JP5040647B2 - Surface light source reflective member film - Google Patents

Description

  The present invention relates to a film for a surface light source reflecting member that is easy to distinguish 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. Furthermore, the present invention relates to a direct type liquid crystal backlight for a liquid crystal display using the surface light source reflecting member film, a reverse prism type liquid crystal backlight, and a backlight lamp reflector.

A liquid crystal display uses a backlight that illuminates a liquid crystal cell (hereinafter referred to as a liquid crystal backlight). LCD monitors use edge-light type LCD backlights, and LCD TVs use direct-type LCD backlights. 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 of bubbles is generally used (Patent Document 1). Furthermore, in order to prevent yellow discoloration of the film due to ultraviolet rays radiated from the cold cathode tube, a white film in which an ultraviolet absorbing layer is laminated has been proposed (Patent Documents 2 and 3). Moreover, in order to provide adhesiveness, the white film which controlled the glossiness of both surfaces of the film is also proposed (patent document 4).
JP-A-8-262208 JP 2001-166295 A JP 2002-90515 A JP 2005-125700 A

  In many cases, the reflective film is used by being bonded 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 is used as a reflection film alone. In these manufacturing processes, since both sides of the reflective film provided with the function-imparting layer are white, it is difficult to visually distinguish the surface provided with the function-imparting layer from the opposite surface. Since these are difficult to identify, there is a problem that extra time is required in the backlight manufacturing process and productivity is lowered.

  In particular, in a reflective film having a resin layer containing a light stabilizer and / or UV absorber on one side, due to these problems, the surface provided with a resin layer containing a light stabilizer and / or UV absorber is mistakenly provided. It may stick to an aluminum plate or a stainless steel plate. If it is mistakenly applied, the surface without the resin layer containing the light stabilizer and / or the UV absorber is exposed to the light of the cold cathode tube and deteriorates. As a result, there arises a serious problem that the luminance of a product such as a liquid crystal television using the reflective film decreases with time during use.

  In addition, in a reverse prism type liquid crystal backlight, which is one type of edge light type backlight, a reflective film having a large number of regular reflection components is suitable for improving luminance, and therefore a reflective film having a high glossiness is required. On the other hand, when the liquid crystal backlight is assembled, the housing of the liquid crystal backlight and the reflective film may come into contact with each other as shown in FIG. Notebook PCs to which edge-light type backlights are applied are regarded as important in terms of weight reduction, and the liquid crystal backlight casing is also provided with a cavity to reduce weight. In the edge light type backlight, scratches on the reflective film can be seen through this cavity. The 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.

The present invention employs the following means in order to solve such problems. That is, for a surface light source reflecting member film of the present invention is constituted by a white polyethylene terephthalate film, the difference .DELTA.G of glossiness (60 °) between one surface and the other surface is, .DELTA.G> with 80%, whereas The glossiness of the surface is 100% or more and less than 130% .

Moreover, the preferable aspect of the film for surface light source reflective members of this invention is as follows.
(1) The white polyethylene terephthalate film has a resin layer on one surface, and the glossiness (60 °) of the other surface of the white film is 100 % or more and less than 130% (2) the resin layer The resin layer contains an ultraviolet absorber and / or a light stabilizer.
(3) The thermal shrinkage rate in the film longitudinal direction and film width direction after heat treatment at 90 ° C. for 30 minutes is from −0.1% to 0.2%. (4) The white polyethylene terephthalate film is A 3 layer constitution of layer / B layer / A layer, B layer is a layer containing fine bubbles, A layer is a layer containing inorganic particles and / or organic particles in polyester, and its particle content Is 0.5 wt% or less with respect to the total weight of each A layer,
(5) The white polyethylene terephthalate film has a three-layer configuration of A layer / B layer / C layer, the B layer is a layer containing fine bubbles, and the A layer and / or the C layer are inorganic particles and / or polyester. Or a layer containing organic particles, the particle content is 0.5 wt% or less with respect to the total weight of each layer containing particles,
It is.

  The direct type liquid crystal backlight, the liquid crystal backlight lamp reflector, and the reverse prism type liquid crystal backlight of the present invention use the surface light source reflecting member film of the present invention.

