JP2012203105A - Light-diffusing film, optical module and display device - Google Patents

Abstract

An optical module capable of adjusting optical characteristics by improving utilization efficiency of light source light.
An optical module includes a light polarizer including a polarizer and a polarizing plate having a protective sheet bonded to the polarizer, and a light emitter disposed at a position facing the protective sheet of the polarizing plate. And comprising. The protective sheet includes a light diffusion film 60 having a binder part and a diffusion component dispersed in the binder part. The refractive index of the diffusion component is lower than the refractive index of the binder part.
[Selection] Figure 1

Description

  The present invention relates to a light diffusion film having an excellent light diffusion function and exhibiting high light utilization efficiency. The present invention also relates to an optical module having a polarizing plate including the light diffusion film as a protective film, and a light emitter disposed at a position facing the polarizing plate, and a display device including the optical module. .

  Nowadays, an optical module having a polarizing plate including a polarizer and a light emitter arranged at a position facing the polarizing plate is used by being incorporated in an optical device. As a typical use example, the optical module is used in a display device, particularly a liquid crystal display device. The liquid crystal display device includes a liquid crystal display panel and a surface light source device that functions as a backlight that illuminates the liquid crystal display panel.

  As shown in FIG. 17, 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. 17, 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. 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. 17, the liquid crystal display panel includes a liquid crystal cell 11 capable of controlling the orientation of the liquid crystal for each pixel, a lower polarizing plate 13 disposed on the light incident side of the liquid crystal cell, and a liquid crystal cell. 11 and an upper polarizing plate 12 disposed on the light output side. 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).

  However, a sufficient diffusion function cannot be imparted to the protective film to the extent that one surface of the protective film is matted. For this reason, as shown in FIG. 17, in the conventional display device, it is necessary to provide a large number of optical sheets on the light incident side of the polarizing plate.

Japanese Patent Laid-Open No. 9-258013

  By the way, each optical sheet does not transmit all incident light, and a part of 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. 17) 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. In particular, the light diffusing sheet typically makes the light unevenness (brightness unevenness) inconspicuous by reflecting the light, but on the other hand, a large amount of light loss is lost during reflection. Will be caused. And such a reflection loss (loss of light amount) increases significantly only by increasing the number of optical sheets by one. Therefore, when the surface light source device (display device) includes a large number of optical sheets, the utilization efficiency of the light emitted from the light emitter of the light source is significantly reduced.

  In a surface light source device of a display device that is actually marketed, a light source is constituted by a large number of light emitters. And as the example shown by FIG. 17, in order to eliminate the nonuniformity of brightness (luminance nonuniformity) according to the structure of many light-emitting bodies, the several light-diffusion sheet | seat is provided. According to such a conventional device, on the light emitting surface of the surface light source device, and as a result, on the display surface of the display device, desired optical characteristics, typically high frontal luminance and a wide viewing angle are ensured. On the other hand, the utilization efficiency of the light source is sacrificed. In recent years, interest in energy problems has increased, and it is highly desirable to improve the utilization efficiency of the light source light and, as a result, achieve both high frontal brightness and a wide viewing angle.

  The present invention has been made in consideration of such points, and an object thereof is to make it possible to adjust optical characteristics by improving the utilization efficiency of light source light.

  In the surface light source device and the display device, there are other problems due to the large number of optical sheets provided between the polarizing plate and the light emitter.

  For example, when 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, the heat generated from the light emitter heats the optical sheet, 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 are scratched, and further, residue may be generated, and the display image quality is remarkably deteriorated.

  It is very preferable if the present invention can cope with the problems caused by the provision of a large number of optical sheets between the polarizing plate and the light emitter.

  As a result of intensive research, the inventors of the present invention include a light diffusing film with little light loss in the protective sheet for the polarizing plate, and eliminates the conventional optical sheet to face the polarizing plate at the position facing the polarizing plate. By arranging this, it was possible to ensure sufficient optical characteristics as a display device. In particular, in this apparatus, the utilization efficiency of the light source light is greatly improved. For example, by adjusting the optical characteristics of the light diffusion film, the relative arrangement position of the light source and the polarizing plate, etc. It may also be possible to form the light source only with the illuminant. The present invention is based on such knowledge of the present inventors.

The optical module according to the present invention comprises:
A polarizing plate having a polarizer and a protective sheet bonded to the polarizer;
A light source including a light emitter disposed at a position facing the protective sheet of the polarizing plate,
The protective sheet includes a light diffusion film having a binder part and a diffusion component dispersed in the binder part, and the refractive index of the diffusion component is lower than the refractive index of the binder part.

  In the optical module according to the present invention, the light source may include only one light emitter that extends linearly.

  The display device according to the present invention includes any of the optical modules according to the present invention described above.

A display device according to the present invention comprises:
A liquid crystal cell laminated with the polarizing plate;
A further polarizing plate laminated on the side opposite to the side facing the polarizing plate of the liquid crystal cell;
You may make it further provide the reflecting plate provided in the opposite side to the side which faces the said polarizing plate of the said light-emitting body.

The light diffusion film according to the present invention is:
A binder part;
A diffusion component dispersed in the binder part,
The refractive index of the diffusion component is lower than the refractive index of the binder part.

  According to the present invention, it is possible to improve the utilization efficiency of light source light, and it is possible to improve the optical characteristics due to this.

