JP5674113B2 - Optical film manufacturing method, polarizing plate manufacturing method, and optical film manufacturing apparatus - Google Patents

Description

  The present invention relates to an optical film manufacturing method and manufacturing apparatus, and more particularly to an optical film manufacturing method and manufacturing apparatus capable of changing the traveling direction of light.

  The present invention also relates to a method of manufacturing a polarizing plate for a liquid crystal display panel, and more particularly to a method of manufacturing a polarizing plate that can change the traveling direction of light incident on the liquid crystal display panel.

  Furthermore, the present invention provides a polarizing plate, a liquid crystal display panel, and a display device including a protective film manufactured by such a manufacturing method, and a liquid crystal display panel and a display device including a polarizing plate manufactured by such a manufacturing method. About.

  Today, display devices including a liquid crystal display panel and a surface light source device that illuminates the liquid crystal display panel from the back side are widely used.

  As shown in FIG. 12, the surface light source device includes a light source including a light emitter and a large number of optical sheets for changing the traveling direction of light from the light emitter, and liquid crystal with desired optical characteristics. Designed to illuminate the display panel. In the example of the surface light source device shown in FIG. 12, a diffusion plate A, a lower diffusion sheet B, a condensing sheet C, and an upper diffusion sheet D are provided in this order from the light emitter 26 side of the light source 25. Among these, the condensing sheet C has the function (condensing function) which narrows the advancing direction of light to the front direction and improves the luminance in the front direction. On the other hand, the diffusing plate A, the lower diffusing sheet B, and the upper diffusing sheet D have a light diffusing function of diffusing light from the illuminant 26 of the light source 25 to hide the image of the illuminant 26 (make it inconspicuous). .

  On the other hand, as shown in FIG. 12, the liquid crystal display panel includes a liquid crystal cell 11 that can control the orientation of the liquid crystal for each pixel, and a light incident side polarizing plate (hereinafter referred to as the light incident side of the liquid crystal cell). 1, and a light output side polarizing plate (hereinafter also referred to as an upper polarizing plate) 12 disposed on the light output side of the liquid crystal cell 11. The pair of polarizing plates 12 and 13 is a polarizer that transmits light of a specific polarization component and absorbs light of components other than the specific polarization component, a protective film that is bonded to the polarizer and protects the polarizer, have.

  Of these, the protective film is usually formed as a simple translucent film due to cost constraints, and does not positively affect the transmitted light. In addition, a protective film with an optical function does not exist, but considering the adhesive function with the polarizer and the protective function to protect the polarizer, the protective film on the side that does not actually face the polarizer The surface is merely a mat surface (for example, Patent Document 1).

Japanese Patent Laid-Open No. 9-258013

  However, a sufficient diffusion function cannot be imparted to the protective film to the extent that one surface of the protective film is matted. On the other hand, if the function of actively changing the traveling direction of light can be imparted to the protective film, the degree of freedom in designing the luminance characteristics and viewing angle characteristics of the display device can be significantly improved.

  Moreover, improvement of a manufacturing method and a manufacturing apparatus is calculated | required with respect to the optical film which can change the advancing direction of light, without being restricted to the protective film for polarizing plates.

  The present invention has been made in consideration of such points, and an object thereof is to provide a manufacturing method and a manufacturing apparatus capable of manufacturing an optical film capable of changing the traveling direction of light.

  By the way, various problems have arisen because the surface light source device (display device) includes a large number of optical sheets. First, as the number of optical sheets increases, the manufacturing cost of the display device directly increases. In addition, when the surface light source device (display device) includes a large number of optical sheets, positioning between the optical sheets performed when the surface light source device is assembled and positioning between the optical sheet and the light emitter are complicated. This also increases the manufacturing cost of the display device.

  Further, each optical sheet does not transmit all incident light, and a part of the incident light is reflected by the optical sheet. The light reflected by the optical sheet can be reflected by the reflecting plate 21 (see FIG. 12) provided on the back surface of the light emitter 26 or another optical sheet and reused. However, part of the light is absorbed each time the light is reflected by each optical sheet. Such reflection loss increases significantly only when the number of optical sheets increases by one. That is, when a surface light source device (display device) includes a large number of optical sheets, the utilization efficiency of light emitted from the light emitter of the light source is significantly reduced.

  Furthermore, the optical sheet is heated by heat generated from the light emitter, and the optical sheet may be bent, bent, warped, or the like. At this time, in a surface light source device (display device) provided with a large number of optical sheets, adjacent optical sheets may contact or rub against each other. The portion where the optical sheets are in close contact with each other can no longer exhibit the expected optical function, and the close contact portion may be visually recognized. In addition, when the optical sheets are rubbed with each other, the optical sheets may be scratched, and further, residue may be generated, and the display image quality is remarkably deteriorated.

  If one or more of the many optical sheets incorporated in the conventional surface light source device can be reduced by the present invention, the above problems caused by the existence of the many optical sheets can be reduced or eliminated. Very convenient.

The method for producing an optical film according to the present invention includes:
An extrusion process of heating and extruding the thermoplastic resin to produce a film material;
A center part, a surface layer part forming a molding surface, and a heat insulating property higher than any of the center part and the surface layer part, and provided between the center part and the surface layer part, the surface layer part from the center part A molding step of pressurizing the film material between the molding surface of the molding roll having a heat insulating portion to be spaced apart and backup means,
The molding surface is such that the molding surface of the molding roll has a temperature equal to or higher than the glass transition temperature of the thermoplastic resin forming the film material at least when it starts contact with the film material in the molding step. The surface layer of the roll is heated before it begins to contact the film material.

  The protective film for a polarizing plate may be produced as an optical film by the method for producing an optical film according to the present invention.

  The method for producing an optical film according to the present invention is a step that is performed after the molding step and before the film material is released from the molding roll. The method further includes the step of cooling the film material with the cooling roll while pressurizing the film material between a cooling roll maintained at a temperature lower than the glass transition temperature and the molding surface of the molding roll. You may do it.

  In the method for producing an optical film according to the present invention, the backup means has two or more support rolls and a belt member spanned between the two or more support rolls, and in the molding step, the film material May be pressurized by the belt member of the forming roll and the backup means over a certain length of section along the movement path.

  In the extrusion step of the method for producing an optical film according to the present invention, a diffusion component may be extruded together with the thermoplastic resin to produce a film material in which the diffusion component is dispersed. In the extrusion step of the method for producing an optical film according to the present invention, the second thermoplastic resin is also heated and extruded, and has the thermoplastic resin and the diffusion component dispersed in the thermoplastic resin. A film material including a light diffusion layer and a resin layer formed on the light diffusion layer and made of the second thermoplastic resin may be produced.

The method for producing a polarizing plate according to the present invention comprises:
A step of adhering the optical film manufactured by any one of the above-described optical film manufacturing methods according to the present invention and a polarizer;
The polarizer is bonded to the film material from the side of the optical film that is in contact with the backup means.

  The method for producing a polarizing plate according to the present invention further includes a step of cutting or punching a web-like material having the optical film and the polarizer adhered to each other, and sequentially obtaining a polarizing plate from the web-like material. You may make it prepare.

The polarizing plate according to the present invention is
An optical film manufactured by any one of the above-described optical film manufacturing methods according to the present invention;
A polarizer adhered to the optical film,
The polarizer is bonded to the optical film from the side that is in contact with the backup means of the optical film.

The liquid crystal display panel according to the present invention comprises:
A polarizing plate manufactured by any of the manufacturing methods of the polarizing plate according to the present invention described above, or the polarizing plate according to the present invention described above;
A liquid crystal cell laminated on the polarizing plate.

  The display device according to the present invention includes the above-described liquid crystal display panel according to the present invention.

A manufacturing apparatus for manufacturing an optical film according to the present invention comprises:
An extruder for heating and extruding a thermoplastic resin to produce a film material;
A molding roll having a molding surface on which a concavo-convex shape to be transferred to the film material is formed;
A backup means that is disposed opposite to the molding roll and that pressurizes the film material between the molding surface of the molding roll;
A heating means arranged at a position facing the molding surface of the molding roll,
The molding roll has a center part, a surface layer part forming the molding surface, a heat insulating property higher than any of the center part and the surface layer part, and is provided between the center part and the surface layer part. A heat insulating part that separates the part from the central part,
The heating means is configured so that the molding surface of the molding roll is at a temperature equal to or higher than a glass transition temperature of the thermoplastic resin forming the film material when starting contact with at least the film material. The surface layer of the forming roll is heated before starting contact with the film material.

  The optical film manufacturing apparatus according to the present invention is disposed opposite to the molding roll on the downstream side of the backup means along the movement path of the film material, and between the molding surface of the molding roll and the molding surface. You may make it further provide the cooling means which cools the said film material, pressurizing a film material.

  In the optical film manufacturing apparatus according to the present invention, the backup means may include two or more support rolls and a belt member spanned between the two or more support rolls.

  According to the present invention, an optical film capable of changing the traveling direction of light can be manufactured. By using this optical film, it becomes possible to remarkably improve the degree of freedom in designing the luminance characteristics and viewing angle characteristics of the display device.

