JP2009069223A - Method for producing resin thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase production efficiency of a color filter for liquid crystal and to enhance yield. <P>SOLUTION: A black matrix 10 is formed on a transparent substrate 3 and a color microfilter 12 is formed thereon in such a way that it partially overlaps the black matrix. A cross-sectional shape of the black matrix 10 is regulated so that a large protrusion is not formed at the overlaps and deterioration of the light blocking effect and film peeling at edges of the black matrix are avoided. For this regulation, prebake temperature and conditions in development processing after pattern exposure are set so that undercut parts having a proper depth and length are formed in a thin film material layer before post-bake. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a resinous thin film characterized by the cross-sectional shape of an edge portion.

  The color filter for liquid crystal is a matrix of micro color filters that transmit only basic color light such as blue light, green light, and red light, as well as yellow light and other color light added as necessary, on a transparent substrate. Arranged in a stripe or stripe shape. The micro color filter can be formed by a photolithography method using a color resist, a dyeing method, a printing method, or the like, or an ink jet method.

Prior to the formation of the micro color filter, a light-shielding black matrix having a lattice pattern corresponding to the pixel arrangement of the liquid crystal cell is formed on the transparent substrate. The large number of grid frames that make up the black matrix are partitioned so as to surround the individual outer peripheries of the micro color filter, and when displaying a color image, the color blur between adjacent pixels is eliminated and the contrast is increased. It has. The black matrix can be formed by vacuum-depositing a metal thin film having excellent light-shielding properties such as chromium on a transparent substrate. However, from the background of cost reduction requirements and enlargement of the liquid crystal display element, Patent Document 1 , 2 have been used in many cases.
Japanese Patent No. 3228139 JP 2003-161826 A

  The micro color filter is formed so as to fill the individual openings defined by the black matrix lattice frame. However, the micro color filter does not leak light between the opening edge of the lattice frame and the outer periphery of the micro color filter. The color filter is formed so as to partially overlap a part of the lattice frame beyond the opening edge. However, for example, when a synthetic resin material mixed with a pigment for coloring is used for a micro color filter and is formed using photolithography in the same manner as the black matrix, the cross-sectional shape of the opening edge of the black matrix is the surface of the transparent substrate. If the shape of the micro color filter is overlapped, the portion rises when the outer periphery of the micro color filter is overlapped, and the flatness of the color filter is significantly impaired. As is known in the above patent document, an alignment film and a transparent electrode film are further formed on the upper layer of the color filter. If the color filter has irregularities exceeding the allowable range, the alignment film and the transparent electrode film are formed. Before the process, a process of forming a transparent layer to fill these irregularities and polishing and flattening the surface is inevitable.

  In order to deal with this problem, in the methods described in Patent Documents 1 and 2, the cross-sectional shape line of the opening edge of the black matrix is raised at a gentle angle from the surface of the transparent substrate, and the overshoot when the micro color filter is laminated is performed. The lap part is prevented from rising extremely. Further, in Patent Document 2, even when the micro color filter is formed by the inkjet method, the cross-sectional shape line of the opening edge of the lattice frame is gently raised from the surface of the transparent substrate within a range of 20 ° to 55 °. It is described that it is effective to eliminate the step at the boundary between the black matrix and the micro color filter.

  However, if the cross-sectional shape line of the opening edge that defines the opening of the black matrix is raised from the transparent substrate at a gentle angle, the allowable width that can be overlapped with the micro color filter can be increased, but the lattice frame becomes closer to the opening edge. As a result, the light-shielding property decreases. For this reason, if the overlap amount when forming the micro color filter is insufficient, light leakage occurs at the peripheral portion of the micro color filter, which causes a decrease in the contrast of the color image. Therefore, when stacking micro color filters, the amount of overlap with the grid frame should be secured so that the above-mentioned light leakage does not occur, and the outer periphery of the micro color filter must be managed so that it does not rise significantly on the top surface of the grid frame. I must. Furthermore, if the film thickness of the lattice frame becomes too thin at the opening edge portion, the adhesiveness with the transparent substrate becomes weak and peeling is likely to occur, which causes problems in terms of manufacturing efficiency and yield.

  Such a problem occurs not only when the micro color filter is partially overlapped with the black matrix previously formed as described above, but conversely, the micro color filters of the respective colors are spaced apart from each other on the transparent substrate. This also occurs when the black matrix is formed so as to fill in the gaps between the micro color filters after being sequentially formed. In other words, when different types of thin films made of resin are partially overlapped and laminated, in general, the swell of the overlapped portion is suppressed as much as possible, and each thin film is firmly attached to the substrate and the underlying thin film up to its edge. It is required to be in close contact with.