FIG. 1 is a perspective view showing a schematic configuration of a display device and an optical module for explaining an embodiment according to the present invention. FIG. 2 is a side sectional view showing a schematic configuration of the display device and the optical module. FIG. 3 is a cross-sectional view showing the polarizing plate in a cross section along the normal direction of the polarizing plate. FIG. 4 is a view showing the polarizing plate in the same cross section as FIG. 3, and is a view for explaining a modification of the protective sheet. FIG. 5 is a diagram showing a polarizing plate in the same cross section as FIG. 3, and is a diagram for explaining another modified example of the protective film. FIG. 6 is a diagram showing an in-plane distribution of luminance in the front direction on the light exit side of a polarizing plate of an optical module including a light diffusing film in which the refractive index of the diffusing component is lower than the refractive index of the binder portion as a protective sheet. is there. FIG. 7 is a diagram showing an in-plane distribution of luminance in the front direction on the light exit side of a polarizing plate of an optical module including a light diffusing film in which the refractive index of the diffusing component is higher than the refractive index of the binder portion as a protective sheet. is there. FIG. 8 is a diagram showing an in-plane distribution of luminance in the front direction on the light exit side of a polarizing plate of an optical module including a light diffusing film in which the refractive index of the diffusing component is the same as the refractive index of the binder part as a protective sheet. is there. FIG. 9 shows an angular distribution of luminance measured at the center of the light exit side of a polarizing plate of an optical module including a light diffusing film whose refractive index of the diffusing component is lower than that of the binder portion as a protective sheet. FIG. FIG. 10 shows an angular distribution of luminance measured at the center of the light exit side of a polarizing plate of an optical module including a light diffusing film in which the refractive index of the diffusing component is higher than the refractive index of the binder portion as a protective sheet. FIG. FIG. 11 shows an angular distribution of luminance measured at the center of the light exit side of the polarizing plate of an optical module including a light diffusing film having a refractive index of the diffusing component equal to that of the binder as a protective sheet. FIG. FIG. 12 is a perspective view of a polarizing plate for explaining still another modified example of the protective sheet. FIG. 13 is a cross-sectional view corresponding to FIG. 2 and illustrating a schematic configuration of a display device in which the polarizing plate of FIG. 12 is incorporated. FIG. 14 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 sheet. FIG. 15 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 sheet. FIG. 16 is a perspective view showing a protective sheet, and is a view for explaining still another modified example of the protective sheet. FIG. 17 is a cross-sectional view showing a display device including a conventional surface light source 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 3 are diagrams for explaining an embodiment according to the present invention. Among these, FIG.1 and FIG.2 is the perspective view and side view which show schematic structure of a display apparatus and an optical module. FIG. 3 is a cross-sectional view along the front direction showing the protective sheet included in the polarizing plate of the optical module.

  The 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 image observer side), and a light source And a reflection plate 21 that covers 25 from the back side. The light source 25 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 light incident side polarizing plate 40 and the light source 25 of the pair of polarizing plates of the liquid crystal display panel 15. In the following, in order to distinguish a pair of polarizing plates included in the liquid crystal display panel 15, the light incident side polarizing plate 40 is referred to as a lower polarizing plate regardless of the arrangement state of the display device 10, and the light emitting side polarized light. The plate 12 is called an upper polarizing plate. As shown in FIG. 3, in the present embodiment, the liquid crystal display panel 15, and the pair of polarizing plates 12 and 40 and the liquid crystal cell 11 as components constituting the liquid crystal display panel 15 are rectangular in plan view. It is comprised so that.

  The display device 10 is configured as a liquid crystal display device having a direct-type surface light source device, and a linear light emitter 26 forming the light source 25 is located at a position facing the liquid crystal display panel 15 in the front direction nd. Has been placed. 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 can enter the lower polarizing plate 40 directly.

  As shown in FIGS. 1 and 2, the light source 25 includes a light emitting body 26 extending linearly. As can be understood from FIGS. 1 and 2, the linear light emitters 26 are arranged so that the longitudinal direction thereof is parallel to the panel surface of the liquid crystal display panel 15. As the light emitter 26, various known linear light emitters can be used, and typically, a cold cathode fluorescent lamp (CCFL) can be used.

  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 image observer (hereinafter also simply referred to as an observer) from the light emitter 26 of the light source 25 through the liquid crystal display panel 15 without turning back the traveling direction. This is the downstream side in the traveling direction of light (observer side, the upper side of the paper surface in FIGS. 1 and 2), and “light incident side” refers to the light emitting body 26 of the light source 25 without being folded back in the traveling direction. It is the upstream side in the traveling direction of light traveling toward the observer through the liquid crystal display panel 15.

  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 sheet” includes a member called “protective film”, and the “light diffusion film” also includes a member called “light diffuser sheet”.

  Furthermore, in this specification, the “sheet surface (film surface, plate surface)” refers to the planes of the front and back surfaces of the target sheet-like member when the target sheet-like member is viewed overall and globally. A surface that matches the direction. And in this Embodiment, the panel surface of the liquid crystal display panel 15, the plate surface of the lower polarizing plate 40, the sheet surface of the protective sheet 50 mentioned later, the film surface of the light-diffusion film 60 mentioned later, etc. become mutually parallel. ing. 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.

  Furthermore, the terms used in this specification for specifying the shape and geometric conditions, for example, terms such as “parallel” and “orthogonal” are not limited to strict meaning, and expect similar optical functions. Interpretation will be made including possible errors.

  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 FIG. The lower polarizing plate 40 includes a polarizer 41 that can exhibit an absorption polarization separation function, and a protective sheet 50 bonded to the polarizer 41. As shown in FIG. 3, the protective sheet 50 is laminated on the polarizer 41 from the side not facing the liquid crystal cell 11, in other words, from the light incident side, so that the polarizer 41 functions as a protective member from the outside. It has become.

  Further, an adhesive layer (not shown) is provided between the polarizer 41 and the protective sheet 50 so as to be adjacent to the polarizer 41 and the protective sheet 50 and adheres the polarizer 41 and the protective sheet 50 to each other. It may be. The adhesive layer for improving the adhesion between the polarizer 41 and the protective sheet 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 protection sheet 50 will be described. As shown in FIG. 3, the protective sheet 50 has a light diffusion having a binder part (main part, base material part) 60a made of a resin material and a diffusion component 60b dispersed in the binder part 60a. A film 60 is included. In particular, in the present embodiment, as shown in FIG. 3, the protective sheet 50 is composed only of the light diffusion film 60, and the light diffusion film 60 includes the binder part 60 a and the diffusion component dispersed in the binder part 60 a. It is composed only of 60b. As the resin material forming the binder part 60a, various resin materials having excellent optical characteristics, for example, polycarbonate resins can be used.

  On the other hand, the diffusing component 60b can be composed of a granular material having a lower refractive index than the resin material forming the binder portion 60a. The granular material forming the diffusion component 60b may be a resin, a metal compound, a porous material containing a gas, or may be a simple bubble. Further, the shape of the diffusion component 60b made of a granular material is not particularly limited. Therefore, the diffusion component 60b 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. 1 and 2, the diffusion component 60b is not shown.

