WO2007088797A1

WO2007088797A1 - Film for surface light source reflection member

Info

Publication number: WO2007088797A1
Application number: PCT/JP2007/051343
Authority: WO
Inventors: Yoshihiko Sakaguchi; Osamu Watanabe
Original assignee: Toray Industries, Inc.
Priority date: 2006-02-03
Filing date: 2007-01-29
Publication date: 2007-08-09
Also published as: JP5040647B2; CN101375185A; JPWO2007088797A1; TWI425251B; KR101331888B1; KR20080091128A; CN101375185B; TW200741256A

Abstract

A film for surface light source reflection member, consisting of a white film and having a difference of glossiness (60°) between one surface and the opposite surface, Δ G, satisfying the relationship Δ G>80. Thus, there is provided a film for surface light source reflection member that facilitates visual discrimination between a surface provided with a functionalized layer and its opposite surface to thereby realize enhancing of the productivity in the process of production of liquid crystal backlight.

Description

Specification

Surface light source reflective member film

Technical field

[0001] The present invention relates to a film for a light source reflecting member having a surface that is discriminated between one surface and the other surface. More preferably, the present invention relates to a film for a surface light source reflecting member that causes little decrease in luminance over time. Further, the present invention relates to a direct liquid crystal knock light for a liquid crystal display using the surface light source reflecting member film, a reverse prism liquid crystal backlight, and a lamp reflector for the backlight.

Background art

In a liquid crystal display, a backlight that illuminates a liquid crystal cell (hereinafter referred to as a liquid crystal backlight) is used. The LCD monitor uses an edge-light type LCD backlight, and the LCD TV uses a direct-type LCD backlight. As a film for a surface light source reflecting member (hereinafter referred to as a reflecting film) used for these liquid crystal backlights, a porous white film formed by bubbles is generally used (Patent Document 1). Further, a white film having an ultraviolet absorbing layer laminated has been proposed in order to prevent yellow discoloration of the film due to ultraviolet rays emitted by cold cathode tube force (Patent Documents 2 and 3). In addition, a white film is also proposed in which the glossiness on both sides of the film is controlled in order to provide adhesion (Patent Document 4).

Patent Document 1: Japanese Patent Application Laid-Open No. 8-262208

Patent Document 2: JP 2001-166295 A

Patent Document 3: Japanese Patent Laid-Open No. 2002-90515

Patent Document 4: JP 2005-125700 A

Disclosure of the invention

Problems to be solved by the invention

[0003] In many cases, a reflective film is used by being attached to an aluminum plate or a stainless steel plate in a liquid crystal backlight manufacturing process. In some cases, the lamp reflector does not use a metal plate, but a reflective film alone. In these manufacturing processes, functions are added to one side. Since the reflective film provided with such a layer is white on both sides, it is difficult to visually distinguish the surface provided with the function-imparting layer from the opposite surface. The difficulty of distinguishing these has caused problems such as extra time in the backlight manufacturing process and reduced productivity.

[0004] Particularly, in the case of a reflective film having a resin layer on one side containing a light stabilizer and Z or an ultraviolet absorber, the resin containing a light stabilizer and Z or an ultraviolet absorber is mistakenly caused by these problems. The surface with the layer may be stuck to an aluminum plate or a stainless steel plate. If it is applied by mistake, the surface without the light stabilizer and the resin layer containing Z or UV absorber will be exposed to the light of the cold cathode tube and deteriorate. As a result, the brightness of a product such as a liquid crystal television using the reflective film decreases with time during use, and a serious problem occurs.

[0005] In addition, in an inverted prism type liquid crystal backlight, which is a kind of edge light type backlight,

Since a reflective film with many regular reflection components is suitable for improving luminance, a reflective film having a high glossiness is required. On the other hand, when assembling the LCD knock light, the LCD backlight housing and the reflective film may come into contact with each other as shown in Fig. 2, and may be scratched. The notebook PC to which the edge-light type backlight is applied is regarded as light weight, and the liquid crystal backlight housing is also provided with a hollow space for light weight. In edge light type backlights, scratches on the reflective film can be seen through this cavity. A liquid crystal backlight with visible scratches has a problem that the yield is lowered because the quality of the finished product is lowered. In particular, the reverse prism type liquid crystal backlight uses a reflective film with high glossiness, and this problem is noticeable because it is easily noticeable if scratched.

Means for solving the problem

[0006] The present invention employs the following means in order to solve the hard problem.

That is, the film for a surface light source reflecting member of the present invention is composed of a white film, and the difference AG in gloss (60 °) between one surface and the other surface is AG> 80. It is.

[0007] Further, a preferred aspect of the film for a surface light source reflecting member of the present invention,

(1) The white film has a resin layer on one side and the light on the other side of the white film The degree (60 °) is 90% or more.

(2) The resin layer is a resin layer containing an ultraviolet absorber and Z or a light stabilizer.

(3) The heat shrinkage rate in the film longitudinal direction and film width direction after heat treatment at 90 ° C for 30 minutes is 0.1% or more and 0.2% or less.