  The present invention has been made in consideration of the above circumstances, and after a first thin film layer made of resin having a predetermined pattern is formed on the lower ground such as a transparent substrate, the first thin film layer is partially overlapped. When the second thin film layer is formed, the overlap portion with the second thin film layer may protrude greatly while keeping the adhesion between the edge portion of the first thin film layer and the base surface strong. It is an object of the present invention to provide a manufacturing method for forming the first thin film layer in such a form.

  When manufacturing a color filter used for a liquid crystal display element, a black matrix is formed as the first thin film layer on a transparent substrate, and the micro color filter is partially overlaid on the black matrix as the second thin film layer. Although formed so as to wrap, the present invention can be effectively applied when the black matrix is manufactured.

  In the present invention, a photosensitive colored resin composition formed with a predetermined film thickness on a base surface is formed into a resin thin film having a predetermined plane pattern by photolithography. A first step of pre-baking the colored resin composition at 70 to 120 ° C., and a step of giving pattern exposure to the photosensitive colored resin composition in a predetermined plane pattern under an exposure amount of 40 to 200 mJ after the first step. After the second step and the second step, a developing solution mainly composed of KOH having a concentration of 0.04 to 0.05%, a developing time of 40 to 70 seconds, a developing temperature of 23 ° C. to 27 ° C., a developing solution A third step of removing the unexposed photosensitive coloring composition by developing at a pressure of 0.01 to 0.2 MPa and a fourth step of post-baking are performed in this order.

  Among the above steps, it is more preferable as production conditions that the pre-baking temperature in the first step is 80 to 100 ° C., the developing time in the second step is 50 to 60 seconds, and the developing temperature is 25 to 27 ° C. In addition, by applying the first to third steps, the photosensitive colored resin composition remaining on the base surface has an undercut portion that creates a gap between the edge and the base surface in the depth direction. It is one of the features of the method of the present invention that it becomes possessed. The undercut portion thus formed preferably has a depth direction length in the range of 2.5 μm to 8.0 μm.

  The first to fourth steps are suitably used for producing a black matrix essential for a color filter for liquid crystal. The black matrix constitutes a light-shielding lattice frame that partitions a rectangular opening, and further covers the rectangular opening and partially overlaps the lattice frame. By adding a filter forming step of sequentially forming a plurality of types of resin color filter films each having a different transmitted color light for each color, the present invention provides an efficient liquid crystal color filter in which a plurality of types of resin thin films are combined. It can also be used effectively as a manufacturing method. In this case, the partial overlap length between the lattice frame and the resin color filter thin film is preferably in the range of 1.0 μm to 12 μm.

  According to the present invention, the cross-sectional shape line in the vicinity of the opening edge of the black matrix of the color filter for liquid crystal is improved, the adhesion to the transparent substrate is impaired at the opening edge portion, and the micro color filter is disposed near the opening edge. Even if they are stacked so as to overlap, there is no occurrence of extreme unevenness. In addition, when the first thin film layer in which the second thin film layer is partially laminated is formed on the base surface, not only the black matrix of the liquid crystal color filter, There is an effect that extreme unevenness is not generated in a region where both thin film layers overlap while maintaining tight adhesion with the edge portion of the first thin film layer.

  FIG. 5 schematically shows the basic structure of a liquid crystal display device using the present invention. A polarizing plate 4 serving as a polarizer and a polarizing plate 5 serving as an analyzer are joined to the surface side of the transparent substrates 2 and 3 made of optical glass serving as a support. A plurality of transparent electrodes 8 are arranged in a fixed pattern with the inner surface of the transparent substrate 2 as a base surface, and an alignment film 9 is formed so as to cover these transparent electrodes 8. The transparent electrodes 8 are arranged in a matrix, each of which is used to drive the liquid crystal molecules in the liquid crystal layer 6 in units of pixels.

  A black matrix 10 and a micro color filter 12 are formed using the inner surface of the other transparent substrate 3 as a base surface, and a transparent electrode 13 and an alignment film 14 are formed so as to cover the black matrix 10 and the micro color filter 12. The black matrix 10 has a lattice pattern in which areas facing each of the transparent electrodes 8 provided for each pixel are openings, and the micro color filter 12 is formed so as to close the openings. There are three types of micro color filters 12, a blue light transmission filter, a green light transmission filter, and a red light transmission filter, and one of the micro color filters closes one opening.

