JP2009217949A - Light guide plate, optical sheet, backlight device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide unit, an optical sheet, a backlight device and an electronic apparatus, whereby interference fringes can be prevented from being viewed from shallow angles to a display surface by surely suppressing generation of the interference fringes. <P>SOLUTION: A plurality of the optical sheets 3 include, for example, a reflecting sheet 8 disposed on the back side of a light guide plate 2, two diffusion sheets (a lower diffusion sheet 17 and an upper diffusion sheet 16) disposed on the surface (light emitting surface 2b) 2b side, and a prism sheet 18 disposed between these diffusion sheets 16, 17. For example, the upper surface 2b of the light guide plate 2 which faces the lower surface 17a of the lower diffusion sheet 17 is formed into a non-flat surface. Particularly, the non-flat surface 2b is set to satisfy 0<(P/Ra)<1.02×10<SP>4</SP>when arithmetic average roughness denotes Ra and an average pitch denotes P. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light guide plate, an optical sheet, a backlight device, and an electronic device used for, for example, a liquid crystal display.

  A backlight used in a liquid crystal display generally includes a light source and a light guide unit that guides light from the light source to a liquid crystal panel. The light guide unit includes, for example, a light guide sheet and a plurality of optical sheets. The light guide sheet has a function of guiding light from the light source in a predetermined direction. The optical sheet includes a prism sheet that orients light from the light guide sheet to the front side of the display, or a diffusion sheet that diffuses uniformly.

  For example, when the front surface of the light guide sheet is a flat front surface and the back surface of the diffusion sheet in contact with the light guide sheet surface is flat, light interference easily occurs between the flat surfaces. Interference fringes are likely to occur. The interference fringes are relieved in appearance by the unevenness and the blast surface on the surface side of the diffusion sheet.

  Here, a backlight in which one surface of an opposing optical sheet is formed non-flat is disclosed (for example, see Patent Document 1). Specifically, the embossing is formed on one surface of the optical sheet, so that the two optical sheets are adhered to each other, and the sheet curl phenomenon is suppressed.

JP 2002-251908 (paragraphs [0046], [0047], FIG. 5 and the like)

  However, there are cases where interference fringes cannot be removed simply by providing embossing on the surface of the optical sheet. For example, when light due to the interference fringes passes through the liquid crystal panel, a phenomenon occurs in which the interference fringes generated by the light guide unit itself are emphasized due to the regularity of the structure of the liquid crystal panel and the regularity of the interference fringes.

  For example, in a display device (TV) equipped with a receiver that receives a television broadcast or the like, the user may view the display from a wide angle, that is, the user is shallow with respect to the display surface (an angle from the display surface). Sometimes, the display is viewed at a small angle. In such a case, since the interference fringes are emphasized, the interference fringes cannot be completely removed by simply providing embossing on the surface of the diffusion sheet or the optical sheet.

  In view of the circumstances as described above, an object of the present invention is to reliably suppress the generation of interference fringes and prevent the interference fringes from being seen even at a shallow angle from the display surface. To provide a light device and an electronic apparatus.

In order to achieve the above object, a light guide plate according to the present invention is a light guide plate on which light from a light source is incident, and a light guide part that guides the incident light, and the light that passes through the light guide part. And an emission surface in which the relation between the arithmetic average roughness Ra and the average pitch P is 0 <(P / Ra) <1.02 × 10 ⁴ .

  By using a light guide plate having such an output surface, for example, in the calculation of visible light interference fringes generated between the output surface of the light guide plate and another optical sheet in contact with the output surface The pitch is smaller than 0.5 mm. Therefore, the human eyesight cannot substantially see the interference fringes, which is equivalent to no interference fringes. Thereby, for example, interference fringes can be prevented from being seen from a shallow angle from the display surface.

  For example, the emission surface has a protrusion by embossing. The height of the protrusion is 10 to 50 μm. This is because if the height of the protrusion is lower than 10 μm, there is an influence due to the coherence of visible light. If the height of the protrusion exceeds 50 μm, it is necessary to increase the size of the protrusion (size or diameter in a plane parallel to the light exit surface of the light guide plate), so that the protrusion can be seen by human eyes. Because it becomes.

  Alternatively, the exit surface may be a blasted surface.

