JP2008242175A - Method for forming thin film pattern and method for producing black matrix substrate for color filter - Google Patents

Abstract

In the precision processing of organic thin films, the thermal ablation method is used to deepen the energy transfer depth to the workpiece, shorten the processing time, and efficiently remove the remaining film that becomes a problem during thermal ablation. This method is applied to the manufacture of a black matrix substrate for a color filter.
A thin film 2 made of an organic material is formed on a substrate 1, and a portion to be removed is irradiated with laser light 4 to perform pattern processing by thermal ablation, and then laser ablation is performed. By performing ashing 8 on the entire surface, a pattern in which the remaining film 7 is also efficiently removed is formed. It is advantageous to form a polymer film 3 that can be removed later on the organic thin film 2 and to remove the polymer film 3 after laser ablation. If the organic thin film 2 is a light-shielding resin thin film, a black matrix substrate for a color filter can be manufactured.
[Selection] Figure 1

Description

  The present invention relates to a method for forming a thin film pattern in which an organic thin film, which is a workpiece, is irradiated with laser light, and the organic thin film is partially decomposed and removed by a laser ablation phenomenon occurring at the irradiated portion. More specifically, the present invention relates to a pattern forming method useful for forming an optical element used in a display device such as a liquid crystal display device, for example, a color filter, particularly its black matrix. The present invention also relates to a method for manufacturing a black matrix substrate of a color filter that is suitably incorporated in a liquid crystal display device.

  As a method for forming a thin film pattern, a method of exposing a photosensitive resin film to a mask and forming a latent image in a light irradiation portion, and then removing an unnecessary portion by development (photolithography) is common. Expensive photosensitive resin, exposure equipment, and a photomask are required, and there are limitations such as high processing cost and that the workpiece needs to be stable against chemicals. On the other hand, a direct processing method that does not use a photomask has recently been proposed. In particular, laser ablation processing methods that irradiate various laser beams to locally decompose and remove organic materials are attracting attention.

  For example, in Japanese Patent Laid-Open No. 5-185269 (Patent Document 1), a removable film is formed on the surface of a material to be processed, and an excimer laser is irradiated thereon to decompose the film on the irradiated portion and the material to be processed. There is disclosed a method of performing laser ablation processing to remove, and removing wrinkles generated by laser ablation together with the film after processing.

  Japanese Patent Laid-Open No. 9-80221 (Patent Document 2) discloses that a light-shielding film material mainly composed of graphite containing a polyimide-based polymer organic material as a binder is formed on a substrate, and a predetermined pattern is formed thereon. It is described that a light-blocking matrix is formed by performing photodegradation development by irradiation of excimer laser light through a mask having a mask, and after the light-blocking matrix is formed, it is said to be washed with brush water washing or ashing to remove decomposition products. ing.

  The excimer laser using the stimulated light emission phenomenon from the excited state of the rare gas and the halogen as employed in the above-mentioned Patent Document 1 and Patent Document 2 has a wavelength in the ultraviolet region, so that it absorbs strongly against ultraviolet light. When an organic material such as a polymer is irradiated with a compound having a molecular weight, for example, molecules in the organic material are excited at a high density, and thereafter, photochemical decomposition, that is, a photochemical ablation phenomenon occurs instantaneously from the excited state. Therefore, since excimer laser processing is mainly chemical decomposition, compared to processing using an infrared laser such as Nd-YAG laser (neodymium-yag laser, YAG is yttrium, aluminum, garnet) described later, It is suitable for microfabrication because it can perform clean processing with little heat damage such as melting marks and is a short wavelength laser. However, since the short wavelength is used, there is a problem that the processing efficiency is low due to the shallow energy transmission depth to the workpiece, and the light source (excimer laser) is expensive.