  Thus, due to the diffusion component 60b dispersed in the binder portion 60a, the light diffusion film 60 (protective sheet 50) can exhibit a diffusion function of diffusing light. In particular, since the refractive index of the diffusing component 60b is lower than the refractive index of the binder portion 60a that contains and holds the diffusing component, as shown by the experimental results of the present invention described later, the light amount loss Thus, it is possible to use light from the light source 25 with high utilization efficiency. As a result, it is possible to realize both high luminance in the front direction and wide viewing angle.

  The degree of the diffusion function of the light diffusion film 60 (protective sheet 50) due to the internally added diffusion component 60b is determined by the resin material forming the binder portion 60a, the thickness of the binder portion 60a, the configuration (shape, shape) of the diffusion component 60b. By appropriately setting the size (particle size), refractive index, etc.), the concentration of the diffusion component 60b, etc., it can be adjusted within a very wide range. Specifically, it is possible to set the haze value of the protective sheet 50 within a range that cannot normally be reached by simply matting the surface layer portion, for example, within a range of 60% to 90%. is there.

  Further, as shown in FIG. 3, the light exit side surface 50a (the surface corresponding to the light exit side surface of the light diffusion film 60) that faces the polarizer 41 of the protective sheet 50 is formed as a flat surface. The cage. Thereby, it becomes possible to laminate | stack and adhere | attach the protection sheet 50 (light-diffusion film 60) and the polarizer 41 stably, preventing mixing of air etc. Here, in this specification, “flat” used for the surface 50a facing the polarizer 41 of the protective sheet 50 (light diffusion film 60) means the protective sheet 50 (light diffusion film 60) and the polarizer. The flatness of the grade which can ensure the stable lamination | stacking and adhesion | attachment with 41 is shown. For example, when the surface roughness of the surface 50a facing the polarizer 41 of the protective sheet 50 (light diffusion film 60) is measured as a ten-point average roughness Rz according to JISB0601 (1982), If it is 1.0 μm or less, it can be said to be flat.

  In this way, the light exiting side surface 50a of the protective sheet 50 (the light exiting side surface of the light diffusing film 60) is flat even though the protective sheet 50 is composed of the light diffusing film 60 with the diffusion component 60b internally added. Thus, the protective sheet 50 and the polarizer 41 can be laminated and bonded by so-called “water sticking”. Specifically, the protective sheet 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 sheet 50 and the polarizer 41 can be laminated while preventing the entry of foreign matters such as air. At this time, an adhesive (for example, glue) is mixed in water or an aqueous solution (or suspension), or an adhesive layer is provided in advance on at least one of the protective sheet 50 and the polarizer 41, The protective sheet 50 and the polarizer 41 may be positively bonded.

In addition, in order to promote the removal of moisture from the protective sheet 50 and the polarizer 41 after “water sticking”, the moisture permeability of the protective sheet 50 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.

  In the example shown in FIG. 3, the light incident side surface 50 b (the surface corresponding to the light incident side surface of the light diffusion film 60) opposite to the side facing the polarizer 41 of the protective sheet 50 is also flat. It is formed as a surface. However, without being limited to the example shown in FIG. 3, the light incident side surface 50 b of the protective sheet 50 may be formed as an uneven surface as in the example shown in FIGS. 4 and 5. The light incident side surface 50 b of the protective sheet 50 not only forms the light incident side surface 40 b of the lower polarizing plate 40, but also forms the light incident side surface of the liquid crystal display panel 15. Therefore, the protective sheet 50 shown in FIG. 4 or 5 exhibits not only the diffusion component 60b dispersed in the binder part 60a described above but also the diffusion function due to the unevenness of the light incident side surface 50b. Will come to do.

  In the example shown in FIG. 4, the unevenness provided on the light incident side surface 50b of the protective sheet 50 is caused by the diffusion component 60b dispersed in the binder part 60a, more specifically, the diffusion. The component 60b is exposed or the outline of the diffusion component 60b is raised. On the other hand, in the example shown in FIG. 5, the unevenness provided on the light incident side surface 50b of the protective sheet 50 is formed by an uneven pattern formed on the surface of the binder part 60a.

  As an example, the light diffusion film 60 forming the protective sheet 50 as described above can be manufactured as an extruded material extruded by extrusion molding. Specifically, the protective sheet 50 is formed by extruding the thermoplastic resin material that forms the binder portion 60a together with the granular material that forms the diffusion component 60b with an extruder, that is, by the melt extrusion method. A light diffusion film 60 is obtained. In particular, the light incident side surface 50b is formed as an uneven surface by adjusting the amount of cooling from one side and the amount of cooling from the other side to the extruded material while the extruded material is formed into a sheet shape. Then, the light diffusion film 60 (protective sheet 50) of FIG. 4 in which the light exit side surface 50a is formed as a flat surface can be produced. At this time, the side having a large amount of cooling during molding becomes a flat surface, and the side having a small amount of cooling becomes an uneven surface. Further, while the extrusion material is formed into a sheet shape, by shaping the extrusion material from one side, the light incident side surface 50b is formed as a shaping uneven surface, and the light emission side surface 50a is a flat surface. The formed light diffusion film 60 (protective sheet 50) of FIG. 5 can be produced.

  Next, the operation of the display device 10 will be described.

  2 and 3, most of the light emitted from the light emitter 26 that constitutes the light source 25 is directly incident on the liquid crystal display panel 15. Further, the other light emitted from the light emitter 26 is also reflected by the reflecting plate 21 with a high reflectance and then enters the liquid crystal display panel 15. That is, the light emitted from the light emitter 26 that constitutes the light source 25 enters the liquid crystal display panel 15 with almost no light loss.

  A lower polarizing plate 40 is provided on the most incident light side of the liquid crystal display panel 15. The protective sheet 50 of the lower polarizing plate 40 forms the most incident side surface of the liquid crystal display panel 15. In the present embodiment, the protective sheet 50 of the lower polarizing plate 40 includes the light diffusion film 60 having a diffusion function, and exhibits the light diffusion function with respect to incident light. In this way, the light incident on the liquid crystal display panel 15 can be diffused to some extent by the protective sheet 50 of the polarizing plate 40. Thereby, the in-plane variation in brightness and the angle variation in brightness can be made uniform to some extent.

  As described above, the light diffused by the protective sheet 50 of the lower polarizing plate 40 is then 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 sheet 50. Will head to. 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.

