WO2011162165A1 - Method for manufacturing light-diffusing film, light-diffusing film manufactured by the method, and display device provided with the light-diffusing film - Google Patents

Abstract

Disclosed is a light-diffusing film (1) wherein a laminated body (5) having a multilayer structure is formed by laminating materials that constitute a structural body (4). The structural body (4) is formed by melting the laminated body (5) or by covering the laminated body (5) with a resin. Alternatively, the structural body (4) may be formed by laminating a plurality of tapered layers. In this case, the layer width of the structural body (4) is reduced toward the upper layer from the lower layer, and as a whole, the structural body has a structure having tilted surfaces that are tilted at multiple levels. The shape of the structural body (4) can be controlled by micron size by adjusting the number of layers, height, width and the like of the structural body (4) as needed.

Description

Manufacturing method of light diffusion film, light diffusion film manufactured by the manufacturing method, and display device including the light diffusion film

The present invention relates to a method for producing a light diffusion film suitably used for a display device such as a liquid crystal display device, a light diffusion film produced by the production method, and a display device provided with the light diffusion film.

In recent years, research and development of display devices has been remarkable, and thin flat panel display (FPD) display devices have been widely used instead of display devices using cathode ray tubes, which have been the mainstream in the past. Some FPDs use liquid crystal, light emitting diodes (LEDs), organic electroluminescence (ELs), or the like as display elements.

These display devices emit light toward the display screen, or irradiate light by a backlight or the like provided on the back surface of the display screen (opposite to the observer). An observer visually recognizes the light emitted from the display screen. The display device is designed so that light emitted obliquely from the display screen looks the same as when light emitted from the front of the display screen is viewed. In other words, the display screen is designed to look the same as when the display screen is viewed from the front. However, the design is inadequate and the contrast characteristics when the display screen is viewed from the front are excellent. However, when viewed from the front, the sense of change may be greater than when viewed from the front. Therefore, the display device has a problem that the appearance of the display differs depending on the viewing direction, that is, the viewing angle characteristic is inferior.

Therefore, as one of the methods for improving the viewing angle characteristics of the display device, a method has been developed that enables visual recognition from an oblique direction by providing a film that diffuses light on the viewer side of the display device. Examples of the light diffusing film include those obtained by subjecting the film surface to a concavo-convex treatment, and those containing light diffusing fine particles inside the film. The light diffusion film refracts or totally reflects light from the backlight in multiple directions using a difference in refractive index. The light refracted by the light diffusion film is diffused in multiple directions from the surface and emitted to the viewer side. As described above, when the light diffusion film is used, the display device can be visually recognized from all directions by the diffusion of light. As a result, a display device has been developed in which an image viewed from the front and an image viewed from an oblique direction are combined, and the viewing angle is less changed.

For example, Patent Document 1 discloses a configuration in which a plurality of grooves having a substantially V-shaped cross section are formed in parallel on the observation surface of a light diffusion film. Specifically, the light diffusion film disclosed in this document has a plurality of substantially V-shaped grooves (that is, a plurality of substantially trapezoidal structures), a light transmitting portion, A light reflecting portion formed by filling the groove with a resin having a refractive index lower than that of the transmitting portion. In particular, the surface on which the groove of the light reflecting portion is formed is located on the light incident surface side so as to connect the first inclined surface having an angle for totally reflecting the image light, and the first inclined surface and the light emitting surface. It is characterized by being formed by a slope including a second slope having an angle to refract and transmit the image light.

According to this configuration, the light incident in the vertical direction with respect to the light diffusion film is totally reflected on the first slope, and is emitted from the emission surface through the light transmission part. On the other hand, on the second inclined surface, the light incident in the vertical direction with respect to the light diffusion film is refracted, and is emitted from the emission surface through the light reflecting portion. As described above, the light diffusion film can transmit, totally reflect, or refract the incident image light, so that the image light can be diffused at various angles. As a result, it is possible to improve the light diffusion characteristics of the image light diffused by the light diffusion film. Such an improvement in the light diffusion characteristics is attributed to the discontinuity of the diffusion angle on the second inclined surface that refracts and transmits the image light.

Japanese Patent Publication “JP 2007-148185 A (published on June 14, 2007)”

By the way, in above-mentioned patent document 1, at the time of manufacture of a light-diffusion film, the shaping | molding shape of the groove | channel of the light transmissive part was formed in the surrounding surface, and this mold roll contact | abutted, and a base material is said mold roll A manufacturing apparatus including a nip roll that can be pressed is used. Specifically, when the material constituting the light transmission portion is supplied between the mold roll and the base material that advances along the peripheral surface of the mold roll while rotating the mold roll, the nip portion between the mold roll and the nip roll The material constituting the light transmission portion and the base material are pressed. Thereafter, the light transmissive portion is formed by curing the material. And the light reflection part is formed by filling the groove | channel of the formed light transmissive part with the material which comprises a light reflection part, and also hardening | curing the said material. Thus, as a method for producing a light diffusion film, a method using a roller is generally employed.

In the manufacturing method described above, the grooves of the light transmitting portions are formed at a pitch of about 50 μm, and the depth of the grooves is also formed at about 50 μm. However, when the groove pitch of the light transmitting part is 50 μm or less, or when the groove depth is 50 μm or less, etc., it is necessary to control the forming of the groove with micron size, the above manufacturing method is applied. It is hard to do. This is because it is difficult to control the groove (that is, the structure) at a micron size by a mechanical forming method using a roll as in the above manufacturing method.

Further, as shown in Patent Document 1, it is possible to control transmission of image light, total reflection, or refractive transmission by controlling the inclination angle of the inclined surface of the groove (that is, the structure). Therefore, in order to improve the light diffusion characteristics of the image light, it is desirable to be able to control the inclination angle of the inclined surface of the structure. However, as described above, in the manufacturing method disclosed in Patent Document 1, it is difficult to control the inclination angle of the slope of the micron-sized structure.

