JP2017120714A - Surface light source device, video source unit, and display device - Google Patents

Abstract

An object of the present invention is to provide a surface light source device that can increase the light use efficiency while controlling the viewing angle. The optical sheet includes a light source (25) and an optical sheet (30). The optical sheet has a predetermined cross section, extends in one direction along a sheet surface, and has a predetermined direction in a direction different from the extending direction. An optical function layer (32) comprising: a plurality of light transmitting portions (33) arranged at intervals of; and light absorbing portions (34) formed at intervals between adjacent light transmitting portions to absorb light. It is arranged on the light source side of the layer, arranged at the same position as the light transmitting part in the front view of the optical sheet on the light source side than the light transmitting part, so that the incident light approaches the normal direction of the sheet surface of the optical sheet. A light incident control layer (35) comprising a plurality of unit light incident control elements (35a) for changing the direction. [Selection] Figure 2

Description

  The present invention relates to a display device that provides an image to an observer, a surface light source device provided in the display device, and an image source unit.

  A liquid crystal display device such as a liquid crystal television illuminates a liquid crystal panel having video information with a surface light source device from the back side. As a result, the illumination light is transmitted through the liquid crystal panel to obtain video information and emitted to the viewer side, so that the viewer can view the video. On the other hand, the liquid crystal panel is limited in the light that can be effectively used due to its properties, and a device for efficiently using the light from the light source is necessary.

Patent Document 1 discloses a video source unit in which a surface light source, a prism sheet, an optical functional layer (a layer in which light transmitting portions and light absorbing portions are alternately arranged), and a liquid crystal panel are stacked in this order. Yes. Thereby, the direction of the light incident on the liquid crystal panel is brought close to the normal direction of the panel surface of the liquid crystal panel, and the light use efficiency is increased.
Similarly, in Patent Document 2, a light source, a brightness enhancement film (a sheet in which a plurality of prisms whose tops face the viewer side), a reflective polarizing film, and an LCF (light transmission portions and light absorption portions are alternately arranged). An arrangement in which the arranged film) and the liquid crystal panel are arranged in this order is disclosed. Thereby, the direction of the light emitted from the light source can be brought close to the normal direction of the panel surface of the liquid crystal panel, and the light use efficiency can be improved. In addition, light incident on the LCF at a large angle with respect to the panel surface of the liquid crystal panel is absorbed by the light absorbing portion provided here.

JP 2010-217871 A Special table 2011-501219 gazette

  In a surface light source device having a conventional structure as described in the above-mentioned patent document, light directed in an oblique direction is absorbed. Therefore, when used in an in-vehicle display device (car navigation), image light is reflected on the windshield. Is prevented. However, on the other hand, the amount of light that is absorbed has reduced the light utilization efficiency.

  Therefore, in view of the above problems, an object of the present invention is to provide a surface light source device that can increase the light utilization efficiency while controlling the viewing angle. In addition, an image source unit having the surface light source device and a display device are provided.

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiment.

  The invention according to claim 1 is a surface light source device (20) arranged to face a surface of the liquid crystal panel opposite to the viewer side, the light source (25) and the optical sheet (30). And the optical sheet has a predetermined cross section, extends in one direction along the sheet surface, and a plurality of light transmission portions (33) arranged at predetermined intervals in a direction different from the extending direction, and An optical function layer (32) having a light absorption part (34) formed at an interval between adjacent light transmission parts and absorbing light; and disposed on the light source side of the optical function layer, and being lighter than the light transmission part A plurality of unit light incident control elements (35a) which are arranged at the same position as the light transmission part in the front view of the optical sheet and change the direction so that the incident light approaches the normal direction of the sheet surface of the optical sheet. And a light incident control layer (35).

  The invention according to claim 2 is the surface light source device (20) according to claim 1, wherein the unit light incident control element (35a) is an element having a curved surface.

  According to a third aspect of the present invention, in the surface light source device (20) of the first aspect, the unit light incident control element (35a) has a prism shape.

  According to a fourth aspect of the present invention, in the surface light source device (20) according to any one of the first to third aspects, the unit light incident control element has a thickness of 0.5 μm or more and 6.0 μm or less. Yes.

  According to a fifth aspect of the present invention, in the surface light source device (20) according to any of the first to fourth aspects, the elastic modulus of the light transmission part is 10 MPa or more and 2000 MPa or less.

  The invention according to claim 6 is a liquid crystal panel (15) having a lower polarizing plate (14), an upper polarizing plate (13), and a liquid crystal layer (12) disposed between the lower polarizing plate and the upper polarizing plate. And a surface light source device (20) according to claim 5 arranged on the lower polarizing plate side of the liquid crystal panel.

  A seventh aspect of the invention is a display device in which the video source unit (10) according to the sixth aspect is housed in a housing.

  According to an eighth aspect of the present invention, the direction in which the light transmitting portion (33) and the light absorbing portion (34) provided in the optical function layer (32) of the video source unit (10) according to the sixth aspect extend horizontally is horizontal. And a vehicle-mounted display device in which the direction in which the light transmission portions and the light absorption portions are alternately arranged is the vertical direction.