An optical sheet according to the present invention is an optical sheet that causes a predetermined optical function to act on light from a light source, the incident surface on which the light is incident, the incident light is emitted, and an arithmetic average roughness The relationship between Ra and the average pitch P is 0 <(P / Ra) <1.02 × 10 ⁴ .

Alternatively, the optical sheet has an incident surface in which the relationship between the arithmetic average roughness Ra and the average pitch P is 0 <(P / Ra) <1.02 × 10 ⁴ , and an emission surface that emits the incident light. May be provided.

The backlight device according to the present invention is a sheet-like optical member having an optical surface in which the relationship between the light source, arithmetic average roughness Ra, and average pitch P is 0 <(P / Ra) <1.02 × 10 ⁴ And a light guide unit for diffusing light from the light source in a planar shape.

  For example, the light guide unit includes, as the optical member, a first optical member having the optical surface, a flat surface adjacent to the first optical member, and facing the optical surface, or a regular optical member. And a second optical member having a pattern surface.

The electronic apparatus according to the present invention includes a light source and a sheet-like optical member having a surface in which the relationship between the arithmetic average roughness Ra and the average pitch P is 0 <(P / Ra) <1.02 × 10 ^4. A backlight device having a light guide unit that diffuses light from the light source in a planar shape, and a plurality of pixels, and controls the transmittance of the light emitted from the backlight device for each pixel. And a light transmittance control panel.

  As described above, according to the present invention, it is possible to reliably suppress the generation of interference fringes and prevent the interference fringes from being seen from a shallow angle from the display surface.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic exploded perspective view showing a backlight device according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a display including the backlight device 10 and the light transmittance control panel 9 shown in FIG.

  The backlight device 10 includes a light source unit 5 and a light guide unit 6 that diffuses light emitted from the light source in a planar shape. The light guide unit 6 provides the emitted light 29 with uniform brightness. The light guide unit 6 includes a plurality of sheet-like optical members that cause a predetermined optical function to act on the light from the light source unit 5. For example, these sheet-like optical members include, for example, a light guide plate 2 that guides light from the light source unit 5 and a plurality of optical sheets 3 (see FIG. 2). The light source unit 5 is disposed on both side surfaces 2 c of the light guide plate 2.

  In the present embodiment, a cathode tube (for example, a fluorescent tube) 7 is used as the light source of the light source unit 5. Two cathode tubes 7 are provided on each side of the light guide plate 2, but the number is not limited. Alternatively, one or a plurality of cathode tubes 7 may be provided on one side of the light guide plate 2.

  As a material of the light guide plate 2, glass, transparent resin, and other general materials are used.

  The light source unit 5 includes a reflector 11 provided around the cathode tube 7. The reflector 11 reflects the light emitted from the cathode tube 7 and efficiently causes the reflected light to enter the side surface of the light guide plate 2. The shape of the cross section of the reflector 11 may be a part of a quadrangle, for example, a part of a circle or a curve such as a hyperbola.

  A typical example of the light transmittance control panel 9 is a liquid crystal panel. FIG. 2 shows the structure of the liquid crystal panel. However, any panel may be used as long as the light transmittance of the backlight device 10 is variably controlled for each pixel. The liquid crystal panel includes a liquid crystal 24, a glass substrate 21, a color filter 23, a polarizing plate 22, and the like.

  The plurality of optical sheets 3 include, for example, a reflection sheet 8 arranged on the back side of the light guide plate 2 and two diffusion sheets (the lower diffusion sheet 17 and the light guide plate 2 on the surface (light emitting surface) 2b side). An upper diffusion sheet 16) and a prism sheet 18 disposed between these diffusion sheets 16,17. As the optical sheet 3, other known sheets such as a retardation sheet and a protective sheet may be provided. For example, the upper diffusion sheet 16 may function as a protective sheet. The shape, arrangement, etc. of these optical sheets 3 can be appropriately changed.

  Hereinafter, in FIG. 1 and FIG. 2, for the sake of convenience, the light transmittance control panel 9 side is the upper side, and the reflection sheet 8 side is the lower side.