  By the way, in the present embodiment, as compared with the conventional display device 10 shown in FIG. 17, various optical sheets that have been considered essential in the past are eliminated, and the configuration of the display device is greatly simplified. ing. For this reason, desired optical characteristics, in particular, desired brightness (desired brightness) and desired viewing angle cannot be ensured on the display surface 10a of the display device 10, and furthermore, uneven brightness (luminance) Unevenness) is also expected to occur. However, as a result of extensive research conducted by the inventors, it has been confirmed that the display device according to the present embodiment can sufficiently secure the optical characteristics required for the display device. The mechanism that makes it possible to ensure sufficient optical characteristics on the display surface 10a of the display device 10 according to the present embodiment, whose configuration has been greatly simplified, is not clear, but is considered to be one factor below. A possible mechanism is described. However, the present invention is not limited to the following estimation mechanism.

  First, the light diffusion film 60 that forms the protective sheet 50 includes a binder part 60a and a diffusion component 60b dispersed in the binder part 60a. The diffusion in the light diffusion film 60 due to the internally added diffusion component 60b is caused by matting the surface by shaping or matting the surface by providing a granular material on the surface layer portion. Compared to diffusion, the degree (diffusion intensity) and quality (diffusion uniformity) are much better. Specifically, if the light diffusing function is simply caused by the matted uneven shape, light L43 that passes through may be generated as shown by the two-dot chain line in FIG. On the other hand, according to the light diffusion function caused by the internally added diffusion component 60b, the diffusion component 60b can be dispersed not only in the plane direction but also in the thickness direction. Therefore, the protective sheet 50 (light diffusion film) The light L41 and L42 that are not sufficiently diffused due to the uneven shape on the light incident side surface 50b of 60) can sufficiently change the traveling direction when the light L41 and L42 reach the diffusion component 60b thereafter.

  In addition, in the light diffusion film 60 forming the protective sheet 50, the refractive index of the diffusing component 60b is lower than the refractive index of the binder part 60a. Total reflection may occur at the interface between the diffusion component 60b and the binder portion 60a in the light diffusion film 60. In particular, when the refractive index difference between the diffusing component 60b and the binder part 60a is 0.10 or more, more preferably 0.14 or more, a very effective total reflection phenomenon can occur. Such total reflection does not cause a reflection loss unlike reflection at an interface having a simple refractive index difference or reflection caused solely by the reflectivity of the surface of the diffusion component. That is, the amount of light lost due to the light diffusing action in the light diffusing film 60 can be reduced extremely effectively. Although there is no theoretical upper limit for the refractive index difference, there is a limit to the range of the refractive index of materials that can be obtained and used practically, and if the refractive index difference is increased to some extent in practice, the total reflectivity may also be reduced. In order to saturate, it is sufficient that the difference in refraction is about 0.5 at the maximum.

  Therefore, according to this light diffusion film 60, it exhibits an extremely excellent light diffusion function in terms of degree (strength of diffusion) and quality (uniformity of diffusion), and light is emitted by the light emitter 26 forming the light source 25. Light can be used with extremely high utilization efficiency. As a result, sufficient optical characteristics, specifically, sufficient brightness (sufficient luminance) and sufficient viewing angle can be ensured on the display surface 10a of the display device 10 according to the present embodiment. In addition, it is expected that brightness unevenness (luminance unevenness) can be sufficiently eliminated.

  In the present embodiment, the light source 25 is composed of a single linear light emitter 26. Then, by arranging the linear light emitter 26 in the center of the parallel plane facing the liquid crystal display panel 15, that is, so that the position where the linear light emitter 26 faces the center of the liquid crystal display panel 15 is extended. By arranging the illuminant 26, it is possible to improve the brightness at the center of the display surface 10a where the observer can feel the brightness most sensitively, typically the luminance in the front direction. That is, according to the present embodiment, the brightness can be effectively improved even by the configuration of the light source 25.

  Furthermore, according to the present embodiment, since the light source 25 is composed of a single linear light emitter 26, an observer can compare with a case where a plurality of light emitters are arranged directly below the liquid crystal display panel. The in-plane variation of the brightness to be felt can be made inconspicuous effectively. When the light emitter is disposed immediately below the liquid crystal display panel 15, the brightness at a position immediately above the light emitter tends to increase. Therefore, when a plurality of light emitters are arranged directly below the liquid crystal display panel 15, normally, a plurality of bright areas may occur on the display surface 10a depending on the arrangement position of the light emitters. . Such in-plane variation in brightness is easily perceived by an observer. On the other hand, according to the present embodiment, the edge of the display surface 10a is brightest at the center of the display surface 10a where the brightness is most sensitive to the observer and is insensitive to the observer. An in-plane distribution of brightness that gradually fades toward is formed. And according to this Embodiment like this, the in-plane variation of the brightness perceived by the observer can be effectively eliminated more than the evaluation based on the actually measured luminance value.

  Furthermore, this means that in the present embodiment, it is not necessary to excessively generate light diffusion for eliminating the in-plane variation in brightness according to the configuration of the light source. Therefore, according to the present embodiment, the light emitted from the light emitter 26 constituting the light source 25 can be used effectively from this point.

  In addition, in the present embodiment, in the combination of the configuration of the light diffusing film 60 and the configuration of the light source 25, the light emitter that forms the light source 25 at a position facing the polarizing plate 40 that forms the light incident surface of the liquid crystal display panel 15. 26 is arranged. That is, the diffusion plate A incorporated in the conventional surface light source device (display device 1) shown in FIG. 17 from between the liquid crystal display panel 15 and the light source 25, for example, conventionally provided optical sheets. The lower diffusion sheet B, the light collecting sheet C, the upper diffusion sheet D, and the like are excluded.

  The optical sheets incorporated in the conventional display device 1 are members for correcting the traveling direction of light, but on the other hand, part of incident light is absorbed. In addition, in the conventional display device 1, a lot of light is reflected on any one of the optical sheets, and enters the display panel after returning its traveling direction at least once. 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 present embodiment described above, the light emitter 26 that constitutes the light source 25 faces the protective sheet 50 of the polarizing plate 40, that is, faces without any member 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 can be performed with only one reflection on the reflector 21. The light can enter the polarizing plate 40 of the panel 15 again. For this reason, the utilization efficiency of the light emitted by the light emitter 26 can be significantly increased. As a result, for example, as compared with the conventional display device 1, it is possible to adjust the optical characteristics by effectively using the light emitted by the light emitter 26 that forms the light source 25.

