JPH0949925A - Visual field widening film and liquid crystal display using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a film capable of widening visual field angle without degrading front luminance by arranging plural projecting parts or recessed parts having curved surfaces via a plane parts on a base material and specifying the double refractive phase difference of light to a specific value or above in both of the intra-surface direction and the thickness direction. SOLUTION: The plural projecting parts 1a or recessed parts having the curved surfaces are arranged via the plane parts (a) on the base material and the double refractive phase difference of light is specified to <=60μm in both of the intra-surface direction and the thickness direction. The projecting parts 1a or recessed parts are formed into a circular shape of 0 to 100μm in the radius of section and the plane parts (a) formed to have a length of 20 to 100μm. The sections of the projecting parts 1a or recessed parts are rectangular and these rectangular shapes are formed to have a long side or shot side of 20 to 100μm. The materials used for this visual field widening film includes materials which are translucent or transparent materials retaining the parallel ray transmittance in a normal direction without degradation and have a refractive index of >=1.0; for example, polycarbonate, polymethyl methacrylate, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field widening film applied to a flat display panel such as a plasma display and a thin film EL display to widen a viewing angle of an image, and a liquid crystal display using the field widening film.

[0002]

2. Description of the Related Art Conventional liquid crystal displays have a drawback in that the viewing angle is narrow. The viewing angle is an angular range in which an image can be satisfactorily identified. Looking at the display screen from the front,
Although a good image can be obtained, when it is viewed from an oblique direction with the image shifted from the front, gradation inversion and deterioration in contrast occur, and the image cannot be identified. On a liquid crystal display, this phenomenon occurs only by observing slightly off the front. Since the liquid crystal cell is usually assembled by giving priority to the horizontal viewing angle, the viewing angle is narrowed especially in the vertical direction. By the way, if the image is shifted from the front by 20 ° in the upward direction and 5 ° in the downward direction, the image state becomes bad immediately.

In view of this, in order to widen the viewing angle of an image, the following viewing field expansion films used in liquid crystal display panels are known. (1) A sheet composed of an assembly of convex microlenses whose cross-sectional shape is a kamaboko-shaped aspherical shape or circular shape, which is arranged between the polarizing plate on the observation surface side and the liquid crystal cell is there. In particular, a structure in which minute convex microlenses are densely formed in a zigzag pattern is disclosed in, for example, Japanese Patent Laid-Open No. 6-27453.
JP-A-6-27455. Further, a structure in which minute convex microlenses are closely arranged in parallel and at equal intervals is disclosed in, for example, Japanese Patent Laid-Open No. 5-249453.
No. 6,086,045. Further, one in which a concave lens is formed on a substrate corresponding to each pixel is disclosed in, for example, Japanese Patent Laid-Open No.
It is disclosed in Japanese Patent No. 194819.

(2) One in which a concave lens sheet is installed on the viewer side of the viewing-side polarizing plate is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-2.
It is disclosed in Japanese Patent No. 89071. (3) Spherical fine particles are arranged on a liquid crystal panel, and a black mask having fine holes (holes) corresponding to the respective particles is provided on the liquid crystal panel to enlarge the viewing angle. It is disclosed in Japanese Unexamined Patent Publication No. 6-110053.

[0005]

However, the inventor of the present invention has found that the above-mentioned field-enlarging film has the following problems. That is, when a microlens array in which microlenses are densely molded is used for a liquid crystal display, the light transmitted to the front is only the light near the apex of the microlens (inclination angle 0 °), and the amount of transmitted light decreases. Therefore, the liquid crystal display device becomes dark,
Visibility decreases.

Further, when the field-enlarging film is installed on the viewer side of the viewing-side polarizing plate, the disturbance light is scattered or specularly reflected, and the contrast is lowered. In view of the above-mentioned problems, an object of the present invention is to provide a visual field expansion film capable of expanding the viewing angle without lowering the front luminance and a liquid crystal display using the same.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0008]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows. (1) In the field-of-view magnifying film of the present invention, a plurality of convex portions or concave portions having a curved surface are arranged on a base material via a flat portion, and the birefringence phase difference of light is in both the in-plane direction and the thickness direction. It is set to 60 nm or less.