(4) The white film is a three-layer structure consisting of A layer, ZB layer and ZA layer, B layer is a layer containing fine bubbles, and A layer contains polyester and inorganic particles and Z or organic particles. The particle content of which is not more than 0.5% by weight with respect to the total weight of each A layer,

(5) The white film has a three-layer composition of A layer, ZB layer, and ZC layer, B layer is a layer containing fine bubbles, and A layer and Z or C layer are polyester with inorganic particles and Z or organic particles. A particle content of which is 0.5% by weight or less based on the total weight of each layer containing the particles,

It is.

[0008] Further, the direct type liquid crystal knocklight, the liquid crystal knocklight lamp reflector, and the reverse prism type liquid crystal knocklight of the present invention use the surface light source reflecting member film of the present invention.

The invention's effect

[0009]

According to the film for a surface light source reflecting member of the present invention, it is possible to easily distinguish between a surface provided with a function-imparting layer and a surface on the opposite side visually, and to improve productivity in a liquid crystal knocklight manufacturing process. Can do. When a resin layer containing an ultraviolet absorber and Z or a light stabilizer is provided as a function-imparting layer, a resin layer containing an ultraviolet absorber and Z or a light stabilizer is visually provided. When installing a liquid crystal backlight with a distinction between the opposite surface and the opposite side, a resin layer containing an ultraviolet absorber and Z or a light stabilizer can be installed to face the cold cathode tube side. The decrease in luminance over time can be reduced. In addition, when used in an inverted prism type LCD backlight, the yield as an LCD backlight is less noticeable due to film scratches caused by contact between the backlight housing and the surface light source reflecting member film during assembly. Can be high. Brief Description of Drawings

[0010] [Fig. 1] Direct type liquid crystal backlight using the film for surface light source reflecting member of the present invention. [Fig. 2] Reverse prism type liquid crystal knock light using the film for surface light source reflecting member of the present invention.

Explanation of symbols

[0011] 1: Diffusion film

2: Prism film

3: Diffusion plate

4: Film for surface light source reflecting member

5: Cold cathode tube

6: Housing

7: Prism light guide plate

8: Lamp reflector

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] The present invention has the above-mentioned problem, that is, since a white film having a layer having a function provided on one side is white on both sides, the surface provided with the function-imparting layer is visually discriminated from the opposite side. We investigated the problem that it is difficult to do so, and the difference AG between the glossiness (60 °) of one side and the other side of the film for a surface light source reflecting member (hereinafter referred to as a reflective film) was set to AG> 80 As a result, it became easy to distinguish between the surface with the function-imparting layer and the surface on the opposite side, and it was clarified that the problems to be solved can be solved all at once.

[0013] In the present invention, the value measured based on the glossiness (60 °) and the IS K7105 (1981 version) with the incident angle and the light receiving angle set to 60 °. A Suga Test Instruments digital variable gloss meter (UGV-4D) can be used for measurement.

[0014] The difference AG (60 °) in glossiness (60 °) between one surface and the other surface of the reflective film of the present invention is set to be greater than 80% in order to enable discrimination between the one surface and the other surface. There is a need. AG is preferably 85% or more, more preferably 90% or more. If AG is 80% or less, it will be difficult to identify the surface. There are the following methods to make AG larger than 80%. (1) Make a difference in glossiness between one side and the other side of the white film constituting the reflective film.

(2) A resin layer is provided on one surface of the white film constituting the reflective film, and the luminous intensity of the surface is lowered.

Specific contents of these methods will be described later in detail.

[0015] The white film having a high molecular force used as the reflective film of the present invention preferably has a high visible light reflectance. In order to increase the visible light reflectance, it is preferable to use a white film containing bubbles inside. The white film containing bubbles inside is not particularly limited, but a porous unstretched film, a polypropylene film, or a polyester film is preferably exemplified. Among these, a polyester film is particularly preferable as a white film according to the present invention because of its excellent heat resistance and rigidity.

[0016] The polyester constituting the white film according to the present invention is a polymer obtained by condensation polymerization of diol, dicarboxylic acid and force. Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid, and sebacic acid. The diol is represented by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexane dimethanol and the like. Specific examples include polymethylene terephthalate, polytetramethylene terephthalate, polyethylene p-oxybenzoate, poly 1,4-cyclohexylene dimethylene terephthalate, and polyethylene 2,6 naphthalene dicarboxylate. In the present invention, polyethylene terephthalate and polyethylene naphthalate are particularly preferable.

[0017] Of course, these polyesters may be homopolyesters or copolyesters. Examples of copolymer components include diol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol; Examples include acid components.

[0018] In addition, various known additives are added to this polyester! Examples of the additive include an antioxidant and an antistatic agent. [0019] The polyester used in the white film according to the present invention is preferably polyethylene terephthalate. Polyethylene terephthalate film has excellent water resistance, durability and chemical resistance.

[0020] The reflective film of the present invention preferably has an average reflectance in the wavelength range of 400 to 700 nm of 90% or more on at least one side of the reflective film. In the present invention, the average reflectance refers to the reflectance when an integrating sphere is attached to a spectrophotometer (U-3310) manufactured by Hitachi High-Technologies and the standard white plate (acid aluminum) is 100%. Measured over ~ 700nm, read the reflectance at 5nm intervals from the obtained chart, and averaged values.

[0021] In order to obtain an average reflectance of 90% or more, it is important to make the film white by containing fine bubbles in the film. Since the fine bubbles exert light scattering action, the reflectance can be improved. Preferably, the average reflectance is 95% or more, more preferably 98% or more. The average reflectance is not particularly limited but is preferably 108% or less. This is because in order to increase the average reflectance, it is necessary to increase the amount of nucleating agent, and in this case, the film forming property may become unstable.

