JP2002071921A - Reflecting film for surface light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflecting film for surface light source used in the backlight mechanism of a liquid crystal display using a liquid crystal element. SOLUTION: The reflecting film has an easy-stickable polymer layer on at least one face of a substrate with at least a polyester resin layer containing many microvoids.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reflection film for a surface light source, and more particularly to a reflection film for a surface light source used for a backlight mechanism of a liquid crystal display device using a liquid crystal element.

[0002]

2. Description of the Related Art In recent years, as a display device such as a notebook type computer or a word processor, a liquid crystal display device using a liquid crystal element having a backlight mechanism which can be made thinner and has an easy-to-view image has been used. For such a backlight mechanism, an edge light method in which a linear light source such as a fluorescent tube is provided at one end of a light-transmitting light guide plate is often used. In the case of such an edge light system, a surface light source is often configured such that one surface of a light guide plate is partially covered with a light diffusing substance, and the entire surface is further covered with a reflective material. .

The above-mentioned reflector is required to uniformly reflect the light emitted from the linear light source to the light guide plate. In practice, however, the vicinity of the linear light source becomes locally bright. A phenomenon (generally called a bright line) occurs. In recent years, in order to eliminate the adverse effects caused by the bright lines, a method of providing a printing layer of black ink at a position where the bright lines are generated on the surface of the reflecting material has been adopted.

However, a polyester film conventionally used as a reflector, particularly a polyester film containing a large number of fine voids containing a polyolefin resin, has poor adhesion to an oxidation polymerization type ink or a UV curing type ink. . For this reason, during use of the liquid crystal display device, there has been a problem that the printed layer is peeled off and a problem due to the bright line occurs.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a reflection film for a surface light source having excellent adhesiveness to an oxidation polymerization type ink or a UV curing type ink.

[0006]

The present invention has the following configuration. (1) A reflective film for a surface light source, comprising a substrate having at least one polyester-based resin layer containing a large number of fine cavities, on at least one surface thereof, a polymer easy-adhesion layer. (2) The polymer easy-adhesion layer is provided on the polymer easy-adhesion layer surface,
Adhesion of UV curable ink layer to high polymer adhesive layer when UV curable ink layer is laminated (JIS K540
0 according to JIS K5400 8.5.1.) And the adhesion of the oxidation polymerization type ink layer to the high polymer adhesive layer when the oxidation polymerization type ink layer is laminated.
(Measured based on JIS) is 95% or more, respectively. (3) The polymer easy-adhesion layer is composed of a composition containing a copolymerized polyester resin containing a branched glycol as a component and a resin containing a blocked isocyanate group. 2) The reflective film for a surface light source according to the above.

In the present invention, the thickness of the "film" is not particularly limited, and includes a so-called "sheet".

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The substrate used in the reflection film for a surface light source of the present invention has a polyester resin layer containing at least a large number of fine cavities. The polyester-based resin layer (hereinafter sometimes referred to as A layer) is made of a polyester-based resin, and its configuration is not particularly limited as long as it contains many fine cavities. A polyester resin (a) and a thermoplastic resin (b) incompatible with the polyester resin (a), wherein the thermoplastic resin (b) produces voids.

As the polyester constituting the polyester resin (a), terephthalic acid, isophthalic acid,
A polyester obtained by polycondensing an aromatic dicarboxylic acid such as naphthalenedicarboxylic acid or an ester thereof with a glycol such as ethylene glycol, diethylene glycol, 1,4-butanediol, or neopentyl glycol is exemplified. Representative examples of such polyesters include polyethylene terephthalate, polyethylene butylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, and the like. These polyesters may be a homopolymer, or may be a copolymer obtained by copolymerizing a third component other than the above-mentioned polyester components, but in any case, in the present invention, The ratio of ethylene terephthalate units, butylene terephthalate units, or ethylene-2,6-naphthalate units is
The polyester is preferably at least 70 mol%, more preferably at least 80 mol%, particularly preferably at least 90 mol%, based on all constituent units.

The polyester may be prepared by a method of directly reacting an aromatic dicarboxylic acid with a glycol, a transesterification reaction between an alkyl ester of the aromatic dicarboxylic acid and a glycol, followed by polycondensation, or a method of reacting an aromatic dicarboxylic acid with a glycol. It can also be produced by a method of polycondensing a diglycol ester.

The thermoplastic resin (b) which is incompatible with the polyester resin (a) is incompatible with the base polyester resin (a), and the polyester resin (a) The material is not particularly limited as long as it is uniformly mixed in a dispersed state and causes peeling at the interface with the polyester-based resin (a) due to stretching of the film or the like so as to develop cavities. Preferably, polystyrene-based resins, polyolefin-based resins, polyacryl-based resins, polycarbonate-based resins, polysulfone-based resins, cellulose-based resins and the like are exemplified. These can be used alone or, if necessary,
More than one species can be used in combination. Among them, the use of polystyrene resins and polyolefin resins such as polymethylpentene and polypropylene is particularly preferred.

The amount of the thermoplastic resin (b) to be mixed with the polyester resin (a) is appropriately set according to the amount of cavities required for the obtained layer A, physical properties, production conditions such as stretching, and the like. The thermoplastic resin (b) is preferably 3% by weight or more and less than 40% by weight, based on the total amount of the resin composition comprising the base resin (a) and the thermoplastic resin (b),
More preferably, it is in the range of 5 to 30% by weight.
When the blending amount of the thermoplastic resin (b) is less than 3% by weight, the amount of cavities generated is small, and the reflection performance of the reflective film for a surface light source of the present invention is hardly improved. In addition to the remarkable decrease in stretchability during production, the heat resistance, strength or stiffness tends to decrease.

