JP6053019B2 - Analysis method for hot warpage of liquid crystal polymer injection molded products - Google Patents

Description

  The present invention relates to a method for analyzing a hot warp of a liquid crystal polymer injection molded product.

  Conventionally, a liquid crystal polymer, which is a thermoplastic resin, has been used for small, thin-walled and fine-shaped injection molded products because of its excellent properties such as high fluidity, high elasticity, low linear expansion coefficient, and high heat resistance. It is also used for electronic equipment parts and applications that are exposed to high temperatures of 200 ° C or higher. Liquid crystal polymer injection-molded products usually have different thermal and mechanical properties depending on the orientation direction of the liquid crystal polymer molecules, and may have a multilayer structure. Such liquid crystal polymer injection-molded products are warped and deformed by a thermal load. Therefore, in order to ensure the dimensional accuracy of the molded product, molding is performed in a manner in which warp deformation is unlikely to occur, and warping deformation after molding. It is important to predict and use it.

  The warped deformation of resin molded products is the shape of the molded product, the mode of liquid crystal polymer flow during molding, the distribution of thermal history to the molded product, and the distribution of thermal and mechanical properties such as linear expansion coefficient and Young's modulus in the molded product. And a combination of factors such as heat load on the molded product. The warp deformation that occurs as a response of a molded product to a thermal load, that is, hot warp deformation, depends on the distribution of thermal properties and mechanical properties of the molded product. Regarding such liquid crystal polymer injection-molded products, a prediction method for predicting hot warpage deformation is known in order to suppress warpage deformation of the molded product caused by heating after molding (see, for example, Patent Document 1).

JP 2012-96488 A

  However, although the warpage deformation prediction method as shown in Patent Document 1 described above can predict hot warpage deformation, the prediction is that the residual strain has been removed by annealing by the first temperature rise after molding. This is a hot warpage prediction for a later molded product. In general, in an injection molded product molded from a resin such as a liquid crystal polymer, the warp deformation that occurs at the first temperature rise after molding is different from the warp deformation due to repeated cooling and temperature rise, and thus exhibits hysteresis. Are known. Such anticipation of warpage deformation hysteresis is useful for improving the yield of components for small-sized electronic devices using liquid crystal polymer injection-molded products and improving the reliability of devices incorporating the components.

  However, a method for accurately predicting hot warpage prediction having such hysteresis has not been put into practical use. In addition, for hot warp analysis, anisotropy data of the linear expansion coefficient at each point of the injection-molded product to be analyzed is required, but the linear expansion coefficient at each point of the actual injection-molded product that is becoming smaller. The acquisition of anisotropic data is difficult due to the small size. This is because measurement of the data of the coefficient of linear expansion requires that the measurement test piece has a certain size or more due to the constraints imposed by the apparatus for measuring the coefficient of linear expansion.

  The present invention solves the above-described problems, and is a liquid crystal polymer injection molded product that can accurately predict warpage deformation occurring in a molded product at the first temperature rise after molding even for a small-sized molded product. An object is to provide a hot warpage analysis method.

  In order to achieve the above object, the method for analyzing hot warpage of a liquid crystal polymer injection-molded product of the present invention uses thermal mechanical analysis to analyze thermal expansion data for a plurality of portions where the liquid solidification forms of the liquid crystal polymer in the evaluation injection-molded product differ. Based on the first step to be obtained, the second step for obtaining the temperature and flow velocity of the liquid crystal polymer during molding of the injection molded product for evaluation by numerical calculation, and the thermomechanical analysis in the first step based on the numerical calculation result of the second step For each site where the liquid crystal polymer solidified during flow and the flow stopped, the integrated data of the shear stress accumulated and the length of time until the liquid crystal polymer stopped flowing and reached the solidification temperature A third step for obtaining data, a fourth step for calculating the temperature and flow velocity of the liquid crystal polymer during molding of the injection-molded product to be analyzed by numerical calculation, and a numerical meter for the fourth step Based on the results, for each point of the injection-molded product to be analyzed, data on the integrated value of the shear stress accumulated while the liquid crystal polymer solidifies during flow and stops flowing, and the liquid crystal polymer stops flowing and solidifies Each heat acquired in the first step based on the correlation between the data obtained in the fifth step, the data obtained in the fifth step, and the data obtained in the third step. The sixth step of mapping the expansion data as the thermal expansion data at each point of the analysis target injection molded product, and the structural analysis of the analysis target injection molded product using the thermal expansion data mapped by the sixth step, the analysis target injection And a seventh step of analyzing irreversible hot warpage of the molded product.

  In this hot warpage analysis method for liquid crystal polymer injection-molded products, the third step is based on the numerical calculation result of the second step, and the liquid solidification form of the liquid crystal polymer of the evaluation injection-molded product is the temperature drop during flow In accordance with the result of the determination, the data or time of the integral value of the shear stress is determined. Based on the numerical calculation results of the fourth step, the flow solidification form of the liquid crystal polymer of the injection molding product to be analyzed is solidified and flows as the temperature decreases during the flow. It is determined whether it is a form to stop or a form to stop and solidify due to a dead end, and depending on the result of the determination, data on the integrated value of shear stress or data on the length of time is acquired. It may be.

  In this method for analyzing hot warpage of a liquid crystal polymer injection-molded product, the thermal expansion data of the first step may be acquired for the flow direction and the flow orthogonal direction of the liquid crystal polymer at the time of injection molding.

  In the method for analyzing hot warpage of a liquid crystal polymer injection-molded product, the thermal expansion data of the first step may be acquired for each layer in which the liquid crystal polymer flows in layers during injection molding in the evaluation injection-molded product.

  According to the method for analyzing a hot warp of a liquid crystal polymer injection molded product of the present invention, the thermal warpage data of a reference sample obtained by thermomechanical analysis is mapped to the injection molded product based on a numerical calculation result to analyze the hot warp. Therefore, even a small-sized molded product can predict warp deformation with high accuracy.

