JP2010039236A - Optical regulation member, lighting system, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical regulation member, a lighting system, and a liquid crystal display, solving a problem wherein a bright line is generated and a problem wherein a brightness is not enough. <P>SOLUTION: This optical regulation member is provided with: a base material of a transparent sheet-like base material of emitting a light incident from one face, from the other face; an optical structure formed on the other face of the base material, and for regulating a light characteristic; a transparent binder applied onto the one face of the based material; and a plurality of non-translucent granular materials dispersed at a prescribed density in the binder, and the problem to be solved hereinbefore is solved by providing the optical regulation member having a diameter of the granular material larger than a thickness of the binder. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical adjustment member that suppresses generation of bright lines, and an illumination device and a liquid crystal display device including the same.

  Optical adjustment members such as light directivity control sheets (light-transmitting sheets for light directivity control) that align light beams with a certain extent in a certain direction are used in display fields such as liquid crystal displays and optical communication fields. It has been. The light directivity control sheet is an optical adjustment member having a function of aligning incident light in a predetermined direction by providing a predetermined optical structure on or in a transparent sheet member, for example, a prism. Sheets, lens sheets and the like are typical products.

  These optical adjustment members are also used in illumination devices such as a backlight unit of a liquid crystal display, for example. By using the optical adjustment sheet for the backlight unit of the liquid crystal display, optical characteristics such as the spread and brightness of light from the light source can be adjusted, and the light from the light source can be efficiently guided to the liquid crystal display surface. In this case, the optical adjustment member is generally disposed directly on the light guide plate that guides the light from the light source to the lower side of the liquid crystal display surface or on the diffusion plate that diffuses the light from the light source.

  In general, the surfaces of the light guide plate and the diffusion plate are relatively flat surfaces, uneven surface having a gentle step, or a surface on which substantially parallel striped unevenness is formed. When the optical adjustment member is installed on such a surface, it is known that bright portions and dark portions, that is, luminance spots are generated on the light emission surface of the optical adjustment member. Such luminance spots are caused, for example, by interference between light that travels straight through the interface between the light guide plate or diffusion plate and the optical adjustment member, and light that is multiple-reflected on the surface of the light guide plate or diffusion plate and the surface of the optical adjustment member. This is due to interference fringes (so-called Newton rings).

  In order to prevent the occurrence of such interference fringes, in the lens sheet 500 described in Patent Document 1, as shown in FIG. 15, a surface (back surface) 500b opposite to the lens surface 500a on which the lens 501 is disposed is provided. A large number of micro hill-like projections 503 having a projection height of 1 to 7 μm are formed on the coating layer 502 to be covered. The micro hill-like protrusions 503 are formed of a light-transmitting material (light-transmitting beads) 504 arranged in a dispersed manner in the coating layer 502. With such a small hill-shaped projection 503, a gap 511 of 1 to 7 μm is formed between the back surface 500b of the lens sheet 500 and the smooth surface 510a of the light guide plate 510 adjacent thereto. As a result, the distance between the back surface 500a of the lens sheet 500 and the smooth surface 510a of the light guide plate 510 can be increased to such an extent that no interference occurs between the straight traveling light and the reflected light. Can be suppressed.

  Moreover, in the display apparatus of patent document 2, providing transparent convex dots on the lower surface of the translucent film arrange | positioned on a light-guide plate is disclosed. Providing convex dots to form a gap between the translucent film and the light guide plate to prevent the occurrence of interference fringes, and the convex dots have the effect of taking in light from the light guide plate. (Increased brightness) is realized.

Japanese Patent Laid-Open No. 10-300908 JP-A-6-102506

  The inventors of the present invention, for example, in the case of an optical adjustment member (optical adjustment sheet) in which the generation of interference fringes is suppressed, such as the lens sheet described in Patent Document 1, has a bright spot, a linear shape, or a strip shape. It has been found that bright lines (hereinafter, bright spots and bright lines are simply called bright lines) are generated. According to the knowledge of the inventors, the bright line is considered to be generated by the following mechanism. In the lens sheet 500 described in Patent Document 1, a gap is formed between the light guide plate 510 and the lens 501. Therefore, in the light guide plate 510, light travels while being totally reflected at the interface between the smooth surface 510a of the light guide plate 510 and the air. Some light enters the interface at an angle outside the total reflection condition, and is extracted from the smooth surface 510a of the light guide plate 510 toward the lens 501 side. Here, since the refractive index does not change significantly at the interface between the smooth surface 510a of the light guide plate 510 and the micro hill-like protrusion 503, total reflection does not occur, and the light enters the micro hill-like protrusion 503 side. It is refracted and taken out. Thus, in the smooth surface 510a of the light guide plate 510, the ratio of the light extracted from the light guide plate 510 is higher at the interface with the minute hill-shaped protrusion 503 than at the interface with air. It is considered that the light extracted through the small hill-like projection 503 generates a bright line. Furthermore, the present inventors have found that very strong emission lines are produced when used in combination with a light source having high directivity as described later. Even when not combined with a light source with high directivity, when an optical adjustment member such as a lens sheet described in Patent Document 1 is used for a liquid crystal display, when the screen is pressed with a finger, etc. Also found that a similar strong emission line occurs.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical adjustment member capable of suppressing the generation of bright lines, and an illumination device and a liquid crystal display device including such an optical adjustment member. It is to be.