  According to the present invention, by limiting the viewing angle, it is possible to provide a bright image by suppressing a decrease in luminance while preventing image light from being reflected on the windshield even when mounted on a vehicle. .

FIG. 3 is an exploded perspective view illustrating a video source unit 10. 2 is an exploded view showing one cross section of the video source unit 10. FIG. 4 is an exploded view showing another cross section of the video source unit 10. FIG. It is the figure which expanded the part paying attention to the optical sheet 30 among FIG. FIG. 3 is a partially enlarged view of the optical sheet 30 in FIG. 2. It is a figure explaining the example of the optical sheet. It is a figure explaining the example of the optical sheet.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings. However, the present invention is not limited to these forms. In the drawings, the form of each element is exaggerated or enlarged for easy viewing.

  FIG. 1 is a diagram illustrating one embodiment, and is an exploded perspective view showing a video source unit 10 included in a display device. 2 is a part of an exploded sectional view of the image source unit 10 taken along the line II-II in FIG. 1, and FIG. 3 is a line indicated by III-III in FIG. Each part of the exploded cross-sectional view of the image source unit 10 when cut along the line is shown. In addition to the image source unit 10, the description of the display device is omitted, but the display device operates as a display device, such as a housing for housing the image source unit, a power source for operating the image source unit, and an electronic circuit for controlling the image source unit. It is equipped with the usual equipment required for. Hereinafter, the video source unit 10 will be described.

  The video source unit 10 includes a liquid crystal panel 15, a surface light source device 20, and a functional film 40. In FIG. 1, the upper side of the paper is the observer side.

  The liquid crystal panel 15 includes an upper polarizing plate 13 disposed on the functional film 40 side (observer side), a lower polarizing plate 14 disposed on the surface light source device 20 side, an upper polarizing plate 13 and a lower polarizing plate 14. And a liquid crystal layer 12 disposed between the two. The polarizing plates 13 and 14 decompose the incident light into two orthogonal polarization components (P wave and S wave) and transmit the polarization component (for example, P wave) in one direction (direction parallel to the transmission axis). And has a function of absorbing a polarization component (for example, S wave) in the other direction (direction parallel to the absorption axis) perpendicular to the one direction.

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

  In this way, the liquid crystal panel 15 has a structure for expressing an image by controlling transmission or blocking of light from the surface light source device 20 for each pixel.

The liquid crystal panel is configured to be able to provide an image to the observer based on such a principle. Therefore, when illuminating from the back side of the liquid crystal panel, it is possible to transmit light having a polarization component parallel to the transmission axis of the lower polarizing plate so as to transmit the lower polarizing plate and increase the light use efficiency. .
Furthermore, the liquid crystal panel is excellent in the contrast and efficiency (transmittance) of the emitted light with respect to the incident light from the normal direction of the liquid crystal panel due to its properties. However, with respect to the incident light obliquely with respect to the normal direction of the liquid crystal panel and the observation by the observer from the oblique direction, there are problems of a decrease in contrast and a low efficiency (transmittance). That is, increasing the incident light from the normal direction of the liquid crystal panel is also effective in increasing the light utilization efficiency.

  The kind of liquid crystal panel is not particularly limited, and examples thereof include known types of liquid crystal panels. These include, for example, TN, STN, VA, MVA, IPS, OCB, and the like.

  The upper polarizing plate and the lower polarizing plate can be of a known structure, and are usually configured so that the front and back surfaces of the polyvinyl alcohol (PVA) layer are sandwiched between layers of triacetyl cellulose (TAC).

Next, the surface light source device 20 will be described.
The surface light source device 20 is an illuminating device that is disposed on the side opposite to the observer side with respect to the liquid crystal panel 15 and emits planar light to the liquid crystal panel 15. As can be seen from FIGS. 1 and 2, the surface light source device 20 of this embodiment is configured as an edge light type surface light source device, and includes a light guide plate 21, a light source 25, a light diffusion plate 26, a prism layer 27, and a reflective polarizing plate. 28, an optical sheet 30 and a reflection sheet 39.

  As can be seen from FIGS. 1 to 3, the light guide plate 21 includes a base portion 22 and a back optical element 23. The light guide plate 21 is a plate-like member as a whole formed of a light-transmitting material. In this embodiment, one plate surface side that is an observer side of the light guide plate 21 is a smooth surface, and the other plate surface side opposite to this is a back surface, and a plurality of back optical elements 23 are provided on the back surface. Are arranged.

  Various materials can be used as the material forming the base 22 and the back optical element 23. However, a material that is widely used as a material for an optical sheet incorporated in a display device and has excellent mechanical characteristics, optical characteristics, stability, workability, and the like, and can be obtained at low cost can be used. This includes, for example, a polymer resin having an alicyclic structure, a methacrylic resin, a polycarbonate, a polystyrene, an acrylonitrile-styrene copolymer, a methyl methacrylate-styrene copolymer, an ABS resin, a polyethersulfone, and the like, Examples thereof include epoxy acrylate and urethane acrylate-based reactive resins (ionizing radiation curable resins and the like).

  The base portion 22 is a plate having a predetermined thickness at a portion that serves as a base of the back surface optical element 23 while light is guided therein.

