JP2006215115A - Manufacturing method of light diffusion reflective plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method capable of easily mass-producing a light diffusion reflective plate having an ideal distribution of surface ruggedness without using a photolithography technology and a pressurizing technology by a diamond indentor. <P>SOLUTION: The manufacturing process of the light diffusion reflective plate comprises: a resist film forming stage of forming a resist film 22 on a base body 21; a ruggedness forming initial stage of successively irradiating the resist film 22 with a laser beam L by using a direct imaging device 23 to which CAD data is inputted; a ruggedness forming latter stage of continuously forming irregular hollows 24 having paraboloid on the resist film 22 to obtain the light diffusion reflective plate material; and a subsequent metal reflective film forming stage of forming a thin metal reflective film 25 to a surface of irregular asperities formed on the resist film 22 of the light diffusion reflective plate material in the metal reflective film forming stage by means of plating, deposition, sputtering and the like to complete the light diffusion reflective plate. When the irradiation with laser beam L is performed, the ideal paraboloidal hollows 24 can be continuously formed, the depths and sizes of the hollows 24 are freely changed by changing the amount of exposure and, thereby, the controlled ruggedness can be formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  INDUSTRIAL APPLICABILITY The present invention is mainly used for a liquid crystal display of a liquid crystal display device, and has a function capable of controlling the scattering of reflected light to an optimum state, and can easily mass-produce a light diffusing reflector plate having irregularities formed on the surface. The present invention relates to a method of manufacturing a light diffusing reflector.

  Conventionally, in a liquid crystal display of a liquid crystal display device, a transmissive type product having a backlight unit has been mainstream, but recently, the demand for power saving has increased due to the spread of portable terminals, etc. The demand for reflective liquid crystal displays is increasing.

  Such transflective and reflective liquid crystal displays are required to improve brightness as the display colorization progresses, and accordingly, it is important to improve the reflection efficiency of incident light of the liquid crystal display Is being viewed. In known transflective and reflective liquid crystal displays, a reflective plate made of an aluminum plate or the like is installed at the bottom of the liquid crystal panel, and brightness is obtained by reflecting incident light from the top of the panel. Since the surface of the reflecting plate is flat, the directions in which incident light is reflected are aligned, and there is a problem that the directivity when the user views the liquid crystal display cannot be controlled.

  Therefore, a technique using a light diffusing reflector has been proposed in order to improve such drawbacks in the reflective liquid crystal display. By the way, the light diffusing reflector diffuses the direction of reflection of the reflected light by giving a fine uneven shape to the surface of the reflector, and the same if it is within a certain range even if the viewing angle of the user changes The brightness is obtained. As a method for forming irregularities on the surface of the reflecting plate, a method is known in which after forming fine irregularities on the surface of the reflecting plate by sandblasting, a metal film is formed thereon.

  However, with this method, it is difficult to control the uneven shape of the surface to an arbitrary shape, so the directivity of the diffused light cannot be controlled sufficiently, and as a result, the brightness of the reflected light changes depending on the viewing angle of the user Has occurred.

  In order to solve the problem here, as a technique for controlling the uneven shape on the surface of the light diffusing reflector plate to suppress the luminance change of the reflected light, it is proposed to apply, for example, a photolithography technique which is a semiconductor manufacturing technique (See Patent Document 1).

  The method proposed in Patent Document 1 uses a binary mask, and the shape is controlled by forming a pattern smaller than the resolution determined by the optical system of the exposure apparatus on the binary mask. Outputs grayscale. Specifically, by using a photomask 42 having a perforated mask pattern as a mask pattern, a resist film formed on a substrate is irradiated with an exposure amount showing a stepwise energy distribution. Therefore, when a negative resist is used, a resist film having a fine shape design can be formed as a result. At this time, since the pattern shape of the photomask can be arbitrarily changed, the shape in the thickness direction of the resist film can be freely controlled. Therefore, it is possible to manufacture an ideal light diffusing reflector with little variation in the brightness change of reflected light depending on the viewing angle of the user.