  Here, in FIGS. 6 to 11, the present inventors actually manufactured three types of optical modules according to samples 1 to 3, and investigated the luminance distribution on the light output side of the optical module according to each sample. Shows the results. As shown in FIG. 1 and FIG. 2, the optical module to be investigated is a light source composed of one cold cathode tube, a polarizing plate disposed at a position facing the cold cathode tube, and a light source on the back side. And a reflective plate covering from. The polarizing plate was comprised from the protective sheet which consists only of the light-diffusion film arrange | positioned in the position facing a cold cathode tube, and the polarizer laminated | stacked on the protective sheet. The light diffusion film was composed of a binder part made of resin and light diffusion particles (diffusion component) dispersed in the binder. As shown in the following Table 1, between the samples 1 to 3, the refractive index of the binder part and the refractive index of the light diffusion particles (diffusion component) in the light diffusion film were changed. Other configurations of the light diffusing film, for example, the concentration of the light diffusing particles and the thickness of the light diffusing film were the same among the samples 1 to 3. In addition, the configuration other than the light diffusion film (protective sheet), that is, the polarizer, the light source, and the reflection plate were the same among the samples 1 to 3.

  6 to 8 show in-plane distributions of front direction luminance (luminance measured from the normal direction to the plate surface of the polarizing plate) measured for the optical modules according to Samples 1 to 3, respectively. Yes. 6 to 8, a region surrounded by a rectangular frame is a region facing the display surface 10a on the polarizing plate when the optical module is incorporated in the display device. And it is an area | region where the one cold cathode tube extended in a horizontal direction is arrange | positioned in the position shown with the dashed-two dotted line in FIGS. In FIGS. 6-8, the light emission side surface of a polarizing plate is shown as a ratio with respect to the highest front direction brightness | luminance measured on the light emission side surface (surface on the opposite side to the side which faces a cold cathode tube) of the polarizing plate of each sample. The value of the front luminance measured at each of the above positions was evaluated. 6-8, the area | region where the front direction brightness | luminance of 75 to 100% of the highest front direction brightness | luminance value measured with each sample was shown as S1, and the highest front direction direction measured with each sample is shown. A region where the front direction luminance of 50% or more and less than 75 of the luminance value is measured is shown as S2, and a region where the front direction luminance of 25% or more and less than 50% of the maximum front direction luminance value measured in each sample is measured. Is shown as S3, and an area where only front direction luminance of 0 to less than 25% of the maximum front direction luminance value measured in each sample is measured is shown as S4.

  In FIGS. 9 to 11, the angular distribution of luminance measured from each measurement direction at the center of the light exit side surface of the optical module according to each of samples 1 to 3 is shown as a ratio of the luminance to the luminance in the front direction. The luminance distribution in the direction connecting “left” and “right” in the circular graphs in FIGS. 9 to 11 is within a horizontal plane (a plane parallel to the direction in which the linear cold cathode tube extends in this optical module). Similarly, the angular distribution of the brightness measured in each measurement direction is shown. Similarly, the brightness distribution in the direction connecting “up” and “down” in the circular graph is the vertical plane (linear in this optical module). The angular distribution of the luminance measured in each measurement direction in the plane perpendicular to the longitudinal direction of the cold cathode tube is shown. In addition, the center of the circular graph represents the luminance measured in the front direction, and as the distance from the center of the circular graph in the radial direction increases, the larger the measurement angle (the angle that the luminance measurement direction makes with the front direction) ) Shows the brightness value (ratio to the front direction) measured. In FIGS. 9 to 11, the angle range where the luminance of 75% or more and 100% or less of the front direction luminance value measured in each sample is shown as A1, and the front direction luminance value measured in each sample is shown as A1. The angle range where the luminance of 50% or more and less than 75% was measured is shown as A2, the angle range where the luminance of 25% or more and less than 50% of the luminance value measured in each sample is shown as A3, An angular region where only a luminance of 0 or more and less than 25% of the front direction luminance value measured with the sample is measured is shown as A4.

  In Table 1, the highest front direction luminance measured in Samples 1 to 3 is shown as a relative ratio. Further, Table 1 shows the angle range in the measurement direction in the vertical plane in which the half-value angle in the angular distribution of luminance measured in the vertical plane, that is, the luminance value more than half of the value in the front direction luminance is secured. Each sample is shown as a vertical half-value angle. Similarly, Table 1 shows the half-value angle in the angular distribution of luminance measured in the horizontal plane, i.e., the angular range in the measurement direction in the horizontal plane in which a luminance value equal to or more than half of the front direction luminance value is secured. Each sample is shown as a horizontal half-value angle.

  As demonstrated by the results shown in FIGS. 6 to 11 and Table 1, the light diffusion film 60 in which the refractive index of the diffusion component 60b is lower than the refractive index of the binder part 60a is used as the protective sheet 50. (Sample 1), when a light diffusion film in which the refractive index of the diffusing component is higher than the refractive index of the binder portion is used as the protective sheet (sample 2), or when the refractive index of the diffusing component is the refractive index of the binder portion. Compared with the case where the light diffusing film having the same rate as that of the protective sheet (Sample 3) was used, it was possible to improve both the front luminance and the viewing angle. This is because the light diffusing film 60 in which the refractive index of the diffusing component 60b is lower than the refractive index of the binder portion 60a is used as the protective sheet 50, so that the light emitted from the light emitter that forms the light source has high utilization efficiency. It means that it was able to be used in.

  In addition to the results shown in FIGS. 6 to 11, the protective sheet 50 includes the light diffusing film 60 in which the refractive index of the diffusing component 60 b is lower than the refractive index of the binder portion 60 a in actual visual judgment. When used as a sample (sample 1), a light diffusion film in which the refractive index of the diffusing component is higher than the refractive index of the binder part is used as a protective sheet (sample 2), or the refractive index of the diffusing component is a binder. Compared with the case where the light diffusion film having the same refractive index as the protective sheet was used as the protective sheet (Sample 3), the in-plane variation in brightness and the angle variation in brightness could be further relaxed. .