(2) In the field-of-view enlarging film of the present invention, the convex portion or the concave portion has a cross-sectional radius of 0 to 100.
It is formed in a circular shape of μm, and the length of the plane portion is 20 to 20.
It is formed to 100 μm. (3) In the visual field expanding film of the present invention, the convex portion or the concave portion has a rectangular cross section, and the long side and the short side of the rectangle are formed to have a thickness of 20 to 100 μm.

(4) The visual field expanding film of the present invention has a curved portion having a radius of curvature of 10 to 300 μm between the convex portion or the concave portion and the flat portion. (5) The liquid crystal display of the present invention comprises the means (1),
The visual field expansion film according to (2), (3) or (4), which is mounted on the observation surface side of the liquid crystal cell with the convex portion or the concave portion of the visual field expansion film facing the liquid crystal cell side. Is.

According to the present invention, it is necessary to have a horizontal plane in addition to the light expanding portion in order not to reduce the amount of transmitted light on the front side while ensuring the light expanding effect. When the proportion of the light expansion portion is significantly reduced, the light amount-expansion component other than in the front direction also decreases, but if the proportion of the light expansion portion is optimized, the contrast that does not hinder the use in both the front direction and the diagonal direction is obtained. It is possible to obtain.

About 5% of the light incident on the horizontal portion (the value varies depending on the material of the film or the like) returns to the light source side, but the rest is linearly transmitted without bending the optical path.
In this way, by using the composite type, it is possible to obtain the effect of enlargement while securing the amount of transmission on the front side. The ratio of the horizontal plane portion varies depending on the light-collecting property of the backlight, the amount of light emission, the number of cold cathode tubes, and the like, but may be about 50% with respect to the entire area. UP from 50% to improve front brightness
You can do it.

The convex portion of the present invention has a high ability to collect light from the backlight, that is, the higher the parallelism, the more
The horizontal cross-sectional shape may be close to a circle. When the parallelism is low and a large amount of light is obliquely incident, a convex portion (hereinafter, a concave portion is also included.
(For convenience, it may be abbreviated as a convex portion for convenience.) Part of the light does not refract, but totally reflects back to the backlight side, or is refracted multiple times in an arc to scatter and magnify the enlarged image. There is a possibility that it will change to scattered light that causes it.

If the cross section of the convex portion is circular with the light quantity reduced at the time of incidence, even if the light is diffused in all 360 ° azimuths, the light quantity in each azimuth is low and a sufficient expansion effect is obtained. I can't get it. If you can obtain highly parallel light on the light source side,
By making the cross-sectional shape circular, uniform image quality can be obtained in all directions. Further, when the parallelism is increased, the influence of the angle dependency of the liquid crystal, which looks different depending on the light incident angle, is reduced. A good image that is not affected by the angle dependence can be enlarged in all directions. In this way, it is effective to use a backlight having an improved light-condensing property and expand in all directions in a circular convex shape after passing through the liquid crystal cell in order to view a good image in each direction. The half value width on the backlight side is ± 30 °
In order to achieve the following, two or more commercially available prism sheets may be stacked.

As the prism sheet, for example, "BEF90" manufactured by 3M may be used. Furthermore, in order to improve the light-collecting property, if a prism sheet with an apex angle smaller than 90 ° is turned to the backlight side and is corrected by a light guide plate and made to enter at an optimum angle, light with a half value width of ± 20 ° is obtained. To be When the parallelism is low (when the angle range to reach the half value with respect to the maximum light amount is ± 30 ° or more, this angle range is referred to as the half value width), the cross-sectional shape is a rectangle with the four sides facing in the left-right direction and the vertical direction. (Including square) or 0 at the corner
A radius of curvature R of (short side of rectangle) / 2 may be added, or a chamfered rectangle may be formed.