  On the other hand, laser processing using thermal energy typified by the Nd-YAG laser is in a high vibration state when molecules in organic matter absorb laser light in the infrared region, and surrounding molecules are also affected by vibration energy (thermal energy). It utilizes thermal decomposition, that is, photothermal decomposition and ablation (evaporation) phenomenon. Therefore, in this method, since the vibration of the molecules in the organic matter is used, the periphery of the processed part is thermally damaged, and since the infrared ray is used, it is difficult to reduce the spot diameter, and the point processing makes it possible to reduce the throughput. From the viewpoint, it is not suitable for mass production. However, since a long wavelength is used, there is an advantage that the energy transmission depth to the workpiece is deep and the machining time is short.

  Next, a color filter used in a liquid crystal display device, an image sensor, or the like is used, for example, for colorizing a display image by being incorporated in a liquid crystal display device, or for obtaining a color image incorporated in a solid-state image sensor. These optical elements are usually composed of colored patterns formed adjacent to each other on the same plane on a substrate such as glass, silicon wafer, or transparent resin.

  The coloring pattern includes, for example, three primary color pixels including red (R) pixels, green (G) pixels, and blue (B) pixels, and a black matrix formed at the boundary between the color pixels. Here, each color pixel is a transparent layer colored in each color, and the black matrix is a black layer that does not substantially transmit visible light. If necessary, transparent pixels that are not colored may be formed in addition to the RGB pixels.

  As a method for producing such a color filter, a colored photosensitive resin composition layer comprising a solid content of a colored photosensitive resin composition is formed on a substrate, and the resin composition layer is irradiated with light through a photomask, A photolithography method (pigment dispersion method) is generally known in which a colored pattern is formed by dissolving an unirradiated region in a developer. Not only the black matrix that constitutes a general color filter, but also the red pixel, green pixel, and blue pixel, the gap control mechanism and the structure for liquid crystal alignment can be obtained by repeatedly performing photolithography while changing the photosensitive resin. Sequentially formed.

  In recent years, replacement of expensive photolithography with a cheaper method such as printing or ink-jet has been studied. However, regarding black matrix, pattern anomalies and residual film accuracy are caused by display defects (physical defects and uneven transmittance). Development of alternative technologies is not progressing.

JP-A-5-185269 Japanese Patent Laid-Open No. 9-80221

  Therefore, an object of the present invention is to employ a thermal ablation method in precision processing of an organic thin film, thereby deepening the energy transmission depth to the workpiece and shortening the processing time and causing a problem in thermal ablation. An object of the present invention is to provide a method capable of efficiently removing the remaining film. Another object of the present invention is to provide a method for directly processing a thin film precision pattern by applying the above method to the manufacture of a black matrix substrate of a color filter used for liquid crystal display or the like.

  That is, the thin film pattern forming method according to the present invention forms a thin film made of an organic material on a substrate, irradiates a portion to be removed of the thin film with laser light, and performs pattern processing by thermal ablation. The ashing process is performed on the entire ablated surface.

  The method for producing a black matrix substrate for a color filter according to the present invention comprises forming a light-shielding resin thin film containing a light-shielding pigment on a transparent substrate, and irradiating a portion to be removed with laser light. After performing pattern processing by thermal ablation, the entire surface subjected to laser ablation is subjected to ashing treatment.

  Thus, in the present invention, surface ashing is employed as a means for removing the remaining film generated by thermal ablation without impairing the precision pattern. In the method for forming a thin film pattern or the method for producing a black matrix for a color filter, a polymer film that can be removed later is formed on a thin film made of an organic material or a light-shielding resin thin film. It is preferable to irradiate laser light from above and perform pattern processing by thermal ablation, and then remove the polymer film and then perform ashing. In this case, it is advantageous that the polymer film that can be removed later is made of a water-soluble resin, and the removal of the polymer film after patterning is performed by washing with water. The water-soluble polymer film is preferably made of polyvinyl alcohol.

  According to the present invention, a thin film pattern having a desired shape can be formed without using conventional photomask exposure. If this method is applied to the production of a black matrix substrate for color filters, a resin black matrix substrate having desired optical characteristics and high resolution can be obtained while maintaining high pattern accuracy.

