TWI484226B - Brightness enhancement film, backlight module and liquid crystal display device - Google Patents

Description

Brightening film, backlight module and liquid crystal display device

The present invention relates to an optical film having a reinforcing layer, and more particularly to an optical film excellent in thermal stability, dimensional stability, and deformation resistance.

With the rapid development of technology, in order to meet the people's pursuit of electronic digital products, light, thin, short, and small, the electronic digital products are lighter and thinner to be easy to carry, which promotes the thickness of flat panel LCDs. Lightweight development, in order to achieve this, the thinning of the backlight module is an effective way.

Generally, the basic structure of the backlight module except the light source includes a reflection sheet, a light guide plate, a lower diffusion sheet, a lower brightness enhancement film, an upper brightness enhancement film and an upper diffusion sheet, etc., in order to reduce the thickness of the backlight module, The current methods in the industry are as follows: (1) using a multi-functional composite sheet, that is, a part of the optical film is integrated into one body, for example, combining the upper diffusion sheet and the upper brightness enhancement film into an upper brightening composite sheet. (2) Reducing the thickness of each optical film to achieve the purpose of reducing the total thickness. For example, the brightness enhancement film used in the notebook computer is changed from a substrate having a thickness of 125 μm to a substrate having a thickness of 100 μm or even 75 μm.

However, in the case of the above method (2), particularly in the case of using a substrate having a relatively small thickness, the problem faced is that when a large-sized substrate is used to manufacture a large-sized panel, the substrate itself is The rigidity will become insufficient and it will be easily deformed. In addition, when the light source of the backlight module is in the side light type, since the light source is disposed at a specific portion of the edge of the backlight module, the heat is easily concentrated at the place where the edge temperature of the backlight module is higher than other parts, thereby making the edge of the substrate easy. Deformation due to high temperature, resulting in Problems such as curvature, ripple, and unevenness are more pronounced for substrates with reduced thickness.

The prior art regarding the provision of a coating on a specific layer of a backlight module to achieve a specific purpose can be exemplified as follows.

First, an optical sheet is disclosed in US Pat. No. 5,995,288 (hereinafter referred to as "Patent Document 1"), and a resin coating layer is provided on the opposite side of the substrate on which the tantalum unit side is formed, and the thickness of the coating layer is 2 to 20 μm. When the particles having a particle size of 1 to 10 μm are contained, and the refractive index ratio between the particles and the resin forming the coating layer is 0.9 to 1.1, the purpose of preventing the generation of Newton's rings can be achieved.

Further, US Pat. No. 6,280, 063 (hereinafter referred to as "Patent Document 2") discloses a brightening article in which a matrix is formed on a first main surface of a substrate, and a light scattering layer is formed on a second main surface of the substrate. The light scattering layer has a thickness of 1 to 50 μm and contains a plurality of components protruding from the second main surface. In addition, the brightness of the brightening object is 20 to 60%, and the transmittance is not more than 94%, thereby maintaining a certain brightness enhancement characteristic and having a matting property.

Further, US 2008/0151549 (hereinafter referred to as "Patent Document 3") discloses an anti-scratch optical film which is provided with a hard coat layer as a scratch-resistant layer on the surface of a reflective substrate, and the surface of the scratch-resistant layer The electric resistance is 10 ⁸ to 10 ¹² Ω/□, the thickness is 1 to 20 μm, and the organic particles having a particle diameter of 0.1 to 10 μm are included; according to this configuration, the reflective substrate can have low shrinkage and is less likely to cause warpage, and It has good antistatic and high hardness effects, and has excellent scratch resistance due to its high hardness.

The above Patent Documents 1 to 2 disclose the related art for forming a coating layer containing specific particles on the back surface of the brightness enhancement layer, but the focus is on preventing cattle. The ring ring generates or imparts matting characteristics, but does not contribute to improving the rigidity, dimensional stability, and the like of the brightness enhancing film itself. Further, Patent Document 3 discloses that a hard coat layer is added on the surface of the reflective substrate to prevent the reflective substrate. The warpage increases the hardness and imparts excellent scratch resistance. However, the reflective layer in the backlight unit is used as an improvement target, and the improvement of the brightness enhancement film is as follows.