When evaluating the viewing angle, the horizontal viewing angle and the vertical viewing angle, which are important, can be focused and improved.
In notebook computers, the lid and the liquid crystal display are integrated into the front and back, and you can open the lid to view the liquid crystal display. Since the normal direction of the screen may not match the viewing angle direction depending on how the lid is opened, it is necessary to improve the viewing angle in the vertical direction. Since there are no people, it is not necessary to pay attention to the improvement of the viewing angle in the diagonal direction as much as in the left-right and up-down directions. For this reason, the visual field may be enhanced in the vertical and horizontal directions. The smaller the angle R, the higher the directivity.

Depending on the condensing characteristics of the backlight, there is one in which the light is previously expanded in the left-right direction. In this case, the long side is formed in the vertical direction so that the light is expanded in the vertical direction, and the short side is formed. The ratio should be large. Depending on the case, the short sides may be connected to be continuous. However, if the cross section is made to be a substantially rectangular shape, a personal computer or the like used by about one person is effective, and it is not suitable for a television set viewed by a large number of people. When used in the latter case, a circular cross section type is preferred.

The method for producing the shape includes a method of producing a desired shape with a die and a press, a method of shaping a predetermined shape on a metal roll and pressing it against a heated resin, and a method of applying a photocurable resin. There is a method of hardening with a circular or rectangular mask. All are common shaping methods and are easy to manufacture. In addition, it is desirable that the field-of-view enlarging film is installed between the polarizing element on the observation side and the liquid crystal cell with the light enlarging portion facing the liquid crystal cell side. The reason is that when a field-of-view expansion film is installed on the outermost side, surface treatment such as scratch resistance and antireflection treatment must be performed.
This is because the cost becomes high and the reliability is low in terms of long-term stability. In addition, the effect of preventing character blurring is also included. A character blur is a state in which a character appears to be out of focus, such as when the character appears double. The character blurring is less likely to appear as the field-of-view expansion film is closer to the liquid crystal cell. For this reason as well, it is better to sandwich a field-of-view magnifying film between the polarizers than to place the film on the observation side of the polarizer. For the above reasons, it is desirable to sandwich the field-of-view expansion film between the polarizers.

Optical distortion is the most serious problem when a field-of-view magnifying film or the like is placed between the polarizing element on the observation side and the liquid crystal cell. The state without optical distortion is simply
It does not mean that the field-of-view magnifying film is flat or has a uniform thickness, but that it does not change even after the polarized light incident on the field-of-view magnifying film is transmitted. Specifically, no birefringence occurs in the field-of-view magnifying film. When the birefringence phenomenon occurs, the light that has passed through the liquid crystal is unnecessarily twisted, so that the light that has passed through the viewing-side polarizer is displayed in a different shade from the intended color scheme.

Therefore, the birefringence phase difference in the field-of-view magnifying film must be small. The birefringence phase difference is preferably 60 nm or less both in the field of view expanding film and in the thickness direction,
It is preferably as small as possible. Further, the birefringence phase difference is preferably uniform. The display state is designed from the prescribed voltage and the twist of the liquid crystal, and if a birefringent medium other than the calculation is entered, the load voltage and liquid crystal characteristics must be redesigned, which is a very complicated and time-consuming operation. become. This is a so-called model change. In addition, there are cases where it is not possible to respond physically. If there is no optical distortion, it is easy to mount on the current actual equipment.

As a method for producing a field-enlarging film or the like having no optical distortion, a general method can be used. For example, there is a method of heating a visual field expansion film having an uneven shape. When the glass is heated above the glass transition point of the visual field expanding film resin, the strain remaining in the visual field expanding film is relaxed. A higher temperature is more effective, but if it is too high, it may melt or the corrugated field-of-view film may wavy, so be careful.

Another method is to form a visual field expansion film by a solvent casting method. In the solvent casting, the resin to be made is usually applied on the base film. The applied resin is heated and dried in the drying zone, and then peeled off from the base film. Since the drying is performed on the base film, all the tension in the drying process is applied to the base film and does not apply to the visual field expansion film to be produced. This makes it possible to produce a visual field-enlarging film without distortion.

The material used for the field-of-view magnifying film is a semitransparent material in which the parallel light transmittance in the normal direction does not decrease, or a transparent material having a refractive index of 1.0 or more, such as polycarbonate, polymethylmethacrylate, or polyethylene. Terephthalate, polyether sulfone, polysulfone, polystyrene, polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polyvinyl alcohol, polypropylene, polyacrylonitrile, polyvinyl acetate, nylon 6 and There are nylon 66 and the like.

