JP2012037881A - Protective film, lower polarizing plate, liquid crystal display panel and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective film which can change a traveling direction of light incident to a liquid crystal display panel and which can be inexpensively produced.SOLUTION: The protective film 55 is to be bonded to a polarizer 51 to function as a lower polarizing plate 50 for a liquid crystal display panel. The protective film 55 for a lower polarizing plate comprises a main part 56 of a resin material and a diffusion component 57 dispersed in the main part. At least one surface 55a, which is to face the polarizer 51, of the protective film 55 is flat.

Description

  The present invention relates to a protective film for a lower polarizing plate that is bonded to a polarizer to form a lower polarizing plate for a liquid crystal display panel, and in particular, a protection that can change the traveling direction of light incident on the liquid crystal display panel. Related to film. The present invention also relates to a lower polarizing plate including such a protective film, and a liquid crystal display panel and a display device including the lower polarizing plate.

  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.

  The surface light source device includes a light source and a large number of optical sheets for changing the traveling direction of light from the light source. As in the example of the surface light source device 120 shown in FIG. 14, in many cases, a light diffusion sheet that diffuses light from the light source to hide the image of the light source (make it inconspicuous) in many optical sheets. 29, a diffusion plate 28, and light collecting sheets 30 and 35 having a function (light condensing function) for narrowing the traveling direction of light in the front direction and improving the luminance in the front direction.

  On the other hand, the liquid crystal display panel includes a liquid crystal cell capable of controlling the orientation of the liquid crystal for each pixel, a lower polarizing plate disposed on the light incident side of the liquid crystal cell, an upper polarizing plate disposed on the light output side of the liquid crystal cell, have. The pair of polarizing plates includes a polarizer that transmits light of a specific polarization component and absorbs light of components other than the specific polarization component, and a protective film that is bonded to the polarizer and protects the polarizer. ing.

  Of these, the protective film is usually composed of a simple translucent film due to cost constraints, and does not positively exert an optical effect on 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. Further, there is a possibility that the number of optical sheets incorporated in the surface light source device can be reduced. In this case, the manufacturing cost of the surface light source device and the display device can be directly reduced, and the surface light source device and the display device can be reduced. Can also be made thinner.

  The present invention has been made in consideration of such points, and an object thereof is to provide a protective film that can change the traveling direction of light incident on a liquid crystal display panel.

The first protective film according to the present invention is:
A protective film for a lower polarizing plate that is bonded to a polarizer to form a lower polarizing plate for a liquid crystal display panel,
A main part made of a resin material, and a diffusion component dispersed in the main part,
At least one side surface that faces the polarizer is flat.

  In the first protective film according to the present invention, the other side surface facing the one side surface may be a prism surface formed by unit prisms arranged side by side.

The second protective film according to the present invention is:
A protective film for a lower polarizing plate that is bonded to a polarizer to form a lower polarizing plate for a liquid crystal display panel,
A main part made of a resin material, and a diffusion component dispersed in the main part,
The other side opposite to the one side that faces the polarizer is a prism surface formed by unit prisms arranged side by side.

  The first or second protective film according to the present invention is a main part made of a resin material, a light diffusion part having the diffusion component dispersed in the main part, a resin part in which the diffusion component is not dispersed, May be included.

  The 1st or 2nd protective film by this invention WHEREIN: The said light-diffusion part may be arrange | positioned at the said polarizer side rather than the said resin part.

  In the first or second protective film according to the present invention, a plurality of unit prisms are arranged along an arrangement direction parallel to the film surface of the protective film, each unit prism being parallel to the film surface and the arrangement. It may extend in a direction that intersects the direction.

The first or second protective film according to the present invention is a main part made of a resin material, a light diffusion part having the diffusion component dispersed in the main part, a resin part in which the diffusion component is not dispersed, Including
The unit prism is included in the resin portion,
The light diffusion part may be arranged closer to the polarizer than the resin part.

The first or second protective film according to the present invention further comprises a second resin part in which the diffusion component is not dispersed,
The second resin portion may be disposed closer to the polarizer than the light diffusion portion.

  In the first or second protective film according to the present invention, unevenness formed due to the presence of the diffusion component may be provided on the other side surface facing the one side surface.

  The 1st or 2nd protective film by this invention WHEREIN: The unevenness | corrugation formed by shaping | molding may be provided in the other side facing the said one side.

  The 1st or 2nd protective film by this invention may be the extrusion material extruded by the extrusion process.

  In the first or second protective film according to the present invention, the resin material forming the main part may be a polycarbonate resin.

  In the first or second protective film according to the present invention, the haze value may be 60% or more and less than 100%.

In the first or second protective film according to the present invention, the moisture permeability at a temperature of 40 ° C., a humidity of 90% RH, and 24 hours may be 10 g / m ² · 24 hr or more.

Alternatively, when a sheet-like test sample having a thickness of 80 μm is produced using the same material as the first or second protective film according to the present invention, the temperature of the test sample is 40 ° C., the humidity is 90% RH, 24 The water vapor transmission rate over time may be 10 g / m ² · 24 hr or more.

The lower polarizing plate according to the present invention is
A lower polarizing plate incorporated in a liquid crystal display panel,
A polarizer,
It is either the 1st and 2nd protective film by this invention mentioned above, Comprising: The protective film adhere | attached on the said polarizer from the light-incidence side is provided.

  The lower polarizing plate according to the present invention may further include an adhesive layer that is provided adjacent to the polarizer and the protective film and adheres the polarizer and the protective film to each other.

In the lower polarizing plate according to the present invention, the layer temperature 40 ° C. for the protective film, the moisture permeability of a humidity 90% RH, 24 hours, at 10g / m ² · 24hr or more, the adhesive layer is made of water-based adhesive It may be.

Alternatively, in the lower polarizing plate according to the present invention, when a sheet-like test sample having a thickness of 80 μm is manufactured using the same material as the protective film, the temperature of the test sample is 40 ° C., the humidity is 90% RH, 24 The moisture permeability in time may be 10 g / m ² · 24 hr or more, and the adhesive layer may be a layer made of a water-based adhesive.

  The liquid crystal display panel according to the present invention includes any of the lower polarizing plates according to the present invention described above.

A display device according to the present invention comprises:
Any of the liquid crystal display panels according to the present invention described above;
A surface light source device that illuminates the liquid crystal display panel from the back side.

  According to the present invention, the traveling direction of light incident on the liquid crystal display panel can be changed by the protective film for the lower polarizing plate. For this reason, the freedom degree of design about the brightness | luminance characteristic and viewing angle characteristic of a display apparatus can be improved significantly.

FIG. 1 is a perspective view showing a schematic configuration of a display device for explaining an embodiment according to the present invention. 2 is a cross-sectional view showing a lower polarizing plate incorporated in the liquid crystal display panel of the display device of FIG. FIG. 3 is a partially enlarged view of FIG. 2 and is a view for explaining the operation of the protective film of the lower polarizing plate. FIG. 4 is a diagram for explaining an example of a protective film manufacturing method and a protective film manufacturing apparatus. FIG. 5 is a diagram corresponding to FIG. 3 and is a diagram for explaining a modification of the protective film and the lower polarizing plate. FIG. 6 is a perspective view for explaining another modified example of the protective film and the lower polarizing plate. FIG. 7 is a cross-sectional view showing a schematic configuration of a display device in which the lower polarizing plate of FIG. 6 is incorporated. FIG. 8 is a cross-sectional view showing a modification of the protective film shown in FIGS. 6 and 7. FIG. 9 is a cross-sectional view showing another modification of the protective film shown in FIGS. 6 and 7. FIG. 10 is a diagram for explaining a modification of the protective film manufacturing method and the protective film manufacturing apparatus. FIG. 11 is a graph showing the angular distribution of the luminance ratio with respect to the front direction measured for the display devices according to the example and the comparative example. FIG. 12 is a graph showing the angular distribution of the luminance ratio with respect to the front direction measured for the display devices according to samples A1 to A3. FIG. 13 is a graph showing the angular distribution of the luminance ratio with respect to the front direction measured for the display devices according to samples B1 to B3. FIG. 14 corresponds to FIG. 1 and is a perspective view showing a conventional display device. FIG. 15 is a cross-sectional view corresponding to FIG. 7 and showing a conventional display device.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 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. 1 is a perspective view showing a schematic configuration of the display device. 2 and 3 are cross-sectional views showing the lower polarizing plate in a cross section along the normal direction to the plate surface of the lower polarizing plate. FIG. 4 is a diagram for explaining an example of a method for producing a protective film for the lower polarizing plate.

