JP2004070164A - Antireflection coating, illuminator and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antireflection coating in which breakage of an antireflective grid (AR grid) is prevented even when external pressure such as a pressing is applied from the outside and to provide an illuminator equipped with the antireflection coating. <P>SOLUTION: A large number of guard columns 4 are scattered in the AR grid 5 spreading on the surface of the antireflection coating 17. The guard columns 4 prevent a large number of projecting parts 30 constituting the AR grid 5 from being crushed when the antireflection coating 17 is pressed. When pressure is applied to the antireflection coating 17, a light emitting surface of a light transmission plate being in contact with the antireflection coating 17 comes into contact only with summit faces of the guard columns 4 which are higher than the projecting part 30 of the AR grid 5. Thus, even when excess pressure G is applied to the antireflection coating 17, the projecting part 30 is prevented from being crushed by contact of the light emitting surface with the AR grid 5. The guard column 4 is greatly useful to maintain a function of the antireflection coating 17. <P>COPYRIGHT: (C)2004,JPO

Description

【００３４】
表１によれば、保護柱の高さが１０〜２０μｍの範囲では輝点が認められず、視認性に問題のないことが確認された。また、保護柱の径が１０〜２０μｍの範囲では輝点が認められず、視認性に問題のないことが確認された。保護柱は高さ、径ともに０．０５〜２０μｍ、好ましくは１０〜２０μｍの範囲にすれば視認性が良好に保たれることが判明した。
【００３５】
また、保護柱の適正な存在割合を検証した。検証にあたって、保護柱の凸部に対する存在割合を５，１０，２０％の３種類に設定するととも、各種類の保護柱の径を１０，２０の２種類に設定した合計６種類の反射防止膜をそれぞれ形成したフロントライトが準備された。こうした６種類のフロントライトについて、フロントライト点灯時の光の透過率を測定した結果を表２に示す。
【００３６】
【表２】

【００３７】
表２によれば、保護柱の存在割合が２０％では径の大きさによらず光の透過率が９０％以下に低下した。保護柱の存在割合を５〜１０％の範囲に設定すると透過率を高く保てることが確認された。
【００３８】
【発明の効果】
以上、詳細に説明したように、本発明によれば、外部から押圧など外圧が加えられてもＡＲ格子の破損を防止する反射防止膜や、こうした反射防止膜を備えた照明装置を提供することがてきる。
【図面の簡単な説明】
【図１】図１は、本発明の一実施の形態であるフロントライトの部分斜視図である。
【図２】図２はＡＲ格子の拡大斜視図である。
【図３】図３は、図１に示す反射防止層を示す拡大断面図である。
【図４】図４は、反射層を示す拡大斜視図である。
【図５】図５は、保護柱の作用を示す説明図である。
【符号の説明】
３　タブレット
４　保護柱
５　ＡＲ格子
１０　フロントライト（照明装置）
１２　導光板
１２ａ　側端面（入射面）
１２ｂ　出射面
１２ｃ　反射面
１３　光源
２０　液晶表示ユニット
３０　凸部（突起）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an anti-reflection film used for a lighting device for illuminating a liquid crystal display unit and the like, and more particularly, to an anti-reflection film for protecting an AR grating constituting the anti-reflection film.
[0002]
[Prior art]
Conventionally, a liquid crystal display device provided with an anti-reflection film adjacent to a light guide plate is known. The anti-reflection film prevents external light and illumination light of a lighting device provided on the surface of the liquid crystal display panel from being reflected before reaching the liquid crystal display panel, and thus prevents external light and illumination light from being applied to the liquid crystal display panel. It is known that light is efficiently incident on the liquid crystal panel and greatly helps to improve the visibility of the liquid crystal display device. As an example of this type of antireflection film, for example, a film in which a number of fine protrusions called an AR (anti-reflective) grating are formed on the film surface is known. It is possible to prevent the light from being reflected before entering the liquid crystal display panel.
[0003]
In recent years, there has been known a liquid crystal display device provided with a tablet (touch panel) on the surface thereof in order to directly select or designate an object or the like displayed on a liquid crystal display panel of this type. The tablet realizes a selection operation such as a menu display by pressing or poking a displayed object with a finger or a pointing device.
[0004]
[Problems to be solved by the invention]
The AR grating that constitutes the anti-reflection layer is an aggregate of extremely fine protrusions, and when applied to a liquid crystal display device having the above-described tablet or the like, the AR grating may be crushed or damaged by external pressure due to tablet operation. There is. If the antireflection layer is damaged in this way, there is a concern that the visibility of the liquid crystal display device is reduced or the appearance of the display screen is impaired.
