JP2008270223A - Light guide plate, planar light source, light source panel for liquid crystal display, liquid crystal display, and manufacturing method of light guide plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure of a light guide plate and its manufacturing method capable of improving the luminance of emitted light. <P>SOLUTION: In the light guide plate 1, light is incident on an incident part from a light source; and the incident light is propagated internally and emitted from an emission surface. The emitted light illuminates a display screen. On the opposite surface to the emission surface, a plurality of minutely formed parts 10 are formed and dotted into concave shapes; and the diameter dimension defining the size of the minutely formed parts is smaller than an interval of pixels constituting a display screen. The light guide plate is manufactured by forming a synthetic resin material by fabricating a resist structure, having a top wall surface and sidewall surfaces inclined against the top wall surface, in an intermediate step of the manufacturing process. The resist structure is formed, by forming exposed parts and unexposed parts by irradiating a resist film on a substrate with X-rays or ultraviolet rays, and developing the exposed resist film. By controlling the energy intensity distribution of the X-rays or ultraviolet rays, the inclined surfaces are formed as boundaries of irradiated regions and non-irradiated regions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light guide plate, a surface light source device, a liquid crystal display light source panel and a liquid crystal display device, and a method for manufacturing the light guide plate, and more specifically, in portable information terminals such as mobile phones, personal computers, car navigation devices, and the like. The present invention relates to a liquid crystal display device, a light source panel for liquid crystal display as a surface light source device for illuminating the liquid crystal display panel, a light guide plate used in these liquid crystal display device and light source panel for liquid crystal display, and a manufacturing method thereof.

  Conventionally, in a liquid crystal display device, for example, the liquid crystal display panel does not emit light by itself, so that the liquid crystal display panel can be viewed by irradiating the liquid crystal display panel with light from the outside. In order to realize this, for example, a surface light source device called a so-called lighting panel is arranged on the opposite side of the display screen of the liquid crystal display panel. The light emitted from the surface light source device passes through the liquid crystal display panel to illuminate the display screen. The surface light source device includes a light guide plate that is disposed outside, for example, to convert light from a point light source of a light emitting diode (LED) into a surface light source and uniformly enter the liquid crystal display panel.

Such a surface light source device is required to emit light from a point light source incident on the light guide plate uniformly and efficiently from the light guide plate. In order to improve the brightness of the emitted light, it has been proposed to form various shapes of holes, protrusions, grooves or the like on the exit surface of the light guide plate or the surface opposite to the exit surface. For example, the structure of such a light guide plate is disclosed in JP-A-10-253960 (see Patent Document 1) and JP-A-2001-228338 (see Patent Document 2).
JP-A-10-253960 JP 2001-228338 A

  Incidentally, in recent years, liquid crystal display panels used for display devices of portable information terminals have become complicated and diverse in display content due to color animation. For this reason, the request | requirement for the image quality improvement of a liquid crystal display screen is increasing. In order to meet this demand, the power consumption of the circuit portion and the display portion is increasing in the liquid crystal display device. On the other hand, for a lighting panel, which is a surface light source device as a peripheral component, it is possible to increase the use efficiency of illumination light with lower power consumption and to increase the brightness of emitted light to illuminate a finer display screen. There is a need for something higher.

  Accordingly, an object of the present invention is to provide a structure of a light guide plate capable of improving the luminance of emitted light.

  Another object of the present invention is to provide a surface light source device, a light source panel for liquid crystal display, and a liquid crystal display device capable of increasing the utilization efficiency of illumination light.

  Another object of the present invention is to provide a method for manufacturing a light guide plate capable of improving the luminance of emitted light.

  As a result of intensive studies to meet the demand for higher image quality of liquid crystal display screens, the present inventor has found that the above object can be achieved by using a light guide plate having a specific structure. The present invention has been made based on such knowledge of the inventors.

  A light guide plate according to the present invention has light incident on an incident portion from a light source, propagates the incident light inside to be emitted from an exit surface, and illuminates a display screen with the emitted light. However, it has the following features. On the surface opposite to the emission surface, a plurality of minute shapes are formed so as to be concave and frustoconical, and are arranged so as to be scattered. The diameter dimension that defines the size of the minute shape portion is smaller than the interval between pixels constituting the display screen.