In summary, the prior art does not effectively solve the problems encountered by the above thinned brightness enhancing film for use in a larger size display. Therefore, there is an urgent need in the market for an effective method to enhance the stability of the brightness enhancing film to meet the brightness enhancement. The film is used in the stability requirements of the backlight module.

The present invention has been made in view of the above problems, and an object thereof is to provide a brightness enhancement film in which a matrix structure is formed on one surface of a substrate, and a reinforcing layer is formed on the other surface of the substrate, and a glass transition temperature of the reinforcing layer is formed. (Tg) is 80 to 250 ° C and the thickness is 3 to 50 μm.

In addition, the present invention also provides a backlight module using the brightness enhancement film and a liquid crystal display device including the backlight module.

According to the present invention, since a reinforcing layer having a high glass transition temperature (Tg) and an appropriate thickness is added to the brightness enhancement film, the thermal stability, dimensional stability and deformation resistance of the brightness enhancement film can be improved, so that the brightness enhancement film is provided. It will not cause warping, corrugation or uneven deformation due to overheating of the lamp, and can increase the rigidity of the brightness enhancement film, and can be used on a larger size panel to solve the brightness enhancement film in the backlight module. Common problems of deformation and poor thermal stability.

Hereinafter, the basic constitution and efficacy of the brightness enhancing film of the present invention will be described in detail. As shown in FIG. 1, the brightness enhancement film 1 of the present invention is formed on the surface of one of the substrates 2 with a ruthenium structure 3, and on the other surface of the substrate 2 (the surface of the ruthenium structure 3 is formed). The opposite side, sometimes referred to as the back side, is formed with Reinforce layer 4.

The material of the substrate 2 may be, for example, polycarbonate (PC), polyethylene naphthalate (PEN), or a cyclic olefin copolymer, in addition to polyethylene terephthalate (PET). Plastic optical films such as (mCOC), polyarylate (PAR), polyether oxime (PES), cellulose triacetate (TAC), and polymethyl methacrylate (PMMA). Further, the substrate 2 used has a thickness of between 25 and 300 μm.

The 稜鏡 structure 3 is composed of a plurality of 稜鏡 units (an array), and FIG. 1 shows a case where a plurality of 稜鏡 units having a substantially triangular column shape are formed in parallel on the surface of the substrate 2, but are not limited thereto. The shape and size of the unit, the arrangement interval and arrangement of the unit, and the like can be generally known.

Next, the reinforcing layer 4 of the present invention will be described. In the past, when the brightness enhancement film applied to the backlight module is thinned to a certain extent and used in a large-sized panel, the heat generated by the light source is unevenly distributed on the brightness enhancement film to affect the dimensional stability, thereby causing brightness enhancement. Problems such as warpage, corrugation, and uneven deformation of the film, so that the uniformity of light emission of the entire backlight module is deteriorated. In order to solve this problem, the present invention contemplates the addition of a reinforcing layer 4 in the brightness enhancing film 1, and the most important feature of the reinforcing layer 4 is that it has a specific glass transition temperature (Tg) and a specific thickness.

Regarding the glass transition temperature (Tg) of the reinforcing layer 4, the temperature range is preferably from 80 to 250 ° C and more preferably from 100 to 200 ° C. When the Tg is lower than 80 ° C, the thermal stability and dimensional stability of the reinforcing layer 4 at a high temperature will become insufficient, and warpage, corrugation, uneven deformation, and the like of the brightness enhancing film cannot be prevented; When the Tg is higher than 250 ° C, although sufficient thermal stability can be maintained, the manufacturing cost becomes expensive and economical.

The thickness of the reinforcing layer 4 is preferably from 3 to 50 μm. If the thickness of the reinforcing layer 4 is less than 3 μm, sufficient rigidity, thermal stability, and dimensional stability of the brightness enhancing film 1 cannot be imparted; on the other hand, if the thickness of the reinforcing layer 4 is larger than 50 μm, the brightness enhancing film 1 as a whole The thickness may become too thick, which is disadvantageous for the thinning of the backlight module or the liquid crystal display device. Further, it is preferable that the thickness of the reinforcing layer 4 is simultaneously selected in consideration of the thickness of the substrate 2, and in principle, when the thickness of the substrate 2 to be used is thicker, the thickness of the reinforcing layer 4 also needs to be correspondingly increased.