  In addition, as a method for controlling the uneven shape on the surface of the light diffusing reflector without using photolithography technology, a diamond indenter having an ideal curved surface with a cone is used, and the diamond indenter is placed on a flat metal plate. A technique of forming depressions and projections by sequentially pressing the two has also been proposed (see Patent Document 2). In this Patent Document 2, the depth of pressing the diamond indenter and the interval between the adjacent irregularities are irregularly changed to prevent the occurrence of moire or the like in the reflective liquid crystal display of the final product. First, create a transfer mold made of a resin material using a metal plate with irregularities on its surface as a matrix, then form a resist film on the glass substrate and press the transfer mold on the upper surface to form irregularities. A light diffusing reflector is obtained by providing a metal film after UV curing.

JP 2002-31565 A (paragraphs [0034] to [0038], FIG. 4) JP 2004-4892 A (paragraphs [0010] to [0013])

  As a well-known technique for controlling the uneven shape on the surface of the light diffusing reflector described above to suppress the luminance change of the reflected light, when using the photolithography technique according to Patent Document 1, the light diffusing reflector is a liquid crystal in which it is used. Although an area almost equivalent to the screen is required, it takes a very long time to draw a pattern of such an area by photolithography technology, and the drawing processing process takes a long time. In addition, in order to shorten the time of this drawing processing step, a measure for increasing the exposure amount can be considered, but in such a case, there is a problem that the life of an expensive photomask is reduced.

  Further, in the case of the technique for controlling the uneven shape on the surface of the light diffusive reflector without using the photolithography technique according to Patent Document 2, a step of creating a diamond indenter (push die) in which the shape of the tip is strictly defined In general, however, the distance between the recesses formed by the pressing technique is in the range of several μm to several tens of μm. In this range, it is very difficult to create a pressing die whose shape is strictly controlled. In addition, diamond is hard and difficult to process, relatively easy to chip, and difficult to control when chemical etching is performed. As a result, on a scale that allows mass production of stamping dies. There is a problem that it is technically very difficult to create.

  The present invention has been made to solve such problems, and its technical problem is that the surface unevenness distribution is ideal and mass production can be easily performed without using a photolithography technique or a diamond indenter pressing technique. An object of the present invention is to provide a method for manufacturing a light diffusing reflector.

  According to the present invention, in the manufacture of a light diffusing reflector having a surface with irregularities, a resist film forming step for forming a resist film on the surface of the substrate, and laser light is applied to the resist film without using a photomask. Light having an unevenness forming step for obtaining a light diffusing reflector by forming irregular irregularities on the surface of the resist film by sequentially irradiating and removing a part of the surface of the resist film to provide a concave recess A manufacturing method of a diffuse reflector is obtained.

  Further, according to the present invention, in the method for manufacturing a light diffusing reflector, a method for manufacturing a light diffusing reflector having an approximately parabolic surface in the shape of a concave depression can be obtained in the step of forming irregularities.

  Furthermore, according to the present invention, when manufacturing a light diffusing reflector having a surface with irregularities, the resist film formed on the surface of the substrate is sequentially irradiated with laser light without using a photomask, and the resist Based on the base of the mother mold, a part of the surface of the film is removed to form a mother base by providing irregular concave depressions that approximately form a plane of the surface. A structure in which a depression showing an irregular concave pattern is formed on the surface by pressing the pressing mold against a resist film formed on the surface of the substrate, and a mold creating stage for creating a female mold A method for producing a light diffusive reflector having a pressing die pressing step for obtaining the light diffusive reflector is obtained.

  In addition, according to the present invention, in any one of the above methods for manufacturing a light diffusing reflector, a metal reflecting film is formed on the irregular uneven surface formed on the resist film of the light diffusing reflector. A method for producing a light diffusing reflector having a metal reflecting film forming step for obtaining a light diffusing reflector is obtained. In this light diffusive reflector manufacturing method, it is preferable that the metal reflective film is formed by any one of plating, vapor deposition, or sputtering in the metal reflective film forming stage.

