KR20160016053A - Formulation of UV curable adhesive - Google Patents

Abstract

The present invention relates to an ultraviolet curable adhesive composition which is used for producing a laminated composite sheet used in a LCD backlight. The composite sheet can be produced by using an adhesive composition adding triphenyl phosphate based on 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, and ethoxylated (4) pentaerythritol tetraacrylate. In addition, the composite sheet shows excellent adhesion even if adhesive coating thickness is thin, can obtain excellent brightness, and does not generate delamination when carrying out a cutting process.

Description

Formulation of UV curable adhesive [

The present invention relates to the composition of an ultraviolet curable adhesive used in a prism sheet. As the optical sheet used for the backlight of the liquid crystal display, a prism sheet, a micro lens sheet, a diffusion sheet, a reflective sheet, or the like is used. In recent years, a composite sheet of a prism sheet and a prism sheet, a composite sheet of a prism sheet and a diffusion sheet, and a composite sheet of a prism sheet and a micro lens sheet have been developed and used. In the past, two or four sheets of prism sheet, micro-lens sheet, or diffusion sheet were individually laminated at the time of backlight assembly. In recent years, A composite sheet capable of simultaneously exhibiting the effect of the present invention is used. In order to produce a composite sheet, another sheet is laminated on the prism or microlens pattern, in which case an adhesive is required. If the thickness of the adhesive layer is large when the adhesive is applied, the prism or the microlens pattern is buried in the adhesive layer, resulting in a decrease in luminance. On the other hand, if the coating thickness of the adhesive is thin, the adhesive force is lowered and a peeling problem occurs in the cutting operation. Therefore, it is necessary to develop an adhesive having a thin coating thickness of the adhesive and an excellent adhesive strength. The present invention provides an adhesive composition having a thin coating thickness of an adhesive and an excellent adhesive strength.

Since the LCD is not self-luminous, a light source called a backlight is required on the rear surface of the liquid crystal panel. Cold cathode fluorescent lamp (CCFL) has been used as a backlight source, but is now being replaced by LEDs. Since the LED light source is a point light source, it needs a device that converts it into a surface light source. This is a backlight. In the backlight structure, the LED is disposed on the side surface of the light guide plate, and a diffusion sheet, a prism sheet, and a micro lens sheet are stacked on the upper side of the light guide plate, and a liquid crystal panel is disposed thereon. The light incident from the side surface of the light guide plate repeats total internal reflection within the light guide plate, and is emitted to the surface of the light guide plate when it meets the projection pattern on the surface of the light guide plate. The light emitted from the light guide plate is converted into a uniform surface light source while passing through the diffusion sheet, the prism sheet, and the microlens sheet though the intensity of the light is uneven depending on the position and angle. In general, two or four sheets of optical sheets used in combination with a prism sheet, a diffusing sheet, and a micro lens sheet have been used as the optical sheets to be laminated on the light guide plate. However, with the recent development of optical sheet manufacturing technology, two optical sheets are combined and compounded so that even if only one or two optical sheets are used, the same function can be exhibited. By using a composite sheet in the form of a laminate, it is possible to contribute to the reduction of the production cost of the backlight, the simplification of the assembling process, and the slimming of the backlight. TECHNICAL FIELD The present invention relates to a technique for producing a composite optical sheet in the form of a laminate, and particularly provides a technique relating to an adhesive that plays an important role in manufacturing a composite optical sheet.

As adhesives, there are thermosetting type and ultraviolet ray curing type, and the present invention provides an ultraviolet curing type adhesive composition. The ultraviolet curing type adhesive composition is largely composed of a binder and a photoinitiator. Ultraviolet ray-curable acrylate monomers and oligomers are used as the binder, which is a low molecular weight liquid state before curing, but forms a polymer after curing to exhibit adhesion. Examples of the monomer include monofunctional monomer such as 2-hydroxyphenylbenzene acrylate, 2- (hydroxymethyl) tetrahydrofuran acrylate, 1,3-benzene diamine, 4-methyl acrylate, isobornyl acrylate , Amino diacetic acid acrylate, and various derivatives thereof are used. As the bifunctional monomer, tripropylene glycol diacrylate, 1,6-hexane diol diacrylate, tricyclodecane dimethanol diacrylate, dipropylene glycol di Acrylate, glycol diacrylate, neophenyl glycol diacrylate, ethylene glycol dimethacrylate and derivatives thereof, and trifunctional and polyfunctional monomer may be trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, penta Dimethylol propane triacrylate, trimethylolpropane triacrylate, Dipentaerythritol hexaacrylate, and the like. As the oligomer, acrylic acrylate, aliphatic urethane acrylate, aromatic urethane acrylate, epoxy acrylate, polyester acrylate, polyester-urethane acrylate, and modified poly (ethylene acrylate) are widely used. Various kinds of physical properties such as adhesive strength, curing rate and hardness change depending on the type and combination of monomers and oligomers.

