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EP-3605157-B1 - OPTICAL SHEET, LIGHT CONTROLLING MEMBER, SURFACE LIGHT SOURCE DEVICE, IMAGE SOURCE UNIT, AND DISPLAY

EP3605157B1EP 3605157 B1EP3605157 B1EP 3605157B1EP-3605157-B1

Inventors

  • KASHIWAGI, TSUYOSHI

Dates

Publication Date
20260506
Application Date
20180330

Claims (15)

  1. An optical sheet (30) that is made of a plurality of laminated layers, the optical sheet comprising: an optical functional layer (32) that is one of the plurality of the laminated layers; a light exiting side light controlling layer (35) comprising an optical element layer (35b) that is another one of the plurality of the laminated layers; and a base material layer (31) that is another one of the plurality of laminated layers, wherein: the optical functional layer (32) is provided on one face of the base material layer (31) and the light exiting side light controlling layer (35) is provided on the other face of the base material layer (31); the optical functional layer (32) has a plurality of light transmissive portions (33) extending in one direction, the light transmissive portions (33) being arranged at intervals in a direction different from the one direction, and a light absorbing portion (34) that is arranged between respective adjacent light transmissive portions (33), the light exiting side light controlling layer (35) is configured to control a direction of the light exiting the optical functional layer (32), and the optical element layer (35b) extends so as to be offset from the one direction at an angle of 0° to 45° in a front view of the optical sheet (30), the optical element layer (35b) having a plurality of unit optical elements (35c) that are ridges aligned in a direction different from a direction in which the optical element layer (35b) extends.
  2. The optical sheet (30) according to claim 1, wherein each of the light transmissive portions (33) has a trapezoidal cross section, a longer lower base of the trapezoidal cross section facing the unit optical elements (35c).
  3. The optical sheet (30) according to claim 1 or 2, wherein each of the unit optical elements (35c) has a main refracting face (35d), a rise face (35e), and a triangular cross section, and the main refracting face (35d) is a face inclining in a direction of a normal line of a light exiting face of the optical functional layer (32) at more than 45° and no more than 89°.
  4. The optical sheet (30) according to claim 3, wherein an angle formed by one of the main refracting faces (35d) of the unit optical elements (35c) and the normal line of the light exiting face of the optical functional layer (32) is different between a central area of the optical sheet (30) and an outer circumferential area of the optical sheet (30).
  5. The optical sheet (30) according to claim 4, wherein the optical element layer (35b) is made of a linear Fresnel lens.
  6. The optical sheet (30) according to claim 1, wherein each of the unit optical elements (35c) has a main refracting face (35d), a rise face (35e), and a triangular cross section, and the main refracting face (35d) inclines toward a face of the optical functional layer (32) at more than 0° and less than 17°.
  7. The optical sheet (30) according to claim 6, wherein each of the light transmissive portions (33) has a trapezoidal cross section, a shorter upper base of the trapezoidal cross section facing the unit optical elements (35c).
  8. The optical sheet (30) according to any one of claims 1 to 7, wherein a surface of each of the unit optical elements (35c) is formed into a rough face.
  9. The optical sheet (30) according to any one of claims 1 to 8, wherein P mx is no more than 10000 (µm) where an aligning pitch of the light transmissive portions is P a (µm), an aligning pitch of the unit optical elements is P o (µm), a and b are each integers of 1 to 10, P m = a ⋅ P a ⋅ b ⋅ P o / a ⋅ P a − b ⋅ P o , and largest P m obtained by all combinations of a and b for P a and P o is P mx (µm).
  10. A light controlling member (229), wherein the number of the optical sheets (30) according to any one of claims 1 to 9 arranged is at least two, and an extending direction of the light transmissive portions of one of the optical sheets and that of the light transmissive portions of another one of the optical sheets cross each other in the front view of the optical sheets.
  11. A surface light source device (20) comprising: a light source (25); and the optical sheet (30) according to any one of claims 1 to 9, the optical sheet (30) being arranged closer to a watcher than the light source (25) is.
  12. A surface light source device (20) comprising: a light source (25); and the light controlling member (229) according to claim 10, the light controlling member (229) being arranged closer to a watcher than the light source (25) is.
  13. An image source unit (10) comprising: the surface light source device (20) according to claim 11 or 12; and a liquid crystal panel (15) that is arranged on a light exiting side of the surface light source device (20).
  14. The image source unit (10) according to claim 13, wherein the light transmissive portions (33), the light absorbing portion (34), and the unit optical elements (35c) extend in a horizontal direction, and are aligned in a vertical direction.
  15. A display comprising: a housing; and the image source unit (10) according to claim 13 or 14, the image source unit (10) being housed in the housing.