The white film according to the present invention is preferably whitened by containing fine bubbles inside the film. Formation of fine bubbles is achieved by dispersing a polymer incompatible with a high melting point polyester in a film base material such as polyester and stretching it (for example, biaxial stretching). . During stretching, voids (bubbles) are formed around the incompatible polymer particles, which exhibit a scattering effect on light, and thus are whitened, and a high reflectance can be obtained. Incompatible polymers include, for example, poly-3-methyl phthalene 1, poly-4-methyl pentene 1, polybutyl t-butane, 1,4 trans poly 2,3 dimethyl butadiene, polybutyl cyclohexane, polystyrene, polymethyl styrene, poly 200 ° C or higher melting point selected from dimethylstyrene, polyfluorostyrene, poly-2-methyl-4-fluorostyrene, polyvinyl-t-butyl ether, cellulose triacetate, cellulose tripropionate, polybulufluoride, polychlorofluoroethylene, etc. The polymer. Of these, polyolefin, particularly polymethylpentene, is preferred for the polyester base material. [0023] The addition amount of the incompatible polymer (for example, polyolefin) is preferably 5% by weight or more and 25% by weight or less when the entire layer containing the incompatible polymer is 100% by weight. If it is less than 5% by weight, the effect of whitening is diminished, and it becomes difficult to obtain a high reflectance. If it exceeds 25% by weight, mechanical properties such as strength of the film itself may be too low.

[0024] The incompatible polymer is preferably dispersed uniformly. Due to the uniform dispersion of the incompatible polymer, bubbles are uniformly formed inside the film, and the degree of whitening and thus the reflectance becomes uniform. In order to uniformly disperse the incompatible polymer, it is effective to add a low specific gravity agent as a dispersion aid. A low specific gravity agent is a compound having the effect of reducing the specific gravity, and the effect is recognized for a specific compound. For example, for polyesters, polyalkylene glycols such as polyethylene glycol, methoxy polyethylene glycol, polytetramethylene glycol, polypropylene glycol, ethylenoxide Z propylenoxide copolymer, sodium dodecylbenzenesulfonate, sodium alkylsulfonate. Examples thereof include salts, glycerin monostearate, and tetrabutyl phospho-mparaaminobenzene sulfonate.

[0025] In the case of the white film according to the present invention, as the specific gravity reducing agent, polyalkylene glycol, particularly polyethylene glycol is particularly preferable. A copolymer of polybutylene terephthalate and polytetramethylene glycol is also preferably used for improving the dispersibility of the incompatible polymer. The addition amount of the low specific gravity agent is preferably 10% by weight or more and 25% by weight or less, with the total layer containing the incompatible polymer being 100% by weight. If the amount is less than 10% by weight, the effect of addition is reduced. If it exceeds 25% by weight, the original properties of the film base material may be impaired. Such a low specific gravity agent can be added to the film base polymer in advance to prepare a master polymer (master chip).

[0026] When the white polyester film as described above contains fine bubbles, the apparent specific gravity of the polyester film is lower than that of a normal polyester film. If a lower specific gravity agent is further added, the specific gravity is further lowered. In other words, a white and light film can be obtained. In order to reduce the weight of the white polyester film while maintaining the mechanical properties as a reflective film, the apparent specific gravity is preferably 0.5 or more and 1.2 or less. Furthermore, by making the apparent specific gravity 0.5 or more and 1.2 or less, it is possible to obtain higher reflectance, which is preferable. Good. The apparent specific gravity is more preferably 0.5 or more and 1.0 or less, and particularly preferably 0.5 or more and 0.8 or less.

[0027] In order to make the apparent specific gravity 0.5 or more and 1.2 or less, for example, when polymethylpentene having a specific gravity of 0.83 is used as the incompatible polymer as described above, first, polymethylpentene is used as a film. It should be contained in an amount of 5% to 25% by weight based on the polyester polymer of the base material. Next, an unstretched polyester film is prepared, and the unstretched polyester film can be achieved by stretching the stretch ratio in the machine direction and the transverse direction at 2.5 to 4.5 times. When the apparent specific gravity is in the range of 0.5 or more and 1.2 or less, when used as a reflective film, the brightness of the screen is remarkably excellent.

[0028] The glossiness of the white film according to the present invention is particularly limited if the difference ΔG in glossiness (60 °) between one surface and the other surface of the reflective film using the white film is greater than 80%. However, the glossiness (60 °) of at least one side of the white film is preferably 90% or more. If the glossiness of one side of the white film is 90% or more, decrease the glossiness of the other side of the white film, or provide a resin layer on the other side of the white film to increase the glossiness of that side. By making it smaller, the AG of the reflective film can be easily made larger than 80%. The glossiness of one side of the white film is more preferably 95% or more, then preferably 100% or more, then preferably 115% or more, and most preferably 120% or more. The upper limit of the glossiness is not particularly limited, but is preferably less than 130%. If it exceeds 130%, the film surface friction coefficient becomes high, and it may be difficult to eliminate air at the time of scraping.

