JP2012013756A - Optical deflection element and surface light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical deflection element that is used for a surface light source device having a primary light source arranged adjacent to both side surfaces of a light guide body, and simplifies manufacturing thereof.SOLUTION: An optical deflection element 4 includes a light entrance surface 40 to which light is entered, and a light emission surface 45 that is disposed opposite to the light entrance surface and from which light is emitted. The light entrance surface 40 is provided with a plurality of prism columns substantially in parallel to each other. The plurality of prism columns constitute prism column units each including a pair of prism columns adjacent to each other. The prism column unit includes a first prism column having two asymmetrical prism faces 43 and 44 and a second prism column having two asymmetrical prism faces 41 and 42. In a cross-sectional form orthogonal to an extending direction of the prism column, the two prism faces 41 and 42 of the second prism column are arranged substantially symmetrical to the two prism faces 43 and 44 of the first prism column.

Description

  The present invention relates to an edge light type surface light source device that constitutes a liquid crystal display device and the like used as a display unit in a notebook computer, a monitor, a television, and the like, and an optical deflection element used therefor.

  In recent years, color liquid crystal display devices have been widely used in various fields as monitors for portable notebook computers and personal computers, or as display units for liquid crystal televisions. In addition, with the increase in the amount of information processing, diversification of needs, compatibility with multimedia, and the like, liquid crystal display devices have been increased in screen size and definition.

  The liquid crystal display device basically includes a backlight unit and a liquid crystal display element unit. As the backlight unit, there are a direct type with a light source arranged directly under the liquid crystal display element unit and an edge light type with a light source arranged so as to face the side end face of the light guide. From the viewpoint of making it easier, an edge light type is widely used.

  In recent years, from the viewpoint of reducing power consumption, in order to effectively use the amount of light emitted from the primary light source as an edge light type backlight unit, the spread angle of the light beam emitted from the screen is made as small as possible and the required angle range Those that emit light in a concentrated manner are used. For example, a high-luminance surface light source device can be realized by using an optical deflection element disclosed in Japanese Patent No. 4210053 (Patent Document 1).

  On the other hand, in a monitor, a television, or the like, if the light is concentrated in a narrow angle range, it can be viewed only in a specific angle range. For this reason, it is necessary to keep the luminance moderate while securing the viewing angle.

Japanese Patent No. 4210053

  By the way, in a monitor or a television, a primary light source may be arranged adjacent to both end faces of the light guide to secure a light quantity. In this case, in order to efficiently emit light from the surface light source device and thus the liquid crystal display device, it is preferable that the light deflection element has left-right symmetry in the prism row.

  In this regard, in the optical deflection element described in Patent Document 1, a pair of prism surfaces of each prism row is formed of symmetrical convex curved surfaces.

  However, in this case, it is difficult to manufacture a cutting diamond tool for forming the prism row shape transfer surface of the mold member for transferring and shaping the prism row forming surface of the light deflection element by plastic molding. And there exists a problem that manufacture of a surface light source device using the same is not easy.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a light deflection element that is used in a surface light source device in which a primary light source is disposed adjacent to both end faces of a light guide and is easily manufactured, and a surface light source device using the same. There is.

That is, the optical deflection element of the present invention is
A light deflection surface having a light incident surface on which light is incident and a light exit surface that emits incident light that is located on the opposite side, and a plurality of prism rows are arranged substantially in parallel on the light incident surface An element,
The plurality of prism rows constitute a prism row unit by a pair of adjacent prism rows,
The prism array unit is composed of a first prism array composed of two asymmetric prism surfaces and a second prism array composed of two asymmetric prism surfaces, and the extending direction of the prism array In the cross-sectional shape orthogonal to each other, the two prism surfaces of the second prism row are arranged substantially symmetrically with the two prism surfaces of the first prism row.
It is characterized by that.

