JP2012074308A - Light source unit and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source unit having a light guide plate capable of utilizing a wider region in a light emitting face of the light guide plate as an effective light emitting region of a display.SOLUTION: The light source unit 1 is provided with: a light guide plate 11 which is a platy body having a pair of facing main faces 11a, 11b and an end face 11c between the pair of the main faces 11a, 11b, the pair of the main faces 11a, 11b being a light emitting face and a reflection face, respectively, and the one end face 11c being a light incident face; an LED 13 so arranged that the light is incident on the light incident face 11c of the light guide plate 11; and a diffusion sheet 12 arranged on a light emitting face 11a side of the light guide plate 11. The diffusion sheet 12 is provided with a base material of a sheet shape, a resin layer having an irregular uneven pattern arranged on one main face of the base material, and a non-transparent component ratio adjusting pattern 133 arranged on the one main face or on the other main face of the base material, and the non-transparent component ratio is uneven in a sheet surface.

Description

  The present invention relates to a light source unit including a light guide plate in which a light source is arranged on a light incident surface, and in particular, a light source unit that can be used as an illuminating unit of a liquid crystal display device and can realize a liquid crystal display device having excellent in-plane luminance uniformity. About.

  Currently, liquid crystal display devices are used in a wide range of fields such as mobile phones, PDA terminals, digital cameras, televisions, personal computer displays, and notebook computers. In a liquid crystal display device, for example, a planar illumination device (backlight) is arranged behind a liquid crystal display panel, and an image is displayed by supplying light from the backlight to the liquid crystal display panel. In a backlight used in such a liquid crystal display device, it is required to supply uniform light to the liquid crystal display panel in order to make the displayed image easy to see.

  There are two types of backlights: a direct type in which the light source is installed in the direction of the back of the liquid crystal display panel, and an edge light type in which the light source is installed in the side direction of the liquid crystal display panel. For the backlight of a thin display device, an edge light type illumination device using a light guide plate is often used. As a light source of such an illuminating device, there are a linear light source such as CCFL (Cold Cathode Tube) and a point light source such as LED (Light Emitting Diode), but an LED which is a point light source from the viewpoint of low power consumption. Attention has been paid.

  In an edge light type illuminating device using LEDs, LEDs are arranged on an end surface which is a light incident surface of a light guide plate. In the light guide plate, the light of the LED introduced from the end face of the light guide plate is referred to as the two main surfaces of the light guide plate (hereinafter, the side close to the liquid crystal display panel is referred to as “light emitting surface”, and the far side is referred to as “reflecting surface” The light is diffused in the light guide plate while being totally reflected, and is reflected and diffused by the light reflection diffuser provided on the reflection surface or inside the light guide plate, and is emitted from the light emission surface to the liquid crystal display panel side.

  In order to reflect and diffuse the light from the light source, in general, a white material such as titanium oxide or barium titanate is directly printed on the reflective surface of the light guide plate, or a sheet on which the white material is printed is reflected on the reflective surface of the light guide plate. It is reflected and diffused by pasting it on. In addition, a patterned uneven surface is provided on the reflective surface of the light guide plate, and the light from the light source is diffused in the direction of the light exit surface by the uneven surface, or a reflection diffusing substance is mixed inside the light guide plate to Light can also be diffused. These white materials, fine irregularities, and reflection diffusion materials are collectively referred to as “light reflection diffusers”.

  The light reflection diffuser provided on the light guide plate is usually given a gradation of density or density according to the distance from the light source. This is to compensate for a reduction in the intensity of light propagating in the light guide plate according to the distance from the light source by improving the reflection efficiency from the light reflection diffuser. For example, when a white material is printed as a light reflecting diffuser, a pattern is selected such that the coverage of the white material per unit area of the light guide plate is small at a position close to the light source, and the coverage increases as the distance from the light source increases. The

  By the way, when an LED is used as a light source, since the LED has a strong directivity, even if a light reflection diffuser with the above-mentioned gradation is provided on the light guide plate, various luminance unevenness exists on the light guide plate surface. To do. For example, in a light guide plate provided with a gradation in which the coverage of the white material per unit area of the light guide plate increases as the distance from the LED increases, a uniform luminance distribution is obtained on the light exit surface that is some distance away from the LED, but close to the LED. On the light exit surface, the front part of the LED becomes extremely bright. For this reason, it is known that luminance unevenness called a so-called hot spot occurs in which the portion between the LEDs becomes dark.

  In addition to this, the luminance unevenness in which bright lines and dark lines are repeated in parallel within the light incident surface of the light guide plate, and the luminance unevenness due to the shadow of the boss (support pin provided on the light guide plate for positioning) are also included. , Brightness unevenness caused by deformation of the light guide plate by providing the boss, brightness unevenness reflected by the light guided at the notch provided on the side of the light guide plate to hold the light guide plate, LED is arranged Uneven brightness at the four corners of the light guide plate that cannot be used.

  Therefore, in order to prevent uneven brightness, an LED is formed by forming a notch at the edge of the light guide plate (corresponding to the light incident surface), and reflection absorption is performed along the edge of the light guide plate so as to cover the LED. A backlight device has been proposed in which a sheet is provided and a light absorbing portion is provided on the back side of the reflection-absorbing sheet so as to cover the LED corresponding to the LED (Patent Document 1). In addition, a light guide plate is proposed in which a plurality of elliptical columnar grooves are inscribed in the thickness direction on the light incident surface of the light guide plate (Patent Document 2).

JP 2003-242817 A JP 2007-149672 A

  However, in the backlight device described in Patent Document 1, the light absorbing portion provided so as to cover the LED absorbs light in the vicinity of the LED, and lowers the luminance of the portion where the luminance is high, thereby achieving uniformity. Therefore, although the luminance difference between the light guide plate exit surface in the vicinity of the LED and the light guide plate exit surface between the LEDs decreases, the light emitted from the LED cannot be used effectively. Further, luminance unevenness other than the hot spots described above cannot be sufficiently reduced.

  In addition, in the light guide plate described in Patent Document 2, it is possible to narrow a region where luminance unevenness occurs by providing a plurality of elliptic columnar grooves on the light incident surface of the light guide plate and widening the incident angle of incident light. Since there is a physical limit to widening the incident angle, luminance unevenness cannot be completely removed. For this reason, of the light exit surface of the light guide plate, the light exit area of uneven light with uneven brightness cannot be used as an effective light emitting area, which is insufficient as the light exit surface utilization efficiency and light utilization efficiency. there were.

  This invention is made in view of this point, and provides the light source unit which can utilize the wider area | region in the light emission surface of a light-guide plate as an effective light emission area | region in a light source unit provided with the light-guide plate. Objective.

  As a result of investigations to solve the above-described problems of the prior art, the present inventors have arranged a diffusion sheet having a resin layer having an irregular concavo-convex pattern and a non-transmission component ratio adjustment pattern on the light guide plate. It has been found that the above-mentioned problems can be solved by the light source unit, and the present invention has been completed. The present invention is as follows.

  The light source unit of the present invention is a plate-like body having a pair of opposing main surfaces and an end surface between the pair of main surfaces, wherein the pair of main surfaces are a light output surface and a reflection surface, respectively, and one end surface is A light guide plate that is a light incident surface; a light source disposed so as to allow light to enter the light incident surface of the light guide plate; and a diffusion sheet disposed on the light exit surface side of the light guide plate. The diffusion sheet includes a sheet-like base material, a resin layer having an irregular uneven pattern provided on one main surface of the base material, and the one main surface or the other main surface of the base material. And a non-transmission component rate adjustment pattern provided on the surface, wherein the non-transmission component rate is non-uniform in the sheet surface.

  According to this configuration, since the light emitted from the region where the luminance unevenness in the light exit surface of the light guide plate is generated is effectively diffused by the diffusion sheet, the entire light exit surface of the light guide plate is used as an effective light emission region of the display. it can.

  In the light source unit of the present invention, it is preferable that the relative intensity distribution of the non-transmission component ratio in the sheet surface of the diffusion sheet and the relative intensity distribution of the illuminance in the sheet surface when the diffusion sheet is incident are substantially equal. .

  In the light source unit of the present invention, the diffusion angle of the diffusion sheet is preferably in the range of 1 to 120 degrees.