FIG. 1 is a perspective view showing a schematic configuration of a display device and a display panel for explaining an embodiment according to the present invention. FIG. 2 is a perspective view showing a polarizing plate (lower polarizing plate) incorporated in the liquid crystal display panel of FIG. FIG. 3 is a diagram for explaining the operation of the display device and the liquid crystal display panel, and shows the display device and the liquid crystal display panel in a cross section taken along line III-III of FIG. FIG. 4 is a diagram for explaining an example of a protective film manufacturing method and a protective film manufacturing apparatus for a polarizing plate (lower polarizing plate). FIG. 5 is a diagram corresponding to FIG. 1 and illustrating a modified example of the light emitter of the light source. FIG. 6 is a view showing the polarizing plate in the same cross section as FIG. 3, and is a view for explaining a modified example of the protective film. FIG. 7 is a view showing the polarizing plate in the same cross section as FIG. 3, and is a view for explaining another modified example of the protective film. FIG. 8 is a perspective view showing the protective film, and is a view for explaining still another modified example of the protective film. FIG. 9 is a view showing the polarizing plate in the same cross section as FIG. 3, and is a view for explaining still another modified example of the protective film. FIG. 10 is a view showing the polarizing plate in the same cross section as FIG. 3, and is a view for explaining still another modified example of the protective film. FIG. 11 is a longitudinal sectional view showing the display device and the liquid crystal display panel, and is a view for explaining a modification of the display device and the liquid crystal display panel. FIG. 12 corresponds to FIG. 1 and is a perspective view showing a conventional display device. FIG. 13 is a cross-sectional view corresponding to FIG. 11 and showing a conventional display device.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Hereinafter, an embodiment of the present invention will be described by taking a protective film for a polarizing plate as an example of an optical film. In the drawings attached to the present specification, for the sake of illustration and ease of understanding, the scale, the vertical / horizontal dimension ratio, and the like are appropriately changed and exaggerated from those of the actual ones.

  1 to 4 are diagrams for explaining an embodiment according to the present invention. Among these, FIG. 4 is a figure for demonstrating the manufacturing method and manufacturing apparatus of the protective film contained in a polarizing plate. On the other hand, FIGS. 1 to 3 are diagrams for explaining an example of a protective film that can be produced by the manufacturing method of FIG. 4 and a polarizing plate, a liquid crystal display panel, and a display device that can be produced using the protective film. is there. First, with reference to FIGS. 1-3, the protective film, polarizing plate, liquid crystal display panel, and display apparatus which can be produced by this Embodiment are demonstrated, and the manufacturing method of a protective film is demonstrated after that.

  A display device 10 shown in FIG. 1 is a liquid crystal display device, and includes a liquid crystal display panel 15, a light source 25 disposed on the back side of the liquid crystal display panel 15 (the side opposite to the observer side), and a light source 25. And a reflection plate 21 that covers from the back side. The light source 25 includes a plurality of light emitters 26 and illuminates the liquid crystal display panel 15 from the back side. On the other hand, the liquid crystal display panel 15 functions as a shutter that controls transmission or blocking of light emitted from the light emitter 26 of the light source 25 for each pixel, and forms an image.

  As will be described in detail later, the liquid crystal display panel 15 includes a pair of polarizing plates 12 and 40 and a liquid crystal cell 11 disposed between the pair of polarizing plates. The optical module 20 is formed by the polarizing plate 40 on the light incident side of the pair of polarizing plates of the liquid crystal display panel 15 and the light emitter 26 that forms the light source 25. In the following, in order to distinguish a pair of polarizing plates included in the liquid crystal display panel 15, the polarizing plate of the polarizing plate 40 on the light incident side is referred to as a lower polarizing plate regardless of the arrangement state of the display device 10. The side polarizing plate 12 is referred to as an upper polarizing plate.

  The display device 10 is configured as a direct-type liquid crystal display device, and a light emitter 26 forming a light source 25 is disposed at a position facing the liquid crystal display panel 15 in the front direction nd. That is, the light emitter 26 that constitutes the light source 25 is arranged at a position facing the lower polarizing plate 40 located on the most incident light side of the liquid crystal display panel 15 and the front direction nd. Therefore, no other member is interposed between the light emitter 26 forming the light source 25 and the lower polarizing plate 40 located on the most incident light side of the liquid crystal display panel 15, and the light emitter 26 emits light. The light directly enters the lower polarizing plate 40.

  Various known light emitters such as cold cathode fluorescent lamps can be used as the light emitter 26 forming the light source 25. However, in the illustrated example, the light source 25 is configured by a plurality of light emitting diodes (LEDs) 26. As can be understood from FIG. 1, the multiple light emitters 26 are two-dimensionally arranged on a virtual plane. That is, a large number of light emitters 26 are not arranged in only one direction on the virtual plane but are arranged with a planar spread. In particular, in the example shown in FIG. 1, the light emitters 26 forming the light source 25 are arranged in the first arrangement direction d1 and also arranged in the second arrangement direction d2 orthogonal to the first arrangement direction. Arranged.

  The reflecting plate 21 is a member for directing light emitted from the light emitter 26 of the light source 25 toward the liquid crystal display panel 15. At least the inner surface of the reflecting plate 21 is made of a material having a high reflectance such as metal.

  In the present specification, the “light exit side” refers to the downstream side in the traveling direction of light from the light emitter 26 of the light source 25 to the observer through the liquid crystal display panel 15 without wrapping the traveling direction (observer side, In FIG. 1, the “light-incident side” is the direction in which the light travels from the light emitter 26 of the light source 25 to the viewer through the liquid crystal display panel 15 without being folded back. It is upstream.

  Further, in the present specification, the terms “sheet”, “film”, and “plate” are not distinguished from each other only based on the difference in names. Therefore, for example, a “sheet” is a concept including a member that can also be called a film or a plate. As a specific example, the “protective film” includes a member called a “protective sheet”.

  Further, in this specification, the “sheet surface (film surface, plate surface)” is the same as the planar direction of the target sheet-like member when the target sheet-like member is viewed as a whole and globally. It refers to the surface to be used. In the present embodiment, the panel surface of the liquid crystal display panel 15, the plate surface of the lower polarizing plate 40, the film surface of the protective film 50 described later, the light incident side surface 55b of the main body of the protective film 50 described later, etc. They are parallel to each other. Further, in the present specification, the “front direction” refers to a direction parallel to the normal direction nd to the display surface 10a of the display device 10, and in this embodiment, the plate surface of the lower polarizing plate 40. It is parallel to the normal direction.

  Further, terms used in the present specification for specifying shapes and geometric conditions, for example, terms such as “parallel”, “orthogonal”, and “symmetric” are not limited to strict meanings, Interpretation will be made including errors to the extent that an expected function can be expected.

  Next, the liquid crystal display panel 15 will be described. As described above, the liquid crystal display panel 15 includes the pair of polarizing plates 12 and 40 and the liquid crystal cell 11 disposed between the pair of polarizing plates 12 and 40. Among these, the polarizing plates 12 and 40 have a function (absorption type polarization separation function) of decomposing incident light into orthogonal polarization components, transmitting one polarization component, and absorbing the other polarization component. Yes.

  On the other hand, the liquid crystal cell 11 has a pair of transparent substrates and a liquid crystal layer provided between the transparent substrates. An electric field can be applied to the liquid crystal layer for each region where one pixel is formed. Then, the alignment of the liquid crystal layer applied with an electric field changes. For example, the polarization component in a specific direction (direction parallel to the transmission axis) transmitted through the lower polarizing plate 40 disposed on the light incident side passes through a region of the liquid crystal layer to which an electric field is applied in the liquid crystal cell 11. At that time, the polarization direction is rotated by 90 °, and the polarization direction is maintained when passing through the liquid crystal layer to which no electric field is applied. For this reason, depending on whether or not an electric field is applied to each region of the liquid crystal layer, whether the polarization component in a specific direction transmitted through the lower polarizing plate 40 is further transmitted through the upper polarizing plate 12 disposed on the light output side of the lower polarizing plate 40. Alternatively, it is possible to control whether the light is absorbed and blocked by the upper polarizing plate 12.

  Here, the lower polarizing plate 40 will be described in more detail with reference to FIGS. 2 and 3. The lower polarizing plate 40 includes a polarizer 41 that can exhibit an absorption polarization separation function, and a protective film 50 bonded to the polarizer 41. As shown in FIG. 3, the protective film 50 is laminated on the polarizer 41 from the side that does not face the liquid crystal cell 11, in other words, from the light incident side, and protects the polarizer 41 from the outside.

  Further, an adhesive layer (not shown) is provided between the polarizer 41 and the protective film 50 so as to be adjacent to the polarizer 41 and the protective film 50 and adheres the polarizer 41 and the protective film 50 to each other. It may be. The adhesive layer for improving the adhesion between the polarizer 41 and the protective film 50 can be formed using various conventional adhesives. As one specific example, for example, an adhesive layer can be formed using an aqueous adhesive mainly composed of a polyvinyl alcohol-based resin. In addition, the adhesion in this specification is a concept including adhesion and gluing, and similarly, the adhesive in this specification is a concept including pressure-sensitive adhesive and glue.

  Various polarizers have been developed to date, and any of these polarizers can be used as the polarizer 41. As a specific example, a polarizer 41 having a polyvinyl alcohol film as a base material can be used. The polarizer 41 based on a polyvinyl alcohol film is anisotropic in absorbing light by adsorbing or dyeing a dichroic dye such as iodine or dye on the polyvinyl alcohol film, and then orienting it by uniaxial stretching. Can be imparted to the polyvinyl alcohol film.