The material of the reinforcing layer 4 is not particularly limited as long as it has a glass transition temperature (Tg) of 80 to 250 ° C, and examples thereof include an epoxy resin, an aliphatic acrylic monomer or an oligomer, and a fragrance. An acrylic copolymer obtained by copolymerizing a polyfunctional acryl monomer or oligomer, and an aromatic acrylate monomer or oligomer copolymerized with an aliphatic polyfunctional acrylate monomer or oligomer An acrylic copolymer or the like.

Further, the refractive index of the reinforcing layer 4 is preferably from 1.3 to 1.6. The reason is that when the refractive index of the reinforcing layer 4 is between 1.3 and 1.6, similar anti-reflection can be produced because it is disposed between the substrate 2 having a high refractive index (such as PET, PC, etc.) and the air having a low refractive index. The effect of the layer allows the incident light to enter the brightness enhancement film 1 more efficiently and is concentrated, thereby increasing the brightness of the brightness enhancement film 1.

The reinforcing layer 4 can be formed into a flat surface (not given a special structure) as shown in FIG. 1, and can also be formed with a specific pattern by, for example, embossing technology as shown in FIG. 2 (multiple half is shown in FIG. 2). In the case of a cylindrical column), specific particles 5 are additionally added as needed to achieve specific effects such as eliminating the Newton's ring, increasing the shielding property, increasing the hardness of the back surface of the brightness enhancing film 1 to increase the scratch resistance, and providing a diffusion function.

In addition, the specific pattern formed on the reinforcing layer 4 is in addition to the one shown in FIG. Further, for example, the embodiment of Figs. 3 and 4 can be cited. 3 shows the case where the semi-ellipsoid 6 and the relatively small semi-circular sphere 7 are protruded from the surface of the reinforcing layer 4, and FIG. 4 shows that the semi-spherical sphere of the same size is protruded from the surface of the reinforcing layer 4. 7 situation. However, the present invention is not limited thereto. For example, the semi-ellipsoid 6 in FIG. 3 may be formed to have a smaller size than the semi-spherical sphere 7. The semi-spherical spheres 7 in FIG. 4 may also be formed in different sizes from each other, and the surface of the reinforcing layer 4 may be protruded. The shape of the body may be any other shape (for example, a triangular column shape or an irregular shape), and the arrangement of the protrusion bodies may be a regular arrangement or a random arrangement.

As the particle 5, an organic material such as PMMA, PS, PU, or the like may be used, or an inorganic material such as SiO ₂ , TiO ₂ , Al ₂ O ₃ , ZnO, glass, or the like may be used, or an inorganic material and an organic material may be used. mixture. Further, the particle diameter of the particles 5 is preferably from 1 to 20 μm for the purpose of achieving the aforementioned specific effects (eliminating the Newton's ring, increasing the shielding property, providing a diffusion function, etc.).

The method for producing the brightness enhancement film 1 of the present invention will be described below. First, the substrate 2 is cut to a predetermined size, and then the substrate 2 is used to form the reinforcing layer face up, and the reinforcing layer forming material (for example, an oligomer of an aliphatic or aromatic polyfunctional acrylic) Coating with a low-volatility, low-viscosity acrylic monomer, a photoinitiator, and optionally other components (such as a leveling agent, etc.) on the substrate 2 to achieve a certain thickness, followed by irradiation with UV light for a predetermined period of time After the reinforcing layer 4 is formed, the surface of the substrate 2 for forming the ruthenium structure is turned upward, and a material for forming a ruthenium structure (for example, an acrylic monomer or an oligomer) is applied onto the substrate 2 and The enamel structure 3 is formed by, for example, an imprint technique in combination with UV light irradiation for a predetermined period of time, thereby completing the production of the brightness enhancement film 1. Further, if a special structure is to be applied to the reinforcing layer 4, a material for forming a reinforcing layer may be applied to the substrate 2, and then, for example, an imprint technique may be used. The UV irradiation light is combined to form a desired pattern. If the organic layer and/or the inorganic particles 5 are to be contained in the reinforcing layer 4, the particles 5 may be added to the reinforcing layer forming material in advance. After being coated on the surface of the substrate 2, it is cured to obtain a reinforcing layer 4 containing specific particles 5. Further, the order of formation of the reinforcing layer 4 and the crucible structure 3 is of course not limited to the above-described embodiment, and the reinforcing layer 4 may be formed after the crucible structure 3 is first formed on the substrate 2.