  According to the first aspect of the present invention, an optical adjustment member, which is a transparent plate-like base material that emits light incident from one surface from the other surface, and the base material An optical structure that adjusts light characteristics formed on the other surface, a transparent binder applied to the one surface of the base material, and a non-light-transmitting material dispersed at a predetermined density in the binder There is provided an optical adjusting member including a plurality of granular bodies having a diameter larger than that of the binder.

  According to the optical adjustment member of the present invention, the light incident from the surface of the substrate on which the binder is applied is adjusted in the traveling direction in the optical structure. In addition, a plurality of non-translucent particles are dispersed and arranged in the binder. Since the diameter of the granular material is larger than the thickness of the binder, the surface of the binder and the surface of the other optical member are in direct contact with each other when the optical adjustment member of the present invention is placed on another optical member. There is no. That is, the optical adjustment member makes point contact with other optical members via the granular material. Therefore, it is possible to suppress the occurrence of luminance spots such as interference fringes that occur when the surface of the optical adjustment member and the surface of another optical member are in surface contact. Furthermore, since the granular material is non-translucent, the light that passes through the granular material and directly enters the optical adjustment member from other optical members can be reduced. Therefore, it is possible to suppress the generation of bright lines from other optical members due to light that passes through the granular material and directly enters the optical adjustment member.

  In the present application, being non-translucent means that the transmissivity is approximately 20% or less, and that the diameter of the granular material is larger than the thickness of the binder, the diameter of the granular material is substantially equal. It is larger than the thickness of the binder. For example, when the optical adjustment member of the present invention is placed on another flat plate-like optical member, the surface of the binder is more granular than the thickness of the binder so that it does not directly contact the surface of the plate-like optical member. The body diameter is sufficiently large.

  In the optical adjustment member of the present invention, the optical structure may include a plurality of triangular prisms. In this case, the traveling direction of light can be adjusted by the prism effect of the prism-like optical structure.

  In the optical adjustment member of the present invention, the optical structure may extend in a predetermined extending direction, and a cross section of the optical structure perpendicular to the extending direction may be substantially triangular. Of the three sides formed, one side may be in contact with the base material in parallel and one of the other two sides may be stepped. In this case, chromatic dispersion of the light emitted from the optical adjustment member can be suppressed by the chromatic dispersion suppressing effect of the step-like optical structure, and at the same time, the progression of light can be achieved by the prism effect of the optical structure. The direction can be adjusted.

  In the optical adjustment member of the present invention, the granular material may be formed of a member selected from the group consisting of black beads, white beads, and high reflectance metal particles, and the black beads are acrylic containing carbon black. The white beads may be acrylic beads containing titanium oxide fine particles, and the high reflectance metal particles may be silver particles. In this case, the light transmittance of the granular material can be suppressed to approximately 20% or less (17% or less).

  In the optical adjustment member of the present invention, the light transmittance of the granular material may be 17% or less. In this case, since the light transmittance of the granular material is sufficiently low, generation of bright lines can be suppressed. The diameter of the granular material may be 2 μm or more and 40 μm or less, and the average protrusion height of the granular material from the surface of the binder may be 1.8 μm or more and less than 14.4 μm. In this case, since the average protrusion height is sufficiently high, it is effective that the surface of the optical adjustment member and the surface of the other optical member are in direct surface contact when the optical adjustment sheet is disposed on the other optical member. Can be prevented.

  In the optical adjustment member of the present invention, the granular material may be dispersed in the binder at a density of 1% by volume or less. In this case, since the granular material is sufficiently sparsely dispersed in the binder, the amount of light blocked by the granular material among the light incident on the optical adjustment member can be suppressed.

  According to the second aspect of the present invention, the illumination device is a light source, a plate-like optical member optically connected to the light source, and a light emitting surface that emits light incident from the light source. There is provided an illuminating device comprising: a plate-like optical member having the optical adjustment member according to the first aspect of the present invention optically connected to the light emitting surface of the plate-like optical member.

  According to a third aspect of the present invention, there is provided a liquid crystal display device, the lighting device according to the second aspect of the present invention, a first polarizing element disposed opposite to the optical adjustment member, and a liquid crystal layer And a second polarizing element, and a liquid crystal display device including these liquid crystal display elements stacked in this order is provided.

  According to the illumination device and the liquid crystal display device of the present invention, since the optical adjustment member according to the present invention is provided, it is possible to realize a high-luminance illumination device and a liquid crystal display device while suppressing generation of luminance spots and bright lines. In addition, as a plate-shaped optical member, a diffuser plate and a light guide plate can be used, for example. By arranging the light source on the lower surface of the diffuser plate, the light incident from the lower surface can be diffused in the surface direction and extracted from the upper surface with a substantially uniform intensity distribution. The illumination device (liquid crystal display device) of the present invention includes a direct illumination device (liquid crystal display device) having a diffusion plate and a light source provided on the lower surface of the diffusion plate. In addition, by arranging a light source on the side surface of the light guide plate, light incident from the side surface can be extracted from the upper surface. At this time, by devising the shape of the lower surface of the light guide plate, light having high directivity in a predetermined direction can be extracted from the upper surface. The illumination device (liquid crystal display device) of the present invention also includes an edge light (side light) type illumination device (liquid crystal display device) having a light guide plate and a light source provided on a side surface of the light guide plate.

