JP2007149575A - Light guide plate and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a light guide plate capable of further improving the luminance of emission light in the light guide plate wherein light coming from a light source through an incident part is transmitted in and emitted from an emitting surface. <P>SOLUTION: This light guide plate has a structure in which a plurality of fine structure bodies having tapered convex shapes or tapered concave shapes are formed at least on one of the emitting surface or a surface opposite to the emitting surface. The manufacturing method comprises a selective irradiation process irradiating UV 24 in a state that an UV mask and a resist layer 22 on a substrate 21 are separated only by a distance d (Selection figure (b)). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light guide plate used for, for example, a surface light source device, a liquid crystal display light source panel, and the like, and a method for manufacturing the same.

  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 screen 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 side opposite to the display screen of the panel, and light emitted from the surface light source device passes through the liquid crystal display panel, thereby displaying It is configured to illuminate the screen. The surface light source device includes a light guide plate disposed outside, for example, for converting light incident from a point light source of a light emitting diode (LED) into a surface light source and uniformly emitting it to the liquid crystal display panel.

Such a surface light source device is required to emit light from a point light source incident on a 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. Such a structure of the light guide plate is disclosed in Patent Documents 1 and 2, for example.
JP-A-10-253960 JP 2001-228338 A

  Incidentally, in recent years, demand for higher image quality has been increasing year by year in display devices and the like of portable information terminals, and in order to meet this demand, power consumption of circuit units and display units in liquid crystal display devices is increasing. Therefore, in the surface light source device as a peripheral component, there is a need to increase the luminance of the emitted light in order to increase the use efficiency of the illumination light with lower power consumption and to brightly illuminate a finer display screen. is there.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a light guide plate capable of further improving the luminance of emitted light and a method for manufacturing the same.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to the 1st viewpoint of this invention, the following manufacturing methods of the light-guide plate which propagates the light which injected through the incident part from the light source inside, and radiate | emits it from an output surface are provided. The light guide plate has a configuration in which a plurality of microstructures having a tapered convex shape or a tapered concave shape are formed on at least one of the emitting surface and a surface opposite to the emitting surface. The manufacturing method includes a selective irradiation step of irradiating ultraviolet rays in a state where the optical lithography mask and the resist layer on the substrate are separated from each other.

  With this configuration, ultraviolet light that has passed through the optical lithography mask is obliquely incident on the resist layer, so that a half-shade photosensitivity with a larger area than the ultraviolet light transmissive region of the mask can be obtained, and the tapered fine structure is formed on the light guide plate. Can be easily formed. As a result, a light-guiding light guide plate can be obtained at low cost.

  According to the 2nd viewpoint of this invention, the following manufacturing methods of the light-guide plate which propagates the light which injected through the incident part from the light source inside, and radiate | emits it from an output surface are provided. The light guide plate has a configuration in which a plurality of microstructures having a tapered convex shape or a tapered concave shape are formed on at least one of the emitting surface and a surface opposite to the emitting surface. In the manufacturing method, a selective irradiation step of irradiating ultraviolet rays in a state where the optical lithography mask and the resist layer on the substrate are separated from each other, and a resist structure is formed on the substrate by developing the resist layer. A step of forming a metal structure by electrodepositing metal so as to cover the resist structure and the substrate, a step of removing the resist structure from the metal structure, and the metal structure Forming the taper convex shape or the taper concave shape on the synthetic resin material by using as a mold.

  With this configuration, ultraviolet light that has passed through the optical lithography mask in the selective irradiation step is incident on the resist layer obliquely, so that penumbra exposure with a larger area than the ultraviolet light transmissive region of the mask can be performed. A resist structure having a shape can be easily formed. Then, by transferring the shape of the resist structure to the synthetic resin material via the metal structure, a tapered fine structure can be easily formed on the light guide plate. As a result, a light-luminous light guide plate can be obtained at a low manufacturing cost.

  In the manufacturing method of the said light-guide plate, it is preferable that the taper angle of the said taper convex shape or a taper concave shape is 65 degrees or more and 80 degrees or less.

  With this configuration, excellent light intensity can be obtained, and a light guide plate that achieves both reduction in power consumption and improvement in luminance can be obtained.