  In the case of the light diffusing reflector manufacturing method of the present invention, the resist film formed on the surface of the substrate is sequentially irradiated with laser light without using a photomask, and irregular recesses are sequentially formed in the resist film. In addition, a light diffusing reflector is manufactured by forming a metal reflecting film on the irregular uneven surface of the obtained light diffusing reflector, or based on the matrix substrate obtained. Similarly, a metal reflecting film is similarly formed on the irregular uneven surface of the light diffusing reflector obtained by pressing the created female die against the resist film formed on the surface of the substrate. Since the diffuse reflector is manufactured, the laser beam is irradiated for a long time using a photomask according to the photolithography technique as in the case of Patent Document 1, or the manufacturing is performed as in the case of Patent Document 2. Difficult high-precision diamond Without using an indenter, it is possible to continuously create a hollow shape controlled with high precision by laser light irradiation, and it is also easy to control the depth and width of each hollow independently when forming the hollow. As a result, it is possible to easily mass-produce a light diffusing reflector having an ideal surface unevenness distribution as compared with the prior art.

  Initially, the technical outline | summary which concerns on the manufacturing method of the light-diffusion reflector of this invention is demonstrated. Generally, the unevenness distribution formed on the surface of the light diffusing reflector is constant regardless of the angle at which the user sees the intensity of the reflected light from the light source virtually provided in front of the liquid crystal screen including the light diffusing reflector. Is preferable. However, considering the case of viewing from a shallow angle with respect to the surface of the liquid crystal screen, the amount of reflected light is insufficient, so in fact it can be clearly seen only in the angle range of 20 to 30 degrees from the front, and beyond that Ideally, the reflected scattered light is zero at an angle.

  One example of the uneven surface shape that realizes such visibility of the angular distribution includes a case where each uneven surface forms a parabolic shape. If the paraboloids can be irregularly arranged on the surface of the light diffusing reflector, it is possible to realize a light diffusing reflector having an ideal uneven distribution on the surface. Incidentally, when the arrangement of the paraboloids is regular, there is a possibility that interference fringes are generated on the surface of the liquid crystal surface, which is inappropriate. Note that the paraboloid here may be upwardly convex or downwardly convex in the calculation, but in reality, the effect of the edge that forms the boundary between adjacent paraboloids is added, so only in the case of a downwardly convex depression Is preferably adopted.

  Therefore, in order to form the paraboloids irregularly on the surface of the light diffusing reflector, spot irradiation is performed to sequentially irradiate the resist film formed on the surface of the substrate with laser light without using a photomask. When it does, it becomes possible to form the irregular hollow of the shape close | similar to a paraboloid.

  FIG. 1 is a schematic diagram for explaining the formation of a recess in a resist film on a substrate by irradiation with a laser beam applied to the method of manufacturing a light diffusive reflector of the present invention. FIG. 5B shows the energy distribution in the beam spot expressed by the relationship between the beam width W and the irradiation energy E. FIG. 5B corresponds to the beam expressed by the relationship between the beam width W and the resist film thickness d. The present invention relates to a recess shape to be formed.

  In general, it is known that the energy distribution in a beam spot by a laser beam is substantially Gaussian as shown in FIG. 1A, and the depth when a photosensitive material such as a resist material is irradiated. The photosensitive area in the vertical direction also follows this Gaussian distribution. Therefore, first, a resist film is applied to the surface of the substrate to form a resist film, and then the surface of the resist film is exposed and removed by irradiating with a laser beam. As shown in FIG. 5, it is possible to form a dent in the shape of a Gaussian distribution, that is, a concave depression 11 that forms a downwardly convex object surface M.

  The type of resist material used to enable the removal of the resist film surface is appropriately selected according to the wavelength of the laser beam to be used, and softening, melting, In addition, it may be considered that the decomposition proceeds smoothly. A preferred example is a case where a combination of an excimer laser and a monodisperse polyhydroxystyrene resist film is used.

  By the way, in the case of the Gaussian distribution, in the energy distribution graph shown in FIG. 1A, the region corresponding to the half-value width ΔW surrounded by the dotted line near the median is approximated by a parabola (secondary curve). Is possible. This corresponds to a case where up to a quadratic term is adopted when a Gaussian function is expanded, and a good approximation is shown in the region inside the half-value width ΔW, so that this is formed by laser beam spot irradiation. The shape of the recess 11 is a shape close to the paraboloid M in the vicinity of the center portion thereof.

  Accordingly, the irradiation of the laser beams is performed so as to overlap each other so that the peripheral portion of the irradiation region having the Gaussian distribution shape does not remain as much as possible, and the exposure amount of the laser at that time is changed to have a paraboloid M. Irregular irregularities having a shape in which the depth and size of the recess 11 are freely changed can be formed on the surface of the resist film.

