JP2012221682A - Flexible light guide plate and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible light guide plate capable of being excellent in reproductivity of light source colors over a long period from an initial time and efficiently light-emitting in a uniform state and being flexible and used by bending in an arbitrary shape.SOLUTION: In the flexible light guide plate made of thermosetting polyurethane, the thermosetting polyurethane is provided by making a urethane prepolymer made by reacting at least one of polyol components selected from polyether polyol, polycaprolactone polyol, and polycarbonate polyol, and an aliphatic polyisocyanate component thermosetting under existence of a curing agent, or a mixture of the curing agent and the polyol component, and a non-amine system catalyst.

Description

The present invention relates to a flexible light guide plate, particularly an edge light type or full pitch type flexible light guide plate that can be used for lighting, a liquid crystal display, an advertisement display board, an electric signboard, an electric bulletin board, and the like, and a method for manufacturing the same.

Conventionally, a light guide plate made of a hard and highly transparent resin material such as polymethyl methacrylate (PMMA) or polycarbonate introduces light from the side or back thereof by a fluorescent lamp, a cold cathode tube, an LED, etc. As a planar light source that emits light, it has been used in liquid crystal displays such as televisions, personal computers, and mobile phones, as well as lighting and electric signs.
However, since the light guide plate made of these transparent resin materials is poor in flexibility, when it is used for a curved display, or when it is used for lighting, signboard, etc. having a design such as an arc shape or a wave shape. In order to obtain such a molded product, it is necessary to prepare a mold for each molded product, and the problem is that the versatility is poor and the manufacturing cost is high. was there. It is also possible to reduce the thickness of the light guide plate made of PMMA or polycarbonate to give flexibility, but in this case, it becomes difficult to efficiently guide light from the light source into the light guide plate. However, there are problems such as a reduction in the efficiency of introducing the light guide plate and the light guide plate being easily damaged.

In addition, as a light guide plate having flexibility (flexibility) (referred to as a flexible light guide plate in this specification), a light guide plate made of silicone rubber or a resin composition mainly composed of an acrylic resin. A light guide plate is also proposed (see, for example, Patent Documents 1 to 3).
However, although the light guide plate made of silicone rubber is excellent in transparency, the mechanical strength is low, and particularly the tear strength is low, so that the light guide plate is easily damaged and easily torn.
In addition, the light guide plate mainly composed of acrylic resin is not only difficult to develop into a flexible light guide plate due to its brittleness, but also the emitted light when white light is incident due to the influence of catalyst residues during the synthesis of acrylic resin. There was a problem that became yellowish.

Furthermore, as other materials of the flexible light guide plate, transparent rubbers such as urethane rubber and urethane-based elastomer have been proposed (see, for example, Patent Document 3).
However, with flexible light guide plates made of urethane rubber, urethane elastomer, etc., even when white light is incident, the emitted light may be colored yellow, resulting in inferior light source color reproducibility and reduced display color reproducibility. Or the color of the print media on which advertisements are drawn cannot be accurately reproduced.

On the other hand, in cited document 4, in the light guide plate made of thermoplastic polyurethane resin, the light guide plate deteriorates (yellows), and as a result, the problem that the emitted light is colored yellow when white light is incident is solved. Therefore, it has been proposed to form a deterioration preventing layer made of an acrylic resin on the surface of the flexible light guide plate.

JP 2008-140698 A JP 2008-20748 A JP 2008-34337 A JP 2011-9125 A

As described above, a flexible light guide plate made of polyurethane has already been proposed.
And in the cited document 4, in the light guide plate made of polyurethane, when white light is incident, the problem that the emitted light is colored yellow is caused by deterioration with time (yellowing) of the light guide plate. It has been proposed to form a deterioration preventing layer in order to prevent deterioration.
However, when the present inventors repeatedly examined a flexible light guide plate made of polyurethane, surprisingly, the problem that the emitted light is colored yellow when white light is incident is the deterioration of polyurethane over time ( Not only due to yellowing), but immediately after molding a flexible light guide plate made of polyurethane, there is a problem that the emitted light is colored yellow when white light is incident even if its appearance is colorless and transparent It became clear that there was something.

Therefore, the present inventors have conducted intensive studies to solve the above problems, and thermally cured a urethane prepolymer obtained by reacting a specific polyol component and a specific isocyanate component in the presence of a non-amine catalyst. In a flexible light guide plate made of thermosetting polyurethane, it has been found that the color difference between the incident light color and the emitted light color is small (excellent light source color reproducibility) over a long period of time immediately after production (initial stage). It has also been found that the flexible light guide plate emits light efficiently and uniformly, has high flexibility, and can be bent into an arbitrary shape, thereby completing the present invention.
Moreover, the invention which concerns on the manufacturing method suitable for manufacturing such a flexible light-guide plate was also completed.

The flexible light guide plate of the present invention is a flexible light guide plate made of thermosetting polyurethane, and the thermosetting polyurethane includes at least one polyol component selected from polyether polyol, polycaprolactone polyol and polycarbonate polyol, and a fat. A thermosetting polyurethane obtained by thermally curing a urethane prepolymer obtained by reacting an aromatic polyisocyanate component with a curing agent or a mixture of the curing agent and the polyol component and in the presence of a non-amine catalyst. It is characterized by being.

The flexible light guide plate has a light transmittance measured with a spectrophotometer of 85% or more in the wavelength range of 400 to 500 nm and 90% or more in the wavelength range of 380 to 780 nm (excluding 400 to 500 nm). It is preferable that

The flexible light guide plate preferably has a JIS-A hardness of 85 to 100 °.
In the flexible light guide plate, the thermosetting polyurethane preferably does not contain an acrylic skeleton.

The first flexible light guide plate manufacturing method of the present invention is a method for manufacturing the flexible light guide plate,
After the silicone rubber layer is formed inside the rotatable cylindrical mold, a material composition containing at least the urethane prepolymer and the non-amine catalyst is poured into the mold, and the mold is The material composition is thermoset by rotating while heating.

The second flexible light guide plate manufacturing method of the present invention is a method for manufacturing the flexible light guide plate,
A material composition containing at least the urethane prepolymer and the non-amine catalyst is poured into a gap of a gap maintaining member continuously fed by a pair of spaced apart rolls through a casting machine, The gap maintaining member holding the material composition in the gap is introduced into a heating device, and the material composition is thermally cured while being held by the gap maintaining member.