  In the light guide plate of the present invention, since the minute shape portion formed on the surface opposite to the exit surface is smaller than the pixel interval, the brightness of the emitted light necessary for brightly illuminating a finer display screen is improved. Can do.

  In the light guide plate of the present invention, the ratio of the height dimension to the diameter dimension that defines the size of the minute shape portion is preferably 0.3 or more and 1.0 or less. In this case, the brightness of the emitted light can be increased and the uniformity can be improved.

  A surface light source device according to the present invention includes a light guide plate having any one of the above characteristics, and a point light source arranged so that light enters an incident portion of the light guide plate.

  Furthermore, a light source panel for liquid crystal display according to the present invention includes a light guide plate having any one of the above characteristics, a point light source arranged so that light is incident on an incident portion of the light guide plate, and emission of the light guide plate. And a light control member arranged to control light emitted from the surface.

  A liquid crystal display device according to the present invention includes the above-described light source panel for liquid crystal display and a liquid crystal display panel arranged to be illuminated with light emitted from the light source panel for liquid crystal display.

  The light guide plate manufacturing method according to the present invention includes the following steps. In the following manufacturing method, a lithography technique using ultraviolet rays (UV) may be adopted instead of X-rays.

  (A) A step of forming an X-ray exposed portion and an X-ray non-exposed portion on the resist film by irradiating the resist film formed on the substrate with X-rays.

  (B) A step of forming a resist structure having a top wall surface and a side wall surface inclined with respect to the top wall surface on the substrate by developing the resist film irradiated with X-rays.

  (C) A step of forming a metal structure by electrodepositing a metal so as to cover the resist structure and the substrate.

  (D) A step of forming a synthetic resin material using the metal structure as a mold after removing the resist structure from the metal structure.

  Note that an inclined surface is formed as a boundary between the irradiated region and the non-irradiated region by controlling the energy intensity distribution when the resist film is irradiated with X-rays.

  As described above, according to the present invention, it is possible to obtain a light guide plate capable of improving the brightness of emitted light as compared with the conventional art in order to brightly illuminate a finer display screen. Thereby, in the surface light source device such as a light source panel for liquid crystal display used in the liquid crystal display device, it is possible to increase the use efficiency of illumination light and to reduce power consumption.

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

  FIG. 1 is a schematic plan view conceptually showing a light guide plate according to an embodiment of the present invention. As shown in FIG. 1, the light guide plate 1 has dots as minute shape portions formed in a large number of concave or convex shapes on at least one of its emission surface or the surface opposite to the emission surface. 10 are arranged to be scattered. Light is incident on the light guide plate 1 from an external point light source as indicated by an arrow L. The dots 10 are arranged so that the degree of doting gradually changes from a sparse state to a dense state as the distance from the incident part of the light guide plate 1 increases. FIG. 1 conceptually shows the arrangement pattern of the dots 10 and is not exactly shown.

  FIG. 2 is a diagram for explaining the concept of the arrangement pattern of the dots 10 in the light guide plate 1 of FIG. As shown in FIG. 2, the arrangement density of the dots 10 is the smallest in the incident vicinity region IV where the light is incident as indicated by the arrow L. In the central region III of the light guide plate 1, the arrangement density of the dots 10 is larger than the incident vicinity region IV. Further, in the corner regions II and V of the light guide plate 1, the arrangement density of the dots 10 is larger than that in the central region III. In the corner region I of the light guide plate 1 farthest from the incident part, the arrangement density of the dots 10 is the highest.

  FIG. 3 is a diagram shown for explaining another concept of the arrangement pattern of the dots 10 in the light guide plate 1 of FIG. As shown in FIG. 3A, the dots 10 can be regularly arranged, or as shown in FIG. 3B, the dots 10 can be randomly arranged at random. In order to improve the uniformity of the brightness of the emitted light, it is preferable to arrange the dots 10 at random as shown in FIG.