  In the light source unit of the present invention, it is preferable that the resin layer having an irregular uneven pattern of the diffusion sheet is formed by a speckle pattern by interference exposure.

  In the light source unit of the present invention, it is preferable that the non-transmissive component ratio adjustment pattern of the diffusion sheet contains a light-reflective ink cured product containing a light diffusing agent.

  In the light source unit of the present invention, it is preferable that a reflection sheet is provided below the light guide plate.

  The light source unit of the present invention preferably includes a lens sheet disposed above the diffusion sheet.

  The light source unit of the present invention preferably includes a prism sheet disposed above the diffusion sheet.

  In the light source unit of the present invention, it is preferable to include a reflective polarizing sheet disposed above the diffusion sheet.

  The liquid crystal display device of the present invention includes a liquid crystal display panel and the light source unit that supplies light to the liquid crystal display panel.

  ADVANTAGE OF THE INVENTION According to this invention, the light source unit provided with the light-guide plate can provide the light source unit which can utilize the wider area | region in the light emission surface of a light-guide plate as an effective light emission area | region of a display.

(A) is a typical top view of the light source unit which concerns on embodiment of this invention, (b) is a typical side view of the light source unit which concerns on embodiment of this invention. It is explanatory drawing of the brightness nonuniformity of the light emission surface of the light-guide plate in the light source unit which concerns on embodiment of this invention. It is explanatory drawing which shows the other example of the brightness nonuniformity of the light emission surface of the light-guide plate which concerns on embodiment of this invention. (A)-(c) is a cross-sectional schematic diagram which shows the structural example of the diffusion sheet which concerns on embodiment of this invention. (A) is explanatory drawing of the diffusion angle of the diffusion sheet which concerns on embodiment of this invention, (b) is typical schematic which shows the transmitted light intensity when light injects from the normal line direction of a diffusion sheet FIG. It is a cross-sectional schematic diagram which shows the measurement conditions of the non-permeable component rate of the diffusion sheet which concerns on embodiment of this invention. It is a schematic diagram which illustrates the shape of the dot which comprises the non-transmissive component rate adjustment pattern of the diffusion sheet which concerns on embodiment of this invention. (A)-(e) is a cross-sectional schematic diagram which shows the structural example of the diffusion sheet which concerns on embodiment of this invention. (A)-(c) is a schematic diagram which shows an example of the dot density in the diffusion sheet which concerns on embodiment of this invention. It is a perspective view which shows the other structure of the light source unit which concerns on embodiment of this invention. It is a schematic diagram which shows an example of the backlight unit for composite split panels which concerns on implementation of this invention. (A) is a photograph showing an example of luminance unevenness (hot spot) when the light guide plate of the light source unit according to the example and the comparative example of the present invention is viewed from the light exit surface side, and (b) is the present invention. It is a photograph which shows an example which reduced the hot spot with the diffusion sheet in the light source unit which concerns on this Example. It is a perspective view which shows the structure of the light source unit which concerns on a comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The light source unit according to the present invention includes a light source, a light guide plate, and a diffusion sheet. In the light source unit according to the present invention, the light source is disposed on the light incident surface of the light guide plate, and the diffusion sheet is disposed on the light exit surface of the light guide plate. The diffusion sheet includes a sheet-like base material, a resin layer having an irregular uneven pattern provided on one main surface of the base material, and one main surface or the other main surface of the base material. And the non-transmission component rate adjustment pattern provided, and the non-transmission component rate is non-uniform in the sheet surface. The light guide plate has a light output surface, a reflective surface facing the light output surface, and at least one light incident surface sandwiched between the light output surface and the reflective surface. Hereinafter, a light source unit according to an embodiment of the present invention will be described in detail with reference to FIGS.

(Light source unit)
Fig.1 (a) is a typical top view of the light source unit which concerns on one embodiment of this invention, FIG.1 (b) is a side view of Fig.1 (a).

  As shown in FIGS. 1A and 1B, a light source unit 1 according to the present embodiment includes a light guide plate 11 that guides light from a light source, and a diffusion sheet 12 that diffuses light emitted from the light guide plate 11. The light from the LED 13 serving as the light source enters the light guide plate 11 to be guided, and the light emitted from the light guide plate 11 is diffused by the diffusion sheet 12.

  The light guide plate 11 is a plate-like body having a pair of opposing main surfaces 11a and 11b and end surfaces 11c and 11d between the pair of main surfaces 11a and 11b. An LED 13 as a point light source is disposed in the vicinity of one end face 11c of the light guide plate 11. A plurality of LEDs 13 are arranged in one side end surface 11 c of the light guide plate 11, and light emitted from each LED 13 is arranged so as to enter the light toward the side end surface 11 c of the light guide plate 11. . One end surface 11c of the light guide plate 11 serves as a light incident surface (hereinafter referred to as a “light incident surface 11c”) for entering light from the plurality of LEDs 13 into the light guide plate 11. In addition, one main surface 11a of the light guide plate 11 serves as a light output surface (hereinafter referred to as “light output surface 11a”) from which incident light is emitted from the light guide plate 11, and the other main surface 11b is a reflective surface (light output surface). The surface facing the surface: hereinafter referred to as “reflective surface 11b”). The reflection surface 11 b is provided with a light reflection diffuser 14 that reflects light incident on the light guide plate 11 toward the light output surface 11 a.

  In the light guide plate 11 having such a configuration, the light emitted from the LED 13 enters from the light incident surface 11 c of the light guide plate 11 and propagates while reflecting in the light guide plate 11. When the light reaching the reflection surface 11b hits the light reflection diffuser 14, the reflection angle is changed, the optical path is directed to the light emission surface 11a, and light is emitted from the light emission surface 11a. The light emitted from the light guide plate 11 is angle-controlled by the diffusion sheet 12 disposed above the light exit surface 11a, and is guided to a non-illuminating body such as a liquid crystal display panel and used as illumination light.

  In the light source unit 1 shown in FIGS. 1A and 1B, the case where the light incident surface 11c is the one side end surface 11c is shown. However, depending on the area to be irradiated and its irradiation intensity, The arrangement of the LEDs 13 may be changed. For example, the LED 13 may be disposed on the other side end surface 11d, may be disposed on the two opposing side end surfaces 11c, 11d, or may be disposed on all four side end surfaces including the side end surfaces 11c, 11d. May be.

  Next, with reference to FIG. 2 and FIG. 3 (a)-(d), the brightness nonuniformity in the light emission surface 11a of the light-guide plate 11 in the light source unit 1 which concerns on this Embodiment is demonstrated. FIG. 2 is an explanatory diagram of an example of luminance unevenness of the light exit surface 11a of the light guide plate 11 in the light source unit 1 according to the present embodiment. FIGS. 3 (a) to 3 (d) are views of the light exit surface 11a of the light guide plate 11. FIG. It is explanatory drawing which shows the other example of the brightness nonuniformity. 2 and 3 are schematic plan views of the light source unit 1 shown in FIG. 1 as viewed from the light exit surface 11a side of the light guide plate 11, and the diffusion sheet 12 is omitted for convenience of explanation. Yes.

  As shown in FIG. 2, in the light source unit 1 according to the present embodiment, the incident angle of light that enters the light guide plate 11 from the light incident surface 11 c of the light guide plate 11 from the LED 13 is incident on the light guide plate 11. When it is narrowed by refraction. For this reason, the light exit surface 11a of the light guide plate 11 in a plan view has a high illuminance area A1 having a relatively high illuminance due to irradiation of the plurality of LEDs 13, and a high illuminance area A1 between the high illuminance areas A1. A low illuminance area A2 having relatively low illuminance occurs. As described above, when the high illuminance area A1 and the low illuminance area A2 are generated, luminance unevenness called a hot spot occurs.

  In this way, when a hot spot occurs, the area A3 on the light incident surface 11c side from the broken line L1 shown in FIG. 2 in the light exit surface 11a of the light guide plate 11 cannot be used as an effective light emitting region due to luminance unevenness. Only the area A4 on the opposite side of the light incident surface 11c from L1 can be used as an effective light emitting area without luminance unevenness.