Further, the thermoplastic resin (b) is a thermoplastic resin (b) which is incompatible with the polyester resin (a).
1) and a thermoplastic resin which is incompatible with both the polyester resin (a) and the thermoplastic resin (b1) and has a higher surface tension (surface energy) than the thermoplastic resin (b1). It is preferred to be composed of resin (b2).

By forming the thermoplastic resin (b) from the above two kinds of thermoplastic resin (b1) and the thermoplastic resin (b2), the thermoplastic resin (b1) mainly exerts a cavity generating effect. To become a “cavity developing agent”,
The thermoplastic resin (b2) is incompatible with the thermoplastic resin (b1) and has a higher surface tension than the thermoplastic resin (b1). As a result, a “dispersing action” of effectively dispersing the thermoplastic resin (b1) in the polyester-based resin (a) is achieved, thereby providing a “dispersing resin” having an action of uniformly forming fine cavities. .

The combination of the thermoplastic resin (b1) and the thermoplastic resin (b2) is incompatible with the polyester resin (a), and the thermoplastic resin (b2) is more soluble than the thermoplastic resin (b1). The surface tension (surface energy) is not particularly limited as long as it is large, and examples thereof include the following. When a polyolefin-based resin such as polymethylpentene-based resin, polypropylene-based resin, cyclic olefin polymer, or silicone-based resin is used as the thermoplastic resin (b1), the thermoplastic resin (b2) is
It is preferable to use a polystyrene-based resin, a polycarbonate-based resin, a polyacryl-based resin, a polyphenylene ether-based resin, a polyolefin-based resin modified with a maleimide, a carboxylic acid, or the like, a polystyrene-based resin, or the like. Alternatively, when a polystyrene resin is used as the thermoplastic resin (b1), a polycarbonate resin, a polyacrylic resin, a polyphenylene ether resin, a polyolefin modified with maleimide, carboxylic acid, or the like is used as the thermoplastic resin (b2). It is preferable to use a system resin. Further, the thermoplastic resin (b1) and the thermoplastic resin (b2)
Can be used alone or in combination of two or more resins, if necessary.

The thermoplastic resin (b1) and the thermoplastic resin (b
The blending amount of 2) is not particularly limited as long as a desired void-forming action is obtained with respect to the polyester resin (a), but preferably, the thermoplastic resin (b1) is mixed with 100 parts by weight of the thermoplastic resin (b1). b2) It is preferred that the amount be 0.01 to 20 parts by weight. Thermoplastic resin (b1) 100
The lower limit of the amount of the thermoplastic resin (b2) relative to parts by weight is more preferably 0.02 parts by weight, particularly preferably 0.1 part by weight. The upper limit is more preferably 15 parts by weight, particularly preferably 10 parts by weight.

If the amount of the thermoplastic resin (b2) is less than 0.01 part by weight per 100 parts by weight of the thermoplastic resin (b1), the effect of finely dispersing the thermoplastic resin (b1) as a "dispersible resin" is not obtained. On the other hand, if it exceeds 20 parts by weight, the thermoplastic resin (b2) becomes
It is difficult to obtain a cavity having a desired size, for example, by covering most of 1) and forming a cavity having a length shorter than the thickness. By setting the mixing ratio of the thermoplastic resin (b1) and the thermoplastic resin (b2) within the above range, the thermoplastic resin (b2) having a large surface tension partially replaces the thermoplastic resin (b1) having a small surface tension. The coating or the whole is thinly coated, and the influence on the adhesiveness of the thermoplastic resin (b1) to the polyester resin (a) is negligible. Therefore, the fine dispersion effect of the thermoplastic resin (b2) is effectively exhibited, and the thermoplastic resin (b1) can be finely dispersed in the polyester-based resin (a). Can be obtained in large numbers. In the polyester resin (a), the thermoplastic resin (b2)
There is no particular limitation on the state in which the resin is coated with the thermoplastic resin (b1). For example, a state in which a coated part and an uncoated part are present regularly, such as a mesh, a state in which the coated part is randomly distributed, and a state in which the whole is thinly coated. A state, or a state in which a plurality of the above states coexist, may be mentioned.

When the thermoplastic resin (b) is composed of the above two kinds of thermoplastic resins (b1) and (b2), polyester of the thermoplastic resin (b1) and the thermoplastic resin (b2) The compounding amount in the system resin (a) is
The polyester resin (a), which mainly comprises the A layer, may be appropriately set according to the characteristics required for the reflective film for a surface light source of the present invention, particularly the amount of voids formed in the A layer, the stretching conditions during the production of the A layer, and the like. And thermoplastic resin (b1)
And the sum of the amounts of the thermoplastic resin (b1) and the thermoplastic resin (b2) in the total amount of the thermoplastic resin (b2) is preferably in the range of 3 to 30% by weight, more preferably 5 to 25% by weight. It is better to be. Thermoplastic resin (b
The sum of the amounts of 1) and the thermoplastic resin (b2) is 3% by weight.
If it is less than 30%, the amount of cavities generated in the stretching step at the time of forming the A layer is small, and the reflectance and light scattering in the visible light region are reduced. And the strength or waist strength may also decrease.

In the present invention, the layer A preferably does not substantially contain inorganic particles. By not substantially containing inorganic particles, a high reflectance can be easily obtained.