  Next, the protective film 50 will be described. The protective film 50 described here has a light control function that changes the traveling direction of light. As a specific configuration, the light incident side surface 50b of the protective film 50 is an optical element surface formed by unit optical elements (unit prisms) 60 arranged side by side, as well shown in FIGS. Prism surface). By this optical element surface, the protective film 50 exhibits a light collecting function. The protective film 50 includes a diffusion component 59b dispersed in a binder resin, and the protective film 50 exhibits a light diffusion function by the diffusion component 59b. Hereinafter, the configuration of the protective film 50 will be further described in detail.

  The “unit optical element” in the present specification refers to an element having a function of changing the traveling direction of the light by exerting an optical action such as refraction or reflection on the light. ”,“ Unit prism ”, and“ unit lens ”are not distinguished based only on the difference in designation and elements. Similarly, “prism” and “lens” are not distinguished from each other based solely on the difference in designation.

  As well shown in FIG. 3, the protective film 50 includes a sheet-like main body portion 55 and unit optical elements 60 arranged side by side on the light incident side surface 55 b of the main body portion 55. Each unit optical element 60 extends in a direction intersecting the arrangement direction and parallel to the film surface of the protective film 50. Further, the unit optical elements 60 included in the protective film 50 are configured identically. In the present embodiment, when observed from a direction parallel to the normal direction to the plate surface of the lower polarizing plate 40, the arrangement direction of the unit optical elements 60 is the first arrangement direction d1 of the plurality of light emitters 26 (FIG. 1)).

  By the way, the liquid crystal display panel 15 defines a large number of pixels. The liquid crystal display panel 15 forms an image by controlling transmission and blocking of light for each pixel. When the unit optical elements 60 are observed from a direction parallel to the direction normal to the plate surface of the lower polarizing plate 40, the unit optical elements 60 intersect with the pixel arrangement direction of the liquid crystal cell 11 of the liquid crystal display panel 15, that is, It is preferable to be inclined or orthogonal to the pixel arrangement direction. Specifically, when observed from a direction parallel to the direction normal to the plate surface of the lower polarizing plate 40, the arrangement direction of the unit optical elements 60 and the arrangement direction of the pixels of the liquid crystal cell 11 are 1 ° or more and 45 °. It is preferable to incline at an angle of less than or equal to 0 °, more preferably at an angle of 2 ° to 15 °. In this case, moire (interference fringes) caused by interference between the periodicity caused by the regular arrangement of the pixels and the periodicity caused by the regular arrangement of the unit optical elements 60 can be effectively made inconspicuous. it can. From the viewpoint of making the moire inconspicuous, it is preferable that the arrangement pitch of the unit optical elements 60 is 30 μm or less.

  The cross section shown in FIG. 3 is a cross section (hereinafter also simply referred to as “main cut surface”) along both the arrangement direction of the unit optical elements 60 and the normal direction to the film surface of the protective film 50. As shown in FIG. 3, each unit optical element 60 has a triangular shape on the main cutting plane. In particular, in the illustrated example, the cross-sectional shape of the main cutting surface of the unit optical element 60 is an isosceles triangle that is arranged symmetrically about the normal direction to the film surface of the protective film 50. The angle θa (see FIG. 3) of the isosceles triangle shape can be set to, for example, 15 ° to 100 ° in consideration of the light collecting function.

  Further, as described above, the protective film 50 has the diffusion component 59b, and the protective film 50 exhibits a light diffusion function by the diffusion component 59b. More strictly, the protective film 50 includes a light diffusion layer 51a having a main part 59a made of resin and a diffusion component 59b dispersed in the main part 59a.

  As well shown in FIG. 3, the protective film 50 in the present embodiment includes a light diffusion layer 51a and a resin layer 51b that does not contain the diffusion component 59b. In the illustrated example, the resin layer 51b is disposed on the light incident side with respect to the light diffusion layer 51a. That is, the light diffusion layer 51a is disposed closer to the polarizer 41 than the resin layer 51b.

  The resin layer 51 b constitutes the unit optical element 60 described above and the light incident side portion of the main body portion 55. On the other hand, the light diffusion layer 51a constitutes a part on the light output side of the main body 55 adjacent to the resin layer 51b. Further, due to a manufacturing method described later, there is no optical interface between the main portion 59a of the light diffusion layer 51a and the resin layer 51b. That is, light enters the protective film 50 from the resin layer 51b to the light diffusion layer 51a without being optically affected.

  As the resin material forming the resin layer 51b and the resin material forming the main portion 59a of the light diffusion layer 51a, various resin materials having excellent optical characteristics, for example, polycarbonate resins can be used. The polycarbonate-based resin is suitable as a material used for the lower polarizing plate 40 from the viewpoint of low retardation.

  On the other hand, the diffusing component 59b dispersed in the light diffusing layer 51a can be composed of a granular material having a refractive index different from that of the main portion 59a, or a granular material having its own reflectivity. The particulate material forming the diffusion component 59b may be a metal compound, a porous material containing a gas, or may be a simple bubble. Further, the shape of the diffusion component 59b made of a granular material is not particularly limited. Therefore, the diffusion component 59b does not have to be spherical (particulate) as in the illustrated example, and can have various shapes such as a spheroid shape and a linear shape.

  The protective film 50 can exhibit a diffusion function of diffusing light due to the light diffusion layer 51a including the diffusion component 59b. The degree of the light diffusing function of the protective film 50 due to the internally added diffusion component 59b is as follows. The resin material forming the main portion 59a, the thickness of the main portion 59a, the configuration (shape, size (grain) of the diffusion component 59b (Diameter), refractive index, etc.), the concentration of the diffusing component 59b, and the like can be set within an extremely wide range by appropriately setting. Specifically, the haze value of the protective film 50 is set to a level that cannot normally be reached by simply matting (roughening) the surface layer portion, for example, within a range of 60% to 90%. It is also possible to do.

  Incidentally, the light incident side surface of the lower polarizing plate 40, in other words, the light incident side surface 50 b of the protective film 50 that forms the light incident surface of the liquid crystal display panel 15 is formed as an optical element surface composed of the unit optical elements 60. On the other hand, the light exit side surface 50a of the protective film 50 is formed as a flat surface. Thereby, it becomes possible to laminate | stack and adhere | attach the protective film 50 and the polarizer 41 stably, preventing mixing of air etc.

  In the present specification, “flat” used for the surface 50 a of the protective film 50 facing the polarizer 41, that is, the light exit side surface 50 a of the protective film 50 is the stability of the protective film 50 and the polarizer 41. It refers to flatness to the extent that it is possible to ensure lamination and adhesion. For example, when the surface roughness of the surface 50a facing the polarizer 41 of the protective film 50 is measured as a ten-point average roughness Rz in accordance with JIS B0601 (1982), it may be 1.0 μm or less. It can be said that it is flat.

  Although the protective film 50 is internally added with the diffusing component 59b, the light-exiting side surface 50a of the protective film 50 is flat, so that the protective film 50 and the polarizer 41 are attached by so-called “water sticking”. Can be laminated and glued. Specifically, the protective film 50 and the polarizer 41 are overlapped with each other with an aqueous solution (or suspension) mixed with water or a suitable additive such as a surfactant interposed therebetween. To go. Thereby, the protective film 50 and the polarizer 41 can be laminated | stacked, preventing mixing of foreign materials, such as air. At this time, an adhesive (for example, glue) is mixed with water or an aqueous solution (or suspension), or an adhesive layer is provided in advance on at least one of the protective film 50 and the polarizer 41, The protective film 50 and the polarizer 41 may be positively bonded.

In addition, in order to accelerate | stimulate the removal of the water | moisture content from the protective film 50 and the polarizer 41 after "water sticking", the water vapor transmission rate of the protective film 50 is 10 g / m under the condition of temperature 40 degreeC and humidity 90% RH. It is preferably ² · 24 hours or more. However, if the moisture permeability is too high, warping or bending due to moisture absorption may occur. Therefore, the moisture permeability is preferably 400 g / m ² · 24 hr or less as measured at a temperature of 40 ° C. and a humidity of 90% RH. . In addition, the moisture permeability in this specification refers to the numerical value measured using the cup method based on JISZ0208.

  Next, an example of a method for manufacturing the protective film 50 having the above configuration will be described mainly with reference to FIG. In the following description, the protective film 50 is formed as an extruded material extruded by an extrusion process.

  First, the extrusion apparatus (protective film manufacturing apparatus) 80 used for manufacturing the protective film 50 will be described. As shown in FIG. 4, an extrusion device 80 as a protective film manufacturing apparatus includes an extrusion machine 82 including a die 82 a, a molding roll 84, a backup means 86 disposed to face the molding roll 84, and a molding roll. 84 and guiding means 88 disposed downstream of the backup means 86. The guiding means 88 is configured as a pair of guide rolls 88a. In addition, the extrusion device 80 includes a heating unit 83 that heats the molding roll 84 and a cooling unit 87 that cools the molding roll 84.

  The forming roll 84 has a cylindrical outer shape, and in this example, a groove having a shape corresponding to the cross-sectional shape of the unit optical element 60 is spiral on the cylindrical outer peripheral surface of the forming roll 84. It is formed in a large number or in a circumferential shape. The columnar molding roll 84 is rotatable about a rotation axis passing through the center of the column.

  Further, the molding roll 84 includes a center portion 85a, a surface layer portion 85c, and a heat insulating portion (heat insulating layer) 85b provided between the center portion 85a and the surface layer portion 85c to isolate the surface layer portion 85c from the center portion 85a. doing. The surface layer portion 85c constitutes a molding surface 84a of the molding roll 84, and the molding surface 84a is provided with an uneven shape to be transferred to the film material 90 extruded from the extruder 82. The heat insulating part 85b has higher heat insulating properties than both the surface layer part 85c and the central part 85a. In addition, the level of heat insulation can be evaluated using heat conductivity, and it can be said that heat insulation is so high that the value of heat conductivity is small. As an example, the heat insulation part 85b can be formed from super engineering plastics such as polyether ether ketone or ceramics, and the surface layer part 85c and the center part 85a can be made of steel.