The back optical element 23 is a protruding element formed on the back side of the base 22 (the side opposite to the side on which the reflective polarizing plate 28 is disposed), and in this embodiment, has a triangular prism shape. The back optical element 23 has a columnar shape in which the protruding top ridge line extends in the left-right direction in FIG. 1, and a plurality of back optical elements 23 are arranged side by side at a predetermined pitch in a direction orthogonal to the extending direction. The back surface optical element 23 in this embodiment has a columnar shape with a triangular cross section, but is not limited to this. Any of a columnar shape with a polygonal cross section, a column shape with a semicircular cross section, a hemisphere, a part of a sphere, a lens shape, etc. It may be a cross section in shape. Moreover, the aspect by which the white dot shape was formed by printing may be sufficient.
The arrangement direction of the plurality of back surface optical elements 23 is preferably the light guide direction. That is, the ridge lines of the respective back surface optical elements 23 extend in parallel to the direction in which the light sources 25 are arranged, or in the direction in which the light sources 25 extend if they are one long light source.

  The “triangular shape” in the present specification includes not only a triangular shape in a strict sense but also a substantially triangular shape including limitations in manufacturing technology, errors in molding, and the like. Similarly, terms used in the present specification to specify other shapes and geometric conditions, for example, terms such as “parallel”, “orthogonal”, “ellipse”, “circle”, etc. are bound to the strict meaning. Therefore, it should be interpreted including an error to the extent that a similar optical function can be expected.

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

Returning to FIGS. 1 and 2, the light source 25 will be described. The light source 25 is arrange | positioned among the side surfaces which the base 22 of the light-guide plate 21 has on the one side surface of the direction where the several back surface optical element 23 is arranged. The type of the light source is not particularly limited, but can be configured in various forms such as a fluorescent lamp such as a linear cold cathode tube, a point LED (light emitting diode), or an incandescent bulb. In this embodiment, the light source 25 is composed of a plurality of LEDs, and is configured to be able to individually and independently adjust the lighting and extinction of each LED and / or the lighting brightness of each LED by a control device (not shown). Yes.
In this embodiment, the light source 25 is disposed on the side surface on one side as described above. However, the light source may be disposed on the side surface opposite to the side surface. In this case, the shape of the back optical element is also formed following a known example.

Next, the light diffusion layer 26 will be described. The light diffusion layer 26 is a layer that is disposed on the light output side of the light guide plate 21 and has a function of diffusing and emitting light incident thereon. Thereby, the uniformity of the light emitted from the light guide plate 21 can be further improved, and the scratches existing on the light guide plate 21 can be made inconspicuous.
As a specific embodiment of the light diffusion layer, a known light diffusion layer can be used, and examples thereof include a form in which a light diffusion agent is dispersed in a base material.

As can be seen from FIGS. 1 to 3, the prism layer 27 is a layer provided with a unit prism 27 a that is provided closer to the liquid crystal panel 15 than the light diffusion layer 26 and is convex toward the liquid crystal panel 15. The unit prism 27 a has a predetermined cross section and extends in a direction orthogonal to the light guide direction of the light guide plate 21. A plurality of unit prisms 27a are arranged in the light guide direction. The direction in which the unit prism 27a extends is parallel to the direction in which the light transmission part 33 and the light absorption part 34 described later extend. Thereby, the light traveling to the light transmitting portion 33 and the light absorbing portion 34 can be redirected in the front direction, the light absorbed by the light absorbing portion 34 can be reduced, and the light utilization efficiency can be further increased. .
As the cross-sectional shape of the unit prism of such a prism layer, a known shape can be applied according to a required function. In this embodiment, it is formed so as to have a function of concentrating light in the front direction, but conversely, the light can be further diffused by the shape.

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

  Here, the direction in which the transmission axis of the reflective polarizing plate 28 extends is the same as the direction in which the transmission axis of the lower polarizing plate 14 extends, and a light transmission portion 33 and a light absorption portion 34 of the optical function layer 32 described later. Is preferably 0 ° or more and 41.7 ° or less when the image source unit 1 is viewed from the front. More preferably, it is 0 ° or more and 20 ° or less.

  Next, the optical sheet 30 will be described. As can be seen from FIG. 1 to FIG. 3, the optical sheet 30 is provided on the base material layer 31 formed in a sheet shape and one surface of the base material layer 31 (the surface on the light guide plate 21 side in this embodiment). An optical functional layer 32 and a light incident control layer 35 provided on the side of the optical functional layer 32 opposite to the base material layer 31 are provided. FIG. 4 shows a view focusing on the portion of the optical sheet 30 in FIG. FIG. 5 is an enlarged view of it.

  As will be described later, the optical sheet 30 has a function of changing the traveling direction of light incident from the light incident side and emitting the light from the light output side to improve the luminance in the front direction (normal direction). Accordingly, the viewing angle control is performed to suppress the emission of light in the direction in which the malfunction occurs when the light is emitted, and the light is emitted without changing the direction in the front direction without being absorbed, so that the light can be used effectively. it can. On the other hand, since it also has a function of absorbing light traveling at a large angle with respect to the front direction (light absorption function), unnecessary light such as stray light can be absorbed.