The brightness enhancement film 1 of the present invention can improve the dimensional stability and thermal stability of the brightness enhancement film 1 as a whole by the addition of the reinforcing layer 4 of a specific property, and enhance the ability of the brightness enhancement film 1 to resist deformation under various conditions, and It can be used under more severe conditions, and can be used in large-sized models and uneven heat source distribution models (especially edge-lit liquid crystal display devices) to meet the requirements of the model against deformation. In addition, by selecting a reinforcing layer having a specific refractive index, in addition to improving the stability of the brightness enhancing film, the brightness gain of the brightness enhancing film can be increased to achieve multiple functions.

[Examples]

Hereinafter, the method for producing the brightness enhancement film of the present invention and the method for measuring the characteristics will be described.

(1) Production of brightness enhancement film Example 1

6% by weight of a bisphenol A epoxy resin (CN104, manufactured by Sartomer Co., Ltd.), 45% by weight of dipentaerythritol hexaacrylate, 45% by weight of pentaerythritol triacrylate, and 4% by weight of a photoinitiator (IRGACURE 184, manufactured by BASF Corporation) After mixing for 4 hours at normal temperature, liquid refractive index analysis was carried out, and then the mixture was applied to a 75 μm back surface of PET as a substrate with a thickness controlled within a certain range (5 ± 0.5 μm), and UV was used at 300 mJ/ The cm ² was irradiated to harden it to form a reinforcing layer, and then the crucible structure of the surface of the substrate (the complex triangular prism array, the distance between the crucibles was 24 μm, the height of the crucible was 16 ± 3 μm), and the increase of the example 1 was obtained. Bright film. The Tg analysis of the reinforcing layer and the shrinkage analysis of the brightness enhancing film were carried out, and the results are shown in Table 1.

Example 2

24 weight% of urethane acrylate (PU610, manufactured by Miwon Co., Ltd.), 48% by weight of tripropylene glycol diacrylate, 24% by weight of pentaerythritol triacrylate, and 4 parts by weight of photoinitiator (IRGACURE 184, manufactured by BASF Corporation) After mixing for 4 hours at room temperature, liquid refractive index analysis was carried out, and then the mixture was applied to a 75 μm back surface of PET as a substrate with a thickness controlled within a certain range (5 ± 0.5 μm), and UV was used. 300 mJ/cm ² was irradiated to harden it to form a reinforcing layer, and then the crucible structure of the surface of the substrate (the complex triangular prism array, the inter-turn distance between 24 μm, the crucible height of 16 ± 3 μm) was obtained, and Example 2 was obtained. Brightening film. The Tg analysis of the reinforcing layer and the shrinkage analysis of the brightness enhancing film were carried out, and the results are shown in Table 1.

Example 3

32% by weight of urethane acrylate (PU610, manufactured by Miwon Co., Ltd.), 16% by weight of pentaerythritol triacrylate, 32% by weight of tripropylene glycol diacrylate, and 16% by weight of tricyclododecane dimethanol diacrylate. And 4% by weight of a photoinitiator (IRGACURE 184, manufactured by BASF Corporation) was mixed at room temperature for 4 hours, and then subjected to liquid refractive index analysis, and then the mixture was applied to a thickness within a certain range (5 ± 0.5 μm). After 75 μm of the PET back surface of the substrate, it was hardened by irradiation with UV at 300 mJ/cm ² to form a reinforcing layer, and then the crucible structure of the surface of the substrate was formed (multiple triangular prisms, inter-turn distance) A brightness enhancement film of Example 3 was obtained at 24 μm and a height of 16 ± 3 μm. The Tg analysis of the reinforcing layer and the shrinkage analysis of the brightness enhancing film were carried out, and the results are shown in Table 1.