  The backup means 86 has two or more support rolls 86a and an edgeless belt member (belt) 86b spanned between the two or more support rolls 86a. In the illustrated example, the backup means 86 has two support rolls 86a. Each support roll 86a is formed in a columnar shape, and is rotatable around a rotation axis passing through the center of the column. The rotation axes of the support rolls 86a are parallel to each other, and are also parallel to the rotation axis of the forming roll 84. And the two or more support rolls 86a can drive the belt member 86b spanned over the said support roll 86a by rotating centering around a rotating shaft line.

  In the illustrated example, one of the two support rolls 86 a is configured as a nip roll 86 a 1 that is disposed to face the molding roll 84. The other of the two support rolls 86a is configured as an adjustment roll 86a2 that establishes a moving path of the belt member 86b with the nip roll 86a1.

  As shown in FIG. 4, the belt member 86 b is deformed corresponding to the outer contour of the molding roll 84 by pressing from the molding roll 84 between the nip roll 86 a 1 and the adjustment roll 86 a 2. . For this reason, as will be described later, the film material 90 passing between the belt member 86b and the molding roll 84 is formed by the belt member 86b and the molding roll 84 over a nip section NZ having a certain length along the movement path. It will continue to be pressurized. In the configuration shown in FIG. 4, for example, the length of the nip section NZ can be adjusted as appropriate by adjusting the position of the support roll 86a, particularly the adjustment roll 86a2.

  The forming roll 84, the nip roll 86a1, the adjustment roll 86a2, and the belt member 86b are configured using various materials. For example, as the forming roll 84, the nip roll 86a1, and the adjustment roll 86a2, a metal roll, a roll whose center portion is made of metal and whose surface layer portion is made of an elastic body (for example, rubber) can be used. Further, as the belt member 86b, a durable metal-free belt, for example, a belt-shaped member made of a metal alloy such as a chromium alloy or a nickel alloy can be used.

  In addition, it is not restricted to the above example, The backup means 86 may be comprised from the mere metal roll or the rubber roll.

  As shown in FIG. 4, the heating means 83 is formed at a position just before facing the backup means 86 of the molding roll 84, that is, at a position just before contacting the extruded material 90 of the molding roll 84. 84 can be heated from the molding surface 84a. As the heating means 83, a far-infrared heater 83a can be used as shown in FIG.

  On the other hand, the cooling means 87 is disposed to face the molding roll 84 at a position between the backup means 86 and the adjusting means 88 along the movement path of the extruded material 90. The cooling means 87 can contact the surface layer portion 85c of the molding roll 84 via the extrusion material 90, and can cool the molding roll 84 from the molding surface 84a. As the cooling means 87, a cooling roll 87a in which a circulation path for a refrigerant (for example, cooling water) is formed can be used.

  As described above, the molding roll 84 is adjacent to the surface layer portion 85c that forms the molding surface 84a, and is provided with a heat insulating portion 85b having excellent heat insulating properties. Therefore, it is mainly the surface layer portion 85 c of the molding roll 84 that is heated from the heating means 83, and the surface layer portion 85 c of the molding roll 84 is mainly deprived of heat by the cooling means 87. For this reason, by reducing the thickness of the surface layer portion 85c and reducing the heat capacity of the surface layer portion 85c, the temperature of the surface layer portion 85c of the molding roll 84 can be quickly and greatly increased using the heating means 83 and the cooling means 87. It becomes possible to change to. Specifically, the surface layer portion 85c of the molding roll 84 cooled by the cooling means 87 can be heated in a short time by heating from the heating means 83, and conversely, the molding roll heated by the heating means 83. The surface layer portion 85c of 84 can be cooled in a short time by cooling by the cooling means 87.

  Next, a method for manufacturing the protective film 50 described above using such a manufacturing apparatus (extrusion apparatus) 80 will be described. In the method described here, a film material 90 as an extrusion material including the light diffusion layer 51a and the resin layer 51b described above is manufactured by so-called coextrusion. Then, the obtained film material 90 forms the protective film 50.

  First, the first material that forms the light diffusion layer 51 a and the second material that forms the resin layer 51 b are put into the extruder 82. The first material that forms the light diffusion layer 51a includes a thermoplastic resin that forms the main portion 59a (for example, a pellet-shaped thermoplastic resin material) and a granular material that forms the diffusion component 59b. And are included. The second material that forms the resin layer 51b includes a thermoplastic resin (for example, a pellet-shaped thermoplastic resin material) that forms the resin layer 51b. The second thermoplastic resin included in the second material may be a resin material different from the first thermoplastic resin included in the first material, or may be a thermoplastic resin included in the first material. The same resin material may be used.

  The thermoplastic resin constituting the first and second resin materials charged into the extruder 82 is heated to the glass transition temperature or higher in the extruder 82. Then, the heated and softened first and second resin materials are extruded by the extruder 82.

  As an example, when a polycarbonate resin having a glass transition temperature of around 140 ° C. is used as the thermoplastic resin contained in the first and second resin materials, the temperature of the thermoplastic resin immediately after passing through the die 82a is You may make it heat a thermoplastic resin in the extruder 82 so that it may become about 300 degreeC. Further, when the protective film 50 is produced by extrusion, the average particle diameter of the granular material that forms the diffusion component 59b (the particle diameter calculated by the volume equivalent method, that is, the arithmetic average of the volume equivalent diameter, the same shall apply hereinafter). The content of the granular material that forms the diffusion component 59b may be more than 0% by weight and 40% by weight or less.

  Thus, the first layer (the layer that forms the light diffusion layer 51a) having the thermoplastic resin and the diffusion component dispersed in the thermoplastic resin, and the second layer made of the thermoplastic resin. A film material 90 having (a layer that forms the resin layer 51b) is formed as an extrusion material. At this time, in the die 82a of the extruder 82, the thickness of the film material 90 can be controlled to a desired thickness.

  The film material 90 extruded from the extruder 82 advances between the forming roll 84 and the backup means 86. At this time, the first layer (the layer that forms the light diffusion layer 51a) of the film material 90 having the thermoplastic resin and the diffusion component dispersed in the thermoplastic resin is the backup means 86. The second layer made of the thermoplastic resin (the layer that forms the resin layer 51 b) comes into contact with the molding roll 84. The film material 90 is supported by the endless belt 86b of the backup means 86 from the side of the first layer (the layer that forms the light diffusion layer 51a) made of the thermoplastic resin and the granular material, and the forming roll 84 is pressed from the side of the second layer made of a thermoplastic resin (the layer that forms the resin layer 51b). The pressing of the film material 90 by the edgeless belt 86b and the molding roll 84 of the backup means 86 is continued while the film material 90 proceeds through the section NZ having a predetermined length.

  In this way, the mold surface 84a of the molding roll 84 is pressed against the layer made of the thermoplastic resin of the film material 90 (the layer that forms the resin layer 51b), and the uneven shape of the molding surface 84a is transferred to the film material 90. Is done. Further, the diffusion component is pushed into the film material 90 while the film material 90 is sandwiched between the forming roll 84 and the edgeless belt 86 b of the backup means 86.

  The edgeless belt 86b has a much smaller heat capacity than the molding roll 84, and is not heated by a heater or the like. Therefore, even if the edgeless belt 86 b absorbs heat from the film material 90, it performs sufficient heat dissipation while not in contact with the film material 90. For this reason, when the edgeless belt 86b comes into contact with the film material 90 again, the temperature of the edgeless belt 86b is sufficiently lowered, and the edgeless belt 86b promotes cooling of the film material 90. As a result, when the film material 90 is separated from the edgeless belt 86b of the backup means 86, the first layer (which forms the light diffusion layer 51a) made of the thermoplastic resin and the particulates that are in contact with the edgeless belt 86b of the film material 90 is formed. Layer) is sufficiently cooled. That is, the film material 90 can be sufficiently cooled by the edgeless belt 86b so that the thermoplastic resin contained in the layer reaches a temperature lower than the glass transition temperature.

  In addition, when the temperature of the first layer that forms the light diffusion layer 51a is lowered to below the glass transition temperature of the resin material that forms the main portion 59a of the light diffusion layer 51a in this way. The thermoplastic resin material has a certain degree of deformation resistance. For this reason, the thermal deformation due to the difference between the thermal expansion coefficient of the resin material that forms the main portion 59a and the thermal expansion coefficient of the granular material that forms the diffusion component 59b is less likely to occur. That is, in the subsequent cooling process, the portion of the resin material that forms the main portion 59a recedes and the contour of the granular material that forms the diffusing component 59b is suppressed from rising, and the film material 90 is free of edge. The surface that has been in contact with the belt 86b can be maintained as a flat surface.