The substrate used in the reflection film for a surface light source of the present invention may be a single layer of only the polyester resin layer (A layer) containing a large number of the above-mentioned fine cavities. A multilayer structure having another layer may be used as long as the action is not impaired. In particular, at least on one side of the side having the polymer easy-adhesion layer described later, it is a configuration having a polyester resin layer containing substantially no voids, the adhesion between the substrate and the polymer easy-adhesion layer is further improved Improved and preferred.

In the present invention, if necessary, the layer A and the other layers described above may contain other components such as a fluorescent whitening agent, an antistatic agent, and an ultraviolet absorber as long as they do not impair the function of the present invention. Can be contained in an appropriate amount.

The layer A has an apparent density of 0.6 to 1.3.
g / cm ³ is preferable. When the apparent density is less than 0.6 g / cm ³ , the void content is too high, and the strength of the A layer is reduced, and cracks and wrinkles are easily generated on the surface of the A layer, and the commercial value is reduced. However, those having a high density exceeding 1.3 g / cm ³ have too low a void content, so that it is difficult to obtain desired reflection characteristics in the visible light region.

In the present invention, the method of forming the substrate is not particularly limited, and a generally used film forming method can be used. As a method of forming a film, from the viewpoint of productivity, the materials constituting the base material are mixed, extruded from an extruder, guided to a die to obtain an unstretched sheet, and then the unstretched sheet is stretched biaxially. The method is most preferred. When the base material has a multilayer structure, the layer A and the other layers may be formed simultaneously or separately formed and laminated.

In the present invention, specific examples of a method for forming a substrate will be described below. First, the respective components constituting the base material are mixed and extruded by melt to form an unstretched sheet. Examples of the method for forming the unstretched sheet include, for example, a method in which a mixture of each component such as a resin chip is melted and kneaded in an extruder and then extruded and solidified, and a method in which these components are kneaded in a kneader in advance. A method of dissolving and extruding with an extruder to solidify, in a polymerization step of a polyester constituting the polyester resin (a), adding a thermoplastic resin (b) incompatible with the polyester resin (a), and stirring and dispersing. And a method of dissolving, extruding, and solidifying the obtained chips. The unstretched sheet thus obtained is usually in a non-oriented or weakly oriented state, and the thermoplastic resin (b) incompatible with the polyester resin (a) is
The particles are dispersed in the polyester resin (a) in various shapes such as a spherical shape, an elliptical spherical shape, and a thread shape.

The method of stretching the unstretched film obtained as described above is not particularly limited, but it is preferable to stretch the film in at least one axial direction. By stretching
Peeling occurs at the interface between the polyester resin (a) and the thermoplastic resin (b), and many cavities are generated. The stretching method is
Roll stretching method (a method of stretching between two or more rolls having different peripheral speeds in the running direction of the film), long gap stretching method, tenter stretching method (a stretching method in which the film is held by clips and spread), tubular Any known method such as a stretching method and an inflation stretching method (a stretching method of expanding by air pressure) can be used, and the film is stretched in a predetermined one direction (main stretching direction). In the case of stretching, any of the methods can use sequential biaxial stretching, simultaneous biaxial stretching, monoaxial stretching, and combinations thereof. When biaxial stretching is performed, simultaneous biaxial stretching in which stretching in the vertical and horizontal directions is performed at the same time may be performed. However, in order to obtain a better stretching effect, sequential biaxial stretching in which one of the two is performed first is performed. Good to do. In the case of performing sequential biaxial stretching, the stretching order in the longitudinal and transverse directions may be performed first, but in consideration of the mechanical properties of the obtained film, after stretching in the longitudinal direction corresponding to the flow direction of the film first, Next, stretching in the transverse direction is preferred.

The following is an example of a stretching method in the case of sequentially performing biaxial stretching. In the present invention, the formation of the base material, particularly the layer A, is preferably performed in two or more different temperature ranges when performing lateral stretching, and the final transverse stretching temperature is preferably in the range of 180 ° C. or more. Thus, in the transverse stretching, a stretching temperature generally used (80 to 140 ° C.)
By stretching at a higher temperature, the cavity is sufficiently deformed, and a cavity sufficiently long in thickness can be formed.

In general, when a film containing a large number of cavities is formed, sequential biaxial stretching is performed according to Japanese Patent Application Laid-Open No. 63-16844.
No. 1, JP-A-63-193938, JP-A-Hei 2
-80247, JP-A-2-284929,
JP-A-3-114817, JP-A-4-20254
As described in Japanese Patent Publication No. 0, etc., the unstretched sheet is roll-stretched in the longitudinal direction, then tenter-stretched in the width direction, and then heat-treated at 150 ° C. or higher. Here, in roll stretching (longitudinal stretching), in order to generate a large number of cavities, the stretching temperature is set to 80 to 100 ° C., the stretching ratio is set to 2.0 to 5.0, and then tenter stretching (lateral stretching) is performed to 80 to 140 ° C. ,
Although the stretching ratio is set to 2.8 to 5.0, in the present invention, the sequential biaxial stretching is specifically preferably performed as follows. That is, after the longitudinal stretching of the unstretched film, first the first transverse stretching at 100 to 150 ° C. and a stretching ratio of 2.0 to
3.0 times, and the second horizontal stretching is 180-230.
C. at a stretching ratio of 1.2 to 2.0. Here, the first horizontal stretching magnification is preferably lower than the longitudinal stretching magnification. In this case, the first stretching is to sufficiently generate cavities in the film, and the second stretching is to make the cavities small in thickness and balanced in both length and width. 2. Almost no increase in the number of cavities due to the second stretching is observed. The sum of the first and second horizontal stretching ratios may exceed the vertical stretching ratio. After performing the two-stage transverse stretching as described above, it is preferable to further perform a heat treatment, and the temperature of the heat treatment is preferably 200 ° C.
Or more, more preferably 220 ° C. or more, particularly preferably 2 ° C.
The temperature is preferably 30 ° C. or higher. The heat treatment may be performed after performing a relaxation treatment of 2 to 5%.