  Preferably, the light guide plate manufacturing method includes a step of irradiating the resist layer with ultraviolet rays without passing through the optical lithography mask after the selective irradiation step.

  With this configuration, the degree of freedom in controlling the tapered shape of the fine structure formed on the light guide plate can be further increased.

  In the manufacturing method of the said light-guide plate, it is preferable to perform the said selective irradiation process using a donut-shaped ultraviolet light source.

  With this configuration, the penumbra exposure can be directly controlled without using the ultraviolet diffraction phenomenon, so that the taper shape of the fine structure can be controlled with higher accuracy.

  In the manufacturing method of the said light-guide plate, the said selective irradiation process can be performed using a blue visible ray, a near-ultraviolet ray, or a radiation ray instead of the said ultraviolet-ray. Alternatively, X-rays can be used instead of the ultraviolet rays, and an X-ray lithography mask can be used instead of the optical lithography mask.

  As described above, the selective irradiation step can be performed with light rays other than ultraviolet rays (blue visible light, near ultraviolet light, radiation light, X-rays), and X-ray lithography other than the optical lithography mask as necessary. By using the mask in accordance with the optimum conditions for the combination with the light source, the production conditions can be easily optimized, and a stable method for producing the light guide plate can be provided.

  In the manufacturing method of the said light-guide plate, it is preferable that the said taper convex shape or taper concave shape is a truncated cone shape or a cone shape.

  With this configuration, a light guide plate having excellent uniformity of emitted light can be obtained.

  In the light guide plate manufacturing method, the fine structures are preferably arranged such that the number per unit area increases exponentially as the distance from the incident portion of the light guide plate increases.

  With this configuration, it is possible to provide a light guide plate that can obtain uniform emitted light regardless of the distance from the incident portion.

  In addition, according to the other viewpoint of this invention, the light-guide plate manufactured with the said manufacturing method is provided.

  Next, embodiments of the invention will be described. FIG. 1 is a schematic cross-sectional view showing an overall configuration of a backlight device including a light guide plate according to an embodiment of the present invention.

  As shown in FIG. 1, a backlight device (lighting panel) 11 as a surface light source device shown in FIG. 1 illuminates a transmissive liquid crystal panel (not shown) from the back side includes a light source 12, a light guide plate (light guide) 13, It has. The light guide plate 13 is formed in a rectangular flat plate shape using a transparent material such as polymethyl methacrylate (PMMA), for example, and the light source 12 is disposed so as to face one side of the light guide plate 13. One surface in the thickness direction of the light guide plate 13 is a light emission surface (light emission surface) 14, and a number of microstructures 15 are formed on the emission surface 14. As shown in FIG. 1, this fine structure 15 is formed in a tapered concave shape (more specifically, a truncated cone shape), and its side surface is a tapered surface 16.

  With this configuration, the light from the light source 12 is emitted from the entire surface of the emission surface 14 of the light guide plate 13 by being scattered or reflected by the fine structure 15 (more precisely, the tapered surface 16) provided in the light guide plate 13. The liquid crystal display panel arranged opposite to the emission surface 14 is illuminated from the back side.

  Next, a method for manufacturing the light guide plate 13 having the above configuration will be described with reference to FIGS. FIG. 2 is a diagram for explaining the light guide plate manufacturing process step by step, wherein (a) is a resist layer forming step, (b) is a selective irradiation step of ultraviolet rays, (c) is a uniform irradiation step of ultraviolet rays, d) is a diagram showing a development process. FIG. 3 is a schematic view showing an ultraviolet irradiation device used in the selective irradiation step and the like, and FIG. 4 is a schematic view showing a tapered concave portion formed in the resist pattern structure. FIG. 5 is a diagram showing a change in the shape of the concave portion of the resist pattern structure when the distance between the UV mask and the resist layer is increased from zero in the selective irradiation step. FIG. 6 is a graph showing the relationship between the distance between the UV mask and the resist layer in the selective irradiation step and the taper angle of the concave portion of the resist pattern structure.

  As a method for manufacturing the light guide plate 13, first, as shown in FIG. 2A, a flat substrate 21 is prepared, and a resist is uniformly applied thereon and solidified to form a resist layer 22. As the substrate 21, for example, a silicon substrate can be adopted. Further, as the resist, an ultraviolet photosensitive resin is used, and the thickness may be several tens to 100 μm.