  4 is a schematic cross-sectional view of the light guide plate for conceptually showing various cross-sectional shapes of the dots 10 in the light guide plate 1 of FIG. As shown in FIG. 4A, in one embodiment, the light guide plate 1 is arranged so that a large number of cylindrical recesses 11 are scattered on the surface opposite to the light exit surface. As shown in (B), in another embodiment, a large number of columnar convex portions 12 are disposed on the light exit surface of the light guide plate 1. Moreover, as shown in (C), while the cylindrical convex part 12 is formed in the output surface of the light-guide plate 1, the cylindrical recessed part 11 may be formed in the surface on the opposite side to an output surface. As shown in FIG. 4D, in another embodiment, a large number of truncated cone-shaped concave portions 13 are arranged on the surface opposite to the light exit surface of the light guide plate 1. As shown in (E), in another embodiment, a large number of truncated cone-shaped convex portions 14 are arranged on the light exit surface of the light guide plate 1. Further, as shown in (F), the frustoconical convex portion 14 may be formed on the exit surface of the light guide plate 1, and the frustoconical concave portion 13 may be formed on the surface opposite to the exit surface. .

  In FIG. 4, the dots 11 to 14 having a circular cross section are shown, but polygonal dots 10 such as a triangle, a square, and a rectangle may be formed. Further, in FIGS. 4D to 4F, the truncated cone-shaped dots 10 are shown. However, at least the side wall is inclined with respect to the top wall, or at least the side wall is inclined with respect to the bottom wall. What is necessary is just the recessed part which is doing.

  FIG. 5 is an exploded perspective view showing a schematic configuration of a lighting panel 100 as a liquid crystal display light source panel which is an example of a surface light source device including the light guide plate 1 of the present invention. As shown in FIG. 5, the lighting panel 100 is configured by sequentially laminating a reflection film 5, a light guide plate 1, a diffusion film 2, and lens films 3 and 4. Light enters the light guide plate 1 from a point light source 6 such as a light emitting diode (LED) disposed on the side of the light guide plate 1. In this example, three point light sources 6 are arranged. The light incident on the light guide plate 1 from the point light source 6 is propagated inside the light guide plate 1, converted into a surface light source, and emitted from the emission surface (upper surface in FIG. 5) of the light guide plate 1 toward the diffusion film 2. To do. The reflective film 5 is provided to reflect the light leaking to the opposite side of the light exiting surface of the light guide plate 1 in the light exiting direction and collect it in the light guide plate 1. The light emitted from the light guide plate 1 is diffused in the traveling direction by passing through a diffusion film 2 as a light control member. Light diffused through the diffusion film 2 is concentrated within the viewing angle of the liquid crystal display screen by passing through lens films 3 and 4 called so-called prism sheets as light control members, and light with higher brightness. Illuminates the liquid crystal display screen.

  FIG. 6 conceptually illustrates a liquid crystal display device 500 including the lighting panel 100 of FIG. As shown in FIG. 6, the light incident on the light guide plate 1 from the point light source 6 is repeatedly reflected inside the light guide plate 1 as indicated by an arrow, then exits from the exit surface of the light guide plate 1, and diffused film 2. The liquid crystal cell 200 as a liquid crystal display panel is irradiated through the lens films 3 and 4. The surface opposite to the display screen of the liquid crystal cell 200 is disposed so as to face the light emission surface of the lighting panel 100 (backlight method). The display screen of the liquid crystal cell 200 may be disposed so as to face the light emission surface of the lighting panel 100 (front light method).

  The light incident on the light guide plate 1 from the point light source 6 repeats total reflection due to the difference in refractive index between the light guide plate 1 and air, and propagates inside the light guide plate 1. As shown in FIGS. 1 to 4, as shown in FIGS. 1 to 4, convex or concave dots 10 are formed as a plurality of minute shape portions on at least one of the light exit surface of the light guide plate 1 and the surface opposite to the light exit surface. By being arranged in a scattered manner, the light is refracted by repeating total reflection and is emitted from the emission surface. In the present invention, the diameter dimension that defines the size of the dots 10 in the various cross-sectional shapes shown in FIG. 4 is smaller than the interval between the pixels constituting the display screen of the liquid crystal cell 200. Specifically, since the pixel interval (pitch) of the liquid crystal display screen is at least about 100 μm, the diameter of the dot 100 is 100 μm or less.

  When light from a point light source is incident on the light guide plate 1 shown in FIGS. 1 and 2 in the direction indicated by the arrow L, the light is emitted from the light guide plate 1 when the shape and size of the dots 10 as the minute shape portions are changed. How the brightness of the light changes was examined by a ray tracing simulation experiment using a light guide plate model.