Then, this invention was made | formed in view of the said subject, The objective was manufactured by the manufacturing method of the light-diffusion film which can control shaping | molding of a structure (groove) by micron size, and the said manufacturing method. The object is to provide a light diffusing film and a display device including the light diffusing film.

In order to solve the above problems, the method for producing a light diffusing film according to the present invention comprises a structure forming step of diffusing incident light incident from a light incident surface and forming a plurality of structures emitted from the light emitting surface. A method for producing a light diffusing film, wherein, in the structure forming step, a plurality of structures are formed by laminating a plurality of taper-shaped layers on a substrate. The structure is formed such that the lower surface of the layer located in the upper layer coincides with the upper surface of the layer located immediately below the layer.

According to the above method, a plurality of tapered layers are stacked, and finally a structure having a slope with a graded slope is formed. With such a manufacturing method, it is possible to manufacture a structure having a desired height, pitch, and the like. In the conventional mechanical manufacturing method using rollers, it is difficult to finely control the inclination angle of the inclined surface, such as providing a stepwise inclination to a micron-sized structure. However, according to the manufacturing method according to the present invention, the forming of the structure can be controlled to a micron size.

In the present invention, a plurality of tapered layers are stacked to form a structure having a slope with a multi-step slope. Therefore, a structure having a desired inclination angle can be manufactured by appropriately adjusting the number of layers, the height, the width, or the like of the structure. Moreover, since a structure can be made into a desired shape by changing the height or width of the structure, the structure can be applied as a method for manufacturing a light diffusion film having structures of various shapes.

In addition, the light diffusing film manufacturing method according to the present invention includes a structure forming step of diffusing incident light incident from a light incident surface to form a plurality of structures that are emitted from the light emitting surface. The structure forming step includes a laminate forming step of forming a plurality of laminates in which a plurality of layers are laminated on a substrate, and a melting step of melting the plurality of laminates. In the laminate forming step, for each of the laminates, the length of the layer in the fixed direction at the cut surface when the laminate is cut in a fixed direction is shortened from the lower layer to the upper layer, and The laminate is formed such that the entire lower surface of the layer located in the upper layer is included in the upper surface of the layer located immediately below the layer.

According to the above method, by forming a laminate in which the width of the layer becomes narrower from the lower layer to the upper layer, a structure having a slope with a graded slope is finally obtained. With such a manufacturing method, it is possible to manufacture a structure having a desired height, pitch, and the like. In the conventional mechanical manufacturing method using rollers, it is difficult to finely control the inclination angle of the inclined surface, such as providing a stepwise inclination to a micron-sized structure. However, according to the manufacturing method according to the present invention, the forming of the structure can be controlled to a micron size.

In addition, the light diffusing film manufacturing method according to the present invention includes a structure forming step of diffusing incident light incident from a light incident surface to form a plurality of structures that are emitted from the light emitting surface. In the manufacturing method, the structure forming step includes a laminate forming step of forming a plurality of laminates in which a plurality of layers are laminated on a substrate, and a transparent resin on the laminate for each of the laminates. In the cut surface when the laminate is cut in a certain direction for each of the laminates in the laminate formation step, and a lamination step of further laminating the laminate and a melting step of melting the transparent resin. The length of the layer in the certain direction is shortened from the lower layer to the upper layer, and the entire lower surface of the layer positioned in the upper layer is included in the upper surface of the layer positioned immediately below the layer. Forming the body It is characterized in.

According to the above method, by covering the surface of the laminate with a transparent resin, a structure having a smooth slope with a stepwise slope is finally obtained. In such a manufacturing method, the formation of the structure can be controlled to a micron size, and a structure having a desired inclination angle can be manufactured by appropriately adjusting the number of layers, the height, the width, or the like of the laminate. be able to.

Further, the light diffusion film according to the present invention is characterized by being manufactured by any one of the manufacturing methods described above.

According to the above configuration, a layered body in which the layer width is narrowed from the lower layer to the upper layer or a layered body in which the bottom area of the layer is decreased from the lower layer to the upper layer is formed stepwise. A structure having a slope with a gentle slope is obtained. The light incident on the light diffusion film can be emitted in all directions by using the inclined surfaces having different inclination angles of the structures. As described above, the width of the incident light can be widened and the incident light can be diffused without unevenness by using the structure having the inclined surface with the multi-step inclination. As a result, a light diffusion film having good light diffusion characteristics can be obtained.

Further, the display device according to the present invention is characterized by including the light diffusion film described above.

According to the above configuration, the light of the backlight of the display device is emitted in all directions by the light diffusion film. As described above, in the display device according to the present invention, since the width of diffusing the light of the backlight can be widened, a display device having a wide viewing angle and high contrast and brightness can be obtained.

Other objects, features, and superior points of the present invention will be fully understood from the following description. The advantages of the present invention will become apparent from the following description with reference to the accompanying drawings.

In the manufacturing method according to the present invention, a structure having a slope with multi-step slopes is finally formed. Therefore, a structure having a desired inclination angle can be manufactured by appropriately adjusting the number of layers, the height, the width, or the like of the stacked body. That is, the formation of the structure can be controlled at a micron size. Moreover, since a structure can be made into a desired shape by changing the height or width of the structure, the structure can be applied as a method for manufacturing a light diffusion film having structures of various shapes.

