CN1739050A - Optical film structure, illumination apparatus and liquid crystal display device - Google Patents

Abstract

The present invention provides an optical film structure useful in a liquid crystal display device and capable of using thin optical films without warp and distortion. An optical film structure comprises at least one optical film, at least four film fixing parts arranged at an outer peripheral portion of the optical film, a film tension controlling member fitted at one of the ends thereof to each of the film fixing parts in such a fashion as to be capable of pulling the optical film under tension while maintaining flatness of the optical film, and a film fixing frame to which the other end of the film tension controlling member is connected and which fixes the optical film.

Description

Optical film structure, lighting fixture and liquid crystal display device

The invention relates to an optical film structure, a lighting appliance and a liquid crystal display device. More particularly, the present invention relates to an optical film structure advantageously used in a liquid crystal display device in combination with a lighting unit having at least one optical film, and a lighting fixture and a liquid crystal display device each having such an optical film structure . In the liquid crystal display device according to the present invention, particularly, the periphery of the optical film is mounted to the fixed frame through a film tension control member including a flexible member such as a spring or rubber. Therefore, the deformation of the optical film due to heat and aging can be absorbed, the surface can be kept flat, and thus the decrease in display performance of the liquid crystal display device can be prevented.

Background of the invention

The liquid crystal display device has the characteristics of thin thickness, light weight, and low power consumption. Therefore, it is widely used as a display device in information processing equipment and image equipment. Application examples of liquid crystal display devices include displays for mobile phones, video cameras, digital still cameras, personal computers, television receivers, and others.

Many types of liquid crystal display devices are now commercially available. Generally, a liquid crystal display device includes optical elements with many characteristics, such as optical plates and optical films in front of lighting fixtures, in order to transmit light from lighting fixtures disposed behind the liquid crystal display device and to achieve a brighter and more uniform display screen .

In a liquid crystal display device using a vertical type backlight system, lighting fixtures are provided on a rear surface of a liquid crystal display panel. Light from a lighting fixture, for example, which may include many fluorescent tubes embedded in a transparent resin, is projected onto a diffuser plate through which the diffused light transmitted is radiated to the rear surface of the liquid crystal display panel to provide uniform brightness distribution. A polypropylene resin plate containing fine _SiO2 particles and having a thickness of about 1.5 mm was used as the diffusion plate. When the board is thin, it is not easy to obtain uniform brightness distribution due to warpage and unevenness of the board. As the size of liquid crystal display devices has become larger in recent years, warpage and unevenness of the panel have become more likely to occur, for which reason the thickness of the diffusion plate itself has been increased to alleviate these problems. On the other hand, an increase in the weight of the diffuser plate due to the thickness and area of the plate has become another problem.

In order to avoid the problems of an optical plate such as a diffusion plate, it has recently been proposed to use an optical film, an optical sheet, or the like instead of the optical plate. For example, there is known a liquid crystal display device using a so-called "brightness improving film" on the light guide plate side of the backlight to improve the light emission brightness of the liquid crystal display panel. In this liquid crystal display device, a luminance improving film (prism film) having a prism shape is provided on the light output surface side of the guide plate, and the power consumption-luminance conversion efficiency is remarkably improved. In this arrangement, dot-like light diffusing material is typically printed on the surface of the guide plate opposite the light output surface to obtain uniform light emission. Since the dot pattern causes many bright spots, a light diffusion film is disposed between the brightness improving film and the guide plate in order to conceal the dot pattern and eliminate the problem of uneven brightness.

A liquid crystal display device using a brightness improving film other than the above-described prism film is also known. A liquid crystal display device uses a reflective polarizing film having a brightness improving effect. Although the reflective polarizing film can be utilized alone, it is preferable to use the prismatic film in combination to further improve the brightness improving effect.

Optical films such as the brightness improving films and reflective polarizing films described above are important to the optical design of liquid crystal display devices. However, as the size of liquid crystal display devices has increased in recent years, warpage and deformation of the film have become more likely to occur. In order to solve these problems, the thickness of the optical film itself is increased or a thicker sheet is bonded to the optical film. However, as the attenuation rate of transmitted light becomes higher as the thickness of the optical film increases, there arises a new problem that the brightness improvement effect decreases.

On the other hand, there is also known a liquid crystal display device having a backlight formed by laminating a plurality of light-diffusing films. In order to solve the problem of uneven brightness, a method of increasing the total thickness of the light-diffusing film is generally adopted. Since the light transmission system decreases as the thickness increases, and thus the surface brightness decreases, many thin light diffusion films are stacked in this liquid crystal display device for improving the transmission coefficient and the diffusion performance of the light diffusion film.

However, when this stacking method is employed, there arises a problem that the number of optical films increases and the work of assembling a group of optical films into a liquid crystal display device becomes complicated. A method of bonding the optical film to the backlight body with an adhesive or fixing them with screws is generally employed to assemble the optical film, but this method requires relatively intensive labor.

Various optical films are commercially available with a protective film bonded to the optical film to protect the surface of the film from damage caused by friction or the like. In order to assemble the optical film, it is necessary to tear off the protective film layer by layer, thereby intensifying labor. Also, problems of generation of static electricity and handling debris also arise.

Furthermore, when a light-diffusing film is used in a stacked state as discussed above, the problem of warping or deformation of the film is unavoidable.

Brief description of the drawings

FIG. 1 is a sectional view showing a liquid crystal display device according to a preferred embodiment of the present invention.

FIG. 2 is a perspective view showing an illumination unit of the liquid crystal display device shown in FIG. 1 .

Fig. 3 is a plan view showing a lighting fixture according to a preferred embodiment of the present invention.

FIG. 4 is a cross-sectional view of the lighting fixture taken along line 'IV-IV' in FIG. 3 .

FIG. 5 is a sectional view showing a fixing method of a film tension controller in the lighting fixture shown in FIG. 3 .

FIG. 6 is a cross-sectional view showing a modified example of the fixing method of the film tension control member shown in FIG. 5 .

FIG. 7 is an enlarged cross-sectional view showing an optical film structure in the vicinity of a film tension control member according to a preferred embodiment of the present invention.

8 is an enlarged cross-sectional view showing an optical film structure in the vicinity of a film tension control member according to another preferred embodiment of the present invention.

9 is a plan view showing a fixing method of fixing an optical film to a film fixing frame within an optical film structure according to the present invention.

FIG. 10 is a plan view illustrating another method of fixing an optical film to a film fixing frame within an optical film structure according to the present invention.

11 is a plan view showing still another fixing method of fixing an optical film to a film fixing frame within an optical film structure according to the present invention.