  After the resist layer 22 is dried and solidified, a UV mask 23 as an optical lithography mask is disposed above the resist layer 22 as shown in FIG. This UV mask 23 has a circular pattern 25 through which ultraviolet rays 24 can be transmitted at a position corresponding to the fine structure 15, and the ultraviolet rays 24 pass through the circular pattern 25, and the other portions. It is configured not to pass. The size (diameter) of the circular pattern 25 may be about several tens to 100 μm. The UV mask 23 is arranged with an appropriate interval d with respect to the resist layer 22.

  In this state, as shown in FIG. 2B, the ultraviolet rays 24 are irradiated from above in the drawing (selective irradiation step). Then, the ultraviolet rays 24 that have passed through the circular pattern 25 of the UV mask 23 are incident on the resist layer 22 to sensitize the resist layer 22, but the ultraviolet rays 24 that have passed through the edge of the circular pattern 25 are directed in the direction due to the diffraction phenomenon. Is obliquely incident on the resist layer 22 so as to go around to the back side of the portion through which ultraviolet rays cannot pass (reference numeral 24a). As a result, it is possible to perform half-shadow exposure with a larger area than the area of the circular pattern 25 of the UV mask 23 (photosensitive part 22a), and the light intensity distribution gradually increasing / decreasing at the boundary part of the circular pattern 25. Is obtained. As a result, a tapered photosensitive portion 22a (cross-hatched portion in the figure) is formed so as to substantially match the shape of the circular pattern 25 in the deep layer portion of the resist layer 22 and gradually expand the region as it approaches the surface of the resist layer 22. ) Can be obtained.

  Next, as shown in FIG. 2C, this time, with the UV mask 23 removed, the ultraviolet ray 24 is irradiated from above in the figure, and the ultraviolet ray 24 is incident on the resist layer 22 uniformly and entirely. (Uniform irradiation process). Then, the entire surface of the resist layer 22 is exposed, but the progress of the photosensitive reaction is biased. That is, the progress of the light exposure in the deep layer portion of the resist layer 22 in the photosensitive portion 22a formed by the selective irradiation process of FIG. fast. As a result, it is possible to obtain an effect that the taper angle of the tapered photosensitive portion 22a is increased.

  In addition, the selective irradiation process of FIG.2 (b) and the uniform irradiation process of FIG.2 (c) can be performed with the ultraviolet irradiation apparatus typically shown, for example in FIG. As shown in FIG. 3, this ultraviolet irradiation device is configured so that the ultraviolet rays 24 irradiated from the ultraviolet light source 1 a are reflected by the two mirrors 2 and then enter the UV mask 23 and the resist layer 22. . Thereby, even if the ultraviolet light source 1a that radiates the ultraviolet rays 24 almost radially like a point light source is used, the effective distance between the light source 1a and the resist layer 22 as an irradiation target is made as long as possible. Thus, the ultraviolet rays 24 can be incident on the resist layer 22 almost in parallel. The uniform irradiation process in FIG. 2C can be performed by simply removing the UV mask 23 from the apparatus in FIG.

  Next, as shown in FIG. 2D, the resist layer 22 is developed with an appropriate developer to remove the photosensitive portion 22a. Then, a resist pattern structure (resist structure) 28 in which a truncated cone-shaped recess 26 is formed at a position corresponding to the circular pattern 25 can be obtained. FIG. 4 is a cross-sectional view of the minute shape portion (recessed portion 26) after the development step. The recess 26 corresponds to the fine structure 15 of the light guide plate 13.

  FIG. 5 is a cross-sectional view and a SEM observation photograph showing how the tapered shape of the recess 26 changes depending on the distance between the UV mask 23 and the resist layer 22 (distance d shown in FIG. 2B). . FIG. 5 shows a result of developing by performing only the selective irradiation process of FIG. 2B and omitting the uniform irradiation process of FIG. 2C.

  FIG. 5A shows a state in which the UV mask 23 and the resist layer 22 are brought into contact with each other and the ultraviolet ray 24 is selectively irradiated (that is, d = 0). In this case, the inner peripheral surface 27 of the recess 26 is It can be seen that it has a taper angle of around 20 °. The taper angle is an angle θ formed by conical surfaces (taper surfaces) shown in FIG. The inner bottom surface of the recess 26 is processed slightly deeper at the end than at the center. FIG. 5B shows a case where the UV mask 23 and the resist layer 22 are separated by 100 μm (distance d = 100 μm). At this time, the taper angle θ formed by the inner peripheral surface 27 of the recess 26 is 40 °. Slightly larger before and after.