  In the schematic diagram of FIG. 5, the boundary between the black matrix 10 and the micro color filter 12 is illustrated linearly. However, as shown in an enlarged view in FIG. It is formed so as to partially overlap. FIG. 1 is an enlarged view of one pixel of a color filter for liquid crystal in which a micro color filter 12 is further laminated after forming a black matrix 10 on a transparent substrate 3, but partially overlaps as described above. By matching, no gap is generated between the opening edge 10a of the black matrix 10 and the tip 12a of the micro color filter 12.

  In order to partially overlap the black matrix 10 and the micro color filter 12 and suppress the upward protrusion amount of the micro color filter 12, the black matrix 10 has an opening edge 10a that defines an opening facing the transparent electrode 8. As shown in the drawing, the cross-sectional shape line in which the film thickness gradually increases is formed at the edge part from the edge toward the flat part 10b having a substantially constant film thickness. In order to obtain such a cross-sectional shape line, the black matrix 10 is made of a synthetic resin, and a lattice pattern is applied using photolithography as a planar pattern when the transparent substrate 3 is viewed from above.

  The resin thin film material constituting the black matrix 10 is, for example, a mixture of a black pigment such as carbon black as a light-shielding colorant mixed with an alkali-soluble synthetic resin base material provided with photocurability, and addition of an organic solvent. Fluidity is given by. In addition, as a thin film material, when a dip development is performed in an unexposed developer in a developing solution mainly composed of KOH having a development temperature of 25 ° C. and a concentration of 0.04% to 0.05%. In addition, those having a property of dissolving in 30 to 45 seconds are used.

  After the transparent substrate 3 is cleaned, the thin film material is uniformly applied to the underlying surface with a substantially constant film thickness within a range of 1.0 to 2.0 μm using, for example, a slit coater. In addition, as a coating method, an ink jet method, a screen printing method, or the like can be used. After applying the thin film material, a vacuum drying process is performed to volatilize a part of the excessive organic solvent.

  Next, pre-baking is performed to further evaporate the organic solvent. At this time, the pre-baking temperature is kept low so that the organic solvent does not completely evaporate. In general, the normal pre-bake treatment is performed for the purpose of bringing the thin film material into close contact with the base surface, whereas in the present invention, the pre-bake temperature is 70 ° C. to 120 ° C., more preferably 80 ° C. to 100 ° C. It is carried out for the purpose of keeping a part of the organic solvent on the base surface side while keeping it low and sufficiently evaporating the organic solvent from the surface side of the thin film material. In addition, the amount of the organic solvent remaining on the lower ground side of the thin film material can be adjusted by controlling the pre-baking temperature and the pre-baking time.

Next, in order to give a lattice-like planar pattern to the black matrix 10, pattern exposure is performed from the surface side of the thin film material using an exposure mask having a lattice-like light transmission pattern. A high-pressure mercury lamp is used as a light source for pattern exposure. In addition to g-line (436 nm), i-line (365 nm), and h-line (405 nm) used for general pattern exposure, it is normally cut by filtering j Lines (313 nm) and K lines (393 nm) are also actively used. In the pattern exposure, the thin film material is exposed with an exposure amount of 40 to 200 mJ / cm ² , and the exposed thin film material is cured. By such a pattern exposure process, light energy can be given to the vicinity of the ground surface even for a thin film material having a high light-shielding property by mixing with a black pigment, and a sufficient curing action can be obtained in the depth direction. . However, since the organic solvent remains in the thin film material in the vicinity of the base surface, the curing action is suppressed.

  Next, development processing is performed using an alkaline aqueous solution mainly composed of KOH having a concentration of 0.04 to 0.05%. As a result, a portion that is not exposed during the pattern exposure is eluted in the alkaline aqueous solution. This development process is carried out in the form of shower cleaning the thin film material with an alkaline aqueous solution, but the development intensity is controlled by adjusting the development processing time, shower pressure, supply amount of alkaline aqueous solution per unit time, and environmental temperature. Can do. For this thin film material, the development time is preferably 40 to 70 seconds, more preferably 50 to 60 seconds, and the development temperature is 23 ° C to 27 ° C, more preferably 25 ° C to 27 ° C. Yes, the developer pressure (shower pressure) is preferably 0.01 to 0.2 MPa.

  By performing development processing under such development conditions, the thin film material layer 20 after pattern exposure shown in FIG. 2 (A) goes from the end to the back as shown in FIG. 2 (B). An undercut portion 21 is generated. The height and depth length of the undercut portion 21 can be adjusted not only according to the development conditions but also according to the setting of the pre-baking conditions and the setting of the pattern exposure conditions. In particular, since the organic solvent remains on the base surface side by the above-described pre-bake treatment, the undercut portion 21 is formed with almost no residue even if the shower pressure during the development treatment is adjusted to be low. can do. Although only a part of the undercut portion 21 is shown in FIG. 2, the undercut portions 21 are formed approximately at the same time on each side of the lattice frame surrounding the rectangular opening of the black matrix 10.