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, and to improve productivity in a liquid crystal backlight manufacturing process. it can. Further, when a resin layer containing an ultraviolet absorber and / or a light stabilizer is provided as a function-imparting layer, a surface provided with a resin layer containing an ultraviolet absorber and / or a light stabilizer visually It is easy to distinguish from the opposite side, and when incorporated in the liquid crystal backlight, the resin layer containing the UV absorber and / or the light stabilizer can be surely placed facing the cold cathode tube side, so that A reduction in luminance can be reduced. Furthermore, when used in a reverse prism type liquid crystal backlight, scratches caused by the contact between the backlight housing and the surface light source reflecting member film during assembly are less noticeable, and the yield as a liquid crystal backlight can be reduced. Can be high.

Direct-type liquid crystal backlight using the surface light source reflecting member film of the present invention Reverse prism type liquid crystal backlight using the surface light source reflecting member film of the present invention

Explanation of symbols

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

In the present invention, since the white polyethylene terephthalate 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. And the difference ΔG in the glossiness (60 °) between one surface and the other surface of the surface light source reflecting member film (hereinafter referred to as a reflecting film) is ΔG> 80 . In addition, when the glossiness of one surface is set to 100% or more and less than 130% , it becomes easy to distinguish between the surface provided with the function-imparting layer and the surface on the opposite side, and to solve such problems all at once It has been investigated.

  In the present invention, the glossiness (60 °) refers to a value measured based on JIS K7105 (1981 version) with an incident angle and a light receiving angle of 60 °. For measurement, a digital variable angle gloss meter (UGV-4D) manufactured by Suga Test Instruments Co., Ltd. can be used.

The difference [Delta] G in glossiness (60 [deg.]) Between one surface and the other surface of the reflective film of the present invention needs to be greater than 80% in order to enable discrimination between the one surface and the other surface. . ΔG is preferably 85% or more, and more preferably 90% or more. If ΔG is 80% or less, it becomes difficult to identify the surface. As a method for making ΔG larger than 80%, there are the following methods.
(1) The glossiness of one side and the other side of the white polyethylene terephthalate film constituting the reflective film is differentiated.
(2) A resin layer is provided on one surface of the white polyethylene terephthalate film constituting the reflective film, and the glossiness of the surface is lowered.
Specific contents of these methods will be described later in detail.

The white film made of a polymer used as the reflective film of the present invention should have a higher visible light reflectance. In order to increase the visible light reflectance, it is preferable to use a white film containing bubbles inside. Po Li ester film is heat resistance as a white film containing air bubbles therein, particularly preferred as a white film according to the present invention since the stiffness is excellent.

The polyester constituting the white film according to the present invention is a polymer obtained by condensation polymerization from a diol and a dicarboxylic acid. Examples of the dicarboxylic acid 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, cyclohexanedimethanol and the like. Specific examples include polymethylene terephthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylenedimethylene terephthalate, polyethylene-2,6-naphthalene dicarboxylate. In the case of the present invention, polyethylene terephthalate is particularly used .

  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, and dicarboxylic acids such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, and 5-sodium sulfoisophthalic acid. Examples include acid components.

  Various known additives may be added to the polyester. Examples of the additive include an antioxidant and an antistatic agent.

The polyester used in the white film of the present invention, a polyethylene terephthalate. Polyethylene terephthalate film is excellent in water resistance, durability, chemical resistance and the like.

  The reflective film of the present invention preferably has an average reflectance in a 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 is measured over 400 to 700 nm when an integrating sphere is attached to a spectrophotometer (U-3310) manufactured by Hitachi High-Technologies and the standard white plate (aluminum oxide) is taken as 100%. The reflectance is read from the obtained chart at intervals of 5 nm and averaged.

  In order to obtain an average reflectance of 90% or more, it is important to whiten the film by containing fine bubbles in the film. Since the fine bubbles exhibit the 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 addition amount of the 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 finely dispersing a polymer incompatible with the 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 action on the light, so that it becomes white and high reflectance can be obtained. Incompatible polymers include, for example, poly-3-methylphthalene-1, poly-4-methylpentene-1, polyvinyl-t-butane, 1,4-trans-poly-2,3-dimethylbutadiene, polyvinylcyclohexane, polystyrene. , Polymethylstyrene, polydimethylstyrene, polyfluorostyrene, poly-2-methyl-4-fluorostyrene, polyvinyl-t-butyl ether, cellulose triacetate, cellulose tripropionate, polyvinyl fluoride, polychlorotrifluoroethylene, etc. A polymer having a melting point of 200 ° C. or higher selected from Among them, polyolefin, particularly polymethylpentene is preferable for the polyester base material.