  The case where the distance d is 200 μm is shown in FIG. 5C. At this time, the taper angle θ of the inner peripheral surface 27 of the recess 26 is further increased to around 60 °, and the cross-sectional contour of the recess 26 is slightly rounded. Come on. Furthermore, the case where the distance d is 300 μm is shown in FIG. 5D. In this case, the taper angle of the inner peripheral surface 27 is further increased to around 80 °, and the roundness of the cross-sectional contour becomes stronger.

  FIG. 6 is a graph showing the relationship between the distance d between the UV mask 23 and the resist layer 22 and the taper angle θ. FIG. 6 also shows the result of developing only the selective irradiation process of FIG. 2B and omitting the uniform irradiation process of FIG. 2C.

  As apparent from this graph, the taper angle θ tends to increase as the UV mask 23 is moved away from the resist layer 22, that is, as the distance d is increased from 0. This means that the taper angle θ can be controlled to a desired angle by adjusting the distance between the UV mask 23 and the resist layer 22. For example, a suitable taper angle that can maximize the intensity of the emitted light in the light guide plate 13 is 65 ° to 80 °, and accordingly, the taper angle θ of the resist pattern structure 28 is set to 65 ° to 80 °. According to the graph of FIG. 6, it can be seen that the distance d between the UV mask 23 and the resist layer 22 is preferably about 200 μm to 300 μm.

  In addition, the selective irradiation process of FIG.2 (b) can also be performed with an ultraviolet irradiation apparatus as shown in FIG.7 and FIG.8 instead of the ultraviolet irradiation apparatus of FIG. The ultraviolet irradiation device shown in FIG. 8 includes a doughnut-shaped ultraviolet light source 1b instead of the ultraviolet light source 1a as the point light source of FIG. When this hollow circular line light source is used, the circular pattern 25 of the UV mask 23 can be irradiated with ultraviolet rays obliquely from the beginning (see FIG. 7). The resist layer 22 can be exposed by controlling the shadow exposure using direct light (straight light).

  Next, FIG. 9 shows an SEM observation photograph of the state of the resist pattern structure 28 when the uniform irradiation step of FIG. 2C is performed. FIG. 9A is an SEM observation photograph of the resist pattern structure 28 when only the selective irradiation step of FIG. 2B is performed and the uniform irradiation step of FIG. It is shown. The taper angle θ measured at this time was about 75 °.

FIG. 9B shows a state in which UV exposure is performed at an exposure amount of 100 mJ / cm ² in the uniform irradiation step of FIG. 2C, and the taper angle θ is increased as compared with FIG. 9A. (The measured value of the taper angle θ was about 90 °). Further, FIG. 9C shows a state in the case where UV exposure is performed at an exposure amount of 250 mJ / cm ² in the uniform irradiation process, and it can be seen that the taper angle θ is further increased (measured value of the taper angle θ). Was about 100 °).

  FIG. 10 is a graph showing the relationship between the exposure amount of the resist layer 22 and the taper angle θ in the uniform irradiation step. From this graph, it can be seen that the taper angle θ can be increased by increasing the exposure amount in the uniform irradiation step.

  FIG. 11 is a diagram illustrating a process of manufacturing a light guide plate by forming a mold from the resist pattern structure of FIG. That is, the resist pattern structure 28 shown in FIG. 2D can be used as it is as the light guide plate 13 by peeling off the substrate 21, but the light guide plate 13 can also be manufactured by electroforming. it can. This method is shown in FIG. 11. First, a metal mold 29 is formed by electrodeposition of nickel or the like as a metal so as to cover the resist pattern structure 28 (FIG. 11A). )). Thereby, a convex portion 30 is formed in the mold 29 at a position corresponding to the concave portion 26 of the resist pattern structure 28.

  Subsequently, after removing the resist pattern structure 28 from the mold 29, the mold 29 is pressed against a soft transparent synthetic resin sheet (synthetic resin material) so as to be in a position corresponding to the convex portion 30. The fine structure 15 having a tapered concave shape can be formed. As the synthetic resin sheet, for example, polymethyl methacrylate (PMMA) having a refractive index of 1.49 can be employed.

