JP2006192540A - Polishing film for liquid crystal color filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing film for a liquid crystal color filter, which stably removes foreign matters or the like having various hardness and generated on a filter in a liquid crystal color filter manufacturing process at a high polishing rate, and by which high polishing face quality is obtained. <P>SOLUTION: The polishing film 1 is composed of a substrate film 10 and a polishing layer 20 fixed and formed on the substrate film 10. The polishing layer 20 includes a binder resin 21 and many abrasive grains 22 fixed by the binder resin 21. A carboxyl group-containing polyurethane resin is used as the binder resin 21. A value of breaking energy calculated from a stress-strain curve of the binder resin 21 is set in the range of 0.1±0.05 N/m. The α alumina having an average sphericity Ψw of 0.6 or more and an average particle size of 0.3 μm is used as the abrasive grains 22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an abrasive film for a liquid crystal color filter, and more particularly to an abrasive film (abrasive tape) for removing foreign substances and the like generated on the filter in the production process of a liquid crystal color filter used in a liquid crystal display.

  Liquid crystal displays such as TVs, PCs, and mobile phones use R (red), G (green), and B (blue) color filters in order to achieve full color display. In a liquid crystal display, pixels of an RGB color filter are arranged on one side of an electrode substrate, and a black layer (black matrix: BM) is formed between R, G, and B elements as necessary. On the color filter on which the element is formed, a protective film (overcoat layer) is formed of polyimide or the like for the purpose of protecting the color layer or smoothness.

  Various methods for producing color filters have been developed and studied. Filter manufacturing methods can be broadly classified into organic filters that use organic materials as a colored layer, inorganic filters that use inorganic materials, and composite filters that combine these. Among them, the mainstream is an organic filter, and various methods such as a dyeing method, a dispersion method, a printing method, and an electrodeposition method have been established. The color filter produced by these various methods encloses a liquid crystal through a spacer together with a back TFT glass substrate, and is combined with a polarizing plate or a backlight module to form a liquid crystal display.

  In recent years, the liquid crystal display tends to narrow the gap between the color filter and the TFT glass substrate (cell gap) from about 10 μm to 5 μm or less in order to improve the response speed at the time of moving image reproduction. If there are minute foreign matters or protrusions on the color filter, this narrowing of the gap is hindered and a high response speed cannot be realized, which has been a serious problem.

Conventionally, a process has been established for removing protrusions generated on a color filter after measuring the protrusion height with a dedicated inspection device. In addition, as a method for removing foreign substances, a laser removal method, a removal method using a polishing film, and a method in which these are combined are mainly used. These polishing methods and polishing films are disclosed, for example, in JP-A-8-25205, JP-A-9-57634, JP-A-2001-62696, JP-A-2002-154061, and the like.
JP-A-8-25205 JP-A-9-57634 JP 2001-62696 A JP 2002-154061 A

  However, the foreign matters and protrusions generated on the color filter are, for example, glass cullet generated from the glass substrate, metallic foreign matters mixed in the liquid feeding line, aggregates of the overcoat material, undissolved matter, etc. However, it has been difficult to uniformly remove these foreign matters and protrusions in conventionally used polishing films.

  Therefore, if processing with a polishing film with higher polishing power is attempted, foreign objects and protrusions of metal and glass can be removed relatively efficiently, but the finish surface roughness is poor and the color filter surface is damaged. I will give it. On the other hand, when processing with a polishing film using fine abrasives in consideration of damage to the color filter, the finished surface roughness is good, but the polishing efficiency is poor, so glass and metallic protrusions are removed. There is a problem that it remains without being squeezed or a long time is required for finishing.

  Furthermore, in the color filter inspection process, it is possible to measure the position, shape, and size of foreign objects and protrusions, but it is impossible to classify the types of foreign objects and protrusions. It is practically impossible to use them properly. Therefore, there has been a demand for an abrasive tape that can remove various foreign matters and protrusions uniformly with a single tape without damaging the color filter.

  In addition, in a polishing film using ordinary pulverized powder as an abrasive, it is difficult to control how the size and shape of the fragments are crushed when pulverizing abrasive abrasive grains. The abrasive grains are not uniform and vary in terms of size and shape. Therefore, when such a general abrasive is used as an abrasive grain, the crushed crushing surface has irregular corners, and some have sharp and sharp corners, causing unnecessary damage to the surface of the liquid crystal color filter during polishing. Will give. Further, with such irregular shaped abrasive grains, particularly when removing resinous foreign matters, clogging is likely to occur between the abrasive grains and the abrasive grains, and a high polishing rate could not be maintained for a long time. .