In the method for manufacturing the second flexible light guide plate, the interval maintaining member is preferably made of a polyethylene terephthalate (PET) sheet.
Moreover, in the manufacturing method of said 2nd flexible light-guide plate, it is preferable that the said roll is a heating roll.

The flexible light guide plate of the present invention is composed of a thermosetting polyurethane obtained by thermosetting a urethane prepolymer obtained by reacting a specific polyol component and a specific isocyanate component in the presence of a non-amine catalyst. It is excellent in light source color reproducibility over a long period of time, emits light efficiently and uniformly, and is flexible so that it can be bent into any shape.
Therefore, the flexible light guide plate of the present invention can be suitably used for lighting, a liquid crystal television, a liquid crystal display, an advertisement display board, an electric signboard, and the like.
Moreover, according to the manufacturing method of the flexible light-guide plate of this invention, the flexible light-guide plate of this invention which has the outstanding thickness precision and surface smoothness can be manufactured.

FIG. 1 is a perspective view schematically showing an example of a planar light source using the flexible light guide plate of the present invention. FIG. 2 is a perspective view schematically showing an example of how the planar light source shown in FIG. 1 is used. Fig.3 (a) is sectional drawing which shows typically the centrifugal molding machine used with the manufacturing method of the flexible light-guide plate of 1st this invention, (b) is the sectional view on the AA line of (a). is there. FIG. 4 is a partially enlarged cross-sectional view of a portion B in FIG. FIG. 5 is a schematic view for explaining the method for producing the flexible light guide plate of the second invention. 6 is a color photograph of the flexible light guide plate manufactured in Example 2 before and after entering the LED light. FIG. 7 is a color photograph before and after the LED light of the flexible light guide plate manufactured in Comparative Example 2 is incident.

Hereinafter, embodiments of the present invention will be described in detail.
First, the flexible light guide plate of the present invention will be described.
The flexible light guide plate of the present invention is a flexible light guide plate made of thermosetting polyurethane, and the thermosetting polyurethane contains at least one polyol component selected from polyether polyol, polycaprolactone polyol and polycarbonate polyol, and a fat. A thermosetting polyurethane obtained by thermally curing a urethane prepolymer obtained by reacting an aromatic polyisocyanate component with a curing agent or a mixture of the curing agent and the polyol component and in the presence of a non-amine catalyst. is there.

Since the said flexible light-guide plate consists of thermosetting polyurethane, it becomes a flexible light-guide plate which is less distorted and excellent in transparency compared with what shape | molded the thermoplastic polyurethane.

The thermosetting polyurethane is a urethane prepolymer obtained by reacting at least one polyol component selected from polyether polyol, polycaprolactone polyol and polycarbonate polyol with an aliphatic polyisocyanate component, a curing agent, or It is obtained by thermosetting in the presence of a mixture of a curing agent and the above polyol component and a non-amine catalyst.
The thermosetting polyurethane is obtained by thermosetting a urethane prepolymer obtained by reacting such a specific polyol component and a specific isocyanate component in the presence of a non-amine catalyst. The effects described above, in particular, the light source color reproducibility from the initial state (immediately after manufacture) and the excellent reproducibility can be maintained over a long period of time.

In the thermosetting polyurethane, the polyol component is at least one selected from polyether polyol, polycaprolactone polyol, and polycarbonate polyol. Therefore, in addition to the effects described above, in addition to the following effects.
That is, when the polyol component is a polyether polyol, the thermosetting polyurethane has an effect of being excellent in water resistance (hydrolysis resistance), flexibility, and microbial degradation resistance and reducing permanent set.
In addition, when the polyol component is polycaprolactone polyol, the thermosetting polyurethane has high strength, excellent tear strength and abrasion resistance, and also has excellent hydrolysis resistance compared to the condensed ester polyol. Play.
Moreover, when a polyol component is a polycarbonate polyol, there exists an effect that a thermosetting polyurethane is excellent in water resistance (hydrolysis resistance), weather resistance, and heat resistance.
Therefore, in the present invention, the polyol component may be selected from polyether polyol, polycaprolactone polyol, and polycarbonate polyol, depending on the properties required for the flexible light guide plate.
Condensed ester-based polyester polyols are also known as polyol components, which are urethane material components. However, when the above-mentioned condensed ester-based polyester polyol is used as a polyol component, thermosetting polyurethane is the catalyst residue. It is unsuitable as a polyol component of the thermosetting polyurethane of the present invention because it is easy to be colored due to the influence of inspection, etc., and it is difficult to maintain stable performance over a long period because of poor water resistance.

Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polypropylene triol, polypropylene tetraol, polytetramethylene glycol, polytetramethylene triol, polyalkylene glycols such as copolymers thereof, and side chains introduced into these. And derivatives having a branched structure introduced therein, modified products, and mixtures thereof.

Examples of the polycaprolactone polyol include polycaprolactone glycol, polycaprolactone triol, polycaprolactone tetraol, derivatives in which side chains are introduced or branched structures are introduced, modified products, and mixtures thereof. It is done.

Examples of the polycarbonate polyol include polycarbonate glycol, polycarbonate triol, polycarbonate tetraol, derivatives in which side chains are introduced or branched structures are introduced, modified products, and mixtures thereof.

The polyol preferably has a number average molecular weight of 200 to 10,000.
The reason is that when the number average molecular weight is less than 200, the reaction is too fast and molding becomes difficult, or the molded article loses flexibility and becomes brittle. On the other hand, when it exceeds 10,000, the viscosity becomes too high and molding may become difficult, or the molded product may crystallize and become cloudy.

In the thermosetting polyurethane, the isocyanate component is an aliphatic polyisocyanate.
In the present invention, it is important that the isocyanate component is an aliphatic polyisocyanate. This is because when the isocyanate component is an aliphatic polyisocyanate, the light source color reproducibility can be improved from the initial state.
Further, when the isocyanate component is an aliphatic polyisocyanate, the thermosetting polyurethane is discolored by light or heat emitted from the light source and light or heat from outside such as sunlight, and the light source color reproducibility is lowered (and, This does not cause problems such as a decrease in display color reproducibility due to this, a decrease in color reproducibility of print media on which advertisements are drawn, etc.) and a decrease in brightness of the light exit surface. Excellent light source color reproducibility can be maintained over a long period of time.
On the other hand, when the isocyanate component is an isocyanate component other than the aliphatic polyisocyanate, the above-described problems occur.

Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated 4,4′-diphenylmethane diisocyanate, isophorone diisocyanate, lysine diisocyanate, isopropylidenebis (4-cyclohexylisocyanate), norbornane diisocyanate, and the like. And modified forms and multimers of the above. These may be used alone or in combination of two or more.

The curing agent is not particularly limited, and examples thereof include aliphatic or alicyclic low molecular weight glycols, triols such as trimethylolpropane and glycerin, and polyhydric alcohols such as pentaerythritol and sorbitol.
These may be used alone or in combination of two or more.

The thermosetting polyurethane is obtained by thermosetting in the presence of a non-amine catalyst.
Examples of the non-amine catalyst include organic tin compounds such as di-n-butyltin dilaurate, dimethyltin dilaurate, dibutyltin oxide, and octane tin, organic titanium compounds, organic zirconium compounds, carboxylic acid tin salts, and carboxylic acids. Examples thereof include bismuth acid salts.
And since the said non-amine catalyst is used, the said flexible light-guide plate is excellent in light source color reproducibility from an initial state (immediately after manufacture), and can maintain this outstanding reproducibility over a long period of time. It can be discolored for a long time.
On the other hand, in the thermosetting polyurethane obtained by using an amine-based catalyst as the catalyst, the emitted light tends to become yellow when white light is incident, and the appearance is colored over time. There is a problem that the reproducibility with respect to is also lowered.

The non-amine catalyst is preferably added to the material composition so as to be 0.0005 wt% to 3 wt%.
If the amount is less than 0.0005% by weight, the reaction rate cannot be sufficiently increased, and thus a molded product may not be obtained efficiently. On the other hand, if the amount exceeds 3% by weight, the reaction rate is too high, and thus uniform. It may not be possible to obtain a molded body having a thickness, the heat resistance and weather resistance of the molded body may be reduced, the light transmittance may be reduced, and the molded body may be colored. .

The thermosetting polyurethane is obtained by thermosetting a urethane prepolymer obtained by reacting the polyol component and the polyisocyanate component in the presence of a curing agent and a non-amine catalyst, or the urethane prepolymer. Is cured in the presence of a mixture of a curing agent and the above polyol component and a non-amine catalyst.

That is, the thermosetting polyurethane is a thermosetting polyurethane obtained by a prepolymer method or a pseudo prepolymer method.
In the prepolymer method, a polyol and a stoichiometric excess amount of polyisocyanate are reacted to prepare a prepolymer having an isocyanate group at the terminal, and a predetermined amount of a curing agent is mixed therein to prepare a prepolymer. In this method, a polymer is cured to obtain a thermoset polyurethane molded product.
In the pseudo-prepolymer method, a part of polyol is mixed with a curing agent in advance, a prepolymer is prepared with the remaining polyol and polyisocyanate, and a mixture of the polyol and curing agent is mixed therein. This is a method of obtaining a thermosetting polyurethane molded product by curing.
And since a prepolymer is a viscous liquid, when shape | molding thermosetting polyurethane by the 1st or 2nd manufacturing method mentioned later, scattering and a wave of a prepolymer are small, Therefore, the said thermosetting polyurethane The flexible light guide plate made of is excellent in surface smoothness and thickness accuracy.
In this case, the flexible light guide plate can be obtained with a high yield.

The thermosetting polyurethane preferably does not contain an acrylic skeleton (acrylic skeleton or methacrylic skeleton).
Accordingly, the thermosetting polyurethane is preferably, for example, a thermosetting polyurethane excluding acrylic-modified polyurethane.
Thermosetting polyurethane with an acrylic skeleton may impair the flexibility of the polyurethane and reduce the mechanical strength such as abrasion resistance and tear strength. Furthermore, it is used to introduce an acrylic skeleton or an acrylic skeleton. This is because the emitted light may be colored (for example, yellow) due to the remaining catalyst.

The flexible light guide plate of the present invention is made of such a thermosetting polyurethane.
The flexible light guide plate may be an edge light type light guide plate or a full pitch type light guide plate.

In the case of the edge light system, a reflective layer for reflecting the light inside the light guide plate toward the light emitting surface is provided on the surface opposite to the light emitting surface of the flexible light guide plate. Here, the reflective layer can be formed, for example, by screen-printing a white paint containing titanium oxide particles, silica particles, precipitated barium sulfate particles and the like in a dot pattern.
The reflective layer may be formed by a gravure printing method or a patterning method using an ink jet or a drawing method using a dispenser. Furthermore, it may be formed by a method of providing irregularities using a V-groove cutter, a laser microfabrication device, or a water jet device, a method of transferring a mold having an irregular surface, or a reflective layer made of a cured resin by stereolithography. You may form by the method of laminating.

In addition, the flexible light guide plate contains various additives such as a colorant, a light stabilizer, a heat stabilizer, an antioxidant, an antifungal agent, and a flame retardant as required, as long as the required characteristics are not impaired. You may do it.

The flexible light guide plate has a light transmittance measured with a spectrophotometer of 85% or more in the wavelength range of 400 to 500 nm and 90% or more in the wavelength range of 380 to 780 nm (excluding 400 to 500 nm). It is preferable that
Here, the wavelength range of 400 to 500 nm is a wavelength region in which the light transmittance particularly decreases in the thermosetting polyurethane, and in the present invention, a high light transmittance of 85% or more is secured in this region. This is very important. In addition, by being 90% or more in the wavelength range of 380 to 780 nm (excluding 400 to 500 nm), high light transmittance is ensured as a whole flexible light guide plate.
In the flexible light guide plate, when the light transmittance in the wavelength range of 400 to 500 nm is less than 85%, the emitted light is yellowish, so that the reproducibility of the light source color and the color of the print medium is lowered. Further, when the light transmittance in the wavelength range of 380 to 780 nm (excluding 400 to 500 nm) is less than 90%, the light extraction efficiency may be lowered, and the luminance of the light emitting surface may be lowered.