The photoinitiator absorbs the energy of the ultraviolet wavelength and forms a radical to initiate polymerization of the monomer and the oligomer. Examples of the photoinitiator include benzophenone, 4-methylbenzophenone, 4-benzoyl-4'-methyldiphenylsulfide, methylphenylglyoxylate, methylbenzoylbenzoate, 4-phenylbenzophenone, benzyldimethylketal, 4-dimethylaminobenzoate, ethyl-4-dimethylaminobenzoate, 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis -Trimethylbenzoyl) -phenylphosphine oxide and the like are used.

Fig. 1 shows a triangular prism 1 adhered and joined together by an adhesive. If the thickness of the adhesive coating layer 2 is increased, the area of the upper portion of the prism contacting the adhesive increases to increase the adhesive force. However, since the upper portion of the prism is buried in the adhesive layer, the refraction effect of light, . If the thickness of the adhesive layer is small, the adhesive force is reduced, but the area where the top of the prism is buried in the adhesive layer is reduced, and the brightness is increased. In order to maintain the refraction effect of the prism at a maximum, the composite composite sheet should be coated with the adhesive as thin as possible. On the other hand, the thinner the adhesive thickness, the lower the adhesive force, causing a peeling problem in which the prism is separated from the adhesive during cutting and handling. Therefore, it is important to maximize the adhesive force while minimizing the thickness of the adhesive applied. Therefore, in order to achieve the above object, the present invention provides an adhesive composition having excellent performance.

In the case of a composite composite sheet, the brightness and adhesion must be high, and at the same time, the peeling in the cutting operation must be small. However, since the adhesive force and the luminance are in inverse proportion to each other, the luminance decreases when the adhesive force is increased, and the luminance increases when the adhesive force is decreased. When the adhesive force is reduced, the brightness is increased, but a problem of peeling occurs in the cutting operation.

2 shows a state in which the blade 3 presses the composite sheet when the composite sheet is cut. The blade passes from the upper part to the lower part, and peeling occurs between the adhesive layer and the upper part of the prism. The weaker the adhesive force between the upper portion of the prism and the adhesive layer, the wider the width (4) of peeling off the left and right sides of the blade at the time of cutting. On the other hand, the better the adhesive strength, the smaller the width of peeling.

The present invention provides an adhesive composition for an interlayer composite sheet having improved performance of an ultraviolet curable adhesive used in the production of an interlayer composite sheet and having excellent adhesive strength and brightness at the same time and having little peeling at the time of cutting.

In the present invention, it is preferred that 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ethoxylated (4) pentaerythritol tetraacrylate And triphenyl phosphate is added to the base composition. In particular, when triphenyl phosphate is added, excellent adhesion is exhibited even when the thickness of the adhesive coating is reduced, peeling is not easily caused at the time of cutting, and excellent brightness can be obtained at the same time.

To solve this problem, an adhesive composition having excellent adhesive strength was prepared. That is, as described above, in the present invention, it is preferred that 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ethoxylated (4) It is an adhesive formulation in which lithol tetraacrylate is used as a base and triphenyl phosphate is added thereto. Triphenylphosphate is an additive used as a softener and flame retardant. In the present invention, triphenylphosphate is used to increase flexibility and adhesion to the adhesive coating, which, when used together with the monomer and oligomer as a base, causes a synergistic effect. Therefore, even when the thickness of the adhesive coating is reduced, an excellent adhesive force is exhibited, the peeling is not generated at the time of cutting, and excellent brightness can be obtained at the same time.

When the laminated composite sheet is produced by using the adhesive of the present invention, a composite sheet having excellent adhesion and low peeling width and excellent brightness can be produced.

If the adhesive is the same, the brightness of the composite sheet decreases as the adhesive force increases. That is, if the prism acid is made to be embedded in the adhesive layer, the adhesive force is increased but the luminance is decreased. Therefore, if the prismatic acid is embedded in the adhesive and the adhesive strength is high, it is an excellent adhesive. Accordingly, in the present invention, a composite sheet was prepared and evaluated by using an adhesive composition (Examples 1 to 10) prepared by blending raw materials as a method for providing such an excellent adhesive, and as a result, excellent brightness and adhesion were obtained. The results are described in the concrete contents for carrying out the invention.