  In addition, the distance between the irregularities formed on the surface of the resist film by laser light irradiation is in the range of 1 μm to 100 μm, the depth is in the range of 0.1 μm to 10 μm, and more preferably the distance of 5 μm to 50 μm. It is desirable to set the range and depth in the range of 0.3 μm to 3 μm. This is because the distance between the concaves and convexes must be larger than the wavelength incident on the liquid crystal display and smaller than the length of one side of each cell in the color filter constituting the liquid crystal.

  Further, in order to increase the depth of the recess 11, it is necessary to increase the resist film thickness and increase the amount of laser beam spot irradiation. In this case, it becomes difficult to control the shape of the recess 11 to be formed. In addition, a thick resist film has a problem that it is difficult to form a flat film. On the contrary, if the depth of the depression 11 is made too shallow, the effect of scattering of incident light becomes low, and simple planar reflection occurs. Since there exists a problem that a characteristic will become the same as a board, it is necessary to keep the depth of the hollow 11 in the range mentioned above.

  One of the methods for manufacturing a light diffusing reflector according to the best mode of the present invention based on the above technical outline is to form a resist film on the surface of a substrate when manufacturing a light diffusing reflector having an uneven surface. The resist film is formed irregularly on the surface of the resist film by sequentially irradiating the resist film with laser light without using a photomask and removing a part of the surface of the resist film to provide a concave recess. And a concave / convex forming stage for obtaining a light diffusive reflecting plate material by forming a concave / convex (however, in the concave / convex forming stage, it is preferable that the shape of the concave depression is approximately a paraboloid). One is that the resist film formed on the surface of the substrate is sequentially irradiated with laser light without using a photomask, and a part of the surface of the resist film is removed to form an approximate surface on the surface. A matrix with regular concave depressions By creating a base mold for creating a base, a press mold creating stage for creating a female mold based on the base of the base mold, and pressing the stamp against the resist film formed on the surface of the substrate And a pressing die pressing step for obtaining a light diffusing reflector plate having a depression showing an irregular concave pattern on the surface, and in any case, it is further formed on the resist film of the light diffusing reflector plate. Having a metal reflecting film forming step for obtaining a light diffusing reflecting plate by forming a metal reflecting film on the surface of irregular irregularities (however, in the metal reflecting film forming step, the metal reflecting film is plated, vapor deposited, or It is preferable to form a film by any one of sputtering methods).

  Below, the manufacturing method of the light-diffusion reflector of this invention is demonstrated concretely, giving some examples.

  FIG. 2 is a side cross-sectional view showing a manufacturing process of a light diffusing reflector produced by the method of manufacturing a light diffusing reflector according to Embodiment 1 of the present invention, step by step. FIG. (B) is related to the resist film formation stage, (c) is related to the initial stage of uneven formation, (d) is related to the later stage of uneven formation, and (e) is metal reflection. It relates to the film formation stage.

  In the manufacturing process of the light diffusing reflector according to the first embodiment, a thin plate-like substrate 21 having a predetermined thickness is first prepared in the substrate preparation stage shown in FIG. 2A, and then shown in FIG. In the resist film formation stage, a resist film 22 is formed on the surface of the base 21. The resist film 22 can be formed by spin coating or the like, with a film thickness in the range of 1 μm to 5 μm.

  Further, in the initial stage of forming irregularities shown in FIG. 2 (c), the direct writing device 23 to which the created CAD data has been inputted is sequentially irradiated with the laser beam L onto the resist film 22, and as shown in FIG. 2 (d). As a later stage of the unevenness formation, an irregular recess 24 having a paraboloid is continuously formed on the resist film 22 to obtain a light diffusing reflector. Note that the CAD data input to the direct drawing device 23 at the initial stage of the unevenness formation is stored in the external device as a program indicating a pattern by spot irradiation of the laser beam L for forming the irregular depression 24 in advance. Thus, the direct drawing device 23 controls the position, focus, depth, and irradiation energy of the laser beam L independently according to the CAD data. Unevenness can be formed on the resist film 22.