It is a perspective view showing the whole light diffusion film composition concerning one embodiment of the present invention. It is a figure which shows the cross section of the light-diffusion film which concerns on one Embodiment of this invention. (A) in a figure is a figure which shows an example in the case of fuse | melting a laminated body and forming a structure, (b) in a figure is a structure body by coat | covering the surface of a laminated body with transparent resin. (C) is a figure which shows an example in the case of forming a structure by coat | covering the surface of a laminated body with a transparent resin. It is a figure which shows the optical path of the light which injected into the light-diffusion film which concerns on one Embodiment of this invention. It is a perspective view showing the whole light diffusion film composition concerning one embodiment of the present invention. (A) in the figure is a schematic view showing a cross section of the structure, (b) in the figure is a top view when the structure has a circular bottom surface, and (c) in the figure is It is a top view in case a structure has a rectangular bottom, (d) in a figure is a top view in case a structure has a pentagonal bottom. (A) in the figure is a schematic view showing the optical path of light incident on the structure, and (b) in the figure is a top view showing the optical path of light incident on the structure having a circular bottom surface. (C) in the figure is a top view showing an optical path of light incident on a structure having a rectangular bottom surface, and (d) in the figure is an optical path of light incident on a structure having a pentagonal bottom surface. FIG. It is a perspective view showing the whole light diffusion film composition concerning one embodiment of the present invention. It is a figure which shows the cross section of the light-diffusion film which concerns on one Embodiment of this invention. It is a top view of the light-diffusion film which concerns on one Embodiment of this invention. It is a figure which shows the cross section of the light-diffusion film which concerns on one Embodiment of this invention. It is a figure which shows the cross section of the light-diffusion film which concerns on one Embodiment of this invention. It is the schematic which shows the cross section of the liquid crystal display device provided with the light-diffusion film which concerns on one Embodiment of this invention.

(Outline of light diffusion film 1)
The outline | summary of the light-diffusion film 1 which concerns on this embodiment is demonstrated with reference to FIG. 1 and FIG. FIG. 1 is a perspective view showing the entire configuration of the light diffusion film 1. FIG. 2 is a view showing a cross section of the light diffusion film 1.

The light diffusion film 1 is used by being attached to the front surface of a display screen in a display device such as a liquid crystal display device. Specifically, it is used for diffusing light emitted from a backlight or the like of the display device onto the display screen and emitted to the viewer side, thereby widening the viewing angle. When the light diffusing film 1 is provided in the display device, a linear film called a louver may be arranged between the light source and the light diffusing film 1, and the light source is collimated to parallel light. Alternatively, it may emit substantially collimated light.

As shown in FIG. 1, the light diffusion film 1 has a light transmission part 2 and a substrate 6. Specifically, the light transmission part 2 is formed on the substrate 6, and the light transmission part 2 is constituted by a plurality of columnar structures 4 formed in parallel in a certain direction. Each structure 4 has a substantially triangular (or substantially trapezoidal) cross-sectional shape, and a groove-like gap (hereinafter referred to as a light reflecting portion 3) is formed between adjacent structures 4. Here, as is apparent from the drawings, the substantially triangular shape indicates a shape in which the width becomes narrower from the lower layer toward the upper layer, and the upper layer has a certain width.

As will be described in detail later, each structural body 4 is formed by melting a laminated body 5 in which materials constituting the structural body 4 are laminated, or by covering the surface of the laminated body 5 with a transparent resin. As shown in FIG. 2, the laminate 5 has a multilayer structure, and the length of the layer in the fixed direction on the cut surface when the laminate 5 is cut in a fixed direction is increased from the lower layer to the upper layer. It is shortened. Here, each stacked body 5 is formed such that the entire lower surface of the layer positioned in the upper layer is included in the upper surface of the layer positioned immediately below the layer. As a result, the structure 4 as a whole has a structure having slopes with multiple stages of slopes. Each structure 4 can also be formed by laminating a plurality of tapered layers. In this case, each structure 4 is formed such that the lower surface of the layer located in the upper layer and the upper surface of the layer located immediately below the layer coincide with each other. The taper shape referred to here means a shape in which the width of the structure 4 becomes narrower as the distance from the portion in contact with the substrate 6 increases. That is, it means a shape in which the width of the portion in contact with the substrate 6 is the widest.

In FIG. 1 and FIG. 2, in order to make the configuration of the structure 4 easy to understand, the stacked body 5 as a base of the structure 4 is illustrated, but the stacked structure 5 is formed by melting the stacked body 5. In this case, since the stacked body 5 itself becomes the structure 4, the stacked body 5 cannot be discriminated as shown in the figure. Similarly, when the structure 4 is formed by laminating a plurality of tapered layers, the laminate 5 is not discriminated. In addition, in FIG. 1, in order to make the structural member of a light-diffusion film easy to understand, each member is simplified and shown in figure. Therefore, in this drawing, the surface of the structure 4 is shown in a curved surface shape, but in reality, the structure 4 has a structure having inclined surfaces with multi-step inclinations.

In addition, when providing the light diffusion film 1 in a display device, it arrange | positions so that the board | substrate 6 (lower layer side of the light transmissive part 2) may be located in the light-incidence surface side into which the light from a backlight etc. injects. That is, in the light diffusion film 1, light from a backlight or the like is incident on the substrate 6, and the light is emitted from the light transmission unit 2 through the substrate 6. At this time, the light incident on the light diffusing film 1 passes through the light transmission part 2, and the refractive index of the light transmission part 2 and the light reflection part 3 (gap) at the interface between the light transmission part 2 and the light reflection part 3. Therefore, the light is totally reflected and emitted from the light exit surface. Here, since the light transmission part 2 has a slope with a multi-step inclination, the light incident on the light transmission part 2 is diffused at any angle by these slopes. As a result, the light diffusibility of the light diffusion film 1 is improved. This will be described in detail later.

(Manufacturing method of structure 4)
Below, the manufacturing method of the structure 4 is demonstrated in detail. As described above, the structural body 4 is formed by melting the laminated body 5, coating the surface of the laminated body 5 with a transparent resin, or laminating a plurality of tapered layers. . The structure 4 can be manufactured using a technique such as photolithography or a nanoimprint method, for example. The nanoimprint method is a method of transferring a pattern by pouring a photocurable resin or a thermosetting resin into a mold (mold) having an arbitrary shape. In this method, the laminate 5 or the structure 4 having a desired shape can be produced by engraving the shape of one layer of the laminate 5 or the structure 4 to produce a mold.

On the other hand, the photolithography method is a method of generating a pattern including an exposed portion and an unexposed portion by pattern exposure of the surface of the material coated with a photosensitive material. Hereinafter, an example in which the structure 4 is formed by photolithography will be described. First, a method for forming the structure 4 by melting the laminate 5 or coating the surface of the laminate 5 with a transparent resin will be described.