  In the ray tracing simulation experiment, it was assumed that reflection / refraction of light inside the light guide plate 1 and transmission of light to the outside were taken into consideration, and interference and diffraction of light were not taken into consideration. Further, the thickness of the light guide plate 1 is 1.0 mm, the size of the emission region is 33 mm × 33 mm, the luminous intensity of the point light source is several hundred mcd, and the arrangement pattern of the dots 10 shown in FIG. 1 and FIG. 3 is set so that the degree of doting changes from a sparse state to a dense state as the distance from the incident part increases in accordance with a function having factors of the distance from the point light source and the emission amount per dot. As shown in FIG. The material of the light guide plate was polymethyl methacrylate (PMMA), and the refractive index was 1.49.

  FIG. 7 shows a simulation result when the diameter of the cylindrical dot 10 as the minute shape portion is 60 μm. 7A shows a case where a cylindrical recess 11 is formed on the opposite surface opposite to the exit surface of the light guide plate 1 as shown in FIG. 4 (B), when the cylindrical convex portion 12 is formed on the surface opposite to the exit surface of the light guide plate 1 as the shape of the dot 10, (C) is shown in FIG. 4 (C). Thus, the case where the column-shaped convex part 12 is formed in the output surface of the light-guide plate 1 as a shape of the dot 10, and the column-shaped recessed part 11 is formed in the surface on the opposite side to the output surface of the light-guide plate 1 is shown.

  FIG. 8 shows a simulation result when the diameter dimension of the conical dot 10 as the minute shape portion is 100 μm. 8A shows a case where a conical recess is formed on the surface opposite to the exit surface of the light guide plate 1 in accordance with the truncated cone-shaped recess 13 as the shape of the dot 10 as shown in FIG. 4D. 4B shows a case in which a conical convex portion is formed on the surface opposite to the exit surface of the light guide plate 1 according to the truncated cone-shaped convex portion 14 as the shape of the dot 10 as shown in FIG. 4C, as shown in FIG. 4F, a conical convex portion is formed on the exit surface of the light guide plate 1 according to the truncated conical convex portion 14 as the shape of the dot 10, and the frustoconical concave portion 13 is formed. The case where a conical recessed part is formed in the surface on the opposite side to the output surface of the light-guide plate 1 according to is shown.

  FIG. 9 shows a simulation result when the diameter of the conical dot 10 as the minute shape portion is 60 μm. 9A shows a case in which a conical recess is formed on the surface opposite to the exit surface of the light guide plate 1 according to the truncated cone-shaped recess 13 as the shape of the dot 10 as shown in FIG. 4D. 4B shows a case in which a conical convex portion is formed on the surface opposite to the exit surface of the light guide plate 1 according to the truncated cone-shaped convex portion 14 as the shape of the dot 10 as shown in FIG. 4C, as shown in FIG. 4F, a conical convex portion is formed on the exit surface of the light guide plate 1 according to the truncated conical convex portion 14 as the shape of the dot 10, and the frustoconical concave portion 13 is formed. The case where a conical recessed part is formed in the surface on the opposite side to the output surface of the light-guide plate 1 according to is shown.

  FIG. 10 shows a simulation result when the diameter of the conical dot 10 as the minute shape portion is 30 μm. FIG. 10A shows a case where a conical recess is formed on the surface opposite to the exit surface of the light guide plate 1 in accordance with the truncated cone-shaped recess 13 as the shape of the dot 10 as shown in FIG. 4B shows a case in which a conical convex portion is formed on the surface opposite to the exit surface of the light guide plate 1 according to the truncated cone-shaped convex portion 14 as the shape of the dot 10 as shown in FIG. 4C, as shown in FIG. 4F, a conical convex portion is formed on the exit surface of the light guide plate 1 according to the truncated conical convex portion 14 as the shape of the dot 10, and the frustoconical concave portion 13 is formed. The case where a conical recessed part is formed in the surface on the opposite side to the output surface of the light-guide plate 1 according to is shown.

  7 to 10, the vertical axis represents the average luminance (cd / m 2) of light emitted from the light exit surface of the light guide plate, and the horizontal axis represents the depth of the dot 10 as a minute shape portion in the case of a concave portion. (Μm), the height (μm) is shown in the case of a convex part.

  The following can be understood from these simulation results.