  The present invention has been made paying attention to the above points, and can remove foreign matters and protrusions having various hardnesses generated on the filter in the liquid crystal color filter manufacturing process stably at a high polishing rate, and high polishing. It aims at providing the polishing film for liquid crystal color filters which can obtain a surface quality.

  In order to solve the above-mentioned problems, according to the present invention, in an abrasive film for a liquid crystal color filter in which abrasive particles are fixed on a substrate with a binder resin, the average sphericity Ψw of the abrasive particles is 0.6 to 1. There is provided a polishing film for a liquid crystal color filter, characterized in that the value of fracture energy of the binder resin determined from the stress-strain curve of the binder resin is in the range of 0.1 ± 0.05 N / m.

  In the present invention, plastics such as PET and PEN can be preferably used as the substrate, but are not limited thereto. The thickness of the substrate is preferably 12 to 75 microns, and particularly preferably 25 microns.

  In the present invention, α-alumina can be preferably used as the abrasive particles. The average particle size of the abrasive particles is preferably 0.05 to 1.0 μm.

  The sphericity Ψw of the abrasive particles is a value determined from the ratio of the diameter of the circle in contact with the major axis and the diameter of the circle in contact with the minor axis from the observation result of the particles by an electron microscope. That is, when the value of the sphericity Ψw is 1.0, it is a true sphere, and as the value of Ψw becomes smaller than 1.0, the shape is separated from the sphere.

  In the present invention, abrasive particles having a sphericity Ψw of 0.6 to 1.0 are used. This is due to the following reason.

  In order to verify the influence of the sphericity Ψw of the abrasive particles on the polished surface, abrasive films using abrasive particles (average particle diameter of 0.3 μm) of each sphericity were prepared and evaluated as follows. Each 10 mm × 10 mm × 5 mm quartz glass block was used as a workpiece, the quartz block was polished under conditions of a processing pressure of 500 g, a polishing stroke of 100 mm, and a polishing frequency of 50 cycles, and a differential interference microscope (Axio Plan manufactured by Carl Zeiss, observation magnification × 510.2), scratches on the polished surface were evaluated. Here, when the number of scratches generated in the polished quartz glass was 3 or less, it was judged as good, and when it was 4 or more, it was judged as bad. As a result, it was found that when the sphericity Ψw of the abrasive particles is 0.6 or more, the frequency of occurrence of scratches is low and high polishing surface accuracy can be obtained. On the other hand, when the sphericity Ψw is less than 0.6, it was confirmed that the frequency of occurrence of scratches increased and the object to be polished was significantly damaged. The evaluation results are shown in FIG.

  A spherical abrasive having a sphericity Ψw of 0.6 or more also has an equivalent depth of cutting of the abrasive grains under the same pressure as compared to an irregular abrasive having a normal sharp angle. The contact area on the grains increases. As a result, since the area removed by one abrasive grain also increases, the polishing rate becomes higher than that of the pulverized powder. Also, in the case of spherical particles, in order to remove the object to be polished with a wide contact area, the generated polished surface roughness is better than in the case of pulverized powder that is an aggregate of scratch removal with a sharp tip. Can be kept in.

  Further, when the filling rate (abrasive volume concentration in the binder resin) is equal and relatively high, the spherical particles have a relatively small abrasive-abrasive gap compared to the pulverized powder that is an aggregate of irregular shaped particles. Since it becomes wider, the problem of clogging hardly occurs, and a high polishing rate can be maintained for a long time. In particular, the clogging problem was serious when removing resinous foreign matter, but this problem can also be avoided when spherical particles are used. In addition, the said filling rate determines an optimal value according to a to-be-polished object.

  When the sphericity Ψw is less than 0.6, the shape approaches an indeterminate shape, and the contact area and clogging avoidance characteristics described above are inferior. Since the sphericity Ψw1.0 is a true sphere, the value does not become larger than this.

  In the present invention, the value of the fracture energy obtained from the stress-strain curve of the binder resin is in the range of 0.1 ± 0.05 N / m. The breaking energy of the binder resin means the breaking energy of the cured or dried binder resin in a state where the abrasive particles are restrained and held. Moreover, a stress-strain curve is calculated | required as follows according to the measuring method based on JISK7161.