  3A to 3D show other examples of luminance unevenness. FIG. 3A shows an example in which the luminance unevenness 15 in which the bright line (see L2) and the dark line (see L3) repeat in parallel is generated in the light exit surface 11a of the light guide plate 11, and FIG. Shows an example in which the luminance unevenness 17 is caused by the shadow of the boss 16. FIG. 3C shows an example of luminance unevenness that occurs when the LEDs 13 are arranged on each end side surface of the light guide plate 11. In this example, luminance unevenness 18 occurs at the four corners of the light guide plate 11 where the light source (LED 13) cannot be arranged. This unevenness occurs when LEDs are arranged on all four sides of the light guide plate 11, when arranged on two sides, or when arranged on only one side. FIG. 3D shows luminance unevenness 19 due to leakage of light from the LED 13 when entering the light guide plate 11. In addition to this, the location and intensity generated vary depending on the light source unit to be used, but it is provided on the side of the light guide plate to hold the light guide plate, such as uneven brightness caused by deformation of the light guide plate by providing the boss. There is luminance unevenness caused by reflection of the light guided at the notch.

  In the light source unit, the present inventors can effectively diffuse the light emitted from the light guide plate by disposing a diffusion sheet having a predetermined configuration on the light exit surface side of the light guide plate. On the light exit surface, it has been found that even in a region where the luminance unevenness cannot be sufficiently effectively reduced, the luminance unevenness can be reduced and used as an effective light emitting region, and the present invention has been made. Hereinafter, the diffusion sheet according to the present embodiment will be described in detail.

[Diffusion sheet]
The diffusion sheet 12 according to the present embodiment includes a sheet-like base material, a resin layer having an irregular uneven pattern provided on one main surface of the base material, and one main surface of the base material or And a non-transmission component ratio adjustment pattern provided on the other main surface. Further, in the diffusion sheet 12 according to the present embodiment, the non-transmission component rate is not uniform within the sheet surface. Here, the irregular concavo-convex pattern is preferably a concavo-convex pattern formed using a speckle pattern by interference exposure.

  An outline of a configuration of the diffusion sheet 12 according to the present embodiment will be described with reference to FIGS. 4A to 4C are schematic cross-sectional views illustrating a configuration example of the diffusion sheet according to the present embodiment. As shown in FIGS. 4A to 4C, the diffusion sheet 12 according to the present embodiment is provided on a base 131 having a pair of main surfaces and one main surface of the base 131, A resin layer 132 having an irregular concavo-convex pattern (hereinafter, also simply referred to as “concavo-convex pattern layer 132”) is provided on one main surface side or the other main surface side of the substrate 131, and is not in the sheet surface. A non-transmission component ratio adjustment layer 133 that adjusts the transmission component ratio. The diffusion sheet 12 includes a region having a relatively high non-transmission component rate (hereinafter referred to as “high non-transmission component rate region”) and a region having a relatively low content (hereinafter referred to as “low non-transmission component rate region”). It is provided so that the non-transmitting component rate is non-uniform in the sheet surface of the diffusion sheet 12.

  As a configuration example of the diffusion sheet 12, the uneven pattern layer 132 may be provided on one main surface of the base material 131, and the non-transmissive component ratio adjustment 133 may be provided on the other main surface of the base material 131 (FIG. 4). (See (a)), a non-transmission component rate adjustment layer 133 may be provided on one main surface of the substrate 131, and the uneven pattern layer 132 may be provided on the non-transmission component rate adjustment layer 133 (FIG. 4B). )), An uneven pattern layer 132 may be provided on one main surface of the base material 131, and an impermeable component ratio adjusting layer 133 may be provided on the uneven pattern layer 132 (see FIG. 4C). The non-transmissive component rate adjusting layer 133 may not be completely formed. As described later, the non-transmissive component rate adjusting layer 133 is formed on at least one main surface of the base material 131. It may be non-uniformly distributed so as to be spaced apart (hereinafter, the non-transmission component rate adjustment layer 133 is referred to as “non-transmission component rate adjustment pattern 133”).

  As the configuration of the diffusion sheet 12, it is preferable to provide the concavo-convex pattern layer 132 on one main surface of the substrate 131 and to provide the non-transmission component ratio adjustment pattern 133 on the other main surface (see FIG. 4A). In this case, since the concave / convex pattern layer 132 and the non-transmission component ratio adjustment pattern 133 are arranged to face each other via the base material 131, the distance between the concave / convex pattern layer 132 and the non-transmission component ratio adjustment pattern 133 is large. Become. For this reason, the incident light transmitted and diffused through the concave / convex pattern layer 132 (non-transmission component ratio adjustment pattern 133) is further diffused in the process of transmitting through the base material 131, and the non-transmission component ratio adjustment pattern 133 (protrusion pattern layer 132). ) Can be achieved more effectively.

  In addition, as a configuration of the diffusion sheet 12, a concave / convex pattern layer 132 (non-transmission component ratio adjustment pattern 133) and a non-transmission component ratio adjustment pattern 133 (protrusion pattern layer 132) are sequentially laminated on one main surface of the substrate 131. It is also preferable (see FIGS. 4B and 4C). In this case, since the non-transmissive component ratio adjustment pattern 133 (uneven pattern pattern layer 132) can be physically protected by the uneven pattern layer 132 (non-transmissive component ratio adjustment pattern 133) laminated on the base material 131, the diffusion sheet The strength of 12 can be increased.

  In the diffusion sheet 12 according to the present embodiment, the non-transmission component ratio adjustment pattern 133 is provided according to the illuminance distribution on the sheet surface when the diffusion sheet 12 is incident, so that the non-existence of the region with relatively high illuminance on the sheet surface is provided. By controlling the transmission component ratio to be large, the transmitted light is appropriately leveled and the luminance unevenness of the diffusion sheet 12 can be effectively reduced. That is, in the diffusion sheet 12 according to the present embodiment, the non-transmission component rate adjustment pattern 133 is provided non-uniformly in the sheet surface, and the high non-transmission component rate region and the low non-transmission are formed in a desired region in the sheet surface. Forming a component ratio region, and making the relative intensity distribution of the non-transmission component ratio in the sheet surface of the diffusion sheet 12 substantially equal to the relative intensity distribution of the illuminance in the sheet surface when the diffusion sheet 12 is incident. preferable. Thereby, since it can diffuse moderately according to distribution of illuminance of transmitted light, brightness irregularity can be reduced effectively.

(Uneven pattern layer)
At this time, in the diffusion sheet 12 according to the present embodiment, the concavo-convex pattern layer 132 has a concavo-convex structure having a microscopic irregular height or pitch. Further, the uneven pattern layer 132 has a uniform diffusion angle and non-transmission component rate over the sheet surface of the diffusion sheet 12. For this reason, it is not necessary to align the concave / convex pattern layer 132 with respect to the non-transmission component ratio adjustment pattern 133 formed in order to express a non-uniform non-transmission component ratio, as will be described later. Excellent unevenness reduction capability. In addition, since the diffusion due to the surface structure of the uneven pattern layer 132 can be used, high transmittance and high haze can be achieved, and a desired luminance unevenness suppressing effect can be realized with higher luminance.

  Furthermore, with respect to the non-transmissive component rate adjustment pattern 133 of the diffusion sheet 12, the side where the concavo-convex pattern layer 132 is provided is the light emitting surface, that is, the non-transmissive component rate adjustment pattern 133 is the light incident surface side. Since the distribution of the light diffusion degree generated in the sheet surface of the diffusion sheet 12 by the non-transmission component ratio adjustment pattern 133 is appropriately leveled by the concavo-convex pattern layer 132, the brightness unevenness is effective. Can be reduced.

  Specifically, the concave / convex pattern layer 132 can be manufactured as follows. First, an irregular light intensity distribution (speckle pattern) generated in the space after coherent laser light passes through the diffusion plate by interference exposure is irradiated to the photosensitive material or photoresist via a lens or mask. Development is performed to produce a sub-master type in which irregularities corresponding to the light intensity of a desired speckle pattern are formed. By changing the distance and size between the members constituting the laser irradiation system and adjusting the size, shape and direction of the speckle pattern, the range of the diffusion angle can be controlled and the concavo-convex structure having different diffusion angles can be recorded. .