  FIG. 1 is a schematic cross-sectional view of a preferred embodiment of the method of forming a thin film pattern according to the present invention or the method of manufacturing a black matrix substrate on which such a thin film pattern is formed, step by step. Hereinafter, embodiments of the present invention will be described in detail with reference to this figure.

  In the form shown in FIG. 1, first, as shown in FIG. 1A, an organic thin film 2 is formed on a substrate 1. Next, as shown in (B), a polymer film 3 that can be removed later is formed on the organic thin film 2. Thereafter, as shown in (C), the laser beam 4 is irradiated through a mask 5 having a desired opening 6 corresponding to a portion to be removed of the organic thin film 2. As a result, thermal ablation processing is performed, and the polymer film 3 and the organic thin film 2 in the portion irradiated with the laser beam 4 are removed, and a desired pattern is formed as shown in FIG. Thereafter, as shown in (E), the polymer film 3 formed on the organic thin film 2 is removed. However, when the pattern shown in FIG. 1D is formed or the polymer film 3 shown in FIG. 1E is removed, the polymer film 3 and the organic thin film 2 are removed by thermal ablation. Nevertheless, the thin residual film 7 remains on the substrate 1 in that portion. Therefore, in the present invention, as shown in FIG. 1F, ashing 8 is performed on the entire surface subjected to laser ablation. As a result, the residual film 7 is decomposed and removed, and as shown in (G), a substrate in which a desired pattern made of the organic thin film 2 is formed, for example, a black matrix substrate is completed.

  Here, the description has been made mainly in accordance with the requirements stipulated in the method for forming a thin film pattern described above. However, if “organic thin film 2” in the above description is read as “light shielding resin thin film 2 containing a light shielding pigment”. This will explain the method for manufacturing the black matrix substrate for color filter described above.

  In the present invention, among the steps shown in FIG. 1, the organic thin film forming step (A), the pattern forming step by laser irradiation (thermal ablation) (C) and (D), and (F) and (G) A pattern completion process by ashing is essential. The step of forming the polymer film (B) is optional, but preferably employed. If the step (B) for forming a polymer film 3 that can be removed later is incorporated, wrinkles that are likely to occur during ablation can be removed together with the removal of the polymer film 3. The cleaning of the pattern surface can be expected. Therefore, when the step (B) for forming the polymer film 3 is incorporated, the step (E) for removing the polymer membrane is also incorporated.

  The substrate 1 used for laser ablation processing is not particularly limited, and inorganic glass such as quartz glass, borosilicate glass, aluminosilicate glass, soda lime glass coated with silica on the surface, various plastic films, A sheet or the like is used. Further, an opaque substrate such as with a metal film used in a reflective liquid crystal display device can also be used. The thickness of the substrate 1 is generally about 0.1 mm to 3 mm.

  An organic thin film 2 is formed on the substrate 1. The organic thin film 2 is made of an organic material. When a black matrix substrate for a color filter is manufactured, the organic thin film 2 is composed of a black matrix film, that is, a light-shielding resin thin film containing a light-shielding pigment. Materials used for the black matrix film include a metal thin film, a metal thin film laminated with an oxide film or a nitride film, and a material made of a resin containing a light-shielding pigment. Made of a resin containing a conductive pigment. Examples of the light-shielding pigment include metal oxides, metal nitrides, metal sulfides, carbon black, and various organic black pigments. Among these, carbon black is preferably used. That is, a light-shielding resin film containing carbon black as a light-shielding pigment is preferable because color tone correction is easy.

  When carbon black is used as the light-shielding pigment, a blue pigment or a violet pigment can be used singly or in combination for complementary colors. In addition to these, powders such as metal oxides, metal nitrides, and metal sulfides may be mixed.

  The organic material used for the organic thin film 2 or the light-shielding resin film is generally a resin, and from the viewpoint of heat resistance, light resistance, solvent resistance, etc. of the coating film, epoxy resin, acrylic resin, polyimide resin, urethane resin, polyester resin Polyolefin resins and the like are preferable.

  As a method for forming the organic thin film 2 or the light-shielding resin thin film, dip coating, roll coating, spin coating, die coating, wire bar coating, etc. are generally used, but printing method, transfer method, electrodeposition method, The thin film 2 may be formed by a vacuum deposition method, an electrophotographic method, or the like.