  The lower diffusion sheet 17 flattens the distribution of light emitted from the light exit surface 2b of the light guide plate 2, and controls the optical direction of the light incident on the prism sheet 18 to some extent, so that the optical function of the prism sheet 18 is improved. To promote. The prism sheet 18 has a function of concentrating light emitted from the lower diffusion sheet 17 (a lot of light in all directions) upward. The upper diffusion sheet 16 prevents interference fringes (moire) caused by regular irregularities provided on the upper surface of the prism sheet 18 and the lattice pitch of the light transmittance control panel 9, and protects the prism sheet 18. It has a function to do. Alternatively, the upper diffusion sheet 16 has a function of allowing the user to view the image from the lateral direction with respect to the display by slightly diffusing the light collected upward.

  FIG. 3 is an enlarged cross-sectional view showing the light guide plate 2, the lower diffusion sheet 17, and the prism sheet 18. At least one of the two opposing surfaces among the principal surfaces 2a, 2b, 16a, 16b, 17a, 17b, 18a, and 18b of these optical members 2 and 16 to 18 is formed non-flat.

  For example, in the present embodiment, the upper surface 2b of the light guide plate 2 facing the flat lower surface 17a of the lower diffusion sheet 17 is a non-flat surface. In addition, the lower surface 16a of the upper diffusion sheet 16 facing the prism portion (regular optical pattern surface) 18b formed on the upper surface of the prism sheet 18 is formed to be non-flat. The upper surfaces 17b and 16b of the lower diffusion sheet 17 and the upper diffusion sheet 16 are diffusion surfaces (non-flat surfaces) in order to exhibit their original functions.

  Thus, in this Embodiment, generation | occurrence | production of an interference fringe can be suppressed by preventing flat surfaces from facing each other.

  Hereinafter, the cause of interference fringes will be described.

  FIG. 4 is an enlarged view of the light guide plate and the optical sheet, showing a case where the facing surfaces are flat surfaces. In this example, the light emission surface 102b which is the upper surface of the light guide plate 102 and the lower surface 17a of the lower diffusion sheet 17 face each other, and the emission surface 102b and the lower surface 17a are flat surfaces. Further, the prism portion 18 b which is the upper surface of the prism sheet 18 and the lower surface 116 a of the upper diffusion sheet 116 face each other.

  Here, attention is focused on the light guide plate 102 and the lower diffusion sheet 17 shown in FIG. FIG. 5A is a diagram illustrating a state in which interference fringes are generated by the light guide plate 102 and the lower diffusion sheet 17. As shown in FIG. 5B, when the flat surface 17a of the lower diffusion sheet 17 and the flat surface 102b of the light guide plate 2 come into contact, an interference fringe 30 as shown in FIG. 5A is generated.

  FIG. 6 is a schematic diagram for explaining the principle of generation of the interference fringes 30. When the flat surfaces come into contact with each other, a gap of several times the wavelength of light is generated between the flat surfaces in the vicinity of the contact point. In this case, light transmission and reflection occur as shown in the figure. For example, when the gap is about 1/4 of the wavelength of light, the light 31a that is reflected and reaches the human eye passes through the 1/4 wavelength gap twice, so that the optical path does not reflect and the light reaches the eye Half a wavelength longer than 31b. This means that the phase of the light 31a that arrives after reflection is opposite to that of the light 31b that reaches the eye without being reflected. In other words, the eyes see light with waves that are out of phase with each other, and these lights cancel each other and appear dark.

  When the gap is about ½ of the wavelength, the optical path difference is one wavelength, and these lights 31c and 31d are added and look bright. That is, as the gap increases by ¼ of the wavelength, a bright part and a dark part are generated, and the interference fringes 30 can be seen. This stripe is also called a Newton ring.

  The wavelength of visible light has a band of 380 to 780 nm, but when considering the interference fringe 30, it can be considered as the center wavelength of 550 nm. That is, the interference fringe 30 is generated by a gap about several times as large as 550 nm.

  If this gap is further increased, the coherence between the reflected light 31a and 31c and the unreflected light 31b and 31d is lost. The gap where coherence is lost may be considered to be about 10 to 30 times the wavelength. That is, when the gap is about 15 μm or more, the interference fringes 30 become invisible.