  In general, the range of the diffusion angle depends on the average size and shape of the speckle. If speckle is small, the angle range is wide. Further, the unit structure of the concavo-convex structure is not limited to an isotropic one, and an anisotropic one can be formed, or a concavo-convex structure in which both are combined can be obtained. If the speckle is an oval in the horizontal direction, the shape of the diffusion angle distribution is an oval in the vertical direction. In this way, a speckle pattern is determined according to a desired directivity angle and diffusion angle, and a submaster mold having the diffusion angle is manufactured. A metal is deposited on the sub-master mold by a method such as electroforming, and a speckle pattern is transferred to the metal to produce a master mold. A detailed manufacturing method of this sub-master type is disclosed in Japanese Patent No. 3341519. All this content is included here. A speckle pattern is transferred to the light extraction surface of the photocurable resin layer by forming the photocurable resin layer with ultraviolet rays using the master mold.

  The unevenness height of the surface structure can be judged from, for example, the pitch, aspect ratio, surface roughness, etc. of the cross-sectional shape of the light reflecting sheet observed with a scanning electron microscope. Further, the pitch, aspect ratio, surface roughness, and the like can be read from the observation image of the light reflecting sheet surface by a laser confocal microscope. For example, as the pitch is shorter, the aspect ratio is larger, or the surface roughness is larger, it can be considered that the unevenness height is higher. The pitch of the concavo-convex pattern of the concavo-convex pattern layer 132 is preferably in the range of 0.1 μm to 100 μm and the height is in the range of 0.1 μm to 30 μm.

  In the present invention, the “diffusion angle” refers to an angle (FWHM: Full Width Half Maximum) that is twice the angle (half-value angle) at which the transmitted light intensity attenuates to half of the peak intensity (see FIG. 5A). . This diffusion angle is, for example, from Phonon's Goniometric Radiometers Real-Time Far-Field Angular Profiles Model LD8900 (hereinafter referred to as “LD8900”), from the normal direction of the uneven surface of the diffusion sheet 12 from the uneven surface side. It can be determined by measuring the angular distribution of transmitted light intensity with respect to incident light. Here, the normal direction of the diffusion sheet 12 refers to the direction shown in FIG. In this specification, the diffusion angle of the diffusing sheet 12 refers to a configuration in which only the base material 131 and the single concavo-convex pattern layer 132 are provided without providing the non-transmissive component ratio adjustment pattern 133, and light is incident from the concavo-convex pattern layer 132 side. This is the angle obtained by measurement.

  Moreover, as the concavo-convex pattern layer 132 of the diffusion sheet 12, both an isotropic concavo-convex pattern that can obtain substantially the same diffusion angle regardless of the measurement direction and an anisotropic concavo-convex pattern that has different diffusion angles depending on the measurement direction are used. Can do. An anisotropic uneven | corrugated pattern is an uneven | corrugated pattern from which a diffusion angle differs, for example, when a diffusion angle is measured in two orthogonal directions. In the case of an anisotropic concavo-convex pattern, when the diffusion angle in the most diffusing direction is A degree and the diffusion angle in the least diffusing direction is B degree, the diffusion angle is expressed as “A degree × B degree”. In addition, the preferable diffusion angle range when the uneven | corrugated pattern layer 132 is an anisotropic uneven | corrugated pattern shall mean the preferable diffusion angle range of the diffusion angle of the direction which diffuses most.

  In the diffusion sheet 12 according to the present embodiment, the diffusion angle of the diffusion sheet 12 is preferably 1 degree to 120 degrees. The diffusion angle of the diffusion sheet 12 is more preferably 30 degrees to 110 degrees, and further preferably 50 degrees to 100 degrees. It is 1 degree or more from the viewpoint of sufficiently exhibiting the luminance unevenness suppressing effect, and 120 degrees or less from the viewpoint of preventing a decrease in luminance. The preferable range of the diffusion angle is the same for “A degree” in the diffusion sheet 12 having the anisotropic uneven pattern.

(Non-transmissive component rate adjustment pattern)
The non-transmissive component ratio adjustment pattern 133 is provided on the base material 131 so that the non-transmissive component ratio defined below becomes a predetermined value within the sheet surface of the diffusion sheet 12. In the diffusion sheet 12 according to the present embodiment, by providing the non-transmission component ratio adjustment pattern 133 on one main surface of the base material 131 on which the uneven pattern layer 132 is laminated or the other main surface on the opposite side, It is possible to provide a high non-transmission component rate region and a low non-transmission component rate region in a desired region in the sheet surface. Thus, by providing the high non-transmission component rate region and the low non-transmission component rate region, the non-transmission component rate of the diffusion sheet 12 is adjusted to be non-uniform in the sheet plane. Specifically, as the non-transmission component ratio adjustment pattern 133, a pattern formed by applying light-reflecting ink or light-absorbing ink in the form of dots on the main surface of the substrate 131, or a transparent resin layer The uneven | corrugated pattern provided in the surface is illustrated.

In the present invention, the “non-transmission component ratio” is a component other than a component that is transmitted from the diffusion sheet 12 when light from the light source enters the sheet surface of the diffusion sheet 12 (for example, a reflection component, an absorption component, a scattering component). ). The non-transmissive component ratio in the diffusion sheet 12 according to the present embodiment is measured using, for example, an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, UV-2450, MPC-2200). Further, the non-transmissive component ratio of the diffusion sheet 12 is measured in a state where the base material 131, the uneven pattern layer 132, and the non-transmissive component ratio adjustment pattern 133 are provided. In this case, as shown in FIGS. 6A to 6C, the concavo-convex pattern layer 132 of the diffusion sheet 12 is set in a direction farther from the light source than the non-transmission component ratio adjustment pattern 133, and the transmission wavelength is 550 nm. The incident light intensity and the transmitted light intensity are detected and calculated by the following relational expression (1) and the following relational expression (2).
Light transmittance (%) = (transmitted light intensity at 550 nm) / (incident light intensity at 550 nm) × 100 (1)
Non-transmissible component ratio (%) = 100−light transmittance—formula (2)

  In the diffusion sheet 12 according to the present embodiment, the non-permeable component ratio is preferably 10% or more and 90% or less, more preferably 10% or more and 80% or less, and 20% or more and 80% or less. More preferably. The non-transmissive component ratio is preferably 90% or less from the viewpoint of suppressing a decrease in luminance, and is preferably 10% or more from the viewpoint of effectively reducing luminance unevenness.

  In the present invention, “the non-transmission component ratio is non-uniform” means that when the non-transmission component ratio in the sheet surface of the diffusion sheet 12 is measured at intervals of 1 mm, a value obtained by subtracting the minimum value from the maximum value of the measurement value. It means a state where the non-transmission component ratio in the sheet surface is distributed so as to differ by 2% or more of the average value of all measured points. As described above, as a state where the non-transmission component ratio becomes non-uniform, for example, luminance unevenness that occurs in a high non-transmission component ratio area and a low non-transmission component ratio area in the sheet surface, for example, FIG. The measurement of the non-transmission component rate in each non-transmission component rate region is performed from the maximum value of the measurement value of the non-transmission component rate in each high non-transmission component rate region. A state in which the difference value obtained by subtracting the minimum value exceeds 2% of the average value of the measured values at all points in the sheet surface can be mentioned.

The non-transmissive component ratio adjustment pattern 133 can be produced by applying light reflective or light absorbing ink in a dot shape. In this case, in order to change the non-transmission component ratio in the sheet surface of the diffusion sheet 12 by the non-transmission component ratio adjustment pattern 133, the density of dots of a certain area may be changed depending on the location, The area of the ink may be changed, or the ink film thickness may be changed depending on the place by repeatedly applying ink. When the non-transmission component ratio adjustment pattern 133 is composed of dots, if the dots are too small, the reproducibility at the time of production becomes a problem. If the dots are too large, the diffusion sheet 12 according to the present embodiment is used for a liquid crystal display device. As a result, the dots are visible and the display device becomes defective. Therefore, it is preferable area of each dot is 25 [mu] m ² or more ～250000Myuemu ² or less. When the non-transmission component ratio adjustment pattern 133 is composed of dots, as shown in FIG. 7, the dots may be circular, elliptical, square, or polygonal, such as a star shape. The outer shape of each shape may be a slightly distorted shape.

  As the light reflective ink, white ink is most preferable from the viewpoint of high reflectance and low absorption. Moreover, as a coating method, since the pattern of a white ink hardened | cured material can be formed freely, a printing method is preferable. Here, the white ink cured product means a product obtained by printing and curing a white ink composition. The white ink composition includes a solvent, a white pigment, a dispersant, and a resin as a fixing agent on the surface of an object. Is included as a basic component.