[0005]
The present invention has been made in view of the above circumstances, and has an antireflection film capable of preventing damage to an AR grating even when external pressure such as external pressure is applied, and a lighting device including such an antireflection film. And a liquid crystal display device.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided an AR lattice in which a large number of fine projections are periodically formed, and a protective column scattered in the AR lattice and having a height equal to or higher than the height of the projection. The anti-reflection film characterized by comprising:
[0007]
According to such an anti-reflection film, even if pressure is applied to the anti-reflection film, the pressing force is received by the protection pillar. The danger of the AR grating being pressed hard directly is small. Therefore, the AR grating is prevented from being crushed or damaged, and the function of the antireflection film is properly maintained.
[0008]
It is preferable that the protection column is formed integrally with the same material as the AR lattice. If formed integrally with the same material as the AR grating, the refractive indices of the protective pillar and the AR grating are the same, and good visibility can be maintained. It is preferable that the ratio of the protective pillar to the AR lattice on the surface of the antireflection film be 10% or less per unit area. When the proportion of the protective pillars is set to 10% or less, the transmittance hardly decreases even if the protective pillars are formed. It is preferable that the height and width of the protection column be set to 20 μm or less. If the height and width of the protective pillar are set to 20 μm or less, good visibility can be maintained.
[0009]
According to this antireflection film, even if a pressing force is applied to the lighting device, most of the pressing force is received by the protective pillar. An abnormal pressing force acting on the AR grid is unlikely to occur even when pressure is applied, so that the AR grid is prevented from being crushed or damaged, and the function of the lighting device is properly maintained.
[0010]
If such an antireflection film is applied to a liquid crystal display device, when the coordinate input means is provided on the front surface of the illumination device, even if the antireflection film is abnormally strongly pressed at the time of inputting the coordinates, the damage of the antireflection film will not occur. It is possible to avoid a decrease in the visibility of the liquid crystal display panel.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing one embodiment of a liquid crystal display device including a lighting device to which the antireflection film of the present invention is applied. The liquid crystal display device 1 of this embodiment includes a reflective liquid crystal display unit 20 and a front light (illumination device) 10 disposed on the front surface (upper surface) thereof. Further, the front light 10 includes a tablet 3 as coordinate input means.
[0012]
The front light 10 is an embodiment of the lighting device according to the present invention, and includes a light guide plate 12, a light source 13, and a tablet 3, as shown in FIG. The light guide plate 12 is a transparent substantially flat plate-shaped member made of, for example, an acrylic resin or a polycarbonate resin. The light guide plate 12 has a side end surface 12a on which the light source 13 is disposed as an incident surface. On the upper surface of the light guide plate 12, a reflection surface 12c is formed. The reflection surface 12c is formed by arranging a large number of wedge-shaped protrusions 14 for changing the direction of light introduced from the light source 13 in a triangular wave shape. The lower surface of the light guide plate 12 (the surface facing the liquid crystal display device 20) is an emission surface 12b from which illumination light is emitted.
[0013]
The wedge-shaped convex portion 14 includes a pair of slope portions. One slope of the convex portion 14 is a gentle slope portion 14a, and the other is a steep slope portion 14b formed at a steeper inclination angle than the gentle slope portion 14a. That is, a gentle slope portion 14a and a steep slope portion 14b are alternately and periodically formed on the reflection surface 12c. The shape of the reflection surface 12c is not limited to the above-described shape, and may be any shape as long as light that is introduced from the side end surface 12a and propagates inside the light guide plate 12 can be uniformly guided to the emission surface 12b. Good.
[0014]
An antireflection film 17 is formed on the lower surface (the surface on the side of the liquid crystal display unit 20) 12b of the light guide plate 12. The AR grating 5 is formed on the surface of the antireflection film 17. As shown in FIG. 2, the AR grating 5 has a shape in which a number of fine projections (projections) 30 are periodically arranged. It is preferable that the pitch of these many protrusions 30 is, for example, in a range of 0.1 μm or more and 0.4 μm or less. Further, it is preferable that the height of the convex portion 30 be in a range of, for example, 0.05 μm to 0.8 μm. When the pitch is less than 0.1 μm, it is difficult to increase the height of the projection, and as a result, the antireflection effect is weakened. On the other hand, if the pitch exceeds 0.5 μm, the color tone of the front light 10 will appear colored due to the spectral action of the diffracted light.