In the present invention, the sequential biaxial stretching is performed under the above-mentioned specific conditions, whereby the cavities in the film are easily deformed, and the thermoplastic resin (b) for generating the cavities is, for example, polymethyl. Even when a resin such as a polyolefin resin such as pentene or polypropylene, or a resin such as a polystyrene resin is used, the cavity is easily deformed without collapsing during tenter stretching.

The thickness of the layer A and the entire substrate is not particularly limited. However, when the purpose is to reduce the weight and thickness of the liquid crystal display device using the reflective film for a surface light source of the present invention, the thickness of the entire substrate is considered. Is preferably 200 μm or less, more preferably 150 μm or more and 200 μm or less. When the thickness of the entire substrate is 100 μm or less, it is difficult to obtain sufficient reflection characteristics.

In the present invention, the constituent material and the forming method of the polymer easy-adhesion layer are not particularly limited. However, when the polymer easy-adhesion layer is formed by laminating a UV-curable ink layer on the surface of the polymer easy-adhesion layer, Adhesion (measured in accordance with JIS K5400 8.5. 1) of the UV-curable ink layer to the polymer-friendly adhesive layer and the polymer-easiness of the oxidation-polymerized ink layer when the oxide-polymerized ink layer is laminated Adhesion to adhesive layer (J
(Measured in accordance with IS K5400 8.5.1.) Is preferably 95% or more.

In order to make the adhesion of the UV-curable ink layer or the oxidative polymerization ink layer to the polymer adhesive layer as described above, for example, as a constituent material of the polymer adhesive layer,
Examples include a method using a copolymerized polyester resin containing a branched glycol as a constituent component and a composition containing a resin containing a blocked isocyanate group.

The copolymerized polyester resin containing the above-mentioned branched glycol used for the polymer adhesive layer is water-soluble or water-dispersible. Examples of branched glycol components contained in the copolymerized polyester resin include 2,2-dimethyl-1,3-propanediol,
-Methyl-2-ethyl-1,3-propanediol, 2
-Methyl-2-propyl-1,3-propanediol,
2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-butyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3-propanediol, 2,2 -Diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2-di- n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,
3-propanediol, 2,2-di-n-hexyl-
1,3-propanediol and the like. These may be one kind or two or more kinds.

The above-mentioned branched glycol component is preferably contained in a proportion of at least 10 mol%, more preferably at least 20 mol%, in all the glycol components.

As the glycol component other than the branched glycol component compound contained in the copolymerized polyester resin, ethylene glycol is most preferable. Besides, diethylene glycol, propylene glycol, butanediol, hexanediol, 1,4-cyclohexanedimethanol and the like can be used, but a small amount is preferable.

As the dicarboxylic acid component contained as a constituent component in the copolymerized polyester resin, terephthalic acid and / or isophthalic acid are most preferable. Other dicarboxylic acid components, such as adipic acid, sebacic acid,
A fatty acid dicarboxylic acid such as azelaic acid, or an aromatic dicarboxylic acid such as diphenyldicarboxylic acid or 2,6-naphthalenedicarboxylic acid may be added for copolymerization, but a small amount is preferable.

The above-mentioned copolymerized polyester resin containing a branched glycol as a constituent is usually used in a state of being dissolved or dispersed in a solvent (water or a mixed solvent of water and another solvent). polyester:
Butyl cellosolve: water = 30: 15: 55 (weight ratio).

As the resin containing a block type isocyanate used for the polymer adhesive layer, a heat-reactive water-soluble urethane resin in which terminal isocyanate groups are blocked by a hydrophilic group (hereinafter referred to as a block) is preferable. The heat-reactive water-soluble urethane resin is usually used in a state of being dissolved in a solvent (water or a mixed solvent of water and another solvent). 20:80 (weight ratio).

In the above-mentioned heat-reactive water-soluble urethane resin, examples of the blocking agent for blocking the terminal isocyanate group include bisulfites, phenols containing sulfone groups, alcohols, lactams, oximes, active methylene compounds and the like. Is mentioned. The blocked isocyanate group renders the urethane prepolymer hydrophilic or water-soluble. When heat energy is given to the heat-reactive water-soluble urethane resin in the course of drying or heat setting at the time of film production, the blocking agent separates from the isocyanate group, so that the heat-reactive water-soluble urethane resin has a self-crosslinked network. Then, the copolymerized polyester resin containing the above-mentioned branched glycol mixed together as a constituent is immobilized, and also reacts with the terminal group of the copolymerized polyester resin. When preparing a coating solution for forming a polymer easy-adhesion layer,
The heat-reactive water-soluble urethane resin is poor in water resistance because it is hydrophilic, but when the heat reaction is completed through the steps of coating, drying and heat setting, the hydrophilic group of the heat-reactive water-soluble urethane resin, that is, the blocking agent is used. However, a coating film having good water resistance can be obtained. Among the above blocking agents, bisulfites are particularly suitable as those which are suitable for heat treatment temperature and heat treatment time and are widely used industrially.

The urethane prepolymer used in the heat-reactive water-soluble urethane resin has the following chemical composition: (i) having two or more active hydrogen atoms in the molecule;
Reaction with a compound having a molecular weight of 200 to 20,000, (ii) an organic polyisocyanate having two or more isocyanate groups in the molecule, or (iii) a chain extender having at least two active hydrogen atoms in the molecule. Compounds which are obtained at least and have an isocyanate group at the terminal are exemplified.