The flexible light guide plate has an arithmetic average value of 90% or more of light transmittance measured every 1 nm in a wavelength range of 380 to 780 nm using a spectrophotometer, and 1 nm in a wavelength range of 400 to 500 nm. It is also preferable that the arithmetic average value of the light transmittance measured every time is 85% or more.
This is also because, when satisfying such characteristics, the luminance of the light emitting surface is increased and the reproducibility of the light source color is excellent.

In the present invention, the light transmittance of the flexible light guide plate refers to the light transmittance of a measurement sample having a mirror-like surface and a thickness of 3 mm.

The flexible light guide plate preferably has a JIS-A hardness of 85 to 100 °.
When the JIS-A hardness is less than 85 °, sheets such as a reflection sheet, a diffusion sheet, a color filter, an advertising medium, a prism sheet, a condensing lens sheet, and a surface protection sheet that are usually used in combination with a flexible light guide plate; Since the flexible light guide plate is easily stuck, the flexibility of the flexible light guide plate is impaired, or an air pocket is generated between the sheets and the flexible light guide plate, so that the light emitting surface of the flexible light guide plate does not emit light uniformly. There is a risk of On the other hand, if the rubber hardness exceeds 100 °, the flexibility of the flexible light guide plate is lowered, and distortion and wrinkles tend to remain when the rubber plate is deformed, for example, curved.

Although the thickness of the said flexible light-guide plate is not specifically limited, It is preferable that it is about 0.5-5 mm. If the thickness is less than 0.5 mm, the light source light may not be efficiently incident when used in an edge light system. On the other hand, if it exceeds 5 mm, flexibility may be impaired.
The thickness accuracy of the flexible light guide plate is preferably 0.1 mm or less, and more preferably 0.05 mm or less.

The surface shape of the flexible light guide plate is preferably a mirror surface. This is because a high-luminance and uniform light-emitting surface can be obtained.
Here, in order to make the surface of the flexible light guide plate a mirror surface, for example, the flexible light guide plate may be manufactured by a first or second manufacturing method described later.

The said flexible light-guide plate is so preferable that yellowness (YI) is small. This is because as the yellowness (YI) increases, the light source color reproducibility decreases.
Specifically, the yellowness (YI) in the initial state is preferably 1.0 or less, and a reliability test conducted under a condition of standing for 1000 hours in a thermostatic bath at a temperature of 60 ° C. and a relative humidity of 85%. The subsequent yellowness (YI) is preferably 3.0 or less.

A flexible light guide plate having such a structure is used in various applications as a liquid crystal display for liquid crystal televisions, personal computers, mobile phones, etc., and as a surface light source for lighting, advertisement display boards, electric signboards, electric bulletin boards, etc. Can be used for
FIG. 1 is a perspective view schematically showing an example of a planar light source using the flexible light guide plate of the present invention, and FIG. 2 schematically shows an example of usage of the planar light source shown in FIG. It is a perspective view.

As shown in FIG. 1, the flexible light guide plate 1 of the present invention has, for example, support members 2 and 3 provided with LED light sources (not shown) on both sides thereof, and light from the LED light sources is incident on the side surfaces. The remaining end sides are held by the flexible frame members 4a and 4b while being held in such a manner as to be used as the planar light source 10A.
A reflective layer (not shown) is formed on the back surface of the flexible light guide plate 1 (the lower surface in FIG. 1).

The planar light source 10A can be used as a cylindrical planar light source 10B by deforming the flexible light guide plate 1 so as to be curved as shown in FIG.

Of course, since the flexible light guide plate of the present invention is excellent in flexibility (flexibility), it can be used by being deformed into an arbitrary shape as well as the shape shown in FIG.

Such a flexible light guide plate made of thermosetting polyurethane can be manufactured, for example, by the method for manufacturing a flexible light guide plate of the first or second aspect of the present invention described later. Each of these manufacturing methods is also one aspect of the present invention.

Next, the manufacturing method of a 1st flexible light-guide plate is demonstrated.
The first flexible light guide plate manufacturing method (also simply referred to as the first manufacturing method) is a method of manufacturing the flexible light guide plate,
After the silicone rubber layer is formed inside the rotatable cylindrical mold, a material composition containing at least the urethane prepolymer and the non-amine catalyst is poured into the mold, and the mold is The material composition is thermoset by rotating while heating.

The first manufacturing method uses a centrifugal molding method in which a thermosetting material composition is poured and cured while rotating a heated rotatable cylindrical mold.

In the first production method, a centrifugal molding method is used. However, it is not necessary to use a new molding machine or mold for the centrifugal molding method, and it has been conventionally used as shown in FIG. A centrifugal molding machine 20 can be used. In the figure, 21 is a mold, 22 is a heat insulating chamber, 23 is a heater, 24 is a front door, and 25 is a rotating shaft.

In the first production method, first, a solvent-free two-component liquid silicone rubber is poured into the inside of the mold to form a molded body of the two-component liquid silicone rubber inside the mold.
FIG. 4 is a cross-sectional view schematically showing a part of the mold (corresponding to part B in FIG. 3A) when centrifugal molding is performed by the first manufacturing method.

In the first manufacturing method, a solvent-free two-component liquid silicone rubber is first poured into the mold 21, so that a silicone rubber layer 28 is formed on the inner surface of the mold 21 as shown in FIG. 4. . Since the silicone rubber layer 28 is first formed on the inner surface of the mold 21 by the two-component liquid silicone rubber having excellent releasability, the thermosetting polyurethane 27 formed thereon can be used without using any release agent. The flexible light guide plate can be peeled off very easily.
In the first production method, since the solvent-free two-component liquid silicone rubber to which no organic solvent is added is used, the health of the work environment can be kept good without harming the health of the worker.

The two-component liquid silicone rubber is not particularly limited, and examples thereof include a condensation type two-component liquid silicone rubber and an addition type two-component liquid silicone rubber. Of these, the condensed type is preferable. The addition-type two-component liquid silicone rubber has a rapid change in reaction rate due to temperature. For example, the curing reaction is too early at a temperature around 140 ° C. necessary for molding a thermosetting polyurethane. On the other hand, if a condensation type two-component liquid silicone rubber is used, the reaction rate can be easily controlled.