[0015]
When the height of the projection 30 is less than 0.05 μm or more than 0.8 μm, the antireflection effect on the light exit surface 12b of the light guide plate is reduced. As a result, the contrast when displaying the liquid crystal display unit 20 is reduced.
[0016]
As shown in FIG. 3, many protective pillars 4 are scattered between the AR gratings 5 extending on the surface of the antireflection film 17. As will be described later in detail, the protective column 4 prevents the many convex portions 30 constituting the AR grating 5 from being crushed when the antireflection film 17 is pressed. Such a protective column 4 may be, for example, a square column. In addition, the protection column 4 may have any shape, such as a cylinder, a cone, a quadrangular pyramid, a triangular pyramid, and an elliptical column, as long as it has a height.
[0017]
The height h of the protection column 4 shown in FIG. 3 may be at least higher than the height of the projection 30 constituting the AR grating 5. If the height h of the protection pillar 4 is lower than the height of the protrusion 30, the top of the protrusion 30 may be crushed when an external force is applied. Further, the height h of the protection column 4 is desirably, for example, 20 μm or less. If the height of the protection pillar 4 is higher than 20 μm, there is a high possibility that the protection pillar 4 will be visually recognized as a bright spot when the front light 10 is turned on. The diameter (width) w of the protection column 4 may be any value as long as the protection column 4 maintains a strength that is not easily crushed by an applied external force. It is desirable that the diameter w of the protection column 4 is, for example, 20 μm or less. If the diameter w of the protection pillar 4 is larger than 20 μm, there is a high possibility that the protection pillar 4 will be visually recognized as a bright spot when the front light 10 is turned on.
[0018]
It is preferable that the ratio of the protective pillar 4 to the AR lattice 5 be 10% or less per unit area. If the proportion of the protective column 4 exceeds 10%, the antireflection function is reduced, and light is diffusely reflected on the protective column 4. Further, the interval t between the adjacent protection columns 4 is preferably, for example, 1 mm or less. If the interval t between the protection columns 4 is too large, the possibility that the protrusion 30 will be crushed when an external force is applied increases.
[0019]
The AR grating 5 and the protective column 4 may be formed on the light emitting surface of the light guide plate at the same time as the light guide plate 12 is injection-molded using a resin material. That is, a stamper having an irregular shape reverse to the shape of the AR grating 5 and the protective column 4 is formed on a portion of the light guide plate 12 where the light emitting surface of the light guide plate is formed in the cavity of the injection mold, and injection molding is performed. Just do it. A stamper for forming the AR lattice 5 and the protection pillar 4 can be manufactured using a technique such as Ni electroforming.
[0020]
When the anti-reflection film 17 is formed, the light guide plate 12 may be manufactured by injection molding or the like, and then may be scanned while intermittently irradiating laser light toward the emission surface of the light guide plate. In this way, a part of the light guide plate can be melted and quenched to form the projections 30 and the protection pillars 4. Note that the protection pillar 4 may be formed by another member after the formation of the AR grating 5. In this case, it is preferable that the material forming the protective column 4 has a refractive index of light close to that of the material forming the AR lattice layer 17. For example, it is preferable that the difference in the refractive index between the material forming the protective column 4 and the material forming the AR grating 5 be kept within 0.05. By making the refractive index of the material forming the protective column 4 close to the refractive index of the material forming the AR lattice layer 17, when the liquid crystal display unit 20 is displayed, the display may appear uneven, or the protective column 4 may have a bright spot. Can be prevented from appearing.
[0021]
The light source 13 is provided on one end surface 12 a of the light guide plate 12. The light source 13 is, for example, a rod-shaped light source provided along the side end surface 12 a of the light guide plate 12. The light source 13 may be provided with, for example, a light emitting element such as a white LED (Light Emitting Diode) on one or both end surfaces of a rod-shaped light guide. However, the light source 13 can be used without any problem as long as it can introduce light into the side end surface 12a of the light guide plate 12. For example, the light emitting elements may be arranged along the side end surface 12a of the light guide plate 12.