FIG. 12 is a cross-sectional view of the optical film structure taken along line 'XII-XII' of FIG. 11 .

FIG. 13 is a cross-sectional view showing a modified example of the optical film fixing method shown in FIG. 12 .

14 is a plan view illustrating another fixing method of a film fixing frame for fixing an optical film in an optical film structure according to the present invention.

FIG. 15 is a cross-sectional view of the optical film structure taken along line 'XV-XV' of FIG. 14 .

FIG. 16 is a plan view showing an example in which the optical film fixing method shown in FIGS. 14 and 15 is applied to a corner.

Summary of the invention

According to an aspect of the present invention, there is provided an optical film structure disposed on a light transfer surface of a lighting unit for modulating light emitted from the lighting unit and projecting the modulated light, the structure comprising at least one optical film ; at least four optical film holders disposed on the peripheral portion of the optical film; a film tension control member, one end of which is connected to each film holder in such a manner that the optical film can be pulled under tension. film while maintaining the flatness of the optical film; and, a film fixing frame for fixing the optical film connected to the other end of the film tension control member; wherein the optical film, the film tension control member and the film fixing frame are mutually integrated and constitute a component.

According to another aspect of the present invention, there is provided a lighting fixture comprising a lighting unit comprising at least: at least one light source and a light transfer surface for outwardly guiding light from the light source; An optical film structure according to the present invention on the light transmitting surface.

According to still another aspect of the present invention, there is provided a liquid crystal display device comprising an illumination unit, the illumination unit at least comprising at least one light source and a light transfer surface for outwardly guiding light from the light source;

The optical film structure according to the present invention is disposed on the light transmission surface of the lighting unit; and, the optical film structure disposed on the liquid crystal display device.

Detailed description of the invention

Preferred embodiments of the present invention will be described in detail below. However, it should be noted that the present invention is by no means limited to the following examples.

In the practice of the present invention, it is not particularly limited to a liquid crystal display as long as the optical film according to the present invention is constructed in its lighting unit. Therefore, according to the liquid crystal display of the present invention comprises:

a lighting unit having at least one light source, the lighting unit having at least one light transfer surface for guiding light from the light source to the outside;

an optical film structure according to the present invention disposed on the light transfer surface of the lighting unit; and

A liquid crystal display unit arranged on the optical film structure.

The lighting unit and the liquid crystal display unit may each be of a well-known type in this technical field.

Liquid crystal display devices can be classified into a transmission type liquid crystal device and a reflective or semi-transmissive type liquid crystal display device according to an illumination system. These liquid crystal display devices can be properly used by bringing about most of the characteristics of the corresponding types. Since the present invention exhibits excellent work and effects in terms of the optical film structure employed when the optical film structure is constructed within a liquid crystal display device, the present invention can properly provide a larger transfer type liquid crystal display device.

A transfer type liquid crystal display device includes a liquid crystal display cell having a pair of transparent substrates with liquid crystal interposed therebetween. A lighting fixture, a so-called "backlight unit" as a rear surface light source, is provided behind the liquid crystal display unit. When the backlight in this type of liquid crystal display device is switched on, the image displayed on the liquid crystal panel can be seen from the front surface of the panel. Lamps such as cold cathode fluorescent tubes are used for backlighting. In this transfer type liquid crystal display device, backlighting consumes most of the power. For this reason, the backlighting must remain electrically switched on. Therefore, the backlight is widely used in desktop and notebook personal computers to which power is easily applied.

In particular, in a transmission type liquid crystal device using backlight illumination, light emitted from a backlight provided behind a liquid crystal display panel usually passes through a polarizer and is linearly polarized so that a display can be produced from the thus polarized light. Because ordinary backlights are unpolarized light, polarizers are often used to obtain linearly polarized light. However, the light absorption of the polarizer used here exceeds 50%. In order to reduce this absorption and obtain a bright screen, it is necessary to increase the illuminance of the lighting equipment. In order to meet the demand for improved illuminance, for example, a light source with increased optical power can be used, but in this case there arises the problem of increased power consumption and more heat generation. Because of the above, especially in portable devices such as notebook personal computers, this problem is serious, and countermeasures must be taken. Therefore, the increase in power consumption shortens the battery life, and the increase in heat generation causes a decrease in reliability and life.

There is another reason why it is difficult to increase the illuminance. In order to meet the requirements of saving power and space, the diameter of the lamp is reduced, and a wedge-shaped guide plate is used to reduce thickness and weight. According to the structure of this type of light guide, it is difficult to increase the illuminance at the same time. Another problem arises that handling and assembly are difficult because the shape of the components in this type of guide plate is small and complicated.

In order to solve the problem of increasing illuminance and other optical problems, the liquid crystal display device according to the present invention adopts an optical film on the front surface of the backlight unit or in other words on the rear surface of the liquid crystal display unit, and by using the film fixed The system for fixing the optical film in the liquid crystal display device includes a combination of (1) a film fixing member, (2) a film tension control member and (3) a film fixing frame as will be described in detail later.

The invention makes it possible in particular to constitute a lighting fixture by fitting at least one optical film under tension to a lighting unit by means of the specific film fixing system according to the invention. Accordingly, liquid crystal display devices can provide, for example, the following significant advantages, which will be explained in further detail below:

(1) A film having a large illuminance improving effect which cannot be used in the past can now be used for a large-sized liquid crystal display device and a film structure having a higher illuminance improving effect can be obtained.

(2) It is now possible to use a film with a high illuminance improvement effect that was used alone for a large size and for a medium size independently of the size, and it is possible to provide a film structure (combination of optical films) with a large degree of freedom .

(3) Since the light diffusion film is used instead of the polypropylene diffusion plate, it is possible to provide a diffusion layer of all sizes without deformation and also to reduce the weight.

(4) Since a plurality of optical films can be combined, subsequent steps can be simplified and made more efficient, and a protective film can also be eliminated.

In the practice of the present invention, the optical film used to form the optical film structure is not particularly limited, but the optical film can be used arbitrarily according to the optical characteristics required in the lighting and liquid crystal display of the present invention. In this case, the optical film may be used alone or in any combination of two or more films. Suitable examples of the optical film include, but are not limited to, films having light-diffusing properties (hereinafter referred to as "light-diffusing films"), films having light-reflecting properties (hereinafter referred to as "light-reflecting films"), films having illuminance improvement Effect films (hereinafter referred to as "illuminance improvement film", films with polarizing properties (hereinafter referred to as "polarizing film") and films with a combination of two or more properties of these optical films (hereinafter referred to as "multiple Functional film").