[0029] The white film according to the present invention can be formed in various layer configurations such as a single layer, two layers, and three layers. Above all, it consists of A layer, ZB layer, ZA layer, or A layer, ZB layer, and ZC layer, and the B layer is a layer containing the fine bubbles in order to achieve both high reflectivity and film formability. preferable.

[0030] In addition, various additive agents can be added to each layer of the white film within the range without impairing the effects of the present invention. Examples of additives that can be used include organic and Z or inorganic fine particles, fluorescent brighteners, heat stabilizers, ultraviolet absorbers, and acid-fastening agents. It has these functions due to the difference in glossiness with the surface of It is possible to distinguish which side of the white film is provided with the layer containing the additive. Sarasako, A layer ZB layer In the case of the three-layer structure of ZA layer, the A layer equivalent to the film surface Inorganic polyester and Z or organic particles are added to the polyester, 0.5% by weight based on the total weight of each A layer It is preferable that it is the layer contained below. The content is more preferably 0.1% by weight or less, particularly preferably 0.07% by weight or less. In addition, in the case of a three-layer structure consisting of A layer, ZB layer, and ZC layer, inorganic particles and Z or organic particles are added to polyester, and each layer (inorganic fine particles and Z or organic particles is added to polyester). The layer is preferably 0.5% by weight or less based on the total weight of the contained layer. The content is more preferably 0.1% by weight or less, particularly preferably 0.07% by weight or less. By reducing the content of inorganic fine particles and Z or organic fine particles contained in the A layer (or C layer), the glossiness of the A layer (or C layer) can be increased.

[0031] As described above, the white film according to the present invention preferably has a glossiness of at least 90% on at least one side, but the inorganic fine particles and Z contained in one outermost layer of the white film Alternatively, by setting the content of inorganic fine particles to 0.5% by weight, the glossiness of the surface can be made 90% or more. In addition, by increasing the content of inorganic fine particles and / or inorganic fine particles contained in the other outermost layer of the white film, the glossiness of the surface can be lowered, and one surface of the white film and the other surface can be reduced. It is possible to make a difference in glossiness with the surface. The content of inorganic fine particles and / or inorganic fine particles contained in each layer can be appropriately adjusted according to the desired difference in glossiness.

Next, the method for producing a white film according to the present invention will be described, but the present invention is not limited to this example.

[0033] Polymethylpentene is added as an incompatible polymer, and polyethylene glycol, polybutylene terephthalate and a polytetramethylene glycol copolymer are added as a low specific gravity agent to polyethylene terephthalate. It is thoroughly mixed and dried and fed to Extruder B, which has been heated to a temperature of 270-300 ° C. If necessary, use a material containing inorganic additives such as SiO.

2

Supply ethylene terephthalate to Extruder A in the usual way. Then, in the T die 3 layer die, the polymer of Extruder B comes to the inner layer (B layer) and the polymer of Extruder A comes to both surface layers (A), so that A layer / B layer ZA layer 3 The layers may be laminated. [0034] The molten sheet is closely cooled and solidified by electrostatic force on a drum cooled to a drum surface temperature of 10 to 60 ° C to obtain an unstretched film. The unstretched film is led to a roll group heated to 80 to 120 ° C, stretched 2.0 to 5.0 times in the longitudinal direction, and cooled with a roll group of 20 to 50 ° C. Subsequently, the film is stretched in the direction perpendicular to the longitudinal direction in an atmosphere heated to 90-140 ° C while being guided to a tenter while holding both ends of the longitudinally stretched film with clips. The stretching ratio is 2.5 to 4.5 times in the longitudinal and lateral directions, respectively, and the area ratio (longitudinal stretching ratio X lateral stretching ratio) is preferably 9 to 16 times. If the area magnification is less than 9 times, the resulting white color of the film will be poor. If the area magnification exceeds 16 times, the film tends to be broken during stretching and the film forming property tends to be poor. In order to impart flatness and dimensional stability to the biaxially stretched film, heat setting is performed at 150 to 230 ° C in a tenter, and after uniform cooling, the film is cooled to room temperature. And it winds up with a winder and obtains the white film which concerns on this invention.

[0035] In order to make the difference AG in gloss (60 °) between one surface and the other surface of the reflective film of the present invention greater than 80%, a white resin film may be provided with a resin layer. preferable. By providing the resin layer, the glossiness of one side of the white film can be lowered, and ΔG of the reflective film can be easily increased to more than 80%.

[0036] The resin layer according to the present invention is not particularly limited, but a resin mainly composed of an organic component is preferable. For example, polyester resin, polyurethane resin, acrylic resin, methallyl resin, polyamide resin, Examples include polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyvinyl chloride resin resin, polystyrene resin, polyacetate resin resin, and fluorine-based resin. These coffins may be used alone or in the form of two or more types of copolymers or mixtures. Among them, polyester resin, acrylic resin or methacrylic resin is preferably used in terms of heat resistance, particle dispersibility, coatability, and glossiness.

[0037] Since the white film of the present invention may be deteriorated by light emitted from a lamp such as a cold cathode tube during use, particularly ultraviolet light (for example, optical deterioration such as yellowing or decomposition deterioration that lowers the molecular weight). It is also preferable to use a resin layer containing an ultraviolet absorber and Z or a light stabilizer as the resin layer.