  After the organic thin film 2 or the light-shielding resin thin film is formed, it is dried by heating (baking) using a vacuum dryer, an oven, a hot plate, or the like. The baking conditions vary depending on the resin and solvent used, but it is common to heat at 40 to 200 ° C. for 1 to 60 minutes.

  The light-shielding resin thin film for forming the color filter black matrix preferably has a thickness of about 0.5 to 3 μm. The reason for this is that when the film thickness is less than 0.5 μm, the light-shielding property becomes insufficient. Conversely, when the film thickness exceeds 3 μm, the flatness of the color filter surface is impaired, and the gap adjustment becomes difficult.

  The standard of the light shielding property in the light shielding resin thin film is based on the optical density (OD value). The optical density is expressed as a common logarithm of the reciprocal of the transmittance. In order to improve the display quality of the liquid crystal display device, the optical density of the light-shielding resin thin film is preferably 2.5 or more, particularly preferably 3.5 or more. This value is determined by the relationship with the film thickness of the light-shielding resin thin film.

  When performing laser ablation processing, a polymer film 3 that can be removed later is formed on the organic thin film 2 or the light-shielding resin thin film as described above with reference to FIG. Good. The polymer film 3 that can be removed later is preferably made of a resin that can be removed by peeling or washing after the laser ablation process. The wrinkles that are likely to occur during laser ablation can be easily removed together with the polymer film 3, and the surface of the pattern or black matrix can be expected to be cleaned.

  The polymer film 3 is preferably formed of a water-soluble resin, but may be formed of a material soluble in alcohol or other organic solvent as long as it does not affect the base of the film 3. . Examples of water-soluble resins include polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, and polyvinyl pyrrolidone. Examples of alcohol-soluble resins include nylon, polyethylene glycol, and polyvinyl butyral. On the other hand, examples of resins soluble in other organic solvents include many general-purpose thermoplastic resins such as polystyrene, polyvinyl chloride, and polyester resins.

  In the laser ablation process shown in FIG. 1C, thermal ablation is employed. As described above, thermal ablation means that the organic molecules in the laser-irradiated part absorb the laser beam and become in a high vibration state, and the surrounding molecules also undergo photothermal decomposition by vibrational energy (thermal energy), resulting in ablation (evaporation). ) The phenomenon occurs. The laser light source used for thermal ablation is not particularly limited as long as it does not affect the chemical bonding of the resin component, and its wavelength is generally longer than that of ultraviolet rays, specifically, 380 nm or more. The wavelength of the laser light source is preferably 500 nm or more, and more preferably an infrared laser is used. On the other hand, from the viewpoint of the resolution of the workpiece, the wavelength of the laser is preferably 10 μm or less, and a pulse laser having an oscillation frequency of 1 kHz or more is particularly preferable. Examples of such a laser light source include solid lasers such as sapphire and yttrium aluminum garnet (YAG), and semiconductor lasers.

The energy density of the laser beam is an important factor for shortening the tact time. If the energy density is too large, not only the coating film but also the underlying substrate surface may be damaged. On the other hand, if the energy density is too small, the coating film may not be ablated or the ablation processing time may be increased. Therefore, in order to obtain the optimum energy density, it is possible to control the output of laser light, use laser light pulsed at a frequency under a certain condition, not continuous light, and coating material depending on the number of shots. It is desirable to perform processing under conditions according to the type of film and the film thickness of the coating film. From such a viewpoint, when the film thickness of the organic thin film 2 is 0.5 to 3 μm, the energy density of the laser beam is within the range of about 0.1 to 5 J / cm ² , and the types of coating film materials and the coating film It is preferable to select according to the film thickness.

  For the purpose of performing fine processing, a mask 5 may be used in the middle of the laser beam path as described above with reference to FIG. There is no special restriction | limiting in the material of the mask 5, The metal mask which consists of a silicon | silicone, copper, stainless steel (SUS) etc. can be used independently, respectively, and may use those 2 or more types together. In addition, the mask 5 may be provided with an opening 6 corresponding to the shape of the processed part alone, but a plurality of openings 6 may be provided in order to increase the processing efficiency.