  Subsequently, a post-bake process is performed. The post-bake treatment is a heat treatment for evaporating the organic solvent remaining in the thin film material and sufficiently curing the thin film material, and is performed at a temperature of 200 to 240 ° C. for 20 to 40 minutes. By performing this post-bake treatment, the thin film material protruding in a bowl shape above the undercut portion 21 is thermally deformed and is in contact with and in close contact with the transparent substrate 3 as shown in FIG. As a result, the black matrix 10 having the cross-sectional line shape shown in FIG. 1 is obtained.

  As shown in FIG. 2C, the black matrix 10 not only gradually increases in film thickness from the opening edge 10a toward the flat portion 10b, but also has a cross-sectional shape line of an upward convex curve portion P1, a downward convex curve portion P2, The shape includes the upward convex curve portion P3, and includes at least two inflection points on both sides of the downward convex curve portion P2. Further, the illustrated cross-sectional shape includes a straight line portion having a substantially uniform thickness between the upward convex curve portion P1 and the downward convex curve portion P2, and the overlay latitude S with the micro color filter 12, that is, FIG. As shown in FIG. 2, the minimum overlap width T that does not cause a gap between the micro color filter 12 and the opening edge 10a is secured, and the micro color filter 12 is overlapped with the black matrix 10 at the overlapping portion. This is advantageous in increasing the allowable overlap width S that does not require a large increase.

  In order to widen the overlap allowable width S, it is effective to make the film thickness such that the cross-sectional shape line does not exceed the tangent line Q in the film thickness increasing region from the opening edge 10a to the flat part 10b of the black matrix 10. is there. Due to the heat deformation during the post-baking process described above, curved portions P1 and P3 that are upwardly convex are formed in the vicinity of the opening edge 10b and at the boundary portion with the flat portion 10b, but the tangent line Q is formed in these curved portions P1 and P3. It is a tangent that touches in common. If the cross-sectional shape line of the gradually increasing film thickness region is maintained in a shape that does not exceed the tangent line Q, the allowable overlap width S when the micro color filters 12 are stacked is kept wide.

  As described above, in order to give the black matrix 10 a unique shape to the cross-sectional shape line of the region where the film thickness is gradually increased, as schematically shown in FIG. 4, after the development process, before the post-bake process is performed. In this stage, an undercut portion 21 is formed in the thin film material layer 20. The depth length L of the undercut portion 21 can be basically adjusted by the strength of development processing. The stronger the development process, the longer the undercut length L and the thinner the edge of the thin film material layer 20 (the left end in the figure).

  The undercut length L1 of the thin film material layer 20 shown by the solid line in FIG. 4 is the one when the development processing is most intense, and the undercut lengths L2 and L3 of the thin film material layer shown by the two-dot chain line are relatively in that order. This is a case where development processing is weakened. In the case of the undercut length L1, the film thickness of the edge of the thin film material layer 20 becomes too thin, and problems are likely to occur in terms of light shielding required for the black matrix. Then, when the micro color filter is partially overlapped, a horn-like protrusion is formed in that portion.

  From these facts, there is an appropriate range for the undercut length of the thin film material layer 20 before post-baking, and when the thickness of the black matrix 10 in the flat portion is in the range of 1.5 μm to 2.0 μm, the thin film The undercut length L formed in the material layer 20 is preferably in the range of 2.5 μm to 8.0 μm. By making this range, the height of the horn when the micro color filters are overlapped is suppressed to within 0.5 μm. In addition, the overlap allowable width S can be increased to at least about 3 μm.

  Tables 1, 2 and 3 show the results of confirming how much the undercut length L formed in the thin film material layer 20 varies depending on the post-bake temperature and the development processing conditions. The development processing conditions were such that the development temperature was changed in three stages of 25 ° C., 23 ° C., and 27 ° C., and the development processing time was changed from 30 seconds to 80 seconds at 10 second intervals. The pre-baking temperature was changed in five stages of 70 ° C., 80 ° C., 90 ° C., 100 ° C., and 120 ° C., and the change in the undercut length L was measured by combining these conditions.