Specific examples of the white pigment in the white ink composition include titanium oxide (TiO ₂ , titanium white), calcium carbonate, talc, clay, aluminum silicate, basic lead carbonate (2PbCO ₃ Pb (OH) ₂ , silver White), zinc oxide (ZnO, zinc white), strontium titanate (SrTiO ₃ , titanium strontium white), barium sulfate and the like can be used alone or in a mixed system.

  In particular, titanium oxide has dispersion stability because it has a lower specific gravity than other inorganic white pigments, has a high refractive index and excellent optical scattering properties, and is chemically and physically stable. Thus, since the hiding power and optical scattering property as a pigment are large, it is preferable to use titanium oxide as a main component as the inorganic white pigment. The white pigment can be mixed for the purpose of adjusting the color of the diffused light.

  The mixing ratio of the white pigment is preferably 30% by mass to 60% by mass of the entire white ink composition. A white pigment other than titanium oxide is generally used in an amount up to about 30% of the entire white pigment for the purpose of dispersion aid, if necessary.

  Examples of the resin in the white ink composition include ketone resin, sulfoamide resin, maleic acid resin, ester gum, xylene resin, alkyd resin, rosin, polyvinylpyrrolidone, polyvinyl butyral, acrylic resin, melamine resin, cellulose resin, and vinyl. Resins, phenol resins, ester resins and the like can be used, and among them, acrylic resins can be preferably used.

  The organic solvent in the white ink composition is used for the purpose of dissolving the resin and adjusting the viscosity, and is an aromatic hydrocarbon solvent such as toluene, xylene, ethylbenzene, n-hexane, n-heptane, isoheptane, Aliphatic hydrocarbon solvents such as n-octane and isooctane and cycloparaffin solvents such as methylcyclohexane and ethylcyclohexane can be used alone or as a mixture. The amount of the organic solvent used is about 30% by mass to 60% by mass of the entire white ink composition.

  Moreover, you may contain the optical agent which has an optical effect in a white ink composition. Optical agents are particles having the property of diffusing light, and are roughly classified into inorganic fillers and organic fillers. As the inorganic filler, silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, or a mixture thereof can be used. As the organic filler, acrylic, acrylonitrile, non-yellowing urethane, styrene, or the like can be used. Inorganic fillers are preferable from the viewpoint of low swellability due to printing ink, and urethane fillers are preferable among organic fillers.

  The compounding amount of the optical agent is preferably 10 parts by mass or more and 80 parts by mass or less, and particularly preferably 20 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the resin in the white ink composition. When the blending amount of the optical agent is 10 parts by mass or more, the luminance uniformity effect is sufficiently exhibited, and when the blending amount of the optical agent is 80 parts by mass or less, the white ink composition that forms the non-transmissive component ratio adjustment pattern 133 This makes it easier to apply objects.

  As the light-absorbing ink, black ink is most preferable from the viewpoint of high absorption. Moreover, as a coating method, since the pattern of a black ink hardened | cured material can be formed freely, the printing method is preferable. Here, the black ink cured product means a product obtained by printing and curing a black ink composition. The black ink composition includes a solvent, a black pigment, a dispersant, and a resin as a fixing agent on the surface of an object. Is included as a basic component. Specifically, carbon black can be used as the black pigment in the black ink composition.

  The printing method may be a conventionally known method, and any method such as offset printing, flexographic printing, gravure printing, screen printing, ink jet printing, thermal fusion printing using a thermal transfer ribbon, and thermal sublimation printing. But you can.

  In particular, offset printing enables printing with clear dots, and because the plate does not touch the sheet directly and wears the cylinder, it is suitable for mass printing and can be produced in a relatively short time. It is good in terms of efficiency. In particular, gravure printing enables clear printing of halftone dots, and since the plate is metal, it is less worn and suitable for mass printing, so it is excellent in terms of design reproducibility and production efficiency. Flexographic printing has high printing stability because the printing density is stable and the printing density is relatively high, and the ink density can be controlled by adjusting the cell size of the anilox roll that mediates between the plate and the printed matter.・ Excellent in terms of high concealment and easy printing density control. Screen printing is excellent in that it can easily increase the concealment degree because the ink thickness can be increased.

  The printing ink is not particularly limited as long as it can be used for printing. For example, evaporative drying ink, oxidation polymerization ink, heat-curing ink, two-component reaction ink, ultraviolet-curing ink, heat Examples thereof include melt ink, heat sublimation ink, and the like. Among these, ultraviolet curable inks suitable for film printing are preferable. In order to improve the optical effect, the printing ink is preferably white or gray. However, the diffusion effect may be improved by adding an inorganic filler or an organic filler to the transparent ink.

  Further, when the non-transmissive component ratio is controlled by the non-transmissive component ratio adjustment pattern 133, the non-transmissive component ratio adjustment pattern 133 may be provided as an uneven pattern on the surface of the transparent resin layer. In this case, the concavo-convex pattern of the non-transmissive component ratio adjustment pattern 133 of the same type as the concavo-convex pattern constituting the concavo-convex pattern layer 132 described above can be produced by changing the aspect ratio of the concavo-convex pattern depending on the location. In this case, the aspect ratio of the concavo-convex pattern of the non-transmission component ratio adjustment pattern 133 may change periodically or may exist locally. Moreover, you may change uniaxially along the desired direction of a backlight screen. In either case, a region with a high non-transmission component ratio (a region with a high aspect ratio of the concavo-convex pattern of the non-transmission component ratio adjustment pattern 133) substantially matches a portion where the illuminance of light incident on the diffusion sheet 12 is high. It is preferable to arrange an uneven pattern of the non-transmission component ratio adjustment pattern 133 in The pitch of the concavo-convex pattern of the non-transmissive component ratio adjustment pattern 133 is preferably in the range of 0.1 μm to 100 μm and the height is in the range of 0.1 μm to 30 μm.

  In the light source unit 1 according to the present embodiment, the illuminance distribution on the light incident surface of the diffusion sheet 12 can be measured by, for example, EZCONTRASTXL88 from ELDIM. Specifically, in the light source unit in which the diffusion sheet 12 is provided, the omnidirectional luminance distribution is measured by setting the focal point of the apparatus at a position where the light incident surface of the diffusion sheet 12 is located, excluding the diffusion sheet 12, and from the result. It can be measured by repeating in the in-plane measurement target range to obtain an integrated light intensity (Integrated Intensity). In the diffusion sheet 12 according to the present embodiment, in accordance with the illuminance distribution measured under these measurement conditions, brightness nonuniformity such as hot spots is effectively reduced by controlling the non-transmission component ratio in the sheet surface. can do.

(Diffusion sheet configuration example)
Hereinafter, a specific configuration example of the diffusion sheet 12 according to the present embodiment will be described with reference to FIGS. 8A to 8E are schematic cross-sectional views illustrating a configuration example of the diffusion sheet 12.

  As shown in FIGS. 8A to 8E, the diffusion sheet 12 according to the present embodiment includes a sheet-like base material 131 and a concavo-convex pattern layer 132 provided on one main surface of the base material 131. And the non-transmission component ratio adjustment pattern 133 provided on one main surface side or the other main surface side of the base material 131.

  The non-transmissive component ratio adjustment pattern 133 is provided as a pattern made of a light-reflective ink cured product containing a light diffusing agent, for example. A plurality of non-transmission component ratio adjustment patterns 133 may be provided on the other main surface of the base material 131 so as to be separated from each other (see FIG. 8A). A plurality may be provided so as to be separated from each other between the material 131 and the uneven pattern layer 132 (see FIG. 8B), or a plurality may be provided so as to be separated from each other on the surface of the uneven pattern layer 132 (FIG. 8). (See (c)). Moreover, you may provide an irregular uneven | corrugated pattern as the impermeable component ratio adjustment pattern 133 (refer FIG.8 (d), (e)). In this case, the irregular uneven pattern as the non-transmission component ratio adjustment pattern 133 may exist periodically (see FIG. 8D) or aperiodic (see FIG. 8E). FIG. 8E shows an example in which the aspect ratio of the concavo-convex shape monotonously increases along one direction of the sheet.

