JP2000121802A - Antireflection film and its production as well as image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antireflection film 1 used for more easily executing an antireflection treatment on the screens of various kinds of image display devices. SOLUTION: The antireflection film 1 is formed continuously with may projecting parts 3, 3,... of which the surfaces constitute part of the spherical surface of a base film 2 consisting of, for example, a polycarbonate film on the surface of the base film so as to overlap to each other. A tacky adhesive 4 for affixing the antireflection film 1 to the screen of the image display device is applied to the rear surface of the base film 2. The heights of the projecting parts 3 are randomly formed within the range of prescribed sizes and the pitches between the adjacent projecting parts 3 are also randomly arranged within the range of the prescribed sizes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antireflection film which is attached to a screen of an image display device such as a liquid crystal display device or a plasma display device to prevent reflection or reflection of external light so that the screen can be easily viewed. And its manufacturing method, and an image display device.

[0002]

2. Description of the Related Art In the field of electronic device displays such as liquid crystal display devices, there have been remarkable developments such as reduction in thickness, increase in size, higher definition, and full color. However, in the case of a liquid crystal display device,
In particular, there is a problem that the image is difficult to see when viewing the screen from an oblique side instead of directly in front, that is, a so-called narrow viewing angle,
Various measures have been taken to increase the viewing angle. In addition to the problem of the viewing angle, there is also a problem that sunlight outdoors or illumination light indoors is reflected on the screen, and an image on the user side is reflected on the screen, making it difficult to view the image. Therefore, the screens of these displays are required to have a function of improving the visibility of the screens, such as preventing reflection of external light and reflection of external images, and making the screens easier to see.

Conventionally, as a method of preventing reflection of external light and reflection of an external image, a method of applying a resin mixed with a filler having a light absorbing property on a screen to perform an anti-reflection treatment of the screen, To provide a light diffusion function to the screen surface by arranging a large number of micro lenses over
A method has been employed in which the surface of the screen is lightly etched to slightly roughen the surface to diffusely reflect light.

[0004]

However, in any of the above-mentioned conventional anti-reflection methods, any of the above-mentioned methods is remarkably required for surface treatment such as applying a resin on a screen or performing an etching treatment. This consumes labor and time, and is a factor of reducing productivity in the manufacturing process of the liquid crystal display device. Further, in this processing, it is necessary to simultaneously secure the visibility of the image itself displayed on the screen while reducing the reflection on the screen, and thus a method capable of appropriately controlling both the reduction of the reflection and the visibility of the image. However, the above method was not very controllable. In recent years, liquid crystal display devices have been increasingly applied to portable mobile terminals and the like, and it has become increasingly important to realize screens with excellent visibility even in various use environments.

[0005] Further, an image display device other than a liquid crystal display device,
For example, in the case of a television equipped with a cathode ray tube,
Since the surface of the cathode ray tube is spherical, reflection of external light and reflection of an external image cannot be avoided, and solving these problems has been a long-standing problem. However, even in this case, performing such a complicated surface treatment as described above to prevent reflection and reflection causes various problems. Therefore, it has been desired to provide a method capable of more simply performing antireflection processing on screens of various image display devices.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an anti-reflection film used for more easily performing anti-reflection and anti-glare processing on the screen of various image display devices. An object of the present invention is to provide a manufacturing method thereof and an image display device with high visibility.

[0007]

In order to achieve the above object, an antireflection film of the present invention comprises a transparent film substrate having a surface having a large number of projections or depressions having a curved surface. It is characterized by being formed.
In addition, the height of the convex portion or the depth of the concave portion may be randomly arranged and the pitch between adjacent convex portions and convex portions, between concave portions and concave portions, or between the convex portions and concave portions may be randomly arranged. It is preferable to form the large number of convex portions or concave portions.