  In general, the interference fringes 30 are scattered by the diffusibility of the diffusion sheets 16 and 17 and rarely appear as a striped pattern. FIG. 7 shows a backlight in which the light guide plate 102 in which the interference fringes 30 shown in FIG. 5A are generated and the lower diffusion sheet 17 are incorporated (the backlight in which the prism sheet 18 and the upper diffusion sheet 116 are further incorporated). It is a figure which shows the state which turned on. As shown in FIG. 7, in this case, a dark portion 32 is generated in the portion where the interference fringe 30 is generated. When the backlight is viewed from the front, it is generally bright and the dark part 32 as shown in FIG. However, when viewed from a shallow angle from the surface of the backlight, for example, when viewed from an angle of about 60 to 70 ° from the front, such a dark portion 32 can be seen. These dark parts 32 are also called flare.

  This dark portion 32 appears more emphasized when it passes through the liquid crystal panel 9. The reason is that another interference fringe occurs between the interference fringe 30 shown in FIG. 5A and the pattern such as the color filter 23 (see FIG. 2) of the liquid crystal panel 9, and the interference fringe emphasizes the flare. It is thought that.

  As shown in FIG. 4, the prism portion 18b of the prism sheet 18 can be considered as a pseudo flat surface. That is, the prism portion 18b is not a flat surface, but is not a randomly rough surface such as a diffusing surface or a non-flat surface, but a portion formed by a regular optical pattern. In such a prism portion 18b, light is regularly reflected. Therefore, when the prism portion 18b and the flat surface 116a of the upper diffusion sheet 116 come into contact with each other, an interference fringe 30 is generated.

  On the other hand, in the present embodiment, as shown in FIGS. 2 and 3, the occurrence of interference fringes can be suppressed by preventing the flat surfaces from facing each other.

  In particular, the non-flat surfaces 2b and 16a of the light guide plate 2 and the upper diffusion sheet 16 according to the present embodiment are expressed by the following expression (1) in relation to the arithmetic average roughness Ra and the average pitch P.

0 <(P / Ra) <1.02 × 10 ⁴ (1).

  Hereinafter, the expression (1) will be described.

  FIG. 8 is a diagram illustrating a state in which the surface 2b having the surface roughness is in contact with the flat surface 17a. FIG. 9 is a diagram for geometrically explaining the above equation using the arithmetic average roughness Ra and the average pitch P in FIG. The protrusions 28 shown in FIG. 8 correspond to the protrusions 28 of FIG. 9, and the surface 2b having the surface roughness can be geometrically approximated as shown in FIG.

  The dark and bright portions of the interference fringes have gaps every λ / 2. Therefore, the pitch is F, and F: (λ / 2) = (P / 2): 2Ra based on the similarity of triangles. Therefore, the following formula (2) is derived.

F = Pλ / (8Ra) (2)
λ is 550 nm.

  FIG. 10 is a table showing an example of the length of the interference fringe pitch F with respect to the ratio (P / Ra) of the average pitch P and the arithmetic average roughness Ra based on the equation (2). In this example, Ra = 5 μm is shown, but Ra is not limited to this. In order to prevent the interference fringes from being seen by human eyes, it is necessary to make the pitch F of the interference fringes smaller than a predetermined length. For that purpose, (P / Ra) may be smaller than a predetermined size.

If F = 0.7 mm or less, the distance between the dark line (bright line) and the dark line (bright line) is sufficiently narrow, and the interference fringes are hardly visible to human eyes. From equation (2), when F = 0.7 mm, P / Ra = 1.02 × 10 ⁴ . At F = 0.5 mm, P / Ra = 7.27 × 10 ³ . Accordingly, 0 <(P / Ra) <1.02 × 10 ⁴ or 0 <(P / Ra) <7.27 × 10 ³ may be set. Similarly, the numerical ranges of P / Ra may be set for the upper surfaces 17b and 16b of the lower diffusion sheet 17 and the upper diffusion sheet 16, respectively.

  The non-flat surfaces 2b and 16a may be formed by blasting, for example. Alternatively, when the non-flat surfaces 2b and 16a are formed by mold molding, the mold may be roughened by blasting.

  The non-flat surfaces 2b and 16a may be formed by forming protrusions on the surfaces of the light guide plate 2 and the upper diffusion sheet 16 by embossing. FIG. 14 is a diagram showing a form in which the lower surface of a diffusion sheet (for example, a lower diffusion sheet) 37 facing the light guide plate 2 having a flat emission surface 102b is embossed. By this embossing, a protrusion 37 a is formed on the lower surface of the diffusion sheet 37.