[0038] The resin constituting the resin layer containing the ultraviolet absorber is not particularly limited, but may be an acid. Copolymers containing resin containing inorganic UV absorbers such as titanium fluoride and zinc oxide, resin containing organic UV absorbers such as benzotriazole and benzophenone, or benzotriazole and benzophenone reactive monomers Polymerized rosin can be used.

[0039] As the resin constituting the resin layer containing the light stabilizer, it is preferable to use an organic ultraviolet absorbing resin containing a resin copolymerized with a hindered amine (HALS) reactive monomer.

[0040] As the inorganic ultraviolet absorber, zinc oxide, titanium oxide, cerium oxide, zirconium oxide and the like are generally used. Among these, at least one selected from the group consisting of zinc oxide, titanium oxide, and cerium oxide is preferable because it does not bleed out and is excellent in light resistance. Several types of UV absorbers may be used in combination as needed. Of these, zinc oxide is most preferable from the viewpoints of economy, ultraviolet absorption, and photocatalytic activity. As zinc oxide, FINEX-25LP, FINEX-50LP (manufactured by Sakai Chemical Industry Co., Ltd.) or the like can be used.

[0041] Examples of the organic ultraviolet absorber include a resin containing an organic ultraviolet absorber such as benzotriazole or benzophenone, a resin obtained by copolymerizing a benzotriazole-based or benzophenone-based reactive monomer, and further to these. A resin obtained by copolymerizing a light stabilizer such as a hindered amine (HALS) -based reactive monomer can be used. In particular, a thin layer of organic UV-absorbing resin containing benzotriazole-based and benzophenone-based reactive monomers, as well as those containing hindered amine (HALS) -based reactive monomers. It is more preferable because the ultraviolet absorption effect is high.

[0042] These production methods and the like are disclosed in detail in JP-A-2002-90515, [0019] to [0039]. Among them, HALS HYBRID (registered trademark) (manufactured by Nippon Shokubai Co., Ltd.) containing an acrylic monomer and UV absorber copolymer as an active ingredient can be used.

[0043] In the present invention, various additives can be added to the resin layer within a range that does not impair the effects of the present invention. Additives include, for example, organic and Z or inorganic fine particles, fluorescent brighteners, cross-linking agents, heat stabilizers, antioxidation stabilizers, organic lubricants, nucleating agents, couplings An agent or the like can be used.

[0044] The resin layer according to the present invention can be provided by a coating method. When it is provided by a coating method, the coating liquid can be applied by any method. For example, gravure coating, roll nut, spin nut, reno kusu: pi ot, no: pi ot, screen: pi ot, blade, n te, air knife coat, datebing, etc. Can be used. In addition, the coating liquid for forming the resin layer may be applied at the time of manufacturing the white film of the substrate (in-line coating), or may be applied on the white film after completion of crystal orientation (off-line coating).

[0045] The reflective film of the present invention has a heat shrinkage rate of 0.1% or more and 0.2% or less in the film longitudinal direction and film width direction after heat treatment at 90 ° C for 30 minutes as a reflective film. Is preferred. Preferably it is 0.05-5.15% or less. If the thermal shrinkage in the film longitudinal direction or film width direction is out of the range of 0.1% or more and 0.2% or less, the film becomes squeezed when it reaches a high temperature, and the brightness of the liquid crystal knock light Unevenness is likely to occur. In particular, in the case of a reflective film for use in a reverse prism, when a prism-shaped light guide plate comes into contact with a mirror-like reflective surface, it tends to be noticeable as a screen unevenness on the liquid crystal panel.

[0046] Here, the heat shrinkage rate in the longitudinal direction of the film after the heat treatment at 90 ° C for 30 minutes is a value measured by the following procedure. First, a film sample of a certain size is prepared, and a certain length (L) is measured in the longitudinal direction (extrusion direction during production) at room temperature. Sample 9

0

Corresponds to L after standing in a thermostat kept at 0 ° C for 30 minutes and then slowly cooling to the same room temperature.

Measure the length (L) of the part to be zeroed. The length (L) and initial length (L) force are

0

The obtained value is defined as the heat shrinkage rate in the longitudinal direction of the film.

• Heat shrinkage (%) = {(L -L) / L} X 100

o o

A negative value indicates that the film is stretched.

[0047] The heat shrinkage in the width direction of the film after heat treatment at 90 ° C for 30 minutes is the same as the longitudinal direction of the film in the width direction of the film (perpendicular to the extrusion direction during production). This is the measured value.

[0048] The reflective film of the present invention preferably has an average reflectance of 85% or more at a wavelength of 400 to 700 nm measured from the surface provided with the resin layer. More preferably 87% or more, especially Preferably it is 90% or more. If the average reflectance is less than 85%, the brightness may be insufficient depending on the liquid crystal display used. In addition, when a resin layer containing an ultraviolet absorber and Z or a light stabilizer is provided on both sides of the white film, the average reflectivity measured for any resin layer force should be 85% or more. That's fine.