  By providing the concavo-convex pattern layer 132 on one main surface of the base material 131 and providing the non-transmission component ratio adjustment pattern 133 on the other main surface of the base material 131, the concavo-convex pattern layer 132 and the non-transmission component ratio adjustment pattern 133 This is preferable because the distance between the two becomes larger and the effect of suppressing each luminance unevenness can be further exhibited. When the concave / convex pattern layer 132 and the non-transmission component rate adjustment pattern 133 are stacked on one main surface of the substrate 131, the concave / convex pattern layer 132 (non-transmission component rate adjustment pattern 133) is the non-transmission component rate adjustment pattern. 133 (concavo-convex pattern layer 132) can be physically protected, which is preferable in that the strength can be increased. In particular, when the non-transmission component ratio adjustment pattern 133 is provided on the substrate 131 and the uneven pattern layer 132 is further provided thereon, the light-reflective ink cured product pattern constituting the non-transmission component ratio adjustment pattern 133 is obtained. Since it can be physically protected by the concavo-convex pattern layer 132 composed of the concavo-convex structure, it is preferable from the viewpoint of reducing the restrictions on the mechanical strength of the light-reflective ink cured product and expanding the options.

  The non-transmission component ratio adjustment pattern 133 can be configured, for example, by applying a light reflective material over the entire main surface of the base material 131 or partially. Examples of such light-reflective materials include light-reflective inks such as paints and metal pastes, light diffusing agents such as silicon beads and acrylic beads, light absorbers such as fluorescent brighteners, surface irregularities, organic / inorganic A filler etc. are mentioned, The transmittance | permeability and a reflectance can be controlled by the area, thickness, density, etc. which the light reflective material occupies in a main surface. Among these, light reflective ink is preferable from the viewpoint that the transmittance and reflectance can be easily controlled and the area can be increased, and white ink is most preferable from the viewpoint of high reflectance and low absorption. . Moreover, as a coating method, since the pattern of a white ink hardened | cured material can be formed freely, a printing method is preferable. The white ink cured product and the printing method are as described above.

  The distribution of the non-transmission component ratio can be generated by the distribution of the dot density and the dot density in the non-transmission component ratio adjustment pattern 133 including dots formed of the light-reflective ink cured product.

The dot density of the light-reflective ink cured product is a normal line with respect to the main surface of the substrate 131 at a portion where the light-reflective ink cured product and the substrate 131 are in contact as shown in the following relational expression (3). It refers to the percentage of the value obtained by dividing the area observed from the direction (hereinafter referred to as “ink area”) by the observed unit area. The ink area can be measured, for example, with an ultra-deep color 3D shape measurement microscope (manufactured by Keyence Corporation, VK-9500) or an optical microscope. As the dot density increases, the reflectance at that portion increases and the transmittance decreases.
Dot density (%) = (ink area) / (observed unit area) × 100 (3)

  The dot density of the light-reflective ink cured product is governed by the ink density (ratio of the light reflection component in the ink cured product) and the dot thickness on an arbitrary surface. In this case, since the concentration of the light reflection component in the ink composition is known in advance, the concentration can be grasped every time the type of ink is changed. The dot thickness can be measured, for example, with an ultra-deep color 3D shape measurement microscope (VK-9500, manufactured by Keyence Corporation). Here, the dot thickness represents the dot thickness after the solvent component such as water or solvent is volatilized, for example, when the ink is a water-containing ink or a solvent-containing ink. As the dot density increases, the reflectance at that portion increases and the transmittance decreases.

  The distribution of the non-transmission component ratio is formed by changing the dot density while keeping the dot density of the non-transmission component ratio adjustment pattern 133 (light-reflective ink cured product), that is, the “dot thickness” and the “ink density” constant. It is preferable from the viewpoint that the distribution of light transmittance can be easily controlled. 9A to 9C are schematic diagrams illustrating an example of dot density in the diffusion sheet 12. In changing the dot density of the diffusing sheet 12, the pitch P between dots is made constant, and the dot area of each non-transmissive component ratio adjustment pattern 133 (light-reflective ink cured product) is reduced as the dot density decreases. (FIG. 9A). In addition, the dot area of each non-transmission component ratio adjustment pattern 133 (light-reflective ink cured product) is made constant, and the pitch of each non-transmission component ratio adjustment pattern 133 (light-reflective ink cured product) is reduced as the dot density decreases. P may be increased (FIG. 9B). In addition, as the dot density decreases, the dot area of each non-transmissive component ratio adjustment pattern 133 (light-reflective ink cured product) may be reduced and the pitch P may be increased. (Fig. 9 (c))

  The non-transmission component ratio adjustment pattern 133 (dot pattern of the light-reflecting ink cured product) may be prepared once or may be prepared in a plurality of times. In that case, adjacent dots may overlap each other in a portion where the dot density is high.

(Diffusion sheet manufacturing method)
A mold for producing such an uneven pattern layer 132 of the diffusion sheet 12 can be produced as follows. First, a sub-master type in which a speckle pattern is formed so that a non-transmission component ratio changes depending on the position by irradiating a photosensitive material or a photoresist with a laser beam through a lens or a mask in advance by interference exposure. By controlling the size, shape and direction of the speckle pattern by changing the distance and size between the components constituting the laser irradiation system, the range of the non-transmission component ratio is controlled, and the concavo-convex structure having different non-transmission component ratios is recorded. can do. Furthermore, a metal master mold may be manufactured by electroforming the sub master mold with a metal such as nickel. For example, the concavo-convex pattern layer 132 can be formed on one main surface of the substrate 131 by photocuring an ultraviolet curable resin between the mold and the substrate 131 of the diffusion sheet 12.

Next, the manufacturing method of the diffusion sheet 12 will be described in detail.
In the diffusion sheet 12 shown in FIG. 8A, after the concave / convex pattern layer 132 is formed on one main surface of the base material 131, the non-transmissive component ratio adjustment pattern 133 is printed on the other main surface of the base material 131. Can be manufactured. In addition, the uneven pattern layer 132 may be formed on the other main surface of the base material 131 after the non-transmission component rate adjustment pattern 133 is printed on one main surface of the base material 131, or the non-transmissive component rate adjustment pattern 133 and the uneven pattern layer 132 may be formed at the same time. By manufacturing in this way, the concavo-convex pattern layer 132 and the non-transmissive component rate adjustment pattern 133 made of a light-reflective ink cured product are respectively provided on the pair of main surfaces of the substrate 131. For this reason, since the distance between the uneven | corrugated pattern layer 132 and the non-transmission component ratio adjustment pattern 133 becomes large, it is preferable at the point which can exhibit each brightness nonuniformity suppression effect more.

  Moreover, the diffusion sheet 12 shown in FIG.8 (b) prints the non-permeable component rate adjustment pattern 133 which consists of a light-reflective ink cured material on the one main surface of the base material 131, and also has an uneven | corrugated pattern layer on it. It can be manufactured by providing 132. Thus, when the non-transmissive component rate adjustment pattern 133 made of a light-reflective ink cured product is provided on one main surface of the substrate 131 and the uneven pattern layer 132 is further provided thereon, the non-transmissive component rate adjustment pattern 133 is provided. The pattern of the light-reflective ink constituting the film can be physically protected by the concave / convex pattern layer 132. For this reason, it is preferable in that the mechanical strength of the light-reflective ink is reduced and the options can be expanded.

  Similarly, in the diffusion sheet 12 shown in FIG. 8 (c), an uneven pattern layer 132 is provided on one main surface of the substrate 131, and a non-transmissive component rate adjustment pattern made of a light-reflecting ink cured product is further formed thereon. It can be manufactured by printing 133. Similarly, in the diffusion sheet 12 shown in FIGS. 8D and 8E, the concave / convex pattern layer 132 is provided on one main surface of the base material 131, and the concave / convex pattern is formed on the other main surface of the base material 131. It can be manufactured by providing the non-transmissive component rate adjustment pattern 133.

  In the case of the configuration of the diffusion sheet 12 as shown in FIGS. 8B and 8C, another main surface opposite to the main surface on which the non-transmission component ratio adjustment pattern 133 and the uneven pattern layer 132 are provided is a smooth surface and an uneven surface. It may be a surface, a mat surface, or the like. From the viewpoint of improving the luminance and reducing the luminance unevenness, it is preferable that the surface opposite to the surface having the concavo-convex structure is a smooth surface. In general, when a diffusion sheet is laminated, a very small amount of beads may be applied to the surface opposite to the surface having the concavo-convex structure as long as smoothness is not lost in order to prevent damage. Such a case is also included in the smooth surface.