  The display device 10 shown in FIG. 1 is a liquid crystal display device, and includes a liquid crystal display panel 40, a surface light source device 20 disposed on the back side of the liquid crystal display panel 40 (the side opposite to the observer side), have. The surface light source device 20 is a device that illuminates the liquid crystal display panel 40 in a planar shape from the back side. On the other hand, the liquid crystal display panel 40 functions as a shutter that controls transmission or blocking of light from the surface light source device 20 for each pixel and forms an image.

  As the surface light source device 20, a conventionally known direct type or edge light type backlight can be used. The surface light source device 20 shown in FIG. 1 is configured as a direct-type backlight, and includes a light source 25, a reflecting plate 22 that covers the light source 25 from the back side, and a sheet disposed on the observer side of the light source 25. Shaped optical members 28, 30, and 35. As an example, the light source 25 includes linear cold cathode tubes 25a arranged in parallel. As the sheet-like optical member, a diffusion plate 28, a first light collecting sheet 30, and a second light collecting sheet 35 are provided from the light source side toward the observer side. As will be described later, the surface light source device 20 can be variously modified. For example, the light emitting unit of the light source 25 may be configured by two-dimensionally arranged LEDs.

  The diffusing plate 28 is a member for diffusing the light from the light source 25 to make the uneven brightness uniform according to the configuration of the light source 25. The diffusion plate 28 forms a so-called backlight unit together with the light source 25 and the reflection plate 22.

  The two light collecting sheets 30 and 35 are members for adjusting luminance characteristics, and typically function to improve the luminance in the front direction. More specifically, the light collecting sheets 30 and 35 have an angle formed by the traveling direction of the transmitted light and the front direction nd from the light collecting sheets 30 and 35 more than before the light incident on the light collecting sheets 30 and 35. The traveling direction of the transmitted light is changed so as to tend to decrease after emission.

  As a specific configuration, the two light-collecting sheets 30 and 35 shown in the figure are respectively sheet-like main body portions 32 and 37 and a plurality of unit optical elements 33 and 38 arranged on the main body portions 32 and 37. ,have. The unit optical elements 33 and 38 are arranged side by side along the arrangement direction, and extend linearly in a direction intersecting (more specifically, orthogonal) with the arrangement direction. Each unit optical element 33, 38 has a triangular shape protruding to the light exit side in a cross section orthogonal to the longitudinal direction. In this example, the first light collecting sheet 30 is configured in the same manner as the second light collecting sheet 35.

  The condensing sheets 30 and 35 having such a configuration mainly exhibit a condensing function with respect to light of a component along a direction parallel to the arrangement direction of the unit optical elements 33 and 38. In the example shown in FIG. 1, the arrangement direction of the unit optical elements of the first light collecting sheet 30 located on the light incident side is the same as that of the second unit optical element of the light collecting sheet 30 located on the light exit side. It is orthogonal to the array direction. Thereby, the light which permeate | transmits the two condensing sheets 30 and 35 comes to be condensed from two different directions. In the illustrated example, the arrangement direction of the second unit optical elements of the condensing sheet 30 located on the light output side is parallel to the arrangement direction of the cold cathode tubes 25 a forming the light source 25.

  With the configuration of the sheet-like members 28, 30, and 35 as described above, the light emitted from the arc tube 25a of the light source 25 has a uniform in-plane brightness distribution and a luminance peak in the front direction. The direction of travel is deflected. Thereby, the surface light source device 20 emits light in a planar shape from the light emitting surface 20a, and illuminates the liquid crystal display panel 40 from the back side.

  In the present specification, the “light exit side” refers to the downstream side in the traveling direction of light from the light emitting unit 25a of the light source 25 to the viewer through the liquid crystal display panel 40 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 emitting portion 25 a of the light source 25 through the liquid crystal display panel 40 to the viewer 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. And in this Embodiment, the sheet surface of each condensing sheets 30 and 35, the panel surface of the liquid crystal display panel 40, the plate surface of the lower polarizing plate 50 mentioned later, the film surface of the protective film 55 mentioned later, the display apparatus 10 The display surface 10a and the light emitting surface 20a of the surface light source device are parallel to each other. In this specification, the “front direction” refers to a direction parallel to the normal direction nd to the display surface 10 a of the display device 10.

  Furthermore, terms used in the present specification for specifying shapes and geometric conditions, for example, terms such as “triangle”, “parallel”, “orthogonal”, “symmetric”, etc. are not bound to a strict meaning. Therefore, it should be interpreted including an error to the extent that a similar optical function can be expected.

  Furthermore, “unit optical element”, “unit shape element”, “unit prism”, and “unit lens” in this specification refer to the optical action such as refraction and reflection on the light, and change the traveling direction of the light. It refers to an element having a function to be changed, and is not distinguished from each other based only on a difference in designation. Similarly, “prism” and “lens” are not distinguished from each other based solely on the difference in designation.

  Next, the liquid crystal display panel 40 will be described. As described above, the liquid crystal display panel 40 includes the pair of polarizing plates 45 and 50 and the liquid crystal cell 41 disposed between the pair of deflecting plates 45 and 50. Among these, the polarizing plates 45 and 50 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 41 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. As an example, the polarization component in a specific direction (direction parallel to the transmission axis) transmitted through the lower polarizing plate 50 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 40. 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 50 further transmits through the upper polarizing plate 45 disposed on the light output side of the lower polarizing plate 50. Alternatively, it is possible to control whether the light is absorbed and blocked by the upper polarizing plate 45. In this specification, “upper” and “lower” in the “upper polarizing plate 45” and the “lower polarizing plate 50” refer to the light emitting side, that is, the image observer side with respect to the liquid crystal cell 41. The incident light side is called “below”.

  Here, the lower polarizing plate 50 will be described in more detail with reference to FIGS. The lower polarizing plate 50 includes a polarizer 51 that can exhibit an absorption polarization separation function, and a protective film 55 bonded to the polarizer 51. As shown in FIG. 3, the protective film 55 is laminated on the polarizer 51 from the side that does not face the liquid crystal cell 41, in other words, from the light incident side, and protects the polarizer 51 from the outside.

  Further, an adhesive layer (not shown) is provided between the polarizer 51 and the protective film 55 so as to be adjacent to the polarizer 51 and the protective film 55 and adheres the polarizer 51 and the protective film 55 to each other. It may be. The adhesive layer for improving the adhesion between the polarizer 51 and the protective film 55 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 51. As a specific example, a polarizer 51 based on a polyvinyl alcohol film can be used. A polarizer 51 based on a polyvinyl alcohol-based film absorbs or dyes a dichroic dye such as iodine or a dye on a polyvinyl alcohol-based film, and then uniaxially stretches and aligns to absorb light. Sex can be imparted.