  On the other hand, the temperature of the film material 90 immediately after being extruded from the extruder 82 has risen to about 300 ° C. Immediately before the film roll 90 comes into contact with the film material 90, the molding roll 84 is heated from the side of the molding surface 84a by the heating means 83. The surface layer portion 85c including the molding surface 84a is partitioned from the central portion 85a by the heat insulating portion 85b, and the temperature thereof can be increased rapidly and significantly. At this time, the temperature of the molding surface 84a is equal to or higher than the glass transition temperature of the resin material to be molded by the molding roll 84 of the film material 90, for example, when the molded resin material is polycarbonate. Is heated to about 160 ° C. Thus, the molding material 84a of the molding roll 84 having a surface temperature equal to or higher than the glass transition temperature of the thermoplastic resin in which the film material 90 immediately after being extruded is heated to form the film material 90, and backup means The pressure is applied by 86 edgeless belts 86b.

  The film material 90 is pressed between the edgeless belt 86b of the backup unit 86 and the molding roll 84 while traveling through the section NZ having a predetermined length. During this time, as described above, the film material 90 is deprived of heat by the edgeless belt 86 b of the backup means 86, and the film material 90 is also deprived of heat from the forming roll 84. However, as described above, the heat of the film material 90 is rapidly taken away from the edgeless belt 86 b side, but the molding roll 84 is heated immediately before contacting the film material 90. Therefore, the resin to be molded is pressed by the molding surface 84a of the molding roll 84 for a predetermined time in a state where the resin to be molded is maintained at a high temperature, preferably a temperature equal to or higher than the glass transition temperature. . As a result, a desired uneven shape is accurately formed on the film material 90.

  As shown in FIG. 4, the film material 90 released from the pressure between the backup means 86 and the molding roll 84 is supported by the backup means 86 and the guiding means 88 and thereafter the molding roll 84. It is pressed toward the molding surface 84a. The film material 90 disposed on the molding surface 84 a of the molding roll 84 then passes between the molding roll 84 and the cooling roll 87 a that forms the cooling means 87. The cooling roll 87a is maintained so that the surface temperature thereof is lower than the glass transition temperature of the thermoplastic resin forming the film material. The film material 90 is cooled by the cooling means 87 while being pressed toward the molding surface 84a. Therefore, during this cooling, the film material 90 is pressed against the molding surface 84a, so that deformation is restricted. This effectively prevents the shaped uneven shape of the film material 90 (the uneven shape that forms the unit optical element 60) from being greatly deformed from the shape expected by heat shrinkage. Can do.

  At the same time, the surface layer portion 85c including the molding surface 84a of the molding roll 84 is also cooled by the cooling roll 87a through the film material 90. As a result, the film material 90, together with the surface layer portion 85c of the molding roll 84, is heated to a temperature lower than the glass transition temperature of the resin material forming the film material, for example, 130 when the resin material to be cooled is polycarbonate. It can be stably cooled to about ° C. In this way. Even the temperature of the surface layer portion 85c of the molding roll 84 is cooled to a temperature lower than the glass transition temperature of the resin material forming the film material 90, so that the temperature of the film material 90 again exceeds the glass transition temperature. Accordingly, the shape formed with high accuracy due to the preliminary heating of the molding roll 84 can be maintained as it is.

  The extruded material 90 released from the molding roll 84 is then cooled by the guiding means 88 and guided while being moderately warped and corrected for warping and bending. As described above, the protective film 50 made of the film material (extruded material) 90 formed by extruding the thermoplastic resin material together with the particulates is produced. In addition, the flat light emission side surface 50a of the protective film 50 is formed by the surface which was contacting the backup means 86 of the film material 90, and the light incident side surface 50b in which the unit optical element 60 of the protective film 50 was formed is extruded material. It is formed by the surface that has been in contact with the 90 molding rolls 84.

  According to the manufacturing method described above, the web-like protective film 50 (web-like film material 90) can be produced. For this reason, the sheet-like polarizer 41 having a size corresponding to the lower polarizing plate 40 to be produced (one or a plurality of sheets) is sequentially bonded to the web-shaped protective film 50. Or by adhering the polarizer 41 formed in a web shape, a web-like material is obtained, and this web-like material includes a large number of lower polarizing plates 40 connected to each other. . Then, the lower polarizing plate is sequentially obtained by cutting (or appropriately taking out such as punching) the web-like material.

  That is, according to the manufacturing method described above, the web-like protective film 50 can be produced, and the lower polarizing plate 540 is efficiently produced while handling the protective film 50 on a roll-to-roll basis. be able to. Thereby, according to the above-described method, not only can the protective film 50 be produced at low cost, but also the production of the lower polarizing plate 40 is facilitated by using the produced protective film 50. As a result, The lower polarizing plate 40 can be made extremely inexpensively.

  In the description here, the protective film for the polarizing plate is manufactured as an example of the optical film. However, the present invention is not limited to this example, and an optical film used for various applications can be manufactured with high accuracy.

  Next, the operation of the display device 10 resulting from the protective film 50 will be described mainly with reference to FIG.

  In FIG. 3, the light emitted from the light emitter 26 of the light source 25 travels to the viewer side directly or after being reflected by the reflecting plate 21 and enters the liquid crystal display panel 15. A lower polarizing plate 40 is provided on the most incident light side of the liquid crystal display panel 15. The protective film 50 of the lower polarizing plate 40 forms the most incident light side surface of the liquid crystal display panel 15.

  As described above, the protective film 50 has a light collecting function that changes the traveling direction of the light so that the angle formed by the traveling direction of the light with respect to the front direction nd is reduced as a whole, and a light diffusion that diffuses the light. It has a function. Among these, the light condensing function is expressed by the unit optical element 60 of the protective film 50, and the light diffusion function is mainly expressed by the light diffusion layer 51 a of the protective film 50. The unit optical element 60 forms the light incident side surface of the protective film 50, and the light diffusion layer 51 a is provided on the light outgoing side of the protective film 50. For this reason, the light incident on the protective film 50 is first given a condensing function and then given a light diffusing function.

  As is well shown in FIG. 3, the basic principle of the light collecting function by the unit optical element 60 is that the light L31 and L32 incident from one light incident side surface 60b1 of the unit optical element 60 is changed to the other light incident side surface 60b2. In this case, the angle at which the traveling direction of the light is formed with respect to the front direction nd is reduced. That is, the light condensing function by the unit optical element 60 is mainly exerted on the light component parallel to the arrangement direction of the unit optical elements 60. Then, by appropriately designing the cross-sectional shape of the unit optical element 60, as shown in FIG. 3, the light condensing function of the unit optical element 60 of the protective film 50 is two light emitters adjacent in the arrangement direction. 26, which is a region including a position facing the intermediate point 26 and has a tendency that the brightness tends to decrease.

  In other words, the unit optical element 60 not only collects light components along the arrangement direction but also functions to alleviate unevenness in brightness along the arrangement direction. As described above, since the unit optical elements 60 mainly exhibit an optical function with respect to light components parallel to the arrangement direction, the arrangement directions of the unit optical elements 60 are as shown in the examples shown in FIGS. Is parallel to the arrangement direction of the light emitters 26, the brightness variation along the arrangement direction of the light emitters 26 can be effectively uniformed and made inconspicuous. Therefore, in the example shown in FIG. 1, the first arrangement direction of the light emitters 26 that are two-dimensionally arranged is parallel to the arrangement direction of the unit optical elements 60. Unevenness of brightness can be eliminated, and the in-plane distribution of luminance can be effectively made uniform.

  As described above, the unit optical element 60 of the protective film 50 is useful for improving the luminance in the front direction, and also has uneven brightness (in-plane variation in luminance) due to the configuration (arrangement) of the light emitter 26 of the light source 25. It also helps to alleviate. In addition, in the present embodiment, since the diffusion component 59b is not dispersed in the unit optical element 60, the surface (prism surface) of the unit optical element 60 that functions as the incident surface 60b1 and the total reflection surface 60b2 is diffused. It can be formed with high accuracy as a flat surface without unevenness due to the component 59b. Thereby, the unit optical element 60 of the protective film 50 can exhibit the expected desired optical function.

  The degree of such a light condensing function in the protective film 50 is determined by the arrangement pitch pa1 of the two adjacent light emitters 26 and the light emitting body 26 and the protective film 28 along the normal direction to the film surface of the protective film 50. By appropriately setting the separation distance la1, the shape of the unit optical element 60, the refractive index of the unit optical element 60, etc., it can be adjusted within a very wide range.

  The light incident on the protective film 50 through the unit optical element 60 then travels in the main body portion 55 from the resin layer 51b to the light diffusion layer 51a having a light diffusion function. The light diffusion layer 51a has a main portion 59a and a diffusion component 59b dispersed in the main portion 59a, and expresses a light diffusion function due to the internally added diffusion component 59b. The light diffusing function in the light diffusing layer 51a due to the internally added diffusing component 59b is, for example, matting the surface by molding or providing a granular material on the surface layer to make the surface matte. Compared with the light diffusing function resulting from this, the degree (diffusion intensity) and quality (diffusion uniformity) are remarkably superior.

  Specifically, when the surface is merely matted, light that passes through (the traveling direction cannot be changed) is generated. On the other hand, according to the internally added diffusion component 59b, the diffusion component 59b is dispersed not only in the plane direction but also in the thickness direction. For this reason, the light incident on the light diffusion layer 51a collides with the diffusion component 59b at least once and changes its traveling direction with a high probability. Further, as described above, the resin material forming the main portion 59a, the thickness of the main portion 59a, the configuration (shape, size (particle size), refractive index, etc.) of the diffusing component 59b, the concentration of the diffusing component 59b, etc. are set as appropriate. By doing so, the degree of the light diffusion function of the light diffusion layer 51a can be adjusted within a very wide range.