First, as a material constituting the structure 4 (laminated body 5), a photocurable resin that is cured by light irradiation is used. Examples of the photocurable resin include urethane acrylate and epoxy acrylate. In particular, it is preferable to use a photocurable resin having a refractive index of about 1.45 to 1.65 and having a high visible light transmittance.

The manufacturing procedure of the structure 4 will be described in order. First, the said photocurable resin is apply | coated as a resist on board | substrates 6, such as glass, a triacetyl cellulose, or a polyethylene terephthalate (PET) (application | coating process). Specifically, there is a method of applying a photocurable resin on the substrate 6 by using a spin coating method, or applying the photocurable resin on the substrate 6 by laminating a film type photocurable resin.

Thus, the board | substrate 6 which apply | coated the resist is exposed using the photomask of a predetermined shape, and the said resist is patterned (patterning process). At this time, in order to form a plurality of columnar structures 4 in parallel, a photomask in which line-shaped exposure portions are arranged is used. As a result, the resist is patterned into a rectangular parallelepiped type. The light to be irradiated is preferably ultraviolet light having a wavelength of 365 nm (i-line) (irradiation energy of about 150 mJ / cm ² ).

Subsequently, the patterned resist portion is cured by heating the substrate 6 with a hot plate at about 100 ° C. (curing step). In this way, the first layer of the stacked body 5 is formed.

After forming the first layer of the laminate 5, a resist is applied again on the substrate 6. And the board | substrate 6 which apply | coated the resist is patterned and hardened in the same procedure as the 1st layer. Specifically, a resist is formed by patterning on the first layer of the stacked body 5. At this time, the resist is concentric with the first layer and is smaller than the first layer. To do. That is, the width and length of the resist are made smaller than the width and length of the first layer, respectively. As a result, the second layer is formed on the first layer of the stacked body 5. By repeating the above steps a plurality of times in order, the stacked body 5 that overlaps several layers is formed. The formed laminated body 5 is finally developed with a developer and is completed by washing away excess portions (laminated body forming step). Here, in FIG. 1 and FIG. 2, the laminated body 5 having a four-layer structure is shown, but the number of layers of the laminated body 5 is not particularly limited to this, and a desired number of layers may be formed.

Finally, the structure 4 is produced by smoothing the corners of the laminated body 5. As described above, the structural body 4 can be obtained by melting the laminated body 5 or making the surface of the laminated body 5 transparent resin. The corners of the laminate 5 are smoothed by coating with. The details are shown in FIG. (A) in FIG. 3 is a diagram showing an example of the case where the laminated body 5 is melted to form the structure 4. (B) in FIG. 3 is a diagram illustrating an example of the case where the structure 4 is formed by covering the surface of the laminated body 5 with the transparent resin 7. (C) in FIG. 3 is a diagram illustrating an example in which the structure 4 is formed by covering the surface of the laminated body 5 with the transparent resin 7.

As shown to (a) in FIG. 3, when forming the structure 4 by melting the laminated body 5, the process which heats the board | substrate 6 in which the laminated body 5 was formed on the heated hotplate, or The laminated body 5 is melted by performing a process of putting it in a heated oven and heating it (melting process). At this time, the heating temperature is set to be equal to or higher than the softening point or melting point of the laminate 5. Thereby, the laminated body 5 is melted and the corners of the laminated body 5 are made smooth. In this way, the structure 4 is obtained. On the other hand, when the structure 4 is formed by coating the surface of the laminate 5 with the transparent resin 7 as shown in FIGS. Further, a transparent resin 7 is laminated (lamination process). Then, the transparent resin 7 is formed by performing a step of heating the substrate 6 on which the laminated body 5 with the transparent resin 7 laminated is heated on a hot plate, or a step of heating in a heated oven. Melt (melting process). At this time, the heating temperature is set to the softening point or melting point of the transparent resin 7 or higher. As a result, the transparent resin 7 is melted to cover the laminate 5, and the corners of the laminate 5 are smoothed. In this way, the structure 4 is obtained (melting step). As described above, by forming the stacked body 5 in which the layer width becomes narrower from the lower layer to the upper layer, the structure 4 having an inclined surface with a stepwise inclination is finally formed on the substrate 6. (Structure forming step). In the case where it is desired to obtain a smoother slope of the structure 4, it is preferable to employ a method of manufacturing the structure 4 by coating the surface of the laminate 5 with the transparent resin 7.

Here, the procedure for forming the structure 4 by laminating a plurality of tapered layers is the same as the step of forming the laminate 5 described above. Specifically, when patterning the resist on the substrate 6, the substrate 6 coated with the resist is patterned at a taper shape by exposing the substrate 6 at an angle (from an oblique direction). Subsequently, the patterned resist portion is cured by heating the substrate 6 with a hot plate at about 100 ° C. In this way, a first tapered layer is formed. By repeating the above-described steps a plurality of times in order, the structure 4 in which the taper-shaped layers overlap several layers is formed. The formed structure 4 is finally developed with a developing solution and completed by washing away excess portions.

As described above, the structure 4 having a slope with a graded slope is obtained. With such a manufacturing method, it is possible to manufacture the structure 4 having a desired height, pitch, and the like. In the conventional mechanical manufacturing method using rollers, it is difficult to finely control the inclination angle of the inclined surface, such as providing a stepwise inclination to the micron-sized structure 4 (or the light reflecting portion 3). However, according to the manufacturing method according to the present embodiment, the formation of the structure 4 can be controlled to a micron size.

For example, as shown in Japanese Patent Application Laid-Open No. 7-270604, when the convex structure 4 is formed by melting resin by heat treatment, the slope of the structure 4 and the substrate 6 are formed. It may be difficult to control the angle (hereinafter referred to as the inclination angle of the structure 4) to a desired inclination angle. However, in the present embodiment, the multilayer structure 5 in which the width of the layer becomes narrower as the upper layer is patterned to form the structure 4 having slopes with multi-step slopes. Therefore, as shown in (b) and (c) of FIG. 3, if the number of layers, the height, the width, or the like of the laminate 5 is appropriately adjusted, the structure 4 having a desired inclination angle is produced. be able to. Moreover, since the structure 4 can be made into a desired shape by changing the height or width of the structure 4, etc., it can be applied as a method for manufacturing a light diffusion film having the structure 4 of various shapes. Can do.