  Next, the protective film 55 will be described. As well shown in FIG. 3, the protective film 55 has a main portion 56 made of a resin material and a diffusion component 57 dispersed in the main portion 56. As the resin material forming the main portion 56, various resin materials having excellent optical characteristics, for example, polycarbonate resins can be used.

  On the other hand, the diffusing component 57 can be composed of a granular material having a refractive index different from that of the main portion 56, or a granular material that itself has reflectivity. The granular material forming the diffusion component 57 may be a metal compound, a porous material containing a gas, or may be a simple bubble. Further, the shape of the diffusion component 57 made of a granular material is not particularly limited. Therefore, the diffusion component 57 does not need to be spherical (particulate) as in the illustrated example, and can have various shapes such as a spheroid shape and a linear shape.

  Thus, due to the diffusion component 57 dispersed in the main portion 56, the protective film 55 can exhibit a diffusion function of diffusing light. The degree of the diffusion function of the protective film 55 due to the internally added diffusion component 57 is determined by the resin material forming the main portion 56, the thickness of the main portion 56, the configuration of the diffusion component 57, the concentration of the diffusion component 57, and the like. By setting appropriately, it can be adjusted within a very wide range. Specifically, it is possible to set the haze value of the protective film 55 within a range that is not normally reached by simply matting the surface layer portion, for example, within a range of 60% or more and less than 100%. is there.

  Further, as shown in FIGS. 2 and 3, the light exit side surface 55a that faces the polarizer 51 of the protective film 55 is formed as a flat surface. Thereby, it becomes possible to laminate | stack and adhere | attach the protective film 55 and the polarizer 51 stably, preventing mixing of air etc. On the other hand, in the present embodiment, the light incident side surface 55b opposite to the side facing the polarizer 51 of the protective film 55 is formed as an uneven surface. The unevenness provided on the light incident side surface 55b is caused by the diffusion component 57 dispersed in the main portion 56. More specifically, the diffusion component 57 is exposed or the outline of the diffusion component 57 is raised. Is formed.

  The light incident side surface 55 b of the protective film 55 forms not only the light incident side surface of the lower polarizing plate 50 but also the light incident side surface 40 b of the liquid crystal display panel 40. For this reason, the protective film 55 according to the present embodiment also exhibits a diffusion function due to not only the diffusion component 57 dispersed in the main portion 56 but also the unevenness of the light incident side surface 55b. .

  In the present specification, the term “flat” used for the surface 55a of the protective film 55 facing the polarizer 51 is a level that can ensure stable lamination and adhesion between the protective film 55 and the polarizer 51. Refers to the flatness. For example, when the surface roughness of the surface 55a facing the polarizer 51 of the protective film 55 is measured as a ten-point average roughness Rz in accordance with JISB0601 (1982), it may be 1.0 μm or less. It can be said that it is flat.

  Even though the protective film 55 is internally added with the diffusing component 57, the light exit side surface 50a of the protective film 55 is flat, so that the protective film 55 and the polarizer 51 are attached by so-called “water sticking”. Can be laminated and glued. Specifically, the protective film 55 and the polarizer 51 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 55 and the polarizer 51 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 55 and the polarizer 51, You may make it adhere | attach the protective film 55 and the polarizer 51 positively.

In addition, in order to promote the removal of moisture from the protective film 55 and the polarizer 51 after “water sticking”, the moisture permeability of the protective film 55 is 10 g / m under the condition of a temperature of 40 ° C. and a humidity of 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.

  Here, with reference mainly to FIG. 4, an example of the manufacturing method of the protective film 55 which consists of the above structures is demonstrated. In the following description, the protective film 55 is formed as an extruded material extruded by an extrusion process.

  First, the extrusion apparatus 80 used for manufacture of the protective film 55 is demonstrated. As shown in FIG. 4, the extruding device 80 includes an extruding machine 82 including a die 82 a, a forming roll 84, a backup unit 86 disposed so as to face the forming roll 84, and downstream of the forming roll 84 and the backup unit 86. Guiding means 88 arranged on the side. The guiding means 88 is configured as a pair of guide rolls 88a.

  The molding roll 84 has a cylindrical outer shape, and in this example, the cylindrical outer peripheral surface of the molding roll 84 is a smooth surface. However, when it is desired to positively mold the surface of the extruded material 90, a groove corresponding to the shape to be molded may be formed on the cylindrical outer peripheral surface of the molding roll 84.

  The backup means 86 has a pair of support rolls 86a and an edgeless belt 86b spanned between the pair of support rolls 86a. The extruded material 90 extruded from the extruder 82 can be pressed between the edgeless belt 86 b and the molding roll 84.

  Next, a method for manufacturing the above-described protective film 55 using such an extrusion device 80 will be described. First, the resin material that forms the main portion 56 is put into the extruder 82 together with the granular material that forms the diffusion component 57. The resin material that forms the main portion 56 is heated to a temperature equal to or higher than the glass transition temperature in the extruder 82, and the heated and softened resin material is extruded by the extruder 82. At this time, in the die 82a of the extruder 82, the thickness of the extruded material 90 is controlled to a desired thickness.

  The extruded material 90 extruded from the extruder 82 advances between the molding roll 84 and the backup means 86. Here, the extruded material 90 is pressed by the molding roll 84 while being supported by the edgeless belt 86b of the backup means 86, and the thickness is adjusted. The extruded material 90 is pressed between the edgeless belt 86b of the backup unit 86 and the molding roll 84 while traveling along a path having a predetermined length. During this time, the beltless belt 86 b and the molding roll 84 of the backup means 86 take heat from the extruded material 90.

  Among these, the edgeless belt 86b has a 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 extruded material 90, it performs sufficient heat dissipation while not in contact with the extruded material 90. For this reason, when the edgeless belt 86 b comes into contact with the extruded material 90 again, the temperature of the edgeless belt 86 b is sufficiently lowered, and the edgeless belt 86 b promotes cooling of the extruded material 90. As a result, when the extruded material 90 is separated from the edgeless belt 86b of the backup means 86, the resin that forms the main portion 56 not only in the surface layer portion of the extruded material 90 on the edgeless belt 86b side but also inside the extruded material 90. The extruded material 90 can be sufficiently cooled by the edgeless belt 86b so as to reach a temperature below the glass transition temperature of the material.

  As a result, on the side of the surface 90a that has been in contact with the edgeless belt 86b of the extruded material 90, no significant temperature drop occurs thereafter. Further, when the temperature of the resin material is lowered to the glass transition temperature or lower for the resin material that forms the main portion 56, the resin material has a certain degree of deformation resistance. For this reason, thermal deformation due to the difference between the thermal expansion coefficient of the resin material that forms the main portion 56 and the thermal expansion coefficient of the granular material that forms the diffusion component 57 is less likely to occur. That is, the portion of the resin material that forms the main portion 56 recedes and the contour of the granular material that forms the diffusion component 57 is suppressed from rising, and is in contact with the edgeless belt 86b of the extruded member 90. The flat surface 90a can be maintained as a flat surface.

  On the other hand, the molding roll 84 has a remarkably large heat capacity compared to the edgeless belt 86b, and is normally heated. That is, the cooling effect that the extruded material 90 receives from the molding roll 84 is smaller than the cooling effect that the extruded material 90 receives from the edgeless roll 86 b of the backup means 86. As a result, when the extruded material 90 is separated from the molding roll 84, the extruded material 90 is reduced only to the surface layer portion on the molding roll 84 side to a temperature equal to or lower than the glass transition temperature of the resin material that forms the main portion 56. And the internal temperature of the extrusion material 90 is maintained more than the said glass transition temperature.