Here, the thickness of the silicone rubber layer 28 is preferably 0.5 to 3 mm. If the thickness is less than 0.5 mm, the thickness of the silicone rubber layer 28 is too thin to have strength, and when peeling from the mold, everything cannot be peeled cleanly. In some cases, heat cannot be effectively transferred, and the characteristics of the molded flexible light guide plate may be adversely affected.

In the first manufacturing method, the material composition of the thermosetting polyurethane is subsequently poured into the mold 21 and cured to produce the sheet-like thermosetting polyurethane. In this case, the thickness accuracy of the sheet-like material can be 0.1 mm or less.
Specifically, the already described urethane prepolymer obtained by reacting the polyol component and the polyisocyanate component, the material composition containing the curing agent and the non-amine catalyst, or the urethane prepolymer, What is necessary is just to pour and harden the material composition containing the said polyol component, a hardening | curing agent, and a non-amine-type catalyst.

Here, the curing conditions may be set as appropriate according to the material composition, and are not particularly limited. For example, the curing conditions are a temperature: 60 to 160 ° C., a time: 5 to 180 minutes, and a rotation speed: 200 to 2500 rpm. Just do it.

According to the first manufacturing method, since a mirror-like surface is formed on the air side surface 28a of the silicone rubber layer 28 that has been poured first, the sheet of the thermosetting polyurethane 27 that has been molded by pouring the material composition subsequently. The both-sides 27a and 27b of the shape are mirror-like.
Further, in the first manufacturing method, when the solvent-free two-component liquid silicone rubber is poured into the mold without accurately processing the mold so as to improve the deflection accuracy of the molding mold, The liquid silicone rubber is cured in the form of absorbing the vibration of the mold 21, and the silicone rubber layer 28 having the inner air side surface 28 a having a mirror surface and having high vibration accuracy is formed. Therefore, in the first manufacturing method, the thickness accuracy of the flexible light guide plate can be made extremely high, at least 0.1 mm or less.

In the first manufacturing method, after completion of the molding of the thermosetting polyurethane, the sheet-like material is taken out from the mold and cut into a predetermined size to obtain a flexible light guide plate.
In addition, after taking out from a metal mold | die, you may postcure.

Although it does not specifically limit as a method of cutting the thermosetting polyurethane of the said sheet-like material, For example, it is preferable to cut using an ultrasonic cutter.
This is because the cut surface can be made extremely smooth, and even when this cut surface is used as the light incident surface, the loss upon incidence can be kept small. Further, no polishing process is required.

Next, the manufacturing method of a 2nd flexible light-guide plate is demonstrated.
A second flexible light guide plate manufacturing method (also simply referred to as a second manufacturing method) is a method of manufacturing the flexible light guide plate,
A material composition containing at least the urethane prepolymer and the non-amine catalyst is poured into a gap of a gap maintaining member continuously fed by a pair of spaced apart rolls through a casting machine, The gap maintaining member holding the material composition in the gap is introduced into a heating device, and the material composition is thermally cured while being held by the gap maintaining member.

FIG. 5 is a schematic diagram for explaining the second manufacturing method.
As shown in FIG. 5, in the second production method, a pair of material compositions 30 a containing at least the urethane prepolymer and the non-amine catalyst are disposed apart via a casting machine 31. It is drawn into the heating rolls 33a and 33b and poured into the gap between the continuously fed polyethylene terephthalate sheets (PET sheets) 32a and 32b, and the PET sheets 32a and 32b holding the material composition 30a in the gap are put into the heating device 36. Then, the material composition 30a is thermally cured while being held by the PET sheets 32a and 32b, and the thermosetting polyurethane sheet 30 is formed.

Here, the material composition 30a is the same as the material composition of the thermosetting polyurethane put into the mold by the first manufacturing method.
Further, the PET sheets 32a and 32b have a function as a gap maintaining member, and the gap can be maintained at a constant thickness. Thereby, since the material composition 30a held between the PET sheets 32a and 32b is cured in a state where a certain thickness is maintained, a sheet-like material of thermosetting polyurethane having excellent thickness accuracy is obtained. The thickness accuracy can be made 0.1 mm or less.

Further, when the material composition 30a is supplied from the casting machine 31, the position of the head part 31a of the casting machine 31 is from the central part of the heating rolls 33a and 33b (the central part of the gap formed by the PET sheets 32a and 32b). These are preferably unevenly distributed on the side of one of the heating rolls, and at this time, the uneven distribution distance is preferably not more than the radius of the heating roll. That is, it is preferable that the position directly below the head portion 31a of the casting machine 31 is located at any position from the central portion of the pair of heating rolls 33a and 33b to the center (axis) of one heating roll.
Moreover, it is preferable that the distance (distance with the nearest part of the surface of a heating roll) of the front-end | tip part of the head part 31a and the surface of a heating roll is 3 cm or less.
By disposing the head portion 31a at such a position, the thickness accuracy of the thermosetting polyurethane sheet-like material is further improved, bubbles are less likely to be mixed, and the mixed bubbles are easily removed. .

The heating rolls 33a and 33b are not necessarily heating rolls as long as at least the PET sheets 32a and 32b can be continuously fed out, and may have only a transport function, but are heating rolls. Is preferred.
In this case, since the material composition 30a starts to be cured immediately after being held in the gap between the PET sheets 32a and 32b, the thickness is more uniformly maintained until it is introduced into the heating device 36. This is because it is possible to produce a sheet-like material of thermosetting polyurethane having more excellent thickness accuracy.
Here, it is preferable to set the conveyance surface temperature of the heating rolls 33a and 33b to 10 to 60 ° C.
If it is less than 10 degreeC, while the viscosity of a material composition becomes high and it becomes difficult to remove a bubble, hardening reaction may become slow and the thickness precision of a molded product may fall, On the other hand, if it exceeds 60 degreeC, on a heating roll In some cases, the material composition may harden or bubbles may enter the molded product.