Comparative example 1

28% by weight of urethane acrylate (PU460, manufactured by Miwon Co., Ltd.), 42% by weight of tripropylene glycol diacrylate, 26% by weight of pentaerythritol triacrylate, and 4% by weight of photoinitiator 184 (manufactured by BASF Corporation) After mixing for 4 hours at normal temperature, liquid refractive index analysis was carried out, and then the mixture was applied to a 75 μm back surface of PET as a substrate with a thickness controlled within a certain range (5 ± 0.5 μm), and UV was used at 300 mJ/ The cm ² was irradiated to harden it to form a reinforcing layer, and then the crucible structure of the surface of the substrate (the complex triangular column array, the distance between the crucibles was 24 μm, the height of the crucible was 16 ± 3 μm), and the increase of Comparative Example 1 was obtained. Bright film. The Tg analysis of the reinforcing layer and the shrinkage analysis of the brightness enhancing film were carried out, and the results are shown in Table 1.

Comparative example 2

28% by weight of urethane acrylate (PU460, manufactured by Miwon Co., Ltd.), 42% by weight of tripropylene glycol diacrylate, 26% by weight of pentaerythritol triacrylate, and 4% by weight of photoinitiator 184 (manufactured by BASF Corporation) After mixing for 4 hours at normal temperature, liquid refractive index analysis was carried out, and then the mixture was applied to a 125 μm back surface of PET as a substrate with a thickness controlled within a certain range (5 ± 0.5 μm), and UV was used at 300 mJ/ The cm ² was irradiated to harden it to form a reinforcing layer, and then the crucible structure of the surface of the substrate (the complex triangular column array, the distance between the crucibles was 24 μm, the height of the crucible was 16 ± 3 μm), and the increase of Comparative Example 2 was obtained. Bright film.

Comparative example 3

A enamel structure was formed on the surface of the PET substrate in the same manner as in Examples 1 to 3 except that the reinforcing layer was not formed on the back surface of the PET substrate, and the brightness enhancement film of Comparative Example 3 was obtained.

Example 4

6% by weight of a bisphenol A epoxy resin (CN104, manufactured by Sartomer Co., Ltd.), 45% by weight of dipentaerythritol hexaacrylate, 45% by weight of pentaerythritol triacrylate, and 4% by weight of a photoinitiator (IRGACURE 184, manufactured by BASF Corporation) After mixing at room temperature for 4 hours, the mixture was applied to a 125 μm back surface of PET as a substrate with a thickness controlled within a certain range (5 ± 0.5 μm), and then irradiated with UV at 300 mJ/cm ² to make it. The reinforcing layer was formed to form a reinforcing layer, and then a crucible structure (a plurality of triangular prism arrays, a distance between the crucibles of 50 μm and a crucible height of 30 ± 3 μm) was prepared to obtain a brightness enhancement film of Example 4.

Comparative example 4

6% by weight of a bisphenol A epoxy resin (CN104, manufactured by Sartomer Co., Ltd.), 45% by weight of dipentaerythritol hexaacrylate, 45% by weight of pentaerythritol triacrylate, and 4% by weight of a photoinitiator (IRGACURE 184, manufactured by BASF Corporation) After mixing at room temperature for 4 hours, the mixture was applied to a 125 μm PET back surface as a substrate with a thickness controlled within a certain range (2 ± 0.5 μm), and then irradiated with UV at 300 mJ/cm ² to make it The film was hardened to form a reinforcing layer, and then a crucible structure (a plurality of triangular prism arrays, a distance between the crucibles of 50 μm and a crucible height of 30 ± 3 μm) was prepared to obtain a brightness enhancement film of Comparative Example 4.

(2) Measurement of glass transition temperature (Tg) of reinforcing layer

For the brightness enhancement films of Examples 1 to 3 and Comparative Example 1, a DSC Q2000 differential scanning calorimeter was used, and a temperature scanning analysis was performed from 40 ° C to 150 ° C at a heating rate of 10 ° C / min to determine individual glass transition temperatures ( Tg).

(3) Measurement of refractive index (Refractive Index)

With respect to the mixture which was not subjected to the crosslinking reaction in the production process of the brightness enhancing films of Examples 1 to 3 and Comparative Example 1, the measurement of the individual refractive index was carried out at room temperature using an Abbe refractometer (C9W-2WAJ).

(4) Measurement of shrinkage rate

For the reinforcing layers in the brightness enhancing films of Examples 1 to 3 and Comparative Example 1, 2 g was weighed and measured for shrinkage at room temperature in a specific gravity (MH-300S).