  As a result, on the side of the surface 90b of the extruded material 90 that has been in contact with the molding roll 84, a large temperature drop occurs across the glass transition temperature of the resin material that will form the main portion 56 thereafter. Along with this, thermal deformation caused by the difference between the thermal expansion coefficient of the resin material that forms the main portion 56 and the thermal expansion coefficient of the granular material that forms the diffusion component 57 occurs. As a result, on the surface 90b of the extruded material 90 that has been in contact with the molding roll 84, the portion of the resin material that forms the main portion 56 moves backward, and the granular material that forms the diffusing component 57 rises. . That is, unevenness due to the diffusion component 57 is formed on the surface 90 b of the extrusion material 90 that has been in contact with the molding roll 84.

  The extruded material 90 separated 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 55 made of the extruded material 90 formed by extruding the thermoplastic resin material together with the particulates is produced. The flat light exit side surface 55 a of the protective film 55 is formed by the surface 90 a that is in contact with the backup roll 86 of the extrusion material 90, and the light incident side surface 55 b provided with the unevenness of the protection film 55 is the surface of the extrusion material 90. It is formed by the surface 90 b that has been in contact with the molding roll 84.

  Next, the operation of the display device 10 caused by the protective film 55 will be described with reference mainly to FIG.

  In FIG. 1, the light emitted from the light source 25 travels to the viewer side directly or after being reflected by the reflection plate 22, enters the diffusion plate 28, and isotropically diffuses. The in-plane distribution of brightness is made uniform by isotropic diffusion in the diffusion plate 28. The light diffused by the diffusion plate 28 then enters the first light collecting sheet 30.

  The light incident on the first light collecting sheet 30 is refracted on the light output side surface (prism surface) of the unit optical element 33 when exiting from the light collecting sheet 30. Due to this refraction, the traveling direction (outgoing direction) of the light traveling in the direction inclined with respect to the front direction nd is mainly the front direction compared with the traveling direction of the light just before entering the first light collecting sheet 30. It is bent so that the angle with respect to nd is small. Thus, the 1st condensing sheet 30 exhibits the condensing function with respect to the light from the light source 25. FIG. The light condensed by the first light collecting sheet 30 is a component mainly along the arrangement direction of the unit optical elements 33 of the first light collecting sheet 30.

  The light emitted from the first light collecting sheet 30 then enters the second light collecting sheet 35. Similar to the first light collecting sheet 30, the second light collecting sheet 35 exhibits a light collecting function with respect to light transmitted through the second light collecting sheet 35. However, the light condensed by the second light collecting sheet 35 is a component mainly along the arrangement direction of the unit optical elements 38 of the second light collecting sheet 35, and the component condensed by the first light collecting sheet 30. Is an orthogonal component. Therefore, the angle distribution of the luminance in the plane along two different directions can be adjusted by transmitting the two light collecting sheets 30 and 35.

  As described above, the light from the light source 25 is emitted from the light emitting surface 20 a of the surface light source device 20 formed by the light emitting side surface of the second light collecting sheet 35. As a result, the surface light source device 20 illuminates the liquid crystal display panel 40 in a planar shape. The liquid crystal display panel 40 selectively transmits light from the surface light source device 20 for each pixel. Thereby, the observer of the transmissive display apparatus 10 can observe an image.

  By the way, in the present embodiment, the protective film 55 of the lower polarizing plate 50 of the liquid crystal display panel 40 exhibits a diffusing function. In particular, the protective film 55 includes a main portion 56 and a diffusion component 57 dispersed in the main portion 56. Diffusion in the protective film 55 due to the internally added diffusion component 57 is diffusion due to forming the surface into a matte surface by forming or providing a granular material on the surface layer portion. Compared to the above, the degree (strength of diffusion) and the quality (uniformity of diffusion) are remarkably excellent. More specifically, when the surface is merely matted, light L33 that passes through is generated as shown by a two-dot chain line in FIG. On the other hand, in the protective film 55 according to the present embodiment, the diffusion component 57 is dispersed not only in the plane direction but also in the thickness direction. For this reason, when the light L31 and L32 that are not sufficiently diffused due to the uneven shape on the light incident side surface 55b of the protective film 55 also reaches the diffusion component 57 after that, at the interface between the diffusion component 57 and the main portion 56. The direction of travel can be changed by the refraction or the reflection at the surface of the diffusing component 57.

  As described above, the light from the surface light source device 20 can be diffused to some extent by the protective film 55. Thereby, the angle distribution of the brightness after the light is collected by the two light collecting sheets 30 and 35 can be changed gently.

  In addition, as described above, when the light collecting sheets 30 and 35 are used, the luminance angle is set so that the luminance in the front direction is intensively increased due to the refraction of the light collecting sheets 30 and 35 by the unit optical elements 33 and 38. Changes can be made to the distribution. However, on the other hand, when the condensing sheets 30 and 35 are used, as the cut-off (observation angle (angle of the observation direction with respect to the front direction nd) is increased, the image becomes darker from a certain observation angle. ) And side lobes (a phenomenon in which the second peak occurs in an angular region greatly inclined from the front direction in the angular distribution of luminance). The occurrence of such inconvenience occurs particularly when the unit optical elements 33 and 38 of the light collecting sheets 30 and 35 have a triangular shape in a cross section along the longitudinal direction, as in the illustrated example. It was remarkable. And in order to improve such a malfunction, in the conventional surface light source device 120 comprised using the liquid crystal display panel 150 containing the lower polarizing plate 150 in which the diffusion component 57 is not internally added, in FIG. As shown, a diffusion sheet 29 having a diffusion function was often provided on the light exit side of the second light collecting sheet 35 on the light exit side.

  On the other hand, in the present embodiment, the lower polarizing plate 50 of the liquid crystal display panel 40 includes the protective film 55 that can exhibit an excellent diffusion function and can adjust the degree (strength) of the diffusion function in a wide range. It is out. For this reason, by adjusting the diffusion function of the protective film 55 so that the diffusion function equivalent to that of the diffusion sheet 29 included in the conventional surface light source device 120 can be exhibited, the optical characteristics of the entire display device can be improved. The diffusion sheet 29 can be omitted from the surface light source device 120 while maintaining. As a result, the number of sheet-like members included in the display device 10 (surface light source device 20) can be reduced. In this case, the manufacturing cost of the display device 10 (surface light source device 20) can be directly reduced. In addition, the display device 10 (surface light source device 20) can be thinned.

  The conventional display device 110 shown in FIG. 14 can be configured in the same manner as the above-described display device 10 shown in FIG. 1 except for the presence or absence of the diffusion sheet 29 and the configuration of the lower polarizing plate 150. For this reason, for the conventional display device 110 shown in FIG. 14, the same reference numerals as those used for the corresponding parts in the above-described embodiment are used, and redundant description is omitted.

  According to the present embodiment as described above, the protective film 55 for the lower polarizing plate 50 includes the main portion 56 made of a resin material and the diffusion component 57 dispersed in the main portion 56, and at least One surface 55a is flat. Therefore, the function of actively changing the traveling direction of light can be imparted to the protective film 55, and in addition, the protective film 55 can be stably laminated and bonded to the polarizer 51. Furthermore, such a protective film 55 can be manufactured at low cost by extrusion. For this reason, according to the protective film 55 according to the present embodiment, the degree of freedom of design for the luminance characteristics and viewing angle characteristics of the display device 10 can be significantly improved. Furthermore, there is a possibility that the number of sheet-like members (optical sheets) incorporated in the surface light source device 20 can be reduced. In this case, the manufacturing cost of the surface light source device 20 and the display device 10 can be directly reduced, and the surface light source device 20 and the display device 10 can be thinned.