The heating device 36 is a heating furnace provided with a heater, and may be anything that can raise the temperature in the furnace to the curing temperature of the thermosetting polyurethane.
Moreover, the heating conditions (curing conditions) in the heating device 36 are not particularly limited, and may be appropriately set according to the composition of the material composition, for example, temperature: 40 ° C. to 160 ° C., time: 10 to 180 minutes. It is sufficient to perform under the conditions.

In FIG. 5, reference numeral 34 denotes a conveyance roller for sending out the PET sheets 32 a and 32 b, 35 denotes an auxiliary roller, and 37 denotes a conveyor belt for conveying the PET sheets 32 a and 32 b holding the material composition in the heating device 36. It is.

In the second manufacturing method, the gap maintaining member is not limited to a PET sheet, and may be, for example, a sheet-like material made of another resin material such as a polyolefin resin or a metal material.
However, it is preferable that the gap maintaining member is not subjected to a surface treatment such as a mold release treatment on the portion in contact with the material composition 30a, so that the formed thermosetting polyurethane sheet-like material can be peeled off. A PET sheet is preferred because of its superiority.
The reason why it is desirable that the mold release treatment or the like is not performed is to avoid that the mold release agent adheres to the surface of the flexible light guide plate made of the produced thermosetting polyurethane and the optical characteristics are deteriorated. The surface treatment may be performed as long as the treatment agent is not likely to adhere to the flexible light guide plate.
Moreover, it is preferable that the state of the surface which contacts the material composition 30a of the said gap maintenance member is a mirror surface. This is because a sheet-like material of thermosetting polyurethane having a mirror-like surface can be obtained.
The gap maintaining member may be an endless belt that can be used continuously and repeatedly.
The material of the gap maintaining member needs to be selected according to the curing conditions. For example, when curing at a high temperature around 160 ° C., the gap maintaining member is made of a metal such as a steel belt. It is preferable to select a gap maintaining member.

In the second manufacturing method, after completion of the molding of the thermosetting polyurethane 30 (after removal from the heating device), the sheet-like material is peeled off from the gap maintaining member and cut into a predetermined size to obtain a flexible light guide plate. it can.
In addition, after peeling from the gap maintaining member, post-curing may be performed.

It does not specifically limit as a method of cutting the thermosetting polyurethane of the said sheet-like material, The method similar to a 1st manufacturing method can be used.
According to such a 1st or 2nd manufacturing method, the flexible light-guide plate of this invention can be manufactured suitably.

EXAMPLES Hereinafter, although an Example is hung up and demonstrated in more detail about this invention, this invention is not limited only to these Examples.

Example 1
(1) Prepared by reacting polypropylene glycol having an average molecular weight of 2000 (Asahi Glass Co., Ltd., Preminol S-X4001) and isophorone diisocyanate (IPDI, Sumika Bayer Urethane Co., Ltd., Desmodur I) at 80 ° C. for 4 hours in a nitrogen atmosphere. And a urethane prepolymer having an isocyanate group at the end with an NCO% of 17.3%, and an organic tin-based catalyst (manufactured by Nitto Kasei Co., Ltd.) as a curing agent so as to be 0.05% by weight based on the entire polyurethane obtained. , Neostan U-100) polypropylene triol having an average molecular weight of 430 (Asahi Glass Co., Ltd., Exenol 430) and NCO INDEX (number of moles of isocyanate group in urethane prepolymer and mole of hydroxyl group in curing agent) The ratio to the number = NCO] / [OH]) is 1.05 Mixed to prepare a material composition.

(2) Apart from the above (1), a molding die drum (inner diameter: 700 mm, depth: 500 mm, runout accuracy at room temperature: 0.06 mm, number of rotations during molding: 800 rpm, rough surface state: Ra = 0. 30) is heated to 140 ° C., and a mixed liquid of TSE35 (main agent) and CE (curing agent) manufactured by GE Toshiba Silicone is cured as a two-component liquid silicone rubber material. The silicone rubber layer was formed by pouring into the molding die drum and heating and curing for 30 minutes. The obtained silicone rubber layer had a uniform mirror surface on the air side surface and a thickness of 0.7 mm.

(3) The material composition prepared in the above (1) is put into the molding die drum in which the silicone rubber layer is formed in the above (2), and is heated and cured at a rotation speed of 1200 rpm and a heating temperature of 75 ° C. for 120 minutes. From this, a polyurethane sheet having a thickness of 3 mm was obtained. The obtained polyurethane sheet had a uniform mirror surface on both surfaces.
Thereafter, the obtained polyurethane sheet was cut into 400 × 600 mm with an ultrasonic cutter to complete a flexible light guide plate having a thickness of 3 mm.

(Example 2)
(1) Prepared by reacting polycaprolactone glycol having an average molecular weight of 530 (Daicel Chemical Industries, Plaxel 205) and hexamethylene diisocyanate (HDI, Mitsui Chemicals, Takenate 900) at 80 ° C. for 4 hours in a nitrogen atmosphere. Urethane prepolymer having an isocyanate group at the end with an NCO% of 9.7% and an organic zirconium catalyst (manufactured by Matsumoto Fine Chemical Co., Ltd.) as a curing agent so as to be 0.04% by weight based on the entire polyurethane obtained. , ZC-700) and polycaprolactone triol having an average molecular weight of 850 (Dacel Chemical Industries, Plaxel 308) were mixed so that the NCO INDEX was 1.05 to prepare a material composition. .

(2) The material composition prepared in the above (1) is put into a molding die drum having a silicone rubber layer formed in the same manner as in the step (2) of Example 1, and the rotational speed is 1200 rpm and the heating temperature is 110. A polyurethane sheet having a thickness of 3 mm was obtained by heating and curing at 60 ° C. for 60 minutes. The obtained polyurethane sheet had a uniform mirror surface on both surfaces.
Thereafter, the obtained polyurethane sheet was cut into 400 × 600 mm with an ultrasonic cutter to complete a flexible light guide plate having a thickness of 3 mm.