  The height of the protrusion 37a formed by embossing may be typically 10 to 50 μm.

This is because if the height of the protrusion 37a is lower than 10 μm, there is an influence due to the coherence of visible light. The coherent distance D is obtained by D = λ ² / Δλ. λ is 550 nm, which is the central wavelength of visible light. Δλ is a spectrum width noticed in the system, and is usually a band of light received by cone cells in the human eye. Cone cells are cells in the retina that sense color, and there are three types that feel red, green, and blue. The width of the wavelength to be sensed, that is, the bandwidth is about 100 nm. ^{That, D = 550 2/100 =} 3025nm, namely, about 3 [mu] m. At this point, the coherence is broken.

  Here, the case of white light where the spectrum does not protrude as light has been described. However, in the case of light with a projected spectrum, for example, a short wavelength laser, Δλ becomes small and the coherence distance becomes long. For example, in the case of the cathode tube 7, if attention is paid to the place where the spectrum protrudes, Δλ becomes smaller and the coherence distance becomes longer. Even if these are taken into consideration, there is no problem if the height of the projection 37a is 10 μm or more.

  On the other hand, when the height of the protrusion 37a exceeds 50 μm, it is necessary to increase the size of the protrusion 37a (the size or the diameter in a plane parallel to the emission surface 102b of the light guide plate 102). Therefore, the height of the protrusion 37a may be set to 50 μm or less. Further, if the height exceeds 50 μm, the facing sheet may bend, follow a rough surface, and eventually cause interference fringes.

FIG. 11 is a diagram showing a light guide plate and an optical sheet (for example, a diffusion sheet) according to another embodiment of the present invention. In this embodiment, the output surface 102b of the light guide plate 102 is formed flat, and the lower surface 47a of the diffusion sheet 47 facing the output surface 102b is formed non-planar. For the lower surface 47a of the diffusion sheet 47, the ratio (P / Ra) of the average pitch P to the arithmetic average roughness Ra is 0 <(P / Ra) <1.02 × 10 ⁴ or the like for the same purpose as described above. A range is set.

  FIG. 12 is a view showing a light guide plate and an optical sheet (for example, a diffusion sheet) according to still another embodiment of the present invention. In this embodiment, both the emission surface 2b of the light guide plate 2 and the lower surface 47a of the diffusion sheet 47 are formed non-flat for the same purpose as in the above embodiments.

  FIG. 13 is a diagram showing a prism sheet and other optical sheets (for example, a diffusion sheet) according to still another embodiment of the present invention. In this embodiment, the lower surface 47a of the diffusion sheet 47 facing the prism portion (pseudo flat surface) 18b formed on the upper surface of the prism sheet 18 is non-flat for the same purpose as in the above embodiments. Is formed.

  FIG. 15 is a view showing a light guide plate and an optical sheet (for example, a diffusion sheet 17) according to still another embodiment. A predetermined optical pattern (for example, a prism shape or other uneven shape) 2d is formed on the lower surface 2a facing the emission surface 2b of the light guide plate 2 according to the present embodiment. The optical pattern 2d is, for example, a pattern such as a dot, a straight line, a circle, an ellipse, another curve, or a combination of these when viewed in a plane parallel to the lower surface 2a. The optical pattern 2d is formed by a process such as printing or molding.

  FIG. 16 is a diagram illustrating a light guide plate and a diffusion sheet, which are given as comparative examples of the light guide plate 2 and the diffusion sheet 17 illustrated in FIG. 15. An uneven optical pattern 42d is also formed on the lower surface 42a of the light guide plate 42 according to this example. The upper surface 42b of the light guide plate 42 is a flat surface. For example, in an edge light type backlight in which light from the light source unit 5 enters the inside from the side surface (edge) 42 c of the light guide plate 42, such an optical pattern 42 d is provided on the lower surface 42 a of the light guide plate 42. .

  In FIG. 16, the light incident from the side surface 42c of the light guide plate 42 travels toward the central portion of the light guide plate 42, and when there is no optical pattern 42d, that is, when the lower surface 42a is flat, the light is substantially In addition, since the light is totally reflected in the light guide plate 2, light does not leak to the upper surface, which is the observation side. That is, a light guide plate without such an optical pattern 42d is not useful as a backlight. Therefore, the total reflection condition is broken by providing the optical pattern 42d on the lower surface 42a of the light guide plate 42. If it does so, the light which leaked with the reflective sheet 8 will be reflected, and light will be radiate | emitted from the upper surface 42b.