  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.

  The incompatible polymer is more preferably dispersed uniformly. Since the incompatible polymer is uniformly dispersed, 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. The low specific gravity agent is a compound having an effect of reducing the specific gravity, and the effect is recognized in a specific compound. For example, for polyester, polyalkylene glycol such as polyethylene glycol, methoxypolyethylene glycol, polytetramethylene glycol, polypropylene glycol, ethylene / propylene oxide copolymer, sodium dodecylbenzenesulfonate, alkylsulfonate It is represented by sodium salt, glycerin monostearate, tetrabutylphosphonium paraaminobenzenesulfonate and the like.

  In the case of the white film according to the present invention, polyalkylene glycol, particularly polyethylene glycol is particularly preferable as the low specific gravity agent. 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 whole layer containing the incompatible polymer being 100% by weight. If it 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 in advance to the film base polymer to prepare a master polymer (master chip).

  As described above, when the white polyester film 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. That is, 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, it is preferable that the apparent specific gravity is 0.5 or more and 1.2 or less because higher reflectance can be obtained. 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.

  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 the polyester of the film base material. It is contained in an amount of 5 to 25% by weight based on the polymer. Subsequently, a polyester unstretched film is produced, and the polyester unstretched film can be achieved by stretching the stretch ratio at 2.5 to 4.5 times in both the longitudinal direction and the transverse direction. When the apparent specific gravity is in the range of 0.5 or more and 1.2 or less, when used as a reflection film, the brightness of the screen is remarkably excellent.

Glossiness of the white film of the present invention is the difference ΔG of glossiness between one surface and the other surface of the reflective film using the white film (60 °) is not particularly limited as long greater than 80%, white gloss of one surface of the color film (60 °) is not more than 100%. If the glossiness of one side of the white film is 100 % or more, the glossiness of the other side of the white film is reduced, or a resin layer is provided on the other side of the white film to reduce the glossiness of that side. By doing so, ΔG of the reflective film can be easily made larger than 80%. One gloss surface of the white film, more preferably 1 to 15%, and most preferably at least 120%. The upper limit of the gloss, Ru der less than 130%. If it exceeds 130%, the film surface friction coefficient becomes high, and it may be difficult to exclude air during winding.

  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. Among them, it has a three-layer structure of A layer / B layer / A layer or A layer / B layer / C layer, and the B layer is a layer containing the fine bubbles, so that high reflectivity and film-forming properties can be obtained. It is preferable to achieve both.

  Moreover, various additives can be added to each layer of the white film as long as the effects of the present invention are not impaired. As the additive, for example, organic and / or inorganic fine particles, fluorescent brightening agent, heat stabilizer, ultraviolet absorber, antioxidant, etc. can be used. By the difference in glossiness, it is possible to identify which side of the white film is provided with the layer containing the additive having these functionalities. Further, in the case of a three-layer configuration of A layer / B layer / A layer, the A layer corresponding to the film surface is 0.5 weights of inorganic particles and / or organic particles in the polyester, and 0.5 weight with respect to the total weight of each A layer. % Or less is preferable. The content is more preferably 0.1% by weight or less, particularly preferably 0.07% by weight or less. Further, in the case of a three-layer structure of A layer / B layer / C layer, the A layer and / or C layer corresponding to the film surface is composed of inorganic particles and / or organic particles in polyester, and each layer (inorganic fine particles and / or organic A layer containing 0.5% by weight or less based on the total weight of the layer containing particles) is preferable. The content is more preferably 0.1% by weight or less, particularly preferably 0.07% by weight or less. By reducing the content of the inorganic fine particles and / or organic fine particles contained in the A layer (or C layer), the glossiness of the A layer (or C layer) can be increased.

As described above, the white film of the present invention are those glossiness of the surface of the hand is 100% or more, content of inorganic particles and / or inorganic fine particles contained in the layer of one of the outermost surface of the white film By setting the amount to 0.5% by weight, the glossiness of the surface can be made 100 % 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, 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 a desired difference in glossiness.

  Next, although the manufacturing method of the white film which concerns on this invention is demonstrated, it is not limited to this example.