As can be seen from FIGS. 1 to 3, the base material layer 31 is a flat sheet-like member that supports the optical functional layer 32.
Various materials can be used as the material forming the base material layer 31. However, a material that is widely used as a material for an optical sheet incorporated in a display device and has excellent mechanical characteristics, optical characteristics, stability, workability, and the like, and can be obtained at low cost can be used. Examples thereof include polyethylene terephthalate (PET), triacetyl cellulose (TAC), methacrylic resin, polycarbonate and the like. Among these, considering the combination of the surface light source device 20 and the lower polarizing plate 14, it is preferable to use TAC, methacrylic resin, and polycarbonate having a low birefringence. Furthermore, for applications that require high heat resistance such as in-vehicle applications, polycarbonate having a high glass transition point is desirable. Specifically, the glass transition point of polycarbonate is 143 ° C., which is generally suitable for in-vehicle applications that require durability at 105 ° C.

  The optical functional layer 32 is a layer laminated on one surface of the base material layer 31 (the surface on the light guide plate 21 side in this embodiment), and light transmitting portions 33 and light absorbing portions 34 are alternately arranged along the layer surface. ing.

  The optical functional layer 32 has a cross section shown in FIG. 4 and a shape extending to the back / front side of the paper. That is, in the cross section shown in FIG. 4, the light transmission part 33 having a substantially trapezoidal shape and the light absorption part 34 having a substantially trapezoidal cross section formed between two adjacent light transmission parts 33 are provided.

  The light transmission part 33 is a part whose main function is to transmit light. In this embodiment, in the cross section shown in FIGS. 2 and 4, the base layer 31 side has a long lower bottom, and the opposite side (light guide plate side). ) Having a substantially trapezoidal cross-sectional shape having a short upper base. The light transmissive portions 33 maintain the cross section along the layer surface of the base material layer 31 and extend in the above-described direction, and are arranged at a predetermined interval in a direction different from the extending direction. An interval having a substantially trapezoidal cross section is formed between the adjacent light transmission portions 33. Therefore, the interval has a trapezoidal cross section having a long lower base on the upper base side (light guide plate 21 side) of the light transmission part 33 and a short upper base on the lower base side (liquid crystal panel side) of the light transmission part 33. The light absorbing portion 34 is formed by filling a necessary material described later. In this embodiment, the adjacent light transmission parts 33 are connected on the long bottom side.

  The light transmission part 33 has a refractive index of Nt. Such a light transmission part 33 can be formed by hardening a light transmission part structure composition. Details will be described later. Although the value of the refractive index Nt is not particularly limited, as will be described later, the refractive index is from the viewpoint of appropriately reflecting light (including total reflection) at the interface with the light absorbing portion 34 on the slope of the trapezoidal cross section. It is preferable that it is 1.55 or more. However, since a material with a refractive index that is too high is likely to break, the refractive index is preferably 1.61 or less. More preferably, it is 1.56 or less.

The light absorption part 34 functions as an intermediate part formed at the above-described interval formed between the adjacent light transmission parts 33 and has a cross-sectional shape similar to the cross-sectional shape of the interval. Therefore, the short upper base faces the liquid crystal panel 15 side, and the long lower base becomes the light guide plate 21 side. And the light absorption part 34 is comprised so that a refractive index may be Nr and it can absorb light. Specifically, light absorbing particles are dispersed in a binder having a refractive index of Nr. The refractive index Nr is a refractive index lower than the refractive index Nt of the light transmission part 33. Thus, by making the refractive index of the light absorbing portion 34 smaller than the refractive index of the light transmitting portion 33, the light incident on the light transmitting portion 33 under a predetermined condition is appropriately totally reflected at the interface with the light absorbing portion 34. Can be made. Even when the total reflection condition is not satisfied, some light is reflected at the interface.
The value of the refractive index Nr is not particularly limited, but is preferably 1.50 or less from the viewpoint of appropriately performing the total reflection, and more preferably 1.47 or more from the viewpoint of availability. More preferably, it is 1.49 or more.

  The difference in refractive index between the refractive index Nt of the light transmitting portion 33 and the refractive index Nr of the light absorbing portion 34 is not particularly limited, but is preferably 0.05 or more and 0.14 or less. By increasing the refractive index difference, more light can be totally reflected.

The optical function layer 32 is not particularly limited, but for example, the light transmission part 33 and the light absorption part 34 are formed as follows. That is, it is preferable that the pitch of the light transmission part 33 and the light absorption part 34 represented by _Pk in FIG. 4 is 20 μm or more and 100 μm or less. Further, the angle formed by the interface between the oblique sides of the light absorbing portion 34 and the light transmitting portion 33 indicated by θ _K in FIG. 4 and the normal line of the layer surface of the optical functional layer 32 is 1 ° or more and 10 ° or less. Is preferred. And it is preferable that the thickness of the light absorption part 34 shown by _Dk in FIG. 4 is 50 micrometers or more and 150 micrometers or less. By setting it within these ranges, the balance between light transmission and light absorption can be made appropriate.