  As shown in FIG. 16, for example, when the density of this optical pattern is high on the side surface (edge) 42c of the light guide plate 42, the amount of leaked light near the cathode tube 7 on the side surface 42c increases. That is, it becomes bright near the cathode tube 7 and dark at the center. Therefore, as shown in FIG. 16, when there is incident light from both sides, the density of the optical pattern 42d on the side close to the side surface 42c is low, and the optical pattern 42d is formed so as to be dark at the center, whereby the upper surface 42b. The amount of light leakage from the light guide plate 42 may be set uniformly throughout. That is, the optical pattern 42d may be determined depending on how the light leakage amount and uniformity are designed.

  Here, as shown in FIG. 15, when the upper surface 2 b is formed non-flat like the light guide plate 2 according to each embodiment and generation of interference fringes is suppressed, the upper surface 2 b of the light guide plate 2. As in the case of the optical pattern 42d, the unevenness of the light breaks the total reflection condition of the light guide plate 2, and light is emitted. Therefore, if an optical pattern 42d similar to that shown in FIG. 16 is used in the light guide plate 2 having an uneven surface on the upper surface 2b as shown in FIG. The light leaks from the upper surface 2b, and the vicinity of the cathode tube 7 is bright and the center is dark. In order to eliminate such inconvenience, the density of the optical pattern 2d only needs to be set lower than the density of the optical pattern 42d shown in FIG. Thereby, the uniformity of the light of the backlight apparatus 10 can be maintained.

  FIG. 17 is a schematic perspective view showing a backlight device according to another embodiment of the present invention. The main difference between the backlight device 50 according to the present embodiment and the backlight device 10 shown in FIG. For example, the light guide plate 52 of the backlight device 50 is formed so that its thickness decreases as the distance from the light source unit 5 increases. The light source unit 5 is mounted on one side surface 52 c of the light guide plate 52. Even in the backlight device 50 on which the so-called wedge-type (wedge-type) light guide plate 52 is mounted, the optical member (the light guide plate 2 and / or the optical sheet) having the non-flat surface according to each of the above embodiments. 3) is applicable.

  FIG. 18 is a schematic perspective view showing a backlight device according to another embodiment of the present invention. The difference between the backlight device 60 according to the present embodiment and the backlight device 10 shown in FIG. 1 is a light source. As the light source of the backlight device 60, for example, an LED block 27 is used. In this example, a plurality of LED blocks 27 are arranged along the side surface 2 c of the light guide plate 2. One LED block 27 includes one or a plurality of LEDs. The color of light generated by one LED block 27 is at least one of white, red, green, blue and other colors. The number of the LED blocks 27 may be one, and can be appropriately changed depending on the luminance of the LED blocks 27, the size of the light guide plate 2 (or the liquid crystal panel), and the like.

  Thus, even in the backlight device 60 in which the LED block 27 is mounted as a light source, the optical member (the light guide plate 2 and / or the optical sheet 3) having the non-flat surface according to each of the above embodiments can be applied. is there.

  As the light source of the backlight device 60, an intrinsic EL element may be used instead of the LED (dispersed EL element).

  As described above, the backlight devices 10, 50, 60, the light guide plate 2, and the optical sheet 3 described in each embodiment can be applied to various electronic devices including a display. Examples of electronic devices are shown in FIGS. 19, 20, and 21. FIG. 19 shows a display, FIG. 20 shows a TV, and FIG. 21 shows a laptop PC.

  The electronic devices are not limited to the devices shown in FIGS. 19 to 21, and include PDAs (Personal Digital Assistance), electronic dictionaries, digital cameras, audio / visual devices, mobile phones, robotic devices, and other electrical appliances. .