Polymethylpentene is added as an incompatible polymer, and polyethylene glycol, polybutylene terephthalate and polytetramethylene glycol copolymer are added as a low specific gravity agent to polyethylene terephthalate. The mixture is sufficiently mixed and dried, and then supplied to the extruder B heated to a temperature of 270 to 300 ° C. If necessary, polyethylene terephthalate containing an inorganic additive such as SiO ₂ is supplied to the extruder A by a conventional method. In the T-die three-layer die, the composition of A layer / B layer / A layer is such that the polymer of the extruder B comes to the inner layer (B layer) and the polymer of the extruder A comes to both surface layers (A layer). You may laminate | stack on these 3 layers.

  The melted 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., longitudinally 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 to 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, 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, the whiteness of the film obtained is 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 in this manner, 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 with a winder and obtains the white film which concerns on this invention.

  In order to make the difference ΔG in glossiness (60 °) between one surface and the other surface of the reflective film of the present invention greater than 80%, it is also preferable to provide a resin layer on one surface of the white film. By providing the resin layer, the glossiness of one surface of the white film can be lowered, and ΔG of the reflective film can be easily increased to more than 80%.

  The resin layer according to the present invention is not particularly limited, but is preferably a resin mainly composed of an organic component. For example, polyester resin, polyurethane resin, acrylic resin, methacrylic resin, polyamide resin, polyethylene resin, polypropylene resin, polyvinyl chloride resin. , Polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, fluorine resin, and the like. These resins may be used alone, or two or more copolymers or a mixture thereof may be used. Of these, polyester resins, acrylic or methacrylic resins are preferably used from the viewpoint of heat resistance, particle dispersibility, coatability, and glossiness.

  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 degradation deterioration that lowers the molecular weight), It is also preferable to use a resin layer containing an ultraviolet absorber and / or a light stabilizer.

  The resin constituting the resin layer containing the ultraviolet absorber is not particularly limited, but a resin containing an inorganic ultraviolet absorber such as titanium oxide or zinc oxide, a resin containing an organic ultraviolet absorber such as benzotriazole or benzophenone, Alternatively, a resin obtained by copolymerizing a benzotriazole-based or benzophenone-based reactive monomer can be used.

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

  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 preferably used because it does not bleed out and is excellent in light resistance. Such ultraviolet absorbers may be used in combination of several kinds as required. 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.

  Organic UV absorbers include resins containing organic UV absorbers such as benzotriazole and benzophenone, or resins obtained by copolymerizing benzotriazole and benzophenone reactive monomers, and hindered amine (HALS) reactivity. A resin obtained by copolymerizing a light stabilizer such as a monomer can be used. In particular, organic UV-absorbing resins containing a resin copolymerized with a benzotriazole-based or benzophenone-based reactive monomer, and further a resin copolymerized with a hindered amine (HALS) -based reactive monomer have a high UV absorbing effect in a thin layer. More preferred.

  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.

  In the present invention, various additives can be added to the resin layer as long as the effects of the present invention are not impaired. Examples of additives that can be used include organic and / or inorganic fine particles, fluorescent brighteners, crosslinking agents, heat stabilizers, oxidation stabilizers, organic lubricants, nucleating agents, and coupling agents.

  The resin layer according to the present invention can be provided by a coating method. When providing by a coating method, a coating liquid can be apply | coated by arbitrary methods. For example, methods such as gravure coating, roll coating, spin coating, reverse coating, bar coating, screen coating, blade coating, air knife coating, and dipping can be used. The coating liquid for forming the resin layer may be applied (in-line coating) during the production of the white film of the substrate, or may be applied (off-line coating) on the white film after the completion of crystal orientation.

  In the reflective film of the present invention, it is preferable that the thermal shrinkage in the film longitudinal direction and the film width direction after the heat treatment at 90 ° C. for 30 minutes as the reflective film is −0.1% or more and 0.2% or less. Preferably it is -0.05 to 0.15% or less. If the thermal contraction rate in the film longitudinal direction or film width direction is outside the range of -0.1% or more and 0.2% or less, the film will bend when it reaches a high temperature, and the brightness of the liquid crystal backlight Unevenness is likely to occur. In particular, in the case of a reflective film for use in a reverse prism, when a prismatic light guide plate is brought into contact with a mirror-like reflective surface, it tends to appear noticeably as a screen unevenness on the liquid crystal panel.