In the method for producing an antireflection film of the present invention, the indenter is pressed against the surface of the matrix substrate, and the pressing by the indenter is repeated while changing the position of the indenter on the surface of the matrix substrate. After a large number of concave portions having a curved inner surface are continuously formed on the mold surface of the matrix base material, a mold for film formation is manufactured, and the mold surface of the matrix for film formation is fixed to a film base. By transferring to a surface of a material, an antireflection film having a surface on which a large number of convex portions are formed by inverting the uneven shape of the mold surface is manufactured.

In another method for producing an anti-reflection film of the present invention, similarly to the above-described method, after producing a film forming master, the concave and convex shape of the mold surface is reversed from the mold surface of the film forming master. By manufacturing a transfer mold having a mold surface which was made into a mold, and transferring the mold surface of the transfer mold to the surface of the film substrate, a large number of concave portions were formed by inverting the concave-convex shape of the mold surface of the transfer mold. It is characterized by producing an antireflection film having a surface.

Further, an image display device of the present invention is provided with the above-mentioned antireflection film.

According to the antireflection film of the present invention, since a large number of projections or depressions having a curved surface are formed on the surface of the film substrate, the light incident on the projections or depressions on the film surface is reduced. Is refracted on the film surface near the center point of the convex or concave portion and transmits through the film, while the peripheral portion of the convex or concave portion is scattered in the direction along the film surface and in the direction of the eyes of the user. The ratio of reflection is extremely small. In addition, the light incident on the back surface (the surface opposite to the surface on which the convex portion or the concave portion is formed) of the film is slightly condensed in the case of a convex portion because the film substrate is transparent. In the case of (1), the light is slightly spread, but penetrates the surface side with almost no trouble. Therefore, by adhering the antireflection film of the present invention to the screen of any image display device, reflection of external light and reflection of an external image on the screen surface can be reduced, and an image having excellent visibility can be obtained. A display device can be realized.

In the above antireflection film, the height of the projections or the depth of the depressions is randomly arranged, and the pitch between the adjacent projections and the projections or the depressions and the depressions or the pitch between the projections and the depressions is irregularly arranged. When placed, the direction and amount of incident light on the film surface are also scattered,
The degree of reflection of external light and reflection of an external image on the screen surface can be further reduced.

In producing the antireflection film of the present invention, a matrix for forming a film, in which a large number of concave portions having a curved inner surface are formed on the mold surface of the matrix for the matrix, is produced. A method of transferring the mold surface can be adopted. Thereby, it is possible to manufacture an antireflection film having a large number of convex portions in which the concave and convex shapes of the mold surface of the film forming matrix are inverted. Alternatively, an antireflection film having a large number of concave portions can be manufactured by using the transfer once again.
According to this method, once a film forming master is manufactured, an antireflection film having the same surface shape can be easily manufactured by repeatedly using the master. In addition, by controlling the depth, pitch, and the like of the concave portions when manufacturing the film forming matrix, it is possible to accurately control characteristics such as the degree of reflection and visibility of the antireflection film to be finally manufactured. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing an antireflection film 1 of the present embodiment. As shown in this figure, the antireflection film 1 of the present embodiment has a surface of a base film 2 made of, for example, a polycarbonate resin having a thickness of about 100 μm, and a number of projections 3 whose surface forms a part of a spherical surface. 3,... Are continuously formed so as to overlap with each other. An adhesive 4 for attaching the antireflection film 1 to a screen of an image display device is applied to the back surface of the base film 2. The adhesive 4 may be any material that does not adversely affect the refractive index of light, and for example, a material such as an acrylic adhesive can be used. As an example of the dimensions, the height of the projection 3 is 0.1 to 3 μm.
And the pitch between the adjacent convex portions 3 is preferably smaller than the pitch of the pixels of the image display device, and is randomly arranged in the range of 5 to 50 μm.