  By the way, according to the present embodiment, as described above, the optical characteristics can be appropriately adjusted by improving the utilization efficiency of the light from the light source 25. At this time, for example, by adjusting the degree (intensity) of the light diffusing function that the light diffusing film 60 can express, the distance x (see FIG. 2) from the light emitter 26 forming the light source 25 to the polarizing plate 40, and the like. The optical properties can be controlled. The present inventors actually produced the optical module 20 shown in FIGS. 1 and 2, and the intensity of diffusion of the light diffusion film 60 and the distance x from the light emitter 26 to the polarizing plate 40 (see FIG. 2) Table 2 shows a part of the results of investigating the effects of frontal luminance and brightness on in-plane variations.

  As shown in FIGS. 1 and 2, the optical module according to Samples A to F subjected to the experiment shown in Table 2 faces a light source composed of one cold cathode tube and a cold cathode tube. It comprised from the polarizing plate arrange | positioned in the position to perform, and the reflecting plate which covers a light source from the back side. The polarizing plate was comprised from the protective sheet which consists only of the light-diffusion film arrange | positioned in the position facing a cold cathode tube, and the polarizer laminated | stacked on the protective sheet. The light diffusion film was composed of a binder part made of resin and light diffusion particles (diffusion component) dispersed in the binder. As shown in Table 2, the refractive index of the binder part in the light diffusion film, the refractive index of the light diffusion particles (diffusion component), and the thickness of the light diffusion film were changed between samples A to F. However, other configurations of the light diffusion film, for example, the concentration of the light diffusion particles, and the like were the same among the samples A to F. Further, as shown in Table 2, the distance x along the normal direction from the light-emitting body 26 forming the light source 25 to the polarizing plate 40 to the plate surface of the polarizing plate 40 is 50 mm in the samples A to C, and the samples D to In F, it was set to 100 mm.

  The result of relatively evaluating the brightness (luminance in the front direction) at the light exit side of the optical module according to each sample A to F is shown in the “brightness” column of Table 2. The evaluation was marked with ◎ for the brightest observed sample, and marked with ◯ and Δ in the order of darkening. Moreover, the result of relatively evaluating the degree of unevenness of the brightness on the light exit side of the optical modules according to the samples A to F is shown in the “unevenness” column of Table 2. The evaluation was marked with を for the sample with the least brightness unevenness, and marked with ◯ and △ in the order in which the brightness unevenness became significant.

  As proved in the results of Table 2, when the degree of diffusion of the light diffusion film 60 is increased, the luminance in the front direction is reduced, but the in-plane variation of the luminance is reduced, and conversely, the diffusion of the light diffusion film 60 is reduced. It was confirmed that when the degree of is weakened, the in-plane variation in luminance increases, but the luminance in the front direction increases. On the other hand, when the distance x from the light emitter 26 to the polarizing plate 40 is increased, the luminance in the front direction is reduced, but the in-plane variation of the luminance is reduced, and conversely, the distance x from the light emitter 26 to the polarizing plate 40 is shortened. As a result, it was confirmed that the in-plane variation in luminance increased, but the luminance in the front direction increased.

  In the present embodiment, as described above, optical sheets conventionally provided between the liquid crystal display panel 15 and the light source 25, for example, a conventional surface light source device (display device) shown in FIG. The diffusion plate A, the lower diffusion sheet B, the light collecting sheet C, the upper diffusion sheet D and the like incorporated in 1) are excluded. Therefore, in addition to the above-described effects, according to the present embodiment, the following effects can be enjoyed.

  First, according to the present embodiment, the number of members (optical sheets) incorporated in the display device 10 can be greatly reduced, and the manufacturing cost of the display device 10 can be greatly reduced directly. Further, it is possible to omit a complicated operation such as positioning of optical sheets required when assembling the display device or the surface light source device, and the manufacturing cost of the display device 10 can also be reduced in this respect. Furthermore, the thickness of the display device 10 can be reduced by omitting a member (optical sheet) incorporated in the display device 10. In addition, the protective sheet 50 including the light diffusion film 60 that is provided with an excellent optical function and can provide a large degree of freedom with respect to the luminance characteristics and viewing angle characteristics of the display device 10 is a protective member that protects the polarizer 41. The protective member that functions and has been conventionally considered an essential element for the polarizing plate. From this point, the effect of reducing the manufacturing cost and reducing the thickness according to the present embodiment is considered extremely useful.

  Since optical sheets are not disposed between the light emitter 26 forming the light source 25 and the protective sheet 50 of the polarizing plate 40, there is a problem in that the display image quality is deteriorated due to bending, bending, warping, or the like of the optical sheet. It can be avoided. In the conventional display device, as shown in FIG. 17, the thickness of the member (diffusion plate A) facing the light emitter is not changed due to 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 of the diffusing plate A increases, and as a result, 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, the protective sheet 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 sheet 50 is directly supported by the liquid crystal display panel 15, a special support mechanism for supporting the protective sheet 50 is not necessary, and deformation of the protective sheet 50 is restrained by the liquid crystal display panel 15. . Therefore, the thickness of the protective sheet 50 can be determined from the viewpoint of the optical action expected from the protective sheet 50 and the protective action of the polarizer, and as a result, the manufacturing cost of the display device 10 can be reduced.

  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, the light-incidence side surface 50b of the protection sheet 50 demonstrated the example comprised as an uneven surface for expressing a flat surface or a light-diffusion function. However, as shown in FIGS. 12 and 13, the light incident side surface 50b of the protective sheet 50 is an optical element surface (prism surface, lens) formed by unit optical elements (unit prism, unit lens) 52 arranged side by side. Surface). Hereinafter, the modification shown in FIGS. 12 and 13 will be described.

  In the example illustrated in FIG. 12, the protective sheet 50 includes a sheet-like main body 51 and unit optical elements 52 arranged side by side on the light incident side surface 51 b of the main body 51. Each unit optical element 52 extends in a direction intersecting with the arrangement direction and parallel to the film surface of the protective sheet 50. Further, the unit optical elements 52 included in the protective sheet 50 are configured in the same manner.

  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. The arrangement direction of the unit optical elements 52 intersects with the arrangement direction of the pixels of the liquid crystal cell 11 of the liquid crystal display panel 15 when observed from a direction parallel to the normal direction nd to the plate surface of the lower polarizing plate 40, that is, It is preferable that it is inclined with respect to the arrangement direction of the pixels. Specifically, 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 52 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 0 °, more preferably at an angle of 5 ° to 30 °. 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 52 can be effectively made inconspicuous. it can. From the viewpoint of making the moire inconspicuous, the arrangement pitch of the unit optical elements 52 is preferably 30 μm or less.