In this embodiment, an example in which the interface between the light transmitting portion 33 and the light absorbing portion 34 is straight in the cross section is shown. However, the present invention is not limited to this, and may be a polygonal line shape, a convex curved surface shape, a concave curved surface shape, or the like. Also good. Moreover, the cross-sectional shape may be the same in the some light transmissive part 33 and the light absorption part 34, and a different cross-sectional shape may have predetermined regularity.
Moreover, the said cross section does not necessarily need to be an isosceles trapezoid, and one leg and the other leg are not line-symmetrical, and it may incline so that one and the other may differ.

The light incident control layer 35 is a layer disposed on the side opposite to the base material layer 31 in the optical function layer 32, and a plurality of unit light incident control elements 35a are arranged.
As can be seen from FIG. 3 and FIG. 4, the unit light incident control element 35 a of this embodiment has a convex section with a curved section, and extends in the same direction as the light transmitting portion 33 with this section. The light transmission part 33 and the unit light incident control element 35a are positioned so as to be in the same position when the optical sheet 30 is viewed from the front. In this embodiment, the unit light incident control element 35a is directly disposed on the light incident surface of the light transmitting portion 33 and integrated. Thereby, the unit light incident control element 35a can be arranged with high positional accuracy.
The unit light incident control element 35a controls the direction of light incident on the optical functional layer 32 by using refraction, and is totally reflected at the interface between the light transmitting portion 33 and the light absorbing portion 34 to thereby absorb the light absorbing portion 34. The light is advanced in the direction in which it is difficult to be absorbed in (the normal direction of the sheet surface, the front direction). Therefore, the unit light incident control element 35a is configured to have the function of changing the direction of light in this way. This form is a convex shape having a curved surface, which is a so-called lens shape.

In order to perform such refraction more effectively, the light incident surface of the light incident control layer 35 is in contact with air and is preferably an interface with air.
However, the present invention is not limited to this, and the light incident surface of the light incident control layer 35 may be in contact with the pressure-sensitive adhesive and may be an interface with the pressure-sensitive adhesive layer. And the light-incident control layer 35 and the reflection type deflection | deviation board can also take the aspect which adhere | attaches with an adhesive layer. This pressure-sensitive adhesive layer is preferably formed of a material having a refractive index lower than that of the unit light incident control element 35a. And when it is set as an adhesive layer, it is preferable that they are 20 micrometers or more and 50 micrometers or less. In addition, the thickness of an adhesive layer means the thickness of the thickest part of an adhesive layer. When the thickness of the pressure-sensitive adhesive layer is less than 20 μm, the ability to follow irregularities is lowered, and a problem of biting bubbles occurs. When the thickness exceeds 50 μm, it is difficult to uniformly apply the pressure-sensitive adhesive composition. Furthermore, the storage elastic modulus of the pressure-sensitive adhesive is desirably 0.1 MPa or more and 0.8 MPa or less. If it is larger than this, the followability to unevenness will drop, and the problem of biting bubbles will occur. is there.

  Further, the thickness of the unit light incident control element indicated by H in FIG. 4 is preferably 0.5 μm or more and 6.0 μm or less. If the thickness is less than 0.5 μm, necessary optical characteristics may not be obtained. If the thickness is more than 6.0 μm, it may be difficult to form a light absorbing portion as described later. is there.

  The unit light incident control element only has to have a function of changing the traveling direction of light in the front direction, and the form of the unit light incident control element 35a is not particularly limited. 6 and 7 show examples of the light incident control layers 135 and 235 provided with the unit light incident control elements 135a and 235a according to the modified examples. 6 and 7 are views from the same viewpoint as FIG.

The unit light incident control element 135 a has a triangular cross section and extends in the same direction as the light transmitting portion 33. The light transmitting portion 33 and the unit light incident control element 135a are positioned so as to be in the same position when the optical sheet 130 is viewed from the front. In this embodiment, the unit light incident control element 135a is directly arranged on the light incident surface of the light transmitting portion 33 and is integrated. Thereby, the unit light incident control element 135a can be arranged with high positional accuracy.
The direction of light entering the optical functional layer 32 is controlled by the unit light incident control element 135a, and is totally reflected at the interface between the light transmitting portion 33 and the light absorbing portion 34 and is less likely to be absorbed by the light absorbing portion 34. Light is made to approach (sheet surface normal direction, front direction).
This form is a convex shape having a triangular cross section, and is a so-called prism shape.

The unit light incident control element 235 a has a trapezoidal cross section and extends in the same direction as the light transmitting portion 33. The light transmitting portion 33 and the unit light incident control element 235a are positioned so as to be at the same position when the optical sheet 130 is viewed from the front. In this embodiment, the unit light incident control element 235a is directly arranged on the light incident surface of the light transmitting portion 33 and is integrated. Thereby, the unit light incident control element 235a can be arranged with high positional accuracy.
The direction in which light enters the optical functional layer 32 is controlled by the unit light incident control element 235a, and is totally reflected at the interface between the light transmitting portion 33 and the light absorbing portion 34 and is less likely to be absorbed by the light absorbing portion 34. Light is made to approach (sheet surface normal direction, front direction).
This form is a convex shape having a trapezoidal cross section, and is a so-called prism shape. A long lower base in the trapezoidal cross section is in contact with the light incident side of the light transmitting portion 33, and a short upper base is disposed on the opposite side. According to such a unit light incident control element 235a, as will be described later, the light originally directed to the front direction can be transmitted without changing the direction more than necessary, so that the light is more efficiently transmitted to the front direction. Can be controlled.