  Needless to say, the taper angle and aspect ratio of the fine structure 15 coincide with the taper angle (angle θ in FIG. 4) and aspect ratio of the resist pattern structure 28, respectively. Thus, the light guide plate 13 constituting the backlight device 11 is completed.

  The brightness of the light emitted from the light guide plate 13 tends to improve as the diameter of the fine structure 15 decreases to 100 μm, 60 μm, and 30 μm. However, in consideration of the uniformity of the brightness, the brightness is preferably around 60 μm.

  In addition, the brightness of the light emitted from the light guide plate 13 tends to improve as the depth ratio (aspect ratio) to the diameter of the fine structure 15 increases. However, when the aspect ratio becomes too high, the brightness increases. Saturates or goes lower. Therefore, the aspect ratio is preferably 0.3 or more and 1.0 or less.

  As described above, in the method of manufacturing the light guide plate 13 of the present embodiment, the selective irradiation step of irradiating the ultraviolet ray 24 in a state where the distance between the UV mask 23 and the resist layer 22 on the substrate 21 is separated by the distance d ( 2B) is included.

  As a result, the ultraviolet rays 24 that have passed through the UV mask 23 are obliquely incident on the resist layer 22, thereby making it possible to perform a half-shade photosensitivity with a larger area than the UV-passable region of the UV mask 23, and the tapered fine structure 15. Can be easily formed.

  Further, in the method for manufacturing the light guide plate 13 of the present embodiment, the selective irradiation step of irradiating the ultraviolet rays 24 with the UV mask 23 and the resist layer 22 on the substrate 21 being separated (FIG. 2B). And developing the resist layer 22 to form a resist pattern structure 28 on the substrate 21 (FIG. 2D), and electrodepositing a metal so as to cover the resist pattern structure 28 The step of forming the mold 29 (FIG. 11A), the step of removing the resist pattern structure 28, and the step of forming the fine structure 15 having a tapered concave shape on the synthetic resin sheet by the mold 29 ( 11 (b)).

  As a result, the ultraviolet ray 24 that has passed through the UV mask 23 in the selective irradiation step is incident on the resist layer 22 obliquely, so that a half-shade exposure of an area larger than the ultraviolet ray passable region of the UV mask 23 becomes possible. The tapered recess 26 of the structure 28 can be easily realized. Then, by transferring the shape of the concave portion 26 with the mold 29, the light guide plate 13 provided with the tapered fine structure 15 can be obtained at low cost.

  The tapered concave microstructure 15 is configured such that the taper angle is 65 ° or more and 80 ° or less, so that excellent emission light intensity can be obtained, and both reduction in power consumption and improvement in luminance can be achieved. Can be made.

  Further, after the selective irradiation step (FIG. 2B), the resist layer 22 is subjected to a uniform irradiation step (FIG. 2C) in which ultraviolet rays are irradiated without passing through the UV mask 23, whereby a resist layer is obtained. The taper angle θ of the concave portion 26 formed in 22 can be increased, which can contribute to the improvement of the emitted light intensity.

  The selective irradiation step (FIG. 2B) can also be performed using the doughnut-shaped ultraviolet light source 1b shown in FIGS. 7 and 8. In this method, half shadow exposure is directly performed without using a diffraction phenomenon. Since it can be controlled, the taper angle θ and the like can be controlled with high accuracy.

  Moreover, as shown in FIG. 1, since the tapered concave shape of the fine structure 15 is formed in a truncated cone shape, the light guide plate 13 having excellent uniformity of emitted light can be obtained.

  Next, a dot arrangement pattern as a light guide pattern of the light guide plate 13 will be described with reference to FIGS. 12 is a diagram for conceptually explaining the arrangement pattern of the fine structure in the light guide pattern unit of the light guide plate, FIG. 13 is an overall conceptual diagram of the arrangement pattern of the fine structure of the light guide pattern, and FIG. 14 is for preventing moire. It is a figure explaining the arrangement pattern of the microstructure.