(Example 3)
(1) NCO% prepared by reacting polycarbonate glycol having an average molecular weight of 1000 (Nipporan 981 manufactured by Nippon Polyurethane Industry Co., Ltd.) and hexamethylene diisocyanate (Takenate 900) at 80 ° C. for 4 hours in a nitrogen atmosphere is 12.4%. % Of the urethane prepolymer having an isocyanate group at the terminal and an organic tin-based catalyst (Neostan U-100) as a curing agent so as to be 0.05% by weight based on the whole polyurethane obtained. A material composition was prepared by mixing a mixture of 1,4-butanediol and trimethylolpropane in a weight ratio of 85:15 so that the NCO INDEX was 1.05.

(2) The material composition prepared in (1) above was molded and cut by the same method as in (2) of Example 2 to complete a flexible light guide plate having a thickness of 3 mm. The molded polyurethane sheet had a uniform mirror surface on both surfaces.

Example 4
(1) Tetrahydrofuran-neopentyl glycol copolymer polyether glycol (manufactured by Asahi Kasei Fibers, PTXG-1000) having an average molecular weight of 1000, dicyclohexylmethane diisocyanate (hydrogenated MDI, Sumika Bayer Urethane, Desmodur W) Prepared by reacting for 4 hours at 80 ° C. in a nitrogen atmosphere, and a urethane prepolymer having an isocyanate group at the end of 12.8% NCO%, and 0.05% by weight as a curing agent based on the total polyurethane obtained A mixture of 1,4-butanediol and trimethylolpropane in which an organotin catalyst (Neostan U-100) was dissolved in advance so that the weight ratio was 85:15, NCO INDEX was 1.05 The material composition was prepared by mixing.

(2) The material composition prepared in (1) above was molded and cut by the same method as in (2) of Example 2 to complete a flexible light guide plate having a thickness of 3 mm. The molded polyurethane sheet had a uniform mirror surface on both surfaces.

(Example 5)
(1) Prepared by reacting polypropylene glycol having an average molecular weight of 2000 (Asahi Glass Co., Ltd., Preminol S-X4001) and isophorone diisocyanate (IPDI, Sumika Bayer Urethane Co., Ltd., Desmodur I) at 80 ° C. for 4 hours in a nitrogen atmosphere. The urethane prepolymer having an isocyanate group at the terminal with an NCO% of 17.3% and an organic tin catalyst (manufactured by Nitto Kasei Co., Ltd.) as a curing agent so as to be 1.2% by weight with respect to the entire polyurethane obtained. , Neostan U-100) and polypropylene triol having an average molecular weight of 430 (Exaeno 430 manufactured by Asahi Glass Co., Ltd.) were mixed using a low-pressure casting machine so that the NCO INDEX was 1.05. A composition was prepared.

(2) The material composition prepared in the above (1) was molded into a sheet using a molding method (see FIG. 5) according to the second manufacturing method.
That is, a pair of metallic heating rolls (φ50 mm × length 600 mm) 33a, in which release PET sheets 32a and 32b having a thickness of 100 μm are arranged with a gap of 1.5 mm, temperature adjusted to 30 ° C., and rotated at 50 rpm. , 33b, and the material composition 30a was allowed to flow from the low pressure casting machine 31 into the gap between the release PET sheets 32a and 32b.
At this time, the head portion 31a of the low-pressure casting machine 31 is offset by 20 mm toward the heating roll 33b side from the center portion (gap portion) of the two rolls, and the tip portion of the head portion 31a and the release PET sheet are disposed. The distance from the surface of the heating roll with which the falling material comes into contact was 15 mm.
The viscous material composition 30a cast on the heating rolls 33a and 33b (on the release PET sheets 32a and 32b) is sandwiched between the two release PET sheets 32a and 32b. The polyurethane sheet having a thickness of 1.5 mm was obtained by introducing into a heating furnace, heating and curing at 80 ° C. for 90 minutes, and finally removing the release PET sheet. The obtained polyurethane sheet had a uniform mirror surface on both surfaces.
Thereafter, the obtained polyurethane sheet was cut into 400 × 600 mm with an ultrasonic cutter to complete a flexible light guide plate having a thickness of 1.5 mm.

(Comparative Example 1)
(1) NCO% prepared by reacting polyethylene butylene adipate glycol (Sanyo Kasei Kogyo Co., Ltd., San Ester No. 22) having an average molecular weight of 1000 with hexamethylene diisocyanate (Takenate 900) at 80 ° C. for 4 hours in a nitrogen atmosphere. 13.2% urethane prepolymer having an isocyanate group at the end, and an organotin catalyst (Neostan U-100) dissolved in advance as a curing agent so as to be 0.05% by weight with respect to the entire polyurethane obtained A mixture of 1,4-butanediol and trimethylolpropane having a weight ratio of 85:15 was mixed so that the NCO INDEX was 1.05 to prepare a material composition.

(2) The material composition prepared in (1) above was molded and cut by the same method as in (2) of Example 2 to complete a flexible light guide plate having a thickness of 3 mm. The molded polyurethane sheet had a uniform mirror surface on both surfaces.

(Comparative Example 2)
(1) Polycaprolactone glycol (Daicel Chemical Industries, Plaxel 208) having an average molecular weight of 830 and 4,4′-diphenylmethane diisocyanate (MDI, Nippon Polyurethane Industry, Millionate MT) are mixed at 80 ° C. under nitrogen atmosphere. A urethane prepolymer having an isocyanate group at the terminal with an NCO% of 7.2% prepared by reacting for a period of time, and an organozirconium-based catalyst as a curing agent in advance so as to be 0.04% by weight based on the total polyurethane obtained Polycaprolactone triol (Placcel 308) having an average molecular weight of 850 in which (ZC-700) was dissolved was mixed so that the NCO INDEX was 1.05 to prepare a material composition.

(2) The material composition prepared in (1) above was molded and cut by the same method as in (2) of Example 2 to complete a flexible light guide plate having a thickness of 3 mm. The molded polyurethane sheet had a uniform mirror surface on both surfaces.

(Comparative Example 3)
(1) Polypropylene glycol (Preminol S-X4001) having an average molecular weight of 2000 and isophorone diisocyanate (Desmodur I) were reacted at 80 ° C. for 4 hours in a nitrogen atmosphere for 4 hours. And a polypropylene triol having an average molecular weight of 430 (Exenol 430) in which triethylenediamine, which is an amine-based catalyst, is dissolved in advance so as to be 0.75% by weight based on the entire polyurethane obtained as a curing agent. And NCO INDEX (ratio of the number of moles of isocyanate groups in the urethane prepolymer to the number of moles of hydroxyl groups in the curing agent = NCO] / [OH]) is 1.05. A product was prepared.