Description

Technical Field The present invention relates to optical sheets to control an exiting direction of an incident light, and light controlling members, surface light source devices, image source units, and displays including the optical sheet. Background Art Displays such as monitors for car navigation systems, televisions, and personal computers include an image source from which an image to be displayed exits, and an optical sheet for improving the quality of an image light to give the light on the watcher side. Exiting directions of an image light are mostly the front, and offset up, down, left, and right from the front. This makes it possible to visually recognize an image shown on a screen from a desired position. Exiting directions of light are also limited as necessary, for example, for preventing peeks. For example, Patent Literatures 1 to 3 disclose optical sheets to control light exiting angles. Patent Literature 4 discloses a transmission type screen that displays an image by transmitting image light projected on one side of a surface to the other side of the surface. The transmission type screen includes: an optical functional layer comprising a plurality of light-transmitting sections for transmitting light, which extend in one direction and are juxtaposed in a direction different from the extending direction thereof, and light absorbing sections for absorbing light, each being formed between adjacent light transmitting sections; and a Fresnel lens layer having unit lenses which extend in one direction and are juxtaposed in a direction different from the extending direction. In frontal view, the extending direction of the light transmitting sections and light absorbing sections intersects with the extending direction of the unit lenses. Cited Documents Patent Literature Patent Literature 1: JP 2006-171701 APatent Literature 2: JP 2014-059565 APatent Literature 3: JP 2012-113054 APatent Literature 4: JP 2015 075535 A Summary of Invention Technical Problem Diverse devices in recent years have required different or more precise control of an exiting direction of an image light than before. For example, car navigation systems do not always need a wide viewing angle because positions where people seat themselves are almost determined in an automobile, and thus car navigation systems have only to let images exit toward the positions where people are to exist, especially toward a driver. It is, therefore, easier for a driver to watch an image light exiting obliquely upwards than that exiting to the front. An image light exiting too upwards, however, leads to a problem of a reflection of the image in a windshield. Such a light exiting angle is different according to types of automobiles etc., which requires precise control thereof. For example, those patent literatures encompass the following problems: For example, it is difficult to precisely control a viewing angle using an optical sheet as described in Patent Literature 1. Even if the viewing angle is controlled, the use efficiency of an image light lowers, which is problematic. For example, an optical sheet as described in Patent Literature 2 gives high exiting performance of an image light in a desired direction, but limits the image light exiting in any other direction. This may lead to a relatively dark outer circumferential portion of a screen compared to its center although the center is bright especially when a display has a large screen. This tendency further notably manifests itself especially when the screen is viewed obliquely from the front. For example, a technique as described in Patent Literature 3 requires that light transmissive portions and light absorbing portions on the center of the sheet are significantly different from those on the outer circumferential portion thereof in shape, and does not always make it possible to control light precisely. In this case, increased difficulty in production makes it also difficult to give an accurate shape. An object of the present invention is to provide an optical sheet that makes it possible to efficiently control a light exiting angle as desired, and to provide a light controlling member, a surface light source device, an image source unit, and a display including this optical sheet. Solution to Problem Hereinafter the present invention will be described. One aspect of the present invention is an optical sheet as defined in claim 1, that is made of a plurality of laminated layers, the optical sheet comprising: an optical functional layer that is one of a plurality of the laminated layers; and an optical element layer that is another one of a plurality of the laminated layers, wherein the optical functional layer has a plurality of light transmissive portions extending in one direction, the light transmissive portions being arranged at intervals in a direction different from the one direction, and a light absorbing portion that is arranged between respective adjacent light transmissive portion