  As described above, the light from the surface light source device 20 can be diffused to some extent by the light diffusion layer 51 a of the protective film 50. Thereby, the angle distribution of the brightness after being condensed by the unit optical element 60 of the protective film 50 can be changed smoothly. Moreover, the surface of the brightness | luminance resulting from the arrangement | sequence of the light-emitting body 26 along the 1st arrangement direction d1 and the 2nd arrangement direction d2 by adjusting the grade of the light-diffusion function in the light-diffusion layer 51a of the protective film 50 suitably. It is also possible to effectively uniform the internal distribution and more reliably prevent the image (light image) of the light emitter 26 from being visually recognized.

  The light diffused by the light diffusion layer 51 a of the protective film 50 then travels toward the polarizer 41, the liquid crystal cell 11, and the upper polarizing plate 12 of the lower polarizing plate 40 disposed on the light output side of the protective film 50. At this time, the liquid crystal cell 11 selectively transmits light for each pixel, so that an observer of the display device 10 can observe an image.

  According to the present embodiment as described above, the protective film 50 is produced by subjecting the film material 90 made of an extruded material that has been heated and extruded to a molding process using the molding roll 84. At this time, the molding roll 84 has a heat insulating property higher than that of the center portion 85a, the surface layer portion 85c forming the molding surface 84a, and the center portion 85a and the surface layer portion 85c, and between the center portion 85a and the surface layer portion 85c. And a heat insulating portion 85b that separates the surface layer portion 85c from the central portion 85a. Then, when the molding surface 84a of the molding roll 84 starts to contact the film material 90, the surface layer portion of the molding roll 84 is at a temperature equal to or higher than the glass transition temperature of the thermoplastic resin forming the film material 90. 85c is heated before initiating contact with the film material 90. Since the surface layer portion 85c of the molding roll 84 is separated from the central portion 85a by the heat insulating portion 85, the temperature can be greatly increased in a short time. Thereby, it becomes possible to perform the shaping | molding process using the shaping | molding roll 84 at a very high precision with a high shaping rate. Thereby, the obtained protective film 50 comes to have an excellent light control function capable of changing the traveling direction of light, and in this respect, it is suitably used as a protective film for a polarizing plate, particularly the lower polarizing plate 40. Can be done. Further, such a high-performance protective film 50 can be manufactured at a low cost by so-called extrusion processing.

  As described above, according to the protective film 50 according to the present embodiment, the degree of freedom in designing the luminance characteristics and viewing angle characteristics of the display device 10 can be significantly improved. And according to the quality etc. which are required for the display device 10, the diffusion plate A incorporated in the surface light source device of the conventional display device 1 shown in FIG. It is also possible to delete all or part of the optical sheets such as the diffusion sheet B, the light collecting sheet C, and the upper diffusion sheet D.

  Thus, if the member (optical sheet) incorporated in the display device can be deleted, the manufacturing cost of the display device can be greatly reduced directly. Further, it is possible to omit a complicated operation such as positioning of optical sheets necessary for assembling the display device or the surface light source device, and the manufacturing cost of the display device can also be reduced in this respect. Further, by omitting part or all of the members (optical sheets) incorporated in the display device, the display device can be thinned.

  In addition, the optical sheets incorporated in the conventional display device are members for correcting the traveling direction of light, but on the other hand, a part of incident light is absorbed. In addition, in the conventional display device, a lot of light is reflected by any one of the optical sheets, and enters the display panel after returning its traveling direction one or more times. As a result, most of the light emitted from the light emitter 26 serving as the light source 25 is absorbed by any one of the optical sheets and cannot be used for displaying an image. On the other hand, according to the illustrated embodiment, the illuminant 26 forming the light source 25 faces the protective film 50 of the polarizing plate 40, that is, faces without any member interposed therebetween. Therefore, the light emitted from the light emitter 26 can be directly incident on the polarizing plate 40 of the liquid crystal display panel 15, and even if it is reflected, the liquid crystal display panel can be reflected by a single reflection on the reflection plate 21. It can reenter the 15 polarizing plates 40. For this reason, the utilization efficiency of the light emitted by the light emitter 26 can be significantly increased. As a result, for example, it is possible to significantly widen the viewing angle while maintaining the luminance in the front direction without increasing the output of the light source 25 as compared with the conventional display device.

  Furthermore, if all or part of the optical sheet positioned between the light emitter 26 forming the light source 25 and the protective film 50 of the polarizing plate 40 can be reduced, the optical sheet is caused by deformation such as bending, bending, warping, and the like. It is possible to avoid problems such as display image quality degradation. In the conventional display device, as shown in FIG. 12, the thickness of the member (diffusion plate A) facing the light emitter is not changed by heat generated from the light emitter, and further, It was thick so that the heat transfer toward the member (diffusion sheet or condensing sheet) located on the light exit side could be blocked. Thus, when the thickness of the diffusing plate A increases, the material cost and weight of the diffusing plate A increase, resulting in a problem that the manufacturing cost of the display device increases. Further, when the diffusion plate A having a certain thickness is to be incorporated into the surface light source device, it is necessary to install a corresponding support mechanism. On the other hand, according to the present embodiment described above, the protective film 50 facing the light emitter 26 is laminated on the liquid crystal display panel 15 as a part of the polarizing plate 40. That is, since the protective film 50 is directly supported by the liquid crystal display panel 15, a special support mechanism for supporting the protective film 50 is not necessary, and deformation of the protective film 50 is restricted by the liquid crystal display panel 15. . Therefore, the thickness of the protective film 50 can be determined from the viewpoint of the optical action expected for the protective film 50 and the protective action of the polarizer, and as a result, the manufacturing cost of the display device 10 can be reduced.

  In the conventional display device 1 shown in FIG. 12, the configurations of the light source 25, the reflecting plate 21, the liquid crystal cell 11, and the upper polarizing plate 12 can be configured in the same manner as in the above-described embodiment.

  Various modifications can be made to the above-described embodiment. Hereinafter, an example of modification will be described with reference to the drawings as appropriate. In the drawings used in the following description, the same reference numerals as those used for the corresponding parts in the above-described embodiment are used, and redundant descriptions are omitted.

  In the embodiment described above, an example has been shown in which the light emitters 26 forming the light source 25 of the optical module 20 are two-dimensionally arrayed point light emitters, typically light emitting diodes. However, the light emitter 26 is not limited to the above-described example, and various known light emitters, for example, a cold cathode tube, an EL (electroluminescent material) that emits light in a planar shape, or the like can also be used. FIG. 5 discloses cooling using a linear cold cathode tube as the light emitter 26. In the example shown in FIG. 5, the linear cold cathode tubes forming the light emitter 26 are arranged in a predetermined arrangement direction so as to be parallel to each other. The arrangement direction of the linear cold cathode tubes is parallel to the arrangement direction of the unit optical elements 60 of the protective film 50. According to this aspect, as already described in the above-described embodiment, the in-plane variation in luminance caused by the arrangement of the cold cathode tubes 26 is alleviated by the unit optical element 60, and an image of the cold cathode tube 26 ( Light image) can be made difficult to see.

  Further, in the above-described embodiment, the protective film 50 constituting the polarizing plate 40 includes a main part 59a made of a resin material, a light diffusion layer 51a made of a diffusion component 59b dispersed in the main part 59a, and a diffusion component 59b. And a resin layer 51b made of only a resin material. In other words, the diffusing component 59 b was dispersed only in a part of the protective film 50. However, for example, as shown in FIGS. 6 and 7, the diffusing component 59 b may be dispersed throughout the protective film 50. In such an example, the protective film 50 is composed only of a light diffusion layer 51a having a main part 59a made of a resin material and a diffusion component 59b dispersed in the main part 59a. The optical element 60 is configured as a part of the light diffusion layer 51a. In this case, the degree of the light diffusion function of the protective film 50 can be further freely adjusted.

  Furthermore, in embodiment mentioned above, although the cross-sectional shape in the main cut surface of the unit optical element 60 of the protective film 50 showed the example which consists of a triangle shape, it is not restricted to this, The unit optical element 60 of the protective film 50 The cross-sectional shape at the main cutting plane can be designed in various shapes. For example, the top of the triangular shape that forms the cross-sectional shape of the unit optical element 60 on the main cut surface of the protective film 50 may be chamfered. In addition, as shown by a two-dot chain line in FIG. 3, the two sides extending from the triangular main body 55 described above are deformed on the main cut surface of the protective film so as to be curved outwardly. Also good.

  Furthermore, as shown in FIG. 6, the unit optical element 60 may have a curved outer contour on the main cut surface of the protective film 50. That is, the light incident surface of the unit optical element 60 may be configured as a curved surface. As an example of a specific shape, the unit optical element 60 has a shape corresponding to a part of an ellipse (a semi-ellipse as an example) or a part of a circle (a semi-circle as an example) on the main cut surface of the protective film 50. You may do it. Furthermore, as shown in FIG. 7, the unit optical element 60 may have a shape obtained by removing the above-described triangular top portion of the main cutting surface on the main cutting surface of the protective film 50. As an example of a specific shape, the unit optical element 60 may have an isosceles trapezoidal shape as shown in FIG. 7 on the main cut surface of the protective film 50, or alternatively, the isosceles trapezoidal shape. You may make it have the shape formed by changing an upper base into a curve.

  The protective film 50 shown in FIGS. 6 and 7 can be manufactured using the manufacturing apparatus (extrusion apparatus) 80 already described with reference to FIG. At this time, a molding roll 84 in which grooves having a shape corresponding to the cross-sectional shape of the unit optical element 60 to be manufactured is formed on the molding surface 84a is used. Further, the film material 90 extruded from the extruder 82 becomes a single-layer extrusion material composed of only the layers that form the light diffusion layer 51a.