In addition to thermoplastic resins, UV curable resins and other photocurable resins, epoxy resins, melamine resins,
Thermosetting resins such as urea resin and phenol resin may be used. Further, glass such as soda lime glass may be used, and the surface of the plastic may be subjected to SiO ₂ coating or a protective coating treatment relating to durability such as moisture resistance. The treatment method may be coating, vapor deposition, sputtering, ion beam, or the like. Further, a pressure-sensitive adhesive having no birefringence may be attached to the smooth surface so that the pressure-sensitive adhesive is attached to the polarizing element.

When applying a pressure sensitive adhesive or an adhesive,
When applied to a smooth surface, there is no particular problem if attention is paid to the above-mentioned birefringence, but when applied to a surface having a shape (shaped surface), it is preferable not to fill the unevenness provided. This is because if the uneven shape is filled, the expansion effect is reduced. When it is unavoidable to apply it in the uneven shape, it is necessary that the refractive index is smaller than that of the visual field expanding film. Also,
It is better that the difference in refractive index is as large as possible. As the pressure-sensitive adhesive (adhesive) having a small refractive index, a fluorine-based pressure-sensitive adhesive or the like is preferable.

The cross-sectional shape of the light expanding portion may be convex or concave. Further, it is better to alternately form the light expanding portion and the horizontal portion, and the ratio thereof is determined to be the optimum value according to the application. Further, the contact portion between the convex portion or the concave portion and the horizontal surface may be chamfered or R, and R may occupy most of the slope. The reason is that if the slope is composed of only one straight line, the direction of the field of view to be expanded is determined to be one direction, and there is a risk that the light will not be expanded in any direction other than that direction.

This is because if the light is not continuously expanded, dark spots having a remarkably low light amount may occur in a specific direction. Further, the vertical cross-sectional shape does not necessarily have to be symmetrical when viewed from the center line (normal direction) depending on its application. When it is desired to expand the light only to the upper side with respect to the center line, it is sufficient to form a slope having a larger opening angle from the normal direction on the upper side and reduce the lower slope.

In this sense, even if it is a quarter-sphere shape having a sloping surface only in one direction and the symmetry side being vertical,
Sufficient effect can be obtained if used according to the application. It is desirable that the shape-imparting surface faces the liquid crystal cell side, but it may be facing the observer side if character blurring is not a concern. The convex portions are preferably arranged at equal intervals across the horizontal surface portion, but they may be intermittent or staggered at regular intervals. The convex portion may have a horizontal portion at the top. Further, the ratio of the desired horizontal surface (the entire surface of the film for enlarging the visual field) may be calculated by combining the horizontal portion and the horizontal portion on the top of the convex portion.

When the convex portion is cut in the vertical direction, it is desirable that the cross-sectional shape of the slope has a curved surface. If there are many straight portions, light may be distributed only in a specific direction, and the other portions may become dark areas. Therefore, it is preferable that the curved portions be formed as much as possible. Further, one lens portion and one horizontal surface are called one pitch, and one pitch is preferably smaller than one pixel of the liquid crystal cell, and if one pitch is about 2 to 3 pixels, it is set larger than the liquid crystal cell. May be. 1 if small
It is necessary that the pixel size does not become an integral multiple of the pitch of the field-of-view expansion film or the like. If it happens, 5 times or more is better. This is because moire fringes (interference fringes) are likely to occur when the number is 5 times or less and becomes an integral multiple.

When the field-of-view magnifying film is used in a liquid crystal display, the ridgeline of the field-of-view magnifying film may be perpendicular to the direction in which the viewing angle is desired to be widened. At that time, the lens surface is arranged so that the liquid crystal cell side is located and the observer side is a flat surface. 2 directions to widen the viewing angle
If it is the direction, two field-of-view magnifying films may be used. Also, two or more sheets may be stacked in the same direction. Even when a plurality of visual field expansion films are used at the same time, it is preferable to combine a plurality of lens pitches and pixel pitches so that Moire fringes are difficult to recognize like the relationship between pixel pitches and lens pitches.