  The cross section shown in FIG. 13 is a cross section along the both directions of the arrangement direction of the unit optical elements 52 and the normal direction nd to the sheet surface of the protective sheet 50 (hereinafter referred to as a main cut surface). Each unit optical element 52 has a triangular shape on the main cutting plane. In particular, in the illustrated example, the cross-sectional shape of the unit optical element 52 at the main cut surface is an isosceles triangle that is arranged symmetrically about the normal direction to the film surface of the protective sheet 50. The angle θa (see FIG. 13) of the isosceles triangle shape can be set to, for example, 30 ° or more and 70 ° or less in consideration of the light collecting function.

  In the light diffusing film 60 that forms the protective sheet 50 shown in FIG. 12, the diffusing component 60b is arranged to be biased in the thickness direction. That is, the light diffusion film 60 that forms the protective sheet 50 includes a light diffusion layer 59a that includes the binder resin portion 60a and the diffusion component 60b, and a resin layer 59b that does not include the diffusion component 60b. In the illustrated example, the resin layer 59b is disposed on the light incident side with respect to the light diffusion layer 59a. That is, the light diffusion layer 59a is disposed closer to the polarizer 41 than the resin layer 59b. The resin layer 59 b constitutes the unit optical element 52 described above and the light incident side portion of the main body 51. On the other hand, the light diffusing layer 59a constitutes a light output side portion of the main body 51 adjacent to the resin layer 59b.

  The light diffusing film 60 forming such a protective sheet 50 can be manufactured by extruding two layers of the light diffusing layer 59a and the resin layer 59b by coextrusion molding, and further shaping the unit optical element 52 at the time of molding. . In the protective sheet 50 (light diffusion film 60) produced by such a manufacturing method, there is no optical interface between the binder portion 60a of the light diffusion layer 59a and the resin layer 59b. That is, light enters the protective sheet 50 (light diffusion film 60) from the resin layer 59b to the light diffusion layer 59a without being optically affected.

  The protective sheet 50 made of the light diffusing film 60 shown in FIG. 12 can exhibit not only the light diffusing function in the light diffusing layer 59a but also the light collecting function due to the unit optical element 52 of the resin layer 59b. FIG. 13 shows an example of how the protective sheet 50 (light diffusion film 60) that is expected to have a light collecting function is used. As shown in FIG. 13, the unit optical elements 52 of the protective sheet 50 (light diffusion film 60) are arranged so that the longitudinal direction thereof is parallel to the longitudinal direction of the linear light emitting body 26 forming the light source 25. Has been. And the light which goes to a liquid crystal display panel along the direction largely inclined from the front direction nd injects into the protective sheet 50 through one surface 52b1 of the unit optical element 52, and then the other surface 52b2 of the unit prism 52. And the traveling direction is deflected to the front direction nd side. In this way, the protective sheet 50 can exhibit a light collecting function.

  In addition, the cross-sectional shape in the main cut surface of the unit optical element 52 is not limited to a triangular shape, and can be appropriately designed in various shapes. For example, the top of the triangular shape that forms the cross-sectional shape of the unit optical element 52 on the main cut surface of the protective sheet 50 may be chamfered. In addition, on the main cut surface of the protective sheet, two triangular sides extending from the main body 51 may be deformed so as to form a curved bulge outward (not shown).

  Furthermore, as shown in FIG. 14, the unit optical element 52 may have a curved outer contour on the main cut surface of the protective sheet 50. That is, the light incident surface of the unit optical element 52 may be configured as a curved surface. As an example of a specific shape, the unit optical element 52 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 sheet 50. You may do it. Furthermore, as shown in FIG. 15, the unit optical element 52 may have a shape obtained by removing the triangular top of the main cutting surface described above on the main cutting surface of the protective sheet 50. As an example of a specific shape, the unit optical element 52 may have an isosceles trapezoidal shape as shown in FIG. 15 on the main cut surface of the protective sheet 50, or alternatively, the isosceles trapezoidal shape. You may make it have the shape formed by changing an upper base into a curve. 14 and 15 can be prepared as an extrusion molding material in the same manner as the light diffusion film shown in FIG. However, in the example of the light diffusing film 60 shown in FIGS. 14 and 15, unlike the light diffusing film shown in FIG. 12, the diffusing component 60b is dispersed throughout the thickness direction, and the light diffusing layer 59a. It does not include the above-described resin layer 59b.

  Furthermore, in the above-described embodiment, the example in which the light diffusion film 60 is made of an extruded material obtained by extrusion molding has been shown, but the present invention is not limited thereto. The light diffusion film 60 manufactured by other manufacturing methods such as injection molding can also be used.

  Furthermore, in embodiment mentioned above, although the protective sheet 50 showed only the example which consists of the light-diffusion film 60 obtained by extrusion molding, it is not restricted to this. For example, the protective sheet 50 is a polarization separation film having a function of transmitting a specific polarization component and reflecting other polarization components to return to the light source side, and is disposed on the light output side of the light diffusion film 60. You may make it have further the polarization separation film. According to this example, by providing the polarization separation film, 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 change the polarization state by subsequent reflection and diffusion, and can enter the polarization separation film again. “DBEF” (registered trademark) available from 3M USA can be used as a polarized light separation film 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 polarization separation film.

  As another example, the protective sheet 50 further includes a simple resin film disposed on the light output side of the light diffusion film 60, for example, a triacetyl cellulose film (TAC film) having a pair of parallel main surfaces. You may do it.

  Furthermore, in embodiment mentioned above, although the protective sheet 50 (light-diffusion film 60) showed the example joined to the polarizer 41 by water sticking, it is not restricted to this. For example, an adhesive layer containing an adhesive and a diffusion component dispersed in the adhesive may be disposed between the protective sheet 50 and the polarizer 41. According to this aspect, the degree of the light diffusion function by the adhesive layer can be appropriately adjusted independently of the degree of the light diffusion function caused by the light diffusion film 60 included in the protective sheet 50. 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 60b which can be contained in the protective sheet 50 (light diffusion film 60) can be similarly used for the diffusion component contained in the adhesive layer. Further, the degree of the light diffusion function by the adhesive layer can be appropriately adjusted by the same method as the degree of the light diffusion function in the protective sheet 50 (light diffusion film 60). The light diffusion function of the adhesive layer may be isotropic, or may be anisotropic as described below, for example. Further, the adhesive layer may not have a light diffusion function.