  Furthermore, in the above-described embodiment, an example in which the unit optical elements 60 are one-dimensionally arranged on the main body portion 55, that is, an example in which the linear unit optical elements 60 are arranged in parallel on the main body portion 55. However, the present invention is not limited to this. The unit optical elements 60 may be two-dimensionally arranged on the main body 55 so as to constitute a so-called fly-eye lens (or microlens). In this example, the unit optical elements 60 may be arranged in a regular arrangement on the main body portion 55 or may be arranged in an irregular arrangement. When the point-shaped unit optical elements 60 are two-dimensionally arranged in a regular arrangement on the main body 55, the first arrangement direction of the unit optical elements 60 is the first arrangement direction d1 of the light emitters 26. (See FIG. 1), and the second arrangement direction of the unit optical elements 60 may be parallel to the second arrangement direction d2 of the light emitters 26 (see FIG. 1). Further, the shape of the point-shaped unit optical element 60 constituting the fly-eye lens (or microlens) includes a part of a sphere (for example, a hemisphere), a part of a spheroid (for example, a half-spheroid), a cone, Examples include a pyramid such as a polygonal pyramid such as a quadrangular pyramid, a frustum such as a truncated cone and a polygonal frustum such as a quadrangular pyramid, and the like.

  Furthermore, although the protective film 60 showed the example which has both a light-diffusion function and a condensing function in embodiment mentioned above, it is not restricted to this. For example, if the light from the light emitter 26 is sufficiently scattered, it is not necessary to provide the light diffusion function to the protective film 60. That is, it is not necessary to disperse the diffusing component 59b in the protective film 50. Similarly, if the light from the light emitter 26 is sufficiently condensed, it is not necessary to provide the protective film 60 with a condensing function. That is, it is not necessary to provide the unit optical element 60 on the protective film 50.

  Furthermore, the light diffusion function of the protective film 50 in the above-described embodiment may be an isotropic light diffusion function or an anisotropic light diffusion function. As an example, as shown in FIG. 8, the anisotropic light diffusing function is provided in the protective film by disposing the diffusing component 59b having the longitudinal direction ld in the protective film 50 so as to have an orientation in a predetermined direction od. 50. Here, the longitudinal direction of the diffusion component 59b can be specified as the direction in which the target diffusion component 59b has the longest length. Further, “the diffusion component 59b having the longitudinal direction ld has an orientation in the predetermined direction od” means that the angle formed by the longitudinal direction ld of each diffusion component 59b with respect to the predetermined direction od is 0 ° or more and 45 This means that the diffusion component 59b is arranged with directional regularity with reference to the predetermined direction od.

  The protective film 50 shown in FIG. 8 can be manufactured by the above-described extrusion process using a diffusion component 59b having a longitudinal direction as a raw material together with a resin material that forms the main portion 59a. When the diffusion component 59b having the longitudinal direction passes through the die 82a of the extruder 82 together with the resin material, the diffusing component 59b is directed so that the longitudinal direction ld is along the extrusion direction (machine direction) under high pressure. Thereby, the diffusion component 59b in the extruded material is dispersed in the protective film 50 so as to have an orientation in a specific direction od. In this case, the orientation direction of the diffusion component 59b is parallel to the longitudinal direction of the linear unit optical elements 60 arranged in parallel.

  As the shape of the diffusing component 59b having the longitudinal direction ld, various shapes such as a plate shape, a granular shape (rice granular shape), a needle shape, a scale shape, and a fine plate shape can be adopted as an example. As a specific example, the average aspect ratio (the average value of the ratio of the length of the diffusion component 59b along the longitudinal direction ld to the length of the diffusion component 59b along the direction orthogonal to the longitudinal direction ld) is And bubbles having an average particle diameter of 1.5 to 50 μm and an average particle diameter of the diffusion component 59b (particle diameter calculated by the volume equivalent method, ie, arithmetic average of volume equivalent diameter, the same shall apply hereinafter) The diffusion component 59b having the longitudinal direction ld can be used. Moreover, the diffusion component 59b which consists of heat resistant organic fibers, such as the diffusion component 59b which consists of organic fibers, for example, an aramid fiber, a wholly aromatic polyester fiber, a polyimide fiber, can also be used. Moreover, the diffusion component 59b which consists of fibrous fillers, such as glass fiber, a silica fiber, an alumina fiber, a zirconia fiber, can also be used for the diffusion component 59b which consists of inorganic fibers, for example. Furthermore, a diffusion component 59b made of a thin plate filler (mica) can also be used. Furthermore, a diffusing component 59b made of an amorphous filler, for example, a diffusing component 59b made of an inorganic white pigment such as silica, calcium carbonate, magnesium hydroxide, clay, talc, or titanium dioxide can be used.

  The diffusion component 59b having the longitudinal direction ld exhibits a stronger light diffusion function in a direction perpendicular to the longitudinal direction than in a direction parallel to the longitudinal direction. Therefore, in the embodiment shown in FIG. 8 in which the diffusing component 59b having the longitudinal direction ld is oriented in a direction parallel to the longitudinal direction of the unit optical element 60, light diffusion caused by the light diffusing layer 51a of the protective film 50 is performed. The function is exerted more strongly in the direction parallel to the arrangement direction of the unit optical elements 60 than in the direction parallel to the longitudinal direction of the unit optical elements 60. That is, in the aspect shown in FIG. 8, the direction in which the light collecting function of the protective film 50 is mainly exhibited matches the direction in which the light diffusion function is mainly exhibited. For this reason, it is possible to selectively smooth the angular distribution of the luminance within the plane mainly exerting the light collecting action from the unit optical element 60. As a result, since it is not necessary to diffuse the light incident on the protective film 50 more than necessary, the light can be effectively used.

  In particular, as shown in FIG. 5, when the light source 25 is formed by arranging linear cold cathode tubes 26 in parallel, the light emitter 26 is only diffused along the arrangement direction of the cold cathode tubes 26. Since the unevenness of brightness due to the arrangement of the above can be eliminated, the protective film 50 shown in FIG. 8 can be preferably used.

  Furthermore, in embodiment mentioned above, although the protective film 50 showed the example joined to the polarizer 41 by water sticking, it is not restricted to this. For example, as shown in FIG. 9, an adhesive layer 49 containing an adhesive 49 a and a diffusion component 49 b dispersed in the adhesive 49 a is arranged between the protective film 50 and the polarizer 41. It may be. According to the embodiment shown in FIG. 9, the degree of the light diffusing function by the adhesive layer 49 can be appropriately adjusted independently of the presence or absence of the light diffusing function in the protective film 50 or the degree of the light diffusing function of the protective film 50. it can. Thereby, the degree of the light diffusion function that the lower polarizing plate 40 can exhibit can be designed more freely. In addition, what was illustrated as the diffusion component 59b which can be contained in the protective film 50 can be used similarly for the diffusion component 49b contained in the contact bonding layer 49. FIG. Further, the degree of the light diffusing function by the adhesive layer 49 can be appropriately adjusted by the same method as the degree of the light diffusing function in the protective film 50.

  Furthermore, the light diffusing function of the adhesive layer 49 may be isotropic or anisotropic. When the adhesive layer 49 has an anisotropic light diffusing function, the direction in which the light diffusing function is strongly exerted by the adhesive layer 49 is the arrangement direction of the unit optical elements 60 (as in the embodiment shown in FIG. It may be parallel to the direction in which the light condensing function is exerted strongly, or may be parallel to the longitudinal direction of the unit optical element 60 (the direction in which the light condensing function is not exerted strongly).

  Furthermore, in the above-described embodiment, the example in which the lower polarizing plate 40 includes the polarizer 41 and the protective film 50 bonded to the polarizer 41 from the light incident side is shown. A protective film made of a TAC film, for example, may also be provided on the light output side of the child 41. In addition, a phase difference plate for compensating for the phase difference of light may be provided between the lower polarizing plate 40 and the liquid crystal cell 11, but in this case, the protective film on the light output side of the lower polarizing plate 40, You may make it also serve as the protective film of the light-incidence side of a phase difference plate. Further, as shown in FIG. 10, the lower polarizing plate 40 may further include another member positioned on the incident side with respect to the polarizer 41. As another member located on the incident side with respect to the polarizer 41, for example, a TAC film can be provided.

  In the example shown in FIG. 10, the intermediate film 48 between the protective film 50 and the polarizer 41 has a function of transmitting a specific polarization component and reflecting other polarization components to return to the light source side again. A polarization separation film 48 is provided. That is, by providing the polarization separation film 48, light of a polarization component that can be transmitted through the polarizer 41 can be selectively incident on the polarizer 41, and other light can be returned to the light source side. The light returned to the light source side can be incident again on the polarization separation film 48 with its polarization state changed by subsequent reflection or the like. “DBEF” (registered trademark) available from 3M USA can be used as the polarization separation film 48 that can be useful for improving luminance. In addition to “DBEF”, a high-intensity polarizing sheet “WRPS” available from Shinwha Intertek, Korea, a wire grid polarizer, or the like can be used as the polarizing separation film 48.