When the field-of-view magnifying film is mounted on the liquid crystal display, it need only be laminated on the main body. When it is desired to fix, the whole lens surface may be covered with an adhesive layer and attached to the liquid crystal cell. Further, the adhesive layer may be provided at several places or only at the ends. When the entire lens surface is covered with an adhesive layer, the difference in refractive index between the optical element and the adhesive layer is preferably large. As a fixing method, a method such as screwing using the end portion or fitting may be used. On the plane side, that is, on the observer side polarizing plate side, a conventional polarizing plate mounting method may be used.

[0032]

[Operation] According to the above-mentioned means, since the plurality of convex portions or concave portions having curved surfaces are arranged through the flat portion, the field-of-view magnifying film has a flat portion that does not have a refraction effect. The viewing angle is expanded by the convex portion or the concave portion without relatively impairing the amount of light in the viewing angle range that can be recognized by the liquid crystal display.

When parallel light rays are incident on the field-of-view enlarging film, it is considered that the parallel light transmitted light and the diffused light, and the parallel light transmitted light and the diffused light are divided into light that gently connects. Therefore, the amount of light on the front surface is adjusted in the plane portion parallel to the lower surface, and the magnitude of the viewing angle expansion is adjusted in the convex portion or the concave portion. Since the portion connecting the flat portion and the convex portion or the concave portion is composed of the curved portion, the outgoing light distribution of the light rays is continuous, and character blurring and image blurring do not occur.

1 field-of-view expansion film on the liquid crystal display
By incorporating one or more sheets, the field of view is easily expanded, and complicated steps such as designing and manufacturing a new liquid crystal cell are not required. Therefore, a liquid crystal display having high reliability and a wide field of view can be easily obtained.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for explaining the embodiments, those having the same function are designated by the same reference numerals, and the repeated description thereof will be omitted. [Embodiment 1] FIG. 1 is a sectional view of a visual field expanding film according to a first embodiment of the present invention, FIG. 2 is a plan view of a visual field expanding film according to a first embodiment of the present invention, and FIG. It is a schematic sectional drawing of the liquid crystal display which mounted the visual field expansion film which concerns on 1 Example.

A 100 μm thick base material formed by removing the stress by solvent casting or heating at 150 ° C. for 10 minutes, for example, a polycarbonate resin, a photosensitive resin,
For example, an ultraviolet curable resin was applied to a thickness of 80 μm, and a photomask having an open circular arc diameter of 40 μm and arranged at equal intervals in the vertical direction at a pitch of 50 μm was placed thereon.

After that, an ultraviolet irradiation device (super high pressure mercury lamp)
UV light of 300 mJ / cm ² was irradiated for 30 seconds from the above light source, and the UV curable resin was selectively exposed by a photomask. Next, the UV curable resin is used to
After developing for 1 minute, the unreacted portion was cured by re-exposure with an ultraviolet ray of 100 mJ / cm ² for 20 seconds to fix the shape.
The shape after development is 20 μm as shown in FIGS.
In the cross-sectional shape through the flat surface portion a of m, the upper surface flat portion b is 20 μm, and the sloped curved portion c is 60 μm (each side is 30 μm.
m), a field-enlarging film 1 was obtained in which hemispherical convex portions 1a each having a flat upper surface and having a groove depth d of 40 μm were arranged.

This field-of-view enlarging film 1 was attached to a TFT-LCD as shown in FIG. The liquid crystal display is a long side single light type edge light type 10.4inch TFT color liquid crystal display, and the pixel shape is 280μ in the horizontal direction.
m, and the vertical length is 320 μm. The liquid crystal display includes a TN liquid crystal cell 2 in which a visual field expansion film 1 and a polarizing plate 3 are sequentially arranged on the front surface (observer side) of the TN liquid crystal cell 2.
A polarizing plate 3 and a backlight 4 are sequentially arranged on the rear surface of the rear panel.