  The diffusion sheet according to the present invention may be disposed on a light guide plate or an optical sheet, and may be bonded using a transparent adhesive material or the like. In the case of bonding, since an air layer is not interposed between the light guide plate and the optical sheet, the effect of suppressing luminance unevenness is excellent. Examples of the bonding method include an adhesive material, ultrasonic welding, high frequency welding, excimer laser treatment, plasma laser treatment, thermal lamination, and the like, but it is preferable to use an adhesive material because the process is simple.

〔Light guide plate〕
As the light guide plate 11, a light-transmitting plastic material such as polymethyl methacrylate, polycarbonate, or polystyrene, or a light-transmitting material such as glass can be used.

[Light reflection diffuser]
The light reflecting diffuser 14 is large in accordance with the distance from the light incident surface 11c so that the light emitted from the LED 13 and incident into the light guide plate 11 from the light incident surface 11c can be emitted uniformly over the entire light exit surface 11a. Has been adjusted. The light reflecting diffuser 14 can be provided by printing a white substance such as titanium oxide or barium titanate on the reflecting surface 11b. Further, the light reflecting diffuser 14 may be formed by providing fine irregularities on the reflecting surface 11 b of the light guide plate 11. These light reflecting diffusers 14 are arranged so that light can be emitted efficiently and uniformly from the entire light exit surface 11 a of the light guide plate 11.

  The thickness of the light guide plate 11 is preferably 1 mm to 10 mm, more preferably 2 mm to 5 mm. If it is smaller than 1 mm, the handleability is lowered during processing, and the deflection occurs due to moisture absorption. If it is larger than 10 mm, it is not preferable because the cost is increased and the weight is increased.

〔light source〕
The light source is not limited to the LED 13, and a linear light source such as a cold cathode tube (CCFL) or a point light source such as a laser can be used.

[Other configurations of the light source unit]
In the light source unit 1 according to the above embodiment, the configuration in which the diffusion sheet 12 is disposed on the light exit surface 11a side of the light guide plate 11 has been described. However, the reflection sheet 21 is disposed on the reflection surface 11b side of the light guide plate 11, Furthermore, it is preferable to install various optical sheets on the light exit surface 11a side of the light guide plate 11 for condensing, starting up, and diffusing the emitted light. As the optical sheet, a lens sheet, a prism sheet, a reflective polarizing sheet, or the like can be used.

  FIG. 10 shows another configuration example of the light source unit. In the light source unit shown in FIG. 10, a reflective sheet 21 that reflects light from the LED 13 to the light guide plate 11 is disposed on the reflective surface 11 b side of the light guide plate 11. Further, a lens sheet 22, a prism sheet 23, and a reflective polarizing sheet 24 are arranged in this order above the diffusion sheet 12 arranged on the light exit surface 11a side of the light guide plate 11.

  As the reflection sheet 21, various materials can be used as long as they can reflect light. For example, a resin such as polyester or polycarbonate is foamed and fine air particles are made into a sheet, and a sheet is formed by mixing two or more resins, and resin layers with different refractive indexes are laminated. Sheet, etc. can be used. Moreover, as the reflective sheet 21, the uneven | corrugated shape may be formed in the surface. As these, those having inorganic fine particles added to the surface can be used as necessary.

  As the lens sheet 22, a sheet in which spherical beads of acrylic resin are coated on a sheet of polyester resin, triacetyl cellulose, polycarbonate, or the like can be used. Further, as the lens sheet, a sheet in which a fine concavo-convex structure made of an ultraviolet curable resin is transferred onto a sheet of polyester resin, triacetyl cellulose, polycarbonate, or the like can be used.

  As the prism sheet 23, an optical sheet in which prism rows having a substantially triangular shape, a substantially trapezoidal shape, and a substantially elliptical cross-sectional shape are arrayed on the surface can be used. A shape obtained by rounding the top of the cross-sectional shape can be preferably used from the viewpoint of improving scratch resistance. These prism sheets 23 can be used in a form in which a prism array made of an ultraviolet curable resin is transferred onto a base material sheet such as polyester resin, triacetyl cellulose, or polycarbonate. Since such a prism sheet 23 exhibits retroreflectivity, it has a function of collecting incident light to the front. A prism apex angle of about 90 degrees is preferable because the light collecting function is exhibited well, and a prism array period of about 50 μm can reduce the occurrence of moire when a liquid crystal display device is constructed. Is preferable.

  As the reflective polarizing sheet 24, a sheet having a function of separating polarized light from natural light or polarized light can be used. As a sheet | seat which isolate | separates linearly polarized light, the film etc. which permeate | transmit one of the linearly polarized light orthogonal to an axial direction, and reflect the other are mentioned, for example. Specifically, as the reflective polarizing sheet, a resin having a large birefringence retardation (polycarbonate, acrylic resin, polyester resin, etc.) and a resin having a small birefringence retardation (cycloolefin polymer, etc.) are alternately laminated. A sheet obtained by laminating and uniaxially stretching, a sheet having a structure in which several hundred layers of birefringent polyester resin are laminated (DBEF, manufactured by 3M), and the like can be used.

  The light source unit according to the present invention can be applied to a backlight of a liquid crystal display device as a surface light source, and can be used for an edge light type backlight unit. In addition, the screen (illumination area) can be divided into a plurality of areas and used for a backlight unit for a composite split panel in which application of energy-saving local dimming or the like is considered. It can also be applied as a surface light source such as a signboard. The present invention is also applicable to a composite split panel backlight unit in which a plurality of light guides gather to form a light guide plate for the entire screen.

  FIGS. 11A to 11C are schematic views showing examples of the composite divided panel backlight unit. As shown in FIGS. 11A to 11C, in the composite split panel backlight 30, a plurality of light guides 32 on which light sources 31 are arranged gather to form a light guide plate 33 of the entire screen. For this reason, bright lines may occur at the joints between the adjacent light guides 32. In such a composite divided panel backlight unit, by using the diffusion sheet 12 according to the present embodiment, hot spots in each light guide 32 can be reduced, or the adjacent light guide 32 and light guide. It is also possible to reduce bright lines generated at the seam between the two.

[Liquid Crystal Display]
A liquid crystal display device according to an embodiment of the present invention includes a liquid crystal display panel and a light source unit according to the present invention that supplies light to the liquid crystal display panel.

  Thus, according to the light source unit according to the above-described embodiment, the light emitted from the light exit surface 11a of the light guide plate 11 is diffused by the diffusion sheet 12, so that uneven brightness occurs in the light exit surface 11a of the light guide plate 11. This region can also be used as an effective light emitting region. As a result, in the screen of the liquid crystal display device according to the embodiment of the present invention using the light source unit, the light of the region with relatively high illuminance is reflected without being absorbed, and the region with relatively low illuminance is reflected. Brightness can be achieved, and the brightness and darkness in the screen can be made uniform. Thus, since the light use efficiency is high and the use area of the light source unit can be expanded, it is useful from the viewpoint of energy saving and space saving (narrow frame).

  Next, examples carried out to clarify the effects of the present invention will be described, but the present invention is not limited to these examples.

(Example)

  The light source unit of the example was configured as shown in FIG. As the light guide plate 11, a shinkolite-A (registered trademark) manufactured by Mitsubishi Rayon Co., Ltd. having a thickness of 2 mm was cut into 18.2 cm × 10.9 cm and the end face was flattened.

  A 10.9 cm × 2 mm one-side end surface 11c of the light guide plate 11 was disposed as the light incident surface 11c. A reflective sheet (Lumirror E6SL, manufactured by Toray Industries, Inc.) 21 is disposed on the reflective surface 11b side of the light guide plate 11. A diffusion sheet 12, a lens sheet 22 (TDF-127, manufactured by Shinfa Intertec), a prism sheet 23 (manufactured by BEF-III, 3M), and a reflective polarizing sheet (DBEF, 3M) are provided on the light exit surface 11a side. Arranged in order. As the LED 13, six LEDs mounted on a vehicle-mounted monitor STRADA TR-M80WVS7 manufactured by Panasonic Corporation were used.