  That is, using a test piece (for example, 100 mm × 10 mm, thickness 0.02 mm) manufactured in a certain shape, until the test piece breaks or stress (load) or strain ( The test piece is pulled along the main longitudinal axis at a constant speed until the elongation reaches a specified value, and the load and elongation applied to the test piece during that time are measured. The load during the test and the corresponding increase in the distance between the marked lines and the distance between the crossheads (measurement load cells) are recorded as a stress-strain curve using an automatic recorder. The load applied up to the breaking point of the obtained stress-strain curve is called tensile fracture strength, and the elongation is called tensile fracture elongation.

The tensile fracture strength is calculated by the following formula.
σ = F / A
Here, σ = tensile fracture strength (MPa), F = load (N) at the specified strain at the time of fracture, and A = original minimum cross-sectional area (mm ² ) of the test piece.

Further, the tensile fracture elongation is calculated by the following formula.
ε = (L−Lo) / Lo × 100
Here, ε = tensile elongation at break (%), L = distance between marked lines at maximum load (mm), Lo = original distance between marked lines (mm).

Fracture Energy Density (Gf) represents the area of the stress-strain curve obtained by the above test method (Reference: On the transition from continuum nonlocal damage to quasi-brittle discrete crack models. C. Comi et al 2002 GIMC).
Since the fracture energy indicates the area to the fracture point of the stress-strain curve, the larger the tensile fracture strength and the tensile fracture elongation, the greater the value, indicating that the fracture energy is tough.

  When a binder resin having a fracture energy within the above range is used, it is possible to balance both characteristics of polishing power and polished surface accuracy. When a binder resin having a fracture energy value of 0.05 N / m or less is used, processing progresses mildly with respect to the color filter surface, so that the polishing surface accuracy is excellent but a desired polishing force cannot be obtained. . On the other hand, when a hard binder resin having a fracture energy value of more than 0.15 N / m is used, a high polishing power can be obtained, but damage to the polished surface is great and it is not suitable for correcting a liquid crystal color filter. Thus, the use of a binder resin having a fracture energy value in the range of 0.10 ± 0.05 N / m is an important factor for a polishing film for correcting a liquid crystal color filter.

  When a binder resin having a fracture energy within the above range is used, it is possible to balance both characteristics of polishing power and polished surface accuracy. When a binder resin having a fracture energy value of 0.05 N / m or less is used, processing progresses mildly with respect to the color filter surface, so that the polishing surface accuracy is excellent but a desired polishing force cannot be obtained. . On the other hand, when a hard binder resin having a fracture energy value of more than 0.15 N / m is used, a high polishing power can be obtained, but damage to the polished surface is great and it is not suitable for correcting a liquid crystal color filter. Thus, the use of a binder resin having a fracture energy value in the range of 0.10 ± 0.05 N / m is an important factor for a polishing film for correcting a liquid crystal color filter.

  As the binder resin having the above physical properties, a polyurethane resin is suitable. In particular, the binder resin used in the present invention is preferably a system in which a carboxyl group-containing polyurethane resin is crosslinked with an isocyanate compound. In general, alumina particles are basic particles from the classification of acid-base. Therefore, by using a polyurethane resin in which a carboxyl group is present as a functional group in the binder resin, the alumina abrasive particle surface and the functional group of the binder resin are changed. Interact and improve dispersibility, resulting in improved retention of particles. That is, since the binder resin having an acidic functional group is easily adsorbed to the surface of the alumina abrasive that is a basic pigment, the particle surface can be completely wetted with the binder resin, thereby improving dispersibility, and Since the particle surface is coated with the binder resin, the retention force of the particles is increased as a result. Therefore, during the polishing of the liquid crystal color filter, it is possible to suppress the occurrence of scratches due to the removal of the abrasive particles from the binder resin. In addition, binder resin is used individually or in 2 or more types in arbitrary ratios.

  Hereinafter, preferred embodiments of the present invention will be described.

  FIG. 1 is a schematic cross-sectional view of a polishing film 1 for a liquid crystal color filter according to the present invention. The polishing film 1 includes a base film 10 and a polishing layer 20 fixed and formed on the base film 10. The polishing layer 20 includes a binder resin 21 and a large number of abrasive particles 22 fixed by the binder resin 21. As the base film 10, PET having a thickness of 25 microns was used. As the binder resin 21, a carboxyl group-containing polyurethane resin was used. Further, the value of the fracture energy obtained from the stress-strain curve of the binder resin 21 forming the polishing layer 20 according to the measurement method according to JIS K7161 is in the range of 0.1 ± 0.05 N / m. Prepared. Further, as the abrasive particles 22, α alumina having an average sphericity Ψw of 0.6 or more and an average particle diameter of 0.3 μm was used.