Next, a method of manufacturing the antireflection film having the above structure will be described with reference to FIG. First, as shown in FIG. 2A, a flat base material 5 made of, for example, aluminum, brass or the like and having a flat surface is fixed on a table of a rolling device. Then, the surface of the matrix substrate 5 is pressed by a spherical diamond indenter 6 having a predetermined diameter R at the tip, and the matrix substrate 5 is moved in the horizontal direction.
By repeating the operation of vertically moving and pressing a number of times, a large number of concave portions 7 having different depths and arrangement pitches are rolled on the surface of the matrix base material 5. The concave portion 7 is eventually inverted and becomes the convex portion 3 of the antireflection film 1. The shape of the concave portion 7 determines the shape of the convex portion 3 of the antireflection film 1. Thereafter, nickel electroforming is performed on the surface of the matrix base member 5 to produce a film forming matrix 8 as shown in FIG. 2B.

As shown in FIG. 3, in the rolling device used here, the table for fixing the matrix substrate 5 moves in the X and Y directions in the horizontal plane at a resolution of 0.1 μm, and the diamond indenter 6 Has a function of moving in the vertical direction (Z direction) with a resolution of 0.1 μm. The diameter R of the tip of the diamond indenter 6 is desirably about 20 to 100 μm. For example, when the depth of the recess 7 is about 2 μm, the diameter R is 30 to 50 μm. When the depth of the recess 7 is about 1 μm, the diameter R is 50 to 100.
It is good to use a thing of μm.

The procedure of rolling by the diamond indenter 6 is as follows. FIG. 4 is a plan view showing a rolling pattern. As shown in FIG. 4, the pitches of adjacent recesses in one horizontal row are t1 (= 17 μm) in order from the left,
t3 (= 15 μm), t2 (= 16 μm), t3, t4
(= 14 μm), t4, t5 (= 13 μm), t2, t3,
t3. In addition, the pitches of the concave portions adjacent to each other in one vertical line have the same pattern in order from the top. By pressing four different depths in the range of 1.1 to 2.1 μm (shown as d 1, d 2, d 3, and d 4 in the figure), the radius of the circular concave portion which is an indentation after the pressing is also reduced. r1
(= 11 μm), r2 (= 10 μm), r3 (= 9 μm)
m) and r4 (= 8 μm). For example, the radii of the concave portions in one vertical line are r1, r2, r3, r
1, r4, r2, r4, r3, r1, r4, r1.

The actual order of the rolling is, for example, that after forming all the recesses of the depth d1 in the uppermost horizontal row, the recesses of the depth d2, the recesses of the depth d3, The rolling operation of four patterns of depths is repeated to form a concave portion having a depth d4, and all the concave portions in the uppermost row are formed. Then, it moves to the second horizontal row from the top and repeats the same operation. Thus, all the concave portions in the pattern are formed. FIG.
= 150 μm square showing a rolling pattern,
By repeating this pattern, the entire film forming matrix is constituted. As shown in FIG. 4, since the indentations of the adjacent concave portions partially overlap, the planar shape of the entire concave portion after all the rolling operations are completed is as shown in FIG.

Thereafter, as shown in FIG. 2C, the surface shape of the film forming master 8 is transferred to the film substrate 9 using a transfer device. At this time, the film forming matrix 8 is fixed to one roller 10 of the transfer device, and a film base 9 made of polycarbonate resin, which is a material having good workability, is arranged between the roller 10 and the other roller 11. The matrix 8 and the film substrate 9 are heated and pressed between the rollers 10 and 11. Various conditions such as temperature, pressure, and feed rate during heating and pressurization may be appropriately set in accordance with the material of the matrix 8 and the film base 9. Thereby, FIG. 2 (D)
As shown in (1), a film base material 9 having a large number of convex portions 3 having a concave and convex shape opposite to the large number of concave portions 7 forming the mold surface of the matrix 8 is prepared. Finally, the adhesive 4 is applied to the back surface of the film substrate 9 to complete the antireflection film 1 of the present embodiment.