Here, the thermal contraction rate in the film longitudinal direction 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 ₀ ) is measured in the longitudinal direction (extrusion direction during production) at room temperature. The sample is allowed to stand for 30 minutes in a thermostat kept at 90 ° C., and then slowly cooled to the same room temperature, and then the length (L) of the portion corresponding to the L ₀ is measured. Then, a value calculated from the length (L) and the initial length (L ₀ ) by the following equation is defined as a thermal contraction rate in the film longitudinal direction.
Heat shrinkage rate (%) = {(L ₀ −L) / L ₀ } × 100
Negative values indicate that the film has grown.

  Moreover, the film width direction heat shrinkage after the heat treatment at 90 ° C. for 30 minutes is a value measured in the same manner as the film length direction in the film width direction (perpendicular to the extrusion direction during production). Say.

  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, it is 87% or more, and particularly preferably 90% or more. When the average reflectance is less than 85%, the luminance may be insufficient depending on the applied liquid crystal display. In addition, when the resin layer containing a ultraviolet absorber and / or a light stabilizer is provided on both surfaces of the white film, the average reflectance measured from any resin layer may be 85% or more.

  The reflective film of the present invention can be preferably used for a direct-type liquid crystal backlight for liquid crystal TVs and large monitors. In the direct type liquid crystal backlight, as shown in FIG. 1, a reflective film is installed near the cold cathode tube. At this time, unless the surface provided with the resin layer of the reflective film (preferably, the resin layer containing the ultraviolet absorber and / or the light stabilizer) is directed to the cold cathode tube side, the ultraviolet rays emitted from the cold cathode tube The white film of the base material may turn yellow. Therefore, when the backlight is assembled, it is necessary to distinguish between the surface of the reflective film on which the resin layer is provided and the opposite surface. In the reflective film of the present invention, the surface on which the resin layer is provided and the surface on the opposite side can be easily distinguished, the working efficiency in the assembly process of the backlight is improved, and the productivity is also improved.

  The reflective film of the present invention can be preferably used for a lamp reflector of a liquid crystal backlight. The lamp reflector 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. The lamp reflector is assembled to the backlight so as to cover the cold cathode tube as shown in FIG. Similarly to the direct type backlight, the lamp reflector also has a reflective film disposed 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 / or a light stabilizer) is directed to the cold cathode tube side so that the stainless steel plate and the reflective film are Otherwise, the white film of the base material may turn yellow due to the ultraviolet rays emitted from the cold cathode tubes. Therefore, when bonding, it is necessary to identify the surface provided with the resin layer and the surface on the opposite side. The film for a surface light source reflecting member of the present invention can easily distinguish between a surface provided with a resin layer and a surface on the opposite side, improving work efficiency in the bonding step and improving productivity.

  The reflective film of the present invention can be suitably used for a reverse prism type liquid crystal backlight. As described above, when the backlight is assembled, the casing of the backlight and the reflective film may come into contact with each other and be damaged. In the edge light type backlight, a cavity is provided in the casing of the backlight for weight reduction, and scratches on the reflection film can be seen through the cavity. A backlight with visible scratches reduces 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 become inconspicuous. On the other hand, a reflective film having a high glossiness is demanded for increasing the brightness of the reverse prism type liquid crystal backlight. Therefore, when the reflective film of the present invention is incorporated with the low gloss side facing the backlight housing and the high gloss surface facing the light guide plate, the backlight housing side is damaged. It is possible to achieve both the conspicuousness 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 and increase the brightness without deteriorating the quality of the finished backlight product.

  The measurement method and evaluation method are shown below.

(1) Average reflectance The average reflectance of the surface provided with the resin layer of the reflective film is measured by the following procedure. An integrating sphere is attached to a spectrophotometer (U-3310) manufactured by Hitachi High-Technologies, and the reflectance when the standard white plate (aluminum oxide) is 100% is measured over 400 to 700 nm. The reflectance is read from the obtained chart at intervals of 5 nm, and the average value thereof is calculated to obtain 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. In addition, when the resin layer is not provided in the reflective film, the average reflectance of the surface regarded as “the surface provided with the resin layer” is measured in the measurement of “(3) Glossiness (60 °)”.