  The material constituting the light incident control layers 35, 135, and 235 is not particularly limited, but the same material as that of the light transmission portion 33 can be used.

The optical sheet 30 can be manufactured as follows, for example.
First, the light transmitting portion 33 and the light incident control layer 35 are formed on the base material layer 31. In this embodiment, the light transmission part 33 and the light incident control layer 35 are integrally formed. Therefore, the base material that becomes the base material layer 31 between the mold roll having the shape that can transfer the shape of the light transmitting portion 33 and the light incident control layer 35 on the surface and the nip roll disposed so as to face the die roll. Insert a sheet. At this time, the mold roll and the nip roll are rotated while supplying the composition constituting the light transmitting portion between the base sheet and the mold roll. As a result, a groove corresponding to the light transmitting portion formed on the surface of the mold roll (a shape obtained by reversing the shape of the light transmitting portion) is filled with the composition that constitutes the light transmitting portion, and the composition becomes the surface of the mold roll. It will be along the shape.

Here, examples of the composition constituting the light transmitting portion and the light control layer include ionizing radiation curable resins such as epoxy acrylate, urethane acrylate, polyether acrylate, polyester acrylate, and polythiol. Can do.
At this time, it is preferable that the composition constituting the light transmission part has an elastic modulus after curing of 10 MPa to 2000 MPa. Thereby, also when scraping off the composition which comprises a light absorption part with a doctor blade so that it may mention later, it can suppress that a failure | damage arises, following appropriately the press.

  Light for curing with a light irradiation device is irradiated from the substrate sheet side to the composition constituting the light transmission portion sandwiched between the mold roll and the substrate sheet and filled therein. Thereby, a composition can be hardened and the shape can be fixed. Then, the base material layer 31 and the molded light transmission part 33 and the light control layer 35 are released from the mold roll by the release roll.

  Next, the light absorption part 34 is formed. In order to form the light absorption part 34, first, the composition constituting the light absorption part is filled in the interval between the light transmission parts 33 formed above. Thereafter, the surplus composition is scraped off with a doctor blade or the like. Then, the remaining composition can be cured by irradiating light from the light transmission part 33 side with a light irradiating device to form the light absorbing part 34.

  The material used as the light absorbing portion is not particularly limited, but for example, it is colored in a photocurable resin such as urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, and butadiene (meth) acrylate. And a composition in which the light absorbing particles are dispersed.

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

  Returning to FIGS. 1 to 3, the reflection sheet 39 of the surface light source device 20 will be described. The reflection sheet 39 is a member that reflects the light emitted from the back surface of the light guide plate 21 and makes the light enter the light guide plate 21 again. The reflection sheet 39 is a sheet that is capable of so-called specular reflection, such as a sheet made of a material having a high reflectance such as a metal, a sheet including a thin film (for example, a metal thin film) made of a material having a high reflectance as a surface layer, It can be preferably applied.

  The functional film 40 is a layer that is disposed on the light output side of the liquid crystal panel 15 and has functions of improving the quality of the video light and protecting the video source unit 10. Examples thereof include an antireflection film, an antiglare film, a hard coat film, a color tone correction film, a light diffusion film, and the like, and these are constituted by combining them alone or in combination.

  Next, the operation of the display device having the above configuration will be described with an example of the optical path. However, the optical path example is conceptual for explanation, and does not strictly represent the degree of reflection or refraction.

  First, as shown in FIG. 2, the light emitted from the light source 25 enters the light guide plate 21 through the light incident surface on the side surface of the light guide plate 21. FIG. 2 shows an example of an optical path of the light L21 and L22 incident on the light guide plate 21 from the light source 25 as an example.

  As shown in FIG. 2, the light L21 and L22 incident on the light guide plate 21 repeats total reflection due to a difference in refractive index with air on the light exit side surface of the light guide plate 21 and the back surface on the opposite side, thereby guiding the light guide direction (FIG. Proceed to the right of page 2).

  However, the back optical element 23 is disposed on the back surface of the light guide plate 21. For this reason, as shown in FIG. 2, the light L21, L22 traveling in the light guide plate 21 has its traveling direction changed by the back surface optical element 23, and is incident on the light exit surface and the back surface at an incident angle less than the total reflection critical angle. There is also. In this case, the light can be emitted from the light exit surface of the light guide plate 21 and the back surface on the opposite side.

  Lights L21 and L22 emitted from the light exit surface travel to the light diffusion layer 26 disposed on the light exit side of the light guide plate 21. On the other hand, the light emitted from the back surface is reflected by the reflection sheet 39 disposed on the back surface of the light guide plate 21, enters the light guide plate 21 again, and travels through the light guide plate 21.

  The light traveling in the light guide plate 21 and the light whose direction is changed by the back surface optical element 23 and reaching the light exit surface at an incident angle less than the total reflection critical angle are in each area along the light guide direction in the light guide plate 21. Arise. For this reason, the light traveling in the light guide plate 21 is gradually emitted from the light exit surface. Thereby, the light quantity distribution along the light guide direction of the light emitted from the light exit surface of the light guide plate 21 can be made uniform.