  Furthermore, a light diffusion sheet having a light diffusion function may be provided as an intermediate film 48 between the polarizer 41 of the lower polarizing plate 40 and the protective film 50. At this time, the light diffusion sheet may have an isotropic light diffusion function or an anisotropic light diffusion function. When the light diffusing sheet has an anisotropic light diffusing function, the direction in which the light diffusing function is strongly exerted by the light diffusing sheet is the arrangement direction of the unit optical elements 60 (as in the embodiment shown in FIG. It may be parallel to the direction in which the light condensing function is exerted strongly, or may be parallel to the longitudinal direction of the unit optical element 60 (the direction in which the light condensing function is not exerted strongly).

  Furthermore, in the above-described embodiment, an example in which the light emitter 26 forming the light source 25 is disposed immediately below the polarizing plate 40 including the protective film 50 having a light control function, that is, a protective film having a light control function. Although the example in which the polarizing plate 40 including 50 is applied to the direct-type liquid crystal display device 10 is shown, it is not limited thereto. As shown in FIG. 11, the polarizing plate 40 including the protective film 50 having a light control function may be disposed at a position facing the light guide plate 23 that receives light from the light emitter 26.

  In the example shown in FIG. 11, the polarizing plate 40 is used together with a surface light source device 22 having a light emitter 26 and a light guide plate 23 that receives light from the light emitter 26, and is used as the light guide plate 23 of the surface light source device 22. Arranged to face. In this example, the optical module 20 includes a polarizing plate 40 and a light guide plate 23 disposed at a position facing the protective film 50 of the polarizing plate 40. In the example shown in FIG. 11, the liquid crystal display panel 15 including the polarizing plate 40 can be configured similarly to the above-described embodiment.

  In the example shown in FIG. 11, the surface light source device 22 includes a light guide plate 23, a light emitter 26 disposed on the side of the light guide plate 23, and a reflection sheet 21 a disposed on the back surface of the light guide plate 23. It has a so-called edge light type (side light type) backlight. Light from the light emitter 26 of the light source 25 enters the light guide plate 23 from the side surface (incident surface) of the light guide plate 23, and is guided through the light guide plate 23 while being repeatedly reflected between the pair of main surfaces of the light guide plate 23. Proceed along the direction. The light guide plate 23 is provided with light extraction elements (not shown), for example, white dots provided on the back surface of the light guide plate 23 facing the reflection sheet 21a, diffusion components dispersed in the light guide plate 23, and the like. Light traveling in the light guide plate 23 is emitted from the light guide plate 23 toward the observer so that the amount of emitted light is substantially uniform along the light guide direction. At this time, as shown in FIG. 11, a lot of light L111 emitted from the light guide plate 23 is emitted in a direction greatly inclined from the front direction nd.

  With respect to such a light guide plate 23, the unit optical elements 60 of the protective film 50 are arranged such that the arrangement direction thereof is parallel to the light guide direction of the light guide plate 23. The unit optical element 60 protrudes from the protective film 50 toward the light guide plate 23 side. And the light L111 which goes to the liquid crystal display panel along the direction largely inclined from the front direction nd enters the protective film 50 through one surface 60b1 of the unit optical element 60, and then the other of the unit optical elements 60 The traveling direction is deflected toward the front direction nd side by reflecting (particularly total reflection) on the surface 60b2. In this way, the protective film 50 can exhibit a light collecting function.

  On the other hand, as shown in FIG. 13, a conventional edge light type surface light source device used in combination with a liquid crystal display panel including a conventional lower polarizing plate 13 often has a light output from a light guide plate 23. A condensing sheet (prism sheet, reflection type prism sheet, reverse prism sheet) C was provided on the side. Therefore, the condensing function of the protective film 50 is the same as the condensing function of the condensing sheet (prism sheet, reflective prism sheet, reverse prism sheet) C included in the conventional surface light source device shown in FIG. By carrying out similarly, it becomes possible to omit this condensing sheet C from a surface light source device, maintaining the optical characteristic as the whole display apparatus 1. FIG. Similarly, in the conventional surface light source device shown in FIG. 13, the light diffusion sheet D is provided on the light output side of the light collecting sheet C, but the protective film 50 contains the diffusion component 59b. Therefore, the light diffusion sheet D can be omitted by appropriately adjusting the degree of the light diffusion function caused by the diffusion component 59b. Thereby, also according to the aspect shown in FIG. 11, it is possible to obtain the same function and effect as the above-described embodiment.

  In the conventional display device 1 shown in FIG. 13, the same reference numerals as those used for the already described configuration are used for portions that can be configured the same as the already described configuration. Therefore, duplicate explanation is omitted.

  Although several modifications to the above-described embodiment have been described above, a plurality of modifications can be applied in appropriate combination.

  In addition, in comparison with the conventional display device 1 in which a large number of optical sheets are included between the light emitting body 26 or the light guide plate 23 forming the light source 25 and the liquid crystal display panel, the advantages of the embodiment of the present invention are described. However, this description excludes the use of the display device 10, the polarizing plate 40, and the protective film 50 according to an embodiment of the present invention in combination with an optical sheet disposed on the light incident side thereof. Not what you want. That is, the present invention includes an embodiment in which one or more optical sheets are disposed between the display device 10, the polarizing plate 40, the protective film 50, and the light emitter 26 or the light guide plate 23. In this case, the excellent effects resulting from the protective film 50 can be enjoyed.

  Moreover, although embodiment mentioned above demonstrated the example which manufactures the protective film for polarizing plates as an example of an optical film, it is not restricted to this, The optical film used for various uses can be manufactured.

DESCRIPTION OF SYMBOLS 10 Display apparatus 11 Liquid crystal cell 15 Liquid crystal display panel 20 Optical module 25 Light source 26 Light emitter 40 Polarizing plate, lower polarizing plate 41 Polarizer 48 Intermediate film 49 Adhesive layer 49a Adhesive 49b Diffusion component 50 Protective film, optical sheet 50a Light emission side surface 50b Light incident side surface 51a Light diffusion layer 51b Resin layer 52 Land portion 54 Matte layer 55 Main body portion 55b Light incident side surface 59a Main portion 59b Diffusing component 60 Unit optical element 80 Manufacturing device, extrusion device 82 Extruder 83 Heating means 83a Heater 84 Molding roll 84a Molding surface 85a Center part 85b Heat insulation part, heat insulation layer 85c Surface layer part 86 Backup means 86a Support roll 86b Belt member 87 Cooling means 87a Cooling roll 90 Film material

Claims (7)

An extrusion process of heating and extruding the thermoplastic resin to produce a film material;
A center part, a surface layer part forming a molding surface, and a heat insulating property higher than any of the center part and the surface layer part, and provided between the center part and the surface layer part, the surface layer part from the center part A molding step of pressurizing the film material between the molding surface of the molding roll having a heat insulating portion to be spaced apart and backup means;
A step that is performed after the molding step and before the film material is released from the molding roll, and is provided separately from the backup means and is formed of the thermoplastic resin that forms the film material. Cooling the film material with the cooling roll while pressurizing the film material between the cooling roll maintained at a temperature lower than the glass transition temperature and the molding surface of the molding roll. ,
The molding surface is such that the molding surface of the molding roll has a temperature equal to or higher than the glass transition temperature of the thermoplastic resin forming the film material at least when it starts contact with the film material in the molding step. The surface of the roll is heated before initiating contact with the film material,
The backup means has two or more support rolls, and a belt member spanned between the two or more support rolls,
In the molding step, the film material is pressed by the belt member of the molding roll and the backup means over a section of a certain length along the movement path .   The manufacturing method of the optical film of Claim 1 with which the protective film for polarizing plates is manufactured. The method for producing an optical film according to claim 1 or 2 , wherein in the extrusion step, a diffusion component is also extruded together with the thermoplastic resin, and a film material in which the diffusion component is dispersed is produced. In the extruding step, the second thermoplastic resin is also heated and extruded, and the light diffusion layer having the thermoplastic resin and the diffusion component dispersed in the thermoplastic resin is laminated on the light diffusion layer. The manufacturing method of the optical film of Claim 3 with which the film material containing the resin layer which consists of said 2nd thermoplastic resin is produced. The process which adhere | attaches the optical film manufactured by the manufacturing method as described in any one of Claims 1-4 , and a polarizer,
The manufacturing method of a polarizing plate by which the said polarizer is adhere | attached on the said film material from the side which was contacting the said backup means of the said optical film. The polarizing plate according to claim 5 , further comprising a step of cutting or punching the web-shaped material having the optical film and the polarizer adhered to each other to sequentially obtain a polarizing plate from the web-shaped material. Manufacturing method. A manufacturing apparatus for manufacturing an optical film,
An extruder for heating and extruding a thermoplastic resin to produce a film material;
A molding roll having a molding surface on which a concavo-convex shape to be transferred to the film material is formed;
A backup means that is disposed opposite to the molding roll and that pressurizes the film material between the molding surface of the molding roll;
Heating means disposed at a position facing the molding surface of the molding roll;
The film material is disposed on the downstream side of the backup means along the movement path of the film material so as to face the molding roll, and pressurizes the film material with the molding surface of the molding roll. Cooling means for cooling ,
The backup means has two or more support rolls, and a belt member spanned between the two or more support rolls,
The molding roll has a center part, a surface layer part forming the molding surface, a heat insulating property higher than any of the center part and the surface layer part, and is provided between the center part and the surface layer part. A heat insulating part that separates the part from the central part,
The heating means is configured so that the molding surface of the molding roll is at a temperature equal to or higher than a glass transition temperature of the thermoplastic resin forming the film material when starting contact with at least the film material. The manufacturing apparatus which heats the said surface layer part of a forming roll, before starting contact with the said film material.

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