(2) Thermal contraction rate (longitudinal thermal contraction rate)
A sample of 10 mm width (film width direction) × 230 mm length (film longitudinal direction) is cut out from the reflective film. Marks with an interval of 200 mm are put in the longitudinal direction of the sample, and the distance between the marks is accurately read with a metal scale (L ₀ mm). The sample is left in a hot air oven at 90 ° C. for 30 minutes and then cooled to room temperature. Next, the distance between the marks of the sample is read by the above method (Lmm). The thermal shrinkage rate was calculated from the distance between the marks by the following formula and expressed in%. Three samples were cut out from one 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 rate (%) = (L ₀ −L) / L ₀ × 100
Negative values indicate that the film has grown.

(Heat shrinkage in the width direction)
A sample of 10 mm width (film longitudinal direction) × 230 mm length (film width direction) 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.

(3) Glossiness (60 °)
The glossiness (60 °) of both the surface on which the resin layer of the reflective film is provided 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 the light receiving angle adjusted to 60 °. Three samples were measured for each reflective film, and the average value was defined as the glossiness (60 °) of the reflective film. In addition, when the resin layer is not provided in the reflective film, the surface with the smaller glossiness (one surface when the glossiness is the same on both surfaces) is regarded as the “surface with the resin layer”.

(4) Average reflectance after light resistance test The reflective film was placed in an ultraviolet deterioration accelerating tester iSuper UV Tester SUV-W131 (manufactured by Iwasaki Electric Co., Ltd.) and subjected to a forced ultraviolet irradiation test under the following conditions.
"UV irradiation conditions"
Illuminance: 100 mW / cm ² , temperature: 60 ° C., relative humidity: 50% RH, irradiation time: For the sample after irradiation for 48 hours, the average reflectance was measured according to the method (1).

(5) Discrimination of the surface of the reflective film Ten discriminators selected arbitrarily observed both surfaces of the reflective film by visual observation. If all 10 people could distinguish between the surface provided with the resin layer and the surface on the opposite side, it was judged as “good”. Each reflective film was evaluated with one sample.

(6) Hard to see scratches The surface of the reflective film provided with the resin layer was subjected to three reciprocating frictions at a stroke width of 10 cm and a speed of 30 mm / sec by applying a load of 100 g to # 0000 steel wool. The surface on which the resin layer was provided by 10 arbitrarily selected judges was visually observed. If all 10 people did not see any scratches, it was judged as ○. In addition, when the resin layer is not provided on the reflective film, the surface regarded as the “surface provided with the resin layer” is scratched in the measurement of “(3) Glossiness (60 °)”, and the surface is 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 to which polyethylene glycol having a molecular weight of 4000 and a copolymer of polybutylene terephthalate and polytetramethylene glycol were added at the time of polymerization of polyethylene terephthalate were added at 180 ° C. Vacuum dried for hours.

  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, 5 parts by weight of a copolymer of polybutylene terephthalate and polytetramethylene glycol, polymethyl It mixed so that it might become 20 weight part of pentenes. The mixture was supplied to Extruder B heated to 270 to 300 ° C. (B layer).

  Meanwhile, 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 180 ° C. for 3 hours and then supplied to the extruder A heated to 280 ° C. (layer A).

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

  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 introduced into 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. Subsequently, the film stretched longitudinally in the longitudinal direction is guided to the tenter while grasping both ends with a clip, and stretched by 3.6 times in the film width direction (direction perpendicular to the film longitudinal direction) in an atmosphere heated to 130 ° C. did. Thereafter, heat setting was performed at 230 ° C. in a tenter, and after uniform cooling, the solution was cooled to room temperature. Finally, the film was wound by a winder to obtain a white film having a thickness of 188 μm. The glossiness (60 °) of the obtained white film was 121%.

  As a coating liquid for forming the 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.): 2.1 g, toluene: 54.5 g, silica powder as inorganic fine particles (Fuji Silysia Co., Ltd. Cyphorovic (registered trademark) 100): A coating solution prepared by adding 1.8 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 μm, and a resin layer was provided and dried. The coating liquid was dried at a temperature of 130 ° C. for 1 minute. Thus, a reflective film was obtained. The glossiness (60 °) of the surface provided with the resin layer of the reflective film was 25%.

(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 glossiness (60 °) of the obtained film was 107%.