  Note that 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 embodiment mentioned above, although the example in which the unevenness | corrugation was formed in the light-incidence side surface 55b of the protective film 55 was shown, it is not restricted to this, The light-incidence side surface 55b of the protective film 55 may be a flat surface. . For example, in the manufacturing method of the protective film 55 described above, when the extrusion material 90 is separated from the molding roll 84, not only the surface layer portion of the extrusion material 90 that contacts the molding roll 84 but also the extrusion material 90 from this surface layer portion. Of the protective film 55 formed of the surface 90b of the extruded material 90 on the side in contact with the molding roll 84 by cooling to a temperature not higher than the glass transition temperature of the resin material that forms the main portion 56. The light incident side surface 55b can also be a flat surface.

  In the above-described embodiment, the light incident side surface 55b of the protective film 55 is provided with irregularities formed due to the presence of the diffusion component 57, that is, the outline of the diffusion component 57 is raised. Although the example in which the unevenness is formed has been shown, it is not limited to this. For example, as shown in FIG. 5, the light incident side surface 55b of the protective film 55 may be provided with unevenness formed by shaping. In the manufacturing method of the protective film described above, if the molding roll 84 having a concavo-convex pattern formed on the outer peripheral surface is used, the concavo-convex pattern of the molding roll 84 is transferred to the surface 90b of the extruded material 90 on the side contacting the molding roll 84 Thereby, unevenness | corrugation can be formed in the surface 90b (namely, the light-incidence side surface 55b of the protective film 55) by the side which contacts the shaping | molding roll 84 of the extrusion material 90. FIG. In addition, when unevenness is formed on the light incident side surface 55b of the protective film 55 by shaping, the unevenness due to the presence of the diffusing component 57 may not be formed on the light incident side surface 55b of the protective film 55 (see FIG. 5), or unevenness due to the presence of the diffusion component 57 may be formed in addition to the unevenness due to shaping.

  Further, the light incident side surface 55b of the protective film 55 may be configured as a prism surface formed by unit prisms 60 arranged side by side as shown in FIGS. As an example, such a protective film 55 can be produced by using a molding roll 84 in which a groove having a cross-sectional shape corresponding to a unit prism is formed on the outer peripheral surface in the manufacturing method of the protective film 55 described above. it can. In the example shown in FIGS. 6 and 7, the protective film has a sheet-like main body portion 59 and unit prisms 60 arranged in parallel on the light incident side surface 59 b of the main body portion 59. Each unit prism 60 extends linearly in a direction orthogonal to the arrangement direction. 6 and 7, each unit prism 60 has a triangular shape or a shape formed by chamfering the apex angle of the triangular shape in a cross section orthogonal to the longitudinal direction. Such a protective film 55 can exhibit a light collecting function.

FIG. 7 shows an example of how the protective film 55 is expected to have a light collecting function.
In the example shown in FIG. 7, the surface light source device 20 includes a light guide plate 21, a light source 25 disposed on the side of the light guide plate 21, and a reflection sheet 22 a disposed on the back surface of the light guide plate 21. However, it is configured as a so-called edge light type backlight. Light from the light source 25 enters the light guide plate 21 from the side surface (incident surface) of the light guide plate 21, and repeats reflection between the pair of main surfaces of the light guide plate 21 along the light guide direction. move on. The light guide plate 21 is provided with a light extraction element (not shown), for example, white dots provided on the back surface of the light guide plate 21 facing the reflection sheet 22a, a diffusing component dispersed in the light guide plate 21, and the like. Light traveling through the light guide plate 21 is emitted from the light guide plate 21 toward the viewer so that the amount of emitted light is substantially uniform along the light guide direction. At this time, as shown in FIG. 7, a lot of light L71 emitted from the light guide plate 21 is emitted in a direction greatly inclined from the front direction nd.

  With respect to the light guide plate 21, the unit prisms 60 of the protective film 55 are arranged so that the arrangement direction thereof is parallel to the light guide direction of the light guide plate 21. Further, the unit prism 60 protrudes from the protective film 55 toward the light guide plate 21 side. Then, the light L71 directed toward the liquid crystal display panel along a direction greatly inclined from the front direction nd is incident on the protective film 55 via one surface 60b1 of the unit prism 60, and then the other surface 60b2 of the unit prism 60. And the traveling direction is deflected to the front direction nd side. In this way, the protective film 55 can exhibit a light collecting function.

  As a specific example of the unit prism 60 having the above-described configuration, the arrangement pitch Pp of the unit prisms 60 along the arrangement direction of the unit prisms 60 (see FIG. 7: in the illustrated example, corresponds to the width of the unit light prism 60). To 5 μm to 200 μm. Further, the protrusion height Hp (see FIG. 7) of the unit prism 60 can be set to 1 μm to 150 μm. Further, when the cross-sectional shape of the unit prism 60 is an isosceles triangle shape, from the viewpoint of intensively improving the brightness in the front direction, the apex angle θp (shown in FIG. 7) can be 2 ° or more and 178 ° or less, preferably 30 ° or more and 120 ° or less, and more preferably 60 ° or more and 90 ° or less.

  On the other hand, as shown in FIG. 15, the conventional edge light type surface light source device 220 used in combination with the liquid crystal display panel 140 including the conventional lower polarizing plate 150 often includes the light guide plate 21. A prism sheet (reflective prism sheet, inverted prism sheet) 129 was provided on the light output side. For this reason, the condensing function of the protective film 55 is made the same as the condensing function of the prism sheet (reflective prism sheet, reverse prism sheet) 129 included in the conventional surface light source device 220 shown in FIG. Thus, the prism sheet 129 can be omitted from the surface light source device 220 while maintaining the optical characteristics of the entire display device. Similarly, in the conventional surface light source device 220 shown in FIG. 15, the diffusion sheet 29 is further provided on the light output side of the prism sheet 129, but when the protective film 55 contains the diffusion component 57. It is possible to omit the diffusion sheet 29 by appropriately adjusting the degree of the diffusion function caused by the diffusion component 57. Thereby, by using the protective film 55 of FIG. 6 and FIG. 7, the manufacturing cost of the display device 10 can be significantly reduced, and the display device 10 can be significantly thinned.

  Note that portions of the conventional display device 210 shown in FIG. 15 that can be configured in the same manner as those already described are denoted by the same reference numerals as those used for the configurations already described. Therefore, duplicate explanation is omitted.

  By the way, the protective film 55 described in the present modification is merely an example of a protective film expected to have a light collecting function. Therefore, various modifications can be made to the modification shown in FIGS. For example, in the example shown in FIG. 7, the protective film expected to have a light collecting function may be incorporated in the direct type surface light source device shown in FIG. 1 instead of the edge light type surface light source device. . Moreover, although the example in which the cross-sectional shape of the unit prism (unit optical element) is a triangular shape or a shape formed by chamfering the apex angle of the triangular shape has been shown, it may have a cross-sectional shape other than these. Good. In addition, although the example in which the linearly formed unit prisms are linearly arranged is shown, the unit prisms may be two-dimensionally arranged. That is, the light incident side surface 55a of the protective film 55 may be configured as a micro lens (fly eye lens).