1 is a schematic exploded perspective view showing a backlight device according to an embodiment of the present invention. It is typical sectional drawing which shows the display provided with the backlight apparatus and light transmittance control panel which were shown in FIG. It is an expanded sectional view showing a light guide plate, a lower diffusion sheet, and a prism sheet. It is an enlarged view of a light guide plate and an optical sheet showing a case where facing surfaces are flat surfaces. (A) is a figure which shows the state which the interference fringe generate | occur | produced with the light-guide plate and the lower diffusion sheet, (B) is a figure which shows the state which the light-guide plate and the lower diffusion sheet contacted at arbitrary points. It is a schematic diagram for demonstrating the generation | occurrence | production principle of the interference fringe. It is a figure which shows the state which the backlight incorporating the light-guide plate in which the interference fringe generate | occur | produced in FIG. It is a figure which shows a mode that the surface with surface roughness is in contact with the flat surface. FIG. 9 is a diagram for geometrically explaining the above equation using the arithmetic average roughness Ra and the average pitch P. It is a table | surface which shows the length of the pitch F of an interference fringe with respect to ratio (P / Ra) of the average pitch P and arithmetic mean roughness Ra based on Formula (2). It is a figure which shows the light-guide plate and optical sheet which concern on other embodiment of this invention. It is a figure which shows the light-guide plate and optical sheet which concern on another form of this invention. It is a figure which shows the prism sheet and other optical sheet which concern on another form of this invention. It is a figure which shows the form by which the lower surface of the diffusion sheet which faces a light-guide plate which has a flat output surface was embossed. It is a figure which shows the light-guide plate and optical sheet which concern on another embodiment of this invention. It is a figure which shows the light guide plate and optical sheet which were mentioned as a comparative example of the light guide plate and optical sheet shown in FIG. It is a typical perspective view which shows the backlight apparatus which concerns on other embodiment of this invention. It is a typical perspective view which shows the backlight apparatus which concerns on other embodiment of this invention. It is a figure which shows a display as embodiment of an electronic device. It is a figure which shows TV as other embodiment of an electronic device. It is a figure which shows laptop PC as another embodiment of an electronic device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2, 52, 102 ... Light guide plate 2, 16-18 ... Optical member 2d, 42d ... Optical pattern 2c ... Side surface 3 ... Optical sheet 5 ... Light source unit 6 ... Light guide unit 9 ... Light transmittance control panel (liquid crystal panel)
10, 50, 60 ... Backlight device 16, 17, 37, 47 ... Diffusion sheet 18 ... Prism sheet 28 ... Projection 37a ... Projection

Claims (9)

A light guide plate on which light from a light source is incident;
A light guide for guiding the incident light;
A light guide plate that emits the light passing through the light guide section and has an emission surface in which the relationship between arithmetic average roughness Ra and average pitch P is 0 <(P / Ra) <1.02 × 10 ⁴ . The light guide plate according to claim 1,
The light emission surface has a light guide plate having a protrusion by embossing. The light guide plate according to claim 2,
The light guide plate has a height of 10 to 50 μm. The light guide plate according to claim 1,
The light emitting plate is a surface that is blasted. An optical sheet for causing a predetermined optical function to act on light from a light source,
An incident surface on which the light is incident;
An optical sheet that emits the incident light and has an emission surface in which the relationship between the arithmetic average roughness Ra and the average pitch P is 0 <(P / Ra) <1.02 × 10 ⁴ . An optical sheet for causing a predetermined optical function to act on light from a light source,
An incident surface where the relation between the arithmetic average roughness Ra and the average pitch P is 0 <(P / Ra) <1.02 × 10 ⁴ ;
An optical sheet comprising: an exit surface that emits the incident light. A light source;
It includes a plate-like optical member having an optical surface where the relation between the arithmetic average roughness Ra and the average pitch P is 0 <(P / Ra) <1.02 × 10 ⁴ , and the light from the light source is planarized A backlight device comprising: a light guide unit for diffusing. The backlight device according to claim 7,
The light guide unit, as the optical member,
A first optical member having the optical surface;
And a second optical member having a flat surface or a regular optical pattern surface adjacent to the first optical member and facing the optical surface. A plate-like optical member having a surface where the relationship between the light source and arithmetic average roughness Ra and average pitch P is 0 <(P / Ra) <1.02 × 10 ^4; A backlight device having a light guide unit that diffuses into a shape;
An electronic apparatus comprising: a light transmittance control panel that has a plurality of pixels and controls the transmittance of the light emitted from the backlight device for each pixel.