[0022]
The tablet 3 includes a light-transmitting substrate 11 having flexibility and opposed to the light guide plate 12, a first electrode layer 18 formed on a reflection surface 12 c of the light guide plate 12, and an inner surface of the light-transmitting substrate 11. A second electrode layer formed on the side; and a plurality of spacers formed on the first electrode layer. These electrode layers 18 and 19 have a structure separated by a plurality of spacers 15. The electrode layers 18 and 19 may be formed of a transparent conductive material such as ITO (indium tin oxide). The spacer 15 functions as an insulating layer for electrically isolating the first electrode layer 18 and the second electrode layer 19. The tablet 3 having the above configuration has a function equivalent to that of the resistive tablet, that is, a function of pressing the translucent substrate 11 with the indicator 29 or the like to realize a selection operation of a menu item or the like displayed on the liquid crystal display unit 20. I will provide a.
[0023]
The liquid crystal display unit 20 constituting the liquid crystal display device 1 has a liquid crystal layer 23 sandwiched between an upper substrate 21 and a lower substrate 22 which are arranged to face each other. Then, the liquid crystal layer 23 is sealed with a sealing material 24 provided in a frame shape along the inner peripheral edge of the substrates 21 and 22. A liquid crystal control layer 26 is formed on the inner surface side of the upper substrate 21 (the lower substrate 22 side). On the inner surface side of the lower substrate 22 (on the upper substrate 21 side), a reflection layer 25 including a metal thin film that reflects illumination light of the front light 10 and external light is formed. A liquid crystal control layer 27 is formed on the surface of the reflection layer 25.
[0024]
The liquid crystal control layers 26 and 27 are configured to include electrodes for driving and controlling the liquid crystal layer 23, an alignment film, and the like, and also include a semiconductor element for switching the electrodes. Further, a color filter may be provided.
[0025]
The liquid crystal display unit 20 shown in FIG. 1 is of a reflection type, and performs display by reflecting illumination light incident from the front light 10 or external light incident from the outside by the reflection layer 25. As shown in FIG. 4, for example, the reflection layer 25 is formed by forming a reflection film 25b on an organic film 25a made of an acrylic resin or the like having an uneven surface. The reflection film 25b is preferably a thin metal film of high reflectivity such as aluminum or silver. Further, it is preferable to form a flattening film with a silicon-based resin or the like in order to flatten the uneven shape of the surface on the reflective film 25b.
[0026]
As the shape of the concave portion 25c, a smooth curved surface such as a spherical surface, a shape combining this curved surface and a flat surface, or the like may be applied. By adjusting the inclination angle of the inner surface and the pitch and depth of the concave portion, it is possible to provide a reflective layer having appropriate reflective characteristics in accordance with the design of an electronic device including the liquid crystal display device 1 as a display unit. The reflective layer 25 helps to efficiently reflect the incident light, so that high-luminance display can be performed. Further, when the incident light is external light, regular reflection of light is prevented, and a bright display with excellent visibility can be obtained.
[0027]
The operation of the present invention having the above-described configuration will be described focusing on a lighting device. A voltage capable of forming a potential distribution on the first electrode layer 18 is applied to the tablet 3. When the operator presses or slides an indicator 29 such as a pen or a finger on the outer surface of the translucent substrate 11 (the surface opposite to the light guide plate 12), the flexible translucent substrate 11 is covered. The pressing part is pressed. The first electrode layer 18 and the second electrode layer 19 that have been separated by the spacer 15 during non-operation come into contact with each other at the pressed portion. As a result, a signal corresponding to the position of the pressed portion is output from the second electrode layer 19.
[0028]
Conversely, when the electrode layers 18 and 19 come into contact with a voltage applied to the second electrode layer 19, a signal corresponding to the position of the pressed portion is output from the first electrode layer. Therefore, if the direction of the potential distribution of the first electrode layer 18 and the direction of the potential distribution of the second electrode layer 19 are made to intersect, the instruction on the light-transmitting substrate 11 is made based on the output obtained from each. Two-dimensional coordinate information of the body 29 is obtained.
[0029]
Thus, the operator can perform a coordinate input operation such as a selection operation of an object such as a menu item displayed on the liquid crystal display unit 20 by the coordinate input means. That is, the object can be selected by pressing the position on the surface of the translucent substrate 11 corresponding to the position of the displayed object with the indicator 29.
[0030]
When the operator presses the translucent substrate 11 with the indicator 29 or the like, a pressure G acts on the anti-reflection film 17 as shown in FIG. The emission surface 12b of the light guide plate 12 that is in contact with the antireflection film 17 contacts only the top surface of the protection column 4 that is higher than the projection 30 of the AR grating 5. Therefore, even if a slight pressure G acts on the antireflection film 17, it is possible to prevent the emission surface 12b from coming into contact with the AR grating 5 and crushing the projection 30. The protection pillar 4 greatly helps to maintain the function of the antireflection film 17.