[0049] The reflective film of the present invention can be preferably used in a liquid crystal backlight of a direct type for use in liquid crystal TVs and large monitors. As shown in Fig. 1, a reflective film is installed near the cold cathode tube in the direct-type liquid crystal knock light. At this time, if the surface of the reflecting film provided with the resin layer (preferably, the resin layer containing the ultraviolet absorber and Z or the light stabilizer) is not set facing the cold cathode tube side, it will come out of the cold cathode tube. The white film of the base material may turn yellow due to ultraviolet rays. Therefore, when assembling the knocklight, it is necessary to distinguish between the surface of the reflective film provided with the resin layer and the opposite surface. In the reflective film of the present invention, it is easy to distinguish between the surface on which the resin layer is provided and the surface on the opposite side, the work efficiency in the assembly process of the knock light is improved, and the productivity is also improved.

[0050] The reflective film of the present invention can be preferably used for a lamp reflector of a liquid crystal backlight. The lamp refractor is formed by bonding a stainless steel plate and a reflective film, and press-molding them in a curved shape so that the reflective film is on the inside. Then, the lamp reflector is assembled into a knocklight so as to cover the cold cathode tube as shown in FIG. As with the direct backlight, the lamp reflector is also provided with a reflective film near the cold cathode tube. At this time, the surface of the reflective film provided with the resin layer (preferably a resin layer containing an ultraviolet absorber and Z or a light stabilizer) is directed to the cold cathode tube side so that the stainless steel plate and the reflective film are provided. Otherwise, the white film of the base material may turn yellow due to the ultraviolet rays generated by the cold cathode tube. Therefore, when bonding, it is necessary to distinguish the surface on which the resin layer is provided and the surface on the opposite side. In the surface light source reflecting member film of the present invention, it is easy to distinguish between the surface provided with the resin layer and the surface on the opposite side, the work efficiency in the bonding process is improved, and the productivity is also improved. .

[0051] The reflective film of the present invention can be suitably used for a reverse prism type liquid crystal backlight. As described above, when assembling the knocklight, the knocklight housing and the reflective film may come into contact with each other and be scratched. For edge-light type backlight, for light weight There is a cavity in the case of the knocklight, and scratches on the reflective film can be seen through this cavity. Knocklights with visible scratches will degrade the quality of the finished product, resulting in a decrease in yield. If the glossiness of the reflective film is low, scratches on the surface will be inconspicuous. On the other hand, a reflective film with a high glossiness is required to increase the brightness, especially in the reverse prism type liquid crystal knocklight. Therefore, by incorporating the reflective film of the present invention with the low brightness side facing the backlight housing and the high gloss surface facing the light guide plate, scratches required on the knock light housing are attached. This makes it possible to achieve both the inconspicuousness and the reflection with many specular reflection components required on the light guide plate side. That is, the reverse prism type liquid crystal backlight using the reflective film of the present invention can improve the yield without impairing the quality of the finished knocklight product, and can also increase the brightness. Example

[0052] Measurement methods and evaluation methods are shown below.

[0053] (1) Average reflectance

The average reflectance of the surface of the reflective film on which the resin layer is provided is measured by the following procedure. Attach an integrating sphere to a Hitachi High-Technologies spectrophotometer (U-3310), and measure the reflectivity from 400 to 700 nm when the standard white plate (acid aluminum) is 100%. Read the reflectance at _5nm intervals from the obtained chart, calculate the average value of them, and use it as the average reflectance. Three samples were measured for each reflective film, and the average value was taken as the average reflectance of the reflective film. If the reflective film is not provided with a resin layer, the average reflectivity of the surface regarded as the “surface provided with the resin layer” in the measurement of “(3) Glossiness (60 °;)”. Measure.

[0054] (2) Thermal contraction rate

(Heat shrinkage in the longitudinal direction)

Cut a sample 10mm wide (film width direction) x 230mm long (film longitudinal direction) from the reflective film. Place marks at intervals of 200 mm in the longitudinal direction of the sample, and accurately read the distance between the marks with a metal scale (L mm). Sample in a 90 ° C hot air oven for 30 minutes

0

Let stand for a while and then cool to room temperature. Next, read the distance between the marks of the sample by the above method (Lmm). The distance force between the marks was also expressed in% by calculating the heat shrinkage rate by the following formula. 1 Three samples were cut out of the reflective film, and the average value of the thermal shrinkage rate of each sample was defined as the thermal shrinkage rate of the reflective film.

• Heat shrinkage (%) = (L -L) / L X 100

0 0

A negative value indicates that the film is stretched.

[0055] (Heat shrinkage in the width direction)

A 10 mm wide (film longitudinal direction) x 230 mm long (film width direction) sample was cut out from the reflective film and measured in the same manner as the method for measuring the thermal shrinkage in the longitudinal direction.

[0056] (3) Glossiness (60 °)

The glossiness (60 °) of both the surface of the reflective film provided with the resin layer and the opposite surface is measured by the following procedure. Using a digital variable angle gloss meter (UGV-4D) manufactured by Suga Test Instruments Co., Ltd., the glossiness was measured according to JIS K7105 (1981 version) with the incident angle and light receiving angle adjusted to 60 °. Three samples were measured for each reflection film, and the average value was defined as the glossiness (60 °) of the reflection film. In addition, the oil film layer is provided on the reflective film! In the case of /, NA V, the glossiness is small! /, And the side of the surface (if the glossiness is the same on both sides, one of the sides) is regarded as the “surface with the resin layer”.

[0057] (4) Average reflectance after light resistance test

The reflective film was placed in an ultraviolet degradation acceleration tester iSuper UV Tester SUV-W131 (manufactured by Iwasaki Electric Co., Ltd.), and a forced ultraviolet irradiation test was performed under the following conditions.