The field-of-view enlarging film 1 was attached so that its convex portion 1a faces the TN liquid crystal cell 2 side. Further, the field-of-view enlarging film 1 was installed so that the convex portions 1a were arranged in the horizontal direction of the screen. Therefore, the field of view is enlarged corresponding to about one convex shape or more for one pixel. The display element is a commercially available TFT-LCD TV, 6E-C3
(Made by Sharp) was used. In the commercially available state, only the white diffuser is arranged on the backlight side, and the light collecting property is low. Therefore, two "BEF90" manufactured by 3M were arranged orthogonally to enhance the light collecting property. The full width at half maximum was about ± 30 °.

When the screen was observed in this state, the results shown in Table 1 below were obtained.

[0041]

[Table 1]

The transmittance is lower than that of the conventional product in which the field-of-view magnifying film is not mounted, but there is no problem in actual use.
The viewing angle was remarkably improved as compared with the conventional product, and even when the liquid crystal display was viewed from directly below, gradation inversion (the phenomenon of color inversion) did not occur, and good image quality was obtained. Also,
There was no color shift when viewed from the front. By using the field-of-view magnifying film, the viewing angle of the display device could be significantly improved.

Further, the field-of-view expansion film 1 is used as a TFT-LC.
Since it is attached to the TN liquid crystal cell 2 side (inner side) of the polarizing plate 3 on the observer side of D, surface treatment such as scratch resistance and antireflection treatment is not required, and the cost can be reduced and the reliability can be improved. Can be improved. Further, it is possible to prevent a character from being blurred such that the character appears double. In addition, the birefringence phase difference of light in the in-plane direction of the field-of-view magnifying film 1 is set to 10n.
When the thickness is m or less, optical distortion can be prevented, and the view expanding film 1 can be easily mounted on the liquid crystal display.

[Embodiment 2] FIG. 4 is a cross-sectional view of a visual field widening film which is a second embodiment of the present invention. As in Example 1, an ultraviolet curable resin was applied on a polycarbonate resin and exposed in the same manner as in Example 1. Then, only the developing time was shortened to 1 minute for development, and re-exposure was performed for 20 seconds to fix the shape.

The shape after development is 30 as shown in FIG.
A field-enlarging film 5 having a trapezoidal convex portion 5a having an upper surface flat portion b of 20 μm, a sloped curved portion c of 25 μm, and a groove depth d of 20 μm is obtained in a sectional shape through a flat portion a of μm. Was given. As in Example 1, the field-of-view magnifying film 5 was mounted on a TFT-LCD TV and evaluated for characteristics. The results are shown in Table 2 below.

[0046]

[Table 2]

Although the viewing angle was less widened than in Example 1, the transmittance in the front was improved to 60%, and the transmission was such that no noticeable difference was visually perceived when compared side by side with the conventional product. Is getting the rate. The viewing angle is 60 °,
I think that there is no problem if it is used according to the application. [Embodiment 3] FIG. 5 is a cross-sectional view of a visual field widening film which is a third embodiment of the present invention.

The field-of-view expanding film 7 was obtained by press molding a 100 μm thick polycarbonate film with a mold. The field-of-view magnifying film 7 has a cross-sectional shape and a convex portion 7
a has a radius of curvature R ₁ of 10 μm, a radius of curvature R ₂ between the convex portion 7 a and the plane portion of 7 μm, and a pitch p of 33
μm. The mold used for press-molding the field-of-view magnifying film 7 has a cross-sectional shape and a curvature radius of the curved portion is 1
It has a curve of 0 μm, a radius of curvature between the curved portion and the straight portion of 7 μm, a pitch of 33 μm, a material of the mold is aluminum, an area of 230 mm × 175 mm, and a thickness of 20 mm. A hydraulic press machine is used for press forming, and the press conditions are a temperature of 220 ° C. and a pressure of 20 kgf / cm ² .

As a pre-process for forming the field-of-view magnifying film 7, the residual stress was removed by heating at 150 ° C. for 10 minutes. Also, since annealing was performed after molding at a high temperature, the stress relaxation during molding and the residual stress decreased due to annealing, and the distribution was uniform. The birefringence retardation in the in-plane direction was 5 nm or less, and the birefringence in the thickness direction. A molded product having a phase difference of 3 nm or less was obtained. This field-of-view magnifying film 7 was used in the same way as in Example 1 for TFT-LCD
When mounted on a TV and evaluated for characteristics, the vertical viewing angle is 20 to 30 ° before mounting, but it is 5 after mounting.
It spread from 0 to 60 °, the image was clear, and there was no character blurring.