One or a combination of two or more of these optical films can be used, for example as an optical film structure for a lighting unit of a liquid crystal display device, preferably between the backlight lighting unit and the liquid crystal display unit, on the former .

Single layer structure (using one optical film):

When an optical film is used to form an optical film structure, a light diffusion film, an illumination improvement film (such as a prism film), a polarizing film (such as a reflective polarizing film) or a composite film can be used or two or more of these films can be used. Functional multifunctional optical film.

When using a lighting unit employing a light guide, for example, when the light guide is used in combination with a light diffusing surface of the lighting unit, a light diffusing film or a composite film of a light diffusing film and an illuminance improving film can be used. A vertical type backlight lighting unit equipped with a light guide formed of a polypropylene diffusion plate on its light diffusion surface is a typical example of this lighting unit. By the way, when there is no polypropylene diffuser plate in this lighting unit, the optical film is limited to the light diffuser film or its composite film.

Double-layer structure (using two optical films):

When the optical film structure is constituted using two optical films in combination, an optical film similar to the optical film of the single-layer structure described above can be used as the film on the lighting unit side. The film on the liquid crystal display unit side may be a light-diffusing film, an illuminance improving film such as a prism film, a polarizing film such as a reflective polarizing film, or a composite film thereof.

Three-layer structure (using three optical films):

When the optical film structure is constituted using three optical films in combination, an optical film similar to that used in the single-layer structure can be used as the optical film on the lighting unit side. The intermediate film may be a light-diffusing film, an illuminance improving film (eg, a prism film), a polarizing film (eg, a reflective polarizing film), or a composite film thereof. These films can also be used as the film on the liquid crystal display unit side. However, when a reflective polarizing film is used for the intermediate film, a light-diffusing film is used for the film on the liquid crystal display unit side. The light-diffusing films used in this case are limited to those that do not damage (deflect) the phase of light rays reflected by the reflective polarizing film used as the intermediate film. For this reason, a prism film that would damage the phase of deflected light cannot be used on a reflective polarizing film.

Multi-layer structure (using four or more optical films):

Four or more optical films can be used in combination to form an optical film structure. Here, film combinations similar to those described above up to the three-layer structure can be used. The following are several four-layer structure combinations, which are by no means limiting.

(1) A light-diffusing film, a light-diffusing film, a prism film, and a prism film listed in order from the lighting unit side.

(2) A light-diffusing film, a prism film, a prism film, and a light-diffusing film listed in order from the lighting unit side.

(3) A light-diffusing film, a prism film, a prism film, and a reflective polarizing film listed in order from the lighting unit side.

(4) A light-diffusing film, a prism mold, a reflective polarizing film, and a light-diffusing film listed in order from the lighting unit side.

Although a combination of five or more layers is not described here, a layer combination of five or more layers can be used in combination on the basis of the same concept as described above.

In the case of a vertical type backlight lighting unit without a polypropylene diffuser plate, a combination of light diffusing film, light diffusing film, prism film, and reflective polarizing film listed in order from the side of the lighting unit can be used, or listed in order from the side of the lighting unit Light diffusing film, light diffusing film, light diffusing film, prismatic film and reflective polarizing film.

In the above combinations, composite films or multifunctional films can also be used. In the case of the vertical type lighting unit, the size is larger. Therefore, a composite film obtained by providing diffusion properties and rigidity to a reflective polarizing film (a film obtained by bonding a light-diffusing film to both surfaces of the reflective polarizing film) can be favorably used.

When two or more optical films are used in a laminated or stacked state, the optical films may be stacked with or without a gap therebetween. It is generally preferred to stack the optical films with a small gap between them and secure them to the film holding frame. Here, the gap between the optical films can be changed in a wide range according to the optical system required in the optical film structure, but generally in the range of about 0.3 to 2.0 mm, preferably in the range of about 0.5 to 1.0 mm Inside.

Each optical film used in the practice of the present invention will be further explained.

The light-diffusing film is generally a film having a diffusion surface treatment in which a matte treatment or an embossing treatment is applied to a polymer film. Other diffuse surface treatments can also be used, such as sandblasting or having many fine bumps on the surface. Also, a light diffusing surface can be formed by internally dispersing diffusing particles such as _TiO2 .

It can be obtained from compositions containing polycarbonate resins, polypropylene resins, polyester resins, epoxy resins, polyurethane resins, polyamide resins, polyolefin resins, silicone resins (including modified silicones such as silicone polyurea), etc. A number of molding methods form light diffusing films. Specific examples of the light-diffusing film include a light-diffusing film "Opals series", a product of Keiwa Corporation.

A light-diffusing film of arbitrary thickness can be used depending on the purpose of use, but should generally be selected so as to reduce the thickness and weight of the liquid crystal display device. Therefore, the thickness of the light diffusion film is generally in the range of about 5 to 1,000 microns, preferably in the range of about 5 to 500 microns, and more preferably in the range of about 5 to 200 microns. The thickness of the light diffusing film is optimally in the range of about 5 to 150 microns.

An illuminance improving film generally in this technical field can be used as the illuminance improving film. A typical illuminance improving film is an illuminance improving film having a prism shape (prism film). Specific examples of prism films that can be used in the practice of the present invention include illuminance improving films "BEF II series", "BE III series", "RBEF series" and "NBEF series" (trade names), products of 3M Company.

It is also possible to employ an illuminance improving film of any thickness according to the purpose of use. Generally, the thickness of the illuminance improving film should be selected in such a way as to reduce the size and weight of the liquid crystal display device, and the thickness of the illuminance improving film is usually in the range of about 5 to 1,000 microns, preferably in the range of about 5 to 500 microns, It is further preferably in the range of about 5 to 200 microns.

A film having reflective polarizing properties can be used for the illuminance improving film. Reflective polarizing films are generally polarizing films capable of transmitting light in a direction of vibration parallel to an in-plane axis (transmission axis) but capable of reflecting other light rays. In other words, this film transmits only the light component in the vibration direction parallel to the above-mentioned transmission axis among the rays incident on the polarizing film, showing polarization operation. However, unlike the light-absorbing polarizing plate of the related art, the light that does not pass through the polarizing film is substantially not absorbed by the polarizing film. Therefore, the light once reflected by the polarizing film can be returned to the light source side, and, in turn, can be directed toward the reflective polarizing film by a reflective element provided on the light source side, such as a light reflection film. Of the rays thus returned, only the light component in the vibration direction parallel to the transfer axis is transferred, the rest is reflected again. The repetition of this transfer-reflection operation can increase the intensity of the transmitted polarized light. Specific examples of this reflective polarizing film are "DBEF series" and "DRPF-H series" (trademarks), products of 3M Company. A circular polarizing element can be used instead of this linear polarizing element. An example of a circular polarizing element is a Cholesteric circular polarizing element commercially available from Nitto Denko K.K. under the trade name "Nipocs".