  Furthermore, the light diffusing function of the light diffusing film 60 forming the protective sheet 50 in the above-described embodiment may be an isotropic light diffusing function or an anisotropic light diffusing function. As an example, as shown in FIG. 16, a diffusion component 60b having a longitudinal direction ld has an orientation in a predetermined direction od, and is disposed in the light diffusion film 60, whereby an anisotropic light diffusion function is achieved. It can be applied to the diffusion film 60. Here, the longitudinal direction of the diffusion component 60b can be specified as the direction in which the target diffusion component 60b has the longest length. Also, “the diffusion component 60b 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 60b with respect to the predetermined direction od is 0 ° or more and 45 This means that the diffusion component 60b is arranged with directional regularity with reference to the predetermined direction od.

  Note that the light diffusion film 60 shown in FIG. 16 can be manufactured by extrusion molding using a diffusion component 60b having a longitudinal direction as a raw material together with a resin material that forms the binder portion 60a. The diffusion component 60b having the longitudinal direction is directed so that the longitudinal direction ld is along the extrusion direction (machine direction) under high pressure when passing through the die of the extruder together with the resin material. Thereby, the diffusion component 60b in the extruded material is dispersed in the light diffusion film 60 so as to have an orientation in a specific direction od.

  As the shape of the diffusion component 60b 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 60b along the longitudinal direction ld to the length of the diffusion component 60b along the direction orthogonal to the longitudinal direction ld) is And bubbles having an average particle size (particle size calculated by the volume equivalent method, that is, the arithmetic average of the volume equivalent diameter, the same applies hereinafter) of the diffusion component 60b of 0.5 μm or more and 100 μm or less. The diffusion component 60b having the longitudinal direction ld can be used. Moreover, the diffusion component 60b which consists of heat resistant organic fibers, such as the diffusion component 60b 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 60b which consists of inorganic fillers, for example, the diffusion component 60b which consists of fibrous fillers, such as glass fiber, a silica fiber, an alumina fiber, a zirconia fiber, can also be used. Further, a diffusion component 60b made of a thin plate filler (mica) can also be used. Further, a diffusing component 60b made of an amorphous filler, for example, a diffusing component 60b made of an inorganic white pigment such as silica, calcium carbonate, magnesium hydroxide, clay, talc, or titanium dioxide can also be used.

  The diffusion component 60b having the longitudinal direction ld exhibits a stronger light diffusion function in a direction orthogonal to the longitudinal direction than in a direction parallel to the longitudinal direction. For example, in the above-described embodiment, the light source 25 is composed of a single linear light emitter 26 having a longitudinal direction. Therefore, in the above-described embodiment, it is preferable to mainly diffuse the light component along the direction orthogonal to the longitudinal direction of the linear light emitter 26. From this point, it is preferable that the orientation direction od of the diffusion component 60b having the longitudinal direction ld is parallel to the longitudinal direction of the linear light emitter 26. As a result, it is possible to effectively prevent the light incident on the protective sheet 50 from being diffused more than necessary, and to further effectively use the light.

  Furthermore, in the above-described embodiment, the example in which the lower polarizing plate 40 includes the polarizer 41 and the protective sheet 50 bonded to the polarizer 41 from the light incident side has been described. A protective sheet made of, for example, a TAC film 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 sheet on the light output side of the lower polarizing plate 40 is You may make it also serve as the protective sheet of the light-incidence side of a phase difference plate.

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

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 40b Light incident side surface 41 Polarizer 50 Protective sheet, optical sheet 50a Light emission side surface 50b Light incident side surface 51 Main body portion 52 Unit Optical element, unit shape element, unit lens, unit prism 59a Light diffusion layer 59b Resin layer 60 Light diffusion film 60a Binder part, base material part, main part 60b Diffusion component, diffusion particle

As a result of intensive research, the inventors of the present invention include a light diffusing film with little light loss in the protective sheet for the polarizing plate, and eliminates the conventional optical sheet to face the polarizing plate at the position facing the polarizing plate. By arranging this, it was possible to ensure sufficient optical characteristics as a display device. In particular, in this apparatus, the utilization efficiency of the light source light is greatly improved. For example, by adjusting the optical characteristics of the light diffusion film, the relative arrangement position of the light source and the polarizing plate, etc. It is also possible to form a light source only with a light emitter. The present invention is based on such knowledge of the present inventors.

In addition, in the light diffusion film 60 forming the protective sheet 50, the refractive index of the diffusing component 60b is lower than the refractive index of the binder part 60a. Total reflection may occur at the interface between the diffusion component 60b and the binder portion 60a in the light diffusion film 60. In particular, when the refractive index difference between the diffusing component 60b and the binder part 60a is 0.10 or more, more preferably 0.14 or more, a very effective total reflection phenomenon can occur. Such total reflection does not cause a reflection loss unlike reflection at an interface having a simple refractive index difference or reflection caused solely by the reflectivity of the surface of the diffusion component. That is, the amount of light lost due to the light diffusing action in the light diffusing film 60 can be reduced extremely effectively. Although there is no theoretical upper limit for the refractive index difference, there is a limit to the range of the refractive index of materials that can be obtained and used practically, and if the refractive index difference is increased to some extent in practice, the total reflectivity may also be reduced. In order to saturate, it is sufficient that the difference in refractive index is at most about 0.5.

Claims (4)

A polarizing plate having a polarizer and a protective sheet bonded to the polarizer;
A light source including a light emitter disposed at a position facing the protective sheet of the polarizing plate,
The protective sheet includes an optical joule that includes a light diffusion film having a binder portion and a diffusion component dispersed in the binder portion, and the refractive index of the diffusion component is lower than the refractive index of the binder portion.   The optical module according to claim 1, wherein the light source includes only one light emitter that extends linearly.   A display device comprising the optical module according to claim 1. A binder part;
A diffusion component dispersed in the binder part,
The light diffusion film, wherein the diffusion component has a refractive index lower than that of the binder portion.

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