"UV irradiation conditions"

Illuminance: lOOmWZcm ² , Temperature: 60 ° C, Relative humidity: 50% RH, Irradiation time: 48 hours The average reflectance was measured according to the method of (1).

[0058] (5) Identification of reflective film surface

Ten decision-makers selected arbitrarily observed both sides of the reflective film visually. All 10 people were judged as ◯ if the surface with the resin layer could be distinguished from the opposite surface, and X if even one could not. Each reflective film was evaluated with one sample.

[0059] (6) Hard to see scratches

The surface of the reflective film provided with a resin layer was rubbed 3 times at a stroke width of 10 cm and a speed of 30 mmZsec by applying a load of 100 g of # 0000 steel wool. Arbitrarily selected 10 The surface provided with the rosin layer was visually observed by a name judge. If all 10 people did not see any scratches, it was rated as 〇. If the reflective film is not provided with a resin layer, the surface considered as the “surface provided with the resin layer” was scratched in the measurement of “(3) Glossiness (60 °;)”. The surface was observed. Each reflective film was evaluated with one sample.

[Example 1]

First, a polyethylene terephthalate chip (F20S manufactured by Toray Industries, Inc.) and a master chip containing a polyethylene glycol having a molecular weight of 4000, a copolymer of polybutylene terephthalate and polytetramethylene glycol, added during the polymerization of polyethylene terephthalate are 180 °. Vacuum dried at C for 3 hours.

[0061] Next, 65 parts by weight of polyethylene terephthalate, 10 parts by weight of polyethylene terephthalate copolymerized with 10 mol% of isophthalic acid and 5 mol% of polyethylene glycol, and 5 parts by weight of a copolymer of polybutylene terephthalate and polytetramethylene glycol To 20 parts by weight of polymethylpentene. The mixture was fed to Extruder B heated to 270-300 ° C (B layer).

On the other hand, 97 parts by weight of a polyethylene terephthalate chip and 1 part by weight of a master chip containing 2% by weight of silicon dioxide having a number average particle size of 1.5 μm were mixed. The mixture was vacuum-dried at 1 80 ° C. for 3 hours and then fed to Extruder A heated to 280 ° C. (A layer).

[0063] These polymers were laminated through a laminating apparatus so as to be an A layer, a ZB layer, and a ZA layer (thickness ratio A layer: B layer: A layer = 1: 8: 1), and formed into a sheet from a T die.

[0064] Further, this sheet was cooled and solidified with a cooling drum having a surface temperature of 25 ° C to obtain an unstretched film. Next, the unstretched film was guided to a roll group heated to 85 to 98 ° C, stretched 3.4 times in the longitudinal direction of the film, and cooled with a roll group at 25 ° C. Next, the film stretched in the longitudinal direction is guided to the tenter while holding both ends of the film with clips, and in the atmosphere heated to 130 ° C in the film width direction (direction perpendicular to the film longitudinal direction) 3.6 It was stretched by a factor of 2. After that, heat setting was performed at 230 ° C in a tenter, and after uniform cooling, it was cooled to room temperature. Finally, it was wound up with a winder to obtain a white film having a thickness of 188 μm. The white film obtained had a luminous intensity (60 °) of 121%. [0065] As a coating liquid for forming a resin layer, Hals Hybrid (registered trademark) UV-G13 (acrylic copolymer, 40% concentration solution, manufactured by Nippon Shokubai Co., Ltd.): 41.4 g, desmodur ( (Registered trademark) N3200 (curing agent, concentration 100%, manufactured by Sumika Bayer Urethane Co., Ltd.): 2. lg, toluene: 54.5 g, silica powder as inorganic fine particles (Fuji Silysia Co., Ltd. (Trademark) 100): 1. A coating solution prepared by adding 8 g with stirring was prepared. This coating solution was applied to one side of a white film so that the thickness after drying was 3 m, a resin layer was provided, and the coating was dried. The coating solution was dried at a temperature of 130 ° C for 1 minute. Thus, a reflective film was obtained. The glossiness (60 °) of the surface of the reflective film provided with the resin layer was 25%.

[0066] (Example 2)

A white film was obtained in the same manner as in Example 1 except that the amount of the master chip (silicon dioxide content 2% by weight) mixed in the A layer was 2 parts by weight. The resulting film had a glossiness (60 °) of 107%.

[0067] In the same manner as in Example 1 except that the amount of silica powder (Sciphor Ivic (registered trademark) 100, manufactured by Fuji Silysia Co., Ltd.) 100 in the coating liquid forming the resin layer was changed to 2.3 g. A fat layer was provided to obtain a reflective film. The glossiness (60 °) of the surface of the reflective film provided with the resin layer was 13%

[Example 3]

A white film was obtained in the same manner as in Example 1 except that the amount of the master chip (silicon dioxide content 2% by weight) mixed in the A layer was 3.5 parts by weight. Glossiness of the obtained film

(60 °) was 95%.

[0069] In the same manner as in Example 1 except that the amount of silica powder in the coating liquid for forming the resin layer (Syhoro Bic (registered trademark) 100 manufactured by Fuji Silysia Co., Ltd. 100) was 2.3 g. A fat layer was provided to obtain a reflective film. The glossiness (60 °) of the surface of the reflective film provided with the resin layer was 12%

[0070] (Example 4)

The polymer composition of layer A and layer B, and the temperatures of extruder A and extruder B were the same as in Example 1.