  Incidentally, after obtaining a light diffusive reflecting plate material by forming irregularities on the surface of the resist film 22 by spot irradiation of the laser beam L to the resist film 22, the region of the resist film 22 in the light diffusing reflecting plate material is heated and cured. As a result, the adhesion of the resist film 22 to the substrate 21 can be enhanced. The surface having unevenness of the light diffusing reflection plate material obtained so far has a function of reflecting all of the incident light while scattering it.

  Thereafter, as a step of forming a metal reflection film shown in FIG. 2 (d), the surface of the irregular irregularities formed on the resist film 22 of the light diffusive reflection plate material is subjected to thin metal reflection by a technique such as plating, vapor deposition or sputtering. A film 25 is formed to complete a light diffusing reflector. A function of reflecting incident light is added to the light diffusing reflector obtained here.

  FIG. 3 is an external perspective view showing the unevenness provided on the surface of the light diffusive reflector produced as described above. Here, an irregular recess 24 is formed by introducing an irregular repeating pattern as a spot irradiation pattern of the laser beam L on the surface of the resist film 22, and then a metal reflection film 25 is formed thereon. As a result, it is shown that a light diffusing reflection plate having irregularities having irregular depressions 24 formed on the surface of the metal reflection film 25 is obtained.

  FIG. 4 is a side cross-sectional view showing a manufacturing process of a light diffusing reflector produced by the method of producing a light diffusing reflector according to Example 2 of the present invention, step by step, and FIG. FIG. 5B relates to the stage, and relates to the pressing die pressing stage.

  In the manufacturing process of the light diffusing reflector according to the second embodiment, the substrate preparation stage shown in FIG. 2A of the manufacturing process according to the first embodiment, the resist film forming stage shown in FIG. The initial stage of forming irregularities shown in (c) and the latter stage of forming irregularities shown in FIG. 2D are set as a series of steps, that is, a photomask is used for the resist film 22 formed on the surface of the substrate 21. The substrate subjected to these treatments is irradiated with the laser beam L sequentially, and a part of the surface of the resist film 22 is removed to provide an irregular concave recess 24 having an approximately rectangular surface on the surface. A mother mold creating step is performed in which a mother mold is created by curing by heating. The mother die obtained here has the same structure as that formed through the latter stage of the unevenness formation shown in FIG.

  Next, as a pressing mold making stage shown in FIG. 4A, a resin material is poured into the base of the mother mold having irregular depressions 24 on the surface so as to cover the depressions 24 and left for a certain period of time. Then, the female die 26 is formed by curing. Silicone or the like is suitable as the resin material. The female pressing die 26 obtained here is shown in a state of being taken out from the mother die.

Further, as a pressing mold pressing step shown in FIG. 4B, the pressing mold 26 is pressed against the photosensitive resin layer 28 as a resist film formed on the surface of the substrate 27 for a certain period of time, so that the surface is parabolic. A light diffusing reflector plate material having an irregular concavo-convex pattern in which planar depressions are formed is obtained. Pressure and time during pressing here is determined by the type and thickness of the photosensitive resin layer 28, generally in the range of pressure of ^{10kg / cm 2 ~100kg / cm 2} , the range of several seconds to 10 minutes time The following conditions are appropriate. It is preferable to use a metal or glass plate as the material of the substrate 27, and the photosensitive resin layer 28 is formed by applying a photosensitive resin typified by an acrylic resist on the surface of the substrate 27 by a technique such as spin coating. Thereafter, it is formed by performing pre-baking.

  In this case as well, after the pressing mold pressing step, the pressing mold 26 is removed and cured by irradiation with light such as ultraviolet rays, and post-baking is performed to bak the photosensitive resin layer 28, so that the photosensitive resin layer 28 is baked. It is preferable to strengthen the adhesion to the substrate 27.

  Finally, the metal reflecting film forming step shown in FIG. 2D is executed, and the irregular uneven surface formed on the photosensitive resin layer 28 of the light diffusing reflector is subjected to plating, vapor deposition, sputtering, etc. A thin metal reflection film 25 is formed by a technique, thereby completing a light diffusing reflection plate.