The figure explaining the hot warp analysis method of the liquid crystal polymer injection-molded article concerning one embodiment of the present invention. The flowchart about the analysis method. The figure explaining the correspondence of the data in the same analysis method. The figure explaining the form of fluidization solidification of resin in the analysis method. The figure explaining the shear stress integral value and stop solidification time length in the same analysis method. The figure explaining the role of the shear stress integral value and stop solidification time length in the same analysis method. Sectional drawing explaining the fluidization solidification of resin in a metal mold | die. (A)-(d) is sectional drawing explaining the flow of the resin in a metal mold | die, and the behavior of solidification about a linear flow path. (A)-(d) is sectional drawing explaining the flow of the resin in a metal mold | die, and the behavior of solidification about a bending flow path. (A)-(d) is sectional drawing explaining the flow of the resin in a metal mold | die, and the behavior of solidification about a branch flow path. (A) is a top view of the injection-molded product for evaluation, (b) is a side view thereof, and (c) is a cross-sectional view taken along line (b). (A) is a plan view showing another example of an injection-molded product for evaluation, (b) is a perspective view of an evaluation sample cut out from the injection-molded product for evaluation, and (c) is a division of the sample for evaluation into layers. The perspective view which shows the state which carried out. (A) is a figure which shows the time change of the resin temperature in the case of the form 1 solidified while the resin in the mold flows, and (b) is the resin in the form 2 in which the resin in the mold is solidified after stopping the flow. The figure which shows the time change of temperature. (A) is a figure which shows the time change of the distortion produced in resin in the case of form 1, (b) is a figure which shows the time change of distortion produced in resin in the case of form 2. (A) is a figure which shows the temperature change of the elongation by the heat | fever of the site | part shape | molded by the form 1, (b) is a figure which shows the temperature change of the elongation by the heat | fever of the site | part shape | molded by the form 2. (A) (b) is a figure which shows the temperature change of the curvature deformation with respect to the thermal load of a resin injection molded product which is mutually different. The flowchart about the hot-warp analysis method of the liquid crystal polymer injection molded product which concerns on other embodiment. (A) is a plan view of an analysis target injection-molded product in an embodiment of the same analysis method, (b) is a side view of the same analysis target injection-molded product, (c) is a cross-sectional view taken along line XX of (a), ( d) The perspective view which shows the test piece cut out from the same injection molding product to be analyzed. The figure which shows the change of the curvature deformation amount with respect to a thermal load about each test piece shown in FIG.18 (d). (A) is a top view which shows an example of the injection molded product for evaluation used for the Example, (b) is the same side view. (A)-(d) is a top view which shows the injection molded product for evaluation used for the Example whose molded product full length is 15, 30, 45, 60 mm, respectively. The figure which shows the example of a measurement of the log | history of the hot elongation of the sample for evaluation by the thermomechanical analyzer in an Example. The figure which shows the relationship between the measured value of the thermal expansion coefficient of the sample for evaluation based on the measurement by a thermomechanical analyzer, and a molded article full length about several measurement positions and measurement directions. The figure which shows the relationship between the residual distortion in the sample for evaluation based on the measurement by a thermomechanical analyzer, and a molded article full length about several measurement positions and measurement directions.

(Hot warp analysis method)
Hereinafter, a hot warpage analysis method (hereinafter referred to as this analysis method) of a liquid crystal polymer injection-molded product according to an embodiment of the present invention will be described with reference to the drawings. 1 to 3 show this analysis method. Here, the liquid crystal polymer injection-molded article is a resin injection-molded article using a liquid crystal polymer as a resin, and in the following, the resin is a liquid crystal polymer. In this analysis method, as shown in FIGS. 1 and 2, from the first step (S1) of acquiring thermal expansion data for the evaluation injection-molded product 1, the hot warpage of the analysis-target injection-molded product 2 is analyzed by structural analysis. There are seven steps (S1 to S7) up to the seventh step (S7) to be analyzed. The execution order of each of these seven steps is not limited to the order shown in FIG. 2, and as shown in FIG. The execution order of each other can be changed as appropriate. Hereinafter, each process will be described.

  The first step (S1) is a step of acquiring thermal expansion data Ht1 by thermo-mechanical analysis (TMA) for a plurality of portions having different forms of fluidization and solidification of the resin in the injection-molded product 1 for evaluation. This analysis method is based on the idea that the physical properties of a resin injection-molded product are determined by the form of fluidization and solidification of how the resin flows and solidifies in the mold. This analysis method is based on this idea and supplements the physical property information that cannot be directly measured in the injection molding product 2 to be analyzed with the physical property information obtained for the injection molding product 1 for evaluation.

  The evaluation injection-molded product 1 is a molded product for evaluating physical properties of the injection-molded product by actual measurement in the first step (S1) and numerical calculation in the second and third steps (S2, S3). The physical property data to be evaluated is acquired in association with each other as an actual measurement value and a numerical calculation value at the same part of the evaluation injection molded product 1. The physical properties to be evaluated are different between the actual measurement values and the numerical calculation values. In the actual measurement, for example, the physical properties are related to thermal response, and in the numerical calculation, for example, distortion accumulated in each part of the injection molded product at the time of molding. . The distortion of each part of the molded product is considered to be a result of the flow solidification of the resin at the time of molding, and is considered to reflect information on the form of fluid solidification of the resin in each part.

  The thermal expansion data Ht1 is directly measured by a thermomechanical analyzer as a change in elongation of the evaluation sample with respect to a change in thermal load for the evaluation sample cut out from the evaluation injection-molded product 1. The elongation is not an elongation due to a load, but an elongation due to thermal expansion. From the measured value, the linear expansion coefficient of the part where the evaluation sample in the evaluation injection-molded product 1 is cut out is calculated. The linear expansion coefficient of a resin injection-molded product usually has anisotropy, and the value differs between the flow direction of the resin and the flow orthogonal direction perpendicular to the flow direction. Therefore, the thermal expansion data Ht1 is acquired for a plurality of directions of the same part in consideration of this anisotropy.