The light reflecting portion 3 (gap) between the adjacent structures 4 can be filled with a low refractive index resin as disclosed in Patent Document 1, for example. Specifically, an ultraviolet curable resin such as acrylic, epoxy, or urethane is preferably used as the low refractive index resin. The refractive index of the high refractive index material constituting the light transmitting portion 2 (structure 4) is 1.02 to 1.25 times the refractive index of the low refractive index material constituting the light reflecting portion 3. It is preferable to have. Thus, since there is a difference in refractive index between the light transmitting portion 2 and the light reflecting portion 3, light can be efficiently totally reflected or refracted and transmitted at the interface between the light transmitting portion 2 and the light reflecting portion 3. .

Further, as disclosed in Patent Document 1, the light reflecting portion 3 can contain a light absorbing material. The light reflecting portion 3 containing the light absorbing material absorbs stray light that has entered the light diffusing film 1 or stray light generated in the light diffusing film 1 and absorbs external light that has entered the light diffusing film 1 to increase the contrast. It acts to improve and can function as a so-called black stripe pattern. As the light absorbing material, light-absorbing particles such as carbon black, and black or gray achromatic materials such as black pigments or black dyes are preferably used. A material that selectively absorbs a specific wavelength may be used in accordance with the above characteristics.

(Configuration of structure 4)
Below, the specific structure of the structure 4 is demonstrated.

First, the taper angle of the structure 4 is preferably 60 ° or more and less than 90 °, and more preferably 60 ° or more and 80 ° or less. If the taper angle of the structure 4 is within the above range, incident light can be almost totally reflected at the interface between the structure 4 and the light reflecting portion 3.

Further, in order to totally reflect light internally, the pitch of the structures 4 is preferably 1 μm or more. However, when the light diffusing film 1 is provided in the display device, if the distance between the display device and the light diffusing film 1 is long, image blur such as an oblique double image occurs, and the visibility is lowered. Therefore, it is better that the pitch of the structures 4 is smaller.

The height of the structure 4 is also preferably 1 μm or more in order to totally reflect light internally, but for the same reason as the pitch, the height of the structure 4 is preferably about 50 μm or less. More preferably, it is about several μm.

The pitch of the conventional light diffusing film structure (or the groove of the light transmitting portion) is about 50 μm. Even when the pitch is set to several μm, the light diffusion is performed by general equipment for performing photolithography. The film 1 can be produced.

(Diffusion by light diffusion film 1)
As described above, the light diffusion film 1 is attached to the front surface of a display screen in a display device such as a liquid crystal display device, and diffuses light emitted from a backlight or the like toward the viewer. The optical path of the light incident on the light diffusion film 1 will be briefly described with reference to FIG. In FIG. 4, the optical path of the incident light is schematically shown as arrows (a) to (e).

In the light diffusing film 1, the light incident near the center of the structure 4 of the light transmitting portion 2 passes straight through the light diffusing film 1 as shown by the arrow (b) and reaches the observer. On the other hand, the light incident on the slope portion of the structure 4 is totally reflected at the interface between the structure 4 and the light reflecting portion 3 as indicated by arrows (a) and (c), and is refracted and emitted from the exit surface. To the observer.

Here, in the light transmission part 2 of the light diffusion film 1 according to the present embodiment, the structure 4 has an inclined surface with a multi-step inclination. Therefore, the light that has entered the structure 4 on the slope portion different from the arrows (a) and (c) is reflected at the interface between the structure 4 and the light reflecting portion 3 as indicated by arrows (d) and (e). It is totally reflected, refracted at the exit surface, and exits to the observer. In the arrows (d) and (e), since the light is incident on a slope portion having an inclination angle different from that of the slope portion on which the arrows (a) and (c) are incident, the emission direction on the exit surface side is the arrow (a). And (c) is different.

As described above, the angle at which the light incident on the light diffusion film 1 is emitted from the exit surface side varies depending on the incident portion of the structure 4, that is, the incident inclined surface portion. Therefore, the incident light can be emitted in all directions by using the inclined surfaces having different inclination angles of the structures 4. As described above, in the present embodiment, by using the structure 4 having a slope with a multi-step slope, it is possible to widen the width for diffusing incident light. In particular, the light diffusing film 1 according to the present embodiment is constituted by the light transmission part 2 in which the columnar structures 4 are formed in parallel, so that the incident light is diffused widely in the horizontal direction (left-right direction in FIG. 4). be able to. Therefore, the light diffusion film 1 having a wide viewing angle in the horizontal direction and high contrast and brightness can be obtained.

When the light diffusion film 1 is provided in a display device, light from a backlight or the like is not completely parallel light but has a diffusion angle with a certain width. Therefore, it is preferable to use the light diffusion film 1 having the structure 4 having a change in the taper angle as in this embodiment.
This is because the light from the backlight or the like is strong in linear light, and therefore, when the structure 4 has a single inclination, a specific viewing angle becomes bright and abrupt on the display screen. This is because the change in the image becomes conspicuous. In the present embodiment, the taper angle of the structure 4 can be changed stepwise, so that light from the backlight or the like can be diffused without unevenness. As a result, the light diffusion film 1 having good light diffusion characteristics can be obtained.

(Modification 1)
In the above embodiment, the configuration in which the plurality of columnar structures 4 are formed in parallel is shown, but the present invention is not necessarily limited thereto. For example, like the light diffusing film 1a shown in FIG. 5, you may comprise the light transmissive part 2a with the several cone-shaped structure 4a. FIG. 5 is a perspective view showing an overall configuration of a light diffusion film 1a having a plurality of conical structures 4a.