  In addition, for example, as shown in FIGS. 8 and 9, the protective film 55 includes only a main part 56 made of resin and a light diffusion part (light diffusion layer) 61 a having a diffusion component 57 dispersed in the main part 56. In addition, a resin portion (resin layer) 61b that does not contain the diffusion component 57 may be further included. In the example shown in FIG. 8, the resin portion 61b is disposed on the light incident side to define the light incident side surface 55b of the protective film 55, and the light diffusing portion 61a is disposed on the light outgoing side from the resin portion 61b. The light emission side 55a of 55 is defined. On the other hand, in the example shown in FIG. 9, the protective film 55 includes the first resin portion 61b1 disposed on the most light incident side, the light diffusion portion 61a disposed on the light emission side of the first resin portion 61a, and the light diffusion portion. And a second resin portion 61b2 disposed on the light output side of 61a. In the example shown in FIGS. 8 and 9, the unit prism 60 forms part of the resin portions 61b and 61b1. That is, the prism surface is formed by the resin portions 61b and 61b1 that do not include the diffusion component 57. Therefore, the surface (prism surface) of the unit prism 60 that functions as the incident surface 60 b 1 and the total reflection surface 60 b 2 can be formed with extremely high accuracy as a flat surface without unevenness due to the diffusion component 57. Thereby, the unit prism 60 of the protective film 55 can exhibit the desired optical function expected more reliably.

  The protective film 55 having the light diffusing portion 61a and the resin portion 61b can be manufactured as an extruded material by the above-described extrusion processing, particularly by so-called coextrusion processing. In the protective film 55 manufactured by coextrusion processing, there is no optical interface between the main portion 56 of the light diffusing portion 61a and the resin portion 61b. That is, light enters the protective film 55 from the resin portion 61b located on the light incident side to the light diffusion portion 61a located on the light exit side without being optically affected.

  However, the protective film 55 can be manufactured by a method other than extrusion processing such as injection molding. Here, an example of an apparatus and a method for manufacturing the protective film 55 by molding an ionizing radiation curable resin into a desired shape will be described with reference to FIG.

  In the following description, the unit prism 60 can be formed on the base film 62 by molding using a molding apparatus 65 as shown in FIG. As a material used for forming the unit prism 60, a resin having good moldability and being easily available and having excellent light transmittance (for example, a transparent multifunctional product having a refractive index of 1.57 of a cured product) A crosslinked cured product of a composition of a urethane acrylate oligomer and a dipentaerythritol hexaacrylate monomer is preferably used.

  First, the molding apparatus 65 will be described. As shown in FIG. 10, the molding device 65 has a molding die 68 having a substantially cylindrical outer contour. A cylindrical mold surface (uneven surface) 69 is formed at a portion corresponding to the outer peripheral surface (side surface) of the column of the molding die 68. The molding die 68 having a cylindrical shape has a central axis CA that passes through the center of the outer peripheral surface of the cylinder, in other words, a central axis CA that passes through the center of the cross section of the cylinder. In the mold surface 69, a recess (not shown) corresponding to the unit prism 60 of the protective film 55 is formed. That is, the mold 68 is configured as a roll mold that molds the protective film 55 as a molded product while rotating around the central axis CA as a rotation axis (see FIG. 5).

  As shown in FIG. 10, the molding device 65 includes a molding substrate supply device 72 that supplies a substrate film 62 that extends in a strip shape, and a space between the substrate film 62 that is supplied and the mold surface 69 of the molding die 68. And a material supply device 74 for supplying the material 63 having fluidity, and a curing device 76 for curing the material 63 between the base film 62 and the uneven surface 69 of the molding die 68. . The curing device 76 can be appropriately configured according to the curing characteristics of the material 63 to be cured.

  Next, a method for producing the protective film 55 using such a molding apparatus 65 will be described. First, the base film 62 extending in a strip shape is supplied from a molding base material supply device 72. As an example, the supplied base film 62 can be a film composed of a main part and a diffusion component dispersed in the main part. Such a film can be obtained as an extruded material. As shown in FIG. 10, the supplied base film 62 is fed into a molding die 68 and held by the molding die 68 and a pair of rollers 78 so as to face the uneven surface 69 of the die 68. Will come to be.

  Further, as shown in FIG. 10, with the supply of the base film 62, a material 63 having fluidity is supplied from the material supply device 74 between the base film 62 and the mold surface 69 of the molding die 68. The This material 63 forms the unit prism 60. Here, “having fluidity” means that the material 63 supplied to the mold surface 69 of the molding die 68 has such fluidity that it can enter a recess (not shown) of the mold surface 69. means.

  As the material 63 to be supplied, various known materials that can be used for molding (for example, the composition of a transparent polyfunctional urethane acrylate oligomer having a refractive index of 1.57 as described above and a dipentaerythritol hexaacrylate monomer). Ionizing radiation curable resin comprising a crosslinked cured product of the product. In the description here, an example in which ionizing radiation curable resin is supplied from the material supply device 74 will be described. As the ionizing radiation curable resin, for example, a UV curable resin that is cured by being irradiated with ultraviolet rays (UV) or an EB curable resin that is cured by being irradiated with an electron beam (EB) may be selected. it can.

  Thereafter, the base film 62 as the molding base passes through a position facing the curing device 76 in a state where the space between the mold surface 69 of the mold 68 is filled with the ionizing radiation curable resin. At this time, ionizing radiation including a wavelength corresponding to the curing characteristics of the ionizing radiation curable resin 63 is irradiated from the curing device 76, and the ionizing radiation passes through the base film 62 and is applied to the ionizing radiation curable resin 63. Irradiated. When the ionizing radiation curable resin 63 is an ultraviolet curable resin, the curing device 76 is configured as an ultraviolet irradiation device such as a high-pressure mercury lamp. As a result, the ionizing radiation curable resin 63 filled between the mold surface 69 and the base film 62 is cured, and a unit prism 60 made of the cured ionizing radiation curable resin is formed on the base film 62. Will come to be.

  Thereafter, as shown in FIG. 10, the base film 62 is separated from the mold 68, and accordingly, the unit prism 60 molded in the concave portion of the mold surface 69 is moved by the roller 78 on the right side in the figure. Pulled away from mold 68. In this way, the above-described protective film 55 is obtained.

  In the manufacturing method described above, when the base film 62 is not in contact with the surface 69 of the mold 68, the main body 59 of the produced protective film 55 is bonded to the base film 62 and the base film 62. And a resin part (land part) cured in a sheet form. According to such a method, it is possible to effectively prevent the molded unit prism 60 from partially remaining in the recess of the mold 69 at the time of mold release.

  As described above, while the molding die 68 configured as a roll die is rotated about its central axis CA, the material 63 having fluidity is supplied into the die 68; The process of curing the material 63 supplied in the mold 68 in the mold 68 and the process of removing the cured material 63 from the mold 68 are sequentially performed on the mold surface 69 of the mold 68 to obtain the protective film 55. It is done.

  In the manufacturing method described with reference to FIG. 10, the base film 62 supplied from the molding base material supply device 72 is made of a film containing a diffusion component, for example, an extrusion material containing a diffusion component, and the material. When the material 63 supplied from the supply device 74 does not include a diffusion component, the resin portion 61b that forms the prism surface and the light diffusion portion 61a disposed on the light output side of the resin portion 61b are shown in FIG. A protective film 55 is obtained. In this case, the light diffusion part 61 a of the protective film 55 is formed by the base film 62, and the resin part 61 b of the protective film 55 is formed by the material 63 supplied from the material supply device 74.

  Moreover, when the base film 62 supplied with the ionizing radiation curable resin material 63 is a film material having a resin part and a light diffusion part, the protective film 55 of FIG. 9 can be manufactured. As an example, when the base film 62 supplied from the molding base material supply device 72 is an extrusion material formed by coextrusion and is an extrusion material having a resin portion and a light diffusion portion, Nine protective films 55 can be manufactured. In this case, the light diffusing portion 61a and the second resin portion 61b2 of the obtained protective film 55 are formed by the extrusion material, and the first resin portion 61b1 of the obtained protective film 55 is supplied from the material supply device 74. It is formed from an ionizing radiation curable resin material 63.