  (1) In each of FIGS. 7 to 10, when a convex portion is formed on the exit surface and a concave portion is formed on the opposite surface, only the concave portion is formed on the surface opposite to the exit surface in the case of (C). (A) The brightness | luminance of an emitted light tends to improve rather than (B) when only a convex part is formed in the surface on the opposite side to an output surface.

  (2) When FIG. 7 and FIG. 9 are compared, if the diameter dimension of the dot 10 as the minute shape portion is the same, the cylindrical concave portion or convex portion is formed when the conical concave portion or convex portion is formed. It can be seen that the luminance of the emitted light tends to be improved as compared with the case where is formed.

  (3) Comparing FIGS. 8 to 10, it is recognized that the brightness of the emitted light tends to be improved as the diameter of the dot 10 as the minute shape portion is reduced to 100 μm, 60 μm, and 30 μm.

  (4) As shown in FIGS. 8 to 10, as the ratio of the depth or height to the diameter of the dot 10 as the micro-shaped portion, the so-called aspect ratio increases (the depth or height in the figure is increased). The brightness of the emitted light is improved (as it becomes larger), but when the aspect ratio becomes too high, the brightness value of the emitted light saturates, tends to be lower, or becomes unstable.

  (5) As shown in FIG. 9, when the diameter of the dot 10 as the minute shape portion is 60 μm which is smaller than the pixel interval (pitch) of the liquid crystal display screen, the luminance of the emitted light is increased when the aspect ratio exceeds 1. A tendency to decrease is recognized, and high luminance can be obtained if the aspect ratio is in the range of 0.3 to 1.0.

  From the above results, in order to improve the luminance of the emitted light, a minute shape portion whose diameter is smaller than the pixel interval (pitch) of the liquid crystal display screen is formed, and the shape of the minute shape portion is the emission of the light guide plate. It is most preferable to form a conical or frustoconical convex portion on the surface and a conical or frustoconical concave portion on the opposite surface. A smaller diameter is preferable, but about 60 μm is preferable in consideration of luminance uniformity. The aspect ratio is preferably in the range of 0.3 to 1.0.

  FIG. 11 and FIG. 12 are diagrams showing schematic cross sections according to the order of steps as an embodiment of the method for manufacturing a light guide plate of the present invention. As an example of an embodiment of the manufacturing method, FIG. 11 shows a method for manufacturing a light guide plate in the case of forming a micro-shaped portion made of a cylindrical convex portion, and FIG. 12 shows a micro-shaped portion made of a truncated cone-shaped convex portion. The manufacturing method of the light-guide plate in the case of forming will be shown. The light guide plate of the present invention is manufactured using a so-called LIGA (Lithographie Galvanoformung Abformung) process. Hereinafter, the manufacturing method of a light-guide plate is demonstrated concretely.

  First, the manufacturing method of a light-guide plate in the case of forming the minute shape part which consists of a cylindrical-shaped convex part is demonstrated.

  As shown in FIG. 11A, a resist film 30 such as polymethyl methacrylate (PMMA) having a thickness of about 10 to 100 μm is formed on the surface of a silicon substrate 20.

  As shown in FIG. 11B, the X-ray is irradiated in the direction indicated by the arrow P onto the resist film 30 formed on the substrate 20 using the X-ray mask 40. As X-rays, X-rays generated from a synchrotron radiation (SR) optical device excellent in straightness are used. Thereby, an X-ray exposed portion and an X-ray non-exposed portion having a high aspect ratio are formed on the resist film 30. In this case, the X-ray mask 40 includes a columnar X-ray absorber 41 and an X-ray transmission film 42 that covers the X-ray absorber 41.

  As shown in FIG. 11C, by immersing in a developer, the X-ray exposed portion is dissolved in the developer, the X-ray non-exposed portion remains, and a cylindrical resist pattern 31 is formed as a resist structure on the substrate. 20 is formed. At this stage, the top wall surface may be shaved to adjust the height of the cylindrical resist pattern 31.

  As shown in FIG. 11D, a metal structure 50 is formed by electrodepositing nickel or the like as a metal so as to cover the cylindrical resist pattern 31 and the substrate 20 by using an electroforming method. FIG. 11D shows a state where the columnar resist pattern 31 is removed from the metal structure 50. A cylindrical recess 51 is formed in the metal structure 50.