As shown in FIG. 5, the light diffusion film 1a has a light transmission part 2a configured by aligning a plurality of cone-shaped structures 4a. In this case, each structure 4a has a multi-layer structure, and the bottom area of the layer decreases from the lower layer to the upper layer. Here, the entire lower surface of the layer positioned in the upper layer is formed so as to be included in the upper surface of the layer positioned immediately below the layer. Accordingly, the structure 4a as a whole has a structure having slopes with multi-stage slopes. In addition, in FIG. 5, in order to make the whole structure of the light-diffusion film 1a easy to understand, each member is simplified and illustrated. For this reason, in this drawing, the surface of the structure 4a is shown in a curved shape, but in reality, the structure 4a has a structure having a multi-step inclined surface.

Specifically, the structure 4a has a substantially triangular (or substantially trapezoidal) cross section having a multi-step inclined slope as shown in FIG. The bottom surface shape of the structure 4a can be, for example, the shapes shown in (b) to (d) of FIG. 6B to 6D are views when the structure 4a is viewed from the observer side. Specifically, it can be a circular shape as shown in FIG. 6B, a rectangular shape as shown in FIG. 6C, or a pentagon shape as shown in FIG. 6D. . However, if the structure 4a is a substantially pyramid, the shape of the bottom surface is not particularly limited, and may be an ellipse or a polygon.

The cone-shaped structure 4a is formed by forming a stacked body 5a in which materials constituting the structural body 4a are stacked using a photomask in which exposed portions such as a circle or a polygon are aligned, and the stacked body 5a is melted. Or by covering the surface of the laminate 5a with a transparent resin. Alternatively, the structural body 4a can be formed by laminating a plurality of tapered layers. Since the specific manufacturing method is the same as the procedure for manufacturing the structure 4 of the above-described embodiment, the detailed manufacturing method is not mentioned here. The material applicable to the structure 4a (laminated body 5a) is also equivalent to the structure 4.

When the light diffusing film 1a having the cone-shaped structure 4a as described above is provided in the display device, as shown in FIG. The light enters from the bottom side of the body 4a, and is transmitted or refracted and emitted to the viewer side. Here, for example, when the structure 4a has a circular bottom surface as shown in FIG. 6B, the incident light 15 travels in all directions as shown in FIG. 7B. Diffused in all directions. The same applies to the case where the structure 4a has a rectangular base as shown in FIG. 6C or a pentagonal bottom as shown in FIG. 6D, and (c) and FIG. As shown in FIG. 7D, the incident light 15 is diffused in all directions.

Thus, since the structure 4a has a cone shape and has various taper angles, the incident light 15 from the backlight or the like is emitted in multiple directions. Moreover, since the taper angle of the structure 4a can be changed in a stepwise manner as in the above-described embodiment, the incident light 15 can be diffused without unevenness. Therefore, the light diffusion film 1a of one sheet can diffuse light in multiple directions, and can provide a light diffusion film 1a having a wide viewing angle and high contrast and brightness.

In FIG. 6A and FIG. 7A, the laminated body 5a that is the basis of the structural body 4a is illustrated for easy understanding of the configuration of the structural body 4a. When the structural body 4a is formed by melting 5a, the stacked body 5a itself becomes the structural body 4a, so that the stacked body 5a cannot be discriminated as shown in the figure. Similarly, when the structure 4a is formed by stacking a plurality of tapered layers, the stacked body 5 is not discriminated.

(Modification 2)
In the above-described modified example 1, the structures 4a of the light transmission part 2a are arranged and arranged. However, when such a light diffusion film 1a is used for a display device, a stripe pattern (moire) is formed on the display screen. It may be visually recognized. This is because when a plurality of regular repeating patterns are superimposed, a striped pattern (moire) is visually generated due to a shift in the periodic pattern of the repeating patterns. Therefore, when the light diffusing film 1a having the periodic pattern in which the structures 4a are arranged in a straight line is used for a display device, a strong moire is generated between the periodic pattern of the light diffusing film 1a and the periodic pattern of the display screen. May end up.

Therefore, for example, as in the light diffusion film 1b shown in FIG. 8, a plurality of cone-shaped structures 4b may be randomly arranged to constitute the light transmission portion 2b. FIG. 8 is a perspective view showing the overall configuration of a light diffusion film 1b having a plurality of conical structures 4b.

As shown in FIG. 8, the light diffusion film 1b has a light transmission part 2b configured by randomly arranging a plurality of conical structures 4b. When such a light transmission part 2b is used, since the light transmission part 2b is not provided with a regular periodic pattern, the occurrence of moire can be prevented. This will be described with reference to FIG. 9 and FIG. FIG. 9 is a view showing a cross section of the light diffusion film 1b. FIG. 10 is a view when the light diffusion film 1b is viewed from the observer side. In FIG. 9, in order to make the configuration of the structure 4 b easier to understand, the stacked body 5 b that is a base of the structure 4 b is illustrated, but the structure 4 b is formed by melting the stacked body 5 b. Since the stacked body 5b itself becomes the structure 4b, the stacked body 5b cannot be discriminated as shown in the figure. Similarly, when the structure 4b is formed by laminating a plurality of tapered layers, the laminate 5 is not discriminated. In FIG. 10, it is assumed that the structure 4a has a circular bottom surface as shown in FIG.

As shown in FIG. 9, in the light diffusion film 1b, a plurality of structures 4b are randomly arranged, and the interval between adjacent structures 4b is not constant. Further, as shown in FIG. 10, a plurality of structures 4b are randomly arranged on the substrate 6, and the light diffusion film 1b does not have a periodic pattern. According to this, even if the light diffusing film 1b is provided in the display device, the light diffusing film 1b does not have a periodic pattern, so that it is possible to prevent the occurrence of moire on the display screen. As a result, the display quality of the display device can be improved.