Fig. 1: Composite sheet cross section in which a prism and an adhesive are laminated
Figure 2: Variation of cross section when cutting composite sheet to blade
Figure 3: Width to be peeled off around the blade when cutting the composite sheet to the blade
Figure 4: Graph of luminance and adhesion measurement results in the embodiment of the present invention

Adhesive compositions similar to the examples in Tables 1 to 10 were prepared. As the upper coating base material film, a PET film (trade name: H34P) having a thickness of 125 micrometers manufactured by Kolon Co., Ltd. was prepared, and the adhesive thus prepared was applied. The same PET film (trade name: H34P) having a thickness of 125 micrometers manufactured by Kolon Co., Ltd. was prepared as a lower layer coating base film and subjected to prism coating. At this time, the pitch of the prism is 60 micrometers, and the angle of the prism mountain is 90 degrees. The two films were laminated so that the prism-coated side faces the adhesive coated side. After lapping, the upper surface of the upper coating base film was again subjected to prism coating. At this time, the pitch of the prism is 60 micrometers, and the angle of the prism mountain is 90 degrees.

Example
One




Raw material name function content
(weight%) 1,6-hexanediol diacrylate Monomer 10.5 Tripropylene glycol diacrylate Monomer 10.0 Trimethylolpropane triacrylate Oligomer 11.0 Pentaerythritol tetraacrylate Oligomer 11.0 Ethoxylated (4) pentaerythritol tetraacrylate Oligomer 13.0 Methyl ethyl ketone solvent 20.0 toluene solvent 20.0 1-hydroxycyclohexyl phenyl ketone Photoinitiator 3.0 Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide Photoinitiator 1.5

Example
2



Raw material name function content
(weight%) 1,6-hexanediol diacrylate Monomer 10.5 Tripropylene glycol diacrylate Monomer 10.0 Trimethylolpropane triacrylate Oligomer 11.0 Pentaerythritol tetraacrylate Oligomer 11.0 Ethoxylated (4) pentaerythritol tetraacrylate Oligomer 13.0 Methyl ethyl ketone solvent 40.0 1-hydroxycyclohexyl phenyl ketone Photoinitiator 3.0 Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide Photoinitiator 1.5

Example
3



Raw material name function content
(weight%) 1,6-hexanediol diacrylate Monomer 10.5 Tripropylene glycol diacrylate Monomer 10.0 Trimethylolpropane triacrylate Oligomer 11.0 Pentaerythritol tetraacrylate Oligomer 11.0 Ethoxylated (4) pentaerythritol tetraacrylate Oligomer 13.0 toluene solvent 40.0 1-hydroxycyclohexyl phenyl ketone Photoinitiator 3.0 Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide Photoinitiator 1.5

Example
4



Raw material name function content
(weight%) 1,6-hexanediol diacrylate Monomer 10.5 Tripropylene glycol diacrylate Monomer 10.0 Trimethylolpropane triacrylate Oligomer 11.0 Pentaerythritol tetraacrylate Oligomer 11.0 Ethoxylated (4) pentaerythritol tetraacrylate Oligomer 13.0 Methyl ethyl ketone solvent 10.0 toluene solvent 30.0 1-hydroxycyclohexyl phenyl ketone Photoinitiator 3.0 Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide Photoinitiator 1.5

Example
5




Raw material name function content
(weight%) 1,6-hexanediol diacrylate Monomer 10.5 Tripropylene glycol diacrylate Monomer 10.0 Trimethylolpropane triacrylate Oligomer 11.0 Pentaerythritol tetraacrylate Oligomer 11.0 Ethoxylated (4) pentaerythritol tetraacrylate Oligomer 13.0 Methyl ethyl ketone solvent 30.0 toluene solvent 10.0 1-hydroxycyclohexyl phenyl ketone Photoinitiator 3.0 Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide Photoinitiator 1.5

Example
6




Raw material name function content
(weight%) 1,6-hexanediol diacrylate Monomer 10.185 Tripropylene glycol diacrylate Monomer 9.7 Trimethylolpropane triacrylate Oligomer 10.67 Pentaerythritol tetraacrylate Oligomer 10.67 Ethoxylated (4) pentaerythritol tetraacrylate Oligomer 12.61 Methyl ethyl ketone solvent 19.4 toluene solvent 19.4 1-hydroxycyclohexyl phenyl ketone Photoinitiator 2.91 Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide Photoinitiator 1.455 triphenyl phosphate additive 3.0