  In the illumination device of the present invention, the plate-like optical member may be a light guide plate that emits light having directivity in a predetermined direction from the light emitting surface, and the light source is optically provided on a side surface of the light guide plate. It may be connected to. In this case, it is possible to realize an illuminating device having high front luminance and suppressing generation of luminance spots and bright lines even with edge-light illumination.

  According to the illumination device and the liquid crystal display device of the present invention, since the optical adjustment member of the present invention is provided, the illumination device and the liquid crystal display device are thin while solving the problems of luminance spots and bright lines and insufficient luminance. And cost reduction can be achieved.

  Hereinafter, as an embodiment of the present invention, an optical adjustment sheet (optical sheet) as an example of an optical adjustment member according to the present invention and an illuminating device using the same will be described with reference to the drawings.

  The schematic block diagram of the illuminating device 1 of Example 1 is shown in FIG. The illuminating device 1 includes a light guide plate 5 as a plate-like optical member, an illumination unit 10 attached to a side surface 5d of the light guide plate 5, and an upper surface 5b of the light guide plate 5 (upper surface in FIG. 1, light emission surface). The optical adjustment sheet (optical adjustment member) 20 is disposed.

  The illumination unit 10 includes a high-intensity LED light source 7 and a reflector 6 provided to cover the rear side of the LED light source 7 (the side opposite to the light emission direction of the illumination unit 10). Since the illumination unit 10 includes the reflector 6, it is possible to efficiently emit light from the front by reflecting the light emitted backward from the light emitted from the LED light source 7. The light exit surface of the illumination unit 10 is optically connected to the side surface 5 d of the light guide plate 5. In addition, the light source with the high directivity mentioned later is implement | achieved by combining the illumination unit 10 and the light-guide plate 5. FIG.

  The light guide plate 5 is, for example, a transparent plate-like optical member made of acrylic resin, and has a thickness of 0.1 to 3 mm. The upper surface (light emission surface) 5b of the light guide plate 5 is a flat surface, but a plurality of minute irregularities having a predetermined shape (not shown) are formed on the lower surface 5c. Thereby, as will be described later, a part of the light L traveling inside the light guide plate 5 while repeating total reflection on the upper surface 5b and the lower surface 5c of the light guide plate 5 is scattered by the unevenness of the lower surface 5c and extracted from the upper surface 5b. .

  The optical adjustment sheet 20 disposed on the upper surface 5b of the light guide plate 5 includes a PET base material (PET film) 21 having a thickness of 50 μm, and a lower surface 21b of the base material 21 (a surface facing the light guide plate 5, a light incident surface). ) And a black bead 22 arranged in a dispersed manner in the binder 23. As shown in FIG. 2, a plurality of linear optical structures 25 are arranged at a predetermined pitch P (about 35 μm) on the upper surface (light emitting surface) 21 a of the substrate 21. Each linear optical structure 25 is a triangular prism having a cross section perpendicular to the extending direction, an isosceles triangle having an apex angle θ of 42 ° and a height of about 45.6 μm, and is perpendicular to the plane of FIG. It extends to. The linear optical structure 25 is formed by a 2P (Photo Polymerization) method using a photocurable acrylic resin (refractive index of 1.60 after curing). A binder 23 in which black beads 22 are dispersed is applied to the lower surface 21 b of the substrate 21. Here, the diameter of the black beads 22 is about 4 μm and is dispersed in the binder 23 at a rate of 1% by volume. Since the thickness of the binder 23 is about 2 μm, a part of the black beads 22 protrudes from the surface of the binder 23. The degree to which the black beads 22 dispersedly arranged in the binder 23 protrude from the binder 23 is represented by the average protrusion height. Here, the average protrusion height is an amount defined by the average distance from the tip of the bead to the flat portion of the surface of the binder 23, as shown in FIGS. 3 (a) and 3 (b). In the optical adjustment sheet 20 of the present embodiment, the average protrusion height was 1.8 μm when measured using a laser microscope. In addition, protrusion height was measured about 10 beads selected arbitrarily, and average protrusion height was obtained by averaging them.

  The material and optical characteristics of the black beads 22 will be described in more detail. The black beads 22 of this embodiment are formed of acrylic beads containing carbon black. The light transmittance of the black beads 22 is 8%. The light transmittance of the black beads 22 was measured as follows. First, a transparent optical material having the same refractive index as that of acrylic forming the black beads 22 and the black beads 22 were mixed at a volume ratio of 1: 1. Next, a mixture of the optical material and black beads was molded into a plate having a thickness of about 1 mm to produce an optical sample. The transmittance of the optical sample thus produced was measured with a spectrophotometer to obtain the transmittance of the black beads 22. In the present application, the “black beads” refer to granular materials that reduce light transmission mainly by absorbing light. The “black beads” of the present application typically include acrylic beads containing carbon black, such as the black beads 22 of the present embodiment, but the “black beads” of the present application are not limited thereto. .