  White dots were screen-printed as the light reflecting diffuser 14 on the reflecting surface 11 b of the light guide plate 11. The white dot pattern has a distance from the light incident surface 11c so that the in-plane luminance of a certain region (region A4 on the right side of the broken line L1 in FIG. 2) away from the light incident surface 11c of the light guide plate 11 is uniform. The dot density was adjusted accordingly. Further, the dot density was adjusted to be small so that the brightness of the bright high illuminance area A1 near the LED 13 matched the brightness near the center of the light guide plate 11.

  The diffusion sheet 12 was configured as shown in FIG. A polyethylene terephthalate film (Cosmo Shine A4300, manufactured by Toyobo Co., Ltd.) having a thickness of 250 μm was used as the substrate 131. Further, a photocurable resin layer having an irregular concavo-convex pattern produced using a speckle pattern obtained by interference exposure as the irregular concavo-convex pattern layer 132 and having a diffusion angle of 90 ° was used. As the non-transmission component ratio adjustment pattern 133, a white ink dot-printed as a light reflective ink was used. Here, for dot printing, a thermal transfer printing apparatus and a white ink ribbon (MD-5500, MDC-SCWH, manufactured by Alps Electric Co., Ltd.) dedicated to the printing apparatus were used. Therefore, the dot density is constant over the entire printing area.

Using the illuminance distribution of the hot spot portion of the light guide plate 11 shown in FIG. 12A (the area A3 on the LED 13 side from the broken line L1 shown in FIG. 2) as the original data, white dot printing is performed by the above-described printing machine, and the non-transmissive component. The diffusion sheet 12 on which the rate adjustment pattern 133 was formed was produced. At this time, the non-transmissive component ratio in the high non-transmissive component ratio region was 21%, and the non-transmissive component ratio in the low non-transmissive component region was 1%. The pitch between white dots in the high non-transmissive component ratio region was 283 μm, one dot was a circle having a diameter of 194 μm and an area of 29544 μm ² , and the dot density per unit area was 37%. The unit area was 283 μm × 283 μm = 80089 μm ² . The pitch between white dots in the low non-transmissive component ratio region was 283 μm, one dot was a circle having a diameter of 12 μm and an area of 113 μm ² , and the dot density per unit area was 0.14%. The unit area was 283 μm × 283 μm = 80089 μm ² . This diffusion sheet 12 was used so that the concavo-convex pattern layer 132 was the light exit surface.

  The diffusion sheet 12 is arranged so that the high non-transmission component rate region in the sheet surface overlaps with the high illuminance region A1 in the light guide plate 11 in plan view, and the low non-transmission component rate region in the sheet surface. And the low illuminance region A2 in the light guide plate 11 are arranged so as to overlap each other. Further, the diffusion sheet 12 is arranged so that the distribution of the non-transmission component ratio in the sheet surface changes gently according to the change in the illuminance distribution on the light exit surface 11a of the light guide plate 11. That is, the non-transmission component rate in the sheet surface of the diffusion sheet 12 is directed from the high non-transmission component rate region to the low non-transmission component rate region (from the high illumination region A1 to the low illumination region A2 of the light guide plate 11). A white pattern was provided so as to decrease gently. As a result of disposing the diffusion sheet 12, hot spots on the light guide plate 11 were reduced (see FIG. 12B).

(Comparative example)
As the light source unit of the comparative example, a light source unit obtained by removing the light diffusion sheet 12 from the light source unit of the example was used (see FIG. 13). In the configuration of the light source unit of the comparative example, the dark low illuminance area A2 due to the LED 13 on the light exit surface 11a of the light guide plate 11 is very dark, and the area A3 on the LED 13 side from the broken line L1 shown in FIG. The spot was in a large state (see FIG. 12A). Therefore, only an area A4 on the opposite side of the light incident surface 11c from the broken line L1 shown in FIG. 2 can be used as an effective light emitting area with uniform illuminance. In addition, in the area A3 on the light incident surface 11c side from the broken line L1 shown in FIG. 2, the emitted light is wasted light that cannot be used.

[Evaluation of uneven brightness]
The hot spot reduction effect was measured under the following conditions. First, the luminance of the high illuminance region A1 in the light guide plate 11 was measured using a two-dimensional color luminance meter (Konica Minolta, CA2000). The two-dimensional color luminance meter (CA2000) was installed 70 cm away from the light source unit. The average luminance value measured in the range of 2 mm × 2 mm at the center of the light source unit was defined as the luminance. Then, the brightness | luminance of the low illumination intensity area | region A2 in the light-guide plate 11 was measured similarly, and the brightness nonuniformity value was measured from the following relational expression (4). The closer this value is to 1, the smaller the hot spot. In the light source unit according to the example, the luminance unevenness value decreased to 1.2, but in the light source unit according to the comparative example, the luminance unevenness value increased to 1.9.
(Luminance unevenness value) = (Luminance in high illuminance area A1) / (Luminance in low illuminance area A2) (4)

  Next, the observation result of luminance unevenness in the light source unit according to the example including the diffusion sheet 12 was compared with the observation result of luminance unevenness in the light source unit according to the comparative example not including the diffusion sheet 12. As a result, it was confirmed that the light source unit according to the example including the diffusion sheet 12 had higher uniformity of in-plane luminance near the light incident surface 11c of the light guide plate 11 and was able to dramatically reduce hot spots. . Thus, when the light source unit according to the present invention is used, almost the entire region of the light exit surface 11a of the light guide plate 11 can be used as a screen of a liquid crystal display panel (liquid crystal display device).

  The present invention is not limited to the embodiment described above, and can be implemented with various modifications. For example, the material, arrangement, shape, and the like of the members in the above embodiment are illustrative, and can be implemented with appropriate changes. In addition, various modifications can be made without departing from the scope of the present invention.

  The light source unit according to the present invention is useful for a backlight and can be suitably used in the field of thin liquid crystal display devices.

1 Light source unit 11, 33 Light guide plate 11a Main surface (light-emitting surface)
11b Main surface (reflection surface)
11c End face (incident surface)
11d End face 12 Diffusion sheet 13 LED
DESCRIPTION OF SYMBOLS 14 Light reflection diffuser 15, 17, 18, 19 Brightness irregularity 16 Boss 21 Reflection sheet 22 Lens sheet 23 Prism sheet 24 Reflection type polarization sheet 30 Backlight for compound division panel 31 Light source 32 Light guide 131 Base material 132 Concavity and convexity pattern layer 133 Non-transmission component rate adjustment pattern

Claims (10)

A light guide plate having a pair of opposing main surfaces and an end surface between the pair of main surfaces, wherein the pair of main surfaces are a light exit surface and a reflection surface, respectively, and one end surface is a light entrance surface When,
A light source arranged to receive light into the light incident surface of the light guide plate;
A diffusion sheet disposed on the light exit surface side of the light guide plate;
The diffusion sheet includes a sheet-like base material, a resin layer having an irregular uneven pattern provided on one main surface of the base material, and the one main surface or the other main surface of the base material. And a non-transmission component rate adjustment pattern provided on the surface, wherein the non-transmission component rate is non-uniform in the sheet surface.   The relative intensity distribution of the non-transmission component ratio in the sheet surface of the diffusion sheet and the relative intensity distribution of the illuminance in the sheet surface at the time of incident light of the diffusion sheet are substantially equal. Light source unit.   The light source unit according to claim 1 or 2, wherein a diffusion angle of the diffusion sheet is in a range of 1 to 120 degrees.   The light source unit according to any one of claims 1 to 3, wherein the resin layer having an irregular uneven pattern of the diffusion sheet is formed by a speckle pattern by interference exposure.   The light source unit according to any one of claims 1 to 4, wherein the non-transmission component ratio adjustment pattern of the diffusion sheet contains a light-reflective ink cured product containing a light diffusing agent.   The light source unit according to any one of claims 1 to 5, further comprising a reflection sheet disposed below the light guide plate.   The light source unit according to claim 1, further comprising a lens sheet disposed above the diffusion sheet.   The light source unit according to claim 1, further comprising a prism sheet disposed above the diffusion sheet.   The light source unit according to claim 1, further comprising a reflective polarizing sheet disposed above the diffusion sheet.   A liquid crystal display device comprising: a liquid crystal display panel; and the light source unit according to claim 1 for supplying light to the liquid crystal display panel.