  As shown in FIG. 12A, the light guide pattern 18 is formed in a rectangular shape, and from the LED as a point light source through the lower left corner (incident part) of the four corners of the rectangular region. Is incident in a 45 ° direction or a diagonal direction.

  In this light guide pattern 18, as described above, a large number of fine structures 15 (dots) formed in a truncated conical concave shape are arranged on the exit surface of the light guide plate 13.

  Specific dot pattern examples of the regions indicated by the circled numbers 1 to 5 in FIG. 12A are shown corresponding to FIG. 12B, respectively. As shown in FIGS. 12A and 12B, the arrangement density of the fine structures 15 is the smallest in the vicinity of the incident portion (the region indicated by the circled number 4) in the light guide pattern 18. In the central region of the light guide pattern 18 (the region with the circled number 3), the arrangement density of the fine structures 15 is slightly increased, and in the corner region (the region with the circled number 1) farthest from the incident portion, the fine structure is formed. The arrangement density of the bodies 15 is the largest. In the other two corner areas (areas with circled numbers 2 and 5), the arrangement density of the fine structures 15 is slightly larger than that in the central area.

  As described above, the fine structure 15 in the light guide pattern 18 is changed from a sparse state to a dense state as the distance from the incident part formed at one of the four corners increases. Many are arranged so as to change gradually.

  Specifically, the fine structures 15 are arranged such that the number per unit area increases according to a predetermined exponential function as the distance from the incident portion of the light guide plate 13 increases. Thereby, the intensity of light emitted from the emission surface can be made uniform over the entire region of the light guide pattern 18. The state of the arrangement of the fine structures 15 can also be understood from the overall front view shown in FIG. Note that an arrow L in FIG. 13 indicates the direction of incident light.

  Further, instead of regularly arranging the fine structures 15 as illustrated in FIG. 14A, the fine structures 15 are arranged somewhat irregularly (randomly) as shown in FIG. 14B. You can also In addition, it is preferable to arrange | position the fine structure 15 at random as mentioned above from a viewpoint of the uniformity of the brightness | luminance of the emitted light of the light-guide plate 13, and a moire prevention. Of course, it is preferable that the random arrangement is performed while substantially maintaining the density change tendency of the fine structure 15 described with reference to FIG.

  Next, a schematic configuration of a lighting panel (liquid crystal display light source panel) as an example of a surface light source device including the light guide plate 13 of the present embodiment will be described with reference to an exploded perspective view of FIG.

  In FIG. 15, the lighting panel 100 is configured by sequentially stacking a reflective film 5, the light guide plate 13, a diffusion film 7, and lens films 3 and 4. The LED (light emitting diode) 6 as a point light source is disposed on the side of the light guide plate 13, and light enters the light guide plate 13 from the LED 6. In the example of FIG. 15, three LEDs 6 are arranged side by side on the one side of the light guide plate 13, but the number and arrangement of the LEDs 6 are not limited to this, and correspond to the incident portion of the light guide pattern 18 described above. LED6 should just be provided so that it may do.

  With this configuration, light incident on the light guide plate 13 from the LED 6 is converted into a surface light source by propagating inside the light guide pattern of the light guide plate 13, and is emitted from the light guide plate 13 (upper surface in FIG. 15). To the diffusion film 7. The reflective film 5 is for reflecting the light leaking to the side opposite to the exit surface of the light guide plate 13 in the exit direction and collecting it in the light guide plate 13.

  The light emitted from the light guide plate 13 as described above is diffused in the traveling direction by passing through the diffusion film 7 as a light control member. Further, by passing through the lens films 3 and 4 as light control members, which are called so-called prism sheets, the light concentrated in the viewing angle of the liquid crystal display screen and the light with higher luminance is displayed on the liquid crystal display screen. Irradiate.

  Next, an embodiment in which the resist pattern structure 28 is actually manufactured will be described. As the substrate 21, a 4-inch silicon substrate was used. The substrate 21 was washed with acetone, isopropyl alcohol, and pure water in this order, and dried on a hot plate. Next, OAP (hexamethyldisilazane) was applied onto the substrate 21 with a spin coater and then baked at 120 ° C. for 5 minutes. In the spin coating of OAP (hexamethyldisilazane), the rotation speed was increased to 500 rpm in 10 seconds, and maintained at 500 rpm for 10 seconds, and then stopped in 10 seconds.