Example
7




Raw material name function content
(weight%) 1,6-hexanediol diacrylate Monomer 9.975 Tripropylene glycol diacrylate Monomer 9.5 Trimethylolpropane triacrylate Oligomer 10.45 Pentaerythritol tetraacrylate Oligomer 10.45 Ethoxylated (4) pentaerythritol tetraacrylate Oligomer 12.35 Methyl ethyl ketone solvent 19 toluene solvent 19 1-hydroxycyclohexyl phenyl ketone Photoinitiator 2.85 Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide Photoinitiator 1.425 triphenyl phosphate additive 5.0

Example
8




Raw material name function content
(weight%) 1,6-hexanediol diacrylate Monomer 9.765 Tripropylene glycol diacrylate Monomer 9.3 Trimethylolpropane triacrylate Oligomer 10.23 Pentaerythritol tetraacrylate Oligomer 10.23 Ethoxylated (4) pentaerythritol tetraacrylate Oligomer 12.09 Methyl ethyl ketone solvent 18.6 toluene solvent 18.6 1-hydroxycyclohexyl phenyl ketone Photoinitiator 2.79 Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide Photoinitiator 1.395 triphenyl phosphate additive 7.0

Example
9




Raw material name function content
(weight%) 1,6-hexanediol diacrylate Monomer 9.45 Tripropylene glycol diacrylate Monomer 9 Trimethylolpropane triacrylate Oligomer 9.9 Pentaerythritol tetraacrylate Oligomer 9.9 Ethoxylated (4) pentaerythritol tetraacrylate Oligomer 11.7 Methyl ethyl ketone solvent 18 toluene solvent 18 1-hydroxycyclohexyl phenyl ketone Photoinitiator 2.7 Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide Photoinitiator 1.35 triphenyl phosphate additive 10.0

Example
10




Raw material name function content
(weight%) 1,6-hexanediol diacrylate Monomer 8.925 Tripropylene glycol diacrylate Monomer 8.5 Trimethylolpropane triacrylate Oligomer 9.35 Pentaerythritol tetraacrylate Oligomer 9.35 Ethoxylated (4) pentaerythritol tetraacrylate Oligomer 11.05 Methyl ethyl ketone solvent 17 toluene solvent 17 1-hydroxycyclohexyl phenyl ketone Photoinitiator 2.55 Bis (2,4,6-trimethylbenzoyl) -phenylphenoxide Photoinitiator 1.275 triphenyl phosphate additive 15.0

The composite sheet thus prepared was placed on a backlight and the luminance was measured. The backlight used for the luminance measurement was a 32-inch edge type, and the luminance measuring camera was a Topcon SR-3. The adhesive force was measured at a speed of 100 mm per minute using an adhesive force measuring machine (DH-111-D model manufactured by KAN PRECISION CO., LTD.) By cutting the composite sheet sample to a width of 30 mm. Cutting was carried out using a cutting mold to measure the peeling width.

Table 11 shows the adhesive force and luminance measurement results according to the examples, and FIG. 4 is a graph showing the contents of Table 11 showing the relationship between brightness and adhesive strength in each example. Table 12 shows the peeling widths at the time of cutting according to the examples. Among the adhesive compositions of the present invention, adhesive properties of an adhesive composition containing triphenyl phosphate are excellent. When the content of triphenyl phosphate is less than 5%, the addition effect is insignificant, and when the content is 10% or more, the adhesive force is rather reduced. When the content of triphenyl phosphate is 7 to 10% by weight, excellent adhesion can be obtained (Examples 8 to 9). Therefore, when the composite sheet is manufactured using the adhesive of the present invention, the composite sheet having excellent adhesion and low peeling width and excellent brightness can be produced.

Example Brightness (cd / m ² ) Adhesion (g / 30mm) One 8563 45 2 8522 46 3 8611 45 4 8609 44 5 8655 45 6 8640 45 7 8705 49 8 8708 61 9 8711 60 10 8696 54

Example Peel width (mm) One 1.9 2 2.1 3 1.6 4 1.5 5 1.7 6 1.6 7 1.0 8 0.9 9 0.8 10 1.0

none

Claims (3)

As an ultraviolet curable adhesive composition,
One or more of 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ethoxylated (4) pentaerythritol tetraacrylate, ≪ / RTI &
Adhesive composition including triphenyl phosphate. The adhesive composition according to claim 1, wherein the content of triphenyl phosphate is 5 to 15 wt%. The adhesive composition according to claim 1, comprising 1-hydroxycyclohexyl phenyl ketone or bis (2,4,6-trimethylbenzoyl) -phenyl peroxide as photoinitiator.

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