By the way, the light transmission part 2b forms the laminated body 5b which laminated | stacked the material which comprises the structure 4b using the photomask by which exposure parts, such as circular or a polygon, are arrange | positioned at random, The said laminated body 5b is formed. It is formed by melting or coating the surface of the laminate 5b with a transparent resin. Alternatively, the structure 4b can be formed by stacking a plurality of tapered layers. Since the specific manufacturing method is the same as the procedure for manufacturing the structure 4 of the above-described embodiment, the detailed manufacturing method is not mentioned here.

(Modification 3)
The structures 4 and 4a described above are symmetric solids, but are not necessarily symmetric solids. For example, like the light diffusing film 1c shown in FIG. 11, you may comprise the light transmissive part 2c by arrange | positioning several asymmetrical structures 4c. FIG. 11 is a view showing a cross section of a light diffusion film 1c having a plurality of asymmetric structures 4c.

As shown in FIG. 11, the light diffusion film 1c has a light transmission part 2c configured by arranging a plurality of asymmetric structures 4c. In this figure, each structure 4c has a multilayer structure, and the bottom area of the layer becomes smaller from the lower layer to the upper layer. Here, each structure 4 is formed such that the entire lower surface of the layer located in the upper layer is included in the upper surface of the layer located immediately below the layer, but only a part of the structure 4 is inclined in a multistep manner. It has a structure with a slope.

In the case of such an asymmetric structure 4c, the light incident on the slope portion having the multi-step slope is emitted in all directions. On the other hand, most of the light incident on other than the inclined surface part is transmitted as it is or refracted and transmitted, and its light diffusion characteristic is lower than that of the inclined surface part. Thus, on the side surface of the structure 4c, there are a plurality of portions with different inclination angles, and there are asymmetrical portions with different inclination angles. Therefore, the structure 4c is a portion with high light diffusion characteristics. And a low part. Therefore, the overall light diffusion characteristic of the light diffusion film 1c having the structure 4c is asymmetric, and as a result, the viewing angle characteristic of the light diffusion film 1c is also asymmetric.

If the above configuration is used, for example, when the display screen of the display device is viewed from the viewer side, if the right viewing angle characteristic is low and the left viewing angle characteristic is high, the right viewing angle characteristic is By using the light diffusion film 1c provided with the structure 4c which becomes high, the overall viewing angle characteristic can be made uniform. In this way, partial viewing angle characteristics can be adjusted.

By the way, as shown in FIG. 11, the cross-sectional shape of the structure 4c is substantially triangular (or substantially trapezoidal) similar to that of the structure 4a of Modification 1, and the bottom shape is the same as that of the structure 4a. However, there is no particular limitation. Further, in this example, a configuration in which only a part of the structure 4c has a multi-stage inclination is shown, but the present invention is not particularly limited thereto, and the shape of the structure 4c can be changed as appropriate. Therefore, the structure 4c may be formed into a shape that can obtain a desired viewing angle characteristic.

In addition, the structure 4c forms the laminated body 5c which laminated | stacked the material which comprises the structure 4c using the photomask which has exposure parts, such as circular or a polygon, and fuse | melts the said laminated body 5c, Or it forms by coat | covering the surface of the laminated body 5c with transparent resin. Alternatively, the structure 4c can be formed by stacking a plurality of tapered layers. Since the specific manufacturing method is the same as the procedure for manufacturing the structure 4 of the above-described embodiment, the detailed manufacturing method is not mentioned here. The material applicable to the structure 4c (laminated body 5c) is also the same as that of the structure 4. In FIG. 11, in order to make the configuration of the structure 4c easier to understand, the stacked body 5c that is a base of the structure 4c is illustrated, but the structure 4c is formed by melting the stacked body 5c. Since the stacked body 5c itself becomes the structure 4c, the stacked body 5c cannot be discriminated as shown in the figure. Similarly, when the structure 4c is formed by laminating a plurality of tapered layers, the laminate 5 is not discriminated.

(Modification 4)
As in the light diffusing film 1d shown in FIG. 12, a plurality of symmetric structures 4a and a plurality of asymmetric structures 4c may be arranged to constitute the light transmission portion 2d. FIG. 12 is a view showing a cross section of a light diffusion film 1d having a plurality of structures 4a and a plurality of structures 4c.

As shown in FIG. 12, the light diffusion film 1d has a light transmission part 2d configured by arranging a plurality of symmetrical structures 4a and a plurality of asymmetric structures 4c. In the case of such a light transmission part 2d, the inclination angles of the structures 4a and 4c formed on the substrate 6 are random, and the total reflection angle of the light incident on the light diffusion film 1d varies. As a result, when the light diffusion film 1d is provided in the display device, light from the backlight or the like is emitted in all directions, thereby eliminating unevenness in the viewing angle characteristics of the display device and smoothing the viewing angle characteristics. be able to.

Incidentally, in the light transmission part 2d, a plurality of structures 4a and a plurality of structures 4c are arranged, but the present invention is not limited to this. Three or more types of structures 4a and 4c may be arranged so that desired viewing angle characteristics can be obtained, or structures 4c having a plurality of types of asymmetric shapes may be arranged.

(Usage example of light diffusion film 1, 1a to 1d)
As described above, the light diffusion films 1, 1a to 1d are used by being attached to the front surface of the display screen in a display device such as a liquid crystal display device. As an example when the light diffusion films 1 and 1a to 1d are attached to the display device, a liquid crystal display device including the light diffusion film 1 is shown in FIG. FIG. 13 is a schematic view illustrating a cross section of the liquid crystal display device 10 including the light diffusing film 1.

The liquid crystal display device 10 basically includes a backlight unit and a liquid crystal display element unit. As shown in FIG. 13, the liquid crystal display device 10 includes a light emitting diode (LED) and a semiconductor laser as the backlight unit. (LD) or a backlight 11 such as a cold cathode fluorescent lamp (CCFL). In addition, the liquid crystal display device 10 includes a liquid crystal panel as a liquid crystal display element portion. The liquid crystal panel includes a thin film transistor (TFT), a glass plate 13 on which wiring or the like is formed, a transparent electrode, a color filter, or the like. The liquid crystal layer 14 is sealed between the formed glass plate 13 and the polarizing plate 12 is disposed on both surfaces thereof. The light diffusion film 1 is provided on the front surface (observer side) of the liquid crystal panel (polarizing plate 12).