Next, a reflection type liquid crystal display device of the STN (Super Twisted Nematic) type provided with the above antireflection film 1 will be described. As shown in FIG. 6, in this reflection type liquid crystal display device, a liquid crystal layer 15 is sandwiched between a pair of display side glass substrates 13 and a rear side glass substrate 14, and a polycarbonate resin or the like is provided on the upper surface side of the display side glass substrate 13. One retardation plate 16 made of polyarylate resin or the like and a first polarizing plate 17 are sequentially provided. Then, the antireflection film 1 of the present embodiment is provided on the upper surface of the first polarizing plate 17. In this antireflection film, the surface of the pressure-sensitive adhesive is fixed toward the first polarizing plate. On the lower surface side of the rear glass substrate 14, a second polarizing plate 18 and a reflecting plate 12 are sequentially provided.

The reflecting plate 12 is mounted so that the surface having irregularities is opposed to the lower surface of the second polarizing plate 18, and an adhesive 19 is provided between the second polarizing plate 18 and the reflector 12. Is filled. Transparent electrode layers 20 and 21 made of ITO (indium tin oxide) or the like are formed on the surfaces of the glass substrates 13 and 14 facing each other, and an alignment film made of a polyimide resin or the like is formed on the transparent electrode layers 20 and 21. 22,
23 are provided. These alignment films 22, 2
The liquid crystal in the liquid crystal layer 15 has a twisted arrangement of 240 degrees due to the relationship of 3 and the like.

Further, a color filter (not shown) may be formed between the rear glass substrate 14 and the transparent electrode layer 21 by printing or the like so that the liquid crystal display device can display a color image.

In the antireflection film 1 of the present embodiment, since a large number of projections 3, 3,... Having a curved surface are formed on the surface of the base film 2, as shown in FIG. Light incident on the convex portion 3 on the surface of the film 1 is refracted on the surface of the film 1 near the vertex of the convex portion 3 and transmits through the film 1, while the light at the foot of the convex portion 3 is along the film 1 surface. Direction, and the rate of reflection in the direction of the user's eyes is extremely small. Further, light (transmitted light in the case of a transmissive liquid crystal display device) incident from the back surface of the film 1 (the surface opposite to the surface on which the convex portions are formed) is:
Since the base film 1 is transparent, the light is slightly condensed by the projections 3, but is transmitted to the surface side with almost no trouble.

The result of examining the antireflection effect of the antireflection film 1 will be described. As shown in FIG. 8A, an arbitrary liquid crystal module 25 is used, and the incident angle of incident light on the screen is 30 ° with respect to the normal to the screen.
, And a photomultiplier 27 for measuring the intensity of the reflected light is provided on the normal line. Then, using a sample (Example) in which the antireflection film 1 of the present embodiment was adhered on the screen of the liquid crystal module 25 and a sample (Comparative Example) in which the antireflection film was not adhered (Comparative Example), The reflection characteristics of the incident light when shaken right and left were measured. FIG. 8B shows the result, in which the vertical axis represents the output voltage [V] of the photomultiplier (corresponding to the intensity of the reflected light), and the horizontal axis represents the viewing angle [°] (the angle at which the sample was swung right and left). Equivalent). In the figure, points indicated by “□” are data of the example, and points indicated by “○” are data of the comparative example.

As apparent from FIG. 8B, in the sample of the comparative example to which the antireflection film was not attached, the photomultiplier showed an extremely large output voltage peak when the viewing angle was -15 °. Therefore, if the user looks at the screen from the direction of the photomultiplier with respect to the liquid crystal module at this time, very strong reflected light is recognized, and it can be seen that it is extremely difficult to view the image. On the other hand, in the sample of the example in which the antireflection film was adhered, broad reflection characteristics were obtained over all viewing angles, and the peak as in the comparative example was not observed. From this result, it was verified that the antireflection film 1 of the present embodiment has a sufficient antireflection effect.

As described above, by attaching the antireflection film 1 of the present embodiment to a screen of an arbitrary image display device, reflection of external light and reflection of an external image on the screen surface can be reduced as compared with the related art. An image display device which can be sufficiently reduced and has excellent visibility can be realized. Also, unlike the conventional method of performing an anti-reflection treatment such as applying a light-absorbing resin on a screen or performing etching, the reflection can be achieved simply by attaching the anti-reflection film 1 on the screen after assembling the liquid crystal display device. -It is a very simple method because it can prevent reflection.