  The progress of light in the illumination device 1 having the above-described structure will be described. As shown in FIG. 2, the light L emitted from the LED light source 7 enters the side surface 5 d of the light guide plate 5 from the light exit surface of the illumination unit 10 and proceeds to the inside of the light guide plate 5. As shown in FIG. 4, the light incident on the inside of the light guide plate 5 from the side surface 5d of the light guide plate 5 is totally reflected by the upper surface (light emitting surface) 5b and the lower surface 5c and spreads in the surface direction of the light guide plate 5. To go. Here, an air layer is interposed between the upper surface 5 b of the light guide plate 5 and the surface of the binder 23 of the optical adjustment sheet 20. Since the refractive index differs greatly at the interface between the upper surface 5b of the light guide plate 5 and the air, all the light traveling from the inside of the light guide plate 5 toward the upper surface 5b of the light guide plate 5 at a predetermined incident angle satisfying the total reflection condition. Reflected. As described above, since minute irregularities having a predetermined shape are formed on the lower surface 5 b of the light guide plate 5, a part of the light is scattered on the lower surface 5 c of the light guide plate 5. Part of the light incident on the upper surface 5b of the light guide plate 5 at an angle outside the total reflection condition is extracted from the upper surface 5b of the light guide plate 5 toward the air layer. The light extracted from the upper surface 5 b of the light guide plate 5 enters the lower surface 21 b of the base material 21 of the optical adjustment sheet 20 through the binder 23. Since the above-described linear optical structure 25 is formed on the base material 21 of the optical adjustment sheet 20, the light passing through this is bent upward and emitted from the optical adjustment sheet 20 (prism effect). .

  In addition, on the lower surface 5c of the light guide plate 5, light is not scattered in a random direction but strongly scattered in a predetermined direction. Therefore, the light extracted from the upper surface 5b of the light guide plate 5 has a strong luminance peak in a predetermined direction (luminance peak light beam). That is, the light extracted from the upper surface (light emitting surface) 5b of the light guide plate 5 has a strong directivity.

  FIG. 5 shows a graph in which the angular distribution of light intensity is plotted for two light sources (first light source and second light source) in which the illumination unit 10 and the light guide plate 5 are combined in the illumination device 1 of the present embodiment. . According to the graph of FIG. 5, the half-value widths of the intensity distributions of the light extracted from the first and second light sources are 25.7 ° and 23.1 °, respectively. Compared with relatively strong directivity.

  The optical adjustment sheet 20 is disposed on the upper surface 5b of the light guide plate 5 of such a light source having strong directivity. Here, the lower surface 21 b of the base material 21 of the optical adjustment sheet 20 is disposed so as to face the upper surface 5 b of the light guide plate 5. As described above, the binder 23 in which the black beads 22 are dispersed is applied to the lower surface 21 b of the base 21 of the optical adjustment sheet 20. Since the diameter of the black beads 22 is larger than the thickness of the binder 23, the optical adjustment sheet 20 makes point contact with the upper surface 5 b of the light guide plate 5 through the black beads 22 protruding from the binder 23. That is, when the optical adjustment sheet 20 is arranged on the upper surface 5 b of the light guide plate 5, the surface of the binder 23 applied to the lower surface 21 b of the base 21 of the optical adjustment sheet 20 and the upper surface 5 b of the light guide plate 5 are between. A predetermined gap is formed. As described above, since the upper surface 5b of the light guide plate 5 and the surface of the binder 23 are not in surface contact, no luminance spots are generated on the light emitting surface of the optical adjustment sheet 20 (the upper surface 21a of the base material 21).

  Further, the optical adjustment sheet 20 and the light guide plate 5 are in point contact via the black beads 22. Here, since the light transmittance of the black beads 22 is very low (the light transmittance is about 8%), the amount of light transmitted from the light guide plate 5 through the black beads 22 and incident on the optical adjustment sheet 20 is Compared with the case where the optical adjustment sheet 20F and the light guide plate 5 are brought into contact with each other through transparent beads 22F (light transmittance is about 92%) as will be described later, the number is significantly reduced. Therefore, when the optical adjustment sheet 20F and the light guide plate 5 are in point contact via the transparent beads 22F, bright lines (bright spots) resulting from the light transmitted through the transparent beads 22F can be visually confirmed. Such a bright line was not confirmed in the light source unit of this example. In addition, luminance spots generated when the light guide plate 5 and the optical adjustment sheet 20 are brought into surface contact were not visually confirmed.