  As shown in FIG. 11E, the light guide plate 1 is obtained by injection molding a synthetic resin such as a cycloolefin-based high transferable resin using the metal structure 50 as a mold. In this step, the synthetic resin may be compression molded. FIG. 11E shows a state where the metal structure 50 is removed from the light guide plate 1. The light guide plate 1 includes a cylindrical convex portion 12 as a minute shape portion.

  Next, a method for manufacturing a light guide plate in the case of forming a minute shape portion composed of a truncated cone-shaped convex portion will be described.

  As shown in FIG. 12A, a resist film 30 such as polymethyl methacrylate (PMMA) having a thickness of about 10 to 100 μm is formed on the surface of a silicon substrate 20.

  As shown in FIG. 12B, the X-ray mask 40 is used to irradiate the resist film 30 formed on the substrate 20 with X-rays in the direction indicated by the arrow P. As X-rays, X-rays generated from a synchrotron radiation (SR) optical device excellent in straightness are used. Thereby, an X-ray exposed portion and an X-ray non-exposed portion having a high aspect ratio are formed on the resist film 30. In this case, the X-ray mask 40 includes a frustoconical X-ray absorber 43 and an X-ray transmission film 42 that covers the X-ray absorber 43.

  As shown in FIG. 12C, by immersing in a developing solution, the X-ray exposed portion is dissolved in the developing solution, and the X-ray non-exposed portion remains, and a frustoconical convex resist pattern is formed as a resist structure. 32 is formed on the substrate 20. At this stage, the top wall surface may be shaved to adjust the height of the frustoconical convex resist pattern 32.

  As shown in FIG. 12D, the metal structure 50 is formed by electrodepositing nickel or the like as a metal so as to cover the frustoconical convex resist pattern 32 and the substrate 20 by using an electroforming method. Form. FIG. 12D shows a state where the frustoconical convex resist pattern 32 is removed from the metal structure 50. The metal structure 50 is formed with a truncated cone-shaped recess 52.

  As shown in FIG. 12E, the light guide plate 1 is obtained by injection molding a synthetic resin such as a cycloolefin-based high transfer resin using the metal structure 50 as a mold. In this step, the synthetic resin may be compression molded. FIG. 12E shows a state where the metal structure 50 is removed from the light guide plate 1. The light guide plate 1 includes a truncated cone-shaped convex portion 14 as a minute shape portion.

  FIG. 13 is a cross-sectional view showing a partially enlarged manufacturing process of the light guide plate 1 shown in FIGS. As shown in FIG. 13A, the X-ray mask 40 includes a truncated cone-shaped X-ray absorber 43. The frustoconical X-ray absorber 43 has inclined surfaces at both ends. On this inclined surface, some X-rays leak from the X-ray mask 40 in accordance with the thickness of the X-ray absorber and the irradiated X-ray energy intensity, and the resist film 30 is irradiated and exposed. For this reason, in the irradiated resist film 30, the boundary between the X-ray non-irradiated region 32a and the X-ray irradiated region 32b is formed as an inclined surface. When this resist film 30 is developed, a frustoconical convex resist pattern 32 having an inclined surface corresponding to the inclined surface of the resist film 30 is formed as shown in FIG.

  FIG. 14 is a schematic cross-sectional view according to the order of steps as an embodiment of the method of manufacturing the X-ray mask used in FIGS. 12B and 13A.

  As shown in FIG. 14A, a resist film 45 having a cylindrical through hole 45a is formed on the surface of a silicon substrate 44.

  As shown in FIG. 14B, an X-ray absorber material such as gold (Au) is deposited by sputtering or plating so as to fill the cylindrical through hole 45a. At this time, the X-ray absorber material is also deposited on the resist film 45 in the vicinity of the outer periphery of the cylindrical through hole 45a. The substantially frustoconical X-ray absorber 46 formed thereby has a top wall surface and a side wall surface inclined with respect to the top wall surface.

  As shown in FIG. 14C, the resist film 45 is removed.

  As shown in FIG. 14D, an X-ray transmitting material layer 47 made of polyimide or the like is formed on the substrate 44 so as to cover the substantially frustoconical X-ray absorber 46.

  As shown in FIG. 14E, an X-ray transmission window is formed by removing the central portion of the substrate 44 by etching. In this way, an X-ray mask having a substantially frustoconical X-ray absorber is manufactured.