Further, when manufacturing the film forming master 8, the diamond indenter 6 is moved up and down to move the base 5 for the master.
Only presses the surface of the diamond indenter 6
And the matrix substrate 5 do not rub against each other. As a result, the surface condition of the tip of the diamond indenter 6 is reliably transferred to the matrix side, and the antireflection film 1 having a smooth-shaped convex portion can be manufactured. Furthermore, the height, diameter, pitch, and other dimensions of the projections 3 in the antireflection film 1 of the present embodiment, the surface condition of the projections 3, and the like are all controlled. Thus, the shape of the convex portion of the antireflection film 1 can be made almost as designed. Therefore, according to the present method, the visibility of the image itself displayed on the screen can be sufficiently ensured, and both the reduction of reflection and reflection and the visibility of the image can be appropriately controlled.

The technical scope of the present invention is not limited to the above embodiment, and various changes can be made without departing from the spirit of the present invention. For example, the specific values of the height, diameter, pitch, and the like of the convex portions of the antireflection film in the above embodiment and the rolling pattern shown in FIG. 4 are merely examples, and the design can be changed as appropriate. It is. In addition, materials of various substrates such as an anti-reflection film substrate and a matrix substrate can be appropriately changed.

Further, in the above-described embodiment, an example was given in which a convex portion having a spherical surface was provided. However, the surface shape of the convex portion is not limited to a spherical surface, but may be an aspherical surface such as a secondary curved surface or a cubic curved surface. It may be. In addition, as for the shape of the convex portion, as shown in FIG. 9, the anti-reflection film 30 having a surface shape in which the curved ridges 31 are continuously provided, and as shown in FIG. Can be used, and an anti-reflection film 40 having a surface shape in which a ridge 42 extending linearly in a radial direction is further provided thereon. 9 and 10, the anti-reflection films 30, 40 as shown in FIG.
In the case of producing a film forming master, instead of performing the pressing with the indenter as in the above-described embodiment, grinding using a cutting tool may be performed. 9 and 10, reference numeral 4 denotes an adhesive.

Further, the present invention is not limited to the example of the projections described in the above embodiment, but may be an antireflection film having a large number of depressions. In this case, as the shape of the concave portion, for example, as shown in FIG. 11, an anti-reflection film 50 in which a large number of concave portions 51 having a curved spherical inner surface are continuously provided on the base film 2, as shown in FIG. So, base film 2
The anti-reflection film 60 having a surface shape in which the curved grooves 61 are continuously provided on the upper surface. As shown in FIG. 13, the curved grooves 71 are continuously provided on the base film 2, and furthermore, are radially overlapped therewith. An anti-reflection film 70 having a surface shape provided with grooves 72 extending linearly can also be used. When manufacturing the antireflection films 50, 60, and 70 having a large number of concave portions as shown in FIGS. 11 to 13, after manufacturing the same film-forming master as in the above embodiment, the film-forming master is used. By temporarily manufacturing a transfer mold having a mold surface having the shape of the mold surface reversed from the surface, and transferring the mold surface of the transfer mold to the surface of the film substrate again,
It is possible to manufacture the antireflection films 50, 60, and 70 in which the concave and convex shapes of the transfer mold are inverted, that is, in which a large number of concave portions having the same surface shape as the film forming master are formed. In FIGS. 11 to 13, reference numeral 4 denotes an adhesive.

In addition to the configuration in which only a large number of convex portions are formed on the surface of the antireflection film, the configuration in which only a large number of concave portions are formed, the convex and concave portions are mixed in one surface of the antireflection film. You may. The image display device to which the antireflection film of the present invention can be applied is not limited to a liquid crystal display device, but can be applied to various devices such as a plasma display device and a television.