  In the actual measurement by thermomechanical analysis, it is necessary to prepare a sample for evaluation having predetermined dimensions required from the thermomechanical analyzer, for example, several cm in length, several mm in width, and 1 mm or less in thickness. Such an evaluation sample desirably has uniform physical properties as a whole. Moreover, in order to complement the physical property information that cannot be directly measured in the analysis target injection-molded product 2, the evaluation sample is prepared for various parts having different forms of fluidization and solidification of the resin, and thermal expansion data Ht1 is acquired for each. It is desirable. Therefore, the evaluation injection-molded product 1 is a combination of a plurality of types of molded products in which the resin flow has a uniform flow structure with a wide laminar width, the resin flow length is changed, or a branch structure is provided in the resin flow. Configured (see illustration in FIG. 1). The evaluation sample is provided by being cut out from a plurality of portions of each evaluation injection-molded product 1. When measuring in a plurality of directions of the same part, a plurality of evaluation injection-molded articles 1 having the same conditions are prepared.

  The second step (S2) is a step of obtaining the numerical calculation result CD1 including the temperature and flow velocity data of the resin in the mold during molding of the evaluation injection molded product 1 by numerical calculation. The numerical calculation is performed for all of the plurality of molded articles constituting the evaluation injection molded article 1. The numerical calculation will reproduce the state change from flow to solidification in each part, including the flow and solidification state in the local part such as the step part and corner part of the mold for injection molding, in time and space. To do. In the numerical calculation, boundary conditions regarding the heat balance and the resin flow speed in the wall surface of the inner space of the mold into which the resin flows in, and conditions such as fluctuations in the pressure and viscosity of the resin in the mold are considered. The numerical calculation is performed, for example, by creating a three-dimensional analysis mesh from the three-dimensional CAD data used for designing a mold for injection molding.

  In the third step (S3), based on the numerical calculation result CD1 in the second step (S2), the data of the shear stress integral value ΣStr1 for each part subjected to the thermomechanical analysis in the first step (S1), and This is a step of acquiring data of the time length trx1 of the resin flow stop solidification. The integral value ΣStr1 is a value obtained by temporally integrating the shear stress accumulated in the resin while the resin solidifies during the flow in the mold and stops flowing. The time length trx1 is the time length from when the resin stops in the mold in the fluidized state until the solidification temperature is reached.

  The shear stress of the resin at the time of injection molding changes every moment in each space in the mold while the resin solidifies while flowing in the mold. Each molecule of the liquid crystal polymer resin receives a shearing force during the flow, and the alignment state at the final stop position is determined according to the time for which the force is received. Accordingly, the data of the shear stress integral value ΣStr1 obtained by time-integrating the shear stress is data including information on the molecular orientation state, more generally anisotropy of the resin molded product. The data of the integral value ΣStr1 may be acquired as a vector quantity or a tensor quantity in association with the flow direction of the resin or the orientation direction of the resin, in addition to being acquired as a scalar value in each part.

  The fourth step (S4) is a step of obtaining the numerical calculation result CD2 including the temperature and flow velocity of the resin in the mold at the time of molding for the analysis target injection molded product 2 by numerical calculation. In this step, numerical calculation is performed in the same manner as in the second step (S2) described above, but the target of the numerical calculation is only for one analysis target injection molded product 2 to be noted. In addition, as the analysis target injection molded product 2, it is usually possible to target a small molded product whose thermal expansion data cannot be measured by thermomechanical analysis.

  In the fifth step (S5), based on the numerical calculation result CD2 in the fourth step (S4), the data of the integral value ΣStr2 of the shear stress and the resin flow stop solidification for each point of the injection molding product 2 to be analyzed This is a step of acquiring data of the time length trx2. The integral value ΣStr2 is a value obtained by temporally integrating the shear stress accumulated in the resin while the resin solidifies during the flow in the mold and stops flowing. The time length trx2 is the time length from when the resin stops in the mold to the solidification temperature after stopping from the fluid state. In this step, as in the third step (S3) described above, the shear stress integral value and time length data are acquired. The part where each point for acquiring the data is located is a part corresponding to each element for structural analysis in the analysis target injection molded product 2, and is distributed throughout the analysis target injection molded product 2. The integral value ΣStr2 can be acquired as a scalar value, a vector amount, a tensor amount, and the like, similarly to the integral value ΣStr1.

  In the sixth step (S6), the thermal expansion at each point of the analysis target injection-molded product 2 based on the data obtained in the first step (S1), the third step (S3), and the fifth step (S5). Data Ht2 is obtained and each value is mapped to each element of the structural analysis model. The structural analysis is, for example, a finite element analysis using the finite element model 20 (illustration in FIG. 1). The value of the thermal expansion data Ht2 is determined based on the correlation between the data in the fifth step (S5) and the data in the third step (S3) for each point of the analysis target injection-molded product 2. It is obtained by selecting one of the thermal expansion data Ht1 acquired in S1). In the seventh step (S7), the structural analysis of the injection molding product 2 to be analyzed is performed using the thermal expansion data Ht2 mapped in the sixth step (S6), and the irreversible hot warpage of the injection molding product 2 to be analyzed is analyzed. It is a process to do.

  With reference to FIG. 3, the concept of the present analysis method, particularly the mapping concept of the above-described sixth step (S6) will be further described. The aggregate of the thermal expansion data Ht1 measured by the thermomechanical analysis in the first step (S1) constitutes a database space (referred to as TMA measurement DB space). Each point in the DB space is accompanied by a pair of measured values of thermal expansion data Ht1 measured in both the flow direction MD of the resin and the flow orthogonal direction TD orthogonal to the flow direction MD. Further, each point in the space K1 made up of the integral value ΣStr1 and the time length trx1 data in the third step (S3) has a one-to-one correspondence with each point in the DB space. The space K1 is divided into three regions of form 1, form 2, and form 3 according to the form of fluidization and solidification of the resin (described later, FIG. 4).

  Similarly, the data of the integral value ΣStr2 and the time length trx2 in the fifth step (S5) constitutes a space K2. The space K2 is divided into three regions of form 1, form 2, and form 3, as with the space K1. Each point of the space K2 has a one-to-one correspondence with each element of the finite element model 20 representing the analysis target injection molded product 2. The mapping process of the sixth step (S6) selects one of the thermal expansion data Ht1 under a predetermined condition for one element of the finite element model 20, and selects the selected thermal expansion data Ht1 as the element. This is a process for assigning the thermal expansion data Ht2 to each element. An interpolation step may be provided in which new thermal expansion data Ht2 is assigned to a value obtained by performing linear interpolation between other elements to elements for which thermal expansion data Ht2 has not been assigned. As the linear interpolation, for example, triple linear interpolation can be used.