The compound (i) generally includes two or more hydroxyl groups, carboxyl groups, amino groups, or mercapto groups at the terminal or in the molecule. Particularly preferred compounds are , Polyether polyols, polyester polyols, polyether ester polyols and the like. Examples of the polyether polyol include compounds obtained by polymerizing alkylene oxides such as ethylene oxide and propylene oxide, styrene oxide and epichlorohydrin,
Alternatively, compounds obtained by performing random copolymerization, block copolymerization, or addition polymerization to a polyhydric alcohol may be mentioned. Polyester polyols and polyetherester polyols mainly include linear or branched compounds, and succinic acid, adipic acid, phthalic acid, polyvalent saturated or unsaturated carboxylic acids such as maleic anhydride, and the like. Carboxylic acid anhydrides and the like, ethylene glycol, diethylene glycol, 1,
4-butanediol, neopentyl glycol, 1,6
By condensing polyhydric saturated or unsaturated alcohols such as hexanediol and trimethylolpropane, polyalkylene ether glycols such as relatively low molecular weight polyethylene glycol and polypropylene glycol, and a mixture of these alcohols. What can be produced are mentioned. Furthermore, polyester polyols include polyesters obtained from lactones and hydroxy acids, and polyether ester polyols include polyesters produced in advance,
Examples include polyetheresters to which ethylene oxide, propylene oxide, or the like has been added.

Examples of the organic polyisocyanate (ii) include isomers of toluylene diisocyanate,
Aromatic diisocyanates such as 4′-diphenylmethane diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate, alicyclic diisocyanates such as 4,4′-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, Aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate,
Alternatively, polyisocyanates in which a single kind or plural kinds of these compounds are added in advance to trimethylolpropane or the like can be mentioned.

Examples of the chain extender having at least two active hydrogen atoms (iii) include ethylene glycol, diethylene glycol, 1,4-butanediol,
Glycols such as 1,6-hexanediol, polyhydric alcohols such as glycerin, trimethylolpropane and pentaerythritol, diamines such as ethylenediamine, hexamethylenediamine and piperazine, aminoalcohols such as monoethanolamine and diethanolamine And thiodiglycols such as thiodiethylene glycol, and water.

In order to synthesize the urethane prepolymer having the chemical composition of the above (iii), it is preferably 150 ° C. or lower, more preferably 70 ° C. or less, by a one-stage or multi-stage isocyanate polyaddition method using the above chain extender.
A method of reacting at a temperature of 120 ° C. for 5 minutes to several hours is exemplified. The equivalent ratio of isocyanate groups to active hydrogen atoms can be freely selected as long as it is 1 or more, but it is necessary that free isocyanate groups remain in the obtained urethane prepolymer. Further, the content of free isocyanate groups may be 10% by weight or less, but is preferably 7% by weight or less in consideration of the stability of the aqueous urethane prepolymer solution after blocking.

The urethane prepolymer having the chemical composition of the above (i) to (iii) is preferably blocked by using bisulfite. The specific method is as follows, for example. The urethane prepolymer and the aqueous solution of bisulfuric acid are mixed, and the reaction is allowed to proceed with good stirring for about 5 minutes to 1 hour. The reaction temperature is preferably set to 60 ° C. or lower. Thereafter, the mixture is diluted with water to an appropriate concentration to obtain a heat-reactive water-soluble urethane composition. When the urethane composition is used,
It is adjusted to an appropriate concentration and viscosity.
When heated to around ° C, the bisulfite of the blocking agent is dissociated, and the active isocyanate groups are regenerated. Thus, a polyurethane polymer is formed by intramolecular or intermolecular polyaddition reaction of the prepolymer or other functional groups. It has the property of causing addition to a group.

As the heat-reactive water-soluble urethane resin, commercially available resins can be used, and as one example, Elastron H-3 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. is typically exemplified. Elastrone is obtained by blocking an isocyanate group with sodium bisulfite, and is water-soluble because a carbamoyl sulfonate group having strong hydrophilicity is present at a molecular terminal.

In the present invention, the compounding ratio of the copolymerized polyester resin containing a branched glycol as a constituent and the resin containing a block type isocyanate group in the composition constituting the high polymer adhesive layer is based on the solid content. In a weight ratio of, a copolymerized polyester resin containing a branched glycol as a constituent component / a resin containing a blocked isocyanate group = 10/90 to 90/10, more preferably 30/70 to 70/30. It is. If the proportion of the copolymerized polyester resin containing a branched glycol as a component in the solid content is less than 10% by weight, the adhesion of the polymer easy-adhesion layer to the base material is apt to be reduced, and the oxidative polymerization type ink is used. Of the adhesive becomes poor. Also, 9
If the content exceeds 0% by weight, the adhesion of the ink layer when the ink layer composed of the UV-curable ink is formed on the surface of the polymer easily-adhesive layer tends to decrease.

In the present invention, it is preferable to add a surface roughening substance to the composition constituting the high polymer adhesive layer in order to impart surface smoothness. The surface roughening material is not particularly limited as long as it is a particle that adheres to the resin constituting the polymer adhesive layer, and is particularly preferably an inorganic particle or an organic particle having an average particle diameter of 0.6 to 6 m. Is preferred. More preferably, as the inorganic particles, silica particles, calcium carbonate particles, as organic particles melamine particles,
Benzoguanamine / melamine copolymer resin particles may have excellent adhesion to the resin constituting the high polymer adhesive layer. In the case of particles having another composition, the adhesion to the resin constituting the high polymer adhesive layer is reduced. These may be used as a mixture of two or more. When the average particle size of the particles is out of the range of the average particle size, even if the particle composition is silica-based particles, calcium carbonate-based particles, melamine-based particles, benzoguanamine / melamine copolymer resin particles, Adhesion with the resin constituting the molecular adhesion layer is reduced.