[0032]

As described above in detail, according to the antireflection film of the present invention, since a large number of projections or depressions having a curved surface are formed on the surface of the film substrate, The incident light that has entered the convex or concave portion of the surface is scattered, and the proportion of the incident light that is reflected in the direction of the user's eyes becomes extremely small. Therefore, by adhering the antireflection film of the present invention to the screen of any image display device, reflection of external light and reflection of an external image on the screen surface can be reduced, and an image having excellent visibility can be obtained. The display device can be easily realized. Further, according to the method for manufacturing an antireflection film of the present invention, once a master for film formation is manufactured, an antireflection film having the same surface shape can be easily and easily obtained by repeatedly using the master. It can be manufactured with high productivity.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an antireflection film according to an embodiment of the present invention.

FIG. 2 is a process flow chart showing a manufacturing process of the antireflection film in order.

FIG. 3 is a view showing a process of manufacturing a matrix used for forming the antireflection film, and showing a state where the matrix substrate is pressed with a diamond indenter.

FIG. 4 is a plan view showing a pattern of rolling by a diamond indenter in a manufacturing process of the matrix.

FIG. 5 is a plan view showing the shape of the entire recess after rolling.

FIG. 6 is a cross-sectional view illustrating a configuration of a reflective liquid crystal display device according to an embodiment of the present invention.

FIG. 7 is a diagram for explaining the principle of anti-reflection of the anti-reflection film.

8A and 8B show the results of measuring reflection characteristics by viewing angles of a sample to which an antireflection film is adhered and a sample to which no antireflection film is attached. FIG. 8A is a diagram showing a measurement method. FIG. 8 (B) is a diagram showing a measurement result.

FIG. 9 is a perspective view showing another embodiment of the antireflection film having a large number of projections of the present invention.

FIG. 10 is a perspective view showing still another embodiment of the antireflection film having a large number of projections of the present invention.

FIG. 11 is a perspective view showing an embodiment of an antireflection film having a large number of concave portions of the present invention.

FIG. 12 is a perspective view showing another embodiment of the antireflection film having a large number of projections of the present invention.

FIG. 13 is a perspective view showing still another embodiment of the antireflection film having a large number of projections of the present invention.

[Explanation of symbols]

 1, 30, 40, 50, 60, 70 Anti-reflection film 2 Base film 3 Convex part 4 Adhesive 5 Base for base 6 Diamond indenter 7, 51 Depression 8 Base for film formation 9 Film base 31, 41, 42 ridges (projections) 61, 71, 72 grooves (recesses)

Claims (5)

[Claims] 1. An anti-reflection film comprising a transparent film substrate and a large number of projections or depressions having a curved surface continuously formed on the surface of the transparent film substrate. 2. The anti-reflection film according to claim 1, wherein the height of the protrusion or the depth of the recess is randomly arranged, and adjacent protrusions, protrusions or recesses, and recesses or protrusions are adjacent to each other. An antireflection film, wherein the plurality of protrusions or recesses are formed such that pitches between recesses are arranged randomly. 3. An indenter is pressed against the surface of the matrix substrate, and the pressing by the indenter is repeated while changing the position of the indenter on the surface of the matrix substrate. By continuously forming a large number of concave portions having a curved inner surface to produce a film-forming matrix, the mold surface of the film-forming matrix is transferred to the surface of a film substrate, thereby forming the mold. A method for producing an anti-reflection film, comprising producing an anti-reflection film having a surface on which a large number of projections having inverted surface irregularities are formed. 4. An indenter is pressed against the surface of the matrix substrate, and the pressing by the indenter is repeated while changing the position of the indenter on the surface of the matrix substrate. After forming a large number of concave portions having a curved inner surface in succession and manufacturing a film forming master, the mold surface of the film forming mother mold with the concave and convex shape of the mold surface reversed. An anti-reflection having a surface in which a number of concave portions are formed by inverting the concave and convex shape of the mold surface of the transfer mold by manufacturing a transfer mold having the mold surface and transferring the mold surface of the transfer mold to the surface of the film substrate. A method for producing an antireflection film, comprising producing a film. 5. An image display device comprising the anti-reflection film according to claim 1.