  In one aspect of the present invention, the first prism row is substantially a triangle formed by a straight line connecting the apex of the prism row and two valleys in a cross section orthogonal to the extending direction of the prism row. It is an isosceles triangle, and the apex angle formed by two equilateral sides sandwiching the apex of the prism row is 60 to 80 degrees. In one aspect of the present invention, at least a part of one prism surface of the first prism array has a convex curve shape in a cross section orthogonal to the extending direction of the prism array, The ratio d / P between the maximum distance d from the straight line connecting the apex and the valley of the prism surface and the arrangement pitch P of the prism rows is 0.004 to 0.05. In one aspect of the present invention, the convex curve shape of one prism surface of the first prism row is an arc shape, and the ratio r / of the radius of curvature r of the arc shape and the arrangement pitch P of the prism rows is P is 2-50. In one aspect of the present invention, the other prism surface of the first prism row is a flat surface.

Moreover, according to the present invention,
A light source having a primary light source, a light incident end surface on which light emitted from the primary light source is incident, a light emitting surface for guiding and emitting the incident light, and a light emitting surface of the light guide are disposed adjacent to each other. And the above optical deflection element,
The surface light source device, wherein the primary light source is disposed so as to face two light incident end faces composed of two side end faces facing each other of the light guide,
Is provided.

  In one aspect of the present invention, the light deflection element is disposed such that the light incident surface faces the light exit surface of the light guide.

  According to the present invention, it is possible to provide a light deflection element that is used in a surface light source device in which a primary light source is disposed adjacent to both end surfaces of a light guide and is easily manufactured, and a surface light source device using the same. it can.

It is a typical perspective view which shows embodiment of the surface light source device by this invention. It is explanatory drawing of the cross-sectional shape of the prism row | line | column in embodiment of the optical deflection | deviation element by this invention. It is a figure which shows an example of the outgoing light luminous intensity distribution of the light guide in the surface light source device by this invention dependent on the outgoing angle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic perspective view showing one embodiment of a surface light source device according to the present invention. As shown in FIG. 1, in the surface light source device of the present invention, two side end surfaces located on opposite sides are used as a light incident end surface 31, and one surface substantially orthogonal thereto is used as a light emitting surface 33. The light guide 3, the primary light source 1 disposed to face the light incident end surface 31 of the light guide 3, the light deflection element 4 and the light diffusion element disposed on the light emitting surface 33 of the light guide 3 6 and the light reflecting element 5 disposed to face the back surface 34 of the light guide 3 opposite to the light emitting surface 33. Although not shown in the drawing, the primary light source 1 is similarly arranged on the light emitting surface 31 on the left side of FIG.

  The light guide 3 is arranged in parallel with the XY plane and has a rectangular plate shape as a whole. The light guide 3 has four side end faces, and a pair of side end faces parallel to the YZ plane is a light incident end face 31. The light incident end face 31 is disposed to face the primary light source 1, and the light emitted from the primary light source 1 enters the light incident end face 31 and is introduced into the light guide 3.

  Two main surfaces that are substantially orthogonal to the light incident end surface 31 of the light guide 3 are respectively positioned substantially parallel to the XY plane, and one of the surfaces (the upper surface in the drawing) serves as the light emitting surface 33. At least one of the light emitting surface 33 and the back surface 34 located on the opposite side thereof has a directional light emitting function portion formed of a rough surface, a prism array, a lenticular lens array, a V-shaped groove, and the like. By providing a directional light emitting function unit composed of lens surfaces in which lens rows are formed in parallel, the light incident on the light incident end surface 31 is guided through the light guide 3 while the light incident end surface 31 is exposed to the light incident end surface. In the outgoing light distribution in the plane (XZ plane) orthogonal to both 31 and the light emitting surface 33, light having directivity is emitted. When the angle between the direction of the peak of the outgoing light distribution in the XZ plane (appearing on both sides with respect to the Z direction) and the light outgoing surface 33 is a, this angle a is preferably 10 to 40 degrees. The full width at half maximum is preferably 10 to 40 degrees.

  In the present invention, light diffusing fine particles are mixed and dispersed in the light guide instead of or in combination with the light emitting surface 33 or the back surface 34 as described above. What provided the directional light emission function may be used. Further, the light guide 3 is not limited to a substantially parallel plate shape (that is, the XZ cross-sectional shape is rectangular) as shown in FIG. 1, but at least in a portion adjacent to the light incident end surface. Those having a wedge shape in which the thickness gradually decreases as the distance from the head is increased, or those having various XZ cross-sectional shapes such as a hull shape can be used.