  In the method according to the second embodiment in which the above-described female mold 26 is formed and pressed against the photosensitive resin layer 28, it is possible to create a large number of light diffusing reflectors with one female mold 26. In addition, the time required for manufacturing to form the unevenness by pressing can be shortened. As described above, the method of creating the light diffusing reflector using the female pressing die 26 is more suitable for mass production than the case where the unevenness is individually drawn by laser light on each light diffusing reflector described in the first embodiment. In actual production, the method of Example 2 is considered to be the mainstream.

  In addition, about the material of the base | substrate 21 demonstrated in each Example, the board | substrate 27, the type | mold of the photosensitive resin which is the material for forming the resin and the photosensitive resin layer 28 for producing the female die 26, and those curing methods The present invention is not limited to the disclosed contents. Irregularities that approximately form a surface of the object by irradiating the surface of the resist film 22 with laser light without using a photomask, which is a basic technique common to the embodiments. As long as the concave recess 24 can be formed, it is applicable in any case.

  The light diffusing reflector obtained by the method for producing a light diffusing reflector of the present invention has a surface irregularity distribution more ideal than the conventional one and can control the scattering of reflected light to an optimum state. It can be used not only for improving the angle but also for improving the viewing angle of the screen by applying it to the surface of a projection screen used together with a projector (projector), for example.

It is the schematic diagram shown in order to demonstrate formation of the hollow with respect to the resist film on a base | substrate by the irradiation of the laser beam applied to the manufacturing method of the light-diffusion reflector of this invention, (a) is the width of a beam, and irradiation energy (B) relates to the shape of the depression formed corresponding to the beam represented by the relationship between the width of the beam and the thickness of the resist film. It is side surface sectional drawing which showed the manufacturing process of the light-diffusion reflecting plate produced by the manufacturing method of the light-diffusion reflecting plate based on Example 1 of this invention according to the step, (a) is related with a base | substrate preparation step, (b) Is related to the resist film formation stage, (c) is related to the initial stage of uneven formation, (d) is related to the later stage of uneven formation, and (e) is related to the metal reflective film formation stage. It is the external appearance perspective view which showed the unevenness | corrugation provided in the surface of the light-diffusion reflecting plate produced through the manufacturing process demonstrated in Fig.2 (a)-(e). It is side surface sectional drawing which showed the manufacturing process of the light-diffusion reflecting plate produced by the manufacturing method of the light-diffusion reflecting plate concerning Example 2 of this invention according to the step, (a) is related with a stamping die preparation step, (b ) Relates to the pressing die pressing stage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11,24 Indentation 21 Base body 22 Resist film 23 Direct drawing apparatus 25 Metal reflective film 26 Stamping die 27 Substrate 28 Photosensitive resin layer

Claims (5)

  In manufacturing a light diffusive reflector having a surface with irregularities, a resist film forming step of forming a resist film on the surface of the substrate, and sequentially irradiating the resist film with laser light without using a photomask, And a step of forming irregularities on the surface of the resist film by removing a part of the surface of the resist film so as to obtain a light diffusing reflection plate material. A manufacturing method of a diffuse reflector.   2. The method of manufacturing a light diffusing reflector according to claim 1, wherein, in the step of forming the irregularities, the shape of the concave depression is approximately a paraboloid.   When manufacturing a light diffusing reflector with irregularities formed on the surface, the resist film formed on the surface of the substrate is sequentially irradiated with laser light without using a photomask, and a part of the surface of the resist film is removed. A mother die making step for creating a mother die base by providing irregular concave depressions that approximately form a surface on the surface, and a female die is created based on the mother die substrate. And a light diffusing reflector having a structure in which a depression showing an irregular concave pattern is formed on the surface by pressing the stamp against the resist film formed on the surface of the substrate. A method for producing a light diffusing reflector, comprising: a pressing die pressing step to obtain.   The method of manufacturing a light diffusing reflector according to any one of claims 1 to 3, wherein a metal reflecting film is formed on the surface of the irregular irregularities formed on the resist film of the light diffusing reflector. A method for producing a light diffusing reflector, comprising the step of forming a metal reflecting film to obtain a light diffusing reflector. 5. The method of manufacturing a light diffusing reflector according to claim 4, wherein, in the metal reflecting film forming step, the metal reflecting film is formed by any one of plating, vapor deposition, or sputtering. A manufacturing method of the reflector.

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