  As a method of manufacturing a frustoconical resist pattern, there is a method of moving an X-ray mask other than the method shown in FIG.

  FIG. 15 is a diagram illustrating a method of forming a frustoconical through-hole resist pattern as an example. As shown in FIG. 15A, an X-ray mask 40 in which an X-ray absorber layer 48 having a cylindrical through hole 48a is formed on an X-ray transparent material layer 49 is used. As an object to be irradiated with X-rays, a resist film 30 is formed on the substrate 20. The X-ray mask 40 is irradiated with X-rays through the X-ray mask 40 while continuously moving the entire X-ray mask 40 along the circumference Q centering on the center R of the cylindrical through hole 48a. At this time, the X-ray energy intensity distribution is controlled as shown in (A) according to the thickness and X-ray absorption characteristics of the X-ray absorber layer 48 and the X-ray irradiation time, that is, the X-ray irradiation energy. be able to. As a result, an inclined surface is formed on the resist film 30 as a boundary between the X-ray irradiation region 33b and the X-ray non-irradiation region 33a. By developing the resist film 30, a frustoconical through-hole resist pattern 33 is formed on the substrate 20 as shown in FIG.

  In the light guide plate manufacturing method described above, a resist pattern is formed using X-rays generated from a synchrotron radiation (SR) light device, and a so-called LIGA process using emitted light is employed. -8 (manufactured by Microlithography Chemical Corp.) is used to form a resist pattern by a lithography technique using ultraviolet (UV) applied in the normal semiconductor device manufacturing process, and so-called LIGA in SU-8 A like process may be employed. Here, SU-8 is a photocationic polymerization resist composed of a binder polymer, an epoxy monomer, and a photoacid generator.

  Further, in the above simulation experiment, the conical uneven portion is described as the minute shape portion, and in the embodiment of the present invention, the truncated conical uneven portion is described as the minute shape portion. The effect of this can be achieved. In particular, when a conical concavo-convex portion is employed as the minute shape portion, the apex angle of the cone is preferably within a range of 45 to 50 °, and most preferably approximately 45 °.

  Furthermore, in the above-described embodiment, the arrangement pattern of the dots as the minute shape portion is changed from a sparse state to a dense state as the dot size is the same and the degree of dot separation is away from the incident portion. It is set. That is, the density of the dots having the same diameter is made sparse at a place close to the incident part, and the density of the dots having the same diameter is made dense at a place far from the incident part. However, using dots with different diameters, make the dot diameter relatively small in the sparse area near the incident area, and relatively large in the dense area away from the incident area. Thus, a more uniform surface light source can be realized.

  The embodiment disclosed above should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above embodiments but by the scope of claims, and includes all modifications and variations within the meaning and scope equivalent to the scope of claims.

1 is a schematic plan view conceptually showing a light guide plate according to an embodiment of the present invention. It is a figure shown in order to demonstrate the concept of the arrangement pattern of a dot in the light-guide plate of FIG. It is a figure shown in order to demonstrate another concept of the arrangement pattern of a dot in the light-guide plate of FIG. FIG. 2 is a schematic cross-sectional view of a light guide plate for conceptually showing various cross-sectional shapes of dots in the light guide plate of FIG. 1. It is a disassembled perspective view which shows schematic structure of a lighting panel as a light source panel for liquid crystal displays which is an example of the surface light source device provided with the light-guide plate of this invention. It is a figure which shows notionally the liquid crystal display device provided with the lighting panel of FIG. It is a figure which shows the simulation result when the diameter dimension of the column-shaped dot as a micro-shaped part is 60 micrometers. It is a figure which shows the simulation result when the diameter dimension of the cone-shaped dot as a micro shape part is 100 micrometers. It is a figure which shows the simulation result when the diameter dimension of the cone-shaped dot as a micro-shaped part is 60 micrometers. It is a figure which shows the simulation result when the diameter dimension of the cone-shaped dot as a micro-shaped part is 30 micrometers. It is a figure which shows the schematic cross section according to process order as embodiment of the manufacturing method of a light-guide plate in the case of forming the micro-shaped part which consists of a cylindrical convex part. It is a figure which shows the schematic cross section according to process order as embodiment of the manufacturing method of the light-guide plate in the case of forming the micro shape part which consists of a truncated cone-shaped convex part. It is sectional drawing which expands and shows partially the manufacturing process of the light-guide plate shown by (B) and (C) of FIG. It is a figure which shows the schematic cross section according to process order as embodiment of the manufacturing method of the X-ray mask used by FIG. 12 (B) and FIG. 13 (A). It is a figure which shows the method of forming a truncated cone-shaped through-hole resist pattern.