  A resin layer was provided in the same manner as in Example 1 except that the amount of silica powder (Fuji Silysia Co., Ltd., Cyphorovic (registered trademark) 100) in the coating liquid for forming the resin layer was 2.3 g. A reflective film was obtained. The glossiness (60 °) of the surface provided with the resin layer of the reflective film was 13%.

( Reference Example 1 )
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. The glossiness (60 °) of the obtained film was 95%.

  A resin layer was provided in the same manner as in Example 1 except that the amount of silica powder (Fuji Silysia Co., Ltd., Cyphorovic (registered trademark) 100) in the coating liquid for forming the resin layer was 2.3 g. A reflective film was obtained. The glossiness (60 °) of the surface provided with the resin layer of the reflective film was 12%.

( Reference Example 2 )
The polymer composition of the A layer and the B layer, and the temperatures of the extruder A and the extruder B were the same as those in Example 1.

  97 parts by weight of polyethylene terephthalate chips and 3.5 parts by weight of master chips 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 180 ° C. for 3 hours, and then supplied to an extruder C heated to 280 ° C. (C layer).

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

  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.

The resin layer was formed on the surface of the A layer in the same manner as in Example 1 except that the amount of silica powder (Cyphobic (registered trademark) 100 manufactured by Fuji Silysia Co., Ltd.) in the coating solution for forming the resin layer was 2.3 g. A reflective film was obtained. The glossiness (60 °) of the surface provided with the resin layer of the reflective film 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)
A resin layer was provided in the same manner as in Example 1, except that the amount of silica powder (Cyphobic (registered trademark) 100 manufactured by Fuji Silysia Co., Ltd.) in the coating liquid for forming the resin layer was 0.3 g. A reflective film was obtained. The glossiness (60 °) of the surface provided with the resin layer of the reflective film was 70%.
(Comparative Example 3)
A resin layer was provided in the same manner as in Example 1 except that the amount of silica powder (Cyphobic (registered trademark) 100 manufactured by Fuji Silysia Co., Ltd.) in the coating liquid for forming the resin layer was 0.9 g. A reflective film was obtained. The glossiness (60 °) of the surface provided with the resin layer of the reflective film was 50%.

(Comparative Example 4)
The resin layer described in Example 1 was formed on one side of a white film (Lumirror (registered trademark) E60L manufactured by Toray Industries, Inc., glossiness (60 °): 30%) made of 188 μm porous biaxially stretched polyethylene terephthalate. A reflective film was obtained. The glossiness (60 °) of the surface provided with the resin layer of the reflective film was 25%.

In Examples 1 and 2, the difference in glossiness was larger than 80%, and the surface on which the resin layer was provided and the surface on the opposite side could be easily identified. Further, in Examples 1 and 2, the glossiness of the surface having a small glossiness (surface on which the resin layer was provided) was 25% or less, and the scratches on the surface were not easily visible.

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

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

Claims (9)

It is composed of white polyethylene terephthalate film, and the difference ΔG in glossiness (60 °) between one surface and the other surface is ΔG> 80%, and the glossiness of one surface is 100% or more and less than 130% A film for a light source reflecting member. 2. The surface light source reflection according to claim 1, wherein the white polyethylene terephthalate film has a resin layer on one surface, and the glossiness (60 °) of the other surface of the white polyethylene terephthalate film is 100 % or more and less than 130%. Film for members. The film for a surface light source reflecting member according to claim 2, wherein the resin layer is a resin layer containing an ultraviolet absorber and / or a light stabilizer. The film for a surface light source reflecting member according to claim 1, wherein the heat shrinkage in the film longitudinal direction and the film width direction after heat treatment at 90 ° C for 30 minutes is from -0.1% to 0.2%. The white polyethylene terephthalate film has a three-layer structure of A layer / B layer / A layer, the B layer is a layer containing fine bubbles, and the A layer is a layer in which inorganic particles and / or organic particles are contained in polyester. 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 layer A. The white polyethylene terephthalate film has a three-layer structure of A layer / B layer / C layer, the B layer is a layer containing fine bubbles, and the A layer and / or the C layer are inorganic particles and / or organic particles in the polyester. 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 layer containing particles. A direct-type liquid crystal backlight using the surface light source reflecting member film according to claim 1. The lamp reflector for liquid crystal backlights using the film for surface light source reflective members in any one of Claims 1-6. A reverse prism type liquid crystal backlight using the surface light source reflecting member film according to claim 1.

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