[Comparative Example] FIG. 6 is a sectional view of a visual field expanding film as a comparative example, and FIG. 7 is a plan view of a visual field expanding film as a comparative example. UV curable resin is applied on acrylic resin, pitch p is 100 μm, and cross-sectional shape is 1 /
The acrylic microlens array film 6 in which the convex lenses 6a having two arcs are continuously molded is mounted on the same LCD as in the above-mentioned embodiment, and the characteristics are measured. The results are shown in Table 3 below.

[0051]

[Table 3]

Since the light is expanded in all directions, the front transmittance is remarkably reduced. It is dim and very difficult to see as a display element. The contrast is also reduced. There is no hindrance when viewed from the diagonal direction only. In addition, since a birefringence phenomenon occurs due to residual stress, when an image is displayed as a moving image, the tint is strange and unnatural compared to when there is no film. It was not suitable for display elements such as televisions.

As described above, the invention made by the present inventor is:
Although the present invention has been specifically described based on the embodiments, it goes without saying that the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention.

[0054]

The effects obtained by the typical ones of the inventions disclosed in this application will be briefly described as follows.
It is as follows. According to the visual field expansion film of the present invention, since the convex portions (or concave portions) and the flat surface portion are alternately formed on the base material, the light rays are not bent in the flat surface portion and are transmitted to the front surface, and the convex portion is formed. Since it has the effect of expanding the field of view, the field of view in the vertical direction of the screen is expanded without dimming the image in front of the screen of the liquid crystal display, and it is possible to prevent gradation inversion when the screen is viewed from an oblique direction.

Further, according to the liquid crystal display of the present invention, since the field-enlarging film is arranged between the liquid crystal cell and the observer-side polarizing plate so that the convex portion faces the liquid crystal cell side, the image becomes clear, A wide viewing angle can be obtained without complicating the conventional liquid crystal cell manufacturing process, and a larger size can be achieved along with a higher viewing angle.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a visual field widening film that is a first embodiment of the present invention.

FIG. 2 is a plan view of a visual field expanding film that is a first embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a liquid crystal display on which the field-of-view magnifying film according to the first embodiment of the present invention is mounted.

FIG. 4 is a cross-sectional view of a visual field widening film that is a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of a visual field widening film that is a third embodiment of the present invention.

FIG. 6 is a cross-sectional view of a visual field widening film of a comparative example.

FIG. 7 is a plan view of a visual field widening film of a comparative example.

[Explanation of symbols]

 1, 5, 7 Field of view expansion film 1a, 5a, 7a Convex part 2 TN liquid crystal cell 3 Polarizing plate 4 Backlight 6 Micro lens array film 6a Convex lens

Claims (5)

[Claims] 1. A plurality of convex portions or concave portions having a curved surface are arranged on a substrate through a flat portion, and the birefringence phase difference of light is 60 nm or less in both the in-plane direction and the thickness direction. A characteristic field-of-view expansion film. 2. The convex portion or the concave portion is formed in a circular shape having a cross-sectional radius of 0 to 100 μm, and the flat portion is formed to have a length of 20 to 100 μm. Item 1. The visual field expansion film according to item 1. 3. The convex portion or the concave portion has a rectangular cross section, and the long side and the short side of the rectangle are 20 to 10.
The visual field expanding film according to claim 1, wherein the visual field expanding film is formed to have a thickness of 0 μm. 4. The visual field enlarging film according to claim 2, wherein a curved portion having a radius of curvature of 10 to 300 μm is provided between the convex portion or the concave portion and the plane portion. 5. The field-of-view magnifying film according to claim 1, 2, 3 or 4 is mounted on the viewing surface side of the liquid crystal cell with the convex or concave part of the field-of-view magnifying film facing the liquid crystal cell side. Liquid crystal display that is characterized.