  Next, positive resist AZ-P4903 manufactured by Clariant was applied in two steps on the substrate 21 with a spin coater to form a resist layer 22. The conditions for the first spin coating were as follows: the rotation speed was increased to 500 rpm in 15 seconds, held at 500 rpm for 15 seconds, then increased to 4500 rpm over 15 seconds, maintained at 4500 rpm for 40 seconds, and then for 15 seconds. I stopped it. After the first application, baking was performed at 110 ° C. for 7 minutes.

  In the second spin coating, the rotation speed is increased to 500 rpm in 15 seconds, held at 500 rpm for 15 seconds, then increased to 1200 rpm over 15 seconds, held at 1200 rpm for 40 seconds, and then stopped for 15 seconds. I made it. After the second application, the film was baked at 110 ° C. for 11 minutes. As a result, a resist layer 22 having a layer thickness of about 30 μm was formed on the substrate 21.

And the glass mask as the UV mask 23 was installed in the position which floated 300 micrometers from the said resist layer 22 (d = 300 micrometers). The glass mask used was one in which a large number of circular patterns 25 having a diameter of φ = 30 μm were drawn. And it exposed using the ultraviolet exposure apparatus (selective irradiation process of FIG.2 (b)). The exposure amount at this time was 550 mJ / cm ² . Note that the uniform irradiation step in FIG.

  Next, a developer (diluted with a ratio of pure water 4 with respect to AZ400K developer 1 manufactured by Clariant) is put in a container, and the substrate 21 and the resist layer 22 are immersed for 50 minutes while stirring with a magnetic stirrer as appropriate. did. As a result, a conical recess having a taper angle of about θ = 70 ° was formed at the position of the circular pattern 25 in the resist layer 22, and the resist pattern structure 28 could be created.

  Although the preferred embodiment of the present invention has been described above, the above is an example, and can be modified as follows, for example.

  The fine structure 15 can be formed only on the opposite side of the emission surface 14 or on both sides, instead of being formed only on the emission surface 14. Further, the fine structure 15 can be formed in a tapered convex shape instead of being formed in a tapered concave shape. FIG. 16 shows photographs of an example in which a large number of fine structures having a truncated cone shape having a truncated cone shape are arranged with different magnifications from (a) to (c). The tapered concave shape and the tapered convex shape can be formed not only in a truncated cone shape but also in a conical shape, for example.

  The resist pattern structure 28 in which the deepest layer of the resist layer 22 is exposed in the selective irradiation step of FIG. 2B or the uniform irradiation step of FIG. 2C and the surface of the substrate 21 is exposed by development is formed. Can be changed. Even in this case, it is possible to manufacture the light guide plate 13 by electroforming described with reference to FIG. 11 without any problem.

  The selective irradiation process of FIG. 2B and the uniform irradiation process of FIG. 2C are performed using other light (blue visible light, near ultraviolet light, radiation light, X-ray) instead of the ultraviolet light 24. Can be changed as follows. In this case, instead of the UV mask 23, an appropriate optical lithography mask is used according to the type of light. When using X-rays, an X-ray lithography mask may be used instead of the UV mask 23.