(5) Observation of brightness film warpage and ripple

The brightness enhancement films of the above Examples 1 to 3 and Comparative Examples 1 to 3 were cut into fixed sizes (297 mm × 210 mm), and the warpage of the four corners thereof was measured (see Fig. 5 (A)) and The surrounding ripple occurs (see Figure 5(B)). Then placed in the environmental test machine, under the test conditions of temperature 85 ° C, continued to stand for 24 hours, removed and placed on the marble countertop, after 10 minutes, measured and recorded four corner warping of the film surface The situation and the occurrence of waviness around the four sides, comparative analysis of the warpage of the reinforcing film (Examples 1-3, Comparative Examples 1-2) and the non-reinforcing layer (Comparative Example 3) before and after the temperature reliability test Changes in warpage and waviness before and after temperature reliability testing of the change in corrugation and the material of the different reinforcing layers (Examples 1 to 3 and Comparative Examples 1 and 2). The results are shown in Table 2 and Table 3.

As can be seen from Table 2 and Table 3, the brightness enhancing films of Examples 1 to 3 did not show significant warpage or ripple before the temperature reliability test. In addition, after the temperature reliability test of the brightness enhancement film of Example 1 was carried out at 85 ° C / 24 hours, the warpage of the sheet was between 6.4 and 8.8 mm, and the maximum ripple was about 1.3 mm; the brightness enhancement film of Example 2 After the temperature reliability test at 85 ° C / 24 hours, the warpage of the sheet is between 4 and 8 mm, and the maximum ripple is about 1 mm; After the brightness enhancement test of the brightness enhancement film at 85 ° C / 24 hours, the warpage of the sheet is between 2 and 7 mm, and the maximum ripple is about 0.5 mm. It is generally believed that this is because the anti-warping ability of the brightness enhancing film is mainly related to the shrinkage rate of the reinforcing layer, and the brightness increasing films of Examples 1 to 3 have similar shrinkage rates, and thus the anti-warping ability is also close. Further, the brightness enhancement film of Example 3 was superior in the anti-corrugation ability to the brightness enhancement film of Examples 1 and 2.

On the other hand, the brightness enhancement film of Comparative Example 1 has a warpage amount of 3 to 16 mm after the temperature reliability test, which may be due to the low shrinkage rate of the brightness enhancement film, and thus is in the same manner as in Examples 1 to 3. The anti-warpage ability of the brightness enhancement film having the same reinforcing layer thickness is poor; in addition, the degree of peripheral corrugation after the temperature reliability test is as high as 2 to 2.3 mm, and the degree of waviness is significantly higher than that of the brightness enhancement film of Examples 1 to 3. The reason may be that the Tg of the reinforcing layer of the brightness enhancing film of Comparative Example 1 is low, and thus the obtained brightness enhancing film is inferior in heat resistance and stability. In addition, the brightness of the brightness enhancement film of Comparative Example 2 decreased to 2.3 to 4.5 mm after the temperature reliability test, but the degree of waviness reached 1 to 1.3 mm, which was compared with the brightness enhancement film of Examples 1 to 3. Large, this result indicates that the use of a high Tg reinforcing layer material can achieve better heat resistance and deformation resistance at a lower thickness than a low Tg reinforcing layer material.

In addition, the brightness-enhancing film of the uncoated reinforcing layer of Comparative Example 3 had a warpage amount of 8 to 20 mm and a maximum ripple of 3 mm after the temperature reliability test, which exceeded the specifications acceptable to the industry.

The above results show that when the brightness enhancement film has a reinforcing layer, it will improve the dimensional stability and thermal stability of the product, and increase the resistance to deformation under various conditions, and the effect of the reinforcing layer to achieve such effects is related to two factors. One is the Tg of the reinforcing layer. When the reinforcing layer Tg is higher, the effect of the reinforcing layer on the thermal stability will be better. From the above results, when the Tg of the reinforcing layer is Good thermal stability can be provided above 87 °C; second is the thickness of the reinforcing layer. When the reinforcing layer with Tg higher than 87 °C is used on a thin substrate, the thickness of the reinforcing layer can be good as long as it is about 5 μm. .