The light emitted from the backlight 11 passes (irradiates) the liquid crystal panel as shown by the arrows shown in FIG. The light of the backlight 11 is diffused in the light diffusion film 1 and emitted to the viewer side. At this time, the light of the backlight 11 is emitted in all directions by the inclined surfaces having different inclination angles of the structures 4. As described above, in the liquid crystal display device 10 provided with the light diffusion film 1, the width for diffusing the light of the backlight 11 can be widened, so that the liquid crystal display device 10 having a wide viewing angle and high contrast and brightness can be obtained. Can do.

Needless to say, a display device including the light diffusing films 1a to 1d can also be used. In the display device including the light diffusing films 1a to 1d, a high viewing angle characteristic and a high display quality can be obtained. can get.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

[Summary of Embodiment]
As described above, in the method of manufacturing a light diffusion film according to the present invention, in the laminate forming step, a plurality of the laminates in which a plurality of the rectangular parallelepiped layers are laminated are formed in parallel in the certain direction on the substrate. It is characterized by doing.

According to the above method, even when the structure is formed in a line shape, the formation of the structure can be controlled to a micron size. Moreover, the light diffusion film which can diffuse an incident light widely in a horizontal direction or a vertical direction by said method is obtained.

The light diffusing film manufacturing method according to the present invention is characterized in that, in the laminate formation step, a plurality of the laminates in which a plurality of the columnar layers are laminated are formed on the substrate.

According to the above method, even when the structure is formed into a cone shape, the formation of the structure can be controlled to a micron size. In addition, a light diffusion film capable of widely diffusing incident light in all directions can be obtained by the above method.

Moreover, the manufacturing method of the light-diffusion film which concerns on this invention WHEREIN: The said laminated body formation process apply | coats the material which comprises the said laminated body on the said board | substrate, and the patterning which patterns the said material after the said application | coating process The step and the curing step of curing the material after the patterning step are repeated a plurality of times in order.

Moreover, the method for producing a light diffusion film according to the present invention is characterized in that the laminate forming step is performed by photolithography.

According to the above method, a layer having a desired shape can be patterned, and finally a laminated body having a desired shape can be formed.

The specific embodiments or examples made in the detailed description section of the invention are merely to clarify the technical contents of the present invention, and are limited to such specific examples and are interpreted in a narrow sense. It should be understood that various modifications may be made within the spirit of the invention and the scope of the following claims.

The present invention can be used in manufacturing a light diffusion film that is used in a display device such as a liquid crystal display device and expands the viewing angle of the display device.

DESCRIPTION OF SYMBOLS 1,1a-1d Light diffusion film 2, 2a-2d Light transmission part 3 Light reflection part 4,4a, 4c Structure 5,5a-5c Laminated body 6 Substrate 7 Transparent resin 10 Liquid crystal display device 11 Backlight 12 Polarizing plate 13 Glass plate 14 Liquid crystal layer 15 Incident light

Claims (9)

1. A method for producing a light diffusion film comprising a structure forming step of diffusing incident light incident from a light incident surface to form a plurality of structures that are emitted from the light exit surface,
   In the structure forming step,
   A plurality of the above structures are formed by laminating a plurality of tapered layers on a substrate,
   For each structure, the structure is formed such that the lower surface of the layer located in the upper layer and the upper surface of the layer located immediately below the layer coincide with each other. Method.
2. A method for producing a light diffusion film comprising a structure forming step of diffusing incident light incident from a light incident surface to form a plurality of structures that are emitted from the light exit surface,
   The structure forming step includes
   A laminated body forming step of forming a plurality of laminated bodies in which a plurality of layers are laminated on a substrate;
   A melting step of melting the plurality of laminates,
   In the laminated body forming step, for each of the laminated bodies, the length of the layer in the constant direction is shortened from the lower layer to the upper layer in the cut surface when the laminated body is cut in a certain direction, and the upper layer is formed. A method for producing a light diffusing film, wherein the laminate is formed such that the entire lower surface of the layer positioned is included in the upper surface of the layer positioned immediately below the layer.
3. A method for producing a light diffusion film comprising a structure forming step of diffusing incident light incident from a light incident surface to form a plurality of structures that are emitted from the light exit surface,
   The structure forming step includes
   A laminated body forming step of forming a plurality of laminated bodies in which a plurality of layers are laminated on a substrate;
   For each of the laminates, a lamination step of further laminating a transparent resin on the laminate,
   A melting step of melting the transparent resin,
   In the laminated body forming step, for each of the laminated bodies, the length of the layer in the constant direction is shortened from the lower layer to the upper layer in the cut surface when the laminated body is cut in a certain direction, and the upper layer is formed. A method for producing a light diffusing film, wherein the laminate is formed such that the entire lower surface of the layer positioned is included in the upper surface of the layer positioned immediately below the layer.
4. 4. The light diffusing film according to claim 2 or 3, wherein, in the laminate forming step, a plurality of the laminates obtained by laminating a plurality of layers of a rectangular parallelepiped type are formed in parallel in the certain direction on the substrate. Manufacturing method.
5. The method for producing a light diffusing film according to claim 2 or 3, wherein, in the laminate formation step, a plurality of the laminates in which a plurality of the columnar layers are laminated are formed on the substrate.
6. The laminated body forming step includes a coating step of applying a material constituting the laminated body on the substrate, a patterning step of patterning the material after the applying step, and a curing for curing the material after the patterning step. The method for producing a light diffusing film according to any one of claims 2 to 5, wherein the steps are repeated a plurality of times in order.
7. The method for producing a light diffusing film according to claim 6, wherein the laminate forming step is performed by photolithography.
8. A light diffusion film produced by the method for producing a light diffusion film according to any one of claims 1 to 7.
9. A display device comprising the light diffusing film according to claim 8.

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