The light emitted from the light guide plate 21 then reaches the light diffusion layer 26 and the uniformity is improved. Then, the light is condensed or diffused as necessary by the prism layer 27 (in this embodiment, condensed), and the light emitted from the prism layer 27 then reaches the reflective polarizing plate 28. Here, the light in the polarization direction along the transmission axis of the reflective polarizing plate 28 passes through the reflective polarizing plate 28 and travels toward the optical sheet 30.
On the other hand, the light in the polarization direction along the reflection axis of the reflective polarizing plate 28 is reflected and returned to the light guide plate 21 side as shown by dotted arrows L21 ′ and L22 ′ in FIG. The returned light is reflected by the light guide plate 21, the back surface optical element 23, or the reflection sheet 39 and travels again toward the reflective polarizing plate 28. During this reflection, the polarization direction of a part of the light is changed, and a part of the light is transmitted through the reflective polarizing plate 28. Other light is returned to the light guide plate side again. Thus, the light reflected by the reflective polarizing plate 28 can be transmitted through the reflective polarizing plate 28 by repeating the reflection. Thereby, the utilization factor of the light from the light source 25 is increased.
Here, the light emitted from the reflective polarizing plate 28 has a polarization direction in a direction along the transmission axis of the lower polarizing plate 14, and is polarized light transmitted through the lower polarizing plate 14.

The light emitted from the reflective polarizing plate 28 enters the light incident control layer 35. Here, the light incident on the light incident control layer 35 is preferably as follows. In other words, the incident light has a viewing angle of 45 °, and the direction in which the optical function layer can control the incident angle is 10% or more and 50% or less with respect to the luminance of the front (sheet normal direction). It is desirable that the brightness be. More desirably, it is 20% or more and 40% or less.
If it is larger than 50%, the control effect by the incident control layer is lost in the case of light that is not controlled as in complete diffusion. If it is smaller than 10%, the incident light itself is already controlled in view angle, and optical This is because the viewing angle control effect itself of the functional layer is unnecessary.

The light refracted by the light incident control layer 35 is transmitted through the light transmitting portion of the optical function layer 32 as light L51 and L52 (see FIG. 5), for example, and emitted from the base material layer 31 side toward the liquid crystal panel. . That is, light such as the light L51 is refracted by the light incident control layer 35 and emitted with the direction changed to the front. Thereby, the brightness | luminance in a front direction can be raised.
Light such as the light L52 is refracted by the light incident control layer 35, thereby reaching the interface at an angle larger than the total reflection critical angle at the interface between the light transmitting portion 33 and the light absorbing portion 34, As can be seen from FIG. 5, the light is totally reflected here and changed in the front direction and emitted.
In addition, light incident at a large angle that does not totally reflect even at the interface between the light transmitting portion 33 and the light absorbing portion 34 is absorbed by the light absorbing portion 34. Such light is not preferable from the viewpoint of controlling the viewing angle of the video display device, and can be appropriately absorbed here.

In this way, the light incident control layer 35 and the optical function layer 32 increase the light totally reflected by the optical function layer 32 in the light incident control layer 35, and also provide the liquid crystal panel with light that has been absorbed by the light absorption unit in the past. can do. As a result, the luminance is increased.
Furthermore, since the refraction of the light incident control layer 35 and the total reflection at the optical function layer 32 both limit the viewing angle and change the direction of light closer to the front, It is possible to suppress the emission of light in the direction of the windshield and prevent so-called reflection.

  The examples of the light incident control layers 135 and 235 shown in FIGS. 6 and 7 are basically the same. In FIGS. 6 and 7, the light L61, the light L62, L71, and L72 are the light L51 and L52, respectively. Proceed in the same way.

  In the light incident control layer 235 shown in FIG. 7, since there is no curved or inclined surface at the top of the unit light incident control element 235, unnecessary light diffusion can be prevented as in L71, for example. In addition, since the leg portion is linear and is disposed at a position close to the light absorbing portion, the light incident on the position close to the light absorbing portion is appropriately controlled as in L72 to efficiently perform all the operations. The direction can be changed to reflect.

  Further, the optical path will be described. The light emitted from the surface light source device 20 as described above enters the lower polarizing plate 14 of the liquid crystal panel 15. The lower polarizing plate 14 transmits one polarization component of incident light and absorbs the other polarization component. The light transmitted through the lower polarizing plate 14 selectively passes through the upper polarizing plate 13 according to the state of electric field application to each pixel. In this way, the liquid crystal panel 15 selectively transmits light from the surface light source device 20 for each pixel, so that an observer of the liquid crystal display device can observe an image. At that time, the image light is provided to the observer through the functional film 40, and the quality of the image is improved.

  In the present embodiment, each of the above members has been described as a configuration disposed between the light incident control layer 35 and the light source 25. However, the present invention is not limited to such a configuration, and the light incident control is performed. A known structure can be applied as long as it can emit appropriate light to the layer 35. For example, a member having a plurality of convex shapes may be arranged on the light guide plate side between the light guide plate and the light incident control layer.