A reflective polarizing film of arbitrary thickness can also be used according to the purpose of use. Generally, the thickness of the reflective polarizing film should be selected to reduce the size and weight of the liquid crystal display device, and the thickness is usually in the range of about 15 to 1,000 microns, preferably in the range of about 30 to 500 microns, and more preferably ground in the range of about 50 to 200 microns.

The optical films specifically described above and other optical films useful for the practice of the invention can be used in any shape and any size in the same manner as their thickness. For example, the optical film may have any shape including circle, ellipse, polygon, etc., but usually and preferably has a rectangle (square or rectangle). The area of this optical film includes a small area to a large area, depending on the purpose of use of the optical film structure, generally in the range of about 1 square centimeter to 2.0 square meters. In the practice of the present invention, the film fixation system used in combination with optical films has been shown to work most effectively when the area of the optical film is larger. Therefore, deformation and warpage of the film can be prevented while maintaining the straightness of the film surface. Therefore, it is recommended to use an optical film with a larger area. For example, the area of the optical film used in the present invention in conjunction with the preferred screen size of a liquid crystal television unit is typically from about 15 to 20 inches or more. In the case of this large-screen TV unit, a vertical backlight unit is generally used as its lighting unit. When the optical film structure is used on the backlighting unit, disadvantages such as non-uniform diffusion of light, deformation and warping of the film, etc. do not occur. The inventors of the present invention have confirmed that the optical film shows excellent effect in a television unit having a screen size close to 37 inches.

The use of the optical film will be further specifically explained. In the liquid crystal display device according to the present invention, the polarizing film may be provided as an optical film on the light exit surface (light transmission surface) of the backlight unit. A reflective polarizing film may be used instead of the polarizing film. Reflective polarizing films are linear polarizing elements such as multilayer reflective polarizing films (eg, "DBEF series" (trade name)) and single-layer diffuse reflective polarizing films (eg, "DRPF-H series" (trade name)). Needless to say, this linear polarizing element may be replaced with or combined with a general beam reflecting element such as an illuminance improving film (for example, "BEF system" (trade name)) when necessary. In the liquid crystal display device according to the present invention, polarizing films or a combination of polarizing films and light reflection elements are used for backlighting fixtures, and these films are fixed to the film fixing frame of the film fixing system according to the present invention. Therefore, the present invention can provide a thin polarized light source that is excellent in light utilization efficiency and has no film fixation problem. Alternatively, the polarizing film may be a circular polarizing element and may be a cholesteric circular polarizing element commercially available from NittoDenko K.K. under the trade name of "Nipocs".

Specifically, polarizing films such as DBEF and DRPF-H transmit P-polarized light and reflect S-polarized light. Although the S-polarized light thus reflected is repeatedly reflected between the guide plate of the lighting unit and the light reflection member provided near the guide plate, the polarization is eliminated every time the S-polarized light passes through the diffusion plate. Therefore, a part of the S-polarized light is converted into P-polarized light and is effectively utilized and passed through the polarizing film again. When a multilayer reflective film is used as the light reflective element associated with the guide plate during this multiple reflection, light attenuation due to reflection can be minimized and the polarizing film can work efficiently.

DBEF and DRPF-H used as polarizing films in the prior art have problems of deformation due to heat or other factors given to the film for some reason and unevenness of illuminance due to film deformation. Such problems can however be avoided when using the membrane fixation system according to the invention.

When DRPF-H and other polarizing films are used instead of DBEF, since DRPF-H emits white reflected light and has a single-layer structure, it is possible to provide a polarized light source emitting only P-polarized light without color unevenness and color development.

Preferably, the optical film detailed above is provided in the form of an optical film structure incorporating (1) a film fixing member, (2) a film tension control member and (3) a film fixing frame. This optical film structure can be advantageously used as a member of a lighting fixture for a liquid crystal display device and its operation and effect can be sufficiently exhibited.

The optical film structure according to the present invention comprises:

the above-mentioned at least one optical film;

at least four film fixing members respectively disposed at peripheral portions of the optical film;

a film tension control member attached to each film holder in such a manner that one end of the member is pullably attached to the film holder under tension while maintaining the straightness of the optical film; and

The film fixing frame is used for fixing the optical film, and the other end of the film tension control member is connected to the film fixing frame.

In this optical film structure, the optical film, the film tension control member and the film fixing frame are preferably integrated with each other as a member.

The optical film structure according to the present invention uses a film fixing member as a structure for fixing the film to the film fixing frame. The required number of film mounts is typically discreetly fitted to the peripheral portion of the optical film in such a way that it does not interfere with the light path of the optical film. The number of fixing members and their fitting positions are not particularly limited. However, usually at least four fixing members are used, which must be fitted to the four corners of the optical film. When the size of the optical film becomes larger, the number of film fixing members can be increased in a manner corresponding to the increase in size. When using a large number of film holders for each optical film, it is recommended to install the film holders at the appropriate positions of the optical films, taking into account the balance so that the optical film can be under tension in the resulting optical film structure without Causing slack and warping.

Membrane mounts can be manufactured from many materials by processing methods such as molding, casting and machining. Suitable examples of materials for the film fixing member include, but not limitatively, resin materials such as polypropylene resin, metal materials such as aluminum and stainless steel, and other materials. These film holders can be used in a variety of forms, but the size is preferably as small as possible. Therefore, the film holder is preferably a small piece having a short shape or other shape.

The film fixing member may be installed on one of the surfaces of the peripheral portion of the optical film. When the holding of the optical film and the installation of the film tension control member are still unstable, the film fixing member may be installed on both surfaces of the optical film. A number of fastening methods can be used for mounting membrane fastenings. The usual method is to use a binder. A polypropylene type adhesive or a urine melt type adhesive each having a higher adhesive strength may be used. Methods of stamping, fitting, push fit, etc. may be used instead of or in combination with adhesives. For example, a U-shaped film holder is prepared, the end of the optical film is inserted into the gap in the center, and then the film and the film holder are pressurized to form an integral body combining the film holder and the optical film.

Then install the film tension control member on the film fixing member installed on the optical film. The membrane tension control member is generally a longitudinally elongated member, one end of which is mounted to each of the membrane holders as described above. The optical film must be at least pulled under tension while maintaining its straightness, for which purpose this film tension control is attached to the optical film (or a film holder attached to the optical film). In the case where this step is omitted, problems of warping and deformation of the optical film will occur.