  Most of the light that comes out of the light guide plate 5 and enters the black beads 22 is absorbed by the black beads 22 and cannot pass through the black beads 22. Therefore, when the content of the black beads 22 contained in the binder 23 increases, the proportion of the light emitted from the light guide plate 5 that is absorbed by the black beads 22 increases, and the amount of light extracted from the optical adjustment sheet 20 is reduced. There is a risk of lowering. In the present embodiment, as described above, the black beads 22 are contained in the binder 23 only by about 1% by volume. That is, the black beads 22 are sparsely dispersed in the binder 23 applied to the lower surface 21 b of the base 21 of the optical adjustment sheet 20. Therefore, the proportion of light emitted from the light guide plate 5 that is absorbed by the black beads 22 is very low, and the amount of light extracted from the optical adjustment sheet 20 does not decrease. In addition, when the front luminance of the illuminating device 1 of the present embodiment was measured, it was compared with the front luminance in the illuminating device in which the light guide plate 5 and the optical adjustment sheet 20 were joined using only the binder 23 (not containing the black beads 22). Thus, it was found that the front brightness was reduced by only 0.5%. Thus, in the illuminating device 1 of the present embodiment, the light guide plate 5 and the optical adjustment sheet 20 are in point contact via the black beads 22. For this reason, luminance unevenness that occurs when the light guide plate 5 and the optical adjustment sheet 20 are brought into surface contact with each other is prevented, and the black beads 22 with low light transmittance are used. Occasionally bright lines can be prevented. Furthermore, by suppressing the ratio of the black beads 22 contained in the binder 23, it was possible to suppress the decrease in the front luminance very low.

  As shown in FIG. 6, the illumination device 1 </ b> A according to the present embodiment uses the optical adjustment sheet 20 </ b> A having a base material 21 having a thickness of 100 μm and uses white beads 22 </ b> A having a diameter of about 40 μm instead of the black beads 22. And having the same configuration as that of the lighting device 1 of Example 1, except that the binder 23 in which the white beads 22A are dispersed is applied with an average thickness of 30 μm. Therefore, the same reference numerals are given to configurations common to the first embodiment, and description thereof is omitted as appropriate.

  In this embodiment, the white beads 22A are used as described above. The white beads 22A of the present embodiment are formed by containing titanium oxide fine particles in acrylic beads and are dispersed in the binder 23 at a density of about 1% by volume. When the transmittance of the white beads 22A was measured by the same measurement method as that described in Example 1, it was 17%. Moreover, it was 9.6 micrometers when the average protrusion height in a present Example was measured using the laser microscope. When the front luminance of the illuminating device 1A of this example was measured, the front luminance was only 1.9% compared to the front luminance in the illuminating device in which the optical adjustment sheet 20A coated only with the binder 23 was disposed on the light guide plate 5. It was found that the brightness did not decrease. Furthermore, also in the illuminating device 1A of a present Example, the brightness spot and the bright line were not confirmed visually.

  As described above, even when the white beads 22A are used in place of the black beads 22, the occurrence of luminance spots and bright lines can be suppressed as in the case where the black beads 22 are used. Furthermore, there was almost no decrease in front luminance.

  In the present application, the “white beads” mean granular materials that reduce light transmittance by diffusing light mainly by irregular reflection and refraction. A typical example of the “white bead” of the present application is an acrylic bead containing titanium oxide fine particles such as the white bead 22A of the present embodiment, but the “white bead” of the present application is not limited to this.

  As shown in FIG. 7, in the illumination device 1B of the present embodiment, the optical adjustment sheet 20B uses silver particles 22B having a diameter of about 10 μm instead of the black beads 22, and a binder 23 in which the silver particles 22B are dispersed. Is applied in an average thickness of 5 μm, and has the same configuration as that of the lighting device 1 of the first embodiment. Therefore, the same reference numerals are given to configurations common to the first embodiment, and description thereof is omitted as appropriate.

  In this embodiment, silver particles 22B are used as described above. The silver particles 22B are dispersed in the binder 23 at a density of about 1% by volume. When the transmittance of the silver particles 22B was measured by the same measurement method as that described in Example 1, it was 7%. When measuring the transmittance, an acrylic resin having a refractive index of 1.6 was used as an optical material mixed with the silver particles 22B. Moreover, it was 4.8 micrometers when the average protrusion height in a present Example was measured using the laser microscope. When the front luminance was measured for the lighting device 1B of this example, the front luminance was only 1.1% compared to the front luminance in the lighting device in which the light guide plate 5 and the optical adjustment sheet 20 were joined using only the binder 23. It was found that the brightness did not decrease. Furthermore, also in the illuminating device 1B of a present Example, the brightness spot and the bright line were not confirmed visually.

  As described above, even when the silver particles 22B are used instead of the black beads 22, the occurrence of luminance spots and bright lines can be suppressed as in the case where the black beads 22 are used. Furthermore, there was almost no decrease in front luminance.

  In addition, the silver particle 22B of a present Example is an example of a "high reflectance metal particle". Here, the “high reflectance metal particle” refers to a metal granule that reduces light transmittance mainly by irregularly reflecting light. The “high reflectivity metal particles” of the present application are not limited to silver particles, and may be fine particles of a metal having a high reflectivity such as gold or aluminum, or an alloy mainly containing these metals.

  Next, in order to compare with the above-described embodiment, a lighting device in which the particle size, density, transmittance, etc. of the beads are changed is prepared. Similar to the above-described embodiment, measurement of front luminance, presence of luminance spots and bright lines are performed. Was confirmed.

[Comparative Example 1]
As shown in FIG. 8, the lighting device 1C of Comparative Example 1 uses white beads 22C having a diameter of about 50 μm instead of the white beads 22A, and an average thickness of the binder 23 in which the white beads 22C are dispersed is 35 μm. It has the same configuration as the illuminating device 1A of the second embodiment except that the coating is applied.