  When a polymer film 3 that can be removed later as shown in FIG. 1B is provided, the polymer film 3 is removed after laser ablation as shown in FIG. When the polymer film 3 is composed of a water-soluble resin, the removal is performed by washing with water. The water used for washing may be pure water or an aqueous solution containing an appropriate solute. As a cleaning method, depending on the solubility of the polymer film 3, an immersion method, a showering method, a high-pressure spray method, etc. can be adopted, and each may be applied alone or in combination of a plurality of types. Also good.

  In the thermal ablation process, the organic thin film absorbs the energy of the laser, so that the part can be removed by evaporation, but a thin residual film 7 may remain in the processed part. The cause is not necessarily clear, but when the work piece is thin, the energy (heat) of the laser light absorbed by the film is dissipated to the ground (for example, glass), so that the work piece is decomposed. It is considered that it does not advance to the substrate surface.

  Therefore, in the present invention, after forming a pattern by laser ablation, or when a polymer film 3 that can be removed later is formed in advance as shown in FIG. 1B, the polymer film 3 is removed after laser ablation. Then, as shown in FIG. 1 (F), ashing 8 is performed on the entire surface subjected to laser ablation. Thereby, the thin residual film 7 as described above is decomposed and removed, and a high transmittance is secured in the ablated portion. Here, ashing refers to a process in which only the outermost surface of an organic substance is oxidized and removed.

  Examples of the ashing method that can be used to remove the thin residual film 7 include a method using oxygen plasma and a method using ultraviolet (UV) and ozone. Ashing with oxygen plasma is often used for resist removal after dry etching in semiconductor manufacturing, and ashing with ultraviolet rays and ozone is often used for surface treatment of liquid crystal cell substrates and color filter substrates. In either case, it is said that oxygen radicals are generated in the atmosphere, and only the outermost surface of the organic substance is oxidized to hydrophilize the surface and remove adhering contaminants on the film surface.

The kind of ultraviolet lamp used for ashing with ultraviolet rays and ozone is not particularly limited, but it is desirable to emit light in a wavelength region that acts on both oxygen gas and ozone gas to generate active oxygen. Also, in ashing with ultraviolet rays and ozone, the effect of ashing varies depending on the irradiation amount of the ultraviolet rays. Therefore, it is preferable to set the ultraviolet irradiation amount to a certain value or more, specifically, 1 J / cm ² or more, It is preferably ³ J / cm ² or more.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. In the examples, the parts and% indicating the content or amount used are based on weight unless otherwise specified.

[Example 1]
As a paint for forming a black resin film, a black resist (model number “V-259 BK66”, a negative resist containing a black pigment) sold by Nippon Steel Chemical Co., Ltd. was used. The above black resist was applied on a glass substrate by a spin coater. From the optical characteristics, the coating conditions were adjusted so that the film thickness after drying was 1.2 μm. After the application, it was placed on a hot plate at 150 ° C. for 15 minutes and dried to form a black resin film.

  Next, a 1.0% polyvinyl alcohol aqueous solution was applied onto the black resin film by a spin coater to form a polyvinyl alcohol film. At this time, the coating conditions were adjusted so that the film thickness after drying was 0.5 μm. After coating, the film was placed on a hot plate at 50 ° C. for 40 seconds and dried to complete the coating film before laser ablation processing.

The above-mentioned coating film formed of a black resin film and a polyvinyl alcohol film is irradiated with an Nd-YAG laser (wavelength: 1,064 nm) through a metal silicon stencil mask to an area to be scraped as a pattern, and laser ablation Processing was performed. The laser processing conditions at this time were an oscillation frequency of 7,500 Hz and an energy density of 0.9 J / cm ² .