The membrane tension control member can be formed from many materials, but is preferably formed from a flexible material. A number of flexible materials can be used for the membrane tension control member. In general, however, viscoelastic wire materials such as springs, piano wire, rubber and other wire materials may be used to advantage. The membrane tension control member may be directly mounted to the membrane holder or indirectly mounted to the membrane holder through a connection structure such as a wire.

When the film tension control member having a wire shape is mounted on the film fixing member, a V-shaped groove in which the wire material can be fitted is formed in advance in the surface of the film fixing member, and after the wire material is embedded in the V-shaped groove, by bonding The agent immobilizes the membrane tension control member. Advantageously, the V-groove side of the film holder is both in contact with the optical film and bonded by an adhesive, so that the film tension control member can be securely fixed to the film holder.

It is also possible to set the piano wire at a predetermined position of the membrane fixing member while applying tension by screw fixing or the like. In this case, a wire installed as a connecting structure to the membrane fixing member is wound and fixed. The portion of the piano wire to which tension is applied can function as a membrane tension control member.

The other end of the film tension control member is connected to the film fixing frame, so that the optical film is fixed to the film fixing frame. The membrane retaining frame is generally shaped in the form of a surrounding peripheral portion and can be formed from a number of materials. Suitable examples of the membrane fixing frame, though not limiting, include materials such as polypropylene resin, polycarbonate resin, metal materials such as aluminum, stainless steel or steel, and the like. It is preferred to utilize light weight materials.

The membrane fixing frame preferably has a sufficiently high mechanical strength in addition to its light weight. Therefore, in order to produce the film fixing frame, it is preferable to reduce the thickness as much as possible, but it is necessary to secure the strength. In other words, it is recommended to add a reinforcing portion such as a rib to the membrane fixing frame or adopt a double-wall structure for the wall portion. Portions of the membrane fixing frame that are not considered to add strength may be cut away when necessary. The membrane fixing frame may be formed using any of methods such as molding, casting, machining or the like. When the membrane fixing frame is formed of a metal material such as bent and cast metal material, a membrane fixing frame having a rigid structure can be obtained. Only the fixing frame may be separately produced and then assembled into the liquid crystal display device, and it is also possible to utilize a cast frame portion for accommodating the light source portion of the liquid crystal display device as the fixing frame.

The membrane tension control member can be attached to the membrane holding frame in a number of ways. For example, as described above, the piano wire can be attached to the membrane fixing frame by welding, gluing, or the like. When the membrane tension control member is a screw or a spring, the membrane tension control member can be mounted on the membrane fixing frame by welding or screw fixing. It is also possible to form a loop in advance at the end of the membrane tension control member and hook a pin or other protrusion previously formed in the membrane fixing frame into the loop.

Preferably, the optical film structure according to the present invention is used while the optical film structure is disposed on a light transfer surface of a lighting unit substantially comprising at least one light source and a light transfer surface for guiding light rays emitted from the light source toward the outside . In this case, the present invention provides a lighting fixture. According to another aspect, the present invention provides a liquid crystal display device when the optical film structure is used between the liquid crystal display unit and the lighting unit. None of the lighting unit of the lighting fixture, the lighting unit of the liquid crystal display device, and the liquid crystal display unit is particularly limited. As will be understood from the following detailed description, a conventional lighting unit and a conventional liquid crystal display unit can be used as the lighting unit and the liquid crystal display unit, or they are modified in an arbitrary manner as the lighting unit and the liquid crystal display unit.

In the device shown according to the invention, the lighting unit comprises at least one light source and a light transfer surface for directing light rays from the light source outwards. Here, the lighting unit is preferably an edge light type backlight lighting unit or a vertical type backlight lighting unit. The vertical type backlight lighting unit is particularly preferable when using a lighting fixture for a large-screen liquid crystal display device of 20 inches or more.

The edge-lit type backlighting unit preferably includes the following components, for example:

(1) at least one light source,

(2) a light guide having a major surface for directing light incident through a side surface outwardly with substantially uniform illumination and having a light source adjacent the side surface; and

(3) A light reflection element (light reflection element) formed of an insulating material, which is arranged to surround the light source and capable of guiding light emitted from the light source into the side surface.

One or more light sources may be provided as a first component on only one side of the light guide, which is generally rectangular, as commonly used in lighting fixtures such as backlight and front light fixtures . Alternatively, one or more light sources may be provided on opposite side surfaces of the light guide. Light sources can sometimes be provided on all four sides of the light guide.

A wide variety of light sources of different sizes and shapes can be used in the practice of the invention. However, when considering the application of lighting fixtures as lighting devices for display devices such as liquid crystal liquid crystal display devices, linear light sources such as fluorescent lamps, especially cold cathode ray tubes or point light sources such as light emitting diodes (LEDs) can be advantageously used . Especially when point light sources are used, a sufficient number of light sources are arranged in a row on the side surface of the light guide to achieve the required illuminance, or rod-shaped light guides (such as glass rod), and light sources are provided at both ends of the light guide. Examples of light sources that may be utilized other than cold cathode ray tubes and LEDs include, but are not limited to, hot cathode ray tubes and electroluminescent (EL) devices. It is also possible to use different types of light sources in combination when necessary.

The light guide as the second component is generally rectangular and can advantageously be employed in the form of a guide plate. The light guide can be wedge-shaped as is commonly used in this technical field and serve as a wedge-shaped guide plate. When a wedge-shaped guide plate is used, the number of light sources may be only one and the guide plate is shaped in such a manner that the thickness decreases from the side surface near the light source to the opposite side surface.

When using the lighting fixture according to the present invention as a backlight in a reflection-type or semi-transmission-type liquid crystal display device, it is preferable to form sawtooth protrusions, slopes or slopes of steps or grooves on the light-extracting surface of the light guide and The light incident on the inclined portion is reflected toward the other opposite surface (bottom surface).

Any materials can be used for the light guides as long as they do not have a detrimental effect on the light guiding effect. However, when processability is considered, many plastic materials such as polypropylene resin, polycarbonate resin, polyolefin resin, epoxy resin and polystyrene resin can be used. Inorganic materials such as glass can be used instead of these plastic materials when necessary.

The third component is a light reflective element arranged for use around the light source. The light reflecting member may have any shape as long as it allows the light emitted from the light source to efficiently enter into the side surface of the light guide. However, when compactness and moldability are considered, it is preferable that the light reflecting member is in a semi-cylindrical shape or a groove shape. It is thus advantageously possible to use light reflective elements in the form of lamp reflections in the same way as in the prior art. Incidentally, when forming a lamp reflector, it is advantageous to use a reflective film formed of an insulating material and substantially free of metal components without the aluminum vacuum sprayed film used in prior art lamp reflectors. Or silver vacuum spray coating. Because the reflective film has insulating properties, it does not have the problem of prior art films accepting leakage current from the light source, and because the film does not substantially reduce the illuminance of the light source. The reflective film is preferably formed of an insulating material capable of guiding light from the light source into the side surface of the light guide with a reflectance of at least 98%.