[0031]
These protective pillars 4 have a height h of 0.05 to 20 μm, preferably 10 to 20 μm, a diameter w of 0.05 to 20 μm, preferably 10 to 20 μm, or an existing ratio of 10% per unit area. By doing so, it is possible to obtain the same visibility as the case where the protective column 4 is not provided.
[0032]
【Example】
The appropriate height and diameter of the protection pillar were verified. In the verification, the height of the protection pillar was set to three types of 10, 20, and 30, and a total of nine types of anti-reflection films in which the diameter of each type of protection pillar was set to three types of 10, 20, and 30, respectively. The formed front light was prepared. Table 1 shows the results of visually confirming the presence or absence of a bright spot when the front lights were turned on for these nine types of front lights. In addition, the sample in which a bright spot was recognized when the front light was turned on was NG, and the sample in which no bright spot was recognized was OK.
[0033]
[Table 1]

[0034]
According to Table 1, when the height of the protective column was in the range of 10 to 20 μm, no bright spot was recognized, and it was confirmed that there was no problem in visibility. Further, in the case where the diameter of the protective column was in the range of 10 to 20 μm, no bright spot was observed, and it was confirmed that there was no problem in visibility. It has been found that if the height and diameter of the protective pillars are both in the range of 0.05 to 20 μm, and preferably in the range of 10 to 20 μm, good visibility can be maintained.
[0035]
In addition, we verified the appropriate proportion of protection pillars. In the verification, a total of six types of anti-reflection coatings were set in which the existence ratio of the protection pillars to the convex portions was set to 5, 10, and 20%, and the diameter of each type of protection pillar was set to 10, 20. , Respectively, were prepared. Table 2 shows the results of measuring the light transmittance of these six types of front lights when the front lights were turned on.
[0036]
[Table 2]

[0037]
According to Table 2, when the protection column presence ratio was 20%, the light transmittance was reduced to 90% or less regardless of the diameter. It was confirmed that the transmittance could be kept high by setting the existing ratio of the protective pillar in the range of 5 to 10%.
[0038]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to provide an antireflection film that prevents damage to an AR grating even when an external pressure such as external pressure is applied, and a lighting device including such an antireflection film. Comes.
[Brief description of the drawings]
FIG. 1 is a partial perspective view of a front light according to an embodiment of the present invention.
FIG. 2 is an enlarged perspective view of an AR grating.
FIG. 3 is an enlarged sectional view showing the antireflection layer shown in FIG.
FIG. 4 is an enlarged perspective view showing a reflection layer.
FIG. 5 is an explanatory diagram showing an operation of a protection column.
[Explanation of symbols]
3 Tablet 4 Protective pillar 5 AR grid 10 Front light (lighting device)
12 Light guide plate 12a side end surface (incident surface)
12b Emission surface 12c Reflection surface 13 Light source 20 Liquid crystal display unit 30 Convex part (projection)

Claims (9)

An anti-reflection film, comprising: an AR lattice in which a large number of fine projections are periodically formed; and a protective pillar scattered between the projections and having a height equal to or higher than the height of the projections. The anti-reflection coating according to claim 1, wherein the protection pillar is formed integrally with the same material as the AR grating. The anti-reflection film according to claim 1, wherein an existing ratio of the protection pillar to the AR lattice is set to 10% or less per unit area. 4. The anti-reflection film according to claim 1, wherein a difference between a refractive index of the protective column and a refractive index of the AR grating is set to 0.05 or less. The anti-reflection film according to any one of claims 1 to 4, wherein the height of the protection pillar is set to 20 µm or less. The anti-reflection film according to claim 1, wherein the width of the protection pillar is set to 20 μm or less. A light source, a light guide plate having an entrance surface and an exit surface and guiding light from the light source toward the exit surface from the entrance surface, and an antireflection film formed adjacent to the exit surface; The illumination device, wherein the antireflection film includes an AR grating in which a large number of fine protrusions are periodically formed, and a protective pillar scattered between the protrusions and having a height equal to or higher than the height of the protrusions. . The lighting device according to claim 7, wherein the lighting device further includes a coordinate input unit. The light source according to claim 1, further comprising: a light source, a light guide plate having an entrance surface and an exit surface, and guiding light from the light source from the entrance surface toward the exit surface, and the light guide plate being formed adjacent to the exit surface. A liquid crystal display device comprising the antireflection film according to any one of the above.

Images