  The substrate after ablation was immersed in a 0.5% strength aqueous potassium hydroxide solution maintained at 24 ° C. for 90 seconds, and the polyvinyl alcohol film was peeled and washed to prepare a resin black matrix substrate. In this state, when the ablation processed part was observed with an optical microscope, a thin residual film was observed in the ablation processed part although the black matrix pattern was obtained with high resolution. With respect to the ablation processed portion at this time, the spectral transmittance in the visible light region was measured using a microspectrophotometer manufactured by Otsuka Electronics Co., Ltd., and the result was plotted in FIG.

The black matrix substrate with the remaining film remaining was passed through an ultraviolet / ozone ashing apparatus, and ashing was performed at room temperature by changing the ultraviolet irradiation dose to two levels of 3,000 mJ / cm ² and 8,000 mJ / cm ² . .

The laser ablation processed part of the black matrix substrate after ashing was measured for spectral transmittance in the visible light region using a microspectrophotometer manufactured by Otsuka Electronics Co., Ltd., and ashing was performed at an ultraviolet irradiation dose of 3,000 mJ / cm ² The spectral transmittance at the time of ashing was plotted in FIG. 2B, and the spectral transmittance when ashing was performed at an ultraviolet irradiation amount of 8,000 mJ / cm ² was plotted in FIG. In FIG. 2, the curve of (B) and the curve of (C) almost overlap each other, and the transmittance is greatly improved compared to (A) before the treatment at any of the two levels of ultraviolet irradiation, and the visible light region. A transmittance of 95% or more was obtained over the entire area. In addition, the black matrix pattern was not affected by ultraviolet irradiation and maintained a high-resolution pattern in any of the two levels of ashing.

[Comparative Example 1]
As a comparative example, a black resin film similar to that in Example 1 is formed on a glass substrate, and a polyvinyl ablation film is not formed, and laser ablation is performed directly on the black resin film under the same conditions as in Example 1. Further, flash cleaning with water was performed to prepare a black matrix substrate. When the spectral transmittance in the visible light region was measured for the ablation portion of this black matrix substrate, the transmittance was 90% or less over the entire visible light region, and the desired optical characteristics could not be obtained. It was.

It is a cross-sectional schematic diagram which shows a preferable form later on for every process about the formation method of the thin film pattern by this invention, or the manufacturing method of a black matrix substrate. In Example 1, it is a figure which shows the spectral transmittance of the ablation processing part before performing ashing (A) and after performing ashing by changing the amount of ultraviolet irradiation (B, C).

Explanation of symbols

1 …… Board,
2 ... Organic thin film (light-shielding resin thin film),
3 …… Polymer film that can be removed later,
4 ... Laser light,
5 …… Mask,
6 …… Opening of the mask,
7 …… Remaining film of ablation processing part,
8 ... Ashing.

Claims (7)

  Forming a thin film made of an organic material on the substrate, irradiating the laser beam to the portion to be removed and performing pattern processing by thermal ablation, and then ashing the entire surface subjected to laser ablation A method for forming a thin film pattern, characterized in that   A polymer film that can be removed later is formed on a thin film made of an organic material, and laser processing is performed on the polymer film to perform pattern processing by thermal ablation, and then the polymer film is removed. The method according to claim 1, wherein an ashing process is performed later.   The method according to claim 2, wherein the polymer film that can be removed later is water-soluble, and the removal of the polymer film after patterning is performed by washing with water.   A light-shielding resin thin film containing a light-shielding pigment was formed on a transparent substrate, and laser ablation was performed after patterning by thermal ablation was performed by irradiating a portion of the thin film to be removed with laser light. A method for producing a black matrix substrate for a color filter, characterized by subjecting the entire surface to ashing treatment.   After forming a polymer film that can be removed later on the light-shielding resin thin film, irradiating laser light on the polymer film to perform pattern processing by thermal ablation, and then removing the polymer film The method according to claim 4, wherein ashing is performed.   The method according to claim 5, wherein the polymer film that can be removed later is water-soluble, and the removal of the polymer film after patterning is performed by washing with water.   The method of claim 6, wherein the later removable polymer film is formed of polyvinyl alcohol.

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