  The light guide 3 of the present invention can be composed of a synthetic resin having a high light transmittance. Examples of such synthetic resins include methacrylic resins, acrylic resins, polycarbonate resins, polyester resins, and vinyl chloride resins. In particular, methacrylic resins are optimal because of their high light transmittance, heat resistance, mechanical properties, and molding processability. Such a methacrylic resin is a resin mainly composed of methyl methacrylate, and preferably has a methyl methacrylate content of 80% by weight or more. When the surface structure of the rough surface of the light guide 3 is formed, the transparent synthetic resin plate may be formed by hot pressing using a mold member having a desired surface structure, screen printing, extrusion molding, The shape may be imparted simultaneously with molding by injection molding or the like. The structural surface can also be formed using heat or a photocurable resin. Furthermore, on a transparent substrate such as a polyester film, acrylic resin, polycarbonate resin, vinyl chloride resin, polymethacrylamide resin, or other transparent substrate or rough surface structure made of an active energy ray curable resin. May be formed on the surface, or such a sheet may be bonded and integrated on a separate transparent substrate by a method such as adhesion or fusion. As the active energy ray-curable resin, polyfunctional (meth) acrylic compounds, vinyl compounds, (meth) acrylic acid esters, allyl compounds, (meth) acrylic acid metal salts, and the like can be used.

  FIG. 2 is an explanatory diagram of the cross-sectional shape of the prism row in the light deflection element 4. FIG. 2 corresponds to the XZ section in FIG. One of the main surfaces of the light deflection element 4 is a light incident surface 40 and the other surface is a light output surface 45. A large number of prism rows are arranged in parallel on the light incident surface 40.

  FIG. 2 shows a prism row unit constituted by a pair of prism rows adjacent to each other. The prism array unit is composed of a first prism array composed of two asymmetric prism surfaces 43 and 44 and a second prism array composed of two asymmetric prism surfaces 41 and 42.

  One prism surface 43 of the first prism row has at least a part, particularly the whole, a convex curve shape, for example, an arc shape, in the XZ cross section orthogonal to the extending direction of the prism row. The maximum distance from the straight line 43 ′ connecting the apex of the prism row and the valley of the prism surface 43 to the prism surface 43 is d. The ratio d / P between the maximum distance d and the arrangement pitch P of the prism rows is preferably 0.004 to 0.05. The ratio r / P between the arc-shaped curvature radius r of one prism surface 43 of the first prism row and the arrangement pitch P of the prism rows is preferably 2 to 50. The ratio r / P is more preferably 2-20. The ratio r / P is suitably 2 to 7 for applications that require a relatively wide viewing angle such as a television, and 7 to 7 for applications where a brighter light is better even if the viewing angle is somewhat narrow, such as a monitor. 20 is suitable. By setting both the ratio d / P and the ratio r / P within the above range, it becomes easier to improve the light condensing characteristics and obtain a desired viewing angle.

  The other prism surface 44 of the first prism row is a flat surface. According to this, it becomes easier to manufacture a cutting diamond tool for forming a prism array shape transfer surface of a mold member for transferring and shaping the prism array formation surface of the light deflection element by plastic molding. Manufacture of an element and a surface light source device using the element is further facilitated. However, the other prism surface 44 is not limited to a flat surface, and may have a curved surface shape that is asymmetric with respect to the one prism surface 43 with respect to the YZ plane or the Z direction. Each of the prism surfaces 43 and 44 may be composed of a combination of a flat surface and a curved surface. In this case, if the surfaces of the prism surfaces 43 and 44 that are closest to the tip of the prism are flat, it is easy to manufacture a cutting diamond tool.

  In the first prism row, in the XZ section orthogonal to the extending direction of the prism row, a triangle formed by a straight line connecting the apex of the prism row and two valleys is a substantially isosceles triangle. The apex angle formed by two equal sides sandwiching the apex of the prism row (the side indicated by the straight line 43 ′ and the straight line indicating the prism surface 44 in FIG. 2) is preferably 60 to 80 degrees.