Explanation of symbols

1: Light guide plate 2: Diffusion film 3, 4: Lens film 5: Reflective film 6: Point light source 10: Dot 11: Cylindrical concave portion 12: Cylindrical convex portion 13: Frustum-shaped concave portion 14: Frustum-shaped convex portion 20 : Substrate 30, 45: Resist film 31: Cylindrical resist pattern 32: Frustum-shaped convex resist pattern 40: X-ray mask 41: Cylindrical X-ray absorber 42: X-ray transmission film 43: Frustum-shaped X-ray absorption Body 44: Substrate 45a: Cylindrical through-hole 46: Substantially truncated cone-shaped X-ray absorber 47: X-ray transmitting material layer 50: Metal structure 51: Cylinder-shaped recess 52: Frustum-shaped recess 100: Lighting panel 200: Liquid crystal Cell 500: Liquid crystal display device

Claims (6)

A light guide plate for making light incident on an incident portion from a light source, propagating the incident light inside to be emitted from an emission surface, and illuminating a display screen with the emitted light,
On the surface opposite to the emission surface, a plurality of minute shape portions are formed so as to be concave and frustoconical and arranged so as to be scattered, and a diameter that defines the size of the minute shape portion The dimension is smaller than the pixel interval that composes the display screen,
The light guide plate is
Irradiating the resist film formed on the substrate with X-rays or ultraviolet rays, and forming an exposed portion and an unexposed portion of X-rays or ultraviolet rays on the resist film;
Developing a resist film having a top wall surface and a side wall surface inclined with respect to the top wall surface by developing the resist film irradiated with the X-rays or the ultraviolet rays; and
Forming a metal structure by electrodepositing metal so as to cover the resist structure and the substrate;
Removing the resist structure from the metal structure and then molding a synthetic resin material using the metal structure as a mold;
Manufactured in a method including
An inclined surface is formed as a boundary between an irradiation region and a non-irradiation region by controlling an energy intensity distribution when the resist film is irradiated with X-rays or ultraviolet rays.   The light-guide plate of Claim 1 whose ratio of the height dimension with respect to the diameter dimension which prescribes | regulates the magnitude | size of the said micro shape part is 0.3 or more and 1.0 or less. The light guide plate according to claim 1 or 2,
A surface light source device comprising: a point light source disposed so that light is incident on an incident portion of the light guide plate. The light guide plate according to claim 1 or 2,
A point light source disposed so that light is incident on an incident portion of the light guide plate;
A light source panel for liquid crystal display, comprising: a light control member arranged to control light emitted from an emission surface of the light guide plate. A light source panel for liquid crystal display according to claim 4,
A liquid crystal display device comprising: a liquid crystal display panel arranged to be illuminated by light emitted from the light source panel for liquid crystal display. Light is incident on an incident part from a light source, the incident light is propagated inside and emitted from an exit surface, and a light guide plate manufacturing method for illuminating a display screen with the emitted light,
In the light guide plate, on the surface opposite to the emission surface, a plurality of minute shape portions are formed so as to be concave and frustoconical, and are arranged so as to be scattered. The diameter that defines the size of the display is smaller than the interval between the pixels constituting the display screen,
The manufacturing method is
Irradiating the resist film formed on the substrate with X-rays or ultraviolet rays, and forming an exposed portion and an unexposed portion of X-rays or ultraviolet rays on the resist film;
Developing a resist film having a top wall surface and a side wall surface inclined with respect to the top wall surface by developing the resist film irradiated with the X-rays or the ultraviolet rays; and
Forming a metal structure by electrodepositing metal so as to cover the resist structure and the substrate;
Removing the resist structure from the metal structure and then molding a synthetic resin material using the metal structure as a mold;
Including
An inclined surface is formed as a boundary between an irradiation region and a non-irradiation region by controlling an energy intensity distribution when the resist film is irradiated with X-rays or ultraviolet rays.

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