The compounding ratio of the above-mentioned surface roughening substance to the composition constituting the polymer adhesive layer is determined based on the solid content of the coating liquid when the coating liquid is used for forming the polymer adhesive layer. It is preferably from 0.5 to 30% by weight, more preferably from 3 to 5% by weight, based on the weight. When the proportion of the surface roughening substance is less than 0.5% by weight, it is difficult to obtain the effect of blending the surface roughening substance, the surface lubricity is reduced, and scratches are likely to occur in a subsequent step. If the ratio of the surface roughening substance exceeds 30% by weight, the adhesion of the polymer easy-adhesion layer to the substrate tends to decrease.

The polymer easy-adhesion layer may further contain, if necessary, an antistatic agent, an antiblocking agent, an antioxidant, a surfactant, a lubricant and the like within a range not to impair the function of the present invention. it can.

In the present invention, there is no particular limitation on the method of forming the easily polymerizable adhesive layer on the base material. Adjust and apply the coating solution onto the substrate using a usual coating device such as a gravure coater, reverse kiss coater, reverse roll coater, multilayer curtain coater, bar coater or air doctor coater, and heat fixing treatment Is performed. Also,
Unstretched, or uniaxially stretched, after applying the coating solution to the substrate that has been subjected to biaxial stretching, may be further subjected to stretching, preferably, coating the coating solution on at least one surface of the substrate stretched in the uniaxial direction Then, a method of stretching in a direction perpendicular to the uniaxial stretching direction is preferred.

When a method for applying a coating solution is used as a method for forming the high polymer adhesive layer on the substrate, the coating thickness of the coating solution is preferably 0.01 to 5 um, more preferably wet. Is 0.05 to 2 m. With such a coating thickness, the thickness of the polymer liquid adhesive layer is about 0.01 to 0.6 um when dried. If the coating thickness is less than 0.01 m, the adhesion of the polymer liquid adhesive layer to the substrate tends to decrease, and the adhesion of the surface roughening substance tends to decrease. When the coating thickness is more than 5 m, it is difficult to apply the coating solution uniformly due to problems such as physical properties and rheology of the coating solution, and facilities.

The reflective film for a surface light source of the present invention may further have another layer as long as the function of the present invention is not impaired. For example, there is a case where a metal thin film layer is laminated on the side opposite to the surface on which the polymer easy-adhesion layer is formed for the purpose of improving the heat ray reflection performance and the concealing property. The type of metal in the metal thin film layer is not particularly limited, but silver is particularly preferred from the viewpoint of reflection performance.

Hereinafter, the effects of the present invention will be described in more detail with reference to Test Examples and Examples. However, the present invention is not limited to these, and modifications may be made within a range not to impair the effects of the present invention. Are all included in the technical scope of the present invention. . Test example Test Method Adhesion of UV-curable Ink Layer The UV-curable ink was applied to the surface of the polymer easy-adhesion layer of the reflective film for surface light source of Examples 1 to 4 and to one surface of the reflective film for surface light source of Comparative Examples 1 and 2. (UVA 710 black,
After applying Seiko Advance Co., Ltd.) with a Tetron screen (# 300 mesh),
It was exposed to UV light at j / cm ² and printed to form a UV curable ink layer. According to the method described in 8.5.1 of JIS-K5400, 100 pieces having a depth reaching the base material through the UV curable ink layer and the polymer adhesive layer (only Examples 1 to 4). Is formed using a cutter guide having a gap of 2 mm, and a cellophane adhesive tape (manufactured by Nichiban Co., Ltd., No. 405, 24 mm width) is stuck on the grid-shaped cut of the UV-curable ink layer, After rubbing with an eraser from above to completely adhere to the UV-curable ink layer, peel off the surface of the UV-curable ink layer in the vertical direction, measure the number of squares peeled off visually, and calculate the peeled area From the results, the adhesiveness was determined from the following equation. Adhesiveness (%) = (1−peeled area / evaluated area) × 100

Adhesion of Oxidation Polymerization Type Ink Layer An oxidation polymerization type ink layer was formed on the surface of the easily adhesive polymer layer of the reflection film for surface light source of Examples 1 to 4 and on one surface of the reflection film for surface light source of Comparative Examples 1 and 2. Ink (Tetron ink # 990 black
80% by weight and 20% by weight of tetron standard solvent, both of which are manufactured by Jujo Chemical Co., Ltd.) are printed using a tetron screen (# 250 mesh) and left for 24 hours to prepare an oxidative polymerization type ink. A layer was formed. Thereafter, in the same manner as in the above (1), the adhesion of the oxidation polymerization type ink layer to the reflective film for a surface light source was determined.