  The polishing layer 20 is a solution in which the binder resin 21 and the curing agent are uniformly dissolved with a solvent, and a coating liquid in which abrasive particles 22 are dispersed in the solvent (resin liquid) is applied onto the base film 10. This was produced by drying or curing. The abrasive particles 22 are weighed, mixed, and uniformly dispersed in the resin liquid by a dispersing machine such as a sand mill. As a coating means on a base material, a wire bar coater, a gravure coater, a reverse coater, a knife coater, a nozzle, a die coater, etc. can be used, for example.

  As the curing agent, polyisocyanate can be used, and specific examples include hexamethylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, naphthylene diisocyanate, and the like. These curing agents are used alone or in any proportion of two or more.

  As the solvent used in the coating liquid for forming the polishing layer 20, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, ethyl butyl acetate, tetrahydrofuran, toluene, xylene, ethanol, isopropanol, etc. may be used. However, it is not limited to these. These organic solvents can uniformly dissolve the binder resin 21 and the curing agent, and can stably disperse the abrasive particles 22. Further, the solvent is used alone or in an arbitrary ratio of two or more so that it is completely dried and removed after coating.

  In addition, in the said coating liquid, other surfactant, a coupling agent, etc. can be used as needed.

  Next, Examples 1 and 2 of the present invention, which are specific examples of the above-described liquid crystal color filter polishing film 1, are compared with Comparative Examples 1 to 5, and the effects of the present invention will be described.

  The abrasive film of Example 1 was obtained as follows. A 33 wt% resin solution was prepared using methyl ethyl ketone as an organic solvent and a polyurethane-based resin (trade name “Dyferamin MAU5022” manufactured by Dainichi Seika Co., Ltd.) as a carboxyl group-containing binder resin. For this resin liquid, α-alumina particles (trade name “AKP-50” manufactured by Sumitomo Chemical Co., Ltd.) having an average sphericity of Ψw = 0.75 and an average particle diameter of 0.3 microns were used as abrasive particles with a sand mill. After mixing and dispersing uniformly, an isocyanate cross-linking agent (curing agent) (trade name “Coronate HX”: manufactured by Nippon Polyurethane Industry Co., Ltd.) is added with stirring, followed by coating with a filtering accuracy of 5 μm. A liquid was prepared. The composition of this coating solution is shown in Table 1. This coating solution was applied with a knife coater onto a polyethylene terephthalate film (trade name “SG-2” manufactured by Teijin Ltd.) having a thickness of 25 μm and subjected to easy adhesion treatment. The drying oven temperature of the coater was set to 120 ° C., and after coating, left at room temperature for 24 hours, and then aged at 40 ° C. for 48 hours to obtain the abrasive film.

  The abrasive film of Example 2 (the composition of the coating solution is shown in Table 2) is a polyurethane resin containing sulfobetaine group (trade name “Takelac E-780” manufactured by Mitsui Takeda Chemical Co., Ltd.) In this way, it was fabricated in the same manner as in Example 1.

  As a comparative example for Examples 1 and 2, the abrasive film of Comparative Example 1 was crushed with abrasive particles having an average sphericity of Ψw = 0.5 and an average particle diameter of 0.3 microns with respect to the abrasive film of Example 1. Alumina particles (trade name “WA20000”: manufactured by Fujimi Incorporated), the abrasive film of Comparative Example 2 is a silicone carbide abrasive material having an average sphericity Ψw = 0.36 and an average particle diameter of 0.2 microns ( Product name “GC30000”: manufactured by Fujimi Incorporated). Tables 3 and 4 show the compositions of the coating liquids of Comparative Examples 1 and 2.

  The polishing film of Comparative Example 3 is a non-polar binder resin (trade name “MAU9022” manufactured by Dainichi Seika) with respect to the polishing film of Example 1, and the polishing film of Comparative Example 4 is a binder resin. Were changed to basic ones (trade name “MAU4308” manufactured by Dainichi Seika). Furthermore, the polishing film of Comparative Example 5 was prepared by changing the binder resin to a polyester resin containing a carboxyl group (trade name “Byron GK890” manufactured by Toyobo Co., Ltd.) with respect to the polishing film of Example 1. It is a thing. The compositions of the coating liquids of Comparative Examples 3 to 5 are shown in Tables 5 to 7.