  In addition, as a specific resin material of the thin film material layer 20, “CK-9910L (trade name)” manufactured by FUJIFILM Electronics Materials Co., Ltd. is used. This resin material has a development temperature of 25 ° C. and a concentration of 0. It exhibits physical properties that dissolve in 30 to 45 seconds when dip development is performed in an unexposed developer in a developer containing 04% to 0.05% KOH as a main component. The pattern exposure is performed with an exposure amount of 40 to 200 mJ as described above. “CDK-1 (trade name)” manufactured by FUJIFILM Electronics Materials Co., Ltd. is used as a developing solution, and this developing solution contains KOH having a concentration of 0.04 to 0.05% as a main component. It is an example of things.

  From the above results, it has been confirmed that the pre-baking temperature, the developing solution temperature and the developing time are elements for adjusting the length of the undercut length L, and the developing temperature is set to 23 ° C. to 27 ° C. Pre-bake temperature is preferably in the range of 70 ° C. to 120 ° C., preferably 80 ° C. to 100 ° C., and the development time is adjusted in the range of 40 to 70 seconds. It was found that it was appropriate as a condition suitable for mass production.

  As described above, according to the present invention, the development time and the pre-bake temperature are adjusted by adjusting the development time and the pre-bake temperature while suppressing the development temperature in the range of 23 ° C. to 27 ° C. in order to prevent deterioration of the development processing solution. An undercut portion having an appropriate undercut length can be formed in the thin film material layer 20. For this reason, after forming the black matrix 10, when the micro color filter 12 is laminated by photolithography using a resin thin film, the black matrix depends on how much accuracy can be ensured in the lamination process and pattern exposure process. Since the shape of the ten edge portions can be adjusted, the color filter for liquid crystal can be easily manufactured and the yield can be greatly improved.

  As described above, the present invention has been described based on the black matrix 10 used for the color filter for liquid crystal. However, the present invention is not limited to the black matrix but can be applied to other resin thin films. For example, when a micro color filter is formed by photolithography using a resin thin film, the difference between a micro color filter and a black matrix is technically mixed or colored with a light-shielding pigment on a synthetic resin substrate. The only thing to do is mix the pigments. Therefore, when three types of micro color filters are first arranged in a matrix in a discrete manner on a transparent substrate, and then the gaps between the micro color filters are filled with a black matrix, the present invention is applied at the time of forming the micro color filter. Can be applied as well.

It is a partial expanded sectional view of the color filter for liquid crystals. It is explanatory drawing which shows the manufacturing process of a black matrix. It is a partial expanded sectional view which shows the boundary part of a black matrix and a micro color filter. It is a conceptual diagram of the undercut part formed in a thin film material layer. It is a schematic diagram which shows the outline of a structure of a liquid crystal display element.

Explanation of symbols

3 Transparent substrate 6 Liquid crystal layer 10 Black matrix 12 Micro color filter 20 Thin film material layer 21 Undercut part P1, P2, P3 Curve part

Claims (7)

A first step of pre-baking the photosensitive colored resin composition formed at a predetermined film thickness on the lower ground at 70 to 120 ° C .;
A second step of applying pattern exposure to the photosensitive colored resin composition in a predetermined plane pattern under an exposure amount of 40 to 200 mJ after the first step;
After the second step, a development processing solution mainly composed of KOH having a concentration of 0.04 to 0.05% is used, the development time is 40 to 70 seconds, the development temperature is 23 ° C. to 27 ° C., and the developer pressure is 0.01. A third step of developing at -0.2 MPa to remove the unexposed photosensitive coloring composition;
A fourth step of post-baking;
In this order, and forming the resin thin film having the planar pattern on the base surface.   The resin according to claim 1, wherein the pre-baking temperature in the first step is 80 to 100 ° C, the developing time in the second step is 50 to 60 seconds, and the developing temperature is 25 ° C to 27 ° C. A method for producing a thin film.   The photosensitive colored resin composition left on the ground surface in the third step has an undercut portion that creates a gap between the edge and the ground surface in the depth direction. 3. A method for producing a resinous thin film according to 1 or 2.   The method for producing a resinous thin film according to claim 3, wherein the undercut portion has a length in the depth direction of 2.5 μm to 8.0 μm.   The method for producing a resinous thin film according to claim 1, wherein the resin thin film obtained in the fourth step is a black matrix constituting a light-shielding lattice frame that partitions a rectangular opening. .   Including a filter forming step of sequentially forming a plurality of types of resin color filter films having different transmitted color lights for each color so as to cover the rectangular opening and partially overlap the lattice frame. The method for producing a resinous thin film according to claim 5. The method for producing a resinous thin film according to claim 6, wherein a partial overlap length between the lattice frame and the resin color filter thin film is 1.0 μm to 12 μm.

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