1 is a schematic cross-sectional view illustrating an overall configuration of a backlight device including a light guide plate according to an embodiment of the present invention. It is a figure explaining the manufacturing process of a light-guide plate later on, (a) is a resist layer formation process, (b) is a selective irradiation process of ultraviolet rays, (c) is a uniform irradiation process of ultraviolet rays, (d) is development The figure which shows a process. The schematic diagram which shows the ultraviolet irradiation device used in a selective irradiation process etc. FIG. The schematic diagram which shows the taper-shaped recessed part formed in the resist pattern structure. The figure which shows the change of the shape of the recessed part of a resist pattern structure when the distance of UV mask and a resist layer is increased from zero by the selective irradiation process. The graph which shows the relationship between the distance between UV mask-resist layers in a selective irradiation process, and the taper angle of the recessed part of a resist pattern structure. The schematic diagram which shows the example which uses a donut-shaped ultraviolet light source in a selective irradiation process. The schematic diagram which shows the ultraviolet irradiation device used in the example of FIG. The figure which shows a mode that the shape of the recessed part of a resist pattern structure changes with the ultraviolet-ray exposure amount of a uniform irradiation process. The graph which shows the relationship between the ultraviolet-ray exposure amount of a uniform irradiation process, and the taper angle of the recessed part of a resist pattern structure. The figure which shows the process of forming a metal mold | die from the resist pattern structure of FIG.2 (d), and manufacturing a light-guide plate. The figure which illustrates notionally the arrangement pattern of a fine structure in the light guide pattern unit of a light guide plate. The whole conceptual diagram of the arrangement pattern of the fine structure of a light guide pattern. The figure explaining the arrangement pattern of the fine structure for a moire prevention. The disassembled perspective view which shows schematic structure of the lighting panel as a surface light source device using a light-guide plate. The figure which shows the enlarged photograph at the time of making a microstructure into a taper convex shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Ultraviolet light source 1b Donut-shaped ultraviolet light source 2 Mirror 3 * 4 Lens film 5 Reflective film 6 LED (light emitting diode)
7 Diffusion film 11 Backlight device 12 Light source 13 Light guide plate (light guide)
14 Outgoing surface (light emitting surface)
DESCRIPTION OF SYMBOLS 15 Fine structure 16 Tapered surface 18 Light guide pattern 21 Substrate 22 Resist layer 22a Photosensitive part 23 UV mask 24 Ultraviolet light 24a Diffracted ultraviolet ray 25 Circular pattern 26 Concave part 27 Inner peripheral surface 28 Resist pattern structure 29 Mold 30 Protruding part 100 Lighting Panel θ Taper angle d Distance between resist layer and UV mask

Claims (10)

In the manufacturing method of the light guide plate that propagates the light incident from the light source through the incident part and emits the light from the exit surface,
The light guide plate has a configuration in which a plurality of microstructures having a tapered convex shape or a tapered concave shape are formed on at least one of the outgoing surface or a surface opposite to the outgoing surface,
The manufacturing method includes a selective irradiation step of irradiating ultraviolet rays in a state where the optical lithography mask and the resist layer on the substrate are separated from each other. In the manufacturing method of the light guide plate that propagates the light incident from the light source through the incident part and emits the light from the exit surface,
The light guide plate has a configuration in which a plurality of microstructures having a tapered convex shape or a tapered concave shape are formed on at least one of the outgoing surface or a surface opposite to the outgoing surface,
The manufacturing method is
A selective irradiation step of irradiating ultraviolet rays in a state where the optical lithography mask and the resist layer on the substrate are separated from each other;
Forming a resist structure on the substrate by developing the resist layer;
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;
Forming the tapered convex shape or the tapered concave shape in the synthetic resin material using the metal structure as a mold;
The manufacturing method of the light-guide plate characterized by including.   3. The method for manufacturing a light guide plate according to claim 1, wherein a taper angle of the tapered convex shape or the tapered concave shape is 65 ° or more and 80 ° or less. 4.   It is a manufacturing method of the light-guide plate as described in any one of Claim 1-3, Comprising: The process of irradiating an ultraviolet-ray without passing the said optical lithography mask to the said resist layer after the said selective irradiation process is included. A method of manufacturing a light guide plate characterized by the above.   The method for manufacturing a light guide plate according to any one of claims 1 to 4, wherein the selective irradiation step is performed using a donut-shaped ultraviolet light source.   It is a manufacturing method of the light-guide plate as described in any one of Claim 1-5, Comprising: The said selective irradiation process is performed using a blue visible ray, a near-ultraviolet ray, or a radiation ray instead of the said ultraviolet-ray. A method of manufacturing a light guide plate characterized by the above.   6. The method of manufacturing a light guide plate according to claim 1, wherein the selective irradiation step uses X-rays instead of the ultraviolet rays and X-ray lithography instead of the optical lithography mask. A method of manufacturing a light guide plate, characterized by performing using a mask.   The method for manufacturing a light guide plate according to any one of claims 1 to 7, wherein the tapered convex shape or the tapered concave shape is substantially a truncated cone shape or a conical shape. Method.   9. The method for manufacturing a light guide plate according to claim 1, wherein the number of the fine structures per unit area increases as the distance from the incident portion of the light guide plate increases. A method of manufacturing a light guide plate, wherein the light guide plate is arranged so as to increase.   A light guide plate manufactured by the manufacturing method according to claim 1.