[0071] Polyethylene terephthalate chip 97 parts by weight, silicon dioxide having a number average particle size of 1.5 μm A master chip containing 2 wt% was mixed to 3.5 parts by weight. 180 mixture

After vacuum drying at ° C for 3 hours, the mixture was supplied to Extruder C heated to 280 ° C (C layer).

[0072] These polymers were laminated through a laminating apparatus so as to be an A layer, a ZB layer, and a ZC layer (thickness ratio A layer: B layer: C layer = 1: 8: 1), and formed into a sheet form from a T die.

[0073] Further, this sheet was stretched under the same conditions as in Example 1 to obtain a white film. The glossiness (60 °) of the white paper film obtained was 121% on the A layer side and 95% on the C layer side.

[0074] A in the same manner as in Example 1 except that the amount of silica powder in the coating solution for forming the resin layer (Syhoro Bic (registered trademark) 100 manufactured by Fuji Silysia Co., Ltd. 100) was 2.3 g. A reflective film was obtained by providing a resin layer on the layer surface. The glossiness (60 °) of the surface of the reflective film provided with the resin layer was 14%.

(Comparative Example 1)

A reflective film was obtained in the same manner as in Example 1 except that the resin layer was not provided.

(Comparative Example 2)

Resin layer in the same manner as in Example 1 except that the amount of silica powder in the coating liquid forming the resin layer (Sciphor Ibic (registered trademark) 100 manufactured by Fuji Silysia Co., Ltd. 100) was 0.3 g. A reflective film was obtained. The glossiness (60 °) of the surface of the reflective film provided with the resin layer was 70%.

(Comparative Example 3)

Resin layer as in Example 1 except that the amount of silica powder in the coating liquid for forming the resin layer (Sci-Holovik (registered trademark) 100 manufactured by Fuji Silysia Co., Ltd. 100) was 0.9 g. A reflective film was obtained. The glossiness (60 °) of the surface of the reflective film provided with the resin layer was 50%.

[0075] (Comparative Example 4)

As described in Example 1 on one side of a white film made of 188 μm porous biaxially stretched polyethylene terephthalate (Lumirror (registered trademark) E60L, Toray Industries, Inc., glossiness (60 °): 30%)) A resin film was provided to obtain a reflective film. The luminous intensity (60 °) of the surface of the reflective film provided with the resin layer was 25%.

[0076] [Table 1]

[0077] In Examples 1 to 4, it was possible to easily distinguish the surface provided with the resin layer having a gloss difference of more than 80% and the surface on the opposite side. Furthermore, in Examples 1 to 4, the glossiness of the surface with a low glossiness (surface with the resin layer) was 25% or less, and the scratches on the surface were difficult to see.

On the other hand, in Comparative Examples 1 to 4, the difference in glossiness was 80% or less, and it was difficult to distinguish the surface on which the resin layer was provided and the surface on the opposite side. In Comparative Examples 1 and 2, it was confirmed that the surface having a low glossiness (the surface provided with the resin layer) had a glossiness of more than 50%, and the surface was scratched.

Industrial applicability

[0079] The film for a surface light source reflecting member of the present invention can be suitably used for a liquid crystal knocklight. In particular, it can be suitably used for a direct type liquid crystal backlight, a reverse prism type liquid crystal backlight, and a lamp reflector for a liquid crystal backlight.

Claims

The scope of the claims

[1] It is composed of a white film, and the difference in gloss (60 °) between one side and the other side is A

G> 80% surface light source reflecting member film.

[2] The surface light source reflecting member according to [1], wherein the white film has a resin layer on one surface, and the light intensity (60 °) of the other surface of the white film is 90% or more. the film.

3. The surface light source reflecting member film according to claim 2, wherein the resin layer is a resin layer containing an ultraviolet absorber and Z or a light stabilizer.

[4] The surface light source reflecting member according to claim 1, wherein the heat contraction rate in the film longitudinal direction and the film width direction after heat treatment at 90 ° C. for 30 minutes is 0.1% or more and 0.2% or less. the film.

[5] The white film also has a three-layer constitutional power of A layer, ZB layer, and ZA layer, B layer is a layer containing fine bubbles, and A layer is a layer containing inorganic particles and Z or organic particles in polyester. 2. The film for a surface light source reflecting member according to claim 1, wherein the particle content is 0.5% by weight or less based on the total weight of each A layer.

[6] The white film has a three-layer composition of A layer, ZB layer, and ZC layer, B layer is a layer containing fine bubbles, and A layer and Z or C layer are inorganic particles and Z or organic particles in polyester. 2. The film for a surface light source reflecting member according to claim 1, wherein the content of the particles is 0.5% by weight or less based on the total weight of each layer containing the particles.

[7] A direct-type liquid crystal backlight using the surface light source reflecting member film according to any one of claims 1 to 6.

[8] A lamp reflector for a liquid crystal backlight using the surface light source reflecting member film according to any one of claims 1 to 6.

[9] An inverted prism type liquid crystal backlight using the surface light source reflecting member film according to any one of claims 1 to 6.