  According to the surface light source device including the optical sheet as described above, the image source unit including the optical sheet, and the image display device, the luminance in the front direction is improved and the light use efficiency is controlled while appropriately controlling the viewing angle. Can be increased. For example, assuming that the direction in which the light transmission part and the light absorption part extend is horizontal and the direction in which the light transmission part and the light absorption part are alternately arranged is the vertical direction, when this is mounted on a vehicle, light is emitted upward. Can be suppressed, and reflection on the windshield can be prevented. On the other hand, a bright image can be provided to an observer who is in the front direction.

<Example 1>
An optical sheet corresponding to the optical sheet 20 described above as Example 1 was produced to form a surface light source device, which was combined with a liquid crystal panel. As the liquid crystal panel, a 6.5-inch liquid crystal panel (manufactured by Sharp Corporation, LQ065T5GG03) is used, and the direction in which the light transmitting portion and the light absorbing portion of the optical functional layer extend is horizontal, and the alternately arranged direction is the vertical direction. Arranged. The detailed configuration of the optical sheet is as follows.
(Base material layer)
・ Material: Polycarbonate film ・ Thickness: 130 μm
-Rough surface: The surface opposite to the side on which the optical functional layer is disposed is a rough surface having an arithmetic average roughness (Ra) of 0.4 μm. Thereby, the haze of the base material layer became 20.
(Optical function layer)
・ Pitch (see FIG. 4): P _k = 39 μm
· Light absorbing portion upper base width: 4 [mu] m _(W a in FIG. 4)
・ Light absorption part lower bottom width: 10 μm (W _{b in} FIG. 4)
Light absorber thickness: 102 μm (D _{k in} FIG. 4)
-Optical functional layer thickness: 127 μm
-Material and refractive index of light transmission part: UV curable urethane acrylate, refractive index 1.56
-Material and refractive index of light absorbing part: 25% by mass of acrylic beads containing carbon black in UV curable urethane acrylate having a refractive index of 1.49 (light incident control layer)
The light incident control layer was formed integrally with the light transmission part and was curved. The thickness H of the light incident control layer indicated by H in FIG. 4 is 6 μm.

<Example 2>
In Example 2, following the example of FIG. 7, the cross-sectional shape of the light incident control layer was trapezoidal, and the thickness H ″ of the light incident control layer indicated by H ″ in FIG. 7 was 6 μm. Other portions are the same as those in Example 1.

<Comparative Example 1>
In Comparative Example 1, no light incident control layer was formed. The other layers are the same as in Example 1.

<Evaluation method>
As described above, LQ065T5GG03 (6.5 inches) manufactured by Sharp Corporation was used as the liquid crystal module as described above, and LS-110 manufactured by Konica Minolta Co., Ltd. was used as the luminance meter. Thus, the front luminance when only the backlight was used and the front luminance when the optical sheet according to each of the above examples was installed on the outermost surface of the backlight were measured.

<Result>
When the luminance of the backlight alone was 100%, the ratio of the luminance in the front direction when the optical sheet was installed on the outermost surface of the backlight was evaluated as the transmittance. As a result, the transmittance of both Example 1 and Example 2 was higher than that of Comparative Example 1. In Example 2, the improvement in the transmittance on the upper side (range from 0 degree to 20 degrees above the screen normal) was remarkable.

DESCRIPTION OF SYMBOLS 10 Image source unit 15 Liquid crystal panel 20 Surface light source device 21 Light guide plate 25 Light source 26 Light diffusion layer 27 Prism layer 28 Reflective polarizing plate 30 Optical sheet 32 Optical function layer 33 Light transmission part 34 Light absorption part 35 Light incident control layer

Claims (8)

A surface light source device arranged to face a surface of the liquid crystal panel opposite to the viewer side,
A light source and an optical sheet,
The optical sheet is
A light transmitting portion having a predetermined cross section and extending in one direction along the sheet surface and arranged in a direction different from the extending direction at a predetermined interval, and formed between the adjacent light transmitting portions. An optical functional layer comprising a light absorbing part for absorbing light;
Of the optical functional layer, disposed on the light source side, disposed closer to the light source than the light transmitting portion, at the same position as the light transmitting portion in front view of the optical sheet, and incident light of the optical sheet A light incident control layer comprising a plurality of unit light incident control elements that change the direction so as to approach the normal direction of the sheet surface,
Surface light source device.   The surface light source device according to claim 1, wherein the unit light incident control element is an element having a curved surface.   The surface light source device according to claim 1, wherein the unit light incident control element has a prism shape.   The surface light source device according to claim 1, wherein the unit light incident control element has a thickness of 0.5 μm or more and 6.0 μm or less.   5. The surface light source device according to claim 1, wherein the light transmission portion has an elastic modulus of 10 MPa to 2000 MPa. A lower polarizing plate, an upper polarizing plate, and a liquid crystal panel having a liquid crystal layer disposed between the lower polarizing plate and the upper polarizing plate;
An image source unit comprising: the surface light source device according to claim 5 disposed on the lower polarizing plate side of the liquid crystal panel.   A display device, wherein the video source unit according to claim 6 is housed in a housing.   7. The direction in which the light transmission part and the light absorption part provided in the optical function layer of the video source unit according to claim 6 extend is horizontal, and the light transmission part and the light absorption part are alternately arranged. A vehicle-mounted display device whose direction is vertical.

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