  The selection of the thermal expansion data Ht1 is most correlated with the point qi (i = 1, 2,...) In the space K2 from among the points pj (j = 1, 2,...) In the space K1. This is done by selecting a point. That is, when the point pj is selected by the determination based on the correlation, one-to-one correspondence between the point in the space K2 and the point in the finite element model 20 and one-to-one correspondence between the point in the space K1 and the point in the DB space. The thermal expansion data Ht2 to be mapped is determined. The point pj (j = 1, 2,...) Of the space K1 has a value of (ΣStr1, trx1), and the point qi (i = 1, 2,...) Of the space K2 has a value of (ΣStr2, trx2). Therefore, the corresponding point pj having a strong correlation with the point qi can be selected based on these values. For example, when the integral values ΣStr1, ΣStr2 are acquired as a vector amount or a tensor amount in relation to the resin flow direction MD and the flow orthogonal direction TD, the correlation for each component is comprehensively determined, and the point pj Is selected. It should be noted that the selection decision is generally made based on the condition that the corresponding points are points in the spatial region of the same form k (k = 1, 2, 3), and then the corresponding points are narrowed down gradually. You may process.

  Here, the configuration shown in FIG. 3 is roughly divided into three, and numerical calculation of injection molding (IM-CAE) for the injection molded product 2 to be analyzed and injection molding element data (IM-) based on the evaluation injection molded product 1 ED) and structural analysis using a finite element model (FEM-A). Injection molding element data (IM-ED) is a set of TMA measurement DB space data and space K1 data. Then, this analysis method performs numerical calculation (IM-CAE) for any analysis target injection-molded product, and performs structural analysis (FEM-A) using injection-molded element data (IM-ED). It can be summarized as an analysis method for predicting hot warpage deformation. Injection molding element data (IM-ED) can be accumulated based on measurements and calculations, and the accumulated data can be applied to any analysis target injection molded product. Therefore, according to the present analysis method, when the injection molding element data (IM-ED) is accumulated, the injection molding element data (IM-ED) is measured without performing measurement on various analysis target injection molded products having different shapes. The hot warpage deformation can be predicted only by calculation.

(Form of fluidized solidification of resin)
Next, with reference to FIGS. 4 to 10, the form of fluidization and solidification during injection molding of the resin in the mold, which is an important concept in this analysis method, will be described. As shown in FIGS. 4 and 5, whether the resin is solidified by flow or solidification of the process and material factors such as the degree of solidification of the resin and the position of the resin in the mold is close to the dead end position. It is classified into four forms 0 to 3 using a two-dimensional state diagram based on the vertical axis of the shape design factor “no”.

  Form 0 is a form in which the resin is flowing without stopping and appears in an initial state where the resin is injected into the mold, [the fluidity on the horizontal axis is large and the degree of solidification is small; The dead end position on the vertical axis is far away]. This form 0 is a form in which a transition is made to any of the other forms 1, 2, and 3 with the passage of time, and the history is not retained in the molded injection molded product.

  Form 1 is in a state where the resin has stopped flowing due to cooling and solidification, and is in a state of [the fluidity on the horizontal axis is small and the degree of solidification is large; the dead end position on the vertical axis remains far]. In other words, Form 1 corresponds to the case where the resin stops flowing below the solidification temperature while flowing in the mold. Here, the solidification temperature includes a concept of a flow stop temperature at which the viscosity increases and the fluid cannot flow. In this form 1, since the resin is solidified while flowing, the shear stress generated in the resin by the resin flow is large, and the shear stress is accumulated in the resin as a shear strain by the solidification of the resin. Therefore, the integral value ΣStr of the shear stress Is expected to grow. In this form 1, since the resin solidifies and stops flowing later, the time length trx defined as the time length until the resin reaches the solidification temperature after stopping from the flow state in the mold is 0 or 0. Expected to be close to.

  Form 2 is a state in which the resin stops flowing due to a dead end, and the cooling and solidification proceeds in the stopped state, [the fluidity on the horizontal axis is large and the degree of solidification is small; the dead end position on the vertical axis is close] It is in a state of. In other words, form 2 corresponds to the case where the mass flow of the upstream resin is hindered by the flow stop of the downstream resin, and the flow stop is caused by the dead end or solidification of the cavity space of the mold. A dead end due to the finished resin is included. In this form 2, since the resin is solidified in a state where the flow is stopped, the generation of shear stress due to the flow is small, so that the integral value ΣStr of the shear stress is expected to be small. Further, in this form 2, since the resin is solidified after the flow is stopped, the time length trx from the stop to the solidification is expected to be a large value.

  Form 3 is a situation in which the resin is in a mixed state of Forms 1 and 2 and the dead end approaches as the solidified layer grows and stops flowing, [the fluidity on the horizontal axis is small and the degree of solidification is large; The dead-end position on the vertical axis is near]. In this form 3, the integral value ΣStr of the shear stress and the time length trx from stop to solidification each have a value that is not 0, and such a mixed state is present in a wide range of parts of the injection molded product. It is expected to occur.

  As shown in FIG. 6, the physical properties of the injection-molded molded product reflect the molding conditions such as when the resin stops and when it hardens. Therefore, it is important to quantify the behavior of the resin until it solidifies. It is. In other words, it is necessary to quantify two behaviors: the growth behavior of the solidified layer and the relaxation behavior from flow stoppage due to dead ends to solidification. Here, the relaxation behavior is a behavior under a situation where the shear stress in the resin is relaxed while the resin is cooled and solidified after stopping from the fluid state. The former growth behavior is quantified by determining the integral value ΣStr of the shear stress, and the latter relaxation behavior is quantifying by determining the time length trx.