(The real film test of the brightness enhancement film assembled in the backlight module (1))

The brightness enhancement films of Examples 1 to 3 and Comparative Examples 1 and 3 were cut into 12 sizes, assembled in a 12-inch backlight module, and after 10 minutes of lighting, the brightness enhancement film was taken out from the backlight module. The condition and extent of the film surface ripple were observed, and the results are shown in Table 4.

The results in Table 4 show that after the brightness enhancement film of Comparative Example 3 is lit in the backlight module for 10 minutes, the heat resistance and dimensional stability of the film are obviously insufficient due to the absence of the reinforcing layer, and very severe corrugation is generated (see Fig. 6). (A)); In addition, after the brightness enhancement film of Comparative Example 1 was turned on in the backlight module for 10 minutes, although the corrugation condition was slightly improved due to the provision of the reinforcing layer, it still did not reach the demand for the product. Change the standard. On the other hand, after the brightness enhancement film of Examples 1 to 3 is lit in the backlight module for 10 minutes, the Tg of the reinforcing layer is high enough to provide sufficient heat resistance, dimensional stability and rigidity to the entire film surface of the brightness enhancement film. Therefore, no obvious corrugation occurs (see Figure 6(B)), and the degree of corrugation can meet the deformation standard of product demand.

(The real film test of brightness enhancement film assembled in backlight module (2))

The brightness enhancement film of Example 4 and Comparative Example 4 was cut into a size of 14 inches, and the cut sheet was assembled in a 14-inch backlight module. After lighting for 10 minutes, the brightness was removed from the backlight module. The film was observed for the condition and extent of the film surface ripple, and the results are shown in Table 5.

The results in Table 5 show that after the brightness enhancement film of Comparative Example 4 is turned on for 10 minutes in the backlight module, the thickness of the reinforcing layer is thin, so the heat resistance and dimensional stability of the entire film are insufficient, and the corrugation deformation is remarkable ( See Figure 7(A)). On the other hand, after the brightness enhancement film of Example 4 was lit for 10 minutes in the backlight module, no ripple was observed at all (see FIG. 7(B)).

The above results show that even if the reinforcing layer has a sufficiently high Tg, it still needs to be combined with a certain thickness to impart sufficient thermal stability and size to the brightness enhancing film. Stability, in the case of a 14-inch backlight module, the thickness of the reinforcing layer needs to reach 5 μm to show obvious effects.

(Test of luminance gain)

The luminance gain test was carried out at room temperature using a MB7 (SR-3AR) spectrophotometer for a display device in which any of the brightening films of Examples 1 to 3 and Comparative Examples 1 and 3 were assembled, and the results were as follows. 6 is shown.

As is apparent from the results of Table 6, the luminance gain values of the brightness enhancement films of Comparative Example 1 and Comparative Example 3 were 1.530. On the other hand, the brightness enhancement films of Examples 1 to 3 decreased with the refractive index of the reinforcing layer. The brightness of the reinforcing layer is gradually increasing, especially when the refractive index of the reinforcing layer before curing is 1.465 (Example 2), the luminance gain of the brightness enhancing film reaches 2%, and it is known that the low refractive index (RI) is used on the back side of the brightness enhancing film. When the resin is used as a reinforcing layer, it will contribute to the improvement of the brightness of the product.

The preferred embodiments and examples of the present invention have been described above, but the present invention is not limited thereto, and various modifications and changes can be made in accordance with the disclosure of the present invention. It is included in the present invention.

For example, although the above-described brightness enhancement film of the present invention is applied to the case of the edge light type backlight module, the present invention is not limited thereto, and the brightness enhancement film of the present invention can also be applied to a direct type backlight module, and can also be used. The corresponding effect.

1‧‧‧Brightening film

2‧‧‧Substrate

3‧‧‧稜鏡 structure

4‧‧‧ reinforcing layer

5‧‧‧ particles

6‧‧‧ Semi-ellipsoid

7‧‧‧Semi-circle

Fig. 1 is a perspective view showing the structure of a brightness enhancement film according to an embodiment of the present invention.

Fig. 2 is a perspective view showing the constitution of a brightness enhancement film according to still another embodiment of the present invention.

Fig. 3 is a view showing an example of a special structure for forming a reinforcing layer of the present invention.

Fig. 4 is a view showing another example of the special structure for forming the reinforcing layer of the present invention.

