optical sheet provided between the light source of the liquid crystal display device and the liquid crystal panel.
The first base material layer and
An optical functional layer laminated on the first base material layer, which is adjacent to a plurality of light transmitting portions that are arranged along the first base material layer at predetermined intervals and transmit light. An optical functional layer having a louver portion arranged between the light transmitting portions and reflecting or absorbing light, and
A second base material layer arranged so as to face the first base material layer with the optical functional layer interposed therebetween.
An adhesive layer arranged between the optical functional layer and the second base material layer,
With
An optical sheet having a storage elastic modulus of the adhesive layer of 1 × 10 ⁹ Pa to 2 × 10 ^{9 Pa at 85 ° C.} The optical sheet according to any one of claims 1 to 3, wherein the second base material layer includes a reflective polarizing film on the side in contact with the adhesive layer. The optical sheet according to any one of claims 1 to 4,
A liquid crystal display device including a light source and a liquid crystal panel arranged so as to face each other with the optical sheet interposed therebetween. The first base material layer and
An optical functional layer laminated on the first base material layer, which is adjacent to a plurality of light transmitting portions that are arranged along the first base material layer at predetermined intervals and transmit light. An optical functional layer having a louver portion arranged between the light transmitting portions and reflecting or absorbing light, and
A second base material layer arranged so as to face the first base material layer with the optical functional layer interposed therebetween.
A method for manufacturing an optical sheet including an adhesive layer arranged between the optical functional layer and the second base material layer.
A method for manufacturing an optical sheet, which uses a polyurethane resin as the adhesive layer. The method for producing an optical sheet according to claim 6, wherein the polyurethane resin is an acrylic polyol-polyurethane resin. The first base material layer and
An optical functional layer laminated on the first base material layer, which is adjacent to a plurality of light transmitting portions that are arranged along the first base material layer at predetermined intervals and transmit light. An optical functional layer having a louver portion arranged between the light transmitting portions and reflecting or absorbing light, and
A second base material layer arranged so as to face the first base material layer with the optical functional layer interposed therebetween.
A method for manufacturing an optical sheet including an adhesive layer arranged between the optical functional layer and the second base material layer.
A method for producing an optical sheet, wherein, as the adhesive layer, an adhesive layer having a storage elastic modulus of 1 × 10 ⁹ Pa to 2 × 10 ^{9 Pa at 85 ° C. after completion of the optical sheet is used.} The method for producing an optical sheet according to any one of claims 6 to 8, wherein the second base material layer includes a reflective polarizing film on the side in contact with the adhesive layer.

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