(2) The material composition prepared in (1) above was molded and cut by the same method as in (2) of Example 2 to complete a flexible light guide plate having a thickness of 3 mm. The molded polyurethane sheet had a uniform mirror surface on both surfaces.

(Evaluation)
The following evaluation was performed about the flexible light-guide plate manufactured in Examples 1-5 and Comparative Examples 1-3. The results are shown in Table 1.

(1) Appearance The appearance of the flexible light guide plate was observed visually. The results are shown in Table 1.
Here, the presence or absence of coloring and the presence or absence of foreign matter, air, scratches or sink marks were observed.

(2) Light transmittance The light transmittance was measured every 1 nm in a wavelength range of 380 to 780 nm using a spectrophotometer (manufactured by Hitachi High-Technologies Corporation, U-3500).
As a result, in Examples 1 to 5, in the wavelength range of 400 to 500 nm, the light transmittance is less than 85% and in the wavelength range of 380 to 780 nm (excluding 400 to 500 nm). There were no wavelengths below 90%.
Furthermore, the arithmetic average value in the wavelength range of 380 to 780 nm and the arithmetic average value in the wavelength range of 400 to 500 nm were calculated, and the results are shown in Table 1. In addition, about the sample produced in Example 5, this was piled up and it was made to contact | adhere so that air may not enter, and it used for the measurement, after setting total thickness to 3 mm.

(3) Light source color reproducibility A reflective layer (reflective dots) is printed on the back surface (back surface) of the light guide plate, and white light is emitted from an LED light bar in which a plurality of chip-type white LEDs are arranged from both short sides of the light guide plate. The color of the light incident and emitted to the front surface of the light guide plate was visually confirmed. The white color was evaluated as ◯, and the yellow color was evaluated as ×. The reflective layer (reflective dots) was printed by screen printing a white paint containing silica particles in a dot pattern.
Moreover, the color photograph which shows the actual light emission state of Example 2 and Comparative Example 2 is shown in FIGS.

(4) Yellowness Based on JIS K 7105, the yellowness (YI) in the thickness direction of the light guide plate was measured by a transmission method using a photoelectric colorimeter (SE6000 manufactured by Nippon Denshoku Industries Co., Ltd.).

(5) JIS-A hardness It measured using the JIS-A type | mold rubber hardness meter by high molecular meter. Note that two or four samples were stacked and the thickness was measured to be 6 mm or more.

(6) A strip-shaped test piece having a width of 3 cm and a length of 20 cm was cut out from the flexible light guide plate, and the test piece was bent until the two short sides contacted each other. Repeat this 20 times, if there is no problem with bending or cracking and no distortion or whitening is left, ○, breaking or cracking occurs, it does not bend to a predetermined angle, or strain remains even if bent When whitening occurred, it was determined as x.

(7) Long-term stability (durability)
While observing the surface state of the light guide plate left in a constant temperature and humidity chamber at a temperature of 60 ° C. and a relative humidity of 85% for 1000 hours to confirm the presence of color, turbidity and cracking due to hydrolysis, (3) and (4) was evaluated.
In addition, depending on this evaluation, evaluation including hydrolysis resistance, heat resistance, and weather resistance will be performed.

From the results of Examples and Comparative Examples, the flexible light guide plate of the present invention is excellent in light source color reproducibility over a long period from the initial stage, has high light transmittance, and has sufficient flexibility, A flexible light guide plate (Comparative Example 1) in which the polyol component is a polyester polyester of a condensed polyester, a flexible light guide plate (Comparative Example 2) in which the isocyanate component is an aromatic polyisocyanate, and a flexible guide using an amine catalyst as a curing catalyst. The light plate (Comparative Example 3) was found to be inferior in light source color reproducibility and light transmittance over the initial period and / or for a long period of time.

DESCRIPTION OF SYMBOLS 1 Flexible light-guide plate 2, 3 Support member 4a, 4b Frame member 10A, 10B Planar light source 27, 30 Thermosetting polyurethane 28 Silicone rubber layer 32a, 32b PET sheet 33a, 33b Heating roll 36 Heating apparatus

Claims (8)

A flexible light guide plate made of thermosetting polyurethane,
The thermosetting polyurethane is a urethane prepolymer obtained by reacting at least one polyol component selected from polyether polyol, polycaprolactone polyol and polycarbonate polyol with an aliphatic polyisocyanate component, a curing agent, or A flexible light guide plate, which is a thermosetting polyurethane obtained by thermosetting in the presence of a mixture of a curing agent and the polyol component and a non-amine catalyst. The light transmittance measured using a spectrophotometer is 85% or more in the wavelength range of 400 to 500 nm and 90% or more in the wavelength range of 380 to 780 nm (excluding 400 to 500 nm). The flexible light guide plate described. The flexible light guide plate according to claim 1, wherein the JIS-A hardness is 85 to 100 °. The flexible light guide plate according to claim 1, wherein the thermosetting polyurethane does not contain an acrylic skeleton. It is a manufacturing method of the flexible light-guide plate in any one of Claims 1-4, Comprising:
After a silicone rubber layer is formed inside a rotatable cylindrical mold, a material composition containing at least the urethane prepolymer and the non-amine catalyst is poured into the mold, and the mold is A method for producing a flexible light guide plate, wherein the material composition is thermoset by rotating while heating. It is a manufacturing method of the flexible light-guide plate in any one of Claims 1-4, Comprising:
The material composition containing at least the urethane prepolymer and the non-amine catalyst is poured through a casting machine into a gap of a gap maintaining member continuously fed by a pair of spaced apart rolls, A method of manufacturing a flexible light guide plate, wherein the gap maintaining member holding the material composition in a gap is introduced into a heating device, and the material composition is thermally cured while being held by the gap maintaining member. The manufacturing method of the flexible light-guide plate of Claim 6 which the said space | interval maintenance member consists of a polyethylene terephthalate (PET) sheet. The method for manufacturing a flexible light guide plate according to claim 6, wherein the roll is a heating roll.