  As shown in FIG. 7, the resin 9 flowing in the cavity 30 (the space filled with resin) of the mold 3 grows a solidified resin layer 9a from the inner wall side of the cavity 30 that is a resin flow path. However, the fluid resin layer 9b in the center flows along the flow direction MD. Since the fluidized resin layer 9b is cooled and becomes more viscous as it is closer to the mold 3 and the solidified resin layer 9a, the fluidized resin layer 9b is solidified from the inner wall side while receiving shear stress due to a velocity gradient generated in a direction perpendicular to the inner wall of the cavity 30. Stop while accumulating shear stress as internal strain. As shown in this figure, the solidified resin layer 9a formed during the flow is according to the above-described embodiment 1 in which the flow stops due to the growth of the solidified layer. However, the form of fluidization and solidification of the resin is determined by the shape of the cavity of the mold in which the resin is injected, the solidification position of the resin inside the mold, and the like. This will be described below.

  FIGS. 8A to 8D each show a linear flow channel-shaped cavity 30 having a stop 31 at the end of a flow channel that linearly extends in the resin flow direction. FIGS. To (d), the flow path length to the closing part 31 becomes long in order. Here, description will be made assuming that there is no influence (for example, at infinity) of the wall surface in the direction perpendicular to the cross section in each figure. In the case of FIG. 8A, it is considered that the state of form 2 appears, in which the resin in the cavity 30 encounters the stop portion 31 before solidifying and stops, and then solidifies. In the case of FIG. 8D, the resin injected into the cavity 30 continues to flow while the solidified resin layer is grown on the wall surface until the tip portion reaches the closing portion 31. During the flow, the state of Form 1 appears at a position away from the stop portion 31, and it is considered that the state of Form 2 appears around the stop portion 31 after the front end portion of the resin reaches the stop portion 31. In the case of FIGS. 8B and 8C, in addition to the state of Form 2, the state of Form 1 appears in a range corresponding to the length of the flow path.

  The state of form 3 is generally considered to appear in the boundary area between the form 1 area and the form 2 area. It is the thickness of the flow path in the mold (gap between walls) at what ratio each area of form 1, form 2 and form 3 appears in the linear flow path. Depends on conditions such as injection pressure, injection speed, resin temperature, mold temperature, mold heat capacity and heating state. Even if the shape of the cavity 30 is the same, if the injection conditions other than the shape are different, the form of fluidization and solidification will be different.

  9 (a) to 9 (d) each show a cavity 30 having a bent flow path shape formed by bending (bending) a straight flow path linearly extending in the resin flow direction at right angles, and FIG. 9 (a). From FIG. 9 (d), the linear flow path length to the bent portion 32 becomes longer in order. Unlike the closing portion 31 in FIG. 8 described above, the bent portion 32 does not stop the flow of the resin, but affects the flow rate and flow rate distribution of the resin, the filling completion time, and the like. Therefore, the distribution of the flow solidification state of the resin in the region up to the bending point is different from that shown in FIG.

  10 (a) to 10 (d) show ribs 33, which are straight flow paths branched at right angles to a position at a fixed distance on the upstream side in the cavity 30 having the straight flow path shape shown in FIGS. 8 (a) to 8 (d). A branch channel-shaped cavity 30 is shown. In the case of FIG. 10A, the resin injected into the cavity 30 immediately flows into the rib 33 without much difference from the shape of the bent flow path in FIG. In the case of FIG. 10D, since the flow resistance of the flow path toward the rib 33 is larger than the flow resistance in the linear direction, the inflow of the resin to the rib 33 is delayed from the linear direction, The filling completion time in the flow path is also delayed due to the influence of resin branching to the rib 33. In any case, depending on the shape of the cavity 30 as shown in FIG. 10, FIG. 8, and FIG. 9, the resin injection conditions, etc., the form of fluidized solidification of the resin exhibits various aspects. .

(Evaluation injection molded product)
FIGS. 11A, 11B, and 11C show examples of the injection molded product 1 for evaluation. The injection-molded product for evaluation 1 is composed of the continuous sheet-like molded parts F1, F2,... Having a width w orthogonal to the runner 1a and a wall thickness t1, and the resin in each of the sheet-like molded parts F1, F2,. Ribs R1, R2,... Having a width w rising from the end in the flow direction and a thickness t2. Each of the sheet-shaped molded parts F1, F2,... Has a constant sheet length d, and the ribs R1, R2,. The width w is set sufficiently wide so as to constitute a uniform linear flow of resin. The wall thicknesses t1 and t2 are set to be sufficiently thin so as to form a uniform molding state in the thickness direction. The numerical value of each part is, for example, w = 20 mm, t1 = t2 = 0.3 mm, d = 15 mm.

  The injection-molded product for evaluation 1 is molded in any combination in which the number of the respective sheet-like molded portions F1, F2,... And ribs R1, R2,. The The combinations are represented symbolically, for example, (F1), (F1, F2), (F1, R1), (F1, R1, F2),... It is only the case. The total length in the resin flow direction of the evaluation injection-molded product 1 is d × n if the number of sheet-shaped molded parts is n. Since these various types of evaluation injection-molded articles 1 have a repetitive structure, they can be easily molded by preparing a plurality of small types of element molds and combining them. Such various types of evaluation injection-molded articles 1 can reproduce the form of fluidized solidification that appears in various cavity 30 structures as shown in FIGS. 8, 9, and 10.

  The evaluation sample 11 or the evaluation sample 12 to be subjected to thermomechanical analysis is cut out from each of the sheet-like molded parts F1, F2,. The evaluation sample 11 is a sample along the resin flow direction MD, and the evaluation sample 12 is a sample along the resin flow direction TD. In addition, since both samples cannot be cut out from the same sheet-shaped molded part, a plurality of evaluation injection molded articles 1 are prepared. The dimensions of each of the evaluation samples 11 and 12 are, for example, a length a = 13 mm, a width b = 5 mm, and a thickness t1 = 0.3 mm. The same samples 11 and 12 for evaluation are obtained for each of the ribs R1, R2,. The elongation in the longitudinal direction of each of the evaluation samples 11 and 12 is measured by the thermomechanical analyzer, and the linear expansion coefficient in the longitudinal direction is obtained from the measured value.