Preferably, the reflective film serving as the light reflective element is usually formed of a multilayer reflective film. The multilayer reflective film is, for example, a multilayer film of polyethylene terephthalate (PEN) and its copolymer (coPEN) or a multilayer film of PEN and syndiotactic polystyrene (sPS). This multilayer reflective film can be used in an appropriate shape when it has self-supporting properties. Alternatively, a suitable support formed into the shape of the reflector is prepared and the reflective film may be bonded or laminated on the inside of the support. Bonding or lamination of multilayer reflective films can utilize adhesives or double-sided adhesive tapes.

As described above, the lighting fixture according to the present invention can be advantageously used as backlighting in liquid crystal display devices and other display devices. Therefore, the lighting fixture according to the present invention preferably has a light reflection member formed of a multi-layer reflective material as a fourth component.

When the lighting fixture according to the present invention is used as backlighting, it is preferable that the light reflector is arranged on the side surface of the light guide other than the side surface with the light source in the vicinity, and more preferably on all the remaining ones of the light guide. on the three side surfaces and on the bottom surface. In order to distinguish this light-reflecting member from the above-mentioned light-reflecting element, it is specifically called “light-reflecting member”. The light reflection member may be formed of any material as long as the material can exhibit the desired light reflection function. However, when an excellent performance advantage is considered, it is preferable to form the light reflection member from a multilayer reflection film in the same manner as the light reflection member. Examples of suitable multilayer reflective films include multilayer films of polyethylene terephthalate (PEN) and its co-extrusion (coPEN) or multilayer films of PEN and syndiotactic polystyrene (sPS) . For the use of a multilayer reflective film, see Japanese National Application (Kohyo) No. 9-511844.

In the lighting fixture according to the present invention, the light reflecting unit and the light reflecting member are formed of the same material, especially a multilayer reflective film, and the multilayer reflective films integral with each other. This structure can make the lighting appliance compact, reduce the number of components and simplify the production process. Also, the resulting strength can be improved. Especially since the multilayer reflective film does not need to be cut into many small pieces to fit the shape of each part, handling becomes easier and obtaining components and assembling becomes easier. After a sheet of multilayer light reflective film is prepared and initially cut into a predetermined shape, the film is used to cover the light guide to produce light reflective elements and light reflective members. When the light reflection member itself does not have a predetermined degree of shape retention performance, bonding of the light reflection member to the light guide can be performed by using an adhesive, a tackifier, or a double-sided adhesive tape. The light reflector bonding surface of the light reflector to the light guide can be carried out by applying adhesives, tackifiers or double-wrapped adhesive tapes, each of which is optically transparent or in other words each of which has a relatively high transmission coefficient. Part or all of the bonding. In order to minimize reflections at the bonding interface, the bonding may be performed by using an adhesive having a refractive index close to that of the light guide. When the light guide is a polypropylene guide plate, eg a polypropylene type adhesive may advantageously be used.

In addition to the combination parts described above, the lighting fixture according to the present invention may optionally include one or more additional components. An example of a suitable additional component is a light diffusing layer. The light diffusion layer is disposed on the bottom surface of the light guide, and effectively promotes the diffusion of light inside the light guide and produces uniform diffusion. The light-diffusing layer can be formed into many patterns (eg, stripe patterns, dot patterns, etc.) by white pigments containing organic or inorganic materials such as silica, barium sulfide, titanium oxide, glass beads, etc. as light-diffusing particles. In order to form this light diffusion layer, a printing method such as a screen printing method can be advantageously used.

The lighting fixture according to the present invention has been described above as a typical example for an edge-light type backlight unit. By the way, a vertical type backlight unit can basically be constituted in the same manner as an edge-light type backlight unit, However, the setting position of the light source is different. Therefore, detailed description will be omitted here.

The present invention also provides a liquid crystal display device or other display device characterized in that a lighting fixture is equipped with the backlight lighting unit according to the present invention as a rear surface light source.

The liquid crystal display device according to the present invention may have any structure conventional in this technical field. In the case of a transmission type liquid crystal display device, for example, the lighting fixture according to the present invention may be provided as a rear surface light source on the rear surface of a liquid crystal panel having a structure in which liquid crystal is sandwiched by polarizing plates on both sides. Structure. In the case of a semi-transmissive type liquid crystal display device, also, the lighting fixture according to the present invention is provided as a rear surface light source on the rear surface of the liquid crystal panel. The liquid crystal panel itself is not particularly limited in the present invention, and liquid crystal panels are well known to those skilled in the art. Therefore, detailed description will be omitted here.

Liquid crystal displays according to the invention can be advantageously used for display purposes in many household appliances, measuring and other appliances. Application examples of the liquid crystal display according to the present invention, but they are not limiting, include from compact displays such as mobile phones, mobile information terminals, video cameras, digital cameras, etc. to large-sized displays such as personal computers and television receivers . The functions and effects of the present invention can be best exhibited when used for a large-sized display having a display area of 20 or 30 inches or more where deformation and warpage of the optical film may occur.

The lighting fixture according to the present invention can exhibit its excellent functions and effects in fields other than liquid crystal display devices. The lighting fixture can advantageously be used as a front lighting fixture when photographs or printed items are placed under the lighting fixture instead of a liquid crystal display. The lighting fixture of the present invention can be used as a light source of a projector (OHP) by modifying its design. Also, the lighting fixture of the present invention can be used as an optical monitor of various measuring instruments and monitors.

[example]

As noted above, the present invention can be advantageously carried out in a number of embodiments. Accordingly, several examples of the invention will be described with reference to the accompanying drawings. However, it should be understood that the present invention is not limited to the following examples.

1 is an exemplary cross-sectional view showing a transfer type liquid crystal display device according to an embodiment of the present invention and FIG. 2 is a perspective view of a backlight unit used as a rear surface light source in the liquid crystal display device shown in FIG. 1 .