  The composition of the white beads 22C is the same as that of the white beads 22A, and the transmittance thereof is 17%. Further, the white beads 22C are dispersed in the binder 23 at a density of about 1% by volume. When the average protrusion height was measured using a laser microscope, it was 14.4 μm. When the front luminance was measured for the lighting device 1C of Comparative Example 1, the front luminance was 3.6% as compared to the front luminance in the lighting device in which the light guide plate 5 and the optical adjustment sheet 20 were joined using only the binder 23. Was found to have declined. In the lighting device 1C of Comparative Example 1, luminance spots and bright lines were not visually confirmed.

[Comparative Example 2]
As shown in FIG. 9, the lighting device 1D of Comparative Example 2 uses black beads 22D having a diameter of about 2 μm instead of the black beads 22, and an average thickness of the binder 23 in which the black beads 22D are dispersed is 1 μm. It has the same configuration as that of the lighting device 1 of Example 1 except that the coating is applied.

  The composition of the black beads 22D is the same as that of the black beads 22, and the transmittance thereof is 8%. The black beads 22D are dispersed in the binder 23 at a density of about 1% by volume. When the average protrusion height was measured using a laser microscope, it was 0.9 μm. When the front luminance was measured for the lighting device 1D of Comparative Example 2, the front luminance was only 0.1% as compared to the front luminance in the lighting device in which the light guide plate 5 and the optical adjustment sheet 20 were joined using only the binder 23. It was found that was not lowered. However, in the illumination device 1D of Comparative Example 2, generation of bright lines was confirmed visually.

[Comparative Example 3]
As shown in FIG. 10, the lighting device 1E of Comparative Example 3 has the same configuration as the lighting device 1A of Example 2 except that the white beads 22A are dispersed in the binder 23 at a density of 3% by volume. Have

  When the average protrusion height was measured using a laser microscope, it was 9.8 μm. When the front luminance was measured for the lighting device 1E of Comparative Example 3, the front luminance was 5.3% as compared with the front luminance in the lighting device in which the light guide plate 5 and the optical adjustment sheet 20 were joined using only the binder 23. It turned out that it has fallen. In addition, in the illuminating device 1E of Comparative Example 3, luminance spots and bright lines were not visually confirmed.

[Comparative Example 4]
As shown in FIG. 11, the illumination device 1F of Comparative Example 4 has the same configuration as that of the illumination device 1 of Example 1 except that the transparent beads 22F having a diameter of about 4 μm are used instead of the black beads 22. Have

  The transparent beads 22F were formed of a transparent acrylic resin, and the transmittance was measured by the same measurement method as that described in Example 1, and found to be 92%. Moreover, it was 1.7 micrometers when the average protrusion height was measured using the laser microscope. When the front luminance was measured for the lighting device 1F of Comparative Example 4, the front luminance was only 0.2% as compared to the front luminance in the lighting device in which the light guide plate 5 and the optical adjustment sheet 20 were joined using only the binder 23. It was found that was not lowered. However, in the illuminating device 1F of the comparative example 4, generation | occurence | production of the bright line was confirmed visually.

  Examples 1 to 3 and Comparative Examples 1 to 4 described above are summarized in Table 1.

  In Examples 1 to 3, black beads, white beads, and silver particles as high-reflectance metal particles are used, but in any case, generation of bright lines can be suppressed and front luminance is reduced. Can be suppressed. Here, the non-transmittance of light can be considered as the sum of reflectance and absorptance. From such an optical viewpoint, black beads, white beads, and high reflectance metal particles (silver particles) can be considered as optical materials having different ratios of light reflectance and absorptance. In other words, the black beads are optical materials whose light absorption rate is significantly larger than the reflectance, and the white beads are optical materials whose light reflectance is significantly larger than the absorption rate. Further, the high reflectance metal particles (silver particles) are optical materials having a light absorption rate of almost zero and a reflectance of about 1. Thus, from the viewpoints of light reflectance and absorptance, the three types of beads used in Examples 1 to 3 described above have different characteristics from each other, but the light transmittance is low (non-transmissivity). Is common). That is, it can be seen that the beads to be used should have a high non-transmittance, regardless of whether the light reflectance or absorption is high. As in Comparative Example 4, when transparent beads having a high light transmittance are used, the amount of light transmitted through the transparent beads and incident on the optical adjustment sheet increases. It is thought to occur.

  When beads having a large particle diameter are used as in Comparative Example 1, it is considered that the light blocks the progress of light and the front luminance is lowered. On the other hand, when beads having a small particle diameter are used as in Comparative Example 2, the average protrusion height becomes small, and contact between the optical adjustment sheet and the light guide plate cannot be prevented, and bright lines are generated. Could not be suppressed. The average particle diameter of the measured black beads was about 2 μm, whereas the thickness of the binder was about 1 μm, and the average protrusion height was 0.9 μm. However, since the average protrusion height is 1 μm or less and very small, it is considered that a part of the binder actually touched the surface of the light guide plate. Moreover, in the comparative example 3, since the density of the beads dispersed in the binder is too high, the beads block the progress of light, and the front luminance is lowered.