  12 (a), 12 (b), and 12 (c) show another example of the injection-molded product 1 for evaluation. This evaluation injection-molded product 1 corresponds to the case where the thickness t1 of the sheet-like molded parts F1, F2,... In the evaluation injection-molded product 1 shown in FIG. It is a molded product whose state is not uniform. Liquid crystal polymers tend to be formed into layers having different physical properties. Therefore, in the case of the evaluation injection-molded product 1 having a thick sheet-shaped molded part, for example, a thick test piece 10 is cut out for thermomechanical analysis, and the test piece 10 is divided into a plurality of layers for evaluation. Samples 11a to 11e are cut out. Each of the evaluation samples 11a to 11e thus obtained becomes an evaluation sample having uniform physical properties. FIG. 12 shows an example of cutting out five evaluation samples along the flow direction MD of the resin, but the evaluation sample along the flow orthogonal direction TD is cut out, An arbitrary number of samples for evaluation can be cut out according to changes in physical property values. When such an evaluation injection-molded article 1 is used, for example, an evaluation sample in the state of form 3 is obtained.

(Form of fluidized solidification)
13 to 15 show typical forms 1 and 2 in the form of fluidized solidification. As shown in FIG. 13 (a), in Mode 1, the resin temperature in the mold decreases with time, solidification proceeds while the resin flows, and the flow is stopped by solidification at time P1 when the resin temperature reaches the solidification temperature. To do. During the change in temperature and time indicated by the region F in the figure where solidification proceeds while flowing, strain due to shear stress is accumulated and an integral value ΣStr of shear stress is formed. In this case, at the time point P1, the flow stop and the solidification occur simultaneously, and the time length trx until the resin stops flowing and reaches the solidification temperature is zero.

  In addition, as shown in FIG. 13 (b), in Mode 2, the resin temperature in the mold decreases with time, and the resin that has flowed does not reach the solidification temperature, but at a certain point P2 due to a dead end. After the flow is stopped, the resin temperature is lowered and the resin is solidified while the flow is stopped. Although strain due to shear stress is accumulated in the region F up to the time point P2, the shear accumulated before the flow is stopped during the cooling and solidification in the region R up to the time point Q when the resin temperature is lowered to the solidification temperature. Stress distortion is alleviated. Therefore, the time length trx, which is the elapsed time from the time point P2 to the time point Q, is an index of the effect due to the relaxation behavior of the resin, and is an index characterizing the form 2.

  As shown in FIG. 14 (a), the strain in the resin molded through Form 1 increases with time, and settles to the saturation strain value A1 after a certain time M1. The saturation strain value A1 corresponds to a strain released by annealing due to the first temperature rise and temperature drop after the molded product is taken out from the mold. Further, the saturation strain value A1 is in a functional relationship with the integral value ΣStr of the shear stress. The time point M1 corresponds to the time point P1 described above.

  Further, as shown in FIG. 14 (b), the strain in the resin molded through the form 2 increases with time, and after reaching a peak at the time point M2, gradually decreases to a certain strain value. Settle to A2. The elapsed time from the time point M2 to the time point N is the time length trx, and the amount of distortion reduction during that time is the strain relaxation amount Rx. The strain value A2 corresponds to the strain released by annealing due to the first temperature rise and temperature drop after the molded product is taken out from the mold, and the saturation strain in the above-described embodiment 1 due to the presence of the relaxation amount Rx. The value is smaller than the value A1 (A2 <A1). The time point M2 corresponds to the time point P2 described above, and the time point N corresponds to the time point Q described above.

  As shown in FIGS. 15 (a) and 15 (b), the initial elongation responses of the evaluation samples corresponding to form 1 and form 2 to repeated thermal loads of rising and falling respectively show hysteresis. That is, with respect to the path A-B of the elongation response at the first temperature increase, the first temperature decrease, the second temperature increase and the temperature decrease, and the temperature change along the path BC different from the path AB. Elongation response. In other words, the behavior in the path AB is an irreversible hot warping behavior, and the behavior in the path BC is a reversible hot warping behavior. The difference between Form 1 and Form 2 appears in the thermal strain defined by the difference in elongation value between point A and point C in the lowered state. The thermal strain L1 in the case of the form 1 shown in FIG. 15A is larger than the thermal strain L2 in the case of the form 2 shown in FIG. 15B (L1> L2). This is because the thermal strain L1 corresponds to the above-described saturation strain value A1, the thermal strain L2 corresponds to the above-described strain value A2, and the effect of the above-described relaxation amount Rx is reflected in the thermal strain L2.

(Hot warp deformation)
16 (a) and 16 (b) show the warp deformations that occur as a response to repeated heating and cooling of two types of molded products 1 and 2 by liquid crystal polymer injection molding with different manufacturing conditions and shapes. The change of hot warpage deformation is shown. The following description is the same even if the molded product 1 and the molded product 2 are replaced with a warpage measurement sample cut out for warpage measurement from the molded products 1 and 2 instead of the entire molded product. In addition to the shape factor of the molded product, hot warpage deformation is a combination of factors such as the resin flow mode during molding, thermal history, linear expansion coefficient, Young's modulus, and other thermal and mechanical property distributions. As a result. Therefore, as the warped deformation W1 of the molded product 1 and the warped deformation W2 of the molded product 2 are different, the magnitude of the warp deformation is different for different molded products. On the other hand, the hot warping behavior is usually the same behavior repetition for each molded product with respect to the first temperature decrease and the second and subsequent temperature increases and decreases. The hot warpage behavior is predicted relatively easily by the conventional warpage deformation prediction method except for the warp behavior at the first temperature rise, but the prediction is based on the residual strain due to the annealing after the first temperature rise after molding. This is a hot warpage prediction for a molded product after removal of slag.