  In the shape of the XZ cross section orthogonal to the extending direction of the prism rows, the two prism surfaces 41 and 42 of the second prism row are arranged substantially symmetrically with the two prism surfaces 43 and 44 of the first prism row. In other words, the second prism row corresponds to the first prism row obtained by inverting the line in the normal direction (Z direction: vertical direction in FIG. 2) of the light exit surface 45 as a symmetric line. The row and the second prism row have a symmetrical shape. Therefore, using two cutting diamond tools of the same shape (first cutting diamond tool and second cutting diamond tool) arranged in opposite directions, the first cutting diamond tool is set in the first direction. Cutting is performed while moving, and the second cutting diamond bite is cut while moving in the second direction opposite to the first direction, thereby easily forming the prism row shape transfer surface of the mold member. be able to.

  In a monitor or a television, a primary light source may be disposed adjacent to both end faces of the light guide to secure the amount of light. In this case, in order to efficiently emit light from the surface light source device and thus the liquid crystal display device, the light deflecting element has to rise in a predetermined direction from either the left or right side. The most efficient shape of the prism array unit for this purpose is a shape having left-right symmetry. In the present invention, the prism surfaces 43 and 44 of the first prism array and the prism surfaces 41 and 42 of the second prism array This realizes left-right symmetry, which can facilitate manufacturing as follows.

  The light deflecting element 4 is active on a transparent substrate such as a transparent film or sheet made of polyester resin, acrylic resin, polycarbonate resin, vinyl chloride resin, polymethacrylimide resin, or the like having a roughened back surface. A prism structure made of an energy beam curable resin can be formed on the surface. As the active energy ray-curable resin, polyfunctional (meth) acrylic compounds, vinyl compounds, (meth) acrylic acid esters, allyl compounds, (meth) acrylic acid metal salts, and the like can be used. When a prism structure is formed on a transparent substrate such as a transparent film or sheet, a mold material is cut with a diamond tool to form a forming mold (molding mold member). In order to obtain a desired viewing angle characteristic, it is preferable to include a curved surface in a part of the prism row. However, when a curved surface is included in a part of the prism row, it is difficult to produce a cutting tool if the shape is symmetrical. In addition, in order to produce a symmetrical tool, it may be necessary to provide a flat portion at the tip of the prism. Therefore, as shown in FIG. 2, a prism array unit is configured by combining two prism arrays having a horizontally inverted shape, and a bilaterally symmetrical shape is realized within the prism array unit, thereby facilitating the manufacture of a tool. An optical deflection element with good utilization efficiency can be easily obtained.

  As the primary light source 1, for example, a point light source such as an LED light source, a halogen lamp, or a metal halide lamp, or a linear light source extending in the Y direction such as a fluorescent lamp or a cold cathode tube can be used. A plurality of point light sources may be arranged in the Y direction. If necessary, a light source reflector may be installed so as to surround the primary light source. This reflects light that cannot enter the light guide 3 out of the light emitted from the primary light source toward the light guide. As a material, for example, a plastic film having a metal-deposited reflective layer on the surface can be used. A reflection member similar to such a light source reflector may be attached to a side end face other than the side end face 31 that is the light incident end face of the light guide 3.

  The light reflecting element 5 is disposed so as to face the back surface 34 on the side opposite to the light emitting surface 33 of the light guide 3. As the light reflecting element 5, for example, a plastic sheet having a metal vapor deposition reflecting layer on the surface can be used. In the present invention, it is also possible to use a light reflecting layer or the like formed on the back surface 34 of the light guide 3 by metal vapor deposition or the like, instead of the reflecting sheet, as the light reflecting element 5. As a result, the light leaking from the light guide 3 can be returned again into the light guide, and the amount of light emitted from the primary light source can be used effectively.

  The light diffusing element 6 may be integrated with the light deflecting element 4 on the light exiting surface side of the light deflecting element 4, or the light diffusing element 6 may be individually placed on the light exiting surface of the light deflecting element 4. good. When the light diffusing element 6 is individually mounted, the surface adjacent to the light deflecting element 4 of the light diffusing element 6, that is, the incident surface is provided with an uneven structure to prevent sticking with the light deflecting element 4. It is preferable to give. Similarly, it is necessary to consider sticking between the light diffusing element 6 and the liquid crystal display element disposed thereon, and it is preferable to provide a concavo-convex structure on the light emitting surface. When this concavo-convex structure is provided only for the purpose of preventing sticking, the average inclination angle according to ISO4287 / 1-1984 described in paragraphs [0019] and [0020] of the specification of Patent Document 1 is 0. It is preferable to have a structure of 7 degrees or more, more preferably 1 degree or more, and more preferably 1.5 degrees or more.