As shown in FIG. 1, the liquid crystal display device 20 has a liquid crystal panel 21 including a liquid crystal cell 22 and polarizing plates 23 and 24 sandwiching the liquid crystal cell 22 from above and below. The liquid crystal display device 20 is provided with an illuminating device of the present invention and an optical film structure comprising a backlight illuminating unit 10 disposed on the non-display surface side of the liquid crystal panel 21, the optical film structure comprising an optical film 5 and an optical film structure. is provided on the backlight unit 10 . The optical film 5 includes a light diffusing film 5-1 at the lower part and an illuminance improving film 5-2 at the upper part. The optical film 5 is combined with a film fixing member, a film tension control member and a film fixing frame not shown in the drawing to form an optical film structure. The optical film 5 is fixed to the film fixing frame and to the housing of the backlight unit 10 under tension. The backlight unit 10 has a diffuser plate 7 on its light-transmitting surface. Since the structure of the liquid crystal panel 21 is known from many references, its detailed description will be omitted.

As shown in Fig. 2, the backlighting unit 10 includes a rectangular light guide plate 2, light sources 1 arranged near opposite side surfaces of the polarizing plate 2, lamp reflectors 3 arranged to respectively surround the light sources 1, and light reflectors 3 arranged on the guides. Multiple layers of reflective films 4 on the upper and lower surfaces of the side surfaces (two opposite side surfaces) without light sources of the board 2 . The rectangular plate 2 has a dotted light-diffusing layer 5 on the entire bottom surface.

In the backlight unit 10 shown in the drawings, the rectangular light guide plate 2 is formed of a polypropylene resin plate as is usual in this technical field. The light sources 1 provided on both side surfaces of the light guide plate 2 are cold cathode ray tubes of the fluorescent tube type and have almost the same length as the side surfaces. The lamp reflector 3 surrounding each light source 1 is a reflection film, specifically a multilayer reflection film, formed of an insulating material having a high light reflection performance of 98% or more. The reflective film is bonded to the inner surface of a suitably shaped support with an adhesive. The same multilayer reflective film 4 as that used for the lamp reflector 3 is fitted to the remaining side surface of the light guide plate 2 . However, a support is not used therein, and a transparent adhesive is directly bonded to the film. The adhesive is applied to the entire surface of the multilayer reflective film, but depending on circumstances, the adhesive may be applied to a part of the surface or a double-sided adhesive-coated tape may be used instead of the adhesive.

3 is a plan view showing a lighting fixture according to a preferred embodiment of the present invention, and FIG. 4 is a cross-sectional view taken along line 'IV-IV' of the lighting fixture shown in FIG. 3 . As can be understood from these two drawings, the lighting fixture of the present invention includes a vertical type backlight unit having a plurality of light sources 1 arranged on An optical film structure 30 of the invention. The vertical type backlight lighting unit 10 includes a light diffusion plate 7 for allowing light emitted from a light source to be uniformly transmitted to the outside of the lighting unit. As explained above with reference to FIG. 1 , an unillustrated liquid crystal display unit is also provided on the optical film structure 30 .

The vertical type backlight unit 10 is a schematically shown example. The actual backlight unit may have members other than those shown in the drawings or structures other than those shown in the drawings. For example, the light source 1 may have many forms as mentioned in the paragraph of the edge light type backlight lighting unit. In view of strength and moldability, the casing 11 utilizes a casing formed of cast aluminum, but may be formed of other metal materials and resin materials. The shape of the casing 11 may be changed at will in consideration of improving strength. The wall portion may have a double-wall structure or ribs may be formed on the wall as in the modification of the case.

In the illustrated case, the optical film structure 30 has an optical film 5 having a double-layer structure of a lower light diffusion film 5-1 and an upper illuminance improvement film 5-2. The gap between the two optical films is about 0.8 mm. A film holder is mounted on the periphery of each optical film. In the example shown, a total of 26 film holders were installed to prevent deformation of the optical film and to ensure secure fixation. As will be described below with reference to FIG. 9 , when a sufficient effect can be obtained, the film fixing members may be fixed only to four corners of the optical film.

The film fixing member is not particularly limited, and the fixing member may be formed in an arbitrary shape from a resin material or a metal material such as aluminum. In the example case, the membrane fixing member 16 is formed of a resin plate having a V-shaped groove about 0.3 mm deep at the center of one of its surfaces, the thickness of the plate being about 0.5 mm, constituting the membrane tension control A wire 17 of a part of the member fits in the V-shaped groove, and the film fixing member is fixed to the optical film 5 by an adhesive (not shown).

When a metal plate such as an aluminum plate is used as the film fixing member, the film fixing plate 26 can be fixed as shown in FIG. 6 . First, for use as a membrane fixing member, a 0.5 mm thick aluminum plate having a V-shaped groove about 0.3 mm deep at the center of one of the surfaces was first prepared. After the wire 17 constituting a part of the membrane tension control member is set in the V-shaped groove, the wire 17 and the membrane fixing member 26 are fixed with an adhesive 19 . Second, the surface of the aluminum plate opposite to the surface having the V-shaped groove and the optical film 5 are bonded together by an adhesive.

The film tension control member 17 mounted to the film holder 16 is for pulling the optical film 5 under tension while maintaining its straightness. Thus, the rest of the membrane tension control member 17, usually the flexible part with the membrane tension control mechanism, is contained within the membrane holding frame 18, although it is not shown in FIG. 4 . Examples of the flexible portion are a flexible constituent such as elasticity and a resin constituent such as rubber having viscoelasticity. The flexible part of the membrane tension control member 17 may be directly connected to the membrane fixing part 16 or 26, or connected to a connection structure such as a wire which may be further provided between the flexible part and the membrane fixing part.

The distal end of the film tension control member 17 is connected to the film fixing frame 18 so that the optical film can be stably fixed. Although not particularly limited thereto, the film fixing frame 18 is preferably formed of a material that is as light in weight as possible and excellent in strength. The shape of the membrane fixing frame 18 can also be changed at will. It is generally preferred to form the membrane retaining frame 18 from a metal such as aluminum or stainless steel through bending and casting process steps to provide a rigid structure. The shape of the film fixing frame 18 is preferably a box shape or a frame shape formed by removing unnecessary wall portions from the box shape. The film fixing frame 18 is usually attached to the housing 11 of the backlight unit 10, but may be attached to other members as necessary.

The examples shown in FIGS. 3 to 5 use a method of fixing the film fixing member 16 to one of the surfaces of the respective optical films 5-1 and 5-2. However, it is also possible to use a method of fixing the film fixing member 16 to both surfaces of the optical films 5-1 and 5-2, thereby firmly fixing the film fixing member to the optical film as shown in FIGS. 7 and 8 . The shown example uses a method of preparing a bracket-shaped film fixing member 16, inserting the end of the optical film into the gap, and fixing the optical film. Needless to say, two film fixing members can be abutted against each other and then bonded to each other by an adhesive, especially, the film fixing frame 18 is provided on the side surface of the housing 11 of the backlight unit. Therefore, this structure can satisfy the latest requirement that the width of the display frame be preferably as small as possible (typically from about 3 to 4 mm).