[0055]

Example 1 [Production of base material] The compositions constituting each of the layers A and B as shown below were separately charged into two twin screw extruders, and were placed in a T-die. After lamination, the mixture was melted and extruded from a T-die at 290 ° C., then electrostatically contacted with a cooling rotating roll and solidified to obtain an unstretched sheet. Next, the unstretched sheet is set on a roll stretching machine,
After stretching longitudinally 3.1 times at 125 ° C., 125
The film is stretched 2.6 times at ℃,
The film was stretched 1.4 times at 20 ° C. Thereafter, by performing a relaxation heat treatment of 4% at 235 ° C., a laminated film of a layer containing a large number of cavities (A layer) and a layer having substantially no cavities (B layer) is obtained. The substrate was used. The thickness is A
Layer / B = 183/5 μm. <Constituent material of layer (A layer) containing many cavities inside> Polyethylene terephthalate resin (intrinsic viscosity: 0.62 dl / g) 74% by weight Polyethylene resin for general use (PS) [Mitsui Toatsu Chemical Co., Ltd.] Manufactured by T575-57U] 25% by weight Maleimide-modified polystyrene resin (M-PS) [manufactured by Mitsui Toatsu Chemicals, Inc., NH1200] 1% by weight <Constituent material of layer (B layer) having substantially no voids > Polyethylene terephthalate resin (intrinsic viscosity: 0.62 dl / g) 100% by weight [Adjustment of coating liquid for forming polymer easy-adhesion layer] A coating liquid for forming polymer easy-adhesion layer was prepared according to the following method. In the examples, “parts” means “parts by weight”. 95 parts of dimethyl terephthalate, 95 parts of dimethyl isophthalate, 35 parts of ethylene glycol, neopentyl glycol 14
5 parts, zinc acetate 0.1 part and antimony trioxide 0.1
The mixture was charged into a reaction vessel and transesterification was carried out at 180 ° C. for 3 hours. Next, 6.0 parts of 5-sodium sulfoisophthalic acid was added, and the esterification reaction was carried out at 240 ° C. for 1 hour, and then under reduced pressure (27 Pa) at 250 ° C.
To 1333 Pa) for 2 hours to obtain a water-dispersible polyester resin having a molecular weight of 19,500 and a softening point of 60 ° C. 30 of the obtained water-dispersible polyester resin
6, 7 parts of a 20% by weight aqueous dispersion, 20 parts of a 20% by weight aqueous solution of a heat-reactive polyurethane resin containing an isocyanate group blocked with sodium bisulfite (available from Daiichi Kogyo Seiyaku Co., Ltd., trade name: Elastron H-3), 0.5 parts catalyst for Elastron (Daiichi Kogyo Seiyaku; trade name Cat64) and 4 parts water
7, 8 parts and 25 parts of isopropyl alcohol were mixed, and further, 1% by weight of an anionic surfactant was added.
Benzoguanamine / melamine copolymerized organic particles having an average particle diameter of 2 μm (manufactured by Nippon Shokubai Kagaku Co., Ltd.) were added and mixed so as to be 0.5% by weight based on the solid content of the coating solution. did. [Formation of polymer easy-adhesion layer] On the surface of the base material on the layer B side,
Using a coating solution for forming the polymer easy-adhesion layer, a wire bar (N
o. Using 5), apply so that the amount becomes about 10 g per 1 m ² (wet state), then dry at 70 ° C. for 60 seconds, and heat-treat at 200 ° C. for 30 seconds to form a high polymer adhesive layer. Thus, a reflection film for a surface light source was obtained. The adhesion of the UV-curable ink layer to the obtained reflection film for a surface light source was 100%, and the adhesion of the oxidation polymerization type ink layer was 99%.

Example 2 The compositions constituting each of the A layer and the B layer as in Example 1 were separately charged into two twin screw extruders as in Example 1, and were placed in a T-die. After laminating, T-
After being melted and extruded at 290 ° C. by a die, it was electrostatically brought into close contact with a cooling rotating roll and solidified to obtain an unstretched sheet. Next, the unstretched sheet is set on a roll stretching machine,
After longitudinal stretching 3.1 times at 0 ° C, reverse kiss
The following coating solution for forming a polymer easy-adhesion layer is applied by a coating method so as to be about 10 g (wet state) per 1 m ² , and then is horizontally stretched 2.6 times at 125 ° C. by a tenter. And stretched 1.4 times at 220 ° C. Thereafter, by performing a relaxation heat treatment of 4% at 235 ° C.,
Layer with many cavities inside (A layer, thickness 183 μm)
And a layer having substantially no voids (layer B having a thickness of 5 μm), a reflective film for a surface light source having an easily adhesive polymer layer was obtained. The adhesion of the UV curable ink layer and the adhesion of the oxidative polymerization ink layer to the obtained reflection film for a surface light source were both 100%. [Preparation of Coating Solution for Forming Highly Adhesive Layer for Polymer] 16,7 parts of a 30% by weight aqueous dispersion of the water-acidic polyester resin obtained in Example 1 was subjected to a thermal reaction containing an isocyanate group blocked with sodium bisulfite. 20% by weight aqueous solution of polyurethane resin (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Elastron H
3), 20 parts of elastron catalyst (Daiichi Kogyo Seiyaku:
0.5 part of trade name Cat64), 37 and 8 parts of water and 25 parts of isopropyl alcohol were mixed, respectively, further, 1% by weight of an anionic surfactant and an average particle diameter of 2 μm.
m of benzoguanamine / melamine copolymer-containing mechanical system particles (manufactured by Nippon Shokubai Kagaku Co., Ltd.) was added and mixed in an amount of 5% by weight based on the solids of the coating solution to prepare a coating solution for easy adhesion of polymer.

Example 3 In preparing a coating solution for forming a high polymer adhesive layer, except that silica-based inorganic particles having an average particle size of 2.5 μm were used instead of benzoguanamine / melamine copolymerized organic particles,
In the same manner as in Example 1, a reflective film for a surface light source was obtained.
The adhesiveness of the UV curable ink layer and the adhesiveness of the oxidative polymerization ink layer to the obtained reflection film for a surface light source were both 100%.