  From the above, it is desirable that the light transmittance of the beads is low (17% or less, that is, about 20% or less), and the average particle diameter (diameter) of the beads is desirably about 4 to 40 μm, The beads are preferably dispersed in the binder at a density of less than 3% by volume. Further, it is desirable that the average particle diameter of the beads is sufficiently larger than the thickness of the binder. Considering the measurement results of Example 1 and Comparative Example 2, it is desirable that the average particle size of the beads is about 2 μm or more larger than the thickness of the binder.

  In the above examples, a polyethylene terephthalate (PET) sheet was used as a base material for the light guide plate and the optical adjustment sheet. The thickness of the light guide plate and the substrate is preferably in the range of 10 to 500 μm in consideration of the ease of processing of the light guide plate and the optical adjustment sheet, handling properties, and the like. Moreover, as a material for forming the base material of the light guide plate and the optical adjustment sheet, besides PET, polyethylene, polyethylene naphthalate, polystyrene, polycarbonate (PC), polyphenylene sulfide, polyolefin, polypropylene, cellulose acetate, acrylic resin, Any light-transmitting material such as an inorganic transparent substance such as glass can be used. In addition, as in the above-described embodiment, a plurality of linear optical structures are formed on the upper surface of the base material, but these linear optical structures may be formed integrally with the base material. In addition, a plurality of optical structures may be optically connected on a plate-like substrate.

  Further, in the above embodiment, granular materials such as black beads, white beads, and silver particles are dispersed in the binder. However, the present invention is not limited to this, and any material and shape can be used as long as the light transmittance is low. Can be used. As described above, it is sufficient that the light transmittance is about 20% or less. For example, metal particles, oxide particles, nitride particles, colored beads, and the like can be used.

  Further, the number and arrangement of the linear optical structures can be arbitrarily set. In addition, not only the linear optical structure long in one direction but any optical structure can be used. The shape of the optical structure is not limited to a triangular prism shape, and may be arbitrary. For example, a polygonal prism shape, a hemispherical or semi-elliptical spherical lens body, or a semi-cylindrical lenticular land may be used. Further, it may be a microlens array provided with a plurality of microlenses, or a diffusion sheet provided with a diffusion material.

  Alternatively, as shown in FIG. 12, a step-like linear optical structure 124 may be provided on the base material 120. The cross section perpendicular to the extending direction of the linear optical structure 124 includes a first cross section 121a and two second cross sections 122a and 123a having different shapes provided on one side of the first cross section 121a. Is done. Here, in the second cross section 123a located on the apex angle 121e side of the first cross section 121a, the surface of the linear optical structure 124 (second linear prism section) including the inclined side 123c is mainly formed. The surface that refracts the traveling direction of the incident light beam in the thickness direction of the optical adjustment sheet, that is, the surface that condenses the incident light beam (light condensing surface). On the other hand, of the inclined side 123d including the two sides 123f and 123g, the surface of the linear optical structure 124 including the side 123g mainly serves to suppress the color separation of the emitted light from the optical adjustment sheet. (Correction surface). In the other second cross-sectional portion 122a, the surface of the linear optical structure 124 (second linear prism portion) including the inclined side 122c serves as a condensing surface, while the linear optical structure including the side 122d. The surface of the body 124 mainly serves as a surface (correction surface) that acts to suppress color separation of the emitted light from the optical adjustment sheet. As shown in FIG. 13, since the light extracted from the light collecting surface and the light extracted from the correction surface are in the direction of color separation, the color separation can be suppressed by combining these lights. it can.

  In addition, the illuminating device and optical adjustment sheet which concern on the above-mentioned Example can be used for arbitrary uses. For example, as illustrated in FIG. 14, the liquid crystal display device 110 includes a liquid crystal display panel 107 (liquid crystal display element) and the lighting device 1 described above. The liquid crystal display panel 107 includes a first polarizing plate 107a, a glass substrate 107b, a first transparent conductive film 107c forming a pixel electrode, a first alignment film 107d, a liquid crystal layer 107e, a second alignment film 107f, and a counter electrode. A transparent conductive film 107g, a color filter 107h, a glass substrate 107i, and a second polarizing plate 107j are formed, and these layers are stacked in this order. As described above, since the first polarizing plate 107 a is disposed closer to the optical adjustment sheet 20, the light emitted from the optical adjustment sheet 20 is displayed on the liquid crystal display from the first polarizing plate 107 a side of the liquid crystal display panel 107. The light enters the panel 107. Even in this case, as described above, since the lighting device 1 has no bright lines and luminance spots, there is no possibility of disturbing the display of the liquid crystal display panel 107. Moreover, since the illumination device 1 has a high front luminance as described above, the screen display of the liquid crystal display panel 107 can be made clear.