As can be understood from FIGS. 7 and 8, the flexible portion (spring) 37 of the membrane tension control member is accommodated in the box-shaped membrane fixing frame 18 and its ends are fixed. Furthermore, the flexible portion 37 is interconnected to the membrane holder 16 by the wire 17 .

The optical film structure 30 shown in FIG. 3 is representative of the optical film 5 with a total of 26 film holders. However, the film fixing members 16 may be fixed only to the four corners of the optical film provided that the optical film can be stably fixed to the film fixing frame 18 without causing deformation and warpage. As shown in Figure 9. In the case of the optical film structure shown, two film tension control members 17 are fixed to one film fixing member 16 , and the distal end of each film tension control member 17 is mounted to a film fixing frame 18 .

In the practice of the present invention, the mounting of the membrane tension control member 17 to the membrane fixing frame 18 can be performed in a number of configurations.

As shown in FIG. 10 , for example, a metal wire with a membrane tension control mechanism provided at one end thereof is prepared as the membrane tension control member 17 . The other end of the film tension control member 17 is fixed to the film fixing member 16 provided on the outer edge of the optical film 5 . The loop as one end of the membrane tension control member 17 is hooked on a pin 28 provided on the membrane fixing frame 18 . Due to the presence of the loop, the membrane tension control member 17 is flexible and movable.

Alternatively, the membrane tension control member 17 may be fixed to the membrane fixing frame 18 as shown in FIGS. 11 and 12 (sectional views taken along line XII-XII of FIG. 11 ). In this illustrated example, the hook portion (piano wire) 27 is fixed to the film fixing frame 18 by screws 27, and the wire 17 is fixed to the central portion of the piano wire 27. In this case, the portion of the piano wire 27 to which tension is applied functions as a flexible member.

In addition, the piano wire 27 as a flexible member can be installed in a bridging form to an open portion formed in the side surface of the membrane fixing frame 18 as shown in FIG. 13 . Since the film fixing frame 18 is formed of, for example, a steel metal material, the piano wire 27 can be securely fixed by welding or other processing.

The membrane tension control member 17 can be fixed to the membrane fixing frame 18 in a manner shown in FIGS. 14 , 15 (sectional views taken along line "XV-XV" of FIG. 14 ) and FIG. 16 .

In the example shown in the drawing, both end fixing members (aluminum plate) 16 are bonded to the peripheral portion so as to face each other in each of the optical films 5-1 and 5-2, constituting a part of the film tension control member. The distal ends of the wires 17 are supported by V-shaped grooves (not shown) mounted on the respective aluminum plates 16, so the wires 17 function as flexible members capable of accommodating extension and contraction of the optical film.

FIG. 16 shows the installation state of a corner membrane tension control member 17 on the membrane fixing frame 18 . The film tension control members 17 are also installed at the corners in the same manner as the straight portions shown in FIGS. 14 and 15 .

When the membrane tension control member is composed of a combination of piano wire and metal as described above, excellent tension control performance can be obtained, even when there is a slight extension and contraction of the optical film, the membrane tension control member works effectively in this way , that complement extension and contraction and prevent even minute deformation and warpage in the optical film.

As described above in detail, the present invention includes at least one, preferably two or more, optical films and can use each optical film in a thin film state. Therefore, the present invention can reduce the weight and maintain the flatness of the optical film. Therefore, the present invention can provide an optical film structure used in liquid crystal display devices and other display devices without causing warpage and deformation.

The present invention can also provide lighting fixtures having this excellent optical film structure and usable in liquid crystal display devices and other display devices.

The present invention can also provide a liquid crystal display device which is excellent in display performance associated with lighting, can reduce weight, does not need to separately use an optical film according to the film thickness of the device size, can reduce the number of components and It is possible to simplify the assembly operation of components during equipment production.

In addition to the remarkable effects described above, the present invention provides the following effects in liquid crystal display devices, such as:

It is possible to use a film with a high strength improvement effect that was not available before in a large liquid crystal display device, and it is possible to realize a film structure with a higher illuminance improvement effect;

It is possible to use a film with a high illuminance improvement effect previously used alone for large-sized and medium-sized liquid crystal display devices regardless of size, and can provide a film structure (combination of optical films) with a high degree of freedom;

By using a light diffusing film instead of a polypropylene diffusing plate can provide a diffusing layer without distortion for all sizes, and can also reduce weight; and

Since a plurality of optical films can be bonded together, subsequent manufacturing steps can be simplified and higher efficiency can be obtained and protective films can be eliminated.

Claims (10)

1. An optical film structure disposed on a light transfer surface of a lighting unit for modulating light emitted from said lighting unit and emitting modulated light, comprising: at least one optical film; at least four optical film holders disposed at the periphery of the optical film; a film tension control member attached at one end to each of said film holders in such a manner as to hold said optical film under tension while maintaining the flatness of said optical film; and A film fixing frame, which is used to fix the optical film, is connected to the other end of the film tension control member; Wherein, the optical film, the film tension control member and the film fixing frame are integrated with each other and constitute a member. 2. The optical film structure as claimed in claim 1, wherein the optical film is formed from a light diffusion film, a light reflection film, an illumination improvement film, a polarizing film, and a multilayer film having at least two functions of the film. One piece selected from a group consisting of functional optical films. 3. The optical film structure of claim 1 or 2, wherein the film tension control member is formed from an elastic material. 4. The optical film structure according to claim 3, wherein the elastic material is spring or rubber. 5. The optical film structure according to any one of the preceding claims, wherein the at least two optical films are stacked with or without a gap therebetween. 6. The optical film structure according to any one of the preceding claims, wherein the optical film structure is used between a liquid crystal display unit and an illumination unit of a liquid crystal display device. 7. A lighting fixture comprising: a lighting unit comprising at least one light source and a light transfer surface for directing light from said light source outward; and An optical film structure as claimed in any one of claims 1 to 5, which is provided on said light transfer surface of said lighting unit. 8. The lighting fixture according to claim 7, which is used as a backlight lighting unit on the rear surface of the liquid crystal display device. 9. A liquid crystal display device comprising: a lighting unit comprising at least one light source and a light transfer surface for directing light from said light source outward; An optical film structure as claimed in any one of claims 1 to 5, which is disposed on said light transfer surface of said lighting unit; and A liquid crystal display unit is arranged on the optical film structure. 10. The liquid crystal display device according to claim 9, wherein the lighting unit is a backlight lighting unit.

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