  About the abrasive film of the above Example and the comparative example, the value of the fracture energy calculated | required from the stress-strain curve according to the measuring method based on JISK7161 was measured with the orientec company made tensile tester. The measurement conditions were a crosshead speed of 200.0 mm / min, a sample width of 10.0 mm, a thickness of 0.02 mm, and an initial sample length of 50.0 mm. Was used. Table 8 shows the measured values of the fracture energy of each sample.

  The polishing characteristics are assumed to be metallic foreign matter, glass cullet, and foreign matter of various hardness consisting of undissolved resin, which can be present on the actual liquid crystal color filter, respectively, 10mm x 10mm x 5mm sendust block, quartz glass block A polyimide block is prepared, and each block is dummy-polished (using an original machine for dummy polishing and used) under conditions of a processing pressure of 500 g, a polishing stroke of 100 mm, and a polishing frequency of 50 cycles, and the polishing power at that time is obtained. It was.

  In the judgment of the polishing force, a block having almost the same polishing amount for each block having different hardness was evaluated as good, and a block having a large variation in polishing amount due to a difference in hardness was determined as defective.

  Evaluation of the polishing surface (polishing surface of the dummy polishing performed in each of the above blocks) was performed over the entire 10 mm × 10 mm polishing surface of each block using a differential interference microscope (Axio Plan manufactured by Carl Zeiss, observation magnification × 510.2). The scratch was evaluated as follows. That is, ◎ indicates that no scratch is generated, ◯ indicates that 1 to 3 scratches are generated in the observation area, and × indicates that 4 or more scratches are generated.

  Table 9 shows the results of the above polishing force and polished surface evaluation.

  In addition, an actual liquid crystal color filter foreign matter (projection) removal experiment was also performed. In this experiment, the height of each protrusion existing on the liquid crystal color filter is measured in advance, the protrusion is polished with a color filter polishing apparatus, and the number of times of polishing until the protrusion height after polishing becomes 5 microns or less is measured. The processed surface state at that time was evaluated in substantially the same manner as the scratch evaluation. At this time, it is determined that the number of polishing times is 1 and the processed surface state is ◎ or ◯, and the processed surface state is x even when the polishing number is 1, or the processed surface state is ◎ or ○. However, when the number of times of polishing was 2 times or more, it was judged as defective (insufficient polishing power / poor polishing surface). The experimental results are shown in Table 10.

  From the above test and experimental results, the average sphericity Ψw of the abrasive particles is 0.6 to 1, and the value of the fracture energy obtained from the stress-strain curve of the binder resin is 0.1 ± 0.05 N / m. In the polishing film for liquid crystal color filters as in Examples 1 and 2 using a carboxyl group-containing polyurethane as a binder resin, a desired polishing force can be obtained in a short time even for a plurality of foreign matters having different hardnesses. In addition, it was confirmed that the polished surface condition was also good. On the other hand, even if the value of the fracture energy is in the above range as in Comparative Examples 1 to 3, when the sphericity of the abrasive particles is less than 0.6, or using an acidic binder as in Comparative Example 5 However, it was also confirmed that when the value of the breaking energy is outside the above range, the polishing power is insufficient or the polishing surface is defective, which is not suitable for the foreign matter polishing of the liquid crystal color filter.

  As described above, in the liquid crystal color filter polishing film according to the present invention, it is possible to obtain good polishing power and finished surface accuracy in a short time even for foreign matters having different hardnesses. Foreign matters and protrusions having various hardnesses generated on the filter can be stably removed at a high polishing rate, and a high polished surface quality can be obtained.

It is a schematic sectional drawing of the polishing film for liquid crystal color filters which concerns on this invention. It is a graph which shows the relationship between the sphericity Ψw of abrasive particles and the number of scratches on the polished surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polishing film for liquid crystal color filter 10 Base film 20 Polishing layer 21 Binder resin 22 Abrasive particle

Claims (4)

In the polishing film for liquid crystal color filters in which the abrasive particles are fixed with a binder resin on the substrate,
The average sphericity Ψw of the abrasive particles is 0.6 to 1.0,
A polishing film for a liquid crystal color filter, wherein a binder resin has a fracture energy value determined from a stress-strain curve in a range of 0.1 ± 0.05 N / m.   The polishing film for a liquid crystal color filter according to claim 1, wherein the abrasive particles are α-alumina.   The polishing film for a liquid crystal color filter according to claim 1 or 2, wherein the abrasive particles have an average particle diameter of 0.05 to 1.0 µm.   The polishing film for a liquid crystal color filter according to any one of claims 1 to 3, wherein the binder resin is obtained by crosslinking a carboxyl group-containing polyurethane resin with an isocyanate compound.

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