  In the said Example, the optical adjustment sheet | seat 20 which has the film-form base material 21 of 50 micrometers in thickness was mentioned as an example and demonstrated as an optical adjustment member of this invention. However, the optical adjustment member of the present invention is not limited to a sheet-like member having such a thin base material, and may have a thicker base material. As the substrate, an optical member having a thickness of about 10 μm to 100 mm can be used, but it is preferable to use an optical member having a thickness of about 30 μm to 200 μm in the member processing step. In the above embodiment, the edge light type illumination device and the liquid crystal display device in which the light source is arranged on the side surface of the light guide plate are described as examples. However, the illumination device and the liquid crystal display device of the present invention are not limited thereto. Absent. For example, a diffusing plate may be used instead of the light guide plate of the above-described lighting device and liquid crystal display device, and the lighting unit may be optically connected to the lower surface of the diffusing plate. In this case, the light emitted from the illumination unit is incident from the lower surface of the diffusion plate, diffused inside the diffusion plate, and then emitted from the upper surface of the diffusion plate with a substantially uniform intensity. Proceed to (Member). The optical adjustment member of the present invention can also be applied to such direct type illumination devices and liquid crystal display devices, and the same effects as those described above can be obtained. Note that, as described above, the optical adjustment member of the present invention has a high effect of suppressing the occurrence of a baseline when combined with a light source having particularly high directivity. Therefore, as in the above embodiment, it is preferable to combine the optical adjustment member of the present invention with an edge light type illumination device or liquid crystal display device in which a light source is arranged on the side surface of a light guide plate that emits light with high directivity. is there.

  With the optical adjustment member of the present invention, it is possible to suppress the occurrence of bright lines and to suppress the decrease in luminance. In particular, even with an optical adjustment member having a thin base material such as an optical adjustment sheet, bright lines do not occur even if the surface is pressed with a finger or the like. It is suitable for a display device with high possibility of touching.

FIG. 1 is a schematic configuration diagram of a lighting apparatus according to the first embodiment. 2 is an enlarged cross-sectional view of the optical adjustment sheet of Example 1. FIG. 3A and 3B are enlarged photographs of the granular material of the optical adjustment sheet. FIG. 4 is a diagram illustrating the progress of light in the illumination device according to the first embodiment. FIG. 5 is a graph showing the angular distribution of the luminance ratio of the light source. 6 is a view corresponding to FIG. 2 of the optical adjustment sheet of Example 2. FIG. 7 is a view corresponding to FIG. 2 of the optical adjustment sheet of Example 3. FIG. FIG. 8 is a view corresponding to FIG. 2 of the optical adjustment sheet of Comparative Example 1. FIG. 9 is a view corresponding to FIG. 2 of the optical adjustment sheet of Comparative Example 2. 10 is a view corresponding to FIG. 2 of the optical adjustment sheet of Comparative Example 3. FIG. FIG. 11 is an equivalent view of the optical adjustment sheet of Comparative Example 4 in FIG. FIG. 12 is a view corresponding to FIG. 2 of an optical adjustment sheet having a step-like optical adjustment member. FIG. 13 is a diagram showing a state of color separation of emitted light. FIG. 14 is a schematic configuration diagram of a liquid crystal display device. FIG. 15 is a schematic view of a conventional lens sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Illumination device 5 Light guide plate 10 Illumination unit 20 Optical adjustment sheet 21 Base material 22 Black bead 23 Binder 110 Liquid crystal display device

Claims (11)

An optical adjustment member,
A transparent plate-like base material that emits light incident from one surface from the other surface;
An optical structure that is formed on the other surface of the substrate and adjusts the characteristics of light;
A transparent binder applied to one side of the substrate;
A plurality of non-translucent granules dispersed in the binder at a predetermined density;
An optical adjustment member in which the diameter of the granular material is larger than the thickness of the binder.   The optical adjustment member according to claim 1, wherein the optical structure has a plurality of prisms.   The optical structure extends in a predetermined extending direction, and a cross section of the optical structure perpendicular to the extending direction is substantially triangular, and one of three sides defining the cross section The optical adjustment member according to claim 1, wherein the optical adjustment member is in parallel with the base material and one of the other two sides is stepped.   The optical adjustment member according to any one of claims 1 to 3, wherein the granular body is formed of a member selected from the group consisting of black beads, white beads, and high reflectance metal particles.   5. The optical device according to claim 4, wherein the black beads are acrylic beads containing carbon black, the white beads are acrylic beads containing titanium oxide fine particles, and the high reflectance metal particles are silver particles. Adjustment member.   The optical adjustment member according to any one of claims 1 to 5, wherein the light transmittance of the granular material is 17% or less.   The diameter of the granular material is 2 µm or more and 40 µm or less, and the average protrusion height of the granular material from the surface of the binder is 1.8 µm or more and less than 14.4 µm. The optical adjustment member described.   The optical adjusting member according to any one of claims 1 to 7, wherein the granular material is dispersed in the binder at a density of 1% by volume or less. A lighting device,
A plate-shaped optical member optically connected to the light source and the light source, the plate-shaped optical member having a light emitting surface for emitting light incident from the light source;
An illuminating device provided with the optical adjustment member as described in any one of Claims 1-8 optically connected to the said light-projection surface of the said plate-shaped optical member.   10. The light guide plate according to claim 9, wherein the plate-like optical member emits light having directivity in a predetermined direction from the light emitting surface, and the light source is optically connected to a side surface of the light guide plate. The lighting device described. A liquid crystal display device,
The lighting device according to claim 9 or 10,
A liquid crystal display device comprising: a first polarizing element, a liquid crystal layer, and a second polarizing element that are arranged to face the optical adjustment member, and a liquid crystal display element in which these are stacked in this order.