  This analysis method makes it possible to accurately predict the warpage deformation at the first temperature rise of an injection molded product of an arbitrary size using a liquid crystal polymer resin. According to this analysis method, as described in relation to FIG. 3 above, numerical analysis (IM-CAE) is performed on the injection-molded product to be analyzed, and structural analysis is performed using the injection-molded element data (IM-ED). (FEM-A) can be performed to predict warpage deformation during the first temperature increase. Since this analysis method predicts hot warpage deformation only by calculation with reference to the accumulated injection molding element data (IM-ED), a small-sized molded product regardless of the shape of the injection-molded product to be analyzed. Even so, it is possible to accurately predict warpage deformation occurring in the molded product at the first temperature rise after molding. The warp deformation that occurs in the molded product at the first temperature rise after molding is an irreversible change with respect to the temperature change, and is caused by residual strain existing in the molded product after molding. This analysis method uses thermal expansion data for the behavior in which the solidified layer of the resin grows and stops flowing at the time of molding, and in the behavior that solidifies after filling the resin to the end of the mold cavity and forcibly stops flowing. This is based on the assumption that there will be a difference. It is considered that the difference in the thermal expansion data is caused by a difference in shear strain during flow for orienting the molecules of the liquid crystal polymer and the presence or absence of strain relaxation before solidification.

(Other embodiments)
The flowchart of FIG. 17 shows another embodiment of the present analysis method. In this embodiment, the third step (S3) and the fifth step (S5) in the embodiment shown in FIGS. 1 and 2 are replaced with the third step (S31) and the fifth step (S51), respectively. The others are the same. In the third step (S31), based on the numerical calculation result of the second step (S2), it is determined which of the forms 1 and 2 is the flow solidification form of the resin of the evaluation injection-molded product 1, Depending on the determination result, data of the integral value ΣStr1 of the shear stress or the time length trx1 is acquired. In the fifth step (S51), based on the numerical calculation result of the fourth step (S4), it is determined which of the forms 1 and 2 is the flow solidification form of the resin of the injection molding product 2 to be analyzed. Depending on the determination result, data of the integral value ΣStr2 of the shear stress or the time length trx2 is acquired. According to the present embodiment, the flow solidification form of the resin is divided into either the form 1 or the form 2 and the analysis is performed, and the state of the form 3 is not considered, so that the calculation process can be simplified and speeded up. The

(Injection molded product)
18 and 19 show the injection molding product 2 to be analyzed. The analysis target injection-molded product 2 is, for example, a long box-shaped molded product having a length of 17.8 × a width of 1.83 × a height of 0.4 mm, as shown in FIGS. The XX cross section has a bottom thickness of 0.12 mm and a side thickness of 0.163 mm. A position indicated by a pin gate with an arrow at an end portion in the longitudinal direction of the analysis target injection-molded product 2 is a resin injection position. The flow direction of the resin is globally along the longitudinal direction of the injection molded product 2 to be analyzed, but locally, the position in the mold cavity space at the time of molding, the temperature distribution, and the progress of resin solidification in each part Depending on the distribution in various directions.

  Warpage data shown in FIG. 19 was obtained for the test pieces TP1 to TP4 shown in FIGS. 18 (c) and 18 (d). The hot warpage was measured by a laser displacement sensor by controlling the temperature with a commercially available flatness measuring device and using the distance from the reference surface as the amount of warpage. Depending on which part of the injection-molded product 2 to be analyzed is cut from the specimens TP1 to TP4, the measured value of the warp differs depending on the composite state of the flow solidification state of the resin in the mold. ing. The behavior of the warp deformation with respect to the temperature load change is that the test pieces TP1 to TP4 are cut out in parallel with each other, and are almost in the same flow direction, so that the forms of resin flow solidification are close to each other. Are considered to be similar to each other. The entire warpage of the injection-molded product 2 to be analyzed is measured as a result of the warpage appearing on the test pieces TP1 to TP4 of each part being combined with each other. The prediction of the warpage of the injection molded product 2 is realized.

(Evaluation injection molded product and measurement)
20 to 24 show an evaluation injection molded product 1 and measurement examples thereof. As the evaluation injection-molded product 1, for example, as shown in FIGS. 20 (a) and 20 (b), the total length FL of the molded product in the flow direction of the resin having four continuous sheet-shaped molded portions F1 to F4 is 60 mm ( FL = 15 × 4 mm) is formed, and each of the evaluation samples 11 and 12 is prepared. Each of the evaluation samples 11 and 12 in the figure is given a geometric symbol such as a square or a circle for identifying the position of the sample and the longitudinal direction of the sample. As shown in FIGS. 21 (a) to 21 (d), the same injection molded product for evaluation 1 and the respective samples for evaluation 11 and 12 were prepared for the total length of each molded product FL = 15, 30, 45, and 60 mm.

  For example, as shown in FIG. 22, the hot elongation of the sample for evaluation changes along the downwardly convex curved path AB at the time of the first temperature increase, and the first temperature decrease and the second and subsequent times. When the temperature rises and falls, it changes reversibly along the same straight line B-C. The hot elongation was measured in a tensile mode by gripping both ends of a sample for evaluation with gripping portions 10 mm apart from each other of a thermomechanical analyzer. The elongation difference Ld between points AB in the figure indicates the thermal strain of the sample for evaluation (see the description of FIG. 15). The linear expansion coefficient of the sample for evaluation is given by a differential coefficient in the path AB and the path BC. Therefore, the linear expansion coefficient in the curved path A-B has temperature dependence, and the linear expansion coefficient in the linear path B-C is constant with respect to the temperature change.

  FIG. 23 shows the linear expansion coefficient obtained from the above-mentioned linear path BC for each evaluation sample of each evaluation injection-molded product 1 shown in FIG. With respect to the flow direction MD and the flow orthogonal direction TD of the resin, systematic changes with respect to the total length FL of the molded product are observed. In the flow direction MD, in the same sheet-shaped molded part, the linear expansion coefficient decreases as the molded product overall length FL (longest flow length) increases, and the linear expansion coefficient decreases toward the upstream in the same molded product overall length FL. Further, when paying attention to the sheet-shaped molded part F1, the linear expansion coefficient is saturated when the total length FL of the molded product becomes longer. Further, in the region near the end of each molded product full length FL (F1 at FL = 15 mm, F2 at 30 mm, F3 at 45 mm, F4 at 60 mm), the linear expansion coefficient decreases as the molded product full length FL increases.