  It should be noted that the light diffusing element 6 may be removed if the required light emission can be obtained without using the light diffusing element 6.

  A liquid crystal display device is configured by disposing a liquid crystal display element on the light emitting surface of the surface light source device as described above. The liquid crystal display device is observed by an observer through the liquid crystal display element from above in FIG.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

  In addition, the preparation method of the light guide used in the following examples and comparative examples and the measurement method of each physical property are shown below.

[Production of light guide]
A stainless steel plate with an effective area of 195 mm (dimension in the X direction) x 307 mm (dimension in the Y direction) and a thickness of 3 mm is used as the mold material, and stainless steel using glass beads (J220 manufactured by Potters Valotini). Blasting was performed with the distance from the plate to the blast nozzle being 32 cm.

  On the other hand, a mirror-finished effective area of 195 mm (dimension in the X direction) x 307 mm (dimension in the Y direction) and a 3 mm thick nickel-phosphorus plated plate is used as the mold material, and the back surface of the light guide consisting of the lens array forming surface A shape transfer surface for transferring the film was formed by cutting. The lens array on the lens array forming surface had a top tip radius of curvature of 135 μm, an array pitch of 100 μm, and an aspect ratio of 10. Further, the extending direction of the lens array was set to be a direction (X direction) perpendicular to the long side of the mold material.

  A transparent acrylic resin composition is injection-molded by using the above two molding mold members, and has a rectangular shape with a short side of 195 mm and a long side of 307 mm, a constant thickness of 0.8 mm, and one surface (light emitting surface) A light guide made of transparent acrylic resin having a rough surface 33) and a lens array forming surface on the other surface (back surface 34) was obtained.

  54 LEDs (E1S62-YWOS7- manufactured by Toyoda Gosei Co., Ltd.) on one side at equal intervals along the long side so as to face both side end surfaces (light incident end surface 31) of the long side having a thickness of 0.8 mm 07) and a light source reflector. Further, a light scattering reflection sheet (E6SP manufactured by Toray Industries, Inc.) was disposed as a light reflecting element so as to face the back surface 34 of the light guide. The result of measuring the luminous intensity distribution of this light guide by the method shown below is shown in FIG. 3 (luminous intensity is shown as a relative value).

[Measurement of luminous intensity distribution of light guide]
In the configuration in which the light deflecting element 4 and the light diffusing element 6 are removed from the configuration shown in FIG. 1, the primary light source 1 is turned on, and black paper having a 3 mmφ pinhole is pinned on the light emitting surface 33 of the light guide 3. The hole was fixed so as to be located at the center of the light guide. The luminous intensity distribution of the emitted light was measured with a luminance meter while the normal direction of the light emitting surface 33, that is, the Z direction was set to 0 °, and the XZ plane was tilted at 1 ° intervals within a range of + 85 ° to −85 °. Regarding the angle, the side closer to the primary light source 1 was positive, and the opposite side was negative.

[Measurement of peak luminance, peak angle and full width at half maximum of luminance distribution of surface light source device]
In the configuration in which the light diffusing element 6 is removed from the configuration shown in FIG. 1, the primary light source 1 is turned on, the viewing angle of the luminance meter is set to 1 degree, and the measurement position is adjusted to be in the center of the surface light source device. The luminance distribution of the emitted light is measured with a luminance meter while tilting at an interval of 1 ° within a range of + 45 ° to −45 °, with the normal direction of the light exit surface 42 of the light deflecting element 4, that is, the Z direction being 0 degree, The luminance, the peak angle (the angle at which the peak luminance was obtained), and the full width at half maximum of the luminance distribution (the spread angle of the distribution of luminance values greater than or equal to 1/2 the peak luminance value) were determined. Regarding the angle, the side closer to the primary light source 1 was positive, and the opposite side was negative.

Example 1:
A surface light source device (however, the light diffusing element 6 was removed) belonging to the embodiment of FIGS. 1 and 2 was produced as follows.