Example 4 An adhesive (X395-270S-1) was applied to the surface of the reflective film for a surface light source obtained in Example 1 on the surface opposite to the surface of the polymer adhesive layer using a wire bar (No. 8). Co., Ltd.) (Siden Chemical Co., Ltd.) at 30 g / m ² by WET,
It dried at 1 degreeC for 1 minute, and formed the adhesive layer. Then, 1μ
an antioxidant layer having a thickness of 50 m, a silver thin film layer having a thickness of 50 nm,
The surface of the antioxidant layer and the surface of the pressure-sensitive adhesive layer of a silver film (Ag12, manufactured by Saiichi Kogyo Co., Ltd.) having a 2 μm-thick polyester film layer were superposed, guided between two rolls, and bonded by heating and pressing. When bonding the antioxidant layer surface and the pressure-sensitive adhesive layer surface between the two rolls, the surface temperature of each roll was set to 50 ° C, and the pressure at the time of bonding was set to a linear pressure of 1000N.
/ Cm. The adhesiveness of the UV curable ink layer to the obtained reflective film for a surface light source was 100%, and the adhesiveness of the oxidation polymerization type ink layer was 98%.

Comparative Example 1 The same composition as that of the layer A as in Example 1 was charged into a twin screw extruder, melt-extruded from a T-die at 290 ° C., and then electrostatically adhered to a cooling rotary roll. And solidified to obtain an unstretched sheet. next,
The unstretched sheet is set on a roll stretching machine at 80 ° C. and 3.1.
After performing longitudinal stretching twice, it was 2.6 times at 125 ° C. with a tenter.
The film was stretched laterally twice and further stretched 1.4 times at 220 ° C. by a tenter. Thereafter, a 4% relaxation heat treatment at 235 ° C. was performed to obtain a reflective film for a surface light source containing a large number of cavities inside. The thickness was 188 μm. The adhesiveness of the UV curable ink layer to the obtained reflective film for a surface light source was 35%, and the adhesiveness of the oxidation polymerization type ink layer was 56%.

Comparative Example 2 A reflective film for a surface light source was obtained in the same manner as in Example 1 except that the high polymer adhesive layer was not formed. The adhesiveness of the UV curable ink layer to the obtained reflective film for a surface light source is 3
8%, and the adhesion of the oxidation polymerization type ink layer was 65%.

[0061]

The reflection film for a surface light source of the present invention has an easily polymerizable adhesive layer, and is provided at a position where a bright line is generated in the vicinity of the linear light source in order to eliminate the adverse effect of the bright line. It has excellent adhesion to printing layers made of mold inks and UV-curable inks.

[Procedure amendment]

[Submission date] September 1, 2000 (2009.1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction contents]

In the present invention, it is preferable to add a surface roughening substance to the composition constituting the high polymer adhesive layer in order to impart surface smoothness. The surface roughening material is not particularly limited as long as it is a particle that adheres to the resin constituting the polymer easy-adhesion layer.
m, inorganic particles or organic particles are preferred. More preferably, as the inorganic particles, silica particles, calcium carbonate particles, as organic particles melamine particles,
Benzoguanamine / melamine copolymer resin particles may have excellent adhesion to the resin constituting the high polymer adhesive layer. In the case of particles having another composition, the adhesion to the resin constituting the high polymer adhesive layer is reduced. These may be used as a mixture of two or more. When the average particle size of the particles is out of the range of the average particle size, even if the particle composition is silica-based particles, calcium carbonate-based particles, melamine-based particles, benzoguanamine / melamine copolymer resin particles, Adhesion with the resin constituting the molecular adhesion layer is reduced.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0051

[Correction method] Change

[Correction contents]

When a method for applying a coating solution is used as a method for forming the high polymer adhesive layer on the substrate, the coating thickness of the coating solution is preferably 0.01 to 5 μm, more preferably 0 to 5 μm when wet. 0.05 to 2 μm. In the case of such a coating thickness, the thickness of the polymer liquid adhesive layer is about 0.01 to 0.6 μm when dried. Coating thickness is 0.01μm
If it is less than 30, the adhesion of the polymer liquid adhesive layer to the substrate tends to decrease, and the adhesion of the surface roughening substance tends to decrease. If the coating thickness exceeds 5 μm, it becomes difficult to apply the coating solution uniformly due to problems such as physical properties and rheology of the coating solution, and facilities.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H042 BA01 BA15 BA20 DA01 DA11 DA21 DC00 DE00 4F100 AK01B AK04 AK12 AK41A AK41B AK42 AK51B AL01B AL02B AL05B AL07 AT00C BA03 BA07 BA10B BA10C DJ00A GB41 JA20 JL11B J20

Claims (3)

[Claims] At least one surface of a substrate having at least a polyester resin layer containing a large number of fine cavities,
A reflective film for a surface light source, comprising a polymer adhesive layer. 2. The adhesion of the UV curable ink layer to the polymer adhesive layer when the UV curable ink layer is laminated on the surface of the polymer adhesive layer (JIS).
K5400 measured in accordance with 8.5.1.) And the adhesion of the oxidized polymerization ink layer to the high polymer adhesive layer when the oxidized polymerization ink layer is laminated (JIS K5400).
The reflective film for a surface light source according to claim 1, wherein each of the reflection films (measured in accordance with 8.5.1.) Is 95% or more. 3. The high polymer adhesive layer comprises a composition containing a copolymerized polyester resin containing a branched glycol as a constituent and a resin containing a block type isocyanate group. 3. The reflection film for a surface light source according to 1 or 2.