Fig. 5(A) is a view showing a portion of the present invention for observing the presence or absence of warpage of the brightness enhancement film, and Fig. 5(B) is a view showing a portion of the present invention for observing the presence or absence of waviness of the brightness enhancement film.

6(A) is a view showing the occurrence of ripples after the brightness enhancement film of Comparative Example 3 is assembled in a 12-inch backlight module for 10 minutes, and FIG. 6(B) shows the brightness enhancement film of Example 3 being assembled. A picture of the ripple occurrence after 10 minutes of lighting in the 12-inch backlight module.

Fig. 7(A) is a view showing the occurrence of ripples after the brightness enhancement film of Comparative Example 4 is assembled in a 14-inch backlight module for 10 minutes, and Fig. 7(B) shows the brightness enhancement film of the embodiment 4 being assembled. Figure 14 shows the ripple occurrence after lighting in the backlight module for 10 minutes.

1‧‧‧Brightening film

2‧‧‧Substrate

3‧‧‧稜鏡 structure

4‧‧‧ reinforcing layer

Claims (16)

A brightness enhancing film comprising: a support substrate having an upper surface and a lower surface; a stack structure comprising a plurality of crucibles extending in a first direction, wherein the upper surface of the support substrate supports the And a reinforcing layer disposed on the lower surface of the supporting substrate, wherein the reinforcing layer has a glass transition temperature (Tg) of 80 to 250 ° C and the reinforcing layer has a thickness of 3 to 50 μm. The brightness enhancement film of claim 1, wherein the reinforcing layer has a glass transition temperature (Tg) of 100 to 200 °C. The brightness enhancement film of claim 1, wherein the reinforcing layer has a refractive index of 1.3 to 1.6. The brightness enhancement film of claim 2, wherein the reinforcing layer has a refractive index of 1.3 to 1.6. The brightness enhancing film according to any one of claims 1 to 4, wherein the reinforcing layer is made of an acrylic copolymer. The brightness enhancement film of claim 5, wherein the acrylic copolymer is obtained by copolymerizing an aliphatic acrylic monomer or oligomer with an aromatic polyfunctional acrylic monomer or oligomer, or It is a copolymer of an aromatic acrylic monomer or oligomer and an aliphatic polyfunctional acrylic monomer or oligomer. The brightness enhancing film according to any one of claims 1 to 4, wherein the reinforcing layer further comprises a plurality of particles having a particle diameter of 1 to 20 μm. The brightness enhancement film of claim 7, wherein the particles are at least one selected from the group consisting of organic particles and inorganic particles. The brightness enhancing film of any one of claims 1 to 4, wherein the surface of the reinforcing layer is formed with a plurality of protrusions. The brightness enhancement film of claim 9, wherein the protrusions are selected from at least one of a triangular column shape, an irregular shape, a semi-cylindrical shape, a semi-spherical shape, and a semi-elliptical shape, and the The arrangement of the protrusions with each other is a regular arrangement or a random arrangement. The brightness enhancing film according to any one of claims 1 to 4, wherein the supporting substrate has a thickness of 25 to 300 μm. The brightness enhancement film of claim 11, wherein the support substrate is selected from the group consisting of polyethylene terephthalate (PET), polycarbonate (PC), and polyethylene naphthalate (PEN). One of a cyclic olefin copolymer (mCOC), a polyarylate (PAR), a polyether oxime (PES), a cellulose triacetate (TAC), and a polymethyl methacrylate (PMMA). A brightness enhancing film according to claim 1, wherein the reinforcing layer is formed of a single material. The brightness enhancement film of claim 1, wherein the reinforcing layer has a glass transition temperature (Tg) of 105 to 133 °C. The brightness enhancement film of claim 1, wherein the reinforcing layer has a thickness of 3 to 5.5 μm. A brightness enhancing film comprising: a support substrate having an upper surface and a lower surface; a stack structure comprising a plurality of crucibles extending in a first direction; wherein the upper surface of the support substrate supports the a crucible structure; and a rigid reinforcing layer disposed on the lower surface of the supporting substrate, wherein the reinforcing layer has a glass transition temperature (Tg) of 80 to 250 ° C and the reinforcing layer has a thickness of 3 to 50 μm. To increase the rigidity of the brightness enhancing film.