  From the above, regarding the linear expansion coefficient in the flow direction MD, it is considered that the liquid crystal polymer molecules that are strongly oriented due to shear strain are fixed as they are as the time during which solidified layer growth proceeds becomes longer. Also, under conditions where the flow velocity will decrease due to the cooling of the resin or pressure loss due to the solidified layer before reaching the downstream, the shear viscosity will increase and the shear strain will increase due to the decrease in temperature and shearing effect. It is done. On the other hand, in the flow orthogonal direction TD, anisotropy with respect to the flow direction MD is observed, and the anisotropy tends to increase as the molecular orientation increases. The linear expansion coefficient in these evaluation samples is The orientation is considered dominant. This analysis method acquires thermal expansion data along the curved path AB and predicts and uses the temperature-dependent linear expansion coefficient in order to predict warpage deformation at the first temperature rise. The temperature-dependent linear expansion coefficient is mapped to each element of the model for structural analysis at each temperature during structural analysis. In order to simplify the processing, a linear expansion coefficient obtained from the slope of the straight line AB between the two points A and B may be used.

  FIG. 24 shows the residual strain σ for each sample for evaluation. The residual strain σ is obtained from the above-described thermal strain Ld obtained from the elongation temperature curve shown in FIG. 22 described above for each evaluation sample, and is calculated from the thermal strain Ld. For example, in the case of Ld = 150 μm = 0.15 mm, the residual strain σ is σ = Ld / L0 × 100 (%) because the length to be stretched (separated distance of the gripping portion described above, expressed as L0) L0 = 10 mm = 0.15 / 10 × 100 = 1.5 (%). When attention is paid to the sheet-shaped molded part F1, it appears that the anisotropy of the residual strain changes according to the distance to the flow end. In other sheet-shaped molded parts, it varies according to the distance to the flow end, and it is considered that there is an influence of the difference in the fluidized solidification form, but it cannot be said that the same tendency as the sheet-shaped molded part F1, There is no clear tendency as in the case of the linear expansion coefficient. The time length trx from flow stop to solidification related to strain relaxation can be calculated more accurately in consideration of filling time conditions such as filling time and temperature distribution in addition to solidified layer growth information. .

  The present invention is not limited to the above-described configuration, and various modifications can be made. For example, the analysis target injection molded product 2 can be a molded product in which glass fibers are added to a liquid crystal polymer. In this case, the evaluation injection-molded product 1 uses a molded product made of a resin to which the same glass fiber as that of the analysis-target injection-molded product 2 is added. For example, the evaluation injection-molded product 1 and the analysis target injection-molded product 2 are molded from a resin in which glass fibers having a diameter of 10 μm and an average fiber length of 178 μm are added to an I-type liquid crystal polymer. Further, the flow direction MD and the flow orthogonal direction TD can be determined based on geometric shapes such as the shape of the mold cavity and the gate position of the resin injection. In addition, the flow direction MD and the flow orthogonal direction TD can be determined by, for example, the flow velocity direction of the resin by numerical calculation, and are further determined based on the alignment information of the liquid crystal polymer molecules and the alignment information of the glass fibers. Also good.

DESCRIPTION OF SYMBOLS 1 Injection molded product for evaluation 2 Injection molded product to be analyzed 3 Mold 9 Liquid crystal polymer 11 Sample for evaluation along flow direction 12 Sample for evaluation along flow orthogonal direction CD1, CD2 Numerical calculation result Ht1, Ht2 Thermal expansion data MD Flow direction TD Flow orthogonal direction ΣStr, ΣStr1, ΣStr2 Integrated value of shear stress trx, trx1, trx2 Time length of stop solidification

Claims (4)

In the hot warp analysis method for liquid crystal polymer injection molded products,
A first step of acquiring thermal expansion data by thermomechanical analysis for a plurality of portions having different forms of fluidized solidification of the liquid crystal polymer in the injection-molded product for evaluation;
A second step for calculating the temperature and flow rate of the liquid crystal polymer during molding of the evaluation injection-molded product by numerical calculation;
Based on the numerical calculation result of the second step, the integrated value of the shear stress accumulated while the liquid crystal polymer solidifies during the flow and stops flowing for each part subjected to the thermomechanical analysis in the first step. A third step of acquiring data and data of a length of time until the liquid crystal polymer stops flowing and reaches a solidification temperature;
A fourth step for calculating the temperature and flow rate of the liquid crystal polymer during molding of the injection-molded product to be analyzed by numerical calculation;
Based on the numerical calculation result of the fourth step, for each point of the injection molding product to be analyzed, data on the integral value of shear stress accumulated while the liquid crystal polymer solidifies during flow and stops flowing, and A fifth step of acquiring data on the length of time until the liquid crystal polymer stops flowing and reaches the solidification temperature;
Based on the correlation between each data obtained in the fifth step and each data obtained in the third step, each thermal expansion data obtained in the first step is converted into heat at each point of the analysis target injection molded product. A sixth step of mapping as dilation data;
And a seventh step of analyzing the irreversible hot warpage of the analysis target injection molded product by performing a structural analysis of the analysis target injection molded product using the thermal expansion data mapped in the sixth step. A hot warpage analysis method for liquid crystal polymer injection molded products. In the third step, the liquid solidification form of the liquid crystal polymer of the evaluation injection-molded product is solidified as the temperature decreases during the flow, and the flow is stopped based on the numerical calculation result of the second step. It is determined whether or not it is a form that stops and solidifies due to a dead end, and according to the result of the determination, obtains the data of the integrated value of the shear stress or the data of the time length,
In the fifth step, based on the numerical calculation result of the fourth step, the liquid solidification form of the liquid crystal polymer of the injection molding product to be analyzed is solidified as the temperature decreases during the flow and the flow is stopped. It is determined whether there is a form in which flow is stopped and solidified due to a dead end, and according to the result of the determination, data of the integrated value of the shear stress or data of the time length is obtained. The method for analyzing a hot warp of a liquid crystal polymer injection molded product according to claim 1.   The thermal expansion data of the liquid crystal polymer injection molded product according to claim 1 or 2, wherein the thermal expansion data of the first step is acquired with respect to a flow direction and a flow orthogonal direction of the liquid crystal polymer during injection molding. analysis method.   4. The thermal expansion data of the first step is acquired for each layer in which the liquid crystal polymer flows in layers during injection molding in the injection molding for evaluation. 5. The hot warpage analysis method of the liquid crystal polymer injection-molded article described.

Images