  As another example, the base film 62 supplied from the molding base material supply device 72 includes a diffusion component 57 and a resin material that functions as a binder resin (for example, ionizing radiation curable resin or thermosetting resin) The film material produced by forming the mat | matte layer (mat part) comprised from these on a transparent film may be sufficient. In the main part 61a of the light diffusing part in FIG. 9, a thermosetting type resin having a refractive index of 1.56 is used, and an ultraviolet curable type resin is used having a refractive index of 1.51. These refractive indexes may be determined as appropriate, and can be freely designed according to the refractive index difference between the adjacent layers 61b2 and 61b1 and the optical characteristics. In this example, when the resin material as the binder resin in the mat layer functions as the main portion 56, the mat layer forms the light diffusion portion 61 a of the protective film 55. The transparent film that forms the base film together with the mat layer forms the second resin portion 61b2 of the protective film 55, and the first resin of the protective film 55 from the ionizing radiation curable resin material 63 supplied from the material supply device 74. A portion 61b1 is formed.

  Furthermore, in the above-described embodiment, the example in which the lower polarizing plate 50 includes the polarizer 51 and the protective film 55 bonded to the polarizer 51 from the light incident side has been shown. A protective film may also be provided on the light output side of the child 51. In addition, a retardation plate for compensating for the phase difference of light may be provided between the lower polarizing plate 50 and the liquid crystal cell 41. In this case, the protective film on the light output side of the lower polarizing plate 50 is You may make it also serve as the protective film of the light-incidence side of a phase difference plate.

  Further, in the above-described embodiment, the light emitting unit 25a of the light source 25 of the surface light source device 20 is formed of a cold cathode tube extending linearly, but is not limited thereto. As the light source 25, a light emitting unit composed of a dot-like LED (light emitting diode), a planar EL (electroluminescent body), or the like may be provided. Further, in the above-described embodiment, the example in which the protective film 55, the lower polarizing plate 50, and the liquid crystal display panel 40 are applied to the combination with the direct type surface light source device 20 has been shown. However, the present invention is not limited to this as described with reference to FIG. The above-described protective film 55, the lower polarizing plate 50, and the liquid crystal display panel 40 can be used together with the edge light type (also called side light type) surface light source device.

  Furthermore, in the above-described embodiment, an example of the overall configuration of the surface light source device 20 and the transmissive display device 10 has been described, but the present invention is not limited to this. For example, a further optical sheet such as a reflective polarization separation film may be additionally incorporated in the surface light source device 20 and the transmissive display device 10 or a sheet such as the light collecting sheets 30 and 35. Any one or more of the member may be deleted or replaced with another sheet member.

  In addition, although the some modification with respect to embodiment mentioned above has been demonstrated above, it is also possible to apply combining several modifications suitably.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to this Example.

<Survey 1>
Display devices according to examples and display devices according to comparative examples were manufactured, and optical characteristics were compared. The display device according to the example and the display device according to the comparative example were manufactured as follows.

[Display device]
(Example)
A display device having the configuration shown in FIG. 1 was produced as a display device according to the example. As the light source and reflector of the surface light source device, those incorporated in a commercially available liquid crystal television (“Aquos” 32 inch manufactured by Sharp Corporation) were used. A diffusion plate manufactured by Sumitomo Chemical Co., Ltd. (haze value: 88%, total light transmittance: 55%) was used as the diffusion plate. The first condensing sheet and the second condensing sheet use the same optical sheet ("UPVII" manufactured by Dai Nippon Printing Co., Ltd.), and the arrangement directions of the unit optical elements are orthogonal to each other as in the above-described embodiment. Arranged.

  Moreover, the liquid crystal cell of the liquid crystal display panel used what was built in the commercially available liquid crystal television (Sharp Corporation "Aquos" 32 inches). The upper polarizing plate utilized the polarizing plate which has a polarizer and a pair of protective film each water-pasted on the both sides of the polarizer. As a polarizer of the upper polarizing plate, a polarizer obtained by adsorbing iodine to a polyvinyl alcohol film and then imparting light absorption anisotropy to the polyvinyl alcohol film by uniaxial stretching and orientation was used. . A triacetyl cellulose film (TAC film) was used as a pair of protective films for the upper polarizing plate.

  On the other hand, the lower polarizing plate utilized the polarizing plate which has a polarizer, the protective film arrange | positioned at the light-incidence side of a polarizer, and the protective film arrange | positioned at the light emission side of a polarizer. The same polarizer as that of the upper polarizer was used as the polarizer of the lower polarizer. For the light exit side protective film of the lower polarizing plate, an extruded film made of polycarbonate was used and laminated on the polarizer by water bonding.

  The protective film laminated | stacked on the light-incidence side of the polarizer of the lower polarizing plate used the protective film demonstrated in the above-mentioned embodiment. That is, the light incident side protective film of the lower polarizing plate has a main part and a diffusion component dispersed in the main part. This protective film was produced by an extrusion process similar to the production method in the above-described embodiment described mainly with reference to FIG. Specifically, a light incident side protective film of the lower polarizing plate was produced by extruding a polycarbonate resin as a resin material that becomes a main part together with styrene fine particles that become a diffusion component. The average particle diameter (primary particle diameter) of the styrenic fine particles is 5 μm in diameter, and 10 parts by weight of the styrenic fine particles are contained in 100 parts by weight of the polycarbonate resin. Further, the thickness of the light incident side protective film of the lower polarizing plate was 80 μm.

The extrusion conditions for producing the protective film were as follows.
-Heating temperature in the extruder: 290 ° C
-Mold roll temperature: 135 ° C
・ Temperature of support roll for backup means: 90 ℃
-Nip length between the forming roll and the backup belt is 60mm.
・ Pressing force (linear pressure) between the forming roll and the belt without backup means: 100 kgf / mm
-Extrusion speed: 15m / min

The haze value of the light incident side protective film of the lower polarizing plate thus obtained was 86.2%, and the ten point average roughness Rz (JISB0601 (1982)) of the light incident side surface of the protective film was 0.68 μm. Thus, the arithmetic average roughness Ra (JISB0601 (1982)) on the light-emitting side of the protective film was 0.18 μm. In addition, the moisture permeability of the light incident side protective film for the lower polarizing plate having a thickness of 80 μm obtained by the extrusion process is 60 g / m ² · 24 hr at a temperature of 40 ° C. and a humidity of 90% RH for 24 hours. became. The protective film on the light incident side obtained by the extrusion process could be laminated and adhered to the polarizer by water sticking while preventing the entry of air or the like.

(Comparative example)
A display device having the configuration shown in FIG. 14 was manufactured as a display device according to a comparative example. In the display device according to the comparative example, in the surface light source device, a diffusion sheet (manufactured by Keiwa) having a haze value of 87% is further provided on the light output side of the light collecting sheet on the light output side, and the lower polarizing plate is inserted in the liquid crystal display panel. Except having made the light side protective film into the film made from a triacetyl cellulose (TAC film), it comprised identically using the member same as the display apparatus which concerns on an Example.

〔Evaluation methods〕
The angle distribution of luminance was measured in a state where the entire display was white on each display device. The measurement results are shown in FIG. BM-9 manufactured by Topcon was used for measurement of the angular distribution of luminance. Further, regarding the angular distribution of luminance, the luminance in the horizontal direction H is measured by measuring the luminance from various directions within a plane parallel to both the arrangement direction of the unit optical elements of the light collecting side light collecting sheet and the front direction. By creating the distribution and measuring the luminance from various directions in a plane parallel to both the arrangement direction of the unit optical elements (cold cathode tube arrangement direction) and the front direction of the light-collecting sheet on the light emitting side. A luminance distribution in direction V was also created.