  First, the light guide 3 having the emitted light luminous intensity distribution (luminous intensity is shown as a relative value) shown in FIG. 3 was produced. On the light emitting surface 33 of the light guide, the light deflection element 4 manufactured using an acrylic ultraviolet curable resin having a refractive index of 1.506 was placed. The light deflection element 4 is a prism sheet in which a large number of prism rows are formed on the light incident surface, and in each prism row unit, the cross-sectional shape of one prism surface 44 of the first prism row is the exit surface normal direction direction ( (Z direction) is a plane having an angle of 30.14 degrees, the cross-sectional shape of the other prism surface 43 of the first prism row is an arc having a radius of curvature r = 165 μm, and the arrangement pitch P of the prism rows is 50 μm. there were. The second prism row had a shape obtained by horizontally inverting the first prism row with respect to the light exit surface normal direction (Z direction). This prism sheet was placed so that the light incident surface 40 composed of the prism row forming surface faces the light emitting surface 33 of the light guide 3. At this time, the ratio d / P was 0.038, and the ratio r / P was 3.3. Further, the primary light source 1 was arranged on each of the two light incident end faces 31, and the light reflecting element 5 was arranged to obtain a surface light source device.

  The emission light luminance distribution of this surface light source device was measured, and the peak luminance ratio, the peak angle, and the full width at half maximum of the luminance distribution with reference to Comparative Example 1 described later were obtained. The results are shown in Table 1.

Comparative Example 1:
A surface light source device was obtained in the same manner as in Example 1 except that each prism row was composed of a pair of symmetrical prism surfaces, and the cross-sectional shape of this prism surface was a curved surface with a curvature radius r = 165 μm.

  The emission light luminance distribution of this surface light source device was measured, the peak luminance was set to 1.000, the peak angle and the full width at half maximum of the luminance distribution were obtained, and the results are shown in Table 1.

DESCRIPTION OF SYMBOLS 1 Primary light source 3 Light guide 4 Light deflection element 5 Light reflection element 6 Light diffusion element 31 Light incident end surface
33 Light exit surface 34 Back surface 40 Light incident surface 41-44 Prism surface 43 'Straight line 45 Light exit surface

Claims (7)

A light deflection surface having a light incident surface on which light is incident and a light exit surface that emits incident light that is located on the opposite side, and a plurality of prism rows are arranged substantially in parallel on the light incident surface An element,
The plurality of prism rows constitute a prism row unit by a pair of adjacent prism rows,
The prism array unit is composed of a first prism array composed of two asymmetric prism surfaces and a second prism array composed of two asymmetric prism surfaces, and the extending direction of the prism array In the cross-sectional shape orthogonal to each other, the two prism surfaces of the second prism row are arranged substantially symmetrically with the two prism surfaces of the first prism row.
An optical deflection element characterized by that.   In the first prism row, a triangle formed by a straight line connecting the apex of the prism row and two valleys in a cross section perpendicular to the extending direction of the prism row is a substantially isosceles triangle, and the prism 2. The optical deflection element according to claim 1, wherein an apex angle formed by two equal sides sandwiching the apex of the row is 60 to 80 degrees.   One prism surface of the first prism row has a convex curve shape in a cross section orthogonal to the extending direction of the prism row, and the apex of the prism row and the valley of the prism surface 3. The optical deflection element according to claim 1, wherein a ratio d / P between a maximum distance d from a straight line connecting the two and the arrangement pitch P of the prism rows is 0.004 to 0.05. .   The convex curve shape of one prism surface of the first prism row is an arc shape, and the ratio r / P between the radius of curvature r of the arc shape and the arrangement pitch P of the prism rows is 2 to 50. The light deflection element according to claim 3, wherein   5. The optical deflection element according to claim 1, wherein the other prism surface of the first prism row is a flat surface. 6. A light source having a primary light source, a light incident end surface on which light emitted from the primary light source is incident, a light emitting surface for guiding and emitting the incident light, and a light emitting surface of the light guide are disposed adjacent to each other. The optical deflection element according to any one of claims 1 to 5,
The surface light source device, wherein the primary light source is disposed so as to face two light incident end faces composed of two side end faces facing each other of the light guide.   The surface light source device according to claim 6, wherein the light deflection element is disposed so that the light incident surface faces a light emitting surface of the light guide.

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