  The measurement result of the front direction luminance for the display device according to the example was 107% of the measurement result of the front direction luminance for the display device according to the comparative example. In addition, the half-value angle in the angular distribution of luminance was investigated and the following result was obtained. Note that the half-value angle is an inclination angle with respect to the front direction of the measurement direction in which half the peak front direction luminance is obtained. For the display device according to the example, the half-value angle in the horizontal luminance distribution H was 29 °, and the half-value angle in the vertical luminance distribution V was 26 °. On the other hand, for the display device according to the comparative example, the half-value angle in the horizontal luminance distribution H was 34 °, and the half-value angle in the vertical direction luminance distribution V was 24 °.

<Survey 2>
Next, luminance characteristics were simulated for a model obtained by applying the protective film shown in FIG. 8 to the display device shown in FIG. The simulation was performed for a total of six display device models of samples A1 to A3 and samples B1 to B3. The sample A1 to A3 and the sample B1 to B3 were the same as each other except that the protective film was different. Moreover, about the components other than the protective film included in the display device model, specifications of the components of the liquid crystal display device that are actually marketed were adopted.

  About the protective film of sample A1-A3, it was set as the protective film by which the light-diffusion part (light-diffusion layer) and the resin part (resin layer) were shape | molded by coextrusion. About the protective film of sample B1-B3, it was set as the protective film produced by the method of shape | molding the ionizing radiation curable resin demonstrated referring FIG. And in the protective film of sample A1-A3 and sample B1-B3, thickness T1 (refer FIG. 8) of a light-diffusion part (light-diffusion layer) shall be 80 micrometers, and the part which makes the main-body part among resin parts (resin layer) The thickness T2 (see FIG. 8) of the portion corresponding to the land portion in the samples B1 to B3 was set to 10 μm.

  In the protective films of Samples B1 to B3, the cross-sectional shape of the unit prism was an isosceles triangle formed symmetrically about the front direction. In the protective films of Samples B1 to B3, the arrangement pitch (also corresponding to the width) of the unit prisms Px (see FIG. 8) is 150 μm, and the apex angle θx (see FIG. 8) of the unit prisms protruding to the light incident side is 66 °. It was. On the other hand, about the protective film of sample A1-A3, the unit prism of the protective film of sample B1-B3 shall be produced with the shaping rate of 97%. That is, the shape of the unit prisms of the protective films of Samples A1 to A3 so that the unit prisms of the protective films of Samples A1 to A3 have a height that is 97% of the height of the unit prisms of the protective films of Samples B1 to B3. Was made into the shape which attached | subjected the roundness to the top part of the unit prism of the protective film of sample B1-B3.

  For Samples A1 to A3, the refractive index of the main part of the light diffusion part and the resin part was set to 1.59. For Samples B1 to B3, the refractive index of the main part of the light diffusion part was set to 1.59, and the refractive index of the resin part was set to 1.51.

  About sample A1 and sample B1, the haze value of the light-diffusion part of the protective film was 49.0%. About sample A2 and sample B2, the haze value of the light-diffusion part of the protective film was 88.7%. About sample A3 and sample B3, the haze value of the light-diffusion part of the protective film was 99.4%. In addition, the haze value used in this specification is a haze value prescribed | regulated to JISK7150.

  For samples A1 to A3 and samples B1 to B3, the angular distribution of luminance on the display surface was simulated. The angular distribution of luminance was a luminance distribution measured from each direction on a plane parallel to both the unit prism arrangement direction and the normal direction to the display surface of the display panel. The angular distribution of luminance for samples A1 to A3 is shown in FIG. The angular distribution of luminance for samples B1 to B3 is shown in FIG. Further, among the samples A1 to A3, the value of the luminance in the front direction was the highest in the sample A1, and the value of the luminance in the front direction was the lowest in the sample A3. Among the samples B1 to B3, the value of the front direction luminance was the highest in the sample B1, and the value of the front direction luminance was the lowest in the sample B3. It was confirmed that the luminance characteristics of the display device can be greatly changed by adjusting the degree of the light diffusion function of the protective film.

DESCRIPTION OF SYMBOLS 10 Display apparatus 20 Surface light source device 21 Light guide plate 22 Reflection plate 22a Reflection sheet 25 Light source 25a Light emission part 28 Diffusion plate 29 Diffusion sheet 30 Condensing sheet (light-incident side condensing sheet)
32 Main unit 33 Unit optical element 35 Condensing sheet (light-incident light-incident-side condensing sheet)
37 Main unit 37 Unit optical element 40 Liquid crystal display panel 41 Liquid crystal cell 45 Upper polarizing plate 50 Lower polarizing plate 51 Polarizer 55 Protective film 55a Light emission side surface (one side surface)
55b Incident side (other side)
56 Main part 57 Diffusing component 59 Main part 60 Unit prism 61a Light diffusing part, light diffusing layer 61b Resin part, resin layer 120 Surface light source device 129 Prism sheet (reflective prism sheet, inverted prism sheet)
140 Liquid Crystal Display Panel 220 Surface Light Source Device

Claims (14)

A protective film for a lower polarizing plate that is bonded to a polarizer to form a lower polarizing plate for a liquid crystal display panel,
A main part made of a resin material, and a diffusion component dispersed in the main part,
A protective film, wherein at least one side surface facing the polarizer is flat.   The protective film according to claim 1, wherein the other side surface facing the one side surface is a prism surface formed by unit prisms arranged side by side.   The plurality of unit prisms are arranged along an arrangement direction parallel to the film surface of the protective film, and each unit prism is parallel to the film surface and extends in a direction crossing the arrangement direction. The protective film as described in 2. The protective film includes a light diffusion portion containing the diffusion component, and a resin portion in which the diffusion component is not dispersed,
The unit prism is included in the resin portion,
The said light-diffusion part is a protective film of Claim 2 or 3 arrange | positioned rather than the said resin part at the said polarizer side.   The protective film according to claim 4, further comprising a second resin portion that is disposed closer to the polarizer than the light diffusion portion and in which the diffusion component is not dispersed.   The protective film as described in any one of Claims 1-5 with which the unevenness | corrugation formed due to presence of the said diffusion component is provided in the other side surface facing the said one side surface.   The protective film as described in any one of Claims 1-6 by which the unevenness | corrugation formed by shaping | molding is provided in the other side surface which opposes the said one side surface.   The protective film as described in any one of Claims 1-7 which is the extrusion material extruded by the extrusion process.   The protective film as described in any one of Claims 1-8 whose haze value is 60% or more. The protective film according to any one of claims 1 to 9, wherein the moisture permeability at a temperature of 40 ° C, a humidity of 90% RH, and 24 hours is 10 g / m ² · 24 hr or more. A lower polarizing plate incorporated in a liquid crystal display panel,
A polarizer,
It is a protective film as described in any one of Claims 1-10, Comprising: The lower polarizing plate provided with the protective film adhere | attached on the said polarizer from the light-incidence side of the said polarizer.   The lower polarizing plate according to claim 11, further comprising an adhesive layer that is provided adjacent to the polarizer and the protective film and adheres the polarizer and the protective film to each other.   A liquid crystal display panel comprising the lower polarizing plate according to claim 11. A liquid crystal display panel according to claim 13;
A surface light source device that illuminates a liquid crystal display panel from the back side.

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